JP7846856B2 - Magnet fixing structure - Google Patents

Description

This invention relates to a fixing structure for a magnet used to detect the rotational speed of the rotating shaft of a rotating electric machine.

Conventionally, a magnet was fixed to the output shaft of a rotating electric machine, and a Hall IC was placed opposite this magnet.
A technique for detecting the rotational speed of a rotating electric machine by arranging a [specific component] is known (see, for example, Patent Document 1).

The magnet fixing structure described in Patent Document 1 has a collar interposed between the magnet and the rotating shaft. This collar is integrally formed with a fixing portion that is press-fitted onto the rotating shaft, a stress transmission prevention portion that is enlarged from the fixing portion, and a side portion that is bent outward from the stress transmission prevention portion and is adhesively fixed to the magnet. By providing multiple protrusions that contact the inner circumferential surface of the magnet on this stress transmission portion, when the magnet is press-fitted onto the rotating shaft, the stress transmission portion elastically deforms and the deformation stress is absorbed.

Japanese Utility Model Publication No. 6-74074

In recent years, vehicle brakes capable of emergency braking require high-output brushless motors, necessitating accurate detection of the rotational speed of the rotating electric motor. The magnet fixing structure described in Patent Document 1 absorbs deformation stress by having multiple protrusions contact the inner circumferential surface of the magnet. As a result, localized stress is applied to the magnet from the protrusions, potentially causing the magnet to break. If the magnet breaks, it becomes impossible to accurately detect the rotational speed of the rotating electric motor, reducing the reliability of the rotating electric motor.

In light of these circumstances, there is a need for a fixing structure for a magnet that detects the rotational speed of a rotating shaft, which can improve the reliability of rotating electric machines.

(Feature configuration)
The magnet fixing structure according to the present invention is
An annular fixing member attached to the rotating shaft of a rotating electric machine,
The fixed member is attached to at least one magnet for detecting the rotational speed of the rotating shaft,
The aforementioned fixing member,
A cylindrical portion that is fitted over the entire circumference of the aforementioned rotating shaft,
A disc-shaped connecting portion that is bent perpendicularly from the aforementioned cylindrical portion,
It integrally includes a magnet fixing portion located on the same disc as the aforementioned connecting portion but outside the aforementioned connecting portion,
The magnet fixing portion is provided with a first hole into which a part of the magnet is inserted along the extension direction of the rotation shaft.
In the connecting portion, when viewed in the direction along the rotation axis, a second hole is provided between all of the first holes and the cylindrical portion.
The first and second holes are formed on different planes perpendicular to the rotation axis with respect to the inner circumferential surface of the cylindrical portion that abuts against the outer circumferential surface of the rotation axis.

(effect)
The fixing structure of this configuration includes a cylindrical portion that fits over the entire circumference of the rotating shaft. This increases the contact area of the fixing member with respect to the rotating shaft, resulting in a firm fixation of the fixing member to the rotating shaft. Since the magnet is fixed to the rotating shaft via this fixing member, the magnet is also firmly fixed to the rotating shaft. Furthermore, although the magnet is fixed to the fixing member, at least one hole is formed between the magnet fixing portion and the cylindrical portion of the fixing member when viewed in the direction along the rotating shaft. As a result, even if the cylindrical portion expands in diameter when the fixing member is attached to the rotating shaft, this deformation is less likely to affect the magnet. Consequently, damage to the magnet can be prevented. With this configuration, the magnet is firmly fixed to the rotating shaft in a way that makes it less susceptible to damage, thereby improving the reliability of the rotating electric machine.

(effect)
External forces act on the cylindrical portion that fits onto the rotating shaft, radially from the surface of the rotating shaft. In this case, it is desirable that these external forces do not affect the magnet fixing portion. To this end, in this configuration, the cylindrical portion and the magnet fixing portion are formed on different planes perpendicular to the rotating shaft. Even if an external force is transmitted from the cylindrical portion to the magnet fixing portion, the magnet fixing portion is displaced from the direction of the external force's action, so that only a component of the external force is transmitted. As a result, the external force reaching the magnet fixing portion is significantly reduced, minimizing its impact on the magnet's mounting condition.

(Feature configuration)
In the magnet fixing structure according to the present invention, a chamfered portion can be provided at the boundary between the inner surface of the first hole and the surface of the fixing member.

