JPS61190191A - Motor-driven fuel pump for car - Google Patents

Abstract

PURPOSE:To improve the efficiency of pump by making the dimension of diameter of the pitch circle of a high-pressure pump chamber having a labyrinth seal construction smaller than the dimension of diameter of the pitch circle of a low-pressure chamber, and reducing the axial load applied to an impeller in said pump chamber. CONSTITUTION:During the operation of a pump, each pressure on both the low-pressure side and high-pressure side works as a surface pressure load, applying forces which press each other in the axial direction, to the both surfaces of an impeller 5. In order to balance these forces, a pitch circle diameter 18 based on the center of the shaft 9 of a vane part 12 on the high-pressure side is made smaller than a pitch circle diameter 19 based on the center of the shaft 9 of a vane part 11 in a low-pressure chamber. Thus, by reducing a pressure receiving area on the high-pressure side, the forces applied to the impeller 5 on both low-pressure side and the high-pressure side are equalized, reducing axial load applied to the impeller 5 in the pump chamber to improve the efficiency of pump. Furthermore, a labyrinth seal 13 provided on the high-pressure side prevents fuel from leaking from the high-pressure side to the low-pressure side, preventing the lowering of efficiency of pump.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electric fuel pump for a vehicle, and more particularly to a fuel pump device with a built-in fuel tank, which is a feed type pump capable of obtaining high fuel pressure.

[Background of the invention]

In order to apply such a pump to a fuel pump for an electronic fuel injection system that requires high fuel pressure, it is known that the pump chambers are multi-staged. For example, to make this woodcutter's pump into a two-stage pump in order to obtain a certain predetermined pressure, one impeller is provided between the end cover and the casing, and a plurality of independent impellers are installed on both sides of the impeller. The blade part has an arc shape, and the blade part faces the annular groove of the end cover and casing to form a low-pressure and high-pressure pump chamber, and the impeller is arranged from the high-pressure pump chamber to the low-pressure pump chamber side When an axial load is applied to the pump chamber under low pressure, the inner surface of the end cover on the pump chamber side and the surface containing the blades of the impeller come into frictional contact, causing noise and wear, and deteriorating pump performance. Become.

Therefore, in JP-A No. 49-41904, the pump chamber does not constitute two stages of empty, low pressure, and high pressure pump chambers, and the suction hole and discharge hole are common to the first and second stage pump chambers, respectively. It is configured so that the fuel pressure obtained from the first stage pump chamber and the second stage fuel pressure are equal, and the axial surface pressure charge on both sides of the impeller is balanced. Vehicle fuel pumps are known, but in order to obtain high fuel pressure, the number of revolutions of the impeller must be increased or
Or it is necessary to increase the diameter of the impeller. The former affects the durability and noise of the electric motor, and the latter has the disadvantage that the impeller drive torque increases, resulting in a larger core motor. Further, in Japanese Patent Application Laid-Open No. 57-132325, a vehicle fuel pump is known in which a spacer is provided between the inner surface of the end cover on the pump chamber side and the surface having the blades of the impeller. In order to obtain high fuel pressure, the axial clearance between the end cover casing and the impeller, the so-called side gap, is less than 100μ, and it is dimensionally impossible to insert the spacer here, so the side gap must be widened. I don't get it. This causes a large amount of leakage from the discharge side to the suction side, reducing the efficiency of the grain jig. Also, even if you insert a spacer, it will still work as an impeller.

An axial load is applied from the high-pressure pump chamber to the low-pressure pump chamber, and since the spacer is smaller than at least the diameter of the impeller, the load per unit area increases and wear accelerates. Therefore, it becomes extremely difficult to select materials for the spacer and pump chamber parts including the impeller. In addition, this type of pump requires machining accuracy to reduce a radial gap, so-called round gap, formed between the outer diameter of the impeller and the inner diameter of the housing, in addition to the side gap.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel pump with a built-in fuel tank that has high pumping efficiency by reducing the axial load on the impeller in the pump chamber in a feed type pump.

[Summary of the invention]

The present invention aims to reduce the axial load applied to the impeller from the high-pressure side to the low-pressure side in the pump chamber by making the pitch circle diameter of the high-pressure pump chamber smaller than the pitch circle diameter of the low-pressure pump chamber. The structure is such that the surface pressure loads on both sides of the impeller are approximately equal, and therefore, in theory, the workload of the pump with this structure is lower than when the pitch circle diameters of the low-pressure and high-pressure pump chambers are the same diameter. However, the above object is achieved by preventing leakage through the round gap from the high pressure side to the low pressure side by means of a labyrinth structure provided on the high pressure side.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a partial sectional view of a fuel pump device showing an embodiment according to the present invention. Due to the rotation of the shaft 9, fuel flows from the suction hole 2 of the end cover 1 to the annular groove provided in the end cover 1 due to the pump action caused by the rotation of the shaft 9 and the impeller 5 installed floatingly. It flows into Route 4.

