JPH07112347B2 - Direct drive motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a direct drive motor used in the field of factory automation (FA).
More specifically, the present invention relates to a magnetic inductor type synchronous motor, and relates to an outer rotor type direct drive motor that operates as a highly accurate servo actuator by accurately detecting a rotation angle of a rotor. Is.

(Prior Art) Motors required in the field of FA are required to have large torque, high speed, and highly accurate positioning control.

Conventionally, as a servo actuator for FA satisfying such requirements, a combination of a speed reducer and a DC servo motor has been widely used.

(Problems to be Solved by the Invention) However, a conventional servomotor configured in combination with a speed reducer has a problem of torque unevenness due to backlash,
Due to its low rigidity, there were problems such as the effect of lost motion.

The present invention has been made in view of such problems,
The purpose thereof is to realize a direct drive motor which is free from the influence of torque unevenness and lost motion and which can control positioning at high speed and with high accuracy.

(Means for Solving the Problems) The present invention that achieves such an object is to provide an inner stator, an outer rotor arranged outside the inner stator with a slight gap, and an outer rotor. There is a cylindrical rotor hub with the child fixed inside, a cylindrical housing arranged so that many parts fit within the cylindrical shape of this rotor hub, and inside the cylindrical shape of the rotor hub. A bearing that rotatably supports the rotor hub with respect to the housing, and a slit plate are attached to the cylindrical mounting portion that projects from the bottom surface of the rotor hub into the housing. A direct drive motor having an encoder for detecting the rotational displacement of the rotor hub, the mounting position of which is substantially flush with the plane in which the bearing is arranged. .

(Operation) The outer rotor is rotatably supported by the bearing provided inside the cylindrical shape via the cylindrical rotor hub, and is directly driven and rotated by the magnetic induction generated in the inner stator. The rotational displacement of this outer rotor is accurately detected by the encoder.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an axial sectional view showing an example of a direct drive motor according to the present invention, and FIG. 2 is an exploded view.

In these figures, 1 is an inner stator and 2 sets of magnetic materials
11, 12 and consists of a permanent magnet 13 and an exciting coil 14 sandwiched between the magnetic bodies. Each magnetic body 11, 12 has a plurality of (12 in this case) salient poles 11a, 11b around which an exciting coil 14 is wound, and teeth 15 having a pitch P are provided at the tip of each salient pole. ing.

Reference numeral 2 denotes an outer rotor rotatably arranged on the outer side of the inner stator 1 with a slight gap therebetween, and teeth 21 arranged at a pitch P are provided on a surface facing the inner stator 1.

Reference numeral 3 denotes a cylindrical rotor hub which fixes the outer rotor 2 inside the cylindrical shape and rotates together with the outer rotor 2, and a load 4 for taking out a rotational force is attached to the cylindrical bottom portion 31. Reference numeral 32 denotes a cylindrical mounting portion that protrudes inward from the bottom surface portion 31 of the rotor hub 3, and has an encoder 7 to be described later at its tip.
The slit plate 71 of is attached.

Reference numeral 5 denotes a bearing, which supports the outer rotor 2 through a rotor hub 3 in a cantilever structure. Here, a cross roller bearing is used, and the rotary roller 51 and the rotary roller 51 are arranged from above and below. The holding members 52 and 53 are sandwiched (from inside and outside).

54 is a ring member provided inside the cylindrical shape of the rotor hub 3, and 55 is a clamp ring, which is one holding member 53 of the bearing 5.
Is to be fixed to the rotating hub 3 side.

Reference numeral 6 denotes a cylindrical housing that is installed so that many parts are accommodated in the cylindrical rotor hub 3. The inner stator 1 is fixed and the other support member 52 of the bearing 5 is fixed. Reference numeral 61 is a clamp ring for fixing the support member 52 to the housing 6.

Reference numeral 7 denotes an encoder for detecting the rotational displacement of the rotor hub 3, which is a rotary slit plate 71 fixed to the central cylindrical mounting portion 32 of the rotor hub 3, and an LED for irradiating the rotary slit plate 71 with a light beam. A light irradiation unit 72 including a lens and a lens, a light receiving element that receives light that has passed through the slit plate 71, and a signal processing unit that processes a signal from the light receiving element to obtain a signal proportional to the rotation angle of the rotor hub 3 are housed. It is composed of the assembled assembly 73. Incidentally, 74 is a mounting ring for fixing the slit plate 71 to the central cylindrical mounting portion 32.

