I used "quotation" to search for exact phrase, but why do some patents, without the phrase, are showing up?

When you are searching for an exact phrase match, you can use "quotation marks" to only look for keywords or key phrases within the quotation marks. For example, searching for "self-driving" should only produce search results containing “self-driving” and not “self-driven” or “self-drive”.

However, when [Stemming] is checked in your Keyword Search Settings, the system will expand your search to other keywords with the same root.

To illustrate the difference  

• Search the Keyword "self-driving" with Stemming ON will result: 20,290 records
• Search the Keyword "self-driving" with Stemming OFF will result: 19,259 records

You can learn more about this in Stemming.