Liquid pump and method for manufacturing liquid pump

Abstract

Provided are: a liquid pump capable of preventing rust from becoming mixed in fuel that is supplied to an internal combustion engine; and a method for manufacturing the liquid pump.　A fuel pump 1 includes a pump part P and a pump motor M for driving the pump part P. The pump motor M comprises: a stator 10; a rotor 12 rotatably provided inside the stator 10 in the radial direction; and a flow passage 30 which is formed between the stator 10 and the rotor 12 and through which fuel pumped up by the pump part P flows. A plating film is formed by performing electrolytic plating on an externally exposed outer peripheral surface 14c and an inner peripheral surface 14d of a stator core 14 of the stator 10 in a state in which a plurality of coils 17 and a motor cover 18 are attached to the stator core 14. Traces of an electrode left over from the electrolytic plating are formed on the outer peripheral surface 14c of the stator core 14.

Description

Liquid pump and method of manufacturing the liquid pump

[0001] The present invention relates to a liquid pump and a method for manufacturing a liquid pump.

[0002] An example of a liquid pump is a fuel pump for vehicles such as motorcycles and automobiles. This type of fuel pump is a so-called in-tank type, which is disposed inside a fuel tank and submerged in fuel. The fuel pump has a pump motor and a pump unit disposed inside a cylindrical housing case. The pump unit is rotated by the pump motor, thereby pressurizing fuel in the fuel tank. The pressurized fuel passes through a flow path formed in the fuel pump and is supplied to the internal combustion engine from a discharge port.

[0003] In the fuel pump, for example, a stator core including an insulator, a motor cover, etc. is electrolytically plated to form a tin-plated coating (Sn-plated coating) on ​​the stator core, which is known to have corrosion resistance (see, for example, Patent Document 1).

[0004] JP 2015-83828 A

[0005] When electrolytic plating is performed on a stator core, for example, an electrode is brought into contact with the outer peripheral surface of the stator core. In this case, it is difficult to form a plating film at the location of the outer peripheral surface of the stator core where the electrode is brought into contact, leaving a mark. It is conceivable that rust will form in the mark. For example, in a fuel pump, if a fuel flow path is formed between a housing case provided on the outer peripheral surface of the stator and the outer peripheral surface of the stator core, fuel is supplied to an internal combustion engine along the outer peripheral surface of the stator core. Therefore, there is a concern that rust formed on the outer peripheral surface of the stator core will be mixed into the fuel.

[0006] Therefore, the present invention provides a liquid pump that can prevent rust from being mixed into fuel supplied to an internal combustion engine, for example, and a method for manufacturing the liquid pump.

[0007] In order to solve the above problems, a first aspect of the present invention comprises a pump section that pumps up a liquid, and a pump motor that drives the pump section, wherein the pump motor comprises a stator, a rotor that is rotatably arranged radially inside the stator and connected to the pump section, and a flow path formed between the stator and the rotor and through which the liquid pumped up by the pump section flows, and the stator comprises a stator core in which a plurality of electromagnetic steel plates are laminated, a plurality of coils wound around the stator core, and a motor cover that protects the plurality of coils, and when the plurality of coils and the motor cover are attached to the stator core, a plating coating is formed by applying electrolytic plating to exposed portions of the stator core that are exposed to the outside, and electrode contact marks are formed on the outer surface of the stator core of the exposed portions caused by electrodes contacting them when applying the electrolytic plating.

[0008] This configuration prevents the outer peripheral surface of the stator core, where the electrode marks are formed, from becoming a flow path. The electrode marks may not form a plating coating, which could lead to rust. Therefore, the above configuration prevents rust from being mixed into the fuel supplied to an internal combustion engine, even when the liquid pump is used as a fuel pump that supplies fuel to the internal combustion engine.

[0009] In a second aspect of the present invention, the liquid pump of the first aspect may be provided with a housing case having a cylindrical portion, the pump portion being housed within the housing case, and the outer peripheral surface of the stator being fitted to the inner peripheral surface of the cylindrical portion.

