Roller hearth type firing furnace

Abstract

To provide a roller hearth type firing furnace which can suppress a product failure caused by the insufficient sintering of a processed material.SOLUTION: A roller hearth type firing furnace conveys a processed material composed of two members having different sintering temperatures in the order of a temperature increasing zone and a holding zone on a conveyance passage composed of plural conveyance rollers, and fires the same. The roller hearth type firing furnace comprises a first stopper for the temperature rising zone and a second stopper for the holding zone. The conveyance of the processed material is stopped by the first stopper entering the conveyance passage till it reaches a first temperature corresponding to the sintering temperature on the low temperature side of the processed material, the first stopper retreats from the conveyance passage to release the conveyance stop when the temperature of the processed material reaches the first temperature or more, the conveyance of the processed material is stopped by the second stopper entering the conveyance passage till it reaches a second temperature corresponding to the sintering temperature on the high temperature side of the processed material, and the second stopper retreats from the conveyance passage to release the conveyance stop when the temperature of the processed material reaches the second temperature or more.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] A roller hearth type firing furnace for continuously firing processed objects such as ceramic green compacts is known. In this type of firing furnace, a heating zone, a holding zone, and a cooling zone are arranged in this order from the upstream to the downstream in the conveying direction (see, for example, Patent Document 1). The processed object is heated and fired at a relatively low temperature in the heating zone, then heated and fired at a relatively high temperature in the holding zone, and cooled in the cooling zone.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Among ceramic green compacts, there are some mainly composed of two types of members having different sintering temperatures. For example, a general multilayer ceramic capacitor (MLCC) has a structure in which nickel and barium titanate are laminated. However, nickel has a sintering temperature of around 800°C, while barium titanate has a sintering temperature of around 1300°C. In order to manufacture such a product, first, in the heating zone, the processed object is heated to a temperature at which the member with a low sintering temperature can be sintered, and then, in the holding zone, the processed object is heated to a temperature at which the member with a high sintering temperature can be sintered. Thereby, the members having different sintering temperatures that constitute the product can be sintered respectively.

[0005] However, in a conventional roller hearth type firing furnace, sintering in the heating zone and the holding zone was performed without stopping the conveyance of the object to be processed. In this case, although the temperature of the object to be processed has not sufficiently increased, there is a possibility that the object to be processed may be carried out from the heating zone or the holding zone. In such a case, the product is not sufficiently sintered, and there is a possibility of product defects.

[0006] Therefore, an object of the present invention is to provide a roller hearth type firing furnace capable of suppressing product defects caused by insufficient sintering of an object to be processed.

Means for Solving the Problems

[0007] In order to solve the above problems, the present invention provides a roller hearth type firing furnace for firing an object to be processed composed of two members having different sintering temperatures in order of a heating zone and a holding zone on a conveyance path composed of a plurality of conveyance rollers, including a first stopper provided in the heating zone and a second stopper provided in the holding zone, wherein the conveyance of the object to be processed is stopped by the first stopper that has entered the conveyance path until the temperature of the object to be processed reaches a first temperature corresponding to the sintering temperature on the lower temperature side, and when the temperature of the object to be processed becomes equal to or higher than the first temperature, the first stopper retracts from the conveyance path and the conveyance stop is released, and the conveyance of the object to be processed is stopped by the second stopper that has entered the conveyance path until the temperature of the object to be processed reaches a second temperature corresponding to the sintering temperature on the higher temperature side, and when the temperature of the object to be processed becomes equal to or higher than the second temperature, the second stopper retracts from the conveyance path and the conveyance stop is released.

[0008] (2) Among the plurality of conveyance rollers constituting the conveyance path, the high-speed conveyance rollers provided in the high-speed conveyance region from the first stopper to the second stopper convey the object to be processed at a higher speed than the conveyance rollers provided in the regions other than the high-speed conveyance region in the heating zone and the holding zone. The roller hearth type firing furnace according to (1).

[0009] (3) The drive mechanism of the high-speed conveying roller has a first magnetic gear coaxially attached to the longitudinal end of the high-speed conveying roller, and a second magnetic gear provided at a position not in contact with the first magnetic gear. The first magnetic gear and the second magnetic gear are provided at positions where the rotational axis directions are orthogonal to each other. When the second magnetic gear is driven, the first magnetic gear rotates, and the high-speed conveying roller is driven. The roller hearth type firing furnace according to (2).

