JP7772243B2 - Gear cutting tool design method and gear cutting tool design support device - Google Patents

Description

The present invention relates to a method for designing gear cutting tools and a design support device for gear cutting tools.

When gears are subjected to load, deformation of the teeth or shaft can cause the meshing condition to deteriorate, resulting in noise. There is a growing demand for gears to achieve ideal meshing under load and improve quietness, which requires the tooth flank shape to be modified. Modification elements for the tooth flank shape of gear teeth include, for example, tooth trace inclination (also known as "tooth trace twist"), crowning, bias, pressure angle, and tooth profile roundness. Of these, tooth trace inclination, crowning, and bias are modification elements in the tooth trace direction, while pressure angle and tooth profile roundness are modification elements in the tooth profile direction (from the tooth root to the tooth tip).

JP 2021-11011 A (Patent Document 1) describes a technique for applying additional motion to a gear cutting tool to change the modification element in the tooth trace direction of a gear. This is expected to improve the accuracy of the gear teeth in the tooth trace direction.

Japanese Patent Application Laid-Open No. 2021-11011

However, with the above technology, when additional motion is applied to the gear cutting tool to cut a gear, although the accuracy of the gear's tooth trace direction is improved, a problem arises in that errors occur in the shape of the gear's tooth profile direction.

The present invention was made in consideration of these problems and aims to provide a design method for gear cutting tools that can correct errors in the tooth trace direction and tooth profile direction of a gear, and a design support device for gear cutting tools.

One aspect of the present invention is
A method for designing a gear cutting tool for machining gear teeth on a workpiece by moving the workpiece and the gear cutting tool relative to each other while rotating the gear cutting tool and the workpiece synchronously, with an axis parallel to the central axis of the gear cutting tool forming a predetermined crossed-axis angle with respect to a central axis of the workpiece, comprising:
acquiring gear specifications that are specifications of the gear, acquiring tool specifications that are specifications of the gear cutting tool, acquiring a target tooth profile direction modification amount that is a target value of a tooth profile direction modification element of a tooth flank shape of the gear, and provisionally designing a tool edge shape of the gear cutting tool based on the gear specifications, the tool specifications, and the target tooth profile direction modification amount;
a step of acquiring a target modification amount in the tooth trace direction, which is a target value of a modification element in the tooth trace direction of the tooth flank shape, and determining a correction amount of a machining control element during a machining operation based on the target modification amount in the tooth trace direction;
calculating a first tooth flank profile of the gear based on a correction amount of the processing control element and the temporarily designed tool blade profile;
comparing the calculated first tooth flank profile with a target tooth flank profile included in the gear specifications, and calculating a first target error in the tooth profile direction of the first tooth flank profile;
a step of finally designing the tool blade shape based on the tooth profile direction target modification amount and a first object error modification amount for reducing the first object error;
The present invention relates to a method for designing a gear cutting tool having the above-mentioned features.

Another aspect of the present invention is
A design support device for a gear cutting tool that processes gear teeth on a workpiece by moving the workpiece and the gear cutting tool relative to each other while rotating the gear cutting tool and the workpiece synchronously, with an axis parallel to the central axis of the gear cutting tool forming a predetermined crossed axis angle with respect to a central axis of the workpiece, comprising:
a gear specification acquisition unit that acquires gear specifications that are specifications of the gear;
a tool specification acquisition unit that acquires tool specifications that are specifications of the gear cutting tool;
a tooth profile direction target modification amount acquisition unit that acquires a tooth profile direction target modification amount, which is a target value of a tooth profile direction modification element of the tooth flank shape of the gear;
a provisional design unit that provisionally designs a tool blade shape of the gear cutting tool based on the gear specifications, the tool specifications, and the tooth profile direction target modification amount;
a tooth trace direction target modification amount acquisition unit that acquires a tooth trace direction target modification amount, which is a target value of a tooth trace direction modification element of the tooth flank shape;
a correction amount determination unit that determines a correction amount of a machining control element during a machining operation based on the tooth trace direction target modification amount;
a first tooth flank form calculation unit that calculates a first tooth flank form of the gear based on a correction amount of the processing control element and the temporarily designed tool blade form;
a first object error calculation unit that compares the calculated first tooth flank profile with a target tooth flank profile included in the gear specifications and calculates a first object error in the tooth profile direction of the tooth flank profile;
a final design unit that final designs the tool blade shape based on the tooth profile direction target modification amount and a first object error modification amount for reducing the first object error;
The present invention relates to a design support device for gear cutting tools, which is equipped with the above.

According to one and other aspects of the present invention, the tool blade shape of a gear cutting tool T is designed based on a first objective error correction amount for reducing a first objective error that occurs when a machining control element is corrected during machining based on a target modification amount in the tooth trace direction. This makes it possible to suppress errors in the gear tooth flank shape in the tooth profile direction, even when a machining control element is corrected based on a target modification amount in the tooth trace direction.

Note that the symbols in parentheses in the claims indicate their correspondence with the specific means described in the embodiments below, and do not limit the technical scope of the present invention.

