JP5631297B2 - Shrink fit fixing structure - Google Patents

Description

  The present invention relates to a shrink-fit fixing structure for fixing a laminated steel plate constituting a magnetic path to another member by shrink-fit.

  In order to join the outer peripheral surface of the stator made of laminated steel plates of the electric motor to the inner peripheral surface of the stator housing made of a metal ring by shrink fitting, the stator is fitted inside the stator housing that has been heated and thermally expanded, and the stator A device that cools the housing to room temperature and causes heat shrinkage is known from Patent Document 1 below.

JP 2011-15536 A

  By the way, since what was described in the said patent document 1 is comprised by the smooth outer surface of the stator and the inner peripheral surface of a stator housing which are couple | bonded by shrink fitting, a torque acts between a stator and a stator housing. Then, both may slip and rotate relative to each other. In order to avoid this, if the tightening allowance for shrink fitting is set to be large, a strong compressive stress remains in the stator tightened by the stator housing, which may cause a problem that its magnetic characteristics are deteriorated.

  Therefore, according to Japanese Patent Application No. 2011-111788, the present applicant alternately forms spline-like convex portions and concave portions extending in the axial direction on the inner peripheral surface of the rotor made of laminated steel plates, and the outer periphery of the rotor shaft has a circumference. By alternately forming knurl-like convex portions and concave portions extending in the direction, and press-fitting the outer peripheral surface of the rotor shaft into the inner peripheral surface of the rotor, plastic deformation is performed so that the convex portion on the rotor shaft side is pushed down, A press-fit fixing structure was proposed to firmly bond the two while minimizing the residual stress.

  However, in the press-fitting and fixing structure, if the member that is not a laminated steel plate is made of, for example, aluminum, the convex portion may be broken by shearing when the convex portion is rolled down, and the bonding force between the two may be weakened. there were.

  The present invention has been made in view of the above circumstances, and when joining laminated steel sheets to other members by shrink fitting, it is possible to reliably join while preventing the deterioration of magnetic properties by minimizing the stress applied to the laminated steel sheets. The purpose is to do.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a shrink-fit fixing structure for fixing a laminated steel sheet constituting a magnetic path to another member by shrink fitting, and the outer peripheral surface of the laminated steel sheet. The first convex portion and the first concave portion extending in the substantially laminating direction are alternately formed, and the second convex portion and the second concave portion extending in the direction intersecting the laminating direction are alternately formed on the inner peripheral surface of the other member. Then, in a state where the other member is heated and shrink-fitted to the outer periphery of the laminated steel sheet, the first convex portion and the second convex portion are engaged with each other with plastic deformation, and the second convex portion A shrink-fit fixing structure is proposed in which the amount of plastic deformation is larger than the amount of plastic deformation of the first convex portion.

  According to the invention described in claim 2, in addition to the configuration of claim 1, the pitch of the second convex portion is larger than the thickness of the single plate of the laminated steel plate, and the shrink-fit fixing A structure is proposed.

  According to the invention described in claim 3, in addition to the structure of claim 1 or claim 2, a shrink-fit fixing structure is proposed in which the first convex portion has a sawtooth shape.

  The stator 11 of the embodiment corresponds to the laminated steel plate of the present invention, and the stator housing 12 of the embodiment corresponds to the other members of the present invention.

  According to the configuration of the first aspect, when the outer peripheral surface of the laminated steel sheet is fixed to the inner periphery of another member by shrink fitting, the first convex portion and the first concave portion extending in the substantially stacking direction are alternately formed on the outer peripheral surface. The first convex portion of the laminated steel sheet and the second convex portion of the other member in which the second convex portion and the second concave portion that extend in the direction intersecting the lamination direction are alternately formed on the inner peripheral surface are accompanied by plastic deformation. Mesh with each other. Since the amount of plastic deformation of the second convex portion of the other member is larger than the amount of plastic deformation of the first convex portion of the laminated steel plate with the other member heated and shrink-fitted to the outer periphery of the laminated steel plate, the residual stress of the laminated steel plate In addition to the frictional force between the first convex part and the second convex part engaged with each other, the shearing force due to plastic engagement is applied between the first convex part and the second convex part, and the laminated steel sheet and By increasing the slip torque between the other members, both can be firmly fixed so that they cannot be moved relative to each other. And since a laminated steel plate and another member contact in the small area of the front-end | tip of a 1st, 2nd convex part at the time of shrink fitting, the damage of the laminated steel plate by the heat | fever of another member can be suppressed to the minimum.

