Induction motor, compressor having same, and method for manufacturing induction motor

Abstract

Disclosed are an induction motor, a compressor having same, and a method for manufacturing the induction motor. The induction motor includes a rotor. The rotor includes a rotor core and a plurality of rotor bars. The rotor core accommodates a crankshaft and is provided with a plurality of rotor bar accommodation portions radially outward of the crankshaft. The plurality of rotor bars are accommodated inside the rotor core through the plurality of rotor bar accommodation portions. The rotor bars include a first rotor bar, a second rotor bar, and an inclined portion. The first rotor bar has a first radial length. The second rotor bar has a second radial length greater than the first radial length. The inclined portion is formed to be inclined with respect to the crankshaft direction between the first rotor bar and the second rotor bar. Accordingly, the inclined portion may minimize the occurrence of non-molding of the rotor bar during aluminum die casting.

Description

Induction motor, compressor equipped with same, and method for manufacturing induction motor

[0001] The present invention relates to an induction motor capable of securing price and performance competitiveness and a compressor equipped with the same.

[0002] A compressor is a device that has an electric motor and a compression unit, and compresses refrigerant that has passed through an evaporator in a refrigeration and air conditioning device such as a refrigerator or air conditioner, and delivers the compressed refrigerant to a condenser.

[0003] Compressors can be divided into open and closed types depending on their sealing structure.

[0004] Hermetic compressors house the electric motor and compressor within a single, completely sealed housing (also called a “shell”).

[0005] Compressors can be classified into reciprocating, rotary, vane, and scroll types depending on how they compress the refrigerant.

[0006] The compression section of a reciprocating compressor includes a piston and a connecting rod. The piston reciprocates within the cylinder block. The connecting rod converts the rotational motion of the crankshaft, which is pressed into the rotor, into linear motion.

[0007] The piston receives power from the connecting rod and can compress the refrigerant stored in the cylinder block to a preset pressure.

[0008] Recently, as competition in the motor and reciprocating compressor industries has intensified, various research and development efforts are being conducted to secure cost competitiveness.

[0009] Induction motors have a simple structure and excellent manufacturability. Furthermore, they offer reduced maintenance costs. Furthermore, constant-speed induction motors do not require a controller. Consequently, induction motors are cost-effective and cost-effective, effectively securing cost competitiveness.

[0010] Due to the above-mentioned advantages, induction motors can be applied to reciprocating compressors.

[0011] In general, miniaturization of motors is inevitable to improve cost.

[0012] However, although miniaturization of the motor is advantageous in terms of cost, it is disadvantageous in terms of motor performance.

[0013] For example, as the motor size decreases, the rotor size also decreases. As the rotor size decreases, the magnetic flux saturation phenomenon occurs on the inner side of the rotor.

[0014] In particular, the reciprocating compressor adopts a one-sided support method in which a bearing or shaft support surrounding the crankshaft rotatably supports one side of the crankshaft.

[0015] A shaft receiving hole is formed inside the rotor to accommodate a crankshaft. A shaft support member supporting one side of the crankshaft is accommodated in the shaft receiving hole. The diameter of a portion of the shaft receiving hole that accommodates the shaft support member increases.

[0016] As a result, the inner surface of the rotor is formed into a two-stage structure including a first inner surface with a large inner diameter to accommodate the shaft support and a second inner surface with a small inner diameter that does not accommodate the shaft support.

[0017] When the radial length of the rotor bar accommodated inside the rotor core is constant along the stacking direction of the rotor core, the area of ​​the first region between the rotor bar and the first inner peripheral surface is smaller than the area of ​​the second region between the rotor bar and the second inner peripheral surface, so that the magnetic flux density in the first region is greater than the magnetic flux density in the second region.

[0018] Accordingly, the magnetic flux becomes saturated in the first region. Furthermore, the saturation of the magnetic flux has a number of adverse effects on the performance, structure, and reliability of the motor.

[0019] For example, when flux saturation occurs, the magnetic reluctance increases, the applied current increases, and this increases losses, leading to a sharp decline in motor performance and efficiency.

[0020] In relation to improving the performance of the motor, prior art patent CN 117559682 A (hereinafter, Patent Document 1) discloses a rotor punching, a rotor structure, and an electric motor.

[0021] Patent Document 1 can improve the starting characteristics of an induction motor by making the size of the rotor bar dual and alternately spacing out rotor bars of different sizes along the circumference of the rotor core.

[0022] However, the rotor bar structure of Patent Document 1 has a problem in that motor performance deteriorates as the amount of aluminum used decreases.

[0023] In addition, multiple grooves are formed on the outer surface of the rotor to improve the performance of the motor, but this requires additional processing of the grooves on the rotor, which increases the processing cost.

[0024] In addition, the above home has a problem of lowering structural stability and reliability.

[0025] The rotor structure of an induction motor for a compressor is disclosed in prior art patent KR 10-0751944 B1 (hereinafter, patent document 2) that improves the performance reduction of a motor due to miniaturization of the motor.

[0026] Patent Document 2 prevents the phenomenon of magnetic flux saturation due to uneven magnetic field area in a specific region of the rotor by forming a narrow cross-sectional slot area in areas with large shaft holes, while forming a wide cross-sectional slot area in areas with small shaft holes. This effectively improves motor performance degradation.

[0027] However, Patent Document 2 has a problem in that when molten aluminum metal is pressed into a slot by die casting to form a rotor bar, the rotor bar is not formed in a stepped portion where the cross-sectional area of ​​the slot is different.

[0028] The purpose of the present invention is to provide an induction motor having a structure capable of solving the above-described problems and a compressor having the same.

[0029] The first objective is to provide an induction motor with a structure that can secure cost competitiveness and a compressor equipped with the same.

[0030] The second purpose is to provide an induction motor having a structure that enables miniaturization of the motor while minimizing performance degradation of the motor, and a compressor equipped with the same.

[0031] The third purpose is to provide an induction motor having a structure capable of minimizing the occurrence of rotor bar misformation in stepped portions with different slot areas during aluminum die casting, and a compressor equipped with the same.

[0032] The fourth purpose is to provide an induction motor having a structure capable of reducing raw materials for the motor and a compressor equipped with the same.

[0033] As a result of intensive research, the inventors of the present invention have found that the first to fourth objectives of the present invention can be achieved by the following embodiments of the present invention.

[0034] In order to achieve the above-described purpose, (1) an induction motor according to the present invention includes a stator; and a rotor coupled to a crank shaft, and rotatably provided on the inside of the stator with a gap therebetween.

[0035] The rotor comprises a rotor core that accommodates the crankshaft and has a plurality of rotor bar receiving portions radially outward from the crankshaft; and a plurality of rotor bars that are accommodated on the inside of the rotor core through the plurality of rotor bar receiving portions. The rotor bar receiving portions and the rotor bars are arranged to be spaced apart from each other in the circumferential direction of the rotor core.

[0036] Each of the plurality of rotor bars may include a first rotor bar having a first radial length passing through a center of a circumferential width and extending in an axial direction of the crankshaft; a second rotor bar having a second radial length greater than the first radial length and passing through a center of the circumferential width, and extending in the axial direction from one side of the first rotor bar; and an inclined portion formed between the first rotor bar and the second rotor bar to be inclined with respect to the axial direction.

[0037] Through this, the slope can solve the problem of the rotor bar being underformed.

[0038] (2) In the above (1), the inclined portion may include a plurality of stepped portions formed at different radial distances from the outer surface of the crank shaft.

[0039] Through this, the above-mentioned multiple step parts can solve the problem of non-formation of the rotor bar.

[0040] (3) In the above (2), an induction motor in which the radial separation distance of the plurality of step portions increases from the second rotor bar to the first rotor bar.

[0041] Through this, the plurality of step portions can reduce the euro resistance of the rotor bar receiving portion.

[0042] (4) In the above (2), the step portion may include a first portion extending in the radial direction of the crank shaft; and a second portion extending in the axial direction from the first portion.

[0043] Through this, the bonding portion can be formed in a step shape.