[0010] With this configuration, a flow path through which liquid can reliably flow can be formed between the stator and the rotor.

[0011] In a third aspect of the present invention, in the liquid pump of the second aspect, the housing case may have a radial dimension larger than the outer circumferential surface of the stator core.

[0012] This configuration can prevent the plating film from coming into contact with the inner peripheral surface of the housing case and peeling off from the outer peripheral surface of the stator core.

[0013] In a fourth aspect of the present invention, a method for manufacturing a liquid pump includes a pump section that pumps up liquid and a pump motor that drives the pump section, wherein the pump motor includes a stator, a rotor that is rotatably arranged radially inside the stator and connected to the pump section, and a flow path formed between the stator and the rotor and through which the liquid pumped up by the pump section flows.In this method for manufacturing a liquid pump, the stator is formed by a lamination process in which a stator core is formed by stacking a plurality of electromagnetic steel plates, a winding process in which a plurality of coils are wound around the stator core, a molding process in which a motor cover that protects the plurality of coils is formed, and after the molding process, a plating process in which an electrode is abutted against the outer surface of the stator core and electrolytic plating is applied to form a plating coating on exposed portions exposed to the outside of the stator core.

[0014] With this method, even if electrode marks are formed on the outer peripheral surface of the stator core, the outer peripheral surface of the stator core can be prevented from becoming a flow path. There is a possibility that a plating film will not form on the electrode marks, resulting in rust. However, because the outer peripheral surface of the stator core does not become a flow path, even when the liquid pump is used as a fuel pump that supplies fuel to an internal combustion engine, rust can be prevented from being mixed into the fuel supplied to the engine. Furthermore, it is possible to prevent a plating film from being formed on the outer peripheral surface of the stator core when gaps are generated between multiple electromagnetic steel sheets. This prevents a plating film from being formed between the electromagnetic steel sheets, which causes iron loss and reduces motor performance.

[0015] According to the present invention, for example, it is possible to prevent rust from being mixed into fuel supplied to an internal combustion engine.

[0016] Fig. 1 is a perspective view of a fuel pump according to an embodiment of the present invention, as seen from the side; Fig. 2 is a side view of the fuel pump of Fig. 1, with a housing case and a pump motor partially cut away; Fig. 3 is a perspective view of a stator core of a pump motor provided in a fuel pump according to an embodiment of the present invention; Fig. 4 is a perspective view of the stator core of Fig. 3, with an insulator and a plurality of coils provided thereon; Fig. 5 is a perspective view of the stator core of Fig. 4 formed into a primary molded product; Fig. 6 is a perspective view of the primary molded product of Fig. 5 formed into a secondary molded product;

[0017] Next, an embodiment of the present invention will be described with reference to the drawings.

[0018] <Fuel Pump> FIG. 1 is a perspective view of a fuel pump 1 as seen from the side. FIG. 2 is a side view of the fuel pump of FIG. 1 with a housing case 6 and a pump motor M partially cut away. As shown in FIGS. 1 and 2 , the fuel pump 1 is an in-tank type that is disposed immersed in fuel inside a fuel tank of a vehicle such as an automobile or motorcycle. The fuel pump 1 pumps fuel from inside the fuel tank and pumps it to an internal combustion engine 2. In this embodiment, an example will be described in which the fuel pump 1 is disposed vertically inside the fuel tank. However, this is not limited to this, and the orientation of the fuel pump 1 can be selected as desired.

[0019] The fuel pump 1 includes a pump motor M, an outlet cover 4 provided on the pump motor M, a pump section P located on the opposite side of the outlet cover 4 across the pump motor M, and a housing case 6 that houses the pump motor M, outlet cover 4, and pump section P. In the fuel pump 1, the pump motor M, outlet cover 4, pump section P, and housing case 6 are arranged on the same axis O. Hereinafter, the axis O of the fuel pump 1 may be simply referred to as the "axis O," the radial direction about the axis O may be simply referred to as the "radial direction," and the circumferential direction about the axis O may be simply referred to as the "circumferential direction."

