Heat treatment apparatus

Abstract

A heat treatment apparatus (100) is provided with: a heat treatment furnace (10) capable of performing heat treatment of at least one of heating and cooling on an object (1) to be treated; and a fall impact relaxation device (20) provided in a fall path along which the object (1) to be treated falls in the heat treatment furnace (10). In the fall impact relaxation device (20), a plurality of filters are vertically arranged. In each of the filters, a plurality of wires (21) are extended so as to be arranged at an interval greater than a maximum dimension in an arbitrary direction of the object (1) to be treated. The positions of the wires (21) of the plurality of filters are adjusted so that, in a projection diagram in which the plurality of filters are vertically projected on a horizontal plane, the interval between the wires (21) is narrower than the maximum dimension of the object (1) to be treated at least in a region where the object (1) to be treated falls.

Description

Heat Treatment Equipment

[0001] The present invention relates to a heat treatment apparatus for performing heat treatment on an object to be treated.

[0002] Heat treatment devices for rapidly heating or cooling a workpiece are known. Patent Documents 1 and 2 each disclose a method in which the workpiece is dropped from the upper end of a heating furnace and heated at a high rate of about 1000°C / sec while the workpiece is free falling inside the heating furnace. In Patent Document 1, the workpiece is a mixed powder of barium carbonate powder and titanium oxide powder. In Patent Document 2, the workpiece is a molten salt powder mixed with a magnesium salt and a chloride other than magnesium chloride.

[0003] JP2008-133163A JP2008-133163A JP2008-74519A

[0004] When the object to be treated is an electronic component, a possible method is to perform heat treatment by freely dropping the electronic component into a heat treatment furnace, as in the methods described in Patent Documents 1 and 2. However, when it is desired to heat treat the electronic component at a rate lower than 1000°C / sec, for example, a rate of 200°C / sec, the methods described in Patent Documents 1 and 2 do not allow adjustment of the heat treatment rate, making it impossible to perform the desired heat treatment.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a heat treatment apparatus capable of heat treating an object to be treated at a heat treatment speed slower than that when the object is allowed to fall freely.

[0006] The heat treatment apparatus of the present invention is characterized by comprising: a heat treatment furnace capable of performing at least one of heating and cooling heat treatments on a workpiece; and a fall impact mitigation device provided in the path of the workpiece as it falls through the heat treatment furnace, wherein a plurality of filters are arranged vertically, with multiple wires stretched so that the wires are spaced apart at intervals wider than the maximum dimension of the workpiece in any direction, and the positions of the wires of the multiple filters are adjusted so that the spacing between the wires in a projection of the multiple filters vertically projected onto a horizontal plane is narrower than the maximum dimension of the workpiece at least in the area where the workpiece falls.

[0007] According to the heat treatment device of the present invention, when the workpiece is placed inside the heat treatment furnace, it collides with the wire of the drop impact absorbing device, slowing down its falling speed, making it possible to perform heat treatment at a heat treatment speed lower than 1000°C / sec.

[0008] 1 is a cross-sectional view schematically showing the configuration of a heat treatment apparatus in a first embodiment; FIG. 2 is a cross-sectional view schematically showing an example of the configuration of a drop impact mitigation device; FIG. 3 is a perspective view schematically showing a filter constituting a drop impact mitigation device; FIG. 4 is a projection view of multiple filters arranged in a vertical direction, vertically projected onto a horizontal plane; FIG. 5 is a diagram showing the relationship between the elapsed time when multiple workpieces are dropped into a drop impact mitigation device and the drop position; FIG. 6 is a diagram showing the frequency distribution of the drop speeds of multiple workpieces; FIG. 7 is a diagram showing an example of the temperature distribution in a heat treatment furnace when the workpieces are heated; FIG. 8 is a diagram showing the relationship between the drop time and the temperature of the workpieces when the workpieces are dropped at different drop speeds; FIG. 9 is a diagram showing the relationship between the drop time and the temperature rise rate of the workpieces when the workpieces are dropped at different drop speeds; FIG. 10 is a cross-sectional view schematically showing the configuration of a heat treatment apparatus in a second embodiment; FIG. 11 is a diagram showing the relationship between the elapsed time from when the workpieces start to fall and the temperature of the workpieces when the air volume of gas ejected from the gas ejection unit of the heat treatment apparatus in the second embodiment is changed. 1 is a diagram showing the relationship between the elapsed time from when the workpiece starts to fall and the temperature rise rate of the workpiece when the amount of gas ejected from the gas ejection part of the heat treatment device in the second embodiment is changed. FIG. 2 is a cross-sectional view schematically showing the configuration of the heat treatment device in the third embodiment. FIG. 3 is a cross-sectional view schematically showing the configuration of the heat treatment device in the fourth embodiment. FIG. 4 is a diagram showing an example of the temperature distribution in a heat treatment furnace when the workpiece is cooled. FIG. 5 is a diagram showing the relationship between the fall time and the temperature of the workpiece when the workpiece is dropped at different fall velocities in the heat treatment device in the third embodiment. FIG. 6 is a diagram showing the relationship between the fall time and the cooling rate of the workpiece when the workpiece is dropped at different fall velocities in the heat treatment device in the third embodiment.

