JPH0154949B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brushless motor, in which current flowing through a drive coil is switched at ideal timing to minimize uneven rotation of the rotor.

In a so-called Hall motor that uses a Hall element etc. as a position detection sensor for the rotor magnet of a brushless motor, the magnetic flux distribution of the rotor magnet is detected by the Hall element as a Hall output voltage.
This Hall output voltage is used to control the drive current flowing through the drive coil by changing its direction or magnitude.

In a Hall motor, the magnetic flux density distribution of magnetic flux generated from the magnetized surface of a rotor magnet is generally detected by a Hall element, and the drive current is controlled by a Hall output voltage generated in proportion to the magnetic flux density distribution. In other words, when this Hall output voltage reaches O [volts] (the magnetic flux density of the rotor magnet is O [gauss]), the Hall element cuts off the drive current that was passing through the drive coil or changes its direction. or Conventionally, a two-phase winding type Hall motor has a configuration as shown in FIG. Recently, as a method for reducing rotational unevenness of the rotor, a method in which a current proportional to the Hall output voltage detected by a Hall element is caused to flow through a drive coil as a drive current has been attracting attention.
However, with this method, it has been impossible to reduce rotational unevenness at the position of the conventional Hall element.

Hereinafter, the configuration of the conventional Hall motor and its problems will be explained in detail. FIG. 1 is a sectional view of a main part of a conventional Hall motor. First, regarding the structure of the rotor, reference numeral 2 denotes a rotor case made of a magnetic material such as an iron plate, and a cylindrical rotor magnet 3 is fixed to the inside of the rotor case 2. The rotor magnet 3 has a multi-pole structure with six magnetic poles, and the inner peripheral surface thereof is alternately magnetized with north and south poles. Next, we will discuss the configuration of the stator.
is a stator core made of laminated silicon steel plates, etc. Drive coils 5a and 5b are wound around the outer periphery of the stator core with an insulating layer of plastic or the like interposed between them. Note that 10 is a commutative pole that has a phase difference. Hall elements 6b and 6a are used as control elements for controlling the drive currents of the drive coils 5a and 5b.
It is provided on the center line of the drive coils 5a, 5b and facing the drive coils 5a, 5b. The Hall element 6a controls the drive current of the drive coil 5a, and is provided in the gap between the stator core 4 and the rotor magnet 3, around which the drive coil 5b is wound. Similarly, a Hall element 6b for controlling the drive current of the drive coil 5b is provided in the gap between the stator core 4 and the rotor magnet 3, around which the drive coil 5a is wound. These drive coils 5a, 5b and Hall elements 6a, 6b are connected via drive circuits 9a, 9b as shown in FIG. 14.

Next, the waveform of the Hall output voltage output by the Hall element 6a when the rotor is rotating and its problems will be explained. FIG. 2 shows the Hall element 6a
Figure 2A shows the waveform of the Hall output voltage.
2B is a waveform diagram of the Hall output voltage outputted by the Hall element 6a under the influence of only the magnetic flux generated by the rotor magnet 3, and FIG. The waveform diagram of the Hall output voltage to be outputted, FIG. 2C, is a composite waveform of the Hall output voltages of the Hall element 6a shown in FIGS. 2A and 2B, and the Hall element 6a is It actually outputs the Hall output voltage. Note that the drive circuit 9a is
It is configured so that a drive current proportional to the Hall output voltage of the Hall element 6a flows through the drive coil 5a. Similarly, the drive circuit 9b includes the Hall element 6
It is configured so that a drive current proportional to the Hall output voltage of b flows through the drive coil 5b.

Now, when the drive coil 5a and the Hall element 6a are in the positional relationship as shown in FIG. The waveform is shown by the dotted line in FIG. 2C, which is the same as the waveform shown in FIG. 2A. However, when the drive current flowing through the drive coil 5a increases and affects the Hall element 6a, the magnetic flux generated by the drive coil 5a and the magnetic flux generated by the rotor magnet 3 are at an electrical angle of 90 degrees from each other. Because of the phase difference, the composite magnetic flux changes depending on the drive current, and the Hall output voltage actually output by the Hall element 6a has a waveform whose phase is shifted by Δθ in electrical angle, as shown by the solid line in FIG. 2C. Become. In addition,
The rotational position of the rotor shown in FIG. 1 is shown in FIG. 2 as indicated by ▽ in the figure.

As mentioned above, conventionally, the control element that controls the drive coil of one phase generates the Hall output voltage under the influence of the drive current flowing through the drive coil of the other phase, so the composite voltage actually output by the control element is The waveform of the Hall output voltage thus generated is out of phase as shown by the solid line in FIG. 2C. Therefore, the timing of switching between the drive current flowing through the drive coil of one phase and the drive current flowing through the drive coil of the other phase is shifted, making it difficult to accurately control uneven rotation of the rotor magnet. There were flaws.