[0020] <Pump motor> Figure 3 is a perspective view showing the stator core 14 of the pump motor M. Figure 4 is a perspective view showing the stator core 14 of Figure 3 with an insulator 16 and a plurality of coils 17 attached thereto. As shown in Figures 2 to 4, the pump motor M is a so-called brushless motor that does not require brushes to supply power to the stator 10, for example. The pump motor M includes the stator 10 formed in a cylindrical shape, and a rotor 12 that is disposed radially inside the stator 10 and is rotatable relative to the stator 10.

[0021] The stator 10 comprises a cylindrical stator core 14 formed from a plurality of stacked electromagnetic steel plates 15, an insulator 16 covering the teeth 14a of the stator core 14, a plurality of coils 17 wound around the teeth 14a via the insulator 16, and a motor cover 18 protecting the plurality of coils 17.

[0022] The stator core 14 is formed by stacking a plurality of annular electromagnetic steel sheets 15 in the direction of the axis O. The stator core 14 has a plurality of teeth 14a that protrude radially inward. The stator core 14 has slots 14b formed between adjacent teeth 14a in the circumferential direction.

[0023] The insulator 16 is molded from a resin so as to cover the teeth 14a of the stator core 14. The resin used to mold the insulator 16 may be, for example, PPS (polyphenylene sulfide), POM (polyoxymethylene), or PA66 (nylon 66).

[0024] The multiple coils 17 form, for example, a three-phase coil. Terminals 21 (see also FIG. 1 ) are connected to the three-phase coil. By winding the multiple coils 17 around the teeth 14a of the stator core 14 via insulators 16, an appropriate pressing force acts on the multiple electromagnetic steel sheets 15 toward the center in the direction of the axis O (stacking direction). As a result, gaps between the multiple electromagnetic steel sheets 15 are reduced to an almost non-existent size.

[0025] Fig. 5 is a perspective view showing the stator core of Fig. 4 formed into a primary molded product. As shown in Figs. 2 and 5, the motor cover 18 is formed to cover the multiple coils 17 by, for example, molding the stator core 14 with resin using a mold (hereinafter sometimes referred to as primary molding). In this way, the multiple coils 17 are protected by the motor cover 18. Hereinafter, the part formed by primary molding the motor cover 18 on the stator core 14 will sometimes be referred to as the primary molded product Mo1. The resin used to mold the motor cover 18 is, for example, PPS or POM.

[0026] The motor cover 18 is formed, for example, to support a plurality of electromagnetic steel sheets 15 in a stacked state in the direction of the axis O. By supporting the plurality of electromagnetic steel sheets 15 in a stacked state in the direction of the axis O by the motor cover 18, smaller gaps between the plurality of electromagnetic steel sheets 15 in the direction of the axis O are ensured. One end 18a of the motor cover 18 protrudes in the direction of the axis O from the stator core 14 toward the outlet cover 4. An outer peripheral surface 18b at the one end 18a of the motor cover 18 is formed to have a radial dimension slightly larger than that of the outer peripheral surface 14c of the stator core 14. The other end 18c of the motor cover 18 protrudes in the direction of the axis O from the stator core 14 toward the pump section P.

[0027] The rotor 12 includes a rotor core 25 and an output shaft 26 to which the rotor core 25 is fixed. The rotor core 25 is, for example, magnetized with alternating north and south poles in the circumferential direction about the axis O. The output shaft 26 is fixed to the rotor core 25 while passing through it along the axis O, and rotates integrally with the rotor core 25. One end 26a of the output shaft 26 is rotatably supported, for example, by the outlet cover 4 via a bearing (not shown). The other end 26b of the output shaft 26 is rotatably supported by a pump case 41 (described later) via a bearing 28. The other end 26b of the output shaft 26 is connected to an impeller 40 (described later) of the pump section P.

