INSULATION STRUCTURE

Description

TECHNICAL FIELD

[0001] The following disclosure relates to a motor including an insulation structure.BACKGROUND

[0002] A prior interior permanent magnet (IPM)-type motor has a permanent magnet embedded in a rotor, and may be driven by pulse width modulation (PWM) control of an inverter delivering power to a coil assembly. A common mode voltage may be applied to parasitic capacitance of the motor by the PWM control, thus generating an axis voltage between the shaft axis and bearing of the motor.

[0003] When the axis voltage is generated between the shaft axis of the motor and the bearing, and a bearing ball and an inner / outer ring come into contact with each other in a case where the motor is running, an axis current may flow through the bearing due to the axis voltage, which may cause bearing corrosion. The bearing corrosion may cause a bearing noise and excessive vibration, which may cause motor failure in the long term.

[0004] In addition, as specifications required for the motor are gradually increased, a voltage of the power applied to the motor may be increased, and a carrier frequency used by the inverter may tend to be increased. As a result, the axis voltage and the axis current, which are main causes of the bearing corrosion, may also be increased, resulting in an increase in the frequency of failures caused by the bearing corrosion.

[0005] In order to solve this problem, the prior art may use a ceramic bearing, an SGR bearing, or an RGC bearing. However, in this case, a material cost may be increased. In addition, even though using such an anti-corrosion structure, a motor adopting an oil cooling method may have an oil film formed between its structure and a rotor assembly, and thus have a significantly lower anti-corrosion effect.

[0006] EP 3185 405 A1 an electric motor in such a way that even when controlled by a frequency converter or other electronic speed controller no increased bearing load occurs by such high-frequency currents. The shield consists of an outer ring made of plastic, a plastic inner ring and a shield in the form of a metallic ring. The metallic ring is electrically connected to the stator core.

[0007] US 5 979 087 A discloses an electromechanical machine including a stator fixed with respect to a housing structure and a rotor fixed with respect to a driven shaft. A shield is constructed as a sheet assembly including a plurality of sheet member. Each sheet member comprises an insulative layer having a conductive layer on one surface thereof. Each sheet member is oriented such that conductive layer will be radially inward (i.e., closer to shaft) with respect to insulative layer. The sheet members are grounded to core by the direct contact of conductive layer, as disposed on finger portions, with the inside walls of slot.

[0008] WO 2016 / 091360 A2 discloses an electrical machine in which the effects occurring due to the capacitive coupling between the windings carrying the common-mode voltage and the rotor are reduced. The machine includes a closure element, which shields the stator windings extending inside the metal core from the rotor. On the closure element, a conductor region is formed over its entire length, which at the end faces each having a conductor region extension consisting of an electrically conductive film and connected to the housing. A second surface layer is applied on a surface of the conductor region and designed to insulate the conductor region against the laminated core of the stator.

[0009] US 2008 / 238230 A1 discloses a motor in which a magnetic center of a core around which coil are wound is offset from a magnetic center of a magnet in a thrust direction, so that a shaft is attracted to a thrust bearing, and natural vibration can be suppressed during the driving. The motor is provided with a magnetic shield f a magnetic material that shields leakage flux leaking from the magnet o the coil. The motor may include insulating members in addition to the above-mentioned structure, in order to prevent insulation failure between the magnetic shield and the coil. The insulating member is provided between each of the first and / or second shielding plates, which is formed in a substantially annular shape so as to cover one side and / or the other side coils of the coil in the thrust direction and is provided on one side and / or the other side of the coil in the thrust direction, and each of one side and / or the other side coils and / or of the coil in the thrust direction that are covered with the shielding plates. The first and second shielding plates are fixed to the holder that is a part of a housing of the stator.

[0010] WO 2022 / 024365 A1 discloses a rotary electric machine capable of reducing the shaft voltage and ensuring cooling performance. The motor includes an electrostatic shield, a metal that is non-magnetic and has high electrical conductivity. The shield has having a plurality of holes. The electrostatic shield is arranged in a gap formed between the outer peripheral surface of the rotor core and the inner peripheral surface of the stator core.

