Method and apparatus for eliminating bowl plug press-in trim

Abstract

This invention relates to the field of machining and assembly technology, and particularly to a method and apparatus for eliminating the cutting edge during the pressing of a bowl-shaped plug. The method includes: making an arc chamfer at the opening of the bowl-shaped plug hole, so that the arc chamfer forms a tangential transition with the inner hole of the bowl-shaped plug hole, thereby eliminating the sharp angle at the junction of the hole diameter and the chamfer, allowing the bowl-shaped plug to make smooth contact with the tangential arc during the pressing process into the bowl-shaped plug hole. The apparatus includes: a tool with a tangential arc chamfer, a tool holder, a CNC machine tool, and a workpiece. By adopting the technical solution of this invention, the cutting edge problem during the pressing process of the bowl-shaped plug can be completely eliminated from the root, eliminating the need for manual removal of the cutting edge, improving the cleanliness of the part and the sealing reliability, while significantly reducing the maximum pressing force.

Description

Technical Field

[0001] This application relates to the field of machining and assembly technology, and in particular to a method and apparatus for eliminating the pressing-in of a bowl-shaped plug edge. Background Technology

[0002] Cup-shaped plugs are widely used for sealing oil passages, water passages, and air passages in engine blocks, cylinder heads, and other components. An interference fit is used between the cup-shaped plug and its bore to achieve a seal. The opening of the cup-shaped plug bore is typically machined with a chamfer of 30° to 45° to guide the cup-shaped plug during the pressing process.

[0003] In existing technologies, the pressing method for cup-shaped inserts typically involves using a press or manual tapping to force the insert into the cup-shaped insert hole. However, during the pressing process, the sharp corners of the cup-shaped insert and the orifice chamfer are squeezed and cut, causing material to be cut off from the surface of the cup-shaped insert, resulting in cut edges that adhere to the orifice or detach from the part surface. This not only leads to serious cleanliness issues but also damages the surface material of the cup-shaped insert, potentially causing leaks or even insert detachment. Moreover, the larger the interference fit, the more cut edges are generated, and the more severe the material damage.

[0004] To address the aforementioned issues, some existing technologies attempt to reduce edge trimming by using high-strength cup-shaped plug materials or reducing the interference fit. However, these solutions only mitigate the degree of edge trimming and cannot fundamentally eliminate it. Furthermore, reducing the interference fit can also affect sealing performance.

[0005] Existing technologies primarily focus on improving the sealing effect by altering the structure of the cup-shaped plug itself (such as reducing its diameter or changing the cone angle) or by applying sealant. Furthermore, while one existing technology mentions that the sharp edge of the orifice might cut through the oil seal, its proposed solution focuses on machining a 3-5mm radius chamfer at the orifice, which is essentially a conventional solution with a larger chamfer, completely different from the technical concept of this invention. Therefore, there is an urgent need for a method and apparatus that can completely eliminate the pressing of the cup-shaped plug into the cut edge. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for eliminating the cut edge of the cup-shaped plug, so as to solve the problem that the existing technology cannot fundamentally eliminate the cut edge of the cup-shaped plug and the poor sealing performance.

[0007] This invention provides the following solution:

[0008] A method for eliminating the pressing of a bowl-shaped plug into the cut edge includes:

[0009] A rounded chamfer is made at the opening of the bowl-shaped plug hole so that the rounded chamfer forms a tangential transition with the inner hole of the bowl-shaped plug hole, thereby eliminating the sharp corner at the junction of the diameter of the bowl-shaped plug hole and the chamfer at the opening, so that the bowl-shaped plug makes smooth contact with the tangential arc during the process of pressing into the bowl-shaped plug hole.

[0010] Optionally, the rounded chamfer is a small tangent rounded chamfer, the radial dimension of which is not less than the thickness of the cut edge produced when the bowl-shaped plug is pressed in.

[0011] Optionally, the radial dimension is 0.05 mm to 0.15 mm.

