Wheel hub inner ring and manufacturing method thereof, wheel hub assembly and manufacturing method thereof

Abstract

The present invention provides a wheel hub inner ring and a manufacturing method thereof, a wheel hub assembly and a manufacturing method thereof. The wheel hub inner ring is a hollow cylinder and has a plurality of raised structures. The raised structures protrude outward from the outer circumferential surface of the hollow cylinder of the wheel hub inner ring and are obtained during the casting process. The joint surface between the wheel hub and the wheel hub inner ring has a plurality of recessed structures, and the recessed structures are formed on the outside of the corresponding raised structures in a shape-matching manner through an inlay casting process. The wheel hub in the present invention is made of a lightweight alloy material, and the wheel hub inner ring is made of an iron-carbon alloy, so that the weight of the wheel hub can be reduced while meeting the strength requirements of the wheel hub structure. The present invention can also improve the bonding strength and thermal conductivity between the wheel hub and the wheel hub inner ring through the raised structures and the recessed structures.

Description

Technical Field

[0001] The invention relates to the field of vehicle manufacturing, and in particular to a wheel hub inner ring and a manufacturing method thereof, a wheel hub assembly and a manufacturing method thereof. Background Art

[0002] Various types of vehicles have been widely used in the transportation of people and goods. As an important link in the transmission of force between the vehicle body and the ground, the wheel hub’s structural strength affects the vehicle’s carrying capacity, and its weight affects the vehicle’s fuel consumption. Considering the vehicle’s fuel economy index, the smaller the wheel hub’s weight, the more advantages it has, provided that the vehicle’s carrying capacity requirements are met. Therefore, lightweighting is increasingly becoming one of the main indicators in the wheel hub production process.

[0003] In order to meet the strength requirements of the vehicle's wheel hub, traditional wheel hubs are mostly made of cast iron, and the wall surface is usually thick. In order to reduce the weight of the wheel hub, some lightweight metal materials with lower density are used to manufacture the wheel hub, such as aluminum alloy. However, lightweight alloys have disadvantages such as low yield strength, large thermal expansion coefficient, and significant thermal decay, and cannot reliably meet the structural strength requirements of the wheel hub.

[0004] In order to solve the problem that ferrous alloy materials are heavy and aluminum alloy materials are insufficient in strength, the relevant wheel hubs are manufactured with composite materials made of steel and aluminum alloy. Taking the Chinese utility model patent with publication number CN207128439U as an example, the utility model discloses a lightweight steel-aluminum composite wheel hub for commercial vehicles, in which the wheel hub body is made of aluminum alloy material, and the inner and outer bearing hole sleeves are made of steel material, thereby taking into account the technical effects of the light weight of aluminum alloy material and the high strength of steel material.

[0005] However, the wheel hub made of two alloy materials is prone to technical problems such as insufficient bonding strength between different materials and insufficient tight fit. In view of this, although the utility model patent constructs the joint surface between the aluminum alloy wheel hub body and the steel bearing hole sleeve as a grid-shaped or stepped non-plane to improve the bonding strength, the grid-shaped or stepped non-plane has limited effect on the bonding strength between the joint surfaces of different materials. When the wheel hub is subjected to a large working load, it is easy for the joint surfaces of different materials to shift due to insufficient bonding strength, which has an adverse effect on the safety performance of the wheel hub. The mutual shift between the joint surfaces of different materials will produce a large gap, which will lead to low heat transfer efficiency, causing the operating temperature of the bearing or wheel hub to exceed the allowable value, affecting the service life of the wheel hub. Summary of the invention

[0006] In view of this, the present invention provides a wheel hub inner ring and a manufacturing method thereof, a wheel hub assembly and a manufacturing method thereof. The present invention can significantly improve the bonding strength and thermal conductivity between the wheel hub and the wheel hub inner ring in the wheel hub assembly while meeting the wheel hub structural strength and reducing the wheel hub weight.

[0007] In one aspect of the present invention, a hub inner ring is provided. The hub inner ring is in the form of a hollow cylinder. The hub inner ring has a plurality of protrusions, and the protrusions protrude outward from the outer circumferential surface of the hollow cylinder of the hub inner ring.

[0008] Preferably, the protrusion structure comprises a fungus-shaped protrusion, and the fungus-shaped protrusion meets the following requirements:

[0009] A longitudinal section perpendicular to the axial direction is made on the inner ring of the hub, and the longitudinal section passes through the protruding structure to form a longitudinal section figure of the protruding structure. In the longitudinal section figure, a line connecting the lowest points of the two side boundaries of the protruding structure is used as a protruding root reference line, and a boundary distance between the two side boundaries of the longitudinal section figure is measured along a direction parallel to the protruding root reference line. The longitudinal section figure of the protruding structure is then divided into at least two areas by at least one dividing line parallel to the protruding root reference line, and the distance between the dividing line and the protruding root reference line is between 1 / 3 and 2 / 3 of the height of the protruding structure;

[0010] The maximum boundary distance of the longitudinal section figure of at least one region far from the protrusion root reference line is greater than the minimum boundary distance of the longitudinal section figure of at least one region close to the protrusion root reference line.

[0011] Preferably, among the plurality of protrusion structures, the mushroom-shaped protrusions account for 35%-95%.

[0012] Preferably, the protrusion structure further comprises a terrace-shaped protrusion, and the terrace-shaped protrusion meets the following requirements:

[0013] A longitudinal section perpendicular to the axial direction is made on the inner ring of the hub, and the longitudinal section passes through the protruding structure to form a longitudinal section figure of the protruding structure. In the longitudinal section figure, a line connecting the lowest points of the two side boundaries of the protruding structure is used as a protruding root reference line, and a boundary distance between the two side boundaries of the longitudinal section figure is measured along a direction parallel to the protruding root reference line;

[0014] Among them, as the distance relative to the base line of the protrusion root gradually increases, the boundary distance of the longitudinal section figure remains unchanged or gradually decreases.

[0015] Preferably, among the plurality of protrusion structures, the table-shaped protrusions account for 5%-65%.

[0016] Preferably, the average top surface area of ​​the protrusion structure is between 0.1 and 3 mm. 2 , the plane where the top surface area is located is perpendicular to the radial direction of the inner ring of the hub.

[0017] Preferably, the average height of the protruding structure is between 0.3 mm and 1.0 mm.

[0018] Preferably, the average distribution density of the plurality of protrusion structures relative to the inner ring of the hub is between 15 and 50 per cm. 2 .

[0019] In another aspect of the present invention, there is provided a method for manufacturing a wheel hub inner ring according to any one of the above embodiments, comprising the following steps:

[0020] Melting the ingredients of the set ratio into molten iron and performing molten iron treatment on the molten iron;

[0021] Preheating and rotating the wheel hub inner ring casting mold, and evenly coating the coating on the inner wall of the wheel hub inner ring casting mold;

[0022] After the coating is dried, pouring molten iron treated with molten iron into the hub inner ring casting mold;

[0023] Keeping the hub inner ring casting mold rotating; and

[0024] After the molten iron is solidified and formed, the mold is removed, and the coating layer on the surface of the casting after demolding is removed to obtain a hub inner ring casting with a convex structure.

[0025] Preferably, the coating comprises:

[0026] 4% to 7% by mass of sodium bentonite;

[0027] 15% to 25% by mass of diatomaceous earth;

[0028] 0% to 5% by mass of 350 mesh quartz sand;

[0029] 0.0005% to 0.01% by mass of alkyl sulfate; and

[0030] The balance is water.

[0031] Preferably, when applying the coating, the rotation speed of the wheel hub inner ring casting mold is controlled between 700-1200r / min, and the temperature of the wheel hub inner ring casting mold is controlled between 200-300°C; when molten iron is poured into the wheel hub inner ring casting mold, the rotation speed of the wheel hub inner ring casting mold is controlled between 1000-1600r / min.

[0032] Preferably, the material of the hub inner ring includes ductile iron, and the temperature of the molten iron during pouring is 1380-1450°C.

[0033] In another aspect of the present invention, a wheel hub assembly is provided, comprising the wheel hub inner ring according to any one of the above embodiments, and the wheel hub assembly further comprises:

[0034] A wheel hub located at the periphery of the inner ring of the wheel hub, the wheel hub being provided with a bearing hole; and

[0035] A wheel hub bearing located in the inner ring of the wheel hub, wherein the outer ring of the wheel hub bearing is fixedly arranged on the inner circumferential surface of the hollow cylinder of the inner ring of the wheel hub;

[0036] The wheel hub is formed on the outer peripheral surface of the hollow cylinder of the wheel hub inner ring by an insert casting process, so that the joint surface between the wheel hub and the wheel hub inner ring has a plurality of recessed structures matched with the plurality of raised structures.