[0009] The features of the present invention will be specifically described below by showing embodiments of the present invention. <First Embodiment> Fig. 1 is a cross-sectional view schematically showing the configuration of a heat treatment apparatus 100 according to a first embodiment. In Fig. 1, the X-axis direction and the Y-axis direction are horizontal directions, and the Z-axis direction is vertical.

[0010] The heat treatment apparatus 100 according to the first embodiment includes a heat treatment furnace 10 and a drop impact cushioning device 20. As shown in Fig. 1, the heat treatment apparatus 100 may further include a plate 13 on which the workpiece 1 that has dropped inside the heat treatment furnace 10 is placed, and a transport device 14 for transporting the plate 13 to another heating treatment section or another cooling treatment section.

[0011] The heat treatment furnace 10 is configured to be capable of performing at least one of heating and cooling heat treatments on the workpiece 1. The heat treatment furnace 10 has an opening 11 at a position vertically above it, into which the workpiece 1 can be introduced. The workpiece 1 is introduced through the opening 11 and falls inside the heat treatment furnace 10, undergoing heat treatment while falling.

[0012] There are no restrictions on the type of workpiece 1 to be heat-treated. The workpiece 1 may be, for example, a semi-finished chip-type electronic component. As an example, the workpiece 1 may be an unfired ceramic body for producing a chip-type ceramic electronic component such as a multilayer ceramic capacitor.

[0013] The heat treatment furnace 10 is, for example, part of a roller hearth furnace. As shown in FIG. 1 , a plurality of drive rollers 15 constituting a conveying device 14 are arranged at regular intervals within the furnace. A plate 13 is arranged on the drive rollers 15, and the workpieces 1 that fall within the heat treatment furnace 10 are deposited on the plate 13. When the drive rollers 15 are driven, the plate 13 moves on the drive rollers 15, and the workpieces 1 deposited on the plate 13 are transported to the next process, for example, another heating process or another cooling process. The plate 13 is made of, for example, ceramic.

[0014] However, the heat treatment furnace 10 is not limited to being a part of a roller hearth furnace, and may be a part of another type of heat treatment furnace.

[0015] The heat treatment furnace 10 includes a heating unit 12 such as a heater. When the heat treatment furnace 10 is a heating furnace for heating the workpiece 1, the temperature inside the heat treatment furnace 10 is configured to be higher at the position where the workpiece 1 finishes falling than at the position where the workpiece 1 starts falling. For example, the heat treatment furnace 10 includes multiple heating units 12 arranged in the vertical direction, and is configured so that the set temperatures of the heating units 12 located vertically lower are higher than those of the heating units 12 located vertically upper. For example, the set temperatures of the heating units 12 located vertically upper are 500°C, and the set temperatures of the heating units 12 located vertically lower are 1000°C. For example, the workpiece 1, which has been preheated to a temperature of approximately 500°C before being placed into the heat treatment furnace 10, is heated by radiant heat transfer while falling inside the heat treatment furnace 10.

[0016] When the heat treatment furnace 10 is a heating furnace for cooling the workpiece 1, the temperature inside the heat treatment furnace 10 is configured to be lower at the position where the workpiece 1 finishes falling than at the position where the workpiece 1 starts falling. For example, the heat treatment furnace 10 is provided with multiple heating sections 12 in the vertical direction, and is configured so that the set temperatures of the heating sections 12 located vertically lower are lower than those of the heating sections 12 located vertically upper. For example, the set temperatures of the heating sections 12 located vertically upper are 800°C, and the set temperatures of the heating sections 12 located vertically lower are 400°C. For example, the workpiece 1, which has been preheated to a temperature of about 900°C before being placed into the heat treatment furnace 10, is cooled by radiant heat transfer while falling inside the heat treatment furnace 10.

[0017] The drop impact cushioning device 20 is provided in the heat treatment furnace 10. Fig. 2 is a cross-sectional view showing a typical configuration of the drop impact cushioning device 20. The cross-sectional view shown in Fig. 2 is a view seen in the extending direction of a wire 21, which will be described later. Fig. 3 is a perspective view showing a typical filter 22 constituting the drop impact cushioning device 20.

