This application claims priority to Japanese Patent Application No. 2006-251619 filed on Sep. 15, 2006, the contents of which are hereby incorporated by reference into the present application.
1. Field of the Invention
The present invention relates to a fuel pump that draws in a fuel, increases the pressure thereof, and discharges the pressurized fuel.
2. Description of the Related Art
A known fuel pump generally comprises a casing and an impeller rotatably disposed within the casing. A first group of concavities is formed in a lower surface of the impeller. A second group of concavities is formed in an upper surface. The concavities are repeated in a circumferential direction. A first groove is formed in a first inner surface of the casing in an area that faces the first group of concavities of the impeller. A second groove is formed in a second inner surface of the casing in an area that faces the second group of concavities of the impeller. The first and second grooves extend in a circumference direction from an upstream end to a downstream end, respectively. A pump channel is formed inside the casing by the groups of concavities of the impeller and the grooves of the casing. An intake hole and a discharge hole are formed in the casing. The intake hole links the upstream end of the pump channel and the exterior of the casing. The discharge hole links the downstream end of the pump channel and the exterior of the casing. When the impeller rotates, the fuel is drawn from the intake hole into the pump channel. The fuel drawn into the pump channel flows from the upstream end to the downstream end of the pump channel, while the pressure thereof is increased. The pressurized fuel is discharged to the outside of the casing via the discharge hole.
In this known fuel pump, a clearance is provided between the casing and the impeller. Where the clearance is large, the fuel in the pump channel easily leaks from the pump channel to the clearance and high pump efficiency cannot be obtained. Therefore, in order to obtain high pump efficiency, it is necessary to decrease the clearance and reduce fuel leakage from the pump channel. However, if the clearance is too small, the casing and the impeller come into surface contact and sliding resistance increases, thereby decreasing pump efficiency. Thus, because of this trade-off relationship between the reduction in sliding resistance and reduction in fuel leakage, a technology is required that can realize the two at the same time.
Japanese Laid-open Patent Application Publication No. 6-213195 discloses a fuel pump in order to solve this problem. In this fuel pump, a plurality of concave portions is formed in the entire inner surface of the casing. The concave portions are formed as dots or grooves, and the concave portions are separated from each other. By forming a plurality of concave portions in the inner surface of the casing, the surface tension of the fuel increases and the adhesion force of the fuel inside the clearance between the casing and the impeller increases. As a result, sealing capacity can be improved without unnecessarily reducing the clearance between the casing and the impeller. Thus, with this fuel pump, both the reduction of fuel leakage and the reduction of sliding resistance can be realized.
In the above-described fuel pump, because a plurality of concave portions is formed in the inner surface of the casing, it is necessary to perform complex cutting of the casing. Moreover, because a high degree of precision is required for this cutting operation, manufacturing cost increases. Moreover, where the concave portions are formed by mechanical processing such as cutting, there is a variation in the shape of concave portions. As a result, there is a variation in pump efficiency. For these reasons, with the above-described technology, it is difficult to realize both the reduction in fuel leakage and the reduction in sliding resistance at a low manufacturing cost and with good stability.
It is one object of the present teachings to provide a fuel pump that can be manufactured at a low cost and in which both the reduction of fuel leakage and the reduction in sliding resistance can be realized with good stability.
In one aspect of the present teachings, a fuel pump is provided with a casing and a substantially disc-shaped impeller rotatably disposed within the casing. A first group of concavities is formed in a lower surface of the impeller. The concavities forming the first group are arranged in concentric circles with respect to the rotational axis of the impeller. A second group of concavities is formed in an upper surface of the impeller. The concavities forming the second group are arranged in concentric circles with respect to the rotational axis of the impeller. A first groove is formed in a first inner surface of the casing. The first groove extends from an upstream end to a downstream end in an area that faces the first group of concavities. A second groove is formed in a second inner surface of the casing. The second groove extends from an upstream end to a downstream end in an area that faces the second group of concavities. An intake hole is formed in the casing. The intake hole passes from the exterior of the casing to the upstream end of the first groove. A discharge hole is formed in the casing. The discharge hole passes from the exterior of the casing to the downstream end of the second groove. At least one seal portion is disposed on at least one of the first inner surface, the second inner surface, the lower surface and the upper surface. The seal portion comprises one layer or a plurality of layers of thin film.
