JP6182997B2 - Fuel pump - Google Patents

Description

  The present invention relates to a fuel pump that pumps fuel by rotation of an impeller.

  Conventionally, a fuel pump that rotates an impeller by a driving force of a motor or the like and pressure-feeds fuel sucked from a suction port to a discharge port, in particular, suppresses a decrease in flow rate at a high temperature by suppressing vapor generation at a high temperature. It has been. For example, the fuel pump disclosed in Patent Document 1 is characterized in that the flow path cross-sectional depth of the introduction flow path section from the suction port to the pressurization flow path section and the position of the deepest portion are changed. Further, the fuel pump of Patent Document 2 has a flow path expanding portion between the upstream end of the fuel flow path and a position slightly upstream from the opening of the gas discharge hole formed in the middle of the fuel flow path. .

Japanese Patent No. 2757646 Japanese Patent Laid-Open No. 03-160192

  Both Patent Documents 1 and 2 focus on the shape of a C-shaped flow path (introduction flow path portion, fuel flow path) formed on the surface facing the impeller. However, depending on the flow rate class and mode of the fuel pump, even if the shape of the flow path is changed, a great effect may not be obtained, or improvement from existing products may be difficult.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a fuel pump that suppresses a decrease in flow rate due to the generation of vapor, particularly by focusing on the opening area of the suction connection portion. .

The present invention relates to a fuel pump having a shaft, an impeller, a cover, and a casing, wherein the opening area of the suction connection portion where the passage space between the suction port of the cover and the introduction passage overlaps is reduced in flow rate due to vapor generated in the fuel. the rate is it is configured to be less than 20%.

When the fuel temperature rises due to heat transfer or the like, volatile components in the fuel may vaporize and stay in the flow path as vapor. Thereby, since the impeller rotates while biting the vapor, there arises a problem that the flow rate is reduced. In view of this, an increase in the opening area of the suction connection portion is intended to suppress a decrease in flow rate due to the generation of vapor.
For example, as a result of evaluation with a fuel pump having an inner edge diameter of about 24 mm and an outer edge diameter of about 30 mm, it was found that the opening area of the suction connection portion is preferably 22 mm ² or more.

Furthermore, in the present invention, the seal length, which is the length from the outer edge of the concave portion in the radial direction connecting the central axis of the cover and the suction port to the inner edge of the introduction flow path, is generated by foreign matter interposed between the impeller and the cover. flow reduction rate due to the wear of the end face of the cover is set to a predetermined length or more such that less than 20%.

If the width of the introduction flow path is made too wide in order to increase the opening area, it is considered that the seal length becomes insufficient and the pressure balance acting on the impeller is lost. For this reason, when the impeller is pressed against the cover, the cover end surface is worn by foreign matter interposed therebetween, and as a result, a part of the sucked fuel leaks and the pumping efficiency is reduced, so that the flow rate reduction rate is increased.
For example, as a result of evaluation with a fuel pump in which the material of the impeller is PPS resin and the material of the cover is an aluminum alloy, it has been found that the seal length is preferably 6.4 mm or more.

  Here, the reason why the required specification for the flow rate reduction rate is “less than 20%” is that the initial flow rate of the fuel pump is generally set with a margin of 25% or more with respect to the flow rate assumed during normal use. This is because this is technical common sense in the technical field, and it is considered that a flow rate drop of up to 20% is allowed during normal use.

1 is an axial sectional view of a fuel pump according to an embodiment of the present invention. It is the top view (a) and axial sectional view (b) of a cover. It is the bottom view (b) and axial sectional view (a) of the casing. It is the bottom view (b) and axial sectional view (a) of the impeller. It is explanatory drawing explaining the influence of the negative pressure which generate | occur | produces with a fuel flow. Evaluation product No. It is a three-dimensional figure showing the flow-path space of the suction connection part of 1 (comparative example). Evaluation product No. It is a three-dimensional view showing the flow path space of the suction connection part of 2 (first embodiment). Evaluation product No. FIG. 3 is a three-dimensional view showing a flow path space of a suction connection part 3 (second embodiment). It is a graph which shows the relationship between the opening area of a suction connection part, and a flow rate fall rate. It is a graph which shows the relationship between an operating time and a flow rate fall rate.

