Fuel pump and method for manufacturing fuel pump

Abstract

A fuel pump (100) according to the present disclosure comprises: a pump unit (10) that is disposed at one end of a shaft (4); a resin cover (7) that covers the other end of a motor unit and has a fuel discharge port (9) for discharging, to the outside, fuel supplied from the pump unit (10) through the motor unit; and a bearing (5) that is embedded in a bearing-holding hole (7h) that forms an opening in the cover (7) at a facing surface (7fr) with respect to a rotor (3), and supports the shaft (4) at the other end thereof. A rotor-side end surface (5fr) of the bearing (5) has formed therein an inclined surface (5frt) that is recessed from an outer circumferential surface (5fr), and the cover (7) has formed therein a biting section (7p) that bites into the inclined surface (5frt) from the outside in the radial direction.

Description

Fuel pump and method for manufacturing the fuel pump

[0001] SUMMARY The present disclosure relates to fuel pumps and methods of manufacturing fuel pumps.

[0002] A fuel pump is mounted in a vehicle's fuel tank to pump fuel from the tank to the outside. A fuel pump has a structure in which a pump section that pressurizes the fuel and a motor section that drives the pump section are aligned along a rotary shaft, and the rotor rotating shaft, which is the armature of the motor section, extends to the pump section and rotates the impeller of the pump section to draw in, pressurize, and discharge the fuel.

[0003] The bearings that support the rotor shaft are installed in two places: on the casing side that forms the pump section, and on the cover side where the power supply brush and discharge port are located. The cover is a molded resin part made of polyacetal (POM: Polyoxymethylene) or similar, and is held in place by insert molding the bearing or by press-fitting it after molding, which forces the resin into close contact with the outer periphery of the bearing.

[0004] In recent years, there has been an increasing demand for fuel pumps that can handle high-concentration alcohol fuels, such as E50, in order to reduce vehicle exhaust emissions. Fuel pumps are immersed in fuel within a fuel tank, and during operation, fuel pressurized by the pump section flows into the motor section and is then discharged. Therefore, it is anticipated that the resin cover will swell and deform due to the high-concentration alcohol fuel, causing the bearing to lose its holding state and fall off. To address this issue, a technology has been disclosed that prevents the bearing from falling off in the axial direction due to swelling and deformation of the resin by integrally molding the bearing with a resin end cover section, with the end cover resin shaped to cover the end face of the bearing (see, for example, Patent Document 1).

[0005] JP 2019-154105 (paragraphs 0014 to 0021, Figures 1 to 4)

[0006] However, forming the portion covering the end face increases the axial length, making the pump bulky.

[0007] The present disclosure is intended to solve the above-mentioned problems, and has an object to provide a small fuel pump that does not cause bearing detachment even when using high-concentration alcohol fuel.

[0008] The fuel pump of the present disclosure comprises a motor section comprising a shaft, a rotor attached to an axial middle portion of the shaft, and a stator concentrically disposed on the outer circumferential surface of the rotor; a pump section disposed on one axial end of the shaft and configured to draw in fuel, pressurize it, and discharge it toward the other axial end as the shaft rotates; a resin cover that covers the other axial end of the motor section and is formed with a fuel discharge port for discharging fuel supplied from the pump section through the motor section to the outside; and a bearing that is embedded in a retaining hole that opens into a surface of the cover facing the rotor that is perpendicular to the axis of the cover and supports the shaft at the other end, wherein a recess that recesses from the outer circumferential surface is formed on the rotor-side end surface of the bearing, and a biting section that bites into the recess from the radially outside is formed in the cover.

[0009] According to the fuel pump of the present disclosure, even if the resin swells due to high-concentration alcohol fuel, adhesion in the axial direction is maintained, so that a small fuel pump can be obtained that does not cause bearing detachment.

