JP7226189B2 - motor - Google Patents

Description

The present invention relates to motors.

2. Description of the Related Art Conventionally, a motor is known that includes a cylindrical stator around which a coil is wound, and a rotor that has a plurality of magnetic poles and is provided radially inside the stator, and rotates the rotor by electromagnetic force generated by energizing the coil. It is

For example, the electric motor disclosed in Patent Document 1 constitutes an electric actuator that presses a brake disc via an interlocking conversion mechanism in a brake system.

JP 2017-104010 A

The background of motor technology in vehicle braking systems will now be described. In recent years, there has been an increase in the use of automatic braking systems to meet the needs for automotive accessory systems accompanying automatic driving and to improve safety functions. In addition, with the increase in hybrid vehicles and electric vehicles, the adoption of hydraulic electric brake systems , etc., in which an electric motor replaces the pressurization source, which was formerly provided by the negative pressure of the engine, is increasing.

Hydraulic brake systems include a type that converts motor rotation into linear motion with a ball screw to actuate the piston in the cylinder to generate brake hydraulic pressure, and others that directly transmit the motor rotation to the gear mechanism and There is a type of gear pump that generates brake hydraulic pressure by transporting fluid in the meshing part.

In addition, hydraulic brakes are required to have a hydraulic holding force to maintain the braking force when the vehicle is stopped, and a high followability to the braking operation. Therefore, a motor used in a hydraulic electric brake system is required to achieve both high restraint torque in a low rotation region and high rotation in a no-load (or low-load) region. In order to achieve both, an interior permanent magnet (hereinafter "IPM") motor is selected.

In addition, in motor drive control, there is known a technology of a sensorless drive system that does not use a position sensor for detecting the rotation angle of the rotor for the purpose of reducing the number of components and saving space. In this specification, the ratio of q-axis inductance to d-axis inductance (Lq/Ld) is referred to as "salient pole ratio". In sensorless driving, the difference between the q-axis inductance and the d-axis inductance is large, and the salient pole ratio should be away from 1. Preferably, when the salient pole ratio is greater than 1, by providing salient pole portions between magnetic poles adjacent in the circumferential direction, an effect of increasing the salient pole ratio can be obtained.

However, when a motor having a salient pole portion is driven without a sensor, if the salient pole portion and the teeth of the stator face each other and are energized at a rotational position near the lead angle of 0 degrees, the salient pole portion is likely to be magnetically saturated. There is a problem that it is difficult to maintain the salient pole ratio required for estimation.

The present invention was created in view of the above points, and its object is to provide a motor in which salient pole portions are provided between magnetic poles, in which the salient pole portions are less susceptible to stator excitation and are less likely to be magnetically saturated. to provide.

The present invention is applied to a brake system of a vehicle, and is a motor for generating brake hydraulic pressure by output , comprising a cylindrical stator (60) wound with a coil (68) and ten magnetic poles in the circumferential direction. (57) is provided and comprises a rotor (50) rotatable inside the stator. The stator has a plurality of teeth (62) protruding radially inward from a core back (61). formed. The rotor consists of an IPM structure with ten magnetic poles embedded in the rotor core (51).

The magnetic poles are covered radially outwardly by a front yoke portion (55), and a salient pole portion (53) is formed between adjacent magnetic poles in the circumferential direction. In axial projection about the rotation axis (O) of the rotor, the radially outer end (531) of the salient pole portion is inside the concentric circle passing through the circumferential end point (P1) of the outer edge of the front yoke portion (55). Located in

In the motor of the present invention, the radial outer ends of the salient pole portions are formed so as to be recessed radially inward with respect to the front yoke portion, and the radial outer ends of the salient pole portions are separated from the inner ends of the teeth. Therefore, even when the motor is energized and started at a rotational position near the lead angle of 0 degrees where the salient poles and the teeth face each other, the salient poles are less likely to be affected by the stator excitation, and magnetic saturation is less likely to occur. Therefore, it becomes easier to maintain the salient pole ratio required for position estimation in the sensorless drive system.