Hereinafter, a fuel pump according to an embodiment of the present invention will be described with reference to the drawings.
The configuration shown in FIG. 1 shows a basic configuration common to the fuel pumps 12 and 13 as an embodiment of the present invention and the fuel pump 11 as a comparative example for comparison with the embodiment. The difference between the fuel pumps 12 and 13 of the embodiment and the fuel pump 11 of the comparative example is only the difference in the shape and opening area of the suction connection part 25 between the suction port 24 of the cover 20 and the introduction flow path 26, and FIG. 1 does not appear prominently. The difference will be described after describing the common basic configuration.

  The fuel pumps 11, 12, and 13 are applied to a fuel supply system that supplies fuel in a fuel tank to a fuel injection device of an engine in a vehicle. The fuel pumps 11, 12, and 13 are impeller pumps in which the motor unit 5 is integrated, and the pressure of the fuel sucked from the suction port 24 is increased and discharged from the discharge port 65 to the outside by the rotation of the impeller 40.

  The impeller 40 is accommodated in a pump chamber 34 formed in the casing 30 and rotates about the central axis O with the upper side of FIG. 1 sandwiched between the casing 30 and the lower side of FIG. . As a result, the fuel sucked from the suction port 24 of the cover 20 is boosted by the boosting portion 44 of the impeller 40, and is discharged from the discharge flow path 39 from the introduction flow path 26 of the cover 20 through the outlet flow path 36 of the casing 30. leak.

The motor unit 50 as a “rotation drive source” is configured by a brushed DC motor, and includes a housing 59, a motor cover 61, an armature 54, a commutator 55, a permanent magnet 56, and the like.
The housing 59 is formed in a cylindrical shape, and its outer diameter typically represents the size of the fuel pumps 11, 12, 13. In the present embodiment, the outer diameter of the housing 59 is 38 mm. 1, the upper end of the housing 59 is fixed by crimping the housing 59 with the motor cover 61 fitted. The lower end of the housing 59 is fixed by crimping the housing 59 with the casing 30 housing the impeller 40 and the cover 20 fitted therein.

  The motor cover 61 is made of resin and covers the upper portion of the housing 59 in FIG. In the motor cover 61, a bearing portion 62 is formed around the central axis O, and a space around the bearing portion 62 is a fuel chamber 63. The fuel chamber 63 communicates with the discharge port 65 via the communication path 64. A check valve portion 70 is provided between the communication passage 64 and the discharge port 65 to prevent the backflow of fuel from the downstream while adjusting the discharge pressure. The motor cover 61 is formed with a brush housing chamber 660 that houses the brush 66 and the spring 67.

The armature 54 is configured by winding a coil around a core, and the shaft 51 is integrally fixed along the central axis O. The shaft 51 is rotatably supported at the upper end portion of the armature 54 in FIG. 1 by a bearing 52 fitted into the bearing portion 62 of the motor cover 61. Further, the lower shaft portion of the armature 54 is rotatably supported by a bearing 53 fitted in the bearing hole 31 of the casing 30.
The lower end of the shaft 51 is formed in a D-shape with one side of the side cut, and is inserted into the shaft hole 41 of the impeller 40. As a result, the shaft 51 and the impeller 40 are prevented from rotating in the rotation direction and rotate together.

A commutator 55 is provided at the end of the armature 54 on the motor cover 61 side. The commutator 55 includes a plurality of segments divided in the circumferential direction, and rotates together with the armature 54.
The permanent magnets 56 are arranged concentrically with respect to the central axis O, and magnets having different polarities are alternately fixed along the inner wall of the housing 59.
The brush 66 housed in the brush housing chamber 660 of the motor cover 61 is pressed against the sliding surface of the commutator 55 by the force of the spring 67. The brush 66 is electrically connected to the terminal 69 via the choke coil 68. Electric power is supplied to the terminal 69 from the outside.

