Patent Description:
An electric pump is used for supplying hydraulic fluid to various movable mechanisms of a vehicle, for example. The electric pump includes a motor portion and a pump portion. In a case where the electric pump is operated, a rotation drive force of a rotary shaft of the motor portion is transmitted to a gear pump of the pump portion. The electric pump suctions and discharges the hydraulic fluid by a rotation of the gear pump.

The motor portion and the pump portion of the electric pump are generally separately produced and are thereafter assembled on each other so that displacement between an axis of the motor portion and an axis of the pump portion is minimized, i.e., concentricity serving as a degree of displacement between the two axes is minimized. Complete coaxiality where the concentricity between the two axes is zero is practically not achieved. Nevertheless, in order to efficiently rotate the gear pump (electric pump) by effectively transmitting the rotation drive force of the rotary shaft of the motor portion to the gear pump, the concentricity should be reduced.

Patent document <NUM> discloses an electric pump including a motor portion and a pump portion. In the electric pump, the motor portion includes a fitting projection portion made of resin and the pump portion includes a pump housing recess portion made of metal. The electric pump in Patent document <NUM> includes a spigot structure where the fitting projection portion of the motor portion is fitted into the housing recess portion of the pump portion. As a result, the electric pump with small concentricity between an axis of the motor portion and an axis of the pump portion is assembled.

Patent document <NUM> also discloses an electric pump including a motor portion and a pump portion. In the electric pump, the motor portion includes an annular case portion made of resin and the pump portion includes a boss portion made of metal. The electric pump in Patent document <NUM> includes a spigot structure where, in an opposite manner to the electric pump in Patent document <NUM>, the boss portion of the pump portion is fitted into the annular case portion of the motor portion so that the electric pump with small concentricity between an axis of the motor portion and an axis of the pump portion is assembled.

<CIT> discloses a pump unit with a pump body formed of a pump housing and a pump plate provided in front of the pump housing. A motor housing is fixed to a rear end of the pump housing and accommodates a pump driving electric motor.

<CIT> discloses an electric pump apparatus with a closing cover integrally including a cover main body and a ventilation cap body.

<CIT> discloses an electric pump unit with a motor housing that accommodates a pump-driving electric motor and a controller that controls the electric motor being fixed to a pump body of a pump that sucks and discharges oil.

<CIT> discloses an electric pump device in accordance with the preamble of claim <NUM>.

In each of the electric pumps disclosed in Patent documents <NUM> and <NUM>, the projection or the recess portion made of resin provided at the motor portion and the recess portion or the projection mad of metal provided at the pump portion are fitted to each other to obtain the spigot structure. The electric pump is accordingly assembled so that the concentricity between the axes of the motor portion and the pump portion is reduced. Nevertheless, because dimensional accuracy of the projection or the recess portion made of resin is smaller than that of the recess portion or the projection made of metal, an issue is raised that decrease of the concentricity between the axes of the motor portion and the pump portion is limited in a case where the projection or the recess portion of the motor portion and the recess portion or the projection of the pump portion are fitted to each other.

Therefore, an electric pump with small concentricity between an axis of a motor portion and an axis of a pump portion than a known pump is desired.

One embodiment of an electric pump according to the present invention includes a pump portion including a pump housing and a gear pump which is housed in the pump housing, the pump portion suctioning and discharging a hydraulic fluid by a rotation of the gear pump, a motor portion arranged adjacent to the pump portion in a direction along an axis of the pump portion and including a rotor which rotates synchronously with the gear pump and coaxially with the axis, the motor portion including a stator which is arranged at an outer periphery of the rotor and disposed coaxially with the axis, the stator applying a rotation drive force to the rotor, and a resin portion integrally surrounding at least an outer periphery of the pump housing and an outer periphery of the stator. The resin portion is provided at outer peripheral surfaces of the stator of the motor portion and the pump housing of the pump portion, and the resin portion and the pump housing are firmly integrated with each other. The pump housing includes a recess portion at an outer surface, the recess portion into which resin of the resin portion is fitted.

