HEAT TREATMENT APPARATUS

Abstract

The present invention provides a heat treatment apparatus for carrying out heat treatment for a circular workpiece. The heat treatment apparatus includes a treatment room configured to carry out a predetermined treatment for the workpiece, a transportation mechanism configured to transport the workpiece into the treatment room and out of the treatment room, and a mounting table on which the workpiece transported into the treatment room is mounted. The transportation mechanism is provided with a transportation arm which mounts and transports the workpiece. The transportation arm is provided with at least three transport support pins which support the workpiece when the workpiece is transported, and the mounting table is provided with at least three mounting table support pins which support the workpiece.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat treatment apparatus for carrying out carburizing and quenching treatment for a workpiece.

2. Description of the Related Art

Generally, to improve wear resistance of a low alloy steel or the like (hereinafter referred to as “workpiece”), carburizing treatment and quenching treatment are carried out to allow the surface layer of the workpiece to interstitially absorb carbon.

An example of a conventional carburizing and quenching treatment apparatus includes such carburizing and quenching treatment apparatuses disclosed in Japanese Patent Application Laid-Open No. H10-53809, Japanese Patent Application Laid-Open No. 2010-266176, Japanese Patent Application Laid-Open No. 2003-183728, and Japanese Patent Application Laid-Open No. H8-285462. As for carburizing and quenching treatment apparatuses described in Japanese Patent Application Laid-Open No. H10-53809, Japanese Patent Application Laid-Open No. 2010-266176, and Japanese Patent Application Laid-Open No. 2003-183728, a workpiece is mounted on a transportation fork and transported. When carburizing and quenching treatment is carried out in an online-machining-production-system described in Japanese Patent Application Laid-Open No. H10-53809, one or more workpieces are treated by a treatment unit as required in each treatment means. Apparatuses described in Japanese Patent Application Laid-Open No. 2010-266176, Japanese Patent Application Laid-Open No. 2003-183728, and Japanese Patent Application Laid-Open No. H8-285462 are a vacuum carburizing and quenching apparatus in which a plurality of workpieces stacked on a tray is treated. Further, in a carburizing and quenching treatment apparatus described in Japanese Patent Application Laid-Open No. H8-285462, a workpiece is transported to a desired treatment room by pushing the workpiece with a pusher.

However, in a conventional carburizing and quenching treatment apparatus, a mounting position of the workpiece may shift from the intended mounting position when the workpiece is mounted on the mounting table. In this case, during a heating process of the workpiece, the distance between the periphery of the workpiece and a heat source (e.g., induction heating coil) become nonuniform so that the workpiece cannot uniformly be heated. Further, during cooling of the workpiece in the quenching treatment, the workpiece cannot uniformly be cooled because of the shift in the position. Therefore, the carburizing and quenching treatment for the workpiece might not uniformly be carried out. Recently, it has become apparent that when the temperature change in the workpiece is not uniform, a large heat treatment strain is produced, which results in failure to satisfy dimensional accuracy required for the workpiece.

The mounted state of the workpiece during transportation also have an effect on the heat treatment strain. Regarding the transportation and mounting of the workpiece, when a contact area between a transport mechanism or a mounting table and the workpiece is large, the temperature change in the contact portion differs from the other portion of the workpiece, which might cause a large heat treatment strain resulting in failure to satisfy a dimensional accuracy required for the workpiece.

For example, in a carburizing and quenching treatment apparatus of the online-machining-production-system described in Japanese Patent Application Laid-Open No. H10-53809, the mounting position of the workpiece might shift from an intended position by tilting, vibration, or the like of a transportation fork. Further, since the treatment is carried out without placing the workpiece in a tray, the mounting position of the workpiece might shift from a suitable position when workpieces of different diameters are transported. Further, since a contact area between the workpiece and the transportation fork or a contact area between the workpiece and a mounting table is large and partial, temperature change (temperature distribution) in a workpiece will not be uniform. Therefore, the degree of thermal expansion and contraction in a workpiece varies which produces heat treatment strain to cause deformation of the workpiece. This might result in failure to keep the dimensional accuracy within a predetermined range after carburizing and quenching. Further, when one workpiece is transported at a time by a fork as described in Japanese Patent Application Laid-Open No. H10-53809 (or transported by a pusher as will be described below), the workpiece might slide on the fork or the like to be damaged.

