JP4484030B2 - Electric pump unit - Google Patents

Description

  The present invention relates to an electric pump unit in which an internal gear pump and a motor are substantially integrated, and more particularly, to a small and high-efficiency electric pump unit suitable for mounting in an automobile.

  An inner gear pump having a structure in which an inner gear having a tooth shape formed on the inner periphery is meshed with an inner gear having the same tooth shape formed on the outer periphery and having an eccentric shaft with respect to the outer gear, and these are accommodated in a housing. Trochoid pumps that use trochoidal tooth profile are suitable for mounting in automobiles because they have relatively low discharge pressure but lower noise and less pulsation than other gear pumps, especially drive train clutches and couplings. It is suitable for a hydraulic pump for a hydraulic actuator such as a transmission.

  However, a normal internal gear pump has a structure in which a motor, which is a power source, is connected to the pump body in the axial direction by coupling or the like, which requires a large space and is not limited in size reduction. The number of parts is large, and there is a limit to cost reduction.

  Therefore, in order to achieve the downsizing and cost reduction of this type of electric pump, there has conventionally been an electric pump unit having a structure in which a permanent magnet is fixed to the outer periphery of the outer gear and the outer gear is directly rotated as a motor rotor. It has been proposed (see, for example, Patent Document 1).

  In this proposal, as shown in the cross-sectional view perpendicular to the axis in FIG. 3, a core 321 having a plurality of teeth 321a in a housing 31, and a motor stator 32 in which a coil 322 is wound around each of the teeth 321a. And an internal gear pump in which an inner gear 34 having four teeth meshes with an outer gear 33 having five teeth, and four segment-type permanent magnets 35 on the outer periphery of the outer gear 33 are magnetized. It has a structure in which the adjacent ones are fixed so that they are opposite to each other. The housing 31 has an import port and an out port (both not shown) penetrating the outside in the axial direction.

In the above-described structure, current flows through each coil 322 of the motor stator 32 at a predetermined timing, thereby generating torque by interacting with the magnetic flux as the field, and the outer gear 33 rotates as the rotor of the brushless motor. The inner gear 34 meshing with the outer gear 33 rotates to generate a pump action, and the working fluid is sucked from the import and discharged from the outport.
JP 2003-129966 A

  By the way, in the electric pump unit as described above, the outer gear 33 is formed of a magnetic material, and the magnetic flux directed to the inside of the magnetic flux of the permanent magnet 35 that is fixed to the outer periphery and forms the magnetic pole passes through the outer gear 33. That is, the outer gear 33 forms a magnetic path of the permanent magnet 35 and affects the motor performance. In order to obtain high motor performance, it is necessary to increase the cross-sectional area of the portion forming the magnetic path of the permanent magnet 35.

  However, since the outer gear 33 has a tooth shape on the inner side, the thickness in the radial direction is not uniform, and the cross-sectional area of the magnetic path is different for each of the plurality of magnetic poles formed on the outer periphery. There is a problem that non-uniformity occurs. This problem leads to the result that magnetic saturation occurs in any one of the magnetic poles and the output decreases. In the example shown in FIG. 3, for example, although the cross-sectional area of the magnetic path indicated by A in the drawing is large, the cross-sectional area of the magnetic path indicated by B in the drawing is small, and magnetic saturation occurs in the portion indicated by B. There is a high possibility that it will cause the motor output to decrease.

  The present invention has been made in view of such circumstances, and in an electric pump unit in which an outer gear of an internal gear pump is also used as a rotor of a brushless motor, magnetic paths of a plurality of magnetic poles formed on the outer periphery of the outer gear are An object of the present invention is to provide an electric pump unit that can be made identical to each other in magnetic poles, eliminates magnetic non-uniformity between magnetic poles, improves motor efficiency, and is small and can provide high output.

