Induction motor and compressor equipped therewith

Abstract

An induction motor and a compressor equipped therewith are disclosed. The induction motor comprises a stator and a rotor. The rotor may be coupled to a crankshaft. The rotor may be rotatably provided on the inside of the stator with a gap between the stator and the rotor. The inner circumferential surface of the stator may include a first inner circumferential surface and a second inner circumferential surface. Here, M is a natural number greater than or equal to 2. The second inner circumferential surface may be formed to be recessed from the first inner circumferential surface toward the radial outside of a crankshaft. The first inner circumferential surface has a first inner diameter. The second inner circumferential surface has a second inner diameter that is larger than the first inner diameter. Accordingly, the multi-layered structure of the stator can avoid interference between the stator and the rotor, thereby enhancing structural stability.

Description

Induction motor and compressor equipped therewith

[0001] The present invention relates to an induction motor capable of improving motor performance 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 electric motor and can compress the refrigerant stored in the cylinder block to a preset pressure.

[0008] The electric motor of a reciprocating compressor can be composed of an induction motor.

[0009] An induction motor is a representative example of an AC motor, in which a rotating magnetic field created by a stator generates an induced current in the rotor of a conductor, generating a rotational torque corresponding to the slip.

[0010] Induction motors can be divided into single-phase induction motors and three-phase induction motors depending on the type of AC power input.

[0011] Single-phase induction motors are small motors and have inferior characteristics to three-phase induction motors, but they have the great advantage of being able to use commercial power. While three-phase induction motors are mainly used for industrial purposes, single-phase induction motors are widely used in products such as home appliances.

[0012] When AC power is supplied to the single-phase winding of a single-phase induction motor, a pulsating magnetic field is generated, and an induced current flows in the rotor conductor due to the pulsating magnetic field.

[0013] Since a single-phase induction motor rotates at synchronous speed according to the pulsating magnetic field once it is started, it is important to start it initially.

[0014] That is, in order to start a single-phase induction motor, it is important to obtain starting torque by making the magnetic field equilibrium unbalanced.

[0015] Typically, reciprocating compressors have bearings located on one side of the crankshaft due to their structural characteristics, supporting the crankshaft from one side. For example, the bearings may support the upper side of a vertically aligned crankshaft.

[0016] Because of this, reciprocating compressors can experience wheeling during normal operation, causing the lower ends of the stator and rotor to interfere with each other when positioned opposite the bearings (shaft supports).

[0017] In particular, a single-phase induction motor consists of a main winding and sub-windings. The main and sub-windings are wound on the stator core at 90-degree intervals. When the motor starts, a high level of current flows in the main winding, which can exert a force in a unidirectional direction (radial direction) perpendicular to the axis.

[0018] For this reason, in the case of a reciprocating compressor to which a single-phase induction motor is applied, the force acting in one direction may have a relatively large impact (structural instability) on a reciprocating compressor that adopts a one-sided support method.

[0019] For example, there is a problem in that the lower parts of the stator and rotor, which are opposite to the shaft support, come into contact with each other due to the force acting in the above-mentioned direction when the motor starts, thereby generating noise (hammering noise).

[0020] In addition, there is a problem that the gap between the stator and the rotor is not uniform along the axial direction due to the force acting in the above-mentioned direction, which reduces the performance of the motor.

[0021] In general, induction motors are designed to have a large mutual inductance between the rotor and stator to improve motor performance.

[0022] The simplest way to increase inductance is to reduce the air gap.

[0023] However, if the gap is made small to increase the inductance, a problem occurs in which the stator and rotor interfere with each other due to the force acting in one direction when the single-phase induction motor is started.

[0024] In addition, if the gap is made large to avoid interference between the stator and rotor, there is a problem that the mutual inductance is reduced and the performance of the motor deteriorates.

[0025] 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.

[0026] The first purpose is to provide an induction motor having a structure capable of increasing structural stability by avoiding interference between a stator and a rotor, and a compressor equipped with the same.

[0027] The second purpose is to provide an induction motor having a structure capable of improving motor performance by increasing the mutual inductance of the rotor and the stator, and a compressor equipped with the same.

[0028] The third purpose is to provide an induction motor having a structure that can secure freedom in motor design by flexibly responding to the one-sided support method of the bearing, which is a structural characteristic of a reciprocating compressor, and a compressor equipped with the same.

[0029] The fourth purpose is to provide an induction motor having a structure capable of minimizing hammering noise during initial startup of a single-phase induction motor and a compressor equipped with the same.

[0030] 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.

[0031] To achieve the above-described purpose, (1) an induction motor according to one embodiment of the present invention includes a stator and a rotor. The rotor may be coupled to a crankshaft. The rotor may be rotatably provided on the inside of the stator with a gap therebetween.

[0032] The inner surface of the above stator may include a first inner surface to an M-th inner surface. Here, M is a natural number greater than or equal to 2. The second inner surface to the M-th inner surface may be formed to be recessed from the first inner surface toward the radial outer side of the crankshaft.

[0033] The first inner surface has a first inner diameter. The second inner surface has a second inner diameter that is larger than the first inner diameter.

[0034] Through this, the multi-layered laminated structure of the stator can avoid interference between the stator and the rotor, thereby increasing structural stability.

[0035] (2) In the above (1), the second inner surface may be arranged on one side of the first inner surface with respect to the axial direction of the crank shaft.

[0036] Through this, when applied to a compressor in which one side of the crankshaft is supported on one side, the second inner surface forms a two-stage gap, thereby preventing one end of the stator and rotor located in the opposite direction to the shaft support from interfering with each other.

[0037] (3) In the above (1), a step may be formed between the first inner surface and the second inner surface.

[0038] Through this, the step forms a boundary between the first inner surface and the second inner surface, and can connect the first inner surface and the second inner surface.

[0039] (4) In the above (1), the outer diameter of the rotor can be maintained constant along the axial direction of the crankshaft. The first gap between the first inner surface and the outer surface of the rotor can be smaller than the second gap between the second inner surface and the outer surface of the rotor.

[0040] Through this, the first gap is smaller than the second gap, so that the mutual inductance of the stator and the rotor can be increased and the motor performance can be improved.

