A method for machining cylinder bores and a tool structure

Abstract

The present invention discloses a cylinder bore machining method and a tool structure. Specifically, a bar stock is provided, and the bar stock has a prefabricated hole. Rough machining: Rough boring the prefabricated hole to a first allowance hole diameter to form a machining bottom hole. Semi-finishing: Divide the machining bottom hole into a first hole section and a second hole section along its length direction, and sequentially cut the first hole section and the second hole section to a second allowance hole diameter through the tool structure to form a semi-finished cylinder bore. Finishing: Precision boring the semi-finished cylinder bore to a preset hole diameter to obtain a finished cylinder bore, wherein the preset hole diameter, the second allowance hole diameter, and the first allowance hole diameter decrease step by step. Rough boring the prefabricated hole of the bar stock to form the machining bottom hole, and sequentially performing semi-precision boring on the first hole section and the second hole section with different cutting parameters and cutting to the second allowance hole diameter, thus avoiding the problem that vibration marks are likely to be generated at the bottom after semi-precision boring of the machining bottom hole, resulting in workpiece scrapping.

Description

Technical Field

[0001] The present invention relates to the technical field of hole machining, and particularly relates to a method for machining cylinder holes and a tool structure. Background Art

[0002] The cylinder liners of engine cylinder blocks are usually made of cast iron. The cylinder holes of the cylinder liners are generally machined by a horizontal machining center. However, due to the small spindle torque, poor rigidity, and relatively low maximum spindle speed of the horizontal machining center, it is more suitable for machining products made of aluminum alloy materials. After semi-finish boring the cylinder holes of the cast iron cylinder liners by using a horizontal machining center, vibration marks are likely to occur at the bottom of the cylinder holes, resulting in scrapping of the workpieces. Summary of the Invention

[0003] The main object of the present invention is to provide a method for machining cylinder holes and a tool structure, aiming to solve the problem that vibration marks are likely to occur at the bottom of the cylinder holes after semi-finish boring the cylinder holes of the cast iron cylinder liners by using a horizontal machining center, resulting in scrapping of the workpieces.

[0004] To achieve the above object, the present invention provides a method for machining cylinder holes, including the following steps:

[0005] Provide a bar stock having a prefabricated hole;

[0006] Rough machining: Rough bore the prefabricated hole to a first allowance hole diameter to form a machining bottom hole;

[0007] Semi-finish machining: Divide the machining bottom hole into a first hole section and a second hole section along its length direction, and sequentially cut the first hole section and the second hole section to a second allowance hole diameter through a tool structure to form a semi-finished cylinder hole;

[0008] Finish machining: Finish bore the semi-finished cylinder hole to a preset hole diameter to obtain a finished cylinder hole, wherein the preset hole diameter, the second allowance hole diameter, and the first allowance hole diameter decrease step by step.

[0009] Optionally, the step of "Rough machining: Rough bore the prefabricated hole to a first allowance hole diameter to form a machining bottom hole" includes:

[0010] Select a rough boring tool according to the size of the prefabricated hole;

[0011] Control the rough boring tool to work with a first cutting parameter to rough bore the prefabricated hole to a first allowance hole diameter.

[0012] Optionally, the step of "Semi-finish machining: Divide the machining bottom hole into a first hole section and a second hole section along its length direction, and sequentially cut the first hole section and the second hole section to a second allowance hole diameter through a tool structure to form a semi-finished cylinder hole" includes:

[0013] Select a semi-finishing boring tool according to the size of the machined bottom hole. Among them, the semi-finishing boring tool has a plurality of cutting head units, and the plurality of cutting head units together form the cutting head of the semi-finishing boring tool;

[0014] Control the semi-finishing boring tool to work with the second cutting parameters to machine the first hole section to the second allowance hole diameter;

[0015] Control the semi-finishing boring tool to work with the third cutting parameters to machine the second hole section to the second hole diameter allowance to form a semi-finished cylinder hole.

[0016] Optionally, the second cutting parameters include the spindle speed S1 and the feed rate F1, and the third cutting parameters include the spindle speed S2 and the feed rate F2, where S1 > S2 and F1 > F2.

[0017] Optionally, the length of the machined bottom hole is L, the length of the first hole section is L1, and the length of the second hole section is L2, where 0.145L ≤ L2 ≤ 0.222L.