[0010] 1A and 1B are cross-sectional views including a rotating shaft of a fuel pump according to a first embodiment. 2A and 2B are cross-sectional views including the rotating shaft showing a cover-side bearing and its surrounding area, and a cross-sectional view of the bearing, respectively. 3A and 3B are cross-sectional views perpendicular to the rotating shaft of a fuel pump according to a first embodiment. 4A to 4C are cross-sectional views including the rotating shaft showing the respective states of the surrounding area of ​​a bearing retaining hole at each stage when a cover-side bearing is fixed to a cover by heat caulking in a manufacturing method of a fuel pump according to a second embodiment. 4B are cross-sectional views including the rotating shaft of a fuel pump according to a third embodiment. 6A and 6B are cross-sectional views including the rotating shaft showing a cover-side bearing and its surrounding area of ​​a fuel pump according to a third embodiment, and a cross-sectional view of the bearing. 3C are cross-sectional views perpendicular to the rotating shaft of a fuel pump according to a third embodiment.

[0011] 1 to 3 are diagrams illustrating the configuration and operation of a fuel pump according to a first embodiment, with Fig. 1 being a cross-sectional view including the rotating shaft of the fuel pump, Fig. 2A being a cross-sectional view showing the cover-side bearing and its surrounding area in the cross section shown in Fig. 1, and Fig. 2B being a cross-sectional view including the rotating shaft of the cover-side bearing. Also, Fig. 3 is a cross-sectional view taken along line A-A in Fig. 1, perpendicular to the rotating shaft of the fuel pump.

[0012] The fuel pump according to the first embodiment is mounted in a fuel tank of a vehicle (not shown) to supply fuel to an internal combustion engine, and its drive components are roughly divided into a motor section and a pump section. As shown in Fig. 1, the motor section, which is the main component of the fuel pump 100, has a cylindrical housing 1 having a magnet 2, which serves as a stator (an armature), mounted on the inner circumferential surface thereof, and a rotor 3, which serves as an armature having windings (not shown), mounted on the inner circumferential surface thereof.

[0013] A pump section 10 is disposed at one end (lower side in the figure) of the housing 1 along the rotation axis Ar, and a cover 7 made of a resin such as polyacetal is disposed at the other end. The rotor 3 is attached to a shaft 4 and is supported for free rotation about the rotation axis Ar via a bearing 5 held by the cover 7 at the radial center and a bearing 6 held by the pump section 10.

[0014] The cover 7 holds a bearing 5 in the radial center, and is also formed with a brush housing 7b that holds a power supply brush 8 that supplies current to the commutator of the rotor 3, as well as a fuel discharge port 9. A pump section 10 that is responsible for suction, pressurization, and discharge of fuel is disposed coaxially with the shaft 4, and is configured to be driven by the rotation of the motor section (strictly speaking, the shaft 4 to which the rotor 3 is attached).

[0015] The following describes the details of the structure in which the bearing 5 on the cover 7 side is held by the resin that constitutes the cover 7. As shown in FIG. 2A , the bearing 5 is located at the radial center of the surface 7fr of the cover 7 that faces the rotor 3, i.e., concentric with the rotation axis Ar, and is held by insert molding such that the outer peripheral surface 5fo of the bearing 5 tightly fits into the bearing retaining hole 7h of the cover 7 without any gaps. The bearing retaining hole 7h also has a support portion 7s that protrudes from the bottom toward the rotor 3 so as to fit closely from the end surface 5fx of the bearing 5 on the opposite side of the rotor 3 to the inner peripheral surface 5fi. This allows the end surface 5fx of the bearing 5 to be tightly held by the resin of the cover 7 from both the radially outer and inner sides and from the axial side away from the rotor 3.

[0016] 2B , the rotor-side end surface 5fr of the bearing 5 is formed with an inclined surface 5frt that tapers at an angle θ with respect to a plane perpendicular to the rotation axis Ar. In contrast, the resin on the opposing surface 7fr side of the cover 7 is formed with a biting portion 7p that extends along the inclination of the inclined surface 5frt and bites radially inward beyond the outer circumferential surface 5fo. The axial tip of the bearing 5 on the rotor 3 side is located at approximately the same position as the opposing surface 7fr of the cover 7, but the biting portion 7p is held in close contact with the resin of the cover 7 from both the radially outer side and the axial rotor 3 side relative to the inclined surface 5frt of the bearing 5.