(effect)
The magnet fixing portion is formed as a first hole in a part of the fixing member. In this case, a part of the magnet is inserted and fixed into the first hole. Therefore, in this configuration, a chamfer is formed around the first hole to prevent the edge of the first hole from locally contacting the magnet. This prevents damage to the magnet, which has a relatively brittle structure. In particular, when the magnet is insert-formed by filling the first hole with magnet material, the edge of the first hole and the magnet come into complete close contact. In such cases, if a chamfer is formed, localized stress from the fixing member on the magnet is prevented, and a highly durable rotating electric machine can be obtained.

(Feature configuration)
In the magnet fixing structure according to the present invention, the first hole and the second hole can be configured to extend along the circumferential direction of the rotation axis .

(effect)
As in this configuration, by providing the first and second holes on the same plane of the fixing member, the structure of the fixing member is simplified. Furthermore, since the second hole extends along the circumferential direction of the rotation axis, it can broadly prevent external forces from affecting the first hole, which fixes the magnet on its outside. In addition,
Since the second hole extends along the circumferential direction and can be formed, for example, in a groove shape, the size of the fixing member can be reduced in diameter.

(Feature configuration)
In the magnet fixing structure according to the present invention, the first hole and the second hole can each be formed of a plurality of elongated holes that overlap in a radial view.

(effect)
External forces act on the cylindrical portion that fits onto the rotating shaft, radially from the surface of the rotating shaft. In this case, it is desirable that these external forces do not affect the magnet fixing portion. Therefore, in this configuration, the second
Since the second hole is an elongated hole that overlaps with the first hole in a radial view, it is possible to reliably prevent external forces from being applied to the first hole that secures the magnet on the outside of the second hole. This prevents damage to the magnet, which has a relatively brittle structure.
Furthermore, the magnet fixing structure according to the present invention is:
An annular fixing member attached to the rotating shaft of a rotating electric machine,
The fixed member is attached to at least one magnet for detecting the rotational speed of the rotating shaft,
The aforementioned fixing member,
A cylindrical portion that is fitted over the entire circumference of the aforementioned rotating shaft,
A disc-shaped connecting portion that is bent perpendicularly from the aforementioned cylindrical portion,
It integrally includes a magnet fixing portion located on the same disc as the aforementioned connecting portion but outside the aforementioned connecting portion,
The magnet fixing portion is provided with an elongated first hole along the circumferential direction of the rotation shaft, into which a portion of the magnet is inserted along the extending direction of the rotation shaft.
The connecting portion is provided with an elongated second hole that, when viewed in the direction along the rotation axis, is located between all the first holes and the cylindrical portion, extends along the circumferential direction of the rotation axis, and overlaps with the first holes in a radial view.
The first and second holes can be formed on different planes perpendicular to the rotation axis with respect to the inner circumferential surface of the cylindrical portion that contacts the outer circumferential surface of the rotation axis.
(effect)
In this configuration, the inner surface of the cylindrical portion that contacts the outer surface of the rotating shaft, and the first and second holes are formed on different planes perpendicular to the rotating shaft. Therefore, although the cylindrical portion is subjected to external forces directed radially outward from the rotating shaft, the external force reaching the magnet fixing portion is significantly reduced. As a result, damage to the magnet is prevented, and the reliability of the rotating electric machine can be improved.

This is a cross-sectional view of a rotating electric machine. This is a perspective view of the fixing member and magnet from one side and the other side. This is a plan view of the fixing member. This is a side cross-sectional view of the fixing member. This is a magnified cross-sectional view of a part of a rotating electric machine.

The following describes embodiments of the magnet fixing structure according to the present invention with reference to the drawings. In this embodiment, an actuator used in an automobile brake system is described as an example of a rotating electric machine equipped with a magnet fixing structure. However, the invention is not limited to the following embodiments, and various modifications are possible without departing from the gist of the invention.

Vehicle brakes capable of sudden braking require high-output brushless motors, and it is necessary to accurately detect the rotational speed of the rotating electric motor. Therefore, as shown in Figures 1 to 5, the magnet unit 4 in this embodiment is equipped with a fixing structure for the magnet 42 that can accurately detect the rotational speed of the rotating shaft 3. The basic configuration of the rotating electric motor 100 in this embodiment will be described below, followed by a detailed description of the fixing structure of the magnet 42.

