Patent Application
20240305167
The present invention relates to an electric actuator and a method for manufacturing the same.
An electric actuator that includes a motor is used to drive various movement mechanisms such as an opening/closing mechanism (sliding device) for a sliding door of an automobile as described in Patent Document 1. A typical electric actuator includes components such as a brushless motor having a stator and a rotor, and a control board that controls the operation of the brushless motor. Examples of such electric actuators are described in Patent Documents 2 and 3. In the electric actuator described in Patent Document 2, short electrical components of the control board are arranged in an inner region which faces the electric motor, and tall electrical components of the control board are arranged in an outer region. In the electric actuator described in Patent Document 3, a portion of a resin part that holds a rotor magnet extends in a direction approaching a magnetic sensor, and the sensor magnet is attached to this extending part.
It is preferable that some of the electrical components mounted on the control board, such as a magnetic sensor (Hall IC) for detecting the position and rotational state of the rotor, be placed as close to the rotor as possible. On the other hand, the stator coil and the control board cannot be placed very close to each other.
In the structure of Patent Document 2, the rotor is made longer than the stator in the rotation axis direction of the rotor, so that the rotor is brought close to the control board. Therefore, some of the electrical components mounted on the control board can be brought close to the rotor. However, the length of the rotor in the rotation axis direction, which is extended to be brought close to the control board, does not equal the length of the stator in the rotation axis direction. Therefore, a deviation occurs between the center position of the rotor in the direction of the rotation axis and the center position of the stator in the direction of the rotation axis. As a result, the rotational inertia of the rotor increases and vibration (backlash) in the axial direction occurs when the rotor rotates, and these factors may reduce the durability of the electric motor. Furthermore, increasing the length of the rotor in the rotation axis direction causes the electric actuator to become larger and more expensive.
In the structure of Patent Document 3, it is possible to place the sensor magnet and the magnetic sensor close to each other. However, a portion of the resin part is extended in the direction of increasing proximity of the resin part to the magnetic sensor, and the sensor magnet is attached to the extended part, and these factors result in a more complicated structure, cumbersome manufacturing, and an increase in the size and expense of the electric actuator.
Therefore, an object of the present invention is to provide an electric actuator and a method for manufacturing the same that allow a rotor of the electric actuator to rotate stably, that allow some electric components of a control board to be placed close to the rotor, and that suppress increase in the size and cost of the electric actuator.
An electric actuator of the present invention comprises an electric brushless motor having a rotor and a stator, and a control board that has a plurality of electric components and that controls operation of said brushless motor, wherein said control board comprises a main board and a small board which has a smaller planar shape than said main board and which is connected to said main board via a connecting member, and wherein said small board has one or more of said electric components, faces said rotor, and is arranged at a position closer to said rotor than said main board in the rotation axis direction of said rotor.
Said electric component(s) included on said small board may be a magnetic sensor that detects a magnet of said rotor.
Said small board may overlap a part of said main board when viewed in said rotation axis direction.
Said main board may have a convex portion that protrudes toward said rotor when viewed in the rotation axis direction, and said small board may overlap with said convex portion when viewed in the rotation axis direction.
Said small board may have the planar shape included within the planar shape of said convex portion.
Said small board may be fixed to said main board by a screw.
Said main board may have an electronic control unit at a position that does not overlap with said small board when viewed in the rotation axis direction.
A method for manufacturing an electric actuator of the present invention comprises steps of installing an electric brushless motor having a rotor and a stator; cutting a board material which has a plurality of electrical components to separate said board material into a main board and a small board which has a smaller planar shape than said main board and which has one or more of said electrical components; arranging said small board at a position which faces said rotor and is closer to said rotor than said main board in the rotation axis direction of said rotor; and connecting said small board to said main board by a connecting member.
Said electric components included on said small board may include a magnetic sensor that detects a magnet of said rotor, and said small board may be arranged such that said magnetic sensor faces said magnet.
Said small board may be arranged to partially overlap said main board when viewed in the rotation axis direction.
Said main board may have a convex portion that protrudes toward said rotor when viewed in the rotation axis direction, a protruding portion that will become said small board may be integrally formed of said board material at a position adjacent to a portion that will become said convex portion of said main board, and said protruding portion may be cut from said board material to separate said small board and said main board.