[0012] Optionally, the inner hole of the bowl-shaped plug hole is tangent to the arc chamfer and the outer end of the arc chamfer retains the original chamfer.

[0013] According to another aspect of the present invention, a processing apparatus for eliminating the pressing edge of a bowl-shaped plug is provided, comprising: a tool with a tangential circular arc chamfer, the tool being configured to finish the diameter of the bowl-shaped plug hole and to perform a small tangential circular arc chamfer on the opening of the bowl-shaped plug hole at the finishing end;

[0014] The tool holder is connected to the tool with the tangential circular arc chamfer.

[0015] CNC machine tool, wherein the tool holder is mounted on the CNC machine tool;

[0016] And the workpiece being processed, which has the aforementioned bowl-shaped plug hole;

[0017] The tool with tangent circular arc chamfering, after finishing the diameter of the bowl-shaped plug hole, processes a small circular arc chamfer at the hole opening that is tangent to the finished diameter.

[0018] Optionally, the tool with tangent circular arc chamfer is a tool that integrally forms a fine-machining hole diameter and a small tangent circular arc chamfer at the hole opening.

[0019] Optionally, it also includes a tool setter, on which the tool with tangent circular arc chamfer and the tool holder are set and the tool compensation value is extracted. By positioning the workpiece on the special fixture and controlling the CNC tool compensation value of the CNC machine tool, the positional accuracy of the bowl-shaped plug hole and the machining depth of the micro tangent circular arc chamfer are controlled.

[0020] Optionally, the roughing and chamfering of the bowl-shaped plug hole are performed on the same CNC machine tool as the finishing process.

[0021] Optionally, the chamfering tool with tangential arc includes an arc insert with an arc radius of 0.8 mm to 1.5 mm, and the axial machining allowance of the micro tangential arc chamfer is 0.3 mm to 0.6 mm.

[0022] Optionally, after the chamfered tool with tangent arc chamfer completes the machining of the small tangent arc chamfer, its hypotenuse does not interfere with the original chamfer of the opening of the bowl-shaped plug hole.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention completely eliminates shavings, significantly improving cleanliness and sealing reliability. By machining a tiny, perfectly tangent arc transition at the orifice of the cup-shaped plug, it fundamentally eliminates the sharp corner at the junction of the orifice diameter and the chamfered orifice, a problem found in previous technologies. When the cup-shaped plug is press-fitted in, its surface is no longer cut by the sharp corner of the orifice, thus completely preventing shavings. This improvement avoids cleanliness issues caused by shavings adhering to the orifice or falling off the part surface, and also eliminates sealing failures such as leakage and detachment caused by damage to the surface material of the cup-shaped plug. Compared to existing technologies that use high-strength materials or reduce the interference fit, which only "mitigate" but not "eliminate" shavings, this invention solves the problem at its geometrical source, eliminating the need for subsequent manual removal of shavings. This improves production efficiency and ensures consistent part cleanliness and long-term sealing reliability.

[0025] In particular, because the sharp corner of the orifice is eliminated, the cup-shaped plug is no longer affected by cutting resistance during the pressing process, resulting in a smoother pressing action. According to actual measurements, after adopting the method of this invention, the maximum pressing force of the cup-shaped plug is reduced from 10.833KN in the original technology (with sharp corners) to 5.411KN, a reduction of approximately half. This significant decrease in pressing force directly reduces the power requirements of pressing equipment (such as electric cylinders and hydraulic cylinders), allowing for the selection of smaller, lower-cost power sources, thereby reducing the investment cost of pressing equipment. Simultaneously, the smoother pressing process and reduced resistance fluctuations effectively reduce the noise level generated during pressing, improving the working environment.

