MOTOR

The present invention provides a motor including a shaft, a rotor coupled to the shaft, a stator positioned to correspond to the rotor, a holder disposed at one side of the shaft, and a sensing magnet disposed on the holder, wherein the shaft includes a body and a screw extending from the body in a radial direction, and the screw is disposed in the holder.

TECHNICAL FIELD

The present invention relates to a motor.

BACKGROUND ART

A motor includes a rotor and a stator. The rotor rotates due to an electrical interaction between the rotor and the stator. In addition, a shaft coupled to the rotor rotates. A detection unit including a magnetic element is disposed inside the motor. The magnetic element detects a magnetic force of a sensing magnet which rotates with the shaft to check a current position of the rotor.

However, since a fixing force between the sensing magnet and the shaft is low, there is a possibility that the sensing magnet is separated from the shaft. Accordingly, there is a problem of reducing the sensing sensitivity of the magnetic element.

DISCLOSURE

Technical Problem

Accordingly, the present invention is directed to providing a motor in which a fixing force between a shaft and a holder is increased.

Technical Solution

One aspect of the present invention provides a motor including a shaft, a rotor coupled to the shaft, a stator positioned to correspond to the rotor, a holder disposed at one side of the shaft, and a sensing magnet disposed on the holder, wherein the shaft includes a body and a screw extending from the body in a radial direction, and the holder includes a groove in which the screw is disposed.

Advantageous Effects

According to an embodiment, a shaft and a holder can be fastened using a screw to increase a fixing force between the shaft and the holder, and a sensing magnet can be stably fixed to improve the detection performance of a magnetic element.

According to an embodiment, the management of a press-fit tolerance between a holder and a shaft is easy, and the shaft can be coupled to the holder without a press-fit process in some cases, and thus a motor which is easy to manufacture and is reliable is provided.

MODES OF THE INVENTION

A direction parallel to a longitudinal direction (vertical direction) of a shaft is referred to as an axial direction, a direction perpendicular to the axial direction of the shaft is referred to as a radial direction, and a direction along a circle having a radius in the radial direction from the shaft is referred to as a circumferential direction.

FIG.1is a cross-sectional view illustrating a motor according to one embodiment of the present invention.

Referring toFIG.1, a motor includes a shaft100, a rotor200, a stator300, a housing400, a holder500, a sensing magnet600, and a circuit board700.

Hereinafter, the term “inward” is a direction from the housing400toward the shaft100which is a center of the motor, and the term “outward” is a direction opposite to “inward,” that is, a direction from the shaft100toward the housing400.

The shaft100may be coupled to the rotor200. When a current is supplied and an electromagnetic interaction occurs between the rotor200and the stator300, the rotor200rotates, and the shaft100rotates in conjunction with the rotor200. The shaft100may be coupled to a steering system of a vehicle to transmit power to the steering system.

The rotor200rotates due to an electrical interaction between the rotor200and the stator300. The rotor200may be disposed inside the stator300. The rotor200may include a rotor core and a rotor magnet disposed on the rotor core.

The stator300is disposed outside the rotor200. The stator300may include a stator core, a coil, and an insulator mounted on the stator core310. The coil may be wound around the insulator330. The insulator is disposed between the coil and the stator core. The coil induces an electrical interaction with the rotor magnet.

The housing400may be disposed outside the stator300. The housing400may be a cylindrical member of which one side is open. A shape or a material of the housing400may be variously changed, and a metal material which can withstand high temperatures may be selected.

The holder500is coupled to the shaft. The holder500rotates in conjunction with the rotor200and the shaft100. The holder500may be a non-magnet.

The sensing magnet600is coupled to the shaft100to operate in conjunction with the rotor200. The sensing magnet600is a device for detecting a position of the rotor200.

The circuit board700may be disposed to be spaced apart from the shaft100. The circuit board700may be a printed circuit board (PCB). In addition, a sensor710may be mounted on the circuit board700. The sensor710may be disposed to face the sensing magnet600. The sensor710may be spaced apart from the sensing magnet600. The sensor710may be a Hall integrated circuit (IC). The sensor710may detect changes in N and S poles of the sensing magnet600to generate a sensing signal.