  Moreover, according to the structure of Claim 2, since the pitch of a 2nd convex part is larger than the board thickness of the single plate of a laminated steel plate, the single plate which contacts the front-end | tip of a 2nd convex part among the single plates of a laminated steel plate, Although a single plate that does not come into contact is generated, the single plate that does not come into contact with the tip of the second convex portion does not directly receive a load from another member, and therefore, a decrease in magnetic properties of the single plate can be minimized.

  According to the configuration of claim 3, since the first convex portion of the laminated steel sheet has a sawtooth shape, the first convex portion surely bites into the second convex portion of the other member, thereby reducing the stress of the laminated steel plate. The slip torque can be increased while suppressing.

The disassembled perspective view of the stator and stator housing of an electric motor. FIG. 2 is an enlarged view of part 2 of FIG. 1. 3 is an enlarged view of part 3 of FIG. Action | operation explanatory drawing at the time of shrink fitting of a stator and a stator housing. Action explanatory drawing at the time of press-fitting of a stator and a stator housing (comparative example). The figure which shows the relationship between the thickness of the single plate of a stator, and the pitch of the 2nd convex part of a stator housing. The figure which compares and demonstrates the effect of embodiment and a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the stator 11 of the inner rotor type electric motor is configured by a laminated steel plate in which a plurality of single plates made of electromagnetic steel plates having the same shape are laminated. The outer peripheral surface 11a of the stator 11 is formed of a cylindrical surface, and a plurality of teeth 11b for winding a coil are provided projecting radially inward on the inner periphery thereof. The stator housing 12 is a member formed in an annular shape with a metal material (for example, aluminum) whose hardness is lower than that of the laminated steel plate of the stator 11, and an inner peripheral surface 12 a thereof is configured by a cylindrical surface.

  2, the outer peripheral surface 11a of the stator 11 has a large number of first protrusions 13 and a large number of first recesses 14 extending in the axial direction of the stator 11, that is, in the stacking direction of the laminated steel plates. It is formed alternately in the circumferential direction. The first convex portion 13 and the first concave portion 14 are formed in a sawtooth shape, the height thereof is 0.32 mm, the apex angle and the base angle are 60 °, and the apex is pointed in a triangle, The bottom radius is 0.15 mm. The first convex portions 13 and the first concave portions 14 can be formed by, for example, press punching. It is desirable that the tops of the first convex portions 13 are as sharp as possible.

  3, the inner peripheral surface 12a of the stator housing 12 is formed with a plurality of second convex portions 15 and a plurality of second concave portions 16 extending in the circumferential direction alternately in the stacking direction. The The second convex portion 15 and the second concave portion 16 are formed in a sine wave shape, the pitch is 1.50 mm, the apex angle and the base angle are 60 °, and the top and bottom radii are 0.10 mm. And the distance between the top and the bottom is 1.19 mm. The second convex portions 15 and the second concave portions 16 can be formed by rolling, for example.

  The outer peripheral surface 11a of the stator 11 and the inner peripheral surface 12a of the stator housing 12 are coupled by shrink fitting. That is, with the stator housing 12 heated to, for example, 300 ° C. and thermally expanded, the outer peripheral surface 11a of the stator 11 at room temperature is fitted to the inner peripheral surface 12a of the stator housing 12, and the stator housing 12 is moved in that state. When cooled to room temperature, the stator housing 12 is thermally contracted and coupled to the stator 11. The fastening allowance at this time is set to 100 μm, for example.