Further, in carburizing and quenching treatment apparatuses described in Japanese Patent Application Laid-Open No. 2010-266176 and Japanese Patent Application Laid-Open No. 2003-183728 workpieces are transported by a transportation fork on a tray, and the mounting position of the workpiece might shift from a suitable position by, for example, tilting of the transportation fork. Further, in the carburizing and quenching treatment apparatus described in Japanese Patent Application Laid-Open No. H8-285462, a tray is transported by a pusher, and shifting from a suitable position might occur due to variation in, for example, a push stroke of a pusher

Further, as described in Japanese Patent Application Laid-Open No. 2010-266176, Japanese Patent Application Laid-Open No. 2003-183728, and Japanese Patent Application Laid-Open No. H8-285462, a method of carrying out carburizing and quenching treatment for a plurality of workpieces in a tray is conventionally used. In such method, naturally, the temperature differs for each location in which each workpiece is placed in the tray, and therefore, the temperature is controlled within a predetermined range of temperature distribution. However, in recent years, some workpieces require particularly strict dimensional accuracy after carburizing and quenching. It has become apparent that for such workpieces, it is difficult to satisfy the requirement by the method of carrying out carburizing and quenching treatment for a plurality of workpieces in a tray.

SUMMARY OF THE INVENTION

To solve the problem mentioned above, the object of the present invention is to provide a heat treatment apparatus which can mount a workpiece in a suitable position on a mounting table as well as reduce the contact area between the workpiece and other parts during a treatment process, that is, to provide a heat treatment apparatus which can carry out carburizing and quenching treatment providing high dimensional accuracy of a workpiece after carburizing and quenching.

To achieve the object, the present invention provides a heat treatment apparatus for carrying out carburizing treatment and/or quenching treatment for a circular workpiece including a treatment room configured to carry out a predetermined treatment for a workpiece, a transportation mechanism configured to transport the workpiece into the treatment room or out of the treatment room, and a mounting table, provided inside the treatment room, on which the workpiece transported into the treatment room is mounted. The feature of the heat treatment apparatus is that the transportation mechanism includes a transportation arm which mounts and moves the workpiece, at least three transport support pins which support the workpiece during transportation are provided on the transportation arm, and at least three mounting table support pins which support the workpiece are provided on the mounting table.

According to the present invention, the workpiece can be mounted on a suitable position on the mounting table when carburizing treatment and/or quenching treatment is carried out for the workpiece. Further, the contact area between the workpiece and other parts can be reduced. In this manner, uniform temperature change in the workpiece can be provided, thereby allowing uniform carburizing treatment and/or quenching treatment for the workpiece to be carried out as well as restraining heat treatment strain produced in the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal cross sectional view of a heat (carburizing) treatment apparatus according to an embodiment of the present invention;

FIG. 2 is a cross sectional view taken along the line A-A in FIG. 1 (top view of a mounting table and a transportation arm when the figure is cut at A-A line);

FIG. 3 is a figure illustrating a configuration of a supporting a workpiece formed of a circular top portion and a cylindrical side portion;

FIG. 4 is a longitudinal cross sectional view taken along the line B-B in FIG. 3;

FIG. 5 is a figure illustrating a heat (carburizing) treatment process according to an embodiment of the present invention;

FIG. 6 is a figure illustrating a heat (carburizing) treatment process according to an embodiment of the present invention;

FIG. 7 is a figure illustrating a heat (carburizing) treatment process according to an embodiment of the present invention;

FIG. 8 is a figure illustrating a heat (carburizing) treatment process according to an embodiment of the present invention;

FIG. 9 is a figure illustrating a heat (carburizing) treatment process according to an embodiment of the present invention;

FIG. 10 is an enlarged view of FIG. 8; and

FIG. 11 is a longitudinal cross sectional view taken along the line B-B in FIG. 3 according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will be described based on a heat treatment apparatus 1 for carrying out vacuum carburizing and quenching treatment for a circular workpiece W below. Note that, the circular workpiece indicates a workpiece having a column shape or a ring shape, or a workpiece formed of a circular top portion and a cylindrical side portion, that is, a workpiece having a circular shape such as a lid, a tray, and a bowl. Specifically, a mechanical part such as a gear is an object to be treated. Further, in the specification and the drawings, a component having essentially the same functional configuration is appended with the same reference sign to omit repeated description.