[0018] Optionally, after the step of selecting a semi-finishing boring tool according to the size of the machined bottom hole, it further includes:

[0019] Measure the actual cutting head diameter and actual cutting head length of the semi-finishing boring tool through a tool setting gauge;

[0020] Compare the actual cutting head diameter with a preset diameter threshold to adjust the size of the actual cutting head diameter and control the diameter difference between the cutting head units;

[0021] Compare the actual cutting head length with a preset length threshold to adjust the size of the actual cutting head length and control the length difference between the cutting head units.

[0022] Optionally, the diameter difference between the cutting head units is ΔD, and ΔD ≤ 0.01 mm.

[0023] Optionally, the length difference between the cutting head units is ΔL, and ΔL ≤ 0.02 mm.

[0024] In addition, the present invention also proposes a tool structure, and the tool structure includes:

[0025] A boring bar, and a plurality of receiving grooves are provided on the outer side surface of the boring bar, and the plurality of receiving grooves are evenly spaced along the circumferential side of the boring bar;

[0026] A plurality of blade mounting units are respectively movably mounted in the plurality of receiving grooves so as to be movable along the length direction and the diameter direction of the boring bar; and,

[0027] A plurality of cutter head units are respectively installed on the plurality of blade mounting units to form the cutter head of the semi-finishing boring tool for cutting the machined bottom hole.

[0028] Optionally, on the length direction of the boring bar, the bottom wall of each receiving groove is provided with a first threaded mounting hole and a second threaded mounting hole;

[0029] Each blade mounting unit further includes a length adjustment screw, a first through hole and a second through hole. The length adjustment screw is arranged on the blade mounting unit and is oppositely arranged with the cutter head unit for adjusting the circumferential clearance between the blade mounting unit and the boring bar. The first through hole and the first threaded mounting hole are correspondingly arranged to connect the blade mounting unit and the boring bar through a first connecting screw. The second through hole and the second threaded mounting hole are correspondingly arranged to adjust the radial clearance between the blade mounting unit and the boring bar through a second connecting screw.

[0030] In the technical solution of the present invention, a blank is provided, and the blank has a prefabricated hole; rough machining: the prefabricated hole is rough bored to a first remaining hole diameter to form a machined bottom hole; semi-finishing machining: the machined bottom hole is divided into a first hole section and a second hole section along its length direction, and the first hole section and the second hole section are sequentially cut to a second remaining hole diameter through a tool structure to form a semi-finished product cylinder hole; finishing machining: the semi-finished product cylinder hole is precision bored to a preset hole diameter to obtain a finished product cylinder hole, wherein the preset hole diameter, the second remaining hole diameter and the first remaining hole diameter decrease step by step. The prefabricated hole of the blank is rough bored to form the machined bottom hole, and the first hole section and the second hole section are semi-finished bored with different cutting parameters in sequence and cut to the second remaining hole diameter. In this way, the problem that vibration marks are easily generated at the bottom after the semi-finishing boring of the machined bottom hole and the workpiece is scrapped is avoided. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0032] Figure 1 It is a schematic flow chart of an embodiment of the cylinder hole processing method provided by the present invention;

[0033] Figure 2 For Figure 1 the three-dimensional structure schematic diagram of the tool structure in

[0034] Figure 3 ForFigure 2 Schematic diagram of the tool structure from another perspective (the tool head unit is not shown).

[0035] Explanation of the reference numerals in the drawings:

[0036]

[0037]

[0038] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] It should be noted that if there are directional indications (such as up, down, left, right, front, back,...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0041] In addition, if there are descriptions such as "first", "second", etc. involved in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution where A and B are satisfied simultaneously. In addition, the technical solutions between the embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0042] The cast iron cylinder liner of the engine cylinder block is usually made of cast iron. The machining of the cylinder bore of the cylinder liner generally uses a horizontal machining center. Since the horizontal machining center has a small spindle torque, poor rigidity, and a relatively low maximum spindle speed, it is more suitable for machining products made of aluminum alloy materials. After semi-finish boring the cylinder bore of the cast iron cylinder liner with a horizontal machining center, vibration marks are likely to occur at the bottom of the cylinder bore, resulting in workpiece scrapping.

[0043] In view of this, the present invention provides a cylinder bore machining method, which semi-finishes boring the first hole section and the second hole section in sequence with different cutting parameters and cuts to the second allowance hole diameter, thus avoiding the problem that vibration marks are likely to be generated at the bottom after semi-finishing boring the machining bottom hole, resulting in workpiece scrapping. As Figures 1 to 3 shown, it is an embodiment of the cylinder bore machining method provided by the present invention.

