CROSS-REFERENCE TO RELATED APPLICATION

This application is a 371 of international application of PCT application serial no. PCT/JP2018/014565, filed on Apr. 5, 2018, which claims the priority benefits of Japan application no. JP 2017-077701, filed on Apr. 10, 2017. The entirety of each of the abovementioned patent applications is hereby incorporated by reference herein and made a part of this specification.

TECHNICAL FIELD

The present invention relates to a pump device configured to drive an impeller in a pump chamber by a motor.

BACKGROUND ART

Japanese Unexamined Patent Application Publication No. 2016-3580 (hereinafter, referred to as Patent Literature 1) describes a pump device including a pump chamber provided with a fluid inlet port and a fluid outlet port, an impeller arranged in the pump chamber, and a motor configured to rotate the impeller. In the pump device according to Patent Literature 1, the motor includes a rotor, a cylindrical stator arranged at an outer peripheral side of the rotor, and a housing. The housing includes a partition wall member by which a space between the rotor and the stator is partitioned, and a resin sealing portion adapted to cover the stator from an outer peripheral side of the partition wall member. The pump chamber is defined by the housing and a case body provided on the housing to cover the housing. The fluid inlet port and the fluid outlet port are provided in the case body.

The rotor includes a cylindrical sleeve, a magnet arranged in an annular pattern at an outer peripheral side of the sleeve, and a holding member holding the sleeve and the magnet. A fixation shaft is inserted into the sleeve to extend through the sleeve, and the rotor is rotatably supported by the fixation shaft. A bearing member extending radially outward is attached to a halfway portion of the fixation shaft in an axial direction thereof. The bearing member functions as a thrust bearing, and the sleeve is brought into slidable contact with the bearing member from one side in the axial direction. The impeller is fixed to the holding member and located together with the rotor in the pump chamber.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2016-3580

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

When the motor operates to rotate the impeller, fluid flows from the fluid inlet port toward the fluid outlet port through the pump chamber. Here, the fluid passing the pump chamber flows into a gap between the impeller and the partition wall member; therefore, pressure in the gap increases. Consequently, a force moving the impeller toward the case body acts on the impeller. When the impeller is pressed toward the case body by such a force, the rotor (the sleeve) is pressed against the bearing member. As a result, high heat is generated between the bearing member and the rotor by a sliding movement. Accordingly, in a case where the sleeve and the holding member that configure the rotor are made of resin or in a case where the members by which the pump chamber is defined are made of resin, the resin members may be deformed by the generated heat.

Thus, in view of such a point, an object of the present invention is to provide a pump device configured such that when an impeller is driven by a motor to circulate fluid, the impeller can be prevented from being moved toward a case body by which a pump chamber is defined.

Means for Solving the Problem

In order to achieve the aforementioned object, a pump device according to the present invention includes a motor provided with an output shaft, a case body provided to cover an end wall portion located at an output side of the motor through which the output shaft extends, a pump chamber defined by the end wall portion and the case body, a fluid inlet port and an outlet port provided in the case body to be communicated with the pump chamber, an impeller attached to the output shaft to be arranged in the pump chamber, and a suction power generation mechanism configured to generate suction power sucking the impeller toward the end wall portion when the impeller is driven by the motor, and the fluid is flowing from the fluid inlet port toward the fluid outlet port through the pump chamber.

The pump device according to the present invention is configured such that when the impeller is driven by the motor, and the fluid is flowing from the fluid inlet port toward the fluid outlet port through the pump chamber, the suction power generation mechanism suctions the impeller toward the end wall portion of the motor. Accordingly, the fluid passing the pump chamber flows into a gap between the impeller and the end wall portion of the motor. Therefore, pressure in the gap increases and a force moving the impeller toward the case body acts on the impeller. Even in such a case, the force can be inhibited. Consequently, since the force pressing the output shaft to which the impeller is connected toward the case body can be inhibited, the rotor provided with the output shaft in the motor can be inhibited from being pressed against a bearing member that is slidably contactable with the rotor from the output side. As a result, heat generated by a sliding movement of the rotor with the bearing member can be inhibited.

According to the present invention, the impeller may include a shroud extending in a direction intersecting with an axis line of the output shaft, a front blade protruding from the shroud toward the opposite side of the end wall portion, and a back blade protruding from the shroud toward the end wall portion, and the suction power generation mechanism may include the back blade. If the impeller includes the back blade protruding from the shroud toward the end wall portion of the motor, the fluid drawn out radially outward from the gap between the impeller and the end wall portion may collide with the fluid flowing into the gap between the impeller and the end wall portion. Thus, since the fluid flowing into the gap between the impeller and the end wall portion is inhibited, the pressure in the gap can be inhibited from increasing. In addition, when the fluid is drawn out by the back blade radially outward from the gap between the impeller and the end wall portion, a negative pressure is generated between the impeller and the end wall portion. Therefore, the impeller can be sucked by the negative pressure toward the end wall portion of the motor. In other words, the back blade of the impeller configures the suction power generation mechanism configured to generate suction power sucking the impeller toward the end wall portion.

According to the present invention, in order to allow the fluid to be drawn out by the back blade radially outward from the gap between the impeller and the end wall portion when the impeller is driven to circulate the fluid through the pump chamber, the shroud may extend perpendicularly to the axis line, and the back blade may be configured such that a protrusion amount from the shroud toward the end wall portion is radially constant. In addition, a ring-shaped facing surface of the end wall portion overlapping a rotation trajectory of the back blade when viewed in the axis direction may be a flat surface in parallel with the back blade.

