Insert member for rotary electric machine

Abstract

[Problem] To provide an insert member, the thermal conductivity of which can be satisfactorily controlled. [Solution] Provided is a substantially cylindrical insert member to be cast in an aluminum alloy motor case of a rotary electric machine. A plurality of protrusions and recesses are formed on the outer circumferential surface of the insert member. When a line along the contour of the outer circumferential surface including the contour of the plurality of protrusions and recesses is defined as a contour line in the range of a predetermined axial length in a cross-section appearing when the insert member is cut into two parts along the axial direction by a virtual plane including the central axis of the insert member, the outer circumferential surface length ratio, which is a value obtained by dividing the length of the contour line by the predetermined axial length, is 1.15 or more.

Description

Inserts for rotating electrical machines

[0001] The present invention relates to an insert member for a rotating electrical machine.

[0002] Generally, aluminum alloys are widely used as structural members for motor cases of rotating electrical machines. To provide additional strength to the motor case, a high-strength, approximately cylindrical, iron-based insert member may be used in the area where the stator is located. In this regard, it has been proposed to provide irregularities on the outer peripheral surface of the insert member, which is integrated into the motor case by press-fitting or casting (see, for example, Patent Documents 1 and 2).

[0003] JP 2001-169500 ​​A Japanese Patent No. 6655560 A

[0004] However, insert members made of iron-based materials have poorer thermal conductivity than aluminum alloys, which are commonly used as structural members for motor cases. Therefore, while the unevenness on the outer surface of the insert member increases the bond strength with the motor case, it is unable to efficiently dissipate heat generated by heating elements such as the stator, which can lead to reduced motor output and a decrease in the magnetic force of the magnets used in the motor.

[0005] The technology of the present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to provide an insert member that can effectively control the thermal conductivity at the interface between the insert member and the motor case.

[0006] In order to solve the above problems, the technology of the present invention employs the following configuration: An insert member for a rotating electric machine as one aspect of the technology of the present invention is a substantially cylindrical insert member that is cast into an aluminum alloy motor case of a rotating electric machine, the outer peripheral surface of the insert member being formed with an uneven portion including concave and convex portions, and when the insert member is cut axially into two parts by an imaginary plane including a central axis of the insert member, one of the cut surfaces that appears on either side of the central axis, when a contour line is defined as a line along the contour of the outer peripheral surface that includes the contour of the uneven portion within a predetermined axial length, an outer peripheral surface length ratio, which is the value obtained by dividing the length of the contour line by the predetermined axial length, is 1.15 or more.

[0007] Furthermore, the insert member defines, within the range of the predetermined axial length, a solid portion region where the insert member overlaps on a line segment parallel to the inner peripheral surface of the insert member when the line segment is superimposed on the entire cross section, and a non-solid portion region where the insert member does not overlap on the line segment, and the line segment is moved in the entire cross section of the insert member at a predetermined pitch along the height direction of the uneven portion from the tip end of the most protruding convex portion of the uneven portion toward the base end side of the convex portion, and the values ​​of the solid portion ratio at each measurement point are plotted in order, with the horizontal axis representing the solid portion ratio. a solid body summary diagram in which the solid body ratios at the measurement points based on the plurality of cross sections are plotted in order is called an average solid body summary diagram; a position in the average solid body summary diagram where the average solid body ratio is 0 is called the tip end on the diagram; a position where the average solid body ratio, plotted in order from the tip end side toward the base end side, first exceeds 0.98 is called the base end on the diagram; and the distance from the tip end on the diagram to the base end on the diagram is called the average maximum height of the uneven portion. The average maximum height of the uneven portion may be 0.15 mm or more and 1.50 mm or less.

[0008] Furthermore, when the average solid portion ratio at a position moved 0.10 mm in height from the base end portion in the figure toward the tip end portion in the figure is defined as A, and the value obtained by dividing the outer circumferential surface length ratio by A is defined as a first interface parameter, the first interface parameter may be 1.30 or more.

[0009] Furthermore, when the thickness of the insert member is half the value obtained by subtracting the inner diameter from the outer diameter of the insert member, the thickness of the insert member may be 0.8% or more of the outer diameter of the insert member.

[0010] The outer peripheral surface may be subjected to a roughening treatment.

[0011] Furthermore, the outer peripheral surface of the insert member may have, in a portion in the axial direction, at least one of a region in which the outer peripheral surface length ratio is less than 1.15 and a region in which the first interface parameter is less than 1.30.

[0012] Furthermore, in the average solid part summary diagram, when an average non-solid part ratio is defined as a value obtained by subtracting the average solid part ratio at a certain measurement height from the average solid part ratio at the base end on the diagram, and the average non-solid part ratio at a position moved 0.10 mm in height from the base end on the diagram toward the tip end on the diagram is defined as B, 0.10 / B≦1.30 may be satisfied.

[0013] Furthermore, in the average solid part summary diagram, when an average non-solid part ratio is defined as a value obtained by subtracting the average solid part ratio at a certain measurement height from the average solid part ratio at the base end on the diagram, and the average non-solid part ratio at a position moved 0.10 mm in height from the base end on the diagram toward the tip end on the diagram is defined as B, 0.10 × B ≧ 0.01 may be satisfied.

[0014] In addition, in the average solid portion summary diagram, the height from the base end to the position where the average solid portion ratio is 0.30 on the diagram may be 0.40 mm or less.

[0015] Furthermore, in the average solid portion summary diagram, a second interface parameter, which is a value obtained by dividing the outer circumferential surface length ratio by the height from the base end to a position on the diagram where the average solid portion ratio is 0.30, may be 4.00 or more.

[0016] According to the present invention, it is possible to provide an insert member that can effectively control the thermal conductivity at the interface between the insert member and the motor case.