[0044] (5) In the above (1), a shaft support member extending in the axial direction is further included to support one side of the crank shaft. The shaft support member is accommodated on one side of the rotor core. The first rotor bar may be arranged to overlap the shaft support member in the radial direction.

[0045] Through this, the first rotor bar can increase the radial thickness of the back yoke on one side of the rotor core in which the shaft support is received.

[0046] (6) In the above (5), the second rotor bar can be arranged so as not to overlap with the shaft support part in the radial direction.

[0047] Through this, the second rotor bar can increase the radial thickness of the back yoke on the other side of the rotor core coupled with the crank shaft.

[0048] (7) In the above (1), the rotor bar may include an outer curved portion adjacent to the outer surface of the rotor in the radial direction; an inner curved portion disposed opposite the outer curved portion in the radial direction and adjacent to the center of the rotor; and a plurality of flat portions connecting one end and the other end of the outer curved portion and the inner curved portion, respectively.

[0049] The length between the circumferential center of the first outer curved portion of the first rotor bar and the circumferential center of the first inner curved portion may be smaller than the length between the circumferential center of the second outer curved portion of the second rotor bar and the circumferential center of the second inner curved portion.

[0050] Through this, the radial thickness of the back yoke between the first rotor bar and the inner surface of the first rotor core can be increased, thereby minimizing magnetic flux saturation.

[0051] (8) In the above (1), each of the plurality of rotor bar receiving portions may include a first rotor bar receiving portion having a first radial length passing through the center of the circumferential width and extending in the axial direction of the crank shaft; a second rotor bar receiving portion having a second radial length that is larger than the first radial length and passing through the center of the circumferential width, and extending in the axial direction from one side of the first rotor bar receiving portion; and an inclined portion formed to be inclined with respect to the axial direction between the first rotor bar receiving portion and the second rotor bar receiving portion.

[0052] Through this, the inclined forming part can minimize the resistance during die casting of molten aluminum metal.

[0053] (9) In the above (8), the rotor bar receiving portion includes an outer surface portion adjacent to the outer surface of the rotor in the radial direction; an inner surface portion disposed to face the outer surface portion in the radial direction and adjacent to the center of the rotor; and a plurality of side surfaces connecting one end and the other end of each of the outer surface portion and the inner surface portion.

[0054] The radial length between the circumferential center of the outer surface of the first rotor bar receiving portion and the circumferential center of the inner surface may be smaller than the radial length between the circumferential center of the outer surface of the second rotor bar receiving portion and the circumferential center of the inner surface.

[0055] Through this, the radial length of the first rotor housing can be reduced to increase the magnetic flux flow area.

[0056] (10) In the above (8), the rotor core may include a first rotor core having a first inner diameter; and a second rotor core having a second inner diameter smaller than the first inner diameter and arranged on one side of the first rotor core.

[0057] Through this, even if the first rotor core accommodates the shaft support on the inside, the rotor and the shaft support can avoid interference with each other.

[0058] (11) In the above (10), the radial thickness B of the back yoke formed between the second rotor bar receiving portion and the inner surface of the second rotor core is

[0059] B=k*A, where k is a constant value in the range of 0.5 to 1.5, and A is the radial length of the second rotor bar.

[0060] Through this, the radial thickness of the back yoke of the second rotor core is formed to be 0.5 to 1.5 times the radial length of the second rotor bar, thereby securing an appropriate magnetic field area while minimizing performance degradation due to miniaturization of the motor.

[0061] (12) In the above (1), the radial length C of the first rotor bar is

[0062] C=k*A, where k is a constant value in the range of 0.5 to 1, and A is the radial length of the second rotor bar.

[0063] Through this, the radial length of the first rotor bar relative to the radial length of the second rotor bar can be limited to the above numerical range, thereby resolving the flux saturation problem.

[0064] (13) In the above (10), the stacking length D of the first rotor core is

[0065] D=k*(D+E), where k is a constant value greater than 0 and less than or equal to 0.5, and E is the stacking length of the second rotor core.

[0066] Through this, the stacking length of the first rotor core is limited to the above numerical range relative to the stacking length of the rotor core, thereby securing a stacking length of the first rotor core that the shaft support can accommodate, thereby increasing structural stability.

[0067] (14) In the above (2), the axial length J of the plurality of step portions is

[0068] H / 2≤J≤2*H, and H is the radial length of the plurality of step portions.

[0069] Through this, the axial length of the plurality of step portions can be limited to the numerical range compared to the radial length of the plurality of step portions, thereby minimizing the resistance to flow.

[0070] (15) In the above (2), the rotor core may include a first rotor core having a first inner diameter; and a second rotor core having a second inner diameter smaller than the first inner diameter and arranged on one side of the first rotor core.

[0071] The axial length I of the above first rotor bar is

[0072] I=k*F, where k is a constant value in the range of 1 to 1.2, and F is the axial length of the shaft support portion accommodated inside the first rotor core.

[0073] By doing so, by limiting the axial length of the first rotor bar relative to the axial length of the shaft support accommodated inside the first rotor core to the above numerical range, the radial thickness and axial length of the back yoke of the first rotor core can not only compensate for the area of ​​the shaft narrowed due to the shaft support, but also secure the structural stability of the crankshaft by the shaft support.

[0074] (16) A compressor according to the present invention comprises: a shell; an induction motor provided inside the shell according to any one of (1) to (15); and a compression unit that compresses refrigerant using power received from the induction motor.

[0075] (17) In the above (16), the compression unit may include a frame; a cylinder provided on one side of the frame along the radial direction of the crankshaft and forming a compression chamber; a piston that performs a linear reciprocating motion in the compression chamber; and a connecting rod that is coupled to the crankshaft and the piston and converts the rotational motion of the crankshaft into a linear motion of the piston.

[0076] Through this, the compression unit can convert the rotational motion of the crankshaft into reciprocating motion to compress the refrigerant.

[0077] (18) In the above (17), the compression member may include a shaft support member that is formed to protrude axially to surround one end of the crank shaft from the frame and rotatably supports one end of the crank shaft.

[0078] The above-mentioned shaft support member is accommodated on one side of the rotor core.

[0079] The first rotor bar and the shaft support member may be arranged to overlap in the radial direction of the crank shaft.

[0080] Through this, the shaft support member can secure the structural stability of the compressor, and the first rotor bar can secure the radial thickness of the back yoke that can minimize magnetic flux saturation.

[0081] (19) In the above (18), the second rotor bar can be arranged so as not to overlap with the shaft support part in the radial direction.

[0082] Through this, the second rotor bar can increase the radial thickness of the back yoke on the other side of the rotor core coupled with the crank shaft.

[0083] (20) In a method for manufacturing an induction motor according to any one of the above (1) to (15),

[0084] The method comprises the steps of: inserting a rotor core having a rotor bar receiving portion formed thereon into a mold; and forcing molten aluminum metal into the rotor bar receiving portion along an axial direction at a preset pressure. The rotor bar received in the rotor bar receiving portion can be formed by die casting the molten aluminum metal.

[0085] Through this, the inclined forming portion of the rotor bar receiving portion can minimize the resistance to flow during die casting of molten aluminum metal, thereby solving the problem of non-forming of the rotor bar.

[0086] According to an embodiment of the present invention, the following effects can be achieved.

[0087] First, as the radial length of the first rotor bar becomes smaller than the radial length of the second rotor bar, the radial thickness of the first back yoke arranged between the first rotor bar and the inner surface of the first rotor core may become larger than or equal to the radial thickness of the second back yoke arranged between the second rotor bar and the inner surface of the second rotor core.

[0088] Through this, even if the inner diameter of the first rotor core in which the shaft support is received is larger than the inner diameter of the second rotor core coupled with the crankshaft, the magnetic flux of the first back yoke can be prevented from becoming saturated as the radial length of the first rotor bar becomes smaller than the radial length of the second rotor bar.

[0089] Second, as the magnetic flux density of the first white yoke decreases, the current applied to the main winding decreases. Furthermore, this reduced current not only reduces losses but also improves motor performance.

[0090] Third, it can significantly contribute to miniaturization and cost reduction of motors without degrading motor performance.

[0091] Fourth, a slope can be formed between the first and second rotor bars.