[0028] Here, a fuel flow path 30 is formed by a gap between the outer peripheral surface 25a of the rotor core 25 and the inner peripheral surface 14d of the stator core 14. The fuel flow path 30 is a flow path through which the fuel pumped up by the pump section P passes.

[0029] <Outlet Cover> Figure 6 is a perspective view showing the state in which the primary molded product in Figure 5 has been formed into a secondary molded product. As shown in Figures 2 and 6, the outlet cover 4 is formed by molding the motor cover 18 around the stator core 14 in the primary molding, and then, for example, molding the motor cover 18 of the primary molded product Mo1 with resin using a mold (hereinafter sometimes referred to as secondary molding). The resin used to mold the outlet cover 4 is, for example, PPS or POM.

[0030] The outer periphery 4a of the outlet cover 4 is formed to have a radial dimension larger than the outer periphery 14c of the stator core 14. The outer periphery 4a of the outlet cover 4 is formed, for example, to have the same radial dimension as the outer periphery 18b of one end 18a of the motor cover 18. A discharge port 4b is formed in the outlet cover 4 on the opposite side of the axis O from the pump motor M. The discharge port 4b is a portion through which fuel pumped up by the pump section P of the fuel pump 1 is guided via a flow path 30 of the pump motor M. A check valve (not shown) is provided in the discharge port 4b to prevent backflow of fuel. A cover step 4c for crimping the housing case 6 is formed on the outer periphery of the outlet cover 4.

[0031] Hereinafter, the part in which the outlet cover 4 is molded onto the motor cover 18 of the primary molded product Mo1 may be referred to as the secondary molded product Mo2. That is, the secondary molded product Mo2 includes the stator core 14, the insulator 16, the plurality of coils 17, the motor cover 18, and the outlet cover 4. In the secondary molded product Mo2, a tin plating film C is formed by electrolytic plating on exposed portions E of the secondary molded product Mo2 that are exposed to the outside of the stator core 14. The exposed portions E are the outer peripheral surface 14c and inner peripheral surface 14d of the stator core 14.

[0032] <Pump Section> As shown in FIG. 2 , the pump section P is, for example, a non-positive displacement pump having an impeller 40. The pump section P pumps fuel from inside a fuel tank (not shown). The pump section P includes the impeller 40 and a pump case 41 that entirely covers the impeller 40. The impeller 40 is formed of resin in a disk shape. The impeller 40 is connected to the other end 26b of the output shaft 26 of the pump motor M so as not to rotate relative to the other end 26b. The impeller 40 has a plurality of blades (not shown) formed along the outer periphery 40a in the circumferential direction centered on the axis O. The impeller 40 is rotatably housed inside the pump case 41.

[0033] The pump case 41 includes a first case portion 42 and a second case portion 43 that overlap in the direction of the axis O. The first case portion 42 is provided at the end of the pump motor M opposite the outlet cover 4 (i.e., the other end 18c of the motor cover 18). The second case portion 43 is provided at the end of the first case portion 42 opposite the pump motor M. A suction pipe 43a is formed in the second case portion 43 on the opposite side of the second case portion 43 in the direction of the axis O. The suction pipe 43a is a portion through which fuel is pumped into the interior of the pump portion P (i.e., the fuel flow path 30).

[0034] <Housing case> As shown in Figures 1 and 2, the housing case 6 has, for example, a cylindrically formed case body (an example of a tubular portion in the claims) 50, a crimping portion 51 formed at the end on the outlet cover 4 side, and a flange 52 formed at the end on the second case portion 43 side.

[0035] The case body 50 is formed in a cylindrical shape so as to cover the pump motor M, the outlet cover 4, and the pump section P. One end 50a of the case body 50 is fitted in contact with the outer circumferential surface 18b of one end 18a of the motor cover 18 and the outer periphery 4a of the outlet cover 4. The other end 50b of the case body 50 is fitted in contact with the outer periphery 41a of the pump case 41.