[0037] Preferably, the material of the wheel hub comprises a light alloy, and the material of the wheel hub inner ring comprises an iron-carbon alloy.

[0038] In another aspect of the present invention, there is provided a method for manufacturing a wheel hub assembly according to any one of the above embodiments, comprising the following steps:

[0039] a) Manufacturing of wheel hub: the manufactured wheel hub inner ring is arranged at the center hole position of the wheel hub casting mold, the light alloy in molten liquid state is injected into the mold cavity of the wheel hub casting mold, and the light alloy in molten liquid state is injected into the mold cavity of the wheel hub casting mold by insert casting, and the light alloy is demolded after cooling and shaping in the wheel hub casting mold, and after the wheel hub with the wheel hub inner ring is inlaid and cast, the wheel hub is machined to the target size;

[0040] b) Assembly of wheel hub bearing and wheel hub inner ring: Install the wheel hub bearing to the inner circumference of the hollow cylinder of the wheel hub inner ring.

[0041] Preferably, the casting method of injecting the molten liquid light alloy into the cavity of the wheel hub casting mold is pressure casting, and during the pressure casting process, the liquid light alloy in the cavity of the wheel hub casting mold is kept warm and pressurized until the liquid light alloy is completely solidified.

[0042] Therefore, according to the embodiment of the present invention, different components in the wheel hub assembly are made of different materials, so that the weight of the wheel hub can be reduced while meeting the strength requirements of the wheel hub structure, thereby improving the fuel economy of the car. In addition, through the mutual cooperation between the raised structure and the recessed structure, the bonding strength and thermal conductivity between the wheel hub inner ring and the wheel hub can be improved, thereby increasing the safety factor and life of the wheel hub during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic structural diagram of the wheel hub assembly in the present invention;

[0044] Figure 2 It is a schematic diagram of the outer peripheral surface of the hollow cylinder of the inner ring of the wheel hub in the present invention and the raised structure thereon;

[0045] Figure 3 It is a structural schematic diagram of a longitudinal section of a table-shaped protrusion on the outer peripheral surface of a hollow cylinder of the inner ring of the wheel hub in the present invention;

[0046] Figure 4 A schematic diagram of the metallographic structure of a longitudinal section of a table-shaped protrusion on the outer peripheral surface of the hollow cylinder of the inner ring of the wheel hub in the present invention;

[0047] Figure 5 A schematic diagram of the metallographic structure of a longitudinal section of another terrace-shaped protrusion on the outer peripheral surface of the hollow cylinder of the inner ring of the hub in the present invention;

[0048] Figure 6 It is a schematic diagram of the longitudinal section structure of the mushroom-shaped protrusions on the outer peripheral surface of the hollow cylinder of the inner ring of the wheel hub in the present invention;

[0049] Figure 7 It is a schematic diagram of the metallographic structure of the longitudinal section of some mushroom-shaped protrusions on the outer peripheral surface of the hollow cylinder of the inner ring of the wheel hub in the present invention;

[0050] Figure 8 A schematic diagram of the metallographic structure of a longitudinal section of some protruding structures on the outer peripheral surface of the hollow cylinder of the inner ring of the wheel hub in the present invention;

[0051] Fig. 9 A schematic diagram of the metallographic structure of some protruding structures on the outer peripheral surface of the hollow cylinder of the inner ring of the wheel hub in the present invention from a top view;

[0052] Fig.10 It is a schematic diagram of the distribution of the test sampling area between the inner ring of the wheel hub and the wheel hub in the present invention;

[0053] Fig.11 A schematic diagram of thermal conductivity test of the test sampling area in the present invention;

[0054] Fig.12 A schematic diagram of the bonding strength test of the test sampling area of ​​the present invention;

[0055] Fig.13 It is a schematic diagram of the corresponding relationship between the bonding strength of the protrusion structure and the height of the protrusion structure in the test sampling area of ​​the present invention;

[0056] Fig.14 A schematic diagram of the variation trend of the bonding strength of the protrusion structure and the height of the protrusion structure in the test sampling area of ​​the present invention;

[0057] Fig.15 It is a schematic diagram of the corresponding relationship between the thermal conductivity of the protrusion structure in the test sampling area of ​​the present invention and the height of the protrusion structure;

[0058] Fig.16 A schematic diagram of the variation trend of the thermal conductivity of the protruding structures and the height of the protruding structures in the test sampling area of ​​the present invention;

[0059] Fig.17 It is a schematic diagram of the corresponding relationship between the bonding strength of the protrusion structure and the distribution density of the protrusion structure in the test sampling area of ​​the present invention;

[0060] Fig.18 A schematic diagram of the variation trend of the bonding strength of the protrusion structures and the distribution density of the protrusion structures in the test sampling area of ​​the present invention;

[0061] Fig.19 It is a schematic diagram of the corresponding relationship between the thermal conductivity of the protrusion structure and the distribution density of the protrusion structure in the test sampling area of ​​the present invention;

[0062] Fig. 20 A schematic diagram of the variation trend of the thermal conductivity of the protrusion structure and the distribution density of the protrusion structure in the test sampling area of ​​the present invention;

[0063] Fig.21 This is a schematic diagram of the shape of a complete mushroom-shaped protrusion when a longitudinal section of the protrusion structure is taken in the present invention;

[0064] Fig. 22 This is a schematic diagram of the shape of a mushroom-shaped protrusion with its cap falling off when a longitudinal section of the protrusion structure is taken according to the present invention;

[0065] Fig.23 This is a schematic diagram of the shape of a terrace-shaped protrusion when a longitudinal section of the protrusion structure is taken according to the present invention.

[0066] Description of reference numerals:

[0067] 1-wheel hub 11-bearing hole 2-wheel hub bearing

[0068] 3-wheel hub inner ring 31-first positioning step 32-second positioning step

[0069] 4-protrusion structure 41- mushroom-shaped protrusion 42- table-shaped protrusion

[0070] 51-first top surface area 52-second top surface area 53-third top surface area

[0071] 54-the fourth top surface area 55-the fifth top surface area 61-the first test sampling area

[0072] 62-Second test sampling area 63-Bonding strength test tooling 64-Tensile force direction

[0073] q1-first area q2-second area q3-third area

[0074] A-first lowest pointB-second lowest pointC-boundary distance

[0075] D-maximum boundary distance d-minimum boundary distance DETAILED DESCRIPTION

[0076] Various exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative and is not intended to be any limitation on the present invention and its application or use. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to make the present invention thorough and complete and to fully disclose the scope of protection of the present invention to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative positions of the components, steps, components of materials, numerical expressions and numerical values ​​described in these embodiments should be interpreted as being merely exemplary and not as limitations.

[0077] In a first aspect of the present invention:

[0078] like Figures 1 to 8 As shown, a hub inner ring is provided, wherein the hub inner ring 3 is a hollow cylinder and has a plurality of protrusion structures 4 , and the protrusion structures 4 protrude outward from the outer circumferential surface of the hollow cylinder of the hub inner ring 3 .

[0079] like Figure 2 As shown, the plane pointed to by the reference numeral 3 illustrates the outer peripheral surface of the inner ring 3 of the wheel hub. On the outer peripheral surface of the inner ring 3 of the wheel hub, there are multiple protrusion structures 4, and the multiple protrusion structures 4 have different shapes and types. Figure 2 Several different types of protrusion structures 4 are collectively illustrated.

[0080] Those skilled in the art should understand that on the outer peripheral surface of the wheel hub inner ring 3, the protrusion structures 4 of different shapes and types should be distributed irregularly. Figure 2 The order in the above does not restrict the actual distribution of the different types of protrusion structures 4 on the outer peripheral surface of the wheel hub inner ring 3: the different types of protrusion structures 4 can coexist on the outer peripheral surface of a wheel hub inner ring 3, or can exist independently on the outer peripheral surface of a wheel hub inner ring 3. Figure 1 As shown, the outer peripheral surface of the wheel hub inner ring 3 is basically a cylindrical surface. Figure 2 The cross section in FIG. 1 is also a circle, however, in order to conveniently illustrate and describe the multiple protrusion structures 4 on the outer peripheral surface of the inner ring 3 of the hub, Figure 2The outer circumferential surface of the middle hub inner ring 3 is drawn as a straight line.

[0081] Since the wheel hub 1 is combined with the outer peripheral surface of the hollow cylinder of the wheel hub inner ring 3 by the casting process, the protrusion structure 4 can improve the thermal conductivity and the bonding strength between the wheel hub 1 and the wheel hub inner ring 3. The details will be described below.