[0041] (5) In the above (1), the second inner surface extends in the axial direction of the crankshaft, and the axial height A of the second inner surface may be A=a*B. The a is a constant greater than 0 and less than or equal to 0.5. The B is the axial height of the stator.

[0042] (6) In the above (1), the second gap C between the second inner surface and the outer surface of the rotor may be C=b*C'. The b is a constant greater than or equal to 1 and less than or equal to 1.4. The C' is the first gap between the first inner surface and the outer surface of the rotor.

[0043] Through this, the second gap is larger than the first gap, so that interference between the stator and rotor caused by a force acting in one direction due to overcurrent when starting a single-phase induction motor can be avoided.

[0044] (7) In the above (1), the second inner surface may be formed to be sunken along the circumferential direction in a portion of the inner surface of the stator.

[0045] Through this, structural stability can be secured by avoiding interference between the stator and rotor due to the unidirectional force generated by the overcurrent flowing in the main winding when starting a single-phase induction motor.

[0046] (8) In the above (1), the stator may include a stator core; and a stator coil wound around the stator core.

[0047] The above stator coil includes a main winding wound in a portion of the stator core along the circumference thereof; and a sub winding wound in another portion of the stator core along the circumference thereof and having a phase difference of 90 degrees from the main winding.

[0048] The above second inner surface can be formed to correspond to a section of the stator core on which the main winding is wound.

[0049] Through this, even if the lower end of the rotor moves radially outward due to a force acting in one direction according to the overcurrent flowing in the main winding when the single-phase induction motor is started, the second inner surface of the stator core forms a wider gap with the outer surface of the rotor, thereby preventing contact with the rotor.

[0050] (9) In the above (8), the stator core may include a back yoke; a plurality of teeth formed to protrude radially from the inner side of the back yoke; and a pole shoe formed to protrude circumferentially from the inner end of the teeth.

[0051] The thickness of the pole shoe may be formed between the radially outer surface and the inner surface of the pole shoe. The radially inner surface of the pole shoe may form the inner surface of the stator core.

[0052] The thickness of the second pole shoe forming the second inner surface is smaller than the thickness of the first pole shoe forming the first inner surface. As a result, the second inner surface can form a wider gap with the thickness of the pole shoe.

[0053] (10) A compressor according to the present invention includes a shell, an induction motor, and a compression unit. The induction motor is provided inside the shell. The induction motor is according to any one of (1) to (9). The compression unit can compress refrigerant using power received from the induction motor.

[0054] The above induction motor includes a stator and a rotor. The rotor is coupled to a crankshaft. The rotor may be rotatably provided on the inside of the stator, with a gap between the rotor and the stator.

[0055] The inner surface of the stator may include a first inner surface having a first inner diameter; and a second inner surface having a second inner diameter larger than the first inner diameter and formed to be recessed radially outward from the first inner surface of the crankshaft.

[0056] Through this, the second inner surface can form a wider gap, thereby securing the structural stability of the motor.

[0057] (11) In the above (10), the compression unit may be arranged on one side of the induction motor along the axial direction of the crankshaft.

[0058] Through this, the compression member can support the crankshaft of the fluid motor on one side.

[0059] (12) In the above (10), 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 coupled to the crankshaft and the piston and converting a rotational motion of the crankshaft into a linear motion of the piston.

[0060] Through this, the piston can receive power from the crankshaft and compress the refrigerant filled in the compression chamber.

[0061] (13) In the above (12), the crankshaft may further include an eccentric shaft formed to protrude axially from one end of the crankshaft and arranged eccentrically from the center of the crankshaft; and a counterweight extending radially in the opposite direction to the eccentric shaft from one end of the crankshaft.

[0062] Through this, the eccentric shaft can transmit the rotational kinetic energy of the crankshaft through the connecting rod. The counterweight is arranged in a direction opposite to the movement of the center of gravity of the eccentric shaft, thereby achieving weight balance in the radial direction of the crankshaft.

[0063] (14) In the above (12), the compression member includes a shaft support. The shaft support can extend from the frame in the axial direction toward the rotor. The shaft support can be coupled to at least a portion of the outer circumferential surface of the crankshaft so as to be rotatable together with the crankshaft.

[0064] The rotor may include an axial hole passing through the axial center.

[0065] The above shaft hole may include a first shaft hole and a second shaft hole. The first shaft hole may be press-fitted to at least a portion of the crankshaft. The first shaft hole may be located axially lower than the rotor.

[0066] The second shaft hole can accommodate at least a portion of the shaft support. The second shaft hole can form a step radially outward from the first shaft hole. The second shaft hole can be located at an upper portion of the rotor.

[0067] The region of the above second shaft hole can be arranged radially inside the first inner surface.

[0068] Through this, the compressor can support one end of the crankshaft through the shaft support. The second inner surface can avoid interference between the stator and the rotor by widening the second gap at the lower end of the stator and the rotor, which are located in the opposite direction to the shaft support.

[0069] (15) In the above (14), the compression member may further include a plurality of stator coupling members formed to protrude axially from the frame toward the stator and coupled with the stator.

[0070] Through this, the stator coupling part can be connected to the compression part and the induction motor.

[0071] According to an embodiment of the present invention, the following effects can be achieved.

[0072] First, the gap formed between the inner surface of the stator core and the outer surface of the rotor core may have a two-stage gap along the axial direction. The two-stage gaps may have different sizes. The gap (C') between the outer surface of the rotor core and the first inner surface of the stator core, which is located close to the shaft support, may be maintained smaller than the gap (C) between the outer surface of the rotor core and the second inner surface of the stator core.

[0073] This allows the mutual inductance between the rotor and stator to be increased by forming a smaller gap. This, in turn, improves motor performance by increasing the mutual inductance.

[0074] The first inner surface of the stator core may be arranged axially close to the upper end of the crankshaft. The first inner surface of the stator core may be arranged close to the frame of the cylinder block.

[0075] The first inner surface of the stator core may be arranged radially outside the axial support portion of the frame. The first inner surface of the stator core may be arranged to overlap the axial support portion of the frame in the radial direction.

[0076] Second, the second inner surface of the stator core may be arranged axially close to the lower portion of the crankshaft. The second inner surface of the stator core may be arranged farther away from the frame of the cylinder block in the opposite direction.

