Pump Driving Apparatus

Abstract

A pump driving apparatus that can suppress backflow of a liquid in a pump chamber and improve pump efficiency is provided.A guide tube 23 is provided coaxially with an output shaft 4 of a motor M inside a pump chamber 8, and the ends in the axial direction of the guide tube 23 are fitted into and make sliding contact with a case inner wall surface that forms the pump chamber 8 and a shaft core-side inner wall surface 25 of an impeller 9 enclosed inside the pump chamber 8.

Description

TECHNICAL FIELD[0001]The present invention relates to a pump driving apparatus that draws liquid in an axial direction into a pump chamber and expels the liquid in a circumferential direction by rotating an impeller provided inside the pump chamber.BACKGROUND ART[0002]First, one example of a pump driving apparatus will now be described. In FIG. 6, a rotor magnet 53, which has been magnetized with two poles at 180° intervals, is provided on a back yoke 52 of a rotor 51. The back yoke 52 is connected to a magnet case 56. A coupling magnet 55 is fitted onto the upper surface of the magnet case 56. The magnet case 56 is rotatably fitted onto a motor-side fixed shaft 54a via a bearing 57. A pump-side fixed shaft 54b, which is connected to a motor-side fixed shaft 54a by screw engagement, is integrally provided on a pump chamber 58. A rotation vane (impeller) 59 is fitted onto the pump-side fixed shaft 54b via a bearing 60. The impeller 59 slidably rotates via the bearing 60 around the pu...

AI Technical Summary

Benefits of technology

[0014]When the pump driving apparatus according to the present invention is used, a guide tube is provided inside the pump chamber so as to be coaxial with the fixed shaft, wherein ends of the guide tube in the axial direction are fitted to and make sliding contact with a case wall surface that forms the pump chamber and a core-side wall surface of the impeller enclosed inside the pump chamber. This means that when the impeller is rotated to draw in low-pressure liquid in the axial direction into the pump chamber and expel the liquid toward the outer periphery, high-pressure liquid that flows back toward the core from the outer periphery of the pump chamber via a gap between the impeller and the pump case due to the pressure difference in the pump chamber can be effectively blocked by the guide tube. Therefore, it is possible to prevent vigorous collisions between high-pressure liquid that has flowed back in the pump chamber and the low-pressure liquid drawn in at the core due to the pressure difference inside the pump chamber, and therefore pump efficiency can be improved. Also, since it is possible to reduce the gap between the impeller and the pump case, it is possible to reduce redundant capacity of the pump chamber and make the pump chamber more compact.

[0015]Also, since each sliding contact surface formed on the guide tube or on an erected wall, which is erected in the axial direction inside the pump chamber, of the pump case or the impeller is formed for example of a spherical surface portion that is produced by having an outer circumferential surface of the guide tube or the erected wall swell outward and whose center lies on an axis of the fixed shaft, the guide tube will become inclined in keeping with any inclination of the impeller due to fluctuations in pressure inside the pump chamber or the strength of the fixed shaft. This means that the sliding contact between the guide tube and the case wall surface and wall surface of the impeller is maintained. As a result, it is possible to prevent vigorous collisions between high-pressure liquid that flows back from the outer periphery and the low-pressure liquid drawn in at the core due to the pressure difference inside the pump chamber, so that stable pump operation with little fluctuation in pressure inside the pump chamber can be maintained.

Problems solved by technology

Firstly, it is necessary to prevent interference due to insufficient precision in the dimensions of the pump case 62 that is integrally molded.

In addition, centering is difficult for the impeller 59 which is formed by welding together an upper portion, where the radial protruding ribs 67 are formed, and a lower portion, where the coupling magnet 61 is enclosed, which means that it is difficult to manufacture a pump driving apparatus with components that are precisely concentric.

However, a pressure difference is produced inside the pump chamber 58, resulting in the problem that high-pressure liquid in the outer periphery flows back, via the gap S between the impeller 59 and the pump case 62, in the direction of the arrow R toward the periphery of the shaft that is at low pressure and collides with the liquid being drawn in the direction of the arrow P. thereby lowering the pump efficiency.

When the fixed shafts 54a, 54b are inclined, there is a further problem in that the gap S will vary, resulting in greater fluctuations in pressure inside the pump chamber 58, which makes the pump operation unstable.

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