JP2006223015A - Motor with excellent iron core magnet characteristic and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor with excellent iron core magnet characteristics and a manufacturing method for the motor. <P>SOLUTION: This motor is of an inner rotor type having a motor case and a stator. A portion of the motor case is brought into contact with a yoke of the stator, and tensional stress is applied to the stator by a contact part toward an outer side in the radial direction of the stator. The contact part can be the outer periphery and/or the inner periphery of the yoke of the stator. Besides, it is preferable that a range in which the tensional stress is 10-150 MPa is at least 50 volume% of the total yoke. Moreover, the motor is manufactured by inserting the stator in the motor case in such a state that the temperature of the stator iron core is higher than the temperature of the motor case and then fixing the stator with the motor case. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric motor, and more particularly to an inner rotor type motor in which a stator is arranged on the outside and a rotor is arranged on the inside, and a manufacturing method thereof.

  In recent years, with the increasing need for energy consumption reduction, the importance of improving the efficiency of various motors has increased. For this reason, brushless DC motors that can achieve high efficiency are increasingly used as motor types. In addition, lower iron loss and higher magnetic flux density of iron core materials have greatly contributed to improving motor efficiency. However, even when a motor is manufactured using such a high-grade electrical steel sheet having excellent magnetic properties such as low iron loss and high magnetic flux density, the motor efficiency may not necessarily be improved as expected. ing. This is presumably because there are various factors that degrade the magnetic properties of the electromagnetic steel sheet in the process of manufacturing the iron core by processing the electromagnetic steel sheet and incorporating it as a motor. Accordingly, it can be said that the higher the electromagnetic steel sheet, the more the motor needs to be manufactured under appropriate conditions.

  As one of the causes of iron core performance deterioration occurring in the motor manufacturing process, there is a processing (fixing) process such as shrink fitting and press-fitting, which is employed to fix the stator to the motor case. For example, as shown in FIG. 1, the fixing method by shrink fitting is performed by increasing the temperature of the motor case 9 to thermally expand the motor case 9, inserting the stator 10 having an appropriate size, As shown in FIG. 2, the stator 10 is fixed to the motor case 9 by returning it to room temperature and thermally contracting the motor case 9. In this method, the dimensions of the motor case and the stator are such that the strength for fixing both is sufficiently maintained in the range from the normal temperature to the upper limit of the use temperature of the motor.

  Moreover, in the fixing method by press-fitting, the iron core is pushed into the motor case at around room temperature, and the iron core is fixed to the case.

  In these fixing methods, for example, in an inner rotor type motor having a rotor on the inside, the motor case applies a stress (in the direction of the arrow in FIG. 2) acting on the stator from the outside to the inside of the stator. And the motor case are fixed. However, in such a case, circumferential compressive stress acts on the yoke portion of the stator. It is known that the magnetic properties of an electrical steel sheet deteriorate significantly when stress in the compression direction is applied. That is, an increase in iron loss and a decrease in magnetic permeability occur due to compressive stress. The increase in the iron loss of the yoke portion promotes the increase in the motor iron loss, and the decrease in the magnetic permeability promotes the increase in the copper loss.

  As described above, when the stator is press-fitted into the motor case, compressive stress is applied to the stator, resulting in deterioration of motor characteristics. In particular, in an inner rotor type motor that is frequently used, iron loss deterioration due to such compressive stress occurs in a yoke portion located outside the tooth portion and having a large area occupying the entire stator.

  For example, Patent Document 1 discloses a method for preventing deterioration of iron loss magnetic characteristics due to compressive stress from a motor case. In Patent Document 1, a motor case is brought into contact with a protrusion arranged around a stator, and a caulking portion is provided inside the protrusion serving as a contact portion, thereby preventing deterioration of core characteristics due to stress. However, this method has a problem in that when an excessive stress is applied to the protrusion, the iron core magnetic properties may be deteriorated due to an increase in local stress.

