Electric vehicle motor controller with temperature variation...

Details Electric vehicle motor controller with temperature variation... Electric vehicle motor controller with temperature variation...

2000-09-07

2002-05-21

Nappi, Robert E. (Department: 2837)

Electricity: motive power systems

Automatic and/or with time-delay means

Responsive to thermal conditions

C318S472000, C318S473000, C318S432000

Reexamination Certificate

active

06392376

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor controller for driving a motor using an electric converter which incorporates power elements.
2. Description of the Prior Art
A prior art motor controller which controls a current to be applied to a motor by controlling the switching of power elements will be described hereinunder.
FIG. 17
is a block diagram showing the constitution of a prior art motor controller. This is an example of car motor controller to be mounted on a vehicle and a three-phase AC motor is used as a motor.
In
FIG. 17
, reference numeral
1
denotes a motor controller,
2
a motor,
3
an arithmetic and control unit, and
4
a power conversion semiconductor as a power converter. The power conversion semiconductor
4
has three phase switching arms (U-phase arm, V-phase arm, W-phase arm). The U-phase arm, one of the switching arms, comprises an upper arm switching element
5
a
, lower arm switching element
5
b
, upper arm free wheeling diode
6
a
and lower arm free wheeling diode
6
b
. The V-phase arm and the W-phase arm have a similar structure and comprise upper arm switching elements
5
c
,
5
e
, lower arm switching elements
5
d
,
5
f
, upper arm free wheeling diodes
6
c
,
6
e
and lower arm free wheeling diodes
6
d
,
6
f
, respectively. One switching element
5
(
5
a
to
5
f
) and one free wheeling diode
6
(
6
a
to
6
f
) constitute one power element
7
(
7
a
to
7
f
). Denoted by
8
(
8
a
to
8
c
) are U-phase, V-phase and W-phase current detectors arranged on power lines for the motor
2
external to the power conversion semiconductor
4
.
As shown in the figure, two power elements
7
are connected in series for each phase of three-phase AC. One power element connected to the high potential side of DC power input is called “upper arm” and the other power element connected to the low potential side of DC power input is called “lower arm”.
A description is subsequently given of the operation of this motor controller.
The motor controller
1
converts DC power from an unshown power source into AC power and supplies the AC power to the motor
2
. The conversion of DC power into AC power is carried out by switching the switching elements
5
constituting the power elements
7
of the power conversion semiconductor
4
. The arithmetic and control unit
3
computes a current instruction value to be applied to the motor
2
to cause the motor
2
to carry out desired operation and generates gate drive signals for turning on or off the switching elements
5
so that a current corresponding to the current instruction value runs through the motor
2
. The gate drive signals are transmitted to the gates G of the switching elements
5
of the three phases.
The control of the motor
2
by a vector control method which is frequently used to control the generation torque of the motor
2
accurately will be described hereinunder.
In this method, the amounts of voltage and current of three-phase AC are decomposed into vectors which are plotted on the axis (d axis) of coordinates rotating in the same direction as a magnetic flux and the axis (q axis) of coordinates rotating in a direction perpendicular to the above direction to control generation torque by controlling voltage and current on the rectangular coordinates.
The relationship between voltage and current on the rotary rectangular coordinates (d and q coordinates) is represented by the following expression when a permanent magnet type synchronous machine is used as the motor
2
:
[
V
d
V
q
]
=
[
R
a
-
ω
·
L
ω
·
L
R
a
]
·
[
i
d
i
q
]
+
[
0
ω
·
φ
a
]
(
1
)
wherein Vd is the voltage of the d axis, Vq is the voltage of the q axis, id is the current of the d axis, iq is the current of the q axis, Ra is a primary resistance, L is an inductance, ø a is the magnetic flux of the magnet and &ohgr; is a rotation angle speed.
The generation torque &tgr;m of the motor
2
at this point is represented by the following expression:
&tgr;
m
=P
m
·ø
a
·i
q
  (2)
wherein Pm is the polar logarithm of the motor
2
.
The polar logarithm Pm and the magnetic flux ø a are fixed by the motor
2
, and the adjustment of the generation torque&tgr;m is carried out by controlling the amount of the current iq of the q axis. Therefore, the accurate control of the motor
2
means the accurate control of the generation torque of the motor
2
, that is, the amount of the current iq of the q axis. Therefore, three-phase AC running through the motor
2
is detected by the current detectors
8
and decomposed into vectors on the d axis and q axis to compute the current id of the d axis and the current iq of the q axis. Further, voltage Vd on the d axis and voltage Vq on the q axis are computed from id and iq to obtain desired generation torque &tgr;m based on which gate drive signals are generated.
Since the control accuracy of generation torque is connected with the acceleration and deceleration of a vehicle when the car motor controller
1
is used for an electric car using the motor
2
as a drive source, it is an important factor which affects riding comfort. When the car motor controller
1
is used for a hybrid car which uses the motor
2
and an internal combustion engine as drive sources, control accuracy becomes more important because both the generation torque of the motor
2
and the generation torque of the internal combustion engine are controlled in a well balanced manner to reduce fuel consumption and harmful substances contained in exhaust gas. Thus, high control accuracy is required of the car motor controller
1
. As described above, since a current running through the motor
2
is detected by the current detectors
8
to control the generation torque of the motor
2
directly, high-accuracy control is possible.
However, since the current detectors
8
are arranged external to the power conversion semiconductor
4
to detect the three-phase current of the motor
2
in the prior art motor controller
1
, fixing members constituting the current detectors
8
are required and also signal lines for connecting the current detectors
8
to the arithmetic and control unit
3
are required, thereby increasing the number of assembly steps. Further, when these signal lines are affected by noise and exert a bad influence upon detection current values, or disconnected due to the deterioration of a harness after long-time use or the loose contacts of connectors, they cause a sudden change in generation torque during operation. This may impair the continuity of control of the car motor controller
1
and exert a bad influence upon the behavior of a vehicle.
To overcome the above problems, a motor controller described below has recently been developed.
In the motor controller disclosed by Japanese Laid-open Patent Application No. 11-149928 which was filed by the present applicant, current detectors which have resistance characteristics are used, arranged on the same substrate as power elements and built in a power conversion semiconductor, and the power conversion semiconductor and an arithmetic and control unit are stored in the same container.
This eliminates an increase in the number of assembly steps caused by the external arrangement of the current detectors, reduces the number of constituent elements and the number of trouble possible sites, and shortens the signal lines between the current detectors and the arithmetic and control unit, thereby reducing the influence of noise.
SUMMARY OF THE INVENTION
In the motor controller which comprises current detectors having resistance characteristics, arranged on the same substrate as power elements and stored in a power conversion semiconductor, the current detectors have such a problem that the reliability of current values detected by the current detectors is low because the current detectors are readily affected by changes in ambient environment, particularly temperature variations. This tendency is marked when the current detectors are arranged exte

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