[0017] The angle θ is preferably 45° or greater and 60° or less. For example, if the angle θ is less than 45°, the resin will not fill the recess during molding, reducing the rigidity of the biting portion 7p and its holding power for the bearing 5. Furthermore, if the angle θ is increased to, for example, 75°, greater than 60°, it will not be possible to obtain sufficient force to restrict the axial movement of the bearing 5. However, if the angle θ is set to 60° or less, it will be possible to obtain a reliable holding power. Furthermore, the range within which the inclined surface 5frt is formed is set so that the outer radius Rx at the rotor-side end surface 5fr is reduced to a value obtained by adding the inner radius Ri to a value not greater than 50% of the radial thickness t5. If the angle θ exceeds 50%, the range supported by the biting portion 7p will be too small, resulting in a weak holding power for the bearing 5.

[0018] The support portion 7s is in close contact with and holds the inner peripheral surface 5fi of the bearing 5 to an extent that does not affect support of the shaft 4. With this structure, when the resin swells, the outer peripheral surface of the support portion 7s expands in a direction that brings it into closer contact with the inner peripheral surface 5fi of the bearing 5, pressing the bearing 5 in the radial direction and suppressing shaft wobble.

[0019] Similarly, the biting portion 7p adheres tightly to and holds the inclined surface 5frt of the bearing 5 at an angle relative to the radial and axial directions within a range that does not affect the rotation of the shaft 4. With this structure, even when the resin swells, the biting portion 7p maintains contact with the inclined surface 5fr on the rotor-side end face 5fr side, pressing the bearing 5 in both the radial and axial directions, preventing it from falling off and suppressing shaft wobble.

[0020] Therefore, even if the fuel pump 100 is immersed in high-concentration alcohol fuel and the resin of the cover 7 swells, it is possible to maintain support for the bearing on both radial and axial sides. Furthermore, by forming the inclined surface 5frt on the rotor-side end face 5fr of the bearing 5, the biting portion 7p of the cover 7 can support the bearing 5 from the rotor side in the axial direction without increasing the axial length of the motor unit.

[0021] 3, the area around the bearing retaining hole 7h in the cover 7 has a complex shape because it has multiple functions, such as the fuel outlet 9 and the brush housing portion 7b that houses the power supply brush 8. Therefore, even if the bearing 5 can be held by resin as described above, if the resin is not uniform in thickness and swells, the position of the bearing retaining hole 7h itself may deform so as to be displaced from the rotation axis Ar, which could result in misalignment of the axis of rotation.

[0022] Therefore, in the fuel pump 100 of the present disclosure, when the X-axis and Y-axis coordinates are set on a plane perpendicular to the rotation axis Ar with the rotation axis Ar as the origin, the pair of power supply brushes 8 are arranged separately on the positive and negative sides of the Y axis, and are electrically connected to each other by the power supply terminal 12 and the pigtail 11, respectively.

[0023] The power supply brush 8 is arranged symmetrically with respect to the X-axis, which passes through the bearing 5 and the fuel discharge port 9, and is arranged so as to be biased to one side with respect to the Y-axis, which intersects the X-axis at a right angle, and the cover 7 forms a brush housing portion 7b that surrounds and holds the power supply brush 8 along the shape of the brush housing portion 8. In this way, a pseudo housing portion 7sb formed in a similar shape to the brush housing portion 7b is formed in a position symmetrical with respect to the Y-axis, with respect to the brush housing portion 7b that is arranged so as to be biased to the positive side of the X-axis.

[0024] In other words, in a plane perpendicular to the rotation axis Ar, the shape and thickness of the resin around the bearing retaining hole 7h of the cover 7 are made symmetrical with respect to the bearing 5. This prevents the bearing 5 from shifting from the rotation axis Ar even if the resin constituting the cover 7 swells due to alcohol fuel, thereby preventing coaxial misalignment between the bearing 5 on the cover 7 side and the bearing 6 on the pump side.