[0010] (4) The support mechanism of the high-speed conveying roller has a bearing disposed above the high-speed conveying roller and in contact with the high-speed conveying roller, a plate portion attached to the bearing and capable of moving up and down, and an elastic body provided on the upper surface of the plate portion and extending in the vertical direction. The elastic body generates a biasing force that presses the bearing against the high-speed conveying roller in response to being compressed through the plate portion as the high-speed conveying roller is displaced upward. The roller hearth type firing furnace according to (3).

[0011] (5) The object to be processed is a laminated ceramic capacitor in which nickel and barium titanate are laminated. The roller hearth type firing furnace according to any one of (1) to (4).

[0012] (6) The high-speed conveying roller has a large-diameter roller portion and a first small-diameter roller portion having an outer diameter smaller than that of the large-diameter roller portion. The first small-diameter roller portion is located inside the furnace, and the large-diameter roller portion extends from both ends of the first small-diameter roller portion. The roller hearth type firing furnace according to (2), characterized in that.

[0013] (7) The first small-diameter roller portion has a roundness smaller than that of the large-diameter roller portion. The roller hearth type firing furnace according to (6), characterized in that.

[0014] (8) A second small-diameter roller portion having a roundness smaller than that of the large-diameter roller portion is formed at the end of the large-diameter roller portion. The second small-diameter roller portion is rotatably supported by a support mechanism. The roller hearth type firing furnace according to (6) or (7), characterized in that.

Advantages of the Invention

[0015] According to the roller hearth type firing furnace of the present invention, since the sintering of the object to be processed can be sufficiently performed, it is possible to suppress product defects and the like due to insufficient sintering.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0017] (First Embodiment) Hereinafter, with reference to the drawings, a first embodiment of the roller hearth type firing furnace of the present invention will be described. (Configuration of Roller Hearth Type Firing Furnace 1) Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view in the transport direction of a roller hearth type firing furnace 1 according to this embodiment. Referring to FIG. 1, the roller hearth type firing furnace 1 is a facility for heating and firing a workpiece 100. The workpiece 100 is not particularly limited as long as it is mainly composed of two types of members having different sintering temperatures. Here, the case where a multilayer ceramic capacitor (MLCC) is used as the workpiece 100 will be described.

[0018] In the roller hearth type firing furnace 1, a heating zone 2, a holding zone 3, and a cooling zone are provided in this order from the upstream side in the transport direction. For the sake of convenience in explaining the present invention, the illustration of the cooling zone is omitted. The heating zone 2 is a zone mainly for raising the temperature of the workpiece 100 toward a predetermined temperature (a first temperature T1 corresponding to the lower sintering temperature). The holding zone 3 is a zone mainly for holding the workpiece 100 at a predetermined temperature (a second temperature T2 corresponding to the higher sintering temperature, T2 > T1). The first temperature T1 and the second temperature T2 will be described later.

[0019] In the heating zone 2 and the holding zone 3, a large number of transport rollers 10 penetrating the side wall in the thickness direction are horizontally provided to form a transport path. By rotating each transport roller 10 in the same direction around the axis, the workpiece 100 is transported on the transport path. The transport roller 10 may be made of, for example, ceramics. The interiors of the heating zone 2 and the holding zone 3 are partitioned into respective small rooms 5 by partition walls 4 extending from the top wall and the bottom wall, and heaters 6 are provided above and below each transport roller 10. Note that the heaters to be installed can be appropriately changed according to the set temperature of each small room 5. For example, the small room 5b located at the most upstream of the holding zone 3 is located immediately after the heating zone 2, and since a rapid temperature rise is required, it is preferable to use a heater more powerful than the heaters 6 of the other small rooms 5. In addition to the heater 6, a gas injection pipe (not shown) can also be provided above the transport roller 10 in order to directly blow high-temperature gas onto the workpiece.

[0020] In the small chamber 5a formed at the most downstream of the small chambers 5 provided in the temperature rising zone 2, a first detection unit 21, a first temperature measurement unit 22, and a first stopper 23 are provided. The first detection unit 21 is configured to detect the workpiece 100 conveyed in the temperature rising zone 2, and a known sensor (for example, a laser sensor) can be used. The first temperature measurement unit 22 is configured to measure the temperature of the workpiece 100 conveyed in the temperature rising zone 2. The first stopper 23 includes an operating device 231 composed of an air cylinder, but the operating device 231 may be composed of, for example, a hydraulic cylinder or an electric cylinder in addition to the air cylinder. The operating device 231 includes a piston rod 232, and a stop portion 233 is provided at the tip of the piston rod 232. When the workpiece 100 is detected by the first detection unit 21, the operating device 231 operates and the piston rod 232 extends upward, and the stop portion 233 advances into the conveyance path from the gap between the conveyance rollers 10 adjacent in the conveyance direction. When the workpiece 100 comes into contact with the stop portion 233, the workpiece 100 stops at the position where it contacts the stop portion 233.