As shown in Figure 1, the rotating electric machine 100 comprises an annular stator 1, a rotor 2 provided radially inward of the stator 1, a rotating shaft 3 that rotates the rotor 2, and a magnet unit 4 fixed to a different part of the rotating shaft 3 from the rotor 2 and rotating integrally with the rotating shaft 3. The rotating electric machine 100 is housed in a housing 5, and a sensor unit 6 is fixed to the housing 5 at a position opposite the magnet unit 4.

The stator 1 is formed by stacking core plates, each made of multiple electromagnetic steel sheets, along the axial direction of the rotating shaft 3. The stator 1 also has multiple (12 in this embodiment) segmented cores 1A that are divided along the circumferential direction. The teeth portion of each segmented core 1A is wound with the windings of the coil 7, divided into three phases (U phase, V phase, and W phase).

The rotor 2 is formed by stacking multiple electromagnetic steel sheets along the axial direction of the rotating shaft 3. Multiple permanent magnets 21 are fixed to the rotor 2 in a position opposite the stator 1. The multiple permanent magnets 21 are arranged with either north or south poles along the circumferential direction of the rotating shaft 3, and the magnetic flux generated by energizing the coil 7 flows between the stator 1 and the rotor 2, causing the rotor 2 to rotate together with the rotating shaft 3.

Furthermore, as the magnet unit 4 rotates together with the rotation axis 3, the sensor unit 6 rotates together with the rotation axis 3
The rotational speed is detected. In other words, the magnet 42 of the magnet unit 4 is provided to detect the rotational speed of the rotating shaft 3. Here, the rotational speed of the rotating shaft 3 is a concept that includes the rotational speed per unit time and the rotation angle of the rotating shaft 3. The sensor unit 6 includes a magnetic flux detection element 61 such as a Hall IC, and the rotational speed of the rotating shaft 3 can be detected by the pulse signal output from this magnetic flux detection element 61.

The magnet unit 4 has a fixing structure for the magnet 42, which will be described in detail below. As shown in Figures 2 to 5, the fixing structure for the magnet 42 (magnet unit 4) includes an annular fixing member 41 attached to the rotating shaft 3 of the rotating electric machine 100, and a fixing member 41 attached to the rotating shaft 3
It has at least one magnet 42 for detecting the rotation speed of the rotating shaft 3. In this embodiment, the fixing member 41 is made of an iron plate, and the magnet 42 includes permanent magnets arranged in a ring shape. Note that the magnet 42 is not made of a single permanent magnet, but rather the rotating shaft 3
It may be composed of multiple permanent magnets divided in the circumferential direction.

As shown in Figures 3 to 5, the fixing member 41 is a cylindrical portion 4 that is fitted around the entire circumference of the rotating shaft 3.
1A and a magnet fixing part 41 that fixes the magnet 42 at the outer circumference of the cylindrical part 41A
The fixing member 41 integrally includes a B and a connecting portion 41C that connects the cylindrical portion 41A and the magnet fixing portion 41B. In a view along the rotation axis 3 shown in Figure 3, at least one hole 41Ca is provided in the connecting portion 41C between the magnet fixing portion 41B and the cylindrical portion 41A of the fixing member 41. The cylindrical portion 41A is cylindrical in shape along the axial direction of the rotation axis 3, and the connecting portion 41C and the magnet fixing portion 41B are disc-shaped, bent perpendicularly from the cylindrical portion 41A.

As shown in Figures 2 and 3, the magnet 42 integrally comprises an annular portion 42A and a plurality (five in this embodiment) of protruding portions 42B that protrude from the annular portion 42A. In this embodiment, the protruding portions 42B have a cross-section that is arc-shaped and fits tightly into the first hole 41Ba, which will be described later. The cross-section of the protruding portion 42B is formed of an arc portion 42Ba that is along the circumferential direction of the rotation axis 3 and semicircular portions 42Bb formed at both ends of the arc portion 42Ba. Because the protruding portion 42B has semicircular portions 42Bb, the external force applied to the protruding portion 42B when the magnet 42 rotates is distributed.