As illustrated in FIG. 1, the heat treatment apparatus 1 includes a vacuum sealable treatment room 2 for carrying out a predetermined treatment for a workpiece, a transportation mechanism 3 for transporting the workpiece W into the treatment room or out of the treatment room, and a mounting table 4 on which the workpiece W transported into the treatment room is mounted. Note that, the predetermined treatment is a process such as preheating, carburizing, diffusion, cooling, and quenching (including gas quenching), required in a conventional vacuum carburizing treatment.

A driving device 5 is arranged in the lower part of the treatment room 2. The driving device 5 is provided with a drive arm 6 extending upward from the driving device 5. The distal end of the drive arm 6 penetrates the bottom of the treatment room 2 to be connected to the mounting table 4. The drive arm 6 functions as a strut of the mounting table 4. Since the driving device 5 is configured to allow the drive arm 6 to ascend and descend, the mounting table 4 can move to ascend and descend together with the drive arm 6.

As illustrated in FIG. 2, the mounting table 4 is configured with three protruding portions 8 (hereinafter referred to as “support fan 8”) provided so as to radially protrude from the center 7 (distal end of the drive arm 6 illustrated in FIG. 1) of the mounting table 4 in a plan view (top view). The angle between neighboring support fans 8 is the same. A mounting table support pin 9 for supporting the workpiece W is provided on the distal end of each support fan 8. The workpiece W is transferred to the mounting table support pin 9 from the transportation arm 10, which will be described below, and thereby the workpiece W is supported on the mounting table 4 by a three-point support. Note that, as a material of each support fan 8 and the mounting table support pin 9, SUS304 or the like is used. Further, in FIG. 2, only the outer edge of the workpiece W is illustrated in a dashed line.

Note that, as illustrated in FIG. 3 and FIG. 4, when the workpiece W has a shape formed of, for example, a circular top portion W1 and a cylindrical side portion W2, that is, for a workpiece having a hollow bottomed shape like a circular tray facing downward, such as a gear, the workpiece W can also be supported by arranging three mounting table support pins 9 on the mounting table 4 so as to contact the top portion W1 of the workpiece W in the inner side of the hollow portion of the workpiece W. In this case, the mounting table support pin 9 is preferably configured that the inner diameter of the side portion W2 of the workpiece W and the diameter of a circle (an imaginary circle) determined so as distal ends of three mounting table support pins 9 to be on the circle are approximately the same. The mounting table support pin 9 having such relationship between the workpiece W can also provide a function of positioning of the workpiece W.

As illustrated in FIG. 1, the transportation mechanism 3 is configured with the transportation arm 10 which mounts and transports the workpiece W and a transportation device, not shown in the drawing, for horizontally moving the transportation arm 10. As illustrated in FIG. 2, the distal ends of the transportation arm 10 form in a trifurcated shape and these distal ends are provided to protrude toward the center 7 of the mounting table 4 (protruding portion 11). Each protruding portion 11 is arranged so as to be able to support the workpiece W between support fans 8 when viewed in a plan view. The angle between neighboring protruding portions 11 is the same. Near the distal end of each protruding portion 11, a transport support pin 12 which supports the workpiece W during transportation of the workpiece W is provided. The workpiece W is supported by the transport support pin 12 with a three-point support.

Note that, as illustrated in FIG. 3 and FIG. 4, when the workpiece W has a shape formed of, for example, a circular top portion W1 and a cylindrical side portion W2, that is, for a workpiece having a hollow bottomed shape like a circular tray facing downward, such as a gear, the workpiece W can also be supported by arranging three transport support pins 12 on the transportation arm 10 so as to contact the top portion W1 of the workpiece W in the inner side of the hollow portion of the workpiece W. In this case, the transport support pin 12 is preferably configured that the inner diameter of the side portion W2 of the workpiece W and the diameter of a circle (an imaginary circle) determined so as distal ends of three transport support pins 12 to be on the circle are approximately the same. The relationship between the workpiece W and the transport support pin 12 can provide positioning of the workpiece W by moving the transportation arm 10 so as to allow the transport support pin 12 to contact and support the top portion W1 of the workpiece W in the inner side of the hollow portion of the workpiece W. That is, the transport support pin 12 also provides a function of positioning.

