JP2010239803A - Rotor of motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor having a permanent magnet to be fixed securely to the rotor under a temperature environment where the motor is used and achieving high reliability at low cost. <P>SOLUTION: The rotor 30 of the motor 10 includes: a rotor core 31 having a through-hole formed at the center of stacked thin core plates 36, a plurality of permanent magnets 32 fixed into a plurality of magnet fixing holes 33 that are arranged in a circumferential row at predetermined intervals on the rotor core 31 to axially penetrate therethrough, and a shaft 11 fitted in the through-hole of the rotor core 31. The rotor 30 also includes nonmagnetic metal cases 37 each having an insertion hole 37c for fitting the permanent magnet 32 therein, and a fixing means which mechanically fixes the cases 37 into the magnet fixing holes 33. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotor of a motor in which permanent magnets are arranged.

  A permanent magnet brushless DC motor is known in which permanent magnets are embedded in a rotor core at equal intervals in the circumferential direction, and the rotor is rotated with the permanent magnets opposed to the magnetic poles of a stator. Among them, in a normal structure in which a plurality of permanent magnets called interior permanent magnet types (also called IPM types for short) are fixed at equal intervals in the circumferential direction of the rotor core, the magnetic flux generated by the permanent magnets is not affected. Air gaps are formed on both sides in the circumferential direction of the permanent magnet in order to prevent an appropriate increase in wraparound (that is, leakage magnetic flux) and to effectively use the magnetic flux. That is, the circumferential width of the long hole is set to be larger than the circumferential width of the permanent magnet, and the magnetic flux of the permanent magnet is prevented from expanding in the circumferential direction by the gaps provided on both sides of the permanent magnet. A permanent magnet having a narrower width in the circumferential direction than the long hole is fixed in the long hole. At this time, various measures are taken to ensure that the permanent magnet is fixed, and fluctuations in magnetic characteristics caused by the displacement of the permanent magnet, or the permanent magnet moves in the long hole and collides with the inner wall of the long hole. The damage of the permanent magnets generated by the above is prevented.

  For example, in the one shown in Patent Document 1, a magnet is inserted into the magnet insertion hole of the core. And a non-magnetic metal pipe is inserted in the gap for preventing magnetic flux leakage provided on both sides in the circumferential direction of the magnet insertion hole, both ends of the pipe protrude beyond the magnet, and the protruding end is plastically deformed to magnet The movement is regulated and fixed in the slot.

  Moreover, in what is shown to patent document 2, an adhesive agent is attached to the surface of a permanent magnet, an adhesive sheet | seat is formed on the magnet surface by pressing it, making it harden | cure by a predetermined method, Then, it inserts in the magnet insertion hole of a core. The rotor core is heated to foam the adhesive sheet, thereby adhering and fixing the magnet to the insertion hole.

JP 2002-10544 A JP 2007-151362 A

  However, in the one shown in Patent Document 1, the magnet insertion hole of the rotor core expands and expands at a high temperature (for example, 160 ° C.). However, since the coefficient of thermal expansion of the rotor core is larger than that of the permanent magnet inserted into the magnet insertion hole, a difference occurs in the amount of expansion. Therefore, at high temperatures, there may be a gap between the inner wall of the rotor core magnet insertion hole and the permanent magnet, which causes the permanent magnet to move within the rotor core magnet insertion hole due to various vibrations generated during motor rotation. There is a risk that the motor will be rocked and worn, causing a reduction in motor performance and life, or damage.

  At a low temperature (for example, −30 ° C.), the nonmagnetic metal pipe having a thermal expansion coefficient larger than that of the permanent magnet is greatly contracted and it is difficult to fix the permanent magnet. As a result, the permanent magnets are vigorously swung and worn when the motor is rotated, as in the case of high temperatures, and there is a possibility that the performance and life of the motor may be reduced or damaged. Further, by providing the fixing pipe, magnetic flux leakage is likely to occur, and the motor efficiency may be deteriorated.

  Moreover, since the thermal expansion coefficient of the permanent magnet and the adhesive sheet formed on the surface of the permanent magnet is significantly different (about ten times), the one shown in Patent Document 2 is subject to repeated expansion and contraction at high and low temperatures. Cracks may occur at the interface between the adhesive, the permanent magnet, and the rotor core, and the ability to fix the magnet with the adhesive may be reduced. As a result, the permanent magnet may be swung and worn in the magnet insertion hole of the rotor core due to various vibrations generated during the rotation of the motor, which may cause a reduction in performance or life of the motor, or may be damaged. Further, since the thermal conductivity of the adhesive is low, the adhesive acts as a heat insulating layer for the permanent magnet, which may prevent heat dissipation when the motor generates heat, which may cause a reduction in motor performance and reliability.

  The present invention has been made in view of the above problems, and an object thereof is to provide a low-cost and highly reliable motor that can securely fix a permanent magnet to a rotor in a temperature environment where the motor is used. To do.

  In order to solve the above-mentioned problem, a feature of the invention according to claim 1 is that a rotor core having a through-hole formed in a central portion of a laminated thin plate core plate and a predetermined pitch parallel to the rotor core in a circumferential direction. In a rotor of a motor having a plurality of permanent magnets respectively fixed to a plurality of magnet fixing holes formed penetrating in the axial direction and a shaft fitted in the through hole of the rotor core, the permanent magnet is fitted. A non-magnetic metal case having an insertion hole to be attached; and a fixing means for mechanically fixing the case to the magnet fixing hole.

  According to a second aspect of the present invention, in the first aspect, the permanent magnet is provided with a fitting allowance at normal temperature so that a predetermined fitting allowance is secured in the insertion hole of the case even at a high temperature. When the thermal expansion coefficient of the permanent magnet is αm and the thermal expansion coefficient of the case is αk, αk> αm.