  On the other hand, FIG. 3 is a diagram showing the relationship between the stress in the magnetization direction and the iron loss W15 / 50 of the non-oriented electrical steel sheet (50A700). It is known that the iron loss of a steel sheet is remarkably deteriorated when compressive stress is applied as shown in this figure, and is improved when tensile stress is applied. Therefore, if the compression stress when the iron core is fixed to the motor case by shrink fitting or the like can be reduced, it is expected that the efficiency can be improved by reducing the motor iron loss. Moreover, since the iron loss is improved in the tensile stress side, it can be said that the iron loss value of the material can be further reduced by applying tensile stress to the stator. From such a viewpoint, there are Patent Document 2 and Patent Document 3 as techniques for improving the iron loss of the motor core. These methods are mainly intended to leave a stress that reduces iron core iron loss by utilizing the temperature difference inside the iron core during annealing. However, it is practically difficult to perform annealing and cooling while properly controlling such a temperature difference, and the present invention discloses a measure for preventing deterioration of core characteristics due to shrink fitting and press fitting. It has not been.

Patent Document 4 discloses a technique for applying a tensile stress to the outer peripheral portion of the iron core with resin in a resin-sealed electric motor stator. Although this technology uses a resin as a stress medium, the use of such a resin not only increases the manufacturing cost, but also attempts to impart a desired stress to the iron core due to a problem of insufficient strength of the resin itself. There is a risk that defects such as cracks may occur in the resin portion due to stress received from the iron core. Furthermore, since the thermal contraction rate of the resin is larger than that of the electromagnetic steel sheet, there is a limit to applying the desired tension even if the resin is cured with the iron core deformed, and sufficient iron loss reduction is possible. There is a problem that it is difficult to obtain the effect.
Japanese Patent Laid-Open No. 4-325846 JP 2003-319857 JP JP2003-319618 Japanese Patent Laid-Open No. 2003-79113

  The present invention has been made in view of the above points, and not only prevents deterioration of the iron core magnetic characteristics due to the method of fixing the stator to the motor case, but also positively improves the magnetic characteristics of the iron core from the viewpoint of the motor structure. Therefore, it is intended to provide a motor having excellent iron core magnetic characteristics.

  As a result of studying to solve the above problems, in the present invention, unlike the conventional method of fixing the stator to the motor case while applying compressive stress to the yoke portion of the stator, tensile stress is applied to the yoke portion. By fixing the stator to the motor case while applying, a fixing method that does not deteriorate the iron core magnetic characteristics has been devised, and the present invention has been achieved. That is, the gist of the present invention is that a part of the motor case comes into contact with the yoke portion of the stator, and a tensile stress is applied to the stator toward the radially outer side of the stator by the contact portion. By doing so, the deterioration of the iron core magnetic characteristics is prevented, and a motor with excellent iron core magnetic characteristics is provided.

  The present invention has been made based on such findings, and the gist thereof is as follows.

  [1] In an inner rotor type motor having a motor case and a stator, a part of the motor case comes into contact with a yoke portion of the stator, and the contact portion causes the stator to be in a radial direction of the stator. A motor excellent in iron core magnetic characteristics, characterized in that tensile stress is applied to the outside.

  [2] In the motor according to [1], the contact portion is an outer peripheral portion and / or an inner peripheral portion of the yoke portion of the stator.

  [3] A motor having excellent iron core magnetic characteristics, wherein the region in which the tensile stress is 10 to 150 MPa is 50% by volume or more of the entire yoke portion in [1] or [2].

  [4] When manufacturing an inner rotor type motor with the stator fixed by the motor case, the stator is inserted into the motor case in a state where the temperature of the stator core is higher than the temperature of the motor case, and then fixed. A method for manufacturing a motor with excellent iron core magnetic characteristics.

  According to the present invention, a motor having excellent iron core magnetic characteristics is provided. Further, in the inner rotor type motor, by fixing the stator and the motor case by the motor manufacturing method of the present invention, the stator can be fixed to the motor case without deteriorating the magnetic characteristics of the yoke portion. As a result, the iron loss of the material can be further improved by applying a tensile stress in the circumferential direction of the yoke portion, and a highly efficient motor can be realized.

First, the present inventors examined a structure in which a motor case exerts a tensile stress on an outer peripheral portion of a stator in an inner rotor type motor in which a stator is directly fixed to a metal motor case.

