JP5561094B2 - Motor core with low iron loss degradation under compressive stress - Google Patents

Description

  The present invention relates to a motor core used in a compressor motor of a home air conditioner, a drive motor or a generator (hereinafter simply referred to as “motor”) of a hybrid electric vehicle (EV), and more specifically, compression. The present invention relates to a motor core that is small in iron loss degradation (small increase in iron loss) even in the presence of stress.

  Compressor motors for home air conditioners are generally operated at variable speeds with a maximum frequency of about 200 to 400 Hz, and are controlled by PWM (Pulse Width Modulation) type inverter control. The frequency is superimposed and used. Recently, drive motors and generators of hybrid electric vehicles that are rapidly spreading are also driven at a frequency of about several kHz from the viewpoint of achieving high output and miniaturization.

  A material (core material) used for a core such as a stator (stator) or a rotor (rotor) of the motor as described above is required to have low iron loss from the viewpoint of improving energy efficiency. Therefore, in order to reduce the iron loss in the high frequency region to be used, a high-grade non-oriented electrical steel sheet to which Si and Al are added in total of about 3 to 4 mass% is used for the motor core material.

  By the way, in a compressor motor of an air conditioner or a motor of a hybrid electric vehicle, a shrink fitting method or a press-fitting method is adopted as a method for fixing the stator to the housing (motor case). A compressive stress of about several tens to 100 MPa is generated. Moreover, since the resin motor is generally applied to the drive motor of the hybrid electric vehicle, a compression stress is also applied to the motor core. In the presence of such compressive stress, it is known that the magnetic properties of the electrical steel sheet constituting the core are greatly deteriorated (iron loss increases).

Therefore, it is desired to develop an electromagnetic steel sheet with small iron loss degradation due to compressive stress. As such a material, for example, Si: 2.6 to 4 mass% is added to Patent Document 1 and the specific resistance is 50. A non-oriented electrical steel sheet having a grain size of ˜75 × 10 ⁻⁸ Ωm and an average crystal grain size of more than 60 μm and 165 μm or less is disclosed.

Japanese Patent No. 4023183

  However, the non-oriented electrical steel sheet of Patent Document 1 has only a specific resistance and a crystal grain size equivalent to those of a currently available high-grade electrical steel sheet. Therefore, even if a motor core is manufactured using this material, the degree of iron loss deterioration due to compressive stress is not significantly different from that of conventional materials. Therefore, development of a technique that can further reduce the stress dependence of iron loss is required.

  Accordingly, an object of the present invention is to provide a motor core in which deterioration of iron loss characteristics at high frequency is small even in the presence of compressive stress.

  The inventors diligently studied to solve the above problems. As a result, by irradiating the back yoke part of a magnetic steel sheet (hereinafter also referred to as “stator core material”) coated with a glassy insulating film that constitutes the stator, the deterioration of iron loss characteristics due to compressive stress is suppressed. The present invention has been completed by finding out what can be done.

  That is, the present invention provides a motor core in which electromagnetic steel sheets coated with a vitreous insulating coating are laminated and a compressive stress of 10 MPa or more is applied in the circumferential direction. It is a motor core characterized by being irradiated with laser at intervals of ˜5 mm.

  The magnetic steel sheet in the motor core of the present invention has Si: 4 mass% or less, Al: 3 mass% or less, Mn: 0.05 to 3 mass%, S: 0.005 mass% or less, N: 0.005 mass% or less, O: 0 0.010 mass% or less, and the balance is a component composition of Fe and inevitable impurities.

  In addition to the above component composition, the electromagnetic steel sheet in the motor core of the present invention further contains one or two selected from Sn and Sb in a total amount of 0.20 mass% or less.

  According to the present invention, it is possible to provide a motor core with a small increase in iron loss at high frequencies even in the presence of compressive stress. Accordingly, the motor core of the present invention is a compressor motor for an air conditioner used in a state where compressive stress is applied by shrink fitting, press fitting, resin molding, or the like, a drive motor for a hybrid vehicle (HV) or an electric vehicle (EV), It can be suitably used for a generator, a drive motor of a fuel cell vehicle (FCEV), a high-frequency rotating machine of a high-speed generator, and the like.