[0026] In particular, the micro-tangential circular arc chamfering of this invention requires only the removal of an extremely thin allowance of 0.05mm to 0.15mm in the radial direction and 0.3mm to 0.6mm in the axial direction, resulting in a very small cutting amount. Therefore, even if the hole finishing and circular arc chamfering are combined on the same tool, there will be no significant increase in the overall cutting force of the tool, no reduction in tool life, and no impact on the machining accuracy and surface quality of the hole. Furthermore, since the interference of the cutting edge on the pressing process is eliminated, the pressure-displacement curve during the pressing of the cup-shaped plug can accurately reflect the changes in frictional resistance and the yield strength of the material. This significantly improves the fit between the finite element analysis results and the actual pressing results, providing a reliable basis for the accurate simulation and optimized design of the assembly process. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the structure of the bowl-shaped plug being pressed into the bowl-shaped plug hole of the present invention;

[0028] Figure 2 yes Figure 1 A magnified view of the chamfered area where the bowl-shaped plug enters the orifice;

[0029] Figure 3 yes Figure 2 A further enlarged view of the slit edge formed by the extrusion of the sharp corner shows the state before the sharp corner was treated;

[0030] Figure 4 yes Figure 3 The finished product image after the sharp corner has been rounded into a tangent arc;

[0031] Figure 5 This is a schematic diagram of the combined processing of the tangent arc chamfer of the bowl-shaped plug hole in this invention;

[0032] Figure 6 yes Figure 5 Enlarged view of the intermediate and precision machined holes and the rounded chamfers;

[0033] Figure 7 yes Figure 6 A further enlarged view of the machining process, including the removal of sharp corners using a medium-precision machining method and the diameter of the bore.

[0034] Figure 8 yes Figure 7 The finished product after finishing;

[0035] Figure 9 It is a pressure-displacement curve of the cup-shaped plug insertion process when using existing technology (with sharp corners);

[0036] Figure 10 It is a pressure-displacement curve diagram of the cup-shaped plug pressing process when the method of the present invention (forming a tangent circular arc) is used.

[0037] Explanation of the reference numerals in the figure:

[0038] 1. Chamfering tool with tangent circular arc; 2. Tool holder; 3. Machine tool; 4. Part (before machining); 4-1. Cut-off sharp corner; 4-2. Part with a small tangent circular arc after cutting off the sharp corner; 5. Cup-shaped insert; 6. Contouring pressure head; 7. Power source. Detailed Implementation

[0039] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] In the description of this invention, it should be understood that the terms "front," "rear," "axial," etc., indicating orientation or positional relationships are based on the orientation that the operator is accustomed to facing during testing, and are only for the convenience and simplification of description. They do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "installation," "connection," and "fixing" should be interpreted broadly, for example, referring to a fixed connection, a detachable connection, or an integral connection, unless otherwise explicitly specified and limited.

[0041] Example 1:

[0042] like Figure 1-4 As shown, this embodiment provides a method for eliminating the pressing of the bowl-shaped plug into the cut edge.

[0043] Figure 1 The process of pressing the bowl-shaped plug 5 into the bowl-shaped plug hole of the part 4 is illustrated. The bowl-shaped plug 5 contacts the bottom of the bowl through the conforming head 6, and the conforming head 6, driven by the power source 7, presses the bowl-shaped plug 5 into the hole of the part 4. The power source 7 can be a hand-tapping tool, or a power device such as a hydraulic cylinder or an electric cylinder.

[0044] Figure 2 and Figure 3 The microscopic state of the sharp angle of the orifice when the bowl-shaped plug 5 and the hole of part 4 just come into contact is shown in a progressively magnified manner. For example... Figure 3 As shown, the orifice of part 4 has a sharp corner. When the cup-shaped plug 5 is pressed in, not only is its diameter contracted to form a sealing pressure, but its surface material is also cut axially by the sharp corner, resulting in the cut edges falling off or getting stuck at the chamfer. The larger the interference fit, the more cut edges there are, and the more severe the material damage.

