Method for grinding a gear wheel by means of a worm grinding wheel, and a dressing roll for dressing the worm grinding wheel

A method for grinding a gear wheel by means of a worm grinding worm in a grinding machine, wherein the tooth flanks of the gear wheel are ground with the abrasive flanks of the profiling of the grinding worm, wherein the gear wheel has an axis of rotation, wherein the grinding worm has an axis of rotation, and wherein a toothing of the gear wheel to be ground has a base circle diameter, a root circle diameter and a tip circle diameter, wherein the method comprises the steps of:

• a) Calculation of engagement ratios between the abrasive flanks of the profiling of the grinding worm and the tooth flanks of the gear wheel when the gear wheel and the grinding worm are engaged for grinding, wherein a section is regarded along a plane which includes the axis of rotation of the grinding worm and which is perpendicular to the axis of rotation of the gear wheel;
• said calculation comprising:
• a1) Determination of a first line of engagement resulting from contact points between a first two successive abrasive flanks and a first two successive tooth flanks;
• a2) Determination of a second line of engagement resulting from contact points between a second two successive abrasive flanks opposite the first two successive abrasive flanks and a second successive tooth flanks opposite the first two successive tooth flanks;
• a3) Determination of an intersection point of the first and second lines of engagement;
• a4) Determination of a line passing through the intersection point and tangent to the base circle diameter of the toothing of the gear wheel;
• a5) Determination of an intersection point of the line with the root circle diameter and determination of an intersection point of the line with the tip circle diameter;
• a6) Determination of a line that results at an intersection of the plane with a second plane that contains the axis of rotation of the gear wheel, that is perpendicular to the plane and that contains the intersection of the first and second lines of engagement;
• a7) Determination of a first distance between the intersection point of the line with the root circle diameter and the line at the intersection of the planes;
• a8) Determination of a second distance between the intersection point of the line with the tip circle diameter and the line at the intersection of the planes;
• b) Determination of a geometry obtained with changed engagement ratios compared to a geometry of the engagement ratios determined according to step a) by changing the position of the line which is tangent to the base circle diameter of the toothing of the gear wheel in such a way that the first and second distances are equal;
• c) Profiling of the grinding worm with the changed geometry of the engagement ratios that results when the first and second distances are equal;
• d) Grinding of the gear wheel with the grinding worm profiled according to step c).