Near zero degree horizontal axis gear cutter and method of gear cutting using such a cutter

Abstract

A gear cutting tool (308) for cutting internal gear teeth in a workpiece (312) to form a gear is provided. The gear cutting tool is configured to rotate about a longitudinal gear cutter rotational axis (354). The workpiece is configured to rotate about a workpiece rotational axis (374). The gear cutting tool includes a gear cutter having a plurality of cutting teeth (332). Each cutting tooth of the plurality of cutting teeth has a tooth face (341) defining a transverse axis tooth angle (350) defined between the tooth face and a line (352) transverse to the longitudinal gear cutter rotational axis. The transverse axis tooth angle is between one and fifteen degrees. A transverse axis tool angle (372) of the gear cutting tool defined between the longitudinal gear cutter rotational axis and the workpiece rotational axis is substantially close to zero degrees.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Patent Application No. 63 / 091,675, filed October 14, 2020. The disclosure of the above application is incorporated herein by reference. Technical Field

[0003] This disclosure relates in its entirety to a gear cutter that forms gear teeth on the inner diameter of a workpiece and an associated coolant delivery assembly. Background Technology

[0004] Gear manufacturers utilize various machining processes and corresponding cutting tools to produce gears. Exemplary processes may include hobbing, shaping, milling, shearing, and grinding. The process chosen by a gear manufacturer may depend on the type of gear being machined and the gear's production tolerances. Other considerations when selecting a method may include the gear's dimensions, the configuration of its internal cross-section or flange, the number of gears to be produced, the gear ratio, and cost.

[0005] Gear teeth adjacent to other component features are currently limited to production methods such as gear shaping or rack rolling. For internal gear teeth, gear shaping or broaching are traditional manufacturing methods, but each process is limited by the component type. In other words, broaching requires a completely unobstructed component layout so that the cutter can pass completely through the component. Gear shaping allows for close contact with interfering surfaces for cutting teeth, but it is inherently slower in terms of machine cycle time and flexibility.

[0006] Gear scraping is the latest development in gear manufacturing, reducing the cycle time of traditional gear shaping by up to 80%. Although traditional gear scraping is very fast, it is limited by cutter clearance and component configuration. Summary of the Invention

[0007] A gear cutting tool is provided for cutting internal gear teeth in a workpiece to form a gear. The gear cutting 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 cutting tool includes a gear cutter having a plurality of cutting teeth. Each of the plurality of cutting teeth has a tooth face that defines a transverse tooth angle defined between the tooth face and a line transverse to the longitudinal gear cutter rotation axis. The transverse tooth angle is between one degree and fifteen degrees. The transverse cutter angle of the gear cutting tool defined between the longitudinal gear cutter rotation axis and the workpiece rotation axis is substantially close to zero degrees.

[0008] Depending on the additional features, the transverse gear cutter angle is between one and six degrees. In other features, the transverse gear cutter angle is between one and five degrees. In other features, the transverse gear cutter angle is between one and four degrees. In other features, the transverse gear cutter angle is three degrees. In other features, the transverse gear cutter angle is two degrees. In other features, the transverse gear cutter angle is one degree. In some arrangements, the longitudinal gear cutter axis is transverse relative to the workpiece. The transverse gear tooth angle can be between ten and fifteen degrees. In other arrangements, the transverse gear tooth angle can be between one and ten degrees.

[0009] A method for cutting internal gear teeth in a workpiece to form a gear using a gear cutting tool includes providing a gear cutter having a plurality of cutting teeth. Each of the plurality of cutting teeth has a tooth face that defines a transverse tooth angle defined between the tooth face and a line transverse to the longitudinal axis of rotation of the gear cutter. The transverse tooth angle is between one degree and fifteen degrees. The workpiece rotates about its axis. The gear cutting tool rotates about the longitudinal axis of the gear cutter. The workpiece axis and the longitudinal axis of the gear cutter define the transverse cutter angle between them. The workpiece is cut using the plurality of teeth. The transverse cutter angle is substantially close to zero degrees.

[0010] According to the additional feature, the transverse axis tool angle is between one and six degrees. In other features, the transverse axis tool angle is between one and five degrees. In other features, the transverse axis tool angle is between one and four degrees. In other features, the transverse axis tool angle is three degrees. In other features, the transverse axis tool angle is two degrees. In other features, the transverse axis tool angle is one degree. The transverse axis tooth angle can be between ten and fifteen degrees. In other arrangements, the transverse axis tooth angle can be between one and ten degrees. Attached Figure Description

[0011] This disclosure will be more fully understood in light of the specific embodiments and accompanying drawings, wherein:

[0012] Figure 1A This is a schematic perspective view of an exemplary prior art gear cutter system including a gear cutter configured to cut an internal gear in an initial orientation.

