Rotary-vane pump with improved discharge rate control means

A rotary-vane pump comprising:

• pumping means including a plurality of pumping chambers, control pressure producing means for producing a control fluid pressure variable in response to rotational speed of said pump, and an outlet port communicable with said pumping chambers;
• a housing accommodating said pumping means and having a discharge port;
• discharge passage means for providing communication between said outlet port and said discharge port;
• said discharge passage means including a pair of discharge passages which are provided with orifices, respectively;
• first flow control valve means for regulating the pressure differential across said orifices to a constant value;
• and
• second flow control valve means for controlling fluid flow through one of said discharge passages;
• said second flow control valve means including a spool bore extending across said one discharge passage, a spool axially movable in said spool bore and forming at one axial end a control pressure chamber and at the other end a spring chamber, said spring chamber being in communication with said discharge port, said control pressure chamber being in communication with said control pressure producing means so that said spool is urged by said control fluid pressure in the direction to close said one discharge passage, and a spring disposed in said spring chamber for urging said spool in the direction to open said one discharge passage, said spool having a pair of axially spaced first and second lands, an annular relieved section between said first and second lands and a guide post section protruding from said second land into said spring chamber, said spring having one end retained by said second land and said guide post section, said relieved section cooperating with said spool bore to define an annular chamber which constitutes part of said second discharge passage to fully or partly open said second discharge passage, said annular chamber being fluidly separated from said spring chamber by said second land.

A rotary-vane pump comprising:

• pumping means including a rotor, a plurality of vanes radially movably installed on said rotor, a cam ring accommodating said rotor with said vanes to form a plurality of pumping chambers, a plurality of undervane working chambers variable in volume in response to radial movement of said vanes, a plurality of undervane balancing chambers communicated with said undervane working chambers, orifice means for developing in a predetermined group of said undervane balancing chambers a control fluid pressure variable in proportion to rotational speed of said pump, an outlet port communicable with said pumping chambers;
• a housing accommodating said pumping means to form, around said cam ring, a pressure chamber in communication with said outlet port and having a discharge port;
• first flow control valve means associated with said pressure chamber for regulating a fluid pressure in said pressure chamber to a constant value irrespective of rotational speed of said pump;
• discharge passage means for providing communication between said pressure chamber and said discharge port;
• said discharge passage means including a pair of discharge passages which are provided with orifices, respectively;
• and
• second flow control valve means for controlling fluid flow through one of said discharge passages;
• said second flow control valve means including a damper orifice, a spool bore extending across said one discharge passage, a spool axially movable in said spool bore and forming at one axial end a control pressure chamber and at the other end a spring chamber, said spring chamber being in communication with said discharge port, said control pressure chamber being in communication with said predetermined group of said undervane balancing chambers by way of said damping orifice so that said spool is urged by said control fluid pressure in the direction to close said one discharge passage, and a spring disposed in said spring chamber for urging said spool in the direction to open said one discharge passage, said spool having a pair of axially spaced first and second lands, an annular relieved section between said first and second lands and a guide post section protruding from said second land into said spring chamber, said spring having one end retained by said second land and said guide post section, said first land being of such a length as to be capable of fully closing said one discharge passage, said relieved section cooperating with said spool bore to define an annular chamber which constitutes part of said second discharge passage to fully or partly open said second discharge passage, said annular chamber being fluidly separated from said spring chamber by said second land.