JP4648470B2 - Electric motor cooling device - Google Patents

Description

  The present invention relates to an electric motor cooling device that cools an electric motor by a flow of a cooling medium around the electric motor.

  2. Description of the Related Art Conventionally, there has been known an apparatus in which an outer peripheral portion of a stator core is surrounded by a cylindrical casing and a cooling passage through which a coolant flows is processed on the inner peripheral surface of the casing to cool an electric motor (for example, Patent Documents). 1). In the apparatus described in Patent Document 1, after proceeding from one end in the axial direction to the other end as the cooling passage on the inner circumferential surface of the casing, the other end from the axial direction returns to the one end, and further from the one end in the axial direction to the other end. A spiral groove is formed so as to advance to the part.

Japanese Patent Laying-Open No. 2005-204496

  However, in the apparatus described in Patent Document 1, since the spiral groove is formed by reciprocating between the one end portion and the other end portion in the axial direction, the length of the cooling passage becomes long. As a result, the pressure loss increases and it becomes difficult to flow the required flow rate. Further, since the temperature of the coolant gradually increases in the flow direction, if the length of the cooling passage is increased, a sufficient cooling effect cannot be obtained in the latter half of the passage.

The present invention includes a first cylindrical member provided with a stator having a winding as a main heat source on the inside, and a cylindrical cavity fitted to the outer peripheral surface of the first cylindrical member. And a cooling passage that is formed on a fitting surface between the first cylindrical member and the second member and through which the cooling medium passes from one axial end to the other axial end. The plurality of passages are formed so as to turn in the circumferential direction while traveling in the axial direction from one axial end to the other axial end, in parallel so as not to cross each other, and to be substantially parallel to each other. A plurality of spiral passages formed by multiple spiral grooves obtained by removing the outer peripheral surface of the first tubular member, a first tubular member, and a second spiral passage One end of the fitting surface with the member and the other end in the axial direction have a plurality of spiral passages across the entire circumference. It is formed, and having a pair of annular passage which communicates the inlet of the cooling medium and an outlet portion and a plurality of spiral passages each axial end portion and the other axial end, respectively.

  According to the present invention, since a plurality of spiral passages are provided in parallel as cooling passages outside the stator, the length of each cooling passage is shortened, and the cooling effect due to the flow of the cooling medium can be enhanced.

It is sectional drawing which shows the structure of the electric motor cooling device which concerns on embodiment of this invention. It is a perspective view of the cooling jacket and cooling housing which constitute the electric motor cooling device concerning this embodiment. FIG. 3 is a development view of the outer peripheral surface of the cooling jacket of FIG. 2. (A)-(c) is an expanded sectional view of the helical channel | path of 1 groove | channel, 3 groove | channel, and 8 groove | channel, respectively.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view schematically showing a configuration of an electric motor M to which the electric motor cooling device according to the present embodiment is applied. The electric motor M includes a cylindrical stator 1 and a rotor (not shown) that is rotatably supported inside the stator 1.

  The stator 1 includes a stator core 11 formed by laminating thin plate-like magnetic bodies such as electromagnetic steel plates, and windings 12 wound around the stator core 11 by concentrated winding or distributed winding. Is covered with a resin 13 mixed with a material having good thermal conductivity. A power line 14 is taken out from the end of the stator 1, and a driving current is supplied from the outside to the winding 12 through the power line 14, thereby forming a rotating magnetic field around the rotor and rotating the rotor.

  Since such an electric motor M generates heat due to iron loss of the stator core 11 and copper loss of the winding 12, it is necessary to cool the electric motor M and suppress the heat generation of the electric motor M. In particular, when the electric motor M is used for driving a spindle of a machine tool, if the spindle of the machine tool is thermally deformed due to heat transfer, the machining accuracy is adversely affected, so that it is highly necessary to suppress the heat generation of the electric motor M. In the present embodiment, the cooling device 2 is configured as follows to cool the electric motor M.

  The cooling device 2 includes a substantially cylindrical cooling jacket 20 that is fitted to the outer circumferential surface of the stator 1, and a cooling housing 30 that is fitted to the outer circumferential surface of the cooling jacket 20. FIG. 2 is a perspective view showing a state in which the cooling housing 30 is disassembled from the cooling jacket 20. The cooling housing 30 does not need to have a cylindrical shape on the outer side, except that the cooling housing 30 includes a cylindrical cavity for containing the cooling jacket 20 therein. In the case of the main shaft, the outer shape of the main shaft is not limited, such as being a part of a structural material that supports the main shaft.

