Method of manufacturing a shaft

Abstract

The present application provides a shaft manufacturing method capable of expanding the range of choices of materials for pipe members and also capable of improving mass productivity. The shaft manufacturing method is a method of manufacturing a shaft (1) provided with a joint member (3) at the end of a cylindrical member (2), and the shaft manufacturing method includes the following steps: a grinding step of grinding the end surface of a metal plate material; a bending step of bending the metal plate material into a cylindrical shape or an arc shape; a diffusion bonding step of butting the ground end surfaces of the metal plate materials opposite each other in the state of being bent into a cylindrical shape, or butting the ground end surfaces of a plurality of metal plate materials bent into an arc shape into a cylindrical shape, and performing diffusion bonding by heating the butted portions, thereby forming the cylindrical member (2); a cooling step of cooling the cylindrical member (2) after the diffusion bonding step; and a joint member bonding step of bonding the joint member (3) to the end of the cylindrical member (2).

Description

Technical Field

[0001] This invention relates to a method for manufacturing a shaft. Background Technology

[0002] As shafts for motors and the like, hollow shafts are sometimes used where the two ends of an existing tubular component are joined by friction pressing to form connecting parts equipped with gears or splines (see Patent Document 1). For example, hollow shafts are often used in applications where lightweighting is a strong requirement, such as shafts for electric vehicle (EV) motors.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-258236 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, when using readily available tubular components, one must choose from off-the-shelf products prepared in advance by the manufacturer, which limits the available materials.

[0008] The present invention was made in view of the above-mentioned situation, and its object is to provide a method for manufacturing shafts that has not existed until now, which can expand the range of materials to be selected for tubular components and also improve mass production.

[0009] Methods for solving problems

[0010] The main points of the invention will be described with reference to the accompanying drawings.

[0011] The first aspect of the present invention is a method for manufacturing a shaft, wherein a shaft 1 is provided with a connecting member 3 at the end of a cylindrical component 2, characterized in that the method for manufacturing the shaft includes the following steps: a grinding step, grinding the end faces of a metal sheet; a bending step, bending the metal sheet into a cylindrical or arc shape; a diffusion bonding step, abutting the ground end faces of the metal sheets in the bent cylindrical state together, or arranging multiple metal sheets bent into an arc shape into a cylindrical shape and abutting the ground end faces of the multiple metal sheets together, heating the abutting portion to perform diffusion bonding, thereby forming the cylindrical component 2; a cooling step, cooling the cylindrical component 2 after the diffusion bonding step; and a connecting member bonding step, bonding the connecting member 3 to the end of the cylindrical component 2.

[0012] Furthermore, the second aspect of the present invention is a shaft manufacturing method according to the first aspect, characterized in that, in the grinding process, grinding is performed in such a way that the surface roughness Ra of the end face of the metal plate is less than 2 μm.

[0013] Furthermore, the third aspect of the present invention is a shaft manufacturing method according to any one of the first and second aspects, characterized in that the shaft manufacturing method includes an external finishing process for finishing the outer surface of the connection portion between the cylindrical component 2 and the connecting component 3.

[0014] Furthermore, the fourth aspect of the present invention is a shaft manufacturing method according to any of the first to third aspects, characterized in that the shaft manufacturing method includes an internal finishing process for finishing the inner surface of the mating portion of the cylindrical component 2.

[0015] Furthermore, the fifth aspect of the present invention is a method for manufacturing a shaft according to any of the first to fourth aspects, characterized in that the connecting component joining process is performed by friction pressing or hot pressing.

[0016] Furthermore, the sixth aspect of the present invention is a method for manufacturing a shaft according to the fifth aspect, characterized in that the connecting component joining process is performed in the cooling process.

[0017] Furthermore, the seventh aspect of the present invention is a method for manufacturing a shaft according to any of the first to sixth aspects, characterized in that, in the bending process, the metal sheet is bent into a semi-cylindrical shape, and in the diffusion bonding process, the ground end faces of a pair of semi-cylindrical metal sheets are joined together to perform diffusion bonding.