In this fuel pump, the seal portion that seals leakage of the fuel comprises one layer or a plurality of thin films. The formation of a thin film is easier and processing accuracy is higher than in the case of shaping by mechanical processing such as cutting. Thus, even if a seal portion has a complex shape, the seal portion can be manufactured at a low cost by using a thin film. Furthermore, a seal portion using a thin film has high accuracy. As a result, both the reduction in fuel leakage and the reduction in sliding resistance can be realized at a low manufacturing cost and with good stability.
Other objects, features and advantages of the present teachings will be readily understood after reading the following detailed description together with the accompanying drawings and claims. The additional features and aspects disclosed herein may be utilized singularly or, in combination with the above-described aspect and features.
Preferred embodiments of the present teaching will be described below.
(Feature 1)
A seal layer is formed from one thin film.
(Feature 2)
A seal layer is formed from two or more laminated thin films, and the cross section of the seal layer in the laminated portion has a step-like shape.
A first embodiment of the present teachings will be explained below. A fuel pump of the present embodiment is a fuel pump for an automobile. The fuel pump is disposed within a fuel tank and serves to supply fuel to the automobile engine. As shown in
The pump unit 14 is accommodated in the lower portion of the housing 16. The pump unit 14 comprises a substantially disk-shaped impeller 36. A group of concavities 36a is provided in the upper surface of the impeller 36. The concavities 36a are arranged side by side at the outer peripheral edge of the impeller 36. A group of concavities 36b are provided in the lower surface of the impeller 36. The concavities 36b is arranged side by side at the outer peripheral edge of the impeller 36. A through hole is provided in the center of the impeller 36. The shaft 20 fits into the through hole of the impeller 36. Therefore, when the shaft 20 rotates, the impeller 36 also rotates.
The casing 37 that accommodates the impeller 36 is composed of a pump cover 38 and a pump body 40. In the pump cover 38, a groove 38a, having a width almost twice as large as the width of the group of concavities 36a in the radial direction, is formed in the area that faces the outer peripheral edge of the impeller 36. As shown in
As shown in
When the impeller 36 rotates inside the casing 37, fuel is drawn into the pump channel 44 via the intake hole 42. While the fuel flows in the pump channel 44, the fuel pressure is increased. The pressurized fuel is discharged out from the discharge hole 50 toward the motor unit 12. The discharged fuel passes through the motor unit 12 and is discharged out from a discharge port 48 formed in the top cover 32.
As shown in
As shown in
In the fuel pump of the present embodiment, seal layers 52, 54 are formed on the inner surfaces of the casing 37. The seal layers 52, 54 are formed directly inside the grooves 38a, 40a. As a result, the leakage of the fuel from the pump channel 44 into the clearances between the casing 37 and impeller 36 can be reduced. Furthermore, by forming the seal layers 52, 54, it is possible to ensure large clearances C1, C3 in the areas where the seal layers 52, 54 have not been formed. Therefore, sliding resistance can be also reduced, while reducing the leakage. The seal layers 52, 54 are formed by well-known thin film forming technology. Such method makes it possible to attain processing accuracy higher than that attained with shaping methods based on mechanical processing such as cutting. Therefore, the occurrence of variation in product performance can be inhibited. In addition, because the processing operations in thin film formation are simpler than those of cutting, the manufacturing cost can be reduced.
A second embodiment of the present teachings will be explained below. The fuel pump of the second embodiment is a partial modification of the fuel pump of the first embodiment. Accordingly, only the difference between the fuel pump of this embodiment and that of the first embodiment will be explained to avoid redundant explanation. Furthermore, components that are common for the fuel pump of the second embodiment and the fuel pump of the first embodiment will be denoted by similar reference symbols. The same is true for the below-described third to eleventh embodiments.
As shown in
As shown in
In the fuel pump of the second embodiment, the seal layers 62, 64 are formed on the surfaces of casing 67. As a result, the fuel leakage from the pump channel 74 can be reduced. The cross section of the seal layers 62 and 64 has a step-like shape. The upper layers 62b, 64b on the side of the impeller 36 serve as seal portions. The width of the upper layers 62b, 64b is less than the width of the lower layers 62a, 64a on the side of the casing 67. Therefore, a large clearance can be ensured in the area outside the upper layers 62b, 64b. Therefore, sliding resistance can be effectively reduced, while reducing the fuel leakage. The seal layers 62, 64 are also formed by well-known thin film forming technology. Therefore, the seal layers 62, 64 can be shaped with good accuracy and at a low manufacturing cost despite a complex step-like shape.