[0044] The present invention provides a cylinder bore machining method and a tool structure. A bar stock is provided with a prefabricated hole. After rough boring the prefabricated hole, a machining bottom hole is formed. The machining bottom hole is semi-finished bored in indexing sections through the tool structure, and when semi-finishing boring the machining bottom hole in indexing sections, different spindle speeds and feed rates are adopted, thus avoiding the problem that vibration marks are likely to be generated at the bottom after semi-finishing boring the machining bottom hole, resulting in workpiece scrapping.

[0045] As Figure 1 shown, it is a schematic flow chart of a specific embodiment of a cylinder bore machining method of the present invention.

[0046] Please refer to Figure 1 , in this embodiment, the cylinder bore machining method includes the following steps:

[0047] Step S10: Provide a bar stock having a prefabricated hole;

[0048] Step S20: Rough machining: Rough bore the prefabricated hole to the first allowance hole diameter to form a machining bottom hole;

[0049] Step S30: Semi-finishing machining: Divide the machining bottom hole along its length direction into a first hole section and a second hole section, and sequentially cut the first hole section and the second hole section to the second allowance hole diameter through the tool structure to form a semi-finished cylinder bore;

[0050] Step S40: Finishing machining: Finish bore the semi-finished cylinder bore to a preset hole diameter to obtain a finished cylinder bore, wherein the preset hole diameter, the second allowance hole diameter, and the first allowance hole diameter decrease step by step.

[0051] The above cylinder bore machining method is applicable to the machining of cylinder bores of cast iron cylinder liners in engine cylinder blocks. The pre - drilled hole is rough - bored to a first - allowance hole diameter to form a machining base hole; the machining base hole is divided into a first hole section and a second hole section along its length direction, and the first hole section and the second hole section are sequentially cut to a second - allowance hole diameter through a tool structure to form a semi - finished cylinder bore; the semi - finished cylinder bore is finish - bored to a preset hole diameter to obtain a finished cylinder bore, wherein the preset hole diameter, the second - allowance hole diameter, and the first - allowance hole diameter decrease step by step. The pre - drilled hole of the rough - boring bar stock is used to form the machining base hole, and the first hole section and the second hole section are semi - finish - bored successively with different cutting parameters and cut to the second - allowance hole diameter. In this way, the problem that vibration marks are easily generated at the bottom after the semi - finish boring of the machining base hole, resulting in workpiece scrapping, is avoided.

[0052] Further, step S20 specifically includes:

[0053] Step S21: Select a rough - boring tool according to the size of the pre - drilled hole;

[0054] Step S22: Control the rough - boring tool to work with a first cutting parameter to rough - bore the pre - drilled hole to the first - allowance hole diameter.

[0055] According to the diameter difference between the pre - drilled hole and the first - allowance hole diameter, select appropriate feed times and appropriate first cutting parameters, rough - bore the pre - drilled hole to form the machining base hole, and ensure the machining efficiency of rough - boring. It should be noted that the selection of the first cutting parameter in rough - boring can be made according to actual machining needs and relevant experience, while ensuring machining accuracy, improving machining efficiency as much as possible.

[0056] Further, step S30 specifically includes:

[0057] Step S31: Select a semi - finish - boring tool according to the size of the machining base hole, wherein the semi - finish - boring tool has a plurality of cutting - head units, and the plurality of cutting - head units together form the cutting head of the semi - finish - boring tool;

[0058] Step S32: Control the semi - finish - boring tool to work with a second cutting parameter to machine the first hole section to the second - allowance hole diameter;

[0059] Step S33: Control the semi - finish - boring tool to work with a third cutting parameter to machine the second hole section to the second - hole - diameter allowance to form a semi - finished cylinder bore.

[0060] The cutter head of the semi-finishing boring tool is formed by a plurality of the cutter head units. The diameter and length of the cutter head of the semi-finishing boring tool are adjusted to within a suitable tolerance range, so that during the semi-finishing boring process, the radial cutting forces generated by the cutter head units are basically the same, and the axial cutting forces are also basically the same. In this way, the semi-finishing boring tool is balanced in force during boring, and no alternating radial force and alternating axial force are generated, thereby eliminating the vibration source and avoiding the problem that vibration marks are easily generated at the bottom of the machined bottom hole after semi-finishing boring, resulting in workpiece scrapping. It should be noted that in semi-finishing boring, the second cutting parameter and the third cutting parameter can be selected according to actual processing needs and relevant experience to improve the processing efficiency while ensuring the semi-finishing accuracy.