[0025] Second Embodiment. In the first embodiment, an example of a method for manufacturing a fuel pump in which a cover-side bearing is integrated with the cover by insert molding has been described, but the present invention is not limited to this. In the manufacturing method for a fuel pump according to this embodiment, an example of forming a structure for holding the bearing in the molded cover by heat staking will be described. Figures 4A to 4C are diagrams illustrating a manufacturing method for a fuel pump according to the second embodiment. These diagrams are cross-sectional views including the rotation axis showing the states of the area around the bearing holding hole at each stage when the cover-side bearing is fixed to the cover, and are upside-down views of Figure 2A used in the description of the first embodiment. The structure of the fuel pump is the same as that of the first embodiment, and therefore a description of similar parts will be omitted, and Figures 1 to 3 used in the first embodiment will be used.

[0026] As shown in Fig. 4A, the bearing 5 is inserted into the molded cover 7 along the bearing retaining hole 7h. The diameter of the bearing retaining hole 7h is sized to provide a press-fit relationship with the outer peripheral surface 5fo of the bearing 5, and after insertion, the bearing 5 is fixed by press-fitting into the cover 7. After insertion, as shown in Fig. 4B, the bearing 5 is press-fitted so that the height of the tip end portion in the axial direction of the rotor-side end surface 5fr is toward the cover body side (downward in the figure) relative to the axial position of the opposing surface 7fr of the cover 7.

[0027] Then, a thermal crimping head 900 having a taper 900 fpt for forming the biting portion 7p, for example, for pressing the tapered portion 900 fpt against the bearing hole 7h, melting and deforming the opposing surface 7fr portion around the periphery of the bearing hole 7h. As a result, as shown in FIG. 4C , the biting portion 7p is formed into the inclined surface 5fr, and the axial position of the opposing surface 7fr can be made the same as the tip of the rotor-side end surface 5fr. This allows the fuel pump 100 having the structure described in the first embodiment to be obtained.

[0028] Third Embodiment In the first and second embodiments, an example was described in which an inclined surface was formed on the rotor-side end face of the bearing. In the third embodiment, an example will be described in which a stepped portion is formed on the rotor-side end face of the bearing. Figures 5 to 7 are used to explain the configuration and operation of a fuel pump according to the third embodiment. Figure 5 is a cross-sectional view including the rotating shaft of the fuel pump, Figure 6A is a cross-sectional view of the cover-side bearing and its surrounding area in the cross section shown in Figure 5, and Figure 6B is a cross-sectional view including the rotating shaft of the bearing. Also, Figure 7 is a cross-sectional view perpendicular to the rotating shaft of the fuel pump taken along line B-B in Figure 5.

[0029] As shown in FIGS. 5, 6A, and 6B, in the fuel pump 100 according to the third embodiment, a stepped portion 5frs ​​recessed from the outer peripheral surface 5fo is formed on the rotor-side end surface 5fr of the bearing 5, and a biting portion 7p that bites into the recessed portion (stepped portion 5frs) is formed on the cover 7.

[0030] The formation range of the stepped portion 5frs ​​is set so that the radial recession amount Dr relative to the outer peripheral surface 5fo is 30% to 50% of the radial thickness t5 of the bearing 5. In other words, the outer radius Rx at the rotor-side end surface 5fr is set to a value obtained by adding the inner radius Ri of the bearing 5 to a value that is 50% to 70% of the radial thickness t5. Furthermore, the axial recession amount Da is set to a range that is equal to or greater than the radial recession amount Dr but is not greater than twice the radial recession amount Dr.

[0031] The stepped portions 5frs ​​of the bearing 5 and the biting portions 7p that bite into the recessed portions formed by the stepped portions 5frs ​​are evenly and intermittently arranged in the circumferential direction, as shown in Fig. 7. This intermittent arrangement in the circumferential direction makes it possible to suppress loosening of the bearing 5 in the axial direction, as well as in the radial and rotational directions, due to swelling of the resin that makes up the cover 7, even without the support portions 7s that protrude from the bottom surface, as described in the first embodiment. Note that the inclined surfaces 5frt in the first embodiment are also recessed relative to the outer circumferential surface 5fo, and so by arranging them intermittently in the circumferential direction, loosening of the bearing 5 in the radial and rotational directions can similarly be suppressed.

