GB2239487A

GB2239487A - A circumferential flow type liquid pump

Info

Publication number: GB2239487A
Application number: GB9025699A
Authority: GB
Inventors: Hiroshi Yoshioka; Shingo Iwai
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1989-12-26
Filing date: 1990-11-27
Publication date: 1991-07-03
Anticipated expiration: 2010-11-27
Also published as: KR910012550A; DE4039712C2; JPH073239B2; DE4039712A1; GB2239487B; JPH03199693A; KR950006578Y1; GB9025699D0

Abstract

A circumferential flow liquid pump comprises an impeller 4 with vanes 5 on its outer periphery, and a pump casing assembly 1 defining an arcuate pump flow path 7 along the outer periphery of the impeller and a suction inlet (8, Fig. 1) and a discharge outlet (9) at opposite ends of the pump flow path. The pump casing assembly includes a gas venting path 11 which opens in the inner periphery of the pump flow path near the impeller with a step extended from the bottom of the pump flow path and radially inwardly, and a through-hole 12 much larger in sectional area than the gas venting path, through which the gas venting path communicates with the outside of the pump casing assembly, whereby bubbles formed by vaporization of the liquid in the pump flow path are positively discharged from the pump casing assembly, and vapor locking is avoided. <IMAGE>

Description

p 1 CIRCUMFERENTIAL FLOW TYPE LIQUID PUMP

Background of the Invention

This invention relates to circumferential flow type liquid pump, and more particularly to a circumferential flow type liquid pump used as a f uel pump f or pumping a liquid-phase fuel such as gasoline from the fuel tank in a vehicle's internal combustion engine.

Figs. 4 and 5 are sectional views showing a pump which is the same in type as a conventional circumferential flow type liquid pump as disclosed by Japanese Patent Application (OPI) No. 79193/1985 (the term "OPI" as used herein means an llunexamined published application"). In these figures, reference numeral 1 designates a pump casing assembly which comprises a pump casing body 2 and a cover 3. The pump casing assembly accommodates an impeller 4 with vanes 5 on its is periphery. The impeller 4 is mounted on a central shaft 6 so that it is rotated around the central axis with respect to the pump casing assembly 1.

In the pump casing assembly 1, an arcuate elongated pump flow path 7 with a suction inlet 8 and a discharge outlet 9 at both ends is defined in such a manner that it is extended along the outer periphery of the impeller 4 and receives the vanes 5 of the impeller 4.

The upstream end portion of the pump flow path 7 which is on the side of the suction inlet is formed into an enlarged 71.

is flow path 7a having a predetermined length which is larger in section than the remaining portionj and accordingly lower in internal pressure than the latter, and has a step 7b at the end where its sectional area is decreased in other words, the remaining portion of the pump flow path 7 between the step 7b and the discharge outlet 9 is smaller in sectional area than the enlarged flow path 7a. and accordingly higher in internal pressure than the latter 7b. A small hole, namely, a gas venting hole 14 is formed in the enlarged flow path near the step 7b so that the pump f low path is communicated with the pump casing assembly 1.

The central shaf t 6 of the impeller 4 is the rotary shaft of the rotor 16 of an electric motor 15, and it is rotatably supported by bearings 17 and 18 at both ends.

Further in Fig. 4, reference numeral 19 designates an end cover which has a check valve 22 and a liquid outlet 23, and supports a bracket 24.

The pump casing assembly 1 is coupled to the end cover 19 through the yoke 20 of the motor 15. The yoke 20 accommodates the rotor 16, and forms a liquid chamber 21 between the pump casing assembly 1 and the end cover 19 to store a liquid such as a liquid fuel discharged through the discharge outlet 9. Permanent magnets 25 serving as stator are mounted on the inner wall of the yoke. The liquid chamber 21 is communicated with the liquid outlet 23 with the check valve 22 which is provided in the end cover 19. The bracket 24 c e, e 3 supports brushes 27 which are held in slide contact with the commutator 26 of the rotor 16._ The operation of the circumferential flow type liquid pump thus constructed will be described.

As the impeller 4 is rotated clockwise. in Fig. 5, by -the electric motor 15, a liquid such as a liquid fuel is sucked into the pump f low path 7 through the suction inlet 8. The liquid thus sucked is increased in pressure by the fluid friction resistance which is provided by high speed rotation of the vanes of the impeller, so that it is caused to flow clockwise in Fig. 5 and then flow through the discharge outlet 9 into the liquid chamber 21. On the other hand, when the vanes of the impeller contact the liquid, the latter is partially vaporized, thus forming bubbles in the liquid. The bubbles thus formed are also allowed to flow into the liquid chamber 21. If the bubbles are supplied through the liquid chamber 21 into the internal combustion engine, then a variety of difficulties are caused. In order to eliminate these difficulties, the gas venting hole 14 is formed in the enlarged f low path near the step to discharge the bubbles out of the pump casing assembly 1.