[0082] Regarding thermal conductivity, the raised structure 4 can increase the contact area between the wheel hub inner ring 3 and the wheel hub 1, thereby enhancing the thermal conductivity between the wheel hub inner ring 3 and the light alloy wheel hub 1, so that the heat generated by the wheel hub bearing 2 during operation can be quickly transferred to the light alloy wheel hub 1 through the wheel hub inner ring 3, thereby reducing the operating temperature of the wheel hub bearing 2, reducing thermal deformation of the wheel hub bearing, and reducing the friction coefficient of the wheel hub bearing.

[0083] Regarding the bonding strength, in the process of casting the wheel hub 1 onto the wheel hub inner ring 3, the multiple protruding structures 4 on the outer peripheral surface of the hollow cylinder of the wheel hub inner ring 3 can engage with the recessed structures on the wheel hub 1 to form a mortise and tenon structure, so that the wheel hub 1 and the wheel hub inner ring 3 are tightly combined together, thereby improving the torque transmission capacity of the wheel hub 1 and the wheel hub inner ring 3 along the circumferential direction, and reducing the relative displacement of the wheel hub 1 and the wheel hub inner ring 3 during repeated thermal expansion and contraction due to the use of different materials.

[0084] In order to facilitate the structural description of the wheel hub inner ring 3 and the protruding structure 4, the present application establishes a cylindrical coordinate system with the central axis of the hollow cylinder of the wheel hub inner ring 3 as the axis for discussion. Based on the cylindrical coordinate system, it should be noted that:

[0085] First, due to the manufacturing method, the outer circumference of the hollow cylinder of the inner ring 3 of the wheel hub has a plurality of protruding structures 4. These protruding structures 4 and the recessed areas between adjacent protruding structures 4 will make the actual outer circumference of the hollow cylinder of the inner ring 3 of the wheel hub uneven. Therefore, when defining the position and shape of the protruding structures 4 on the outer circumference of the hollow cylinder of the inner ring 3 of the wheel hub, in order to make the definition more accurate, the outer circumference of the hollow cylinder of the inner ring 3 of the wheel hub is referred to as the reference surface during the roughness measurement. The reference surface during the roughness measurement refers to a cylindrical surface formed by taking the central axis of the hollow cylinder as the axis, the axial height of the lowest point around the bottom of each protruding structure as the statistical object, and the arithmetic mean as the radius. When taking the lowest point around the bottom of each protruding structure, the pits formed by casting defects should be excluded from the selection range of the lowest point.

[0086] Secondly, the outer peripheral surface of the hollow cylinder of the hub inner ring 3 is a cylindrical surface, which is correspondingly circular in the longitudinal section perpendicular to the axial direction. However, in order to facilitate the comparison of the morphological differences between different protrusion structures, Figure 2 , Figure 3 and Figure 6The outer circumference of the inner ring 3 of the middle wheel hub is drawn as a straight line, and the circular contour lines with the outer circumference of the hollow cylinder of the inner ring 3 of the wheel hub as the reference plane are also drawn as straight lines. For this, those skilled in the art should understand that the outer circumference of the hollow cylinder of the inner ring of the wheel hub, which is a straight line here, should actually be a cylindrical surface, and the contour lines, which are straight lines, should actually be circular contour lines.

[0087] Third, the direction in which the protruding structure 4 protrudes outward refers to the direction from the outer peripheral surface of the hollow cylinder of the wheel hub inner ring 3 to the top or top surface of the protruding structure 4. Generally, the direction in which the protruding structure 4 protrudes outward is consistent with the radial direction of the wheel hub inner ring. However, considering the errors that may occur during the manufacturing process, the angle between the protruding direction of the protruding structure 4 and the radial direction of the wheel hub inner ring should be within a range of less than 30°, which should also be considered to be permissible.

[0088] Types of raised structures

[0089] like Figure 3-5 As shown, in a preferred embodiment, the protrusion structure 4 includes a table-shaped protrusion 42, and the table-shaped protrusion 42 meets the following requirements:

[0090] A longitudinal section perpendicular to the axial direction is made on the inner ring 3 of the hub. The longitudinal section passes through the protruding structure to form a longitudinal section figure of the protruding structure. In the longitudinal section figure, the line between the lowest points of the two side boundaries of the protruding structure is used as the protruding root reference line, and the boundary distance between the two side boundaries of the longitudinal section figure is measured along the direction parallel to the protruding root reference line;

[0091] Among them, as the distance from the base line of the protrusion root gradually increases, the boundary distance C of the longitudinal section figure remains unchanged or gradually decreases.

[0092] by Figure 3-5 Take the following as an example: Figure 3-5 It is a longitudinal section of the inner ring 3 of the hub perpendicular to the axial direction, and the longitudinal section passes through a plurality of protrusion structures 4 to form a longitudinal section diagram of a plurality of protrusion structures 4. Figure 4 and Figure 5 The schematic diagram of the metallographic structure of the longitudinal section of the convex structure is shown in FIG. 1 . The edge of the longitudinal section in the metallographic structure schematic diagram is drawn to form the following Figure 3 The schematic diagram of the longitudinal section of the protrusion structure is shown. On this basis, to determine whether a protrusion structure is a table-shaped protrusion, it is necessary to determine whether the boundary distance C of the longitudinal section no longer increases as it moves away from the protrusion root reference line.

[0093] Specifically, in Figure 3In the method, first, a line AB is drawn between the lowest points of the two sides of the raised structure (the first lowest point A and the second lowest point B), and the line AB is the raised root reference line of the raised structure. Secondly, multiple boundary distances C are measured at the same height as the line AB. Finally, for each raised structure, it is determined whether the length of the multiple boundary distances C no longer increases as they are farther away from the raised root reference line. Figure 3 The longitudinal sections of the two protrusion structures shown both meet the structural feature requirements of a terrace-shaped protrusion, and therefore both belong to the terrace-shaped protrusion 42 .

[0094] In order to facilitate the measurement of each protrusion structure, Figure 3 In the figure, the arc-shaped raised root reference line (line AB) and the boundary distance C are drawn as straight lines. However, those skilled in the art should understand that the outer circumference of the hollow cylinder of the inner ring of the hub is a circle in cross-section perpendicular to the axial direction, and the raised root reference line of each raised structure is a small section of the circular cross-section. Figure 3 The ridge root reference line in the figure should be in the shape of an arc. Similarly, the boundary distance C of the longitudinal section figure should also be the arc length of multiple circular contour lines based on the circular cross-sectional shape that fall within the range of the longitudinal section figure.

[0095] The combination of the terrace-shaped protrusion 42 and the corresponding concave structure can increase the heat transfer area between the wheel hub and the wheel hub inner ring and the ability to transmit torque along the circumferential direction. In addition, the boundary distance of the longitudinal section of the terrace-shaped protrusion 42 gradually decreases radially outward from the wheel hub inner ring 3, which can make the metal fill more fully around the terrace-shaped protrusion 42 during the casting process of the wheel hub.

[0096] like Figure 6 , 7 As shown, in another preferred embodiment, the protrusion structure includes a mushroom-shaped protrusion, and the mushroom-shaped protrusion meets the following requirements:

[0097] A longitudinal section perpendicular to the axial direction is made on the inner ring 3 of the hub, and the longitudinal section passes through the protruding structure to form a longitudinal section figure of the protruding structure. In the longitudinal section figure, the line between the lowest points of the two sides of the protruding structure is used as the protruding root reference line, and the boundary distance between the two sides of the longitudinal section figure is measured along the direction parallel to the protruding root reference line, and then the longitudinal section figure of the protruding structure 4 is divided into at least two areas by at least one dividing line parallel to the protruding root reference line, and the distance between the dividing line and the protruding root reference line is between 1 / 3 and 2 / 3 of the height of the protruding structure;

[0098] The maximum boundary distance D of the longitudinal section figure of at least one region far from the protrusion root reference line is greater than the minimum boundary distance d of the longitudinal section figure of at least one region close to the protrusion root reference line.

[0099] by Figure 6 , 7 Take the following as an example: Figure 6 , 7 It is a longitudinal section of the inner ring 3 of the hub perpendicular to the axial direction, and the longitudinal section passes through a plurality of protrusion structures 4 to form a longitudinal section diagram of a plurality of protrusion structures 4. Figure 7 The schematic diagram of the metallographic structure of the longitudinal section of the convex structure is shown in FIG. 1 . The edge of the longitudinal section in the metallographic structure schematic diagram is drawn to form the following Figure 6 On this basis, to determine whether a specific protrusion structure is a mushroom-shaped protrusion, it is necessary to compare whether the maximum boundary distance D of the longitudinal section of the area far from the protrusion root baseline is greater than the minimum boundary distance d of the longitudinal section of the area close to the protrusion root baseline.

