Method and apparatus for manufacturing a gearbox housing

Abstract

Method for manufacturing a gearbox housing (10) comprising the following: Positioning a cast housing with multiple fluid drain holes (22) below a central axis (X) of the cast housing; Drilling and face milling of several internal bores (72) and several surfaces (74) of the housing to form a rough-machined housing; and Blowing off machining chips (44) from the rough-machined housing through the fluid drain holes.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a method and a machining line for manufacturing a gearbox housing. BACKGROUND

[0002] Large gearbox housings are cast and then machined to tight tolerances required for the installation of gears, clutches, and other critical components. In conventional gearbox housing machining lines, the housing is cooled and lubricated by flooding with a water / oil emulsion coolant during both roughing and finishing operations. The roughing drilling and face milling processes generate a significant amount of heat, which builds up in the housing and in the chips removed from it. Flooding with the water / oil emulsion coolant was previously considered essential for cooling the housing and for flushing away large quantities of hot chips from the workpiece and tooling.

[0003] Large quantities of water / oil emulsion coolant require extensive coolant circulation systems for chip removal and cooling of the circulating coolant. The coolant and chips contribute to an increased amount of waste from a plant and drive up processing costs. Water / oil emulsion coolants are recyclable. Chips from metal cutting recovered from the coolant can be processed, but they are less valuable than chips produced in dry metal cutting. Coolant circulation systems are expensive and occupy valuable production space. Operating water / oil emulsion coolant systems consumes a significant amount of energy.

[0004] Minimum quantity lubrication (MQL) systems have been developed to provide a lubricating mist in the air for milling, drilling, and tapping relatively small features of a gearbox housing with a diameter of less than 200 mm. The underside of the gearbox housing, enclosed by the gearbox fluid sump, is machined by milling, drilling, and tapping operations with the underside inverted for easier access. Due to the heat generated by drilling and face milling operations, no MQL systems have been developed for roughing and finishing drilling machines. The hot chips carried away from the housing contribute to the heat load. To date, flood cooling has been considered the only way to provide cooling for the housing and lubrication for the drilling and face milling machines.

[0005] Specialized boring machines with large boring bars, equipped with multiple cutting tools, are used for machining large housings where internal diameters need to be drilled and surfaces milled with diameters exceeding 200 mm, such as gearbox housings for rear-wheel drive systems and the like. These specialized boring machines are expensive to purchase and have long lead times. Changing the setup for a different workpiece or workpiece design, as well as changing tools, is very time-consuming, resulting in significant line downtime. Specialized boring machines on a machining line are typically part of a single conveyor, meaning the entire line must be shut down when the boring machine requires maintenance.

[0006] DE 10 2010 054 401 A1 discloses the machining of gearbox housings with various tools. DE 10 2005 034 923 A1 discloses a method for the dry machining of aluminum castings. DE 11 2011 103 349 T5 discloses a system for cooling an electric machine. DE 197 01 606 A1 discloses a tool holder. DE 20 2004 008 566 U1 discloses a reamer used for machining with a minimum quantity lubrication system. DE 10 2007 023 168 A1 discloses finishing tools with integrated coolant / lubricant supply. DE 193 99 68 U discloses a housing for a gear-change transmission. DE 300 19 35 A1 discloses a compact three-shaft transmission. DE 10 2013 212 165 A1 discloses a cast housing with different pressure tightness in two sections. DE 10 2007 044 289 A1 discloses a machine tool device with a machine bed. DE 20 2013 000 225 U1 discloses a machining unit with two work spindles.

[0007] The above problems and other problems are addressed by this revelation, which is briefly outlined below. SUMMARY

[0008] According to one aspect of the present disclosure, a method for manufacturing a transmission housing from a housing "in the as-cast condition" is provided, wherein a minimum amount of lubrication is supplied as an oil mist in compressed air during the rough drilling and face milling of the housing. The transmission housing is a cast housing that defines several transmission fluid drain holes for the drainage of transmission fluid from the transmission when installed in a vehicle. The housing is positioned such that the fluid drain holes are located below a central axis of the housing in the as-cast condition, and several internal bores and surfaces on the housing are drilled and face milled to form a rough-drilled housing. Machining chips are blown off the rough-drilled housing through the fluid drain holes and through the bell-shaped end of the housing.Machining chips are also blown away by the airflow turbulence generated by rotating the tool while retracting it from the housing.

