Motor shell machining method based on numerical control machining

Abstract

The invention relates to a motor shell machining method based on numerical control machining, which comprises the following steps: S1, preparing an aluminum block blank and a pre-machined inner cylinder, and carrying out shape milling on the aluminum block blank to form a first shell semi-finished product with a preliminary shape; s2, primary rough machining is carried out on the first shell semi-finished product, so that a second shell semi-finished product with a mounting cavity and a speed reduction cavity is formed; s3, the inner cylinder is assembled into the mounting cavity of the second shell semi-finished product through hot pressing operation, then the inner cylinder is welded into the mounting cavity in a friction stir welding mode, and thus a third shell semi-finished product is obtained; s4, carrying out secondary rough machining on the third shell semi-finished product to obtain a fourth shell semi-finished product; and S5, stress release is conducted on the fourth shell semi-finished product in a natural aging mode, after stress release is completed, finish machining is conducted on the fourth shell semi-finished product, and therefore a shell finished product is obtained. Deformation in the machining process of the shell semi-finished product and the inner cylinder can be effectively reduced, and the machining precision and the assembly precision are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of machining, and in particular to a machining method for a motor housing based on numerical control machining. Background Art

[0002] Through the collaborative design of the double-cylinder cooling motor with a double-layer nested structure of the inner cylinder - outer cylinder and forced circulation of the coolant, an exponential optimization of the motor heat flux density is achieved, and it is widely used in new energy vehicles.

[0003] In the prior art, for the manufacture of the housing of a double-cylinder cooling motor, it includes a machining process and a welding process. The outer housing of the housing and the inner cylinder are respectively machined through the machining process. In the welding process, the inner cylinder is hermetically welded in the outer cylinder provided on the housing of the outer shell by means of gas shielded welding, so as to manufacture a housing suitable for a double-cylinder cooling motor. However, during the welding process, the local rapid heating and cooling of the inner cylinder and the outer cylinder result in welding stress and deformation in the weld area, thereby reducing the coaxiality between the inner cylinder and the outer cylinder, and further reducing the machining accuracy and affecting the subsequent assembly accuracy. Summary of the Invention

[0004] The applicant of the present invention aims at the above-mentioned disadvantages in the existing production technology, and provides a machining method for a motor housing based on numerical control machining, which can effectively reduce the deformation during the machining of the housing semi-finished product and the inner cylinder, improve the coaxiality between the inner cylinder and the installation cavity, and effectively improve the machining accuracy and assembly accuracy.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A machining method for a motor housing based on numerical control machining includes the following steps:

[0007] S1. Prepare an aluminum block blank and a pre-machined inner cylinder, and perform profile milling on the aluminum block blank to form a first housing semi-finished product with a preliminary profile.

[0008] S2. Perform a first rough machining on the first housing semi-finished product to form a second housing semi-finished product with an installation cavity and a reduction cavity.

[0009] S3. Assemble the inner cylinder into the installation cavity of the second housing semi-finished product through a hot pressing operation, and then weld the inner cylinder in the installation cavity by means of friction stir welding to obtain a third housing semi-finished product.

[0010] S4. Perform a second rough machining on the third housing semi-finished product to obtain a fourth housing semi-finished product.

[0011] S5. Use the natural aging method to release the stress of the fourth housing semi-finished product. After the stress release is completed, perform finish machining on the fourth housing semi-finished product to obtain the finished housing.

[0012] As a further improvement of the above technical solution:

[0013] In S3, the hot pressing operation includes the following steps:

[0014] First, keep the temperature at 180°C for 4 hours, so that the installation cavity of the second housing semi-finished product expands;

[0015] Subsequently, align and place the inner cylinder into the installation cavity;

[0016] Finally, wait for the second housing semi-finished product to cool naturally to lock the installation cavity, thus realizing the hot pressing assembly of the inner cylinder and the installation cavity.

[0017] The upper and lower tolerances of the outer circle of the inner cylinder are +0.07 and +0.09 respectively.

[0018] The upper and lower tolerances of the inner circle of the installation cavity are 0 and +0.02 respectively.