Further, in the embodiment, as illustrated in FIG. 1 and FIG. 2, an assist pin 13 is provided in the periphery of each transport support pin 12. The assist pin 13 prevents falling of the workpiece W or determines the mounting position against the transport support pin 12 when the workpiece W is mounted on the transport support pin 12. Each assist pin 13 is arranged in a location so as to face the side surface of the workpiece W when the workpiece W is mounted on the transport support pin 12. Further, a portion of the side, facing the side surface of the workpiece W, of each assist pin 13 is formed in a tapered shape which becomes thinner toward the top end of the assist pin 13 (tapered portion 13a).

For example, in a case, when the workpiece W does not have a circular shape having a hollow portion as described above, the workpiece which happens not to be in the suitable mounting position when being mounted on the transport support pin 12 moves along the tapered portion 13a of each assist pin 13 to be correctly positioned. In this manner, when the workpiece W is transferred between the mounting table 4 and the transportation arm 10, the mounting position of the workpiece W against the transport support pin 12 is always the same. Further, at a point of time when the workpiece W is mounted on the transport support pin 12, shifting of the position or falling of the workpiece W is restricted by each assist pin 13 facing (or making contact with) the side surface of the workpiece W. Therefore, during transportation of the workpiece W, shifting of the mounting position against the transport support pin 12 or falling of the workpiece W will not occur. Note that, as a material of the transport support pin 12 and the assist pin 13, SUS304 or the like is used.

Further, each mounting table support pin 9 and each transport support pin 12 are preferably provided so as to be arranged on the same circumference in a plan view when the workpiece W is mounted on the mounting table 4. In this manner, tilting or such of the workpiece, when transferring the workpiece W to the mounting table 4 from the transportation arm 10, can be reduced, thereby restraining shifting of the workpiece W from the suitable mounting position.

Further, as illustrated in FIG. 1, the treatment room 2 is provided with an aperture 14 allowing transporting the workpiece W into and out of the treatment room 2. Further, an open/close door 15 which seals the treatment room 2 by closing the aperture 14 is provided adjacent to the treatment room 2. The open/close door 15 is configured to be able to move upward and downward by an open/close mechanism not shown in the drawing. Further, an induction heating coil 16 which heats the workpiece during carburizing is provided above the mounting table 4 inside the treatment room. Note that, the heat treatment apparatus 1 according to the embodiment includes other configurations necessary for carrying out a conventional vacuum carburizing such as an exhaust mechanism and a carburizing gas introducing mechanism though not shown in the drawing.

A carburizing method using the heat treatment apparatus 1 configured as described above will be described.

First, as illustrated in FIG. 5, a workpiece W, which a preheating treatment according to the previous process of the carburizing treatment process is completed, is transported, mounted on the transportation arm 10, into the evacuated treatment room 2.

The workpiece W is transferred to the transport support pin 12 of the transportation arm 10 from a mounting table (not shown in the drawing) of the treatment room of the previous process. Further, since each assist pin 13 faces the side surface of the workpiece W, shifting of the mounting position against the transport support pin 12 or falling of the workpiece W during transportation of the workpiece W will not occur. Further, the transportation arm 10 extending into the treatment room is controlled so as to extend to be in a location in which the distance between the periphery of the workpiece W mounted on the mounting table 4 and the induction heating coil 16 is uniform when the mounting table 4 is in the ascended position as described below. That is, the workpiece W transported into the treatment room 2 is supported at a location in which the distance between the periphery of the workpiece W and the induction heating coil 16 is uniform in a plan view.

Note that, as illustrated in FIG. 3 and FIG. 4, when the workpiece W has, for example, a hollow bottomed shape like a circular tray facing downward, such as a gear, the workpiece W can also be positioned by arranging three transport support pins 12 on the transportation arm 10 so as to contact the top portion W1 in the inner side of the hollow portion and to contact (or to be located very close to) the side portion W2. That is, when the workpiece W has a shape formed of the circular top portion W1 and the cylindrical side portion W2, and when the transport support pin 12 is arranged on the protruding portion 11 so as to be on a circumference having an approximately the same diameter as the inner diameter of the side portion W2 of the workpiece W, the transport support pin 12 can also provide a function of positioning.

Now, as illustrated in FIG. 6, the mounting table 4 ascends by the drive arm 6 made to ascend by the driving device 5. Then the workpiece W supported on the transport support pin 12 is transferred to the mounting table support pin 9 provided on the mounting table 4. In this step, the movement of the mounting table 4 is only ascending and descending, so that the mounting position of the workpiece W will not shift from the suitable position. Then, the mounting table 4 ascends to the location where the induction heating coil 16 is provided.