[0009] According to other aspects of the present disclosure, the step of drilling and face milling the internal bores and surfaces may further comprise supplying a stream of compressed air and an oil mist to a cutting head of a machine tool through an internal passage in the cutting head. The compressed air and oil mist are sprayed from the cutting head to cool and lubricate the drilling and face milling tools. Compressed air supplied through the cutting head without oil mist is also used to cool the housing.

[0010] The cast housing may include a bell-shaped end and a rear end. The flow of compressed air and oil mist is permitted when the cutting head is inside the cast housing and is prevented during tool changes when the cutting head is outside the housing. Chips formed during drilling and face milling operations are blown off the machined housing through the bell-shaped end and fluid drain holes in the housing during and after drilling and face milling of multiple internal bores and multiple surfaces.

[0011] The process can further include creating multiple reference points and positioning the rough-machined housing at these reference points, with the drain holes located above a central axis of the cast housing. The rough-machined housing is then further drilled and milled using finishing drills and face mills, which are also supplied with compressed air and an oil mist through the cutting head of the machine tool.

[0012] The cast housing can include a bell-shaped end and a rear end. Initially, the cast housing is positioned so that the bell-shaped end faces a machine tool holder, and is then repositioned so that the rear end faces a machine tool holder. Finally, a rear bore in the cast housing is drilled and face milled.

[0013] The step of drilling and face milling several internal bores and several surfaces of the cast housing to form a rough-machined housing can be carried out by a CNC-controlled (Computerized Numerical Control) machining center with a tool magazine.

[0014] The step of drilling and face milling of multiple internal bores and multiple surfaces of the cast housing is carried out by drilling tools and interpolating face milling tools that perform the face milling operations.

[0015] According to another aspect of the present disclosure, a machining center for machining a housing is disclosed, comprising a holding device, several interchangeable tools, and a compressed air / oil mist lubrication system. The holding device holds the housing, which defines several fluid drain holes arranged below a central axis of the housing. Interchangeable tools are provided for drilling and face milling several bores and surfaces of the housing. The air / oil mist lubrication system lubricates and cools the interchangeable tools during drilling and face milling of the housing and also blows machining chips away from the housing through the fluid drain holes.

[0016] According to other aspects of the present disclosure relating to a machining center, the air / oil mist lubrication system may include flow channels defined by the interchangeable tools. The air / oil mist lubrication system may include a control that allows the air / oil mist to flow when the interchangeable tool is in the housing and prevents the air / oil mist from flowing during a tool change. The air / oil mist lubrication system blows machining chips away from the housing after the interchangeable tool has been withdrawn from the housing. The air / oil mist flow rates are adjustable and could be varied for each different type of cutting tool used to machine the cast housing.

[0017] The housing may include a bell-shaped end and a rear end, and the machining center may further include a positioner or pivot designed to change the orientation of the housing. The positioner holds the bell-shaped end of the housing facing the machine tool holder when multiple internal bores and surfaces are being drilled and face-milled, and positions the rear end facing the machine tool holder when the rear bore of the housing is being drilled and face-milled.

[0018] The above aspects of the present revelation and other aspects are described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a partially separated side view of a gearbox housing for a rear-wheel drive and a drilling tool. Fig. Figure 2 is a schematic view of part of a machining line for machining a gearbox housing, as shown in Fig. 1 shown. Fig. 3 is a flowchart showing the steps of a procedure for machining a gearbox housing, such as the one in Fig. 1 shown, illustrates. Fig. Figure 4 is a perspective view of a roller of a machining center holding a gearbox housing in an upside-down orientation. Fig. Figure 5 is a side view of the roller of a machining center holding a gearbox housing in an upside-down orientation and swiveled horizontally by 180 degrees. Fig. Figure 6 is a perspective view of a roller of a machining center holding a gearbox housing in an upside-down orientation. DETAILED DESCRIPTION

[0019] The embodiments shown are disclosed with reference to the drawings. It is understood, however, that the disclosed embodiments are merely examples that can be implemented in various and alternative forms. The figures are not necessarily to scale, and some features may be exaggerated or minimized to show details of certain components. The disclosed specific structural and functional details should not be interpreted as limiting, but rather as a representative basis for teaching a person skilled in the art how to implement these disclosed concepts.