Furthermore, the magnet 42 may be a magnetic material in which a permanent magnet has been pre-inserted,
The magnetic material may be a magnetic body formed by sintering magnetic powder in advance, or a permanent magnet may be insert-molded into the fixing member 41. If the fixing member 41 and the permanent magnet are integrally molded, assembly steps can be eliminated, thus reducing costs.

Thus, since the fixing member 41 has a cylindrical portion 41A that fits over the entire circumference of the rotating shaft 3, the contact area of the fixing member 41 with respect to the rotating shaft 3 increases, and the fixing member 41 is firmly fixed to the rotating shaft 3. Since the magnet 42 is fixed to the rotating shaft 3 via this fixing member 41, the magnet 42 is also firmly fixed to the rotating shaft 3. Furthermore, since the connecting portion 41C is provided with at least one hole 41Ca, even if the cylindrical portion 41A expands in diameter when the fixing member 41 is attached to the rotating shaft 3, this deformation is less likely to affect the magnet 42. As a result,
This prevents damage to the magnet 42.

As shown in Figures 4 and 5, the cylindrical portion 41A and the magnet fixing portion 41B are formed on different planes perpendicular to the rotation axis 3, while the magnet fixing portion 41B and the connecting portion 41C are formed on the same plane perpendicular to the rotation axis 3. In other words, the inner circumferential surface of the cylindrical portion 41A that abuts the outer circumferential surface of the rotation axis 3 is offset toward the sensor unit 6 from the plane including the magnet fixing portion 41B and the connecting portion 41C. That is, the cylindrical portion 41A that fits onto the rotation axis 3 has
An external force acts radially from the surface of the rotating shaft 3, but the magnet fixing part 41B is displaced from the direction of the external force, so that a component of the external force is transmitted. As a result, the external force reaching the magnet fixing part 41B is greatly reduced, and the effect on the mounting state of the magnet 42 can be minimized.

As shown in Figures 2 and 3, the magnet fixing portion 41B is formed as a first hole 41Ba consisting of a plurality (five in this embodiment) of elongated holes arranged at equal intervals along the circumferential direction of the rotation axis 3. By making the first hole 41Ba elongated, it is possible to secure a large contact area with the magnet 42, and the magnet 42 can be firmly fixed to the fixing member 41. Also, as shown in Figure 4, a chamfered portion 41b is provided on the fixing member 41 at the boundary between the inner surface of the first hole 41Ba and the surface of the fixing member 41 (both sides of the magnet fixing portion 41B), which is chamfered in an arc shape or inclined shape. When a part of the magnet 42 is inserted and fixed into the first hole 41Ba, the first hole 4
Because a chamfered portion 41b is formed around 1Ba, the edge of the first hole 41Ba does not come into local contact with the magnet 42. This prevents damage to the magnet 42, which has a relatively brittle structure. In particular, when the magnet 42 is insert-formed by filling the first hole 41Ba with magnet material, the edge of the first hole 41Ba and the magnet 42 come into complete close contact. In such cases, if the chamfered portion 41b is formed, the magnet 42
This prevents localized stress from being applied from the fixing member 41, making it possible to obtain a highly durable rotating electric machine 100.

As shown in Figure 4, the first hole 41Ba is such that a part of the magnet 42 extends in the direction of the rotation axis 3.
It is open to allow insertion along the axial direction. As shown in Figure 3, the hole 41Ca includes a plurality (five in this embodiment) of second holes 43, which are elongated holes extending along the circumferential direction of the rotation axis 3 in the same plane (connecting portion 41C) as the first hole 41Ba of the fixing member 41. These first hole 41Ba and second holes 43 are each formed of a plurality of elongated holes that overlap in a radial view.

Furthermore, multiple circular holes 44 for magnetization are provided between the multiple second holes 43 in the connecting portion 41C. These circular holes 44 also function as the aforementioned holes 41Ca, so that even if the cylindrical portion 41A expands in diameter when the fixing member 41 is attached to the rotating shaft 3, this deformation is less likely to affect the magnet 42. One of the circular holes 44 is a larger diameter circular hole 441.
The position of this circular hole 441 serves as a guide for the magnetization direction. However, instead of providing a circular hole 441 of a different size, a notch (not shown) can be provided on the inner diameter side of the second hole 43 to serve as a guide.