  The direct current supplied to the terminal 69 from the outside is supplied to the coil of the armature 54 via the commutator 55 in contact with the brush 66 to generate a magnetic force. Then, the armature 54 and the commutator 55 rotate due to the attractive repulsion between the magnetic force of the armature 54 and the magnetic field of the permanent magnet 56. At this time, the contact between each segment of the commutator 55 and the brush 66 is repeated, so that the current supplied to the coil is rectified, so that the armature 54 continues to rotate in the same direction.

  By rotating the motor unit 50 in this way, the impeller 40 rotates with the rotation of the shaft 51, and the pump function for pumping the fuel sucked from the suction port 24 is executed. Next, detailed configurations of the cover 20, the casing 30, and the impeller 40, which are main members for executing the pump function, will be described with reference to FIGS.

The cover 20 is made of an aluminum alloy and is subjected to a surface treatment. As shown in FIG. 2, the cover 20 has a concave portion 21 at the center portion of the end surface 23 on the side in contact with the impeller 40, and is formed in a groove shape around the concave portion 21 along the boosting portion 44 of the impeller 40. An introduction channel 26 is provided. The introduction channel 26 extends in a C shape from a start end portion 27 communicating with the suction port 24 toward a terminal end portion 28 which is the other end in the circumferential direction.
Here, the length from the outer edge of the recess 21 in the radial direction connecting the central axis O of the cover 20 and the suction port 24 to the inner edge of the introduction flow path 26 is defined as “seal length Ls”.

Examples of dimensions of the cover 20 are as follows.
Recess 21 outer edge diameter φDc1 ≈ 9 mm
Inner edge diameter of introduction flow path 26 φDc2≈24 mm
Outer flow path outer edge diameter φDc3≈30 mm
Cover 20 outer diameter φDc5 ≈ 37 mm

  As shown in FIG. 3, the casing 30 forms a pump chamber 34 that houses the impeller 40 by the peripheral wall 32 and the bottom surface 33. The casing 30 has a bearing hole 31 that receives the bearing 53 in the central portion of the bottom surface 33 of the pump chamber 34, and has a lead-out flow path 36 that faces the introduction flow path 26 of the cover 20 around the bearing hole 31. ing. The casing 30 also has a discharge passage 39 through which the pressurized fuel is discharged. The lead-out flow path 36 is formed from the start end portion 37 corresponding to the start end portion 27 of the introduction flow channel 26 of the cover 20 toward the end portion 38 corresponding to the end flow portion 28 of the introduction flow channel 26 and communicating with the discharge flow path 39. It extends in a letter shape.

Examples of dimensions of the casing 30 are as follows.
Inner edge diameter φDk2≈24 mm (≈φDc2) of the outlet channel 36
Outer flow path outer edge diameter φDk3≈30 mm (≈φDc3)
Inner diameter of pump chamber 34 φDk4 ≈ 34 mm
Outer diameter of casing 30 φDk5≈37 mm (≈φDc5)
Depth of pump chamber 34 dk ≒ 4mm

  The impeller 40 is formed in a disk shape with PPS (polyphenylene sulfide) resin. As shown in FIG. 4, a D-shaped shaft hole 41 into which the shaft 51 is inserted is formed at the center of the impeller 40. Further, the impeller 40 has an annular booster 44 in which a plurality of blades 42 are arranged in the circumferential direction. The plurality of blades 42 are formed to be inclined with respect to the end surfaces 432 and 433 of the impeller 40, and the fuel introduced into the space between the blades 42 is pressurized in the process of flowing as a swirling flow.

  The impeller 40 rotates while one end surface 432 faces the end surface 23 of the cover 20 and the other end surface 433 faces the bottom surface 33 of the casing 30. If the fuel pressure balance is lost during rotation, the impeller 40 may be inclined with respect to the shaft, and the impeller end surface 432 and the cover end surface 23 or the impeller end surface 433 and the casing bottom surface 33 may partially contact each other.