[0077] The second inner surface of the stator core may be arranged in a direction opposite to the axial support portion of the frame. The second inner surface of the stator core is formed to surround the lower portion of the outer surface of the rotor core.

[0078] The gap (C) between the outer surface of the rotor core and the second inner surface of the stator core can be maintained larger than the gap (C') between the outer surface of the rotor core and the first inner surface of the stator core.

[0079] Through this, the lower ends of the stator core and rotor core can be prevented from interfering with each other due to the force acting in one direction (radial direction) due to the overcurrent of the main winding when the compressor is supported on one side and the single-phase induction motor is started.

[0080] Accordingly, structural stability can be secured not only for the upper portions of the stator core and rotor core, which are relatively stably positioned by the shaft support, but also for the lower portions of the stator core and rotor core, which are relatively unstable.

[0081] Therefore, the multi-stage stacked structure of the stator according to the present embodiment can not only improve the performance of the motor but also secure the structural stability of the motor.

[0082] Third, the multi-stage stacked structure of the stator can reduce hammering noise that may occur at the initial start-up of the motor due to the structural characteristics of the stator coil of a single-phase induction motor, namely, the main winding and sub-winding are arranged perpendicular to each other at a 90-degree spatial angle.

[0083] Fourth, it can flexibly cope with constraints such as one-sided support of a reciprocating compressor.

[0084] FIG. 1 is a conceptual diagram showing a reciprocating compressor according to one embodiment of the present invention.

[0085] Figure 2 is a conceptual diagram showing the upper shell of Figure 1 omitted and the compression part positioned above the power unit.

[0086] Figure 3 is a conceptual diagram showing the shell omitted from Figure 2, with the compression unit and the power unit coupled to each other.

[0087] Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3, and is a conceptual diagram for explaining that the lower portions of the stator and the rotor, which are positioned in the opposite direction to the shaft support, interfere with each other.

[0088] Figure 5 is a conceptual diagram showing the arrangement relationship of the main winding and sub-winding constituting the stator coil in Figure 4.

[0089] Fig. 6 is a circuit diagram showing the circuit of the induction motor in Fig. 5.

[0090] Figure 7 is a graph showing the current waveforms of the main winding and sub-winding over time in Figure 5.

[0091] Figure 8 is a conceptual diagram showing the inner surface of the stator core in Figure 4 formed in two stages.

[0092] Figure 9 is a conceptual diagram showing the entire second inner surface of the stator core formed along the circumferential direction in Figure 8.

[0093] Figure 10 is a conceptual diagram showing the second inner surface of Figure 9 actually applied to the stator core.

[0094] Figure 11 is a conceptual diagram showing the second inner surface of the stator core in Figure 8 partially formed along the circumferential direction.

[0095] Figure 12 is a conceptual diagram showing the second inner surface of Figure 11 actually applied to the stator core.

[0096] Fig. 13 is a graph for explaining the effect of the two-stage laminated structure of the stator according to the present invention.

[0097] 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.

[0098] In the following description, descriptions of some components may be omitted to clarify the features of the present invention.

[0099] 1. Definition of Terms

[0100] 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.

[0101] 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.

[0102] As used herein, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0103] As used herein, “radial” or “radial” means a shape that extends out in all directions from a central point like spokes of a wheel.

[0104] “Axial” as used in the following description means the longitudinal direction of the crankshaft.

[0105] “Axial” as used in the following description may mean the vertical direction.

[0106] 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).

[0107] As used in the following description, “circumferential” means the direction of the circumference of a circle.

[0108] 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.

[0109] 2. Description of the configuration of a compressor according to one embodiment of the present invention

[0110] In this embodiment, the compressor can be applied to a hermetic compressor.

[0111] In this embodiment, the compressor can be applied to a reciprocating compressor.

[0112] FIG. 1 is a conceptual diagram showing a reciprocating compressor according to one embodiment of the present invention.

[0113] Figure 2 is a conceptual diagram showing the upper shell (101) omitted from Figure 1, with the compression section positioned above the electric section.

[0114] Figure 3 is a conceptual diagram showing the shell (100) omitted from Figure 2, and the compression section and the power section being coupled to each other.

[0115] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3, and is a conceptual diagram for explaining that the lower portions of the stator (120) and the rotor (130), which are positioned in the opposite direction to the shaft support member (154), interfere with each other.

[0116] Figure 5 is a conceptual diagram showing the arrangement relationship of the main winding (128) and sub-winding (129) constituting the stator coil (127) in Figure 4.

[0117] Fig. 6 is a circuit diagram showing the circuit of the induction motor in Fig. 5.

[0118] Fig. 7 is a graph showing the current waveforms of the main winding (128) and sub-winding (129) over time in Fig. 5.

[0119] Figure 8 is a conceptual diagram showing the inner circumferential surface (1261, 1262) of the stator core (121) in Figure 4 formed in two stages.

[0120] Figure 9 is a conceptual diagram showing the entire shape of the second inner surface (1262) of the stator core (121) in Figure 8 formed along the circumferential direction.

[0121] Figure 10 is a conceptual diagram showing the second inner surface (1262) of Figure 9 actually applied to the stator core (121).

[0122] A compressor according to the present embodiment may be configured to include a shell (100), a compression unit (150), and an induction motor (110).

[0123] 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.

[0124] A compression member (150) and an induction motor (110) can be accommodated inside the shell (100).

[0125] The shell (100) may include a lower shell (102) and an upper shell (101).

[0126] 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.

[0127] 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).

[0128] An induction motor (110) may include a stator (120) and a rotor (130).

[0129] 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).

[0130] The rotor (130) can be rotatably installed on the inside of the stator (120).

[0131] The stator (120) may include a stator core (121) and a stator coil (127).

[0132] 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.

[0133] The stator core (121) may be formed with a back yoke (122), a plurality of teeth (123), and a plurality of slots (124). The back yoke (122) may be formed in a circular ring shape.

[0134] The teeth (123) may be formed to protrude radially from the inner surface of the back yoke (122). The slot (124) may be formed to penetrate along the axial direction on the inner side of the stator core (121).