FIG. 1 is a perspective view showing a processing device according to a first embodiment. FIG. 1 is a diagram showing a workpiece and a gear cutting tool in gear skiving processing when a crossed-axis angle is set, viewed in the radial direction of the gear cutting tool. 2 viewed in the direction of the central axis of the gear cutting tool. FIG. 10 is a diagram illustrating the operation of gear skiving, as viewed in the radial direction of the gear cutting tool. 4 viewed in the direction of the central axis of the machining tool. FIG. FIG. 1 is a view of a workpiece and a gear cutting tool in gear skiving processing when an offset angle is set, viewed in the radial direction of the gear cutting tool. FIG. 10 is a diagram showing the amount of crowning correction of the correction element. FIG. 10 is a diagram showing the amount of bias correction of a correction element. FIG. 10 is a diagram showing the amount of correction of the tooth trace inclination of the correcting element. FIG. 10 is a diagram showing the amount of pressure angle modification of a correcting element. FIG. 10 is a diagram showing the amount of correction of the tooth profile roundness of the correcting element. FIG. 10 is a diagram showing a motion that changes the center distance between the central axis of a gear cutting tool and the central axis of a workpiece in a parabolic manner relative to the position of the face width. FIG. 10 is a diagram showing a movement for linearly changing the cross-axis angle between the central axis of the gear cutting tool and the central axis of the workpiece relative to the position of the tooth width. 10 is a diagram showing a movement in which the rotation angle of the workpiece relative to the rotation angle of the gear cutting tool is changed linearly relative to the position of the face width; FIG. 10 is a graph showing a correlation between a change amount in the Y-axis and a modification amount of crowning, a correlation between a change amount in the Y-axis and a modification amount of bias, and a correlation between a change amount in the Y-axis and a modification amount of tooth trace inclination. FIG. 10A and 10B are diagrams showing the correlation between the amount of change in the B axis and the amount of crowning modification, the correlation between the amount of change in the B axis and the amount of bias modification, and the correlation between the amount of change in the B axis and the amount of tooth trace inclination modification. 10A and 10B are diagrams showing the correlation between the amount of change in the Cw axis and the amount of crowning modification, the correlation between the amount of change in the Cw axis and the amount of bias modification, and the correlation between the amount of change in the Cw axis and the amount of tooth trace inclination modification. FIG. 10 is a diagram showing the correlation between the amount of change in the X and Y axes and the amount of crowning modification, the correlation between the amount of change in the X and Y axes and the amount of bias modification, and the correlation between the amount of change in the X and Y axes and the amount of tooth trace inclination modification. FIG. 1 is a diagram showing the configuration of a design support apparatus according to a first embodiment. 3 is a flowchart showing the operation of the design support apparatus and the main flow of a design method. 10 is a flowchart showing a provisional design process for a tool blade shape. 10 is a flowchart showing a correction amount determination process. 10 is a flowchart showing the design process. FIG. 10 is a perspective view showing a state in which a first target error is calculated based on a cross section perpendicular to the axis at one location in the center of the gear in the face width direction. 10 is a flowchart showing a second error calculation process. 10 is a flowchart showing a redesign process. 10 is a flowchart showing a correction amount redetermining process. FIG. 11 is a perspective view showing a state in which a first target error is calculated based on an axis-perpendicular cross section at any one location in the face width direction of a gear in the second embodiment. FIG. 11 is a perspective view showing a state in which a first target error is calculated based on axis-perpendicular cross sections at multiple locations in the face width direction of a gear in the third embodiment. FIG. 11 is a perspective view showing a state in which a first target error is calculated based on the entire range in the face width direction of a gear in the fourth embodiment. FIG. 13 is a perspective view showing a state in which a first target error is calculated based on a partial range in the face width direction of a gear in embodiment 5.

(Embodiment 1)
1. Configuration of the gear cutting device A design method and design support device for a gear cutting tool (also referred to as a "gear skiving cutter") according to a first embodiment of the present invention are applied to the design of a gear cutting tool for machining a workpiece. The workpiece according to this embodiment is supported by the gear cutting device, and gear teeth are formed on the workpiece by the gear cutting tool attached to the gear cutting device.

The configuration of the gear cutting device will be described with reference to Figure 1. In this embodiment, the gear cutting device 1 cuts gear teeth on the workpiece W by moving the workpiece W and the gear cutting tool T relative to each other while rotating the gear cutting tool T and the workpiece W synchronously, with an axis parallel to the central axis RT of the gear cutting tool T at a predetermined cross-axis angle α with respect to the central axis RW of the workpiece W.

As shown in FIG. 1, the gear machining device 10 is, for example, a five-axis machining center having three linear axes and two rotational axes as drive axes that change the relative position and posture of the workpiece W and the gear machining tool T. In this embodiment, the gear machining device 10 has three orthogonal linear axes (X-axis, Y-axis, and Z-axis) as linear axes, and the B-axis and Cw-axis as rotational axes. In this embodiment, the B-axis is a rotational axis about the central axis RB of the rotary table 14, which is parallel to the Y-axis, and the Cw-axis is a rotational axis about the central axis RW of the workpiece W. The gear machining device 10 also has a Ct-axis, which is a rotational axis about the central axis RT of the gear machining tool T, and when the Ct-axis is included, it becomes a six-axis machining center.

The gear machining device 10 is equipped with a tool spindle 11 that supports a gear machining tool T and is rotatable about the Ct axis, and is movable in the Y and Z axes. Furthermore, the gear machining device 10 is equipped with a workpiece spindle 12 that supports a workpiece W and is rotatable about the Cw axis, is rotatable about the B axis, and is movable in the X axis. In this embodiment, a case where gear teeth are machined on the workpiece W by gear skiving will be described. Note that the configuration is not limited to the above, and the tool spindle 11 and workpiece spindle 12 may be configured to be movable relative to each other.

2. Gear Skiving Gear skiving will be described with reference to Figures 2, 3, 4, 5, and 6. As shown in Figures 2 and 3, gear skiving is performed by positioning the central axis RT of a gear cutting tool T at an intersecting axis angle α with an axis parallel to the central axis RW of a workpiece W. When viewed from the X-axis direction, the central axis RT of the gear cutting tool T and the central axis RW of the workpiece W are parallel. The center-to-center distance between the central axis RT of the gear cutting tool T and the central axis RW of the workpiece W is defined as D.

As shown in Figures 4 and 5, this method machines gear teeth on the workpiece W by feeding the gear cutting tool T in the direction of the center axis RW of the workpiece W relative to the workpiece W while synchronizing the rotation of the workpiece W about its center axis RW with the rotation of the gear cutting tool T about its center axis RT. In gear skiving, each tooth groove portion of the workpiece W is machined only once by the gear cutting tool T during one rotation of the workpiece W.

Figure 6 shows the offset angle γ. The offset angle γ is the angle when the gear cutting tool T and the machining point of the workpiece W are shifted in the circumferential direction of the workpiece W. The reference position where the offset angle γ is zero is the position of the gear cutting tool T corresponding to the machining point at which the center-to-center distance D is greatest when the center axis RT of the gear cutting tool T and the center axis RW of the workpiece W are parallel and viewed from a direction perpendicular to the center axis RW of the workpiece W (in this embodiment, the X-axis direction) when the machining point is changed in the circumferential direction of the workpiece W.

3. Tooth Flank Modification Elements The tooth flank modification elements used to modify the shape of a gear tooth flank will be explained with reference to Figures 7 to 11. As shown in Figures 7 to 11, the shape modification elements for the tooth flank Gf of a gear tooth G include modification elements in the tooth trace direction and modification elements in the tooth profile direction. Modification elements in the tooth trace direction include crowning (Figure 7), bias (Figure 8), and tooth trace inclination (Figure 9). Modification elements in the tooth profile direction include pressure angle (Figure 10) and tooth profile radius (Figure 11). Crowning refers to making the center of the face width higher than both ends in the tooth trace direction. Bias refers to continuously changing the pressure angle in the tooth trace direction to give the tooth flank a twist.

As shown in Figure 7, the crowning modification amount Mc is expressed as the distance through which the measurement diameter passes at the center position of the evaluation range Dc in the tooth trace direction on the tooth flank Gf of tooth G (in this embodiment, the center position of the tooth width). As shown in Figure 8, the bias modification amount Mb is expressed as the difference between the pressure angles Mp1 and Mp2 at both end positions of the evaluation range Db in the tooth trace direction on the tooth flank Gf of tooth G (in this embodiment, positions Db/2 on both sides from the center of the tooth width).

