JP7548124B2 - Cooling structure for rotating electrical machines - Google Patents

Description

The present invention relates to a cooling structure for a rotating electrical machine.

Conventionally, as in Patent Document 1, for example, rotating electric machines have been proposed that have a cooling structure that guides cooling air to a radiator by the rotation of a fan connected to a rotating shaft. In addition, rotating electric machines that use an air-cooling system in which a blower introduces air into a housing to cool a coil are also known.

JP 2008-125172 A

In an air-cooled rotating electric machine that introduces outside air into the housing from a radial direction intersecting the rotating shaft, the air flow from the blower to the inlet duct is a contracting flow, and the air flow from the inlet duct to the inside of the rotating electric machine is an expanding flow. In this case, if there is a large geometric discontinuity in the shape of the flow path before and after the inlet duct, air vortexes are generated, causing pressure loss (energy loss). From the perspective of improving the cooling efficiency of the coil, it is important to suppress such pressure loss.

The present invention was made in consideration of the above situation, and provides a cooling structure for a rotating electric machine that can suppress pressure loss when air is introduced into the housing from a direction intersecting the rotation axis.

A cooling structure for a rotating electric machine according to one aspect of the present invention includes a housing that houses a stator and a rotor, and a duct that introduces cooling air into the housing from a direction intersecting with the rotation axis direction of the rotor to cool a coil of the stator , the duct having a pair of vortex suppression parts therein that change a flow passage width in a height direction intersecting with the rotation axis direction and the extension direction of the duct in a curved shape. Each of the vortex suppression parts has a convex shape having a first region facing an inlet side of the duct and narrowing the flow passage width in the height direction, and a second region connected to the first region and widening the flow passage width in the height direction toward an outlet side of the duct.

The length of the second region of the vortex suppression portion in the extension direction of the duct may be set to be longer than the length of the first region of the vortex suppression portion in the extension direction of the duct.
The vortex suppressor may also be configured as a member that can be retrofitted to the inner surface of the duct.
Furthermore, the outlet end of the duct and the housing may be connected at a position facing a coil end provided on the stator.

The cooling structure for a rotating electric machine according to one aspect of the present invention can suppress pressure loss when air is introduced into the housing from a direction intersecting the rotation axis.

1 is a perspective view showing an external appearance of an example of a rotating electric machine according to an embodiment of the present invention; 2 is a cross-sectional view taken along line AA of FIG. 1. FIG. 11 is a diagram illustrating an air flow in a cooling structure in a comparative example. FIG. 11 is an enlarged view showing a schematic view of the air flow on the air inlet duct side of the comparative example. 5A is a diagram showing a schematic diagram of an air flow in the cooling structure of the present embodiment, and FIG. 5B is a diagram showing an example of the configuration of a vortex suppression section. 4 is an enlarged view showing a schematic view of the air flow on the air inlet duct side in this embodiment. FIG. FIG. 2 is a diagram showing an analysis model of a thermal fluid analysis in the embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the embodiments, in order to make the description easier to understand, structures and elements other than the main parts of the present invention will be described in a simplified or omitted manner. In addition, in the drawings, the same elements are given the same reference numerals. Note that the shapes, dimensions, etc. of each element shown in the drawings are shown only for illustrative purposes, and do not represent the actual shapes, dimensions, etc.

The drawings also show an XYZ coordinate system as a three-dimensional Cartesian coordinate system where appropriate. In the XYZ coordinate system, the Z direction is parallel to the axis of rotation. The X direction is perpendicular to the Z direction, and corresponds to the left-right direction in FIG. 2. The Y direction is perpendicular to both the X and Z directions, and corresponds to the depth direction of the paper in FIG. 2. In the drawings, the axis of rotation of the rotating electric machine is indicated by the symbol AX as necessary.

Figure 1 is a perspective view showing the appearance of an example of a rotating electric machine according to this embodiment. Figure 2 is a cross-sectional view of the XZ plane of Figure 1. The rotating electric machine of this embodiment is applied, for example, to a test device (dynamometer) that generates a load on the drive wheels of a vehicle to reproduce road conditions. Note that the rotating electric machine of this embodiment is not limited to dynamometers and may be applied to other uses.

The rotating electric machine 1 is, for example, an inner rotor type motor, and includes a stator 2, a rotor 3, a motor shaft 4, and a housing 5.