Schematic diagram of a vehicle braking system. Axial sectional view of the motor of each embodiment. FIG. 3 is a radial cross-sectional view along line III-III of FIG. 2; The IV part enlarged view of FIG. (a) A radially enlarged cross-sectional view near the salient pole portion of the motor of the first embodiment, (b) A radially enlarged cross-sectional view near the salient pole portion of the motor of the comparative example. FIG. 5 is a schematic diagram showing radial outer end positions of salient pole portions of motors according to the second, third, and fourth embodiments; FIG. 5 is a radially enlarged cross-sectional view showing a tooth shape of another embodiment;

As used herein, "embodiment" means an embodiment of the present invention. A plurality of embodiments of the motor will be described below with reference to the drawings. The motor of this embodiment is a motor that is applied to a brake system of a vehicle and that generates brake fluid pressure by output. The same reference numerals are assigned to substantially the same configurations in a plurality of embodiments, and descriptions thereof are omitted. The following first to fourth embodiments will be collectively referred to as "this embodiment".

FIG. 1 schematically shows a vehicle braking system 90 . Hydraulic pressure generated by the hydraulic device 91 by the output of the motor 80 is supplied to the brake caliper 93 via the pipe 92 . The brake caliper 93 presses the pads against the brake disc 94 to brake the wheel.

Next, the configuration of the motor 80 will be described with reference to FIGS. 2 to 4. FIG. The motor 80 of this embodiment is a three-phase brushless motor, and a housing 70, a stator 60, a rotor 50, and the like are provided coaxially with respect to the rotation axis O. As shown in FIG.

As shown in FIG. 2 , the housing 70 has a bottomed tubular shape including a tubular portion 72 and a bottom portion 73 . A collar portion 71 is formed around the open end of the tubular portion 72 . A bearing accommodating portion 74 is formed in the center of the bottom portion 73 to accommodate a bearing 77 on the bottom portion side. A housing cover 75 mounted on the opening side of the housing 70 has a bearing accommodating portion 76 formed in the center thereof for accommodating a bearing 78 on the opening side.

The cylindrical stator 60 is accommodated inside a cylindrical portion 72 of the housing 70, and a three-phase coil 68 is wound in a slot. The rotor 50 is provided inside the stator 60 and has a shaft 59 fixed at its center. Both ends of the shaft 59 are rotatably supported by bearings 77 and 78 . Although the rotor 50 shown in FIG. 2 is configured by stacking a plurality of thin plate-like rotor cores in the axial direction, it may be configured by an integral rotor core.

As shown in FIGS. 3 and 4 , the rotor 50 is provided with a plurality of (for example, 10 poles) magnetic poles 57 of permanent magnets in the circumferential direction, and is rotatable inside the stator 60 . A plurality of recessed portions 52 are formed in a radially intermediate portion of the rotor core 51 . The rotor 50 of this embodiment has an IPM structure in which a plurality of magnetic poles 57 are embedded in a rotor core 51 . Specifically, the plurality of magnetic poles 57 are embedded in a radially outer annular portion of the reduced thickness portion 52 . The magnetic poles 57 are covered radially outwardly by a front yoke portion 55, and salient pole portions 53 are formed between the magnetic poles 57 adjacent in the circumferential direction.

The stator 60 has a plurality of (for example, 12) teeth 62 protruding radially inward from the core back 61 . Three-phase coils 68 are wound in slots between adjacent teeth 62 . The stator 60 illustrated in FIGS. 3 and 4 is composed of split cores divided in the circumferential direction, but may be composed of an integral core.

Further, the tooth 62 of the present embodiment is formed in a straight shape in which the width in the circumferential direction is the same between the tip portion 63 and the root side. This configuration is disclosed in Japanese Patent No. 5862145 (corresponding US publication: US9531222B2).

The brushless motor 80 having such a configuration rotates due to interaction between the rotating magnetic field formed in the stator 60 by energization of the coil 68 and the magnetic field generated by the magnetic poles 57 of the rotor 50, and outputs torque. Here, a motor used in a hydraulic electric brake system is required to achieve both high restraint torque in a low rotation region and high rotation in a no-load (or low-load) region. In the present embodiment, an IPM motor is selected to achieve both.