[0020] Referring to Fig. Figure 1 shows a gearbox housing 10 of a rear wheel drive (RWD) with a drilling tool 12, which may also be referred to herein as a drilling and milling tool or an interchangeable tool. The tool 12 has a larger length-to-diameter ratio of up to 2.5:1 to facilitate penetration into the housing 10. Additionally, the spindle of the CNC machining center is used to penetrate the housing 10 from the bell end 16 to minimize the overall length of the drilling tools 12. The housing 10 has a bell-shaped end 16 or bell end and a rear end 18. The gear sets, couplings, and other components of the gearbox (not shown) are installed in the bell end 16, and the drive shaft (not shown) is installed in the rear end 18. A lower side 20 of the housing 10 defines several fluid drain holes 22 and other openings.Fluid drain holes are provided to allow a transmission fluid circuit in the completed gearbox. A transmission fluid pan 24 covers and surrounds the underside of the housing 10.

[0021] The casing has a Fig. 1. Middle axis marked with “X”, which corresponds to the axis of the main shaft of the gearbox (not shown).

[0022] The drilling and face milling tool 12 is designed to be mounted on a tool holder of a machining center (in Fig. (2 shown) is attached by a quick-connect fitting 26. The quick-connect fitting 26 defines a concentric fluid opening 28 aligned with the X-axis. A compressed air source and an oil source are connected to the tool 12 via the quick-connect fitting 26 to provide a compressed air / oil mist 34 through internal passages 36 in the tool 12. The flow of air and oil mist can be controlled separately by an air valve 38 and an oil valve 40. Compressed air supplied through the tool 12 without oil can also be used to cool the workpiece. The fitting 26, the internal passages 36, the air source 30, the oil source 32, the air valve 38, and the oil valve 40 can be generally referred to as a lubrication system.

[0023] The tool 12 is provided with several cutting inserts 42, which are used for drilling and face milling the housing 10. The cutting inserts 42 cut into the housing 10 and produce machining chips 44. The lubrication system cools the housing and the machining chips 44 by directing the compressed air / oil mist 34 through nozzles 46 and onto the housing 10 in the area where the cutting inserts 42 are used to machine the housing 10. The compressed air / oil mist 34 cools the housing 10 and the machining chips 44 during the machining process. The compressed air / oil mist 34 also serves to blow the machining chips 44 out of the housing 10 and through the fluid drain holes 22, as well as through other openings, such as... B. the bell-shaped end 16 of the housing 10. During a tool change, the oil valve 40 and the air valve 38 can be controlled separately, so that both can be closed to stop spraying of the air / oil mist 34.Alternatively, only the oil valve 40 can be closed to reduce or eliminate oil in the air / oil mist 34 while the tool 12 is retracted from the housing 10. In this way, compressed air can be used to remove machining chips 44 from the housing 10 without wasting oil or spraying oil into the machining center. The machining chips 44 are also blown away from the housing 10 by the airflow turbulence generated by the propeller-like movement of the rotating tool 12.

[0024] Referring to the Fig. 2 and Fig. 3 is in Fig. 2 a processing line is shown and in Fig. 3 A flowchart is provided that describes the steps of the process. The first part of the machining line is a loading station 52, where a gearbox housing "in its as-cast state" is fed into the machining line. The gearbox housing 10 is transferred to a datum machining station 54, where datum surfaces are produced on the housing at the locations where the gearbox housing is to be clamped as it passes through the machining line 50.

[0025] In the next step, at 56, the housing is in the Fig. In the position shown in Figure 4, rough drilling and face milling are performed with the lower side 20 of the housing 10 facing downwards. The fluid drain holes 22 on the lower side 20 of the housing 10 collect the machining chips 44, and the air / oil mist 34 falls through the holes 22 due to the pressure of the compressed air and gravity. Several drilling and face milling tools can be inserted successively into the bell-shaped end 16 of the housing 10 to complete the rough drilling and face milling of the housing 10. The gearbox housing has internal bores and surfaces to be milled measuring between 205 mm and 295 mm². Drilling and milling such large surfaces has previously only been considered possible in conjunction with flood cooling due to the heat generated by the large amount of material removed.

[0026] The housing is then machined in the machining center by rotating it 180° in a horizontal plane “H” (in Fig. 5 shown) in the in Fig. The tool is repositioned to the position shown in Figure 5 to provide access to the rear end 18 of the housing 10. Roughing drilling and face milling tools are successively inserted into the housing 10 through the rear end 18, while the air / oil mist is sprayed into the housing through the internal passages in the tools 12. Again, a large quantity of chips 44 is removed from the housing 10, and a significant amount of heat generated by the process and retained in the machining chips 44 is dissipated through the fluid drain holes 22 in the lower side 20 of the housing 10.

