Electricity: motive power systems – Motor-reversing – Armature or primary circuit control
Reexamination Certificate
2000-08-28
2002-04-30
Dang, Khanh (Department: 2837)
Electricity: motive power systems
Motor-reversing
Armature or primary circuit control
C318S432000, C318S701000
Reexamination Certificate
active
06380705
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention is directed to a chopping energization control device including a switching element interposed between one end of an electric coil of a motor and one terminal of a power supply and another switching element interposed between the other end of the electric coil of the motor and the other terminal of the power supply and energizing the electric coil in chopping mode in such a manner that both of the switching elements are turned on and off (are made to be conductive and nonconductive), the motor is in synchronization, and such operations are repeated. This chopping energization device is used, for example, to energize each of plural phase coils of an SR motor (Switched Reluctance Motor).
For example, an energizing device for SR motor such as an SR motor driver makes switching plural phases (e.g. three phases) or switching energization (ON) of the phase coil (electric coil) and de-energization (OFF) of the phase coil (electric coil). In addition, in order to derive a required torque from the SR motor, ON/OFF control is conducted for maintaining a target current in such a manner that a chopping operation or alternating turn-on and off operation is made on a pair of switching elements allocated to each of the phase coils or an upper sided one of the switching elements. For maintaining or controlling the motor current at the target current amount, some modes have been provided. One of them is soft chopping mode, another is hard chopping mode, and a combination of these modes established depending on motor conditions. These modes are disclosed in detail in Japanese Patent laid-open print No. Hei.8(1996)-172793. The soft chopping mode is to make chopping on one of the pairs of switching elements allocated to each of the phase or electric coils. The hard chopping mode is to turn on and off both of the switching elements in synchronizing fashion.
In addition to the aforementioned soft chopping mode and hard chopping mode, in recent years, compulsory soft chopping mode, frequency reduction mode, and 0V loop soft chopping mode have been provided. The compulsory soft chopping mode is, for the reduction of noise upon switching from one to another the phase coil that is to be energized, to turn on and off one of the switching elements cyclically in compulsion while the other of the switching elements is being turned on in continual fashion. The frequency reduction mode is to lower the chopping frequency so as to prevent overheat of the switching circuit for chopping control or motor driver. The 0V loop soft chopping mode, for raising electric consumption efficiency, is to drive the motor in a very short time of the switching element by the consumption of the electromagnetic at the phase coil which has been stored therein as a result of turning off of upside energizing circuit which is earlier than the ordinal energization off timing.
However, none of these modes are valid throughout all driving stages of the electric motor. For example, lowering the chopping frequency for the protection of the switching circuit from heat generated brings in torqwue variation. The compulsory soft chopping mode is ineffective when the electric motor is in a stage when the energization is made for a very short time or when the current is required to be high in magnitude. In addition, in cases where the 0V loop soft chopping mode is used when the motor is driven to start the electric powered vehicle, if the rotor is resting at an angular position which turns off only the upside energization circuit, no current flows through the electric motor, which results in the motor failing to start.
SUMMARY OF THE INVENTION
It is, therefore, a principal objective of the present invention to provide a chopping energization control device which makes it possible to drive an electric motor in smooth fashion while restricting of a motor drive resulting from chopping energization.
A second objective of the present invention is to provide a chopping energization control device which makes it possible to drive an electric motor in smooth fashion while the chopping noise is reduced.
A third objective of the present invention is to provide a chopping energization control device which makes it possible to drive an electric motor in smooth fashion while the electric power consumption efficiency of the electric motor becomes possible to increase.
In order to attain the foregoing objectives, a first aspect of the present invention provides a chopping energization control device which comprises:
first switching means (
18
a
) interposed between one end of an electric coil (
1
a,
1
b,
1
c
) of an electric motor (
1
) and one terminal (
18
e
) of a power supply;
second switching means (
18
b
) interposed between the other end of the electric coil (
1
a,
1
b,
1
c
) and the other terminal (
18
f
) of the power supply;
signal generation means (
11
-
17
) for generating an energization indication signal (S
8
) which makes the first switching means (
18
a
) and the second switching means (
18
b
) conductive in order to establish a chopping energization of the electric coil (
1
a,
1
b,
1
c
) at a chopping frequency on the basis of a target driving torque, (Trq) and a rotation number (Nm) of the electric motor (
1
); and
control means (
11
) for making the chopping frequency smaller when the rotation number, or motor speed value, (Nm) of the electric motor (
1
) is equal to or less than a predetermined value (w
1
) than when the rotation number (Nm) of the electric motor (
1
) is greater than the predetermined value (w
1
).
It is to be noted that the foregoing reference numerals and reference codes which correspond to those in the drawings and are later described are added in parentheses to facilitate easy understanding of the invention.
In accordance with the first aspect of the present invention as defined above, while the electric motor (
1
) operates at a low speed, the electric motor (
1
) is being energized for a longer time and therefore the heat generation at the switching means (
18
a,
18
b
) becomes large which are active in chopping energization. However, at this time, the chopping frequency (fc) is lowered, which makes it possible to prevent overheat of the switching means (
18
,
18
b
). On the other hand, while the electric motor (
1
) operates at a high speed, the electric motor (
1
) is being energized for a shorter time and therefore no over heat occurs at the switching means (
18
a,
18
b
) even though the chopping frequency is raised for smoothing the rotation of the electric motor (
1
).
A second aspect of the present invention provides a chopping energization control device which comprises:
first switching means (
18
a
) interposed between one end of an electric coil (
1
a,
1
b,
1
c
) of an electric motor (
1
) and one terminal (
18
e
) of a power supply;
second switching means (
18
b
) interposed between the other end of the electric coil (
1
a,
1
b,
1
c
) and the other terminal (
18
f
) of the power supply;
signal generation means (
11
-
17
) for generating an energization indication signal (S
8
) which makes the first switching means (
18
a
) and the second switching means (
18
b
) conductive in order to establish a chopping energization of the electric coil (
1
a,
1
b,
1
c
) on the basis of a target driving torque (Trq) and a rotation number (Nm) of the electric motor (
1
);
a current sensor (
2
-
4
) for detecting an amount of current which flows through the electric coil (
1
a,
1
b,
1
c
); and
control means (
11
-
17
) for controlling the electric coil (
1
a,
1
b,
1
c
) in soft chopping mode and compulsory soft chopping mode if the target driving torque (Trq) becomes larger than a predetermined value (t
1
) and becomes equal to or smaller than the predetermined value (t
1
), respectively (Ac region, Cb region), while the electric coil (
1
a,
1
b,
1
c
) is in its energization period,
the soft chopping mode making one of the first switching means (
18
a
) and the second switching means (
18
b
) turned-on when the current amount de
Honma Chiaki
Inagaki Hiroyuki
Sugiyama Masanori
Suzuki Yoshihide
Yamada Daisuke
Aisin Seiki Kabushiki Kaisha
Dang Khanh
Sughrue & Mion, PLLC
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