According to the electric pump including the aforementioned construction, the stator and the pump housing are integrally held by the resin portion. Thus, concentricity between an axis of the stator and an axis of the pump housing before the resin portion is formed may be maintained by the resin portion. The resin portion is formed in a state where the concentricity between the axis of the stator and the axis of the pump housing is reduced, so that the concentricity between the axis of the stator and the axis of the pump housing at the electric pump including the resin portion may be greatly reduced as compared to a case where the electric pump is assembled by a spigot structure. In a case where the concentricity between axes of the motor portion and the pump portion decreases, the concentricity between the axis of the stator and an axis of the rotor of the motor portion decreases. Thus, an air gap between the stator and the rotor may decrease to thereby improve driving efficiency of the motor. That is, with the same driving efficiency, an amount of usage of a magnet employed at the motor portion may decrease. According to the electric pump including the aforementioned construction, the resin portion and the pump housing are firmly integrated with each other. The pump housing is inhibited from moving relative to the resin portion. In addition, because of the resin fitted into the recess portion, the hydraulic oil hardly leaks to the outside of the electric pump by flowing through a boundary between the pump housing and the resin portion even if the hydraulic oil leaks from the gear pump.

In the one embodiment of the electric pump <NUM>, each of the pump housing and the stator includes a circular outermost configuration as viewed in the direction along the axis of the pump portion. The pump housing and the stator include same outermost diameters as each other. At this time, the resin portion desirably includes a constant thickness in a radial direction of the resin portion.

In a case where each of the pump housing and the stator includes the circular outermost configuration as viewed in the direction along the axis and the pump housing and the stator include the same outermost diameters as each other, flow resistance when the resin fills the forming die is small to thereby increase filling ability when forming the resin portion by insert molding, for example. In addition, a thickness of the resin portion in the radial direction thereof may be easily constant. With the constant thickness of the resin portion in the radial direction, an entire periphery of the resin portion is evenly cooled so that shrinkage of the resin portion may be unlikely to occur and displacement of the axes of the stator and the pump housing may be unlikely to occur after cooling of the resin portion.

In the one embodiment of the electric pump <NUM>, each of the pump housing and the gear pump is made of a ferrous material.

In order to stably drive the electric pump for a long period of time, each of the pump housing and the gear pump is desirably made of the ferrous material with high strength. As long as the pump housing and the gear pump are made of the same material, thermal expansion coefficients of the pump housing and the gear pump are the same as each other. Thus, in a case where a surrounding temperature varies, a clearance between the pump housing and the gear pump is restrained from changing. At this time, the ferrous material has a problem of being corroded when used in contact with outside air for a long period of time. Nevertheless, according to the electric pump including a construction where the outer peripheral surface of the pump housing is surrounded by the resin portion, the outer peripheral surface of the pump housing is inhibited from contacting air. Thus, the pump housing even made of the ferrous material is inhibited from being corroded. Performance and lifetime of the electric pump are inhibited from decreasing, which may lead to stable performance of the electric pump for a long period of time.

One embodiment of a method for producing an electric pump includes a step for placing a stator in a cylindrical form onto an outer peripheral surface of a fixed die of a forming die in a state where an inner peripheral surface of the stator makes contact with the outer peripheral surface of the fixed die, the forming die being configured to open and close and including the fixed die and a movable die, a step for placing a pump housing which includes a protruding portion in a cylindrical form in a state where an outer peripheral surface of the protruding portion makes contact with an inner peripheral surface of a dent which is provided at an upper surface of the fixed die, the dent including a circular cross-section in a direction orthogonal to an axis of the fixed die, and a step for forming a resin portion by flowing resin into the forming die to harden the resin after the movable die is pressed against the fixed die to close the forming die, the resin portion integrally surrounding at least an outer periphery of the pump housing and an outer periphery of the stator. The resin portion is provided at outer peripheral surfaces of the stator of the motor portion and the pump housing of the pump portion, and the resin portion and the pump housing are firmly integrated with each other. The pump housing includes a recess portion at an outer surface, the recess portion into which resin of the resin portion is fitted.

Because the fixed die used for insert molding is processed by cutting, for example, processing accuracy is extremely high. Therefore, dimensional accuracy of an outer diameter of an outer peripheral surface of the fixed die in a column form and an inner diameter of the dent may increase. In addition, the concentricity between an axis of the outer peripheral surface and an axis of the dent is greatly reduced so that the concentricity between the axes of the stator and the pump housing in a case where the stator and the pump housing are placed onto the fixed die may be greatly reduced. In the aforementioned state, the resin portion is formed to thereby integrate the stator and the pump housing while a relative position therebetween is maintained. As a result, the electric pump with the greatly reduced concentricity may be produced.

