The preferred features of the present invention will be described below.
A first embodiment of the fuel pump of the present invention will be described below with reference to
In a fuel pump 1 such as shown in
The impeller 10 is substantially disk shaped and comprises a central opening 10a in the center thereof for receiving a motor shaft 2a so that the motor shaft 2a cannot rotate relative to the impeller 10. When the motor shaft 2a rotates, the impeller 10 also rotates in the casing 60. In the vicinity of outer circumference of an impeller upper surface 17, boost ports 12 (concavities) are formed repeatedly along the outer circumference. In the vicinity of outer circumference of an impeller lower surface 19, boost ports 14 are formed repeatedly along the outer circumference.
In a surface 37 (referred to hereinbelow as “first surface 37”) of the lower casing 30 that faces the impeller lower surface 19, a first boost groove 34 is formed facing a plurality of boost ports 14 formed in the lower surface 19 of the impeller 10. In a surface 27 (referred to hereinbelow as “second surface 27”) of the upper casing 20 that faces the impeller upper surface 17, a second boost groove 22 is formed facing a plurality of boost ports 12 formed in the upper surface 17 of the impeller 10. In a plan view of the first and second surfaces 27, 37, the first boost groove 34 and the second boost groove 22 are formed to have an almost C-like shape from an upstream end to a downstream end along the rotational direction of the impeller 10. A first boost path 44 is formed by a plurality of boost ports 14 provided in the lower surface 19 of the impeller 10 and the first boost groove 34 formed in the lower casing 30. A second boost path 42 is formed by a plurality of boost ports 12 provided in the upper surface 17 of the impeller 10 and the second boost groove 22 formed in the upper casing 20. A fuel intake hole 32 connected to the first boost groove 34 is formed at the upstream end of the first boost groove 34. A fuel discharge hole 24 connected to the second boost groove 22 is formed at the downstream end of the second boost groove 22.
When the motor is driven, the impeller 10 rotates between the upper casing 20 and the lower casing 30, the fuel is sucked in from the fuel intake hole 32 into the pump unit 3 and introduced into the first boost path 44 and the second boost path 42. The fuel whose pressure increases while it flows in the first boost path 44 and the second boost path 42 is pumped out from the fuel discharge hole 24 into the motor unit. The fuel that is pumped out into the motor unit passes through the motor unit and is pumped out to the outside from a port (not shown in the figure) formed in the upper part of the fuel pump 1.
A plurality of depressions 18 for reducing the frictional force acting upon the impeller 10 when it rotates is formed in the lower surface 19 of the impeller 10. The plurality of depressions 18 is formed on the inside of the plurality of boost ports 14. A plurality of depressions 16 for reducing the frictional force acting upon the impeller 10 when it rotates is formed in the upper surface 17 of the impeller 10. The plurality of depressions 16 is formed on the inside of the plurality of boost ports 12. The shape of depressions 16, 18 is described below.
In a region between the upper surface 17 of the impeller 10 and the upper casing 20 wherein the second boost path 42 is not formed, and in a region between the lower surface 19 of the impeller 10 and the lower casing 30 wherein the first boost path 44 is not formed, the fuel is carried along by the impeller 10 rotating at a high rate, due to its own viscosity, at a certain rate (according to the level of viscosity thereof) in the impeller rotational direction. However, the rotation rate of the impeller 10 is obviously higher than the rotation rate of the fuel being pulled by the impeller 10. Therefore, part of the fuel rotating with the rotation rate lower than that of the impeller 10 is introduced, as shown in
In the depressions 16, 18, a region from the deepest portion P to the rear edge B1 in the impeller rotational direction is a region where the aforementioned pressure is generated. In the depressions 16, 18 of the fuel pump 1 of the present embodiment, the figure of this region is required to initiate a flow of fuel from the deepest portion P toward the casing, so this region is not required to be formed with any particular high degree of dimensional accuracy and an allowable margin of error becomes large. Accordingly, the cost of forming the depressions 16, 18 can be reduced. As a result, the production cost of the fuel pump 1 can be reduced.
In the depressions 16, 18, the width of the front edge F1 in the impeller rotational direction widens, thereby facilitating the introduction of fuel into the depressions 16, 18. Further, the width of the rear edge B1 narrows and the cross-sectional area thereof decreases from the deepest portion P toward the rear edge B1. Therefore, the fuel introduced into the depressions 16, 18 is pushed into the narrowing channel and flows under a comparatively strong force from the deepest portion P toward the casings. As a result, a comparatively large pressure can be generated in the direction of separating the impeller 10 from the casings.
Further, the depressions 16, 18 are formed on the inner circumferential side of the boost ports 12, 14 that are formed close to the outer periphery. The region on the inside of the boost ports 12, 14 is wider than the region on the outside. Therefore, the depressions 16, 18 can be easily formed.