[0013] Figure 1B yes Figure 1A A schematic perspective view of the system, showing that the cutter has produced a precision internal gear in its final orientation;

[0014] Figure 2 yes Figure 1A A schematic end view of the system, showing the center distance between the rotation axis of the cutter and the rotation axis of the internal gear;

[0015] Figure 3 yes Figure 1AA schematic side view of the cutter and internal gear, showing the transverse angle between the axis of rotation of the cutter and the axis of rotation of the internal gear;

[0016] Figure 4 This is a schematic side view of a prior art gear cutter;

[0017] Figure 5 This is a schematic side view of a gear cutter according to an example of this disclosure;

[0018] Figure 6 This is a schematic diagram of the proposed tooth surface superimposed on the leading edge face of a conventional tooth;

[0019] Figure 7 It is Figure 5 and Figure 6 A schematic side-by-side illustration comparing gear cutters;

[0020] Figure 8A This is a sectional view of a conventional gear;

[0021] Figure 8B This is a cross-sectional view of a conventional gear cutter shown at a 6-degree transverse axis angle, illustrating its interference with the workpiece;

[0022] Figure 9A It is a sectional view of a conventional gear; and

[0023] Figure 9B This is a cross-sectional view of a gear cutter constructed according to this disclosure and shown at a transverse axis angle substantially close to zero degrees, showing no interference with the workpiece. Detailed Implementation

[0024] An exemplary involute gear cutter system (hereinafter referred to as the "System") includes a computer numerical control (CNC) machine tool and a modified gear ratio cutter (hereinafter referred to as the "Cutter") configured to cut a gear in an initial orientation to remove chips from the gear in multiple passes to produce a precision gear in its final orientation. The CNC machine tool includes a chuck and a movable counterspindle, i.e., rotary motion controlled by CNC control. The Cutter may be mounted on a spindle, and the gear in its initial configuration may be attached to the chuck. More specifically, the Cutter may have multiple cutting teeth, and each of the cutting teeth may have a pair of cutting edges configured to cut the gear in its initial orientation to provide a gear in its final orientation.

[0025] In its final orientation, the gear has an involute tooth profile comprising multiple cutting teeth and multiple valleys therebetween. The cutting edge can be configured to cut the gear in its initial orientation such that the gear in its final orientation comprises effective cross-sections and operating pitch circle diameters spaced apart from each other. Therefore, the cutter can apply a substantially constant force along the surface of the gear in a single or unilateral direction to increase the accuracy of gear machining within, for example, 0.0010-inch tolerances, without requiring special cutting tools or cutting systems.

[0026] refer to Figures 1A to 3 An exemplary prior art system 100 includes a computer numerical control (CNC) machine tool 102, which partially includes a chuck 104 and a spindle 106. System 100 also includes a cutter 108 attached to the spindle 106, which is then configured to rotate the cutter 108 about a cutting axis 110 to cut a gear 112 in an initial orientation. Figure 1A ), and produce gear 114 in final orientation ( Figure 1B The cutter 108 of this type is an external gear configured to cut an internal gear 112 in an initial orientation to produce an internal gear 114 in a final orientation. The internal gear 114 in the final orientation has a plurality of cutting teeth 116. The teeth 116 have an involute tooth profile 118 including an effective section 120, which is a portion of each tooth surface configured to contact the opposing teeth of the meshing gears.

[0027] The gear 112, in its initial orientation, is mounted to a chuck 104, which is configured to allow the gear 112 to revolve around a cutting axis 122. Figure 1A Rotate so that the cutting axis 122 and the cutting axis 110 are spaced apart by a center distance CD. W Additionally, when gear 114 is in its final orientation, cutting axis 122 and cutting axis 110 are positioned relative to each other at a transverse angle α. As used herein, the term "transverse axis" is an angle that defines the difference between the two axes of rotation of the gear workpiece and the cutting tool.

[0028] System 100 may also include a flushing device 124 configured to deliver fluid to gear 112 during multiple passes of machining when spindle 106 rotates cutter 108 to cut gear 112, in order to remove shavings, debris, or dust from gear 112. The fluid may also remove heat from system 100. In one example, flushing device 124 is a fluid line 126 in communication with reservoir 128 to supply water, nitrogen, or another fluid to outer gear 112. In its final orientation, gear 114 has an involute tooth profile comprising a plurality of cutting teeth 116 and a plurality of valleys therebetween. The involute tooth profile 118 includes an effective profile 120, and when gear 114 is in its final orientation, the operating pitch circle diameter is spaced apart from the effective profile. Additional description of prior art scraping tools can be found in commonly owned U.S. Patent No. 10,016,827, the contents of which are expressly incorporated herein by reference.