[0045] The core improvement of this embodiment lies in: instead of using the conventional large-sized rounded chamfer, a tiny rounded transition that is completely tangent to the inner diameter of the hole is machined at the orifice to address the thickness of the cut edge generated by pressing in the cup-shaped plug (usually within 0.05mm). For example... Figure 4 As shown, the material at the sharp corner of the hole in part 4 (such as...) Figure 3 The part 4 (as shown in reference numeral 4-1) is removed, transforming part 4 into part 4-2. Specifically, a small arc transition tangent to the inner diameter of the hole is machined at the orifice. The radial dimension of this small arc is not less than 0.05 mm, preferably 0.05 mm-0.15 mm, thereby completely eliminating the sharp corner of the orifice. In this way, when the cup-shaped plug 5 is pressed into the hole of part 4-2, the entire contact process is a smooth contact, and no cutting occurs, thus completely eliminating the generation of cut edges.

[0046] As a preferred option, the end of the orifice extending outwards by the small arc retains the original chamfer. This is because the cup-shaped plug 5 will continuously shrink during the pressing process and will not come into contact with the original chamfer, thus requiring no further treatment.

[0047] Example 2:

[0048] like Figure 5-8 As shown, this embodiment provides a processing device for eliminating the pressing of the bowl-shaped plug into the cut edge, used to implement the method of Embodiment 1.

[0049] like Figure 5 As shown, the device includes a tangential circular arc chamfering tool 1, a tool holder 2, a CNC machine tool 3, and a workpiece 4. The tangential circular arc chamfering tool 1 is a composite tool that integrates finishing of the hole diameter and machining of a small tangential circular arc chamfer. The tool 1 is mounted in the tool holder 2, which is mounted on the CNC machine tool 3. Before machining, the tool 1 and tool holder 2 are precisely set on a tool setter, and the tool compensation value is extracted. During machining, the precise position control of the bowl-shaped plug hole and the machining depth control of the circular arc chamfer are achieved through the CNC tool compensation value control of the CNC machine tool 3 and the positioning of the workpiece 4 on a special fixture.

[0050] It should be noted that the roughing of the diameter and the chamfering of the bowl-shaped plug hole have been completed before finishing with tool 1. Furthermore, to prevent unevenness in the small tangential arc chamfering due to positioning errors between different machine tools, the roughing and chamfering are preferably performed on the same CNC machine tool 3 as the finishing.

[0051] In some specific embodiments of the present invention, in order to achieve precise position control of the bowl-shaped plug hole and control of the machining depth of the minute tangential arc chamfer, the following operations are performed before machining:

[0052] First, mount the tool 1 with the tangential circular chamfer onto the tool holder 2. Then, place the tool holder 2 onto a tool setter (either an external offline tool setter or an internal tool setter) for tool setting. The tool setter accurately measures the axial length (i.e., the distance from the tool holder reference surface to the cutting tip) and radial radius of the tool 1. The difference between the measured actual size and the theoretical size is the tool compensation value. Input this tool compensation value into the tool compensation parameter table of the CNC machine tool 3, corresponding to length compensation and radius compensation respectively.

[0053] The workpiece 4 to be machined is precisely mounted onto the worktable of the CNC machine tool 3 using a special fixture. This special fixture has a positioning reference surface and a positioning pin, which can establish a unique correspondence between the design reference (including the hole axis and the hole end face) of the cup-shaped plug hole on the workpiece 4 and the machine tool coordinate system. The workpiece origin (that is, the zero point position in the X, Y, and Z directions) of the cup-shaped plug hole in the machine tool coordinate system is determined by program setting or manual measurement.

[0054] In the CNC machining program, when tool 1 is called for machining, its corresponding length compensation (e.g., G43 Hxx) and radius compensation (e.g., G41 / G42 Dxx) are simultaneously invoked. Radius compensation ensures that the actual cutting point and the theoretically programmed trajectory of the tool precisely match in the X and Y planes (radial), thus ensuring the accuracy of the hole diameter and center position after finishing. Length compensation ensures that the distance the tool travels from the reference point to the workpiece origin in the Z-axis plane is accurate. Because the axial machining allowance of the micro-tangential circular arc chamfer of this invention is only 0.3mm to 0.6mm, it is very sensitive to depth control. Therefore, length compensation is necessary to eliminate the length error of the tool clamping, ensuring the accuracy of the starting and ending positions of the circular arc chamfer, and achieving the desired micro-arc precisely machined just as the hole finishing is completed.