Said small board may have the planar shape included within the planar shape of said convex portion, and said small board may be arranged to overlap said convex part when viewed in the rotation axis direction.
Said small board may be fixed to said main board by a screw, and the distance between said small board and said rotor may be adjusted by said screw.
Said main board may have an electronic control unit, and said small board may be arranged so as not to overlap said electronic control unit when viewed in the rotation axis direction.
According to the present invention, it is possible to obtain an electric actuator in which the rotor can rotate stably, some electrical components of the control board can be placed close to the rotor, and increase in size and cost can be suppressed.
Embodiments of the present invention will next be described with reference to the drawings.
Control board 3 includes main board 10 and small board 11 having a smaller planar shape than main board 10. Main board 10 has convex portion 10a that protrudes toward rotor 6 when viewed in rotation axis direction A. Small board 11 includes a magnetic sensor (such as a Hall IC) 12 that detects some electrical components, such as magnet 5 of rotor 6. Small board 11 has the planar shape that is included within the planar shape of convex portion 10a of main board 10. Small board 11 is arranged at a position that overlaps convex portion 10a when viewed in the direction of rotation axis A. Small board 11 is fixed to the main board 10 by screws 13 and is electrically connected to main board 10 via connecting member 14. Small board 11 faces rotor 6 and is disposed at a position closer to rotor 6 than main board 10 in a direction perpendicular to rotation axis direction A of rotor 6, that is, when viewed along rotation axis direction A. Magnetic sensor 12 faces magnet 5. Main board 10 has electronic control unit (ECU) 15 and connector 16. ECU 15 and connector 16 are located at positions that do not overlap small board 11 when viewed in rotation axis direction A. In this structure, control board 3 that controls the operation of motor 2 is composed of two members (main board 10 and small board 11). Only small board 11 having magnetic sensor 12 is close to rotor 6 in rotation axis direction A of rotor 6.
The technical idea of electric actuator 1 of this embodiment will next be explained. Conventionally, control board 3 that controls the operation of motor 2 is composed of a single plate-shaped member. It is difficult to simultaneously achieve the following two features: one feature being the placement of some of the electrical components mounted on control board 3 such as a magnetic sensor (Hall IC, etc.) 12 close to magnet 5 of rotor 6, and the other feature being the arrangement of control board 3 remote from coil 8 and fixing mechanism 9a of stator 9. In the structures described in Patent Documents 2 and 3, when the length of rotor 6 in rotation axis direction A is increased or when an additional member such as a sensor magnet is provided on rotor 6, magnet 5 of rotor 6 can be brought close to control board 3. However, this configuration may lead to unstable rotation of rotor 6, an increase in the size and cost of motor 2, and a complicated manufacturing process. Therefore, the present invention adopts a novel structure in which rotor 6 is not brought close to control board 3 but a part of control board 3 is brought close to magnet 5 of rotor 6. Specifically, in the present invention, control board 3 is separated into two members, one of which is placed at a position that faces stator 9 but that is remote from coil 8, and the other of which is placed at a position that faces rotor 6 but that is close to magnet 5. In this specification, the portion that faces stator 9 is referred to as main board 10, and the portion that faces rotor 6 has a smaller planar shape than main board 10 and is referred to as small board 11.
In the present invention, main board 10 and small board 11 are arranged at different positions from each other in rotation axis direction A. Therefore, as described above, main board 10 that faces stator 9 is located away from coil 8, and small board 11 that faces rotor 6 is located close to magnet 5. As a result, it is possible to suppress the influence on control board 3 caused by coil 8 of stator 9 as well as to use magnetic sensor 12 to detect magnet 5 of rotor 6 with high precision. Furthermore, since rotor 6 does not extend in rotation axis direction A and the lengths of rotor 6 and stator 9 in rotation axis direction A are substantially equal, it is possible to match their center positions in rotation axis direction A. As a result, rotor 6 can be rotated stably, and increase in size and cost of the motor 2 can be suppressed. Furthermore, arranging ECU 15 at a position that does not overlap with either small board 11 or motor 2 when viewed in rotation axis direction A suppresses increase of the thickness in rotation axis direction A, improves space efficiency, and decreases the size of electric actuator 1.