As shown in FIG. 2, a spiral groove 21 (spiral groove) is formed on the outer peripheral surface of the cooling jacket 20 so as to rotate in the circumferential direction from one end side to the other end side in the axial direction. On both outer sides in the axial direction, annular grooves 22 and 23 (annular grooves) are formed over the entire circumference. Further, O-ring mounting grooves 24 and 25 are formed on both outer sides in the axial direction of the annular grooves 22 and 23, respectively. These grooves 21 to 25 are processed by, for example, a composite lathe having a milling shaft. 1 shows a case where the depth of the annular grooves 22 and 23 is deeper than that of the spiral groove 21, and FIG. 2 shows that the spiral grooves 21 and the annular grooves 22 and 23 have the same depth.

  On the one end side and the other end side in the axial direction of the cooling housing 30, a plurality (3 in the figure) are arranged in the circumferential direction so as to match the positions of the annular grooves 22 and 23 when the cooling housing 30 is fitted to the cooling jacket 20. Through-holes 31 and 32 are opened. The through holes 31 and 32 respectively constitute an inlet part PA4 and an outlet part PA5 of a cooling passage which will be described later.

  The cooling jacket 20 is fitted and fixed to the outer peripheral surface of the stator 1 by, for example, an interference fit, and the cooling housing 30 is also fitted and fixed to the outer peripheral surface of the cooling jacket 20 by, for example, an interference fit. In consideration of assembly, the cooling housing 30 may be fitted to the outer peripheral surface of the cooling jacket 20 as a gap fit or an intermediate fit.

  As shown in FIG. 1, when the cooling housing 30 is fitted to the cooling jacket 20, the fitting surface includes the inner peripheral surface of the cooling housing 30 and the grooves 21 to 23 of the cooling jacket 20 from the one end side in the axial direction to the other end. A cooling passage is formed on the side. That is, the spiral passage PA1 is formed by the spiral groove 21 of the cooling jacket 20, and the annular passages PA2 and PA3 are formed by the annular grooves 22 and 23, respectively.

  Although not shown in the drawings, a cooling liquid supply source such as a pump is connected to each inlet PA4 (through hole 31) of the cooling passage via a pipe, and is connected to each outlet PA5 (through hole 32) of the cooling passage. Is connected to a coolant recovery unit such as a tank via a pipe. Accordingly, when the cooling liquid is supplied from the outside into the cooling passage through the inlet PA4, the cooling liquid sequentially flows through the annular passage PA2, the spiral passage PA1, and the annular passage PA3, and then flows out through the outlet portion PA5. . The cooling liquid flow removes heat from the surface of the cooling jacket 20 and cools the electric motor M. The plurality of inlet portions PA4 and outlet portions PA5 are connected to the coolant supply source and the recovery portion, for example, via branch pipes, and the coolant flows out equally to each inlet portion PA and each outlet portion PA5. Enter.

  In such a configuration of the cooling device, the cooling effect increases as the flow rate of the coolant increases and as the surface area of the cooling passage as the fin portion increases. In this regard, if the surface area of the cooling passage is simply increased, for example, a spiral passage PA1 is formed by a single groove to reduce the passage pitch p (distance between adjacent passages in the axial direction) This is possible by forming the spiral groove 21 deeply.

  However, if the passage pitch p is reduced, the pressure loss increases and it becomes difficult to flow the necessary flow rate. Further, in order to form the spiral groove 21 deeply, a sufficient thickness of the cooling jacket 20 is necessary, which not only hinders the miniaturization of the entire electric motor, but also increases the cutting amount of the groove processing, resulting in a processing cost. Invite the rise. Therefore, in the present embodiment, a plurality of spiral grooves 21 (multiple spiral grooves) are processed in parallel so as not to cross each other on the surface of the cooling jacket 20 as described below, and the spiral passage PA1 is connected to the parallel passage. Configure.

  FIG. 3 is a development view of the outer peripheral surface of the cooling jacket 20 schematically showing the flow of the cooling liquid, and shows an example in which the spiral passages PA11 to PA13 having three grooves are processed on the outer peripheral surface of the cooling jacket 20. . These spiral passages PA11 to PA13 are formed substantially parallel to each other, and the passage width w1, the passage depth (d2 in FIG. 4), the curvature of the passage (spiral curve), and the distance between adjacent passages. (Passage pitch p) is constant. In other words, each of the passages PA11 to PA13 has the same shape only by shifting the phase of the start position by 120 °, for example, and the spiral passages PA11 to PA13 are densely formed on the entire surface of the cooling jacket. Yes. In the figure, the passage width w1 and the width w2 of the land portion between the passages are substantially equal, but w1 may be larger or smaller than w2.