A third embodiment of the present teachings will be explained below. As shown in
As shown in
Since the pressure of the fuel at the discharge hole 50 is highest and the pressure of the fuel at the intake hole 42 is lowest, the fuel leakages between the discharge hole 50 and the intake hole 42 is larger than the fuel leakage in other areas. In the fuel pump of the third embodiment, the seal layers 82, 84 are formed in the surfaces of the casing 87. Further, the seal layers 82, 84 reach the areas between the discharge hole 50 and the intake hole 42. As a result, sealing ability between the discharge hole 50 and the intake hole 42 is improved and the fuel leakage can be reduced even more effectively. Furthermore, the width of the upper layers 82b, 84b is less than the width of the lower layers 82a, 84a. Therefore, a large clearance can be ensured in the area outside the upper layers 82b, 84b. Therefore, sliding resistance can be effectively reduced.
A fourth embodiment of the present teachings will be explained below. As shown in
The casing 107 is composed of a pump cover 108 and an pump body 110. In the pump cover 108, a groove 108a is formed in an area that faces the group of concavities 106a. As shown in
When the impeller 106 rotates, fuel is drawn into the pump channels 114 and 116. While the drawn fuel flows in the pump channels 114, 116, the fuel pressure is increased. The pressurized fuel is discharged out from the discharge hole 50 toward the motor unit 12.
As shown in
As shown in
In the fuel pump of the fourth embodiment, the seal layers 102, 104 are formed between the upstream ends and downstream ends of the grooves 108a, 110a. As a result, sealing ability in the discharge hole 50 and intake hole 42 can be improved and the fuel leakage can be effectively reduced.
A fifth embodiment of the present teachings will be explained below. As shown in
As shown in
In the fuel pump of the fifth embodiment, the seal layers 122, 124 are formed around the respective grooves 128a and 130a. As a result, the fuel leakage from the pump channels 134, 136 can be reduced. In particular, because the seal layers 122, 124 are also formed on the outside of the grooves 128a, 130a, the fluid can be prevented from leaking to the clearance between the outer peripheral edges of the impeller 106 and the pump cover 128.
A sixth embodiment of the present teachings will be explained below. As shown in
As shown in
In the fuel pump of the sixth embodiment, the seal layers 142, 144 are formed around the respective grooves 148a, 150a and in the area between the upstream end and downstream end of grooves 148a, 150a. As a result, the fuel leakage from pump channels 154, 156 can be reduced. Furthermore, the seal layers 142, 144 are formed of three thin films (142a, 142b, 142c), (144a, 144b, 144c), respectively. These thin films (142a, 142b, 142c), (144a, 144b, 144c) have a simple shape and may be disposed in respective adequate locations. Therefore, the seal layer of a complex shape can be easily formed with good accuracy and at a low cost. If necessary, the locations in which the thin films are disposed and the number of laminated thin films can be changed. Therefore, the degree of freedom in designing the clearance between the casing 147 and the impeller 106 can be increased.
A seventh embodiment of the present teachings will be explained below. As shown in
As shown in
In the fuel pump of the seventh embodiment, the seal layers 162, 164 are formed around the respective grooves 168a, 170a and in the area between the upstream end and downstream end of grooves 168a, 170a. As a result, the fuel leakage from pump channels 174, 176 can be reduced. Further, the seal layers 162, 164 are formed of two thin films (162a, 162b), (164a, 164b), respectively. In the thin films 162b, 164b that are laminated as top film, notches are formed in the vicinity of the discharge hole 50 or intake hole 42. When viewed as a longitudinal cross-section along the radial direction of the impeller, cross-sectional area of the clearances between the thin films 162b, 164b and the casing 167 changes gradually in the vicinity of the discharge hole 50 or intake hole 42. As a result, periodic pressure fluctuations caused by rotation of the impeller 106 can be relaxed and noise generation can be reduced.
An eighth embodiment of the present teachings will be explained below. As shown in
In the fuel pump of the eighth embodiment, a group of spiral notches 182a is formed in the seal layer 182 of the pump cover 188, and a similar group of notches is formed in the seal layer of the pump body. As a result, respective groups of spiral grooves (these grooves will be hereinafter referred to as spiral grooves) are formed in the surface of the pump cover 188 that faces the impeller 106 and in the surface of the pump body that faces the impeller 106. The end portion on the center side of the spiral groove is shifted with respect to the end portion on the outer periphery side in the rotation direction of the impeller 106. As a result, when the impeller 106 rotates, the fuel in the clearance between the impeller 106 and the casing is drawn into the spiral grooves and flows from the end portion on the outer periphery side of the spiral groove to the end portion on the center side of the spiral groove. When the fuel drawn into the spiral grooves flows from the outer periphery side toward the center, the pressure of the fuel in the grooves acts upon the upper and lower surfaces of the impeller 106, and the impeller 106 is held between the pump cover 188 and the pump body. Thus, even if a clearance between the casing and the impeller 106 is decreased, increasing the sliding resistance is prevented. Therefore, both the reduction in the fuel leakage and the reduction in sliding resistance can be realized. Further, because the seal layer is formed by a well-known thin-film forming technology, a high processing accuracy can be obtained at a low cost. Therefore, a group of notches 182a can be formed with good accuracy at a low cost.