[0017] Fig. 1 is an overall view of an insert member for a rotating electrical machine according to an embodiment, and an enlarged view of a portion of its outer circumferential surface. Fig. 2 is a cross-sectional view showing an example of a predetermined cut surface of the insert member for a rotating electrical machine according to an embodiment. Fig. 3 is an average solid portion summary diagram illustrating the relationship between the measurement height and the average solid portion ratio of the insert member for a rotating electrical machine according to an embodiment.

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The configurations described in the following embodiments are not intended to limit the technical scope of the invention unless otherwise specified. Each configuration and combination thereof in the following embodiments is merely an example, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope of the gist of the present invention.

[0019] 1 is an overall view of an insert member 1 for a rotating electrical machine according to an embodiment (hereinafter referred to as "insert member 1"), and an enlarged view of a portion of its outer circumferential surface. In this embodiment, the direction along the central axis C of the insert member 1 is defined as the axial direction, and the direction perpendicular to the axial direction, extending from the central axis C toward the outer circumferential surface of the insert member 1, is defined as the radial direction. The direction around the central axis C along the outer circumferential surface of the insert member 1 is defined as the circumferential direction. The axial, radial, and circumferential directions are merely directions used to indicate the relative positional relationships of the various elements in the insert member 1.

[0020] The insert member 1 according to this embodiment is, for example, a cast iron material formed into a substantially cylindrical shape centered on a central axis C, with multiple protrusions 10 formed on its outer circumferential surface (surface). Here, the portions that are recessed relative to the protrusions 10 are referred to as "recesses 13," and the structure including the protrusions 10 and recesses 13 is referred to as the "uneven portion." A rotating electric machine to which the present invention is applicable is, for example, a rotating electric machine used in an electric vehicle or the like. However, the rotating electric machine to which the present invention is applicable is not limited thereto. In this embodiment, the outer diameter OD of the insert member 1 is formed within a range of 150 mm to 300 mm, but this may be changed as appropriate depending on the intended use. Furthermore, the outer diameter OD is a value corresponding to the distance between two parallel planes when the insert member 1 is placed between the two parallel planes and the tip ends 11 of the protrusions 10 on the outer circumferential surface of the insert member 1 are brought into contact with the two parallel planes. Here, the thickness of the insert member 1 is defined as half the value obtained by subtracting the inner diameter ID from the outer diameter OD. The thickness of the insert member 1 is preferably 0.8% or more of the outer diameter OD of the insert member 1. If the thickness of the insert member 1 is less than 0.8% of the outer diameter OD, the strength will be insufficient when integrating the insert member 1 with the motor case, increasing the risk of cracking the insert member 1. Furthermore, since it is desirable for the insert member 1 to be lightweight, the thickness of the insert member 1 is preferably less than approximately 4% of the outer diameter OD.

[0021] A rotating electric machine is composed of components such as a rotating shaft, a rotor, a stator, a motor case, and bearings. The motor case has a cylindrical section hollowed out in a cylindrical shape. The stator, generally made of electromagnetic steel sheet or the like, is fitted to the inner periphery of the cylindrical section. The insert member 1 is disposed in the motor case's fitting portion with the stator. The insert member 1 is cast into the inner periphery of the aluminum alloy motor case. This results in the motor case and the insert member 1 forming a composite structure in which at least a portion of the outer periphery of the insert member 1 is covered with aluminum alloy. The stator fitted to the inner periphery of the insert member 1 generates heat as the rotating electric machine operates. However, by appropriately shaping the outer periphery of the insert member 1, the thermal conductivity at the interface between the insert member 1 and the motor case can be well controlled, allowing the generated heat to be efficiently dissipated to the motor case.

[0022] As mentioned above, the material of the insert member 1 is preferably cast iron, which has higher thermal conductivity than steel, but is not particularly limited to this. Typically, flake graphite cast iron, such as JIS FC250 equivalent material, can be used, taking into consideration thermal conductivity and workability.

[0023] The uneven portion on the outer peripheral surface of the insert member 1 may be formed by a method of transferring the unevenness of a mold wash in a centrifugal casting method, a method of directly subjecting the outer peripheral surface of the insert member to machining such as cutting, a method of subjecting the outer peripheral surface to a roughening treatment, or a combination of these methods. Examples of the roughening treatment include surface treatments such as thermal spraying, cold spraying, and shot blasting. Examples of thermal spray materials include, but are not limited to, aluminum alloys. However, the material of the insert member 1 and the method of forming the uneven portion described above are merely examples and are not particularly limited.

[0024] FIG. 2 is a cross-sectional view showing an example of a predetermined cut surface of the insert member 1 according to the embodiment. The predetermined cut surface in this embodiment is a full cross section, which is one of the cut surfaces that appear on both sides of the central axis C when the insert member 1 is cut into two parts along the axial direction by an imaginary plane including the central axis C of the insert member 1. The axial length of the full cross section is equal to or greater than the length d1 described below. In FIG. 2, the A-A' cross section in FIG. 1 is shown as an example of the predetermined cut surface. Below, the uneven portion provided in the insert member 1 according to this embodiment will be described using FIG. 2.

[0025] The convex portions 10 in the uneven portion are part of the insert member 1 and are formed on the outer peripheral surface of the insert member 1. The convex portions 10 may be arranged in multiple locations and at random intervals in the axial and circumferential directions, or may be arranged in multiple locations and at regular intervals in the axial and circumferential directions. The convex portions 10 have a tip end 11 and a base end 12, and are formed to protrude from the base end 12 to the tip end 11 radially outward of the insert member 1. However, the shapes of the convex portions 10 and the concave portions 13 are not particularly limited.

[0026] Furthermore, the locations where the plurality of protrusions 10 are formed on the outer peripheral surface of the insert member 1 may be limited to a certain area, or processing such as scraping off some of the plurality of protrusions 10 may be performed. As a result, the plurality of protrusions 10 may be formed only in a certain area of ​​the outer peripheral surface of the insert member 1.