Further, pluralities of depressions 16, 18 are formed equidistantly in the circumferential direction in the impeller 10. The pressures generated by each of the depressions 16 are added up to obtain a resultant pressure corresponding to the number of depressions 16 (eight in the present embodiment). The pressures generated by the depressions 18 are added up to obtain a resultant pressure corresponding to the number of depressions 18 (eight in the present embodiment). Therefore, a comparatively large pressure is generated in the direction of separating the impeller 10 from the upper casing 20 and the lower casing 30.
In the present embodiment, a case is explained in which depressions 16 are formed in the upper surface 17 of the impeller 10, and depressions 18 are also formed in the lower surface 19 of the impeller 10, but it is also possible to form only the depressions 18 in the lower surface 19. Generally, part of the fuel under high pressure that is pumped out to the motor unit of the fuel pump is refluxed into the space between the upper casing 20 and the lower casing 30 via the clearance around the motor shaft. This high-pressure fluid acts upon the upper surface 17 of the impeller 10 and pushes the impeller 10 down. As a result, the impeller 10 can be easily caused to rotate in a state of being pressed against the lower casing 30. To prevent such a state, it is sometimes sufficient to form the depressions 18 only in the lower surface 19 of the impeller 10. In this case, the number of depressions can be decreased and cost of the depression formation process can be reduced.
The depressions 16, 18 may also not be disposed along the circumferential direction of the impeller 10 (that is, in the direction along the boost ports 12, 14).
Further, in the embodiment described hereinabove, the depressions 16, 18 have a trapezoidal shape in a planar view thereof, but the shapes of the depressions 16, 18 are not limited, and the depressions may have any shape. The depressions 16, 18 may be of a shape in which the width of the rear edge B1 in the impeller rotational direction is less than the width of the front edge F1. For example, the edge on the rear side in the impeller rotational direction may have an arched shape, and the edge on the front side may have a linear shape.
The second embodiment of the fuel pump of the present invention will be described below. The components that differ from those of the fuel pump 1 of the first embodiment will be mainly explained.
As shown in
Further, part of the fuel located between the lower surface 19a of the impeller 10a and the lower casing 30 is introduced into the depression 18a of the impeller lower surface 19a. The fuel introduced into the depression 18a flows along the bottom wall surface of the depression 18a in the direction opposite to the impeller rotational direction (counter-flows).
Further, when a gap between the upper surface 17a of the impeller 10a and the upper casing 20 is wider than a gap between the lower surface 19a of the impeller 10a and the lower casing 30, part of the fuel located between the upper surface 17a of the impeller 10a and the upper casing 20 is introduced into the depression 18a through the connection hole 11 (solid line arrow shown in
When the gap between the lower surface 19a of the impeller 10a and the lower casing 30 is wider than the gap between the upper surface 17a of the impeller 10a and the upper casing 20, part of the fuel located between the lower surface 19a of the impeller 10a and the lower casing 30 is introduced into the depression 16a through the connection hole 11 (dotted line arrow shown in
In the depressions 16a, 18a, the deepest portion P is formed in the rear half thereof with respect to the impeller rotational direction. Therefore, the fuel introduced into the depression 16a flows from the deepest portion P of the depression 16a toward a second surface 27 of the upper casing 20. As a result, pressure is generated in the direction of separating the impeller 10a from the upper casing 20. Further, the fuel introduced into the depression 18a flows from the deepest portion P of the depression 18a toward a first surface 37 of the lower casing 30. As a result, pressure is generated in the direction of separating the impeller 10a from the lower casing 30. The height of the impeller 10a is adjusted to the height where the two pressures are balanced, and the impeller 10a is rotated in a state of being separated from the upper casing 20 and the lower casing 30. As a result, the impeller 10a is prevented from rotating in a state of being pressed against the upper casing 20 or the lower casing 30, and frictional force acting upon the impeller 10a when the impeller rotates is reduced.
In the present embodiment, for example, where depressions 18a are formed in the impeller lower surface 19a, the fuel on the side of the upper surface 17a of the impeller 10a is also introduced into the depressions 18a via the connection holes 11. Therefore, the amount of fuel introduced into the depressions 18a is increased and a comparatively large pressure can be generated in the direction of separating the impeller 10a from the lower casing 30.
In the present embodiment, a case is explained in which depressions 16a are formed in the upper surface 17a of the impeller 10a, and depressions 18a are also formed in the lower surface 19a of the impeller 10a, but it is also possible to form only the depressions 18a in the lower surface 19a.