[0021] The temperature of the workpiece 100 stopped by the first stopper 23 is measured by the first temperature measurement unit 22. When the temperature of the workpiece 100 measured by the first temperature measurement unit 22 is less than the preset first temperature T1, it is determined that "the temperature rise in the temperature rising zone 2 is not sufficient", and while the workpiece 100 is stopped by the first stopper 23 for a predetermined time, the workpiece 100 is heated by a heater 6 or the like in the small chamber 5a during this stop time, so that the temperature of the workpiece 100 can be increased. When the temperature of the workpiece 100 becomes equal to or higher than the first temperature T1, it is determined that "the temperature has risen sufficiently in the temperature rising zone 2", the stop portion 233 retracts from the conveyance path, and the conveyance is restarted. The first temperature T1 is set corresponding to the sintering temperature of the member having the lower sintering temperature among the two types of members mainly constituting the workpiece 100. In the present embodiment, since the workpiece 100 is a multilayer ceramic capacitor (MLCC), the first temperature T1 can be set to, for example, 850°C in accordance with the general sintering temperature of nickel (about 800°C).

[0022] In the small room 5b formed near the loading entrance among the small rooms 5 provided in the holding belt 3, a second detection unit 31, a second temperature measurement unit 32, and a second stopper 33 are provided. The second detection unit 31 is configured to detect the processed object 100 conveyed by the holding belt 3, and a known sensor (for example, a laser sensor) can be used. The second temperature measurement unit 32 is configured to measure the temperature of the processed object 100 stopped by the second stopper 33. The components of the second stopper 33 have an operating device 331, a piston rod 332, and a stopping unit 333, similar to the components of the first stopper 23. However, since the functions of these components are the same as those of the components of the first stopper 23, the description will not be repeated. When the processed object 100 is detected by the second detection unit 31, the operating device 331 operates and the piston rod 332 extends upward, and the stopping unit 333 advances into the conveyance path from the gap between the conveyance rollers 10 adjacent in the conveyance direction. When the processed object 100 contacts the stopping unit 333, the processed object 100 stops at the position where it contacts the stopping unit 333.

[0023] The temperature of the processed object 100 stopped by the second stopper 33 is measured by the second temperature measurement unit 32. When the temperature of the processed object 100 measured by the second temperature measurement unit 32 is less than the preset second temperature T2, it is considered that "the temperature rise in the holding belt 3 is not sufficient", and while the processed object 100 is stopped by the second stopper 33 for a predetermined time, the processed object 100 is heated by the heater 6 or the like in the small room 5b during this stop time, so that the temperature of the processed object 100 can be increased. When the temperature of the processed object 100 becomes equal to or higher than the second temperature T2, it is determined that "the temperature has risen sufficiently in the holding belt 3", the stopping unit 333 retracts from the conveyance path, and the conveyance is restarted. The second temperature T2 is set corresponding to the sintering temperature of the member with the higher sintering temperature among the two types of members mainly constituting the processed object 100. In this embodiment, since the processed object 100 is a multilayer ceramic capacitor (MLCC), the second temperature T2 can be set to, for example, 1350°C in accordance with the sintering temperature of barium titanate (about 1300°C).

[0024] In a conventional roller hearth type firing furnace, sintering is performed in the heating zone 2 and the holding zone 3 while continuously conveying the object to be processed 100. Unlike the roller hearth type firing furnace 1 in the present embodiment, it does not have a configuration for stopping the object to be processed 100 by the first stopper 23 and the second stopper 33. Therefore, the temperature of the object to be processed 100 cannot be directly measured, and the temperature of the object to be processed 100 is estimated by measuring the temperature of the furnace atmosphere. However, with this conventional temperature measurement method, the temperature of the object to be processed 100 could not be accurately obtained, resulting in insufficient sintering of the object to be processed 100 and the possibility of product defects. On the other hand, in the roller hearth type firing furnace 1 in the present embodiment, since the object to be processed 100 can be stopped by the first stopper 23 and the second stopper 33, the temperature of the object to be processed 100 can be directly measured while the object to be processed 100 is stopped, and the temperature of the object to be processed 100 can be accurately obtained. Thereby, the temperature control of the object to be processed 100 can be performed with higher precision, and the possibility of product defects can be reduced. The first temperature measurement unit 22 and the second temperature measurement unit 32 are not particularly limited as long as they can directly measure the temperature of the object to be processed 100. For example, a radiation thermometer can be preferably used.