[0100] Specifically, in Figure 6 In the method, first, the line between the lowest points of the two sides of the raised structure is used as the raised root reference line (line AB). Secondly, the longitudinal section of the raised structure 4 is divided into three areas by two dividing lines parallel to the raised root reference line and whose distance from the raised root reference line is between 1 / 3 and 2 / 3 of the height of the raised structure. These three areas are named the first area q1, the second area q2 and the third area q3 in order from the distance from the raised root reference line to the farthest. On this basis, the maximum boundary distance D and the minimum boundary distance d are measured in each area of ​​the longitudinal section of the raised structure. Finally, for each raised structure, it is determined whether there is a region where the maximum boundary distance D is greater than the minimum boundary distance d of another region, and the region where the maximum boundary distance D is located is farther away from the raised root reference line (line AB) than the region where the minimum boundary distance d is located.

[0101] For the cross-sectional figure of the first protrusion structure from the left, the maximum boundary distance D of the third area is greater than the minimum boundary distance d of the second area, and the third area is farther away from the protrusion root reference line than the second area. This size relationship meets the requirements of a fungus-shaped protrusion, so the protrusion structure is identified as a fungus-shaped protrusion. For the second to sixth protrusion structures from the left, similarly to the second protrusion structure from the left, they can be judged as fungus-shaped protrusions.

[0102] and Figure 3 Similarly, the outer circumference of the hollow cylinder of the inner ring of the hub is Figure 6 The cross-sectional shape in is also circular, and the maximum boundary distance D and the minimum boundary distance d of each protruding structure are also obtained by the circular contour lines falling within the range of the longitudinal section figure. Figure 6 In the figure, the protrusion root reference line (line AB), the maximum boundary distance D and the minimum boundary distance d are also drawn as straight lines to facilitate the measurement of each protrusion structure.

[0103] Since the fungiform protrusion has the characteristic that "the maximum boundary distance D of the longitudinal section figure of at least one area farther from the protrusion root baseline is greater than the minimum boundary distance d of the longitudinal section figure of at least one area closer to the protrusion root baseline", the fungiform protrusion forms a structural feature between at least one combination composed of two different areas (for example, a combination composed of the third area and the second area), in which the position with a larger boundary distance is farther from the protrusion root baseline and the position with a smaller boundary distance is closer to the protrusion root baseline, thereby achieving an improvement in structural strength and thermal conductivity.

[0104] Specifically, considering that there is a reasonable range of angle difference between the height direction of the protrusion structure and the radial direction of the inner ring of the wheel hub, the distance from the base line of the protrusion root is equivalent to the distance along the radial direction. Therefore, for the mushroom-shaped protrusion with the structural feature that the position with a larger boundary distance is closer to the outside and the position with a smaller boundary distance is closer to the inside, the wheel hub will form a concave structure corresponding to the structural feature of the mushroom-shaped protrusion on the joint surface with the inner ring of the wheel hub: the concave structure corresponding to the position with a smaller boundary distance in the mushroom-shaped protrusion will form a hole area with a similarly smaller boundary distance, and the concave structure corresponding to the position with a larger boundary distance in the mushroom-shaped protrusion will form a hole area with a similarly larger boundary distance. Therefore, if the joint surface between the wheel hub and the inner ring of the wheel hub is subjected to radial load, the position with a larger boundary distance in the mushroom-shaped protrusion will be hooked with the hole area with a smaller boundary distance in the concave structure, preventing the wheel hub and the inner ring of the wheel hub from being separated from each other in the radial direction, thereby improving the bonding strength between the inner ring of the wheel hub and the wheel hub.

[0105] And Figure 6 Taking the mushroom-shaped protrusion 41 shown in the figure as an example, the cross-sectional figure of the mushroom-shaped protrusion forms a first boundary distance change between the first area and the second area, and a second boundary distance change between the second area and the third area. These two changes in boundary distances enable the mushroom-shaped protrusion 41 to have a larger specific surface area (surface area / volume) within the same height range, thereby improving the heat conduction performance between the hub inner ring 3 and the light alloy hub 1.

[0106] The proportion of different types of raised structures.

[0107] In a preferred embodiment, among the plurality of protrusion structures 4 , the mushroom-shaped protrusions 41 account for 35%-95%.

[0108] The mushroom-shaped protrusions 41 account for more than 35%, and the mushroom-shaped protrusions can be used to improve the bonding strength and thermal conductivity between the inner ring of the wheel hub and the wheel hub. Specifically, the mushroom-shaped protrusions can increase the size of the mutual engagement in the mortise and tenon fitting relationship between the protrusion structure and the recessed structure, and in particular, can form a radial engagement between the protrusion structure and the recessed structure, thereby helping to improve the bonding strength between the wheel hub and the inner ring of the wheel hub. Moreover, in the longitudinal section of the mushroom-shaped protrusion perpendicular to the axial direction, its boundary distance will change along the radial direction of the inner ring 3 of the wheel hub, so that the mushroom-shaped protrusions 41 have a larger specific surface area within the same height range, increasing the heat transfer area between the mushroom-shaped protrusions and the corresponding recessed structure, thereby helping to improve the thermal conductivity between the wheel hub and the inner ring of the wheel hub.

[0109] If the proportion of mushroom-shaped protrusions 41 is less than 95%, the metal fluidity of the wheel hub during the casting process can be guaranteed, and the filling of the recessed structure can be more full. Specifically: during the casting process of the wheel hub, the liquid light alloy used to make the wheel hub needs to first flow through the area of ​​the protrusion structure that is far away from the protrusion root baseline before it can be filled into the area of ​​the protrusion structure that is close to the protrusion root baseline. However, the area with a larger boundary distance in the longitudinal section of the mushroom-shaped protrusion 41 is far away from the protrusion root baseline, making it difficult for the liquid light alloy to bypass the area with a larger boundary distance in the longitudinal section of the mushroom-shaped protrusion during the casting process and fill the surrounding area of ​​the area with a smaller boundary distance, which leads to the shape of the recessed structure being not full enough, and it is easy to produce tiny gaps between the protrusion structure and the wheel hub. These tiny gaps will affect the ratio of the effective heat transfer area between the protrusion structure and the recessed structure to the total contact area, thereby affecting the heat transfer performance between the wheel hub and the inner ring of the wheel hub.

[0110] In another preferred embodiment, among the plurality of protrusion structures 4 , the proportion of the terrace-shaped protrusions 42 is 5%-65%.

[0111] By limiting the proportion of the terrace-shaped protrusions 42 to no more than 65%, it is possible to ensure that the multiple protrusion structures 4 include a sufficient proportion of mushroom-shaped protrusions, thereby ensuring the thermal conductivity and bonding strength between the hub and the inner ring of the hub by increasing the heat transfer area, increasing the bite size of the tenon-and-mortise joint, and ensuring the radial bite capability of the mushroom-shaped protrusions. By limiting the proportion of the terrace-shaped protrusions 42 to no less than 5%, the sufficient proportion of the terrace-shaped protrusions 42 can ensure the metal fluidity of the hub during the casting process, especially during the pressure casting or gravity casting process, so that the filling of the concave structure is more full.

[0112] In another preferred embodiment, among the plurality of protrusion structures 4 , the mushroom-shaped protrusions 41 account for 35%-95%, and the terrace-shaped protrusions 42 account for 5%-65%.

[0113] Therefore, by simultaneously controlling the proportion of the mushroom-shaped protrusions 41 and the proportion of the terrace-shaped protrusions 42, it is possible to ensure that the bonding strength and thermal conductivity between the hub inner ring 3 and the hub 1 meet the requirements while making the metal fluidity during the casting process better and the filling of the recessed structure fuller.

[0114] The impact of the statistical method of the types of protrusion structures on the proportion of each type:

[0115] When the longitudinal section diagram of the protrusion structure is used as the object for counting the types of the protrusion structure, it should be noted that for the cone-shaped protrusion, the position of the longitudinal section hardly affects the shape of its longitudinal section diagram, that is, at the positions of most longitudinal sections, the longitudinal section diagram of the cone-shaped protrusion is a trapezoidal shape with the lower base close to the protrusion root baseline and the upper base far away from the protrusion root baseline.

[0116] However, if Fig.21 As shown in FIG. 1 , for the mushroom-shaped protrusion, only when the longitudinal section is distributed between L2 and L3, the longitudinal section of the mushroom-shaped protrusion can be made to appear as follows: Fig.21 The shape of the complete fungiform protrusion shown in FIG. 1 is as follows: when the longitudinal section is distributed between L1-L2 or L3-L4, it will appear as follows Fig. 22 The mushroom-like protrusion shape of the cap falling off is shown in FIG. 1 . When the longitudinal section is distributed outside L1 or L4, it presents the following Fig.23 The shape of the terraced protrusion shown.