Examples of dimensions of the impeller 40 are as follows.
Inner diameter of the booster 44 φDi2≈24 mm (≈φDc2≈φDk2)
The outside diameter of the booster 44 φDi3≈30 mm (≈φDc3≈φDk3)
Impeller 40 outer diameter φDi4≈34 mm (≈φDk4)
Impeller 40 thickness ti ≒ 4mm (≒ dk)

  In the fuel pumps 11, 12, and 13 configured as described above, when the shaft 51 rotates together with the armature 54 of the motor unit 50 and the impeller 40 rotates along with the rotation of the shaft 51, the fuel pumps 11, 12 and 13 are sucked from the suction port 24. The guided fuel is boosted by the booster 44 of the impeller 40 and flows out from the discharge channel 39 via the outlet channel 36. Then, the gas passes through the gap between the armature 54 and the permanent magnet 56, and is discharged from the discharge port 65 to the outside of the fuel pumps 11, 12, 13 through the fuel chamber 63, the communication path 64, and the check valve portion 70.

In such a fuel pump, there are various factors that hinder the discharge flow rate. The influence of negative pressure, which is one of the factors on the suction side, will be described with reference to FIG.
As shown in FIG. 5, in the portion where the flow velocity of the fuel flow F flowing from the inlet 24 toward the impeller 40 suddenly increases, it is estimated that the negative pressure Vc generated by the Venturi effect may hinder the fuel flow. The Therefore, the shape of the portion connected from the suction port 24 to the introduction flow path 26 is formed so that negative pressure is hardly generated.

  Further, when the fuel temperature rises due to heat transfer from the engine, peripheral devices, or the like, volatile components in the fuel may be vaporized and stay in the flow path as vapor. Thereby, since the impeller 40 rotates while biting the vapor, there arises a problem that the flow rate decreases. Therefore, the present invention is characterized in that the flow rate drop due to the generation of vapor is suppressed by expanding the opening area of the suction connection portion 25 where the flow path spaces of the suction port 24 and the introduction flow path 26 overlap.

  Three types of fuel pump evaluation products No. 1 having the same basic configuration as described above, but having only the shape of the suction connection portion 25 changed. 1, no. 2, no. 3 was manufactured and the flow rate performance was compared. Evaluation product No. 1, 2, and 3 correspond to “fuel pump 11”, “fuel pump 12”, and “fuel pump 13”, respectively. Evaluation product No. 6, 7, and 8 are schematic views showing “channel space” of the suction connection portions 25 of 1, 2, and 3 by a three-dimensional model.

  6, 7, and 8, the distance Hc from the opening position of the suction port 24 in the vertical direction to the upper end of the introduction flow path 26 corresponds to the height of the cover 20. The height Hc of the cover 20, the mouth diameter φD 0 of the suction port 24, and the width and height of a portion (not shown) downstream from the intermediate portion of the introduction flow path 26 are evaluated product numbers. The same applies to 1, 2, and 3.

Evaluation product No. shown in FIG. 1 (fuel pump 11) has a corner E1 where the gradient changes at a position that does not reach half the height of the suction port 24. Therefore, the cross-sectional area of the flow path is drastically reduced at the bottom side of the corner E1 of the suction port 24. The suction port 24 and the introduction flow channel 26 are connected to each other at a portion where the cross-sectional area of the flow channel decreases, and a suction connection portion 25 is formed. The opening area So1 of the suction connection part 25 according to this embodiment is about 18 mm ² .

Evaluation product No. 1 shown in FIG. 2 (fuel pump 12), the corner E2 of the suction port 24 is formed in the vicinity of the bottom, and the inner diameter gradient is relatively constant from the mouth to the corner E2. Therefore, the reduction in the cross-sectional area of the suction port 24 in the depth direction is relatively small. And the suction connection part 25 is formed in the range of about one third to about one half from the bottom of the suction port 24. The width W2 of the start end portion 27 of the introduction flow channel 26 is an evaluation product No. 1 is equal to the width W1 of the first end portion 27. The opening area So2 of the suction connection part 25 according to this embodiment is about 22 mm ² .

