Pump drive system

1. A fluid displacement pump comprising:

an electric motor having a first end disposed opposite a second end along an axis, the electric motor comprising:

a rotor configured to rotate about the axis, the rotor including a housing with an opening on the second end of the electric motor, the housing formed by a cylindrical body, a first end wall at the first end of the electric motor, and a second end wall at the second end of the electric motor, wherein the second end wall has the opening and the housing rotates with the rotor about the axis; and

a stator located at least partially inside of the rotor, the stator configured to generate electromagnetic fields that interact with the rotor to rotate the rotor around the stator;

a drive connected to the rotor at the first end of the electric motor, the drive configured to convert rotational output from the rotor to reciprocating motion; and

a pump comprising a fluid displacement member linked to the drive to be linearly reciprocated by the drive, the fluid displacement member located closer to the first end of the electric motor than to the second end of the electric motor;

wherein the stator is mounted to an axle, the first end wall of the rotor radially overlaps with the stator along a radial extent of the stator and the second end wall of the rotor at least partially radially overlaps with the stator along the radial extent of the stator such that a line parallel to the axis extends through each of the first end wall, the second end wall, and the stator, and wherein the axle extends through the opening of the second end wall.

2. The fluid displacement pump of claim 1 , wherein the drive comprises an eccentric that rotates.

3. The fluid displacement pump of claim 2 , wherein the eccentric rotates around the axis but offset from the axis.

4. The fluid displacement pump of claim 3 , wherein the eccentric is integrated into the housing of the rotor, the eccentric fixed to the housing and projecting away from the housing.

5. The fluid displacement pump of claim 1 , wherein the drive comprises a screw and a nut, one of the nut and the screw rotates coaxially with the axis, and the fluid displacement member reciprocates coaxially with the axis.

6. The fluid displacement pump of claim 1 , further comprising a support frame, wherein the electric motor further comprises a stator support that extends through the opening of the housing of the rotor to hold the stator stationary relative to the support frame while the housing rotates around the stator.

7. The fluid displacement pump of claim 6 , wherein the support frame includes a frame member disposed at the second end and a pump frame disposed at the first end, the frame member attached to the stator support at the second end of the electric motor, and the frame member connected to the pump frame to brace the stator relative to the pump frame.

8. The fluid displacement pump of claim 7 , wherein the stator support comprises the axle.

9. The fluid displacement pump of claim 1 , wherein the stator receives electrical power through the opening of the housing of the rotor.

10. The fluid displacement pump of claim 1 , wherein the rotor comprises a plurality of magnets that rotate with the housing.

11. The fluid displacement pump of claim 1 , wherein the pump further comprises a cylinder, and the fluid displacement member is a piston that is reciprocated within the cylinder by the drive.

12. A fluid sprayer, the fluid sprayer comprising:

the fluid displacement pump of claim 1 ;

a hose, and

a spray gun that receives fluid from the pump via the hose.

13. The fluid displacement pump of claim 1 , wherein the second end wall is formed separately from the cylindrical body and fixed to the cylindrical body.

14. A fluid displacement pump comprising: a support frame; an electric motor having a first end disposed opposite a second end along a motor axis, the electric motor comprising: a rotor configured to rotate about the motor axis, the rotor including a housing with an opening on the second end of the electric motor; a stator located at least partially inside of the rotor, the stator configured to generate electromagnetic fields that interact with the rotor to rotate the rotor around the stator; and an axle that extends through the opening of the housing of the rotor to hold the stator stationary relative to the support frame while the housing rotates around the stator; a drive connected to the rotor at the first end of the electric motor, the drive configured to convert rotational output from the rotor to reciprocating motion; a pump comprising a fluid displacement member linked to the drive to be linearly reciprocated by the drive along a pump axis, the fluid displacement member located closer to the first end of the electric motor than to the second end of the electric motor; a first bearing disposed between the support frame and the rotor and about an exterior of the housing of the rotor at the first end of the electric motor to support the rotor and allow rotational motion of the rotor with respect to the support frame; and a second bearing disposed between the axle and the rotor at the second end of the electric motor to support the rotor and allow rotational motion of the rotor with respect to the axle; wherein the first bearing and the second bearing are disposed at locations along the motor axis that are on a same axial side of the pump axis.

15. The fluid displacement pump of claim 14 , wherein the support frame and a frame member compress the first bearing and the second bearing therebetween to preload the first bearing and the second bearing.

16. The fluid displacement pump of claim 14 , wherein the second bearing is disposed at the second end of the electric motor.

17. The fluid displacement pump of claim 14 , wherein the second bearing is disposed in the opening through the rotor.

18. The fluid displacement pump of claim 14 , further comprising a third bearing supporting the rotor to allow rotational motion of the rotor with respect to the support frame, wherein the second bearing and the third bearing are disposed on an interior of the housing of the rotor.

19. A fluid displacement pump comprising: an electric motor having a first end disposed opposite a second end along an axis, the electric motor comprising: a rotor configured to rotate about the axis, the rotor including a housing with an opening on the second end of the electric motor; a stator located at least partially inside of the rotor, the stator configured to generate electromagnetic fields that interact with the rotor to rotate the rotor around the stator; and a drive connected to the rotor at the first end of the electric motor, the drive configured to convert rotational output from the rotor to reciprocating motion; a pump comprising a fluid displacement member linked to the drive to be linearly reciprocated by the drive, the fluid displacement member located closer to the first end of the electric motor than to the second end of the electric motor; a support frame includes a frame member disposed at the second end and a pump frame disposed at the first end, a stator support that extends through the opening of the housing of the rotor to hold the stator stationary relative to the support frame while the housing rotates around the stator, wherein the frame member is attached to the stator support at the second end of the electric motor and the frame member is connected to the pump frame to brace the stator relative to the pump frame; and at least one connector that connects the pump frame to the frame member, each connector extending along the exterior of the rotor from the first end to the second end of the electric motor.

20. The fluid displacement pump of claim 19 , wherein the at least one connector comprises at least two connectors spaced around the rotor.

21. The fluid displacement pump of claim 19 , wherein the stator of the electric motor is cantilevered from the pump frame.

22. The fluid displacement pump of claim 19 , wherein the pump is mounted on the pump frame.

23. A fluid displacement pump, the fluid displacement pump comprising:

an electric motor having a first end disposed opposite a second end along an axis, the electric motor comprising:

a rotor configured to rotate about the axis, the rotor including a housing with an opening on the second end of the electric motor;

a stator located inside of the rotor, the stator configured to generate electromagnetic fields that interact with the rotor to rotate the rotor around the stator; and

an axle located inside of the stator and the rotor, the axle extending outside of the rotor through the opening of the housing;

a drive connected to the housing of the rotor at the first end of the electric motor to receive a rotational output from the rotor, the drive configured to convert the rotation output into a reciprocating motion;

a pump comprising:

a cylinder; and

a fluid displacement member mechanically connected to the drive so that the fluid displacement member is reciprocated linearly within the cylinder; and

a support frame comprising:

a frame member connected to the axle at the second end of the motor; and

a pump frame on which the cylinder is mounted, the electric motor located directly between the frame member and the pump frame;

a first bearing supported by the axle and disposed within the housing to support the rotor and allow rotational motion of the rotor with respect to the support frame; and

a second bearing disposed within the housing to support the rotor and allow rotational motion of the rotor with respect to the support frame;

wherein at least part of the stator is positioned between the first bearing and the second bearing along the axis.