  A feature of the invention according to claim 3 is that, in claim 2, the fixing means is that the case fitted with the permanent magnet is press-fitted into the magnet fixing hole, and the thermal expansion coefficient of the rotor core Is αc, αc> αc> αm.

  According to a fourth aspect of the present invention, in the third aspect, the case includes a thin peripheral portion in which the insertion hole into which the permanent magnet is fitted is formed, and the rotor core from both side end surfaces of the peripheral portion. And having a thick protrusion protruding in the circumferential direction.

  The invention according to claim 5 is characterized in that, in claim 1 or 2, the caulking portion formed in the case is inserted into the magnet fixing hole after the case fitted with the permanent magnet is inserted into the rotor core. It is that it is crimped so that it may crimp on both end surfaces.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the permanent magnet is inserted into the case from the insertion hole after the permanent magnet is fitted into the insertion hole. Is provided with a permanent magnet fixing part for preventing the slipping out.

  According to the first aspect of the present invention, the permanent magnet that is easily damaged and difficult to fix is mechanically fixed in the magnet fixing hole of the rotor core after being fitted into the nonmagnetic metal case. As a result, it is possible to securely fix the permanent magnet without any play while protecting the permanent magnet at a low cost with a simple structure as compared with the conventional structure.

  According to the invention of claim 2, the permanent magnet having a small coefficient of thermal expansion is set and press-fitted or shrink-fitted so that the fitting allowance remains sufficiently even at a high temperature in the insertion hole of the case having a large coefficient of thermal expansion. ing. As a result, even when the expansion amount of the case is larger than the expansion amount of the permanent magnet at a high temperature, the case and the permanent magnet are pressed against each other without being separated, and the permanent magnet is securely fixed to the case and reliable. Improvement is achieved. Further, at a low temperature, the case having a large thermal expansion coefficient contracts and the permanent magnet having a small thermal expansion coefficient is tightened, so that the holding force of the case with respect to the permanent magnet is increased. In the case of fixing by shrink fitting, since it can be applied to a material having an elastic coefficient that is difficult to press fit, the options are widened and the design is advantageous.

  According to the invention of claim 3, since there is a relationship of thermal expansion coefficient αk of the case> thermal expansion coefficient αc of the rotor core> thermal expansion coefficient αm of the permanent magnet, the case tends to contract most greatly at low temperatures. However, the case can be shrunk by substantially the same amount as the permanent magnet because it is blocked by the permanent magnet having a small thermal expansion coefficient fixed in the case. Since the rotor core, which has a larger thermal expansion coefficient than the permanent magnet, contracts from the outside of the case, the case is pressed against the permanent magnet in the case and the outer rotor core, and the rotor core, the case, and the permanent magnet are firmly Fixed. As a result, the permanent magnet is prevented from being worn or damaged by rotation or vibration of the rotor.

  According to the invention which concerns on Claim 4, the thick projection part protruded from the case is protruded in the circumferential direction of the rotor core. As a result, at high temperatures, the protrusions of the case having a thermal expansion coefficient αk larger than the thermal expansion coefficient αc of the rotor core try to expand, but cannot be expanded by the rotor core outside the protrusions, and the rotor core and the case are pressed against each other. It is firmly fixed.

  According to the invention which concerns on Claim 5, the case where the permanent magnet was fitted and it was equipped with the crimping | crimped part is inserted in the magnet fixing hole, and it is crimped and fixed by the both end surfaces of a rotor core. This eliminates the need for highly accurate processing and strict dimensional control for press-fitting the case into the magnet fixing hole, thereby reducing costs.

  According to the invention of claim 6, since the permanent magnet fixing portion for preventing the permanent magnet from coming out is provided in the case, there is no possibility that the permanent magnet fitted to the case comes out of the case, and the reliability is improved. Further improvement can be achieved.

It is the fragmentary top view seen from the rotating shaft direction of the motor concerning this embodiment. 1 is a partially exploded perspective view of a rotor according to a first embodiment. FIG. 3 is an enlarged partial view of a case and a permanent magnet according to the first embodiment. FIG. 4 is a sectional view taken along the line 4-4 in FIG. 1. It is the modification 1 concerning 1st Embodiment. It is the modification 2 concerning 1st Embodiment. It is the modification 3 concerning 1st Embodiment. It is a fixed state perspective view of a case and a permanent magnet concerning a 2nd embodiment. It is a fixed state perspective view of the case and permanent magnet concerning a 3rd embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment in which a motor of the present invention is embodied will be described with reference to the drawings. The motor in the present invention will be described as a permanent magnet embedded motor (hereinafter referred to as an “IPM (Interior Permanent Magnet) motor”).

  The IPM motor 10 which is 1st Embodiment is demonstrated with reference to FIGS. FIG. 1 is a partial plan view of the IPM motor 10 of the first embodiment viewed from the direction of the rotation axis. FIG. 2 is a perspective view of a rotor according to the present invention, and FIG. 3 is an enlarged view showing a part of FIG. 4 is a cross-sectional view taken along line 4-4 of FIG.

  The IPM motor 10 includes a stator 20 and a rotor 30 that is provided so as to be rotatable about the rotation axis of a cylindrical shaft 11 with respect to the stator 20. The stator 20 has a stator core 21 in which a plurality of teeth 22 are formed at a predetermined pitch in the circumferential direction. The stator core 21 is formed by laminating electromagnetic steel plates in the axial direction of the rotor 30. The stator 20 forms a magnetic field inside the stator 20 by passing a current through windings (not shown) wound around the teeth 22.