[0025] Furthermore, according to the above-described configuration, the temperature of the object to be processed 100 can be made equal to or higher than the first temperature T1 in the heating zone 2, and the temperature of the object to be processed 100 can be made equal to or higher than the second temperature T2 in the holding zone 3. Therefore, the members constituting the object to be processed 100 can be sufficiently sintered, and the possibility of product defects can be reduced.

[0026] The materials of the stopping portions 233 and 333 of the first stopper 23 and the second stopper 33 are not particularly limited. However, since the heating zone 2 and the holding zone 3 become hot, it is preferable to use materials with heat resistance and high strength. For example, it is preferable to use ceramics such as SiC-based ceramics.

[0027] (Regarding the high-speed conveyance region A) As described above, a general multilayer ceramic capacitor (MLCC) has a structure in which nickel and barium titanate are laminated. However, the sintering temperature of nickel is around 800°C, while that of barium titanate is around 1300°C. Therefore, as described in the configuration of the roller hearth type firing furnace 1 above, after raising the temperature of the workpiece 100 to the sintering temperature of nickel in the heating zone 2, it is necessary to raise the temperature of the workpiece 100 to the sintering temperature of barium titanate in the holding zone 3. Here, the inventors have conducted intensive studies and have come up with the idea that by shortening the time from when nickel is sintered until barium titanate is sintered, the continuous expansion of only nickel for a long time can be suppressed, and the possibility of product defects can be further reduced. Therefore, in order to minimize the time from when nickel is sintered until barium titanate is sintered, it is preferable that the region A in the transport direction from the first stopper 23 to the second stopper 33 in the roller hearth type firing furnace 1 be a high-speed transport region for transporting the workpiece 100 at high speed. Hereinafter, the transport roller 10 in the high-speed transport region A is also referred to as the high-speed transport roller 10a. The rotation speed of the high-speed transport roller 10a is not particularly limited as long as it is higher than that in other regions (regions other than the high-speed transport region A) in the heating zone 2 and the holding zone 3. For example, the rotation speed of the high-speed transport roller 10a can be set to 800 to 1000 rpm, and the rotation speed of the transport roller 10 other than the high-speed transport roller 10a can be set to about 1 to 10 rpm.

[0028] As a driving method for the conveying roller 10, a method using a chain is common. However, if high-speed conveyance is performed by this method, there is a risk of applying an excessive load to the chain. Therefore, the inventors of the present invention conducted intensive studies and came up with the idea of using a magnetic gear for driving the high-speed conveyance roller 10a. FIG. 2 is a view of the longitudinal end of the high-speed conveyance roller 10a as seen in the conveying direction. Referring to FIG. 2, a first magnetic gear 7a is coaxially attached to the longitudinal end of the high-speed conveyance roller 10a, and a second magnetic gear 7b is provided at a non-contact position below the first magnetic gear 7a. The first magnetic gear 7a and the second magnetic gear 7b are arranged such that the rotational axis directions are orthogonal. When a driving device (not shown) operates and the second magnetic gear 7b rotates around the axis, the first magnetic gear 7a rotates by magnetic force, and accordingly, the high-speed conveyance roller 10a is rotationally driven (the rotational direction is indicated by an arrow in FIG. 2). As described above, since the first magnetic gear 7a and the second magnetic gear 7b do not come into direct contact, it is possible to eliminate the driving that applies a load to components such as chain drive.