[0027] The protrusions 10 may be formed by casting while applying centrifugal force using a centrifugal casting method. In this case, the tip ends 11 of the protrusions 10 are formed based on the inner peripheral surface of the mold. Therefore, if the inner peripheral surface of the mold is a perfect circle, the distances from the central axis C of the insert member 1 will be approximately equal, whereas the distances from the central axis C of the base ends 12 may vary. For this reason, the height of the protrusions 10 is measured based on the tip ends 11 in the process of deriving the average maximum height h1 of the uneven portion using the substantial part summary diagram described below. However, the method of forming the protrusions 10 is not limited to this, and they may also be formed, for example, by machining the outer peripheral surface of a cylindrical member, such as by cutting.

[0028] Furthermore, the shape of the protrusion 10 is not particularly limited. The protrusion 10 may have, for example, a spirally continuous shape or a circularly continuous shape along the circumferential direction. For example, the protrusion 10 can be formed into a spiral or circular shape by directly performing machining such as cutting on the outer circumferential surface of the insert member 1. The shape of the protrusion 10 may be any shape that is effective in the actual cutting test, thermal conductivity measurement, surface temperature simulation, and compactness evaluation described below.

[0029] The region where the uneven portion is formed on the outer peripheral surface of the insert member 1 may be limited to a certain region. Furthermore, the outer peripheral surface of the insert member 1 may have, in a portion in the axial direction, at least one of a region where the outer peripheral surface length ratio (described later) is less than 1.15 and a region where the first interface parameter (described later) is less than 1.30. In this case, the region where the outer peripheral surface length ratio is less than 1.15 or the region where the first interface parameter is less than 1.30 may or may not have an uneven portion. Furthermore, the axial length of the region where the outer peripheral surface length ratio is less than 1.15 or the region where the first interface parameter is less than 1.30 is preferably less than 50%, more preferably less than 30%, and even more preferably less than 10% of the total length of the insert member 1. Furthermore, the region where the outer peripheral surface length ratio is less than 1.15 or the region where the first interface parameter is less than 1.30 may be a partial region in the circumferential direction on the outer peripheral surface of the insert member 1, or the entire region in the circumferential direction. By limiting the area where the outer peripheral surface length ratio is less than 1.15 and the area where the first interface parameter is less than 1.30 to a portion of the outer peripheral surface, the areas in the insert member 1 where heat is easily transferred can be changed according to the heat-generating parts of the stator, thereby preventing deformation of the insert member 1 and the motor case due to heat.

[0030] Reference numeral 30 in Fig. 2 indicates a contour line (hereinafter referred to as "contour line 30") of the outer peripheral surface of the insert member 1 that follows the shapes of the protrusions 10 and recesses 13 within a range of length d1 (an example of "predetermined axial length" in the present invention) on a predetermined cross section. Reference numeral 40 indicates an inner peripheral surface (hereinafter referred to as "inner peripheral surface 40") of the insert member 1. Since the insert member 1 is formed in a cylindrical shape, in Fig. 2, the inner peripheral surface 40 is formed as a straight line along the axial direction.

[0031] [Outer peripheral surface length ratio] The outer peripheral surface length ratio is the value obtained by dividing the length of the contour line 30 within the range of length d1 by the length d1. For a given value of the average maximum height h1 of the concave-convex portions, a larger value of the outer peripheral surface length ratio is expected to result in better thermal conductivity. In this case, the outer peripheral surface length ratio is preferably 1.15 or greater, and more preferably 1.30 or greater. The outer peripheral surface length ratio can be easily increased by increasing the average maximum height h1 of the concave-convex portions and the length of the contour line 30. However, if the average maximum height h1 of the concave-convex portions is excessive, the volume occupied by the insert member 1 near the interface between the insert member 1 and the motor case increases, increasing the thermal resistance of conduction and potentially impairing thermal conductivity at the interface. Therefore, it is preferable to set the outer peripheral surface length ratio to 3.00 or less. By setting the outer peripheral surface length ratio within this range and preventing the average maximum height h1 of the concave-convex portions from becoming excessive, excellent thermal conductivity can be achieved at the interface between the insert member 1 and the motor case. Furthermore, since the average maximum height h1 of the uneven portion is not too small, it is possible to suppress separation between the insert member 1 and the motor case. The outer peripheral surface length ratio is measured on multiple cut surfaces, specifically, six cut surfaces, of one insert member 1, and the average value of the outer peripheral surface length ratios is calculated.

[0032] [Solid portion ratio] The protrusion 10 of the insert member 1 defines a solid portion region 21 and a non-solid portion region 22. As shown in Fig. 2, the solid portion region 21 and the non-solid portion region 22 are identified based on whether a line segment 20 having a length d1 overlaps with the protrusion 10 when the line segment 20 is superimposed on a predetermined cross-section. More specifically, within the range of length d1, the region where the line segment 20 overlaps with the protrusion 10 is defined as the solid portion region 21, and the region where the line segment 20 does not overlap with the protrusion 10 is defined as the non-solid portion region 22. The line segment 20 is a virtual line parallel to the inner circumferential surface 40 (i.e., parallel to the central axis C) on the predetermined cross-section, and is provided for convenience in identifying the solid portion region 21 and the non-solid portion region 22.

[0033] The solid body ratio is a value indicating the proportion of the solid body region 21 formed within the range of length d1. By moving the line segment 20 at a predetermined pitch in the direction of arrow A20 in FIG. 2 (from the distal end 11 side to the proximal end 12 side in the radial direction), the length of the solid body region 21 at each measurement height, which is the radial distance from the distal end 11, can be obtained. In this case, the ratio of the total length of the solid body region 21 to the length d1 at any measurement height is referred to as the "solid body ratio." By performing the same operation on multiple predetermined cross sections, aggregating the solid body ratios of the protrusion 10 on each cross section, and averaging the solid body ratios at each measurement height, an average solid body ratio can be obtained, which is the average value of the solid body ratios at each measurement point based on multiple predetermined cross sections at the arbitrary measurement height.