[0117] Among them Fig.21 and 22 The cross-sectional shape shown can only be obtained when the protrusion structure is a mushroom-shaped protrusion. Therefore, counting the protrusion structure into the mushroom-shaped protrusion will not produce statistical deviation. However, for Fig.23 The shape of the terrace-shaped protrusion shown is difficult to distinguish whether it is obtained by intercepting the fungus-shaped protrusion or the terrace-shaped protrusion.

[0118] like Figure 8 As shown in the figure, for the cross-sectional figure of the second complete protrusion structure from the left, its height is relatively low, and it is difficult to judge whether it is obtained by intercepting a mushroom-shaped protrusion or a table-shaped protrusion. In view of this, in the statistical process, protrusion structures with a height less than 0.3mm are not considered, thereby eliminating the statistical deviation caused by "misjudging the shape of a partial table-shaped protrusion obtained by intercepting a mushroom-shaped protrusion as obtained by intercepting a table-shaped protrusion".

[0119]

[0120] It can be seen from Table 5 that when the number of protrusion structures in a detection area is small, the proportion of fungiform protrusions or terrace-shaped protrusions has a large deviation. However, when the statistical results of multiple detection areas are summarized, the proportions of fungiform protrusions and terrace-shaped protrusions will be stably distributed at around 60% and 40%, respectively.

[0121] Taking into account the deviation caused by the statistical method and the deviation caused by the sample size of the protrusion structure in the detection area, the proportion of fungi-shaped protrusions in the present invention is preferably 35%-95%, while the proportion of terrace-shaped protrusions is preferably 5%-65%.

[0122] Top surface area of ​​the raised structure

[0123] In a preferred embodiment, the average top surface area of ​​the protrusion structure 4 is between 0.1 and 3 mm. 2 The surface where the top surface area is located is perpendicular to the radial direction of the hub inner ring 3.

[0124] The average top surface area of ​​the protrusion structure 4 is between 0.1 and 3 mm. 2 , on the basis of ensuring the complete formation of the protruding structure, it is possible to achieve the technical effects of enhancing the thermal conductivity and increasing the bonding strength brought by the protruding structure as much as possible.

[0125] Specifically, the larger the top surface area of ​​the raised structure, the larger the heat transfer area between the inner ring of the hub and the hub increased by the raised structure and the recessed structure, and the larger the bite size of the mortise and tenon joints between the raised structure and the corresponding recessed structure. However, an excessively large top surface area will increase the difficulty of forming the raised structure, making it difficult for the liquid light alloy to bypass the top of the raised structure and fill between the top of the raised structure and the outer circumference of the hollow cylinder of the inner ring of the hub during the casting process of the hub, and easily generating tiny pores between the raised structure and the hub, thereby increasing the gap between the raised structure and the recessed structure during repeated thermal expansion and contraction, affecting the heat transfer performance and bonding strength between the hub and the inner ring of the hub.

[0126] Example of how to calculate the top surface area of ​​a raised structure:

[0127] Taking the outer circumference of the hollow cylinder of the inner ring of the hub as the reference plane, cut a transverse section of the raised structure at a set radial height along a direction perpendicular to the radial direction of the inner ring of the hub, and calculate the area of ​​the transverse section, which represents the top surface area of ​​the raised structure.

[0128] Taking into account that the heights of the various protruding structures are somewhat different, the radial height when intercepting the transverse section is set as follows: the radial height of the highest point of the top of all the protruding structures in the sampling area is used as the statistical object, the arithmetic mean is calculated, and then 0.1 mm is subtracted from the calculated arithmetic mean, so that as many protruding structures as possible can be intercepted by the transverse section.

[0129] For example: 10mm from the upper and lower end faces of the inner ring of the wheel hub, select one area of ​​100mm in each of the four equally divided areas along the circumference. 2 The area (10mm*10mm square) is used as the sampling area. In each sampling area, the outer circumference of the hollow cylinder of the inner ring of the wheel hub is used as the reference, and the transverse section of the protruding structure is intercepted at a set radial height. The area of ​​the transverse section of all the intercepted protruding structures is counted, and the average value is calculated, which is the top surface area of ​​the protruding structure.

[0130] Of course, considering the large number of protrusions on the outer circumferential surface of the hollow cylinder of the inner ring of the hub, it is preferred to use the five-point method to select the four corners of the sampling area (corresponding to Fig. 9 A transverse cross section of a protruding structure is selected from each of the first top area 51, the second top area 52, the fourth top area 54 and the fifth top area 55) and the center position (corresponding to the third top area 53). The average of the areas of the transverse cross sections of all five protruding structures is the average of the top surface areas of the protruding structures in the sampling area.

[0131] Height of raised structure

[0132] In a preferred embodiment, the average height of the protrusion structure 4 is between 0.3 mm and 1.0 mm.

[0133] The height of the protruding structure 4 will affect the thermal conductivity and bonding strength between the wheel hub and the inner ring of the wheel hub.

[0134] Specifically, when the height of the protruding structure is less than 0.3 mm, the protruding structure is mostly in the form of a bulge, and it is difficult to form a mushroom-shaped protrusion or a table-shaped protrusion with complete structural characteristics in the height direction, resulting in a low bonding strength between the protruding structure and the concave structure. In addition, the increase in the heat conduction area of ​​the protruding structure that is too low is also very limited, so that the thermal conductivity coefficient of the wheel hub and the inner ring of the wheel hub does not increase significantly.

[0135] When the height of the raised structure is higher than 1.0mm, the height of the raised structure will make it more difficult to cast the raised structure and the concave structure that matches it, and the shape filling will not be full, which will easily increase the gap between the wheel hub and the inner ring of the wheel hub during repeated thermal barriers and shrinkage, resulting in a decrease in the thermal conductivity of the inner ring of the wheel hub to the wheel hub. In addition, the rigidity of the raised structure that is too high is poor, and it is easy to deform or even break when subjected to radial loads and circumferential loads, affecting the bonding strength between the wheel hub and the inner ring of the wheel hub.

[0136] Selection of the average value of the height of the raised structure:

[0137]

[0138] Combined with Table 1, Appendix Fig.13 and attached Fig.14 As the average value of the height of the protruding structure increases, the bonding strength between the hub and the inner ring of the hub increases first and then decreases. The protruding structure has the maximum bonding strength in the range of 0.69mm to 0.72mm, and the bonding strength is relatively high in the range of 0.51mm-0.95mm, which is basically greater than 17MPa. The bonding strength is relatively low in the range below 0.4mm, which is less than 10MPa.

[0139]

[0140]

[0141] Combined with Table 2, Appendix Fig.15 and attached Fig.16 As the average value of the height of the protruding structure increases, the thermal conductivity from the inner ring of the hub to the hub also shows a trend of first increasing and then decreasing. The protruding structure has a maximum thermal conductivity when the height is around 0.72 mm. The thermal conductivity in the range of 0.22 mm-0.9 mm is relatively high, basically greater than 40 W / m·k. In the range above 0.9 mm, as the height of the protruding structure increases, the thermal conductivity basically does not change.

[0142] Taking into account the influence of the height of the protruding structure on the bonding strength and thermal conductivity, the height of the protruding structure is preferably greater than 0.4 mm and less than 0.9 mm to ensure sufficient bonding strength and efficient thermal conductivity between the hub and the inner ring of the hub. Taking into account the error in the experimental process and the influence of extreme values ​​on the average result during the average calculation process, the average value of the height of the protruding structure 4 is preferably between 0.3-1.0 mm.

[0143] Example of height measurement of raised structures:

[0144] At 10 mm from the upper and lower end faces of the inner ring of the wheel hub, select one of the four equally divided areas along the circumference with an area of ​​100 mm each. 2 The sampling area (10mm*10mm square) is used as the sampling area. The sampling area is scanned by industrial CT to obtain a three-dimensional image containing the protruding structures in the sampling area. The outer peripheral surface of the hollow cylinder of the inner ring of the wheel hub is used as the reference plane, and the radial distance between the top or top surface of each protruding structure and the reference plane is calculated, which is the height of each protruding structure.

[0145] Of course, the height measurement of the protruding structure can also be carried out by Fig. 9 The five-point method shown selects a raised structure at each of the four corners and the center of the sampling area for height measurement.

[0146] And Figure 7 , Figure 8 For example, when measuring the height of a raised structure, a line can be drawn between the lowest point on the left side of the raised structure located on the leftmost side of the longitudinal section figure and the lowest point on the right side of the raised structure located on the rightmost side of the longitudinal section figure, and then the vertical distance between the vertex (or top surface) of the raised structure and the line can be measured, which is the height of the raised structure.

[0147] Since the protruding structure is a cast structure, its dimensional deviation is relatively large, and the height detection accuracy of the protruding structure is generally controlled at 0.1mm.