[0019] An interference fit method is adopted between the inner cylinder and the installation cavity, and the unilateral interference amount between the inner cylinder and the installation cavity is 0.04 mm.

[0020] In S3, when performing friction stir welding, the required effective welding depth is 3.5 mm or 4 mm.

[0021] In S3, when performing friction stir welding, the downward pressure generated by the welding head ranges from 0.8 T to 1.2 T.

[0022] In S5, under natural aging, the standing time of the fourth housing semi-finished product is at least 24 hours.

[0023] The aluminum block blank is forged from aluminum-magnesium alloy AZ91D material.

[0024] The beneficial effects of the present invention are as follows:

[0025] The structure of the present invention is compact and reasonable, and the operation is convenient. By setting five processing steps, it can effectively reduce the deformation during the processing of the housing semi-finished product and the inner cylinder, improve the coaxiality between the inner cylinder and the installation cavity, and effectively improve the processing accuracy and assembly accuracy; by adopting the hot pressing operation to assemble the inner cylinder into the installation cavity, it can ensure the tight fit between the inner cylinder and the installation cavity and improve the position accuracy of the housing finished product after assembly; by adopting the friction stir welding method to weld the inner cylinder to the installation cavity, it can be based on a slight rotational movement without applying external force to the workpiece, reduce the deformation and shrinkage generated during the welding process, and the joint is smoother after welding; by setting the stress release step, the residual stress inside the housing semi-finished product can be released, avoiding cracking or deformation caused by stress concentration after processing, and further improving the assembly accuracy. Description of the Drawings

[0026] Figure 1 Schematic structure of the finished housing in the present invention Figure 1 .

[0027] Figure 2 Schematic structure of the finished housing in the present invention Figure 2 .

[0028] Figure 3 Exploded view of the finished housing in the present invention.

[0029] Wherein: 1, housing body; 2, installation cavity; 3, inner cylinder; 4, gear mounting hole; 5, reduction cavity; 6, first assembly surface; 7, second assembly surface. Specific embodiments

[0030] The following combines the drawings to illustrate the specific embodiments of the present invention.

[0031] As Figures 1-3 shown, the motor housing processing method based on numerical control machining in this embodiment includes the following steps:

[0032] S1. Prepare an aluminum block blank and a pre-processed inner cylinder, and perform contour milling on the aluminum block blank to form a first housing semi-finished product with a preliminary contour;

[0033] In this embodiment, the aluminum block blank is forged from aluminum magnesium alloy AZ91D material, which is light in weight itself, and can ensure that the finished housing processed has the advantage of being light in weight; the aluminum block blank is cube-shaped. Before blanking, first perform data analysis on the motor housing drawing according to the design requirements, determine the processing difficulties and key dimensions, modify and compile the machine tool control program, and select an aluminum block blank with appropriate dimensions for blanking. Then, use a three-axis vertical numerical control machining equipment for contour milling, so as to mill the cube-shaped aluminum block blank into a first housing semi-finished product corresponding to the housing shape, which can maximize the utilization rate, reduce waste, and effectively control the production cost;

[0034] In addition, before assembling the inner cylinder and the housing semi-finished product, it is also necessary to pre-process the inner cylinder to obtain an inner cylinder with dimensional parameters, shape, and position tolerances all meeting the usage requirements.

[0035] S2. Perform a first rough machining on the first housing semi-finished product to form a second housing semi-finished product with an installation cavity and a reduction cavity;

[0036] Specifically, use a three-axis vertical numerical control machining equipment for the first rough machining. By roughing, most of the surplus can be quickly removed, so as to machine an installation cavity and a reduction cavity on the first housing semi-finished product;

[0037] In addition, it is also necessary to perform a first rough machining on the assembly end face of the installation cavity, the assembly end face of the reduction cavity, and the side assembly end face;

[0038] The mounting cavity assembly end face includes a first assembly face (the first assembly face is a flat face) for fitting and mounting with the motor cover, and the internal thread faces of several first threaded holes opened on the first assembly face;

[0039] The reduction cavity assembly end face includes the inner circumferential faces of several transmission gear mounting holes, a second assembly face for fitting and mounting with the lower box cover of the gearbox, and the internal thread faces of several second threaded holes opened on the second assembly face;

[0040] The side assembly end face includes a plurality of fourth assembly faces provided on the outer side wall surface of the machine shell for fitting and mounting with external accessories such as detection equipment.