In this case, as illustrated in FIG. 3 and FIG. 4, when the workpiece W has a hollow bottomed shape like a circular tray facing downward, such as a gear, the workpiece W can also be positioned by arranging three mounting table support pins 9 on the mounting table 4 so as to contact the top portion W1 in the inner side of the hollow portion and to contact (or to be located very close to) the side portion W2. That is, when the workpiece W has the shape formed of the circular top portion W1 and the cylindrical side portion W2, and when the mounting table support pin 9 is arranged on the mounting table 4 so as to be on a circumference having an approximately the same diameter as the inner diameter of the side portion W2 of the workpiece W, the mounting table support pin 9 can also provide a function of positioning.

Then, as illustrated in FIG. 7, the transportation arm 10 moves outside the treatment room, and the open/close door 15 is closed to seal the treatment room 2. Then, carburizing gas is introduced into the treatment room by the carburizing gas introducing mechanism not shown in the drawing. Then, a high-frequency current is supplied to the induction heating coil 16 to heat the workpiece W to the carburizing temperature. Since the workpiece W is supported by a three-point support of the mounting table support pin 9, the contact area between the workpiece W and the mounting table support pin 9 is small. The distal end portion of the mounting table 9 is provided with an arc shape of, for example, R1 to R2 so as to prevent damaging to the workpiece W. However, the contact can be assumed as a point contact. Therefore, the effect of the mounting table support pin 9 is negligible and the workpiece W can uniformly be heated. Further, since the workpiece W is mounted in a location in which the distance between the periphery of the workpiece W and the induction heating coil 16 is uniform, the workpiece W can uniformly be heated. Note that, the carburizing treatment temperature is approximately 850° C. to 1100° C. Further, when the workpiece W having an approximately circular shape such as a gear is heated by the induction heating mentioned above, a concentric temperature distribution from the center of the circle to the outer region is produced. The temperature distribution having a same temperature at locations of which distances from the center of the circle are the same is preferable. The present invention can provide such temperature distribution so that good dimensional accuracy can be obtained.

After carburizing treatment is complete, the carburizing gas is exhausted by the exhaust mechanism not shown in the drawing and the treatment room is vacuumed.

Next, the open/close door 15 ascends and the transportation arm 10 moves into the treatment room. Then, as illustrated in FIG. 8, the mounting table 4 descends to transfer the workpiece W mounted on the mounting table support pin 9 of the mounting table 4 to the transport support pin 12 of the transportation arm 10. In this step, when the location of the workpiece W is not in a suitable mounting position, as illustrated in FIG. 10, the workpiece W moves along the tapered portion 13a of the assist pin 13 in the direction shown in the arrow in FIG. 10 to be mounted on the transport support pin 12. In this manner, even after the carburizing treatment, the workpiece can always be mounted in the same mounting position against the transport support pin 12. Therefore, even when the workpiece W is mounted on the mounting table (not shown in the drawing) in the treatment room for cooling process which is the after process, the workpiece W can be mounted in the suitable position, so that the workpiece W can uniformly be cooled.

Note that, when the workpiece W has the shape formed of the circular top portion W1 and the cylindrical side portion W2, and when the mounting table support pin 9 and the transport support pin 12 are arranged on the mounting table 4 and the transportation arm 10 so as to be on a circumference having an approximately the same diameter as the inner diameter of the side portion W2 of the workpiece W, the mounting table support pin 9 and the transport support pin 12 can also preferably provide a function of positioning or preventing falling of the workpiece W also in the treatment process such as carburizing treatment and quenching treatment.

Finally, as illustrated in FIG. 9, the transportation arm 10 on which the workpiece W is mounted moves outside the treatment room and the carburizing treatment process completes.

As described above, according to the present invention, the contact area between the mounting table and the workpiece as well as the contact area between the transportation arm and the workpiece can be reduced since the workpiece is supported by a three-point support by the mounting table and the transport support pin. In addition, the mounting table support pin and the transport support pin can provide a function of positioning of the workpiece. Therefore, falling of the workpiece can be prevented, and the workpiece can be mounted in the mounting position where the workpiece can uniformly be heated and cooled. Thereby, uniform temperature change of the workpiece can be provided when the workpiece is heated or cooled. As a result, the heat treatment strain in the workpiece is restrained and at the same time, uniform carburizing treatment can be provided.

