Technical Field
The present invention relates to a rotary joint.
Background Art
A rotary joint is used in relative rotation portions of various rotary apparatuses such as a semiconductor manufacturing apparatus, a medical apparatus, and an apparatus for food. The rotary joint includes a first member and a second member that rotate relative to each other, and it is necessary to cause a plurality of different types of fluids between these two members to flow through different passages. Thus, the rotary joint has a configuration in which a plurality of first flow passages are formed in the first member, a plurality of second flow passages are formed in the second member, and one first flow passage and one second flow passage are connected to each other in a one-to-one relation, for causing the fluids to flow therethrough (see, e.g., Japanese Laid-Open Patent Publication No. 2002-22076).
FIG. 4 is a cross-sectional view of a conventional rotary joint. The rotary joint 90 includes a cylindrical case body 91 (the above first member) and a shaft body 92 (the above second member) provided inside the case body 91. Upper and lower two first flow passages 95 are formed in the case body 91, and upper and lower two second flow passages 96 are formed in the shaft body 92. An opening of the upper first flow passage 95 and an opening of the upper second flow passage 96 are located at the same position in an axial direction, and these flow passages 95 and 96 are connected to each other to form a single flow passage 97. In addition, an opening of the lower first flow passage 95 and an opening of the lower second flow passage 96 are located in the same position in the axial direction, and these flow passages 95 and 96 are connected to each other to form a single flow passage 97. For preventing fluids flowing through the upper and lower flow passages 97, 97, respectively, from leaking to the outside, a plurality of seal rings 93 are provided between the case body 91 and the shaft body 92.