  The rotor 30 includes a rotor core 31, a case 37, a permanent magnet 32, a shaft 11, and an end plate 40. The rotor 30 is provided to be rotatable with respect to the stator 20 with an air gap interposed inside the stator 20. The rotor 30 receives a magnetic force from the teeth 22 of the stator core 21 that has become a magnetic pole when current is passed through the windings of the stator 20, and rotates about the rotation axis of the shaft 11. Thereby, the IPM motor 10 outputs a predetermined torque from the rotating shaft of the shaft 11.

  The rotor core 31 is formed by laminating a core plate 36, which is a thin electromagnetic steel plate having a through hole in the center, in the direction of the rotation axis. The rotor core 31 includes a magnet fixing hole 33, a central through hole 31 a, and a rotor core body 38. In the through hole 31a, two key portions 31b projecting toward the center of the through hole 31a are provided across both end faces of the rotor core 31 in parallel with the axis. The rotor core 31 and the shaft 11 are fitted and engaged with each other by engaging the key portion 31b of the rotor core 31 with the two groove portions 11a parallel to the axis engraved over the entire length of the shaft 11. Is regulated.

  A plurality of magnet fixing holes 33 are provided in parallel in the circumferential direction of the rotor core 31 at a predetermined pitch, and a plurality of magnet fixing holes 33 are provided in the axial direction. In this embodiment, eight magnet fixing holes 33 are provided. As shown in FIG. 3, the magnet fixing hole 33 includes a magnetic pole inner surface 33 a that is an inner surface disposed radially inward of the rotor core 31 and a magnetic pole inner surface 33 b that is an inner surface disposed radially outward of the rotor core 31. And a stop portion 33c, both inner surfaces 33d formed in a substantially elliptical shape forming the gap portion 33f, and a connecting portion 33e that connects the stop portion 33c and the both side inner surfaces 33d. A slot 31e is formed between the magnetic pole inner surface 33b and the connecting portion 33e in the magnet fixing hole 33, and a projection 37a of the case 37 described later is press-fitted.

  The permanent magnet 32 is a magnet that is formed in a flat plate shape and is magnetized in the thickness direction, and is formed of, for example, a neodymium magnet or the like. And the permanent magnet 32 with reversed polarity is arranged and fixed in the magnet fixing hole 33 of the adjacent rotor core 31.

  Generally, a permanent magnet has a low mechanical strength and cannot withstand a large press-fit load. Therefore, in the present invention, the permanent magnet 32 is not directly press-fitted into the magnet fixing hole 33 of the rotor core 31 where there is a possibility that a uniform press-fit surface is not formed. This is because the magnet fixing hole 33 is formed by laminating thin electromagnetic steel plates. First, it is press-fitted and fixed in the insertion hole 37c of the case 37 made of, for example, an aluminum alloy, which has a relatively low longitudinal elastic modulus and is easily press-fitted. By doing so, the permanent magnet 32 is protected by the case 37 and easy to handle.

  Then, with the permanent magnet 32 fitted in the case 37, the case 37 is mechanically fixed to the magnet fixing hole 33 by press-fitting as a fixing means. At this time, the inner surface 37f of the case 37 and the magnetic pole inner surface 33a of the magnet fixing hole 33 are pressed against each other in the radial direction of the rotor core 31 of the case 37, and the outer surface 37g of the case 37 is radially outward of the rotor core 31. And the magnetic pole inner surface 33b of the magnet fixing hole 33 are pressed and fixed.

  The case 37 is made of the above-described aluminum alloy (other than SUS, copper-based metal, etc.) made of a nonmagnetic metal so as not to affect the magnetic flux generated by the stator 20. As shown in FIG. 3, the case 37 includes a thin peripheral portion 37b, an insertion hole 37c, a thick protrusion 37a, and a stop portion 37d.

  The thin peripheral edge 37b has a substantially uniform thickness and surrounds the periphery to form an insertion hole 37c. In the present embodiment, the thickness of the peripheral edge portion 37 b is set to 1/10 or less of the thickness of the permanent magnet 32 in consideration of the ease of press-fitting the permanent magnet 32.

  The insertion hole 37c is a space for the permanent magnet 32 to be fitted by press fitting. The length of the short side of the inlet hole 37c inlet portion rectangle and the thickness of the permanent magnet 32 is such that the maximum operating temperature of the IPM motor 10 is, for example, 160 ° C., and the permanent magnet 32 press-fitted into the insertion hole 37c even at the maximum operating temperature; A predetermined holding force (or fitting allowance) is set between the case 37 and the case 37. When the thermal expansion coefficient of the permanent magnet 32 is αm and the thermal expansion coefficient of the case 37 is αk, the relationship between αm and αk is configured to satisfy αk> αm.

  The thick protrusion portion 37a is press-fitted into the slot portion 31e of the magnet fixing hole 33, and has a function of restricting the relative movement between the case 37 and the rotor core body 38 at a high temperature exceeding normal temperature and firmly fixing it. The protrusions 37 a extend from the opposite end surfaces of the thin peripheral edge 37 b in the circumferential direction of the rotor core 31 by a predetermined amount in the circumferential direction of the rotor core 31, and are formed over the entire length of the case 37 in the press-fitting direction. . The radial thickness of the protrusion 37 a in the rotor core 31 is formed to be approximately the same as the thickness of the permanent magnet 32.

  The stop portion 37d has a function of restricting the circumferential movement of the case 37 in the rotor core 31. In the circumferential direction of the rotor core 31, the stop portion 37 d also functions as a part of both end surfaces of the peripheral edge portion 37 b of the case 37, and moves in contact with the stop portion 33 c provided in the magnet fixing hole 33 of the rotor core body 38. Is regulated.