  As a result of the study, the tensile stress in the circumferential direction is applied to the yoke part by applying outward stress to the stator (stress directed radially outward of the stator) at the same time that the motor case contacts from the outside or inside of the stator. It was found that can be applied. And by applying the tensile stress of the circumferential direction to a yoke part, deterioration of the iron core magnetic characteristic resulting from fixation to the motor case of a stator is prevented, and a magnetic characteristic improves further. That is, in the motor having excellent iron core magnetic characteristics according to the present invention, a part of the motor case contacts the outer periphery of the yoke portion of the stator, and the contact portion directs the stator toward the outer side in the radial direction of the stator. Or a part of the motor case is in contact with the inner periphery of the stator yoke, and the contact portion pulls the stator toward the outside in the radial direction of the stator. It is a motor to which stress is applied.

  Hereinafter, the present invention will be described in detail with reference to the drawings. For example, FIG. 4 is a diagram illustrating an embodiment of the present invention. In FIG. 4, the motor case 1 a is manufactured to be slightly larger than the outer periphery of the stator 2, and the stator 2 and the motor case 1 a have fitting portions 3 at appropriate intervals. Here, the dimensions of the stator 2 and the motor case 1a are determined in consideration of the coefficient of thermal expansion.

  In the present invention, when the stator 2 is fixed to the motor case 1a, the motor case 1a is first set in a state where the temperature of the stator 2 is higher than the temperature of the motor case 1a, contrary to the normal shrink fitting. The stator 2 is inserted into. For example, when the temperature of the stator 2 is increased and expanded or the motor case 1a is cooled and contracted, the diameters of the stator 2 and the motor case 1a and the fitting portions 3 are appropriately fitted. Insert the stator 2 with. Subsequently, it returns and fixes to normal temperature.

  As described above, since the motor case 1a fixes the stator 2 while pulling the stator 2 outward (in the direction of the arrow in FIG. 4), no compressive stress is applied to the yoke portion 4 of the stator 2, and A tensile stress is given to the circumferential direction of the iron part 4, and the iron loss of the yoke part 4 falls. As a result, the motor efficiency was improved by about 2% with the same type of motor performed by the method of FIG.

  For example, FIG. 5 is a diagram showing another embodiment of the present invention. In FIG. 5, the motor case 1 b does not achieve fixing while being in contact with the stator 2 from the outside, but a part of the motor case 1 b comes into contact with the inside of the stator 2 (hereinafter referred to as the slot interior), and the stator By applying a stress in the outward direction to 2, a substantially uniform tensile stress is applied to the yoke portion, so that the retention of the iron core and the improvement of the magnetic properties can be achieved at the same time.

  In FIG. 5, the holding member 5 (not shown) integrated with the bottom of the motor case contacts the stator 2 from the inside of the slot, and exerts stress on the stator 2 outward (in the direction of the arrow in FIG. 5). The stator 2 is held and, at the same time, a circumferential tensile stress is applied to the yoke portion. The tensile stress applied in this way is more uniform than in the case of FIG. 4, and iron loss of the yoke portion can be reduced regardless of the motor specifications. Therefore, it can be said that it is particularly effective when strict dimensional accuracy and temperature control are required.

  6 is an elevational cross-sectional view taken along section 11 of FIG. 5, and FIG. In FIG. 6, in order to increase the strength of the holding member 5. The motor case upper surface part mounting bolt 6 is fixed from the upper surface part 8 side. When the holding member 5 has sufficient strength, it is not particularly necessary to perform additional fixing. However, in order to increase the strength, the motor case upper surface portion mounting bolt 6 or the like is also used for fixing from the upper surface portion 8 side as described above. Is preferred. 6 and 7, the bolt 7 is fixed from the upper surface portion 8 side in order to attach the upper surface portion 8 of the motor case 1b to the outer peripheral portion of the motor case 1b.

  The motor case may be in contact with both the outer peripheral portion and the inner peripheral portion of the stator yoke portion.