It is a schematic diagram explaining the motor core of this invention. It is a figure explaining the method to measure the high frequency iron loss of a stator core. It is a graph which shows the influence which the compressive stress has on the iron loss of a motor core. It is a schematic diagram explaining the other example of the motor core of this invention.

First, the basic technical idea of the present invention will be described.
In drive motors such as compressor motors for home appliance air conditioners and hybrid electric vehicles, shrink fitting or press-fitting methods are generally employed as means for fixing the core to the motor case. It is said that the compressive stress applied in the circumferential direction of the motor core by this shrink-fitting method or press-fitting method is about 20 to 150 MPa. This compressive stress degrades the iron loss characteristics of the electrical steel sheet that constitutes the motor core, and consequently greatly reduces the motor efficiency. Therefore, there is a demand for a motor core with little deterioration in iron loss characteristics even under compressive stress.

  Therefore, the inventors investigated the high-frequency iron loss characteristics under the compressive stress of the electrical steel sheet constituting the stator of the motor, and in the presence of the compressive stress, not only the hysteresis loss but also the eddy current loss increased. It became clear. In general, motors such as compressor motors for air conditioners and hybrid vehicles are driven with harmonics of several kHz superimposed on them in order to control the inverter in addition to the high fundamental frequency. . Therefore, in order to improve the high frequency iron loss characteristic, it is an important issue to suppress an increase in eddy current loss.

  Therefore, the cause of the increase in eddy current loss in the presence of compressive stress was investigated. It changes to face the direction perpendicular to the compressive stress. Therefore, when trying to magnetize this steel plate, it is necessary to change the direction of the magnetization vector greatly compared to the case where there is no compressive stress, and the eddy current for that flow flows in the steel plate surface. As a result, eddy current loss increased.

  Therefore, the inventors have repeatedly studied a motor core (stator) in which eddy current loss does not increase even when compressive stress is applied. As a result, if the back yoke part of the laminated electromagnetic steel plates (stator core material) constituting the stator is irradiated with laser, the path of the eddy current flowing in the steel plate surface can be reduced, and consequently the iron loss due to the eddy current can be reduced. We thought that the increase in the amount could be effectively suppressed. However, as a result of investigations by the inventors, an electromagnetic steel sheet coated with an organic resin-inorganic mixed film, an organic resin film, or an inorganic (phosphate) film, which is usually used as an insulating film for non-oriented electrical steel sheets. Then, the film of the part irradiated with the laser disappears, and when this is laminated and made into a core, a short circuit occurs at the place where the film is burnt down, and the iron loss characteristic is lowered. It has been found that an electromagnetic steel sheet coated with a glassy insulating film can obtain the effect of laser irradiation because the film remains without being lost even when irradiated with laser. Hereinafter, the experiment that became the basis for finding the above knowledge will be described.

Components of Si: 3.5 mass%, Al: 0.5 mass%, Mn: 0.3 mass%, S: 0.003 mass%, N: 0.0010 mass%, Sb: 0.03 mass%, O: 0.0012 mass% Thickness of composition: on a steel plate surface of 0.30 mm, an organic resin-inorganic mixed coating (aluminum dichromate-acrylic resin emulsion-ethylene glycol) and a glassy insulating coating (SiO ₂ -B ₂ O ₃ ) as an insulating coating -ZnO-based) two types of non-oriented electrical steel sheets, a 12-slot stator core material was punched with an outer diameter of 100 mmφ and a back yoke width of 16 mm, and then the stator core material back As shown in FIG. 1, the yoke was irradiated with laser at 1 mm intervals in a concentric manner in the circumferential direction. In the laser beam irradiation, a steel sheet surface was irradiated with a YAG laser having a wavelength of 1.06 μm with a beam diameter of 0.2 mm.