A ninth embodiment of the present teachings will be explained below. As shown in
In the fuel pump of the ninth embodiment, group of spiral notches are formed in the seal layers of the pump cover 208 and pump body. As a result, when the impeller 106 rotates, the fuel in the clearance between the impeller 106 and the casing is drawn into the spiral grooves and flows from the end portion on the center side of the spiral groove to the end portion on the outer periphery side of the spiral groove. When the fuel inside the spiral grooves flows from the center side toward the outer periphery side, the pressure of the fuel in the spiral grooves acts upon the upper and lower surfaces of the impeller 106, and the impeller 106 is held between the pump cover 208 and the pump body. Because contact between the impeller 106 and the casing is prevented by the pressure of fuel flowing in the spiral grooves, the clearance between the casing and the impeller 106 can be reduced. Therefore, both the reduction in leak flow rate and the reduction in sliding resistance can be realized.
A tenth embodiment of the present teachings will be explained below.
As shown in
In the fuel pump of the tenth embodiment, the seal layer 222 is formed on the upper surface of the impeller 236, and a seal layer similar to the seal layer 222 is also formed in the lower surface of the impeller 236. Therefore, the fuel leakage from the pump channel can be reduced. Furthermore, the seal layers are formed by a well-known thin film formation technology. As a result, they can be formed with high accuracy at a low cost. Because the seal layers can be formed with high accuracy, the clearance between the impeller and the casing can be decreased and pump efficiency can be increased.
An eleventh embodiment of the present teachings will be explained below. As shown in
In the fuel pump of the eleventh embodiment, since the seal layers are formed in the upper and lower surfaces of the impeller 256, the fuel leakage from the pump channel can be reduced. Furthermore, because groups of spiral notches are formed in these seal layers, when the impeller 256 rotates, the fuel in the clearance between the impeller 106 and the casing 107 is drawn into the spiral grooves and flows from the end portion on the center side of the spiral groove to the end portion on the outer periphery side of the spiral groove, and the pressure of the fuel in the spiral grooves acts upon the upper and lower surfaces of the impeller 256. As a result, the impeller 256 is held between the pump cover 108 and the pump body 110. Since contact between the casing 107 and the impeller 106 is prevented by the pressure of fuel flowing in the spiral grooves, the clearance between the casing 107 and the impeller 106 can be decreased. Therefore, both the reduction in fuel leakage and the reduction in sliding resistance can be realized.
In the fuel pumps of the above-described embodiments 1 to 11, the seal layers use a synthetic resin as a material for a thin film constituting the seal layer. However, the present teachings are not limited such configuration, For example, a material obtained by adding an additive to a synthetic resin may be also used as a material for the thin film. When graphite, PTFE (polytetrafluoroethylene (trade name: Teflon)), and molybdenum disulfide that increase sliding ability are used as the additive, sliding resistance can be reduced and wear of the seal layer can be inhibited. Furthermore, where an inorganic filler such as talc and silica is used as an additive to adjust viscosity, an appropriate viscosity can be obtained and operability can be improved.
Furthermore, as shown in
Alternatively, a porous material may be used as a base material 272, as shown in
Furthermore, as shown in
As described hereinabove, with the fuel pumps of embodiments 1 to 11, a seal layer is formed on the surface of a casing or an impeller by a thin film formation technology that enables accurate processing in an easy manner and at a low cost. As a result, two problems that have in a trade-off relationship, namely, the reduction in fuel leakage and the reduction in sliding resistance, can be resolved with good stability. Therefore, pump efficiency can be significantly improved.
Several preferred embodiments of the present teachings have been described above, but these embodiments are merely illustrating examples and do not limit the scope of the claims. Various alternatives and modifications to the above specific examples are included in the technology described in the scope of the patent claims.
Furthermore, the technological elements disclosed in the present specification and appended drawings have technical utility individually or in various combinations thereof and are not limited to the combinations described in the claims at the time of filing. Moreover, the art disclosed in the present specification and appended drawings achieve a plurality of objects simultaneously, and have technical utility by achieving one of these objects.
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