Proximal point cross-axis angle gear cutter and gear cutting method using such tool
The gear cutter tool with a reduced cross-axis angle and CNC machine tool system facilitates precise and efficient cutting of internal gear teeth, overcoming limitations of traditional methods by minimizing interference and reducing machine complexity.
Patent Information
- Authority / Receiving Office
- KR · KR
- Patent Type
- Patents
- Current Assignee / Owner
- EATON INTELLIGENT POWER LTD
- Filing Date
- 2021-10-14
- Publication Date
- 2026-07-29
AI Technical Summary
Existing gear manufacturing methods, such as shaping and broaching, are limited by part layout and require non-blocking surfaces, while skiving is fast but limited by cutter clearance and part configuration, making it difficult to cut internal gear teeth efficiently.
A gear cutter tool with a cross-axis tooth angle of 1 to 15 degrees, allowing the workpiece and cutter axes to be nearly identical, enabling precise cutting without interference and reducing chip formation, and a CNC machine tool with a flushing device for debris removal.
Enables efficient cutting of internal gear teeth with high accuracy and flexibility, reducing machine cycle time and cost by eliminating interference and allowing cutting in previously inaccessible areas.
Smart Images
Figure 112023051166761-PCT00006_ABST
Abstract
Description
Technology Field
[0001] Cross-reference regarding related applications
[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 091,675 filed on October 14, 2020. The disclosures of said application are incorporated herein by reference.
[0003] Technology field
[0004] The present invention generally relates to a gear cutter that forms gear teeth on the inner diameter of a workpiece and an associated coolant transfer assembly. Background Technology
[0005] Gear manufacturers utilize various machining processes and corresponding tools to produce gears. Exemplary processes may include hobbing, shaping, milling, shearing, and grinding. The process selected by the gear manufacturer depends on the type of gear being machined and the tolerances for which the gear is produced. Other considerations in selecting a method may include the size of the gear, the configuration of the internal section or flange, the quantity of gears to be produced, the gear-to-pinion ratio, and cost.
[0006] Gear teeth adjacent to other part features are currently limited to production methods such as shaping or rack rolling. For internal gear teeth, shaping or broaching are traditional manufacturing methods, but each process is limited by the part type. In other words, the part layout must have a non-blocking blocking surface so that the tool can pass through the part completely. Gear shaping allows the teeth to be cut against the interference surface, but it is inherently slow in terms of machine cycles and flexibility.
[0007] Gear skiving is a recent development in gear manufacturing that reduces traditional gear shape cycle time by up to 80%. Although extremely fast, traditional skiving is limited by cutter clearance and part configuration.
[0008] A gear cutter tool is provided for cutting internal gear teeth into a workpiece to form a gear. The gear cutter tool is configured to rotate about a longitudinal gear cutter rotation axis. The workpiece is configured to rotate about a workpiece rotation axis. The gear cutter tool comprises a gear cutter having a plurality of cutting teeth. Each of the plurality of cutting teeth has a tooth face that defines a cross-axis tooth angle defined between the tooth face and a line crossing the longitudinal gear cutter rotation axis. The cross-axis tooth angle is 1 to 15 degrees. The cross-axis tool angle of the gear cutter tool defined between the longitudinal gear cutter rotation axis and the workpiece rotation axis is substantially 0 degrees.
[0009] According to additional features, the cross-axis tool angle is 1 to 6 degrees. In another feature, the cross-axis tool angle is 1 to 5 degrees. In another feature, the cross-axis tool angle is 1 to 4 degrees. In yet another feature, the cross-axis tool angle is 3 degrees. In yet another feature, the cross-axis tool angle is 2 degrees. In yet another feature, the cross-axis tool angle is 1 degree. In some arrangements, the longitudinal gear cutter axis crosses the workpiece. The cross-axis tooth angle may be 10 to 15 degrees. In other arrangements, the cross-axis tooth angle may be 1 to 10 degrees.
