CN116505685A - Motor - Google Patents

Abstract

The invention provides a motor. The accuracy of the position estimation of the rotor is improved. The rotor of the motor according to one embodiment includes: a rotor core (31) formed of a magnetic material; a plurality of magnets (33 a-33 j), wherein the plurality of magnets (33 a-33 j) are arranged on the rotor core (31) along the rotation direction of the rotor; and a plurality of Hall elements which are arranged on a common mounting surface (41 a) and can detect the magnetic fields of the magnets (33 a-33 j). The lower end surfaces (38) of the magnets (33 a-33 j) that face the mounting surface (41 a) are at a constant height relative to the mounting surface (41 a). On the other hand, the height of the lower end surface (31 b) of the rotor core (31) facing the mounting surface (41 a) relative to the mounting surface (41 a) varies along the rotation direction of the rotor.

Description

Motor

Technical Field

The present invention relates to a motor.

Background

Motors having a position sensor for detecting the position of a rotor are known. The position sensor uses an optical sensor, a magnetic sensor, or the like. An optical encoder is given as an example of the optical sensor, and a hall element is given as an example of the magnetic sensor.

Patent document 1: japanese patent No. 6233532

In a motor having a plurality of hall elements serving as position sensors, the position of a rotor may be estimated using characteristics of voltages (hall signals) output from the hall elements.

The size, shape, material characteristics, mounting positions, and the like of the plurality of hall elements mounted on the 1 motor are not exactly the same. That is, there is a deviation in the plurality of hall elements mounted on 1 motor. As a result, the hall signals output from the hall elements have unique characteristics due to the variations. Therefore, by causing the microcomputer to learn the features present in the hall signals output from the hall elements, the microcomputer can be caused to infer the position of the rotor.

However, the characteristics of the hall signal are randomly generated due to various deviations. Therefore, it is occasionally possible to mount 2 or more hall elements that output hall signals having the same or substantially the same characteristics on 1 motor. In this case, the position of the rotor may be erroneously estimated.

Disclosure of Invention

The motor of one embodiment has a stator and a rotor. The rotor has: a rotor core formed of a magnetic material; a plurality of magnets arranged on the rotor core along a rotation direction of the rotor; and a plurality of magnetic sensors disposed on a common mounting surface, the plurality of magnetic sensors being capable of detecting a magnetic field of the magnet. The lower end surface of each of the magnets facing the mounting surface is constant in height with respect to the mounting surface. On the other hand, the height of the lower end surface of the rotor core facing the mounting surface with respect to the mounting surface varies along the rotation direction of the rotor.

According to one embodiment of the present invention, a motor is provided in which accuracy of position estimation of a rotor is improved.

Drawings

Fig. 1 is an exploded perspective view showing the construction of a motor of an embodiment.

Fig. 2 is a perspective view showing the configuration of a motor of an embodiment.

Fig. 3 is a sectional view showing the configuration of a motor of an embodiment.

Fig. 4 is a functional block diagram of a motor of one embodiment.

Fig. 5 is a front view of a rotor of an embodiment.

Fig. 6A is a side view of a rotor core of an embodiment.

Fig. 6B is a perspective view of a rotor core according to an embodiment.

Fig. 7 is a schematic view showing an overlapping area of a rotor core and each magnet according to one embodiment.

Fig. 8A is a side view of a rotor core according to another embodiment.

Fig. 8B is a perspective view of a rotor core according to another embodiment.

Fig. 9 is a schematic view showing the overlapping area of the rotor core and each magnet according to another embodiment.

Description of the reference numerals

1A: a motor; 10: a housing; 11a: a base member; 11b: a cover member; 12: a bottom wall portion; 13a, 13b: a fixing piece; 14a, 14b: a rib; 15: a through hole; 16: a shaft holder; 17: a peripheral wall portion; 18: a top wall portion; 20: a stator; 21: a stator core; 22: teeth; 23: an insulating member; 24: a coil; 30: a rotor; 31. 131: a rotor core; 31a, 131a: an outer peripheral surface; 31b, 131b: a lower end surface; 31c, 131c: an upper end surface; 131d: a concave portion; 32: a rotor hub; 32a: a side surface portion; 32b: an upper surface portion; 33. 33a, 33b, 33c, 33d, 33e, 33f, 33g, 33h, 33i, 33j: a magnet; 34: a shaft; 35a, 35b: a bearing; 36: a spring washer; 37: a pinion gear; 38: a lower end surface; 40: a substrate; 41: a main body portion; 41a: a surface (mounting surface); 42: a lead-out part; 50. 50u, 50v, 50w: a Hall element; 60: an amplifying section; 61: a position estimating unit; 62: a control unit; 63: a driving section; c: a central axis; d1, d2: spatial distance.