  In the rotor core 31, a thick portion 39 is provided on the outer side in the radial direction of the magnet fixing hole 33. The thick portion 39 becomes a magnetic pole when the permanent magnet 32 is fixed to the magnet fixing hole 33. In the circumferential direction of the rotor core 31, bridges 35 are formed outside both end portions of the thick portion 39. The bridge 35 is thinnest at point A on the inner surface 33d on both sides forming the magnet fixing hole 33 to form a thin portion 35a.

  The thin portion 35a of the bridge 35 functions as a flux barrier that reduces leakage magnetic flux. The leakage magnetic flux is a magnetic flux short-circuited with a part of the magnetic flux by the permanent magnet 32 fixed to the adjacent magnet fixing hole 33 among the magnetic flux by the permanent magnet 32 fixed to the magnet fixing hole 33. Since the leakage magnetic flux does not contribute to the rotational drive of the rotor 30, the magnetic characteristics can be improved by reducing the leakage magnetic flux. The shape of the thin portion 35 a is appropriately set in consideration of the magnetic circuit based on the diameter of the rotor core 31 and the magnetic flux density of the permanent magnet 32.

  When the thermal expansion coefficients of the permanent magnet 32, the case 37, and the rotor core 31 constituting the rotor 30 configured as described above are αm, αk, and αc, respectively, the thermal expansion coefficients αm, αk, and αc are αk> αc. > Αm is established.

  As shown in FIG. 4, the end plate 40 is a plate-like member attached so as to close the plurality of magnet fixing holes 33 at both axial ends of the rotor core 31, and may be omitted in the first embodiment. .

  Next, in this embodiment, the effect of the IPM motor 10 having the above-described configuration will be described. In a practical state of the IPM motor 10, first, a magnetic field is formed inside the stator 20 by passing a current through the windings of the stator 20. The rotor 30 generates torque by the magnetic force between the magnetic field of the stator 20 and the eight permanent magnets 32 accommodated in the rotor 30, and is rotationally driven with respect to the stator 20 in a certain direction.

  When the IPM motor 10 continues to rotate, the IPM motor 10 generates heat and the temperature rises, and may reach a maximum use temperature of 160 ° C., for example. Therefore, first, the behavior of the permanent magnet 32 on the high temperature side exceeding the normal temperature (for example, 25 ° C.) and having the maximum temperature of 160 ° C. will be described.

  In the present embodiment, the permanent magnet 32 and the case 37 are set and press-fitted so that the fitting margin in the radial direction of the rotor 30 becomes 0 when the temperature is 160 ° C. + ΔT ° C. as described above. At this time, ΔT ° C. is an arbitrary temperature. The case 37 is press-fitted with the magnet fixing hole 33 in a state where a slight fitting allowance is secured in the radial direction of the rotor 30. The protrusion 37 a provided on the case 37 is also press-fitted into the slot 31 e of the magnet fixing hole 33 in a state where a slight fitting allowance is secured in the radial direction of the rotor 30. The thermal expansion coefficient αm of the permanent magnet 32, the thermal expansion coefficient αk of the case 37, and the thermal expansion coefficient αc of the rotor core 31 are configured to satisfy a relationship of αk> αc> αm.

  In the first embodiment configured as described above, when the IPM motor 10 starts to rise in temperature from the normal temperature state, the permanent magnet 32, the case 37, and the magnet fixing hole 33 are respectively in accordance with the respective thermal expansion coefficients αm, αk, αc. Start thermal expansion.

  At this time, between the permanent magnet 32 and the case 37, the fitting margin in the radial direction of the rotor 30 is set so as to be 0 when the temperature is 160 ° C. + ΔT ° C., and therefore reaches 160 ° C. However, a predetermined fitting margin remains. Therefore, until the temperature reaches 160 ° C., the permanent magnet 32 falls off from the case 37 or a gap is generated between the permanent magnet 32 due to a predetermined predetermined fitting allowance, and the permanent magnet 32 is caused by vibration or the like. There is no risk of wear or breakage due to the rocking.

  Next, the relationship between the case 37 and the magnet fixing hole 33 into which the case 37 is press-fitted will be described. First, if the elongation amount expanded by heat is ΔL, the elongation amount ΔL can be calculated by ΔL = thermal expansion coefficient α × length at normal temperature (thickness) L × temperature change ΔT from normal temperature.

  As shown in FIG. 3, the permanent magnet 32 has a thickness elongation ΔLm at a temperature P ° C. higher than the normal temperature, for example, when the normal temperature is 25 ° C. × αm × (P ° C.−25 ° C.).

  Similarly, if the thickness of the thin peripheral edge portion 37b of the case 37 is L1k, the extension amount ΔL1k of the thickness of one side of the peripheral edge portion 37b at a temperature P ° C exceeding the normal temperature is ΔL1k = L1k × αk × (P ° C− 25 ° C.).

  The total elongation amount ΔLkT of the case 37 at a higher temperature than the elongation amounts ΔL1k × 2 on both sides of the thin peripheral edge portion 37b of the case 37 and the elongation amount ΔLm of the permanent magnet 32 press-fitted into the insertion hole 37c of the case 37. Therefore, ΔLkT = ΔLm + ΔL1k × 2.

  Next, as the temperature rises, the inner surface of the magnet fixing hole 33 is expanded and the hole shape is expanded. At this time, as shown in FIG. 3, when the distance between the magnetic pole inner surface 33a and the magnetic pole inner surface 33b of the magnet fixing hole 33 at normal temperature is Lc3, the elongation amount ΔLc3 of Lc3 at a temperature P ° C. higher than normal temperature is ΔLc3 = Lc3. × αc × (P ° C.−25 ° C.)