  Next, the stator core material was laminated to a stack thickness of 30 mm to produce a stator core, and the shrink-fitting allowance was changed in a range of 0 to 100 μm and fixed to a non-magnetic stainless steel ring imitating a motor case. At this time, the circumferential compressive stress generated by shrink fitting was measured by attaching a strain gauge to the central portion of the back yoke. Here, the shrinkage allowance of 0 μm means a free state in which the stator core is not fixed to the ring at all.

Next, an excitation coil and a pickup coil are wound around the back yoke portion including the stainless steel ring on the stator core fixed to the stainless steel ring, as shown in FIG. _{10 / 1k} ) was measured. FIG. 3 shows the result of the above measurement as a relationship between the compressive stress in the circumferential direction of the stator generated by shrink fitting and the high-frequency iron loss.

  From FIG. 3, in the motor core with 0 PMa compressive stress without shrink fitting, the iron loss increases due to laser irradiation, and in the motor core without laser irradiation, the iron loss increases rapidly as the compressive stress increases. However, in the laser-irradiated motor core, the increase in iron loss due to compressive stress is small, and when the insulating coating is an organic resin-inorganic mixed coating and a glassy insulating coating, the latter has a smaller increase in iron loss. As a result, it can be seen that in the mocore in which compressive stress due to shrink fitting is generated at 10 MPa or more, by increasing the iron loss due to the compressive stress by irradiating the back yoke part with laser as compared with the case where it is not irradiated.

  Therefore, in order to investigate the cause of the decrease in iron loss due to laser irradiation, when the core loss separation of the shrink-fit core was performed, the hysteresis loss increased slightly by laser irradiation, but the eddy current loss decreased greatly by laser irradiation. It became clear that The cause of the decrease in eddy current loss due to laser irradiation has not yet been clarified, but the tensile stress was applied to the steel sheet due to thermal strain due to laser irradiation, and as a result, the effect of compressive stress due to shrink fitting was alleviated. Conceivable.

  Moreover, the reason why the laser irradiation effect is not sufficient in the motor core using the steel sheet coated with the insulating coating of the organic resin-inorganic mixed coating is that the short-circuit occurs between the steel plates because the insulating coating is destroyed and disappears by the laser irradiation. This is thought to be because the effect of reducing eddy current loss due to laser irradiation was offset.

  It is well known that a vitreous tension-added insulating coating is effective in improving the magnetic properties of a grain-oriented electrical steel sheet. It is also known to apply a phosphate-colloidal silica-based vitreous tension-added insulating coating to a non-oriented electrical steel sheet (for example, JP-A-06-188115). However, the vitreous insulating film in the present invention does not need to be a tension-adding insulating film like the above-described insulating film, and it is only required to be vitreous. That is, the feature of the present invention is that, in the organic resin-inorganic mixed coating normally used as the insulating coating of the non-oriented electrical steel sheet, a short circuit occurs between the steel sheets by the laser irradiation, and the iron loss reduction effect by the laser irradiation is offset. However, the use of a vitreous insulating coating prevents the insulating coating from being destroyed by laser irradiation and is intended to enjoy the effect of reducing iron loss. This is based on the knowledge that the vitreous insulating coating easily transmits laser, so that energy can be effectively applied to the steel sheet.

  Moreover, it is thought that the reason why the core loss increased by laser irradiation in the core not shrink-fitted was that the hysteresis loss increased due to thermal strain due to laser irradiation. Therefore, irradiating the teeth portion where no shrink fitting stress occurs with a laser leads to an increase in iron loss. Therefore, in the present invention, laser irradiation is performed only on the core back portion to which compressive stress is applied. I decided to do it.

  The laser irradiation direction may be either the circumferential direction or the radial direction of the back yoke part, or may be discontinuously irradiated as shown in FIG.