According to the present invention, the protrusion amount of the back blade may be equal to or greater than 50% of a separate distance between the shroud and the facing surface. With such a configuration, a distance between the back blade and the end wall portion of the motor can be reduced; therefore, the fluid can be easily drawn out by the back blade radially outward from the gap between the impeller and the end wall portion.

According to the present invention, a first distance between the back blade and the facing surface may be smaller than a second distance between the front blade and a case body side facing surface which faces the facing surface in the axis line in the case body. In other words, the distance between the back blade and the end wall portion of the motor is preferably smaller than the distance between the front blade and the case body. With such a configuration, negative pressure is easily generated between the back blade and the end wall portion of the motor.

According to the present invention, a plurality of the back blades may be provided at equal angular intervals around the axis line in order that the fluid is drawn out by the back blade radially outward from the gap between the impeller and the end wall portion.

According to the present invention, the impeller may include a cylindrical portion being coaxial with the axis line and protruding from the shroud toward the end wall portion, and a ring-shaped rib provided at a radially outer side of the cylindrical portion and coaxially with the cylindrical portion. The output shaft may be inserted to extend through a center hole of the cylindrical portion. The back blade may extend from an outer circumferential surface of the ring-shaped rib toward the radially outer side. A length dimension from the outer circumferential surface of the ring-shaped rib to a radially outer end in the back blade may be equal to or greater than a distance between the cylindrical portion and the ring-shaped rib. With such a configuration, the impeller can be held by the output shaft extending through the cylindrical portion so as not to be inclined. In addition, dusts or the like contained in the fluid can be prevented or inhibited from reaching the surroundings of the output shaft. In addition, since the length dimension from the outer circumferential surface of the ring-shaped rib to the radially outer end in the back blade is equal to or greater than the distance between the cylindrical portion and the ring-shaped rib, the radial length dimension of the back blade can be secured. Therefore, the fluid is easily drawn out by the back blade radially outward from the gap between the impeller and the end wall portion.

According to the present invention, the motor may include a rotor provided with the output shaft, and a bearing member supporting the output shaft so that the output shaft is rotatable. The bearing member may include a sliding surface with which the rotor is slidably contactable from the opposite side of the output side. The rotor may include a resin holding member holding the output shaft from a radially outer side, a magnet held by the holding member, a first metallic member fixed to the output shaft to extend from the output shaft toward the radially outer side and held by the holding member, a rotor-side sliding surface slidably contactable with the sliding surface, and a second metallic member held by the holding member in a state where the first metallic member is in contact with the second metallic member from the opposite side of the output side.

With such a configuration, the resin holding member holding the output shaft from the radially outer side holds the first metallic member fixed to the output shaft to extend from the output shaft toward the radially outer side. Therefore, a position of the holding member relative to the output shaft can be prevented or inhibited from changing in the axis line consequently, a position of the magnet held by the holding member can be prevented or inhibited from changing in the axis line and thus rotation accuracy of the rotor can be maintained. Further, since the first metallic member fixed to the output shaft is held by the holding member, heat generated by a sliding movement of the bearing member with the rotor can be released via the metallic member toward the output side. Therefore, the resin holding member can be prevented or inhibited from being deformed by the heat generated by the sliding movement of the bearing member with the rotor. Furthermore, since a portion of the rotor, which is slidable with the bearing member is the second metallic member, the portion slidable with the bearing member is not deformed by the heat generated by the sliding movement. Moreover, the first metallic member fixed to the output shaft is in contact with the second metallic member from the opposite side of the sliding surface. Therefore, even when the output shaft is moved toward the case body, the position of the second metallic member does not change in a direction to separate from the sliding surface in the axis line. Further, since the first metallic member is in contact with the second metallic member, the heat generated by the sliding movement of the bearing member with the rotor is released from the second metallic member via the first metallic member toward the output shaft.

Furthermore, the second metallic member is held by the holding member and is not fixed to the output shaft. Therefore, the second metallic member can be avoided from being deformed by fixation to the output shaft. As a result, flatness of the rotor-side sliding surface can be maintained and thus the rotation accuracy of the rotor is easily secured.

According to the present invention, the output shaft may be made of metal. With such a configuration, the heat generated by the sliding movement of the rotor with the bearing member is easily released via the output shaft.

Effect of the Invention

According to the present invention, the fluid is drawn out by the back blade of the impeller radially outward from the gap between the impeller and the end wall portion of the motor in the pump chamber. Therefore, pressure in the gap between the impeller and the end wall portion of the motor can be inhibited from increasing when the fluid passes the pump chamber to flow into the gap. Also, since the fluid is drawn out by the back blade of the impeller radially outward from the gap between the impeller and the end wall portion of the motor, a negative pressure is generated between the impeller and the end wall portion of the motor. The negative pressure is suction power moving the impeller toward the motor; therefore, the impeller is inhibited from being pressed toward the case body. Consequently, since the output shaft to which the impeller is connected is inhibited from being pressed toward the case body, the rotor provided with the output shaft in the motor can be inhibited from being pressed against the bearing member that is slidably contactable with the rotor from the output side. As a result, heat generated by a sliding movement of the rotor with the bearing member can be inhibited.

