Energy accumulator for piston-type fuel pump
AssigneeStanadyne Operating Company LLC
InventorNicola Fachechi
Life of this patent
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Abstract
To reduce the peak torque required by an electric motor-driven high-pressure piston-type fuel pump, a drive assembly between the motor and pump includes an energy accumulator configured to accumulate energy during a low force portion of the pump cycle and return that energy to the pumping plunger during a high force portion of the pump cycle. This arrangement reduces the peak torque required from the motor and allows a smaller, less expensive and less energy intensive electric motor to drive the pump.
Claims14
A drive assembly for a piston-type fuel pump, said drive assembly comprising:
- a drive housing defining a drive chamber;
- a cam shaft supported within said drive chamber for rotation about a shaft axis;
- a circular cam rigidly connected to the cam shaft, said cam having a circular outer periphery defining a circular cam surface, said cam surface having a cam surface axis eccentric from said shaft axis;
- a cam roller having a sliding relationship to said cam surface;
- a cam follower surrounding the cam roller and including a first driven surface and a second driven surface, said first and second driven surfaces arranged on diametrically opposite sides of said cam roller, said cam follower having a first end axially outward of said first driven surface and a second end axially outward of said second driven surface, said cam follower having an outside surface guided on a complementary surface of said drive housing for movement along a drive axis perpendicular to said shaft axis, rotation of said cam shaft causing said cam follower to reciprocate along said drive axis between a first cam follower position and a second cam follower position;
- an energy accumulator arranged at the second end of the cam follower, said energy accumulator comprising at least one bias element between the second end of the cam follower and the drive housing, movement of the cam follower from the first cam follower position to the second cam follower position compressing said at least one bias element and movement of the cam follower from the second cam follower position to the first cam follower position allowing the at least one bias element to extend, thereby returning energy from the bias element to the cam follower to assist movement of the cam follower from the second cam follower position to the first cam follower position.
A method of returning energy to a cam in a drive assembly, said method comprising:
- supporting a circular cam surface on a cam shaft having a cam shaft axis of rotation, said circular cam surface have a cam axis of rotation offset from the cam shaft axis of rotation;
- coupling a cam follower to the circular cam surface to that the cam follower is moved along a drive axis perpendicular to the cam shaft axis of rotation between a first cam follower position and a second cam follower position;
- connecting an energy accumulator to the cam follower to receive axial force from the cam follower as the cam follower moves from the first cam follower position to the second cam follower position,
- wherein said axial force received by said energy accumulator compresses a bias element and said energy accumulator returns energy to the cam by extension of the bias element as the cam follower moves from the second cam follower position to the first cam follower position.
Dependencies are inferred from the claim text.