FIG.2is a perspective view illustrating the shaft, andFIG.3is a perspective view illustrating the holder.FIG.4is a perspective view illustrating the shaft, the holder, and the sensing magnet, andFIG.5is an exploded perspective view illustrating the shaft, the holder, and the sensing magnet.

Referring toFIGS.2to5, the shaft100may include a body110and a screw120. The body110may include a first end portion111and a second end portion (not shown). The first end portion111may be press-fitted into the holder500. A rounded portion111R may be disposed at an edge of the first end portion111. In addition, the body110may include a protrusion111S disposed on the first end portion111. A diameter of the protrusion111S may be smaller than a diameter of the body110.

The shaft100includes the screw120. The screw120may be disposed closer to the first end portion111than the second end portion (not shown). The screw120may be disposed at a predetermined distance from the first end portion111. The screw120may protrude from an outer circumferential surface of the shaft100in a radial direction. In addition, the screw120may extend in a helical shape. However, the present invention is not limited thereto, and the screw120may be designed in a variety of shapes protruding from the body110in the radial direction. The screw120may be inserted into the holder500. In this case, the shaft100may rotate to be inserted into the holder500. In addition, in a process in which the shaft100is inserted into the holder500, the screw120may rotate and form a helical groove502in the holder500.

The shaft100may be formed of a steel material. The body110and the screw120may be integrally formed. In this case, thermal processing may be performed on the screw120before the screw120is press-fitted into the holder500. The thermal processed screw120may have a hardness greater than a hardness of the body110.

The holder500may have a cylindrical shape. The holder500may have an inner space. The sensing magnet600may be disposed at one side in the space. The sensing magnet600may be press-fitted into the holder500. In addition, the first end portion111of the shaft100may be disposed at the other side in the space. The shaft100may be press-fitted into the holder500. In this case, the first end portion111may be disposed at an axial distance from the sensing magnet600. Accordingly, a gap G may be formed between the first end portion111and the sensing magnet600. An adhesive may be disposed in the gap G.

The holder500may include a hole501. The hole501may be provided as a plurality of holes501. The holes501may be disposed in a circumferential direction. The plurality of holes501may be disposed at equal intervals. The adhesive may fill the gap G through the holes501. The holes501may pass through the holder500from an inner circumferential surface500A to an outer circumferential surface500B. In addition, a diameter of the hole501formed in the inner circumferential surface500A may be smaller than a diameter of the hole501formed in the outer circumferential surface500B.

The holder500may include the groove502formed in the inner circumferential surface500A. The groove502may be formed in the helical shape. The screw120may be disposed in a part of the groove502. The holder500may be formed of a steel material. The holder500may have a hardness lower than the hardness of the screw120.

The shaft100may be press-fitted into the holder. The first end portion111may be disposed in the holder500. The sensing magnet600may be fixed in the holder500. The sensing magnet600may be in contact with a part of the inner circumferential surface500A of the holder500. In addition, the shaft100may be in contact with another part of the inner circumferential surface500A of the holder500.

The shaft100may rotate to be press-fitted into the holder500. Accordingly, the screw120may rotate and rub against the inner circumferential surface500A. In this case, the screw120may have the hardness greater than a hardness of the inner circumferential surface500A. According to the embodiment, the groove502may be formed so that the inner circumferential surface500A is worn by the screw120in a process in which the shaft100is press-fitted into the holder500. The groove502may be formed in a region through which the screw120passes. In addition, after the shaft100is press-fitted into the holder500, an adhesive may be injected through the hole501to increase a fixing force between the shaft100and the holder500.

The groove502may include a first region502A and a second region502B. The screw120may be disposed in the first region502A. In addition, the second region502B may be a region other than the first region502A. The screw120may not be disposed in the second region502B. The second region502B may be formed while the screw120passes.

