JPS63224688A - Brushless dc motor - Google Patents

Abstract

PURPOSE:To operate a brushless DC motor accurately by mounting a magnetizing section to one part of the outer circumferential surface of a rotor, using the magnetizing section as a reference point and employing an MR sensor for detecting pulses and a counter. CONSTITUTION:A bipolar type blushless DC motor is constituted of three-phase driving coils C1-C3 and a first transistor(Tr) group T1-T3 and a second Tr group T4-T6 forming current paths from a DC power to the coils C1-C3. The brushless DC motor also has an MR sensor M1 for detecting frequency, filters 100, waveform shapers 101, an F-V converter 102, a counter 105, and a voltage comparator 103, and DC supply voltage is controlled by a voltage- power amplifier 106. A magnetizing section is fitted only at one position of the upper section of the outer circumferential surface of a rotor in order to determine the relationship of the position of a rotor and the number of the counter, and an MR sensor M2 for detecting pulses is set up so as to use the magnetizing section as a reference point. Accordingly, the number of pulses from said sensor M2 is counted, and the Tr groups T1-T6 are changed over in six manners by the counting values and the motor is driven.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brushless DC motor in which current paths to three-phase coils are switched by transistors.

[Conventional technology]

Conventionally, a brushless DC motor requires three elements or devices for detecting the position of the rotor magnet in order to switch the current path to the three-phase coils. Currently used are a magnetoelectric conversion method using a Hall element, a photoelectric conversion method using a light emitting diode, and a high frequency switching method using an inductance change. Among these, the system using a Hall element as shown in FIGS. 5 and 6 is mainly used. When the rotor 1 rotates, the magnetic flux generated by the rotor magnet 3 acts on the Hall element 4, causing the Hall voltage to change almost like a sine wave. Switching is performed by sending this signal to the six drive transistors, and the rotor continues to rotate without stopping even momentarily. Further, when the rotor rotates, a frequency proportional to the number of rotations is generated in the frequency detection MR sensor 5. By passing this signal through the F-Vi converter, the power supply voltage sent to the drive coil 6 is adjusted, thereby controlling the rotation speed.

[Problem that the invention seeks to solve]

The conventional brushless DC motor described above has the disadvantages that it has a large number of parts, and requires precision in the positional relationship between the Hall elements, making it difficult to assemble and difficult to reduce costs. .

Furthermore, the Hall voltage of the Hall element is affected by temperature, and since the Hall element is installed between the coil and rotor, where the most heat is generated in the motor, temperature compensation measures are required and the number of parts increases. It has the disadvantage of high cost.

[Means for solving problems]

The brushless DC motor of the present invention has an annular magnet having n sets (n is an integer) of main calm poles on the inner circumferential surface and a frequency generating magnetic pole section on the end surface, and a pulse generating magnetic pole section on a part of the outer circumferential surface. The equipped rotor, a three-phase coil that interlinks with the main magnetic flux of the rotor, and an MR cell for frequency detection arranged opposite to the magnetic pole part for frequency generation and the brain pole part for pulse generation, respectively.
a first drive transistor group that forms a current path from the DC power supply to the three-phase coil, and a second drive transistor group that forms a current return path from the three-phase coil to the DC power supply. a pulse detection means that detects the voltage from the MR sensor for frequency detection to obtain pulses; and a pulse detection means that receives the pulses from the MR sensor for pulse detection and counts the number of pulses from the MR sensor for frequency detection. and means for sending the results to the switching controller.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of an embodiment of the present invention.

In the figure, three-phase drive coils CI, C2, C3 and a first transistor group TI, T2. It represents a bipolar brushless free current motor having T3 and a second group of transistors T4, 'r, , T, forming a current path from the three-phase coils to the DC power supply. Ml is an MR sensor for frequency detection, and an alternating current similar to a sine wave with a frequency proportional to the rotational speed of the motor appears. Filter 1 for the above sine wave
00a, 100b and waveform shapers 101a, 101b, it is converted into a pulse signal, and the F-V converter 102,
It is sent to the counter 105, and in the F-V converter 102,
The voltage is determined by generating a voltage proportional to the frequency of the input pulse signal and comparing it with the speed setting voltage using the voltage comparator 103.

A power amplifier 106 controls the voltage of the DC power supply.

Further, the frequency detection MR and sensor used for speed control are also used to detect the position of the rotor and control the motion transistor. Pulses from the MR and sensor for frequency detection are counted, and the position of the rotor is detected based on the counted number, and the transistor TI-T6 is switched. However, if there is no reference point on the rotor, the number of counts and the position of the rotor cannot be matched. Relationship not determined. Therefore, as shown in Figure 3, we set up a magnetized part on the upper part of the outer peripheral surface of the rotor as a reference point, and used it as a pulse detection device as shown in Figure 2 M2 to notify that the reference point has passed. By installing the MR sensor, one pulse is generated every time the rotor makes one revolution (Figure 4A), and this is used as a start signal to count the number of pulses from the MR sensor for frequency detection (Figure 4B). The transistor group is switched and driven in six ways depending on the count value.

〔Effect of the invention〕

As explained above, in the present invention, a magnetized part is provided on a part of the outer peripheral surface of the rotor as a reference point, and by using an MR sensor for pulse detection and a counter, position detection is performed with a single sensor and brushless. The motor can be driven in three phases. Therefore, it is easy to assemble, has a small number of parts, is not affected by temperature, and has the effect of enabling accurate operation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a sectional view of the brushless motor used in FIG. 1, and FIG. 3 is a top plan view of the brushless motor used in FIG. 1. Fourth
The figure is a waveform diagram showing pulse signals from the MR sensor for frequency detection and the MR sensor for reference point detection, FIG. 5 is a product diagram showing a conventional example, and FIG. 6 is a developed diagram of the conventional structure. a1 to a6...Amplifier, TI-T,...
...Drive transistor, cl-c3...Drive coil, Ml...MR for frequency detection, sensor, M
2...MR sensor for reference point detection, H1 to H3
......Hall element, A...Pulse signal from Ml, B...Pulse signal from M2, 1.
...Rotor, 2...Rotating shaft, 3...
... Law agent Patent attorney Uchihara Sei Figure 2 Figure 3 ω

Claims (1)

[Claims] An annular magnet having n main magnetic pole pairs (n is an integer) on its inner circumferential surface and a frequency signal generating magnetic pole section on its end surface, and a rotor equipped with a pulse generating magnetic pole section on a part of its outer circumferential surface. , a three-phase coil interlinked with the main magnetic flux of the rotor, a frequency detection MR sensor and a pulse detection MR sensor disposed opposite to the frequency generation magnetic pole part and the pulse generation magnetic pole part, respectively, and a direct current a first drive transistor group forming a current path from the power source to the three-phase coil; a second drive transistor group forming a current return path from the three-phase coil to the DC power source; and a second drive transistor group for frequency detection. M.R.
A brushless brushless device comprising a pulse detection means for detecting a voltage signal from a sensor to obtain a pulse, and a means for counting the number of pulses from the frequency detection MR sensor after receiving the pulse from the pulse detection MR sensor. A brushless DC motor, characterized in that the number of position detection elements is reduced to one by switching the energization of the first and second drive transistor groups every time the number of pulses from the frequency detection MR sensor is constant. .