An embodiment of the present invention is explained below with reference to the attached drawings.

As illustrated in <FIG>, an electric pump <NUM> is constructed by a motor portion <NUM>, a pump portion <NUM> driven by the motor portion <NUM>, a control portion <NUM> controlling the motor portion <NUM>, and a resin portion <NUM> provided at outer peripheries of the motor portion <NUM> and the pump portion <NUM> to extend from the motor portion <NUM> to the pump portion <NUM>. The electric pump <NUM> is employed for pumping lubricant at an engine of a vehicle as hydraulic oil to hydraulic equipment. Alternatively, the electric pump <NUM> may be applied to a hydraulic device of other than the vehicle. In addition, instead of the hydraulic oil, a medicine or a chemical substance in liquid form may be used as a pumping object, for example. The hydraulic oil serves as an example of hydraulic fluid.

As illustrated in <FIG>, the pump portion <NUM> includes a pump housing <NUM>, an internal gear pump <NUM> and a pump cover <NUM>. The internal gear pump <NUM> serves as an example of a gear pump.

The pump housing <NUM> is made of ferrous metallic material. The pump housing <NUM> includes a columnar outer configuration. A housing portion <NUM> including a bottom and a circular cross-section is provided at an end surface of the pump housing <NUM> facing the pump cover <NUM>. A protruding portion <NUM> in a cylindrical form is provided at an opposite end surface from the housing portion <NUM>. An oil seal <NUM> is inserted to be positioned at an inner side of the protruding portion <NUM>. An inlet port <NUM> and an outlet port <NUM> are provided at a bottom surface of the housing portion <NUM>. A bearing bore <NUM> is provided at a center of the pump housing <NUM>. As illustrated in <FIG>, an axis of the housing portion <NUM> is eccentric to an axis X of the bearing bore <NUM>. A rotary shaft <NUM> is inserted to be positioned within the bearing bore <NUM> in a state penetrating through the oil seal <NUM>, the bearing bore <NUM> and an inner rotor <NUM> of the internal gear pump <NUM>. The rotary shaft <NUM> is rotatably supported at the bearing bore <NUM>. An axis of the rotary shaft <NUM> and an axis of the inner rotor <NUM> are both coaxial with the axis X. The rotary shaft <NUM> and the inner rotor <NUM> integrally rotate with each other. The "coaxiality" in the embodiment does not only mean that displacement of plural axes (which is hereinafter referred to as concentricity) is zero but also mean that the concentricity is approximately zero including zero.

The internal gear pump <NUM> which is housed in the housing portion <NUM> includes the inner rotor <NUM> and an outer rotor <NUM>. Each of the inner rotor <NUM> and the outer rotor <NUM> is made of ferrous metallic material. As illustrated in <FIG>, the internal gear pump <NUM> is constructed so that outer teeth provided at the inner rotor <NUM> and inner teeth provided at the outer rotor <NUM> are meshed with one another. With the rotation of the inner rotor <NUM>, the outer rotor <NUM> rotates around the inner rotor <NUM> by following the rotation of the inner rotor <NUM>. Plural pump chambers <NUM> of which volumes increase and decrease depending on the rotation are defined between a teeth portion of the inner rotor <NUM> and a teeth portion of the outer rotor <NUM>.

As long as the outer rotor <NUM> of the internal gear pump <NUM> and the pump housing <NUM> are made of the same ferrous metallic material, thermal expansion coefficients of the outer rotor <NUM> and the pump housing <NUM> are the same as each other. Thus, in a case where a surrounding temperature varies, a clearance between an inner periphery of the housing portion <NUM> and an outer periphery of the outer rotor <NUM> is restrained from changing.

The pump cover <NUM> is made of resin and is arranged adjacent to the pump housing <NUM>. The pump cover <NUM> is joined to the resin portion <NUM> which is explained later by welding, for example. The pump cover <NUM> includes the same outer diameter as the resin portion <NUM>. The pump cover <NUM> and the resin portion <NUM> are joined and integrated so that the internal gear pump <NUM> is held within the housing portion <NUM>. The pump cover <NUM> includes an inlet port <NUM> at a side opposite to the inlet port <NUM> relative to the housing portion <NUM> and an outlet port <NUM> at a side opposite to the outlet port <NUM> relative to the housing portion <NUM>. An inlet passage <NUM> extends outward from the inlet port <NUM> and an outlet passage <NUM> extends outward from the outlet port <NUM>.