[0034] [Solid Body Summary Diagram] As shown in FIG. 2 , the line segment 20 is moved toward the base end 12 of the insert member 1 (along the direction of arrow A20) at a predetermined pitch, and the solid body ratio is repeatedly obtained until the solid body ratio reaches 1.00. The obtained solid body ratios are plotted on a graph, thereby enabling the shapes of multiple protrusions 10 appearing on a predetermined cross section to be summarized and represented as a single graph. This graph is called a "solid body summary diagram." The solid body summary diagram is a graph in which the vertical axis represents the measured height, which is the distance from the tip end 11 in the height direction of the irregularities, and the horizontal axis represents the solid body ratio. Furthermore, by calculating the solid body ratio for multiple predetermined cross sections and sequentially plotting the average solid body ratios obtained from the multiple predetermined cross sections, the formation state of the protrusions 10 in the insert member 1 can be grasped on average. In this case, for each predetermined cut surface, the reference point in the height direction is the "tip 11 of the most protruding convex portion 10 among the multiple convex portions 10 within the range of length d1," and the pitch at which the line segment 20 is moved is also set to the same pitch. This allows the measurement height to be uniquely determined for multiple predetermined cut surfaces. Figure 3 shows an average solid portion summary diagram of an example of the insert member 1 according to this embodiment, in which the average solid portion ratios obtained intermittently from six predetermined cut surfaces of a sample are plotted in order, with the predetermined pitch set to 0.05 mm and the length d1 set to 14.7 mm.

[0035] The average maximum height h1 of the uneven portion is the absolute value of the value from the tip end to the base end on the vertical axis of the average solid body summary diagram. In the solid body summary diagram, the tip end corresponds to the tip 11 of the most protruding convex portion 10 among the multiple convex portions 10 within the range of length d1. The measured height at the tip end is 0 mm, and the solid body ratio is 0. In the solid body summary diagram, the base end is the position where the solid body ratio, plotted sequentially from the tip end 11 side toward the base end 12 side, first exceeds 0.98. In the average solid body summary diagram, it is the position where the average solid body ratio, plotted sequentially from the tip end 11 side toward the base end 12 side, first exceeds 0.98. Note that the solid body ratio at each measurement point on the solid body summary diagram is measured from the tip 11 side of the convex portion 10 located at the top toward the central axis C located below, so the measured height at each measurement point is displayed as a negative value. Similarly, in an average solid body chart obtained from multiple solid body charts, the actual height of the uneven portion and the average maximum height h1 of the uneven portion are the absolute values ​​of the vertical axis on the average solid body chart, and the average maximum height h1 is the distance from the base end to the tip end on the chart. Also, the line connecting each measurement point plotted on the average solid body chart is called the "average solid body curve."

[0036] The length d1 of the line segment 20, which is the predetermined axial length, is set to 14.7 mm in principle, but may be changed as appropriate in consideration of the sizes of the convex portions 10 and concave portions 13 of the measurement sample.

[0037] [Measurement Method] [Preparation of Measurement Sample] The following describes a method for measuring the length of the contour line 30 and the solid portion ratio. First, a method for preparing a measurement sample will be described. The insert member 1 is cut in a direction including the central axis C and along the axial direction, and then cut into cross sections perpendicular to the axial direction to a size that allows resin embedding and polishing. Resin embedding is performed so that all cross sections used to measure the length of the contour line 30 and the solid portion ratio serve as polished surfaces. After the resin has solidified, the sample is polished under running water using waterproof emery paper. The grit sizes of the waterproof emery paper are changed in the following order: #220, #400, #800, #1000, and #1500. After polishing is complete, the length of the contour line 30 and the solid portion ratio are measured. The observation surface after polishing corresponds to the specified cut surface.

[0038] [Method for Measuring the Outer Surface Length Ratio] In this embodiment, the length of the contour line 30 was measured using a Hirox Corporation digital microscope RX-100. The objective lens magnification during measurement was 20x or 40x. When the average maximum height h1 of the uneven portion was large, e.g., exceeding 0.30 mm, 20x magnification was used. With the equipment used here, when the objective lens magnification was 20x, the length of the horizontal axis of the monitor was 14.7 mm, which was taken as the length d1. After setting the polished measurement sample, the measurement sample was set so that the inner surface 40 of the insert member 1 was parallel to the horizontal axis of the grid displayed on the observation monitor. The measurement sample was then translated to a position where the outer surface could be observed. Using the "automatic area" tool in the microscope's software, the area and circumference of the insert member 1 portion could be automatically measured based on the difference in gradation between the insert member 1 and the resin used for embedding. The gradation was set to a value that selected the insert member 1 without excess or deficiency. Since the measured circumference is the entire circumference of the insert member 1 on the monitor, the length corresponding to the portion of the insert member 1 other than the contour line 30 is found and subtracted from the measured entire circumference. The length of the contour line 30 is found in this way. In this case, the length of the portion other than the contour line 30 can be found using the "auto width" tool attached to the microscope. The outer peripheral surface length ratio can be found by dividing the length of the contour line 30 found in this way by the length d1.