Next, the main parts of a method for manufacturing electric actuator 1 shown in
On the other hand, although not described in detail, rotor 6 is rotatably held and stator 9 is fixed to surround rotor 6 using a method similar to a conventional method. Convex portion 10a of main board 10 faces rotor 6, the remainder of main board 10 faces stator 9, and magnetic sensor 12 of small board 11 faces magnet 5 of rotor 6. Control board 3 is fixed so that small board 11 is closer to rotor 6 than main board 10 in rotation axis direction A of rotor 6. In this way, electric actuator 1 shown in
According to the manufacturing method of this embodiment, main board 10 and small board 11 can be integrally formed at the same time by an ordinary wiring board manufacturing method. Therefore, it is possible to achieve a structure in which main board 10, which occupies most of control board 3, is kept away from coil 8 of stator 9, while magnetic sensor 12 is positioned close to magnet 5 of rotor 6 as described above, by simply adding relatively easy steps. These steps include a step for cutting board material 3a, a step for fixing small board 11 to main board 10 by screws 13, and a step for electrically connecting main board 10 and small board 11 by means of connecting member 14. Namely, electric actuator 1 which provides the above-described effects can be manufactured without significantly complicating the manufacturing process. In particular, by providing a protruding portion that is to become small board 11 in the empty space on one side of convex portion 10a, it is possible to efficiently form main board 10 and small board 11 while reducing waste of the board material 3a. Furthermore, in this embodiment, the distance between magnetic sensor 12 of small board 11 and magnet 5 of rotor 6 can be adjusted by adjusting the tightness of screw 13 that fixes small board 11 to main board 10, whereby the position of magnet 5 can be detected under optimal conditions and more precise detection can be achieved.
In this electric actuator 1, bearing 21a is attached to case 20 formed by joining two case members 20a and 20b, and one end of rotating shaft 4 of rotor 6 is rotatably held by bearing 21a. Stator 9 is arranged to surround rotor 6 and is fixed to case 20. Main board 10 is arranged on the opposite side of case 20 in rotation axis direction A when viewed from rotor 6 and stator 9. Small board 11, which is fixed to main board 10, is located close to rotor 6. Terminal ground 22 is sandwiched between main board 10 and stator 9. Further, cover 23 is arranged at a position that faces case member 20a with rotor 6 and stator 9 disposed in between. Cover 23 is fixed to stator 9 and case 20 by screws. Bearing 21b is attached to cover 23, and a part of the other end portion of rotating shaft 4 of rotor 6 is rotatably held by bearing 21b. Gear 4a is attached to the end (other end) of rotating shaft 4 that passes through cover 23 and bearing 21b and that projects to the side opposite case 20.
Electric actuator 1 having the abovementioned structure is used as a drive device that drives various movement mechanisms by utilizing the rotation of rotor 6 that is generated when electric power is supplied to coil 8 of stator 9. For example, this electric actuator 1 is used as a drive device for an opening/closing mechanism of a sliding door of an automobile as shown in
Outer gear 37b of gear 37 meshes with gear 4a of rotating shaft 4 of motor 2 of electric actuator 1, and outer gears 36a, 36b mesh with inner gear 37a of gear 37, so that either door-opening cable 35a or door-closing cable 35b applies pull force to center roller unit 33 to move sliding door 25 in the opening direction or the closing direction.
By thus using electric actuator 1 of the present invention as a driving device for the opening/closing mechanism of sliding door 25 of an automobile, thin flat brushless motor 2 can be mounted, magnet 5 of rotor 6 can be detected by small board 11 that overlies main board 10, and ECU 15 can be placed in a position that does not overlie motor 2, whereby, the size of electric actuator 1 (in particular, the size in the rotation axis direction A) can be reduced, and electric actuator 1 can be easily arranged inside or near sliding door 25 in which many members are accommodated. Electric actuator 1 thus uses space efficiently and allows a high degree of freedom of arrangement. Furthermore, by using this type of brushless motor 2, rotational operation can be performed stably. Further, sliding door 25 can be easily stopped temporarily at an intermediate position between the fully open state and the fully closed state, and the stop position can be precisely controlled. However, electric actuator 1 of the present invention is not limited to use as a drive device for an opening/closing mechanism of sliding door 25 of a vehicle and can be widely used as a drive device for various moving mechanisms.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-035561 | Mar 2023 | JP | national |