[0092] The inclined portion is formed to be inclined at a preset angle with respect to the axial direction. The inclined portion may be formed to be inclined at a preset angle with respect to the first inner curved portion of the first rotor bar or the second inner curved portion of the second rotor bar.

[0093] An inclined portion is formed between the first rotor bar receiving portion and the second rotor bar receiving portion.

[0094] The inclined portion is formed to be inclined at a preset angle with respect to the axial direction. The inclined portion may be formed to be inclined at a preset angle with respect to the first inner side surface of the first rotor bar receiving portion or the second inner side surface of the second rotor bar receiving portion.

[0095] Through this, the inclined portion of the rotor bar can be formed by the inclined portion of the rotor bar receiving portion during aluminum die casting.

[0096] When molten aluminum is forced into the inclined portion of the rotor bar receiving section, the inclined portion can reduce flow resistance. Accordingly, when the inclined portion is formed in the inclined portion, the problem of under-formed rotor bars can be resolved.

[0097] Additionally, multiple steps can be formed between the first rotor bar and the second rotor bar.

[0098] The plurality of step portions may be formed to be inclined at a preset angle with respect to the axial direction. The plurality of step portions may be formed to be inclined at a preset angle with respect to the first inner curved surface of the first rotor bar or the second inner curved surface of the second rotor bar. The step portions may be formed in the shape of steps.

[0099] A step forming portion is formed between the first rotor bar receiving portion and the second rotor bar receiving portion.

[0100] The step-forming portion is formed to be inclined at a preset angle with respect to the axial direction. The step-forming portion may be formed to be inclined at a preset angle with respect to the first inner side surface of the first rotor bar receiving portion or the second inner side surface of the second rotor bar receiving portion.

[0101] Through this, the step portion of the rotor bar can be formed by the step forming portion of the rotor bar receiving portion during aluminum die casting.

[0102] When molten aluminum is forced into the stepped portion of the rotor bar receiving section, the stepped portion can reduce flow resistance. Accordingly, the problem of rotor bar under-formation can be resolved when the stepped portion is formed in the stepped portion.

[0103] FIG. 1 is a cross-sectional view showing a compressor according to one embodiment of the present invention.

[0104] Figure 2 is a conceptual diagram showing the compressor with the upper shell removed in Figure 1.

[0105] Figure 3 is a conceptual diagram showing the arrangement relationship between the induction motor and the compression unit in Figure 1.

[0106] Fig. 4 is a cross-sectional view taken along III-III in Fig. 3, and is a conceptual diagram showing the shaft support portion being accommodated inside the rotor.

[0107] Fig. 5 is a perspective view showing the inner diameter of the rotor core being dualized to avoid interference between the shaft support and the rotor in Fig. 4.

[0108] Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5.

[0109] Figure 7 is a plan view showing the rotor as seen from above in Figure 5.

[0110] Figure 8 is a bottom view showing the rotor as seen from below in Figure 5.

[0111] Figure 9 is a conceptual diagram showing a plurality of multi-stage structures formed between the first rotor bar and the second rotor bar having different radial lengths in Figure 4.

[0112] Fig. 10 is a conceptual diagram showing a multi-stage structure formed between the first rotor bar and the second rotor bar to improve the non-formability of the rotor bar in Fig. 9.

[0113] Figure 11 is a graph comparing the motor efficiency of the conventional and the present invention according to the inner diameter of the rotor.

[0114] Hereinafter, an induction motor and a compressor equipped with the same according to an embodiment of the present invention will be described in detail with reference to the attached drawings.

[0115] In the following description, descriptions of some components may be omitted to clarify the features of the present invention.

[0116] 1. Definition of Terms

[0117] Terms that include ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another.

[0118] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0119] As used herein, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0120] As used herein, “radial” or “radial” means a shape that extends out in all directions from a central point like spokes of a wheel.

[0121] “Axial” as used in the following description means the longitudinal direction of the crankshaft.

[0122] “Axial” as used in the following description may mean the vertical direction.

[0123] As used in the following description, “radial direction” means the longitudinal direction of a line segment from the center of a circle or cylinder to a point on the circumference (circumference).

[0124] As used in the following description, “circumferential” means the direction of the circumference of a circle.

[0125] The crankshaft used in the following explanation is a shaft that converts rotational motion into linear motion, and is mainly used to move the piston.

[0126] The journal used in the following description refers to a shaft part supported by bearings, etc.

[0127] 2. Description of the configuration of a compressor according to one embodiment of the present invention

[0128] (1) Description of the compressor configuration

[0129] In this embodiment, the compressor can be applied to a hermetic compressor.

[0130] In this embodiment, the compressor can be applied to a reciprocating compressor.

[0131] FIG. 1 is a cross-sectional view showing a compressor according to one embodiment of the present invention.

[0132] Figure 2 is a conceptual diagram showing the appearance of a compressor with the upper shell (101) removed from Figure 1.

[0133] Figure 3 is a conceptual diagram showing the arrangement relationship between the induction motor (110) and the compression unit (150) in Figure 1.

[0134] FIG. 4 is a cross-sectional view taken along line III-III in FIG. 3, and is a conceptual diagram showing the shaft support member (154) accommodated inside the rotor (130).

[0135] Figure 5 is a perspective view showing the inner diameter of the rotor core (131) being dualized to avoid interference between the shaft support (154) and the rotor (130) in Figure 4.

[0136] Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5.

[0137] Figure 7 is a plan view showing the rotor (130) in Figure 5 as viewed from above.

[0138] Figure 8 is a bottom view showing the rotor (130) in Figure 5 as seen from below.

[0139] A compressor according to the present embodiment may be configured to include a shell (100), a compression unit (150), and an induction motor (110).

[0140] The shell (100) forms the exterior of the compressor. An accommodation space is provided inside the shell (100). The accommodation space of the shell (100) may be configured to be sealed.

[0141] A compression member (150) and an induction motor (110) can be accommodated inside the shell (100).

[0142] The shell (100) may include a lower shell (102) and an upper shell (101).

[0143] The lower shell (102) may be formed in a semi-cylindrical or hemispherical shape. The lower shell (102) is placed at the bottom of the upper shell (101). The lower shell (102) may be formed to be open upward.

[0144] The upper shell (101) is combined to cover the upper portion of the lower shell (102). Through this, the upper shell (101) and the lower shell (102) can seal the receiving space of the shell (100).

[0145] The compression unit (150) may be configured to include a cylinder block (151) and a piston (156).

[0146] The cylinder block (151) can be placed on the upper side of the induction motor (110). The cylinder block (151) can be coupled to the upper side of the stator (120) of the induction motor (110) and be elastically supported by the shell (100).

[0147] The cylinder block (151) may be configured to include a frame (152), a plurality of stator coupling parts (153), a shaft support part (154), and a cylinder (155).

[0148] The frame (152) may extend radially perpendicular to the axial direction. The frame (152) may be configured to include a hub (1521) and a radially extending portion (1522). The hub (1521) may be formed in a circular shape. The radially extending portion (1522) may extend radially from the outer periphery of the hub (1521).

[0149] The stator coupling portion (153) may be formed to protrude downward from the outer end of the radial extension portion (1522) toward the stator (120) to be described later. The stator coupling portion (153) may be coupled to the stator (120). The stator coupling portion (153) may be coupled to the stator (120) using a fastening bolt.

[0150] A plurality of stator coupling parts (153) can be arranged at equal intervals in the circumferential direction of the hub (1521).

[0151] Through this, the cylinder block (151) can be elastically supported on the lower shell (102) together with the stator (120). The cylinder block (151) can be supported on the stator (120) at three points by the stator coupling part (153).

[0152] The shaft support member (154) may extend axially from the hub (1521) of the frame (152). An shaft receiving hole may be formed to penetrate axially on the inside of the shaft support member (154).

[0153] The crankshaft (139) described later is penetratedly connected to the shaft support (154) through the shaft receiving hole, and can be penetratedly connected to the hub (1521) of the frame (152) and rotatably mounted.

[0154] A journal bearing may be placed or omitted between the inner surface of the shaft support member (154) and the outer surface of the crankshaft (139). In this embodiment, the journal bearing is omitted.