[0061] Furthermore, the second cutting parameter includes the spindle speed S1 and the feed rate F1, and the third cutting parameter includes the spindle speed S2 and the feed rate F2, where S1 > S2 and F1 > F2. The first hole section is semi-finished bored using the second cutting parameter, and the second hole section is semi-finished bored using the third cutting parameter. In this way, segmented cutting of the machined bottom hole is achieved, and the semi-finishing efficiency is ensured.

[0062] Furthermore, the length of the machined bottom hole is L, the length of the first hole section is L1, and the length of the second hole section is L2, where 0.145L ≤ L2 ≤ 0.222L. Affected by the insufficient rigidity of the machine tool spindle and the insufficient rigidity of the fixture for clamping the workpiece, vibration marks are likely to appear in the second hole section after semi-finishing boring of the machined bottom hole. According to the length relationship between the machined bottom hole and the second hole section, the lengths of the first hole section and the second hole section are determined to facilitate segmented semi-finishing boring of the machined bottom hole.

[0063] Furthermore, after the step of selecting the semi-finishing boring tool according to the size of the machined bottom hole in step S31, the following steps are also included:

[0064] Step S311: Measure the actual cutter head diameter and actual cutter head length of the semi-finishing boring tool through a tool setter;

[0065] Step S312: Compare the actual cutter head diameter with a preset diameter threshold to adjust the size of the actual cutter head diameter and control the diameter difference between the cutter head units;

[0066] Step S313: Compare the actual cutter head length with a preset length threshold to adjust the size of the actual cutter head length and control the length difference between the cutter head units.

[0067] The actual tool tip diameter and the actual tool tip length are directly measured by a tool setter for the semi-finishing boring tool, the actual tool tip diameter is compared with the preset diameter threshold, and the actual tool tip diameter is adjusted to be within the preset diameter threshold range, and the diameter difference between the tool tip units is ensured. Similarly, the actual tool tip length is compared with the preset length threshold, and the actual tool tip length is adjusted to be within the preset length threshold range, and the length difference between the tool tip units is ensured. In this way, during the semi-finishing boring process, the radial cutting forces generated by the tool tip units are basically the same, and the axial cutting forces are also basically the same, so that the semi-finishing boring tool is in a balanced force state during boring, avoiding the generation of alternating radial forces and alternating axial forces, eliminating the vibration source, preventing vibration marks from appearing at the bottom of the machined bottom hole after semi-finishing boring, improving the workpiece yield rate, and at the same time increasing the tool service life.

[0068] Furthermore, the diameter difference between the tool tip units is ΔD, and ΔD ≤ 0.01 mm. In this way, the radial cutting forces generated by the tool tip units are basically the same, avoiding the generation of alternating radial forces.

[0069] Furthermore, the length difference between the tool tip units is ΔL, ΔL ≤ 0.02 mm. In this way, the axial cutting forces generated by the tool tip units are basically the same, avoiding the generation of alternating axial forces.

[0070] As Figure 2 and Figure 3 shown, it is an embodiment of the tool structure provided by the present invention.

[0071] As Figure 2 and Figure 3 shown, the present invention also proposes a tool structure 100, the tool structure 100 includes a boring bar 1, a plurality of blade mounting units 2 and a plurality of tool tip units 3. A plurality of receiving grooves 11 are provided on the outer side surface of the boring bar 1, and the plurality of receiving grooves 11 are evenly spaced along the circumferential side of the boring bar 1; the plurality of blade mounting units 2 are respectively movably mounted in the plurality of receiving grooves 11 so as to be movable along the length direction and the diameter direction of the boring bar 1; the plurality of tool tip units 3 are respectively mounted corresponding to the plurality of blade mounting units 2 to form the tool tip of the semi-finishing boring tool for cutting the machined bottom hole. In this way, the machined bottom hole is semi-finished bored by the plurality of tool tip units 3, making the force on the tool structure 100 more uniform.

