Diesel engine cylinder cover small-angle crossed deep hole machining method

Abstract

The invention provides a diesel engine cylinder cover small-angle crossed deep hole machining method and belongs to the technical field of machining. The method comprises the following steps: firstly, clamping a workpiece on a special fixture by taking a central oil injector hole of the cylinder cover as a process positioning reference, and enabling the center of the fixture to coincide with the center of a B axis of a machine tool; then, a specially-made hard alloy composite platform guide drill is adopted for machining deep guide holes of the two cross holes step by step, the guide drill has the front end centering function and the rear end long guiding function, and initial sliding of a tool and deflection in the machining process can be effectively prevented; and finally, a gun drill is used for completing final depth machining along the guide hole. Through the innovative tool design and the machining sequence of completing one hole and then guiding another hole, the problems that in the small-angle crossed deep hole machining process, a tool is prone to deflection and breakage are solved, and high-precision, high-efficiency and high-reliability machining is achieved.

Description

Technical Field

[0001] This invention belongs to the field of machining technology, specifically relating to a method for machining small-angle cross-deep holes in a diesel engine cylinder head. Background Technology

[0002] The cylinder head of a diesel engine is made of QT500-7 ductile iron. Its structure features two intersecting deep holes with a diameter of φ12mm, an intersection angle of 27°, and depths of 414mm and 504mm respectively, resulting in length-to-diameter ratios of 34.5 and 42. A casting cavity exists in the center of each hole. Both holes are threaded with M16×1.5 threads (e.g., ...). Figure 1 In existing technology, when machining such cross holes on a horizontal machining center, the following method is generally used: first, a flat-bottomed drill is used to countersink the end faces of the two holes, then a carbide twist drill is used to drill the guide hole, and finally, an integral carbide internal cooling twist drill is used to machine the cross hole by reducing the spindle speed and feed.

[0003] The existing method for machining small-angle intersecting deep holes has the following drawbacks: 1. Difficulty in tool positioning: Due to the small cross angle, the contact between the drill bit and the workpiece surface during cutting is an asymmetrical inclined surface contact, which is very easy to slip and deviate.

[0004] 2. Unstable machining process: When the drill bit cuts to the area where two holes intersect, especially when there is a cavity in the middle, the force on both sides of the tool becomes uneven instantly, generating a huge lateral impact force, which can easily cause the drill bit to wobble or break.

[0005] 3. Low machining accuracy and efficiency: When drilling the intersection of two holes using conventional carbide twist drills, the spindle speed and feed rate must be significantly reduced to protect the tool, resulting in low machining efficiency, long debugging cycle and high cost. Summary of the Invention

[0006] The technical problem solved by this invention: The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for machining small-angle intersecting deep holes in diesel engine cylinder heads. This method, through innovative tool design and optimized machining sequence, effectively suppresses tool entry runout and cutting vibration at the intersection point, thereby achieving efficient, high-precision, and stable machining.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The method for machining small-angle cross-shaped deep holes in a diesel engine cylinder head includes the following steps: Step S1: Using the injector hole at the center of the cylinder head as the process positioning reference, clamp the workpiece on the special fixture and make the center of the fixture coincide with the rotation center of the B axis of the machine tool table. Step S2: By controlling the rotation angle of the B-axis and the movement of the X-axis of the machine tool table, the end faces of the two holes are countersunk and the threaded bottom holes of the two holes are machined. Step S3: Use a carbide composite platform to guide the drilling of the deep pilot hole of hole A, drilling to a depth exceeding the surface of the casting blank by a certain depth; Step S4: Using the deep guide hole processed in step S3 as a guide, use a sizing drill bit to process hole A to the final depth; Step S5: Use the carbide composite platform to guide the drilling of the pilot hole of hole B, drilling to a depth exceeding the theoretical connection point of the two holes by a certain depth; Step S6: Using the guide hole processed in step S5 as a guide, use a sizing drill bit to process hole B to the final depth; Step S7: Machin the threads at the openings of the two holes.