[0041] S3. Assemble the inner cylinder into the mounting cavity of the second machine shell semi-finished product through hot pressing operation, and then weld the inner cylinder in the mounting cavity by friction stir welding to obtain the third machine shell semi-finished product;

[0042] In this embodiment, in order to obtain good friction stir welding effect and hot pressing effect, it is required that the upper and lower tolerances of the outer diameter of the inner cylinder are +0.07 and +0.09 respectively, the upper and lower tolerances of the inner diameter of the mounting cavity are 0 and +0.02 respectively, the inner cylinder and the mounting cavity adopt an interference fit method, and the unilateral interference amount between the inner cylinder and the mounting cavity is 0.04mm.

[0043] S3.1. The hot pressing operation includes the following steps:

[0044] First, place the second machine shell semi-finished product in an oven and keep it at a temperature of 180°C for 4 hours, so that the mounting cavity of the second machine shell semi-finished product expands;

[0045] Then, align and place the inner cylinder into the mounting cavity;

[0046] Finally, wait for the second machine shell semi-finished product to cool naturally so that the mounting cavity is locked, thus realizing the hot pressing assembly of the inner cylinder and the mounting cavity;

[0047] By heating the second machine shell semi-finished product in an oven at 180°C for 4 hours, the mounting cavity opened on the second machine shell semi-finished product can be uniformly expanded to facilitate the placement of the inner cylinder into the mounting cavity; after it cools down, the mounting cavity is uniformly locked, thus realizing the fixation between the inner cylinder and the mounting cavity. Adopting the hot pressing operation can ensure the tight fit and position accuracy between the outer wall surface of the inner cylinder and the inner wall surface of the mounting cavity.

[0048] When performing friction stir welding, it is required that the effective welding depth is 3.5mm or 4mm, which can enhance the connection strength and sealing performance between the motor and the mounting cavity.

[0049] S3.3. When performing friction stir welding, the downward pressure generated by the welding head ranges from 0.8T to 1.2T. In addition, it is required to set solid materials below the weld seam for support to prevent product deformation.

[0050] Friction stir welding refers to the process of locally melting the welded material by using the heat generated by the friction between a high-speed rotating welding tool and the workpiece. When the welding tool moves forward along the weld seam, the plasticized material flows from the front of the welding tool to the rear under the action of the rotational friction force of the welding tool, and a dense solid-phase weld seam is formed under the extrusion of the welding tool. It is suitable for welding between aluminum materials, and the resulting weld seam is strong. At the same time, friction stir welding is based on a slight rotational movement, without applying external force to the workpiece, reducing the deformation and shrinkage generated during the welding process, and making the joint smoother after welding.

[0051] S4. Perform secondary rough machining on the third housing semi-finished product to obtain the fourth housing semi-finished product;

[0052] Specifically, use a three-axis vertical CNC machining equipment to perform secondary rough machining on the installation cavity (i.e., its inner circumferential surface), the assembly end face of the installation cavity, the assembly end face of the reduction cavity, and the side assembly end face, and adjust the dimensions and shapes to provide a basis for subsequent finish machining.

[0053] S5. Use natural aging to release the stress of the fourth housing semi-finished product. After the stress release is completed, perform finish machining on the fourth housing semi-finished product to obtain the housing finished product;

[0054] In this embodiment, the housing finished product includes a housing body 1. An installation cavity 2 and a reduction cavity 5 are respectively formed on the housing body 1. An inner cylinder 3 is fitted and installed in the installation cavity 3, and several gear installation holes 4 are formed in the reduction cavity 5;

[0055] A first assembly surface 6 is formed on the top wall surface of the housing body 1, and a second assembly surface 7 is formed on the bottom wall surface of the housing body 1.