The stator 2 is cylindrical and houses the rotor 3 in a central space centered on the rotation axis AX. A number of slots (not shown) are formed along the axial direction on the inner circumference of the stator 2, and a coil is wound in each slot. The coil end portions 6 of the coil protrude from the stator 2 at both axial ends of the stator 2 (the load side and the anti-load side of the rotating electric machine 1), and form a ring shape in a plane (XY plane) that intersects with the axial direction.

The rotor 3 has an iron core in which permanent magnets (not shown) are arranged, and is disposed inside the stator 2 across a small air gap. The motor shaft 4 is fitted into the center of the iron core of the rotor 3 along the rotation axis AX, and is rotatably supported by bearings 7a and 7b provided in the housing 5. The load side of the motor shaft 4 penetrates the housing 5 and protrudes to the outside of the rotating electric machine 1.

In the rotating electric machine 1, the magnetic field of the stator 2 is switched in sequence by controlling the current through the coil, which generates an attractive or repulsive force with the magnetic field of the rotor 3. This causes the rotor 3 and the motor shaft 4 to rotate, driving the rotating electric machine 1. At this time, the coil generates heat as a result of the current passing through it.

The housing 5 has a main body 10 that has an overall shape of a substantially cylindrical shape. The main body 10 houses the stator 2 and rotor 3 and supports the motor shaft 4. The housing 5 also has an air inlet duct 11 and an air exhaust duct 12 for air-cooling the coil end portions 6 on the load side and anti-load side, respectively.

Two air inlet ducts 11 are provided in the housing 5 with a gap between them in the axial direction. Each air inlet duct 11 extends in a radial direction (X direction) perpendicular to the rotation axis AX, and is a duct with a rectangular outer shape and cross-sectional shape. One end of each air inlet duct 11 communicates with the outside of the housing, and the other end is connected to a position facing the coil end portion 6 of the main body portion 10. In addition, a blower 13 is disposed on one end of the air inlet duct 11. As a result, by driving the blower 13, cooling air passes through the air inlet duct 11 and is introduced into the main body portion 10 of the housing 5, and the coil end portions 6 are air-cooled.

Similar to the air inlet duct 11, two air exhaust ducts 12 are provided in the housing 5 with an axial gap between them. Each air exhaust duct 12 extends in a radial direction (X direction) perpendicular to the rotation axis AX, and has a rectangular outer shape and cross-sectional shape. One end of each air exhaust duct 12 is connected to a position facing the coil end portion 6 of the main body 10, and the other end communicates with the outside of the housing 5. In addition, one end of the air exhaust duct 12 is located in a position that is 180° rotationally symmetrical about the rotation axis AX on the XY plane with respect to the other end of the air inlet duct 11. In other words, a pair of air inlet ducts 11 and air exhaust ducts 12 is arranged for each coil end portion 6 in the main body 10 of the housing 5.

Figure 3 is a diagram showing the air flow in the cooling structure of the comparative example. The air introduced into the main body 10 of the housing 5 from the other end of the air inlet duct 11 flows inside the main body 10 from both the left and right directions along the outer periphery of the coil end portions 6, and heads toward the air exhaust duct 12 while removing heat from the coil end portions 6. This allows each coil end portion 6 to be air-cooled all around. After that, the air that has exchanged heat with the coil end portions 6 is exhausted outside the housing via the air exhaust duct 12.

Figure 4 is an enlarged view showing the air flow on the air inlet duct 11 side of the comparative example. In the rotating electric machine 1 having the above configuration, the air flow from the blower 13 to the air inlet duct 11 is a contracting flow, and the air flow from the air inlet duct 11 to the main body 10 of the housing 5 is an expanding flow. At this time, as in the comparative example shown in Figures 3 and 4, if the geometric discontinuity of the flow path shape before and after the air inlet duct 11 is large, air vortices vo1 and vo2 are generated in front of the air inlet duct 11 and in the main body 10 of the housing 5. Such vortices vo1 and vo2 lead to pressure loss (energy loss) of the air flow, and are one of the factors that reduce the cooling efficiency when air-cooling the coil end portion 6.

As a countermeasure against such an event, the air introduction duct of this embodiment is provided with a vortex suppression section 14 in order to increase the geometric continuity of the flow passage shape. The configuration of the vortex suppression section 14 will be described below with reference to Figs. 5 and 6.
Here, the configuration of the vortex suppression portion 14 is common to both the load side and anti-load side air inlet ducts 11. Therefore, in the following description, the configuration of the air inlet duct 11 on the load side of the rotating electric machine 1 will be described, and any duplicated description of the configuration on the anti-load side will be omitted.