As shown in Figure 9, the tooth trace inclination adjustment amount Mh is expressed as the difference in height in the tooth trace direction between the two end positions of the evaluation range Dh in the tooth trace direction on the tooth surface Gf of tooth G (in this embodiment, the position of one end surface of the tooth and the center position of the tooth width).

As shown in Figure 10, the pressure angle modification amount Mp is expressed as the inclination error in the tooth depth direction at the center position of the evaluation range Dp in the tooth trace direction on the tooth flank Gf of tooth G (in this embodiment, the center position of the tooth width). As shown in Figure 11, the tooth profile roundness modification amount Mr is expressed as the amount of protrusion of the tooth profile error at the center position of the evaluation range Dr in the tooth trace direction on the tooth flank Gf of tooth G (in this embodiment, the center position of the tooth width).

4. Fundamentals of Tooth Flank Modification Method Among the tooth flank shape modification elements, the pressure angle and tooth profile roundness are modifications in the tooth profile direction and are a transcription of the tool cutting edge shape. That is, they can be modified using the cutting edge shape of the gear cutting tool T. Additionally, modification may be performed using tool specifications such as the number of flutes, addendum shift coefficient, helix angle, cutting edge angle, and rake angle. On the other hand, among the tooth flank shape modification elements, crowning, bias, and tooth trace inclination are modifications in the tooth trace direction and are a transcription of the motion trajectory of the gear cutting device 10. That is, they can be modified using the Cw-axis, B-axis, X-axis, and Y-axis, which are the processing control elements of the gear cutting device 10. Although the pressure angle and tooth profile roundness can also be modified using the processing control elements of the gear cutting device 10, in this embodiment they are modified based on the tool cutting edge shape (specifications) of the gear cutting tool T.

Specifically, as shown in Figure 12, crowning can be formed by changing the center distance D (shown in Figures 3 and 5) between the center axis RT of the gear cutting tool T and the center axis RW of the workpiece W relative to the position of the face width in a parabolic manner as the tool moves in the face width direction. Therefore, crowning can be corrected by controlling the operation of the Y-axis in the gear cutting device 10.

As shown in Figure 13, the bias can be formed by linearly changing the cross-axis angle α between the central axis RT of the gear cutting tool T and the central axis RW of the workpiece W relative to the position of the face width as the gear moves in the face width direction. Therefore, the bias can be adjusted by controlling the rotation of the gear cutting tool T around an axis parallel to the Y axis. However, since the gear cutting tool T does not rotate in the gear cutting device 10, the bias can be adjusted by controlling the movement of the B axis, which is the rotation axis of the workpiece W (workpiece rotation angle (cross-axis angle α)).

Also, although not shown in the figure, the bias can also be formed by changing the offset angle γ when the gear cutting tool T and the processing point of the workpiece W are shifted circumferentially around the workpiece W as it progresses in the tooth width direction, so this can be adjusted by controlling the operation of the X-axis and Y-axis in the gear cutting device 10.

As shown in Figure 14, tooth trace inclination can be formed by linearly changing the rotation angle β of the workpiece W relative to the rotation angle of the gear cutting tool T relative to the position of the tooth width as it moves in the tooth width direction. Therefore, tooth trace inclination can be corrected by controlling the operation of the Cw axis in the gear cutting device 10. Note that the horizontal axis in Figures 12 to 14 indicates the tooth width position of the gear cutting tool T and the machining point of the workpiece W, i.e., from the position of the right tooth flank on one end face of the tooth (machining start position) to the position of the right tooth flank on the other end face of the tooth (machining end position).

5. Correlation between Modification Elements and Processing Control Elements Next, the correlation between each modification element and each processing control element will be described with reference to Figures 15 to 18. Here, the correlation between each modification element and each processing control element varies depending on the specifications of the gear cutting tool T. The tool specifications of the gear cutting tool T are determined based on the specifications of the gear to be machined on the workpiece W. Therefore, each correlation shown in Figures 15 to 18 represents the correlation for a certain gear cutting tool T, and different gear cutting tools T will exhibit different correlations. Furthermore, modification elements include crowning, bias, and tooth trace inclination, which are modification elements in the tooth trace direction, and processing control elements include the Y-axis, B-axis, Cw-axis, and offset angle γ (two synchronous axes consisting of the X- and Y-axes).

Figure 15 shows the correlation between the Y-axis change amount ΔY and the crowning modification amount Mc, the correlation between the Y-axis change amount ΔY and the bias modification amount Mb, and the correlation between the Y-axis change amount ΔY and the tooth trace inclination modification amount Mh. Each correlation is calculated based on the error between the gear tooth flank shape obtained by the gear cutting simulation and the reference tooth flank shape when a gear cutting simulation is performed with only the Y-axis changed from the reference cutting control element.

For example, each correlation is calculated using, for example, a quadratic function to represent the correlation between the modification element and the processing control element based on the gear tooth flank shape obtained by the gear cutting simulation. Specifically, the error between the gear tooth flank shape obtained by the gear cutting simulation and the tooth flank of an involute helicoid, which is the reference tooth flank shape, is calculated, and the correlation between the calculated error and the amount of change in the processing control element (Y-axis) is calculated.

In more detail, multiple tooth flank shapes are calculated by gradually changing the Y-axis, a processing control element, using a gear processing simulation. This process is repeated sequentially to calculate the overall shape of the tooth flank. The correlation is then calculated by calculating the modification amounts Mc, Mb, and Mh of crowning, bias, and tooth trace inclination, which are modification elements in the tooth trace direction of each tooth flank shape, and a graph is created by correlating the calculated modification amounts Mc, Mb, and Mh of crowning, bias, and tooth trace inclination with the change ΔY in the Y-axis, a processing control element.

The change in the Y-axis, ΔY, includes multiple values obtained by changing the reference value in the positive direction and multiple values obtained by changing the reference value in the negative direction. As shown in Figure 15, changing the Y-axis can significantly change the crowning. However, changing the Y-axis also changes the bias and tooth trace inclination.

Here, gear machining simulation is described, for example, in JP 2017-144502 A. Reference machining control elements are machining control elements for machining gears that have not been given crowning, bias, modified tooth trace inclination, pressure angle, or tooth profile rounding. Note that modified tooth trace inclination refers to the tooth trace inclination relative to the reference tooth trace inclination, which is a gear specification.

Figure 16 shows the correlation between the change in the B axis ΔB and the crowning modification amount Mc, the correlation between the change in the B axis ΔB and the bias modification amount Mb, and the correlation between the change in the B axis ΔB and the tooth trace inclination modification amount Mh. Each correlation is calculated based on the error between the gear tooth flank shape obtained by the gear cutting simulation and the reference tooth flank shape when a gear cutting simulation is performed with only the B axis changed from the reference cutting control element. The change in the B axis ΔB is controlled by the workpiece rotation angle (crossed axis angle α).