Here, the central cylindrical mounting portion 32 of the rotor hub 3 is installed inside the cylindrical housing 6, and the slit plate 71 is substantially at the tip of the central cylindrical mounting portion 32 with the plane PL on which the bearing 5 is installed. It is mounted so as to be arranged on the same plane.

Next, a method of assembling the direct drive motor configured as described above will be described with reference to FIG.

First, the outer rotor 2 is inserted into the cylindrical inner side of the rotor hub 3 and fixed so that they are integrated by, for example, an adhesive or a screw, or both an adhesive and a screw.

Also, insert the inner stator 1 into the cylindrical portion of the housing 6,
The both are fixed by, for example, an adhesive so as to be integrated. Further, the light irradiation part 72 is fixed inside the cylinder of the housing 6 by, for example, a screw.

Next, the housing 6 is inserted into the cylindrical shape of the rotor hub 3, the bearing 5 is positioned at a predetermined position inside the rotor hub 3 and outside the housing 6, and the upper support member 53 of the bearing 5 is held by the clamp ring 55. The ring member 54 of the rotor hub 3
The lower support member 52 of the bearing 5 is pressed and fixed to the housing 6 by the clamp ring 61. As a result, the bearing 5 is supported between the rotor hub 3 and the housing 6 via the clamp rings 55 and 61. Here, in each of the clamp rings 55 and 61, notches 50 and 60 are formed in the pressing portions against the supporting members 52 and 53, respectively, so that the pressing force applied to the bearing 5 is appropriately absorbed and appropriate The bearing can be supported by pressing force.

Next, the slit plate 71 of the encoder 7 is fixed to the tip of the central cylindrical mounting portion 32 of the rotor hub 3 by the mounting ring 74. Further, the signal processing unit assembly 73 is positioned so that the light beam from the light irradiation unit 72 passes through the slit holes 71a and 71b of the slit plate 71 and accurately strikes the image sensor 73a, while the inside of the housing 6 is being positioned. Attach to and complete.

In the direct drive motor of the present invention having such a structure, the torque is directly obtained from the outer rotor, and the housing supporting the outer rotor via the bearing 5 has a cylindrical shape of the rotor hub 2. Since it has a structure installed inside, the entire structure can be made small, and it is possible to obtain a large torque while being small. Further, the encoder having the slit plate 71 which is directly attached to the rotor hub 2 and which rotates is provided inside the housing 6, and the signal necessary for position control can be accurately obtained from here. Furthermore, by setting the installation position of the slit plate 71 on substantially the same plane as the plane on which the bearing 5 is provided, the slit plate 71 due to rotational vibration is
It is possible to obtain a highly accurate position signal by reducing the inclination of, and not being affected by vibration or the like.

Next, the details of each component will be described.

FIG. 3 shows an exciting coil 14 provided on the inner stator 1.
It is a figure which shows how to wind. Here, a three-phase excitation circuit consisting of A-phase, B-phase, and C-phase is used, and A-phase is salient pole 11a,
Every other two salient poles 11d, 11g, 11j are wound in series on a total of four salient poles, B-phase is wound in series on salient poles 11b, 11e, 11h, 11k, and C-phase is salient. It is wound in series on 11c, 11f, 11i and 11l. The positional relationship of the teeth 15 and 21 provided on the facing surfaces of the inner stator 1 and the outer rotor 2 is the same as that of the PM type three-phase pulse motor, and the details are omitted.

FIG. 4 is an explanatory view showing the principle of rotation of the outer rotor 2.

In the inner stator 1, the magnetic flux at the salient poles 11a is
It is formed by the sum of the bias magnetic flux φM due to 3 and the exciting magnetic flux φC generated by passing the exciting current through the exciting coil 14 wound around the salient pole 11a, φO = φM + φC. Salient pole
The current flowing in the exciting coil 14 for exciting 11a is, for example, A
By making the phase, B phase, and C phase have a phase difference of 120 ° in this order, the excitation magnetic flux φC moves in order of A phase, B phase, and C phase, and the sum expressed by φM + φC Since the magnetic flux portion also moves, the outer rotor 2 is attracted by this and rotates.