Further, as described in the embodiment of the present invention, when the assist pin having a tapered portion is provided on the transportation arm, the workpiece which happens not to be in the suitable mounting position when being mounted on the transport support pin can move along the tapered portion of each assist pin, and thereby, the workpiece can be mounted in the suitable position. In this manner, uniform temperature change of the workpiece can be provided when the workpiece is heated or cooled, and thereby, the heat treatment strain in the workpiece is restrained and at the same time, uniform carburizing treatment can be provided.

The preferable embodiment of the present invention is described above. However, the present invention is not limited to such example. It is apparent that those skilled in the art can make various alterations or modifications within the scope of the technical idea described in the claims, which naturally fall within a scope of the art of the present invention.

For example, in the embodiment, the assist pin is provided on the transportation arm, though the assist pin can be provided on the mounting table instead of the transportation arm. In this case, when the workpiece is transferred from the transportation arm to the mounting table, the workpiece moves along the tapered portion of the mounting table support pin provided on the mounting table so as to be mounted on the mounting table support pin. In this manner an effect similar to the effect as described in the embodiment can be obtained. Further, when the assist pin is provided on both the mounting table and the transportation arm, the effect of preventing the shifting of the mounting position of the workpiece can further be improved.

Further, in the embodiment, a portion of the side, facing the side surface of the workpiece, of the assist pin is formed in a tapered shape, though all sides of the assist pin may be formed in a tapered shape. Further, the number and arrangement of the mounting table support pin and the transport support pin are suitably changed according to the shape and size of the workpiece. That is, as long as the workpiece can be supported without tilting when mounted on each support pin, any number and any arrangement may be provided. Similarly, the number of the support fan of the mounting table and the angle between each support fan as well as the number of the protruding portion of the transportation arm and the angle between each protruding portion may suitably be changed.

Further, in the embodiment, the mounting table ascends to transfer the workpiece between the mounting table and the transportation arm. However, an ascend-and-descend mechanism may be provided to the transportation mechanism to make the transportation arm ascend and descend. In this case, the workpiece can be mounted on the mounting table without ascending or descending the mounting table. Further, a rotation mechanism can be provided to the driving device which makes the mounting table ascend and descend. In this case, the mounting table can be rotated during the heating and cooling of the workpiece, so that the workpiece can further uniformly be heated and cooled.

Further, in the embodiment, the vacuum carburizing treatment apparatus is used as an example of a heat treatment apparatus in the description, though it is not limited to the vacuum carburizing treatment apparatus, and other treatment apparatus may be used. Similarly, in other processes in the carburizing treatment, that is, a preheating process, a diffusion process, and a cooling (soaking) process, the heat treatment apparatus of the present invention can be used.

Further, the heat treatment apparatus according to the present invention can be applied for quenching treatment. For example, when the quenching treatment by gas cooling is carried out, instead of using a coil for induction heating, a cooling device configured to blow a cooling gas, uniformly in a plan view, to the outer circumference of the circular workpiece W is preferably used to carry out quenching (cooling) keeping uniformity of the temperature during cooling.

Further, in the present invention, it is preferable to carry out treatment for one workpiece at a time to obtain a workpiece having excellent dimensional accuracy. However, if geometric symmetry with reference to a heat source or a cooing source can be maintained during temperature control of the workpiece, treatment can be carried out for two or more workpieces at a time.

Further, as illustrated in FIG. 11, a workpiece W having a certain form may be heat treated on a tray. In this case, a tray T supporting the workpiece W is supported by the transport support pin 12 of the transportation arm, and transported into the treatment room by the transportation arm. Then, the tray T transported into the treatment room is transferred from the transport support pin 12 to the mounting table support pin 9 by, for example, ascending and descending of the mounting table. In this step, it is preferable to provide at least three tray support pins 17 for supporting the workpiece W on the top surface of the tray T.