[0011] US 7 113 365 B1 discloses a disk drive comprising a spindle motor having a windings shield for reduced disk voltage coupling. A first ring-shaped shield is disposed in the first vertical gap between the windings and the hub to reduce the voltage coupled to the surface of the disk. A first ring-shaped insulator is disposed between the first ring-shaped shield and the windings. The ring-shaped insulator may be a separate element installed into the spindle motor during the assembly process. In an alternative embodiment, the ring-shaped insulator is attached to, or otherwise integrated with, the first ring-shaped shield using, for example, any suitable adhesive. The first ring-shaped shield is coupled to the base in order to ground the first ring-shaped shield to the base.

[0012] US 2022 / 255394 A1 discloses an electrical machine comprising a stator, a rotor rotatable around a rotation axis and a bearing assembly for supporting the rotor so as to improve protection of the bearing arrangement from common mode voltage effects in electrical machines. The machine is provided a shielding element that includes a ring part extending in the radial direction of the motor and a circumferential part extending the axial direction.SUMMARY

[0013] This Summary is provided to introduce a selection of concepts in simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0014] A motor including an insulation structure according to the present invention is set forth in claim 1. The insulation structure may reduce a production cost by adopting a method of reducing a magnitude of an axis voltage itself instead of using an expensive ceramic bearing and proposing an insulation structure that may be directly applied to an end coil to thus minimize a motor failure caused by corrosion, and simultaneously use an inexpensive steel ball bearing.

[0015] In one general aspect, the insulation structure applied to each of two ends of a stator in an axial direction to block an electric field of an end coil assembly from being applied to a motor shaft includes: a conducting part extending in a predetermined induction direction parallel to a direction in which the end coil assembly is pulled out from the stator and inducing the electric field of the end coil assembly to be directed in the induction direction; and an insulating part positioned between the conducting part and the end coil assembly to insulate the conducting part.

[0016] The conducting part is positioned inside the end coil assembly, and the insulating part surrounds the conducting part, and includes an insulating paper having a first surface in contact with an inner surface of the end coil assembly.

[0017] The insulating paper includes a first insulating part bent and surrounding an entire outer surface of the conducting part, and a coupling part formed by pulling out and coupling both ends of the first insulating part to each other.

[0018] The conducting part may extend in the induction direction to be longer than a maximum length of the end coil assembly pulled out from each of the two ends of the stator.

[0019] A second surface of the insulating paper may be in contact with the motor housing, and one of the first and second surfaces of the insulating paper may be spaced apart from the motor shaft and a rotor structure by a predetermined distance.

[0020] The conducting part may include a first conducting part positioned inside the end coil assembly, a second conducting part positioned on each of the two ends of the stator and positioned outside the end coil assembly, and a connecting part having two ends to which the first conducting part and the second conducting part are respectively connected, and the insulating paper surrounds the conducting part, and is in contact with the inner surface of the end coil assembly and each of the two ends of the stator.

[0021] The insulating paper may include a fourth insulating part surrounding an entire outer surface of the first conducting part and in contact with the inner surface of the end coil assembly, a fifth insulating part surrounding an entire outer surface of the second conducting part and in contact with either end of the stator, and a sixth insulating part surrounding an entire outer surface of the connecting part.

[0022] A thickness of the insulating paper may be smaller than a shoe thickness of a stator core of the stator.

[0023] Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a cross-sectional view showing an internal structure of a motor using a first embodiment of an insulation structure of the present disclosure. FIG. 2 is a schematic view showing an application form of a first embodiment of the insulation structure of the present disclosure. FIG. 3 is a schematic view showing an example of the insulation structure, which does not form part of the present invention but contains useful information for understanding the present invention. FIG. 4 is a schematic view showing a third embodiment of the insulation structure of the present disclosure. FIG. 5 is a perspective view showing a third embodiment of the insulation structure of the present disclosure. FIG. 6 is a perspective view of a stator using a third embodiment of the insulation structure of the present disclosure. FIG. 7 is a partial plan view of a stator using the insulation structure of the present disclosure. DETAILED DESCRIPTION

[0025] Hereinafter, the present disclosure is described in more detail with reference to the accompanying drawings. Terms and words used in the specification and claims are not to be construed as general or dictionary meanings, and are to be construed as meanings and concepts based on a principle in which the inventors may appropriately define the concepts of terms in order to describe their inventions in the best mode.