Detailed Description

An embodiment of the present invention will be described below with reference to the drawings. In all the drawings referred to for the purpose of describing the embodiments, the same or substantially the same structures are denoted by the same reference numerals. In addition, the structure already described is not repeated in principle.

Fig. 1 is an exploded perspective view showing the structure of a motor 1A of the present embodiment. Fig. 2 is a perspective view showing the configuration of the motor 1A. Fig. 3 is a cross-sectional view showing the structure of the motor 1A. The cross section shown in fig. 3 is a cross section when the motor 1A is cut along the line X-X in fig. 2.

Summary of motor

The motor 1A includes a housing 10, a stator 20, a rotor 30, a base plate 40, and the like. The rotor 30 housed in the casing 10 is disposed radially inward of the stator 20 similarly housed in the casing 10, and is rotatable with respect to the stator 20. That is, the motor 1A is an inner rotor type motor.

< Shell >

The housing 10 is composed of 2 parts combined with each other. More specifically, the housing 10 is constituted by a base member 11a and a cover member 11 b. In fig. 2 and 3, the cover member 11b is not shown. The base member 11a has a bottom wall portion 12, a pair of fixing pieces 13a, 13b, and a pair of ribs 14a, 14b.

The bottom wall portion 12 of the base member 11a is circular or substantially circular, and a through hole 15 is provided at the center thereof. A cylindrical shaft holder 16 communicating with the through hole 15 is provided in the bottom wall portion 12 of the base member 11 a.

The fixing pieces 13a, 13b extend from the edge of the bottom wall portion 12 in parallel with the bottom wall portion 12. On the other hand, the ribs 14a, 14b stand perpendicularly from the edge of the bottom wall portion 12 to the bottom wall portion 12. Screw holes through which screws for fixing the motor 1A at a predetermined position are inserted are formed in the respective fixing pieces 13a, 13 b. In addition, the ribs 14a, 14b are curved along the edges of the bottom wall 12.

The cover member 11b has a cylindrical peripheral wall portion 17 and a top wall portion 18 closing one end of the peripheral wall portion 17. When the base member 11a and the cover member 11b are combined, the peripheral wall portion 17 of the cover member 11b is disposed outside the ribs 14a, 14b of the base member 11a, and the top wall portion 18 of the cover member 11b is opposed to the bottom wall portion 12 of the base member 11 a. As a result, a storage space surrounded by the peripheral wall 17 is formed between the bottom wall 12 and the top wall 18. Further, a part of the storage space is doubly surrounded by the ribs 14a, 14b and the peripheral wall 17.

< stator >

The stator 20 is formed in a ring shape surrounding the rotor 30 and is fixed to the inside of the casing 10. A predetermined gap (air gap) is provided between the stator 20 and the rotor 30.

The stator 20 has a stator core 21 fixed to the inner peripheral surface of the housing 10. The stator core 21 is formed of a plurality of stacked electromagnetic steel sheets. The stator core 21 has a plurality of teeth 22 protruding toward the radial inside (toward the rotor 30). More specifically, the stator core 21 has 12 teeth 22 arranged at 30-degree intervals. In other words, the stator 20 has 12 slots.

The stator 20 has, in addition to the stator core 21, an insulator 23 provided around each tooth 22 and a coil 24 provided around each insulator 23.

The insulator 23 is formed of an insulating material (for example, a resin material). The coil 24 is formed of a wire (e.g., copper alloy wire) wound around the insulator 23.

4 of the 12 coils 24 are U-phase coils, the other 4 are V-phase coils, and the remaining 4 are W-phase coils. In other words, three-phase currents whose phases are shifted 120 degrees each time are input to the stator 20. The coils 24 of the U-phase, V-phase, and W-phase are excited when a current (coil current) is supplied thereto, and generate a magnetic field acting on the rotor 30.