[0148] Distribution density of protrusion structures

[0149] In a preferred embodiment, the average distribution density of the plurality of protrusion structures 4 relative to the hub inner ring 3 is between 15 and 50 protrusions / cm 2 .

[0150] The distribution density of the protrusion structure 4 will also affect the thermal conductivity and bonding strength between the hub and the inner ring of the hub:

[0151] When the average distribution density of the protrusions 4 is less than 15 / cm 2 When the protrusions are sparsely distributed within a unit area, the heat conduction area increased by the protrusions and recesses and the engagement area of ​​the mortise and tenon joints are relatively limited, and the increase in the thermal conductivity and bonding strength of the hub and the hub inner ring is not obvious.

[0152] When the average distribution density of the protrusions 4 is greater than 50 / cm 2 When the protrusions are too densely distributed, it is easy to make the forming of the protrusions and the recessed structures more difficult, so that the protrusions and the recessed structures have gaps during the repeated thermal barrier and shrinkage process due to insufficient shape, which affects the bonding strength and thermal conductivity of the hub and the inner ring of the hub.

[0153] Selection of the average value of the distribution density of the protrusion structure:

[0154]

[0155] Combined with Table 3, Appendix Fig.17 and attached Fig.18 As the average distribution density of the protrusions increases, the bonding strength between the inner ring of the hub and the hub increases first and then decreases. 2 The maximum bonding strength is obtained in the interval near 8 pieces / cm 2 -40 pieces / cm 2 The bonding strength in the range of 48 / cm is relatively high, basically greater than 15MPa, and at 2The bonding strength in the above range is relatively low, basically less than 1MPa.

[0156]

[0157]

[0158] Combined with Table 4, Appendix Fig.19 and attached Fig. 20 As the average value of the protrusion structure distribution density increases, the thermal conductivity from the inner ring of the hub to the hub increases first and then decreases. 2 The maximum value of thermal conductivity is 22 / cm 2 -50mm 2 The thermal conductivity in the above range is relatively high, basically greater than 35W / m·k, and at 16 / cm 2 In the following distribution densities, the thermal conductivity is low, basically less than 25W / m·k.

[0159] Considering the influence of distribution density on bonding strength and thermal conductivity, the distribution density is preferably greater than 16 / cm 2 And less than 48 / cm 2 , to ensure sufficient bonding strength and thermal conductivity. Considering the error in the experimental process and the influence of extreme values ​​on the average result during the average calculation, the average distribution density of the protrusion structure is between 15-50 / cm 2 .

[0160] Measurement of the distribution density of protrusion structures:

[0161] At 10 mm from the upper and lower end faces of the inner ring of the wheel hub, select one of the four equally divided areas along the circumference with an area of ​​100 mm each. 2 The area (10mm*10mm square) is taken as the sampling area. The convex structures with complete structures in the sampling area are counted, and then the convex structures falling on the upper boundary (or lower boundary) and the right boundary (or left boundary) of the sampling area are counted. The sum of the two counting results is the total number of convex structures in the sampling area, and then divided by the area of ​​the sampling area to get the distribution density of the convex structures.

[0162] Example of measurement of bond strength and thermal conductivity

[0163] About the measurement of thermal conductivity:

[0164] As attached Fig.10As shown, the test sample is cut radially from the joint surface of the wheel hub and the inner ring of the wheel hub. During the cutting process, the total thickness of the test sample and the thickness occupied by the inner ring of the wheel hub are limited: when the total thickness of the test sample is a±0.05mm, it is necessary to ensure that the thickness occupied by the inner ring of the wheel hub is 1 / 4*a±0.05mm.

[0165] During the sampling process, 4-6 test specimens are cut evenly along the circumference, and at each circumferential angle, a test specimen is cut along the axial direction at the position where the bearing is set on the inner ring of the hub. Fig.10 A first test sampling area 61 and a second test sampling area 62 are shown.

[0166] Considering the small size of the experimental sample, especially the thin thickness, Fig.11 As shown, after the experimental sample is cut out, the thermal conductivity of the experimental sample is preferably measured by a laser flash method: under constant temperature conditions, a laser lamp or a flash xenon lamp instantly emits a light pulse from one side of the experimental sample cut from the inner ring of the wheel hub, and evenly irradiates the surface of the experimental sample cut from the inner ring of the wheel hub, so that the surface absorbs light energy and the temperature rises instantly, and as a hot end, the energy is transmitted to the surface of the experimental sample cut from the wheel hub in a one-dimensional heat conduction manner, and the temperature rise process of the experimental sample cut from the wheel hub is measured, and then the thermal conductivity of the experimental sample is calculated based on the relationship curve of the temperature rise corresponding to time.

[0167] The thermal conductivity coefficient characterizes the speed of heat transfer from the inner ring of the wheel hub to the wheel hub. The higher the thermal conductivity coefficient, the better the heat conduction effect from the inner ring of the wheel hub to the wheel hub, and the faster the heat can be transferred, thus reducing the operating temperature of the bearing.

[0168] For bond strength measurements:

[0169] The test sample is cut in the same way as the thermal conductivity measurement. However, there is no special size requirement for the thickness of the test sample during the cutting process. It only needs to ensure that the two parts of the test sample cut from the inner ring of the wheel hub and the wheel hub can be fixed and clamped respectively.

[0170] After the test sample is cut out, Fig.12 As shown, the two parts cut from the inner ring of the wheel hub and the wheel hub are respectively clamped on the corresponding bonding strength test fixture 63, and a tensile force is applied to the bonding strength test fixture by a material testing machine. Then, as the tensile force is gradually loaded, the tensile force when the joint surface between the inner ring of the wheel hub and the wheel hub of the experimental sample is separated is divided by the area of ​​the joint surface in the experimental sample, and the bonding strength between the inner ring of the wheel hub and the wheel hub is obtained.

[0171] In order to avoid the influence of random errors in a single experiment on the accuracy of the measurement results, the average value of multiple experimental data is used in the process of obtaining the measurement results of thermal conductivity and bonding strength. In addition, the maximum and minimum values ​​of each experiment are recorded to discuss the influence of the range on the average calculation results.

[0172] Take the measurement of thermal conductivity with an average protrusion height of 0.22 mm as an example: a total of five samples with an average protrusion height of 0.22 mm were used for thermal conductivity experiments, and the experimental results (W / m·k) were 33.49, 35.46, 36.47, 37.53 and 39.86, respectively. The maximum value of this set of data is 39.86, the minimum value is 33.49, and the average value is 36.56, which are recorded in the statistical table respectively.

[0173] Considering that the joint surface between the two parts cut from the wheel hub and the inner ring of the wheel hub in the experimental sample usually includes multiple protrusions, it is necessary to select products obtained under different production conditions for the experiments on bonding strength and thermal conductivity. For example, there are 10 experimental samples with an average height of 0.22 mm for the protrusions. The distribution density (pieces / cm 2 ) are: three pieces of 38, one piece of 39, two pieces of 40, two pieces of 41, one piece of 42, and one piece of 44, so 2 pieces / cm 2 For the interval, the density was selected as 38, 40, 42, and 44 / cm 2 The thermal conductivity and bonding strength experiments were carried out on the samples to make the selection of experimental data with the distribution density of the protrusion structure as the independent variable more uniform.

[0174] In a second aspect of the present invention:

[0175] The present invention also provides a method for manufacturing a wheel hub inner ring, comprising the following steps: melting ingredients of a set ratio into molten iron, and performing molten iron treatment on the molten iron; preheating and rotating the wheel hub inner ring casting mold, and evenly applying the configured coating on the inner wall of the wheel hub inner ring casting mold; after the coating is dry, pouring the molten iron treated with molten iron into the wheel hub inner ring casting mold; keeping the wheel hub inner ring casting mold rotating; demolding after the molten iron is solidified and formed, removing the coating layer on the surface of the casting after demolding, and obtaining a wheel hub inner ring casting with a protruding structure.

[0176] In a preferred embodiment, the coating comprises: 4% to 7% by mass of sodium bentonite; 15% to 25% by mass of diatomaceous earth; 0% to 5% by mass of 350 mesh quartz sand; 0.0005% to 0.01% by mass of alkyl sulfate; and the balance is water.

[0177] The process of forming the raised structure on the outer circumferential surface of the hollow cylinder of the inner ring of the wheel hub is described as follows: a water-based coating with added surfactant is applied to the inner surface of the wheel hub inner ring casting mold that has been heated and kept rotating, thereby forming a casting coating layer. The water in the casting coating layer vaporizes under the action of preheating to produce bubbles. At this time, the surfactant in the casting coating layer is applied to each bubble, which increases the surface tension of the bubble. Adjacent small bubbles gradually merge and increase in volume to become large bubbles. At the same time, the unsolidified casting coating layer squeezes the bubbles under the action of centrifugal force.