[0026] Hereinafter, the description describes a basic configuration of an insulation structure 1000 and a first embodiment of the present disclosure with reference to FIG. 1.

[0027] The insulation structure 1000 of the present disclosure is applied to each of two ends of a stator S in an axial direction to block an electric field of an end coil assembly C from being applied to a motor shaft, and serves to prevent the electric field from the coil assembly inserted into the stator S from being delivered to a rotor structure R. In detail, the insulation structure 1000 of the present disclosure includes a conducting part 100 and an insulating part 200. The conducting part 100 extends in an induction direction parallel to a direction in which the end coil assembly C is pulled out from the stator S, and thus induce the electric field of the end coil assembly C to be directed in the induction direction. In addition, the insulating part 200 is positioned between the conducting part 100 and the end coil assembly C to insulate the conducting part 100.

[0028] In detail, as shown in a first embodiment shown in FIG. 1, in the present disclosure of the insulation structure 1000, the conducting part 100 is positioned inside the end coil assembly C (to be close to the rotor structure R), and the insulating part 200 surrounds the conducting part 100. Here, the insulating part 200 includes an insulating paper having one surface in contact with an inner surface of the end coil assembly C. Here, the insulating paper includes a first insulating part 210 bent and surrounding an entire outer surface of the conducting part 100, and a coupling part 220 formed by pulling out and coupling both ends the first insulating part 210 to each other. The coupling part 220 may be formed by bond-coupling both the ends of the first insulating part 210 to each other.

[0029] The electric field of the end coil assembly C may be moved along the conducting part 100 by adopting a first embodiment of the insulation structure 1000 of the present disclosure, thus minimizing the electric field delivered to the rotor structure R. In addition, the insulating part 200 surrounds the entire surface of the conducting part 100, and the conducting part 100 and the end coil assembly C are insulated from each other without a current flowing therebetween. Accordingly, compared to a method of inducing the electric field by grounding to the end coil, it is possible to induce the electric field without connecting each end coil strand with the conducting part 100, thereby increasing manufacturing convenience and stability. In addition, the insulating part 200 may protect the conducting part 100 from an external stimulus such as cooling oil, thus maintaining durability of a motor.

[0030] Further, the coupling part 220 may be disposed at each of two ends of the conducting part 100 in an extension direction, and in contact with each of the two ends of the stator S. Accordingly, the coupling part 220 may not interfere with an electric field delivery path, thus maximizing an axis voltage reduction effect, and prevent the bonding of the coupling part 220 from being damaged by the cooling oil or a motor housing H.

[0031] The following is a comparison of changes in a charge on a surface of the rotor structure R based on whether a first embodiment of the insulation structure 1000 of the present disclosure is applied thereto. As a result, it is confirmed that the charge remains on the surface of the rotor structure R when the insulation structure 1000 is not applied to the end coil assembly C. On the other hand, it may be confirmed that the charge on the surface of the rotor structure R is reduced when a first embodiment of the insulation structure 1000 is applied to the end coil assembly C. It is confirmed also from an experiment that the axis voltage is decreased by about 69% in an experimental group to which a first embodiment of the insulation structure 1000 of the present disclosure is applied, compared to a non-experimental group.

[0032] In addition, the insulating part 200 of the insulation structure 1000 of the present disclosure may be formed by depositing insulation coating of the end coil assembly C, and the conducting part 100 may be in contact with the deposited insulation coating of the end coil assembly C.

[0033] Hereinafter, the description describes an application form of a first embodiment of the insulation structure 1000 of the present disclosure in more detail with reference to FIG. 2.

[0034] In a first-1-th embodiment of the insulation structure 1000 of the present disclosure shown in FIG. 2, the conducting part 100 may extend in the induction direction to be longer than the maximum length of the end coil assembly C pulled out from each of the two ends of the stator S. Accordingly, the insulation structure 1000 of the present disclosure may more reliably shield the electric field of the end coil assembly C from being delivered to the rotor structure R.