[0027] The housing is then transferred to 58 multiple machining centers and rotated in a vertical plane “V” (in Fig. 6 shown) in the in Fig. The fluid drain holes 22 in the lower side 20 of the housing 10 are repositioned as shown in Figure 6, with the fluid drain holes 22 facing upwards. The lower side 20 of the housing 10 is milled, drilled, and tapped in several machining centers to form openings, passages, and other features of the housing 10. The machining centers used to mill, drill, and tap the housing remove only a limited amount of chips and can utilize minimum quantity lubrication systems because less material is removed.

[0028] In the next step, at position 60, the housing is transferred to a finishing drilling and face milling station. The housing is inserted into the vertical plane "V" in the Fig. The tool is swivelled to the position shown in Figure 4, with the fluid drain holes located on the lower side 20 of the housing 10, and drilling and face milling tools are used to create smooth surfaces on the internal bores and surfaces of the housing 10. The air / oil mist 34 is directed onto the housing while the tools machine the bell-shaped end of the housing 10.

[0029] The housing 10 is rotated again by 180° in a horizontal plane “H” in the processing station. Fig. The tool is swivelled to the position shown in Figure 5. Finishing drilling and face milling tools 12 are successively inserted into the housing 10 through the rear end 18, while the air / oil mist is sprayed onto the housing through the internal passages in the tools 12. Again, a large quantity of chips is removed from the housing, but the quantity is less than that removed during the roughing drilling and face milling operation. The chips 44 and the air / oil mist 34 are guided by the compressed air / oil mist and gravity through the fluid drain holes in the lower side 20 of the housing 10.

[0030] After the finishing drilling and face milling process, the housing 10 is subjected to a high-pressure rinsing process at 62 to clean the housing 10 and remove any residues of the air / oil mist 34 and machining chips 44.

[0031] The housing is then dried at 64 and tested for leaks, and unloaded from line 50 at an unloading station 66.

[0032] Referring to Fig. Figure 4 shows a pivot pin 68, which is part of the machining centers that form the machine line 50. The housing 10 in Fig. 4 is held at the reference points 76, which are used to position the housing in a holding device 70 or positioner with the lower side 20 facing downwards. In this position, the fluid drain holes 22 are positioned in such a way that the machining chips 44 and excess air / oil mist 34 can fall through the fluid drain holes 22, the fluid drain holes 22 being arranged below the central axis “X”. Fig. Figure 4 shows internal bores 72 and surfaces 74 formed by the drilling and face milling tools (as in Fig. 1 shown).

[0033] Referring to Fig. Figure 5 shows the pivot pin 68 with an arc-shaped arrow “H” to represent the horizontal pivoting movement in which the housing is pivoted to provide access to either the bell-shaped end or the rear end of the housing 10. The housing 10 is held in the receiving device 70 with its lower side 20 facing downwards.

[0034] Referring to Fig. Figure 6 shows the pivot pin 68, with the housing 10 shown with its lower side 20 facing upwards and positioned above the central axis “X”. The housing 10 is held in the receiving device 70, and the bores 72 and surfaces 74 are also shown. The pivot pin 68 pivots the housing in the vertical plane indicated by the arcuate arrow “V”.

[0035] The embodiments described above are specific examples that do not represent all possible forms of disclosure. The features of the illustrated embodiments can be combined to form further embodiments of the disclosed concepts. The words used in the description are descriptive and not limiting. The scope of protection of the following claims is broader than that of the specifically disclosed embodiments and also includes modifications of the illustrated embodiments.