[0018] The fall impact mitigation device 20 has a plurality of filters 22 arranged in the vertical direction, each of which has a plurality of wires 21 stretched so that they are spaced apart in a predetermined direction at intervals wider than the maximum dimension in any direction of the workpiece 1. Preferably, a plurality of filters 22 is arranged in the vertical direction, each of which has a plurality of wires 21 stretched in parallel at intervals wider than the maximum dimension in any direction of the workpiece 1. The fall impact mitigation device 20 has a structure in which the relative positions of the wires 21 of the plurality of filters 22 can be adjusted so that the spacing between the wires 21 in a projection of the plurality of filters 22 vertically projected onto a horizontal plane is narrower than the maximum dimension of the workpiece 1 at least in the area where the workpiece 1 falls.

[0019] In the configuration example shown in FIG. 3 , the filter 22 has a structure in which multiple wires 21 are arranged in a predetermined direction inside a rectangular frame 23. However, the filter 22 is not limited to the configuration shown in FIG. 3 as long as the multiple wires 21 are arranged in parallel at intervals that allow the workpiece 1 to pass through. In the example shown in FIG. 3 , eight wires 21 are arranged in parallel, but the number of wires is not limited to eight and can be any number. Note that when the filter 22 having a rectangular frame 23 is viewed from a direction perpendicular to the main surface of the filter 22, adjacent wires 21 are not necessarily parallel to each other and may be arranged at an angle. As shown in FIG. 2 , multiple frame bodies 23 are stacked in the Z direction. At least a portion of the frame body 23 has a structure that can be displaced in the Y direction so that the relative position of the frame body 23 in the Y direction can be adjusted.

[0020] The wire 21 is made of a heat-resistant material, for example, a metal such as Ni or a Ni alloy. If the interior of the heat treatment furnace 10 is an oxygen-free atmosphere, it is possible to use carbon fiber or the like as the wire 21. When the wire 21 is cut along a plane perpendicular to its extension direction, the cross section has a circular shape, for example, and a diameter of 0.1 mm, for example.

[0021] The distance D1 between two adjacent wires 21 is wider than the maximum dimension in any direction of the workpiece 1. In other words, the distance D1 between two adjacent wires 21 is a distance that allows the workpiece 1 to pass through when dropped. As an example, if the length of the workpiece 1, which is approximately rectangular parallelepiped, is 1.0 mm, the width is 0.5 mm, and the height is 0.5 mm, the maximum dimension of the workpiece 1 in any direction is the diagonal dimension of approximately 1.2 mm, and the distance D1 between two adjacent wires 21 is 2 mm.

[0022] The reason why the distance D1 is set to 2 mm can be considered as follows: For example, 1.6 times the maximum diagonal dimension of the workpiece 1, which is 1.2 mm, is approximately 1.9 mm. Taking this into consideration, the distance D1 between the wires 21 is set to 2 mm, which is a dimension somewhat larger than 1.9 mm.

[0023] Here, the vertical distance between the layers in which the wires 21 are arranged is defined as D3. When two adjacent stacked filters 22 are considered, the distance D3 is set so that the minimum distance between the wires 21 belonging to one filter 22 and the wires 21 belonging to the other filter 22 is greater than the maximum distance in any direction of the workpiece 1.

[0024] As described above, the fall impact cushioning device 20 has a structure in which a plurality of filters 22 are arranged in the vertical direction. In the example shown in Fig. 2, 14 filters 22 are arranged in the vertical direction. However, the number of filters 22 is not limited to 14 and can be any number.

[0025] In the configuration example shown in FIG. 2 , the filters 22 in the first, fifth, ninth, and thirteenth layers from the bottom are horizontally offset relative to the other filters 22. Here, the filters 22 in the first, fifth, ninth, and thirteenth layers from the bottom are referred to as first filters 22a, and the filters 22 in the second to fourth, sixth to eighth, tenth to twelfth, and fourteenth layers from the bottom are referred to as second filters 22b. As an example, if the distance D1 between two adjacent wires 21 is 2 mm, the first filter 22a is horizontally offset by 1 mm relative to the second filter 22b. Here, as an example, the first filter 22a is horizontally offset by 1 mm relative to the second filter 22b. However, it is sufficient that the first filter 22a is positioned midway within the distance D1, and it is preferable that the first filter 22a is positioned at the center of the distance D1. Here, as described above, the description will continue assuming the first filter 22a is horizontally offset by 1 mm. In the configuration shown in Figure 2, there is a possibility that the workpiece 1 may get caught on the wall surface at the boundary between the first filter 22a and the second filter 22b, but it is possible to appropriately modify the structure to prevent the workpiece 1 from getting caught.