The laser beam used for the laser irradiation is a YAG laser having a wavelength of 1 to 2 μm, a VO ₄ laser, a disk laser, a fiber laser, and these second and third harmonic lasers, a CO ₂ laser having a wavelength of 10.6 μm, and the like. Can be used. Laser output forms include continuous oscillation and pulse oscillation. Furthermore, pulse oscillation includes normal pulse oscillation and Q-switch pulse oscillation. However, since the Q-switch pulse oscillation in the school building is irradiated with a high output instantaneously, there is a possibility that damage to the insulating film is increased. Therefore, a continuous wave or normal pulsed laser is preferable. Moreover, it is preferable to make the beam diameter at the time of irradiation into the range of 0.02-1 mm. If the thickness is less than 0.02 mm, the energy density is too high, and the steel sheet may partially melt. On the other hand, if it exceeds 1 mm, the strain region is wide, so that the deformation of the steel sheet may increase.

  Laser irradiation is preferably performed in a linear or broken line manner as shown in FIGS. 1 and 4, with the line interval being preferably about 0.3 to 5 mm. . If it is less than 0.3 mm, a large strain is introduced into the steel sheet due to thermal strain caused by laser irradiation, and iron loss increases or the core material is deformed. On the other hand, if it exceeds 5 mm, the effect of reducing iron loss by laser irradiation cannot be obtained sufficiently. In addition, when irradiating to radial direction, it is preferable to set it as the space | interval of 0.3-5 mm on both an inner diameter side and an outer diameter side.

  In addition, in the present invention, the reason why the value of the compressive stress generated in the motor core is limited to 10 MPa or more is that the motor core cannot be sufficiently fixed at less than 10 MPa, and as shown in FIG. This is because the iron loss reduction effect cannot be obtained.

Next, the component composition of the electrical steel sheet used as the material for the motor core of the present invention will be described.
Si: 4 mass% or less Si is an element effective for increasing the specific resistance of steel. However, when it exceeds 4 mass%, the magnetic flux density of the motor core also decreases as the saturation magnetic flux density decreases. Further, when rolling to the final plate thickness, there is a possibility that the plate breaks even if it is warm-rolled, so the upper limit is preferably 4 mass%. In addition, although a minimum in particular is not restrict | limited, From a viewpoint of raising specific resistance, it is preferable that it is 0.1 mass% or more. More preferably, it is the range of 1-4 mass%.

Al: 3 mass% or less Al is an element effective for increasing the specific resistance. However, if it exceeds 3 mass%, the magnetic flux density of the motor core decreases as the saturation magnetic flux density decreases. Therefore, the upper limit is set to 3 mass%. Is preferred. More preferably, it is 2 mass% or less.

Mn: 0.05-3 mass%
Mn is an element necessary for preventing red heat brittleness due to S, and it is preferable to add 0.05 mass% or more. On the other hand, if the addition exceeds 3 mass%, the saturation magnetic flux density decreases, so the upper limit is preferably 3 mass%. More preferably, it is the range of 0.1-2 mass%.

S: 0.005 mass% or less S is an impurity that is inevitably mixed. When the content of S is increased, a large amount of sulfide inclusions are formed, which causes an increase in iron loss. Therefore, in the present invention, the upper limit is preferably set to 0.005 mass%. More preferably, it is 0.002 mass% or less.

N: 0.005 mass% or less N is an impurity that is inevitably mixed in as in S, and if the content is large, a large amount of nitride is formed, causing iron loss to increase. Is preferably 0.005 mass%.

O: 0.010 mass% or less O, like S and N, is an impurity that is inevitably mixed in. If the content is large, a large amount of oxide inclusions are formed, and the iron loss increases. Therefore, the upper limit is preferably 0.010 mass%.

The electrical steel sheet used for the motor core of the present invention may contain Sn and Sb in the following ranges in addition to the above components.
One or two types selected from Sn and Sb: 0.20 mass% or less in total Sn and Sb not only improve the texture by improving the texture, but also oxynitriding of the steel sheet surface layer and the accompanying surface layer It is an element that has the effect of preventing the deterioration of magnetic properties by suppressing the formation of fine particles. However, if the total content of the above elements exceeds 0.20 mass%, the growth of crystal grains is inhibited and the magnetic properties are deteriorated. Therefore, when added, the content should be 0.20 mass% or less. preferable.