If the phases of the exciting currents flowing through the A-phase, B-phase, and C-phase are switched between advanced and delayed, the rotation direction becomes opposite.

Here, the thrust (torque) T of the outer rotor 2 is proportional to the square of the sum ΦO of the bias magnetic flux φM and the exciting magnetic flux ΦC, and is expressed by the equation (1): T∝ (φM + φC) ² (1 The motor of the present invention can generate a large torque because the generator of the torque T expressed by the equation (1) is located on the outer peripheral portion of the motor.

FIG. 5 is a configuration block diagram of essential parts showing an example of the encoder 7 for detecting the rotation angle of the outer rotor 2 (proportional to the rotation angle of the rotor hub 3).

The slit plate 71, which rotates together with the outer rotor 2, is provided with two slit plates 71a and 71b in the circumferential direction. The number of slits in the outer slit row 71a is n ₁
The number of slits in 1b is n ₂ , and the difference between these slits is n ₁ −n
_{The number 2} corresponds here to the number of teeth 21 provided on the outer rotor 2. 72a is a light source like LED, 72b
Is a lens for collimating the light from the LED into parallel rays. These two sets are provided for the upper slit row 71a and the lower slit row 71b, respectively, and are provided by the light irradiation unit 72 (see FIG. 2). Is held. An image sensor 73a receives the light transmitted through the slit, and is composed of, for example, eight photodiodes arranged in an array. A photodiode 73b for detecting a zero point receives the light transmitted through the zero point slit 71c provided on the slit plate 71. 73c is an image sensor
This is a signal processing circuit that processes the signal from the 73a and the signal from the photodiode 73b. This circuit is composed of switches S1 to S8 for sequentially extracting signals from eight photodiodes at a fixed timing, an amplifier OP1 for amplifying the signals extracted through each switch, and a sine wave signal component from the output signal of this amplifier. low-pass filter LPF for extracting and outputting a signal f _1, f ₂ of the periodic function waveform obtained from the low-pass filter LPF, for example, by performing predetermined signal processing with one of the signal f _1, the rotational position signal of the slit plate 71 It consists of an encoder interface ECIF which includes a microprocessor which obtains Dp and uses _two signals f ₁ and f ₂ to obtain a signal θe related to the positional deviation of the teeth of the stator 1 and the rotor 2.

Here, the method of obtaining the position signal Dp from the periodic function f ₁ or f ₂ is a method of obtaining the position signal by performing signal processing from the spatial filter, and the method of obtaining the tooth position deviation signal θe is two signals. It is a method to find the phase difference between f ₁ and f ₂ ,
The details are disclosed in Japanese Patent Application No. 61-249363.

FIG. 6 is a block diagram of the configuration when the motor of the present invention is operated as a servo actuator.

In the figure, 81 is a position control unit, which is configured to include a microprocessor, and receives a signal from a counter CU that counts serial pulses as a position command signal and a position signal Dp from an encoder interface ECIF. ing. The position controller 81 performs, for example, PID calculation based on the position signal Dp and the position command signal X output from the encoder interface ECIF to obtain the speed command value output ED ₁ of the outer rotor 2. , This is output as an analog signal E ₁ by the D / A converter DA. Reference numeral 82 denotes an adder circuit, which obtains the difference between the analog signal E ₁ from the D / A converter DA and the velocity feedback signal θe from the encoder interface ECIF, which is passed through commutation means 83, 84 to obtain a pulse width conversion circuit ( PWM
Circuit) give to 85. 86 is a gate control circuit, PWM circuit 85
Receiving the signal from the motor unit MO, the exciting current flowing through the A-phase winding, the B-phase winding, and the C-phase winding of the motor unit MO is controlled by using the respective switch elements Qa to Qc. Here, the current flowing through the B-phase winding and the C-phase winding is fed back to the PWM circuit 85.

The servo actuator thus configured forms a third-order servo system of feedback by the position signal Dp, feedback by the speed signal θe, and current feedback by the signal corresponding to the exciting current, so that the influence of disturbance due to load fluctuation A high-speed, high-accuracy servo actuator can be easily configured without receiving the force.