[0036] The outer peripheral surface 18b of one end 18a of the motor cover 18 and the outer periphery 4a of the outlet cover 4 are formed to have a larger radial dimension than the outer peripheral surface 14c of the stator core 14. As a result, a space S is formed between the outer peripheral surface 14c of the stator core 14 and the case body 50.

[0037] The flange 52 is bent radially inward into an annular shape from the other end 50b of the case body 50. The flange 52 is engaged with a case step 43b formed at the end of the second case part 43. The crimped part 51 is crimped radially inward from one end 50a of the case body 50, and is thereby engaged with a cover step 4c of the outlet cover 4.

[0038] Before the crimping portion 51 is crimped, the housing case 6 is fitted from the second case portion 43 side to the cover step 4c of the outlet cover 4. By fitting the crimping portion 51 up to the cover step 4c, the flange 52 is locked to the case step 43b. In this state, the crimping portion 51 is locked to the cover step 4c by crimping it radially inward. As a result, the housing case 6 is fixed in a fitted state to the pump motor M, outlet cover 4, and pump unit P. As a result, the outlet cover 4 and pump unit P are integrated with the pump motor M.

[0039] 3 to 6, a method for manufacturing the fuel pump 1 will be described. As shown in Fig. 3, first, a plurality of electromagnetic steel plates 15 are stacked in the axial direction O to form the stator core 14 (stacking step).

[0040] Next, as shown in Fig. 4, the teeth 14a of the formed stator core 14 are covered with insulators 16. Then, by winding multiple coils 17 (see Fig. 2) around the insulators 16, the multiple coils 17 are wound around the teeth 14a (see Fig. 3) of the stator core 14 via the insulators 16 (winding process). The wound multiple coils 17 form a three-phase coil, and terminals 21 are connected to the three-phase coil. After the winding process, an appropriate pressing force acts on the multiple electromagnetic steel sheets 15 toward the center in the direction of the axis O, reducing the gaps between the multiple electromagnetic steel sheets 15 to an almost zero level.

[0041] Next, as shown in Figures 5 and 6, with multiple coils 17 (see Figure 2) wound around the stator core 14, a motor cover 18 is primarily molded with resin onto the stator core 14. By primarily molding the motor cover 18 onto the stator core 14, a primary molded product Mo1 is formed. As a result, the multiple coils 17 are covered by the motor cover 18. Furthermore, by secondarily molding the outlet cover 4 with resin onto the primary molded product Mo1, a secondary molded product Mo2 is formed (molding process).

[0042] When the primary molded product Mo1 and the secondary molded product Mo2 are molded, appropriate pressure is applied to the stator core 14 by a mold or the like (not shown). Therefore, the plurality of electromagnetic steel sheets 15 are closely spaced, and gaps between the plurality of electromagnetic steel sheets 15 are maintained to an extent that they are almost non-existent.

[0043] Next, the secondary molded product Mo2 is washed in a washing process, and in a process after the washing, the stator core 14 of the secondary molded product Mo2 is subjected to electrolytic plating to form a tin-plated coating C (plating process). Specifically, an electrode (not shown) is brought into contact with the outer peripheral surface 14c of the stator core 14, and electrolytic plating is applied to the stator core 14. As a result, the tin-plated coating C is formed on the exposed portion E (outer peripheral surface 14c, inner peripheral surface 14d) of the stator core 14.

[0044] At this time, no tin plating film C is formed on the outer peripheral surface 14c of the stator core 14 at the locations where the electrodes (not shown) are in contact, and electrode contact marks T (see FIG. 6) remain (are formed) due to the electrodes being in contact. This completes the manufacture of the stator 10. In this manner, the stator 10 is formed by carrying out the lamination process, winding process, molding process, and plating process in the manufacturing method of the fuel pump 1.

[0045] <Operation of Fuel Pump> Next, operation of the fuel pump 1 will be described with reference to Fig. 2. As shown in Fig. 2, when the pump motor M of the fuel pump 1 is driven, the pump section P is driven thereby. Specifically, driving the pump motor M rotates the output shaft 26, which in turn rotates the impeller 40, which is connected to the output shaft 26 so as not to rotate relative to it. As the impeller 40 rotates, fuel inside the fuel tank is pumped up into the pump section P through the suction pipe 43a.