As illustrated in <FIG>, the inlet port <NUM> is a curved groove and is provided communicating with the pump chambers <NUM> of the internal gear pump <NUM> along a range where the volumes of the pump chambers <NUM> of the internal gear pump <NUM> increase. In the same manner, as illustrated in <FIG>, the outlet port <NUM> is also a curved groove and is provided communicating with the pump chambers <NUM> of the internal gear pump <NUM> along a range where the volumes of the pump chambers <NUM> of the internal gear pump <NUM> decrease. The inlet port <NUM> includes the same configuration and the same size as the inlet port <NUM>. The outlet port <NUM> includes the same configuration and the same size as the outlet port <NUM>.

As illustrated in <FIG>, the motor portion <NUM> is arranged adjacent to the pump portion <NUM> in a direction along the axis X. The motor portion <NUM> includes a sensorless brushless DC motor <NUM>. As illustrated in <FIG> and <FIG>, the sensorless brushless DC motor <NUM> is constructed by a rotor <NUM> in a cylindrical form and a stator <NUM> in a cylindrical form, the stator <NUM> being arranged at an outer periphery of the rotor <NUM> with a small clearance therebetween in a radial direction. The rotor <NUM> and the stator <NUM> are both coaxial with the axis X. The stator <NUM> includes an outermost diameter which is the same value as an outermost diameter of the pump housing <NUM>.

The rotor <NUM> is obtained by a magnet <NUM> embedded and fixed in a rotor core <NUM> including a cylindrical form, the rotor core <NUM> being formed by laminated magnetic steel sheets. The rotor <NUM> integrally rotates with the rotary shaft <NUM>. The stator <NUM> includes a stator core <NUM> formed by laminated magnetic steel sheets, a coil support frame <NUM> formed by an insulator such as resin, for example, which covers teeth of the stator core <NUM>, and a coil <NUM> wound at the teeth from above the coil support frame <NUM>. The coil <NUM> constitutes a three-phase winding, each phase of the coil <NUM> being applied with a three-phase alternating current by an electric power supply from the control portion <NUM> at an outside which is explained later. The sensorless brushless DC motor <NUM> does not include a magnetic pole sensor such as a Hall element, for example. The sensorless brushless DC motor <NUM> detects a rotation position of the rotor <NUM> by utilizing an induced voltage induced to the coil <NUM> by the rotation of the rotor <NUM> and switches the power supply to the phases of the three-phase winding based on magnetic position information obtained on a basis of the rotation position of the rotor <NUM>. The teeth of the stator core <NUM> magnetized by the power supply to the coil <NUM> and the magnet <NUM> are repeatedly suctioned and repelled to thereby rotate the rotor <NUM>. With the rotation of the rotor <NUM>, the inner rotor <NUM> rotates via the rotary shaft <NUM>. Accordingly, the stator <NUM> applies a rotation drive force to the rotor <NUM>.

The control portion <NUM> is arranged adjacent to the motor portion <NUM> in the direction along the axis X. As illustrated in <FIG>, the control portion <NUM> is constructed by implementation of an electric power control element, a capacitor, a resistor and a control component such as a motor driver for deciding timing of power control, for example, on a control board <NUM>. The control board <NUM> is mounted and fixed to the resin portion <NUM> which is explained later by screwing, for example. The control portion <NUM> functions to generate a rotating magnetic field by sequentially supplying the electric power to the coil <NUM> so as to control a rotating speed of the rotor <NUM> by controlling a rotation speed of the rotating magnetic field. The control portion <NUM> is covered by a cover member <NUM> mounted to the resin portion <NUM> by welding, for example.

As illustrated in <FIG>, the resin portion <NUM> is provided at outer peripheral surfaces of the stator <NUM> of the motor portion <NUM> and the pump housing <NUM> of the pump portion <NUM> to extend from the stator <NUM> to the pump housing <NUM>. The resin portion <NUM> surrounds the outer peripheral surface of the pump housing <NUM> and surrounds the stator core <NUM> except for a part of the teeth thereof facing the rotor <NUM>, the coil <NUM> and the entire coil support frame <NUM>. A thickness of resin of the resin portion <NUM> at a radially outer side of an outermost circumference of the stator <NUM> and of an outermost circumference of the pump housing <NUM> is constant. The motor portion <NUM> and the pump portion <NUM> are integrated by the resin portion <NUM>. The resin portion <NUM> is formed by insert molding at the stator <NUM> and the pump housing <NUM>. In the electric pump <NUM>, because the motor portion and the pump portion are not combined by a spigot structure, a clearance is formed between an outer periphery of the protruding portion <NUM> of the pump housing <NUM> and an inner periphery of the resin portion <NUM> facing the aforementioned outer periphery in the radial direction. Details of forming method of the resin portion <NUM> by insert molding are explained later.

