Connection structure of oil passage

A connection structure of oil passages, comprising:

• a first oil passage-forming member forming a first oil passage therein;
• a second oil passage-forming member connected to said first oil passage-forming member and forming therein a second oil passage to be connected to said first oil passage;
• and
• a seal member disposed between said first oil passage-forming member and said second oil passage-forming member, for keeping oil seal between said first oil passage and said second oil passage;
• wherein
• a large diameter part having a diameter larger than a bore diameter of said second oil passage is formed in an opening of said first oil passage at a connection side with said second oil passage for fitting said seal member;
• and
• a channel is formed to extend from said first oil passage to an outside of said first oil passage-forming member in a radial direction from said large diameter part for connecting said first oil passage and said outside of the first oil passage-forming member;
• and wherein
• said seal member blocks communication between said first oil passage and said outside of the first oil passage-forming member through said channel, whereby keeping said oil seal between said first oil passage and said second oil passage.