Compressor impeller, compressor, and turbocharger

A compressor impeller comprising:

• an impeller body which includes a boss portion and a plurality of compressor blades disposed on an outer peripheral surface of the boss portion;
• and
• a connection portion which is disposed on a side of a back surface of the impeller body and is configured to be connectable to one end of a rotational shaft,
• wherein a ratio D1/D2 satisfies 0.18 or less, where D1 is a diameter of the boss portion on leading edges of the compressor blades, and D2 is a maximum outer diameter of the compressor blades,
• wherein the compressor blades include fillet portions in blade root parts thereof, the fillet portions each being disposed on a connection part with the boss portion,
• wherein a ratio Σt/L has a maxi mu m value at a position at which a meridional length ratio is greater than 0 and not greater than 0.5, where t is blade thicknesses of the compressor blades including:
• the fillet portions in the blade root parts, Σt is a total of the blade thicknesses t of the compressor blades in a circumferential direction, L is a perimeter of the boss portion, and the maximum value satisfies 0.5 or more, and the meridional length ratio is a ratio of a length on a meridional plane from the leading edge of each of the compressor blades to an entire length of said each of the compressor blades along the meridional plane of said each of the compressor blades,
• wherein the ratio Σt/L increases from the leading edge of said each of the compressor blades toward the position so as to reach the maximum value at the position.