In the air inlet duct 11 of this embodiment, vortex suppression sections 14 are formed on a pair of wall surfaces in the height direction (Y direction) perpendicular to the rotation axis direction and the extension direction of the air inlet duct, facing each other above and below. The vortex suppression sections 14 are configured to change the flow path width in the height direction (Y direction) in a curved shape along the extension direction (X direction) of the air inlet duct, and the shape of the flow path in the width direction (Z direction) is constant.

The shape of the vortex suppression section 14 is the same for all of the wall surfaces of the duct in the Y direction, and as shown in FIG. 5(b), the contour on the flow path side is convex toward the inside of the duct. The vortex suppression section 14 has, in order from the inlet side along the extension direction of the air introduction duct 11, a first region 14a and a second region 14b with different contour shapes on the flow path side.

The first region 14a of the vortex suppression section 14 faces the inlet side of the air inlet duct 11 and has a shape in which the amount of protrusion in the Y direction toward the inside of the duct increases in a curved shape. In other words, when a pair of vortex suppression sections 14 are arranged facing each other in the air inlet duct 11, the flow path width in the Y direction of the air inlet duct 11 narrows in a curved shape toward the outlet side in the area of the first region 14a. As a result, in the reduced flow on the inlet side of the air inlet duct 11, the shape of the flow path changes to a curved shape, suppressing the generation of separated flow, making it difficult for vortices to occur on the inlet side of the air inlet duct 11. Therefore, the vortex vo1' in Figure 6 is smaller than in the comparative example in Figure 4.

The second region 14b of the vortex suppression section 14 is connected to the first region 14a, and has a shape in which the amount of protrusion in the Y direction decreases in a curved manner toward the outlet side of the air inlet duct 11. In other words, when a pair of vortex suppression sections 14 are arranged in the air inlet duct 11 facing each other, the flow path width in the Y direction of the air inlet duct 11 expands in a curved manner toward the outlet side at the second region 14b. As a result, in the expanding flow from the air inlet duct 11 to the main body 10 of the housing 5, the shape of the flow path changes to a curved shape, suppressing the generation of separated flow, and the change in shape at the connection part between the air inlet duct 11 and the main body 10 becomes gentle, making it difficult for vortices to occur in the main body 10 of the housing 5. Therefore, the vortex vo2' in FIG. 6 is smaller than the comparative example in FIG. 4.

Here, regarding the flow path shape of the air intake duct 11 defined by the vortex suppression section 14, even if the gradient on the inlet side is steep, a separated flow is unlikely to occur, but if the gradient on the outlet side is steep, a separated flow is likely to occur. Therefore, it is preferable that the shape of the vortex suppression section 14 is such that the gradient on the outlet side is smaller than the gradient on the inlet side.

From the above viewpoints, the length of the second region 14b in the extension direction of the air inlet duct 11 is set to be longer than the length of the first region 14a. As a result, the gradient in the first region 14a of the vortex suppression section 14 is steeper than the second region 14b, while the gradient in the second region 14b is gentler than the first region 14a. For example, the length of the second region 14b in the extension direction of the air inlet duct 11 is set to be at least twice as long as the length of the first region 14a so that it is sufficiently long. Note that the shorter the length of the first region 14a in the extension direction of the air inlet duct 11, the longer the length of the second region 14b, and the gentler the gradient in the second region 14b in the extension direction of the air inlet duct 11 becomes.

The contour shape of the flow path side of the vortex suppression section 14 can be set as appropriate, for example, by combining a circular arc shape and an elliptical shape. For example, the contour shape of the flow path side of the vortex suppression section 14 may be a shape that combines two types of 1/4 ellipses with different lengths of the major and minor axes. In addition, the airfoil shape defined by NACA may be applied as the contour shape of the flow path side of the vortex suppression section 14.

Here, the vortex suppression section 14 may be formed integrally with the air inlet duct 11, or may be formed by later fixing the components of the vortex suppression section 14 inside the air inlet duct 11 by gluing, bolts, etc. When the components of the vortex suppression section 14 are later attached, it is also easy to fine-tune the flow path shape of the air inlet duct 11 by replacing the parts.