When, in a circumferential flow type liquid pump used as a f uel pump, bubbles are f ormed in the pump f low path by vaporization of the fuel and stayed therein, then so-called Ilvapor locking" is caused to obstruct the flow of liquid, thus lowering the pumping capacity greatly. In order to overcome i V-- this difficulty, in a conventional circumferential flow type liquid pump, as was described above the gas venting hole is formed in the pump flow path to communicate the latter with the outside of the pump casing assembly, so that bubbles formed in the pump f low path by vaporization of the liquid are discharged through the gas tenting hole into the outside of the pump casing assembly.

However, since the gas venting hole is a small hole f ormed in the bottom of the enlarged f low path, there are various problems to be solved. That is, when the vanes of the impeller contact the liquid such as liquid f uel in the pump flow pathr bubbles are formed therein, and the bubbles flows along the inner circular periphery of the pump f low path because of the difference between the bubbles and the liquid both in centrifugal force and in specific gravity. Hence, in order to discharge the bubbles out of the pump casing assembly, it is necessary to discharge a large quantity of substantially bubble-free liquid which is present near the bottom of the pump flow path out of the pump casing assembly. Furthermore, since the gas venting hole is a small hole formed in the enlarge f low path as was described before, great flow resistance is induced when the bubbles together with the liquid f low through the small hole.

Furthermore, since the gas venting hole is vertical with respect to the bottom of the pump flow path, the dynamic pressure of the vortex in the pump flow path cannot be utilized 1 A 4 in discharging the bubbles out of the pump casing assembly; that isr the bubbles must be discharged only by the static pressure in the pump flow path. Accordingly, under the condition that the fuel is vaporized very much, sometimes the bubbles formed by vaporization of the fuel not discharged from the pump casing assembly; that is. it is difficult to prevent the occurrence of vapor locking.

SUMMARY OF THE INVENTION

Accordingly, an object of the invention is to eliminate the above-described difficulties accompanying a conventional circumferential flow type liquid pump.

More specifically, an object of the invention is to provide a circumferential flow type liquid pump in which bubbles formed by vaporization of the fuel in the pump flow path are positively discharged from the pump casing assembly, whereby no vapor locking is caused.

The foregoing object and other objects of the invention have been achieved by the provision of a circumferential flow type liquid pump comprising an impeller with vanes on its outer periphery, and a pump casing assembly defining an arcuate elongated pump flow path along the outer periphery of the impeller and a suction inlet and a discharge outlet at both ends of the pump flow path, in which, according to the invention, the pump casing assembly includes: a gas venting path which is opened in the inner periphery of the pump flow 1 6 path near the impeller with a step extended from the bottom of the pump f low path and is extended radially inwardly, and a through-hole much larger in sectional area than the gas venting path, through which the gas venting path is communicated with the outside of the pump casing assembly.

In the circumferential flow type liquid pump according to the invention, the bubbles formed in the liquid in the pump flow path by vaporization to flow along the inner periphery of the pump flow path near the impeller are discharged as follows:

The bubbles are caused to flow into the gas venting path which is opened in the inner periphery of the pump flow path near the impeller with the step extended f rom the bottom of the pump flow path and is extended radially or in the direction of the vortex formed in the pump f low path by the impeller, by the is static pressure induced in the pump flow path by pumping and the dynamic pressure induced by the vortex in the pump flow path while being substantially separated from the liquid present near the bottom of the pump flow path. The bubbles are then discharged out of the pump casing assembly through the through-hole much larger in sectional area than the gas venting path while being substantially free from flow resistance. Thus, the bubbles formed in the pump flow path are removed out of the pump casing assembly with high efficiency; that is, the difficulty that bubbles stay in the pump casing assembly is eliminated according to the invention.

4 1 The nature, principle and utility of the invention will becomes more apparent from the-following detailed description when read in conjunction with the accompanying drawings, in which like parts are designated by like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

Fig. 1 is a vertical sectional view showing one example of a circumferential flow type liquid pump according to this invention; Fig. 2 is a sectional view taken along line II-II in Fig. 1; Fig. 3 is an enlargel sectional view taken along line III-III in Fig. 2; Fig. 4 is a vertical sectional view showing a conventional circumferential flow type liquid pump; and Fig. 5 is a sectional view taken along line IV-IV in Fig. 4.

DETAILED DESCRIPTION OF THE INVENTION

One example of a circumferential flow type liquid pump according to this invention will be described with reference to Figs. 1 through 3.

In these -figures, reference numeral 1 designates a pump casing assembly which comprises a pump casing body 2 and a cover 3. The pump casing assembly 1 accommodates an impeller 1 1 4 with vanes 5 on its periphery. The impeller 4 is mounted on a central shaf t 6 so that it is rotated around the central axis with respect to the pump casing assembly 1.

In the pump casing assembly 1, an arcuate elongated pump flow path 7 with a suction inlet 8 and a discharge outlet 9 at both ends is defined in such a manner that it is extended along the outer periphery of the impeller 4 and receives the vanes 4 of the impeller 5.

The pump casing assembly 1, or more specifically the cover 3, as shown in Fig. 3, has a gas venting path 11 and a through- hole 12 which is much larger in sectional area than the gas venting path 11. The gas venting path 11 is opened in the inner periphery of the pump flow path 7 near the impeller with a step extended from the bottom 10 of the pump flow path 7. Through the through-hole 12 the gas venting path 11 is communicated with the outside of the pump casing assembly 1.