[0008] Further defining the above scheme, the front end of the carbide composite platform guide drill is provided with a centering drill tip for initial positioning, and the rear end is provided with a precision guide post with a length-to-diameter ratio greater than 5 for providing support in the guide hole.

[0009] Further defining the above scheme, the diameter of the guide post of the carbide composite platform guide drill is matched with the diameter of the subsequent sizing drill bit, and its tolerance zone is h7 grade.

[0010] To further limit the above scheme, in step S5, when machining the guide hole of hole B, its drilling depth must be ensured to be at least 25mm deeper than the theoretical connection point of the two holes.

[0011] Further defining the above scheme, the sizing drill bit mentioned in steps S4 and S6 is a carbide-embedded gun drill.

[0012] Further defining the above scheme, the intersection angle of the small-angle intersecting deep hole is less than 30° and the length-to-diameter ratio is greater than 30.

[0013] To further define the above solution, the design of the special fixture ensures that its central positioning guide hole precisely coincides with the rotation center of the B-axis of the machine tool table.

[0014] Advantages of this invention compared to existing technologies: 1. This solution has high precision: it effectively controls the straightness and angular accuracy of the hole axis, avoiding skewness and out-of-tolerance. 2. This solution boasts high efficiency: Due to the significantly improved tool rigidity and stability, higher cutting parameters can be used compared to traditional processes, while reducing tool change and setup time. Practical experience has shown that overall machining efficiency is approximately 50% higher than traditional methods. 3. This solution has high reliability: it fundamentally reduces the risk of drill bit breakage, improves the safety and stability of the machining process, and reduces tool wear and production costs. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the small-angle cross-shaped deep holes in the cylinder head of a diesel engine according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the cemented carbide composite platform guide drill used in the processing of this invention; Figure 3 This is a schematic diagram of the special fixture structure for machining small-angle cross-deep holes in diesel engine cylinder heads according to the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0017] Example: like Figure 1 As shown, the diesel engine cylinder head 1 has two intersecting deep holes with a diameter of φ12mm, namely hole A1-1 and hole B1-2, with an intersection angle of 27°, depths of 414mm and 504mm respectively, and length-to-diameter ratios of 34.5 and 42 respectively. Both holes are threaded with M16x1.5 threads.

[0018] Step S1: Workpiece positioning and clamping With the combustion surface of cylinder head 1 facing down, the injector hole in the center of the cylinder head is used as a precision machining reference hole, and the cylinder head is clamped onto a special fixture. This special fixture consists of a base, a screw nut, and a pressure plate, as shown below. Figure 3 As shown, the design of the special fixture ensures that its central positioning guide hole precisely coincides with the rotation center of the B-axis of the machine tool table.

[0019] Step S2: Pre-treatment of the end face of the borehole and machining of the threaded pilot hole The B-axis rotation angle of the machine tool worktable is controlled by the CNC program, and the X-axis is moved in conjunction with it. The end face drill is used to countersink the end faces of the two holes, and the M16×1.5 threaded bottom holes φ14.5m7 of the two holes are drilled.

[0020] Step S3: Machining the deep guide hole of hole A1-1 Adopting such Figure 2The specially designed carbide composite platform guide drill 2 shown is used to machine the deep guide hole of hole A1-1. After drilling to the surface of the cast blank, the guide drill continues to drill 25mm deeper to form a stable and precise deep guide hole.

[0021] Step S4: Complete the final depth machining of hole A1-1 Using the deep guide hole processed in step S3 as a guide, use a φ12 gun drill to process hole A1-1 to the final depth required by the drawing.

[0022] Step S5: Machining the through guide hole of hole B1-2 Adjust the B-axis of the machine tool table to the theoretical angle of hole B1-2, and use the same carbide composite platform guide drill 2 described in step S2 to machine the guide hole for the second intersecting hole (hole B1-2). This guide hole needs to be drilled to a depth at least 25mm beyond the theoretical connection point of the two holes.