[0055] It should be noted that the roughing of the bowl-shaped plug hole diameter and the chamfering of the original hole opening are also completed on the same CNC machine tool 3 as the finishing steps mentioned above. In other words, the roughing and finishing use the same workpiece coordinate system and the same clamping and positioning, avoiding the positioning errors caused by processing the part on different machine tools or re-clamping. This ensures that the tiny tangential arc chamfer is uniform around the hole opening.

[0056] Figure 6 and Figure 7 The working process of tool 1 is shown in a progressively magnified manner. Tool 1 first performs finishing machining on the diameter of the bowl-shaped plug hole in part 4. At the end of the finishing machining, its arc-shaped insert performs a small tangential arc chamfering on the hole opening to remove the protruding material. Figure 7The sharp corner material 4-1 is shown by the dashed line. The radius of the arc of this cutting tool can be controlled between 0.8mm and 1.5mm. During machining, it is necessary to ensure that the sharp corner of the hole is tangent to an arc of a predetermined radius, and also to ensure that the bevel of the tool 1 does not interfere with the original chamfer of the hole after the arc machining is completed. Specifically, as shown... Figure 7 As shown, the downward-extending inclined edge of tool 1 after the arc is completed should be higher than the chamfer that has been machined at the opening of the bowl-shaped plug of part 4. This is a non-interference state. Conversely, if the inclined edge is lower than the original chamfer, interference will occur, resulting in cutting vibration, hole opening vibration marks, or hole ellipse.

[0057] In actual machining, the cutting allowance for micro-tangential circular chamfers is extremely small, ranging from 0.3mm to 0.6mm in the axial direction and from 0.05mm to 0.15mm in the radial direction. Because the cutting amount is so small, it adds almost no extra cutting force to the entire tool, thus not affecting tool life or reducing hole machining accuracy.

[0058] Figure 8 The image shows the finished product after finishing. The inner hole of the bowl-shaped plug hole in part 4-2 is tangent to the arc of the hole opening and is integrated with it. The outer part of this arc still retains the original chamfer.

[0059] As a specific embodiment of the present invention Figure 9 The pressure-displacement curves of the cup-shaped plug insertion process are shown when using existing technology (with a sharp corner at the orifice). Figure 10 The pressure-displacement curves of the cup-shaped plug insertion process are shown when the method of the present invention (the orifice forms a small tangential arc) is used.

[0060] from Figure 9 and Figure 10 The comparison clearly shows that in the existing technology, the press-fitting equipment needs to increase the pressure by nearly double (the measured maximum pressing force decreased from 10.833KN to 5.411KN) to overcome the cutting resistance generated by the cutting edge; while after adopting the method of the present invention, the maximum pressure of the pressing process is significantly reduced, and the curve can truly reflect the change of frictional resistance of the cup-shaped plug and the degree of material yielding, providing a reliable basis for finite element analysis.

[0061] Specifically, this invention proposes a method and apparatus for eliminating the cutting edge during the pressing of bowl-shaped plugs. Its core lies in fundamentally solving the long-standing problem of cutting edge during the pressing of bowl-shaped plugs in the engine industry with extremely low processing costs (requiring only a radial tangent arc of more than 0.05 mm to be machined at the orifice). Unlike existing technologies that attempt to reduce the degree of cutting edge by increasing the strength of the plug material or reducing the interference, this invention directly eliminates the root cause of cutting edge—the sharp corner of the orifice—thus simultaneously achieving multiple technical benefits: firstly, it completely eliminates the contamination of part cleanliness by the cutting edge; secondly, it eliminates the risk of leakage and detachment caused by the cutting of the plug surface; thirdly, it significantly reduces the pressing force required for press-fitting (measured to be reduced by approximately half), thereby saving equipment investment and energy consumption; and fourthly, it makes the finite element analysis results more realistic and reliable. Furthermore, the composite tool processing scheme adopted in this invention utilizes the characteristics of small cutting allowances to achieve high-precision machining without increasing the tool load, and by cleverly avoiding interference between the tool bevel and the original chamfer, it ensures the stability of processing quality. It can be said that this invention achieves a comprehensive improvement in assembly quality, sealing reliability, production efficiency, and cost control at a very low cost, and has significant technological advancement and industrial application value.