[0010] A method for cutting internal gear teeth into a workpiece to form a gear using a gear cutter tool comprises the step of providing a gear cutter having a plurality of cutting teeth. Each of the plurality of cutting teeth has a tooth face that defines a cross-axis tooth angle defined between a tooth face and a line crossing the longitudinal gear cutter rotation axis. The cross-axis tooth angle is 1 to 15 degrees. The workpiece is rotated about the workpiece axis. The gear cutter tool is rotated about the longitudinal gear cutter axis. The workpiece and the longitudinal gear cutter axis define a cross-axis tool angle between them. The workpiece is cut into a plurality of teeth. The cross-axis tool angle is substantially 0 degrees.
[0011] According to additional features, the cross-axis tool angle is 1 to 6 degrees. In another feature, the cross-axis tool angle is 1 to 5 degrees. In another feature, the cross-axis tool angle is 1 to 4 degrees. In yet another feature, the cross-axis tool angle is 3 degrees. In yet another feature, the cross-axis tool angle is 2 degrees. In yet another feature, the cross-axis tool angle is 1 degree. The cross-axis tooth profile angle may be 10 to 15 degrees. In another arrangement, the cross-axis tooth profile angle may be 1 to 10 degrees. Brief explanation of the drawing
[0012] The present invention will be more fully understood from the detailed description and the accompanying drawings. FIG. 1a is a schematic perspective view of an exemplary prior art gear cutter system comprising a gear cutter configured to cut an internal gear in a blank orientation. FIG. 1b is a schematic perspective view of the system of FIG. 1a, illustrating a cutter that produces a precision internal gear in final orientation. FIG. 2 is a schematic end view of the system of FIG. 1a, illustrating the center distance between the rotation axis of the cutter and the rotation axis of the internal gear. FIG. 3 is a schematic side view of the cutter and internal gear of FIG. 1a, illustrating the angle of the cross axis between the axis of rotation for the cutter and the axis of rotation for the internal gear. Figure 4 is a schematic side view of a gear cutter of the prior art. FIG. 5 is a schematic side view of a gear cutter according to an example of the present invention. Figure 6 is a schematic diagram of the proposed tooth profile surface superimposed across the traditional tooth profile tip plane. Figure 7 is a schematic side-by-side drawing comparing the gear cutters of Figures 5 and 6. FIG. 8a is a cross-sectional view of a conventional gear. FIG. 8b is a cross-sectional view of a conventional gear cutter shown at a 6-degree cross-axis angle illustrating interference with a workpiece. FIG. 9a is a cross-sectional view of a conventional gear. FIG. 9b is a cross-sectional view of a gear cutter constructed according to the present invention and illustrated at a substantially 0-degree cross-axis angle that does not show interference with the workpiece. Specific details for implementing the invention
[0013] An exemplary involute gear cutter system (hereinafter “System”) comprises a computer numerical control (CNC) machine tool configured to cut a gear in a blank orientation to remove debris from the gear in a plurality of paths to produce a precision gear in a final orientation, and a modified tooth ratio gear cutter (hereinafter “Cutter”). The CNC machine tool includes a chuck and an active sub-spindle, i.e., controlled rotational motion through CNC control. The cutter may be mounted on the spindle, and the gear in a blank configuration may be attached to the chuck. More specifically, the cutter may have a plurality of cutting teeth, and each of the cutting teeth may have a pair of cutting edges configured to cut the gear in a blank orientation to provide the gear in a final orientation.
[0014] In the final orientation, the gear has an involute tooth profile comprising a plurality of cutting tooth sections and a plurality of valleys between them. The cutting edge can be configured to cut the gear in the blank orientation such that the gear in the final orientation includes spaced-apart active profile sections and working pitch diameters. Thus, the cutter can apply a generally constant force in a single or unidirectional direction along the surface of the gear to increase the accuracy of machining the gear, for example, within a tolerance of 0.0010 inches, without requiring a special cutting tool or cutting system.