[0046] The fuel pumped into the pump section P is pressurized inside the pump section P, and the pressurized fuel is discharged into the pump motor M through a fuel flow path hole (not shown). The fuel discharged into the pump motor M passes through a fuel flow path 30 inside the pump motor M and is discharged to the discharge port 4b of the outlet cover 4. The fuel flow path 30 is formed by a gap between the outer peripheral surface 25a of the rotor core 25 and the inner peripheral surface 14d of the stator core 14. The fuel guided from the fuel flow path 30 to the discharge port 4b is guided to the internal combustion engine 2 (see FIG. 1).

[0047] <Effects of the Embodiment> As shown in FIGS. 4 to 6 , the fuel pump 1 of the embodiment includes a secondary molded product Mo2 including the stator core 14, the insulator 16, the plurality of coils 17 (see FIG. 2 ), the motor cover 18, and the outlet cover 4. In the secondary molded product Mo2 thus formed, electrodes (not shown) were abutted against the outer peripheral surface 14c of the stator core 14, and electrolytic plating was performed. As a result, a tin plating film C was formed on the outer peripheral surface 14c and the inner peripheral surface 14d of the stator core 14. For this reason, it is difficult to appropriately form the tin plating film C at the locations on the outer peripheral surface 14c of the stator core 14 where the electrodes abut. This results in electrode abutment marks T, and rust may form on the electrode abutment marks T.

[0048] 2, the fuel flow path 30 in the pump motor M is formed in the gap between the outer peripheral surface 25a of the rotor core 25 and the inner peripheral surface 14d of the stator core 14. This prevents the fuel supplied to the internal combustion engine 2 (see FIG. 1) from flowing onto the outer peripheral surface 14c of the stator core 14. This prevents rust that has formed at the electrode contact marks T on the outer peripheral surface 14c of the stator core 14 from being mixed into the fuel supplied to the internal combustion engine 2.

[0049] Furthermore, the housing case 6 is formed to be larger in radial dimension than the outer peripheral surface 14c of the stator core 14. A tin-plated coating C is formed on the outer peripheral surface 14c of the stator core 14. Therefore, for example, when the stator 10 is housed in the housing case 6, the inner periphery of the housing case 6 can be prevented from coming into contact with the tin-plated coating C of the stator core 14. This prevents the inner periphery of the housing case 6 from coming into contact with the tin-plated coating C and peeling off from the outer peripheral surface 14c of the stator core 14.

[0050] Furthermore, by forming the housing case 6 to be larger in radial dimension than the outer peripheral surface 14c of the stator core 14, a space S is formed between the outer peripheral surface 14c of the stator core 14 and the case body 50 of the housing case 6. Therefore, rust that has developed at the electrode abutment marks T on the outer peripheral surface 14c of the stator core 14 can escape into the space S. This prevents the rust that has developed at the electrode abutment marks T from entering the gaps between the electromagnetic steel sheets 15.

[0051] 2 and 6, in the manufacturing method of the fuel pump 1 according to the embodiment, a plating process is performed after the laminating process, the winding process, and the molding process. In this plating process, a tin plating film C is formed on the outer peripheral surface 14c and the inner peripheral surface 14d of the stator core 14. Specifically, in the plating process, an electrode (not shown) is brought into contact with the outer peripheral surface 14c of the stator core 14, and electrolytic plating is performed to form the tin plating film C on the outer peripheral surface 14c and the inner peripheral surface 14d of the stator core 14.