  In FIG. 3, the coolant that has flowed into the annular passage PA2 via the inlet portion PA4 is divided into the spiral passages PA11 to PA13, and the solid line, the dotted line, and the alternate long and short dash line along the spiral passages PA11 to PA13, respectively. It flows as shown by the arrow. Thereafter, these cooling liquids merge in the annular passage PA3 and flow out through the outlet part PA5.

  Although the electric motor M is cooled by such a flow of the coolant, in this embodiment, since the spiral passages PA11 to PA13 are provided in parallel, the passages are formed on the surface of the cooling jacket 20 as shown in FIG. Even when PA11 to PA13 are formed densely, the passage length of each passage PA11 to PA13 can be suppressed, and a sufficient cooling effect can be obtained over the entire passage.

  Here, if the flow passage areas of the passages PA11 to PA13 are S1 to S3, respectively, the total flow passage area S is S = S1 + S2 + S3. For this reason, a sufficient flow path area S can be ensured, and the passage pitch p can be reduced without reducing the flow rate of the coolant. When the passage pitch p is reduced, the surface area of the entire cooling passage is increased, so that the cooling effect can be enhanced.

  FIG. 4 is an enlarged cross-sectional view of the spiral passage PA1, and FIGS. 4A to 4C are diagrams in which the spiral passage PA1 has a single groove, a triple groove, and an eight groove, respectively. If the passage areas in these figures are Sa, Sb, and Sc, respectively, the flow passage areas S of the entire passage are Sa, 3 × Sb, and 8 × Sc, respectively. 4 (a) to 4 (c), the overall flow passage areas S are set to be substantially equal to each other. At this time, the passage pitch p2 of the three grooves is about ½ times the passage pitch p1 of the one groove, and the passage pitch p3 of the eight grooves is about ３ times the passage pitch p1 of the one groove. It is. In addition, the groove depths d1 to d3 in each figure are d1> d2> d3, and the groove depth d3 of the eight grooves is about half of the groove depth d1 of the one groove.

  Here, based on the surface area and the cutting amount of the entire channel of the single groove, the surface area and the cutting amount of the entire channel of the three grooves are about 1.2 times and about 0.7 times, respectively. The total surface area and cutting amount are about 1.2 times and about 0.4 times, respectively. Therefore, by forming the cooling passage PA1 with the multi-row spiral groove, not only the surface area can be increased without changing the entire flow path area S, but also the cutting amount can be reduced. As a result, the machining time can be shortened, the wear of the cutting tool can be suppressed, and the machining cost can be reduced. Note that the number of spiral grooves 21 may be other than three or eight as long as it is plural, and is determined in consideration of necessary cooling performance and processing cost.

According to the present embodiment, the following operational effects can be achieved.
(1) A plurality of spiral grooves 21 were processed so as not to cross each other on the outer peripheral surface of the cooling jacket 20, and spiral passages PA11 to PA13 were formed in parallel. Thus, the surface area of the cooling passage can be increased without increasing the passage length of each of the spiral passages PA11 to PA13, and the cooling effect can be enhanced. That is, if the spiral passage PA1 having a small passage pitch p is formed by a single (in-line) spiral groove 21, the entire length of the cooling passage is increased and the pressure loss is increased. As a result, it becomes difficult to flow a required amount of coolant, and a sufficient cooling effect of the electric motor M cannot be obtained. In contrast, in the present embodiment, since a plurality of spiral passages PA11 to PA13 are provided in parallel, an increase in the pressure loss of the passage can be suppressed while ensuring the entire flow passage area, and the electric motor M is sufficiently provided. A cooling effect can be obtained.

(2) Since the spiral passages PA11 to PA13 are formed so as to be substantially parallel to each other, the spiral passage PA1 is provided uniformly over the entire outer peripheral surface of the cooling jacket 20, and the entire motor can be efficiently cooled.
(3) Annular passages PA2 and PA3 are provided on both sides in the axial direction of the spiral passage PA1, respectively, and an inlet portion PA4 and an outlet portion PA5 of the cooling liquid and one axial end of the spiral passage PA1 through the annular passages PA2 and PA3, and Since the other ends in the axial direction are communicated with each other, the cooling liquid can be evenly flowed through the spiral passages PA1, and a sufficient cooling effect can be obtained.
(4) Since a plurality of inlet portions PA4 and outlet portions PA5 of the coolant are arranged in the circumferential direction in the cooling housing 30, a large amount of coolant can be supplied to the surface of the cooling jacket 20.