[0018] Furthermore, the eighth aspect of the present invention is a method for manufacturing a shaft, wherein a shaft 1 is provided with a connecting member 3 at the end of a cylindrical component 2, characterized in that the method for manufacturing the shaft includes the following steps: a bending step, in which a metal sheet is bent into a cylindrical or arc shape; a diffusion bonding step, in which the end faces of the metal sheets facing each other in the bent cylindrical state are joined together, or multiple metal sheets bent into arc shapes are arranged into a cylindrical shape and the end faces of the multiple metal sheets are joined together, and the joined portion is heated to perform diffusion bonding, thereby forming the cylindrical component 2; a cooling step, in which the cylindrical component 2 after the diffusion bonding step is cooled; and a connecting member bonding step, in which the connecting member 3 is joined to the end of the cylindrical component 2 by friction pressing or hot pressing, wherein the connecting member bonding step is performed in the cooling step.

[0019] Furthermore, the ninth aspect of the present invention is a method for manufacturing a shaft according to any one of the first to eighth aspects, characterized in that the shaft 1 is the shaft 1 of a motor for an electric vehicle.

[0020] Invention Effects

[0021] As described above, this invention is therefore a shaft manufacturing method that has not existed until now, which can expand the range of materials to be selected for tube components and further improve mass production. Attached Figure Description

[0022] Figure 1 It is a schematic three-dimensional diagram showing a portion of the shaft after it has been cut out.

[0023] Figure 2 This is a schematic diagram illustrating the motor used in EVs.

[0024] Figure 3 This is a process description diagram of Example 1.

[0025] Figure 4 This is a process description diagram of Example 2. Detailed Implementation

[0026] The function of the invention is illustrated with reference to the accompanying drawings, and preferred embodiments of the invention are briefly described.

[0027] A metal sheet is bent into a cylindrical shape, and the opposite ends are joined together to form a diffuse joint, thereby creating a cylindrical component 2 that serves as the main body of the shaft 1. Furthermore, a connecting component 3, which has gears or splines formed on it, is joined to the end of the cylindrical component 2 by friction pressing or hot pressing, thereby obtaining a shaft 1 for a rotating body such as an EV motor.

[0028] At this point, the cylindrical component 2 is manufactured by bending a metal sheet into a cylindrical shape and then performing diffusion bonding. Therefore, the range of materials that can be selected is relatively large, enabling the formation of hollow shafts made from materials suitable for various applications. That is, through diffusion bonding, even steels with a high carbon content (high-carbon steel) or alloy steels with a high alloy content (high-alloy steel) can be formed into cylindrical components without quenching cracks. In contrast, when welding bent metal sheets, quenching cracks are easily generated during welding, limiting the available materials to low-carbon steel or low-alloy steel.

[0029] Alternatively, cylindrical components can be manufactured in the same manner as described above by bending a metal sheet into an arc shape, arranging the bent metal sheet into multiple cylindrical shapes, and joining opposite ends together for diffusion bonding.

[0030] Furthermore, diffusion welding does not require large equipment (such as forging machines) and can be achieved using versatile equipment such as vacuum furnaces with heating devices.

[0031] In addition, the present invention grinds the ends of the metal sheet that will become the bonding surface by means of a grinding process before diffusion bonding, thereby enabling diffusion bonding to be performed efficiently in a shorter time and thus improving mass production capability accordingly.

[0032] Therefore, according to the present invention, by using, for example, a high-strength alloy steel that is not available in readily available tubular components, a lightweight shaft 1 and the like can be manufactured with high strength most suitable for use in EV motors.

[0033] In addition, for example, when cooling the cylindrical component 2 after diffusion bonding, the connecting component 3 can also be joined by friction pressing or hot pressing. In this case, the heat during diffusion bonding can be utilized, and the heating process before joining the connecting component can be omitted after diffusion bonding in the diffusion bonding equipment (vacuum chamber), thereby enabling the manufacture of a hollow shaft with extremely high efficiency.

[0034] Example 1

[0035] A specific embodiment 1 of the present invention will be described with reference to the accompanying drawings.

[0036] This embodiment describes a method for manufacturing a hollow shaft 1 with a connecting component 3 at the end of a cylindrical component 2.