[0029] This disclosure makes gear tooth scraping, previously impossible, possible using the present method, because it enables precise workpiece cutting while eliminating certain cutter / workpiece interference. Conventional scraping methods involve a rotary gear cutter mounted on an axis different from the workpiece's axis. Conventional scraping methods are limited by workpiece clearance when the cutting tool is held at its rotational transverse axis angle. The transverse axis angle of the gear cutter generates the cutting motion that produces chips. A larger transverse axis angle allows for more cutting motion and increases chip formation. The expected transverse axis angle for conventional systems is typically 20 degrees, but smaller angles, such as 15 degrees or 12 degrees, are possible. Under such design parameters, tool clearance must be considered, limiting the application of the scraping process.

[0030] As will be described in detail herein, this disclosure allows the workpiece axis and the tool axis to be the same or substantially the same (within a range of substantially one to six degrees), thereby completely eliminating or greatly reducing the transverse axis angle. Smaller transverse axis angles are desirable when there is a small gap between the cutter and workpiece geometry. The proposed disclosure allows for a very small transverse axis tool angle by adding a local tooth face angle modification, which provides better cutting action while still allowing for a very small operating transverse axis angle. At this point, minimizing or eliminating the tool's transverse axis angle eliminates points of interference. Minimizing or eliminating the transverse axis angle allows the tool to reach areas that were previously impossible.

[0031] Conventional gear scraping tools are manufactured with a helix angle equal to the cross-axis angle of the scraping machine. This prior art is readily available commercially. Chip formation occurs when the cross-axis angle of the cutter sweeps across the workpiece teeth and cuts off the material. The cross-axis angle produces this cutting action and is made possible by the cross-action of the machine (gear cutter). This disclosure moves the cross-axis angle from the macroscopic level of the workpiece and machine axis to the microscopic level of each tooth on the gear cutter itself. This allows the cutter to be maintained at a near-zero cross-axis angle while still providing the cross-axis necessary for chip formation by utilizing the local cross-axis angle on each tooth of the cutter. As used herein, near or substantially zero is used to refer to an angle between one and six degrees. The advantage of doing so is that the tool can be moved closer to obstructing locations on the workpiece, which was previously impossible. In this respect, this disclosure pioneers scraping for a wider range of workpiece types, shoulder work, and clearance-challenging applications. Furthermore, this disclosure pioneers a scraping process for machines without a cross-axis between the workpiece and the cutting tool axis. Compared to custom-made scraping machines, using standard machine tools can significantly reduce machine tool costs.

[0032] Now for reference Figure 4 This illustration shows a gear cutter or cutting tool constructed according to an example of the prior art, and the gear cutter is generally identified by reference numeral 208. The gear cutter 208 includes a plurality of teeth 232. Each tooth 232 defines a tooth face 241 having a tooth face angle 242 relative to a workpiece 212. A transverse axis angle 250 is defined between the longitudinal axis of rotation 252 of the gear cutter 208 and a transverse axis 254 (also referred to herein as the axis of rotation of the workpiece 212) passing through the workpiece 212. The transverse axis angle 250 of the gear cutter 208 creates small clearance distances at certain locations 258 of the workpiece 212. The maximum transverse axis angle depends on the workpiece geometry and clearance. Figure 4 As shown, the tooth face angle 242 is parallel to the face of the workpiece 212. The workpiece 212 is cut at 270 by the tooth 232. During the cutting, both the gear cutter 208 and the workpiece 212 rotate (the gear cutter 208 rotates about the longitudinal cutting axis 282, and the workpiece 212 rotates about the rotation axis 254), but at different revolutions per minute (RPM).

[0033] refer to Figure 5 and Figure 6This illustration shows a gear cutting tool constructed according to an example of the present disclosure, and the gear cutting tool is generally identified by reference numeral 308. The gear cutter 308 includes a plurality of teeth 332. Each tooth 332 defines a tooth face 341. Each tooth 332 has a transverse tooth angle 350 located at each tooth 332 rather than the entire cutter 308. The transverse tooth angle 350 is not zero and is defined as the angle between the tooth face 341 and a line 352 transverse to the longitudinal axis (or axis of rotation) 354 of the gear cutter 308. According to the present disclosure, a tooth angle 350 between one degree and fifteen degrees has been provided, allowing the gear cutting tool 308 to be arranged at an improved angle (relative to the workpiece) to reach previously inaccessible areas of the workpiece.