[0015] Referring to FIGS. 1a through 3, an exemplary prior art system (100) comprises a computer numerical control (CNC) machine tool (102) having a chuck (104) and a spindle (106). The system (100) further comprises a cutter (108) attached to the spindle (106), which is configured to subsequently rotate the cutter (108) around a cutting axis (110) to cut a gear (112) in a blank orientation (Fig. 1a) and produce a gear (114) in a final orientation (Fig. 1b). A cutter (108) of this type is an external gear configured to cut an internal gear (112) in a blank orientation to produce an internal gear (114) in a final orientation. The internal gear (114) in the final orientation has a plurality of cutting tooth profiles (116). The tooth portion (116) has an involute tooth portion profile (118) comprising an active profile section (120) which is part of the surface of each tooth portion configured to contact the opposing tooth portion of the mesh-type gear.
[0016] The blank-oriented gear (112) is mounted on a chuck (104) configured to rotate the gear (112) around a cutting axis (122) (Fig. 1a), and the cutting axis (122) and the cutting axis (110) are at a center distance (CD WThey are spaced apart from each other by ). In addition, the cutting axis (122) and the cutting axis (110) are positioned at an angle of cross axis (α) relative to each other when the gear (114) is in final orientation. As used herein, the term “cross axis” is an angle defining the difference between the two axes of rotation of the gear workpiece and the cutting tool.
[0017] The system (100) may further include a flushing device (124) configured to deliver fluid to the gear (112) to remove debris, chips, or dust from the gear (112) as the spindle (106) rotates the cutter (108) to cut the gear (112) in a plurality of paths. The fluid may also remove heat from the system (100). In one example, the flushing device (124) is a fluid line (126) communicating with a reservoir (128) to supply water, nitrogen gas, or other fluid to the external gear (112). In the final orientation, the gear (114) has an involute tooth profile comprising a plurality of cutting tooth sections (116) and a plurality of valleys between them. The involute tooth profile (118) includes an active profile section (120), and the working pitch diameter is equally spaced when the gear (114) is in the final orientation. Further description of a skiving tool of the prior art can be found in the jointly owned U.S. Patent No. 10,016,827, the contents of which are expressly incorporated herein by reference.
[0018] The present invention enables the skiving of gear tooth profiles, which was previously impossible with current methods, due to the ability to accurately cut the workpiece while eliminating specific cutter / workpiece interference. Traditional skiving methods consist of rotary gear cutters mounted on an axis that is not the same as the axis of the workpiece. Traditional skiving methods are limited by the workpiece clearance when the cutting tool is maintained at a rotary cross-axis angle. The cross-axis angle of the gear cutter generates a cutting action that produces chips. A larger cross-axis angle enables a larger cutting action and increased chip formation. The desired cross-axis angle for conventional systems is typically 20 degrees, but it can be a lower angle, such as 15 or 12 degrees. With these design parameters, the tool clearance must be considered and limit the application of the skiving process.
[0019] As described in detail herein, the present invention enables the cross-axis angle to be completely or significantly reduced by making the axis of the workpiece and the axis of the tool identical or essentially identical (substantially within 1 to 6 degrees). A smaller cross-axis angle is required in situations where a small gap exists between the cutter and the workpiece geometry. The proposed invention allows for a very low cross-axis tool angle by adding a local tooth face angle modification that provides better cutting action while still allowing for a very small operating cross-axis angle. In this regard, minimizing or eliminating the cross-axis angle of the tool eliminates points of interference. Minimizing or eliminating the cross-axis angle allows the tool to reach areas that were previously impossible.
[0020] Traditional gear skiving tools are produced with a helix angle equal to the cross-axis angle of the skiving machine. This modern technology is readily available commercially. Chip formation occurs when the cross-axis angle of the cutter swipes across the tooth profile of the workpiece and cuts the material. The cross-axis angle creates this cutting action and is made possible by the cross-action (gear cutter) of the machine. The present invention shifts the cross-axis angle to the micro-level relative to each tooth profile of the gear cutter itself from the macro-level workpiece and machine axis. This allows the cutter to maintain a cross-axis angle of nearly 0 degrees, while still providing the cross-axis necessary for chip formation by utilizing the local cross-axis angle of each tooth profile of the cutter. As used herein, "near" or substantially 0 is used to refer to an angle between 1 and 6 degrees. The advantage of this is that the tool can be moved closer to the interference location of the workpiece, which was previously impossible. In this regard, the present invention enables skiving for more types of workpieces, shoulder work, and applications with clearance issues. Furthermore, the present invention enables a skiving process on a machine without an intersecting axis between the workpiece and the cutting tool axis. Machine tool costs can be significantly reduced by utilizing a custom-made skiving machine instead of a standard machine tool.