[0037] Specifically, the process includes the following steps: a cutting step, cutting a metal sheet from the base material; a grinding step, grinding the end faces of the metal sheet; a bending step, bending the metal sheet into a cylindrical shape; a diffusion bonding step, joining the ground end faces of the metal sheets in the bent cylindrical state together, heating the joined portion to perform diffusion bonding, thereby forming the cylindrical component 2; a cooling step, cooling the cylindrical component 2 after the diffusion bonding step; a connecting component joining step, joining the connecting component 3 to the end of the cylindrical component 2; and an external finishing step.

[0038] like Figure 1 As shown, in this embodiment, the shaft 1 has metal connecting parts 3, which are provided with gears or splines, at both ends of the metal cylindrical component 2. For example, it is used as... Figure 2 The EV motor shaft 1 is shown as depicted. Figure 2 In the diagram, number 4 is the rotor, number 5 is the stator, number 6 is the housing, and number 7 is the bearing.

[0039] Cylindrical component 2 is formed by bending a metal sheet into a cylindrical shape and then bonding opposite ends together. The metal sheet can be a steel sheet or a non-ferrous metal sheet (e.g., high-tensile steel sheet, stainless steel sheet, or titanium alloy sheet, etc.) cut to a specified size.

[0040] Each process is described in detail.

[0041] In the cutting process, a metal sheet B of a specified size is cut from the base material A. Figure 3 (a)

[0042] In the grinding process, the opposite ends of the metal sheet B, which are bent into a cylindrical shape during the bending process, are ground. Specifically, both ends are ground to a surface roughness Ra of less than 2 μm. This grinding process allows for good diffusion of atoms in the bonding surface, resulting in a strong diffusion bond that is formed in a short time.

[0043] Next, in the bending process, the metal sheet B, whose ends have been ground, is rolled into a cylindrical shape using a forging or bending roller machine, etc. Figure 3 (b) In the case of sheet materials made of high-strength materials or sheet materials with large thickness, the sheet is rolled up while being heated to a warm state (around 300℃~800℃) or a hot state (around 1000℃~1300℃). Alternatively, the order of the grinding process and the bending process can be reversed.

[0044] Next, in the diffusion bonding process, the metal sheets are placed in a vacuum furnace (diffusion bonding furnace C), and the ground end faces of the rolled cylindrical metal sheets are joined together. A rod-shaped jig with a circumferential surface along the inner surface of the metal sheet is placed on the inside, and a cylindrical jig with a circumferential surface along the outer surface of the metal sheet is placed on the outside. The mating parts are clamped from both inside and outside and pressed under a specified pressure (approximately 5 MPa to 10 MPa), and heated to approximately 900°C to 1000°C, and held for a specified time (tens of minutes to several hours). Figure 3 (c)). Additionally, during heating and holding, the temperature is maintained for 10 minutes inside a vacuum furnace. -6 Pa~10 -3 A vacuum atmosphere of approximately Pa.

[0045] By using diffusion bonding, homogeneous strength and properties can be obtained throughout the circumference compared to bonding using welding.

[0046] Next, in the cooling process, the heating is stopped, and the cylindrical component 2 after the diffusion bonding process is naturally cooled in a vacuum furnace.

[0047] Next, in the connecting component joining process, the connecting components 3, which have gear portions or splines, are joined by friction pressing or hot pressing.Figure 3 (d)

[0048] Friction pressing is performed using a standard friction pressing machine. Alternatively, hot pressing is performed, for example, at a temperature of 150°C to 180°C.

[0049] Next, in the outer finishing process, cutting, grinding, and other finishing processes are performed to remove unevenness or other defects on the outer surface of the connection between the cylindrical component 2 and the connecting component 3. Figure 3 (e)).

[0050] Furthermore, the connecting component 3 adopts the following structure: after hollowing the material by cold forging or hot forging in a manner where the diameter gradually decreases towards the outer edge, a gear portion or spline portion is formed on the outer surface by machining (cutting, gear machining, spline rolling, etc.). Additionally, the friction contact surface with the cylindrical component 2 is formed by cutting.

[0051] The shaft 1 can be formed through the above processes, but an internal finishing process may also be included as needed. The internal finishing process is performed after the diffusion bonding process and before the connecting component bonding process. It is a finishing process such as cutting and grinding to remove unevenness or other defects on the inner surface of the mating part of the cylindrical component 2.