[0135] A plurality of teeth (123) may be arranged alternately with a plurality of slots (124) in a circumferential direction. A pole shoe (125) may be provided at an inner end of the teeth (123). The pole shoe (125) may be formed to protrude from the inner end of the teeth (123) to both sides along the circumferential direction. A radial thickness of the pole shoe (125) may be formed between the radially outer surface and the inner surface of the pole shoe (125).

[0136] The stator coil (127) can be wound on the stator core (121) through a slot (124).

[0137] Referring to Fig. 5, the stator coil (127) of the induction motor can be composed of a main winding (128) and a sub-winding (129).

[0138] The main winding (128) and the sub-winding (129) can be arranged perpendicular to each other along the circumference of the stator core (121). The main winding (128) and the sub-winding (129) can be arranged at a 90-degree interval from each other along the circumference of the stator core (121).

[0139] The main winding (128) may include an end coil. The end coil of the main winding (128) may be formed to protrude outward from the slot. The end coil of the main winding (128) may extend to protrude in the left-right direction. Here, the left-right direction is based on FIG. 5.

[0140] The plurality of slots (124) may be composed of the first slot to the Nth slot. In the embodiment of Fig. 5, the plurality of slots (124) are shown as composed of the first slot to the 20th slot. However, the number of slots (124) is not limited thereto.

[0141] The plurality of slots (124) may be configured as the first slot to the twentieth slot, which are spaced apart from each other in a counterclockwise direction starting from the 3 o'clock direction.

[0142] The main winding (128) may be composed of a first partial coil (128a) and a second partial coil (128b). The first partial coil (128a) may be placed on the left side with respect to a center line passing vertically through the center of the stator core (121).

[0143] One of the first partial coils (128a) protrudes from the sixth slot, extends counterclockwise, and can be introduced into the fifteenth slot. The other of the first partial coils (128a) protrudes from the seventh slot, extends counterclockwise, and can be introduced into the fourteenth slot.

[0144] Another one of the first partial coils (128a) may protrude from the eighth slot, extend counterclockwise, and be introduced into the thirteenth slot. Another one of the first partial coils (128a) may protrude from the ninth slot, extend counterclockwise, and be introduced into the twelfth slot.

[0145] The second partial coil (128b) can be placed on the right side with respect to the center line passing through the center of the stator core (121) in the vertical direction.

[0146] One of the second partial coils (128b) protrudes from the fifth slot, extends clockwise, and can be introduced into the sixteenth slot. The other of the second partial coils (128b) protrudes from the fourth slot, extends clockwise, and can be introduced into the seventeenth slot.

[0147] Another one of the second partial coils (128b) may protrude from the third slot, extend clockwise, and be introduced into the 18th slot. Another one of the second partial coils (128b) may protrude from the second slot, extend counterclockwise, and be introduced into the 19th slot.

[0148] The sub-winding (129) may include an end coil. The end coil of the sub-winding (129) may be formed to protrude outwardly from the slot (124). The end coil of the sub-winding (129) may extend to protrude in a vertical direction. Here, the vertical direction is based on FIG. 5.

[0149] The sub-winding (129) may be composed of a first partial coil (129a) and a second partial coil (129b). The first partial coil (129a) may be positioned above a center line passing through the center of the stator core (121) in the left-right direction.

[0150] One of the first partial coils (129a) may protrude from the first slot, extend counterclockwise, and be introduced into the tenth slot. Another of the first partial coils (129a) may protrude from the second slot, extend counterclockwise, and be introduced into the ninth slot. Another of the first partial coils (129a) may protrude from the third slot, extend counterclockwise, and be introduced into the eighth slot.

[0151] The second partial coil (129b) can be placed on the lower side based on the center line passing through the center of the stator core (121) in the left and right directions.

[0152] One of the second partial coils (129b) protrudes from the 20th slot, extends clockwise, and can be introduced into the 11th slot. Another of the second partial coils (129b) protrudes from the 19th slot, extends clockwise, and can be introduced into the 12th slot. Another of the second partial coils (129b) protrudes from the 18th slot, extends clockwise, and can be introduced into the 13th slot.

[0153] The main winding (128) can be composed of a total of eight partial coils. The sub winding (129) can be composed of a total of six partial coils.

[0154] Referring to Fig. 6, a single-phase AC power supply can be applied to the stator coil (127).

[0155] The AC power source can be connected to each of the main winding (128) and the sub-winding (129). A plurality of capacitors (170) can be connected to the sub-winding (129).

[0156] The capacitor (170) can control the size of the current by changing the phase difference of the current flowing in the main winding (128) and the sub-winding (129) when the induction motor is started.

[0157] Referring to Fig. 7, when the induction motor is started (5 to 10 ms), the size of the current flowing in the main winding (128) (approximately 22 A) can be approximately 4 to 10 times larger than the size of the current flowing in the sub-winding (129) (approximately 2.5 A).

[0158] The stator core (121) can be fixed to the lower surface of the stator coupling portion (153) of the cylinder block (151) by a fastening bolt.

[0159] 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).

[0160] 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).

[0161] The rotor (130) may include a rotor core (131) and a plurality of permanent magnets or a plurality of rotor bars (133). In this embodiment, a plurality of rotor bars (133) are shown mounted on the inside of the rotor core (131).

[0162] 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.

[0163] A first shaft hole (1311) may be formed to penetrate axially through the center of the rotor core (131). The first shaft hole (1311) may be press-fitted to at least a portion of the crank shaft (136). The first shaft hole (1311) may be located at the lower portion of the rotor core (131).

[0164] The crankshaft (136) can be coupled to the rotor core (131) through the first shaft hole (1311).

[0165] A rotor bar receiving hole may be formed to penetrate along the axial direction on the inner side of the rotor core (131). The rotor bar (133) may extend in the axial direction. The rotor bar (133) may be formed of a conductor such as aluminum or an aluminum alloy.

[0166] The rotor bar (133) can be axially inserted and coupled into the interior of the rotor core (131) through the rotor bar receiving hole. A plurality of rotor bars (133) can be spaced apart from each other along the circumference of the rotor core (131).