Plural groove portions <NUM> each of which includes an annular form are provided at an outer surface of the pump housing <NUM>. The resin of the resin portion <NUM> is fitted into the groove portions <NUM>. Thus, the resin portion <NUM> and the pump housing <NUM> are firmly integrated with each other. The pump housing <NUM> is inhibited from moving relative to the resin portion <NUM>. In the present embodiment, the groove portions <NUM> are provided at the pump hosing <NUM>. Alternatively, instead of the groove portions <NUM>, knurls including shallower groove portions than the groove portions <NUM>, for example, may be provided. The resin of the resin portion <NUM> is also fitted into the groove portions of the knurls to thereby firmly fix the resin portion <NUM> and the pump housing <NUM> to each other. Each of the groove portions <NUM> and the groove portions of the knurls serves as an example of a recess portion.

Because of the resin fitted into the groove portions <NUM>, the hydraulic oil hardly leaks to the outside of the electric pump <NUM> by flowing through a boundary between the pump housing <NUM> and the resin portion <NUM> even if the hydraulic oil flows from the internal gear pump <NUM> through a clearance between the rotary shaft <NUM> and the bearing <NUM> and leaks from the oil seal <NUM>. This is because the hydraulic oil leaking from the oil seal <NUM> reaches the outside of the electric pump <NUM> via the groove portions <NUM> when flowing through the boundary between the pump housing <NUM> and the resin portion <NUM>, a creepage distance by which the hydraulic oil reaches the outside of the electric pump <NUM> is elongated as compared to a case where the groove portions <NUM> are not provided. As a result, without usage of a component such as an annular seal, for example, for inhibiting leakage of the hydraulic oil, the leakage of the hydraulic oil to the outside of the electric pump <NUM> may be effectively inhibited. The electric pump <NUM> may be constructed at a low cost accordingly.

Next, an operation of the electric pump <NUM> is explained. The coil <NUM> of the stator <NUM> is applied with the three-phase alternating current by a command from the control portion <NUM> to thereby rotate the rotor <NUM>. With the rotation of the rotor <NUM>, the inner rotor <NUM> of the internal gear pump <NUM> rotates via the rotary shaft <NUM>. When the inner rotor <NUM> rotates, the outer rotor <NUM> which is meshed with the inner rotor <NUM> rotates by following the rotation of the inner rotor <NUM>. The volumes of the pump chambers <NUM> increase within the range where the pump chambers <NUM> are in communication with the inlet ports <NUM> and <NUM> and decrease within the range where the pump chambers <NUM> are in communication with the outlet ports <NUM> and <NUM> based on the rotations of the inner rotor <NUM> and the outer rotor <NUM>. According to the aforementioned pump operation of the internal gear pump <NUM>, the hydraulic oil which flows through the inlet passage <NUM> is suctioned to the pump chambers <NUM> from the inlet port <NUM> by a negative pressure and is thereafter pumped out to the outlet port <NUM> from the inlet port <NUM> by a positive pressure so as to flow through the outlet passage <NUM> by being discharged from the outlet port <NUM>.

Next, an assembly method of the electric pump <NUM> is explained in detail with reference to the attached drawings. An assembly process of the electric pump <NUM> is characterized by the resin portion <NUM> which is formed by insert molding at the stator <NUM> and the pump housing <NUM>. The other processes such as an assembly of the rotor <NUM>, an assembly of the stator <NUM>, an assembly of the control portion <NUM> and a mounting of the internal gear pump <NUM> to the pump housing <NUM>, for example, are known and therefore detailed explanation is omitted.

