Hidehiro Yoshino

Relief Grinding of Worm Hobs with a Pencil Wheel.

A new method for calculating the profile of a pencil-type grinding wheel to finish worm hobs is proposed using the element removal method. The method realizes the finishing of worm hobs with an arbitrary profile and a large lead angle, without depending on the experience and perception of an expert. In this paper, a worm hob (mn=5 mm, Nh=3, rh=18.5 mm) is used as an example of profile calculation and finishing tests. The regrinding errors of the cutting edge profiles of the hobs to be finished with the pencil wheel and disk wheel are discussed by calculating the changes in the rack profiles expressed by the hob cutting edges after regrinding. To show the usefulness of the proposed method, the finishing tests of the worm hob were conducted on the CNC relief grinding machine with the pencil wheel attachment made by the authors. The accuracy of the finished worm hob was in the zero class of JIS.

Studies on 3-D Tooth-Surface Modification of Helical Gears. Form Grinding of Gears with Arbitrarily Modified Tooth Traces.

In general, in finishing helical gears with modified tooth traces, it is necessary to consider an additional motion between the work and tool in the manufacturing process. In this paper, shapes of tooth surfaces of gears ground with the threaded wheel or profiled wheel with three kinds of additional motions between the work and wheel are shown by means of contour lines, and it is clarified that form grinding with the profiled wheel is the most suitable for finishing gears with three-dimensionally modified tooth surfaces. Moreover, a method of calculating amounts of the additional motions for 3-D tooth-surface modification when the approaching and excessive helical motions are used as a combination of the additional motions in form grinding is proposed. To demonstrate the usefulness of this method, the grinding tests of the helical gears were conducted on the CNC gear grinder. The shapes of the ground tooth surfaces were almost the same as those of modified ones in the design stage.

Studies on gear pumps with 2 to 5 teeth.

In order to obtain as large a delivery as possible without changing the inner space Vc of a gear pump casing, the authors introduced a method to design and make gear pumps with teeth of Z1 =Z2 =2 to 5. They presented a new tooth profile of helical gears suitable for the pumps producing no fluctuations in delivery. Equations were derived for calculating the theoretical delivery Vth of the gear pumps and also the thrust which occurs on the gears. Experiments were conducted using four kinds of trial gear pumps with teeth of Z1 =Z2 =3 or 4. In the case of the gear pump with Z = 3 and a transverse module of 15.65, the volumetric efficiency was about 98% and the total efficiency was about 90% when the pump was operated at about 1.5 MPa using a machine oil as pumping fluid. The volume ratio Vth/Vc of the trial pump was about 0.5 while it was about 0.2 in the case of a conventional gear pump with almost the same delivery.