  In the electrical steel sheet used for the motor core of the present invention, the balance other than the above components is Fe and inevitable impurities. However, as long as the effects of the present invention are not impaired, the inclusion of components other than those described above is not rejected.

  The motor to which the motor core of the present invention can be applied may be of any type as long as compressive stress is applied to the motor core. For example, a concentrated winding type permanent magnet motor or a distributed winding type permanent magnet motor. It can be applied to a split core type permanent magnet motor, an induction motor, a reluctance motor, and the like.

  Steel having the composition shown in Table 1 was melted and continuously cast into a steel slab by a generally known refining process such as converter-degassing. Next, this steel slab was reheated at 1120 ° C. × 1 hr, and hot rolled to a finish rolling finish temperature of 850 ° C. to obtain a hot rolled sheet having a thickness of 2.0 mm. After hot-rolling sheet annealing at 1000 ° C. × 30 sec, pickling, cold rolling to form cold-rolled sheets with thicknesses of 0.30 mm and 0.20 mm, and finishing annealing at 1000 ° C. × 10 sec A non-oriented electrical steel sheet was manufactured by applying the insulating coating shown in Table 1.

The following evaluation was performed on the electromagnetic steel sheet.
<Measurement of magnetic flux density B ₅₀ >
From the magnetic steel sheet, an Epstein specimen having a width of 30 mm and a length of 280 mm was taken from the rolling direction and the direction perpendicular to the rolling direction, and the magnetic flux density B ₅₀ when magnetized at 5000 A / m was measured according to JIS C2550.
<Motor core iron loss measurement>
After punching the non-oriented electrical steel sheet into a stator core material having the same 12 slots as in FIG. 1 and having an outer diameter of 100 mmφ and a back yoke width of 16 mm, a continuous wave YAG laser having a wavelength of 1.06 μm is used. A laser was irradiated to the back yoke portion of the stator core material under various conditions shown in Table 1.
Next, the laser-irradiated core material is laminated at a stacking thickness of 30 mm to produce a stator core, and this stator core is shrink-fit into a nonmagnetic stainless steel ring having an inner diameter of about 100 mmφ with a shrinkage allowance of 0 to 100 μm. Then, compressive stress was generated in the circumferential direction of the stator. The compressive stress was measured using a strain gauge attached to the center of the back yoke of the stator. Next, as shown in FIG. 2, an excitation coil and a pickup coil including the stainless steel ring are wound around the back yoke portion, and the iron loss W _{10 / in the} circumferential direction of the motor core at a frequency of 1 kHz and a maximum magnetic flux density of 1T. _1k was measured.

  Table 1 also shows the results of the above measurements. From this result, it was confirmed that the stator core irradiated with laser under the conditions suitable for the present invention can suppress the deterioration of the iron loss property under the compressive stress.

  The motor core technology of the present invention can be applied to high-speed motors that are fixed by shrinkage fitting, such as drive motors and generators for hybrid electric vehicles, compressor motors for air conditioners, and spindle motors for machine tools.

1: Stator core 2: Laser irradiation position 3: Rotor 4: Permanent magnet 5: Stainless steel ring (non-magnetic)
6: Winding

Claims (3)

In a motor core in which electromagnetic steel sheets coated with a glassy insulating coating are laminated and a compressive stress of 10 MPa or more is applied in the circumferential direction, a laser is provided at intervals of 0.3 to 5 mm on the back yoke portion of the electromagnetic steel sheet constituting the motor core. A motor core characterized by being irradiated. The magnetic steel sheet has Si: 4 mass% or less, Al: 3 mass% or less, Mn: 0.05 to 3 mass%, S: 0.005 mass% or less, N: 0.005 mass% or less, O: 0.010 mass% or less, The motor core according to claim 1, wherein the balance has a composition composed of Fe and inevitable impurities. 3. The motor core according to claim 1, wherein the electromagnetic steel sheet further contains one or two selected from Sn and Sb in a total of 0.20 mass% or less in addition to the component composition.

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