A graph that correlates the crowning, bias, and tooth trace inclination adjustment amounts Mc, Mb, and Mh with the change amount ΔB on the B-axis, which is a processing control element, is created essentially in the same way as the Y-axis described above. The change amount ΔB on the B-axis includes multiple values that are changed in the positive direction from the reference value and multiple values that are changed in the negative direction from the reference value. As shown in Figure 16, changing the B-axis can significantly change the bias. However, changing the B-axis also changes the crowning and tooth trace inclination.

Figure 17 shows the correlation between the change in the Cw axis ΔCw and the crowning modification amount Mc, the correlation between the change in the Cw axis ΔCw and the bias modification amount Mb, and the correlation between the change in the Cw axis ΔCw and the tooth trace inclination modification amount. Each correlation is calculated based on the error between the gear tooth flank shape obtained by the gear cutting simulation and the reference tooth flank shape when a gear cutting simulation is performed with only the Cw axis changed from the reference cutting control element. The change in the Cw axis ΔCw is controlled by the workpiece rotation angle β.

Graphs that correlate the crowning, bias, and tooth trace inclination adjustment amounts Mc, Mb, and Mh with the change amount ΔCw of the Cw axis, a processing control element, are created essentially in the same way as the Y axis described above. The change amount ΔCw of the Cw axis includes multiple values obtained by changing the Cw axis in the positive direction from the reference value and multiple values obtained by changing the Cw axis in the negative direction from the reference value. As shown in Figure 17, changing the Cw axis can significantly change the tooth trace inclination. Note that changing the Cw axis results in almost no change in crowning and bias.

Figure 18 shows the correlation between the change in offset angle γ and each modification element. Here, offset angle γ is the angle when the gear cutting tool T and the machining point of the workpiece W are shifted in the circumferential direction of the workpiece W. Therefore, offset angle γ can be expressed by synchronizing the X-axis and Y-axis. In other words, the change in offset angle γ can be expressed by the changes ΔX and ΔY due to the two synchronized axes of the X-axis and Y-axis. Hereinafter, the change in offset angle γ will be expressed as ΔX and ΔY.

In other words, Figure 18 shows the correlation between the change in offset angle γ ΔX, Y and the crowning modification amount Mc, the correlation between the change in offset angle γ ΔX, Y and the bias modification amount Mb, and the correlation between the change in offset angle γ ΔX, Y and the tooth trace inclination modification amount Mh. Each correlation is calculated based on the error between the gear tooth flank shape obtained by the gear cutting simulation and the reference tooth flank shape when a gear cutting simulation is performed with only the offset angle γ changed from the reference processing control element.

A graph showing the relationship between the crowning, bias, and tooth trace inclination adjustment amounts Mc, Mb, and Mh and the change in offset angle γ, ΔX and ΔY, respectively, which is a processing control parameter, can be created in a manner similar to the Y-axis described above. As shown in Figure 18, changing the offset angle γ can significantly change the bias. However, changing the offset angle γ also changes the crowning and tooth trace inclination.

As can be seen from the above, each modification element and each processing control element influence each other. Therefore, even when modifying one modification element, the other modification elements will be affected, and therefore modification of those other modification elements will be necessary. Note that, although each processing control element (Y-axis, B-axis, Cw-axis, offset angle γ) was changed independently in the above example, multiple elements may also be changed in synchronization based on specified synchronization conditions. In this case, too, it is possible to obtain a correlation between the processing control elements and the modification elements.

6. Method for Calculating Error from Reference Tooth Flank As described above, each correlation is calculated based on the error between the tooth flank shape of the gear and the reference tooth flank shape when each processing control element is changed. The reference tooth flank shape is, for example, an involute tooth flank. A method for calculating the error from the reference tooth flank is described, for example, in JP 2021-11011 A.

7. Configuration of Design Support Device 20 The configuration of the design support device 20 will be described with reference to Fig. 19. The design support device 20 is a device that can support machining of gear teeth by modifying the tooth flank shape. The design support device 20 can be, for example, an embedded system (microcomputer) such as a PLC (Programmable Logic Controller) or a CNC (Computerized Numerical Control) device, or it can also be a personal computer, a server, or the like.

As shown in FIG. 19 , the design support device 20 includes a memory device 21 that stores gear specifications, which are the specifications of the gear, tool specifications, which are the specifications of the gear cutting tool T, target tooth profile direction modification amounts, which are target values of the tooth profile direction modification elements of the gear tooth flank shape, and target tooth trace direction modification amounts, which are target values of the tooth profile direction modification elements of the tooth flank shape. The design support device 20 includes a gear specification acquisition unit 22 that acquires the gear specifications from the memory device 21, a tool specification acquisition unit 23 that acquires the tool specifications from the memory device 21, a target tooth profile direction modification amount acquisition unit 24 that acquires the target tooth profile direction modification amount from the memory device 21, and a target tooth trace direction modification amount acquisition unit 25 that acquires the target tooth trace direction modification amount from the memory device 21. The tooth profile direction modification elements include at least one of pressure angle and tooth profile roundness, and the tooth trace direction modification elements include at least one of crowning, bias, and tooth trace inclination.

The preliminary design unit 26 acquires gear specifications from the gear specification acquisition unit 22, acquires tool specifications from the tool specification acquisition unit 23, and acquires the target tooth profile direction modification amount from the tooth profile direction target modification amount acquisition unit 24. The preliminary design unit 26 provisionally designs the tool blade shape of the gear cutting tool T based on the gear specifications, tool specifications, and target tooth profile direction modification amount.

The correction amount determination unit 27 acquires the target tooth trace direction modification amount from the tooth trace direction target modification amount acquisition unit 25. The correction amount determination unit 27 determines the correction amount of the machining control elements during machining operations based on the target tooth trace direction modification amount acquisition unit 25. The machining control elements include at least one of the crossed-axis angle α, the offset angle γ representing the position of the gear cutting tool T in the circumferential direction of the workpiece, the center-to-center distance D between the central axis of the workpiece and the central axis of the gear cutting tool T, and the relative rotational speed between the workpiece and the gear cutting tool T.

The first tooth flank shape calculation unit 28 acquires the provisionally designed tool blade shape of the gear cutting tool T from the provisional design unit 26, and acquires the correction amount of the processing control element from the correction amount determination unit 27. The first tooth flank shape calculation unit 28 calculates the first tooth flank shape of the gear based on the provisionally designed tool blade shape and the correction amount of the processing control element.

The first object error calculation unit 29 acquires the first tooth flank shape from the first tooth flank shape calculation unit 28 and acquires the target tooth flank shape included in the gear specifications from the gear specification acquisition unit 22. The first object error calculation unit 29 compares the calculated first tooth flank shape with the target tooth flank shape and calculates the first object error in the tooth profile direction of the tooth flank shape.