As described above, the rotating electric machine 1 of the above embodiment includes a main body 10 that houses the stator 2 and the rotor 3, and an air inlet duct 11 that introduces cooling air into the main body 10 from a radial direction intersecting with the rotation axis direction of the rotor 3. The air inlet duct 11 has therein a pair of vortex suppression parts 14 that change the flow passage width in a height direction intersecting with the rotation axis direction and the extension direction of the air inlet duct in a curved shape. Each of the vortex suppression parts 14 has a convex shape having a first region 14a that narrows the flow passage width in the height direction and a second region 14b that widens the flow passage width in the height direction toward the outlet side of the air inlet duct 11.
The vortex suppressor 14 described above changes the shape of the flow passage into a curved shape at the inlet and outlet sides of the air introduction duct 11, thereby suppressing separated flows and making it possible to suppress pressure loss.

(Example)
A thermal fluid analysis according to an embodiment of the present invention will now be described.
In the example, a thermal fluid analysis was performed on a two-dimensional analysis model on the XY plane for a rotating electric machine having a similar configuration to that of this embodiment, and the change in pressure loss due to the presence or absence of a vortex suppression unit was confirmed. Fig. 7 is a diagram showing the analysis model for the thermal fluid analysis of the example.

The analytical model in Figure 7 mimics the coil end of a dynamometer. The dimensions of each part of the analytical model correspond to the typical dimensions of a dynamometer. In addition, in the analytical model, the upstream and downstream flow paths are each extended into a rectangular shape to stabilize the flow.

As shown in FIG. 7, the flow path dimensions of the inlet and outlet extensions are 400 mm long and 170 mm wide, and the dimensions of the duct parts (air inlet duct, air exhaust duct) connected to the housing are 112.57 mm long and 150 mm wide. The inner diameter of the housing is 460 mm (R230 mm), the outer diameter of the coil end is 340 mm, and the distance between the coil end and the housing is 60 mm. The dimensions of the vortex suppression part are 112.57 mm long, 15 mm long for the first region, and 30 mm protrusion into the duct.

In the thermal fluid analysis, the outlet pressure was set to 0 Pa, the flow rate to 39 m/s, and the inlet pressure value was calculated as the pressure loss value. In the comparative example without a vortex suppression section, the pressure loss value was 1532 Pa. In contrast, in the example with a vortex suppression section, the pressure loss value was 1366 Pa. Therefore, in the example with a vortex suppression section, the effect of reducing pressure loss by approximately 11% was achieved compared to the comparative example.

The present invention is not limited to the above-described embodiment, and various improvements and design changes may be made without departing from the spirit of the present invention.

For example, the arrangement of the air inlet duct 11 and the air exhaust duct 12 in the above embodiment is one example and is not limited to the above embodiment. For example, the air inlet duct 11 and the air exhaust duct 12 may extend at an angle to the radial direction. Also, multiple pairs of air inlet ducts 11 and air exhaust ducts 12 may be arranged for one coil end portion 6. For example, the air inlet ducts 11 and air exhaust ducts 12 may be arranged alternately in the circumferential direction, with two pairs of air inlet ducts 11 and two pairs of air exhaust ducts 12 shifted by 90°.

In addition, in this embodiment, an example is shown in which the air inlet duct 11 is arranged on both axial sides of the main body, but the air inlet duct 11 may be provided only on one axial side, and cooling air may be sent to the other side through the air gap between the stator 2 and rotor 3.

In addition, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

Reference Signs List 1: rotating electric machine, 2: stator, 3: rotor, 4: motor shaft, 5: housing, 6: coil end portion, 10: main body portion, 11: air inlet duct, 12: air exhaust duct, 13: blower, 14: vortex suppression portion, 14a: first region, 14b: second region

Claims (4)

A housing that houses the stator and the rotor;
a duct that introduces cooling air for cooling a coil of the stator into the housing from a direction intersecting a rotation axis direction of the rotor,
the duct has therein a pair of vortex suppression sections that change a flow passage width in a height direction intersecting with the rotation axis direction and an extension direction of the duct in a curved shape,
A cooling structure for a rotating electric machine, wherein each of the vortex suppression sections has a convex shape having a first region facing the inlet side of the duct and narrowing the flow path width in the height direction, and a second region connected to the first region and widening the flow path width in the height direction toward the outlet side of the duct. 2. The cooling structure for a rotating electric machine according to claim 1, wherein a length of the second region of the vortex suppression portion in the extension direction of the duct is set longer than a length of the first region of the vortex suppression portion in the extension direction of the duct. 3. The cooling structure for a rotating electric machine according to claim 1, wherein the vortex suppression portion is configured as a member that can be later attached to the inner surface of the duct. 4. The cooling structure for a rotating electric machine according to claim 1, wherein the housing and an outlet end of the duct are connected to each other at a position facing a coil end provided in the stator.

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