<FIG> illustrate a process for forming the resin portion <NUM> by insert molding at the stator <NUM> and the pump housing <NUM>. First, as illustrated in <FIG>, the stator <NUM> is placed onto a fixed die <NUM> of a forming die <NUM>, the forming die <NUM> consisting of the fixed die <NUM> and a movable die <NUM>. The fixed die <NUM> includes a stator contact portion <NUM> in a column form, a step <NUM> provided at a lower end of the stator contact portion <NUM>, and a dent <NUM> provided at an upper surface <NUM> and including a circular cross-section in a direction orthogonal to an axis of the fixed die <NUM>. Because the fixed die <NUM> is processed by cutting, for example, processing accuracy is extremely high. Therefore, dimensional accuracy of an outer diameter of the stator contact portion <NUM> and an inner diameter of the dent <NUM> may increase. In addition, the concentricity between an axis of the stator contact portion <NUM> and an axis of the dent <NUM> is greatly reduced so that the stator contact portion <NUM> and the dent <NUM> are coaxial with each other. In the following, each of the axis of the stator contact portion <NUM> and the axis of the dent <NUM> is referred to as an axis Y.

As illustrated in <FIG>, in a case where the stator <NUM> is placed onto the fixed die <NUM> while being fitted therein, an inner peripheral surface of the stator <NUM> makes contact with an outer peripheral surface of the stator contact portion <NUM>. Accordingly, an axis of the stator <NUM> and the axis Y of the stator contact portion <NUM> match each other to achieve positioning in the radial direction. In the stator <NUM>, an inner diameter of the coil support frame <NUM> is slightly greater than an inner diameter of the stator core <NUM>. The step <NUM> is provided corresponding to a difference between the aforementioned inner diameters. By the placement of the stator <NUM>, an end surface of the stator core <NUM> makes contact with the step <NUM> so that the stator <NUM> is positioned relative to the fixed die <NUM> in a direction along the axis Y.

Next, as illustrated in <FIG> and <FIG>, after the stator <NUM> is placed onto the fixed die <NUM>, the pump housing <NUM> is placed onto the fixed die <NUM> so that the protruding portion <NUM> is fitted in the dent <NUM>. The inner diameter of the dent <NUM> is substantially equal to an outer diameter of the protruding portion <NUM> of the pump housing <NUM>. By the placement of the pump housing <NUM>, an outer peripheral surface of the protruding portion <NUM> makes contact with an inner peripheral surface of the dent <NUM>. Accordingly, an axis of the pump housing <NUM> and the axis Y of the fixed die <NUM> match each other to achieve positioning in the radial direction. In addition, by the placement of the pump housing <NUM>, a surface at a radially outer side than the protruding portion <NUM> in the pump housing <NUM> makes contact with the upper surface <NUM> so that the pump housing <NUM> is positioned relative to the fixed die <NUM> in the direction along the axis Y.

In a state illustrated in <FIG>, the axis of the stator <NUM> and the axis of the pump housing <NUM> both match the axis Y of the fixed die <NUM>. The outermost diameter of the stator <NUM> is the same as the outermost diameter of the pump housing <NUM>.

Next, as illustrated in <FIG>, the movable die <NUM> is pressed against the fixed die <NUM> so as to close the forming die. Afterwards, as illustrated in <FIG>, melted thermoplastic resin such as polyphenylene sulfide (PPS) resin, for example, is brought to flow into the forming die <NUM> from a gate <NUM>. When the inside of the forming die <NUM> is filled with the thermoplastic resin, the resin is cooled and hardened in the closed die. The hardened thermoplastic resin forms the resin portion <NUM>. Because the outermost diameter of the stator <NUM> is the same as the outermost diameter of the pump housing <NUM>, flow resistance when the resin fills the forming die <NUM> is small to thereby increase filling ability. In addition, a thickness of the resin portion <NUM> in the radial direction thereof may be easily constant. With the constant thickness of the resin portion <NUM>, an entire periphery of the resin portion <NUM> is evenly cooled so that shrinkage of the resin portion <NUM> may be unlikely to occur and displacement of the axes of the stator <NUM> and the pump housing <NUM> may be unlikely to occur after cooling of the resin portion <NUM>.

Once the thermoplastic resin is hardened, the forming die <NUM> is opened to take out an intermediate assembly <NUM> which is obtained by the stator <NUM> and the pump housing <NUM> which are integrated by the resin portion <NUM> as illustrated in <FIG>. Even in the state of the intermediate assembly <NUM>, the axis of the stator <NUM> and the axis of the pump housing <NUM> maintain matching each other.