[0155] The shaft support (154) surrounds the crankshaft (139), and the outer surface of the crankshaft is in surface contact with the outer surface of the shaft support (154). Through this, the crankshaft can be rotatably supported by the shaft support (154). The shaft support (154) can restrict the crankshaft (139) from moving in the radial direction.

[0156] The shaft support (154) is relatively inexpensive compared to conventional ball bearings, which can significantly contribute to cost improvement. An oil film can be formed between the inner surface of the shaft support (154) and the outer surface of the crankshaft (139). Through this, the shaft support (154) can perform the function of a journal bearing.

[0157] An oil passage (1391) is formed inside the crankshaft (139). An oil passage groove (1392) may be formed in a spiral direction on the outer surface of the crankshaft (139). The oil passage groove (1392) may be connected to the oil passage (1391).

[0158] An oil pump (140) may be provided at the lower end of the crankshaft (139). The upper end of the oil pump (140) may be connected to the oil passage (1391) of the crankshaft (139). The lower end of the oil pump (140) may be arranged to be submerged in oil stored in the lower shell (102).

[0159] Through this, the oil pump (140) can pump oil and supply oil to the inner surface of the shaft support member (154) through the oil passage (1391) and oil passage groove (1392) of the crankshaft (139).

[0160] A cylinder (155) is provided on one edge of the frame (152). The cylinder (155) may be arranged eccentrically radially outward from the center of the frame (152).

[0161] A cylindrical hollow portion is formed inside the cylinder (155). The cylinder (155) may extend radially with respect to the crankshaft (139). The hollow portion may be formed to penetrate the shell (100) in the front-rear direction. The hollow portion may penetrate radially from the center of the frame (152).

[0162] A piston (156) may be accommodated inside a cylinder (155). The rear side of the piston (156) may be formed with an open structure, and the front side of the piston (156) may be formed with a closed structure. Here, the front side of the piston (156) is arranged facing in the opposite direction of a connecting rod (143) to be described later, and the rear side of the piston (156) is arranged facing the connecting rod (143).

[0163] A connecting pin (157) may be provided on the rear side of the piston (156). The connecting pin (157) may be coupled with the piston coupling portion (145) of the connecting rod (143). Through this, the piston (156) may receive driving force from the induction motor (110) through the connecting rod (143).

[0164] A valve assembly (160) may be coupled to the front side of the cylinder (155). The front side of the cylinder (155) is arranged in the opposite direction to the connecting rod (143). The front side of the piston (156) may form a compression chamber (1551) inside the cylinder (155) together with the valve assembly (160).

[0165] The suction / discharge unit may be configured to include a valve assembly (160), a suction muffler (165), and a discharge muffler (169). The valve assembly (160) and the suction muffler (165) may be sequentially coupled from the outer opening end of the cylinder (155).

[0166] The valve assembly (160) may include a valve plate (161), an intake valve (162), a discharge valve (163), and a discharge cover (164).

[0167] The valve plate (161) is installed to cover the front opening of the compression chamber (1551). The valve plate (161) can be fastened to the cylinder block (151).

[0168] A valve plate (161) may be provided with an inlet and a plurality of outlets. The inlet may be formed through the center of the valve plate (161). The outlet may be formed through the periphery of the inlet. The plurality of outlets may be arranged at predetermined intervals along the periphery of the inlet.

[0169] The suction valve (162) can be rotatably mounted on the rear side of the valve plate (161) toward the piston (156). The suction valve (162) is configured to open and close the suction port. The suction valve (162) can be elastically deformed depending on the pressure difference between the compression chamber (1551) and the discharge chamber, which will be described later.

[0170] The discharge valve (163) can be rotatably mounted on the front side of the valve plate (161) in the opposite direction to the piston (156). The discharge valve (163) is configured to open and close the discharge port. The discharge valve (163) can be elastically deformed depending on the pressure difference between the compression chamber (1551) and the discharge chamber, which will be described later.

[0171] The suction valve (162) and the discharge valve (163) can be selectively opened and closed in opposite directions. The suction valve (162) can be opened and the discharge valve (163) can be closed during the suction stroke of the piston (156). Alternatively, the suction valve (162) can be closed and the discharge valve (163) can be opened during the discharge stroke of the piston (156).

[0172] The discharge cover (164) can be fastened to cover the compression chamber (1551) at the outer opening end of the cylinder. The discharge chamber can be formed to be sunken in the inner side of the discharge cover (164).

[0173] The suction muffler (165) may have a suction space formed therein. The inlet of the suction muffler (165) may be connected to the suction pipe (166) and the outlet of the suction muffler (165) may be connected to the suction side of the valve assembly (160).

[0174] The suction muffler (165) can be fixed to the valve assembly (160). The suction muffler (165) can be connected to the suction port of the valve plate (161). The suction muffler (165) can transfer the refrigerant sucked through the suction pipe (166) to the compression chamber (1551) of the cylinder (155).

[0175] The discharge muffler (169) can be installed detachably from the cylinder block (151). A discharge space can be formed inside the discharge muffler (169). The inlet of the discharge muffler (169) can be connected to the discharge side of the valve assembly (160). The outlet of the discharge muffler can be connected to a discharge pipe.

[0176] An induction motor (110) may include a stator (120) and a rotor (130).

[0177] The stator (120) can be accommodated in the accommodation space of the shell (100). The stator (120) can be elastically supported on the bottom surface of the lower shell (102).

[0178] The rotor (130) can be rotatably installed on the inside of the stator (120) with a gap (138) therebetween.

[0179] The stator (120) may include a stator core (121) and a stator coil (123).

[0180] The stator core (121) can be formed by laminating and bonding multiple electrical steel plates. The stator core (121) can be formed in a square shape.

[0181] A plurality of slots (122) may be formed on the inside of the stator core (121). The slots (122) may be formed to penetrate the stator (120) along the axial direction. The plurality of slots are arranged to be spaced apart from each other in the circumferential direction of the stator core.

[0182] The stator coil (123) can be wound on the stator core (121) through a slot (122). In the case of a single-phase induction motor (110), the stator coil (123) can be composed of a main winding (not shown) and a sub-winding (not shown).

[0183] The main winding and the sub-winding can be arranged perpendicular to each other along the circumference of the stator core (121). The main winding and the sub-winding can be arranged at a 90-degree interval from each other along the circumference of the stator core (121).

[0184] The stator core (121) can be fixed to the lower part of the cylinder block (151) by a fastening bolt through the stator coupling part (153).

[0185] The stator core (121) can be elastically supported by a support spring (103) on the bottom surface of the lower shell (102). Through this, the support spring (103) can suppress vibrations generated during operation of the compressor from being directly transmitted to the shell (100).

[0186] A rotor receiving hole may be formed along the axial direction on the inside of the stator core (121). The rotor receiving hole may be formed in a cylindrical shape. The stator (120) may be configured to surround the rotor (130). The rotor (130) may be received in the rotor receiving hole of the stator core (121).

[0187] The rotor (130) may include a rotor core (131) and a plurality of rotor bars (134). The plurality of rotor bars (134) are mounted on the inside of the rotor core (131).

[0188] The rotor core (131) can be formed by laminating and bonding multiple electrical steel plates. The rotor core (131) can be formed in a cylindrical shape.

[0189] The rotor core (131) may include a first shaft hole (1321), a second shaft hole (1322), and a plurality of rotor bar receiving portions (133).

[0190] A first shaft hole (1321) may be formed to penetrate axially through the center of the rotor core (131). The first shaft hole (1321) may be press-fitted to at least a portion of the crankshaft (139). The first shaft hole (1321) may be located at the lower portion of the rotor core (131).

[0191] The crankshaft (139) can be coupled to the rotor core (131) through the first shaft hole (1321).

[0192] The second shaft hole (1322) is positioned above the first shaft hole (1321). The second shaft hole (1322) is configured to accommodate the shaft support member (154). The diameter of the second shaft hole (1322) may be formed to be larger than the diameter of the first shaft hole (1321).