A feature of the present invention is that the control element that controls the drive current flowing through the drive coil of one phase out of a pair of control elements is configured to combine the magnetic flux generated by the drive coil of the one phase with the magnetic flux generated by the rotor magnet. The control element is characterized in that both magnetic fluxes have a phase difference of 0 with respect to the control element, and that the control element is disposed at a location where it is not affected by the magnetic flux generated by the drive coil of the other phase.

Next, one embodiment of the present invention will be described based on the drawings.

In FIG. 3, 2 is a rotor case, 3 is a rotor magnet, and 4 is a stator core around which drive coils 5a and 5b are wound.These structures are the same as the conventional structure described above, but the Hall element is 6
The mounting positions of a and 6b are different. More specifically, the Hall elements 6a and 6b are respectively disposed at the peripheral edge of the tip of the stator core 4, and are disposed at positions offset from the central axes of the drive coils 5a and 5b, respectively.
In this case, it is most desirable to place the Hall elements 6a, 6b close to the periphery of the tip end of the stator core 4 from the viewpoint of effectively utilizing the magnetic flux. Here, the Hall element 6a functions as a control element that controls the drive current flowing through the drive coil 5a, and
The Hall element 6b functions as a control element that controls the drive current flowing through the drive coil 5b.

FIG. 4 is a waveform diagram in which the horizontal axis is time and the vertical axis is the Hall output voltage output by the Hall element 6b. FIG. 4B is a waveform diagram of the Hall output voltage output by the Hall element 6b under the influence of only the magnetic flux generated by the drive coil 5b.
FIG. 4C is a composite waveform of the Hall output voltage of the Hall element 6b shown in FIGS. 4A and 4B, and the Hall element 6b actually outputs this composite Hall output voltage. It is something. here,
The rotor magnet 3 is rotating clockwise,
In FIG. 3, the north pole of the rotor magnet 3 faces the Hall element 6b. The Hall element 6b senses the north pole of the rotor magnet 3 and outputs a positive voltage. Furthermore, in order to rotate the rotor magnet 3 clockwise, an S pole is generated in the drive coil 5b at the tip of the stator core 4 on the Hall element 6b side, and opposite to the tip on the Hall element 6b side. A drive current is applied so that a north pole is generated at the tip of the side. Since the waveform of this drive current is similar to the waveform of the Hall output voltage shown in FIG. 4C, it changes as the rotor magnet 3 rotates. When the rotor magnet 3 is in the position shown in FIG. 3, that is, in the state indicated by □1 in FIG. 4, the magnetic flux passing through the Hall element 6b is the magnetic flux generated from the N pole of the rotor magnet 3, and The magnetic flux generated from the S pole of the stator core 4 is radially inward in the same direction (phase difference 0), and these two magnetic fluxes are added together and pass through the Hall element 6b. Note that when the rotor magnet 3 is in the position shown in FIG. 3, the Hall output voltage of the Hall element 6b is maximum.

As described above, the Hall output voltage output by the Hall element 6b is obtained by adding the Hall output voltage generated by the magnetic flux of the rotor magnet 3 and the Hall output voltage generated by the magnetic flux of the drive coil 5b in the same phase. Ru. To explain this in more detail with reference to FIG. 10, the north pole of the rotor magnet 3 is located on the left side of the Hall element 6b, and a magnetic flux shown by a solid line is generated. On the other hand, since a drive current flows through the drive coil 5b in the direction shown in the figure, an S pole is generated on the right side of the Hall element 6b, and a magnetic flux shown by a broken line is generated. Since both of these magnetic fluxes have the same direction, these magnetic fluxes are added to pass through the Hall element 6b, increasing the magnetic flux density, so the Hall output voltage output by the Hall element 6b increases by that amount. .

FIG. 5 is a comparative example to the previous embodiment of the invention, which is similar in method to one embodiment of the invention, but is actually very different.

In FIG. 5, the general structure is the same as that of the above-described embodiment, but only the mounting positions of the Hall elements 6a and 6b are different.