[0023] Step S6: Complete the final depth machining of hole B1-2 Using the guide hole processed in step S5 as a guide, use a φ12 gun drill to process hole B1-2 to the final depth required by the drawing.

[0024] Step S7: Thread machining Use taps to machine the M161.5 threads at both ends of the hole.

[0025] Specifically, the front end of the carbide composite platform guide drill 2 is provided with a centering drill tip 2-1 for initial positioning, and the rear end is provided with a precision guide post 2-2 with an aspect ratio greater than 5 for providing support in the guide hole. The diameter of the guide post 2-2 of the carbide composite platform guide drill 2 matches the diameter of the subsequent sizing drill bit, and its tolerance zone is h7 grade.

[0026] Preferably, the sizing drill bit mentioned in steps S4 and S6 is a carbide-embedded gun drill.

[0027] The special fixture is designed to ensure that its center positioning guide hole is precisely aligned with the rotation center of the B-axis of the machine tool table.

[0028] Working principle: The core of this invention lies in the optimization of tool design and machining sequence. The front centering drill tip 2-1 of the carbide composite platform guide drill 2 can quickly cut into the inclined blank, preventing initial slippage; the rear long guide post 2-2 provides full circumferential support within the machined guide hole, significantly enhancing tool rigidity. The machining strategy of "completing one hole before guiding another" ensures that when machining the second hole, the guide hole has extended beyond the intersection point, avoiding tool wobbling or breakage caused by sudden force changes in the intersection area. Gun drilling along the guide hole further guarantees the straightness and dimensional accuracy of the hole.

[0029] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0030] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for processing small-angle cross deep hole of diesel engine cylinder head, characterized in that: The method comprises the following steps: Step S1: using the oil injector hole in the center of the cylinder head (1) as a process positioning reference, clamping the workpiece on a special fixture, and making the center of the fixture coincide with the rotation center of the machine tool workbench B axis; Step S2: through controlling the rotation angle of the machine tool workbench B axis and the movement of the X axis, the two hole orifice end faces are processed by counter sinking, and the threaded holes of the two hole orifices are processed; Step S3: using a hard alloy composite platform guide drill (2) to process the deep guide hole of hole A (1-1), drilling to a depth exceeding the casting blank surface by a certain depth; Step S4: using the deep guide hole processed in step S3 as a guide, using a sizing drill bit to process hole A (1-1) to the final depth; Step S5: using the hard alloy composite platform guide drill (2) to process the guide hole of hole B (1-2), drilling to a depth exceeding the theoretical through point of the two holes by a certain depth; Step S6: using the guide hole processed in step S5 as a guide, using a sizing drill bit to process hole B (1-2) to the final depth; Step S7: processing the threads of the two orifice parts.

2. The method of claim 1, wherein: The front end of the hard alloy composite platform guide drill (2) is provided with a centering drill point (2-1) for initial positioning, and the rear end is provided with a precision guide column (2-2) with a length-diameter ratio greater than 5 for providing support in the guide hole.

3. The method of claim 2, wherein: The diameter of the guide column (2-2) of the hard alloy composite platform guide drill (2) matches the diameter of the subsequent sizing drill bit, and the tolerance band is h7 level.

4. The method of claim 1, wherein: In step S5, when processing the guide hole of hole B (1-2), the drilling depth needs to ensure a depth of at least 25mm exceeding the theoretical through point of the two holes.

5. The method of claim 1, wherein: The sizing drill bit in steps S4 and S6 is a hard alloy gun drill.

6. The method of small angle cross deep hole machining of a diesel engine cylinder head of claim 1, wherein: The intersection angle of the small-angle intersection deep hole is less than 30°, and the length-diameter ratio is greater than 30.

7. The method of small angle cross deep hole machining of a diesel engine cylinder head of claim 1, wherein: The design of the special fixture ensures that the center positioning guide hole coincides with the rotation center of the machine tool workbench B axis.

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