Motor-driven pump with a plurality of impellers

Details Motor-driven pump with a plurality of impellers Motor-driven pump with a plurality of impellers

2001-02-06

2003-02-04

Freay, Charles G. (Department: 3746)

Pumps

Motor driven

Including means utilizing pump fluid for augmenting cooling,...

C417S352000, C417S371000, C417S423500, C415S102000

Reexamination Certificate

active

06514053

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a motor-driven pump with a plurality of impellers.
A motor-driven pump of this type is used to increase a discharge amount of fluid discharged therefrom and known from, for example, Japanese Patent Application KOKAI Publication No. 58-8295.
The motor driven pump described in the Publication No. 58-8295 comprises an electric motor and a pump unit having a rotational center shaft coupled to the output shaft of the electric motor. Both end portions of the rotational center shaft of the pump unit are rotatably supported by both side walls of a pump housing through a pair of bearings, and a pair of impellers are fixed to a central portion of the center shaft in its longitudinal direction. The paired impellers have a pair of fluid inlet regions opening toward the both end portions of the central shaft from the neighborhood of the longitudinal center portion of the rotational center shaft in an inner space of the pump housing, and one fluid discharge region opening outward in a radial direction of the rotational center shaft from the neighborhood of the central portion. Namely, in the paired impellers, a pair of fluid channels from the paired fluid inlet regions toward the one fluid discharge region are joined together in the vicinity of the fluid discharge region. In the pump housing, a spiral shaped chamber is formed in a portion facing the fluid discharge region of the paired impellers. An outlet of the spiral shaped chamber is connected to a conduit, not shown, and a distal end of this conduit reaches a position to which fluid is to be moved by this motor-driven pump. In addition, in the inner space of the pump housing, fluid to be moved by this motor-driven pump is flowed into on the both side portions of the paired impellers through conduits not shown.
In case of the conventional motor-driven pump described above, when the rotational center shaft is rotated in a predetermined direction by the output shaft of the motor, the fluid in the paired fluid inlet regions of the paired impellers are given kinetic energy by a centrifugal force and are directed toward the one fluid discharge region through the paired fluid channels and further toward the position to which the fluid is to be moved by this motor driven pump through the spiral shaped chamber and the conduit, not shown, of the pump housing. At the same time, fluid on the both side portions of the paired impellers in the inner space of the pump housing is sucked into the paired fluid inlet regions of the paired impellers.
In case of the above-described conventional motor-driven pump, a pair of fluid flows from the paired fluid inlet regions toward the one fluid discharge region through the paired fluid channels in the paired impellers collide against each other at a joint point of the paired fluid channels in the vicinity of the fluid discharge region. As a result, a joined fluid flow at the joint point applies the paired impellers with a force, which varies in a direction along the rotational center shaft and applies the rotational center shaft with a varying thrust force. Besides, if the discharge amount and discharge pressure of the fluid discharged from the motor-driven pump increase, the thrust force thereof is intensified accordingly.
For these reasons, in case of the conventional motor-driven pump described above, one of the bearings is a radial bearing and the other is a radial-thrust bearing. The thrust bearing disadvantageously complicates a constitution of the pump unit, increases an outside dimension thereof, and increases its weight and manufacturing cost thereof.
BRIEF SUMMARY OF THE INVENTION
The present invention has been derived from these circumstances. It is, therefore, an object of the present invention to provide a motor-driven pump having a plurality of impellers, capable of dispensing with a thrust bearing for a high thrust force, simple in constitution, small in outer dimension, small in weight and low in manufacturing cost.
To achieve the above object, a motor-driven pump with a plurality of impellers according to the present invention, comprises:
an electric motor including an output shaft, a motor frame rotatably supporting the output shaft while at least one end portion of the output shaft is protruded outward, and a rotation driving mechanism provided in the motor frame and rotating the output shaft in a predetermined direction when the mechanism is supplied with electric power;
a pump housing provided on a side of the one end portion of the output shaft in the electric motor, having two fluid inlet port regions on a side near the electric motor and on a side away from the electric motor in a longitudinal direction of the output shaft, respectively, and having one fluid discharge port region between the two fluid inlet port regions; and
an impeller unit including a pair of impellers having a partition wall concentrically fixed to the one end portion of the output shaft in an inner space of the pump housing, directing to the one fluid discharge port region, spreading outward in a radial direction of the output shaft and partitioning the inner space into a portion near the electric motor and a portion away from the electric motor, and a pair of blade means provided on both sides of the partition wall, respectively, the impeller unit moving fluid on the both sides of the partition wall from inside to outside in the radial direction along the pair of blade means of the pair of impellers by a centrifugal force in the inner space when the impeller unit is rotated by the output shaft of the electric motor in the predetermined direction.
With this constitution, while the fluids on the both sides of the partition wall are moved from inside to outside in the radial direction of the output shaft by the pair of blade means on the both sides of the partition wall in the inner space of the pump housing and reach the one fluid discharge port region of the pump housing, the fluids on both sides are separated from each other by the partition wall. Accordingly, the fluids moved as stated above are not mixed with each other on the both sides of the partition wall, and thrust forces applied to the impeller unit by the fluids moved on the both sides of the partition wall as stated above, does not vary. Then, it is possible to set that the fluids moved on the both sides of the partition wall as stated above always mutually cancel the thrust forces applied to the impeller unit.
Due to this, the motor-driven pump with a plurality of impellers according to the present invention dispenses with a thrust bearing for a high thrust force, is simple in constitution, small in outer dimension, small in weight and low in manufacturing cost.
In the motor-driven pump with a plurality of impellers according to the invention constituted as described above, a radial bearing rotatably supporting the other end portion of the output shaft can be provided in an opposite portion to the pump housing in the motor frame of the electric motor; and another radial bearing rotatably supporting the one end portion of the output shaft can be provided in a portion adjacent the pump housing in the motor frame of the electric motor.
Alternatively, a radial bearing rotatably supporting the other end portion of the output shaft can be provided in an opposite portion to the pump housing in the motor frame of the electric motor; and another radial bearing rotatably supporting the one end portion of the output shaft can be provided in a portion, located outward from the one end portion in the longitudinal direction of the output shaft, in the pump housing of the electric motor.
In the motor-driven pump according to the invention constituted as described above, in the pump housing, the fluid inlet port region on the side away from the electric motor can open outward in the longitudinal direction of the one end portion of the output shaft; and in the pump housing, the fluid inlet port region on the side adjacent the electric motor can open outward in the radial direction of the output shaft.
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