In this way, by providing the first hole 41Ba and the second hole 43 on the same plane, the fixing member 4
The configuration of 1 is simplified. Also, since the second hole 43 extends along the circumferential direction of the rotating shaft 3, it can widely prevent external forces from being applied to the first hole 41Ba that fixes the magnet 42 on its outside. In particular, since the second hole 43 is an elongated hole that overlaps with the first hole 41Ba in a radial view, it can reliably prevent external forces from being applied to the first hole 41Ba that fixes the magnet 42 on its outside. Furthermore, since the second hole 43 extends along the circumferential direction, it can be formed not only as a through hole as in the embodiment described above, but also, for example, as a groove, etc.
The size of the fixing member 41 can be reduced in diameter.

[Other Embodiments]
(1) In the above-described embodiment, the cylindrical portion 41A only needs to be shaped to be in close contact with the entire circumference of the rotating shaft 3. If the cross-section of the rotating shaft 3 is rectangular, for example, the cylindrical portion 41A will be rectangular.
(2) The magnet fixing portion 41B and the cylindrical portion 41A may be arranged on the same plane. In this case as well, the magnet 42 is connected by at least one hole 41Ca provided in the connecting portion 41C.
Damage can be suppressed.
(3) The number, arrangement, shape, etc. of the first hole 41Ba, the second hole 43, and the round hole 44 are not particularly limited, and should be configured in an effective way that can prevent damage to the magnet 42.

This invention can be used in a fixing structure for a magnet used to detect the rotational speed of the rotating shaft of a rotating electric machine.

3 Rotating shaft 4 Magnet unit 41 Fixing member 41A Cylinder portion 41B Magnet fixing portion 41Ba First hole 41C Connecting portion 41Ca Hole portion 41b Chamfered portion 42 Magnet 43 Second hole 100 Rotating electric machine

Claims (5)

An annular fixing member attached to the rotating shaft of a rotating electric machine,
The fixed member is attached to at least one magnet for detecting the rotational speed of the rotating shaft,
The aforementioned fixing member,
A cylindrical portion that is fitted over the entire circumference of the aforementioned rotating shaft,
A disc-shaped connecting portion that is bent perpendicularly from the aforementioned cylindrical portion,
It integrally includes a magnet fixing portion located on the same disc as the aforementioned connecting portion but outside the aforementioned connecting portion,
The magnet fixing portion is provided with a first hole into which a part of the magnet is inserted along the extension direction of the rotation shaft.
In the connecting portion, when viewed in the direction along the rotation axis, a second hole is provided between all of the first holes and the cylindrical portion.
A magnet fixing structure in which the first hole and the second hole are formed on different planes perpendicular to the rotation shaft with respect to the inner circumferential surface of the cylindrical portion that abuts against the outer circumferential surface of the rotation shaft . The magnet fixing structure according to claim 1 , wherein a chamfered portion is provided at the boundary between the inner surface of the first hole and the surface of the fixing member. The magnet fixing structure according to claim 2, wherein the first hole and the second hole extend along the circumferential direction of the rotation axis . The magnet fixing structure according to claim 3 , wherein the first hole and the second hole are each formed of a plurality of elongated holes that overlap in a radial view. An annular fixing member attached to the rotating shaft of a rotating electric machine,
The fixed member is attached to at least one magnet for detecting the rotational speed of the rotating shaft,
The aforementioned fixing member,
A cylindrical portion that is fitted over the entire circumference of the aforementioned rotating shaft,
A disc-shaped connecting portion that is bent perpendicularly from the aforementioned cylindrical portion,
It integrally includes a magnet fixing portion located on the same disc as the aforementioned connecting portion but outside the aforementioned connecting portion,
The magnet fixing portion is provided with an elongated first hole along the circumferential direction of the rotation shaft, into which a portion of the magnet is inserted along the extending direction of the rotation shaft.
The connecting portion is provided with an elongated second hole that , when viewed in the direction along the rotation axis, is located between all the first holes and the cylindrical portion, extends along the circumferential direction of the rotation axis, and overlaps with the first holes in a radial view.
A magnet fixing structure in which the first hole and the second hole are formed on different planes perpendicular to the rotation axis with respect to the inner circumferential surface of the cylindrical portion that the outer circumferential surface of the rotation axis abuts .