Method for manufacturing hermetic compressor and hermetic compressor

Abstract

In a case where the coaxial accuracy of the main shell having a plurality of diameters before machining is poor, it is necessary to increase a cutting margin by machining, the number of steps required for machining increases, and the minimum plate thickness of the main shell decreases.SOLUTION: The coaxial precision of the cylindrical parts having different diameters is secured by providing a simultaneous tube expansion process for simultaneously expanding cylindrical parts having different diameters of a middle shell comprising a plurality of cylindrical parts having different diameters, a compression mechanism part for compressing a refrigerant, and a motor for rotating a main shaft connected to the compression mechanism part by using a die from the inner peripheral side of a cylindrical body.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a hermetic compressor and a hermetic compressor. [Background technology]

[0002] Patent Document 1 discloses a scroll compressor in which a compression mechanism unit and a drive mechanism unit equipped with a fixed scroll and an orbiting scroll are built inside a main shell, and the main shell is composed of a first straight pipe section extending along the central axis, a second straight pipe section having an outer diameter smaller than that of the first straight pipe section, and a third straight pipe section having an outer diameter smaller than that of the second straight pipe section, and the fixed scroll is fixed within the first straight pipe section, the frame is fixed within the second straight pipe section, and the drive mechanism unit is fixed within the third straight pipe section. Patent document 2 also discloses a method for manufacturing a cylindrical body used for a sealed container of a hermetic compressor, etc., with the aim of improving the cylindrical precision of the cylindrical body by multiple expansion or contraction molding processes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2023 / 063243 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-125759 Summary of the Invention [Problem to be solved by the invention]

[0004] In a shell having cylindrical portions of multiple diameters, as in Patent Document 1, a manufacturing method that ensures coaxial accuracy between the cylindrical portions of the shell with multiple diameters is required to accurately assemble the internal components. For example, one method ensures coaxial accuracy by machining the areas that require coaxial accuracy without re-gripping the shell. However, if the coaxial accuracy of the shell before machining is poor, it is necessary to increase the machining allowance, which increases the number of steps and reduces the minimum shell thickness. Therefore, ensuring coaxial accuracy between the cylindrical portions of the shell with multiple diameters before machining is a challenge.

[0005] Patent Document 1 and Patent Document 2 disclose a manufacturing method for forming a shell by expanding or shrinking the shell, and a manufacturing method for improving the cylindrical accuracy of a cylindrical body by multiple expansion or shrinking moldings. However, they do not disclose a method for ensuring coaxial accuracy between cylindrical portions of multiple diameters, and are therefore unable to solve the problem of ensuring coaxial accuracy between cylindrical portions of multiple diameters of a shell such as the one described above.

[0006] The present disclosure discloses a technique for solving the above-described problems, and can ensure coaxial accuracy between cylindrical portions of multiple diameters that make up the middle shell. [Means for solving the problem]

[0007] The method for manufacturing a hermetic compressor disclosed herein is a method for manufacturing a hermetic compressor that includes a middle shell composed of cylindrical portions of multiple diameters, a compression mechanism portion that compresses refrigerant, and an electric motor that rotates a main shaft connected to the compression mechanism portion, in which the compression mechanism portion and the electric motor are respectively fixed to cylindrical portions of different diameters of the middle shell, and is characterized by including a simultaneous tube expansion process in which the cylindrical portions of different diameters of the middle shell are simultaneously expanded and formed from the inner side of the cylinder using a mold. [Effects of the Invention]