The fuel flowing into the annular groove 4 accumulates energy due to the centrifugal force and the frictional force of the fuel as the impeller rotates 50 times, and is guided to the annular groove 6 provided in the casing 7. Furthermore, energy is stored and is pumped through the discharge hole 8 of the casing 7, through the inside of the stain machine, and into the piping from the discharge pipework 0.

Here, the explanation will be given with reference to detailed drawings of the pump chamber in FIGS. 2 and 3. A housing 20 is placed between the end cover 1 and the casing 7.
is provided, an impeller 5 is provided inside the housing 20,
The impeller 5 has an annular groove 4 provided in the end cover 1.
The cage jig 7 has a blade part 11 facing oppositely to the ring groove 6, and a blade part 12 facing the annular groove 6 provided on the cage jig 7. Furthermore, the casing 7 and the impeller 5 have a labyrinth seal 13 structure. The pump chamber, which is composed of the annular groove 4 and the vane part 11, is on the low pressure side, and the annular groove 6 and the vane part 1 are located on the low pressure side.
The pump chamber composed of 2 is on the high pressure side. Further, the pitch circle diameter 18 of the blade portion 12 with respect to the center of the shaft 9 is smaller than the pitch circle diameter 19 of the blade portion 11 with the center of the shaft 9 as a reference. The energy stored on the low pressure side, so-called pressurized fuel, is
The fuel passes through the discharge hole 14 of the end cover 1 through the fuel passage 15 of the housing 2o, enters the high pressure side through the suction hole 16 of the casing 7, and is further pressurized.
Discharged into the motor. While the pump continues to operate,
The respective pressures on both the low-pressure side and the high-pressure side serve as surface pressure loads, and a force acts to push both surfaces of the impeller 5 against each other in the axial direction. Therefore, in order to balance this force, the pitch circle diameter 18 on the high pressure side is made smaller than the pitch circle diameter 19 on the low pressure side, the pressure receiving area on the high pressure side is made smaller, and the impeller 5 on the low pressure side and the high pressure side is The working forces are equal. In theory, if this structure is adopted, the pump efficiency of this structure will be lower than when the impeller diameters on the low pressure side and the suppression side are the same diameter, but due to the labyrinth seal 13 provided on the high pressure side, the housing 20 The structure prevents fuel from leaking from the high pressure side to the low pressure side through the round gap 21 formed by the outer diameter of the impeller 5, so that the pump efficiency does not decrease. This labyrinth seal 13
Additionally, the round gap 21 can be made larger, making processing easier.

〔Effect of the invention〕

As described above, according to the present invention, while obtaining high fuel pressure, frictional contact between pump parts is prevented, resulting in good durability and noise reduction, and efficiency due to the structure that reduces leakage from the high pressure side to the low pressure side. A fuel pump with good quality and easy machining can be obtained.

Furthermore, the fact that the pitch diameters of the low-pressure and high-pressure pump chambers are different allows the thickness of the impeller to be reduced, reducing the load on the blades and making the motor more compact.

[Brief explanation of drawings]

FIG. 1 is a partial vertical sectional view of a fuel pump device showing an embodiment of the present invention, and FIGS. 2 and 3 are sectional views of details of a pump chamber. l... End cover, 2... Suction hole, 3... Suction pipe, 4... Annular groove, 5... Impeller, 6... Annular groove, 7... Casing, 8...Discharge hole, 9...
Shaft, 10...Discharge pipe, 11...Blade portion, 12
... Wing part, 13... Labyrinth seal, 14...
・Discharge hole, 15... Fuel passage, work 6... Suction hole, 1
7...Fuel flow, 18...Pitch circle diameter, 19.
...Pitch circle diameter, 20...Housing, 21...
round gap.

Claims (2)

[Claims] 1. The impeller is sunk in a vehicle fuel tank and is provided with an impeller between an end cover and a casing, and both sides of the impeller have a plurality of independent blades in an arc shape, and the blades, the end cover, and A fuel pump comprising low-pressure and high-pressure pump chambers facing an annular groove in a casing, characterized in that the pitch diameter of the high-pressure pump chamber is smaller than the pitch diameter of the low-pressure pump chamber. Electric fuel pump for vehicles. 2. An electric fuel pump for a vehicle, characterized in that the fuel pump according to claim 1 has a labyrinth seal structure on the high pressure pump chamber side.