[0035] Further, in a first-2-th embodiment of the insulation structure 1000 of the present disclosure shown in FIG. 2, the other surface of the insulating paper may be in contact with the motor housing H by an extension length of the conducting part 100, and one surface or the other surface of the insulating paper may be spaced apart from the motor shaft and the rotor structure R by a predetermined distance. Accordingly, as shown by an arrow in FIG. 2, the electric field may be moved (or delivered in an order of the end coil assembly C, the insulation structure 1000, and then the motor housing H). Therefore, an electric field movement path may be more clearly secured compared to a basic form of a first embodiment.

[0036] Hereinafter, the description describes an example of the insulation structure 1000 with reference to FIG. 3, which does not form part of the present invention but contains useful information for understanding the present invention.

[0037] In an example of the insulation structure 1000 in FIG. 3, which does not form part of the present invention but contains useful information for understanding the present invention, the insulating paper may include a second insulating part 230 bent and surrounding one surface of the conducting part 100, and a third insulating part 240 formed by pulling out both ends of the second insulating part 230 and bending the same to partially surround the other surface of the conducting part 100. Here, a length 'a' of the third insulating part 240 surrounding the other surface of the conducting part 100 may be 2 mm or more, and may be less than 0.5 times the extension length of the conducting part 100. In addition, a length a+b of the third insulating part 240 extending from the second insulating part 230 may be 2 mm or more. In addition, an open portion of the conducting part 100 may be bonded to protect the conducting part 100 from an external environment such as the cooling oil.

[0038] It is thus possible to lower a cost of materials used for the insulating part 200 by adopting the example of the insulation structure 1000. In addition, the insulating part 200 may be partially open, and the conducting part 100 may thus be easily attached and detached even after the insulating part 200 is bent, thereby increasing convenience in product repair and supplementation.

[0039] Hereinafter, the description describes a third embodiment of the insulation structure 1000 of the present disclosure in more detail with reference to FIGS. 4 to 6.

[0040] In a third embodiment of the insulation structure 1000 of the present disclosure shown in FIG. 4, the conducting part 100 may include a first conducting part 110 positioned inside the end coil assembly C, a second conducting part 120 positioned on each of the two ends of the stator S and positioned outside the end coil assembly C, and a connecting part 130 connecting the first conducting part 110 with the second conducting part 120. Here, the insulating paper may surround the conducting part 100, and be in contact with the inner surface of the end coil assembly C and each of the two ends of the stator S.

[0041] In detail, as shown in FIG. 5, the insulating paper may include a fourth insulating part 250 surrounding an entire outer surface of the first conducting part 110 and in contact with the inner surface of the end coil assembly C, a fifth insulating part 260 surrounding an entire outer surface of the second conducting part 120 and in contact with either end of the stator S, and a sixth insulating part 270 surrounding an entire outer surface of the connecting part 130.

[0042] Here, two or more connecting parts 130 may be provided and spaced apart from each other at equal intervals. It is thus possible to lower a failure rate of the electric field movement path. Only one connecting part 130 may be provided when the failure rate does not need to be considered (that is, when production accuracy is secured). In addition, a width of connecting part 130 may be smaller than 80% of a tooth thickness of the stator S. Accordingly, the insulating part 200 may not interfere with the pulling out of the end coil assembly C.

[0043] As shown by an arrow in FIG. 6, the electric field may be moved in an order of the end coil assembly C, the first conducting part 110, the connecting part 130, the second conducting part 120, and then the motor housing H by adopting a third embodiment of the insulation structure 1000 of the present disclosure. That is, the electric field may be induced outside the stator S (that is, opposite to the rotor structure R, and toward the motor housing H). Accordingly, there may be no limitation in designing the motor using the insulation structure 1000 of the present disclosure. That is, it is possible to clearly secure the electric field movement path, and minimize the delivery of the electric field to the rotor structure R even when the two ends of the end coil assembly C and motor housing H of the motor are not adjacent to each other. It is confirmed also from an experiment that the axis voltage is decreased by about 28% in an experimental group to which a third embodiment of the insulation structure 1000 of the present disclosure is applied, compared to a non-experimental group.