[0008] According to the manufacturing method for a hermetic compressor of the present disclosure, the cylindrical portions of the middle shell with multiple diameters are simultaneously expanded from the inside of the cylindrical body using a mold, thereby ensuring coaxial accuracy between the cylindrical portions with multiple diameters. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a scroll compressor according to a first embodiment. [Figure 2] 4 is a flowchart showing steps of a method for manufacturing the middle shell of the scroll compressor according to the first embodiment. [Figure 3] 3 is a vertical cross-sectional view of a state in which a cylindrical body is placed in a first mold for manufacturing the middle shell of the scroll compressor according to the first embodiment. FIG. [Figure 4] 3 is a bottom view of a state in which a cylindrical body is placed in a first mold for manufacturing the middle shell of the scroll compressor according to the first embodiment. FIG. [Figure 5] 3 is a vertical cross-sectional view of a state in which a first core bar is pressed into a first die for manufacturing the middle shell of the scroll compressor according to the first embodiment. FIG. [Figure 6] 4 is a bottom view showing a state in which a first core bar is pressed into a first die for manufacturing the middle shell of the scroll compressor according to the first embodiment. FIG. [Figure 7] 4 is a vertical cross-sectional view of a state in which a cylindrical body is placed in a second mold for manufacturing the middle shell of the scroll compressor according to the first embodiment. FIG. [Figure 8] 4 is a bottom view of a state in which a cylindrical body is placed in a second mold for manufacturing the middle shell of the scroll compressor according to the first embodiment. FIG. [Figure 9] 4 is a vertical cross-sectional view of a state in which a second core bar is pressed into a second die to manufacture the middle shell of the scroll compressor according to the first embodiment. FIG. [Figure 10] 4 is a bottom view showing a state in which a second core bar is pressed into a second die for manufacturing the middle shell of the scroll compressor according to the first embodiment. FIG. [Figure 11]10 is a flowchart showing steps in a method for manufacturing a scroll compressor according to a second embodiment. [Figure 12] FIG. 10 is a vertical cross-sectional view of a state in which a cylindrical body is placed in a third mold for manufacturing the middle shell of the scroll compressor according to the second embodiment. [Figure 13] 10 is a top view showing a state in which a cylindrical body is placed in a third mold for manufacturing the middle shell of the scroll compressor according to the second embodiment. FIG. [Figure 14] FIG. 10 is a vertical cross-sectional view showing a state in which a jig is pressed into a third die for manufacturing the middle shell of the scroll compressor according to the second embodiment. [Figure 15] 10 is a view seen from the jig side showing a state in which the jig is pressed into a third mold for manufacturing the middle shell of the scroll compressor according to the second embodiment. FIG. [Figure 16] 10 is a flowchart showing steps in a method for manufacturing a scroll compressor according to a third embodiment. [Figure 17] FIG. 11 is a vertical cross-sectional view of a state in which a cylindrical body is placed in a first mold for manufacturing a middle shell of a scroll compressor according to a third embodiment. [Figure 18] FIG. 11 is a vertical cross-sectional view showing a state in which a first core bar is pressed into a first die for manufacturing a middle share of a scroll compressor according to a third embodiment. [Figure 19] FIG. 11 is a vertical cross-sectional view showing a state in which a jig is pressed into a third mold for manufacturing the middle shell of the scroll compressor according to the third embodiment. [Figure 20] 10 is a bottom view showing a state in which a second core bar is pressed into a second die for manufacturing a middle shell of a scroll compressor according to a fourth embodiment. FIG. [Figure 21] FIG. 21 is an enlarged view of the dividing plane A in FIG. 20. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, preferred embodiments of a method for manufacturing a hermetic compressor according to the present disclosure will be described with reference to the drawings. The same components and corresponding parts are designated by the same reference numerals, and detailed descriptions thereof will be omitted. Similarly, in the following embodiments, redundant descriptions of components designated by the same reference numerals will be omitted.

[0011] Embodiment 1 In the first embodiment, a scroll compressor will be described as an example of a hermetic compressor. Similarly, in the second to fourth embodiments, a scroll compressor will be described as an example, but the present invention is not limited to this. 1 is a cross-sectional view of a scroll compressor. The scroll compressor is configured to include a compression mechanism 30, which is made up of mechanical components such as a frame 34, an orbiting scroll 33, a fixed scroll 32, and a discharge valve 31, inside a pressure vessel made up of a middle shell 10, an upper shell 22, and a lower shell 23, and an electric motor 40, which is made up of a stator 42, a rotor 41, etc.

