Electricity: motor control systems – Closed loop speed control system for dc motor with commutator – Field control – or field and armature control – by analog...
Reexamination Certificate
2000-06-27
2003-06-17
Ro, Bentsu (Department: 2837)
Electricity: motor control systems
Closed loop speed control system for dc motor with commutator
Field control, or field and armature control, by analog...
C388S801000, C388S803000, C318S244000
Reexamination Certificate
active
06580874
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a separately excited DC brush motor wherein a field and an armature current can be controlled separately, and more particularly to a field current control method when the overrotation or reverse rotation of motors is detected.
2. Description of the Related Art
FIG. 7
shows a separately excited DC brush motor and its control circuits. An armature current control circuit for feeding power to the armatures
61
of motors ML and MR, and a field current control circuit for feeding power to a field system
62
form separate systems and are independently controllable except that both the control circuits share a battery B
2
between them. The armature current control circuit includes a capacitor
63
, a diode
64
, one FET
65
, an armature current sensor
66
a
, and a battery voltage sensor
66
b
, the armature current being turned on electricity in only one direction. The field current control circuit includes a capacitor
67
, four FETs
68
. . . , and a field current sensor
69
. And the field current control circuit is capable of varying the direction of the field current (the direction of magnetic flux of the field system) and the intensity of the field current (intensity of the magnetic flux of the field system) by controlling the four FETs
68
. . . under PWM control.
SUMMARY OF THE INVENTION
When front wheels of a front-and-rear wheel drive vehicle are driven by an engine with the rear wheels driven by separately excited brush motors ML and MR, the motors ML and MR may be overrotated or reversely rotated by the driving force reversely transmitted from the rear wheels. When the motors ML and MR are overrotated, the motors ML and MR function as generators for generating a voltage higher than the voltage of the battery and this may result in damaging the current control elements of armature current control circuits connected to the armatures
61
of the motors ML and MR. In a case where the dielectric strength of the armature current control circuits is increased in order to prevent such damage, there arises a problem of increasing costs. Even when the motors ML and MR are reversely rotated, the motors ML and MR that function as generators allow an excessive current to flow into the diode
64
even when the FET
65
of the armature current control circuit is turned off. In a case where the current capacitance and heat radiability of the diode
64
are increased, there also develops a problem of increasing costs.
An object of the present invention made in view of the situation above is to prevent an armature current control circuit from being damaged when motors are overrotated or reversely rotated by the driving force transmitted from a driven portion.
In order to accomplish the object, according to the invention in a first aspect of this invention, proposed is a field current control method in motors such as a separately excited DC brush motor wherein a field current and an armature current are separately controllable. Also the method comprises the step of reducing the field current when overrotation or reverse rotation of motors is detected.
With the arrangement above, since the field current is reduced when the overrotation and reverse rotation of the motors is detected, the motors are prevented from functioning as generators for generating an excessive current and an excessive voltage, whereby the armature current control circuit of the motors can be prevented from being damaged without particularly increasing the dielectric strength and current capacitance.
According to the invention in a second aspect of this invention, proposed is, in addition to the arrangement in the first aspect, a field current control method has feature that the overrotation is detected from a rise in the voltage of a battery for feeding power to motors.
With the arrangement above, since the overrotation of the motors is detected from a rise in the voltage of the battery for feeding power to the motors, the overrotation can be detected exactly without providing a sensor for detecting the number of rotations of the motors.
According to the invention in a third aspect of this invention, proposed is, in addition to the arrangement in the first aspect, a field current control method by which the overrotation is detected from backward flow of the armature current of the motors.
With the arrangement above, since the overrotation of the motors is detected from the backward flow of the armature current of the motors, the overrotation can be detected exactly without providing a sensor for detecting the number of rotations of the motors.
According to the invention in a fourth aspect of this invention, proposed is, in addition to the arrangement in the first aspect, a field current control method by which the reverse rotation is detected according to the actually measured value of the armature current or the PWM value of the armature current of the motors.
With the arrangement above, since the reverse rotation of the motors is detected according to the actually measured value of the armature current or the PWM value of the armature current of the motors, the overrotation can be detected exactly without providing a sensor for detecting the number of rotations of the motors.
REFERENCES:
patent: 3183427 (1965-05-01), Hawkins et al.
patent: 3193698 (1965-07-01), Henderson et al.
patent: 3828235 (1974-08-01), Price et al.
patent: 3911342 (1975-10-01), Herwig
patent: 3967175 (1976-06-01), Turley
patent: 5039924 (1991-08-01), Avitan
patent: 5070283 (1991-12-01), Avitan
patent: 5264763 (1993-11-01), Avitan
patent: 5349279 (1994-09-01), Avitan
patent: 5585706 (1996-12-01), Avitan
patent: 5903130 (1999-05-01), Rice et al.
patent: 6021251 (2000-02-01), Hammer et al.
patent: 6153942 (2000-11-01), Roseman et al.
patent: 456-344 (1991-03-01), None
patent: 456-345 (1991-11-01), None
Asaumi Hisao
Kuribayashi Takashi
Sekiya Shigenobu
Tsuchiya Kouji
Honda Giken Kabushiki Kaisha
Ro Bentsu
LandOfFree
Field current control method in motor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Field current control method in motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Field current control method in motor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3155500