Brushless DC motor having structures for mounting a hall element and a magnetic ring outside a motor casing

A brushless DC motor including a motor casing, a stator component, and a rotor component. The stator component and the rotor component are respectively arranged inside the motor casing. The rotor component includes a rotor iron core and a rotating shaft supporting the rotor iron core. A shaft extension end of the rotating shaft is arranged with a magnetic ring. One end of the motor casing is provided with an end cover. The center of the outer end surface of the end cover is provided with a groove. The magnetic ring is arranged inside the groove. A Hall induction device is arranged outside the groove and close to the magnetic ring. The motor is reasonably structured, compact, cost-effective, installation friendly, and highly reliable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a brushless DC motor.

2. Description of the Related Art

Magnetic materials used in a rotor iron core of a high performance brushless DC motor are divided into two categories: one is weak magnetic ferrite or bonded rubidium iron boron while the other one is sintered rubidium iron boron made of strong magnetic materials. Disadvantages of above materials are as follows: 1) when weak magnetic ferrite or bonded rubidium iron boron are used in a rotor iron core, the motors, often having a Hall element and a magnetic ring inside, will have a large volume and consume large amounts of copper and iron. The cost will be relatively high; 2) when sintered rubidium iron boron made of strong magnetic materials are used for a rotor iron core, the magnetism will be extremely strong; if a Hall element and a magnetic ring are arranged inside a motor casing, the Hall element will suffer from great interference when sensing signals. Thus, the measurement accuracy will be affected leading to inaccurate or even unsuccessful control.

To solve above problems, some motor manufacturers arrange the Hall element and the magnetic ring outside the motor end cover, but following problems still exist: mounting structure layout of the Hall element and the magnetic ring is not reasonable, installation is unfriendly, reliability is poor, and cost is high.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is one objective of the invention to provide a brushless DC motor with an external magnetic ring and Hall element that is reasonably structured, compact, cost-effective, installation friendly, and highly reliable.

To achieve the above objective, in accordance with one embodiment of the invention, there is provided a brushless DC motor comprising: a motor casing, a stator component, and a rotor component, wherein the stator component and the rotor component are respectively arranged inside the motor casing; the rotor component comprises a rotor iron core and a rotating shaft supporting the rotor iron core, a shaft extension end of the rotating shaft is arranged with a magnetic ring; one end of the motor casing is arranged with an end cover, the center of the outer end surface of the end cover is arranged with a groove; the magnetic ring is arranged inside the groove; a Hall induction device is arranged outside the groove and close to the magnetic ring.

In a class of this embodiment, the Hall induction device comprises a circuit board mounted with a Hall element and an installation kit, one end of the installation kit is connected with the circuit board and the other end supports the outer end of the end cover.

In a class of this embodiment, the installation kit is arranged with a plurality of uprights; the circuit board is disposed with a plurality of through holes, the through holes are fit together with the uprights.

In a class of this embodiment, the middle part of the installation kit is arranged with a convex ring body embedded in the groove; an outer edge surface of the convex ring body fits closely with a wall surface of the groove.

In a class of this embodiment, the outer side of the groove forms a cylinder body with an installation foot arranged outside; the installation foot is arranged with a screw hole; strip-shaped holes are arranged on corresponding upper and lower positions of the circuit board and the installation kit, respectively; screws passes through the strip-shaped holes and screw holes to connect the circuit board, the installation kit, and the installation feet together.

In a class of this embodiment, the strip-shaped holes are arc-shaped and concyclic.

In a class of this embodiment, inside the groove, the magnetic ring is mounted on the shaft extension end of the rotating shaft via a circular magnetic ring bracket; the magnetic ring is mounted on outer side of the magnetic ring bracket; a hollow shaft seat engaging with the rotating shaft is arranged in the middle of the magnetic ring bracket; an outer end of the hollow shaft seat is sheathed with an axial connecting seat and an outer end of the axial connecting seat is arranged with a locknut; the locknut locks the shaft extension end of the connecting rotating shaft and tightens the axial connecting seat.