[0029] FIG. 3 is a view of the periphery of the high-speed conveyance roller 10a as seen in the axial direction of the high-speed conveyance roller 10a. Referring to FIG. 3, in order to suppress the lifting and sinking of the high-speed conveyance roller 10a, bearings 81, 82, and 83 are in contact with the lower left, lower right, and upper parts of the high-speed conveyance roller 10a, respectively, to support the high-speed conveyance roller 10a. A vertically movable plate portion 84 is attached to the upper bearing 83, and an elastic body 85 extending in the vertical direction is provided on the upper surface of the plate portion 84. Since the high-speed conveyance roller 10a rotates faster than the other conveyance rollers 10, the high-speed conveyance roller 10a itself tends to lift upward. On the other hand, according to the configuration of the present embodiment, as the high-speed conveyance roller 10a lifts, the bearing 83 is displaced upward and the elastic body 85 contracts via the plate portion 84. However, the restoring force of the elastic body 85 acts on the bearing 83 with a biasing force that pushes the plate portion 84 downward, and the bearing 83 presses the high-speed conveyance roller 10a downward. Thereby, the lifting of the high-speed conveyance roller 10a can be suppressed. As the elastic body 85, for example, a spring or a rubber member can be preferably used.

[0030] In addition, when the workpiece 100 that has been rapidly conveyed in the high-speed conveyance area A comes into contact with the second stopper 33, since the conveyance speed of the workpiece 100 is high, there is a risk that an excessive load will be applied to the second stopper 33. Therefore, by relatively slowing down the rotation of only the high-speed conveyance roller 10a in the vicinity of the second stopper 33 in the high-speed conveyance area A, the conveyance speed of the workpiece 100 can be slowed down, and it is possible to prevent an excessive load from being applied to the second stopper 33.

[0031] As described above, since the high-speed conveyance roller 10a rotates at a higher speed than the other conveyance rollers 10, when the workpiece 100 transfers from the high-speed conveyance roller 10a to the other conveyance rollers 10 or vice versa, the member (saya) on which the workpiece 100 is loaded is likely to meander. In the present invention, since the direction of the saya can be corrected by stopping the workpiece 100 with the first stopper 23 and the second stopper 33, the above-described meandering of the saya can be suppressed. In general, the saya is made of metal, ceramic, or the like.

[0032] (Flow of Roller Hearth Type Firing Furnace 1) Next, with reference to FIGS. 4 and 5, the flow of the roller hearth type firing furnace 1 in the present embodiment will be described. FIG. 4 is a block diagram of the roller hearth type firing furnace 1 in the present embodiment. FIG. 5 is a flowchart of the roller hearth type firing furnace 1 in the present embodiment. With reference to FIGS. 4 and 5, in the flowchart shown in FIG. 5, the control of the first detection unit 21, the first temperature measurement unit 22, the first stopper 23, the second detection unit 31, the second temperature measurement unit 32, and the second stopper 33 can be executed by the control device 1000. The control device 1000 can use a general computer device including an arithmetic device such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), a main storage device such as a RAM (Random Access Memory), and an auxiliary storage device such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a flash memory. The arrangement of the control device 1000 is not particularly limited, and for example, it may be provided at a position separated from the roller hearth type firing furnace 1.

[0033] With reference to FIG. 5, first, the workpiece 100 conveyed in the heating zone 2 by the conveying roller 10 is detected by the first detection unit 21 (S10 Yes). When the workpiece 100 is detected by the first detection unit 21, the operating device 231 of the first stopper 23 operates, and the stopping unit 233 advances into the conveyance path (S20). When the workpiece 100 is not detected by the first detection unit 21 (S10 No), the detection operation is continued.

[0034] When the processed object 100 detected by the first detection unit 21 contacts the stop portion 233 of the first stopper 23 and stops, the temperature of the processed object 100 is measured by the first temperature measurement unit 22 (S30), and it is determined whether the temperature of the processed object 100 is equal to or higher than the first temperature T1 (S40). If the temperature of the processed object is lower than the first temperature T1 (S40 No), it is considered that "the temperature rise in the temperature rise zone 2 is not sufficient", and by maintaining the state in which the stop portion 233 has entered the conveyance path, the processed object is retained for a predetermined time, and during the retention time, the processed object 100 is heated by the heater 6 etc. in the small room 5a to raise the temperature of the processed object 100. Then, the temperature of the processed object 100 is measured again (S30), and it is determined whether the temperature of the processed object 100 is equal to or higher than the first temperature T1 (S40). When the temperature of the processed object becomes equal to or higher than the first temperature T1 (S40 Yes), it is determined that "the temperature has risen sufficiently in the temperature rise zone 2", the first stopper 23 is driven to retract the stop portion 233 from the conveyance path (S50), and the conveyance of the processed object 100 is resumed. The processed object 100 is rapidly conveyed from the temperature rise zone 2 to the holding zone 3 by the high-speed conveyance roller 10a in the high-speed conveyance region A.