[0056] In this embodiment, under natural aging, the standing time of the fourth housing semi-finished product is at least 24h. By performing stress release treatment on the fourth housing semi-finished product after rough machining, the residual stress inside the material can be released, thereby reducing the deformation during subsequent processing and use, avoiding cracking and deformation caused by stress concentration after processing, and effectively improving the stability and reliability of the product.

[0057] After the stress release is completed, use a five-axis horizontal CNC machining equipment to perform finish machining, and perform finish machining on the installation cavity (i.e., its inner circumferential surface), the assembly end face of the installation cavity, the assembly end face of the reduction cavity, and the side assembly end face of the fourth housing semi-finished product respectively to obtain the housing finished product; through finish machining, further improve the dimensional accuracy and surface quality of the housing finished product to ensure that the finished product meets the design requirements and improve the overall performance and reliability of the product.

[0058] In addition, since the motor housing of this embodiment is made of aluminum-magnesium alloy AZ91D material, cutting fluid is required during the processes of contour milling, primary rough machining, secondary rough machining, and finish machining to improve machining efficiency, extend the tool life, improve the surface quality, and maintain the geometric accuracy of the workpiece.

[0059] The above description is an explanation of the present invention, not a limitation thereof. The scope defined by the present invention is referred to the claims, and any form of modification can be made within the protection scope of the present invention.

Claims

1. A machining method for a motor housing based on numerical control machining, characterized in that: It includes the following steps: S1. Prepare an aluminum block blank and a pre-processed inner cylinder, and perform contour milling on the aluminum block blank to form a first semi-finished housing with a preliminary contour. S2. Perform primary rough machining on the first semi-finished housing to form a second semi-finished housing with an installation cavity and a reduction cavity. S3. Assemble the inner cylinder into the installation cavity of the second semi-finished housing through hot pressing operation, and then weld the inner cylinder in the installation cavity by friction stir welding to obtain a third semi-finished housing. S4. Perform secondary rough machining on the third semi-finished housing to obtain a fourth semi-finished housing. S5. Release the stress of the fourth semi-finished housing by natural aging. After the stress release is completed, perform finish machining on the fourth semi-finished housing to obtain a finished housing.

2. The machining method of the motor housing based on numerical control machining according to claim 1, wherein: In S3, the hot pressing operation includes the following steps: First, place the second semi-finished housing in an oven and keep it at a temperature of 180°C for 4 hours, so that the installation cavity of the second semi-finished housing expands. Subsequently, align and place the inner cylinder into the installation cavity. Finally, wait for the second semi-finished housing to cool naturally so that the installation cavity locks, thereby realizing the hot pressing assembly of the inner cylinder and the installation cavity.

3. The machining method of the motor housing based on numerical control machining according to claim 2, wherein: The upper and lower tolerances of the outer circle of the inner cylinder are +0.07 and +0.09 respectively.

4. A method for machining a motor housing based on numerical control machining according to claim 2, characterized in that: The upper and lower tolerances of the inner circle of the installation cavity are 0 and +0.02 respectively.

5. The machining method of a motor housing based on numerical control machining according to claim 2, characterized in that: An interference fit is adopted between the inner cylinder and the installation cavity, and the unilateral interference amount between the inner cylinder and the installation cavity is 0.04 mm.

6. The machining method of a motor housing based on numerical control machining according to claim 1, characterized in that: In S3, when performing friction stir welding, the required effective welding depth is 3.5 mm or 4 mm.

7. A machining method for a motor housing based on numerical control machining according to claim 1, characterized in that: In S3, when performing friction stir welding, the downward pressure generated by the welding head ranges from 0.8 T to 1.2 T.

8. A machining method for a motor housing based on numerical control machining according to claim 1, characterized in that: In S5, under natural aging, the standing time of the fourth semi-finished housing is at least 24 hours.

9. A method for machining a motor housing based on numerical control machining according to claim 1, characterized in that: The aluminum block blank is forged from aluminum magnesium alloy AZ91D material.

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