[0193] The second shaft hole (1322) can accommodate at least a portion of the shaft support portion (154). The second shaft hole (1322) can form a step radially outward from the first shaft hole (1321). The second shaft hole (1322) can be located on the upper portion of the rotor core (131). A gap can be formed between the inner surface of the second shaft hole (1322) and the outer surface of the shaft support portion (154).

[0194] Through this, the rotor core (131) can rotate with respect to the shaft support (154).

[0195] The inner surface of the rotor core (131) can be formed into a multi-stage structure. In this embodiment, the inner surface of the rotor core (131) is shown to be formed into a two-stage structure.

[0196] The inner surface of the rotor core (131) may include a first inner surface and a second inner surface. The inner surface of the rotor core (131) may be formed in a cylindrical shape.

[0197] The first inner surface has a first inner diameter. The first inner surface can form a second shaft hole (1322) of the rotor core (131). A gap can be formed between the first inner surface and the outer surface of the shaft support member (154).

[0198] The second inner surface has a second inner diameter. The second inner diameter is smaller than the first inner diameter. The second inner surface can form a first shaft hole (1321) of the rotor core (131). The second inner surface is in surface contact with the crankshaft, and the crankshaft (139) can be press-fitted to the second inner surface.

[0199] A step (1344) may be formed between the first inner surface and the second inner surface. The step (1344) may extend radially between the lower end of the first inner surface and the upper end of the second inner surface. With respect to the step (1344), the first inner surface may be positioned on the upper side, and the second inner surface may be positioned on the lower side.

[0200] A plurality of rotor bar receiving portions (133) are provided on the inside of the rotor core (131). The rotor bar receiving portions (133) may be formed to penetrate along the axial direction. The plurality of rotor bar receiving portions (133) may be arranged to be spaced apart from each other along the circumferential direction of the rotor core (131).

[0201] The rotor bar (134) may extend in the axial direction of the rotor core (131). The rotor bar (134) may be formed of a conductor such as aluminum or an aluminum alloy. The rotor bar (134) may be filled into the rotor bar receiving portion (133) by die casting.

[0202] The rotor bar (134) can be coupled to the interior of the rotor core (131) through the rotor bar receiving portion (133). A plurality of rotor bars (134) can be provided. The plurality of rotor bars (134) can be arranged spaced apart from each other along the circumference of the rotor core (131).

[0203] The end ring (137) can extend in the circumferential direction. The end ring (137) can prevent the rotor bar (134) from axially detaching from the rotor bar receiving portion (133). The end ring is configured to electrically connect a plurality of rotor bars (134).

[0204] A first end ring (137) can be coupled to the upper end of the rotor core (131). A second end ring (137) can be coupled to the lower end of the rotor core (131).

[0205] Through this, when an external power source is applied to the stator coil (123), a magnetic field can be formed around the stator coil (123). The rotor (130) can rotate by electromagnetic interaction with the stator (120). The induction motor (110) can generate power for the reciprocating motion of the compression unit (150).

[0206] An eccentric shaft (141) is provided at the upper end of the crankshaft (139). The eccentric shaft (141) may be arranged eccentrically to one side in the radial direction from the upper end of the crankshaft (139). A counterweight (142) may be formed to protrude radially outward from the upper end of the crankshaft (139). The eccentric shaft (141) may protrude upward from one side of the counterweight (142).

[0207] The counterweight (142) can be arranged at the upper end of the crankshaft (139) in the opposite direction to the eccentric shaft (141) with respect to the crankshaft (139). The counterweight (142) is a weight.

[0208] Through this, the counterweight (142) can balance the center of rotation with respect to the eccentric shaft (141) based on the crank shaft (139).

[0209] A connecting rod (143) may be placed between the induction motor (110) and the compression unit (150). The connecting rod (143) is configured to convert the rotational motion of the induction motor (110) into the reciprocating motion of the compression unit (150).

[0210] An eccentric shaft coupling portion (144) may be formed in a ring shape at one end of the connecting rod (143). The eccentric shaft coupling portion (144) may be wrapped around the eccentric shaft (141). The eccentric shaft (141) may be accommodated inside the eccentric shaft coupling portion (144), so that the eccentric shaft (141) and the eccentric shaft coupling portion (144) may be coupled to each other.

[0211] A piston coupling portion (145) may be formed in a ring shape at the other end of the connecting rod (143). The piston coupling portion (145) is configured to surround a connecting pin (157). The connecting pin (157) may be coupled to the inside of the piston (156).

[0212] The connecting pin (157) can be connected to the piston connecting portion (145) by passing through the piston connecting portion (145) in the vertical direction. The connecting rod (143) can be connected to the piston (156).

[0213] Through this, the eccentric shaft (141) can rotate along the crank shaft (139) with the crank shaft (139) as the center. The connecting rod (143) can convert the rotational motion of the eccentric shaft (141) into the reciprocating motion of the piston (156).

[0214] The compressor's operating process is as follows.

[0215] When power is applied to the stator coil (123), a rotating magnetic field is generated around the coil. The stator (120) and the rotor (130) interact electromagnetically, and an induced current is induced in the rotor (130) by the rotating magnetic field, thereby inducing a rotating magnetic field. Through this, the rotor (130) can rotate with respect to the stator (120).

[0216] In particular, in the case of a single-phase induction motor (110), when a single-phase AC power source is applied to the main winding and sub-winding of the stator coil (123), the phase of the current flowing in the sub-winding is 90 degrees ahead of the phase of the current flowing in the main winding by the capacitor (170), and a rotating magnetic field is generated.

[0217] Here, the method of starting a single-phase induction motor (110) by connecting a capacitor (also called a condenser) to the sub-winding to flow a current 90 degrees ahead and generating a rotating magnetic field by the current flowing in the main winding and the sub-winding can be named a capacitor-starting type. The sub-winding can be named a starting winding.

[0218] The crankshaft (139) rotates together with the rotor (130). One side of the connecting rod (143) is coupled with the eccentric shaft (141) of the crankshaft (139) and rotates along the rotational motion of the eccentric shaft (141). The other side of the connecting rod (143) is coupled with the piston (156) and thus repeatedly moves forward and backward in the radial direction of the crankshaft (139).

[0219] The piston (156) can reciprocate forward and backward inside the cylinder (155). When the piston (156) moves backward in the cylinder (155), the volume of the compression chamber (1551) expands and the pressure of the compression chamber (1551) decreases. The refrigerant filled in the suction muffler (165) passes through the suction valve (162) of the valve assembly (160) and is sucked into the compression chamber (1551).

[0220] Conversely, when the piston (156) moves forward in the cylinder (155), the volume of the compression chamber (1551) is compressed and the pressure increases. The refrigerant filled in the compression chamber (1551) is compressed and discharged through the discharge valve (163) of the valve assembly (160) into the discharge chamber of the discharge cover (164).

[0221] The discharged refrigerant moves to the discharge space of the discharge muffler (169) through the loop pipe (168) and then passes through the loop pipe (168) and the discharge pipe (167) to be discharged to the refrigeration cycle, repeating a series of processes.

[0222] (2) Description of the two-stage structure of the rotor bar (134)

[0223] The rotor bar (134) can be formed by pressing molten aluminum metal into the rotor bar receiving portion (133) of the rotor core (131) through die casting. The rotor bar receiving portion (133) of the rotor core (131) and the rotor bar (134) are formed to correspond to each other. Here, corresponding means that the shape and size are the same or similar to each other.

[0224] The rotor core (131) may include a plurality of teeth (1311). The plurality of teeth (1311) may extend radially outward from the back yoke (1312, 1313) toward the outer surface of the rotor core (131).

[0225] The rotor housing (133) and teeth (1311) are arranged alternately along the circumferential direction.

[0226] The rotor bar receiving portion (133) is arranged adjacent to the outer surface of the rotor core (131). The rotor bar receiving portion (133) may include an outer surface portion (1331), an inner surface portion (1332), and a side portion. The outer surface portion (1331) is formed concavely toward the outer surface of the rotor core (131). The outer surface portion (1331) is formed in an arc shape.