[0062] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for eliminating the pressing of a bowl-shaped plug into the cut edge, characterized in that, include: A rounded chamfer is made at the opening of the bowl-shaped plug hole so that the rounded chamfer forms a tangential transition with the inner hole of the bowl-shaped plug hole, thereby eliminating the sharp corner at the junction of the diameter of the bowl-shaped plug hole and the chamfer at the opening, so that the bowl-shaped plug makes smooth contact with the tangential arc during the process of pressing into the bowl-shaped plug hole.

2. The method for eliminating the pressing edge of the bowl-shaped plug according to claim 1, characterized in that, The circular chamfer is a small tangent circular chamfer, and its radial dimension is not less than the thickness of the cut edge produced when the bowl-shaped plug is pressed in.

3. The method for eliminating the pressed-in edge of the bowl-shaped plug according to claim 2, characterized in that, The radial dimension is 0.05 mm to 0.15 mm.

4. The method for eliminating the pressing edge of the bowl-shaped plug according to claim 1, characterized in that, The inner hole of the bowl-shaped plug is tangent to the circular chamfer and the original chamfer is retained at the outward-extending end of the circular chamfer.

5. A processing apparatus for eliminating the pressing of bowl-shaped plugs into the cut edges, characterized in that, include: A chamfering tool with tangent circular arc is configured to finish the diameter of a bowl-shaped plug hole and perform a small tangent circular arc chamfer on the opening of the bowl-shaped plug hole at the finishing end. The tool holder is connected to the tool with the tangential circular arc chamfer. CNC machine tool, wherein the tool holder is mounted on the CNC machine tool; And the workpiece being processed, which has the aforementioned bowl-shaped plug hole; The tool with tangent circular arc chamfering, after finishing the diameter of the bowl-shaped plug hole, processes a small circular arc chamfer at the hole opening that is tangent to the finished diameter.

6. The processing apparatus for eliminating the pressing-in edge of the bowl-shaped plug according to claim 5, characterized in that, The tool with tangent circular arc chamfer is a tool that integrates the precision machining hole diameter and the small tangent circular arc chamfer at the hole opening.

7. The processing apparatus for eliminating the pressing edge of the bowl-shaped plug according to claim 5, characterized in that, It also includes a tool setter, on which the tool with tangential circular arc chamfer and the tool holder are set and the tool compensation value is extracted. By positioning the workpiece on the special fixture and controlling the CNC tool compensation value of the CNC machine tool, the positional accuracy of the bowl-shaped plug hole and the machining depth of the micro tangential circular arc chamfer are controlled.

8. The processing apparatus for eliminating the pressing-in edge of the bowl-shaped plug according to claim 5, characterized in that, The roughing and chamfering of the bowl-shaped plug hole are performed on the same CNC machine tool as the finishing process.

9. The processing apparatus for eliminating the pressing edge of the bowl-shaped plug according to claim 5, characterized in that, The chamfering tool with tangential arc includes an arc insert with an arc radius of 0.8 mm to 1.5 mm, and the axial machining allowance of the micro-tangential arc chamfer is 0.3 mm to 0.6 mm.

10. The processing apparatus for eliminating the pressing-in edge of the bowl-shaped plug according to claim 5, characterized in that, After the chamfered edge of the tool with tangent circular arc is completed, its hypotenuse does not interfere with the original chamfer of the opening of the bowl-shaped plug hole.

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