[0026] Fig. 4 is a vertical projection of a plurality of filters 22 arranged in the vertical direction onto a horizontal plane. The projection shown in Fig. 4 shows both the wires 21 of the first filter 22a and the wires 21 of the second filter 22b. In the projection shown in Fig. 4, the distance D2 between two adjacent wires 21 is narrower than the maximum dimension of the workpiece 1 in any direction. One of the two adjacent wires 21 in the projection is the wire 21 of the first filter 22a, and the other is the wire 21 of the second filter 22b.

[0027] In the above-described numerical example, the distance D2 between two adjacent wires 21 in the projection is 1 mm. As described above, the maximum dimension in any direction of the workpiece 1, which has a length of 1.0 mm, a width of 0.5 mm, and a height of 0.5 mm, is approximately 1.2 mm. In this case, unless there is a special circumstance in which the surface defined by the width and height directions of the workpiece 1 faces vertically downward and the workpiece 1 falls without changing its posture, the workpiece 1 cannot pass between two adjacent wires 21 in the projection. As a result, the workpiece 1 introduced through the opening 11 of the heat treatment furnace 10 collides with the wire 21 of the fall impact cushioning device 20 at least once during the fall. Furthermore, as the workpiece 1 collides with the wire 21 during the fall, its posture and falling position change, causing it to collide with another wire 21.

[0028] That is, in the heat treatment apparatus 100 of this embodiment, a fall impact cushioning device 20 is provided in the heat treatment furnace 10, so that the workpiece 1 falling within the heat treatment furnace 10 repeatedly collides with the multiple wires 21 of the fall impact cushioning device 20, thereby slowing the falling speed. This makes it possible to avoid extremely rapid heating or cooling, such as reaching 1000°C / s, as occurs in conventional heat treatments using free fall, and instead allows heat treatment to be performed at a heat treatment rate lower than 1000°C / s, for example, at a rate of 50°C / s to 150°C / s. If the workpiece 1 is a semi-finished electronic component, extremely rapid heating or cooling, such as reaching 1000°C / s, may result in damage due to thermal factors. However, the heat treatment apparatus 100 of this embodiment can prevent such damage from occurring.

[0029] The falling speed of the workpiece 1 can be adjusted by adjusting the number of filters 22, the spacing between the wires 21 in the vertically projected view, and the like.

[0030] Furthermore, in conventional configurations where heat treatment is performed by free fall, the drop speed is so fast that a height difference of 2 to 3 m is required to perform sufficient heat treatment, but in the heat treatment apparatus 100 of this embodiment, which performs heat treatment by braked fall, the height difference in the heating space of the heat treatment furnace 10 can be set to, for example, about 300 mm or more and 1000 mm or less, which allows the heat treatment furnace 10 to be made smaller.

[0031] Furthermore, in the heat treatment apparatus 100 of this embodiment, the workpieces 1 collide with the multiple wires 21 of the drop impact cushioning device 20, causing them to change posture while rotating at high speeds of several rotations per second to several tens of rotations per second. This allows for uniform heat treatment across the entire surface of the workpieces 1. Furthermore, even if multiple workpieces 1 are stuck together before being dropped, they separate when they collide with the wires 21. This allows for heat treatment to be performed on the multiple workpieces 1 while they are stuck together, thereby preventing partial temperature variations on the surfaces of the workpieces 1.

[0032] When the workpiece 1 is a semi-finished electronic component, conventional heat treatment using free fall can cause a large impact on the workpiece 1 when it lands, potentially resulting in damage to the workpiece 1. However, in the heat treatment apparatus 100 of this embodiment, the workpiece 1 collides with the multiple wires 21 of the fall impact cushioning device 20, thereby reducing the falling speed and preventing a large impact from being applied when it lands. This can prevent damage to the workpiece 1.

[0033] Furthermore, in the heat treatment apparatus 100 of this embodiment, heat treatment is performed by dropping the workpiece 1 into the heat treatment furnace 10 one after another, so the processing capacity is greater than in a configuration in which heat treatment is performed while the workpiece 1 is placed on something like a plate.

[0034] In addition, the heat treatment furnace 10 is a heating furnace, and the plate 13 on which multiple heated workpieces 1 are piled up is transported by a transport device 14 to another heat treatment section, so that additional heat treatments according to the purpose can be performed continuously.

[0035] 2, only a small portion of the multiple filters 22 stacked vertically are designated as first filters 22a and are arranged offset from the remaining filters, the second filters 22b, but this is merely an example. For example, the multiple filters 22 stacked vertically may be arranged offset one by one. In other words, when viewed in the same direction as in FIG. 2, the wires 21 may be arranged in a staggered pattern.