[0021] Now, referring to FIG. 4, a gear cutter or cutting tool configured according to one prior art example is illustrated and is generally identified as reference (208). The gear cutter (208) comprises a plurality of tooth profiles (232). Each tooth profile (232) defines a tooth profile face (241) having a tooth profile face angle (242) with respect to the workpiece (212). The cross axis angle (250) is defined between the longitudinal rotation axis (252) of the gear cutter (208) and the transverse axis (254) through the workpiece (212) (also referred to herein as the workpiece (212) rotation axis). The cross axis angle (250) of the gear cutter (208) creates a small clearance distance at a specific location (258) of the workpiece (212). The maximum cross axis angle depends on the workpiece geometry and clearance. As illustrated in FIG. 4, the tooth face angle (242) is parallel to the face of the workpiece (212). The workpiece (212) is cut at 270 by the tooth portion (232). During cutting, both the gear cutter (208) and the workpiece (212) rotate (the gear cutter (208) around the longitudinal cutting axis (282) and the workpiece (212) around the rotation axis (254), but at different revolutions per minute (RPM).
[0022] Now, referring to FIGS. 5 and 6, a gear cutter tool configured according to an example of the present invention is illustrated and is generally identified by reference numeral 308. The gear cutter (308) comprises a plurality of tooth profiles (332). Each tooth profile (332) defines a tooth profile face (341). Each tooth profile (332) has a cross-axis tooth profile angle (350) localized to each tooth profile (332) rather than the entire cutter (308). The cross-axis angle (350) is not zero and is defined as the angle between the tooth profile face (341) and a line (352) crossing the longitudinal axis (or rotation axis) (354) of the gear cutter (308). According to the present invention, it is illustrated that by providing a tooth profile angle (350) of 1 to 15 degrees, the gear cutter tool (308) is arranged at an improved angle (relative to the workpiece) to reach areas of the workpiece that were previously impossible.
[0023] By creating a local cross-axis tooth angle (350) at each tooth section (332), the cross-axis tool angle (372) defined between the longitudinal axis (354) of the gear cutter (308) and the rotation axis (374) of the workpiece (312) can be significantly reduced to nearly 0 degrees. Again, it is shown that an angle between 1 and 6 degrees can be used to achieve successful cutting and improved tool reach. In this regard, the longitudinal axis (354) of the gear cutter (308) can be arranged parallel to or near the rotation axis (374) of the workpiece (312). Rather than requiring the entire gear cutter (308) to be tilted (see FIG. 4 of the prior art), each tooth section (341) has its own local cross-axis angle (350). Thus, skiving can be successfully performed up to the shoulder of the workpiece (312). Additionally, the path of the cutting tool (308) may further penetrate into an area of the workpiece (312) previously restricted by the part geometry. The workpiece (312) is cut at 370 (an internal spline of the workpiece in FIG. 5) by the tooth portion (332). During cutting, both the gear cutter (308) and the workpiece (312) rotate (the gear cutter (308) around the longitudinal cutting axis (372), and the workpiece (312) around the rotation axis (274), but rotate at different RPMs.