[0052] Additionally, depending on the requirements, the joining process of connecting components can also be performed during the cooling process.

[0053] Specifically, the connecting component 3 can be joined to the end of the cylindrical component 2 by friction pressing or hot pressing after a predetermined temperature is reached during the cooling process of the cylindrical component 2 after diffusion bonding. For example, to prevent oxidation, the cylindrical component 2 can be placed in a vacuum furnace until it reaches approximately 200°C, and then removed from the vacuum furnace for hot pressing after reaching approximately 200°C. In this case, the heat from the diffusion bonding can be used to join the connecting component 3. Then, it can be naturally cooled to room temperature.

[0054] Alternatively, the diffusion bonding process, cooling process, and connecting component bonding process can be performed in the same vacuum furnace. That is, the cylindrical component 2 can be joined without removing it from the vacuum furnace after diffusion bonding, and the connecting component 3 can be joined after reaching the specified temperature, and the joined cylindrical component 2 and connecting component 3 can be removed after cooling.

[0055] As described above, this embodiment allows for a wide range of material choices, enabling the formation of shaft 1 using materials suitable for various applications. That is, through diffusion bonding, even high-carbon steel or high-alloy steel can be formed into cylindrical components without quenching cracks.

[0056] Furthermore, diffusion welding does not require large equipment and can be achieved using versatile equipment such as vacuum furnaces with heating devices.

[0057] In addition, the ends of the metal sheets that will become the bonding surface are ground by a grinding process before diffusion bonding, which enables diffusion bonding to be performed efficiently in a shorter time, thereby improving mass production capability.

[0058] Therefore, by using high-strength alloy steel, which is not available in readily available tubular components, it is possible to manufacture lightweight shafts, etc., with high strength that is most suitable for EV motor applications.

[0059] Therefore, this embodiment becomes a shaft manufacturing method that can expand the range of materials to be selected for tube components, and further improve mass production capabilities.

[0060] Example 2

[0061] In Example 1, a cylindrical component 2 is obtained by rolling a metal sheet into a cylindrical shape and then performing diffusion bonding. In contrast, in this example, multiple metal sheets (each forming part of a cylindrical component) are bent into arc shapes, and the cylindrical component 2 is obtained by arranging them into a cylindrical shape and then performing diffusion bonding.

[0062] Specifically, in this embodiment, during the bending process, the metal sheet B is clamped using the upper die D (punch) and the lower die E (die), and by making... Figure 4 As shown in (a), the two metal sheets B cut from the parent material A are bent into semi-cylindrical shapes, mimicking the concavity and convexity of the upper and lower molds. Figure 4 (b) Therefore, bending time is reduced, and the required molds are also reduced.

[0063] Then, the end faces of the pair of semi-cylindrical metal plates B are joined together facing each other, and a diffusion joint is performed on the joined ends to obtain the cylindrical component 2. Figure 4 (c)).

[0064] Subsequently, similarly to Embodiment 1, the connecting member 3, on which the gear portion or spline portion is formed, is joined to both ends of the cylindrical member 2 by friction pressing or hot pressing. Figure 4 (d) Next, in order to remove the unevenness or other defects on the outer surface of the connection between the cylindrical component 2 and the connecting component 3, finishing processes such as cutting and grinding are performed. Figure 4 (e)).

[0065] In the diffusion bonding process of this embodiment, two semi-cylindrical metal plates are clamped and pressed from above and below by a jig to be arranged opposite each other in a cylindrical shape, and the mating end faces are pressurized and heated to be held for a predetermined time. As the jig for clamping and pressing from above and below, a jig is used that is set as a pair of upper and lower jigs and has a concave curved surface along the outer peripheral surface (convex curved surface) of each semi-cylindrical metal plate.

[0066] Alternatively, when using a jig to clamp and press from above and below, a cylindrical (or cylindrical) jig that supports the metal plate from the inside can be pre-positioned on the inside of the semi-cylindrical metal plate.

[0067] Furthermore, by using two semi-cylindrical metal plates, when finishing the mating end faces, the parallel end faces can be mated together simply by setting a horizontal plane (without needing to calculate the angle of the end faces), making grinding and other processes easy and inexpensive. In addition, the pressure vector used for diffusion bonding can be in the vertical direction (the direction perpendicular to the mating end faces), which makes it easy to apply pressure (and maintain it) (simplifying the construction of the fixture).