[0012] The middle shell 10 is made of metal and consists of a cylindrical portion 11 that houses the compression mechanism portion 30 and a cylindrical portion 12 that houses the electric motor 40, the inner diameter of the cylindrical portion 11 being larger than the inner diameter of the cylindrical portion 12. A suction pipe 13 is attached to the side of the middle shell 10 by brazing or the like, and low-temperature, low-pressure refrigerant before compression is sucked into the inside of the scroll compressor through the suction pipe 13.

[0013] The upper shell 22 is approximately hemispherical, and a portion of its side wall is connected to the upper end of the middle shell 10 by welding or the like, covering the upper opening of the middle shell 10. A discharge pipe 21 is attached to the upper shell 22, and the high-temperature, high-pressure refrigerant compressed inside the scroll compressor is discharged to the outside of the scroll compressor. Here, the temperature and pressure of the refrigerant both increase before and after compression, so the comparison before and after compression is expressed as a low-temperature, low-pressure refrigerant before compression and a high-temperature, high-pressure refrigerant after compression, but the actual temperature and pressure will vary depending on the type of refrigerant and operating conditions such as the outside air temperature.

[0014] The lower shell 23 is substantially hemispherical, and a portion of its side wall is connected to the lower end of the middle shell 10 by welding or the like, covering the lower opening of the middle shell 10. A leg plate 24 is attached to the housing of the lower shell 23 via rubber or the like.

[0015] Next, the electric motor 40 will be described. The electric motor 40 is primarily composed of a stator 42 and a rotor 41. The stator 42 is fixed to the cylindrical portion 12 of the middle shell 10 by shrink fitting, welding, or other means. The rotor 41 is fixed to the main shaft 44 by press fitting, shrink fitting, or other means. The frame 34 is fixed to the cylindrical portion 11 of the middle shell 10 by shrink fitting, welding, or other means, and the subframe 47 is fixed to the cylindrical portion 12 of the middle shell 10 by shrink fitting, welding, or other means. The main shaft 44 is supported by a plain bearing metal 36 attached to the frame 34 and a rolling bearing 46 attached to the subframe 47. Therefore, by assembling the frame 34, subframe 47, and stator 42 coaxially with high precision, the performance of the electric motor can be improved. Furthermore, two balance weights, a first balancer 43 and a second balancer 45, are attached to the main shaft 44 to achieve rotational balance. One end of the main shaft 44 is connected to the orbiting scroll 33 via an Oldham coupling (not shown). When current is applied to the stator 42 , the main shaft 44 rotates and transmits power to the orbiting scroll 33 .

[0016] Next, the compression mechanism 30 will be described. The compression mechanism 30 is a scroll compression mechanism equipped with a fixed scroll 32 and an orbiting scroll 33. An enclosed space is formed between the frame 34 and the fixed scroll 32, and the refrigerant is compressed by the orbiting motion of the orbiting scroll 33 within the enclosed space. A discharge valve 31 is attached to the fixed scroll 32, and when the compressed refrigerant reaches or exceeds a predetermined pressure, the discharge valve opens and the compressed refrigerant is discharged into the muffler 35. After passing through the muffler 35, the compressed refrigerant passes through the discharge pipe 21 and is discharged to the outside of the scroll compressor.