  FIG. 4 shows the stator 11 and the stator housing 12 coupled by shrink fitting. Since the stator 11 made of laminated steel has higher hardness than the aluminum stator housing 12, the stator 11 meshing with each other by shrink fitting is shown. Of the first convex portion 13 and the second convex portion 15 of the stator housing 12, the second convex portion 15 of the stator housing 12 undergoes large plastic deformation, and the amount of plastic deformation of the first convex portion 13 of the stator 11 is as follows. Get smaller. That is, the stator 11 and the stator housing 12 are coupled so that the first convex portions 13 of the stator 11 bite into the second convex portions 15 of the stator housing 12.

  FIG. 5 shows a case where the press-fit fixing structure proposed by the present applicant in Japanese Patent Application No. 2011-111788 is applied to the coupling of the stator 11 made of laminated steel plates and the stator housing 12 made of aluminum. When the stator housing 12 is made of aluminum, the tip of the second convex portion 15 of the stator housing 12 is sheared by the tip of the first convex portion 13 of the stator 11 due to a load during press fitting, and is broken. The coupling force between the stator 11 and the stator housing 12 may be reduced.

  On the other hand, according to the present embodiment described with reference to FIG. 4, the stator 11 and the stator housing 12 are coupled by shrink fitting instead of press-fitting, so even if the stator housing 12 is made of aluminum, the second of the stator housing 12 is used. The convex portions 15 are not broken, and the first convex portions 13 bite into the second convex portions 15 so that the stator 11 and the stator housing 12 can be firmly coupled. Slip torque increases.

  At this time, since the amount of plastic deformation of the first protrusions 13 of the stator 11 is smaller than the amount of plastic deformation of the second protrusions 15 of the stator housing 12, the residual stress of the stator 11 after shrink fitting is suppressed to a small value. 11 can reduce the iron loss and improve the magnetic properties.

  As shown in FIG. 6A, the pitch P (1.5 mm) of the second protrusions 15 is larger than the plate thickness T (0.3 mm) of the single plate of the stator 11, so that the shrink-fitted stator Among the 11 single plates, a single plate that contacts the tip of the second convex portion 15 and a single plate that does not contact the tip are generated. Since the single plate that does not come into contact with the tips of the second convex portions 15 does not directly receive the load from the stator housing 12, it is possible to minimize the deterioration of the magnetic characteristics of the stator 11. As shown in FIG. 6 (B), if the pitch P of the second protrusions 15 is equal to or less than the plate thickness T of the single plate of the stator 11, all the single plates of the stator 11 are of the second protrusion 15 ... Since the load is directly received in contact with the tip, the magnetic characteristics of the stator 11 are greatly deteriorated.

  FIG. 7 shows a comparison between the effects of the present embodiment and the effects of the comparative example. FIG. 7A shows a comparative example, in which the outer peripheral surface 11a of the stator 11 without unevenness and the inner peripheral surface 12a of the stator housing 12 without unevenness are tightened to 300 μm by heating the stator housing 12 to 300 ° C. Direction residual stress in the circumferential direction (see solid line), radial residual stress (see broken line), and direction inclined by 45 ° with respect to the radial direction when shrink-fitted in the core Residual stress (see the alternate long and short dash line) and the temperature of the stator 11 (see the alternate long and two short dashes line).

  On the other hand, FIG. 7B shows an embodiment, and the residual stress in the circumferential direction (see the solid line) near the outer peripheral surface 11a of the stator 11 and the residual in the radial direction, measured under the same conditions as in the comparative example. The stress (see the broken line), the residual stress in the direction inclined by 45 ° with respect to the radial direction (see the one-dot chain line), and the temperature of the stator 11 (see the two-dot chain line) are shown. A negative stress corresponds to a compressive stress, and a positive stress corresponds to a tensile stress.