Further, in the sensorless drive system, it is preferable that the salient pole portion 53 having the effect of improving the salient pole ratio is provided between the magnetic poles 57 . However, when the motor 80 having the salient pole portion 53 is driven without a sensor, when the salient pole portion 53 and the teeth 62 of the stator 60 face each other and are energized at a rotational position near the lead angle of 0 degrees, the salient pole portion 53 is activated. There is a problem that magnetic saturation is likely to occur and it is difficult to maintain the salient pole ratio necessary for position estimation. Therefore, the motor 80 of the present embodiment is configured such that the salient pole portions 53 are less likely to be affected by stator excitation and are less likely to be magnetically saturated.

(First embodiment)
Next, with reference to FIG. 5(a), a detailed configuration near the salient pole portion 53 in the motor of the first embodiment will be described. In FIG. 5A, the magnetic pole 57 is covered with a front yoke portion 55 on the radially outer side. The radial width of the front yoke portion 55 is the widest at the circumferential center of the magnetic pole 57 and becomes narrower toward the circumferential ends. The front yoke portion 55 and the salient pole portion 53 are connected via the bridge portion 54 . A gap 56 facing the circumferential end of the magnetic pole 57 is formed radially inside the bridge portion 54 .

A circumferential end point P<b>1 of the outer edge of the front yoke portion 55 is positioned at the boundary with the bridge portion 54 . In the drawing, a concentric circle passing through the circumferential end point P1 of the outer edge of the front yoke portion 55 is indicated by a chain double-dashed line. In the first embodiment, in axial projection about the rotation axis O of the rotor 50, the radial outer end 531 of the salient pole portion 53 is the inner side of a concentric circle passing through the circumferential end point P1 of the outer edge of the front yoke portion 55. Located in

Although it is self-evident, the “concentric circles” are concentric circles centered on the rotation axis O of the rotor 50 . That is, in the first embodiment, the maximum distance from the rotation axis O of the rotor 50 to the radially outer end 531 of the salient pole portion 53 is specified based on the shape of the outer edge of the front yoke portion 55 .

FIG. 5B shows a salient pole portion 53 of a comparative example. In the comparative example, the radially outer end 539 of the salient pole portion 53 is located substantially on the same circle as the concentric circle passing through the circumferential end point P1 of the outer edge of the front yoke portion 55 . 5B, that is, at a rotational position near the lead angle of 0 degrees where the salient pole portion 53 and the tooth 62 face each other. Since the distance between the outer end 539 and the inner end 630 of the tooth 62 is short, the salient pole portion 53 is likely to be affected by stator excitation and is likely to be magnetically saturated. Therefore, it becomes difficult to maintain the salient pole ratio required for position estimation in the sensorless drive system.

On the other hand, in the first embodiment shown in FIG. 5A, the radial outer end 531 of the salient pole portion 53 is formed so as to be recessed radially inward with respect to the front yoke portion 55. The radial outer end 531 is separated from the inner end 630 of the tooth 62 . Therefore, even when the salient pole portion 53 and the teeth 62 face each other and are energized and started at a rotational position near the lead angle of 0 degrees, the salient pole portion 53 is less likely to be affected by stator excitation and is less likely to be magnetically saturated. Therefore, it becomes easier to maintain the salient pole ratio required for position estimation in the sensorless drive system.

Furthermore, in the present embodiment, since the tip portions 63 of the teeth 62 are formed in a straight shape, compared to the shape shown in FIG. Leakage magnetic flux to the front yoke portion 55 can be suppressed. Therefore, the salient pole portions 53 are less likely to be affected by stator excitation and are less likely to be magnetically saturated.

(Second, third and fourth embodiments)
Next, with reference to FIG. 6, second, third, and fourth embodiments will be described in which the limit position of the radially outer end of the salient pole portion 53 is different from that of the first embodiment. The limit positions of the radially outer ends 532, 533, 534 in the second, third, and fourth embodiments are specified with the position of the magnetic pole 57 as a reference. FIG. 6 schematically shows only the limit positions of the magnetic poles 57 and radial outer ends 532 , 533 , 534 of the salient pole portions 53 with respect to the rotation axis O of the rotor 50 .

As a premise common to the second, third, and fourth embodiments, in the axial projection of the rotor 50, the magnetic poles 57 are symmetrical with respect to the radial center line Cr passing through the rotation axis O of the rotor 50 and extending in the radial direction. It has a rectangular shape.