  From the above results, in order to obtain the fitting state between the case 37 and the magnet fixing hole 33 at high temperature, the total elongation amount ΔLkT (= ΔLm + ΔL1k × 2) of the case 37 at (P ° C.−25 ° C.), ( A comparison may be made with the amount of elongation ΔLc3 (= Lc3 × αc × (P ° C.−25 ° C.)) between the magnetic pole inner surface 33a and the magnetic pole inner surface 33b of the magnet fixing hole 33 at P ° C.−25 ° C.

  Therefore, for example, the thermal expansion coefficient αm of the permanent magnet 32 = 6.3E-6 / ° C. (refer to the thermal expansion coefficient of the neodymium magnet), the thermal expansion coefficient αk of the case 37 = 23.6E-6 / ° C. (thermal expansion of the aluminum alloy) Coefficient) and the thermal expansion coefficient αc of the rotor core 31 = 11.7E−6 / ° C. (refer to the thermal expansion coefficient of iron). In addition, as described above, the thickness L1k of the peripheral edge portion 37b of the case 37 is 1/10 of the thickness Lm of the permanent magnet 32. Then, a relationship of ΔLkT> ΔLc3 is obtained by substituting a predetermined value for the thickness Lm of the permanent magnet 32 and substituting a predetermined value for the temperature P ° C.

  Thereby, as the temperature of the IPM motor 10 rises, the case 37 always fixes the magnetic pole inner surface 33a and the magnetic pole inner surface 33b that form the magnet fixing hole 33 by pressing with the 37f surface and the 37g surface outside the case 37. Become. Therefore, the case 37 is not dropped from the magnet fixing hole 33 or a gap is generated between the case 37 and the case 37 is swung by vibration or the like, so that the permanent magnet 32 is not worn or damaged. However, the peripheral portion 37b of the case 37 press-fitted into the magnet fixing hole 33 in the above is thin. Therefore, when ΔLkT> ΔLc3, the value of ΔLkT does not become extremely larger than ΔLc3. However, it has been confirmed that the case 37 has a sufficient fixing force to be fixed to the magnet fixing hole 33.

  Next, the relationship between the protrusion 37a provided on the case 37 and the slot 31e of the magnet fixing hole 33 into which the protrusion 37a is press-fitted will be described with reference to FIG.

  The protrusion 37a has a thickness Lk that is approximately the same size as the thickness Lm of the permanent magnet 32 at room temperature. Then, the side surface of the protruding portion 37a is press-fitted into the slot portion 31e with a slight fitting dimension. The protrusion 37a has a thermal expansion coefficient αk larger than the thermal expansion coefficient αc of the rotor core 31. Therefore, the extension amount ΔLk of the protrusion 37a at a high temperature P ° C. exceeding normal temperature is ΔLk = Lk × αk × (P ° C.−25 ° C.).

  If the width of the slot 31e at normal temperature is Lc2, the elongation amount ΔLc2 of Lc2 at a high temperature P ° C. is ΔLc2 = Lc2 × αc × (P ° C.−25 ° C.). Then, as described above, when Lk≈Lc2 and ΔLk and ΔLc2 are compared, the extension amount of the thickness Lk of the protrusion 37a is equal to the difference between the thermal expansion coefficients αc and αk, that is, αk / αc times. It can be seen that it is larger than the amount of elongation of the width Lc2.

  Thus, as the temperature of the IPM motor 10 rises, the protrusion 37a expands at a speed (αk / αc) times that of the slot 31e, and the protrusion 37a is always pressed against the slot 31e. Therefore, the case 37 and the magnet fixing hole 33 are firmly and securely fixed at a high temperature.

  Next, the case of a low temperature Q ° C. below normal temperature will be described. When the IPM motor 10 is placed in an environment at a temperature lower than the normal temperature, the permanent magnet 32, the case 37, and the magnet fixing hole 33 have the thermal expansion at the high temperature described above according to the respective thermal expansion coefficients αm, αk, αc. Contracts in the opposite direction. At the low temperature Q ° C., the temperature change amount ΔT is only changed to Δt with respect to the high temperature elongation amount ΔL = L × α × ΔT. To explain.

  First, the relationship between the case 37 and the permanent magnet 32 press-fitted into the case 37 will be described. Between the case 37 and the permanent magnet 32, the case 37 having a thermal expansion coefficient αk larger than the thermal expansion coefficient αm of the permanent magnet 32 tends to contract faster than the permanent magnet 32. However, the case 37 is blocked by the permanent magnets 32 and cannot be shrunk much beyond the amount of contraction ΔLm of the permanent magnets 32. Therefore, at the low temperature Q ° C., the permanent magnet 32 is tightened more strongly by the case 37 than at the normal temperature. As a result, the permanent magnet 32 is not dropped from the case 37 or a gap is generated between the permanent magnet 32 and the permanent magnet 32 is not swung or damaged due to vibration or the like.

  Next, the relationship between the case 37 and the magnet fixing hole 33 into which the case 37 is press-fitted will be described. As described above, the shrinkage amount ΔLkT of the case 37 cannot greatly shrink beyond the shrinkage amount ΔLm of the permanent magnet 32 and is substantially the same as ΔLm at the low temperature Q ° C. below the normal temperature. However, the thermal expansion coefficient αc of the magnet fixing hole 33 into which the case 37 is press-fitted is larger than the thermal expansion coefficient αm of the permanent magnet 32. Therefore, if the contraction amount of the magnet fixing hole 33 is ΔLc3, the relationship of the contraction amount ΔLkT (≈ΔLm) of the case 37 <the contraction amount ΔLc3 of the magnet fixing hole 33 is obtained by the same calculation formula as that at high temperature.