Evaluation product No. shown in FIG. 3 (fuel pump 13), the shape of the suction port 24 including the position of the corner E3 is the evaluation product no. Same as 2. Further, the width W3 of the start end portion 27 of the introduction flow channel 26 is the evaluation product No. 2 is formed to be larger than the width W2. In other words, the suction port 24 and the introduction flow channel 26 are evaluated product Nos. In the radial direction of the suction port 24. 1, no. The connection is wider than 2. The opening area So3 of the suction connection part 25 according to this embodiment is about 27 mm ² .

  Further, the seal length Ls of the cover end surface 23 in FIG. 1, no. 2 is about 6.4 mm, and the evaluation product No. 2 in which the width W3 of the start end portion 27 is increased. 3 is about 5.0 mm.

The above evaluation product No. As for the first, second, and third evaluations, the first evaluation is “flow rate reduction rate due to vapor generation in intake fuel”, and the second evaluation is “flow rate reduction rate due to wear of end face 23 of cover 20. Was evaluated.
As a result of this evaluation , the fuel pump that satisfies both the requirements of the first evaluation and the second evaluation corresponds to the “embodiment for carrying out the invention according to claim 1 ”.

In the first evaluation, the fuel pumps 11, 12, and 13 were operated at a predetermined number of revolutions in a 60 ° C. thermostat reflecting the assumed maximum temperature. As vapor was generated in the fuel pumps 11, 12, 13, the flow rate decreased to a certain level with respect to the initial stage. The ratio of the difference between the initial flow rate and the minimum flow rate (decrease flow rate) with respect to the initial flow rate at this time was determined as the flow rate reduction rate.
The results of the first evaluation are shown in Table 1 and FIG.

  Here, the required specification for the flow rate reduction rate was “less than 20%”. In this embodiment, the initial flow rate of the fuel pump is set with a margin of 25% or more with respect to the flow rate assumed during normal driving of the vehicle. Moreover, it is common technical knowledge in the technical field to allow such a margin when setting the required specification of the initial flow rate. Therefore, even if the flow rate falls within 20% from the initial flow rate, it is considered that there is no immediate significant influence on the normal running of the vehicle. On the other hand, when the flow rate is reduced by 20% or more from the initial flow rate, the fuel supplied to the engine is insufficient, and there is a possibility that suitable running cannot be performed. In addition, from the viewpoint of further improving the reliability, the required specification for the flow rate reduction rate may be “less than 15%”.

Under such a premise, No. ¹ having an opening area of 18 mm ² is used. 1, the flow rate reduction rate is 22%, so the required specifications are not satisfied. On the other hand, No. having an opening area of 22 mm ² . ² , 27 mm ² No. Since No. 3 has a flow rate reduction rate of 13%, it satisfies any required specification of less than 20% or less than 15%. From this result, it is considered that when the opening area is 22 mm ² or more, the flow rate can be suppressed from being reduced due to vapor generation at high temperature.

Next, in the second evaluation, an operation durability of 500 hours was performed using a fuel mixed with predetermined foreign matters. When the PPS impeller 40 is pressed by the pressing force on the end surface 23 of the aluminum cover 20, it is predicted that the cover end surface 23 is worn by foreign matter interposed between the impeller 40 and the cover 20. Under the hypothesis that when the cover end face 23 is worn away, a part of the sucked fuel leaks from the introduction flow path 26 and the pumping efficiency is lowered, the flow rate is lowered.
The results of the second evaluation are shown in Table 2 and FIG.

  The required specification for the rate of decrease in the flow rate after wear of the cover end face 23 was based on “less than 20%” as in the first evaluation. In this case, the required specification for the flow rate reduction rate may be “less than 15%” from the viewpoint of further improving the reliability.

As a result of the operation durability of 500 hours, the seal length Ls is 6.4 mm. 1, no. In No. 2, the flow rate reduction rate was about 10%, whereas the seal length Ls was 5.0 mm. In No. 3, the flow rate reduction rate reached about 50%. This is no. If the width W of the introduction flow path 26 is increased too much in order to increase the opening area So of the suction connection portion 25 as shown in FIG. 3, the seal length Ls becomes insufficient, the pressure balance acting on the impeller 40 is lost, and the impeller 40 This is presumably because the wear of the cover end face 23 increases due to the force pressed against the cover 20.
From this result, it is considered necessary to secure the seal length Ls of 6.4 mm or more in order to reduce the flow rate due to wear to less than 20% or less than 15%.