< rotor >)

The rotor 30 includes a rotor core 31, a rotor hub 32, a magnet 33, and a shaft 34, and the rotor 30 is rotatable about a central axis C as a rotation axis. Here, the direction of the central axis C is defined as the up-down direction. According to this definition, the base member 11a and the cover member 11b constituting the housing 10 are opposed in the up-down direction. More specifically, the bottom wall portion 12 of the base member 11a and the top wall portion 18 of the cover member 11b face each other in the up-down direction. In the following description, for convenience, the side of the bottom wall portion 12 may be referred to as "lower side" or "lower side", and the side of the top wall portion 18 may be referred to as "upper side" or "upper side". The rotation direction of the rotor 30 with the central axis C as the rotation axis is sometimes referred to as a "circumferential direction".

The rotor core 31 is formed of a magnetic material and has a cylindrical shape extending in the up-down direction. A rotor hub 32 is provided inside the rotor core 31, and a plurality of magnets 33 are provided outside the rotor core 31. The shape of rotor core 31 will be described in detail later.

The rotor hub 32 has a cylindrical side surface portion 32a having an outer diameter smaller than the inner diameter of the rotor core 31, and a disc-shaped upper surface portion 32b closing one end of the side surface portion 32 a. The side surface portion 32a and the upper surface portion 32b are integrally formed of a nonmagnetic material.

Rotor hub 32 is fitted inside rotor core 31, and both are fixed so as not to rotate relative to each other. More specifically, the inner peripheral surface of rotor core 31 and the outer peripheral surface of rotor hub 32 are fixed to each other. That is, rotor core 31 is integrated with rotor hub 32.

The plurality of magnets 33 are arranged on the rotor core 31 along the rotation direction (circumferential direction) of the rotor 30. More specifically, 10 magnets 33 are arranged on rotor core 31 at equal intervals in the circumferential direction. The 10 magnets 33 are arranged such that N poles and S poles are alternately arranged in the circumferential direction. Further, each magnet 33 is fixed (bonded) to the outer peripheral surface of rotor core 31.

The shaft 34 is fixed to the rotor hub 32. More specifically, the base end of the shaft 34 penetrates the shaft holder 16 to protrude from the shaft holder 16. And, the base end of the shaft 34 protruding from the shaft holder 16 is pressed into the center of the rotor hub 32.

The shaft 34 is rotatably supported by bearings 35a and 35b provided in the shaft holder 16. The bearings 35a and 35b are stacked one above the other, and a spring washer 36 is interposed between these bearings 35a and 35 b.

On the other hand, the tip end of the shaft 34 penetrates the bottom wall portion 12 of the base member 11a and protrudes from the housing 10. A pinion 37 is attached to the tip of the shaft 34 protruding from the housing 10.

< substrate >

The substrate 40 is a flexible substrate. A part of the substrate 40 is disposed inside the case 10, and another part of the substrate 40 is led out of the case 10. In the following description, a part of the substrate 40 disposed in the case 10 is sometimes referred to as a "main body portion 41", and another part of the substrate 40 drawn out of the case 10 is sometimes referred to as a "drawn-out portion 42". However, such distinction is merely for convenience of explanation.

The main body 41 of the base plate 40 has a disk shape covering substantially the entire area of the bottom wall 12 of the base member 11a so as to avoid the shaft holder 16. On the other hand, the lead portion 42 has a strip shape extending outside the case 10 through between the fixing piece 13a of the base member 11a and the rib 14b.

< magnetic sensor >)

A plurality of magnetic sensors capable of detecting the magnetic field of the magnet 33 provided to the rotor 30 are mounted on the substrate 40. More specifically, 3 hall elements 50u, 50v, 50w are mounted on the substrate 40. As the magnetic sensor, an element that outputs a change in magnetic flux as an analog signal, such as a hall element or a linear hall IC, is used, but in the present invention, a hall element is used as a representative. The hall elements 50u, 50v, 50w are mounted on the surface 41a of the main body 41 at equal intervals in the circumferential direction. That is, the surface 41a of the body 41 is a mounting surface shared by the 3 hall elements 50u, 50v, and 50 w. Therefore, in the following description, the surface 41a of the body portion 41 may be referred to as "mounting surface 41a". The hall elements 50u, 50v, and 50w may be collectively referred to as "hall element 50".

The hall element 50U is a magnetic sensor for detecting the magnetic field strength of the U phase, and outputs a voltage (hall signal/differential signal) corresponding to the magnetic field strength of the U phase. The hall element 50V is a magnetic sensor for detecting the magnetic field intensity of the V-phase, and outputs a voltage (hall signal/differential signal) corresponding to the magnetic field intensity of the V-phase. The hall element 50W is a magnetic sensor for detecting the magnetic field strength of the W phase, and outputs a voltage (hall signal/differential signal) corresponding to the magnetic field strength of the W phase.

