Wikipedia says the difference between the spelling in Toyoda's name and Toyota is deliberate - that there were aesthetic and connotative reasons for spelling the company different from the family name. Although obviously, I'm not sure how the exact Japanese writing would work for that.
> But Risaburō Toyoda, who had married into the family and was not born with that name, preferred "Toyota" (トヨタ) because it took eight brush strokes (a lucky number) to write in Japanese, was visually simpler (leaving off the diacritic at the end) and with a voiceless consonant instead of a voiced one (voiced consonants are considered to have a "murky" or "muddy" sound compared to voiceless consonants, which are "clear").
> But Risaburō Toyoda, who had married into the family and was not born with that name, preferred "Toyota" (トヨタ) because it took eight brush strokes (a lucky number) to write in Japanese, was visually simpler (leaving off the diacritic at the end) and with a voiceless consonant instead of a voiced one (voiced consonants are considered to have a "murky" or "muddy" sound compared to voiceless consonants, which are "clear").
http://en.wikipedia.org/wiki/Toyota
Obviously, though, I don't speak Japanese. Would both the family name and the company name be Latinized as Toyoda?