  As is apparent from FIG. 7, the circumferential compressive residual stress (see solid line) and the compressive residual stress in the direction inclined by 45 ° with respect to the radial direction (see the alternate long and short dash line) in this embodiment are comparative examples. It can be seen that the magnetic characteristics of the stator 11 are improved by this embodiment. On the other hand, the tensile residual stress in the radial direction of this embodiment (see the broken line) is slightly increased compared to that of the comparative example, but the residual stress that affects the magnetic characteristics of the stator 11 is mainly compressive residual stress. Since the tensile residual stress hardly affects the magnetic characteristics of the stator 11, an increase in the radial tensile residual stress (see the broken line) in the present embodiment is not a problem.

  Further, if the heat of the stator housing 12 heated to 300 ° C. during the shrink fitting is transmitted to the stator 11, the temperature of the stator 11 may rise temporarily and damage the magnetic characteristics. However, according to the present embodiment, since the stator 11 and the stator housing 12 are in contact with each other only in a narrow area at the tips of the first convex portions 13 and the second convex portions 15, the stator 11 and the stator housing 12 are transmitted from the stator housing 12 to the stator 11. By reducing the amount of heat, thermal damage to the stator 11 can be reduced.

  That is, as apparent from FIG. 7, in the comparative example, the temperature of the stator 11 rises to about 135 ° C. immediately after shrink fitting, but in this embodiment, the temperature is suppressed to about 110 ° C. I understand that.

  In addition, when the tightening allowance for shrink fitting in the embodiment of FIG. 7 and the comparative example is 200 μm, the slip torque of the comparative example is 780 N · m, whereas the slip torque of the embodiment is 1040 N · m. It can be seen that the stator 11 and the stator housing 12 can be more firmly coupled according to the embodiment. In the present embodiment, since the engagement is accompanied by plastic deformation of the second convex portions 15 of the stator housing 12, a sufficient slip torque can be obtained even if the tightening allowance for shrink fitting is set small. The heating temperature at the time of shrink fitting can be set low.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, the present invention is not limited to the case where the stator 11 and the stator housing 12 of the electric motor are coupled by shrink fitting, and can be applied to the case where any laminated steel sheet is shrink fitted to any other member. At this time, the material of the other member is not limited to aluminum.

  Moreover, the direction of the 1st convex part 13 ... and the 1st recessed part 14 ... of the stator 11 does not need to correspond exactly with the lamination direction of a laminated steel plate, and should just be substantially corresponded.

  The directions of the second convex portions 15 and the second concave portions 16 of the stator housing 12 do not necessarily have to be orthogonal to the directions of the first convex portions 13 and the first concave portions 14 of the stator 11. , As long as you cross.

11 Stator (Laminated steel sheet)
11a Peripheral surface of stator (laminated steel plate) 12 Stator housing (other member)
12a Inner peripheral surface 13 of stator housing (other member) 1st convex part 14 1st recessed part 15 2nd convex part 16 2nd recessed part P Pitch T of 2nd convex part Thickness of single plate of laminated steel sheet

Claims (3)

A shrink-fit fixing structure for fixing the laminated steel plate (11) constituting the magnetic path to the other member (12) by shrink-fit,
While forming the 1st convex part (13) and 1st recessed part (14) which extend in a substantially lamination direction on the outer peripheral surface (11a) of the said laminated steel plate (11) alternately, the inner peripheral surface of the said other member (12) ( 12a) are alternately formed with second convex portions (15) and second concave portions (16) extending in a direction intersecting with the laminating direction, and the other member (12) is heated to obtain an outer periphery of the laminated steel plate (11). The first convex portion (13) and the second convex portion (15) mesh with each other with plastic deformation, and the amount of plastic deformation of the second convex portion (15) is A shrink-fit fixing structure characterized by being larger than the amount of plastic deformation of the first convex portion (13).   The shrink-fit fixing structure according to claim 1, wherein a pitch (P) of the second convex portions (15) is larger than a plate thickness (T) of a single plate of the laminated steel plate (11).   The shrink-fit fixing structure according to claim 1 or 2, wherein the first convex portion (13) and the first concave portion (14) have a sawtooth shape.

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