[0036] Fig. 5 is a diagram showing the relationship between the elapsed time and the drop position when multiple workpieces 1 are dropped onto the drop impact cushioning device 20. In Fig. 5, the drop position is shown as the distance in the drop direction, with the position of the uppermost wire 21 of the drop impact cushioning device 20 being set to 0 mm. Fig. 6 is a diagram showing the frequency distribution of the drop speeds of multiple workpieces 1.

[0037] The dropped workpiece 1 had a substantially rectangular parallelepiped shape, measuring 1.0 mm in length, 0.5 mm in width, and 0.5 mm in height. The drop impact mitigation device 20 had 50 filters 22, with the first filter 22a disposed every fourth layer, as shown in the configuration example shown in FIG. 2 . The distance D1 between two adjacent wires 21 of one filter 22 was 2 mm, and the first filter 22a was disposed with a horizontal offset of 1 mm relative to the second filter 22b. Sixty-two workpieces 1 were placed sequentially into the drop impact mitigation device 20, spaced 2 mm apart horizontally.

[0038] 5 also shows the relationship between the elapsed time and the drop position when the workpiece 1 is allowed to free fall. As shown in FIG. 5, when the workpiece 1 is dropped onto the fall impact cushioning device 20, the drop speed can be slower than when the workpiece 1 is allowed to free fall. That is, the drop time when the workpiece 1 is dropped onto the fall impact cushioning device 20 is 0.6 seconds or more, while the drop time when the workpiece 1 is allowed to free fall is 0.2 seconds or less.

[0039] 6, the drop speed of most of the workpieces 1 was in the range of 115 mm / sec to 155 mm / sec, i.e., within a range of ±15% around 135 mm / sec. Therefore, the temperatures of the workpieces 1 were determined when the workpieces 1 were dropped from a height of 400 mm in the heat treatment furnace 10 at drop speeds of 115 mm / sec, 135 mm / sec, and 155 mm / sec.

[0040] 7, the temperature distribution in the heat treatment furnace 10 is, for example, 600°C at the drop start position, 1100°C at the midpoint, and 1100°C at the drop end position. That is, the temperature gradually increases from the drop start position to the midpoint, and remains constant at 1100°C from the midpoint to the drop end position. In this way, the temperature is the same from the position between the position where the workpiece 1 starts to drop and the position where the drop of the workpiece 1 ends to the position where the drop of the workpiece 1 ends, so that the temperature of the workpiece 1 after heat treatment can be stably maintained at a desired temperature.

[0041] Fig. 8 is a graph showing the relationship between the time elapsed since the workpiece 1 started to fall and the temperature of the workpiece 1. Fig. 9 is a graph showing the relationship between the time elapsed since the workpiece 1 started to fall and the rate of temperature rise of the workpiece 1. As shown in Fig. 8, the faster the fall speed, the higher the temperature of the workpiece 1 becomes. However, within the range of 115 to 135 mm / sec, there is no significant difference in the temperature of the workpiece 1 due to the difference in fall speed. As shown in Fig. 9, the rate of temperature rise is high, exceeding 50°C / sec, for fall speeds of 115 mm / sec, 135 mm / sec, and 155 mm / sec, and the maximum rate of temperature rise is 300°C / sec or less.

[0042] Here, the number of filters 22 in the fall impact cushioning device 20 can be, for example, 200. In this case, the variation in the average fall speed when the workpieces 1 are dropped is statistically half that when the number of filters 22 is 50. Therefore, the average fall speed of most workpieces 1 is within the range of 135±10 mm / sec, the temperature variation of the workpieces 1 is even smaller than that shown in FIG. 8, and the variation in the temperature rise rate is even smaller than that shown in FIG. 9.

[0043] 10 is a cross-sectional view schematically illustrating the configuration of a heat treatment apparatus 100A according to a second embodiment. The heat treatment apparatus 100A according to the second embodiment further includes a gas ejection unit 30 in addition to the configuration of the heat treatment apparatus 100 according to the first embodiment.

[0044] The gas ejection unit 30 ejects gas into the interior of the heat treatment furnace 10. The gas ejection unit 30 may be any unit capable of ejecting gas into the interior of the heat treatment furnace 10. For example, the gas ejection unit 30 has a U-shaped gas line connected to the interior of the heat treatment furnace 10, and is configured to alternately perform a process of sucking gas from one end of the gas line and ejecting the gas from the other end into the heat treatment furnace 10 using a fan installed inside the gas line, and a process of sucking gas from the other end of the gas line and ejecting the gas from the one end into the heat treatment furnace 10.