[0167] The end ring (134) can extend in the circumferential direction. A first end ring (134) can be coupled to the upper side of the rotor core (131). A second end ring (134) can be coupled to the lower side of the rotor core (131). Through this, the end ring (134) can prevent the rotor bar (133) from being axially separated from the rotor bar receiving hole.

[0168] Through this, when an external power source is applied to the stator coil (127), a magnetic field can be formed around the stator coil (127). A pulsating magnetic field is generated in the stator.

[0169] The rotor (130) generates an induced current by the pulsating magnetic field of the stator (120). The rotor can rotate with respect to the stator (120). Through this, the induction motor (110) can generate power for the reciprocating motion of the compression unit (150).

[0170] An eccentric shaft (138) is provided at the upper end of the crankshaft (136). The eccentric shaft (138) may be arranged eccentrically radially to one side from the upper end of the crankshaft (136). A counterweight (139) may be formed to protrude radially outward from the upper end of the crankshaft (136). The eccentric shaft (138) may protrude upward from one side of the counterweight (139).

[0171] A counterweight (139) may be arranged at the upper end of the crankshaft (136) in the opposite direction to the eccentric shaft (138) with respect to the crankshaft (136). The counterweight (139) may be a weight. Through this, the counterweight (139) can balance the center of rotation with respect to the eccentric shaft (138) with respect to the crankshaft (136).

[0172] A connecting rod (140) may be placed between the induction motor (110) and the compression unit (150). The connecting rod (140) is configured to convert the rotational motion of the induction motor (110) into the reciprocating motion of the compression unit (150).

[0173] An eccentric shaft coupling portion (141) may be formed in a ring shape at one end of the connecting rod (140). The eccentric shaft coupling portion (141) may be wrapped around an eccentric shaft (138). The eccentric shaft (138) may be accommodated inside the eccentric shaft coupling portion (141), so that the eccentric shaft (138) and the eccentric shaft coupling portion (141) may be coupled to each other.

[0174] A piston coupling portion (142) may be formed in a ring shape at the other end of the connecting rod (140). The piston coupling portion (142) is configured to surround a connecting pin (157) to be described later. The connecting pin (157) may be coupled to the inside of the piston (156). The connecting pin (157) may penetrate the piston coupling portion (142) in the vertical direction and be coupled to the piston coupling portion (142). The connecting rod (140) may be coupled to the piston (156).

[0175] Through this, the eccentric shaft (138) can rotate together with the crank shaft (136) around the crank shaft (136). The connecting rod (140) can convert the rotational motion of the eccentric shaft (138) into the reciprocating motion of the piston (156).

[0176] The compression unit (150) may be configured to include a cylinder block (151) and a piston (156).

[0177] 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).

[0178] The cylinder block (151) can be configured to include a frame (152), a stator coupling part (153), a shaft support part (154), and a cylinder (155).

[0179] The frame (152) may be formed to extend in a horizontal direction intersecting the axial direction. The frame (152) may be formed in a flat shape.

[0180] The stator coupling portion (153) may be formed to protrude downward from the edge of the frame (152) toward the stator (120). A plurality of stator coupling portions (153) may be provided. In the present embodiment, there may be three stator coupling portions (153). A plurality of stator coupling portions (153) may be arranged at equal intervals in the circumferential direction along the periphery of the frame.

[0181] The stator coupling part (153) can be coupled with the stator (120). The cylinder block (151) can be coupled with the stator (120) using a fastening bolt.

[0182] Through this, the cylinder block (151) can be elastically supported on the lower shell (102) together with the stator (120).

[0183] The shaft support member (154) may extend axially from the central portion of the frame (152). An axial receiving hole may be formed to penetrate axially on the inside of the shaft support member (154).

[0184] The crankshaft (136) is connected to the shaft support member (154) through the shaft receiving hole, so that it can be rotatably mounted inside the frame (152).

[0185] A journal bearing may be arranged or omitted between the inner surface of the shaft support member (154) and the outer surface of the crankshaft (136). The journal bearing may be formed in a cylindrical shape. The inner surface of the journal bearing is configured to surround the outer surface of the crankshaft (136).

[0186] The inner surface of the journal bearing can be in surface contact with the outer surface of the crankshaft (136). The outer surface of the journal bearing is configured to surround the inner surface of the shaft support member (154). The outer surface of the journal bearing can be in surface contact with the inner surface of the shaft support member (154).

[0187] Through this, the journal bearing can support the crankshaft (136) so that the crankshaft (136) can rotate with respect to the shaft support (154). The journal bearing can limit the radial movement of the crankshaft (136).

[0188] Journal bearings are relatively inexpensive compared to conventional ball bearings, and thus can significantly contribute to cost reduction. In this embodiment, the journal bearing may be omitted. However, an oil film may be formed between the inner surface of the shaft support member (154) and the outer surface of the crankshaft (136). This allows the shaft support member (154) to function as a journal bearing.

[0189] An oil passage (1361) is formed inside the crankshaft (136). An oil passage groove (1362) may be formed in a spiral direction on the outer surface of the crankshaft (136). The oil passage groove (1362) may be connected to the oil passage (1361).

[0190] An oil pump (137) may be provided at the lower end of the crankshaft (136). The upper end of the oil pump (137) may be connected to the oil passage (1361) of the crankshaft (136). The lower end of the oil pump (137) may be arranged to be submerged in oil stored in the lower shell (102).

[0191] Through this, the oil pump (137) can pump oil and supply it to the inner surface of the shaft support (154) through the oil passage (1361) and oil passage groove (1362) of the crankshaft (136).

[0192] The shaft support member (154) can be accommodated in the second shaft hole (1312) of the rotor core (131). The second shaft hole (1312) can be formed with a large diameter at the upper end of the first shaft hole (1311) of the rotor core (131).

[0193] The second shaft hole (1312) can accommodate at least a portion of the shaft support portion (154). The second shaft hole (1312) can form a step radially outward from the first shaft hole (1311). The second shaft hole (1312) 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 (1312) 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] 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).

[0196] A cylindrical hollow portion is formed inside the cylinder (155). The cylinder (155) may extend radially with respect to the crankshaft (136). 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).

[0197] 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 (140) to be described later, and the rear side of the piston (156) is arranged facing the connecting rod (140).