[0035] Subsequently, the processed object 100 conveyed in the holding zone 3 by the high-speed conveyance roller 10a is detected by the second detection unit 31 (S60 Yes). When the processed object 100 is detected by the second detection unit 31, the operating device 331 of the second stopper 33 operates, and the stop portion 333 enters the conveyance path (S70). When the processed object 100 is not detected by the second detection unit 31 (S60 No), the detection operation is continued.

[0036] When the workpiece 100 detected by the second detector 31 contacts the stop portion 333 of the second stopper 33 and stops, the temperature of the workpiece 100 is measured by the second temperature measuring unit 32 (S80), and it is determined whether the temperature of the workpiece 100 is equal to or higher than the second temperature T2 (S90). If the temperature of the workpiece 100 is lower than the second temperature T2 (S90 No), it is considered that "the temperature rise in the holding zone 3 is not sufficient", and the state where the stop portion 333 is entered into the transfer furnace is maintained, so that the workpiece is retained for a predetermined time. During this retention time, the workpiece 100 is heated by the heater 6 etc. in the small room 5b to raise the temperature of the workpiece, and then the temperature of the workpiece 100 is measured again (S80), and it is determined whether the temperature of the workpiece 100 is equal to or higher than the second temperature T2 (S90). When the temperature of the workpiece 100 becomes equal to or higher than the second temperature T2 (S90 Yes), it is determined that "the temperature has risen sufficiently in the holding zone 3", the second stopper 33 is driven to retract the stop portion 333 from the transfer path (S100), and the transfer of the workpiece 100 is resumed. The workpiece 100 is transferred from the holding zone 3 to a cooling zone (not shown).

[0037] (Second Embodiment) Hereinafter, a second embodiment of the roller hearth type firing furnace of the present invention will be described with reference to the drawings. The roller hearth type firing furnace 1' of the present embodiment is different from the first embodiment in the shape of the high-speed transfer rollers arranged in the high-speed transfer region A. Since the configurations of the other roller hearth type firing furnaces are the same as those of the first embodiment, the description thereof will be omitted. FIG. 6 and FIG. 7 are schematic views of the high-speed transfer region A of the roller hearth type firing furnace 1', FIG. 6 is a view seen from the transfer direction, and FIG. 7 is a plan view.

[0038] The high-speed transfer roller 20a consists of a first small-diameter roller part 201a and large-diameter roller parts 202a extending from both ends of the first small-diameter roller part 201a. The first small-diameter roller part 201a is located inside the furnace, and the large-diameter roller parts 202a penetrate the furnace wall 1a' and extend outside the furnace. A shaft 105 is placed on the first small-diameter roller part 201a, and a workpiece (not shown) is loaded on this shaft 105. The large-diameter roller parts 202a are rotatably supported with respect to a drive unit mechanism 91 (corresponding to a support mechanism) and a driven unit mechanism 92 (corresponding to a support mechanism) arranged outside the furnace, and the large-diameter roller parts 202a are configured to perform a rotational operation by the power generated by the drive unit mechanism 91. Since the first small-diameter roller part 201a and the large-diameter roller parts 202a are integrally formed, the first small-diameter roller part 201a rotates together with the large-diameter roller parts 202a. The shaft 105 and the workpiece are conveyed by the rotational operation of the first small-diameter roller part 201a.

[0039] The first small-diameter roller part 201a is set to have a smaller roller diameter than the large-diameter roller parts 202a. When the roller diameter of the first small-diameter roller part 201a is d1 and the diameter of the large-diameter roller parts 202a is d2, the difference between the diameter d2 and the diameter d1 is preferably 1 mm or less, and more preferably 0.4 mm or more and 0.6 mm or less.

[0040] The high-speed transfer roller 20a can be manufactured by cutting a transfer roller (i.e., a roller without a small-diameter part) having the same shape as the other transfer roller 10. The cut part becomes the first small-diameter roller part 201a, and the uncut part becomes the large-diameter roller parts 202a.

[0041] Here, when using the same conveyor roller as the other conveyor roller 10 as the high-speed conveyor roller, since the accuracy of the outer diameter dimension of the roller is not sufficient, the sleeve 105 may bounce or snake during high-speed rotation. Note that since the ceramic conveyor roller 10 shrinks before and after firing, distortion, crushing, and warping are likely to occur. Therefore, the unprocessed conveyor roller 10 does not have sufficient accuracy in the outer diameter dimension. In the present embodiment, since the connecting portion between the first small-diameter roller portion 201a and the large-diameter roller portion 202a has a stepped shape, the bouncing sleeve 105 collides with the stepped portion and is returned to the first small-diameter roller portion 201a, so that snaking can be suppressed.