[0045] Fig. 11 is a diagram showing the relationship between the time elapsed since the workpiece 1 starts to fall and the temperature of the workpiece 1 when the flow rate of gas ejected from the gas ejection part 30 is changed. Fig. 12 is a diagram showing the relationship between the time elapsed since the workpiece 1 starts to fall and the rate of temperature rise of the workpiece 1 when the flow rate of gas ejected from the gas ejection part 30 is changed. The flow rates of gas ejected from the gas ejection part 30 were set to 1 L / min, 15 L / min, 30 L / min, and 60 L / min.

[0046] 11, the temperature of the workpiece 1 increases with an increase in the volume of gas ejected from the gas ejection part 30. Also, as shown in FIG. 12, the temperature of the workpiece 1 increases with an increase in the volume of gas ejected from the gas ejection part 30.

[0047] According to the heat treatment apparatus 100A of the second embodiment, the gas ejection unit 30 that ejects gas inside the heat treatment furnace 10 is provided, so that convective heat transfer as well as radiative heat transfer is performed for the workpiece 1 falling inside the heat treatment furnace 10. This allows the temperature rise rate when heating the workpiece 1 to be increased.

[0048] If the heat treatment furnace 10 is a cooling furnace rather than a heating furnace, the cooling rate at which the workpiece 1 is cooled can be increased.

[0049] Third Embodiment The workpiece 1 to be dropped into the heat treatment furnace 10 can be preheated in advance.

[0050] 13 is a cross-sectional view schematically illustrating the configuration of a heat treatment apparatus 100B according to the third embodiment. The heat treatment apparatus 100B according to the third embodiment further includes a preheating unit 40 in addition to the components of the heat treatment apparatus 100 according to the first embodiment.

[0051] The preheating unit 40 heats the workpieces 1 before they are placed in the heat treatment furnace 10. For example, as shown in FIG. 13 , the preheating unit 40 includes a preheating furnace 41 and a belt conveyor 42. The belt conveyor 42 is made of, for example, steel or a heat-resistant resin. The plurality of workpieces 1 are transported by the belt conveyor 42 so as to move through the preheating furnace 41, and are heated while moving through the preheating furnace 41. The preheating unit 40 heats the workpieces 1, for example, from room temperature to a temperature of about 500° C.

[0052] The workpieces 1 heated by the preheating unit 40 are introduced into the heat treatment furnace 10. In the configuration example shown in FIG. 13 , the workpieces 1 leaving the preheating unit 40 are configured to enter the temperature holding unit 43, drop at the end of the belt conveyor 42 in the temperature holding unit 43, and are introduced into the heat treatment furnace 10 through the opening 11. At the end of the belt conveyor 42, multiple workpieces 1 may be scraped off to be introduced into the heat treatment furnace 10. The workpieces 1 that have dropped inside the heat treatment furnace 10 are piled up on the plate 13. The multiple workpieces 1 piled up on the plate 13 are transported to the next process by the plate 13 moving on the drive rollers 15.

[0053] Below, we will explain in chronological order the process in which the workpiece 1 heated by the preheating section 40 is placed inside the heat treatment furnace 10, falls onto the plate 13, and is transported to the next process.

[0054] While the belt conveyor 42 of the preheating unit 40 is driving, a plurality of workpieces 1 transported by the belt conveyor 42 are successively introduced into the heat treatment furnace 10 through the opening 11. Here, the explanation will be given assuming that the time T=0 when the driving of the belt conveyor 42 starts. If the moving speed of the belt conveyor 42 is 5 mm / sec, the belt conveyor 42 moves 150 mm in the 30 seconds from T=0 to T=30 seconds, and the workpieces 1 placed on the 150 mm length of the belt conveyor 42 are introduced into the heat treatment furnace 10. At the time T=30 seconds, the driving of the belt conveyor 42 is stopped.

[0055] The time it takes for the workpieces 1 to fall inside the heat treatment furnace 10 is, for example, 3 to 4 seconds. Therefore, all of the workpieces 1 that were put into the heat treatment furnace 10 during the 30 seconds from T=0 to T=30 seconds are piled up on the plate 13 by T=35 seconds.

[0056] At time T=35 seconds, the movement of plate 13 begins. That is, by starting to drive drive rollers 15 constituting transport device 14, plate 13 moves on drive rollers 15, and the plurality of workpieces 1 on plate 13 are transported to the next process, for example, to another heating treatment section or another cooling treatment section.

[0057] Furthermore, by driving the driving roller 15, the next empty plate 13 moves to the drop position of the workpiece 1. When the driving roller 15 is stopped at the time T=40 seconds, the next plate 13 stops at the drop position of the workpiece 1.

[0058] At the time T=40 seconds, the belt conveyor 42 of the preheating unit 40 is restarted, and the belt conveyor 42 is driven for 30 seconds from T=40 to T=70 seconds, whereby the plurality of workpieces 1 are sequentially fed into the heat treatment furnace 10 through the opening 11.

