JPS60210151A - Magnet rotary type motor - Google Patents

Abstract

PURPOSE:To enable to detect a pole in high reliability by using a magnetically anisotropic ferrite magnet for a rotor, and mounting a pole for detecting the pole made of a full-ring shape isotropic ferrite magnet of 180 deg. of magnetizing angle separately from the anisotropic ferrite magnet. CONSTITUTION:Two magnetically anisotropic ferrite magnets 11 are mounted on a rotor yoke 10, and opposed to a stator 5. Further, a full-ring shape isotropic ferrite magnet 12 is mounted at the position not opposed to the stator 5 on the same yoke 10. The magnet 12 has two poles at 180 deg. of magnetizing angle, a pole detection sensor 6 is opposed to the magnet 12, and connected with a controller 7. Thus, even if a magnetic anisotropic ferrite magnet which cannot be formed at the magnetizing angle theta at 180 deg. is used for the rotor, the pole position can be accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnet-rotating electric motor which eliminates the need for a commutator and replaces brushes, thereby extending its life.

Construction of a conventional example and its problems First, the construction of this type of electric motor will be explained based on FIG. 1. In the figure, reference numeral 1 denotes a rotating shaft, and magnets 3 are fixed to this rotating shaft 1 via a yoke 2, and these constitute a rotor. A stator 5 having a coil 4 wound thereon is disposed around the outer periphery of the rotor with a gap interposed therebetween. Reference numeral 6 denotes a magnetic pole detection sensor, which has a control circuit 7 that generates a rotating magnetic field in the stator 5 in response to a signal from the sensor 6.

8.9 is a bearing that receives the rotating shaft 1.

Next, there is a problem with the magnet-rotating electric motor having the above structure. As shown in FIG. 1, the magnetic pole detection sensor 6 is arranged near the magnet 3 in order to detect the leakage magnetic flux of the magnet 3. However, since the length of the magnet 8 is generally approximately the same as the length of the stator 5, the magnetic pole detection sensor 6 is inevitably located near the coil 4. For this reason, it will be affected by the magnetic field generated by the coil 4 or the magnetic flux from the stator 5, but if the current flowing through the coil 4 increases, that is, if the motor has a large capacity,
The influence of the magnetic field generated by the coil 4 or the stator 5 causes the sensor 6 to malfunction, which not only makes it impossible to obtain normal characteristics but also damages the control circuit 7.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides a magnet-rotating electric motor that enables more reliable magnetic pole detection.

Composition of the Invention The magnet rotating electric motor of the present invention includes a rotor having a rotary shaft fixed to a magnet having two magnetic poles in the radial direction through a yoke;
A stator has a coil wound around the outer periphery of the rotor with a gap in between, a magnetic pole position detection sensor detects the magnetic pole position of the rotor, and a rotating magnetic field is generated in the stator in response to signals from this sensor. The magnets include a first magnet consisting of two magnetically anisotropic ferrite magnets facing the stator, and a second magnet consisting of one full-ring isotropic ferrite magnet not facing the stator. This second magnet also has two magnetic poles, one of which is
The magnetization angle of the pole is 18o0, and the magnetic pole position detection sensor is disposed at a position to detect the magnetic pole of this second magnet, so that the magnetic pole position of the rotor can be accurately detected.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. 1st
The same parts as those in the figures are given the same reference numerals, and the explanation is omitted, and only the different points will be explained in detail.

In FIGS. 2, 3, and 4, 10 is a yoke that is longer in the axial direction than the stator 5, and 11 is composed of two magnetically anisotropic ferrite magnets fixed to the rotating shaft 1 via this yoke 10. The first magnet faces the stator 5 and has two magnetic poles, N and S, in the radial direction. The yoke 1o 12 is attached to the rotating shaft 1 without facing the stator 5.
The second magnet is made up of one full-ring isotropic ferrite magnet that is fixed via 180
It is set to 0. A magnetic pole position detection sensor 6 is disposed at a position for detecting the magnetic pole of the second magnet 12.

With the above configuration, that is, by providing the second magnet 12, the magnetic pole position detection sensor 6 is moved away from the coil 4 and the stator 6. Therefore, there is no fear of malfunction due to the magnetic field from the coil 4 or stator 5 as in the prior art. The second magnet 12 is positioned so as to keep the distance between the coil 4 and the magnetic pole position detection sensor 6 as appropriate depending on the magnitude of the input current to the coil 4 (the magnetic field is proportional to the product of the number of turns of the coil and the input current). It goes without saying that this can be implemented by design within the scope of the present invention.

Further, by setting the magnetization angle of one pole of the second magnet 12 to 1800, the magnetic pole position of the sensor 6 can be detected more sharply, and as a result, the position can be detected with high accuracy even at high speed rotation.