[0068] In addition, in this embodiment, the cylindrical component 2 is formed from two metal sheets (of approximately the same shape) bent into a semi-cylindrical shape, but the cylindrical component 2 may also be formed from three or more metal sheets (of approximately the same shape) bent into an arc shape.

[0069] The rest is the same as in Example 1.

Claims

1. A method for manufacturing a shaft, comprising manufacturing a shaft having a connecting component provided at the end of a cylindrical component, characterized in that, The manufacturing method of this shaft includes the following steps: The grinding process involves grinding the end face of the metal sheet to achieve a surface roughness Ra of less than 2μm. The bending process involves bending the metal sheet into a semi-cylindrical shape. In the diffusion bonding process, a pair of metal plates bent into a semi-cylindrical shape are arranged into a cylindrical shape so that the ground end faces of the pair of metal plates are directly joined together. The joined part is heated to perform diffusion bonding, thereby forming the cylindrical component. A cooling process is used to cool the cylindrical component after the diffusion bonding process; The connecting component joining process involves joining the connecting component to the end of the cylindrical component; and The internal finishing process involves cutting or grinding the inner surface of the mating portion of the cylindrical component after the diffusion bonding process. In the diffusion bonding process, the end faces of the two semi-cylindrical metal plates, which are parallel horizontal planes, are directly abutted together. The end faces are then diffuse-bonded as a whole while being pressed together in a direction perpendicular to the end faces. The diffusion bonding process, the cooling process, and the connecting component bonding process are performed in the same vacuum furnace, and the connecting component bonding process utilizes the heat generated during the diffusion bonding.

2. The method for manufacturing a shaft according to claim 1, characterized in that, The method for manufacturing the shaft includes an external finishing process for finishing the outer surface of the connection between the cylindrical component and the connecting component.

3. The method for manufacturing a shaft according to claim 1, characterized in that, The connection component joining process is carried out by friction pressing or hot pressing.

4. The method for manufacturing a shaft according to claim 3, characterized in that, The joining process of the connecting components is carried out in the cooling process.

5. The method for manufacturing a shaft according to any one of claims 1 to 4, characterized in that, The shaft is the shaft of a motor used in electric vehicles.

6. A method for manufacturing a shaft, comprising manufacturing a shaft having a connecting component provided at the end of a cylindrical component, characterized in that, The manufacturing method of this shaft includes the following steps: The grinding process involves grinding the end faces of the metal sheet. The bending process involves bending the metal sheet into a semi-cylindrical shape. In the diffusion bonding process, a pair of metal plates bent into a semi-cylindrical shape are arranged into a cylindrical shape so that the ground end faces of the pair of metal plates are directly joined together. The joined part is heated to perform diffusion bonding, thereby forming the cylindrical component. A cooling process is performed to cool the cylindrical component after the diffusion bonding process; and In the connecting component joining process, during the cooling process, the connecting component is joined to the end of the cylindrical component by friction pressing or thermoforming. In the diffusion bonding process, the end faces of a pair of semi-cylindrical metal plates, which are parallel horizontal planes, are abutted together, and the end faces are diffusely bonded together by pressing them together in a direction perpendicular to the end faces. The diffusion bonding process, the cooling process, and the connecting component bonding process are performed in the same vacuum furnace, and the connecting component bonding process utilizes the heat generated during the diffusion bonding.

7. The method for manufacturing a shaft according to claim 6, characterized in that, In the grinding process, the grinding is carried out in a manner that makes the surface roughness Ra of the end face of the metal sheet less than 2 μm.

8. The method for manufacturing a shaft according to claim 6, characterized in that, The method for manufacturing the shaft includes an external finishing process for finishing the outer surface of the connection between the cylindrical component and the connecting component.

9. The method for manufacturing a shaft according to claim 6, characterized in that, The method for manufacturing the shaft includes an internal finishing process for finishing the inner surface of the mating portion of the cylindrical component.

10. A method for manufacturing a shaft according to any one of claims 6 to 9, characterized in that, The shaft is the shaft of a motor used in electric vehicles.

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