[0032] Although various exemplary embodiments and examples are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless modifications not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0033] For example, in the above example, the rotor-side end surface 5fr of the bearing 5 is provided with an inclined surface 5frt or a stepped portion 5frs ​​as a recess recessed from the outer circumferential surface 5fo, but this is not limitative. As long as the rotor-side end surface 5fr is recessed from the outer circumferential surface 5fo, it may have any other shape, not limited to the inclined surface 5frt or the stepped portion 5frs.

[0034] Furthermore, although the fuel pump 100 of the present disclosure has been described as an example of a brushed motor, the present disclosure is not limited to this, and may be a brushless motor as long as the cover through which the fuel passes and which supports the bearing 5 is made of resin.

[0035] As described above, the fuel pump 100 of the present disclosure includes a motor section including the shaft 4, the rotor 3 attached to the middle portion of the shaft 4 in the axial direction (direction along the rotation axis Ar), and the stator (magnet 2) concentrically arranged on the outer circumferential surface side of the rotor 3; a pump section 10 arranged on one end side of the shaft 4 in the axial direction and which draws in fuel, pressurizes it, and discharges it toward the other end side in the axial direction as the shaft 4 rotates; and a pump section 11 covering the other end side of the motor section in the axial direction and supplying fuel from the pump section 10 through the motor section. The cover 7 is made of resin and has a fuel discharge port 9 formed therein for discharging fuel stored in the cover 7 to the outside. The cover 7 also has a bearing 5 embedded in a retaining hole (bearing retaining hole 7h) that opens in a surface (opposing surface 7fr) of the cover 7 facing the rotor 3, which is perpendicular to the axis (rotation axis Ar) of the cover 7. The bearing 5 is embedded in a retaining hole (bearing retaining hole 7h) that opens in a surface (opposing surface 7fr) facing the rotor 3 and perpendicular to the axis (rotation axis Ar) of the cover 7, and supports the shaft 4 at the other end. The end surface (rotor-side end surface 5fr) of the bearing 5 facing the rotor 3 is formed with a recess (inclined surface 5frt, stepped portion 5frs) recessed from the outer circumferential surface 5fo. The cover 7 is formed with a biting portion 7p that bites into the recess from the radially outer side. This maintains contact between the biting portion 7p and the inclined surface 5frt, even if the resin constituting the cover 7 swells upon exposure to high-concentration alcohol fuel, without increasing the axial length. This presses the bearing 5 in both the radial and axial directions, preventing it from falling off and suppressing axial wobble.

[0036] If the recess is formed as an inclined surface 5frt that slopes radially inward from the outer peripheral surface 5fo toward the rotor 3 and has an outer radius Rx at the rotor side end surface (rotor side end surface 5fr) that is the inner radius Ri of the bearing 5 plus a value that is 50% or less of the radial thickness t5, then it is possible to easily form a biting portion 7p that securely holds the bearing 5.

[0037] Alternatively, by forming a stepped portion 5frs ​​as the recess, which becomes smaller in steps from the outer peripheral surface 5fo toward the rotor 3 and has a recess amount Dr in the radial direction relative to the outer peripheral surface 5fo that is 30% or more and 50% or less of the radial thickness t5 of the bearing 5, it is possible to form a biting portion 7p that reliably suppresses axial movement and radial movement.

[0038] In this case, if the recesses are formed intermittently along the circumferential direction, it is possible to restrict movement in the rotational direction as well.

[0039] A support portion 7s is formed on the bottom surface of the retaining hole (bearing retaining hole 7h) that protrudes toward the rotor 3 and supports the bearing 5 in close contact with the inner surface 5fi, thereby enabling the bearing 5 to be supported more reliably.

[0040] The cover 7 has a pair of brush accommodating sections 7b, which each accommodate a pair of brushes (power supply brushes 8) for supplying current to the rotor 3, formed in a plane perpendicular to the axial direction, in a biased range on one side of a first line (Y-axis) passing through the axial center (rotation axis Ar), and separated into positions that are symmetrical with a second line (X-axis) perpendicular to the first line as the axis of symmetry, and pseudo accommodating sections 7sb, each shaped to resemble the pair of brush accommodating sections 7b, are formed in positions that are symmetrical with the pair of brush accommodating sections 7b with the first line as the axis of symmetry, thereby suppressing biased deformation of the resin and eliminating misalignment of the axial center.