[0039] [Method for Measuring the Solid Portion Ratio] To measure the solid portion ratio, a Hirox Corporation digital microscope RX-100 was used. The objective lens magnification during measurement was 20x or 50x. When the average maximum height h1 of the uneven portion was large, e.g., 0.20 mm or greater, 20x magnification was used. The grid and automatic width tool provided by the microscope's software were used. The polished measurement sample was set so that the inner peripheral surface 40 of the insert member 1 was parallel to the horizontal axis of the grid displayed on the observation monitor. The observation sample was then translated to a position where the outer peripheral surface could be observed. Next, the automatic width tool was used to measure the measurement sample in the horizontal axis direction. Measurements using the automatic width tool were performed automatically using gradation density, so the gradation density was adjusted each time to ensure proper automatic identification of the insert member area corresponding to the solid portion region 21 and the resin area corresponding to the non-solid portion region 22. The measurement was then performed at a predetermined pitch, and the length of the solid portion region 21 at an arbitrary measurement height was measured. In this embodiment, the line segment 20 indicates the measurement position of the automatic width tool. By moving the line segment 20 at a predetermined pitch along the radial direction of the insert member 1 from the tip end 11 toward the base end 12, the axial length of the solid body region 21 at any measurement height from the tip end 11 can be measured. In this case, the line segment 20 is moved at a predetermined pitch of 0.05 mm or 0.025 mm from the tip end 11 of the most protruding convex portion 10 within the length d1 toward the base end 12 in all cross sections, and the measurement is performed. When using an objective lens with a magnification of 50x, the predetermined pitch is preferably 0.025 mm.

[0040] FIG. 2 illustrates the case where the line segment 20 is at position 20a and the case where it is at position 20b. Position 20a is the position of the tip 11 of the protrusion 10 that protrudes most within the range of length d1. When the line segment 20 is at the measurement height indicated by position 20a, the line segment 20 overlaps with the tip 11 of the protrusion 10. Using this as a reference, the line segment 20 is moved in the direction indicated by arrow A20 (toward the base end 12) at a predetermined pitch. Position 20b is an example of a measurement height obtained when the line segment 20 is repeatedly moved at a predetermined pitch an arbitrary number of times. When the line segment 20 is at the measurement height indicated by position 20b, it can be said that the insert member 1 defines a substantial region 21 of the line segment 20 indicated by a dashed line and a non-substantial region 22 indicated by a solid line. Line segment 20 is moved along arrow A20, and from the position where the solid body ratio (described below) exceeds 0.98 for the first time, line segment 20 is further moved along arrow A20 until the entire range of length d1 on line segment 20 falls within solid body region 21 (i.e., when the solid body ratio becomes 1.00), and the measurement is terminated.

[0041] [Non-solid part ratio] The non-solid part ratio is a value for which the following relationship holds in a solid part summary chart: [Non-solid part ratio at any measurement height] = [Solid part ratio at the base end on the chart] - [Solid part ratio at any measurement height]. Also, in an average solid part summary chart, the following relationship holds: [Average non-solid part ratio at any measurement height] = [Average solid part ratio at the base end on the chart] - [Average solid part ratio at any measurement height].

[0042] [Parameters of the Average Solid Portion Summary Diagram] It is preferable to form the convex portions 10 and concave portions 13 so that the average maximum height h1 of the concave-convex portions is in the range of 0.15 mm to 1.50 mm in the average solid portion summary diagram. More preferably, the average maximum height h1 of the concave-convex portions is in the range of 0.20 mm to 1.00 mm. In this case, increasing the average maximum height h1 of the convex-convex portions can increase the length of the contour line 30. However, if the average maximum height h1 of the convex-convex portions is too large, the volume occupied by the convex portions 10 near the interface between the insert member 1 and the motor case increases, increasing the thermal resistance of conduction and potentially impairing thermal conductivity. In contrast, increasing the length of the contour line 30 while keeping the average maximum height h1 of the convex-convex portions at 1.50 mm or less, i.e., increasing the interface length ratio, can improve thermal conductivity from the insert member 1 to the motor case and heat dissipation from the motor case.

[0043] Furthermore, by setting the average maximum height h1 of the uneven portion to 1.50 mm or less, the insert member 1 can be made lighter and more compact. However, if the average maximum height h1 of the uneven portion is too small, the bonding strength between the insert member 1 and the motor case will be insufficient, and there is a risk of the insert member 1 and the motor case peeling off. Generally, the greater the bonding strength between the insert member 1 and the motor case, the better the thermal conductivity. Therefore, in order to maintain the bonding strength between the insert member 1 and the motor case, it is preferable to set the average maximum height h1 of the uneven portion to 0.15 mm or more. This makes it easier to prevent the insert member 1 from peeling off the motor case.

[0044] Here, the average solid portion ratio at a position 0.10 mm in height from the base end toward the tip end in the average solid portion summary diagram is referred to as the "first average solid portion ratio," and the average non-solid portion ratio calculated based on the first average solid portion ratio is referred to as the "first average non-solid portion ratio." The value of the first average solid portion ratio is designated as A, and the value of the first average non-solid portion ratio is designated as B. Here, the value obtained by dividing the outer peripheral surface length ratio by A is referred to as the "first interface parameter" for convenience. The first interface parameter helps to understand the shape of the proximal end 12 of the protrusion 10. For example, a heating element such as a stator is disposed inside the insert member 1. In this case, heat generated by the heating element is transmitted from the proximal end 12 of the protrusion 10 toward the tip end 11 where a motor case or the like is disposed. Therefore, in order to efficiently transmit heat from the heating element to the motor case, it is preferable that the shape of the proximal end 12 of the insert member 1 be as flat as possible. Therefore, it is preferable that the first average solid portion ratio be as small as possible. In other words, it is preferable that the first interface parameter be a large value. In Figure 3, the first average solid portion ratio at a position shifted 0.10 mm in height from the base end toward the tip end is shown as A, and the first average non-solid portion ratio at that position is shown as B.