  As a result, the magnetic pole inner surface 33a and the magnetic pole inner surface 33b of the magnet fixing hole 33 catch up with the contraction of the surfaces 37f and 37g of the case 37 and firmly fix the case 37. Therefore, at a low temperature Q ° C., which is lower than normal temperature, the case 37 falls off from the magnet fixing hole 33, or a gap is generated between the case 37 and the case 37 swings due to vibration or the like, so that the case 37 is worn. And will not be damaged. As a result, the permanent magnet 32 press-fitted into the case 37 is not worn or damaged.

  Next, with reference to FIG. 3, the relationship between the protrusion 37a provided on the case 37 and the slot 31e of the magnet fixing hole 33 will be described.

  As described at the high temperature, the protrusion 37a has a thermal expansion coefficient αk larger than the thermal expansion coefficient αc of the rotor core body 38. The protrusion 37a has a thickness Lk that is approximately the same as the thickness Lm of the permanent magnet 32 at room temperature. A contraction amount of the protrusion 37a at a low temperature Q ° C., which is lower than normal temperature, is ΔLk. Further, the width of the slot 31e at normal temperature is Lc2, and the contraction amount of the width of the slot 31e at low temperature Q ° C. is ΔLk.

  When Lk≈Lc2 and ΔLk and ΔLc2 are compared in the same manner as at high temperature, it can be seen that the amount of contraction of the protrusion 37a is large by the difference between the thermal expansion coefficients αc and αk, that is, (αk / αc) times. . As a result, at the low temperature Q ° C., the protrusion 37a contracts at a speed that the thickness Lk is larger than the width Lc2 of the slot 31e and is separated from the width Lc2 of the slot 31e.

  As a result, at a low temperature Q ° C. below normal temperature, the case 37 is fixed to the rotor core 31 only by a portion where the case 37 having the permanent magnet 32 fitted therein is press-fitted into the magnet fixing hole 33 and fixed.

  As a result, the case 37 drops off from the magnet fixing hole 33 even at a low temperature Q ° C., which is lower than the normal temperature, or a gap is generated between the case 37 and the case 37 swings due to vibration or the like, and the case 37 is worn. It will not be damaged. As a result, there is no possibility that the permanent magnet 32 press-fitted into the case 37 is worn or damaged.

  In the first embodiment, the permanent magnet 32 is fixed by press-fitting into a case 37 formed of a non-magnetic metal. However, the permanent magnet 32 may be fixed in the case 37 not by press fitting but by heating the case 37 and shrink fitting. Also at this time, the fitting allowance between the permanent magnet 32 and the case 37 at the normal temperature may be set so as to have the same fitting dimension as that at the time of press-fitting, and the same effect as that at the time of press-fitting can be expected.

  Further, in the first embodiment, the case 37 is provided with a thick protrusion 37a having a shape as shown in FIG. However, the protrusion 37a may have a shape like the protrusion 37h shown in the first modification of FIG. In the modification shown in FIG. 5, the protrusion 37 h extends a predetermined amount in the circumferential direction of the rotor core 31 from the substantially central portion of both end surfaces of the case 37, and the protrusion 37 h is outward in the radial direction of the rotor core 31. Further, stop portions 37j and 37k are provided at two locations on the inner side. This also provides the same effect as that of the first embodiment.

  Furthermore, as shown in Modification 2 in FIG. 6 and Modification 3 in FIG. 7, the case 37 may have a shape in which the protrusions 37 a and 37 h are not provided. In this case, the case 37 is fixed at a high temperature only at a portion where the permanent magnet 32 is press-fitted into the case 37. As described in the first embodiment, the peripheral portion 37b of the case 37 press-fitted into the magnet fixing hole 33 is thin. Thus, when the elongation amount ΔLkT of the case 37> the elongation amount ΔLc3 of the magnet fixing hole 33, the value of ΔLkT does not become extremely larger than ΔLc3. Therefore, the force for fixing the case 37 is reduced as compared with the case where the projecting portions 37a and 37h are provided, but it has been confirmed that a sufficient fixing force for practical use is ensured, and the effect can be obtained sufficiently. .

  As is apparent from the above description, in the first embodiment, the permanent magnet 32 that is easily damaged and hard to be fixed is fitted into the nonmagnetic metal case 37 and then mechanically fixed to the magnet fixing hole 33 of the rotor core 31. Has been. As a result, it is possible to securely fix the permanent magnet without any play while protecting the permanent magnet at a low cost with a simple structure as compared with the conventional structure.

  Further, in the first embodiment, the permanent magnet 32 having a small thermal expansion coefficient remains sufficiently in the insertion hole 37c of the case 37 having a large thermal expansion coefficient even at a high temperature, for example, 160 ° C. It is set so that it is press-fitted or shrink-fitted. Thus, even when the elongation amount ΔL1k of the case 37 is larger than the elongation amount ΔLm of the permanent magnet 32 at a high temperature, the case 37 and the permanent magnet 32 are pressed against each other without being separated, and the permanent magnet 32 is reliably connected. Reliability is improved by being fixed to the case 37. At a low temperature, the case 37 having a large thermal expansion coefficient contracts, and the permanent magnet 32 having a small thermal expansion coefficient is tightened, so that the holding force of the case 37 on the permanent magnet 32 is increased. In addition, in the case of fixing by shrink fitting, since it can be applied to a material having an elastic coefficient that is difficult to press-fit, the options are widened and the design is advantageous.

