Electricity: motive power systems – Battery-fed motor systems
Reexamination Certificate
2002-10-29
2004-08-10
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Battery-fed motor systems
C318S430000, C318S431000
Reexamination Certificate
active
06774590
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of starting an electric brushless rotating machine and particularly to a method of starting an electric brushless rotating machine appropriated for generating a large torque at the startup stage.
2. Description of the Related Art
A brushless motor is provided as an electric rotating machine where the energization of three-phase stator windings for driving a rotating member (referred to as a rotor hereinafter) is switched from one to another whenever the rotor rotates through 120 degrees of the electric angle. Such a conventional brushless motor has commonly a position detector element such as a Hall device for detecting the rotating position of the rotor. Recently, another type of brushless motor which includes no position detector element has been developed in response to the demand for down-sizing of the brushless motor.
For example, a brushless motor is disclosed in Japanese Patent Publication (Heisei)5-24760 where, in view of any two different phases of the three-phase stator windings being energized in a sequence, the voltage induced at the remaining not-energized phase is measured and used for calculating the rotating position of the rotor. As the brushless motor produces non of the induced voltage at the startup stage which is used for calculating the rotating position of the rotor, its rotor has slightly be driven by forced commutation. The forced commutation means that any two desired phases of the stator, e.g. U and V, are energized regardless of the position of the rotor (which is hence referred to as one-phase energization hereinafter). The position of the rotor is detected from the induced voltage and then a common procedure of the energization will follow in relation to the detected rotor position.
The positional relationship between the rotor and the stator when they stop their movement as the motor has been deenergized is determined by attracting and repulsing forces of the magnets. For example, when the motor is an outer rotor type brushless motor having three-phase stator windings, its positional relationship between the rotor and the stator is expressed by six different pausing modes, p1 to p6, shown in FIG.
13
.
FIG. 13
illustrates an arrangement of a primary part of the brushless motor in addition to the six pausing modes of the position relationship between the rotor and the stator of which the movement stops as the motor has been deenergized.
As shown in
FIG. 13
, the counter clockwise direction is the forward direction Rs of the rotor while the clockwise direction is the reverse direction Rr. The stator
100
and the rotor
200
of the brushless motor are disposed inward and outward respectively. The stator
100
has magnetic poles
300
of U, V, and W phase. The magnetic poles
300
incorporate windings. The rotor
200
has a row of permanent magnets m
1
, m
2
, m
3
, . . . of which the polarity alternates between N and S along the circumference.
A movement of the rotor from the initial pausing mode p1 to p6 when is driven by forced commutation between U phase and W phase without initial magnetization will be explained. When an electric current is supplied through U phase to W phase, the U phase is magnetized to positive (N) pole and the W phase is magnetized to negative (S) pole.
At the initial pausing mode p1, the magnet m
2
at S is attracted by the U phase at N but repulsed by the W phase at S. This causes the rotor
200
to rotate at a maximum torque in the forward direction Rs. At the initial pausing mode p2, the U phase at N attracts the magnet m
2
at S but repulses the magnet m
3
at N hence allowing the rotor
200
to rotate at the maximum torque in the forward direction Rs. At the initial pausing mode p3, the attraction between the U phase at N and the magnet m
2
at S is balanced with the attraction between the W phase at S and the magnet m
1
at N. This permits no movement of the rotor
200
.
At the initial pausing mode p4, the magnet m
2
at N is attracted by the W phase at S while the magnet m
1
at S is repulsed by the same. This causes the rotor
200
to rotate in the reverse direction Rr. At the initial pausing mode p5, the U phase at N attracts the magnet m
3
at S but repulses the magnet m
2
at N hence allowing the rotor
200
to rotate further in the reverse direction Rr. At the initial pausing mode p6, the repulsion between the U phase at N and the magnet m
2
at N is balanced with the repulsion between the W phase at S and the magnet m
1
at S. This permits no movement of the rotor
200
.
As described, the startup torque may be generated non or too small at the initial pausing modes p3 and p6 thus disallowing the brushless motor to start up. In particular, when the brushless motor is linked to a heavy load and thus required to generate a large torque, this disadvantage will be significant. For example, the motor for starting an internal combustion engine, even if its output is great, may fail to generate a desired level of the startup torque because the friction in the engine is too high. At the initial pausing modes p4 and p5, the rotor rotates in the reverse direction and fails to generate a desired magnitude of the induced voltage needed for detecting the position of the rotor, hence inhibiting any normal energizing action. More particularly, by force commutation, the motor when remains free in the movement can be rotated in the forward direction two times out of six trials or at ⅓ of the probability.
SUMMARY OF THE INVENTION
It is hence an object of the present invention to provide a method of starting an electric brushless rotating machine which can generate a great level of the startup torque with no use of rotor position detecting elements. Another object of the present invention is to provide a method of starting an electric brushless rotating machine which can shift from the force commutation to a common operation simply and smoothly.
It is a further object of the present invention to provide a method of starting an electric brushless rotating machine which can continue to supply an upper limit level of current during the forced commutation thus to generate a climb over torque.
A first feature of the present invention is that a method of starting an electric brushless rotating machine for driving an internal combustion engine which has a magnetic rotor joined to an output shaft of the internal combustion engine and a set of stator windings of a first phase, a second phase, and a third phase arranged at equal phase intervals of an electric angle of 120 degrees so that the stator windings are energized in a sequence for forced commutation according to a rotating position detecting signal from the rotor, comprising the steps of, energizing between any two of the first, second, and third phase stator windings for initial magnetization at the startup to hold the magnetic rotor at a position, carrying out the forced commutation to energize the windings of the phases in a sequence while gradually increasing the level of the energization for forcefully rotating the magnet rotor, and generating the rotating position detecting signal from a voltage signal induced on the not-energized windings during the forced commutation and carrying out a normal action of the energization based on the rotating position detecting signal thus allowing the magnetic rotor to drive the output shaft of the internal combustion engine, and canceling the energization when the number of revolutions or the full turning motion in the internal combustion engine determined from the rotating position detecting signal reaches its predetermined level or times.
According to this feature, the internal combustion engine can be started up by a large level of the startup torque with no help of position detecting elements. The electric brushless rotating machine can hence be used as a brushless starter motor.
A second feature of the present invention is that the timing for switching from the forced commutation to the normal energization is taken when the number
Iijima Yoshihiro
Inagawa Toshinori
Nakamura Mitsuru
Wakitani Tsutomu
LandOfFree
Method for starting an electric brushless rotating machine... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for starting an electric brushless rotating machine..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for starting an electric brushless rotating machine... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3341298