[0017] Next, a method for manufacturing the middle shell 10 will be described. The middle shell 10 can be made by machining a steel pipe, or by rolling a steel plate and welding it into a cylindrical shape. However, in this embodiment, a method for forming a cylindrical body 100 with a single diameter into a middle shell 10 composed of cylindrical portions with multiple diameters will be described. FIG. 2 shows the steps of the manufacturing method. The steps will be explained below. FIG. 3 shows a vertical cross-sectional view of a cylindrical body 100 placed on the outside of a first mold 101, and FIG. 4 shows a view from below of the state in which the cylindrical body 100 is placed on the outside of the first mold 101. In order to form a cylindrical portion 11 having an inner diameter larger than that of the cylindrical portion 12 of the middle shell 10 shown in FIG. 1, the first mold 101 is divided into multiple parts in the circumferential direction, and the inner periphery of the cylindrical body 100 is placed on the outer periphery of the first mold 101 as shown in FIG. 3 (step S01 in FIG. 2). Here, the diameter of the cylindrical body 100 is smaller than that of the cylindrical portion 12.

[0018] FIG. 5 is a vertical cross-sectional view of the first metal core 102 pressed into the first mold 101, and FIG. 6 shows a view from below of the first metal core 102 pressed into the first mold 101. The inner periphery of the first mold 101 has a surface that is inclined with respect to the axial direction P of the cylinder. As shown in FIG. 5, the first metal core 102, which has a truncated cone shape with the same angle as the inclined surface of the first mold 101, is pressed from above using a press, causing the first metal cores 101 to move radially from the center of the cylinder in the horizontal direction (perpendicular to the axial direction P), thereby expanding the cylinder 100 (step S02). After the first metal core 102 is pressed to a predetermined position, the first metal core 102 is removed, thereby removing the load generated at the contact surface between the first mold 101 and the cylinder 100, and the cylinder 100 can be removed (step S03). Here, the predetermined position is a position having a diameter smaller than the inner diameter of the cylindrical portion 11 of the middle shell 10.

[0019] FIG. 7 is a vertical cross-sectional view of the cylindrical body 100 placed on the outside of the second mold 103, and FIG. 8 is a view from below of the state in which the cylindrical body 100 is placed on the outside of the second mold 103. The second mold 103 is composed of cylindrical portions of two different diameters, and the two cylindrical portions are machined with high coaxial precision and are divided into multiple pieces in the circumferential direction. As shown in FIG. 7, the cylindrical body 100 is placed on the outside of the second mold 103 (step S04). The difference between the two different diameters of the second mold 103 is set to be equal to the difference in diameter between the cylindrical portion 11 and the cylindrical portion 12.

[0020] Fig. 9 is a vertical cross-sectional view of when the second core bar 104 is pressed into the second mold 103, and Fig. 10 is a view from below of the state in which the second core bar 104 is pressed into the second mold 103. As shown in Fig. 7, the inner peripheral side of the second mold 103 has a surface that is inclined with respect to the axial direction P of the cylinder, and as shown in Fig. 9, the second core bar 104, which has a truncated cone shape with the same angle as the inclined surface of the second mold 103, is pressed from above by a press, whereby the second molds 103 move radially from the center of the cylinder 100 in the horizontal direction (direction perpendicular to the axial direction P), and the cylindrical portions 11 and 12, which have different inner diameters of the cylinder 100, are simultaneously pressed and expanded (step S05).

[0021] The contact portion between the first mold 101 and the first core bar 102 described in step S01, or the contact portion between the second mold 103 and the second core bar 104 described in step S05, is not limited to a curved surface, and the first core bar 102 or the second core bar 104 may have a truncated pyramidal shape with a flat surface at the same angle as the oblique surface of the first mold 101 or the second mold 103. Comparing the angle of the oblique surface of the second mold 103 with that of the first mold 101, it is found that by reducing the angle of the oblique surface of the second mold 103, the load required when pressing can be reduced.

[0022] The second core metal 104 is pushed to a predetermined position until the diameters of the cylindrical portions 11 and 12 become the diameters determined by specifications, etc., and then the second core metal 104 is pulled out, thereby removing the load generated on the contact surface between the second mold 103 and the cylindrical body 100, and the cylindrical body 100 can be removed (step S06).