To solve the above problems, with the electric pump unit of the invention according to claim 1, to form a outer gear of the inscribed gear pump comprising a outer gear and the inner gear meshing with each other in a magnetic material, the outer periphery of its permanent magnet In the electric pump unit in which four or more even-numbered magnetic poles are provided, a motor stator is disposed outside the magnetic poles, and the outer gear rotates as a motor rotor by energization of the motor stator. The number of teeth is the same as the number of the magnetic poles (claim 1).

Here, in the present invention, it is more preferable to adopt a configuration in which the boundary between the magnetic poles coincides with the circumferential center of the tooth tip of each tooth of the outer gear (Claim 2).

  The present invention seeks to achieve the intended object by matching the number of teeth of the outer gear with the number of magnetic poles formed on the outer periphery thereof.

  That is, when the number of teeth of the outer gear and the number of magnetic poles by the permanent magnets fixed to the outer periphery thereof are matched, the teeth of the outer gear and the magnetic poles exist at the same pitch in the circumferential direction, and the magnetic path for each magnetic pole The cross-sectional areas of the magnetic poles can be made equal to each other, and magnetic nonuniformity for each magnetic pole is reduced.

Since the magnetic flux density from each magnetic pole tends to be highest at the boundary portion of the magnetic pole by the permanent magnet, the circumferential center of the outer gear tooth tip is located at the boundary portion of the magnetic pole as in the invention according to claim 2. By adopting the configuration, it is possible to reduce the possibility of magnetic saturation as much as possible, and to construct a small and high output motor.

  According to the present invention, the cross-sectional areas of the magnetic paths through which the magnetic flux from each magnetic pole passes can be made the same for each magnetic pole, and magnetic nonuniformity between the magnetic poles can be reduced. Can be suppressed and motor efficiency can be increased. Therefore, when used as a hydraulic pump for actuating a hydraulic actuator for an automobile drive system, fuel efficiency can be improved.

  Further, by adopting a configuration in which the center of the teeth of the outer gear is located at the boundary of the magnetic pole as in the invention according to claim 2, the cross-sectional area of the magnetic path of the portion where the magnetic density is highest for each magnetic pole is large. Therefore, it is possible to reduce the possibility of magnetic saturation as much as possible, and a small and highly efficient motor can be integrally built outside the internal gear pump, so that it can be installed in automobiles and the like. An electric pump unit suitable for improving the degree of freedom in space design and fuel efficiency can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an axial cross-sectional view of an embodiment of the present invention, and FIG. 2 is an axial parallel cross-sectional view thereof.

  Inside the cup-shaped housing 1, the motor stator 2, the outer gear 3, four permanent magnets 4 fixed to the outer periphery thereof to form magnetic poles, and the non-magnetic fixed to cover the outer periphery of each permanent magnet 4 A ring 5, an inner gear 6 that meshes with the outer gear 3, and a nonmagnetic case 7 are accommodated, and an opening of the housing 1 is closed by a nonmagnetic plate 8.

  The motor stator 2 is composed of a stator core 21 having six teeth 21b projecting inward from an annular base portion 21a, and electromagnetic coils 22 wound around the teeth 21b. A direct current is supplied to each of the electromagnetic coils 22 in order from the driver.

  The outer gear 3 is made of a magnetic material and has a trochoidal tooth profile formed inside thereof, and the number of teeth is four. Four permanent magnets 4 are fixed to the outer periphery of the outer gear 3 so as to form four magnetic poles as a motor rotor, and the outer sides of the permanent magnets 4 are covered with nonmagnetic rings 5. Each permanent magnet 4 is of a segment type having a shape obtained by dividing a cylindrical body into four in the circumferential direction, and is magnetized in a direction connecting the inner circumference and the outer circumference, and the magnets adjacent to each other have a magnetization direction. It is the opposite.

  The permanent magnets 4 are fixed so that their boundary b coincides with the circumferential center c of the four teeth of the outer gear 3.

  The structure in which the outer gear 3, the permanent magnet 4, and the nonmagnetic ring 5 covering the outer periphery thereof are integrated is housed in a cup-shaped nonmagnetic case 7, and the outermost peripheral surface of the structure is nonmagnetic. The outer peripheral surface of the ring 5 is supported so as to be rotatable and slidable with respect to the inner peripheral surface of the nonmagnetic case 7.