Although the rotor hub 3 is supported by using the cross roller bearing in the above embodiment, a bearing having another structure may be used. In addition, the encoder is a fifth encoder using an optical encoder in which a slit plate is attached to a rotor hub.
Although the structure shown in the figure is taken as an example, the slit plate or code plate is attached to the cylindrical mounting portion 32 that protrudes from the bottom of the rotor hub toward the inside of the housing, and the mounting position is the bearing. Other structures may be used as long as they are configured to be substantially on the same plane as the plane on which is arranged. Further, in the structure of the motor part, the inner stator has 12 salient poles and the three-phase excitation circuit is used, but the invention is not limited to such a structure. Further, although the permanent magnet that gives the bias magnetic flux is provided in the inner stator, it may be provided in the outer rotor.

(Effects of the Invention) As described in detail above, according to the present invention, torque can be obtained directly from the rotor hub 3, there is no influence of torque unevenness and lost motion, and the overall size is small. A large torque can be obtained.

Further, in the present invention, the rotor hub is provided with a cylindrical mounting portion 32 protruding from the bottom surface thereof toward the inside of the housing, and the encoder for detecting the rotational displacement of the rotor hub is provided with the slit plate thereof. Is attached to the cylindrical mounting portion 32, and the mounting position is substantially flush with the plane on which the bearing is arranged.

Therefore, even when the rotor hub rotates with some vibration, the inclination due to the rotation of the slit plate can be kept small, and the rotational displacement of the rotor can be detected with high accuracy without being affected by vibration or the like. it can.

Further, the bearing is configured to be fixed by a clamp ring between the rotor hub and the housing, and cutouts 50 and 60 are provided in a portion of the clamp ring that presses the bearing, so that the force applied to the bearing is applied to the cutout. By making the adjustment possible, there is an effect that the life of the bearing can be extended.

FIG. 7 is a diagram showing the relationship between the weight of the motor according to the present invention and the output (starting torque × rated speed). The broken line shows the characteristics of a conventional DC / motor with a reducer.

Further, according to the present invention, since an encoder that accurately corresponds to the rotational displacement of the rotor hub is provided inside, it is possible to realize a direct drive motor that can perform positioning control with high speed and high accuracy.

[Brief description of drawings]

FIG. 1 is an axial sectional view showing an example of a direct drive motor according to the present invention, FIG. 2 is an exploded view of the assembly, FIG. 3 is a drawing showing winding of an exciting coil, and FIG. 4 is a principle of rotation. And FIG. 5 is a block diagram of a main part of an encoder, FIG. 6 is a block diagram of a structure when the motor of the present invention is operated as a servo actuator, and FIG. 7 is a characteristic diagram of the motor of the present invention. is there. 1 ... Inner stator, 11, 12 ... Magnetic material, 13 ... Permanent magnet, 14 ... Excitation coil, 2 ... Outer rotor, 3 ... Rotor hub, 4 ... Load, 5 ... Bearing , 6 ... Housing, 7 ... Encoder, 55, 61 ... Clamp ring.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruo Higuchi 2-9-32 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Mitsuhiro Nikaido 2-9-32 Nakamachi, Musashino City, Tokyo Horizontal (56) References JP-A-62-37044 (JP, A) JP-A-48-93856 (JP, A)

Claims (2)

[Claims] 1. An inner stator (1), an outer rotor (2) arranged outside the inner stator with a slight gap, and a cylindrical shape having the outer rotor fixed therein. A rotor hub (3), a cylindrical housing (6) arranged so that many parts fit within the cylindrical shape of the rotor hub and fixing the inner stator, and a cylindrical shape of the rotor hub It has a bearing (5) inside which rotatably supports the rotor hub with respect to the housing, and a slit plate, and the slit plate is projected from the bottom surface of the rotor hub into the housing. An encoder (7) for detecting the rotational displacement of the rotor hub, which is mounted on the cylindrical mounting portion (32) and whose mounting position is substantially flush with the plane on which the bearing is arranged. Direct dry Motor. 2. A bearing (5) is fixed between a rotor hub (3) and a housing (6) by a clamp ring (55, 61), and a bearing is pressed in the clamp ring. The direct drive motor according to claim 1, wherein notches (50, 60) are provided in the portions, and the force applied to the bearing can be adjusted by the notches.