The sectional areas of the gas venting path 11 and the through-hole 12 depend on the capacity of the pump. In the case of the ordinary vehicle, the gas venting path 11 is rectangular in section, for instance, 4 mm in width and 0.2 mm in height, and the through-hole 12 is a circular hole, for instance, 2.5 mm in diameter.

The central shaf t 6 of the impeller 4 is the rotary shaft of the rotor 16 of an electric motor 15 coupled to the circumferential flow type liquid pump. The shaft of the rotor Z% i 1 16 is rotatably supported at both ends through bearings 17 and 18 by the pump casing assembly__ and a bracket 24.

The pump casing assembly 1 is coupled to an end cover 19 through the yoke 20 of. the motor 15. The yoke 20 accommodates the rotor 16, and forms a liquid chamber 21 between the pump casing assembly 1 and the end cover 19 to store a liquid such as liquid fuel discharged through the discharge outlet 9. Permanent magnets 25 serving as stator are mounted on the inner wall of the yoke. The liquid chamber 21 is communicated with a liquid outlet 23 with a check valve 22 which is provided in the end cover 19. The bracket 24 supports brushes 27 which are held in slide contact with the commutator 26 of the rotor 16.

In the circumferential flow type liquid pump thus is constructedi as the impeller 4 is rotated clockwise, in Fig. 2, by the motor 15, a liquid such as liquid fuel is sucked into the pump flow path 7 through the suction inlet 8. The liquid thus sucked flows clockwise, in Fig. 2, and flows through the discharge outlet 9 -into the liquid chamber 21. During this pumping operation. the vanes 5 of the impeller 4 contacts the liquid in the pump flow path 7 to vaporize it. thus forming bubbles in it. The bubbles thus formed are different from the liquid both in centrifugal force and in specific gravity. Hence, they are allowed to flow together with the liquid while being collected along the inner periphery of the pump flow path 7 near the impeller; that is, they flow in the same direction as the impeller 4. When the bubbles come to the gas venting path 11 which. as was described -before, is opened in the inner periphery of the pump flow path 7 near the impeller with the step extended from the bottom 10 of the pump f low path 7 and is extended in the same direction as the vortex 13 formed in the pump flow path 7 by the impeller, the static pressure induced in the pump flow path 7 by pumping and the dynamic pressure of the vortex 13 formed in the pump flow path 7 by the impeller act on the bubbles collected near the impeller, so that the bubbles are caused to.flow into the gas venting path 11 while being substantially separated from the liquid present near the bottom 10 of the pump flow path. The bubbles thus moved into the gas venting path 11 is discharged out of the pump casing assembly 1 through the through-hole 12 much larger in section than the gas venting path, being substantially free from flow resistance.

As was described above, in the circumferential flow type liquid pump, its pump casing assembly includes the gas venting path 11 which is opened in the inner periphery of the pump f low path 7 near the impeller 4 with the step extended from the bottom of the pump flow path and is extended radially inwardly, and the through-hole 12 much larger in sectional area than the gas venting path 11. communicating the gas venting path 11 with the outside of the pump casing assembly 1. Hence, the bubbles formed by vaporizing the liquid in the pump flow path 7 are discharged out of the pump casing assembly 1 m 11 forcibly through the gas venting path 11 and the through-hole 12 by the static pressure and dynamic pressure induced in the pump flow path 7 while being substantially separated from the liquid. Therefore, the bubbles formed In the liquid in the pump flow path are discharged positively with high efficiency; that is, the difficulty is eliminated that bubbles are stayed in the pump flow path whereby the pumping capacity is lowered as much.

While there has been described in connection with the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is aimed, therefore, to cover in the appended claims all such changes and modifications as fall within the true spirit and scope of the invention.

4 11 - t )21- 1 2 3 4 5 6 7 a 9 10 11 12 13 2 3 4

Claims

1. A circumferential flow type liquid pump comprising an impeller with vanes on the outer periphery thereof, and a pump casing assembly defining an arcuate elongated pump Elow path along the outer periphery of said impeller and a suction inlet and a discharge outlet at both ends of said pump f low path, in which said pump casing assembly includes:

a gas venting path which is opened in the inner periphery of said pump flow path near said impeller with a step extended from the bottom of said pump flow path and is extended radially inwardly; and a through-hole much larger in sectional area than said gas venting path.. through which said gas venting path is communicated with the outside of said pump casing assembly.

2. A circumferential flow type liquid pump according to claim 1, in which said gas venting path 11 is extended in_ the same direction as the vortex formed in said pump flow path by the impeller

3. A circumferential flow type liquid pump substantiall.y -,z herein described with reference to Figures 1 to 3 of the accompany'---z drawings.

Published 1991 at The Patent Office. State House. 66171 High Holborn. London WC1R47P. Further copies my be obtained from sales Branch, Unit 6. Nine Mile Point. Cwrnfelinfach. Cross Keys. Newport NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray. Kent.