Claims

[1] Method for manufacturing a gearbox housing (10) comprising the following: Positioning a cast housing with multiple fluid drain holes (22) below a central axis (X) of the cast housing; Drilling and face milling of several internal bores (72) and several surfaces (74) of the housing to form a rough-machined housing; and Blowing off machining chips (44) from the rough-machined housing through the fluid drain holes. [2] Method according to claim 1, wherein the step of drilling and face milling the internal bores (72) and surfaces (74) further comprises: Supplying a compressed air / oil mist (34) to a cutting head through an internal passage in the cutting head; and Spraying the compressed air / oil mist (34) through the cutting head to cool and lubricate the drilling and face milling tools. [3] Method according to claim 2, wherein the housing comprises a bell-shaped end and a rear end, the method further comprising: Controlling the compressed air / oil mist (34) to allow flow when the cutting head is inside the housing and to prevent flow during a tool change operation when the cutting head is outside the housing; and Blowing off machining chips (44) from the machined housing through the bell-shaped end (16) of the machined housing after the step of drilling and face milling several internal bores (72) and several surfaces (74) of the housing. [4] Method according to claim 3, wherein during the step of controlling the compressed air / oil mist (34) the method further comprises stopping an oil mist component of the compressed air / oil mist (34) and continuing to provide a stream of compressed air to cool the housing during a withdrawal of the tool. [5] The method of claim 1, further comprising: Positioning the rough-machined housing at several reference points (76), wherein the fluid drain holes (22) are located over a central axis (X) of the cast housing; and Drilling and face milling of the rough-machined housing with a compressed air / oil mist (34) by a finishing cutting tool, whereby chips removed from the housing fall through the fluid drainage holes (22) due to gravity. [6] Method according to claim 1, wherein the housing comprises a bell-shaped end (16) and a rear end (18), the method further comprising: Positioning the housing such that the bell-shaped end (16) faces a machine tool mounting holder; Repositioning the housing so that the rear end (18) faces the machine tool mounting bracket; and Drilling a rear hole in the housing. [7] Method according to claim 1, wherein the step of drilling and face milling several internal bores (72) and several surfaces (74) of the cast housing to form a rough-machined housing is carried out by a CNC-controlled (Computerized Numerical Control) machining center with a tool magazine, wherein the method further comprises: Rotating a cutting head to create a turbulence that blows chips away from the housing. [8] Method according to claim 1, wherein the step of drilling and face milling of several internal bores (72) and several surfaces (74) of the housing to form a rough-machined housing is carried out by drilling tools (12) and interpolating face milling tools with a diameter between 205 mm and 295 mm. [9] The method of claim 1, further comprising: Positioning the machined housing with the fluid drain holes (22) above a central axis (X) of the machined housing; Milling the machined housing with the fluid drain holes (22) over a central axis (X) of the machined housing; Drilling the machined housing with the fluid drain holes (22) over a central axis (X) of the machined housing; Thread drilling of the machined housing with the fluid drain holes (22) over a central axis (X) of the machined housing; Positioning the machined housing with the fluid drain holes (22) below a central axis (X) of the machined housing; Drilling and face milling of several internal bores (72) and several surfaces (74) of the rough-machined housing with a finishing drilling and face milling operation to form a finished housing; and Blowing off machining chips (44) from the simply machined housing through the fluid drainage holes. [10] Machining center for machining an enclosure comprising the following: a receiving device that holds the housing, which defines several fluid drainage holes (22) aligned below a central axis (X) of the housing; several interchangeable tools for drilling and face milling multiple bores (72) and surfaces (74) of the housing; and a lubrication system that lubricates and cools the interchangeable tools with a compressed air / oil mist (34) during drilling and face milling of the housing, and blows machining chips (44) away from the housing through the fluid drain holes (22). [11] Machining center according to claim 10, wherein the lubrication system comprises flow channels defined by the interchangeable tools. [12] Machining center according to claim 10, wherein the interchangeable tools comprise drilling tools (12), interpolating face milling tools and interpolating grooving tools. [13] Machining center according to claim 10, wherein the lubrication system comprises a control which allows the compressed air / oil mist (34) to flow when the interchangeable tool is in the housing and which prevents the flow of an oil mist portion of the compressed air / oil mist (34) during a tool change. [14] Machining center according to claim 13, wherein the compressed air / oil mist (34) is limited to a stream of compressed air which blows machining chips (44) away from the housing while the replaceable tool is retracted from the housing. [15] Machining center according to claim 10 in combination with a finishing machining center, wherein the receiving device which holds the housing which defines the multiple fluid drain holes (22) is aligned below the central axis of the housing, wherein the finishing machining center further comprises: several interchangeable finishing cutting tools for finishing drilling and face milling of the several bores (72) and surfaces (74) of the housing, wherein the lubrication system lubricates the interchangeable finishing cutting tools with the compressed air / oil mist (34) during a finishing operation and cools and blows machining chips from the housing through the fluid drainage holes (22) and through a bell-shaped end (16) of the housing. [16] Machining center according to claim 10, wherein the interchangeable tools are rotated when not drilling or face milling the housing to generate an airflow turbulence for removing chips from the housing.

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