In a class of this embodiment, three positioning holes are arranged on the inner wall surface of the convex ring body to accommodate the Hall element.

In a class of this embodiment, three spokes are arranged on top of the end cover and at outer side of the cylinder body.

In a class of this embodiment, the installation kit and the circuit board are bonded together to form a whole portion, and both the installation kit and the axial connecting seat are made of nylon and glass fiber materials.

In a class of this embodiment, the rotor iron core comprises an outer ring body, an inner ring body, and a plurality of ribs connecting the outer ring body and the inner ring body, the outer side of the outer ring body is mounted with a magnetic tile and the inner ring body is sleeved with the rotating shaft.

In a class of this embodiment, the outer side wall of the magnetic ring bracket is arranged with a positioning groove, the inner wall of the magnetic ring is arranged with a positioning convex portion engaging together with the positioning groove to enable the magnetic ring to be mounted outside the magnetic ring bracket.

In a class of this embodiment, a retaining ring is arranged at the end of the magnetic ring bracket and the bottom of the positioning groove to block the bottom of the positioning convex portion.

In a class of this embodiment, the end surface of the magnetic ring bracket is arranged with a buckle; a groove is arranged on the end surface of the magnetic ring; the buckle and the groove cooperate with each other to enable the magnetic ring bracket to axially hold the magnetic ring.

In a class of this embodiment, the inner wall of the central hole of the magnetic ring bracket is arranged with a flat surface, which is cooperatively positioned with a sliced plane of the rotating shaft.

Advantages of the invention are as follows.

1) One end of the motor casing is arranged with an end cover, the center of the outer end surface of the end cover is arranged with a groove with a magnetic ring arranged inside; a Hall induction device, close to the inductive magnetic ring, is also arranged outside the groove. Consequently it is reasonably structured, installation friendly, reliable, and cost-effective. Since the interference is low when magnetic field signals of the inductive magnetic ring of the Hall element changes, it ensures sensing accuracy and stability with low noise and effective control;

2) Since the Hall element is installed on the circuit board and arranged inside the positioning hole of and a number of strip-shaped holes are arc-shaped and concyclic, it ensures installation concentricity of the Hall elements, which is installation and commissioning friendly with high sensing precision;

3) The magnetic ring is mounted on the shaft extension end of the rotating shaft through the circular magnetic ring bracket, the magnetic ring is mounted on outer side of the magnetic ring bracket; a hollow shaft seat engaging with the rotating shaft is arranged in the middle of the magnetic ring bracket; outer end of the hollow shaft seat is sheathed with an axial connecting seat and outer end of the axial connecting seat is arranged with a locknut, which locks the shaft extension end of the connecting rotating shaft and tighten the axial connecting seat, thus the structure is compact and stable;

4) A rotor iron core is composed of an outer ring body, an inner ring body and several ribs connecting the outer ring body and the inner ring body, the outer side of the outer ring body is mounted with a magnetic tile, which is characterized in that it has a reasonable structure and saves materials and costs; and

5) The outer side wall of the magnetic ring bracket is arranged with a positioning groove, the inner wall of the magnetic ring is arranged with a positioning convex portion engaging the positioning groove so as to enable the magnetic ring to be mounted on outer side wall of the magnetic ring bracket; a retaining ring is arranged at the end of the magnetic ring bracket and the bottom of the positioning groove to block the bottom of the positioning convex portion; the end surface of the magnetic ring bracket is arranged with a buckle clamping the groove arranged on end surface of the magnetic ring so as to enable the magnetic ring bracket to axially hold the magnetic ring. The magnetic ring and the magnetic ring bracket can be simply and firmly installed with accurate positioning.

DETAILED DESCRIPTION OF THE EMBODIMENTS

This invention is explained in further detail below with the aid of the example embodiments and attached drawings.