[0052] Incidentally, when forming the tin plating film C on the outer peripheral surface 14c and the inner peripheral surface 14d of the stator core 14, it is possible to perform the plating process on the stator core 14 alone. However, in this case, gaps may occur between the stacked electromagnetic steel sheets 15, and plating liquid may remain between the electromagnetic steel sheets 15. This may result in unevenness in the tin plating film C, rust, or the like on the outer peripheral surface 14c and the inner peripheral surface 14d of the stator core 14. Furthermore, the plating film may form between the electromagnetic steel sheets 15, causing iron loss and resulting in a decrease in motor performance. In order to prevent the occurrence of uneven plating, rust, and the like, as well as the decrease in motor performance due to iron loss, it is important to manage the type and conditions of the plating film, and in this respect, there is still room for improvement.

[0053] Furthermore, when forming a tin-plated coating C on the outer peripheral surface 14c and inner peripheral surface 14d of the stator core 14 alone, a plurality of coils 17 (see FIG. 2) are wound around the stator core 14 on which the tin-plated coating C has been formed. After the plurality of coils 17 are wound, the motor cover 18 and the outlet cover 4 are molded onto the stator core 14 using a mold. Here, the mold used to mold the motor cover 18 and the outlet cover 4 onto the stator core 14 has strict dimensional accuracy requirements for the molded products. Therefore, if the tin-plated coating C is not stably formed on the outer peripheral surface 14c and inner peripheral surface 14d of the stator core 14, the stator core 14 may not be set properly in the mold, or the tin-plated coating C may peel off from the stator core 14.

[0054] Therefore, in the secondary molded product Mo2, in which the motor cover 18 and the outlet cover 4 are molded onto the stator core 14, electrolytic plating is applied to the stator core 14 to form a tin plating film C on the outer peripheral surface 14c and the inner peripheral surface 14d of the stator core 14. Prior to forming the secondary molded product Mo2, multiple coils 17 (see FIG. 2) are wound around the teeth 14a of the stator core 14 via insulators 16. This ensures small gaps between the multiple electromagnetic steel sheets 15 in the direction of the axis O. In this state, the multiple electromagnetic steel sheets 15 are supported by the motor cover 18 in a stacked state in the direction of the axis O by the primary molded product Mo1. This further ensures small gaps between the multiple electromagnetic steel sheets 15 in the direction of the axis O.

[0055] Therefore, in the secondary molded product Mo2, the multiple electromagnetic steel sheets 15 of the stator core 14 are closely spaced. Therefore, there are almost no gaps between the multiple electromagnetic steel sheets 15. As a result, the infiltration of plating liquid into the gaps between the multiple electromagnetic steel sheets 15 can be prevented, and the tin plating film C can be formed only on the outer peripheral surface 14c and inner peripheral surface 14d of the stator core 14 where plating is required. Plating liquid does not remain between the multiple electromagnetic steel sheets 15, preventing unevenness in the tin plating film C. Furthermore, a stable tin plating film C can be formed on the outer peripheral surface 14c and inner peripheral surface 14d of the stator core 14. This prevents the formation of a plating film between the electromagnetic steel sheets 15, which causes iron loss and reduces motor performance. Furthermore, the type and conditions of electrolytic plating can be easily controlled, simplifying the production process. Furthermore, this prevents deterioration of the mold settling and peeling of the tin plating film C.

[0056] Furthermore, the insulator 16, motor cover 18, and outlet cover 4 are formed using resin such as PPS, POM, or PA66. PPS, POM, and PA66 are chemically resistant to the cleaning process required for pre-treatment before electrolytic plating of the stator core 14. Therefore, by forming a tin plating film C on the outer peripheral surface 14c and inner peripheral surface 14d of the stator core 14 in the secondary molded product Mo2, it is possible to prevent the quality of the insulator 16, motor cover 18, and outlet cover 4 from being affected.

[0057] In addition, the multiple coils 17 (see FIG. 2) are overmolded with the insulator 16, motor cover 18, etc. Therefore, in the cleaning process required for pre-treatment before electrolytic plating of the stator core 14, the multiple coils 17 can be protected by the insulator 16, motor cover 18, etc. from the cleaning solution used for cleaning. This prevents the quality of the multiple coils 17 from being affected by electrolytic plating of the secondary molded product Mo2 to form a tin plating film C on the outer peripheral surface 14c and inner peripheral surface 14d of the stator core 14.