The third embodiment of the fuel pump of the present invention will be described below. The components that differ from those of the fuel pump 1 of the first embodiment will be mainly explained. The fuel pump of the third embodiment has through holes of an almost wedge-like cross section that pass through the upper and lower surfaces of the impeller on the inside of the group of boost ports formed in the impeller.
In the fuel pump, part of the fuel located between the upper surface 17b of the impeller 10b and the upper casing 20 is introduced from the larger opening S1 formed in the upper surface 17b of the impeller 10b into the through hole 13. The fuel introduced into the through hole 13 flows, while being pushed into a narrowing channel toward the smaller opening S2 in the lower surface 19b of the impeller 10b. The pushed fuel is further pushed, and flows toward the first surface 37 of the lower casing 30 via the smaller opening S2. Therefore, a pressure is generated in the direction of separating the lower surface 19b of the impeller 10b from the lower casing 30. As a result, the impeller 10b is prevented from rotating in a state of being pressed against the lower casing 30.
In the present embodiment, a case is explained in which the inner wall surface 13b on the rear side is perpendicular to the impeller upper surface 17b and lower surface 19b, but the present invention is not limited to this configuration. For example, the inner wall surface 13b on the rear side may be inclined forward from the lower surface 19b of the impeller 10b toward the upper surface 17b of the impeller 10b along the impeller rotational direction. At this case, an inclination angle of the inner wall surface 13a on the front side with respect to the lower surface 19b of the impeller 10b should be smaller than an inclination angle of the inner wall surface 13b on the rear side with respect to the lower surface 19b of the impeller 10b so that an opening of the through hole 13 formed in the upper surface 17b is larger than an opening formed in the lower surface 19b. A pressure is generated in the direction of separating the lower surface 19b of the impeller 10b from the lower casing 30.
Further, as in an impeller 10c shown in
In such the fuel pump 1c, part of the fuel located between the upper surface 17c of the impeller 10c and the upper casing 20 is introduced into the combined hole 15 from an opening S3 formed in the upper surface 17c of the impeller 10c. The fuel introduced into the combined hole 15 flows toward an opening S4 in the lower surface 19c of the impeller 10c (toward the lower casing 30), while being pushed into the channel that is narrowed in the intermediate portion thereof. Part of the fuel located between the lower surface 19c of the impeller 10c and the lower casing 30 is introduced into a depression 18c formed in the lower surface 19c of the impeller 10c. This fuel flows inside the depression 18c along the bottom wall surface of the depression 18c in the direction opposite to the impeller rotational direction (counter-flows). The fuel introduced into the depression 18c does not flow via the through hole 13c from the apex point Q of the convex portion W (portion where the combined hole 15 is the narrowest) toward the upper surface 17c of the impeller 10c. This is because the flow from the upper surface 17c of the impeller 10c toward the opening S4 on the lower surface 19c of the impeller 10c is stronger than the flow from the lower surface 19c of the impeller 10c toward the opening S3 on the upper surface 17c. The flow of fuel in the combined hole 15 from the opening S3 toward the opening S4 and the flow of fuel in the depression 18c merge, and pressure is generated at the opening S4 in the direction of separating the impeller 10c from the lower casing 30. This pressure prevents the impeller 10c from rotating in a state of being pressed against the lower casing 30, and when the impeller 10c rotates, frictional force acting thereupon is reduced.
In the present embodiment of the fuel pump 1c, the apex point Q of the convex portion W is disposed below a central line M (shown by a dot-dash line in
In the present embodiment of the fuel pump 1c, the inner wall surface 15a on the front side that is positioned on the lower surface 19c side of the convex portion W is inclined gentler than the inner wall surface 15a that is positioned on the upper surface 17c side of the convex portion W. However, as in an impeller 10c shown in
Further, in the present embodiment, an example is explained in which the inner wall surface 15b on the rear side is inclined forward from the lower surface 19c of the impeller 10c toward the upper surface 17c of the impeller 10c along the impeller rotational direction, but as in an impeller 10c shown in
The fourth embodiment of the fuel pump of the present invention will be described below. The components that differ from those of the fuel pump 1 of the first embodiment will be mainly explained. In the fuel pump of the fourth embodiment, a plurality of depressions is provided in the inner surface of the casing that faces the impeller.
In the impeller 10d that is different from the impeller 10 of the first embodiment, depressions for reducing frictional force acting upon the impeller when the impeller rotates are not provided. Other features of the impeller 10d are identical to those of the impeller 10 and explanation thereof is herein omitted.
As shown in
When the impeller 10d rotates between the upper casing 20d and the lower casing 30d, the fuel is sucked in from the fuel intake hole 32 into the pump unit and introduced into the first boost path 44d and the second boost path 42d. The fuel whose pressure increases while it flows in the first boost path 44d and the second boost path 42d is pumped out from the fuel discharge hole 24 into the motor unit. The fuel that is pumped out into the motor unit passes through the motor unit and is pumped out to the outside from a port (not shown in the figure) formed in the upper part of the fuel pump 1d.