In the second embodiment, the radially outer end 532 of the salient pole portion 53 is positioned inside a concentric circle passing through the radially outer corner P2 of the magnetic pole 57 . The radially outer corner P2 of the magnetic pole 57 is located inside the circumferential end point P1 of the outer edge of the front yoke portion 55 by substantially the width of the front yoke portion 55 in the radial direction. Therefore, in the second embodiment, the radially outer ends 532 of the salient pole portions 53 are further separated from the inner ends 630 of the teeth 62 compared to the first embodiment, so that the salient pole portions 53 are less susceptible to stator excitation. Magnetic saturation becomes difficult.

In the third embodiment, the radially outer end 533 of the salient pole portion 53 is located inside a concentric circle passing through the radially outermost point P3 of the magnetic pole 57 on the radial centerline Cr. The radially outermost point P3 of the magnetic pole 57 is located inside the radially outer corner P2. Therefore, in the third embodiment, compared to the second embodiment, the salient pole portions 53 are less likely to be affected by stator excitation and are less likely to be magnetically saturated.

In the fourth embodiment, the radial outer end 534 of the salient pole portion 53 is located inside a concentric circle passing through the radial midpoint P4 of the magnetic pole 57 on the radial center line Cr. The radial middle point P4 of the magnetic pole 57 is located further inside the radial outermost point P3. Therefore, in the fourth embodiment, compared to the third embodiment, the salient pole portions 53 are less likely to be affected by stator excitation and are less likely to be magnetically saturated.

(Other embodiments)
(a) In the above embodiment, the teeth 62 of the stator 60 are straight. On the other hand, as shown in FIG. 7, the tip portions 639 of the teeth 62 may have a shape that spreads to both sides in the circumferential direction. If the radially outer end 531 of the salient pole portion 53 is formed so as to be recessed radially inwardly with respect to the front yoke portion 55, the effect of suppressing magnetic saturation can be obtained to some extent even if the teeth 62 are not straight. .

(b) The 3-phase brushless motor shown in FIGS. 3 and 4 has 10 poles and 12 slots, but the number of magnetic poles and slots (or teeth) is not limited to this. Also, the motor is not limited to a three-phase motor, and may be a multi-phase motor having four or more phases.

(c) The motor of the present invention may be applied not only to the vehicle brake system 90 but also to any system that utilizes motor torque. Further, the driving of the motor is not limited to the sensorless driving method, and may be driven by a method in which the rotation angle is fed back by a position sensor.

As described above, the present invention is not limited to such an embodiment, and can be embodied in various forms without departing from the spirit of the present invention.

50 ... rotor, 51 ... rotor core,
53 ... salient pole portion, 531-534 ... radial outer end,
57 ... Magnetic pole,
60... Stator, 68... Coil,
80... Motor.

Claims (4)

A motor that is applied to a vehicle brake system and generates brake hydraulic pressure by output,
a cylindrical stator (60) around which a coil (68) is wound;
a rotor (50) provided with ten magnetic poles (57) in the circumferential direction and rotatable inside the stator;
with
The stator has a plurality of teeth (62) protruding radially inward from a core back (61). formed in the shape of
The rotor comprises an IPM structure in which the ten magnetic poles are embedded in a rotor core (51),
The magnetic poles have their radially outer sides covered with a front yoke portion (55), and a salient pole portion (53) is formed between the magnetic poles adjacent in the circumferential direction,
In axial projection about the rotation axis (O) of the rotor, the radially outer end (531) of the salient pole portion is located inside a concentric circle passing through the circumferential end point (P1) of the outer edge of the front yoke portion. motor located in In axial projection of the rotor, the magnetic poles present a rectangular shape symmetrical with respect to a radial centerline (Cr) extending radially through the axis of rotation of the rotor,
A motor according to claim 1, wherein the radially outer ends (532) of the salient pole portions are located inside concentric circles passing through the radially outer corners (P2) of the poles. 3. The motor according to claim 2, wherein the radially outer ends (533) of the salient pole portions are positioned inside concentric circles passing through the radially outermost points (P3) of the magnetic poles on the radial centerline. 4. The motor of claim 3, wherein the radially outer ends (534) of the salient pole portions are located inside concentric circles passing through the radial midpoint (P4) of the magnetic poles on the radial centerline.

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