  As described above, the motor having excellent iron core magnetic characteristics according to the present invention is manufactured with a stator and a motor case having dimensions that allow appropriate stress to be applied at room temperature, and the stator temperature is higher than the motor case temperature. It is manufactured by inserting the stator into the motor case in a high state (for example, heating the stator or cooling the motor case), then returning to normal temperature and fixing.

  Further, when the stator is inserted into the motor case by press-fitting, it is preferable to use a motor having the structure shown in FIG. 5, and after manufacturing the fitting dimension between the inner side of the stator and the holding member, press-fitting By doing so, it is possible to fix the yoke part while applying a stress in the tensile direction.

  Further, since the holding member is inserted into the slot, it occupies a space in the slot, which may cause a decrease in the winding space factor. For this reason, it is preferable that the holding member has a minimum volume that ensures a sufficient holding force. In addition, the holding member does not necessarily have the form as shown in FIG. 5; the shape and size may be changed as necessary, a plurality of holding members may be provided in a divided form, or only a few slots may be provided. It is possible to provide it limited to. It is also possible to make a hole for inserting the holding member inside the stator and insert the holding member with the stator heated or the motor case cooled. It has the effect of.

  Furthermore, in the present invention, in the yoke portion of the stator, the region where the tensile stress is 10 to 150 MPa is preferably 50% by volume or more of the entire yoke portion. In order to improve the iron loss by the tensile stress applied to the yoke portion, 10 to 150 MPa is appropriate as the circumferential stress in the yoke portion. According to FIG. 3, it can be seen that the iron loss increases as the compressive stress is applied, and the iron loss decreases as the tensile stress is applied. However, as the tensile stress is further applied, the iron loss increases again. And when tensile stress is less than 10MPa or exceeds 150MPa, it turns out that sufficient iron loss reduction effect is not acquired. Moreover, even when the region to which such tensile stress is applied is less than 50% by volume, the iron loss reduction effect is insufficient, and a sufficient iron loss reduction effect cannot be obtained. Therefore, from the above, the region where the tensile stress is 10 to 150 MPa is 50% by volume or more of the entire yoke portion. Here, the yoke portion is an outer peripheral portion of the stator excluding a tooth portion (tooth portion) as shown in FIG.

  As described above, the present invention not only prevents the deterioration of the iron core magnetic characteristics due to the method of fixing the stator to the motor case, but also attempts to positively improve the iron core magnetic characteristics from the viewpoint of the motor structure. Is. Furthermore, there is a problem of deterioration of the iron core magnetic properties (iron loss) of the iron core, especially the yoke, which occurs when the motor case and the stator are fixed using strong stress acting on the outer surface of the motor core, such as shrink fitting and press fitting. On the other hand, the present invention is intended not only to prevent such deterioration, but also to provide a method for improving the iron core magnetic characteristics from those expected from the material. From such a point, the present invention is optimal for an inner rotor type motor having a large adverse effect of the compressive force applied to the yoke portion because the yoke portion has a long circumference.

  A motor having the same shape and structure as in FIG. 4 was produced as follows. As a stator for concentrated winding brushless DC motors, they were stamped from JIS50A400 grade non-oriented electrical steel sheets and integrated by caulking. Further, the stator was fixed by winding. The motor case was manufactured by aluminum die casting. The rotor was a surface magnet type, and a rare earth magnet was used as the magnet. In fixing the stator to the motor case, the stator was heated to 150 ° C. and thermally expanded, and then the stator was inserted into the motor case and then returned to room temperature and fixed. Here, the dimensions of the motor case, the stator, and the fitting portion were designed so that a tensile stress of 50 MPa was applied to the stator yoke portion when the motor case was inserted at the above temperature and then returned to room temperature.

  The obtained motor was subjected to stress analysis by a finite element method. As a result, the region of the portion where the tensile stress in the outer peripheral direction of the yoke portion is in the range of 10 to 150 MPa was 75% of the entire yoke portion.

  On the other hand, as a comparative example, a conventional motor in which a motor case as shown in FIG. 9 exerts compressive stress on the iron core was manufactured. Here, the stator was fixed to the motor case by shrink fitting so that the average value of the compressive stress applied to the outer periphery of the yoke portion was about 50 MPa.