[0023] In this way, by expanding the middle shell 10 using the second mold 103, which is composed of cylindrical portions of two different diameters and has been machined with high coaxial precision, it is possible to manufacture with high precision the middle shell 10 in which the inner diameter of the cylindrical portion 11 is larger than the inner diameter of the cylindrical portion 12. By fixing the compression mechanism 30 to the cylindrical portion 11 of the middle shell 10 manufactured in this way and fixing the electric motor 40 to the cylindrical portion 12, the central axis of the stator 42 and the rotation axis of the rotor 41 are aligned, thereby improving the performance of the scroll compressor. Furthermore, even when machining the middle shell 10 after the tube expansion, because the cylindrical portions 11 and 12 have high coaxial precision before machining, the machining allowance can be reduced, resulting in effects such as shortening the machining time and increasing the minimum plate thickness after machining.

[0024] Embodiment 2 In the second embodiment, a manufacturing method will be described in which a cylindrical body 100 is subjected to tube contraction molding, followed by tube expansion molding to achieve coaxial precision of two cylindrical portions of different diameters. FIG. 11 shows the steps of the manufacturing method according to the second embodiment. FIG. 12 shows a longitudinal cross-sectional view of the cylindrical body 100 placed inside a third mold 111, and FIG. 13 shows a view of the third mold 111 and the cylindrical body 100 as seen from above. In order to form the cylindrical portion 11 of the middle shell 10, which has a larger inner diameter than the cylindrical portion 12, the cylindrical body 100 is placed in the doughnut-shaped third mold 111 divided into multiple pieces in the circumferential direction as shown in FIG. 12, so that the outer periphery of the cylindrical body 100 contacts the inner periphery of the third mold 111 (step S11).

[0025] The outer periphery of the third mold 111 has a surface that is oblique to the axial direction of the cylinder, and as shown in Fig. 14, a jig 112 having a curved surface at the same angle as the oblique surface of the third mold 111 is pressed from above by a press, causing the third mold 111 to move radially in the horizontal direction toward the center of the cylinder 100, thereby compressing and shrinking the cylinder 100 (step S12). Fig. 15 is a view of the third mold 111 and cylinder 100 in the state of Fig. 14 as seen from the jig 112 side.

[0026] In addition, in order to expand the tube in a subsequent step, the jig 112 is pushed to a predetermined position so that the inner diameter of the cylindrical body 100 is smaller than the final required dimension. After the jig 112 is pushed in, the jig 112 is pulled out, thereby removing the load acting on the contact surface between the third mold 111 and the cylindrical body 100, and the cylindrical body 100 can be taken out (step S13). Here, the contact surface between the third mold 111 and the jig 112 is not limited to a curved surface, and the jig 112 may have a flat surface at the same angle as the oblique surface of the third mold 111. The subsequent steps are the same as those of the first embodiment.

[0027] In addition to the effects of the first embodiment, the second embodiment has the advantage that the cylindrical body 100 is formed by shrinkage, thereby improving the thickness and strength of the cylindrical portion 12 of the middle shell 10. This is because the circumference of the cylindrical portion 12 becomes smaller due to shrinkage, and the thickness increases as the forming process progresses. Furthermore, the middle shell 10 is used to seal a high-pressure refrigerant inside, and therefore a tensile force is applied to the middle shell 10 due to the internal pressure. In this embodiment, a force opposite to the force generated during compressor operation can be applied in advance during the forming of the middle shell 10, thereby increasing the pressure resistance during compressor operation.

[0028] Furthermore, since the tube shrinking process involves pressing a mold against the outer periphery of the cylindrical body 100, the precision of the inner periphery of the cylindrical body 100 is not high. However, in this embodiment, after the tube shrinking process, the tube is expanded using a mold that is made up of two cylindrical sections of different diameters, and these two cylindrical sections are machined with high coaxial precision, thereby achieving the effect of manufacturing a middle shell 10 with high precision, in which the inner diameter of cylindrical section 11 is larger than the inner diameter of cylindrical section 12.