  In the first embodiment, the thermal expansion coefficient αk of the case 37> the thermal expansion coefficient αc of the rotor core> the thermal expansion coefficient αm of the permanent magnet. Therefore, at a low temperature, the case 37 tends to contract most greatly, but the case 37 can be contracted by substantially the same amount as the permanent magnet 32 by being blocked by the permanent magnet 32 fixed in the case 37 and having a small thermal expansion coefficient. Since the magnet fixing hole 33 (rotor core 31) having a larger thermal expansion coefficient than the permanent magnet 32 contracts from the outside of the case 37, the case 37 has a permanent magnet 32 in the case 37 and an outer magnet fixing hole 33. The rotor core 31, the case 37, and the permanent magnet 32 are firmly fixed. As a result, the permanent magnet is prevented from being worn or damaged due to rotation or vibration of the rotor 30.

  Furthermore, in the first embodiment, a thick protrusion 37 a protruding from the case 37 protrudes in the circumferential direction of the rotor core 31. As a result, at a high temperature P ° C. exceeding normal temperature, the protrusion 37a of the case 37 having a thermal expansion coefficient αk larger than the thermal expansion coefficient αc of the rotor core 31 tends to expand. However, the rotor core 31 and the case 37 cannot be expanded due to being blocked by the slot 31e of the rotor core 31 on the outer side of the protrusion 37a, and are firmly pressed against each other.

  Next, a second embodiment will be described with reference to FIG. The second embodiment differs from the first embodiment only in that the fixing means for fixing the case 37 to the magnet fixing hole 33 of the rotor core 31 is not crimped but crimped. Components similar to those in the first embodiment are denoted by the same reference numerals and description thereof is omitted, and description of similar operations is also omitted, and only changes are described.

  In the second embodiment, as shown in FIG. 8, the permanent magnet 32 is press-fitted and fitted into the insertion hole 47 c of the case 47 with the same fitting margin as that of the first embodiment at room temperature. The case 47 is made of, for example, an aluminum alloy made of a nonmagnetic metal. After the case 47 fitted with the permanent magnet 32 is inserted into the magnet fixing hole 33, the caulking portions 48 formed in the case 47 are crimped so as to be crimped to both end faces of the rotor core 31, and the case 47 is connected to the rotor core 31. It is firmly fixed to.

  As shown in FIG. 8, the case 47 includes a thin peripheral portion 47 b, an insertion hole 47 c, a thick protrusion 47 a, a stop portion 47 d, and a caulking portion 48.

  The thin peripheral edge 47b has a substantially uniform thickness and surrounds the periphery to form an insertion hole 47c. In the present embodiment, the thickness of the peripheral portion 47 b is set to 1/10 or less of the thickness of the permanent magnet 32 in consideration of the ease of press-fitting the permanent magnet 32.

  The insertion hole 47c is a space for the permanent magnet 32 to be fitted by press fitting. The length of the short side of the rectangular inlet portion of the insertion hole 47c and the thickness of the permanent magnet 32 are such that the maximum operating temperature of the IPM motor 10 is, for example, 160 ° C., and the permanent magnet 32 press-fitted into the insertion hole 37c even at the maximum operating temperature. A predetermined holding force (or fitting allowance) is secured between the case 47 and the case 47. Further, when the thermal expansion coefficient of the permanent magnet 32 is αm and the thermal expansion coefficient of the case 47 is αk, the relationship between αm and αk is configured to satisfy αk> αm.

  The thick protrusion portion 47a is press-fitted into the slot portion 31e of the magnet fixing hole 33, and has a function of firmly fixing the relative movement between the case 47 and the rotor core body 38 at a high temperature exceeding normal temperature. The protrusions 47 a extend from the opposite end surfaces of the thin peripheral edge 47 b in the circumferential direction of the rotor core 31 by a predetermined amount in the circumferential direction of the rotor core 31, and are formed over the entire length of the case 47 in the press-fitting direction. . The radial thickness of the protrusion 47 a in the rotor core 31 is formed to be approximately the same as the thickness of the permanent magnet 32.

  The stop portion 47d has a function of restricting movement in the circumferential direction in the rotor core 31 of the case 47. In the circumferential direction of the rotor core 31, the stop portion 47 d is used as a stop portion 47 d with part of both end faces of the peripheral edge portion 47 b of the case 47, and contacts the stop portion 33 c provided in the magnet fixing hole 33 of the rotor core body 38. It is touched and movement is restricted.

  The caulking portion 48 has a function of firmly fixing the case 47 inserted into the magnet fixing hole 33 of the rotor core 31. The caulking portion 48 is initially formed such that a predetermined amount of the peripheral portion 47b is erected from a substantially central portion of the longitudinal portion of the thin peripheral portion 47b. Further, the caulking portions 48 are provided at both ends of the opening of the case 47 in order to be caulked at both ends of the rotor core 31.

  The case 47 is inserted into the penetrating magnet fixing hole 33, and the caulking portions 48 protruding from both end faces of the rotor core 31 are crimped as shown in FIG. Fixed. That is, by bending the caulking portions 48 on both end surfaces of the rotor core 31 perpendicularly from the root portion of the caulking portion 48 toward the end surface direction of the rotor core 31, the flat portion of the caulking portion 48 and both end surfaces of the rotor core 31 are pressure-bonded. The case 47 is firmly fixed to the magnet fixing hole 33 by sandwiching both end surfaces of the rotor core 31 with the flat portion of the caulking portion 48.