[0042] When forming the first small-diameter roller portion 201a, it is desirable to perform a cutting process so as to satisfy a predetermined roundness condition. As defined in JIS B 0621-1984, roundness means the magnitude of deviation from a geometrically correct circle of a circular body. When the roundness of the first small-diameter roller portion 201a is smaller than the roundness of the large-diameter roller portion 202a, it can be considered that a predetermined roundness condition is satisfied. When defining the predetermined roundness condition numerically, it is preferably "0.01 or less". Note that the roundness can be calculated from the calculation formula of (maximum value of outer diameter - minimum value of outer diameter) ÷ 2. It is desirable that such a roundness condition is guaranteed throughout the first small-diameter roller portion 201a.

[0043] By the first small-diameter roller portion 201a satisfying a predetermined roundness condition, the phenomenon of the sleeve 105 bouncing can be suppressed. By suppressing the bouncing phenomenon, the load applied to the contact points between the drive unit mechanism 91 and the driven unit mechanism 92 and the high-speed conveyor roller 20a can also be reduced.

[0044] (Modification 1) In the above-described embodiment, an example in which a multilayer ceramic capacitor (MLCC) is adopted as the object to be processed 100 has been described. However, the object to be processed in the roller hearth type firing furnace 1 is not limited to this, and any object mainly composed of two types of members having different sintering temperatures may be used. The sintering temperatures of the two types of members mainly constituting the object to be processed preferably have a predetermined temperature difference, for example, a temperature difference of about 200°C to 500°C is preferable.

[0045] (Modification 2) In the above-described embodiment, the first stopper 23 is operated when the object to be processed 100 is detected by the first detection unit 21, and the second stopper 33 is operated when the object to be processed 100 is detected by the second detection unit 31. However, the operating timings of the first stopper 23 and the second stopper 33 are not limited to this. For example, when the roller hearth type firing furnace 1 is operated, the first stopper 23 and the second stopper 33 may be operated, and the stop portions 233, 333 may be allowed to enter the conveying furnace in advance before the object to be processed 100 is conveyed. Also, both the first stopper 23 and the second stopper 33 may be operated when the object to be processed 100 passes through a predetermined position (the detection position by the first detection unit 21 or a position upstream of this detection position).

[0046] (Modification 3) In the above-described embodiment, the first detection unit 21 is provided in the same small room 5a as the first temperature measurement unit 22 and the first stopper 23. However, the position where the first detection unit 21 is provided is not limited to this, and it may be provided upstream of the small room 5a in the conveying direction. Similarly, the second detection unit 31 may also be provided upstream of the small room 5b in the conveying direction.

[0047] (Modification 4) In the above-described embodiment, the first stopper 23 is provided in the small chamber 5a, and the second stopper 33 is provided in the small chamber 5b. However, the positions where the first stopper 23 and the second stopper 33 are provided are not limited to this. The position of the first stopper 23 is not particularly limited as long as it is inside the temperature-rising zone 2, and the position of the second stopper 33 is not particularly limited as long as it is inside the holding zone 3. In this case, the first detection unit 21 and the first temperature measurement unit 22 are provided according to the position of the first stopper 23, and the second detection unit 31 and the second temperature measurement unit 32 are provided according to the position of the second stopper 33.

[0048] These modification examples 1 to 4 are common modification examples of the first embodiment and the second embodiment. The following modification example 5 is a modification example of the second embodiment. (Modification Example 5) FIG. 8 is a view of the roller hearth type firing furnace of this modification example as seen from the conveying direction, corresponding to FIG. 6. The high-speed conveying roller 20a of this modification example is different from the high-speed conveying roller 20a of the second embodiment in that the second small-diameter roller portion 203 is formed at the end of the large-diameter roller portion 202a. The second small-diameter roller portion 203a has a smaller roundness than the large-diameter roller portion 202a and is supported by the drive unit mechanism 91 and the driven unit mechanism 92. Since the configurations of the other roller hearth type firing furnaces are the same as those of the second embodiment, detailed descriptions thereof are omitted.