[0029] Embodiment 3 In the third embodiment, a manufacturing method is described in which a cylindrical body 100 is heated and expanded at a high temperature, and then expanded to achieve coaxial precision of two cylindrical portions with different diameters. FIG. 16 shows the manufacturing process of the third embodiment. FIG. 17 shows a longitudinal cross-sectional view of the cylindrical body 100 placed outside a first mold 101. To form the cylindrical portion 11 of the middle shell 10, which has a larger inner diameter than the cylindrical portion 12, the first mold 101 is divided into multiple parts in the circumferential direction, and the cylindrical body 100 is placed outside the first mold 101 (step S21). Furthermore, a heating means 121 is placed outside the cylindrical body 100. In this embodiment, a high-frequency heating device is used as the heating means 121, which heats the cylindrical body 100 by an induced current generated in the cylindrical body 100 by a magnetic field of a high-frequency current passed through a coil. However, the heating means 121 is not limited to a high-frequency heating device and may be other means, such as an infrared heater. As the cylindrical body 100 is heated, the first mold 101 also becomes hot, so it is desirable that the first mold 101 be provided with a cooling means such as a water-cooling duct.

[0030] 18 shows a vertical cross section of the first metal core 102 pressed into the first mold 101. The inner periphery of the first mold 101 has a surface that is inclined relative to the axial direction of the cylinder. When the first metal core 102, which is shaped like a truncated cone at the same angle as the inclined surface of the first mold 101, is pressed in from above by a press, the first metal core 102 moves radially from the center of the cylinder in the horizontal direction, thereby expanding the cylinder 100 (step S22). Here, the contact area between the first mold 101 and the first metal core 102 is not limited to a curved surface, and the first metal core 102 may be in the shape of a truncated pyramid with a flat surface at the same angle as the inclined surface of the first mold 101. By performing this tube expansion molding operation while the cylinder 100 is heated to a high temperature by the heating means 121, the 0.2% yield strength of the cylinder 100 decreases compared to when it is at room temperature, and the first core 102 can be pressed to a predetermined position with a smaller pressure force than when it is at room temperature (step S22).

[0031] After the first core metal 102 is pushed in to a predetermined position, the first core metal 102 is removed, thereby removing the load acting on the contact surface between the first die 101 and the cylindrical body 100, and the cylindrical body 100 can be removed (step S23). After the cylindrical body 100 is cooled to room temperature (step S24), the cylindrical body 100 is placed outside the second die 103. The subsequent steps of the tube expansion molding operation using the second die 103 are the same as those in the first embodiment.

[0032] Furthermore, a heating means 121 may be used for the tube shrinking of the cylindrical body 100 described in the second embodiment. For example, as shown in FIG. 19, a high-frequency heating device, which is the heating means 121, is disposed inside the cylindrical body 100 shown in FIG. 14 described in the second embodiment. By performing this tube expansion operation while the cylindrical body 100 is heated to a high temperature by the heating means 121, the 0.2% proof stress of the cylindrical body 100 is reduced compared to that at room temperature, and the jig 112 can be pressed to a predetermined position with a smaller pressure force than at room temperature. Thereafter, the cylindrical body 100 is cooled to room temperature and the jig 112 is removed, thereby removing the load acting on the contact surface between the third mold 111 and the cylindrical body 100, and the cylindrical body 100 can be removed. The subsequent steps of the tube expansion operation using the second mold 103 are the same as those in the first embodiment.

[0033] In addition to the effects obtained in the first or second embodiment, the present embodiment has the effect of reducing the press pressure required for expanding the cylindrical body 100 due to changes in the physical properties of the cylindrical body 100, because the cylindrical body 100 is expanded while heated to a high temperature. This makes it possible to reduce the size of the manufacturing equipment, and to manufacture scroll compressors at low cost. Furthermore, if the shell is molded at a high temperature and then cooled to room temperature, there is a concern that the molding precision may deteriorate due to thermal deformation. However, by subsequently expanding the shell using a mold that is made up of two cylindrical sections of different diameters and in which the two cylindrical sections are machined with high coaxial precision, it is possible to manufacture with high precision a middle shell 10 in which the inner diameter of cylindrical section 11 is larger than the inner diameter of cylindrical section 12. In addition, the surface of the expanded / contracted portion of the cylinder 100 heated by the heating means leaves heat marks, such as discoloration of the inner and outer surfaces of the cylinder 100 to a color different from that of the unheated surface.

