Grinding cylindrical bores

Abstract

Method of reducing the thickness of a bore of a cylindrical workpiece for use as a gear. The method involves the steps of: mounting a cylindrical workpiece having a horizontal central axis and an outer diameter in a grinding machine; and grinding the bore of the cylindrical workpiece to reduce its thickness using a grinding wheel that has a diameter that is from 40% to 80% of the outer diameter of the cylindrical bore and has a direction of rotation about an axis of rotation that is parallel to the horizontal central axis of the cylindrical workpiece. The axis of rotation of the grinding wheel may be located from 90 degrees to 180 degrees, in the direction of rotation of the grinding wheel, from a plane that extends vertically through the workpiece when it is mounted in the grinding machine. The gear may be one of a planetary, sun, parallel axis or helical gear.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is based upon and claims the benefit of priority from United Kingdom patent application number GB 1818823.5 filed on Nov. 19, 2018, the entire contents of which are incorporated herein by reference.BACKGROUNDTechnical Field[0002]The present disclosure relates to a method of grinding the internal bore of a gear, for example a gear for use in a gas turbine engine.Description of the Related Art[0003]Current gas turbine engines typically do not spin at optimal speeds as they are limited by the speed of the fan system. It is known that the use of a gearbox placed in between the fan and the compressors can overcome this problem. The gears of such a gear box have to be manufactured to exacting standards to achieve the performance criteria required in such an engine. This is because the gears are required to be strong enough in use to withstand the forces acting upon them and yet light enough so that they do not add drastically t...

AI Technical Summary

Benefits of technology

The patent describes a method for grinding the internal bore of a cylindrical workpiece to reduce its thickness using a grinding wheel that rotates about a parallel axis to the workpiece. This method allows for the use of a standard 5-axis machine, which reduces the number of set up steps required for the gear and reduces production time. The same machine can also be used for other operations such as turning and milling. This method also leads to greater conformance as errors created by changing and resetting equipment are not present when performing multiple stages on the same piece of equipment.

Problems solved by technology

Current gas turbine engines typically do not spin at optimal speeds as they are limited by the speed of the fan system.

However, a gear of this type requires a gap to be manufactured in the centre of the gear.

This gap in turn adds weight and complexity to the gearbox.

However, using cylindrical grinding machines results in a large number of manufacturing steps; this in turn increases the complexity of manufacturing the part.

This conflicting set of features results in cylindrical grinders having the advantage of high conformance, but being limited in their use, as other machines are required to produce the other parts of the gear, such as the teeth.

The use of standard 5-axis machines, which are known for grinding the teeth of gears, however, typically they are not feasible for grinding the internal bore as they are usually dedicated for turning and milling operations.

Certain 5-axis machines are nonetheless able to perform grinding operations; however, the grinding wheels in such instruments are susceptible to wear and are not as stable due to the slow speed of operation.

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