As described above, the evaluation product No. The fuel pump 12 as 2 satisfies both the requirements of the first evaluation and the second evaluation. That is, since the fuel pump 12 is an embodiment for carrying out the invention according to claim 1, it is positioned as the first embodiment of the present invention.
In addition, the evaluation product No. The fuel pump 13 as 3 satisfies the requirement for the first evaluation and does not satisfy the requirement for the second evaluation . Fuel pump 13 is positioned as a second embodiment of a reference embodiment.
On the other hand, an evaluation product No. that does not satisfy the requirements of the first evaluation. The fuel pump 11 as a 1 corresponds to a comparative example to be compared with the fuel pump 12.

(effect)
The effects of the fuel pump according to the embodiment of the present invention are as follows.
(1) The fuel pump 12 of the first embodiment and the fuel pump 13 of the second embodiment prevent the vapor from staying at high temperatures by making the opening area of the suction connection portion 25 22 mm ² or more. It is possible to suppress a decrease in flow rate due to vapor. Therefore, it is possible to meet the increase in the required flow rate in the system to which the fuel pump is applied.

  (2) The fuel pump 12 according to the first embodiment further has the seal length Ls at the cover end surface 23 set to 6.4 mm or more, so that when the impeller 40 whose pressure balance is lost is pressed against the cover 20, the impeller It is possible to suppress wear of the cover end surface 23 caused by foreign matter interposed between the cover 40 and the cover 20, and to suppress a decrease in flow rate due to this wear.

The dimensions and materials exemplified in the above description are merely examples as embodiments, and in other embodiments, appropriate dimensions and materials may be set according to the technical idea of the present invention.
The fuel pump according to the present invention is not limited to being configured integrally with the motor unit 50, but may be an independent fuel pump in which the impeller is rotationally driven via a shaft from a separate rotational drive source. A check valve portion may not be provided at the discharge port. Moreover, it may be applied not only to what is applied to a vehicle but to other uses.
The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from the spirit of the invention.

12, 13 ... Fuel pump,
20 ... cover, 21 ... central recess, 23 ... end face,
24 ... suction port, 25 ... suction connection part,
26 ... Introduction flow path, 27 ... Start end, 28 ... Termination,
30 ... casing, 39 ... discharge flow path,
40 ... impeller, 42 ... vane, 44 ... booster,
50: Motor part (rotation drive source), 51: Shaft,
So ... opening area,
Ls: Seal length.

Claims (3)

A shaft (51) rotated by the driving force of the rotational drive source (50);
An impeller (40) fixed to the shaft, and having an annular pressure-up part (44) in which a plurality of blades (42) are arranged in the circumferential direction;
Provided on one side in the axial direction of the impeller, from a suction port (24) through which fuel is sucked, and from a start end portion (27) communicating with the suction port to a terminal end portion (28) which is the other end in the circumferential direction A cover (20) having an introduction flow path (26) formed in a groove shape along the pressure increasing portion of the impeller,
A casing (30) provided on the other side of the impeller in the axial direction and having a discharge passage (39) through which pressurized fuel flows out;
A fuel pump (12, 13) that pumps inhaled fuel by rotation of the impeller,
The opening area (So) of the suction connection part (25) where the flow path space between the suction port of the cover and the introduction flow path overlaps is such that the flow rate reduction rate due to vapor generated in the fuel is less than 20%. It is set to a predetermined area or more ,
The seal length (Ls), which is the length from the outer edge of the recess (21) in the radial direction connecting the central axis of the cover and the suction port to the inner edge of the introduction flow path, is between the impeller and the cover. A fuel pump, characterized in that it is set to a predetermined length or more so that the rate of flow reduction due to wear of the end face of the cover caused by foreign matter present in the cover is less than 20% . ^2. The fuel pump according to claim 1, wherein an opening area of the suction connection portion is 22 [mm ² ] or more. The fuel pump according to claim 1 , wherein the seal length is 6.4 [mm] or more.

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