[0034] Embodiment 4 In this embodiment, a scroll compressor including a middle shell 10 manufactured by the manufacturing method described in any of the first to third embodiments will be described. In any of the manufacturing methods described in the first to third embodiments, as already described in steps S04 and S05, a second die 103 is used to expand the cylindrical body 100 by pressing a second mandrel 104 into the second die 103. The second die 103 is composed of two cylindrical portions of different diameters, and the two cylindrical portions are machined with high coaxial precision. In this case, a plurality of linear machining marks 19 projecting toward the inner diameter are left along each parting surface A of the second die 103 shown in FIG. 20 through the two cylindrical portions 11 and 12 of different diameters on the inner periphery of the middle shell 10, excluding the area to be machined later, in a continuous line parallel to the axial direction, as shown in FIG. 21 . That is, the machining marks 19 are formed at equal intervals in the circumferential direction along the parting surface A and are connected by the two cylindrical portions 11 and 12 of different diameters. These machining marks are caused by the divided surfaces of the mold divided in the circumferential direction pressing against the inner surfaces of the cylindrical portions 11 and 12 when forming the cylindrical portions 11 and 12 having different diameters.

[0035] The compression mechanism 30 is housed in the frame 34 of the cylindrical portion 11 of the middle shell 10, the electric motor 40 is housed in the cylindrical portion 12, the central axis of the stator 42 coincides with the rotational axis of the rotor 41, and the main shaft 44, supported by the bearing metal 36 of the sliding bearing attached to the frame 34 of the cylindrical portion 11 and the rolling bearing 46 attached to the subframe 47 of the cylindrical portion 12, rotates on the rotational axis. The frame 34, subframe 47, and stator 42 can be assembled with high coaxial accuracy and high precision, improving the performance of the electric motor. This configuration provides a high-performance scroll compressor characterized by the high-precision assembly of the compression mechanism 30 and the electric motor 40. The hermetic compressor is not limited to a scroll compressor, and may be a rotary compressor or other type of compression mechanism.

[0036] Furthermore, since the inner diameter of cylindrical portion 11 is larger than the inner diameter of cylindrical portion 12, a small electric motor can be used, particularly for low GWP (Global Warming Potential) refrigerants which are often used at low pressure, and an inexpensive scroll compressor can be realized.

[0037] Although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not exemplified are conceivable within the scope of the technology disclosed in the specification, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with components of another embodiment. [Explanation of symbols]

[0038] 10: middle shell, 11: cylindrical portion, 12: cylindrical portion, 13: suction pipe, 19: machining marks, 21: discharge pipe, 22: upper shell, 23: lower shell, 24: leg plate, 30: compression mechanism, 31: discharge valve, 32: fixed scroll, 33: oscillating scroll, 34: frame, 35: muffler, 36: bearing metal, 40: electric motor, 41: rotor, 42: stator, 43: first balancer, 44: main shaft, 45: second balancer, 46: rolling bearing, 47: subframe, 100: cylindrical body, 101: first mold, 102: first core bar, 103: second mold, 104: second core bar, 111: third mold, 112: jig, 121: heating means.

Claims

1. A method for manufacturing a hermetic compressor comprising a middle shell composed of cylindrical portions of a plurality of diameters, a compression mechanism for compressing a refrigerant, and an electric motor for rotating a main shaft connected to the compression mechanism, wherein the compression mechanism and the electric motor are respectively fixed to the cylindrical portions of the middle shell of different diameters, the method further comprising a simultaneous tube expansion step for simultaneously expanding the cylindrical portions of the middle shell of different diameters from the inner periphery side of the cylinder using a die.