FIG. 6 is a waveform diagram in which the horizontal axis is time and the vertical axis is the Hall output voltage output by the Hall element 6b. FIG. 6B is a waveform diagram of the Hall output voltage output by the Hall element 6b under the influence of only the magnetic flux generated by the drive coil 5b.
FIG. 6C is a composite waveform of the Hall output voltage of the Hall element 6b shown in FIGS. 6A and 6B, and the Hall element 6b actually outputs this composite Hall output voltage. It is something. Furthermore, the fifth
In the figure, the direction of the drive current flowing through the drive coil 5b is the same as in the previous embodiment. 6A and 6C, when the rotor magnet 3 is in the position shown in FIG. 5, the Hall output voltage output by the Hall element 6b is at its minimum. The Hall output voltage output by the Hall element 6b is the same as the Hall output voltage due to the magnetic flux of the rotor magnet 3, as in the previous embodiment.
It is a combination of the Hall output voltage due to the magnetic flux of the drive coil 5b, but since these two magnetic fluxes have opposite phases to each other, that is, they have a phase difference of 180 degrees in electrical angle, the Hall element 6b actually outputs The Hall output voltage is determined by the following equation.

Vt=Vm-Vc However, Vt is the Hall output voltage actually output by the Hall element 6b, Vm is the Hall output voltage output by the Hall element 6b under the influence of only the magnetic flux of the rotor magnet 3, and Vc is the Hall output voltage output by the drive coil 5b. This is the Hall output voltage output by the Hall element 6b under the influence of only the magnetic flux. Note that the waveform shown by the solid line in FIG. This is the waveform of the Hall output voltage that is affected and output. This will be explained in more detail below.
In Fig. 11, the N pole of the rotor magnet 3 is located on the left side of the Hall element 6b, generating magnetic flux shown by the solid line, and the N pole is generated on the right side of the Hall element 6b by the drive coil 5b. A driving current is applied so that the magnetic flux shown by the broken line is generated. In this way, magnetic fluxes in opposite directions pass through the Hall element 6b, and when the magnetic flux of the rotor magnet 3 is larger than the magnetic flux of the drive coil 5b, the magnetic flux of the rotor magnet 3 becomes the magnetic flux of the drive coil 5b. Therefore, the Hall output voltage actually outputted by the Hall element 6b is lower than the Hall output voltage outputted only by the magnetic flux of the rotor magnet 3. Therefore, when the drive coil 5b and the Hall element 6b are in the positional relationship as shown in FIG. 5, when the drive current increases, the magnetic flux generated by the drive coil 5b also increases in proportion to it.
It is also possible that the Hall output voltage is reversed and malfunctions.

In the explanation with reference to FIG. 3, a case has been described in which the Hall elements 6a and 6b are attached in contact with the gap between the stator core 4 and the rotor magnet 3 or the surface of the stator core 4 that is in contact with the gap. Of course, it is not limited to this.

Next, other embodiments of the present invention will be described.
Here, Hall elements 6a and 6b are used to detect the position using the magnetic flux generated on the end face of the rotor magnet 3.
We will explain the case where the is installed. In FIGS. 7 to 8, a rotor case 2 made of a yoke material is fixed so as to be in contact with the outer peripheral surface of an annular rotor magnet 3 whose inner peripheral surface is magnetized with N and S poles. Reference numeral 7 denotes a motor support member for supporting the Hall motor, and rotatably supports the rotary shaft 1 by means of a bearing 2 in the center thereof. Then, on the outer periphery of the bearing 2,
The stator core 4 around which the drive cores 5a and 5b are wound is fixed. Further, the Hall elements 6a and 6b are arranged on a concentric circle where the motor support member 7 faces the inner diameter of the rotor magnet 3. Here, the positional relationship between the drive coils 5a, 5b and the Hall elements 6a, 6b will be explained in detail below. Note that the other general configurations are the same as in the previous embodiment.

In FIG. 8, the Hall elements 6a and 6b are located at positions that are advanced in the rotational direction of the rotor magnet 3 by a phase difference of 90 degrees in electrical angle from the center of the magnetic flux of the drive coils 5a and 5b, respectively, and are connected to the end face of the rotor magnet 3. Fix it in a place opposite to. Here, the Hall element 6a and the Hall element 6b have a phase difference of 90 degrees in electrical angle. Furthermore, the drive current flowing through the drive coil 5a and the Hall output voltage output from the Hall element 6a are in phase, and the drive current flowing through the drive coil 5b and the Hall output voltage output from the Hall element 6b are also in phase. Note that changing the reference terminal results in a phase difference of 180° in electrical angle. In this way, the drive current flowing through the drive coil 5a is controlled by the Hall output voltage output by the Hall element 6a,
The drive current flowing through the drive coil 5b is controlled by the Hall output voltage output by the Hall element 6b. In addition,
The Hall output voltage outputted by the Hall elements 6a and 6b at the position shown in FIG. 8 is the value shown by the mark □2 in FIG.

