Reactive force generation device

A keyboard apparatus comprising:

• a plurality of keys operable by a user;
• and
• a plurality of reactive force generation devices, each provided in corresponding relation to any one of the plurality of keys,
• each of the plurality of reactive force generation devices comprising:
• a to-be-depressed member including a base section, and a dome section formed of an elastic material and protruding from the base section, a sectional shape of the dome section orthogonal to an axis line of the dome section being substantially line-symmetric about a symmetry axis, the dome section having a three-dimensional shape that is substantially symmetric with respect to a virtual plane containing the symmetry axis and the axis line;
• and
• an opposed member having an opposed surface opposed to a distal end of the dome section, the opposed member in a non-operated state being located remote from the to-be-depressed member,
• at least one of the opposed member and the to-be-depressed member being constructed to make a swinging movement in response to a depressing operation applied thereto via the corresponding key, wherein the opposed member relatively approaches the base section in response to the depressing operation, the dome section deforms by contact between the opposed surface and the distal end during the relative approaching, and the relative approaching is stopped in a depression-completed state corresponding to a maximum movable range of the opposed member relative to the base section,
• the virtual plane being defined so as not to vary throughout an entire depression stroke from an initial state, where no depressing operation is applied yet, to the depression-completed state,
• the to-be-depressed member and the opposed member being constructed in such a manner that, as for a variation amount of an angle of the axis line relative to a normal line of the opposed surface during the depression stroke, an acute-side angle defined between the axis line and the normal line of the opposed surface in the initial state falls in an angle range from a first variation amount of the angle of the axis line relative to the normal line during a transition from the initial state to a state where the distal end of the dome section starts contacting the opposed surface to a second variation amount of the angle of the axis line relative to the normal line during a transition from the initial state to the depression-completed state,
• the first variation amount of the angle of the axis line relative to the normal line being greater than zero degree.