Further, for example, when a tray T having a shape formed of a circular top portion T1 and a cylindrical side portion T2 is used, the mounting table support pin 9 is preferably be arranged on the mounting table so as to be on a circumference having an approximately the same diameter as the inner diameter of the side portion T2 of the tray T. Also by a heat treatment apparatus including such tray T, the effect as described in the embodiment of the present invention can be obtained. Further, when a tray T having the shape formed of the circular top portion T1 and the cylindrical side portion T2 is used, the transport support pin 12 may be arranged on the transportation arm so as to be on a circumference having an approximately the same diameter as the inner diameter of the side portion T2 of the tray T. Also by a heat treatment apparatus including such tray T, the effect as described in the embodiment of the present invention can be obtained.

Furthermore, for example, when the workpiece W having a shape formed of the circular top portion W1 and the cylindrical side portion W2 is supported by a tray T, the tray support pin 17 is preferably be arranged on the tray T so as to be on a circumference having an approximately the same diameter as the inner diameter of the side portion W2 of the workpiece W. A heat treatment apparatus including such tray T is preferable in that the tray T can provide a function of positioning and that the temperature variation in the workpiece W is restrained since the contact area between the tray T and the workpiece W is minimized.

Claims

1. A heat treatment apparatus for carrying out carburizing treatment and/or quenching treatment for a circular workpiece comprising:

a treatment room configured to carry out a predetermined treatment for the workpiece;

a transportation mechanism configured to transport the workpiece into the treatment room and out of the treatment room; and

a mounting table, provided in the treatment room, on which the workpiece transported into the treatment room is mounted, wherein the transportation mechanism includes a transportation arm which mounts and moves the workpiece, the transportation arm provided with at least three transport support pins which support the workpiece when the workpiece is transported, and

at least three mounting table support pins which support the workpiece are provided on the mounting table.

2. The heat treatment apparatus according to claim 1, wherein the mounting table is configured with at least three support fans each provided with the mounting table support pin, and each of the support fans is provided so as to radially protrude from a center of the mounting table in a plan view.

3. The heat treatment apparatus according to claim 1, wherein at least three protruding portions which protrude toward a center of the mounting table and can support the workpiece between the support fans in a plan view are provided on a distal end of the transportation arm, and each of the protruding portions is provided with the transport support pin which is arranged to support the workpiece between the support fans in a plan view.

4. The heat treatment apparatus according to claim 1, further comprising an ascend-and-descend mechanism which makes the mounting table ascend and descend.

5. The heat treatment apparatus according to claim 1, wherein the workpiece has a shape formed of a circular top portion and a cylindrical side portion, and the mounting table support pin is arranged on the mounting table so as to be on a circumference having an approximately a same diameter as an inner diameter of a side portion of the workpiece.

6. The heat treatment apparatus according to claim 1, wherein the workpiece has a shape formed of a circular top portion and a cylindrical side portion, and the transport support pin is arranged on the transportation arm so as to be on a circumference having an approximately a same diameter as an inner diameter of a side portion of the workpiece.

7. The heat treatment apparatus according to claim 1, further comprising a rotation mechanism which rotates the mounting table.

8. The heat treatment apparatus according to claim 1, wherein the mounting table support pin and the transport support pin are arranged on a same circumference when the workpiece is mounted on the mounting table.

9. The heat treatment apparatus according to claim 1, wherein the transportation arm includes an assist pin provided in a periphery of each transport support pin.

10. The heat treatment apparatus according to claim 9, wherein at least a portion of a side, facing a side surface of the workpiece, of the assist pin is formed in a tapered shape which becomes thinner toward a top end of the assist pin.

11. The heat treatment apparatus according to claim 1, further comprising a tray which supports the workpiece, wherein the tray supporting the workpiece is supported by the transport support pin and then transported by the transportation arm to be mounted on the mounting table support pin, and

at least three tray pins which support the workpiece are provided on a top surface of the tray.

12. The heat treatment apparatus according to claim 11, wherein the tray has a shape formed of a circular top portion and a cylindrical side portion, and the mounting table support pin is arranged on the mounting table so as to be on a circumference having an approximately a same diameter as an inner diameter of a side portion of the tray.

13. The heat treatment apparatus according to claim 11, wherein the tray has a shape formed of a circular top portion and a cylindrical side portion, and the transport support pin is arranged on the transportation arm so as to be on a circumference having an approximately a same diameter as an inner diameter of a side portion of the tray.

14. The heat treatment apparatus according to claim 11, wherein the workpiece has a shape formed of a circular top portion and a cylindrical side portion, and the tray support pin is arranged on the tray so as to be on a circumference having an approximately a same diameter as an inner diameter of a side portion of the workpiece.