[0198] 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 (142) of the connecting rod (140). Through this, the piston (156) may receive driving force from the induction motor (110) through the connecting rod (140).

[0199] 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 (140). The front side of the piston (156) may form a compression chamber (1551) inside the cylinder (155) together with the valve assembly (160).

[0200] 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).

[0201] The valve assembly (160) may include a valve plate (161), an intake valve (162), a discharge valve (163), and a discharge cover (164).

[0202] 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).

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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).

[0207] The discharge cover (164) can be fastened to cover the compression chamber (1551) at the outer opening end of the cylinder block (151). The discharge chamber can be formed to be sunken in the inner side of the discharge cover (164).

[0208] The suction muffler (165) may have a suction space formed therein. The inlet of the suction muffler (165) may be connected to a suction pipe, and the outlet of the suction muffler (165) may be connected to the suction side of the valve assembly (160).

[0209] 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 to the compression chamber (1551) of the cylinder (155).

[0210] 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).

[0211] The compressor's operating process is as follows.

[0212] When power is applied to the stator coil (127), 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).

[0213] In particular, in the case of a single-phase induction motor, when a single-phase AC power source is applied to the main winding (128) and sub-winding (129) of the stator coil (127), the phase of the current flowing in the sub-winding (129) is 90 degrees ahead of the phase of the current flowing in the main winding (128) by the capacitor (170), and a rotating magnetic field is generated.

[0214] Here, the method of starting a single-phase induction motor by connecting a capacitor (170; also called a condenser) to the sub-winding (129) to flow a current 90 degrees ahead and generating a rotating magnetic field by the current flowing in the main winding (128) and the sub-winding (129) can be named a capacitor-starting type. The sub-winding (129) can be named a starting winding.

[0215] The crankshaft (136) rotates together with the rotor (130). One side of the connecting rod (140) is coupled with the eccentric shaft (138) of the crankshaft (136) and rotates along the rotary motion of the eccentric shaft (138). The other side of the connecting rod (140) is coupled with the piston (156) and thus repeatedly moves forward and backward in the radial direction of the crankshaft (136).

[0216] 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).

[0217] 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).

[0218] 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.

[0219] As described above, the reciprocating compressor supports one side of the crankshaft (136) by the shaft support member (154). In particular, the shaft support member (154) surrounds the upper end of the crankshaft (136) and rotatably supports it, thereby limiting the upper end of the crankshaft (136) from moving in the radial direction.

[0220] However, since the lower portion of the crankshaft (136) does not have a support structure such as a shaft support portion (154), wheeling may occur at the lower portion of the rotor (130). That is, the lower portion of the rotor (130) may move radially.

[0221] Due to this, there was a problem that the lower part of the rotor (130) interfered with the lower part of the stator (120), resulting in a decrease in the performance of the motor.

[0222] In addition, a single-phase induction motor applied to a reciprocating compressor is started by generating a rotating magnetic field by the current flowing in the main winding (128) and the sub-winding (129).

[0223] When a high level of overcurrent flows in the main winding (128), a force is applied in a radial direction perpendicular to the crankshaft (136).

[0224] Due to this, the lower portions of the rotor (130) and the stator (120) positioned in the opposite direction to the shaft support (154) may interfere with each other.

[0225] The present invention proposes a multi-stage stacked structure of the stator (120) to avoid interference between the lower portions of the rotor (130) and the stator (120).

[0226] The stator core (121) is formed by stacking and joining multiple electrical steel plates. A rotor receiving hole is formed on the inside of the stator core (121). The rotor receiving hole may be formed in a cylindrical shape. The inner circumferential surface (1261, 1262) of the stator core (121) may form the rotor receiving hole.

[0227] The inner circumferential surfaces (1261, 1262) of the stator core (121) may be formed in a multi-stage configuration. Here, the term "multi-stage" refers to a plurality of steps. In the present embodiment, the stator (120) is shown as having a two-stage laminated structure. The inner circumferential surfaces (1261, 1262) of the stator core (121) may be formed in a two-stage configuration.

[0228] The outer surface of the stator core (121) refers to the outer surface of the back yoke (122). The inner surface (1261, 1262) of the stator core (121) may refer to the inner surface of the pole shoe (125).

[0229] The diameter of the inner circumferential surface (1261, 1262) of the stator core (121) may be formed differently along the axial direction. Through this, the gap between the stator (120) and the rotor (130) may be formed differently depending on the inner diameter of the stator core (121). Here, the inner diameter refers to the diameter of the inner circumferential surface.

[0230] For example, the diameter of one side of the first inner surface (1261) of the stator core (121) positioned close to the shaft support (154) may be formed smaller than the diameter of the other side of the second inner surface (1262) of the stator core (121) positioned in the opposite direction to the shaft support (154).

[0231] The inner surface of the stator core (121) may include a first inner surface (1261) to an M-th inner surface. Here, M is a natural number greater than or equal to 2. In the present embodiment, M may be 2.

[0232] The inner surface (1261, 1262) of the stator core (121) includes a first inner surface (1261) and a second inner surface (1262). The first inner surface (1261) and the second inner surface (1262) may have different diameters. The diameter of the first inner surface (1261) may be formed to be smaller than the diameter of the second inner surface (1262).

[0233] The first inner surface (1261) has a first diameter. The first inner surface (1261) can extend axially. The first inner surface (1261) can extend circumferentially.

[0234] The second inner surface (1262) has a second diameter. The second diameter is larger than the first diameter. The second inner surface (1262) can extend axially. The second inner surface (1262) can extend circumferentially.

[0235] The first inner surface (1261) and the second inner surface (1262) have different curves.

[0236] A step (1263) is formed between the first inner surface (1261) and the second inner surface (1262). The step (1263) is formed to connect the lower end of the first inner surface (1261) and the upper end of the second inner surface (1262), which are adjacent in the axial direction.

[0237] The step (1263) may be formed to protrude radially from the upper end of the second inner surface (1262) toward the lower end of the first inner surface (1261). The step (1263) may extend circumferentially along the inner perimeter of the second inner surface (1262).

[0238] The inner end of the step (1263) is connected to the lower end of the first inner surface (1261). The outer end of the step (1263) is connected to the upper end of the second inner surface (1262).