[0045] Furthermore, for convenience, the value obtained by dividing the outer peripheral surface length ratio by the height from the base end to the position where the average solid portion ratio is 0.30 on the diagram is referred to as the "second interface parameter." In FIG. 3 , the "height from the base end to the position where the average solid portion ratio is 0.30 on the diagram" is indicated as h2. In other words, height h2 is the "difference between the measured height of the base end on the diagram and the measured height at the position where the average solid portion ratio is 0.30." Here, if there are multiple positions where the average solid portion ratio is 0.30, the position closest to the base end on the diagram is evaluated. In other words, height h2 is the height from the base end on the diagram to the position closest to the base end on the diagram where the average solid portion ratio is 0.30. The second interface parameter can easily grasp the shape of the protrusion 10 of the insert member 1 from the base end on the diagram to the position where the average solid portion ratio is 0.30 based on the average solid portion summary chart. By using the above-mentioned first interface parameter and second interface parameter, the outer peripheral surface length ratio can be normalized at a certain position in the average solid part summary diagram, making it easier to confirm the correlation between the shape of the uneven part and the thermal conductivity.

[0046] The measurement height at the position where the average solid body ratio is 0.30 can be determined based on two consecutive points on the average solid body chart, namely, a point where the average solid body ratio is less than 0.30 and a point where the average solid body ratio is greater than 0.30. Specifically, it can be determined from a function of a straight line connecting a point on the average solid body chart where the average solid body ratio is less than 0.30 and a point adjacent to that point where the average solid body ratio is greater than 0.30.

[0047] By organizing the shape of the uneven portion in the insert member 1 of the present invention using the first interface parameter and the second interface parameter based on the outer peripheral surface length ratio and the average solid portion summary chart, it is possible to identify an insert member 1 that has even better thermal conductivity at the interface between the insert member 1 and the motor case.

[0048] [Tests and Simulations] The insert members 1 according to Examples 1 to 11 of the present invention and the insert members according to Comparative Examples 1 to 3 were evaluated by tests and simulations using samples. Specifically, the insert members of the Examples and Comparative Examples (hereinafter referred to as Examples, etc.) were subjected to measurement of various parameters, actual cutting tests, thermal conductivity measurements, and surface temperature simulations.

[0049] [Measurement of Various Parameters] Various parameters of the insert members according to the Examples were measured. Table 1 shows the results of each measurement item for the insert members according to the Examples. For Measurement Item 1, the insert members according to the Examples were cut to determine the outer peripheral surface length ratio. For Measurement Items 2 to 8, the respective values ​​were determined using the average solid portion summary chart for each Example. When creating the average solid portion summary chart for each Example, the predetermined pitch was 0.05 mm or 0.025 mm. Furthermore, in measuring the outer peripheral surface length ratio, the predetermined axial length was 14.7 mm for Examples 1 to 3, 6 to 11, and Comparative Examples 1 to 3, and 7.35 mm for Examples 4 and 5. Furthermore, in measuring the average solid portion ratio, the predetermined axial length was 14.7 mm for Examples 1 to 3, 6 to 11, and Comparative Examples 1 and 3, and 5.57 mm for Examples 4, 5, and Comparative Example 2. Note that the units used for each measurement item are in parentheses, and unless otherwise specified, the numbers are dimensionless.

[0050] [1. Outer peripheral surface length ratio] Measurement item 1 was the outer peripheral surface length ratio. In this case, the outer peripheral surface length ratio was determined by cutting and polishing the insert member in the examples along the axial direction using an imaginary plane including the central axis C, and measuring the length of the contour line 30. Furthermore, to ensure a predetermined axial length that would allow the contour line 30 to be obtained, the insert member was also cut in a direction perpendicular to the axial direction (radial direction). The cut surfaces thus obtained were observed using a microscope. The outer peripheral surface length ratio was determined by cutting six predetermined cut surfaces at random from one insert member and calculating the average value.

[0051] [2. Average maximum height h1 (mm) of uneven portion] As measurement item 2, the average maximum height h1 of the uneven portion was measured using the average substance portion summary chart for each example, etc. For Comparative Example 1, the numerical value for the average maximum height h1 of the uneven portion was small, so measurements of other items were not performed.

[0052] [3. First Average Body Ratio A] As measurement item 3, the first average body ratio A was determined using the average body summary chart of each example, etc. As described above, the first average body ratio A is the average body ratio at a position shifted 0.10 mm in height from the base end on the chart toward the tip end on the chart.

[0053] [4. First Interface Parameter] As measurement item 4, the outer peripheral surface length ratio obtained in measurement item 1 was divided by the first average solid portion ratio A obtained in measurement item 3 to obtain the first interface parameter.

[0054] [5. 0.10 / First Average Non-Solid Part Ratio B (mm)] Measurement item 5 was the gradient of the line connecting the measurement position of the first average solid part ratio A and the base end on the average solid part summary diagram of each Example (hereinafter referred to as the slope of the average solid part curve). In each Example, the first average non-solid part ratio B was determined by subtracting the value of the first average solid part ratio A determined in measurement item 3 from the average solid part ratio at the base end on the diagram. Checking the slope of the average solid part curve helps to understand the shape of the protrusions near their base ends. The slope of the average solid part curve was determined by [0.10 / First Average Non-Solid Part Ratio B].

[0055] [6. 0.10 × First Average Non-Substantial Portion Ratio B (mm)] As measurement item 6, the area of ​​a predetermined region in the average solid portion summary diagram of each Example was calculated as follows. As with measurement item 5, the first average non-substantial portion ratio B was calculated in each Example by subtracting the first average solid portion ratio A calculated in measurement item 3 from the average solid portion ratio at the base end on the diagram. Here, the predetermined region is a rectangular region in the average solid portion summary diagram, with a height of 0.10 mm from the base end on the diagram and a width equal to the first average non-substantial portion ratio B, and including the average solid portion curve from the base end on the diagram to a position 0.10 mm in height toward the tip end on the diagram. The area of ​​the predetermined region was calculated by [0.10 × First Average Non-Substantial Portion Ratio B]. This helps to understand the shape of the uneven portions near the base ends of the convex portions.

[0056] [7. Height h2 (mm) from the base end to the position where the average solid portion ratio is 0.30 in the figure] Height h2, which is the height from the base end to the position where the average solid portion ratio is 0.30 in the figure, was determined as measurement item 7. The smaller the height h2, the closer the shape of the insert member from the base end to the position where the average solid portion ratio is 0.30 in the figure becomes to a flat shape.