[0049] The outer diameter of the second small-diameter roller portion 203a can be the same as the outer diameter of the first small-diameter roller portion 201a. Further, the roundness of the second small-diameter roller portion 203a satisfies the "predetermined roundness condition" described in the second embodiment. Thereby, it is possible to suppress the occurrence of vertical movement at the roll end of the high-speed conveying roller 20a during high-speed conveyance. That is, the effect of suppressing the meandering of the sheath 105 can be further enhanced.

[0050] Thus, in this modified example, since the roller end portion of the high-speed conveyance roller 20a is configured by the second small-diameter roller portion 203a that satisfies a predetermined roundness condition, it is possible to suppress the vertical movement of the roller end portion accompanying high-speed conveyance. In the first embodiment, the vertical movement of the roller end portion was suppressed by the cooperation of the plate portion 84 and the elastic body 85, but in this modified example, such a suppressing mechanism can also be omitted. Thereby, the load applied to the contact points between the drive unit mechanism 91 and the driven unit mechanism 92 and the high-speed conveyance roller 20a can be reduced.

Explanation of Reference Numerals

[0051] 1 Roller hearth type firing furnace 2 Heating zone 3 Holding zone 7a First magnetic gear 7b Second magnetic gear 10 Conveyance roller 10a 20a High-speed conveyance roller 23 First stopper 33 Second stopper 83 Bearing 84 Plate portion 85 Elastic body 91 Drive unit mechanism 92 Driven unit mechanism 100 Workpiece 201a First small-diameter roller portion 202a Large-diameter roller portion 203a Second small-diameter roller portion

Claims

1. A roller hearth type sintering furnace in which a workpiece made of two members having different sintering temperatures is sintered by conveying it through a temperature-raising zone and a holding zone in that order on a conveying path made of a plurality of conveying rollers, A first stopper provided in the temperature rising zone; A second stopper provided on the retaining band; Equipped with The first stopper, which has entered the transport path, stops transport of the workpiece until the temperature of the workpiece reaches a first temperature corresponding to a lower sintering temperature, and when the temperature of the workpiece reaches or exceeds the first temperature, the first stopper retreats from the transport path to release the stop of transport; a roller hearth sintering furnace, wherein the transport of the treatment object is stopped by the second stopper that has entered the transport path until the temperature of the treatment object reaches a second temperature corresponding to a higher sintering temperature, and when the temperature of the treatment object reaches or exceeds the second temperature, the second stopper retracts from the transport path to release the stop on the transport.

2. Among the plurality of conveying rollers constituting the conveying path, the high-speed conveying rollers provided in a high-speed conveying region from the first stopper to the second stopper convey the workpiece at a higher speed than the conveying rollers provided in a region other than the high-speed conveying region in the temperature rising zone and the holding zone.

2. The roller hearth firing furnace according to claim 1.

3. The drive mechanism for the high speed conveying rollers includes: a first magnet gear attached coaxially to an end of the high-speed conveying roller in a longitudinal direction; A second magnet gear is provided at a position not in contact with the first magnet gear, The first magnet gear and the second magnet gear are provided at positions where the rotation axis directions are perpendicular to each other, When the second magnet gear is driven, the first magnet gear rotates, and the high-speed conveying roller is driven.

3. The roller hearth firing furnace according to claim 2.

4. The support mechanism for the high speed conveying roller includes: a bearing disposed above the high speed conveying roller and in contact with the high speed conveying roller; A plate portion attached to the bearing and movable up and down; An elastic body provided on an upper surface of the plate portion and extending in a vertical direction, the elastic body generates a biasing force for pressing the bearing against the high-speed conveying roller in response to compression via the plate portion as the high-speed conveying roller is displaced upward. The roller hearth firing furnace according to claim 3.

5. The processed product is a multilayer ceramic capacitor in which nickel and barium titanate are laminated.

5. The roller hearth firing furnace according to claim 1.

6. The high-speed conveying roller has a large diameter roller portion and a first small diameter roller portion having an outer diameter smaller than that of the large diameter roller portion, the first small diameter roller portion is located in a furnace, and the large diameter roller portion extends from both ends of the first small diameter roller portion; 3. The roller hearth firing furnace according to claim 2.

7. The first small diameter roller portion has a smaller circularity than the large diameter roller portion.

7. The roller hearth firing furnace according to claim 6.

8. a second small diameter roller portion having a smaller roundness than the large diameter roller portion is formed at an end of the large diameter roller portion, The second small diameter roller portion is rotatably supported by a support mechanism.

8. The roller hearth firing furnace according to claim 6 or 7.

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