[0227] The inner side portion (1332) is arranged radially opposite to the outer side portion (1331). The inner side portion (1332) is formed concavely toward the inner surface of the rotor core (131). The inner side portion (1332) is formed in an arc shape. The radius of curvature of the inner side portion (1332) may be formed smaller than the radius of curvature of the outer side portion (1331).

[0228] The side portions (1333, 1334) may be composed of a left side portion (1333) and a right side portion (1334). The left side portion (1333) is configured to connect one end of the outer side portion (1331) and one end of the inner side portion (1332). The left side portion (1333) may be formed to be inclined at a preset angle with respect to an imaginary center line that passes radially through the center of the outer side portion (1331) and the center of the inner side portion (1332).

[0229] The right side portion (1334) is configured to connect the other end of the outer side portion (1331) and the other end of the inner side portion (1332). The right side portion (1334) may be formed to be inclined at a preset angle with respect to an imaginary center line that passes radially through the center of the outer side portion (1331) and the center of the inner side portion (1332).

[0230] The rotor bar (134) may include an outer curved portion (1341), an inner curved portion (1342), and a flat portion (13431, 13432).

[0231] The outer curved surface (1341) forms the outer surface of the rotor bar (134). The outer curved surface (1341) is formed convexly toward the outer surface of the rotor core (131). The outer curved surface (1341) is formed in an arc shape.

[0232] The outer curved surface (1341) is arranged to face the outer curved surface (1341) of the rotor bar receiving portion (133).

[0233] The outer curved surface (1341) is positioned adjacent to the outer surface of the rotor (130) in the radial direction.

[0234] The inner curved surface (1342) forms the inner surface of the rotor bar (134). The inner curved surface (1342) is arranged to be radially opposite to the outer curved surface (1341). The inner curved surface (1342) is formed convexly toward the inner surface of the rotor core (131).

[0235] The inner curved surface (1342) is positioned adjacent to the center of the rotor (130).

[0236] The inner curved surface (1342) is formed in an arc shape. The radius of curvature of the inner curved surface (1342) may be formed to be smaller than the radius of curvature of the outer curved surface (1341).

[0237] The flat portions (13431, 13432) form the side surfaces of the rotor bar (134). The flat portions (13431, 13432) extend radially. The flat portions (13431, 13432) may be composed of a left flat portion (13431) and a right flat portion (13432). The left flat portion (13431) is configured to connect one end of the outer curved portion (1341) and one end of the inner curved portion (1342). The left flat portion (13431) may be formed to be inclined at a preset angle with respect to an imaginary center line that passes radially through the center of the outer curved portion (1341) and the center of the inner curved portion (1342).

[0238] The right-side flat portion (13432) is configured to connect the other end of the outer curved portion (1341) and the other end of the inner curved portion (1342). The right-side flat portion (13432) can be formed to be inclined at a preset angle with respect to an imaginary center line that passes radially through the center of the outer curved portion (1341) and the center of the inner curved portion (1342).

[0239] The rotor core (131) can be divided into a first rotor core (131a) and a second rotor core (131b) along the axial direction.

[0240] The first rotor core (131a) may be placed on the upper side of the second rotor core (131b). A second shaft hole (1322) may be formed inside the first rotor core (131a). A first shaft hole (1321) may be formed inside the second rotor core (131b).

[0241] The rotor bar (134) and the rotor bar receiving portion (133) can each be formed into a two-stage structure.

[0242] The inner surface (1332) of the rotor housing (133) may include a first inner surface (13321) and a second inner surface (13322).

[0243] The first inner side portion (13321) is arranged on the upper side of the second inner side portion (13322). The first inner side portion (13321) of the rotor bar receiving portion (133) is arranged to overlap radially with the first inner surface of the first rotor core (131a).

[0244] The second inner side surface (13322) is arranged to overlap radially with the second inner surface of the second rotor core (131b).

[0245] The distance between the outer surface (1331) of the rotor bar receiving portion (133) and the first inner surface (13321) is smaller than the distance between the outer surface (1331) of the rotor bar receiving portion (133) and the second inner surface (13322).

[0246] The rotor bar (134) may be composed of a first rotor bar (134a) and a second rotor bar (134b). The first rotor bar (134a) may be placed above the second rotor bar (134b).

[0247] The first radial length passing through the center of the circumferential width of the first rotor bar (134a) is smaller than the second radial length passing through the center of the circumferential width of the second rotor bar (134b).

[0248] The inner curved surface (1342) of the rotor bar (134) may include a first inner curved surface (13421) and a second inner curved surface (13422).

[0249] The first inner curved surface (13421) is arranged on the upper side of the second inner curved surface (13422). The first inner curved surface (13421) of the first rotor bar (134a) is arranged to overlap radially with the first inner peripheral surface of the first rotor core (131a). The first inner curved surface (13421) of the first rotor bar (134a) and the first inner side surface (13321) of the first rotor bar receiving portion (133a) are arranged to overlap radially.

[0250] The second inner curved surface (13422) is arranged to overlap radially with the second inner peripheral surface of the second rotor core (131b). The second inner curved surface (13422) of the second rotor bar (134b) and the second inner side surface (13322) of the second rotor bar receiving portion (133b) are arranged to overlap radially.

[0251] A first radial length passing through the circumferential center of the first outer curved portion (13411) of the first rotor bar (134a) and the circumferential center of the first inner curved portion (13421) is smaller than a second radial length passing through the circumferential center of the second outer curved portion (13412) of the second rotor bar (134b) and the circumferential center of the second inner curved portion (13422). The first outer curved portion (13411) and the second outer curved portion (13412) may form the same curved surface along the axial direction of the rotor bar (134).

[0252] A back yoke (1312, 1313) may be arranged between the inner surface (1332) of the rotor housing (133) and the inner surface of the rotor core (131). The back yoke (1312, 1313) may extend radially. The back yoke (1312, 1313) may extend circumferentially. The back yoke (1312, 1313) may be formed in a cylindrical shape.

[0253] The white yoke (1312, 1313) can be composed of the first white yoke (1312) and the second white yoke (1313).

[0254] The first back yoke (1312) can be placed between the first inner curved surface (13421) of the first rotor bar receiving portion (133a) and the first inner peripheral surface of the first rotor core (131a).

[0255] The second back yoke (1313) can be placed between the second inner curved surface (13422) of the second rotor bar receiving portion (133b) and the second inner peripheral surface of the second rotor core (131b).

[0256] According to this configuration, the length between the first outer curved surface (13411) and the first inner curved surface (13421) of the first rotor bar (134a) becomes smaller than the length between the second outer curved surface (13412) and the second inner curved surface (13422) of the second rotor bar (134b), so that the radial thickness of the first back yoke (1312) can become greater than or equal to the radial thickness of the second back yoke (1313).

[0257] Through this, even if the inner diameter of the first inner surface of the first rotor core (131a) in which the shaft support member (154) is received is larger than the inner diameter of the second inner surface of the second rotor core (131b), the magnetic flux of the first back yoke (1312) can be prevented from becoming saturated as the first radial length passing through the center of the circumferential width of the first rotor bar (134a) becomes smaller than the second radial length passing through the center of the circumferential width of the second rotor bar (134b).

[0258] Additionally, as the magnetic flux density of the first white yoke (1312) decreases, the current applied to the main winding decreases. Furthermore, as the applied current decreases, not only does loss decrease, but motor performance can also improve.

[0259] In addition, it can greatly contribute to miniaturization and cost reduction of motors without degrading motor performance.

[0260] Referring to FIGS. 6 to 8, the radial thickness B of the second back yoke (1313) has the following relationship with the radial length A of the second rotor bar (134b).

[0261] B=k*A

[0262] k=0.5~1.5 (constant value), A: radial length of the second rotor bar (134b), B: radial thickness of the second back yoke (1313)

[0263] The radial length C of the first rotor bar (134a) has the following relationship with the radial length A of the second rotor bar (134b).

[0264] C=k*A

[0265] k=0.5~1 (constant value), A: radial length of the second rotor bar (134b), C: radial length of the first rotor bar (134a)

[0266] The stacking length D of the first rotor core (131a) has the following relationship with respect to the stacking length of the rotor core (131) (sum of the stacking lengths of the first and second rotor cores (131b)).