  The motor efficiency was measured under the conditions of the rotational speed of 1500 rpm and the load torque of 2.0 Nm for the motors of the present invention and the comparative example obtained as described above. The motor efficiency was evaluated by the ratio between the output and the input power obtained from the torque and the rotational speed (output / input × 100 [%]). The results are shown in Table 1.

  From Table 1, it can be seen that the motor efficiency is higher in the inventive example than in the comparative example.

  A motor having the same shape and structure as in FIG. 5 was produced as follows. As a stator for a stator-shaped concentrated winding brushless DC motor, it was stamped from a JIS35A250 grade non-oriented electrical steel sheet and integrated by caulking. Further, the stator was fixed by winding. The motor case was manufactured by aluminum die casting. The rotor was a surface magnet type, and a rare earth magnet was used as the magnet. When fixing the stator to the motor case, heat the stator to 100 ° C, cool the motor case to -50 ° C, and thermally expand and contract each, then insert the stator into the motor case. , Fixed back to room temperature. The holding member and stator of the motor case are inserted at the above temperature and the tensile stress in the outer peripheral direction applied to the yoke part of the stator when it is at room temperature is 5, 10, 50, 100, 150, 200 MPa. The tightening allowance was adjusted according to the mechanical characteristics of the motor case and iron core material.

  On the other hand, as a comparative example, a conventional motor in which a motor case as shown in FIG. 9 exerts a compressive force on the iron core was produced. A conventional motor was produced in which the motor case exerted a compressive force on the iron core. Here, the stator was fixed to the motor case by shrink fitting so that the compressive stress applied to the outer periphery of the yoke portion was about 50 MPa.

  The motor efficiency was measured and evaluated under the same conditions as in Example 1 for the motors of the present invention and the comparative example obtained as described above. The results are shown in Table 2.

  From Table 2, the motor efficiency of the present invention example is 1.6% or more higher than that of the comparative example in any case. Furthermore, it can be seen that a particularly high motor efficiency is obtained by setting the ratio of the region where the tensile stress in the outer peripheral direction of the yoke portion is 10 to 150 MPa to the yoke portion to 50% by volume or more.

  It is very useful as a rotor core for induction motors, permanent magnet synchronous motors (brushless DC motors), and reluctance motors.

It is a figure which shows the time of the iron core insertion state by the conventional shrink-fitting fixing method. It is a figure which shows the time of the iron core fixed state by the conventional shrink-fitting fixing method. It is a figure which shows the relationship between the stress of a magnetization direction, and the iron loss W15 / 50 of a non-oriented electrical steel sheet (50A700). It is a figure which shows embodiment of this invention. Example 1 It is a figure which shows other embodiment of this invention. (Example 2) FIG. 6 is an elevational sectional view taken along section 13 of FIG. FIG. 7 is an elevational sectional view taken along section 14. It is a figure which shows the yoke part and tooth | gear part in a stator. It is a figure which shows the shape and structure in the conventional motor.

Explanation of symbols

1a 1b Motor case 2 Stator 3 Fitting part 4 Joint part 5 Holding member 6 Motor case top face mounting bolt (outer part of case)
7 Bolt 8 Motor case upper surface 9 Motor case 10 Stator 11, 12 Cross section

Claims (4)

  In an inner rotor type motor having a motor case and a stator, a part of the motor case comes into contact with a yoke portion of the stator, and the contact portion directs the stator toward a radially outer side of the stator. A motor with excellent iron core magnetic properties, characterized by being given tensile stress.   The motor with excellent iron core magnetic characteristics according to claim 1, wherein the contact portion is an outer peripheral portion and / or an inner peripheral portion of a yoke portion of the stator.   3. The motor with excellent iron core magnetic characteristics according to claim 1, wherein a region where the tensile stress is 10 to 150 MPa is 50% by volume or more of the entire yoke portion. When manufacturing the inner rotor type motor by fixing the stator with the motor case,
A method of manufacturing a motor with excellent iron core magnetic characteristics, wherein the stator core is inserted into the motor case in a state where the temperature of the stator core is higher than the temperature of the motor case, and then fixed.

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