The design unit 30 acquires the first object error from the first object error calculation unit 29 and acquires the tooth profile direction target modification amount from the tooth profile direction target modification amount acquisition unit 24. The design unit 30 performs the final design of the tool blade shape based on the tooth profile direction target modification amount and the first object error modification amount for reducing the first object error.

The second tooth flank shape calculation unit 31 obtains the actually designed tool blade shape from the actual design unit 30 and obtains the correction amount of the processing control element from the correction amount determination unit 27. The second tooth flank shape calculation unit 31 calculates the second tooth flank shape of the gear based on the correction amount of the processing control element and the actually designed tool blade shape.

The second target error calculation unit 32 acquires the calculated second tooth flank shape from the second tooth flank shape calculation unit 31 and acquires the target tooth flank shape included in the gear specifications from the gear specification acquisition unit 22. The second tooth flank shape calculation unit 31 compares the calculated second tooth flank shape with the target tooth flank shape and calculates the second target error of the second tooth flank shape.

The redesign unit 33 acquires the target tooth profile direction modification amount from the tooth profile direction target modification amount acquisition unit 24, acquires the target tooth trace direction modification amount from the tooth trace direction target modification amount acquisition unit 25, and acquires the second target error from the second target error calculation unit 32. The redesign unit 33 redesigns the tool blade shape based on at least one of the target tooth profile direction modification amount and the target tooth trace direction modification amount, and the second target error modification amount for reducing the second target error.

The correction amount redetermining unit 34 acquires the target tooth profile direction modification amount from the tooth profile direction target modification amount acquisition unit 24, acquires the target tooth trace direction modification amount from the tooth trace direction target modification amount acquisition unit 25, and acquires the second target error from the second target error calculation unit 32. The correction amount redetermining unit 34 redetermines the correction amount of the processing control element based on at least one of the target tooth profile direction modification amount and the target tooth trace direction modification amount, and the second target error modification amount for reducing the second target error.

However, the design support device of this embodiment may be equipped with both the redesign unit 33 and the correction amount redetermining unit 34, or may be equipped with either one of them.

8. Operation of the design support device 20 (design method)
(1) Main Routine Next, the operation and design method of the design support device 20 of this embodiment will be described. As shown in Fig. 20, when the design support device 20 is started, a provisional design process is executed to provisionally design the tool cutting edge shape of the gear cutting tool T (S1: provisional design step). Next, a correction amount determination process is executed to determine the correction amounts of the machining control elements during the gear machining operation (S2: correction amount determination step). Next, a final design process is executed to finally design the tool cutting edge shape of the gear cutting tool T (S3: final design step).

For a gear formed by machining a workpiece using a gear cutting tool T whose tool blade shape has been determined by executing this design process, a second-objective error calculation process is executed to compare the second tooth flank shape formed on the gear with the target tooth flank shape included in the gear specifications to calculate a second-objective error of the second tooth flank shape (S4: second-objective error calculation process). Next, a redesign process is executed to redesign the tool blade shape based on the second objective error (S5: redesign process). Furthermore, a correction amount redetermining process is executed to redetermine the correction amount of the machining control element based on the second objective error (S6: correction amount redetermining process). However, the order of the redesign process (S5) and the correction amount redetermining process (S6) is not limited. Furthermore, both the redesign process (S5) and the correction amount redetermining process (S6) may be executed, or only one of them may be executed.

(2) Provisional Design Process As shown in FIG. 21 , when the provisional design process is executed, the gear specification acquisition unit 22 acquires gear specifications from the storage device 21 (S11: gear specification acquisition step). The gear specifications include information on the shape, material, etc. of the gear teeth to be machined into the workpiece. Next, the tool specification acquisition unit 23 acquires tool specifications from the storage device 21 (S12: tool specification acquisition step). The tool specifications include information on the shape, material, etc. of the gear cutting tool T. Next, the tooth profile direction target modification amount acquisition unit 24 acquires the tooth profile direction target modification amount from the storage device 21 (S13: target modification amount acquisition step). Next, the provisional design unit 26 provisionally designs the tool blade shape of the gear cutting tool T based on the gear specifications, tool specifications, and tooth profile direction target modification amount (S14: provisional design step). Since the tool blade shape of the gear cutting tool T may be modified in the actual design process described later, the tool blade shape of the gear cutting tool T is provisionally designed. This completes the provisional design process for the tool blade shape.

(3) Correction Amount Determination Process Next, the correction amount determination process (S2) is executed as shown in Fig. 22. A gear cutting simulation is used to calculate multiple tooth flank shapes when the Y-axis, one of the processing control elements, is changed (S21: tooth flank shape calculation process). Next, based on the error between the gear tooth flank shape calculated by the gear cutting simulation and a reference tooth flank shape, the correlation between the Y-axis change amount ΔY and each modification element is calculated (S22: correlation calculation process).

Next, multiple tooth flank shapes are calculated by changing the Cw axis, one of the processing control elements, using a gear cutting simulation (S23: Tooth flank shape calculation process). Next, based on the error between the gear tooth flank shape calculated by the gear cutting simulation and the reference tooth flank shape, the correlation between the Cw axis change amount ΔCw and each modification element is calculated (S24: Correlation calculation process).

Next, multiple tooth flank shapes are calculated by changing the B-axis, one of the processing control elements, using a gear cutting simulation (S25: Tooth flank shape calculation process). Next, based on the error between the gear tooth flank shape calculated by the gear cutting simulation and the reference tooth flank shape, the correlation between the change in the B-axis ΔY and each modification element is calculated (S26: Correlation calculation process). The order in which the correlations for the Y-axis, Cw-axis, and B-axis are calculated may be changed as appropriate.

Next, the correction amount determination unit 27 calculates the correction amount ΔYa for the Y axis (S27: correction amount calculation process). For example, the correction amount determination unit 27 calculates the correction amount ΔYa for the Y axis based on the target crowning modification amount and the correlation between the Y axis change amount ΔY and the crowning modification amount Mc (upper diagram in Figure 15). The Y axis change amount ΔY when the crowning modification amount Mc in Figure 15 becomes the target modification amount is set to the Y axis correction amount ΔYa.

Next, the correction amount determination unit 27 calculates the B-axis correction amount ΔBa (S28: correction amount calculation process). For example, the correction amount determination unit 27 calculates the B-axis correction amount ΔBa based on the target bias adjustment amount, the B-axis change amount ΔB, the bias adjustment amount Mb (middle diagram of Figure 16), and the bias adjustment amount Mb for the Y-axis correction amount ΔYa (middle diagram of Figure 15). For example, the bias adjustment amount Mb of Figure 16 is determined so that the sum of the bias adjustment amount Mb for the Y-axis correction amount ΔYa (middle diagram of Figure 15) and the bias adjustment amount Mb of Figure 16 matches the target adjustment amount. Then, the B-axis change amount ΔB for the determined bias adjustment amount Mb of Figure 16 is set as the B-axis correction amount ΔBa.