[0058] The present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention.

[0059] For example, in the above-described embodiment, the fuel pump 1 has been described as an example of a liquid pump. The fuel pump 1 has been described as an in-tank type that is submerged in fuel inside a fuel tank of a vehicle such as an automobile or motorcycle. However, the present invention is not limited to this, and the above-described configuration can be employed in fuel pumps that supply fuel to various devices. Furthermore, the above-described configuration can be employed in various liquid pumps that pump various liquids, not limited to fuel.

[0060] In the above embodiment, the case where electrolytic plating is performed on the exposed portion E (outer peripheral surface 14 c, inner peripheral surface 14 d) of the stator core 14 to form the tin plating film C has been described. However, this is not limited to this, and various plating films formed by electrolytic plating instead of the tin plating film C may be formed on the exposed portion E of the stator core 14.

[0061] In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate.

[0062] 1...fuel pump (liquid pump), 2...internal combustion engine, 4...outlet cover, 4a...outer periphery, 4b...discharge port, 4c...cover step portion, 6...housing case, 10...stator, 12...rotor, 14...stator core, 14a...teeth, 14b...slot, 14c...outer periphery surface (exposed portion), 14d...inner periphery surface (exposed portion), 15...electromagnetic steel plate, 16...insulator, 17...coil, 18...motor cover, 18a...one end portion, 18b...outer periphery surface, 18c...other end portion, 21...terminal, 25...rotor core, 25a...outer periphery surface, 26...output shaft, 26a...one end, 26b...other end, 28...bearing, 30...flow path, 40...impeller, 40a...outer periphery, 41...pump case, 41a...outer periphery, 42...first case portion, 43...second case portion, 43a...suction pipe, 43b...case step portion, 50...case main body (cylindrical portion), 50a...one end, 50b...other end, 51...crimped portion, 52...flange, C...tin-plated coating, E...exposed portion, M...pump motor, Mo1...primary molded product, Mo2...secondary molded product, O...axis, P...pump portion, S...space, T...electrode abutment mark

Claims

1. A liquid pump comprising: a pump section which pumps up a liquid; and a pump motor which drives the pump section; wherein the pump motor comprises: a stator; a rotor which is rotatably provided radially inside the stator and connected to the pump section; and a flow path formed between the stator and the rotor, through which the liquid pumped up by the pump section flows; wherein the stator comprises: a stator core formed by laminating a plurality of electromagnetic steel plates; a plurality of coils wound around the stator core; and a motor cover which protects the plurality of coils; wherein, with the plurality of coils and the motor cover attached to the stator core, a plating coating is formed by applying electrolytic plating to exposed portions of the stator core which are exposed to the outside, and electrode contact marks are formed on the outer peripheral surface of the stator core of the exposed portions, caused by electrodes coming into contact with the exposed portions when applying electrolytic plating.

2. A liquid pump as described in claim 1, characterized in that it comprises a housing case having a cylindrical portion, the pump portion is accommodated within the housing case, and the outer peripheral surface of the stator is fitted into the inner peripheral surface of the cylindrical portion.

3. The liquid pump according to claim 2, characterized in that the housing case has a radial dimension larger than the outer circumferential surface of the stator core.

4. A method for manufacturing a liquid pump comprising: a pump section for pumping up liquid; and a pump motor for driving the pump section, wherein the pump motor comprises: a stator; a rotor rotatably provided radially inside the stator and connected to the pump section; and a flow path formed between the stator and the rotor, through which the liquid pumped up by the pump section flows; wherein the stator is formed by the following steps: a lamination process for laminating a plurality of electromagnetic steel sheets to form a stator core; a winding process for winding a plurality of coils around the stator core; a molding process for forming a motor cover for protecting the plurality of coils; and a plating process for, after the molding process, contacting an electrode with the outer peripheral surface of the stator core and applying electrolytic plating to form a plating coating on exposed portions of the stator core that are exposed to the outside.

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