  In FIG. 1, in order to suppress an increase in pressure loss in the annular passages PA2 and PA3, the annular passages PA2 and PA3 are formed deeper than the spiral passage PA1, and the flow passage area of the annular passages PA2 and PA3 is increased. Yes. However, if the pressure loss is not a problem, it is preferable from the viewpoint of processing cost to make the depths of the passages PA1 to PA3 equal as shown in FIG.

  In the above embodiment, the grooves 21 to 23 as the cooling passages PA1 to PA3 are processed on the outer peripheral surface of the cooling jacket 20, but instead, the grooves as the cooling passages are similarly formed on the inner peripheral surface of the cooling housing 30. You may process, or you may process a groove | channel on both the outer peripheral surface of the cooling jacket 20, and the internal peripheral surface of the cooling housing 30. FIG. That is, if a plurality of spiral passages PA1 are formed in parallel on the fitting surfaces of the cooling jacket 20 as the first cylindrical member and the cooling housing 30 as the second member, the inner circumference of the cooling jacket 20 The shape of the surface and the outer peripheral surface of the cooling housing 30 may be arbitrary. The stator 1 may be the first cylindrical member, and the spiral passage PA1 may be formed on the outer peripheral fitting surface of the stator 1.

  Without processing grooves on both the inner peripheral surface of the cooling jacket 20 and the outer peripheral surface of the cooling housing 30, a plurality of passage members formed in a coil shape on the fitting surface are inserted out of phase. A plurality of spiral cooling passages PA1 may be formed by the inner peripheral surface, the outer peripheral surface of the cooling housing 30, and the passage member. However, if a separate passage member is provided, the thermal resistance at the contact surface between the passage member and the cooling jacket 20 is large, and the thermal conductivity is deteriorated.

  The spiral groove 21 can be formed by cutting, grinding, hobbing, laser processing, electric discharge machining, or the like, or can be formed by casting. However, when the cooling jacket 20 having the spiral groove 21 is manufactured by casting, cracks and nests are likely to be generated. Therefore, it is preferable in terms of product reliability to form the groove by removal processing from the cylindrical tubular member. .

  The annular passages PA2 and PA3 are provided on both outer sides in the axial direction of the spiral passage PA1, and the coolant is supplied to and discharged from the spiral passage PA1 through the annular passages PA2 and PA3. However, the annular passages PA2 and PA3 are omitted. Then, the coolant may be directly supplied to and discharged from the spiral passage PA1. Although the coolant inlet / outlet portions PA4, PA5 are provided in the cooling housing 30, any configuration may be used for the inlet / outlet portions PA4, PA5, such as the number, shape, and arrangement of the inlet / outlet portions PA4, PA5. The cooling medium flowing through the cooling passage is not limited to liquid such as water or oil, but may be gas.

  The above cooling device can be applied not only to the electric motor M for driving the spindle of the machine tool but also to an electric motor M other than the machine tool. That is, the present invention is not limited to the motor cooling device of the embodiment as long as the features and functions of the present invention can be realized.

20 Cooling jacket 21 Spiral groove 22, 23 Annular groove 30 Cooling housing 31, 32 Through hole PA1 Spiral passage PA2, PA3 Annular passage PA4 Inlet part PA5 Outlet part

Claims (3)

A first tubular member in which a stator having windings is disposed inside;
A second member having a cylindrical cavity to be fitted to the outer peripheral surface of the first tubular member;
A cooling passage formed on a fitting surface between the first tubular member and the second member, and through which a cooling medium passes from one axial end to the other axial end;
The cooling passage is
A plurality of spiral shapes that are formed so as to travel in the axial direction from one axial end to the other axial end while turning in the circumferential direction, in parallel so as not to cross each other and substantially parallel to each other A plurality of spiral passages formed by multiple spiral grooves obtained by removing the outer peripheral surface of the first tubular member,
The cooling medium is formed over the entire circumference of the first cylindrical member and the second member at one end in the axial direction and the other end in the axial direction with the plurality of spiral passages interposed therebetween, respectively. An electric motor cooling device comprising a pair of annular passages for communicating the one inlet portion and the outlet portion of the plurality of spiral passages with one axial end portion and the other axial end portion of each of the plurality of spiral passages . The motor cooling device according to claim 1,
  The motor cooling device according to claim 1, wherein the pair of annular passages is formed by an annular groove provided on an outer peripheral surface of the first cylindrical member. In the electric motor cooling device according to claim 1 or 2,
  The motor cooling device according to claim 1, wherein each of the inlet portion and the outlet portion includes a plurality of through holes penetrating the second member in a radial direction.

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