Pressure generating device with pressure relief means

A pressure generating device having (a) a high-pressure accumulator for storing a fluid under a high pressure and delivering the fluid to a hydraulic component, (b) a high-pressure conduit connected at one end thereof to said high-pressure accumulator via a first check valve, (c) a high-pressure pump connected to the other end of said high-pressure conduit, to supply said high-pressure accumulator with the fluid under the high pressure, (d) a charging accumulator of a piston type including a piston and having a storage chamber connected to said high-pressure pump, for storing the fluid under a low pressure lower than that of the fluid in said high-pressure accumulator, and supplying said high-pressure pump with the fluid under the low pressure, and (e) a charging pump for supplying said charging accumulator with the fluid under the low pressure, wherein the improvement comprises:

• a generally cylindrical buffer piston closed by a bottom wall thereof at one of its opposite axial ends, and fluid-tightly received in a housing of said charging accumulator such that said buffer piston is slidable over a predetermined distance, said buffer piston slidably receiving therein a piston of said charging accumulator, and cooperates with said piston to define therebetween a storage chamber;
• leak means for permitting the fluid stored in said storage chamber, to leak at a low rate;
• a first communication passage provided for communication between said high-pressure conduit and a buffer chamber formed on one of opposite sides of said bottom wall of said buffer piston remote from said storage chamber;
• a second communication passage formed through said bottom wall of said buffer piston, for communication between said buffer chamber and said storage chamber;
• a second check valve disposed in said second communication passage, for preventing a flow of the fluid from said buffer chamber toward said storage chamber;
• a valve actuator is provided on one of said piston of said charging accumulator and a valve member of said second check valve, said valve actuator being abuttable on the other of said piston and said valve member to open said second check valve when said piston is placed in an advanced position thereof at which a volume of said storage chamber is minimum;
• and
• a spring for biasing said buffer piston toward said buffer chamber, a biasing force of said spring being determined so as to hold said buffer piston at an advanced position thereof even when a pressure necessary to retract said piston of the charging accumulator is applied to said buffer piston, said biasing force being further determined so as to allow said buffer piston to be retracted from said advanced position against said biasing force when the pressure in said buffer chamber falls within a range between said pressure necessary to retract said piston of the charging accumulator and a lower limit of said high-pressure accumulator.