[0041] Furthermore, according to the manufacturing method of the fuel pump 100 of the present disclosure, the cover 7 is formed integrally with the bearing 5, so that the fuel pump 100 having the biting portion 7p can be easily obtained.

[0042] Alternatively, according to another manufacturing method of fuel pump 100, even if the manufacturing method includes a step of press-fitting bearing 5 into the retaining hole (bearing retaining hole 7h) and a step of forcing the resin constituting cover 7 into the recess (inclined surface 5frt, stepped portion 5frs) by heat crimping, fuel pump 100 having biting portion 7p can be easily obtained.

[0043] 1: Housing, 2: Magnet (stator), 3: Rotor, 4: Shaft, 5: Bearing, 5fi: Inner peripheral surface, 5fo: Outer peripheral surface, 5fr: Rotor side end face, 5frs: Stepped portion (recess), 5frt: Inclined surface (recess), 6: Bearing, 7: Cover, 7b: Brush accommodating portion, 7h: Bearing retaining hole, 7sb: Pseudo-accommodating portion, 8: Power supply brush, 9: Fuel discharge port, 10: Pump portion, 100: Fuel pump, Da: (Axial) recess amount, Dr: (Radial) recess amount, Ar: Rotating shaft, Ri: Inner radius, Rx: Outer radius, t5: Radial thickness.

Claims

1. A fuel pump comprising: a motor section comprising a shaft, a rotor attached to an axially intermediate portion of the shaft, and a stator concentrically disposed on the outer circumferential surface of the rotor; a pump section disposed on one axial end of the shaft and configured to draw in fuel, pressurize it, and discharge it toward the other axial end as the shaft rotates; a resin cover covering the other axial end of the motor section and having a fuel discharge port formed therein for discharging fuel supplied from the pump section through the motor section to the outside; and a bearing embedded in a retaining hole opening into a surface of the cover facing the rotor that is perpendicular to the axis of the cover, and supporting the shaft at the other end; wherein the rotor-side end surface of the bearing is formed with a recess recessed from the outer circumferential surface, and the cover is formed with a protrusion that protrudes radially outward into the recess.

2. A fuel pump according to claim 1, characterized in that the recessed portion is formed with an inclined surface that slopes radially inward from the outer peripheral surface toward the rotor, and the outer radius of the end surface on the rotor side is the inner radius of the bearing plus a value not exceeding 50% of the radial thickness.

3. A fuel pump according to claim 1, characterized in that the recessed portion is formed with a stepped portion that becomes smaller in steps from the outer peripheral surface toward the rotor, and has a recession amount relative to the outer peripheral surface in the radial direction that is 30% or more and 50% or less of the radial thickness of the bearing.

4. A fuel pump according to any one of claims 1 to 3, characterized in that the recesses are formed intermittently along the circumferential direction.

5. A fuel pump according to any one of claims 1 to 4, characterized in that a support portion is formed on the bottom surface of the retaining hole, protruding toward the rotor and supporting it in close contact with the inner surface of the bearing.

6. A fuel pump as described in any one of claims 1 to 5, characterized in that the cover is formed with a pair of brush accommodating sections, each accommodating a pair of brushes for energizing the rotor, in a plane perpendicular to the axial direction, in an area biased to one side of a first line passing through the axial center, at positions that are line-symmetrical with a second line perpendicular to the first line as the axis of symmetry, and pseudo accommodating sections having shapes that simulate each of the pair of brush accommodating sections are formed in positions that are line-symmetrical with the pair of brush accommodating sections, with the first line as the axis of symmetry.

7. A method for manufacturing a fuel pump according to any one of claims 1 to 6, characterized in that the cover is formed integrally with the bearing.

8. A method for manufacturing a fuel pump according to any one of claims 1 to 6, comprising the steps of: press-fitting the bearing into the retaining hole; and, by heat caulking, forcing the resin constituting the cover into the recess.

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