Next, the correction amount determination unit 27 calculates the correction amount ΔCwa for the Cw-axis (S29: correction amount calculation process). For example, the correction amount determination unit 27 calculates the correction amount ΔCwa for the Cw-axis based on the target tooth trace inclination modification amount, the Cw-axis change amount ΔCw and the tooth trace inclination modification amount Mh (lower diagram in Figure 17), the tooth trace inclination modification amount Mh for the Y-axis correction amount ΔYa (lower diagram in Figure 15), and the tooth trace inclination modification amount Mh for the B-axis correction amount ΔBa (lower diagram in Figure 16). For example, the tooth trace inclination modification amount Mh in Fig. 17 is determined so that the sum of the tooth trace inclination modification amount Mh (lower diagram in Fig. 15) when the Y-axis correction amount ΔYa is used, the tooth trace inclination modification amount Mh (lower diagram in Fig. 16) when the B-axis correction amount ΔBa is used, and the tooth trace inclination modification amount Mh in Fig. 17 matches the target modification amount. Then, the change amount ΔCw on the Cw-axis when the determined tooth trace inclination modification amount Mh in Fig. 17 is set as the Cw-axis correction amount ΔCwa.

Next, the correction amount determination unit 27 calculates the crowning, bias, and tooth trace inclination modification amounts Mc', Mb', and Mh' (S30: modification amount calculation process). The modification amounts Mc', Mb', and Mh' for each modification element are calculated based on the Y-axis correction amount ΔYa, the B-axis correction amount ΔBa, and the Cw-axis correction amount ΔCwa, and their respective correlations. For example, the crowning modification amount Mc' is calculated as the sum of the crowning modification amount Mc for the Y-axis correction amount ΔYa (top diagram in Figure 15), the crowning modification amount Mc for the B-axis correction amount ΔBa (top diagram in Figure 16), and the crowning modification amount Mc for the Cw-axis correction amount ΔCwa (top diagram in Figure 17). The same applies to the bias and tooth trace inclination modification amounts Mb' and Mh'.

Next, the correction amount determination unit 27 determines whether the crowning, bias, and tooth trace inclination modification amounts Mc', Mb', and Mh' approximate the respective target modification amounts (S31: Determination step). If the modification amounts Mc', Mb', and Mh' are not approximate to the respective target modification amounts (S31: N), the correction amount determination unit 27 returns to step S27 and repeats the above-described process. For example, if the crowning modification amount Mc' deviates from the target modification amount, the correction amounts ΔYa, ΔBa, and ΔCwa for each modification element are calculated so that the deviation amount can be additionally corrected.

As described above, the correction amount determination unit 27 calculates the Y-axis correction amount ΔYa, the B-axis correction amount ΔBa, and the Cw-axis correction amount ΔCwa in that order. This is because, as shown in Figures 15 to 17, the changes in the correction amounts Mc, Mb, and Mh of each correction element decrease in the order of Y-axis, B-axis, and Cw-axis. In other words, the B-axis is less influenced by the Y-axis, and the Cw-axis is less influenced by the Y-axis and B-axis. Due to this relationship, even with simple calculations, the correction amounts Mc', Mb', and Mh' of each correction element quickly reach their respective target correction amounts. In other words, the number of iterations of steps S27 to S31 can be reduced when determining the correction amounts ΔYa, ΔBa, and ΔCwa for the Y-axis, B-axis, and Cw-axis.

When the modification amounts Mc', Mb', and Mh' approximate the target modification amounts in S31 (S31: Y), the correction amount determination unit 27 determines the correction amounts ΔYa, ΔBa, and ΔCwa for the calculated machining control elements, the Y-axis, B-axis, and Cw-axis (S32: correction amount determination process). Therefore, the correction amounts ΔYa, ΔBa, and ΔCwa for each modification element can be calculated using a very simple calculation. "Simple calculation" here refers to a calculation that is simpler than calculations using a gear machining simulation.

(4) Main Design Process Next, as shown in FIG. 23 , the first tooth flank form calculation unit 28 calculates the first tooth flank form of the gear through a gear cutting simulation using the correction amounts ΔYa, ΔBa, and ΔCwa for the Y-axis, B-axis, and Cw-axis, which are the processing control elements determined by the correction amount determination unit 27 (S33: first tooth flank form calculation step). The first object error calculation unit 29 acquires the calculated first tooth flank form (S34: first tooth flank form acquisition step). The first object error calculation unit 29 compares the first tooth flank form with the target tooth flank form to calculate a first object error in the tooth profile direction for the first tooth flank form (S35: first object error calculation step). The first object error is an error in at least one of the pressure angle and the tooth profile roundness.

As shown in Figure 24, the first target error is calculated based on the shape of the tooth surface Gf in a cross section PA perpendicular to the axis at one location at the center position of the gear tooth G in the tooth width direction Wd.

Next, the design unit 30 acquires the target modification amount in the tooth profile direction from the storage device 21 (S36: target modification amount acquisition process). The design unit 30 calculates a first target error modification amount to reduce the first target error calculated by the first tooth flank shape calculation unit 28 (S37: first target error modification amount calculation process). The design unit 30 performs a final design of the tool blade shape of the gear cutting tool T by modifying the tool blade shape of the gear cutting tool T in the tooth profile direction based on the target modification amount in the tooth profile direction and the first target error modification amount (S38: final design process).

25 , the second tooth flank form calculation unit 31 acquires the correction amounts ΔYa, ΔBa, and ΔCwa for the Y-axis, B-axis, and Cw-axis, which are the machining control elements determined by the correction amount determination unit 27 (S41: correction amount acquisition step), and acquires the tool blade shape of the gear cutting tool T finally designed by the final design unit 30 (S42: tool blade shape acquisition step). The second tooth flank form calculation unit 31 calculates the second tooth flank form of the gear by gear cutting simulation based on the correction amounts of the machining control elements and the finally designed tool blade shape (S43: second tooth flank form calculation step).

The second target error calculation unit 32 acquires the target tooth flank shape included in the gear specifications from the storage device 21 (S44: Target tooth flank shape acquisition process). The second target error calculation unit 32 compares the second tooth flank shape with the target tooth flank shape to calculate the second target error in the second tooth flank shape (S45: Second target error calculation process). The second target error includes both or either an error in the tooth profile direction and an error in the tooth trace direction.

(6) Redesign Process When a second target error occurs with respect to the tooth profile direction modification element, the redesign unit 33 redesigns the tool blade shape by modifying the tool blade shape of the gear cutting tool T. As shown in Fig. 26 , the redesign unit 33 acquires a target tooth profile direction modification amount from the storage device 21 (S51: target modification amount acquisition step). The redesign unit 33 calculates a second target error modification amount for reducing the second target error with respect to the tooth profile direction modification element (S52: second target error calculation step). The redesign unit 33 redesigns the tool blade shape by modifying the tool blade shape of the gear cutting tool T in the tooth profile direction based on the target tooth profile direction modification amount and the second target error modification amount (S53: tool blade shape redesign step).