Afterwards, the oil seal <NUM>, the rotor <NUM> into which the rotary shaft <NUM> is inserted to be positioned, and the internal gear pump <NUM> are assembled on the intermediate assembly <NUM>. The pump cover <NUM> is then joined to an end portion of the resin portion <NUM> by welding, for example. Finally, the control portion <NUM> is assembled on the resin portion <NUM> and the cover member <NUM> is joined to an end portion of the resin portion <NUM> by welding, for example. As a result, the electric pump <NUM> is completed.

According to the present embodiment, after the stator <NUM> of the motor portion <NUM> and the pump housing <NUM> of the pump portion <NUM> are placed onto the metallic fixed die <NUM> in a state where the axis of the stator <NUM> and the axis of the pump housing <NUM> match the axis Y of the fixed die <NUM>, the resin portion <NUM> is formed by insert molding to integrate the stator <NUM> and the pump housing <NUM>. Thus, in the intermediate assembly <NUM> obtained after the resin portion <NUM> is formed, the axis of the stator <NUM> and the axis of the pump housing <NUM> are maintained matching each other. As a result, the concentricity between the axis of the stator <NUM> and the axis of the pump housing <NUM> at the electric pump <NUM> is greatly reduced as compared to the concentricity between an axis of a motor portion and an axis of a pump portion in a case where the motor portion and the pump portion are separately produced so that a recess portion and a projection of the motor portion and the pump portion are fitted in a spigot structure.

In a case where the concentricity between the motor portion <NUM> and the pump portion <NUM> decreases, the concentricity between the axis of the stator <NUM> of the motor portion <NUM> and an axis of the rotor <NUM> where the rotary shaft <NUM> is inserted to be positioned within the bearing bore <NUM> of the pump portion <NUM> decreases. Thus, an air gap between the stator <NUM> and the rotor <NUM> may decrease to thereby improve driving efficiency of the motor. That is, with the same driving efficiency, an amount of usage of the magnet <NUM> employed at the rotor <NUM> may decrease.

In addition, the outer peripheral surface of the pump housing <NUM> made of ferrous metallic material is covered by the resin portion <NUM> so that the outer peripheral surface of the pump housing <NUM> is inhibited from making contact with air. The pump housing <NUM> is therefore inhibited from being corroded. Thus, performance and lifetime of the electric pump <NUM> are inhibited from decreasing, which may lead to stable performance of the electric pump <NUM> for a long period of time.

In the present embodiment, the resin portion <NUM> extends along the axial direction to an end surface of the pump housing <NUM> at a side facing the pump cover <NUM>. Thus, the pump cover <NUM> formed by the resin is joined to the resin portion <NUM> by welding, for example, so that a bolt which is employed for joining a pump cover at a known electric pump is not necessary. As a result, in the motor portion <NUM> and the pump portion <NUM>, a bore through which the bolt is inserted to be positioned or a protruding portion at a radially outer side where an internal thread is provided for fixing the bolt is not necessary. The electric pump <NUM> may be produced at a reduced cost and a reduced size.

Claim 1:
An electric pump (<NUM>) comprising:
a pump portion (<NUM>) including a pump housing (<NUM>) and a gear pump (<NUM>) which is housed in the pump housing (<NUM>), the pump portion (<NUM>) suctioning and discharging a hydraulic fluid by a rotation of the gear pump (<NUM>);
a motor portion (<NUM>) arranged adjacent to the pump portion (<NUM>) in a direction along an axis of the pump portion (<NUM>) and including a rotor (<NUM>) which rotates synchronously with the gear pump (<NUM>) and coaxially with the axis, the motor portion (<NUM>) including a stator (<NUM>) which is arranged at an outer periphery of the rotor (<NUM>) and disposed coaxially with the axis, the stator (<NUM>) applying a rotation drive force to the rotor (<NUM>); and
a resin portion (<NUM>) integrally surrounding at least an outer periphery of the pump housing (<NUM>) and an outer periphery of the stator (<NUM>),
the resin portion (<NUM>) being provided at outer peripheral surfaces of the stator (<NUM>) of the motor portion (<NUM>) and the pump housing (<NUM>) of the pump portion (<NUM>), and the resin portion (<NUM>) and the pump housing (<NUM>) being firmly integrated with each other,
characterized in that
the pump housing (<NUM>) includes a recess portion (<NUM>) at an outer surface, the recess portion (<NUM>) into which resin of the resin portion (<NUM>) is fitted.