[0178] Because the distribution of diatomaceous earth and quartz sand in the coating is difficult to achieve absolute uniformity, the pressure around each large bubble is different, which results in a variety of large bubble shapes, corresponding to the different shapes of the thicker cap part of the mushroom-like protrusion. As the coating solidifies locally, the pressure inside the large bubble continues to increase. When the internal pressure of the large bubble is greater than the centrifugal force of the coating on its top, the bubble ruptures. The ruptured channel forms a shape corresponding to the smaller stipe in the mushroom-like protrusion. In addition, the impact force when the bubble ruptures pushes the inner surface of the casting coating layer to the surroundings, thereby forming the mycorrhizal part of the mushroom-like protrusion that is thicker than the stipe. Thereafter, the molten iron is poured into the wheel hub inner ring casting mold where the casting coating layer has dried, and the wheel hub inner ring with multiple protrusion structures can be produced.

[0179] For large bubbles with high uniformity of diatomaceous earth and quartz sand distributed around and high internal pressure, they will rupture earlier. Therefore, the channels created by the rupture of the large bubbles and the mycorrhiza formed by the impact force at the time of rupture that pushes the inner surface of the casting coating layer to the surrounding areas will tend to disappear with the long-term centrifugal force during the casting process, making the side walls of the large bubbles closer to a smoother cone surface, corresponding to the formation of a table-like bulge in the convex structure.

[0180] The following is an explanation of the role of each component in the coating:

[0181] Water, as a solvent, plays the role of mixing the various components and vaporizing on the inner surface of the preheated hub inner ring casting mold to generate bubbles;

[0182] Sodium bentonite is used as a suspending agent to keep the thermal insulation aggregate and refractory aggregate suspended in the aqueous solution without precipitation and accumulation.

[0183] Diatomaceous earth, as a heat-insulating aggregate, plays a role in isolating heat energy, preventing the high temperature of liquid iron from being transferred to the mold, causing the mold temperature to rise and deform;

[0184] As a refractory aggregate, quartz sand plays a supporting role, similar to the steel bars in concrete, to enhance the strength of the coating and prevent the holes created by the surfactant from being washed out and burned by the molten iron;

[0185] Alkyl sulfate is used as a surfactant to enhance the surface tension of water in the coating. When the coating comes into contact with a high-temperature mold, the water vapor formed by the water inside the coating gathers together to form bubbles. When the bubbles grow to a certain size (when the internal pressure is greater than its surface tension), they burst on the inner circular surface of the coating layer.

[0186] If the diatomite is less than 15% by weight, the thermal insulation effect of the coating layer will be reduced, and if the diatomite is more than 25% by weight, the coating layer will have a higher viscosity and will not flow as required. If the sodium bentonite is less than 4% by weight, the diatomite and quartz sand in the coating layer will easily settle and accumulate, resulting in reduced thermal insulation and heat preservation properties of the coating layer. If the sodium bentonite is more than 7% by weight, the expansion index and water absorption rate of the coating layer will be reduced.

[0187] In another preferred embodiment, when applying the coating, the rotation speed of the wheel hub inner ring casting mold is controlled between 700-1200r / min, and the temperature of the wheel hub inner ring casting mold is controlled between 200-300°C; thereby making the coating more evenly distributed on the surface of the wheel hub inner ring casting mold and less likely to fall off.

[0188] When the molten iron is poured into the wheel hub inner ring casting mold, the rotation speed of the wheel hub inner ring casting mold is between 1000-1600r / min, so that the molten iron adheres to the inner wall of the coating under the action of centrifugal force to form a hollow pipe. Under the action of centrifugal force, the molten iron can fill the wheel hub inner ring casting mold well in the radial direction, making the raised structure 4 on the outer peripheral surface of the hollow cylinder of the wheel hub inner ring 3 fuller. In addition, the centrifugal force also helps to remove gas and inclusions in the liquid metal, affects the crystallization process of the metal, and improves the mechanical and physical properties of the casting.

[0189] In another preferred embodiment, the material of the inner ring of the hub includes ductile iron, and the temperature of the molten iron during pouring is 1380-1450°C, so that the casting obtains better tensile strength and Brinell hardness, and can relatively save energy consumption in the casting process and reduce manufacturing costs.

[0190] Specifically, when the material of the hub inner ring 3 includes ductile iron, the relationship between its molten iron temperature and strength and hardness is as follows: within the range of 1300-1460°C, as the molten iron temperature increases, the tensile strength and Brinell hardness values ​​both increase; within the range of 1460-1500°C, as the molten iron temperature increases, the tensile strength continues to increase, but the Brinell hardness does not change much; and within the range of 1500-1600°C, as the molten iron temperature increases, the tensile strength still increases, but the Brinell hardness decreases. In addition, there is also a quantitative relationship between the wall thickness of the casting and the pouring temperature: the thicker the casting wall, the lower the pouring temperature should be.

[0191] It can be seen that when the temperature of molten iron pouring is set to 1380-1450℃, the inner ring of the hub can have a higher Brinell hardness, meet the high hardness requirements required for contact with the outer ring of the bearing, and make the inner ring of the hub have sufficient tensile strength. In addition, the molten iron temperature of 1380-1450℃ is lower than the molten iron temperature of 1300-1600℃ for cast iron, which can save energy consumption in the casting process and reduce manufacturing costs.

[0192] In a third aspect of the present invention:

[0193] like Figure 1 As shown, a hub assembly is provided, comprising a hub inner ring 3 of any one of the above embodiments, and the hub assembly further comprises a hub 1 and a hub bearing 2. The hub 1 is located at the periphery of the hub inner ring 3, and the hub 1 is provided with a bearing hole 11; the hub bearing 2 is located inside the hub inner ring 3, and the outer ring of the hub bearing 2 is fixedly arranged on the inner circumference of the hollow cylinder of the hub inner ring 3; and the hub 1 is formed on the outer circumference of the hollow cylinder of the hub inner ring 3 by an inlay casting process, so that the joint surface of the hub 1 and the hub inner ring 3 has a plurality of recessed structures matched with the plurality of raised structures.

[0194] By adding a hub inner ring 3 between the wheel hub 1 and the hub bearing 2, the assembly accuracy of the hub bearing 2 can be improved through the fitting connection between the hub inner ring 3 and the hub bearing 2; and by the mutual fit between the hub inner ring 3 and the bearing hole 11 on the wheel hub 1, the surface stiffness at the hub bearing hole can be improved, while avoiding the wear of the wheel hub 1 caused by the wheel hub bearing 2 being directly assembled inside the bearing hole 11.

[0195] And as described in the first aspect of the present invention, the protruding structure and the recessed structure can improve the thermal conductivity and the bonding strength between the wheel hub and the inner ring of the wheel hub.

[0196] In a preferred embodiment, the material of the wheel hub 1 includes a light alloy, and the material of the wheel hub inner ring 3 includes an iron-carbon alloy. The wheel hub 1 and the wheel hub inner ring 3 in the present invention are made of different materials, and compared with a wheel hub assembly made of the same material, a lightweight design of the wheel hub assembly can be achieved. Specifically:

[0197] The wheel hub 1 is mainly used to transfer the load between the wheel and the axle, so there are certain requirements for the strength and stiffness of the material. In addition, the size of the wheel hub 1 is relatively large, which has a greater impact on the total weight of the wheel hub assembly. Taking all factors into consideration, the wheel hub 1 should be made of lightweight metals with greater strength and stiffness, such as aluminum alloy, magnesium alloy, titanium alloy, etc. Considering the manufacturing difficulty and cost, aluminum alloy is a preferred material.

[0198] The wheel hub inner ring 3 is mainly used for installing the wheel hub bearing 2 in the bearing hole 11. It needs to bear the force, friction and heat dissipation of the wheel hub bearing 2. The size of the wheel hub inner ring 3 is small and has little effect on the total weight of the wheel hub assembly. Therefore, you don’t need to pay too much attention to the density of the material, and consider more materials with high surface stiffness and excellent wear resistance, such as cast iron or alloy steel.

[0199] In addition, the operating temperature variation range of the hub bearing 2 is relatively large, and the thermal deformation coordination problem of the mating surface between the hub bearing 2 and the hub inner ring 3 needs to be considered. Therefore, the hub inner ring 3 can be selected from a material with the same or similar thermal expansion coefficient as the outer ring material of the hub bearing 2, thereby achieving a transition in material properties between the hub bearing 2 and the hub bearing hole.

