Electricity: motive power systems – Limitation of motor load – current – torque or force
Reexamination Certificate
2000-05-05
2002-03-19
Donels, Jeffrey (Department: 2837)
Electricity: motive power systems
Limitation of motor load, current, torque or force
C318S638000, C318S768000
Reexamination Certificate
active
06359405
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a failure detection system in a propulsion system mounted in an electric vehicle, a hybrid vehicle, etc., having an electric motor as a propulsion system.
2. Description of the Related Art
In recent years, internal combustion engines that directly inject fuel into the cylinder of an engine and serving as propulsion device for automobiles have been developed and commercialized with the goals of protecting the environment and energy reduction. Furthermore, hybrid automobiles that have installed a propulsion system that combines this type of engine and an electrical motor for propulsion have been gaining notice.
One type of such a hybrid vehicle is a parallel hybrid vehicle that uses an electrical motor as an auxiliary driving source to supplement the output of the engine. As disclosed in Japanese Unexamined Patent Application, First Publication, No. Hei 7-123509, in order to satisfy the needs of the driver while at the same time maintaining the remaining charge of the battery, this parallel hybrid vehicle carries out various types of control such as supplementing the output of the engine using the electrical motor during acceleration and charging the battery by regenerative deceleration during deceleration.
FIG. 5
shows the main components of a propulsion system installed in this hybrid vehicle. In this figure, reference numeral
3
is a battery that generates direct current for driving the electric motor M. Reference numeral
200
is an inverter that converts the direct current supplied from the battery
3
into three-phase alternating current, and provides transistors (IGBT)
201
,
202
,
203
,
204
,
205
, and
206
whose currents are controlled by signals UL, UH, VL, VH, WL, and WH from a controller
800
, described below.
Here, the transistors
201
and
202
are cooperatively conduction controlled by signals UL and UH, and the U-phase of the alternating current is generated from these connection points. In addition, transistors
203
and
204
are cooperatively conduction controlled by signals VL and VH, and the V-phase of the alternating current is generated from these connection points. Furthermore, transistors
205
and
206
are cooperatively conduction controlled by signals WL and WH, and the W-phase of the alternating current is generated from these connection points.
Reference numeral M is, for example, a brushless DC electric motor driven by the three-phase alternating current supplied from the inverter
200
, reference symbol S
8
is a current sensor that detects the output current of the battery
3
, reference symbol S
9
is a voltage sensor that detects the output voltage of the battery
10
, reference numeral
70
is a magnetic pole position sensor that detects the magnetic pole position of the electric motor
30
, and reference numeral
800
is a controller that generates the signals UL, UH, VL, VH, WL, and WH that provide drive control of the inverter
200
based on the signals from each sensor.
In the following explanations, the inverter
200
and the control systems such as the controller
800
for providing drive control of the electric motor M are called the “motor control system”.
Below, the control operation of the electric motor M by this motor control system is explained.
In the case that the electric motor M is driven by a voltage input, the controller
800
that serves as the motor control system carries out torque control of the electric motor M. That is, the controller
800
inputs each of the signals from the voltage sensor S
9
, the current sensor S
8
, and the magnetic pole position sensor
70
, and monitors the current and voltage supplied from the battery
3
along with the number of revolutions of electric motor M. In addition, according to an externally given target torque and the number of revolutions of the electric motor M, the target current that should be supplied from the battery
3
is found, and each of the voltage values of the signals UL, UH, VL, VH, WL, and WH output to the inverter
200
are controlled so that the product of the current and voltage monitored (that is, the electrical power) agrees with the target electrical power. Thereby, as a result of control of the current (that is, each of the phase currents) flowing through each transistor in inverter
200
, torque control is carried out so that the output torque of the electric motor M attains the target torque.
However, in the system described above, in spite of being subject to severe quality control during manufacture, each part gradually deteriorates over time due to long use, and when the service life has passed, there are cases when there is the occurrence of failure of the type that any one of the phase currents supplied to the electrical motor M becomes obstructed. An example of this failure is the case in which the conduction condition of the gate drive line
810
for supplying the signals from the controller
800
to the gate of the inverter
200
and the three-phase line
210
for supplying three-phase alternating current to the electric motor M from the inverter
200
become defective and short out. Additional examples of possible failure are the conduction of the transistors that form the inverter
200
becoming defective, the windings of the electric motor M being broken, and the magnetic strength of the permanent magnets in the electric motor M attenuating.
Here, in the above-described propulsion system, when there is the occurrence of failure such as the obstruction of the U phase of the current supplied to the electric motor M, according to the above-described motor control system, because the remaining V phase and W phase of the current are increased in order to generate the target torque when the U phase of the current is obstructed, each of the current values of the V phase and the W phase rise abnormally. When this type of torque control is carried out, a large change in the output torque of the electric motor M does not appear, and thus there is the problem that frequently the driver of the vehicle will not notice this failure. In addition, there is also the problem that if this type of failure is left as is over a long time period, the chance of failure due to the abnormal rise in current supplied to the electric motor
30
will increase.
In consideration of the above-described problems, an object of the present invention is to provide a failure detection system for a propulsion system that detects the occurrence of failure such as obstruction of the currents supplied to the electric motor for propulsion in the drive system of, for example, an electric automobile or a hybrid vehicle.
SUMMARY OF THE INVENTION
In order to achieve that above-described objects, the present invention has the following structure.
According to this invention, failure detection system in a propulsion system having an electric motor (an essential component corresponding for example to electric motor M described below) as a drive device that drives the vehicle and a motor control system (an essential component corresponding for example to the battery
3
, the torque control processing circuit
101
, the inverter
200
, the current sensor S
8
, and the voltage sensor S
9
described below) that drives this electric motor by supplying polyphase current to it, wherein each of the phase currents of the polyphase current is changed such that the output torque of this electric motor attains the target torque that this electric motor should generate, and provides an abnormal rise in current detection device (an essential component corresponding for example to the current sensor S
10
, the current limit value calculation circuit
103
, and the comparator
104
described below) that detects an abnormal rise in current in any of the phases of this polyphase current and a failure identification device (an essential component corresponding for example to the counter
105
and the failure identification processor (steps S
1
~S
4
described below) that identifies failure based on the frequency of occur
Donels Jeffrey
Honda Giken Kogyo Kabushiki Kaisha
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