An inner diameter of the holder500may be smaller than or equal to an outer diameter of the shaft100. In this case, the shaft100may be press-fitted into the holder500. The holder500may include the inner circumferential surface500A and the outer circumferential surface500B. The inner circumferential surface500A of the holder may be in contact with the outer circumferential surface of the shaft100. Meanwhile, the inner diameter of the holder500may also be greater than the outer diameter of the shaft100. In this case, the shaft100may slide into the holder500. A first gap (not shown) may be formed between the inner circumferential surface500A of the holder500and the outer circumferential surface of the shaft100. Conventionally, the management of a press-fit tolerance between the holder and the shaft is difficult, but in the motor according to the present invention, managing a tolerance between the inner circumferential surface of the holder and the outer circumferential surface of the shaft is easy.

The sensing magnet600may be press-fitted into the holder500. The sensing magnet600includes a first surface601, a second surface602, and a third surface603. The first surface601and the second surface602are disposed in an axial direction. The first surface601is disposed to face the shaft100. The first surface601may be spaced apart from an end portion of the shaft100. In addition, the second surface602is disposed to face an opposite side of the first surface601. The second surface602may face the sensor710(illustrated inFIG.1). The first surface601and the second surface602are connected by the third surface603. The third surface603may be provided as one or more third surfaces603. The third surface603may be a curved surface but is not limited thereto. The holder500may surround the third surface603.

FIG.6is a cross-sectional view illustrating the shaft, the holder, and the sensing magnet.

Referring toFIG.6, the screw120may be disposed in a part of the groove502. In addition, an outer circumferential surface of the body110may be in contact with the inner circumferential surface500A. Meanwhile, the first gap may be formed between the outer circumferential surface500A of the body110and the inner circumferential surface500A. In this case, the shaft100may be press-fitted into or slid in the holder500.

The screw120may be in contact with the holder500. In addition, the screw120may be fastened to the groove502. The screw120may be fixed in the groove502without movement in axial and radial directions. The radial length of the screw120may be greater than a distance between the body110and the inner circumferential surface500A of the holder500.

The screw120may extend in a helical direction. The screw120may include a blade121disposed to face outward. The blade121may have a shape of which a thickness decreases toward the holder500. In this case, the inner circumferential surface500A of the holder500may be worn by the blade121to form the groove502. A hardness of the blade121may be greater than the hardness of the inner circumferential surface500A of the holder500. The shape of the screw120may be designed in a variety of shapes other than the helical shape.

The adhesive may be injected through the hole501. The injected adhesive may be disposed in the gap G in the holder500. The adhesive may couple the sensing magnet600and the first end portion111. The adhesive may be disposed in the hole501. The hole501may be closed by the adhesive. A width of the hole501may increase from the outer circumferential surface500B toward the inner circumferential surface500A.

FIG.7is a cross-sectional view illustrating a shaft, a holder, and a sensing magnet of a motor according to another embodiment of the present invention. The present embodiment is the same as the motor illustrated inFIG.5except for the shape of the holder. Accordingly, same reference numerals will be assigned to components which are the same as the components inFIG.6, and repetitive descriptions thereof will be omitted.

Referring toFIG.7, a holder800may include a first member810. The first member810may be disposed between a sensing magnet600and a first end portion111. The first member810may include a first groove811. A protrusion111S may be disposed in the first groove811. The first member810may divide an inner space of the holder800. The sensing magnet600may be press-fitted into one side of the divided space, and a shaft100may be press-fitted into the other side.

The holder800may include an inner circumferential surface800A and an outer circumferential surface800B. The inner circumferential surface800A may include a first region A1and a second region A2. The first member810may be disposed between the first region A1and the second region A2. The first region A1may be in contact with the press-fitted sensing magnet600. In addition, the press-fitted shaft100may be disposed in the second region A2. A second groove802in which a screw120is disposed may be formed in the second region A2. In this case, a part of the screw120may not overlap the holder800. According to the embodiment, the shaft and the holder may be connected using the screw to increase a fixing force between the shaft and the holder, and the sensing magnet may be stably fixed to improve the detection performance of a magnetic element.

In the above embodiments, an example of an inner rotor type motor has been described, but the present invention is not limited thereto. The present invention can also be applied to an outer rotor type motor. In addition, the present invention can be used in various devices such as vehicles or home appliances.