[0034] By generating a local transverse tooth angle 350 at each tooth 332, the transverse 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 near zero degrees. Similarly, it has been shown that successful cutting and improved tool reach can be achieved using angles between one and six degrees. In this respect, the longitudinal axis 354 of the gear cutter 308 can be arranged parallel or nearly parallel to the rotation axis 374 of the workpiece 312. It is not required that the entire gear cutter 308 be tilted (see...). Figure 4 (Previous technology), but each tooth surface 341 is its own local transverse axis angle 350. Therefore, scraping can be successfully performed, reaching the shoulder of the workpiece 312. Furthermore, the path of the cutting tool 308 can further penetrate into the area of ​​the workpiece 312 previously limited by the part geometry. At 370 ( Figure 5 The internal spline of the workpiece cuts the workpiece 312 through the gear 332. During the cutting, both the gear cutter 308 and the workpiece 312 rotate (the gear cutter 308 rotates about the longitudinal cutting axis 372, and the workpiece 312 rotates about the rotation axis 274), but the RPMs are different.

[0035] Figure 7 A comparison is shown between a prior art gear cutter 208 and workpiece 212 and a gear cutter 308 and workpiece 312 according to this disclosure. It should be understood that, in Figure 7 In the text, the transverse axis tool angle 372 is more accurately shown as being between one degree and six degrees (and with...). Figure 5 (It is more difficult to see compared to the exaggerated depiction of the same angle in the middle). It is worth noting that an additional clearance 380 is provided on the gear cutter 308 before interfering with the workpiece 312. Figure 8A A cross-sectional view of a conventional gear 412 is shown. Figure 8BA conventional gear cutter 408, shown at a 6-degree transverse axis angle, illustrates the interference with the workpiece 412 at reference 434 as the gear cutter 408 advances along the feed axis 438. As shown, scraping is impossible due to the interference 434 between the gear cutter 408 and the workpiece 412. Figure 9A A cross-sectional view of a conventional gear 512 is shown. Figure 9B This is a cross-sectional view of the gear cutter 308 constructed according to the present disclosure and shown at a transverse angle of substantially near zero degrees as the gear cutter 308 advances along the feed axis 538, showing no interference with the workpiece.

[0036] Traditional scraping machines must have the capability to provide a horizontal axis. In this respect, unlike simple horizontal milling machines, scraping machines must also provide the user with the ability to have a fifth axis table or other tilting axes to achieve the desired horizontal axis. This disclosure eliminates this requirement, allowing the end result to be achieved on much cheaper equipment without providing additional adjustment axes.

[0037] The foregoing description has provided numerous examples for illustrative and descriptive purposes. It is not intended to be exhaustive or limiting of this disclosure. Various elements or features of a particular aspect are generally not limited to that particular example, but are interchangeable where applicable and can be used in the selected example, even if not specifically shown or described. They can also be changed in many ways. Such variations should not be considered as departing from this disclosure, and all such modifications are intended to be included within the scope of this disclosure.

Claims

1. A method for cutting internal gear teeth in a workpiece using a gear cutting tool to form a gear, the method comprising: A gear cutter is provided having a plurality of cutting teeth, each of the plurality of cutting teeth having a tooth face, the tooth face defining a transverse tooth angle defined between the tooth face and a line transverse to the longitudinal axis of rotation of the gear cutter, wherein the transverse tooth angle is between one degree and fifteen degrees. Rotate the workpiece around its axis. The gear cutting tool is rotated about the longitudinal gear cutter axis, and the workpiece axis and the longitudinal gear cutter axis define the transverse axis tool angle therebetween; as well as The workpiece is cut using the plurality of teeth, wherein the cross-axis cutter angle is between one degree and six degrees.

2. The method according to claim 1, wherein the cross-axis tool angle is between one degree and five degrees.

3. The method according to claim 2, wherein the cross-axis tool angle is between one degree and four degrees.

4. The method according to claim 3, wherein the cross-axis tool angle is three degrees.

5. The method according to claim 3, wherein the cross-axis tool angle is two degrees.

6. The method according to claim 3, wherein the cross-axis tool angle is one degree.

7. The method according to claim 1, wherein the transverse tooth angle is between 10 degrees and 15 degrees.

8. The method according to claim 1, wherein the transverse tooth angle is between one degree and ten degrees.

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