2. 2. The method for manufacturing a hermetic compressor according to claim 1, further comprising, before the simultaneous expansion step, a step of expanding or contracting a cylindrical body having a single diameter to form a cylindrical portion having a diameter different from the single diameter.

3. 3. The method for manufacturing a hermetic compressor according to claim 2, wherein the cylindrical body is heated when the cylindrical body having a single diameter is expanded or contracted to form a cylindrical portion having a diameter different from the single diameter.

4. A method for manufacturing a hermetic compressor, comprising: expanding a cylinder to form a first cylindrical portion having a first diameter that houses a compression mechanism portion that compresses a refrigerant; and a second cylindrical portion having a second diameter that houses an electric motor that rotates a main shaft that is connected to the compression mechanism portion, the method comprising: disposing a columnar mold that is divided into multiple pieces circumferentially and has two diameters in the longitudinal direction on the inner circumference of the cylinder; and moving the divided columnar mold horizontally radially from the center of the cylinder toward the outside in an axial direction of the cylinder, whereby the mold having two diameters expands the cylinder, thereby simultaneously forming the cylindrical portions of the first diameter and the second diameter in the axial direction.

5. a first step of expanding a single-diameter cylinder to form a first cylindrical portion having a first diameter and housing a compression mechanism portion that compresses a refrigerant, and a second cylindrical portion having a second diameter and housing an electric motor that rotates a main shaft connected to the compression mechanism portion; and a second step of expanding the single-diameter cylinder by disposing a columnar first mold that is divided into a plurality of pieces circumferentially and has one diameter in a longitudinal direction around the inner periphery of the cylinder, and moving the divided first mold portions radially in a horizontal direction relative to an axial direction of the cylinder from the center to the outside of the cylinder, thereby expanding the cylinder.

6. a first step of forming, from a cylinder of a single diameter, a first cylindrical portion having a first diameter and housing a compression mechanism portion that compresses a refrigerant, and a second cylindrical portion having a second diameter and housing an electric motor that rotates a main shaft connected to the compression mechanism portion, by disposing the first cylindrical portion on the inner periphery of a doughnut-shaped third mold that is divided into a plurality of pieces in the circumferential direction, and moving the divided third mold pieces horizontally and radially toward the center of the cylinder with respect to the axial direction of the cylinder, thereby contracting the cylinder; and a second step of disposing, on the inner periphery of the cylinder, a columnar first mold that is divided into a plurality of pieces in the circumferential direction and has two diameters in the longitudinal direction, by disposing the divided first mold pieces on the inner periphery of the cylinder, and moving the divided first mold pieces horizontally and radially from the center of the cylinder toward the outside with respect to the axial direction of the cylinder, thereby causing the first mold with two diameters to expand the inner surface of the cylinder and the inner surface of the cylinder that was contracted in the first step, thereby simultaneously forming the cylindrical portions of the first diameter and the second diameter in the axial direction.

7. 7. The method for manufacturing a hermetic compressor according to claim 5, wherein the first step is performed by heating the cylindrical body.

8. A hermetic compressor comprising a middle shell composed of cylindrical portions of a plurality of diameters, a compression mechanism portion for compressing a refrigerant, and an electric motor for rotating a main shaft connected to the compression mechanism portion, wherein the compression mechanism portion and the electric motor are respectively fixed to cylindrical portions of different diameters of the middle shell, characterized in that the inner periphery of the middle shell has linear machining marks parallel to the axial direction, and the machining marks are connected by cylindrical portions of a plurality of diameters.

9. 9. The hermetic compressor according to claim 8, wherein the middle shell has a plurality of the machining marks arranged at equal intervals in the circumferential direction.

10. 10. The hermetic compressor according to claim 8, wherein a heat mark is formed on a surface of an inner circumferential side or an outer circumferential side of the cylindrical portion having one of the plurality of diameters.

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