[0057] [8. Second Interface Parameter (1 / mm)] As measurement item 8, the second interface parameter was determined by dividing the outer peripheral surface length ratio determined in measurement item 1 by the height h2 determined in measurement item 7.

[0058] The measurement results of the various parameters measured as described above are shown in Table 1.

[0059] [Substantial Cutting Test] In the substantial cutting test, a composite was produced in each example by casting an insert member into an aluminum alloy as an outer member. The outer member here refers to a member located radially outside the insert member, such as a motor case. The composite was then cut into 20 mm x 20 mm test pieces. For each example, test pieces were cut multiple times to evaluate the bondability between the insert member and the outer member by determining whether or not there was peeling between the insert member and the outer member. Specifically, test pieces were cut from six locations in each example, and the presence or absence of peeling was determined. The evaluation criteria are shown in Table 2.

[0060] [Thermal Conductivity Measurement] From the test pieces used in the actual cutting test that did not peel, test pieces for thermal conductivity measurement with a diameter of 10 mm and a thickness of 3 mm were prepared, and the thermal conductivity was measured using the test pieces for thermal conductivity measurement by the laser flash method. At this time, while observing the side of the test piece for thermal conductivity measurement, the center of the height of the uneven portion was adjusted so that it was located at the center of the thickness of the test piece for thermal conductivity measurement. Note that for test pieces in which the insert member and the outer member peeled off during cutting, the thermal conductivity was not measurable (0 W / m K). For test pieces that peeled off several times in multiple tests or did not peel off in multiple tests, the average value of the test pieces that did not peel off was calculated and shown in Table 6.

[0061] [Surface Temperature Simulation] In each example, a model was created with the insert member having a thickness of 2 mm, the composite portion (interface portion between the insert member and the outer member) having a thickness of 3 mm, and the outer member having a thickness of 2 mm, and the surface temperature of the outer member was simulated. In this case, the inner surface temperature of the insert member was set to 150°C, the fluid temperature on the outer periphery of the outer member was set to 50°C, and the surface temperature of the outer member was calculated assuming that a cooling fluid is present on the outer periphery of the outer member. In addition, the heat transfer coefficient from the surface of the outer member to the fluid was set to 200 W / m ２ Based on the surface temperature of the outer member obtained by the simulation, heat dissipation was evaluated according to the criteria shown in Table 3. In this case, the higher the surface temperature, the more efficiently the internal heat can be transferred, and the better the heat dissipation.

[0062] [Evaluation of Compactness] In the measurement of the various parameters described above, the compactness was evaluated according to the criteria shown in Table 4 based on the average maximum height h1 of the uneven portions, which is measurement item 2.

[0063] The overall evaluation was made based on the evaluation symbols for each measurement item, as shown in Table 5.

[0064] The results of the sample tests measured as described above and the overall evaluation are shown in Table 6.

[0065] From the results shown in Table 6, it was confirmed that in the overall evaluation, all of Examples 1 to 11 were superior to all of Comparative Examples 1 to 3. Furthermore, it was confirmed that Examples 2, 3, 4, and 5 were particularly superior.

[0066] Furthermore, by comparing Examples 1 to 8 and 10 with Comparative Examples 1 to 3, it was confirmed that the thermal conductivity at the interface between the insert member and the motor case is increased by forming the uneven portion so that the first interface parameter is 1.30 or more and the second interface parameter is 4.00 or more.

[0067] Furthermore, in Examples 4, 5, and 10, the outer peripheral surface of the insert member was subjected to a roughening treatment by thermal spraying or cold spraying, and it was confirmed that the thermal conductivity was higher than in other Examples.

[0068] Furthermore, by comparing Examples 1 and 9 with other Examples, it was confirmed that even when the outer peripheral surface length ratio is large, the thermal conductivity does not increase when the average maximum height h1 of the uneven portion is relatively large as in Examples 1 and 9. It was also confirmed that when the average maximum height h1 of the uneven portion is excessively large as in Comparative Example 3, the thermal conductivity at the interface between the insert member and the motor case decreases.

[0069] From the above results, it was confirmed that examples with a small value of the first average solid part ratio A and a large value of the first interface parameter had high thermal conductivity, such as Examples 4 and 5. Among the examples, Example 5, which had the largest first interface parameter, had the largest thermal conductivity at the interface between the insert member and the motor case.

[0070] From the above results, it was confirmed that the slope of the average solid part curve in the average solid part summary diagram is preferably 0.10 / B≦1.30 with reference to Examples 1 to 11. Furthermore, it was confirmed with reference to Examples 2 to 5 that a smaller slope of the average solid part curve results in a higher thermal conductivity at the interface between the insert member and the motor case.

[0071] From the above results, with reference to Examples 1 to 11, it was confirmed that it is preferable that the area of ​​the predetermined region in the average substantial part summary diagram obtained in measurement item 6 is 0.10 × B ≧ 0.01. Furthermore, with reference to Examples 2 to 5, it was confirmed that the larger the area of ​​the predetermined region, the higher the thermal conductivity at the interface between the insert member and the motor case.

[0072] From the above results, it was found that the insert member and the outer member peeled off when the test piece was cut out in the case of the outer peripheral surface length ratio being less than 1.15, as in Comparative Examples 1 and 2. Furthermore, in the case of Examples 6 to 8, in which the outer peripheral surface length ratio was greater than 1.15 and less than 1.30, peeling also occurred, and therefore it was confirmed that the outer peripheral surface length ratio is more preferably 1.30 or more.

[0073] From the above results, it was confirmed that the thermal conductivity was high when the height h2 was 0.40 mm or less, as in Examples 1 to 5. Furthermore, in Examples 6 to 8, although the height h2 was 0.40 mm or less, peeling was observed when cutting out the test pieces, and it was confirmed that the bondability was not necessarily high, resulting in low thermal conductivity.