[0200] In a fourth aspect of the present invention:

[0201] A method for manufacturing a wheel hub assembly is provided, comprising the following steps:

[0202] a) Manufacturing of wheel hub: The manufactured wheel hub inner ring is arranged at the center hole of the wheel hub casting mold, and the molten liquid light alloy is injected into the mold cavity of the wheel hub casting mold by insert casting. After the light alloy is cooled and formed in the wheel hub casting mold, the mold is removed to obtain the wheel hub with the wheel hub inner ring, and then the wheel hub is machined to the target size;

[0203] b) Assembly of wheel hub bearing and wheel hub inner ring: Install the wheel hub bearing to the inner circumference of the hollow cylinder of the wheel hub inner ring.

[0204] The wheel hub assembly provided by the present invention is made of different materials for different components in the wheel hub assembly, thereby reducing the weight of the wheel hub 1 while meeting the structural strength requirements of the wheel hub 1, thereby improving the fuel economy of the wheel hub 1. In addition, the mutual cooperation between the raised structure 4 and the recessed structure is achieved through the inlay casting process, which can also improve the bonding strength and bonding tightness between the components in the wheel hub assembly and reduce the working temperature of the wheel hub bearing 2.

[0205] Preferably, the casting method of injecting the molten liquid light alloy into the cavity of the wheel hub casting mold is pressure casting, and during the pressure casting process, the liquid light alloy in the cavity of the wheel hub casting mold is kept warm and pressurized until the liquid light alloy is completely solidified.

[0206] During the process of casting the wheel hub to the inner ring of the wheel hub, applying pressure to the liquid light alloy in the cavity of the wheel hub casting mold can promote the flow of the liquid light alloy, improve the casting effect, make the shape of the recessed structure on the wheel hub fuller, and thereby reduce the gap formed between the protruding structure and the recessed structure.

[0207] So far, various embodiments of the present invention have been described in detail. However, those skilled in the art should understand that the above examples are only for illustration and are not intended to limit the scope of the present invention. Those skilled in the art should understand that the above embodiments may be modified or some technical features may be replaced by equivalents without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A wheel hub inner ring, characterized in that: The wheel hub inner ring (3) is a hollow cylinder, and the wheel hub inner ring (3) has a plurality of protrusion structures (4). The protrusion structures (4) protrude outward from the outer circumference of the hollow cylinder of the wheel hub inner ring (3), and are used for the wheel hub (1) to be formed on the outer circumference of the hollow cylinder of the wheel hub inner ring (3) by an insert casting process; The average distribution density of the plurality of protrusion structures (4) relative to the hub inner ring (3) is between 15 and 50 per cm. 2 .

2. The wheel hub inner ring according to claim 1, characterized in that: The protrusion structure (4) comprises a mushroom-shaped protrusion (41), and the mushroom-shaped protrusion (41) meets the following requirements: A longitudinal section perpendicular to the axial direction is made on the inner ring of the wheel hub (3), and the longitudinal section passes through the protruding structure (4) to form a longitudinal section figure of the protruding structure (4), in which a line connecting the lowest points of the two side boundaries of the protruding structure is used as a protruding root reference line (AB), and a boundary distance between the two side boundaries of the longitudinal section figure is measured along a direction parallel to the protruding root reference line (AB), and the longitudinal section figure of the protruding structure (4) is divided into at least two areas by at least one dividing line parallel to the protruding root reference line, and the distance between the dividing line and the protruding root reference line is between 1 / 3 and 2 / 3 of the height of the protruding structure; Among them, the maximum boundary distance (D) of the longitudinal section figure of at least one area farther from the protrusion root reference line (AB) is greater than the minimum boundary distance (d) of the longitudinal section figure of at least one area closer to the protrusion root reference line (AB).

3. The wheel hub inner ring according to claim 2, characterized in that: Among the plurality of protrusion structures (4), the mushroom-shaped protrusions (41) account for 35%-95%.

4. The wheel hub inner ring according to claim 2 or 3, characterized in that: The protrusion structure (4) further comprises a terrace-shaped protrusion (42), and the terrace-shaped protrusion (42) meets the following requirements: A longitudinal section perpendicular to the axial direction is made on the inner ring of the wheel hub (3), and the longitudinal section passes through the protruding structure (4) to form a longitudinal section figure of the protruding structure (4), in which a line connecting the lowest points of the two side boundaries of the protruding structure is used as a protruding root reference line (AB), and a boundary distance (C) between the two side boundaries of the longitudinal section figure is measured along a direction parallel to the protruding root reference line; Among them, as the distance relative to the base line of the protrusion root gradually increases, the boundary distance (C) of the longitudinal section figure remains unchanged or gradually decreases.

5. The wheel hub inner ring according to claim 4, characterized in that: Among the plurality of protrusion structures (4), the proportion of the terrace-shaped protrusions (42) is 5%-65%.

6. The wheel hub inner ring according to claim 1, characterized in that: The average top surface area of ​​the protruding structure (4) is between 0.1 and 3 mm 2 The surface where the top surface area is located is perpendicular to the radial direction of the hub inner ring (3).

7. The wheel hub inner ring according to claim 1, characterized in that: The average height of the protruding structure (4) is between 0.3 and 1.0 mm.

8. A method for manufacturing a wheel hub inner ring according to any one of claims 1 to 7, characterized in that: The following steps are involved: Melting the ingredients of the set ratio into molten iron and performing molten iron treatment on the molten iron; Preheating and rotating the wheel hub inner ring casting mold, and evenly coating the coating on the inner wall of the wheel hub inner ring casting mold; After the coating is dried, pouring molten iron treated with molten iron into the hub inner ring casting mold; Keeping the wheel hub inner ring casting mold rotating; as well as After the molten iron solidifies and forms, the mold is removed, and the coating layer on the surface of the casting after demolding is removed to obtain a hub inner ring with a convex structure, wherein the average distribution density of the convex structure relative to the hub inner ring is between 15 and 50 per cm 2 .

9. The method for manufacturing a wheel hub inner ring according to claim 8, characterized in that: The coating comprises: 4% to 7% by mass of sodium bentonite; 15% to 25% by mass of diatomaceous earth; 0% to 5% by mass of 350 mesh quartz sand; 0.0005% to 0.01% by mass of alkyl sulfate; and The balance is water.

10. The method for manufacturing a wheel hub inner ring according to claim 8, characterized in that: When applying the coating, the rotation speed of the wheel hub inner ring casting mold is controlled between 700-1200r / min, and the temperature of the wheel hub inner ring casting mold is controlled between 200-300°C; when pouring molten iron into the wheel hub inner ring casting mold, the rotation speed of the wheel hub inner ring casting mold is controlled between 1000-1600r / min.

11. The manufacturing method according to claim 8, characterized in that: The material of the inner ring of the wheel hub includes ductile iron, and the temperature of the molten iron during pouring is 1380-1450°C.

12. A wheel hub assembly, characterized in that: The wheel hub assembly comprises a wheel hub inner ring (3) according to any one of claims 1 to 7, and further comprises: A wheel hub (1) located outside the wheel hub inner ring (3), wherein the wheel hub (1) is provided with a bearing hole (11); and A wheel hub bearing (2) located in a wheel hub inner ring (3), wherein the outer ring of the wheel hub bearing (2) is fixedly arranged on the inner circumferential surface of the hollow cylinder of the wheel hub inner ring (3); The wheel hub (1) is formed on the outer peripheral surface of the hollow cylinder of the wheel hub inner ring (3) by means of an inlay casting process, so that the joint surface between the wheel hub (1) and the wheel hub inner ring (3) has a plurality of recessed structures that match the plurality of raised structures.

13. The wheel hub assembly according to claim 12, characterized in that: The material of the wheel hub (1) comprises a light alloy, and the material of the wheel hub inner ring (3) comprises an iron-carbon alloy.

14. A method for manufacturing a wheel hub assembly according to any one of claims 12-13, characterized in that: The following steps are involved: a) Manufacturing of the wheel hub: the wheel hub inner ring manufactured by the manufacturing method of the wheel hub inner ring according to any one of claims 8 to 11 is arranged at the center hole position of the wheel hub casting mold, and the light alloy in liquid state is injected into the mold cavity of the wheel hub casting mold by insert casting, and the light alloy is demolded after cooling and shaping in the wheel hub casting mold, and after the wheel hub with the wheel hub inner ring is obtained, the wheel hub is machined to the target size; b) Assembly of wheel hub bearing and wheel hub inner ring: Install the wheel hub bearing to the inner circumference of the hollow cylinder of the wheel hub inner ring.

15. The method for manufacturing a wheel hub assembly according to claim 14, characterized in that: The casting method of injecting the molten liquid light alloy into the cavity of the wheel hub casting mold is pressure casting. During the pressure casting process, the liquid light alloy in the cavity of the wheel hub casting mold is kept warm and pressurized until the liquid light alloy is completely solidified.

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