(7) Correction Amount Redetermining Process The correction amount redetermining unit 34 redetermines the correction amount of the machining control element when a second target error occurs for the tooth trace direction modification element. As shown in Fig. 27, the correction amount redetermining unit 34 acquires a target tooth trace direction modification amount from the storage device 21 (S61: target modification amount acquisition process). The correction amount redetermining unit 34 calculates a second target error modification amount for the tooth trace direction modification element to reduce the second target error (S62: second target error calculation process). The correction amount redetermining unit 34 redetermines the correction amount of the machining control element based on the target tooth trace direction modification amount and the second target error modification amount (S63: correction amount redetermining process). This completes all processing.

9. Example Next, a description will be given of an example in which this embodiment is applied to a specific gear cutting tool T. Table 1 shows the target modification amounts in the tooth profile direction and the tooth trace direction of the gear cutting tool T according to this example.

In this example, the target modification elements in the tooth profile direction, the pressure angle modification amount and the tooth profile roundness modification amount, are set to 0.0 μm. The target modification elements in the tooth trace direction, the tooth trace inclination modification amount, the crowning modification amount, and the bias modification amount, are set to 5.0 μm, 5.0 μm, and 10.0 μm, respectively.

A provisional design process for the tool blade shape is performed for the gear cutting tool T of this example to provisionally design the tool blade shape (S1 in Figure 20).

Next, a correction amount determination process is performed based on the target tooth trace direction modification amount to determine the correction amount of the processing control element during the processing operation (S2 in Figure 20).

Next, the first tooth flank shape of the gear is calculated based on the correction amount of the processing control element and the provisionally designed tool blade shape (S33 in Figure 23). The calculated first tooth flank shape is compared with the target tooth flank shape, and the first target error in the tooth profile direction for the first tooth flank shape is calculated (S35 in Figure 23).

As shown in Table 1, in this example, a first-objective error occurred for the tooth profile direction target modification elements. Specifically, the first-objective error for the pressure angle was 0.6 μm, and the first-objective error for the tooth profile roundness was 0.2 μm. On the other hand, the first-objective errors for the tooth trace inclination, crowning, and bias, which are related to the tooth trace direction target modification elements, were 0.0 μm.

When machining control elements during machining operations are corrected based on the target modification amount in the tooth trace direction, the correction changes the movement path of the gear cutting tool T during the machining operation. This changes the shape removed from the workpiece by the gear cutting tool T. As a result, it is believed that a first target error occurs between the calculated first tooth flank shape and the target tooth flank shape in the tooth profile direction.

Next, the first object error correction amount to reduce the first object error is calculated for the pressure angle and tooth profile roundness (S37 in Figure 23).

For the pressure angle, the target modification amount in the tooth profile direction is 0.0 μm and the first target error is 0.6 μm, so the first target error modification amount is calculated to be -0.6 μm. For the tooth profile roundness, the target modification amount in the tooth profile direction is 0.0 μm and the first target error is 0.2 μm, so the first target error modification amount is calculated to be -0.2 μm.

Next, the tool blade shape of the gear cutting tool T is finally designed based on the target tooth profile direction adjustment amount and the first target error adjustment amount (S38 in Figure 23).

Next, the second tooth flank shape of the gear is calculated based on the correction amount of the machining control element and the tool blade shape of the gear cutting tool T designed (S43 in Figure 25). The calculated second tooth flank shape is compared with the target tooth flank shape, and a second objective error in the second tooth flank shape is calculated (S45 in Figure 25). The second objective error may include both an error in the tooth profile direction and an error in the tooth trace direction, or it may include only one of these.

As shown in Table 1, no second-objective errors occurred in this example. Specifically, the first-objective errors for the pressure angle and the second-objective errors for the tooth profile roundness were 0.0 μm, and the second-objective errors for the tooth trace inclination, crowning, and bias were 0.0 μm.

10. Effects of this Embodiment In this embodiment, since no second target error occurred, the tool blade shape is not redesigned in the tool blade shape redesign process (S5 in FIG. 20), and the compensation amount is not redetermined in the compensation amount redetermining process (S6 in FIG. 20).

In this example, the tool blade shape of the gear cutting tool T is designed based on a first target error correction amount for reducing the first target error that occurs when correcting the machining control element during the machining operation based on the target modification amount in the tooth trace direction. This makes it possible to suppress errors in the gear tooth flank shape in the tooth profile direction, even when the machining control element is corrected based on the target modification amount in the tooth trace direction.

Furthermore, according to this embodiment, the second tooth flank shape of the gear is calculated based on the correction amount of the machining control element and the finally designed tool cutting edge shape, and the calculated second tooth flank shape is compared with the target tooth flank shape to calculate a second objective error of the second tooth flank shape. As a result, even if an unexpected error occurs in the second tooth flank shape of the gear machined with the finally designed gear cutting tool T due to the modification from the provisionally designed tool cutting edge shape to the finally designed tool cutting edge shape, the error can be calculated as a second objective error. This makes it possible to respond even when an unexpected error occurs.

According to this embodiment, if a second object error occurs, the tool blade shape is redesigned or the correction amount for the machining control element is redetermined based on the second object error correction amount to reduce the second object error. This makes it possible to prevent errors from occurring in the gear tooth flank shape when the provisionally designed tool blade shape is corrected to the actual designed tool blade shape.

(Embodiment 2)
Next, a second embodiment will be described with reference to Fig. 28. As shown in Fig. 28, in the correction amount determination process (S2), the correction amount is determined based on the shape of the tooth surface Gf in an arbitrary cross section PA perpendicular to the axis of the gear tooth G in the face width direction Wd.

In the following description, the same components as in embodiment 1 will be given the same symbols and duplicate explanations will be omitted.

According to this embodiment, for example, the first object error can be calculated based on a cross section perpendicular to the axis at one location in the face width direction Wd of the gear tooth G that is particularly affected by the error. This improves the accuracy of calculating the first object error.

(Embodiment 3)
Next, a third embodiment will be described with reference to FIG. 29 . As shown in FIG. 29 , in this embodiment, the first object error is calculated based on the shapes of the tooth flanks Gf at multiple (two in this embodiment) axis-perpendicular cross sections PA1 and PA2 in the face width direction Wd of the gear tooth G (S35 in FIG. 23 ). In this embodiment, for example, the first object error can be calculated based on the average value of the errors at the two axis-perpendicular cross sections PA1 and PA2. According to this embodiment, by using the axis-perpendicular cross sections PA1 and PA2 at multiple locations as the reference, the accuracy of calculating the first object error can be improved.