[0074] [Effects] By forming the uneven portion according to the present invention on the outer peripheral surface of the insert member 1, the thermal conductivity at the interface between the insert member 1 and the motor case can be improved so that the heat generated by a heating element such as a stator can be efficiently dissipated to the outside.

[0075] The multiple protrusions 10 are arranged on the outer peripheral surface of the insert member 1 so that adjacent protrusions 10 are spaced apart at an appropriate distance. This allows the casting material poured into the mold to spread between the multiple protrusions 10, making it possible to prevent voids from forming between the motor case and the insert member 1 and improving thermal conductivity at the interface between the motor case and the insert member 1.

[0076] The insert member 1 of the present invention has the convex portions 10 and concave portions 13 formed within the length d1 so as to ensure the length of the contour line 30 without excessively increasing the concave and convex portions. This makes it possible to effectively control the thermal conductivity at the interface between the insert member 1 and the motor case. This prevents the motor case from becoming larger and heavier due to an increase in the thickness of the motor case, thereby realizing a lightweight and compact rotating electric machine, while improving the thermal conductivity from the insert member 1 to the motor case and the heat dissipation of the rotating electric machine itself.

[0077] Although the embodiments of the present invention have been described above, each aspect disclosed in this specification can be combined with any other feature disclosed in this specification.

[0078] 1: Insert member for rotating electrical machine 10: Convex portion 13: Concave portion 20: Line segment 30: Contour line 40: Inner peripheral surface C: Central axis of insert member

Claims

1. An insert member for a rotating electric machine having a generally cylindrical shape which is cast into an aluminum alloy motor case of a rotating electric machine, wherein an uneven portion including concave and convex portions is formed on the outer peripheral surface of the insert member, and when the insert member is cut axially into two parts by an imaginary plane including the central axis of the insert member, in every cross section which is one of the cut surfaces which appear on either side of the central axis when the insert member is cut axially into two parts by an imaginary plane including the central axis of the insert member, when a line following the contour of the outer peripheral surface including the contour of the uneven portion within a predetermined axial length is taken as a contour line, an outer peripheral surface length ratio, which is the value obtained by dividing the length of the contour line by the predetermined axial length, is 1.15 or more.

2. The insert member, within the range of the predetermined axial length, defines a solid portion region where the insert member overlaps on a line segment parallel to the inner peripheral surface of the insert member when the line segment is superimposed on the entire cross section, and a non-solid portion region where the insert member does not overlap on the line segment, a value indicating the proportion of the solid portion region on the line segment within the range of the predetermined axial length is defined as a solid portion ratio, and the line segment is moved at a predetermined pitch along the height direction of the uneven portion from the tip end of the most protruding convex portion in the uneven portion toward the base end side of the convex portion, and values ​​of the solid portion ratio at each measurement point are plotted in order, the horizontal axis representing the solid portion ratio and the vertical axis representing the distance from the tip end in the height direction as the measurement height is defined as a solid portion summary diagram, 2. The insert member for a rotating electric machine according to claim 1, wherein an average solid part ratio is an average of the solid part ratios at each of the measurement points based on the multiple cross sections, the solid part summary diagram in which the average solid part ratios are plotted in order is an average solid part summary diagram, a position in the average solid part summary diagram where the average solid part ratio is 0 is defined as a tip end on the diagram, and a position where the average solid part ratios plotted in order from the tip end side to the base end side first exceed 0.98 is defined as a base end on the diagram, and an average maximum height of the unevenness is defined as a distance from the tip end on the diagram to the base end on the diagram, 3. An insert member for a rotating electric machine as described in claim 2, wherein when the average solid portion ratio at a position moved 0.10 mm in height from the base end portion on the figure toward the tip end portion on the figure is defined as A and the value obtained by dividing the outer circumferential surface length ratio by A is defined as a first interface parameter, the first interface parameter is 1.30 or more.

4. An insert member for a rotating electric machine as described in claim 1, wherein when the thickness of the insert member is half the value obtained by subtracting the inner diameter from the outer diameter of the insert member, the thickness of the insert member is 0.8% or more of the outer diameter of the insert member.

5. The insert member for a rotating electrical machine according to claim 1, wherein the outer peripheral surface is subjected to a roughening treatment.

6. The insert member for a rotating electric machine according to claim 3, wherein the outer peripheral surface of the insert member has, in a portion in the axial direction, at least one of a region in which the outer peripheral surface length ratio is less than 1.15 and a region in which the first interface parameter is less than 1.

30.

7. The insert member for a rotating electric machine according to claim 3, wherein, in said average solid part summary diagram, an average non-solid part ratio is defined as a value obtained by subtracting said average solid part ratio at said certain measurement height from said average solid part ratio at said base end on said diagram, and said average non-solid part ratio at a position moved 0.10 mm in height from said base end on said diagram towards said tip end on said diagram is defined as B, wherein 0.10 / B≦1.

30.

8. The insert member for a rotating electric machine according to claim 3, wherein, in said average solid part summary diagram, an average non-solid part ratio is defined as a value obtained by subtracting said average solid part ratio at said certain measurement height from said average solid part ratio at said base end on said diagram, and said average non-solid part ratio at a position moved 0.10 mm in height from said base end on said diagram towards said tip end on said diagram is defined as B, wherein 0.10 x B is greater than or equal to 0.

01.

9. An insert member for a rotating electrical machine according to claim 3, wherein in said average solid portion summary diagram, the height from said base end to a position on said diagram where said average solid portion ratio is 0.30 is 0.40 mm or less.

10. An insert member for a rotating electric machine as described in claim 3, wherein in the average solid part summary diagram, a second interface parameter, which is a value obtained by dividing the outer circumferential surface length ratio by the height from the base end on the diagram to a position where the average solid part ratio is 0.30, is 4.00 or more.

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