The hall elements 50u, 50v, 50w are electrically connected to wiring lines formed on the substrate 40. Hall signals output from the hall elements 50u, 50v, 50w are input to a predetermined device, processing unit, control unit, or the like via wiring formed on the substrate 40.

Fig. 4 is a functional block diagram of the motor 1A. The motor 1A includes an amplifying unit 60, a position estimating unit 61, a control unit 62, a driving unit 63, and the like. Hall signals output from the hall elements 50u, 50v, 50w are input to the amplifying section 60 via the substrate 40. The amplifying unit 60 amplifies the input hall signal and outputs the amplified hall signal to the position estimating unit 61.

The position estimating unit 61 is an information processing device for estimating the position of the rotor 30, and includes an arithmetic unit, a storage unit, and the like. The position estimating unit 61 estimates the position of the rotor 30 from a value calculated based on the input hall signal, information stored in the storage unit in advance, and the like, and outputs the estimation result to the control unit 62. The position estimating unit 61 can estimate the position of the stopped rotor 30, the position of the rotating rotor 30, and the like.

The control unit 62 generates a control signal based on the position of the rotor 30 estimated by the position estimating unit 61 and an instruction signal input from an external device, and outputs the control signal to the driving unit 63. The instruction signal is a signal indicating, for example, a rotation direction, a rotation force, a rotation angle, a rotation speed, or the like of the rotor 30. The control signal is, for example, a signal indicating a register value corresponding to the rotation direction indicated by the instruction signal, a signal indicating a current value of the current output from the driving unit 63 to the stator 20, or the like.

The driving unit 63 drives the stator 20 according to the inputted control signal. The driving unit 63 rotates the rotor 30 in the indicated direction at the indicated speed by, for example, supplying three-phase currents of current values indicated by control signals to the coils 24 of the stator 20.

< shape of rotor core >)

Fig. 5 is a front view of the rotor 30. Fig. 6A is a side view of rotor core 31, and fig. 6B is a perspective view of rotor core 31. Fig. 7 is a schematic diagram showing the overlapping area of the outer circumferential surface 31a of the rotor core 31 and each magnet 33. In other words, fig. 7 is an expanded view of rotor core 31.

As described above, 10 magnets 33 having N poles and S poles alternately arranged in the circumferential direction are attached to the outer circumferential surface 31a of the rotor core 31. That is, rotor core 31 is provided behind (inside) 10 magnets 33 arranged in a ring shape, and functions as a back yoke.

The intervals of 10 magnets 33 in the circumferential direction (arrangement direction) are constant, and the heights of 10 magnets 33 with respect to the mounting surface 41a are also constant. Here, the height of the magnet 33 relative to the mounting surface 41a refers to the shortest linear distance from the mounting surface 41a to the lower end surface 38 of the magnet 33 facing the mounting surface 41 a.

In the following description, for convenience, 10 magnets 33 may be referred to as "magnets 33a", "magnets 33b", "magnets 33c", and the like, respectively.

The height of 10 magnets 33 with respect to mounting surface 41a is constant, while on the other hand, the height of rotor core 31 with respect to mounting surface 41a is not constant. More specifically, the height of rotor core 31 with respect to mounting surface 41a varies along the circumferential direction. The height of rotor core 31 relative to mounting surface 41a is the shortest linear distance from mounting surface 41a to lower end surface 31b of rotor core 31 facing mounting surface 41 a.

In other words, the width w of the rotor core 31 continuously narrows toward one circumferential side. In other words, the width w of the rotor core 31 continuously widens toward the other circumferential side. Therefore, when the upper end surface 31c of the rotor core 31 is made horizontal, the lower end surface 31b of the rotor core 31 has a gradient gradually approaching the upper end surface 31c in the circumferential direction (gradually departing from the upper end surface 31 c). As a result, the height of rotor core 31 with respect to mounting surface 41a gradually increases or decreases in the circumferential direction.