[0239] The second inner surface (1262) can be processed by punching an electrical steel plate or cutting using a cutting tool. In this embodiment, the second inner surface (1262) of the stator core (121) can be processed by cutting.

[0240] The thickness of the pole shoe (125) formed on the first inner surface (1261) can be formed thicker than the thickness of the pole shoe (125) formed on the second inner surface (1262).

[0241] The second inner surface (1262) may be partially cut along a circumferential direction or may be completely cut along the entire circumferential direction. In this embodiment, the second inner surface (1262) is shown as having been completely cut along the circumferential direction.

[0242] The height A of the second inner circumference (1262) has the following relationship.

[0243] A=a*B

[0244] A: Height of the second inner surface (1262), a: 0 <a≤0.5mm 범위에서의 상수값, B: 스테이터코어(121)의 적층높이

[0245] The gap C between the outer surface of the rotor (130) and the second inner surface (1262) of the stator core (121) has the following relationship.

[0246] C=b*C'

[0247] C: Air gap (radial distance) between the outer surface of the rotor (130) and the second inner surface (1262) of the stator core (121), b: a constant value in the range of 1≤b≤1.4, C': Air gap (radial distance) between the outer surface of the rotor (130) and the first inner surface (1261) of the stator core (121)

[0248] According to this configuration, the gap (C') between the outer surface of the rotor core (131) and the first inner surface (1261) of the stator core (121) can be maintained smaller than the gap (C) between the outer surface of the rotor core (131) and the second inner surface (1262) of the stator core (121).

[0249] Through this, the size of the gap is formed to be small, so that the mutual inductance between the rotor (130) and the stator (120) can be increased. As a result, the motor performance can be improved by increasing the mutual inductance.

[0250] The first inner circumferential surface (1261) of the stator core (121) may be arranged close to the upper end of the crankshaft (136) in the axial direction. The first inner circumferential surface (1261) of the stator core (121) may be arranged close to the frame (152) of the cylinder block (151).

[0251] The first inner circumferential surface (1261) of the stator core (121) may be arranged radially outside the shaft support portion (154) of the frame (152). The first inner circumferential surface (1261) of the stator core (121) may be arranged to overlap radially with the shaft support portion (154) of the frame (152).

[0252] The second inner circumferential surface (1262) of the stator core (121) may be arranged close to the lower end of the crankshaft (136) in the axial direction. The second inner circumferential surface (1262) of the stator core (121) may be arranged far apart in the opposite direction from the frame (152) of the cylinder block (151).

[0253] The second inner surface (1262) of the stator core (121) can be arranged in the opposite direction to the shaft support portion (154) of the frame (152). The second inner surface (1262) of the stator core (121) is formed to surround the lower portion of the outer surface of the rotor core (131).

[0254] The gap (C) between the outer surface of the rotor core (131) and the second inner surface (1262) of the stator core (121) can be maintained larger than the gap (C') between the outer surface of the rotor core (131) and the first inner surface (1261) of the stator core (121).

[0255] Through this, it is possible to prevent the lower ends of the stator core (121) and the rotor core (131) from interfering with each other due to the force acting in one direction (radial direction) due to the overcurrent of the main winding (128) when the compressor is supported on one side and the single-phase induction motor is started. Accordingly, it is possible to secure structural stability not only of the upper ends of the stator core (121) and the rotor core (131) which are relatively stably positioned by the shaft support (154), but also of the lower ends of the stator core (121) and the rotor core (131) which are relatively unstable.

[0256] Therefore, the multi-stage stacked structure of the stator (120) according to the present embodiment can not only improve the performance of the motor but also secure the structural stability of the motor.

[0257] In addition, the multi-stage stacked structure of the stator (120) can reduce hammering noise that may occur at the initial start-up of the motor due to the structural characteristics of the stator coil (127) of a single-phase induction motor, i.e., the main winding (128) and the sub-winding (129) are arranged perpendicularly to each other at a 90-degree spatial angle.

[0258] In addition, it can flexibly cope with constraints such as one-sided support of a reciprocating compressor.

[0259] 3. Description of the configuration of a compressor according to another embodiment of the present invention

[0260] Fig. 11 is a conceptual diagram showing the second inner surface (2262) of the stator core (221) in Fig. 8 partially formed along the circumferential direction.

[0261] Figure 12 is a conceptual diagram showing the second inner surface (2262) of Figure 11 actually applied to the stator core (221).

[0262] This embodiment is different from the above-described FIGS. 1 to 10 in that the second inner circumferential surface (2262) of the stator core (221) is formed to have an inner diameter that increases from the first inner circumferential surface (2261) of the stator core (221) in a partially formed manner along the circumferential direction.

[0263] The second inner circumferential surface (2262) of the stator core (221) may be formed at the lower portion of the stator core (221). Here, the lower portion of the stator core (221) may be arranged in the opposite direction to the shaft support portion (154) of the frame (152) based on the bisecting line when the length of the stator core (221) is divided into two along the axial direction.

[0264] The main winding (128) of a single-phase induction motor is wound in some sections along the circumference of the stator core (221). For example, the first partial coil (129a) of the main winding (128) can be wound in the 6th to 15th slots.

[0265] Here, referring to FIG. 5, the first partial coil (129a) can be placed on the left side of the stator core (221) based on the center line passing through the center of the stator core (221) in the vertical direction.

[0266] The second partial coil (128b) of the main winding (128) can be wound in the fifth to sixteenth slots. The second partial coil (128b) can be placed on the right side of the stator core (221) based on the vertical center line of the stator core (221).

[0267] The second inner circumferential surface (2262) of the stator core (221) may be formed to be radially recessed from the first inner circumferential surface (2261) of the stator core (221). Here, the first inner circumferential surface (2261) of the stator core (221) may be formed on both the upper and lower portions of the stator core (221).

[0268] However, when the first inner circumference (2261) is formed at the bottom of the stator core (221), the first inner circumference (2261) and the second inner circumference (2262) of the stator core (221) are arranged so as not to overlap each other along the circumferential direction at the bottom of the stator core (221).