[0267] D=k*(D+E)

[0268] k=0~0.5 (constant value>0), D: stacking length of the first rotor core (131a), E: stacking length of the second rotor core (131b)

[0269] However, the two-stage structure of the above rotor bar (134) has the following problems.

[0270] A step (1344) exists between the first rotor bar (134a) and the second rotor bar (134b) due to a difference in radial length. Alternatively, a step (1344) exists between the first rotor bar receiving portion (133a) and the second rotor bar receiving portion (133b) due to a difference in radial length.

[0271] The step (1344) can extend radially between the lower end of the first rotor bar (134a) and the upper end of the second rotor bar (134b).

[0272] The step (1344) is perpendicular to the first inner curved surface (13421) of the first rotor bar (134a). The step (1344) is perpendicular to the second inner curved surface (13422) of the second rotor bar (134b).

[0273] Due to this, when the molten aluminum metal is forced into the rotor bar receiving portion (133) at high pressure by die casting, a problem occurs in which a resistance occurs at the step (1344) and a part of the step (1344) of the rotor bar (134) is not formed.

[0274] To solve this problem, the present invention can form an inclined portion (135) between the first rotor bar (134a) and the second rotor bar (134b).

[0275] The inclined portion (135) is formed to be inclined at a preset angle with respect to the axial direction. The inclined portion (135) may be formed to be inclined at a preset angle with respect to the first inner curved portion (13421) of the first rotor bar (134a) or the second inner curved portion (13422) of the second rotor bar (134b).

[0276] The inclined portion (135) can be formed in a curved shape to correspond to the first inner curved portion (13421) or the second inner curved portion (13422).

[0277] One end of the inclined portion (135) is connected to the first inner curved portion (13421) of the first rotor bar (134a). The other end of the inclined portion (135) is connected to the second inner curved portion (13422) of the second rotor bar (134b).

[0278] An inclined portion (1335) is formed between the first rotor bar receiving portion (133a) and the second rotor bar receiving portion (133b).

[0279] The inclined portion (1335) is formed to be inclined at a preset angle with respect to the axial direction. The inclined portion (1335) may be formed to be inclined at a preset angle with respect to the first inner side portion (13321) of the first rotor bar receiving portion (133a) or the second inner side portion (13322) of the second rotor bar receiving portion (133b).

[0280] The inclined portion (1335) can be formed in a curved shape to correspond to the first inner side portion (13321) or the second inner side portion (13322).

[0281] One end of the slope forming portion (1335) is connected to the first inner side portion (13321) of the first rotor receiving portion (133a). The other end of the slope forming portion (1335) is connected to the second inner side portion (13322) of the second rotor receiving portion (133b).

[0282] Through this, the inclined portion (135) of the rotor bar (134) can be formed by the inclined portion (1335) of the rotor bar receiving portion (133) during aluminum die casting.

[0283] When molten aluminum metal is pushed into the inclined portion (1335) of the rotor bar receiving portion (133), the inclined portion (1335) can reduce flow resistance. Accordingly, when the inclined portion (135) is formed in the inclined portion (1335), the problem of under-forming of the rotor bar (134) can be resolved.

[0284] Figure 9 is a conceptual diagram showing a plurality of multi-stage structures formed between the first rotor bar (134a) and the second rotor bar (134b) having different radial lengths in Figure 4.

[0285] Fig. 10 is a conceptual diagram showing a multi-stage structure formed between the first rotor bar (134a) and the second rotor bar (134b) to improve the non-formed shape of the rotor bar (134) in Fig. 9.

[0286] In this embodiment, a plurality of step portions (136) can be formed between the first rotor bar (134a) and the second rotor bar (134b).

[0287] The plurality of step portions (136) may be formed to be inclined at a preset angle with respect to the axial direction. The plurality of step portions (136) may be formed to be inclined at a preset angle with respect to the first inner curved surface (13421) of the first rotor bar (134a) or the second inner curved surface (13422) of the second rotor bar (134b).

[0288] The step portion (136) may be formed in a step shape. The step portion (136) may be configured to include a first portion (1361) and a second portion (1362). The first portion (1361) may extend radially. The second portion (1362) may extend axially. The first portion (1361) and the second portion (1362) may form one step portion (136).

[0289] By connecting the vertices of each of the plurality of step portions (136) with a line, a single inclined line can be formed. The inclined line extends at a predetermined angle with respect to the axial direction.

[0290] The step portion (136) can be formed in a curved shape to correspond to the first inner curved portion (13421) or the second inner curved portion (13422).

[0291] The plurality of step portions (136) may be composed of the first step portion (136a) to the Nth step portion from the top to the bottom. Here, N is a natural number greater than or equal to 2. In the present embodiment, the plurality of step portions (136) are shown composed of the first step portion (136a) to the third step portion (136c). Among the plurality of step portions (136), the first part (1361) of the first step portion (136a) is connected to the first inner curved part (13421) of the first rotor bar (134a). Among the plurality of step portions (136), the second part (1362) of the third step portion (136c) is connected to the second inner curved part (13422) of the second rotor bar (134b).

[0292] A step forming portion (1336) is formed between the first rotor bar receiving portion (133a) and the second rotor bar receiving portion (133b).

[0293] The step-forming portion (1336) is formed to be inclined at a preset angle with respect to the axial direction. The step-forming portion (1336) may be formed to be inclined at a preset angle with respect to the first inner side portion (13321) of the first rotor bar receiving portion (133a) or the second inner side portion (13322) of the second rotor bar receiving portion (133b).

[0294] The step-forming portion (1336) can be formed in a curved shape to correspond to the first inner side portion (13321) or the second inner side portion (13322).

[0295] One end of the first step-forming portion (1336) among the plurality of step-forming portions (1336) is connected to the first inner side portion (13321) of the first rotor receiving portion (133a). The other end of the third step-forming portion (1336) among the plurality of step-forming portions (1336) is connected to the second inner side portion (13322) of the second rotor receiving portion (133b).

[0296] Through this, the step portion (136) of the rotor bar (134) can be formed by the step forming portion (1336) of the rotor bar receiving portion (133) during aluminum die casting.

[0297] When molten aluminum metal is pushed into the step-forming portion (1336) of the rotor bar receiving portion (133), the step-forming portion (1336) can reduce flow resistance. Accordingly, when the step portion (136) is formed in the step-forming portion (1336), the problem of under-forming of the rotor bar (134) can be resolved.

[0298] Referring to FIGS. 9 and 10, the axial length J of the plurality of step portions (136) has the following relationship with the radial length H of the plurality of step portions (136).

[0299] H / 2≤J≤2*H

[0300] H: Radial length of multiple steps (136), J: Axial length of multiple steps (136)

[0301] The axial length I of the first rotor bar (134a) has the following relationship with respect to the axial length F of the shaft support member (154) accommodated inside the first rotor core (131a).

[0302] I=k*F

[0303] k: constant value in the range of 1 to 1.2, I: axial length of the first rotor bar (134a), F: axial length of the shaft support (154) accommodated inside the first rotor core (131a).

[0304] Fig. 11 is a graph comparing the motor efficiency of the conventional and the present invention according to the inner diameter of the rotor (130).

[0305] Referring to Fig. 11, as the inner diameter of the rotor (130) increases, the motor efficiency increases.

[0306] For example, if the inner diameter of the rotor (130) increases from 12 mm to 17 mm, the motor efficiency decreases by approximately 0.7%.

[0307] However, when the inner diameter of the rotor (130) increases from 17 mm to 19 mm, the motor efficiency decreases significantly to 2.77%.

[0308] Therefore, in order to prevent flux saturation, it is necessary to select an appropriate radial thickness of the back yoke (1312, 1313) of the rotor (130).

[0309] According to the two-stage structure of the rotor bar (134) according to the embodiments of FIGS. 6 to 10 of the present invention, compared to an induction motor to which the structure of the rotor bar (134) according to the prior art (the radial length of the rotor bar (134) is constant along the axial direction) is applied, the motor efficiency of the single-phase induction motor (110) to which the two-stage structure of the rotor bar (134) of the present invention is applied has increased by 2.53% (69.05-66.52).