[0072] Specifically, as Figure 2 and Figure 3As shown in the figure, on the bottom wall of each receiving groove 11 along the length direction of the boring bar 1, there are a first threaded mounting hole and a second threaded mounting hole; each blade mounting unit 2 further includes a length adjusting screw 21, a first through hole and a second through hole. The length adjusting screw 21 is arranged in the blade mounting unit 2 and is oppositely arranged with the cutter head unit 3 for adjusting the circumferential clearance between the blade mounting unit 2 and the boring bar 1. The first through hole and the first threaded mounting hole are correspondingly arranged to connect the blade mounting unit 2 and the boring bar 1 through a first connecting screw 4. The second through hole and the second threaded mounting hole are correspondingly arranged to adjust the radial clearance between the blade mounting unit 2 and the boring bar 1 through a second connecting screw 5. By directly measuring the length of the cutter head unit 3 with a tool setting microscope and adjusting the second connecting screw 5, the diameter of the cutter head unit 3 is adjusted. Through repeated corrections, the diameter difference of each cutter head unit 3 can be controlled within 0.01 mm; similarly, by directly measuring the length of the cutter head unit 3 with a tool setting microscope and adjusting the length adjusting screw 21, the length of the cutter head unit 3 is adjusted. Through repeated corrections, the length difference of each cutter head unit 3 can be controlled within 0.02 mm. Thus, during the semi-finishing boring process, the radial cutting forces generated by each cutter head unit 3 are basically the same, and the axial cutting forces are also basically the same. In this way, the semi-finishing boring tool is in a balanced force state during boring, without generating alternating radial forces and alternating axial forces, thereby eliminating the vibration source and avoiding the problem that vibration marks are easily generated at the bottom of the machined bottom hole after semi-finishing boring, resulting in workpiece rejection.

[0073] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for machining cylinder bores, characterized in that, It includes the following steps: Provide a bar stock which has a prefabricated hole; Rough machining: Rough boring the prefabricated hole to a first allowance hole diameter to form a machining bottom hole; Semi-finishing machining: Divide the machining bottom hole along its length direction into a first hole section and a second hole section, and successively cut the first hole section and the second hole section to a second allowance hole diameter through a tool structure to form a semi-finished product cylinder hole; Finishing machining: Precision boring the semi-finished product cylinder hole to a preset hole diameter to obtain a finished product cylinder hole, wherein the preset hole diameter, the second allowance hole diameter and the first allowance hole diameter decrease step by step; The step of "Semi-finishing machining: Divide the machining bottom hole along its length direction into a first hole section and a second hole section, and successively cut the first hole section and the second hole section to a second allowance hole diameter through a tool structure to form a semi-finished product cylinder hole" includes: Select a semi-precision boring tool according to the size of the machining bottom hole, wherein the semi-precision boring tool has a plurality of tool head units, and the plurality of tool head units jointly form the tool head of the semi-precision boring tool; Control the semi-precision boring tool to work with a second cutting parameter to machine the first hole section to the second allowance hole diameter; Control the semi-precision boring tool to work with a third cutting parameter to machine the second hole section to the second hole diameter allowance to form a semi-finished product cylinder hole; The second cutting parameter includes a spindle speed S1 and a feed rate F1, and the third cutting parameter includes a spindle speed S2 and a feed rate F2, wherein S1 > S2 and F1 > F2; After the step of selecting a semi-precision boring tool according to the size of the machining bottom hole, it further includes: Measure the actual tool head diameter and the actual tool head length of the semi-precision boring tool through a tool setting gauge; Compare the actual tool head diameter with a preset diameter threshold value to adjust the size of the actual tool head diameter and control the diameter difference between the tool head units; Compare the actual tool head length with a preset length threshold value to adjust the size of the actual tool head length and control the length difference between the tool head units; The cylinder hole machining method further includes a tool structure, and the tool structure includes a boring bar, a plurality of blade mounting units and a plurality of tool head units. A plurality of receiving grooves are provided on the outer side surface of the boring bar, and the plurality of receiving grooves are evenly spaced along the circumferential side of the boring bar; the plurality of blade mounting units are respectively movably mounted in the plurality of receiving grooves to be movably arranged along the length direction and the diameter direction of the boring bar; the plurality of tool head units are respectively mounted corresponding to the plurality of blade mounting units to form the tool head of the semi-precision boring tool for cutting the machining bottom hole.

2. The cylinder bore machining method according to claim 1, characterized in that, The step of "Rough machining: Rough boring the prefabricated hole to a first allowance hole diameter to form a machining bottom hole" includes: Select a rough boring tool according to the size of the prefabricated hole; Control the rough boring tool to work with a first cutting parameter to rough bore the prefabricated hole to the first allowance hole diameter.

3. The cylinder bore machining method according to claim 1, characterized in that, The length of the machining bottom hole is L, the length of the first hole section is L1, and the length of the second hole section is L2, wherein 0.145L ≤ L2 ≤ 0.222L.

4. The cylinder bore machining method according to claim 1, characterized in that, The diameter difference between the tool head units is ΔD, and ΔD ≤ 0.01 mm.

5. The cylinder bore machining method according to claim 1, characterized in that, The length difference between each of the cutter head units is ΔL, and ΔL ≤ 0.02 mm.

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