[0059] Thereafter, the above-described process is repeated. That is, the workpiece 1, which has been heat-treated by dropping inside the heat treatment furnace 10 during a 40-second cycle consisting of 30 seconds of driving and 10 seconds of stopping the belt conveyor 42, is deposited on the plate 13 and transported to the next process. As an example, the workpiece 1, which has been heated to 500°C by the preheating unit 40, is heated to 1000°C while dropping inside the heat treatment furnace 10. Thereafter, the workpiece 1 transported together with the plate 13 is moved to a cooling unit set at 800°C or less and cooled, or moved to a heating unit set at a temperature higher than 1000°C, for example, 1200°C, and subjected to further heat treatment.

[0060] 13, plate 13 is configured to move horizontally on drive rollers 15, but may also be configured to move vertically downward. In this case, the plurality of workpieces 1 piled up on plate 13 are transported to a cooling treatment section or a heating treatment section located vertically below.

[0061] According to the heat treatment apparatus 100B of this embodiment, by further including a preheating section 40, a series of continuous heat treatments including preheating and main heating are possible, and a heat treatment production line with high processing capacity can be provided.

[0062] 14 is a cross-sectional view schematically illustrating the configuration of a heat treatment apparatus 100C according to a fourth embodiment. The heat treatment apparatus 100C according to the fourth embodiment further includes a cooling treatment unit 50 in addition to the configuration of the heat treatment apparatus 100B according to the third embodiment. The transport device 14A has a belt 16, and transports the workpiece 1, which has fallen inside the heat treatment furnace 10, to another cooling treatment unit while the workpiece 1 is placed on the belt 16.

[0063] The cooling treatment unit 50 is located after the heat treatment furnace 10 in the movement path of the workpieces 1, and cools the workpieces 1. The heat treatment furnace 10 is, for example, a cooling furnace. The workpieces 1 that have fallen through the heat treatment furnace 10 and cooled are deposited on the belt 16 of the conveying device 14A. The belt 16 is, for example, a metal belt with good breathability. The multiple workpieces 1 deposited on the belt 16 are transported to the cooling treatment unit 50 by the drive of the belt 16, and are cooled, for example, to room temperature by passing through the interior of the cooling treatment unit 50. With such a configuration, cooling treatment to near room temperature can be continuously performed depending on the purpose.

[0064] For example, the external electrodes of a multilayer ceramic capacitor are formed by applying an external electrode paste to the surface of a ceramic body and baking it, and the ceramic body with the baked external electrode paste is placed inside a heat treatment furnace 10 and subjected to a cooling treatment. For example, by cooling the ceramic body baked at 900°C at a cooling rate of 150°C / second or less, it is possible to prevent the glass frit in the external electrode paste from segregating on the surface.

[0065] Here, the relationship between the elapsed time when multiple workpieces 1 were dropped into the heat treatment furnace 10 and the temperature of the workpieces 1 was also investigated in the heat treatment apparatus 100C of this embodiment. Here, as shown in FIG. 15 , the temperature inside the heat treatment furnace 10 was lower at the point where the workpieces 1 stopped falling than at the point where the workpieces 1 started falling. Specifically, the temperature at the start of the drop was 800°C, the temperature at the midpoint was 100°C, and the temperature at the end of the drop was 100°C. That is, the temperature gradually decreased from the start of the drop to the midpoint, and remained constant at 100°C from the midpoint to the end of the drop. In this way, the temperature was the same from the position between the start of the drop and the end of the drop of the workpieces 1 to the position where the drop of the workpieces 1 stopped falling, making it possible to stably maintain the temperature of the workpieces 1 at the desired temperature after heat treatment.

[0066] Fig. 16 is a diagram showing the relationship between the time elapsed since the workpiece 1 started to fall and the temperature of the workpiece 1. Fig. 17 is a diagram showing the relationship between the time elapsed since the workpiece 1 started to fall and the cooling rate of the workpiece 1. As in the first embodiment, the falling speed of the workpiece 1 when falling was changed to 115 mm / sec, 135 mm / sec, and 155 mm / sec, and the temperature of the workpiece 1 and the cooling rate of the workpiece 1 were confirmed.

[0067] As shown in Fig. 16, there is no significant difference in the temperature of the workpiece 1 due to differences in the drop speed. As shown in Fig. 17, the cooling rate of the workpiece 1 increases as the drop speed increases, but high-speed cooling of 50°C / sec or more and 120°C / sec or less is achieved at drop speeds of 115 mm / sec, 135 mm / sec, and 155 mm / sec.