[0269] The first inner circumferential surface (2261) and the second inner circumferential surface (2262) of the stator core (221) can be alternately arranged along the circumferential direction at the bottom of the stator core (221).

[0270] The second inner peripheral surface (2262) of the stator core (221) can be partially cut radially outward from the first inner peripheral surface (2261). The circumferential section D° of the second inner peripheral surface (2262) of the stator core (221) that is partially cut has the following relationship.

[0271] 0° <D°<180°

[0272] The second inner surface (2262) of the stator core (221) may be formed to be sunken radially outward in a portion of the circumferential direction of the stator core (221) wound around the main winding (128).

[0273] In this embodiment, the area of ​​the second inner circumferential surface (2262) of the stator core (221) is smaller than the area of ​​the second inner circumferential surface (2262) of the stator core (221) according to the embodiments of FIGS. 1 to 10 described above.

[0274] The gap (C) between the second inner surface (2262) of the stator core (221) and the outer surface of the rotor core (131) is larger than the gap (C') between the first inner surface (2261) of the stator core (221) and the outer surface of the rotor core (131).

[0275] Through this, even if a force is applied in one direction to the stator core (221) due to a one-sided support structure of a reciprocating compressor and a high level of overcurrent flowing in the main winding (128) when starting a single-phase induction motor, it is possible to avoid interference between the lower end of the stator core (221) and the lower end of the rotor core (131), which are positioned in the opposite direction to the shaft support (154).

[0276] In addition, the area of ​​the second inner surface (2262) of the stator core (221) is smaller than that of the first inner surface (2261) of the stator core (221), and the gap between the first inner surface (2261) of the stator core (221) and the outer surface of the rotor core (131) is reduced, thereby increasing the mutual inductance between the stator and the rotor, thereby further improving the performance of the motor.

[0277] Since other configurations are the same or similar to the embodiments of FIGS. 1 to 10 described above, duplicate descriptions will be omitted.

[0278] Fig. 13 is a graph for explaining the effect of the two-stage stacked structure of the stator (120, 220) according to the present invention.

[0279] Referring to Fig. 13, when the two-stage stacked structure of the stator (120, 220) is applied to the motor, the improvement efficiency of the motor performance increases by approximately 1.4% compared to the motor to which the two-stage stacked structure of the stator is not applied.

[0280] However, the improvement efficiency of motor performance may be inversely proportional to the height of the second inner surface (1262). For example, when the height of the second inner surface (1262) of the stator (120, 220) is greater than 0 and less than 22.5 mm, the improvement efficiency of motor performance may be approximately 0.7% to 1.40%.

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 inner surface of the above stator is A first inner surface having a first inner diameter; An induction motor including a second inner surface to an M inner surface formed to be sunken in the radial outer direction of the crank shaft from the first inner surface.

2. In paragraph 1, The above second inner surface has a second inner diameter that is larger than the above first inner diameter, An induction motor in which the second inner surface is arranged on one side of the first inner surface with respect to the axial direction of the crank shaft.

3. In paragraph 1, An induction motor in which a step is formed between the first inner surface and the second inner surface.

4. In paragraph 1, An induction motor in which the outer diameter of the rotor is maintained constant along the axial direction of the crankshaft, and the first gap between the first inner surface and the outer surface of the rotor is smaller than the second gap between the second inner surface and the outer surface of the rotor.

5. In paragraph 1, The second inner surface extends in the axial direction of the crankshaft, and the axial height A of the second inner surface is An induction motor in which A=a*B, a is a constant greater than 0 and less than or equal to 0.5, and B is the axial height of the stator.

6. In paragraph 1, The second gap C between the second inner surface and the outer surface of the rotor is An induction motor in which C=b*C', b is a constant greater than or equal to 1 and less than or equal to 1.4, and C' is a first gap between the first inner surface and the outer surface of the rotor.

7. In paragraph 1, An induction motor in which the second inner surface is formed to be sunken along the circumferential direction in a portion of the inner surface of the stator.

8. In paragraph 1, The above stator, Statercore; and It includes a stator coil wound around the above stator core, The above stator coil, A main winding wound in a certain area along the circumference of the stator core; and It includes a sub-winding wound in another area along the circumference of the stator core and having a phase difference of 90 degrees from the main winding, An induction motor in which the second inner surface is formed to correspond to a section of the stator core in which the main winding is wound.

9. In paragraph 8, The above stator core is, White York; A plurality of teeth formed to protrude radially from the inner side of the above back yoke; and It includes a pole shoe formed to protrude in a circumferential direction from the inner end of the above teeth, The thickness of the pole shoe is formed between the radially outer surface and the inner surface of the pole shoe, and the radially inner surface of the pole shoe forms the inner surface of the stator core, An induction motor in which the thickness of the second pole shoe forming the second inner surface is smaller than the thickness of the first pole shoe forming the first inner surface.

10. Shell; An induction motor provided inside the shell and according to any one of claims 1 to 9; and A compressor including a compression unit that compresses refrigerant using power received from the above induction motor.

11. In paragraph 10, A compressor in which the compression unit is arranged on one side of the induction motor along the axial direction of the crankshaft.

12. In paragraph 10, 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.

13. In paragraph 12, The above crankshaft, An eccentric shaft formed to protrude axially from one end of the crank shaft and arranged eccentrically from the center of the crank shaft; and A compressor further comprising a counterweight extending radially in the opposite direction from the eccentric shaft from one end of the crankshaft.

14. In paragraph 12, The above compression part, It includes a shaft support portion that extends in the direction of the rotor from the frame in the axial direction and is coupled with at least a portion of the outer surface of the crank shaft so as to be rotatable together with the crank shaft. The above rotor includes an axial hole penetrating the axial center, The above-mentioned congratulatory message is, A first shaft hole press-fitted with at least a portion of the crankshaft and positioned axially lower than the rotor; and A second shaft hole is provided to accommodate at least a portion of the shaft support, and forms a step radially outward from the first shaft hole, and is located on the upper portion of the rotor. A compressor in which the area of ​​the second shaft hole is positioned radially inside the first inner surface.

15. In paragraph 14, The above compression part, A compressor further comprising a plurality of stator coupling parts formed to protrude axially toward the stator from the frame and coupled with the stator.

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