  As described above, also in the second embodiment, a gap is generated between the case 47 and the permanent magnet 32 press-fitted into the case 47 at a low temperature and a high temperature for the same reason as in the first embodiment. There is no fear. Further, between the case 47 and the magnet fixing hole 33, the case 47 is firmly fixed by the caulking and the movement of the case 47 is restricted. As a result, the case 47 falls off at a low temperature or a high temperature, or a backlash occurs between the case 47 and the magnet fixing hole 33, and the case 47 swings due to vibration or the like, and the case 47 is worn or damaged. It will never be done. In addition, the permanent magnet 32 press-fitted into the case 47 is not worn or damaged. Further, since the case 47 is press-fitted into the magnet fixing hole 33, high-precision processing and strict dimensional control are not required on the inner surfaces 33a and 33b of the magnet fixing hole 33, and the cost can be reduced.

  Next, a third embodiment will be described with reference to FIG. The third embodiment is different from the first and second embodiments only in that a caulking portion 47e that is a permanent magnet fixing portion for fixing the permanent magnet 32 to the case 37 more firmly is added. Components similar to those in the first and second embodiments are denoted by the same reference numerals and description thereof is omitted, and description of similar operations is also omitted, and only changes are described. In addition, although 2nd Embodiment is utilized for description, it can apply similarly also about 1st Embodiment.

  In the third embodiment, as shown in FIG. 9, the caulking portion 47 e includes two portions of the peripheral portion 47 b from the two opposite end portions of the thin peripheral portion 47 b of the case 47. A fixed amount is set up and formed. Further, the caulking portions 47 e are similarly provided at both ends of the opening of the case 47 in order to be caulked at the upper end surface and the lower end surface of the permanent magnet 32.

  Then, at normal temperature, the permanent magnet 32 is press-fitted and fitted into the insertion hole 47c of the case 47 with the same fitting allowance as in the first and second embodiments. After the permanent magnet 32 is fitted into the insertion hole 47c, the upper end surface of the permanent magnet 32 and the caulking portion 47e of the case 47 protruding from the lower end surface are, as shown in FIG. The permanent magnet 32 is firmly fixed to the case 47 by being crimped so as to be crimped to the lower end surface.

  In the third embodiment described above, the caulking portion 47e is formed to be erected in a total of four locations, two from the opposite end portions of the thin peripheral portion 47b of the case 47. However, the present invention is not limited to this, and one or more of the four erected caulking portions 47e may be formed and caulked, and a sufficient effect can be obtained.

  Further, the caulking portion 47e is crimped to the upper end surface and the lower end surface of the permanent magnet 32 to firmly fix the permanent magnet 32 and the case 47. However, the present invention is not limited to this, and a configuration may be adopted in which there is a gap between the flat portion of the caulking portion 47 e and the upper end surface and lower end surface of the permanent magnet 32. Also by this, the effect of preventing the permanent magnet 32 from coming out of the case 47 is sufficiently obtained.

  As apparent from the above description, in the third embodiment, the same effects as those in the first and second embodiments can be obtained, and the permanent magnet 32 press-fitted into the case 47 comes out of the case 47. There is no fear, and the reliability is further improved.

  In the first, second, and third embodiments, the inner rotor type motor 10 in which the rotor 30 is disposed inside the stator 20 has been described. However, the present invention is not limited to this, and the stator is disposed in the center. The present invention can also be applied to a so-called outer rotor type motor in which a rotor that is rotated around is arranged.

DESCRIPTION OF SYMBOLS 10 ... Motor, 11 ... Shaft, 20 ... Stator, 21 ... Stator core, 22 ... Teeth, 30 ... Rotor, 31 ... Rotor core, 32 ... Permanent magnet, 33 ... Magnet fixing hole, 35 ... Bridge, 37 ... Case, 37a ... Thick protrusion, 37b ... Thin peripheral edge, 38 ... Rotor core body, 39 ... Thick Meat part, 47 ... case, 47e ... permanent magnet fixing part (crimping part), 48 ... crimping part, Lm ... permanent magnet thickness, Lk ... projection part thickness, Lc2 ... slot Part width, Lc3... Magnet fixing hole width, L1k...

Claims (6)

A rotor core having a through hole formed in the center of the laminated thin plate core plate;
A plurality of permanent magnets respectively fixed to a plurality of magnet fixing holes formed in parallel to the rotor core in the circumferential direction and penetrating in the axial direction at a predetermined pitch;
In a rotor of a motor having a shaft fitted in the through hole of the rotor core,
A non-magnetic metal case in which an insertion hole into which the permanent magnet is fitted is formed;
And a fixing means for mechanically fixing the case to the magnet fixing hole. In Claim 1, the permanent magnet is press-fitted or shrink-fitted into the insertion hole of the case with a fitting allowance at room temperature set so that a predetermined fitting allowance is secured even at high temperatures. ,
A motor rotor, wherein αk> αm, where αm is a thermal expansion coefficient of the permanent magnet and αk is a thermal expansion coefficient of the case. In claim 2, the fixing means is that the case fitted with the permanent magnet is press-fitted into the magnet fixing hole,
The rotor of the motor, wherein αc>αc> αm, where αc is a coefficient of thermal expansion of the rotor core.   The case according to claim 3, wherein the case has a thin peripheral edge portion in which the insertion hole into which the permanent magnet is fitted is formed, and a wall thickness that protrudes in a circumferential direction of the rotor core from both end faces of the peripheral edge portion. A rotor of a motor having a protrusion.   3. The method according to claim 1, wherein after the case fitted with the permanent magnet is inserted into the magnet fixing hole, the crimped portion formed in the case is crimped so as to be crimped to both end faces of the rotor core. The rotor of the motor characterized by the above-mentioned.   6. The permanent magnet according to claim 1, wherein the permanent magnet is prevented from slipping out of the insertion hole after the permanent magnet is fitted into the insertion hole. A motor rotor comprising a fixing portion.

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