[0024] FIG. 7 illustrates a comparison between a gear cutter (308) and a workpiece (312) according to the present invention and a gear cutter (208) and a workpiece (212) of the prior art. In FIG. 7, it will be understood that the cross-axis tool angle (372) is more accurately depicted between 1 and 6 degrees (and is harder to see compared to the exaggerated depiction of the same angle in FIG. 5). In particular, an additional clearance (380) is provided in the gear cutter (308) before interference with the workpiece (312). FIG. 8a illustrates a cross-sectional view of a conventional gear (412). FIG. 8b illustrates a conventional gear cutter (408) depicted at a cross-axis angle of 6 degrees, showing interference with the workpiece (412) at the reference portion (434) as the gear cutter (408) advances along the feed axis (438). As illustrated, skiving is not possible due to interference (434) between the gear cutter (408) and the workpiece (412). FIG. 9a illustrates a cross-sectional view of a conventional gear (512). FIG. 9b is a cross-sectional view of a gear cutter (308) configured according to the present invention and illustrated at a substantially 0-degree cross-axis angle as the gear cutter (308) advances along a feed axis (538) that does not show interference with the workpiece.
[0025] In the case of traditional skiving machines, the machine must have the ability to provide a cross axis. In this regard, instead of simply a horizontal milling machine, the skiving machine must also provide the user with the ability to provide a fifth axis table or other tilting axis to achieve the desired cross axis. The present invention eliminates this requirement so that the final result can be achieved on much less expensive equipment that does not provide additional adjustment axes.
[0026] The foregoing description of many examples is provided for illustrative and illustrative purposes only. It is not intended to be comprehensive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular example, but are interchangeable and may be used in selected examples where applicable, even if not specifically illustrated or described. The same thing may also be varied in many ways. Such changes should not be construed as departing from the invention, and all such modifications are intended to be included within the scope of the invention.
Claims
Claim 1 A gear cutter tool for cutting an internal gear tooth profile into a workpiece to form a gear, wherein the gear cutter tool is configured to rotate around a longitudinal gear cutter rotation axis and the workpiece is configured to rotate around a workpiece rotation axis, and the gear cutter tool comprises: a gear cutter having a plurality of cutting tooth profiles, and each of the plurality of cutting tooth profiles having a tooth profile face that defines a cross-axis tooth profile angle defined between a line crossing the longitudinal gear cutter rotation axis and the cross-axis tooth profile angle defined between the longitudinal gear cutter rotation axis and the workpiece rotation axis, wherein the cross-axis tooth profile angle is 1 to 15 degrees and the cross-axis tool angle of the gear cutter tool defined between the longitudinal gear cutter rotation axis and the workpiece rotation axis is 1 to 4 degrees. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A gear cutter tool according to claim 1, wherein the cross-axis tool angle is 3 degrees. Claim 6 A gear cutter tool according to claim 1, wherein the cross-axis tool angle is 2 degrees. Claim 7 A gear cutter tool according to claim 1, wherein the cross-axis tool angle is 1 degree. Claim 8 In claim 1, the longitudinal gear cutter axis is a gear cutter tool that crosses the workpiece. Claim 9 A gear cutter tool according to claim 1, wherein the cross axis tooth angle is 10 to 15 degrees. Claim 10 A gear cutter tool according to claim 1, wherein the cross axis tooth angle is 1 to 10 degrees. Claim 11 A method for cutting internal gear teeth into a workpiece to form a gear using a gear cutter tool, comprising: a gear cutter having a plurality of cutting teeth; each of the plurality of cutting teeth having a tooth face that defines a cross-axis tooth angle defined between a line crossing a longitudinal gear cutter rotation axis and a tooth face, wherein the cross-axis tooth angle is 1 to 15 degrees; a step of rotating the workpiece around a workpiece axis; a step of rotating the gear cutter tool around a longitudinal gear cutter axis, wherein the workpiece and the longitudinal gear cutter axis define a cross-axis tool rotation angle between them; and a step of cutting the workpiece with the plurality of teeth, wherein the cross-axis tool angle is 1 to 4 degrees. Claim 12 delete Claim 13 delete Claim 14 delete Claim 15 In claim 11, the method wherein the cross-axis tool angle is 3 degrees. Claim 16 In claim 11, the method wherein the cross-axis tool angle is 2 degrees. Claim 17 In claim 11, the method wherein the cross-axis tool angle is 1 degree. Claim 18 In claim 11, the method wherein the cross-axis tooth angle is 10 to 15 degrees. Claim 19 In claim 11, the method wherein the cross-axis tooth angle is 1 to 10 degrees.