The height of the magnet 33 is constant, while the height of the rotor core 31 is changed as described above, so that the overlapping area of the rotor core 31 and each magnet 33 is different. Specifically, the magnets 33a, 33b, 33c, 33d, 33e, 33f, 33g, 33h, 33i, 33j are sequentially arranged in the circumferential direction. The magnets 33a located at one end in the arrangement direction are disposed in the region where the width of the rotor core 31 is the widest, and the magnets 33j located at the other end in the arrangement direction are disposed in the region where the width of the rotor core 31 is the narrowest. In other words, magnet 33a is magnet 33 having the largest overlapping area with rotor core 31, and magnet 33j is magnet 33 having the smallest overlapping area with rotor core 31. The area of the magnets 33 overlapping the rotor core 31 gradually decreases in the order of the magnets 33a to 33 j.

As described above, in the present embodiment, the overlapping area of the rotor core 31 functioning as the back yoke and each magnet 33 is different. Therefore, the magnetic resistance of the magnetic circuit including the magnetic flux of one magnet 33 and the hall element 50 does not coincide with the magnetic resistance of the magnetic circuit including the magnetic flux of the other magnet 33 and the hall element 50.

Therefore, the hall element 50 outputs hall signals having different magnitudes (voltages) for each magnet 33. More specifically, even if the characteristics and the like of the 3 hall elements 50u, 50v, 50w mounted on the motor 1A are accidentally matched, the maximum value and the minimum value of the hall signals outputted from the hall elements 50u, 50v, 50w are different for each magnet 33.

As a result, hall signals having the same or substantially the same characteristics are not output from the hall elements 50 of 2 or more, and the accuracy of estimating the position of the rotor 30 improves.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit and scope thereof. For example, the shape of the rotor core is not limited to the above-described shape. Fig. 8A is a side view of a rotor core 131 in another embodiment, and fig. 8B is a perspective view of the rotor core 131. Fig. 9 is a schematic diagram showing the overlapping area of the outer circumferential surface 131a of the rotor core 131 and each magnet 33.

A plurality of concave portions 131d curved so as to approach the upper end surface 131c are provided along the circumferential direction on the lower end surface 131b of the rotor core 131. When the rotor core 31 (fig. 6A and 6B) of the above-described embodiment is replaced with the rotor core 131 shown in fig. 8A and 8B, the height of the lower end surface 131B of the rotor core 131 with respect to the mounting surface 41a changes along the rotation direction (circumferential direction) of the rotor 30.

As shown in fig. 9, the rotor core 131 and the magnets 33 disposed on the rotor core 131 have different overlapping areas. Therefore, according to the same principle as that described above, the probability of outputting hall signals having the same or substantially the same characteristics from 2 or more hall elements 50 becomes low, and the accuracy of estimating the position of the rotor 30 improves.

However, the shape of rotor core 31 (fig. 6A, 6B) is not symmetrical, while the shape of rotor core 131 (fig. 8A, 8B) is symmetrical. Therefore, when comparing rotor core 31 and rotor core 131, rotor core 31 is more excellent from the standpoint of accuracy of the position estimation of the rotor.

However, when the rotor core 131 (fig. 8A and 8B) is compared with a conventional rotor core (a rotor core in which the upper end surface and the lower end surface are planes parallel to each other), the rotor core 131 is more excellent in accuracy of estimating the position of the rotor.

The number of teeth 22, magnets 33, and hall elements 50 can be changed as appropriate. Fig. 4 shows only one example of the functional block, and the input destination of the hall signal is not limited to the amplifying section 60.

Claims (5)

1. A motor having a stator and a rotor, wherein,

the rotor has:

a rotor core formed of a magnetic material;

a plurality of magnets arranged on the rotor core along a rotation direction of the rotor; and

a plurality of magnetic sensors disposed on a common mounting surface, capable of detecting a magnetic field of the magnet,

the height of the lower end face of each of the magnets facing the mounting face is constant with respect to the mounting face,

a height of a lower end surface of the rotor core facing the mounting surface with respect to the mounting surface varies along a rotation direction of the rotor.

2. The motor according to claim 1, wherein,

the overlapping area of the rotor core and each of the magnets is different.

3. The motor according to claim 1 or 2, wherein,

the height of the lower end face of the rotor core with respect to the mounting face gradually increases or decreases in the rotation direction of the rotor.

4. The motor according to claim 1 or 2, wherein,

the rotor also has a rotor hub formed of a non-magnetic body,

the inner peripheral surface of the rotor core is fixed to the outer peripheral surface of the rotor hub,

the plurality of magnets are fixed to an outer peripheral surface of the rotor core.

5. The motor according to claim 1 or 2, wherein,

the motor includes a position estimating unit that estimates a position of the rotor based on a signal output from the magnetic sensor.