[0068] The present invention is not limited to the above-described embodiments, and various applications and modifications can be made within the scope of the present invention. For example, the characteristic features of each embodiment can be combined as appropriate.

[0069] The heat treatment apparatus in the present application is as follows: <1>. A heat treatment apparatus comprising: a heat treatment furnace capable of performing at least one of heating and cooling heat treatments on a workpiece; and a fall impact cushioning device provided in a path along which the workpiece falls through the heat treatment furnace, the fall impact cushioning device comprising a plurality of filters arranged in the vertical direction, each filter having a plurality of wires stretched in parallel at intervals wider than the maximum dimension of the workpiece in any direction, the positions of the wires of the plurality of filters being adjusted so that the spacing between the wires in a vertical projection of the plurality of filters onto a horizontal plane is narrower than the maximum dimension of the workpiece in at least the area where the workpiece falls.

[0070] <2> The heat treatment apparatus according to <1>, wherein the temperature inside the heat treatment furnace is higher at a position where the workpiece stops falling than at a position where the workpiece starts falling.

[0071] <3> The heat treatment apparatus according to <1>, wherein the temperature inside the heat treatment furnace is lower at a position where the workpiece stops falling than at a position where the workpiece starts falling.

[0072] <4> The heat treatment apparatus according to <2> or <3>, characterized in that the temperature inside the heat treatment furnace is the same from a position between a position where the workpiece starts to fall and a position where the workpiece ends to a position where the workpiece ends to fall.

[0073] <5> The heat treatment apparatus according to any one of <1> to <4>, further comprising a gas ejection unit that ejects gas into the heat treatment furnace.

[0074] <6> The heat treatment apparatus according to any one of <1> to <5>, further comprising: a plate for placing the object to be treated that has dropped inside the heat treatment furnace; and a transport device for transporting the plate to another heat treatment unit.

[0075] <7> The heat treatment apparatus according to any one of <1> to <5>, further comprising a conveying device having a belt and configured to convey the workpiece, which has dropped inside the heat treatment furnace, to another cooling processing unit while the workpiece is placed on the belt.

[0076] <8> The heat treatment apparatus according to any one of <1> to <7>, wherein the object to be treated is a semi-finished chip-shaped electronic component.

[0077] REFERENCE SIGNS LIST 1 Workpiece 10 Heat treatment furnace 11 Opening 12 Heating section 13 Plate 14, 14A Conveying device 15 Drive roller 16 Belt 20 Fall impact cushioning device 21 Wire 22 Filter 22a First filter 22b Second filter 23 Frame 30 Gas ejection section 40 Preheating section 41 Preheating furnace 42 Belt conveyor 50 Cooling treatment section 100, 100A, 100B, 100C Heat treatment device

Claims

1. a heat treatment furnace capable of performing at least one of heating and cooling heat treatment on the workpiece; a fall impact mitigation device provided on a fall path of the workpiece falling within the heat treatment furnace, the fall impact mitigation device comprising a plurality of filters arranged in the vertical direction, each filter having a plurality of wires stretched so that the wires are spaced apart at intervals wider than the maximum dimension of the workpiece in any direction, and the positions of the wires of the filters are adjusted so that the spacing between the wires in a vertical projection of the filters onto a horizontal plane is narrower than the maximum dimension of the workpiece at least in the area where the workpiece falls; A heat treatment apparatus comprising:

2. 2. The heat treatment apparatus according to claim 1, wherein the temperature inside the heat treatment furnace is higher at a position where the workpiece stops falling than at a position where the workpiece starts falling.

3. 2. The heat treatment apparatus according to claim 1, wherein the temperature inside the heat treatment furnace is lower at a position where the workpiece stops falling than at a position where the workpiece starts falling.

4. 4. The heat treatment apparatus according to claim 2, wherein the temperature inside the heat treatment furnace is the same from a position between the position where the workpiece starts to fall and the position where the workpiece ends to the position where the workpiece ends to the position where the workpiece ends to the position where the workpiece ends to the position where the workpiece ends.

5. 2. The heat treatment apparatus according to claim 1, further comprising a gas ejection unit that ejects gas into the heat treatment furnace.

6. a plate for placing the workpiece that has fallen inside the heat treatment furnace; a conveying device for conveying the plate to another heat treatment unit; The heat treatment apparatus according to claim 1 , further comprising:

7. 2. The heat treatment apparatus according to claim 1, further comprising a conveying device having a belt for conveying the workpiece, which has dropped inside the heat treatment furnace, to another cooling processing unit while the workpiece is placed on the belt.

8. 2. The heat treatment apparatus according to claim 1, wherein the object to be treated is a semi-finished chip-type electronic component.

9. The heat treatment method according to claim 1 , wherein the plurality of wires are stretched parallel to one another.