[0044] Hereinafter, the description describes a fourth embodiment of the insulation structure 1000 of the present disclosure in more detail with reference to FIG. 7.

[0045] As described above, the insulating paper of the insulating part 200 may have a circular band shape, and its inner diameter may be larger than an inner diameter of a stator core by a predetermined error range, and the error range may be at least 0.4 mm. In addition, as shown in FIG. 9, a thickness d1 of the insulating paper may be smaller than a shoe thickness d2 of the stator core of the stator S. In addition, the thickness of the insulating paper may be 0.3 mm or more for ease of manufacture.

[0046] As set forth above, the insulation structure of the present disclosure including the above configuration may reduce the production cost by adopting the method of reducing the magnitude of the axis voltage itself instead of using the expensive ceramic bearing and proposing the insulation structure that may be directly applied to the end coil to thus minimize the motor failure caused by the corrosion, and simultaneously use the inexpensive steel ball bearing.

[0047] The scope of the present invention should not be limited to the embodiments described above. The present disclosure may be applied to various fields, and may be variously modified by those skilled in the art within the scope defined by the claims. Therefore, it is obvious to those skilled in the art that these alterations and modifications fall within the scope defined by the appended claims.

Claims

1. A motor comprising: a motor shaft having an axial direction, a rotor (R) supported on the motor shaft, a stator (S) radially outside of the rotor, and a motor housing (H), wherein the stator (S) includes an end coil assembly (C) inserted into the stator (S) and protruding from each of two ends of the stator (S) in the axial direction, wherein the motor further includes an insulation structure (1000), the insulation structure (1000) being applied to each of two ends of the stator (S) in the axial direction to block an electric field of the end coil assembly (C) from being applied to the motor shaft, wherein the insulation structure (1000) includes: a conducting part (100) extending in the axial direction, the conducting layer (100) being electrically conductive; and an insulating part (200) positioned between the conducting part (100) and the end coil assembly (C) to insulate the conducting part (100), the insulating part (200) being electrically insulating, the conducting part (100) is positioned radially inside the end coil assembly (C) so as to be close to the rotor (R), and characterized in that: the insulating part (200) fully surrounds the conducting part (100), and includes an insulating paper having a first surface configured to be in contact with an inner surface of the end coil assembly (C), wherein the insulating paper includes: a first insulating part (210) bent and surrounding an entire outer surface of the conducting part (100); and a coupling part (220) formed by pulling out and bond coupling both ends of the first insulating part (210) to each other.

2. The motor of claim 1, wherein the conducting part (100) includes: a first conducting part (110) positioned inside the end coil assembly (C); a second conducting part (120) positioned on each of the two ends of the stator (S) and positioned outside the end coil assembly (C); and a connecting part (130) having two ends to which the first conducting part (110) and the second conducting part (120) are respectively connected, wherein the insulating paper surrounds the conducting part (100), and is in contact with the inner surface of the end coil assembly (C) and each of the two ends of the stator (S).

3. The motor of claim 2, wherein the insulating paper includes: a fourth insulating part (250) surrounding an entire outer surface of the first conducting part (110) and in contact with the inner surface of the end coil assembly (C); a fifth insulating part (260) surrounding an entire outer surface of the second conducting part (120) and in contact with either end of the stator (S); and a sixth insulating part (270) surrounding an entire outer surface of the connecting part (130).

4. The motor according to any of claims 1 to 3, wherein the conducting part (100) extends in the axial direction to be longer than a maximum length of the end coil assembly (C) pulled out from each of the two ends of the stator (S).

5. The motor according to any of claims 1 to 4, wherein a second surface of the insulating paper is in contact with the motor housing (H), and one of the first and second surfaces of the insulating paper is spaced apart from the motor shaft and the rotor (R) by a predetermined distance.

6. The motor according to any of claims 1 to 5, wherein a thickness (d1) of the insulating paper is smaller than a shoe thickness (d2) of a stator core of the stator (S).