The reason why the first magnet 11 is a magnetically anisotropic ferrite magnet is that its magnetic properties, that is, its energy product are high, and a small and lightweight electric motor can be obtained. However, this magnetic anisotropic ferrite magnet has a central angle θ of 13
It is said that it is very difficult to obtain the magnetic performance of this magnet with a size of 00 or more, that is, to have a magnetization angle of 1300 or more with one magnet. Although the production cost is high, it is technically possible to have a central angle θ (which also means the magnetization angle of one magnet) of up to 160°. However, the reality is that it is hardly used due to its high cost, and it is technically impossible to make one with a central angle θ of 1800 degrees. therefore,
More than that, for example, a full ring as shown in FIG. 4 cannot be made. Therefore, magnetically anisotropic ferrite magnets in which the center angle θ of one magnet is generally 120 to 13oO are often used.

Moreover, the reason why the second magnet 12 is an isotropic ferrite magnet is as follows.
This is because, although its magnetic properties are inferior, unlike the magnetic anisotropic ferrite magnet described above, the magnet can be magnetized at any number of angles, and full-ring magnets can also be produced. That is, in this embodiment, for detecting the magnetic pole position, only the N-pole and S-pole signals are sent to the sensor 6, so the first
The high magnetic performance required for the magnet 11 is not necessary, and instead, it is sufficient to obtain a magnetization angle of 18oO. Therefore, it can be said that this isotropic ferrite magnet is more preferable. Furthermore, in terms of cost, this isotropic ferrite magnet is cheaper.

Therefore, for example, as shown in FIG.
It is also possible to make the first magnet 11 longer in the axial direction to make it longer than the stator 5, but in this case, the magnetization angle of the first magnet 11 is generally 120 to 13o0 as described above, and the part without the magnet is It is obvious that the detection of the magnetic pole position becomes unstable because of this. That is, it is preferable that the N and S poles switch sharply, in other words, it is preferable that the N and S poles each have a magnet over the entire 180° range to generate magnetic flux, and that the N and S poles switch more quickly than the N pole.

Also, in this example, the magnetization angle of the first magnet 11 is 9
00, that is, the central angle θ of the magnet is 90°, and there is a method of using four magnets. In this way, there is no problem that the magnetization angle is 120 to 130 degrees as described above, and magnetization up to 180 degrees is possible.

However, four magnets are required, which is not practical.

Here, to briefly touch on the cost of ferrite magnets, in the case of ferrite magnets, the material costs are low, but the molding costs are high.

Therefore, as the number of magnets increases, the total cost increases even if the weight of the magnets remains the same.

Therefore, if four magnets are used as described above, the cost will naturally be higher than the three magnets used in the embodiment of the present invention (two first magnets and one second magnet). .

Effects of the Invention As described above, the magnet rotating electric motor of the present invention has a first magnet consisting of two magnetically anisotropic ferrite magnets facing the stator.
and a second magnet consisting of one full-ring isotropic ferrite magnet that does not face each other.
By setting the magnetization angle of the magnet to 180°, it is possible to detect the magnetic pole position of the rotor accurately and at low cost. This is effective due to its large capacity and high speed rotation, and its usefulness is high, making it a dog of industrial value.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional example of a magnet rotating electric motor;
The figure is a cross-sectional view of a magnet-rotating electric motor showing an embodiment of the present invention, FIG. 3 is a perspective view showing the rotor of the same motor, FIG. 4 is a perspective view showing a second magnet, and FIG. 6 is for explanation. FIG. 3 is a perspective view showing the rotor of FIG. 1...rotating shaft, 4...coil, 6...
... Stator, 6... Magnetic pole detection sensor,
7...Control circuit, 1゜...Yoke, 1
1...First magnet, 12...Second magnet. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure.・, . ? 8-ma Akira GO-210i51 (4)

Claims (1)

[Claims] A rotor has two magnets fixed to its rotating shaft in the radial direction via a yoke, a stator has a coil wound around the outer periphery of the rotor with a gap in between, and the position of the rotor's magnetic poles is detected. It has a magnetic pole position detection sensor and a control circuit that generates a rotating magnetic field in the stator in response to a signal from the sensor, and the magnet is a first magnet made of two magnetically anisotropic ferrite magnets facing the stator. and a second magnet consisting of one full-ring isotropic ferrite magnet that does not face the stator, and this second magnet also has two magnets.
A magnet rotating electric motor having two magnetic poles, one of which has a magnetization angle of 180°, and the magnetic pole position detection sensor is disposed at a position to detect the magnetic pole of the second magnet.