Gear pump with noise attenuation

Apparatus comprising:

• a reservoir containing hydraulic fluid;
• a gear pump having gears with meshing teeth that induce a flow of hydraulic fluid into said pump through a suction hole at a first pressure and induce a flow of hydraulic fluid from said pump at a second pressure which is greater than the first pressure;
• a hydraulic muffler which is connected in fluid communication with said reservoir and said gear pump, said hydraulic muffler being effective to attenuate noise by damping flow rate fluctuations caused by said meshing gear teeth;
• said hydraulic muffler includes a channel through which hydraulic fluid from said reservoir is conducted to said suction hole, a cavity which is offset from a flow of hydraulic fluid through said channel and is connected in fluid communication with said channel, said cavity is free of connections to sources of fluid other than the flow of fluid through said channel, and a compliant element disposed in said cavity and exposed to fluid pressure in said cavity, said compliant element being movable under the influence of fluid pressure fluctuations resulting from flow rate fluctuations caused by said meshing gear teeth to enable hydraulic fluid to flow from the flow of hydraulic fluid in said channel into said cavity and to discharge hydraulic fluid from said cavity into the flow of hydraulic fluid in said channel.

Apparatus for use in supplying hydraulic fluid to a vehicle power steering system, said apparatus comprising:

• an electric motor;
• a gear pump having gears which are connected with and rotated by said electric motor to induce hydraulic fluid to flow into said gear pump at a first pressure and to flow out of said gear pump to the vehicle power steering system at a second pressure which is greater than the first pressure, said gears having meshing teeth which cause fluctuations in a flow of hydraulic fluid being conducted to said gear pump during rotation of said gears by said electric motor;
• and
• a hydraulic muffler connected in fluid communication with said gear pump and through which the flow of hydraulic fluid is conducted to said gear pump during rotation of said gears by said electric motor;
• said hydraulic muffler includes a channel through which the flow of hydraulic fluid is conducted, a cavity having an opening connected in fluid communication with said channel, and a resiliently compressible material disposed in said cavity and exposed to fluid pressure conducted from said channel, said resiliently compressible material being compressible under the influence of increasing fluid pressure in the fluctuations in flow of hydraulic fluid in said channel during rotation of said gears and being expandable under the influence of the resilience of said resiliently compressible material during decreasing fluid pressure in the fluctuations in flow of hydraulic fluid in said channel during rotation of said gears.

Apparatus comprising:

• a gear pump;
• and
• a hydraulic muffler connected with said gear pump and through which a flow of hydraulic fluid is conducted to said gear pump;
• said hydraulic muffler includes a channel through which the flow of hydraulic fluid is conducted, a cavity having an opening connected in fluid communication with said channel at a location spaced from said gear pump, and a body of resilient material which is disposed in said cavity, said body of resilient material being compressible from a first volume to a second volume under the influence of increasing fluid pressure in fluctuations induced in the flow of hydraulic fluid in said channel by said gear pump during operation of said gear pump and is expandable from the second volume during decreasing fluid pressure in the fluctuations induced in the flow of hydraulic fluid in said channel by said gear pump during operation of said gear pump.