[0310] (3) Description of the manufacturing method of the induction motor (110)

[0311] Hereinafter, a method for manufacturing an induction motor (110) will be described.

[0312] First, the stator (120) and rotor (130) of the induction motor (110) are manufactured.

[0313] For example, a stator (120) can be manufactured by the following assembly process of a stator core and a stator coil (123). The stator core is formed by laminating and bonding a plurality of electrical steel plates.

[0314] The stator coil (123) is wound around the stator core through the slot of the stator core.

[0315] The rotor (130) can be manufactured by the following molding process of the rotor core (131) and rotor bar (134).

[0316] The rotor core (131) is formed by stacking and bonding multiple electrical steel plates.

[0317] The rotor bar (134) can be formed by aluminum die casting. The electrical steel plate of the rotor core (131) can be formed from an iron alloy having a melting point higher than the melting point of aluminum, which will be described later.

[0318] The molding process of the rotor bar (134) is examined in more detail as follows.

[0319] First, a rotor core (131) is mounted in a cavity within a mold. The mold can be divided into a fixed mold and a movable mold. The movable mold and the fixed mold can each have a first cavity and a second cavity formed therein so as to correspond to the shape of the rotor core (131).

[0320] The movable mold is provided to be movable in both directions, either toward or away from the fixed mold. The rotor core (131) can be mounted in the first cavity of the fixed mold.

[0321] When the movable mold moves to the fixed mold and the mold is closed, the first cavity and the second cavity can form one cavity. Die casting can be performed by forcing molten aluminum metal into the rotor bar receiving portion (133) of the rotor core (131) at a preset pressure.

[0322] The inclined portion (1335) of the rotor bar receiving portion (133) can solve the problem of the rotor bar (134) not being formed by minimizing the resistance of the molten aluminum metal when die casting along the axial direction.

[0323] The molten aluminum metal can be formed into a rotor bar (134) through a cooling process.

[0324] After the rotor bar (134) is formed, the movable mold is removed from the fixed mold, and the rotor (130) can be removed from the mold.

Claims

1. Stator; A rotor is coupled to a crankshaft and is rotatably provided on the inside of the stator with a gap between the stator and the rotor, The above rotor, A rotor core that accommodates the crankshaft and has a plurality of rotor bar accommodation portions radially outside the crankshaft; and It includes a plurality of rotor bars accommodated inside the rotor core through the plurality of rotor bar accommodation portions, The above rotor bar receiving portion and the above rotor bar are arranged spaced apart from each other in the circumferential direction of the rotor core, Each of the above plurality of rotor bars, A first rotor bar having a first radial length passing through the center of the circumferential width and extending in the axial direction of the crank shaft; A second rotor bar having a second radial length greater than the first radial length and passing through the center of the circumferential width, and extending in the axial direction from one side of the first rotor bar; and An induction motor including an inclined portion formed inclined with respect to the axial direction between the first rotor bar and the second rotor bar.

2. In paragraph 1, The above slope is, An induction motor including a plurality of stepped portions formed at different radial distances from the outer surface of the crankshaft.

3. In paragraph 2, An induction motor in which the radial separation distance between the plurality of step portions increases from the second rotor bar to the first rotor bar.

4. In paragraph 2, The above step part is, a first portion extending radially from the crankshaft; and An induction motor comprising a second portion extending in the axial direction from the first portion.

5. In paragraph 1, Further comprising a shaft support member extending in the axial direction to support one side of the crank shaft, The above-mentioned shaft support is accommodated on one side of the rotor core, An induction motor in which the first rotor bar is arranged to overlap the shaft support in the radial direction.

6. In paragraph 5, An induction motor in which the second rotor bar is arranged so as not to overlap the shaft support in the radial direction.

7. In paragraph 1, The above rotor bar, An outer curved surface adjacent to the outer surface of the rotor in the radial direction; An inner curved surface disposed radially opposite to the outer curved surface and adjacent to the center of the rotor; and It includes a plurality of flat portions each connecting one end and the other end of the outer curved portion and the inner curved portion, An induction motor in which the length between the circumferential center of the first outer curved portion of the first rotor bar and the circumferential center of the first inner curved portion is smaller than the length between the circumferential center of the second outer curved portion of the second rotor bar and the circumferential center of the second inner curved portion.

8. In paragraph 1, Each of the above plurality of rotor bar receiving sections, A first rotor bar receiving portion having a first radial length passing through the center of the circumferential width and extending in the axial direction of the crank shaft; A second rotor bar receiving portion having a second radial length that is greater than the first radial length and passes through the center of the circumferential width, and extending in the axial direction from one side of the first rotor bar receiving portion; and An induction motor including an inclined portion formed inclined with respect to the axial direction between the first rotor bar receiving portion and the second rotor bar receiving portion.

9. In paragraph 8, The above rotor bar receiving part is, An outer surface portion adjacent to the outer surface of the rotor in the radial direction; An inner surface portion arranged to face the outer surface portion in the radial direction and adjacent to the center of the rotor; and It includes a plurality of side portions each connecting one end and the other end of the outer side portion and the inner side portion, An induction motor in which the radial length between the circumferential center of the outer surface of the first rotor bar receiving portion and the circumferential center of the inner surface is smaller than the radial length between the circumferential center of the outer surface of the second rotor bar receiving portion and the circumferential center of the inner surface.

10. In paragraph 8, The above rotor core is, a first rotor core having a first inner diameter; and An induction motor including a second rotor core having a second inner diameter smaller than the first inner diameter and arranged on one side of the first rotor core.

11. In paragraph 10, The radial thickness B of the back yoke formed between the second rotor bar receiving portion and the inner surface of the second rotor core is An induction motor in which B=k*A, k is a constant value in the range of 0.5 to 1.5, and A is the radial length of the second rotor bar.

12. In paragraph 1, The radial length C of the above first rotor bar is An induction motor in which C=k*A, k is a constant value in the range of 0.5 to 1, and A is the radial length of the second rotor bar.

13. In paragraph 10, The stacking length D of the first rotor core is An induction motor in which D=k*(D+E), wherein k is a constant value greater than 0 and less than or equal to 0.5, and E is the lamination length of the second rotor core.

14. In paragraph 2, The axial length J of the above plurality of step portions is An induction motor in which H / 2≤J≤2*H, and H is the radial length of a plurality of step portions.

15. In paragraph 2, The above rotor core is, a first rotor core having a first inner diameter; and A second rotor core having a second inner diameter smaller than the first inner diameter and disposed on one side of the first rotor core, The axial length I of the above first rotor bar is An induction motor in which I=k*F, k is a constant value in the range of 1 to 1.2, and F is the axial length of the shaft support portion accommodated inside the first rotor core.

16. Shell; An induction motor provided inside the shell and according to any one of claims 1 to 15; and A compressor including a compression unit that compresses refrigerant using power received from the above induction motor.

17. In paragraph 16, The above compression part, frame; A cylinder provided on one side of the frame along the radial direction of the crank shaft and forming a compression chamber; A piston that performs a linear reciprocating motion in the compression chamber; and A compressor including a connecting rod coupled to the crankshaft and the piston and converting the rotational motion of the crankshaft into the linear motion of the piston.

18. In paragraph 17, The above compression part, The frame includes a shaft support portion that is formed to protrude axially to surround one end of the crank shaft and rotatably supports one end of the crank shaft. The above-mentioned shaft support is accommodated on one side of the rotor core, A compressor in which the first rotor bar and the shaft support are arranged to overlap in the radial direction of the crank shaft.

19. In paragraph 18, A compressor in which the second rotor bar is positioned so as not to overlap the shaft support part in the radial direction.

20. In a method for manufacturing an induction motor according to any one of claims 1 to 15, A step of inserting a rotor core having a rotor bar receiving portion formed into the inside of a mold; and A method for manufacturing an induction motor, comprising a step of forcing molten aluminum metal into the rotor bar receiving portion along the axial direction at a preset pressure, wherein the rotor bar received in the rotor bar receiving portion is formed by die casting the molten aluminum metal.

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