  The inner gear 6 is formed with a trochoidal tooth profile that meshes with the outer gear 3 on the outer periphery, and the number of teeth is three, which is one less than that of the outer gear 3. A shaft 61 is fixed to the center of the inner gear 6. The shaft 61 is rotatably supported at one end side by the base portion of the nonmagnetic case 7 and at the other end side by the nonmagnetic plate 8. It is arranged at a position eccentric with respect to the center of the outer gear 3. Further, the nonmagnetic plate 8 is formed with an import 81 and an outport 62 for the working fluid.

  The nonmagnetic case 7, the nonmagnetic plate 8, and the nonmagnetic ring 5 can be made of nonmagnetic stainless steel or resin.

  In the above embodiment, as in the conventional electric pump unit, the direct current is supplied to each electromagnetic coil 22 of the motor stator 2 in order to interact with the magnetic flux as the field of each permanent magnet 4 to generate torque. The outer gear 3 to which the permanent magnet 4 is fixed rotates as a rotor of the brushless motor, and a pumping action is generated by meshing with the inner gear 6.

  The points that should be particularly noted in this embodiment are that the number of teeth of the outer gear 3 and the number of magnetic poles by the permanent magnet 4 are 4 and coincide with each other, and the circumferential center c of the four teeth. This is the point where the boundary b of the four permanent magnets 4 is coincident, so that the magnetic paths through which the magnetic fluxes from the four magnetic poles by each permanent magnet 4 pass are equal to each other, and the magnetic non-uniformity for each magnetic pole is Moreover, since the magnetic path of the boundary portion of the permanent magnet 4 where the density of magnetic flux from each magnetic pole is the highest coincides with the circumferential center of the teeth of the outer rotor 3, that is, the portion where the cross-sectional area is maximum, Magnetic saturation hardly occurs. As a result, the efficiency of the motor is improved, and it is possible to integrally provide a small and large output motor outside the internal gear pump.

  In the above embodiment, an example in which four permanent magnets are fixed to the outer periphery of the outer gear to form a four-pole motor is shown. However, the present invention is not limited to this, and for example, eight permanent magnets are used. In the case of using an 8-pole motor, the number of teeth of the outer gear may be set to 8, and another number of poles and teeth may be used.

  In the above embodiment, an example in which a plurality of segment type permanent magnets are used has been described. However, a cylindrical integral permanent magnet is used, and the direction of magnetization is reversed at a constant pitch in the circumferential direction. In this case, the boundary between the magnetic poles refers to a boundary portion where the magnetization direction is reversed.

  Furthermore, in the above embodiment, an example in which a trochoid pump is used as an internal gear pump has been shown, but it goes without saying that the present invention can be equally applied to an internal gear pump having other tooth profiles.

It is an axis orthogonal sectional view of an embodiment of the invention. It is an axial parallel sectional view of an embodiment of the invention. It is an axis orthogonal sectional view showing the example of composition of the conventional electric pump unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Motor stator 3 Outer gear 4 Permanent magnet 5 Nonmagnetic ring 6 Inner gear 61 Shaft 7 Nonmagnetic cup 8 Nonmagnetic plate b Boundary of permanent magnet 4 c Center of circumferential direction of outer gear 3 teeth

Claims (2)

The outer gear of the inscribed gear pump comprising a outer gear and the inner gear meshing with each other and forming a magnetic material, the outer periphery of its four or more even number of magnetic poles by the permanent magnets is provided, the motor stator on the outside of the pole In the electric pump unit arranged and configured so that the outer gear rotates as a motor rotor by energizing the motor stator,
An electric pump unit characterized in that the number of teeth of the outer gear is the same as the number of magnetic poles. 2. The electric pump unit according to claim 1, wherein a boundary between the magnetic poles coincides with a circumferential center of a tooth tip of each tooth of the outer gear.

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