Fluid pump

1. A fluid pump comprising:

a pump body having a fluid path with an inlet and an outlet;

a diaphragm disposed along the fluid path between the inlet and the outlet;

a non-return valve to control direction of flow along the fluid path;

a diaphragm actuator comprising an unbalanced motor;

a motion constraining unit to constrain a motion of the unbalanced motor; and

a controller configured to adjust an amplitude of the motion of the unbalanced motor by adjusting power to the unbalanced motor,

wherein the motion constraining unit has a hinge and is configured to pivotally mount the unbalanced motor to the pump body through the hinge.

2. The fluid pump according to claim 1 , wherein the unbalanced motor is fixedly connected to the diaphragm.

3. The fluid pump according to claim 2 , wherein a motor body of the unbalanced motor is connected to the diaphragm.

4. The fluid pump according to claim 1 , wherein the motion constraining unit is configured to constrain degrees of freedom of the motion of the unbalanced motor.

5. The fluid pump according to claim 4 , wherein the motion constraining unit is configured to constrain the unbalanced motor to move substantially along one plane.

6. The fluid pump according to claim 5 , wherein the motion constraining unit is configured to restrict the amplitude of the motion of the unbalanced motor.

7. The fluid pump according to claim 6 , wherein the motion constraining unit comprises at least one stopper such that a maximum amplitude of the motion of the unbalanced motor is limited by the at least one stopper.

8. The fluid pump according to claim 7 , wherein the motion constraining unit comprises a resilient member.

9. The fluid pump according to claim 8 , wherein the resilient member is a leaf spring.

10. The fluid pump according to claim 9 , wherein the motion constraining unit is on the pump body or a housing in which the pump body is mounted.

11. The fluid pump according to claim 1 , wherein the unbalanced motor is a low voltage DC motor.

12. The fluid pump according to claim 1 , wherein the controller is configured to operate the unbalanced motor to control a flow rate of the fluid pump.

13. A steam generator comprising a fluid pump, the fluid pump comprising: a pump body having a fluid path with an inlet and an outlet; a diaphragm disposed along the fluid path between the inlet and the outlet; a non-return valve to control direction of flow along the fluid path; a diaphragm actuator comprising an unbalanced motor; a hinge; a motion constraining unit to constrain a motion of the unbalanced motor; and a controller configured to adjust an amplitude of motion of the unbalanced moto motor by adjusting power to the unbalanced motor, wherein the motion constraining unit has a hinge and is configured to pivotally mount the unbalanced motor to the pump body through the hinge.

14. The steam generator of claim 13 , wherein the hinge includes a stopper configured to limit the amplitude of the motion of the unbalanced motor.