As shown inFIGS. 1-4, a brushless DC motor comprises a motor casing1, a stator component2and a rotor component3respectively arranged inside the motor casing1. The rotor component3comprises a rotor iron core4and a rotating shaft5supporting the rotor iron core4and a shaft extension end of the rotating shaft5is arranged with a magnetic ring6. One end of the motor casing1is arranged with an end cover7, the center of the outer end surface of the end cover7is arranged with a groove8with the magnetic ring6arranged inside. A Hall induction device, close to the inductive magnetic ring6, is also arranged outside the groove8.

As shown inFIGS. 1-6, the Hall induction device comprises a circuit board9mounted with a Hall element and an installation kit10, one end of the installation kit10is connected with the circuit board9and the other end supports the outer end of the end cover7. The installation kit10is arranged with a plurality of uprights11. The circuit board9is disposed with a plurality of through holes12. The through holes12fit together with the uprights11. The middle part of the installation kit10is arranged with a convex ring body13, which is embedded in the groove8. The outer edge surface of the convex ring body13fit closely with the wall surface of the groove8. The outer side of the groove8forms a cylinder body14. An installation foot15is arranged outside the cylinder body14. The installation foot15is arranged with a screw hole16. Strip-shaped holes18are arranged on corresponding upper and lower positions of the circuit board9and the installation kit10, respectively. The screws19passes through the strip-shaped hole18and the screw hole16to connect the circuit board9, the installation kit10, and the installation feet15together. The strip-shaped holes18are arc-shaped and concyclic. Inside the groove8, the magnetic ring6is mounted on the shaft extension end of the rotating shaft5through the circular magnetic ring bracket20. The magnetic ring6is mounted on the outer side of the magnetic ring bracket20. The middle of the magnetic ring bracket20is arranged with a hollow shaft seat21engaging with the rotating shaft5. The outer end of the hollow shaft seat21is arranged with an axial connecting seat22, the outer end of the axial connecting seat22is arranged with a locknut23, which locks the shaft extension end of the connecting rotating shaft5and tighten the axial connecting seat22. Three positioning holes24are arranged on inner wall surface of the convex ring body13to accommodate the Hall element. Three spokes25are arranged on top of the end cover7and outer side of the cylinder body14.

The installation kit10and circuit board9are bonded together to form a whole portion, and both the installation kit10and axial connecting seat22are made of nylon and glass fiber materials.

As shown inFIGS. 7-10, the rotor iron core4comprises an outer ring body41, an inner ring body42and a plurality of ribs43connecting the outer ring body41and the inner ring body42. The outer side surface of the outer ring body41is mounted with a magnetic tile25and the inner ring body42is sleeved on the rotating shaft5. The outside wall of the magnetic ring bracket20is arranged with a positioning groove211. The inner wall of the magnetic ring6is arranged with a positioning convex portion61engaging with the positioning groove211so as to enable the magnetic ring6to be mounted outside of the magnetic ring bracket20. A retaining ring212is arranged at the end of the magnetic ring bracket20and the bottom of the positioning groove211and the retaining ring212blocks the bottom of the positioning convex portion61. The end surface of the magnetic ring bracket20is arranged with a buckle213. A groove62is arranged on the end surface of the magnetic ring6. The buckle and the groove cooperate with each other to enable the magnetic ring bracket20to axially hold the magnetic ring6. The inner wall of the central hole214of the magnetic ring bracket20is arranged with a flat surface215, which is cooperatively positioned with a sliced plane51of the rotating shaft5.

The principle of the invention is summarized below: the motor casing is arranged with an external magnetic ring and a Hall element, which is characterized in that it is reasonably structured, compact, cost-effective, installation friendly, and highly reliable. Since the interference is low when magnetic field signals of the inductive magnetic ring of the Hall element changes, it ensures sensing accuracy and stability with low noise and effective control.