Patent attributes
A back-pressure valve comprises a case having first and second oil chambers through which oil passes. A piston is slidably accommodated within the case to partition the first oil chamber and the second oil chamber. A spring urges the piston in a sliding direction. A projecting member and a check valve allow the first oil chamber to communicate with the second oil chamber when the pressure of the oil in the first fluid chamber reaches a predetermined pressure. An area of the piston on which oil pressure is received in the first oil chamber is made lager than an area on which oil pressure is received in the second oil chamber. A part of the piston located at an end thereof opposite to the end thereof which faces the first oil chamber communicates with the outside of the case.