When the impeller 10d rotates, in a region between the upper surface 17d of the impeller 10d and the upper casing 20d where the second boost path 42d is not formed, and in a region between the lower surface 19d of the impeller 10d and the lower casing 30d where the first boost path 44d is not formed, the fuel is carried along by the impeller 10d rotating at a high rate and the fuel itself rotates, due to its viscosity, with a certain rate in the impeller rotational direction. Because the upper casing 20d and the lower casing 30d are fixed, part of the fuel located between the upper surface 17d of the impeller 10d and the upper casing 20d is introduced into the depression 26 formed in the inner surface 27d of the upper casing 20d, as shown in
Further, part of the fuel located between the lower surface 19d of the impeller 10d and the lower casing 30d is introduced into the depression 36 formed in the inner surface 37d of the lower casing 30d, as shown in
The height of the impeller 10d is adjusted to the height where the two pressures are balanced, and the impeller 10d is rotated in a state of being separated from the upper casing 20d and the lower casing 30d. As a result, the impeller 10d is prevented from rotating in a state of being pressed against the upper casing 20d or the lower casing 30d, and frictional force acting upon the impeller 10d when the impeller rotates is reduced.
In the depressions 26, 36, a region from the deepest portion P toward the front edge F2 in the impeller rotational direction is a region where the aforementioned pressure is generated. In the depressions 26, 36 of the fuel pump 1d of the present embodiment, the figure of this region is requested to initiate only a flow of fuel from the deepest portion P toward the surfaces of the impeller 10d, so that this region is not required to be formed with any especially high dimensional accuracy and an allowable margin of error becomes large. Accordingly, a cost of forming the depressions 26, 28 can be reduced. As a result, the production cost of the fuel pump 1d can be reduced.
In the depressions 26, 36, the width of the rear edge B2 in the impeller rotational direction widens, thereby facilitating the introduction of fuel into the depressions 26, 36. Further, the width of the front edge F2 narrows and the cross-sectional area thereof decreases from the deepest portion P toward the front edge F2. Therefore, the fuel introduced into the depressions 26, 36 is pushed into the narrowing channel and flows under a comparatively strong force from the deepest portion P toward the impeller 10d. As a result, a comparatively large pressure can be generated in the direction of separating the impeller 10d from the casings.
Further, the depressions 26, 36 are formed on the inside of boost grooves 22d, 34d, these grooves being formed to have an almost C-like shape close to outer periphery. The region on the inside of the boost grooves 22d, 34d is wider than the region on the outside of the boost grooves 22d, 34d. Therefore, the depressions 26, 36 can be easily formed.
Further, pluralities of depressions 26, 36 are formed equidistantly in the circumferential direction in each casing. The pressures generated by the depressions 26 are added up to obtain a resultant pressure corresponding to the number of depressions 26 (eight in the present embodiment). The pressures generated by the depressions 36 are added up to obtain a resultant pressure corresponding to the number of depressions 36 (eight in the present embodiment). Therefore, a comparatively large pressure is generated in the direction of separating the impeller 10d from the upper casing 20d and the lower casing 30d.
In the present embodiment, a case is explained in which the depressions 26 are formed in the second surface 27d of the upper casing 20d, and the depressions 36 are formed in the first surface 37d of the lower casing 30d, but it is also possible to form only the depressions 36 in the first surface 37d of the lower casing 30d.
Further, in the embodiment described hereinabove, the depressions 26, 36 have a trapezoidal shape in a planar view thereof, but this shape of depressions 26, 36 is not limited, and the depressions may have any shape, provided that the width of the front edge F2 in the impeller rotational direction is less than the width of the rear edge B2. For example, the front edge F2 in the impeller rotational direction in a planar view thereof may have an arched shape, and the rear edge B2 may be formed to have a linear shape.
Further, in the above-described embodiments, fuel pumps were explained in which depressions were formed either in the impeller or in the casings, but the depressions may also be formed both in the impeller and in the casings.
Specific examples of the present invention are described above in detail, but these examples are merely illustrative and place no limitation on the scope of the patent claims. The technology described in the patent claims also encompasses various changes and modifications to the specific examples described above.
Furthermore, the technical elements explained in the present specification and drawings provide technical value and utility either independently or through various combinations. The present invention is not limited to the combinations described at the time the claims are filed. In addition, the purpose of the examples illustrated by the present specification and drawings is to satisfy multiple objectives simultaneously, and satisfying any one of those objectives gives technical value and utility to the present invention.
Number | Date | Country | Kind |
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2006-274735 | Oct 2006 | JP | national |