(Embodiment 4)
Next, a fourth embodiment will be described with reference to FIG. 30. As shown in FIG. 30, in this embodiment, a first object error is calculated from an error in the tooth profile direction calculated over the entire range in the face width direction Wd of the gear teeth G (S35 in FIG. 23). In this embodiment, for example, the first object error can be calculated based on the average value of the error over the entire range in the face width direction Wd of the gear teeth G. According to this embodiment, by using the entire range in the face width direction Wd of the gear teeth G as the reference, the calculation accuracy of the first object error can be improved.

(Embodiment 5)
Next, a fifth embodiment will be described with reference to Fig. 31. As shown in Fig. 31, in this embodiment, a first object error is calculated from an error in the tooth profile direction calculated in a partially continuous range A in the face width direction Wd of the gear teeth G (S35 in Fig. 23). In this embodiment, for example, the first object error can be calculated based on the range A that is particularly affected by the error in the face width direction Wd of the gear teeth G. This improves the calculation accuracy of the first object error.

Claims (13)

A method for designing a gear cutting tool for machining gear teeth (G) on a workpiece (W) by moving the workpiece and the gear cutting tool relative to each other while rotating the gear cutting tool and the workpiece synchronously, with an axis parallel to a central axis (RT) of the gear cutting tool (T) at a predetermined crossed-axis angle (α) with respect to a central axis (RW) of the workpiece, comprising:
a step (S1) of acquiring gear specifications that are specifications of the gear, acquiring tool specifications that are specifications of the gear cutting tool, acquiring a target tooth profile direction modification amount that is a target value of a tooth profile direction modification element of a tooth flank shape of the gear, and provisionally designing a tool blade shape of the gear cutting tool based on the gear specifications, the tool specifications, and the target tooth profile direction modification amount;
a step (S2) of acquiring a target modification amount in the tooth trace direction, which is a target value of a modification element in the tooth trace direction of the tooth flank shape, and determining a correction amount of a machining control element during a machining operation based on the target modification amount in the tooth trace direction;
a step (S33) of calculating a first tooth flank profile of the gear based on the correction amount of the processing control element and the temporarily designed tool blade profile;
a step (S35) of comparing the calculated first tooth flank profile with a target tooth flank profile included in the gear specifications and calculating a first target error in the tooth profile direction of the first tooth flank profile;
a step (S38) of finally designing the tool blade shape based on the tooth profile direction target modification amount and a first object error modification amount for reducing the first object error;
A method for designing a gear cutting tool comprising: a step (S43) of calculating a second tooth flank profile of the gear based on the correction amount of the processing control element and the finally designed tool blade profile;
a step (S45) of comparing the calculated second tooth flank form with the target tooth flank form included in the gear specifications to calculate a second target error of the second tooth flank form;
The method for designing a gear cutting tool according to claim 1, comprising: A method for designing a gear cutting tool as described in claim 2, comprising steps (S53, S63) of redesigning the tool blade shape or redetermining the correction amount of the processing control element based on at least one of the target tooth profile direction modification amount and the target tooth trace direction modification amount, and a second target error modification amount for reducing the second target error. A method for designing a gear cutting tool as described in claim 1, which calculates the first target error in the tooth profile direction at one axis-perpendicular cross section (PA) in the face width direction (Wd) of the gear. A method for designing a gear cutting tool as described in claim 4, wherein the first symmetric error in the tooth profile direction is calculated in a cross section perpendicular to the axis at one central location in the tooth width direction. A design method for a gear cutting tool as described in claim 1, in which the first target error is calculated from the error in the tooth profile direction calculated at multiple axis-perpendicular cross sections (PA1, PA2) in the face width direction of the gear. A design method for a gear cutting tool as described in claim 1, in which the first target error is calculated from the error in the tooth profile direction calculated over the entire range in the face width direction of the gear. A design method for a gear cutting tool as described in claim 1, in which the first target error is calculated from the error in the tooth profile direction calculated in a partial range (A) in the face width direction of the gear. the tooth profile direction modification element includes at least one of a pressure angle and a tooth profile radius;
The method for designing a gear cutting tool according to any one of claims 1 to 8, wherein the tooth trace direction modifying element includes at least one of crowning, bias, and tooth trace inclination. The process control element to be corrected is:
the axis crossing angle (α),
an offset angle (γ) representing the position of the gear cutting tool in the circumferential direction of the workpiece;
the center distance (D) between the central axis of the workpiece and the central axis of the gear cutting tool;
the relative rotational speed between the workpiece and the gear cutting tool;
The method for designing a gear cutting tool according to any one of claims 1 to 8, comprising at least one of the following: A design support device (20) for a gear cutting tool that processes gear teeth (G) on a workpiece (W) by moving the workpiece and the gear cutting tool relative to each other while rotating the gear cutting tool and the workpiece synchronously, with an axis parallel to a central axis (RT) of the gear cutting tool (T) at a predetermined crossed-axis angle (α) with respect to a central axis (RW) of the workpiece, comprising:
a gear specification acquisition unit (22) that acquires gear specifications that are specifications of the gear;
a tool specification acquisition unit (23) that acquires tool specifications that are specifications of the gear cutting tool;
a tooth profile direction target modification amount acquisition unit (24) that acquires a tooth profile direction target modification amount, which is a target value of a tooth profile direction modification element of the tooth flank shape of the gear;
a provisional design unit (26) that provisionally designs a tool blade shape of the gear cutting tool based on the gear specifications, the tool specifications, and the tooth profile direction target modification amount;
a tooth trace direction target modification amount acquisition unit (25) that acquires a tooth trace direction target modification amount, which is a target value of a tooth trace direction modification element of the tooth flank shape;
a correction amount determination unit (27) that determines a correction amount of a machining control element during machining based on the tooth trace direction target modification amount;
a first tooth flank shape calculation unit (28) that calculates a first tooth flank shape of the gear based on a correction amount of the processing control element and the temporarily designed tool blade shape;
a first object error calculation unit (29) that compares the calculated first tooth flank profile with a target tooth flank profile included in the gear specifications and calculates a first object error in the tooth profile direction of the tooth flank profile;
a final design unit (30) that final designs the tool blade shape based on the tooth profile direction target modification amount and a first target error modification amount for reducing the first target error;
A design support device for gear cutting tools equipped with this. a second tooth flank shape calculation unit (31) that calculates a second tooth flank shape of the gear based on the correction amount of the processing control element and the finally designed tool blade shape;
a second object error calculation unit (32) that compares the calculated second tooth flank form with a target tooth flank form included in the gear specifications and calculates a second object error of the second tooth flank form;
The design support device for gear cutting tools according to claim 11, comprising: A design support device for a gear cutting tool as described in claim 12, comprising a redesign unit (33) that redesigns the tool blade shape based on at least one of the target tooth profile direction modification amount and the target tooth trace direction modification amount, and a second target error modification amount for reducing the second target error, or a correction amount redetermining unit (34) that redetermines the correction amount of the processing control element.