In FIG. 8, since the rotor magnet 3 is rotated clockwise, a drive current is passed through the drive coil 5b so that an S pole is generated on the side of the Hall element 6b and an N pole is generated on the opposite side. Then, the magnetic flux generated by the rotor magnet 3 and the magnetic flux generated by the drive coil 5b become in phase, and the added magnetic flux,
So-called magnetic flux with increased magnetic flux density passes through the Hall element 6b. This state is shown in FIG. That is, as in the embodiment described above, the magnetic flux passing through the Hall element 6b is added by the amount of magnetic flux generated by the drive coil 5b compared to the case where only the magnetic flux generated by the rotor magnet 3 is generated. As the flowing drive current increases, the Hall output voltage output from the Hall element 6b increases and is stably input to the drive circuit 9a shown in FIG. 14.

Note that if the rotation direction of the rotor magnet 3 is reversed counterclockwise as shown in FIG. 9, a malfunction as explained in FIG. 5 will occur. That is, the first
As shown in FIG. 3, the magnetic flux of the rotor magnet 3 shown by a solid line and the magnetic flux of the drive coil 5b shown by a broken line pass through the Hall element 6b in opposite directions. Therefore, when the drive current flowing through the drive coil 5b increases and the magnetic flux of the drive coil 5b becomes larger than the magnetic flux of the rotor magnet 3, the polarity of the output voltage output from the Hall element 6b is reversed, as shown in FIG. The drive circuit 9b shown in 2 malfunctions. In other words, brake torque is generated and the rotation of the rotor magnet 3 is stopped, or the switching of the drive current is not performed smoothly, and the short current flows through the drive element (power transistor, etc.) and destroys the drive element. .

Although the above embodiment has been explained using a two-phase winding type brushless motor, the present invention is not limited thereto, and can of course be applied to a three-phase winding type brushless motor or a four-phase winding type brushless motor. Applicable. Further, in the above embodiments, a stator core type Hall motor having convex poles has been described, but the present invention can also be applied to brushless motors such as slotless and coreless motors. Further, the present invention is fully applicable not only to analog energization but also to switching energization, that is, where the drive current flowing through the drive coil is not sinusoidal as in analog energization, but has a rectangular waveform.

The present invention positions the control element that controls the drive coil of one phase so that the control element that controls the drive coil of one phase is not affected by the drive coil flowing through the drive coil of the other phase. In addition, the magnetic flux passing through this control element, that is, the magnetic flux generated by the rotor magnet, and the magnetic flux generated by the drive coil of one phase are in phase and added, so that the control The output voltage output by the element can be efficiently increased, and the timing of switching between the drive current flowing to the drive coil of one phase and the drive current flowing to the drive coil of the other phase does not deviate, making rotation faster than before. This has the effect of reducing unevenness as much as possible. Furthermore, since the control element detects the magnetic flux produced by the drive coil that is in phase with the control element, armature reaction can be properly taken into account. Furthermore, since the output voltage output by the control element increases by the amount of magnetic flux generated by the drive current flowing through the drive coil, the starting torque of the motor increases by that increase, making it possible to control the rotation of the motor with high precision. Can be done.

[Brief explanation of drawings]

Figure 1 shows a cross section of the main parts of a conventional Hall motor.
2 is a waveform diagram showing the Hall output voltage according to FIG. 1, FIG. 3 is a sectional view of a main part showing an embodiment of the present invention, and FIG. 4 is a waveform diagram showing the Hall output voltage according to FIG. 3. , FIG. 5 is a sectional view of main parts showing a comparative example with respect to the one in FIG. 3, FIG. 6 is a waveform diagram showing the output voltage according to FIG. 5, and FIGS. 7 to 8 are other embodiments of the present invention. FIG. 9 is a cross-sectional view of a main part showing an example, and FIG. 9 is a reference diagram showing something that is similar to other embodiments of the present invention but is actually different. FIGS. 10 to 13 show magnetic flux distribution near the control element. The explanatory diagram, FIG. 14, is a circuit connection diagram showing a circuit according to the present invention. 3... Rotor magnet, 4... Stator core, 5a, 5b... Drive coil, 6a, 6b...
Hall element, 9a, 9b...drive circuit.

Claims (1)

[Claims] 1. A rotor magnet with a plurality of magnetic poles magnetized in the circumferential direction, a stator core around which a drive coil is wound opposite to the rotor magnet, and a stator core that detects the magnetic poles of the rotor magnet and cooperates with a drive circuit. a brushless motor comprising at least a pair of control elements that control a drive current flowing to the drive coil of one phase among the control elements, the control element controlling the drive current flowing to the drive coil of one phase; A location where the magnetic flux generated by the drive coil and the magnetic flux generated by the rotor magnet have a phase difference of 0 with respect to the control element,
A brushless motor characterized in that the brushless motor is disposed at a location where it is not affected by the magnetic flux generated by the drive coil of the other phase, and both of the magnetic fluxes are detected by the control element.