Motor for electric pumps

A motor, devoid of balancing weights, for electric pumps comprising:

• an armature core for rotation;
• an armature shaft for rotation with said armature core and having an eccentric portion for driving a piston pump, said armature shaft being rotatably supported only at one side of said armature core near said eccentric portion;
• and
• a balancer formed at two axially and radially opposite positions in said armature core and said armature shaft so that the unbalance caused by a movable part of said piston pump may be offset when said armature shaft is in rotation,
• wherein said balancer includes two hole portions formed in a plurality of core sheets of said armature core at said opposite positions, and wherein the number of said core sheets for each of said hole portions are determined in relation to an axial distance from said eccentric portion and a radial distance from an axial center of said armature shaft.

A motor, devoid of balancing weights, for electric pumps comprising:

• a piston pump;
• an armature shaft forming a motor spindle and having an eccentric portion for driving said piston pump, said armature shaft being rotatably supported only at one axial side closer to said eccentric portion;
• and
• a core disposed on said shaft and having at least two areas where material has been removed therefrom, said two areas being provided axially and radially oppositely to each other and having axial lengths and radial distances from said armature shaft to counter unbalance caused by said eccentric portion wherein one of said axial lengths nearer to said eccentric portion is longer than that of another one of said axial lengths opposite to said one.

A device for countering unbalance found in a pump motor that includes a core having a plurality of core sheets, and an armature shaft on which said core is mounted, said armature shaft including an eccentric portion, said device being devoid of balancing weights and comprising:

• hole portions formed on a first and second side of said core so as to penetrate said core sheets from opposite directions, said hole portions being disposed symmetrically about a central axis of said armature shaft and being spaced different amounts from an axis of said eccentric portion;
• wherein said hole portions include a first and second hole of the same shape, said first hole being disposed on said first side and being 180 rotational degrees from said second hole formed on said second side;
• and
• wherein axial lengths of said hole portions are determined to reduce unbalance of said armature shaft and said core.

A motor, devoid of balancing weight, for electric pumps comprising:

• a piston pump;
• an armature shaft having an eccentric portion for driving said piston pump;
• and
• an armature that fits on said armature shaft, said armature including:
• a core made of a plurality of core sheets, each of which has at least one hole portion formed therein before being stacked on said armature shaft;
• wherein said hole portions in said core sheets act to counter unbalance caused by rotation of said eccentric portion when said core sheets are mounted on said armature shaft,
• wherein said core sheets are formed with a first hole portion on a first axial side of said core facing said eccentric portion and a second hole portion on a second axial side of said core facing away from said eccentric portion,
• wherein said hole portions are provided in said core sheets in a direction parallel to an axis of said eccentric portion, and wherein said hole portions in said core sheets have the same shape and are disposed so that said first hole portion includes a hole formed 180 degrees from said second hole portion.