Abnormality detector for a motor drive system

Details Abnormality detector for a motor drive system Abnormality detector for a motor drive system

2002-11-06

2004-08-24

Martin, David (Department: 2837)

Electricity: motive power systems

Positional servo systems

With particular motor control system responsive to the...

C318S696000, C318S280000, C318S283000, C318S445000, C318S446000, C318S430000, C318S432000, C318S434000

Reexamination Certificate

active

06781341

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an abnormality detector for detecting an abnormality of a motor drive system for use in a drive control, e.g., of a regulating valve of a circulation gas amount or an idle engine speed controlling intake valve, which are mounted in an exhaust gas circulation path of an automobile engine. More particularly, the invention relates to an improved abnormality detector for detecting an abnormality of a motor drive system by which it is easy to detect an abnormality such as disconnection, short circuit or the like in multiphase magnetic field coils themselves, driving open/close elements of the magnetic field coils, wiring between the magnetic field coils and the open/close elements or the like used in the motor drive system.
2. Description of the Related Art
As means for detecting an abnormality such as disconnection, short circuit or the like at a load itself, a driving open/close element, wiring between the load and the open/close elements or the like with magnetic field coils for a stepping motor being the load, a variety of attempts have been disclosed. A typical method thereof is as follows:
A. Load Current Detection Method
This is a method for monitoring a voltage drop generated at current detecting series resistors at the time of power-conducting magnetic field coils acting as a load, and determining whether or not an appropriate current flows. This method is for detecting an abnormality at each part from an overall standpoint by utilizing a fact that a load short circuit, a wiring short circuit or the like causes an excessive current flow, while a load disconnection, a wiring disconnection, a closed circuit abnormality or the like allows only a current of less than a predetermined value to flow.
This load current detection method is effective also in order to prevent the open/close elements from being damaged as a result of automatically interrupting the open/close elements when a short circuit abnormality occurs at the load or wiring. In the case, however, where an electrical load is an inductive load, a delay in current elevation usually takes place just after power-conducting the open/close elements and, therefore a delay detection processing is required so as not to determine impatiently such a state of current elevation as a disconnection abnormality.
B. Leakage Current Detection Method
This is a method for connecting resistors of a high resistance through which a leakage current flows, in parallel to load driving open/close elements, and monitoring a dividing voltage at the resistors of high resistance. Supposing that there is no leakage current flowing to the load when interrupting the open/close elements, an abnormality at each part is detected in an overall manner as a disconnection in load or wiring, or a short circuit abnormality in the open/close elements.
C. Surge Voltage Detection Method
This is a method for detecting a surge voltage generated by an inductive load, at the time of interrupting the load driving open/close elements. Supposing that there is no surge voltage, an abnormality at each part is detected in an overall manner as a disconnection in load or wiring, an interruption abnormality at the open/close elements and an interruption abnormality due to the short circuit in load or wiring. Also in this surge voltage detection method, a delay in generation of surge voltage takes place just after interrupting the open/close elements, and therefore a delay detection processing is required so as not to determine impatiently such a state as a abnormality.
The Japanese Patent Publication (unexamined) No. 203599/1991 (JP No. 2639144) titled “Exhaust Gas Circulation Valve Controller” (literature) discloses an example of a drive control for a stepping motor based on the the mentioned load current detection method. The Japanese Patent Publication (unexamined) No. 257799/1998 titled “Output Open Detector for Multi-Channel Output Device” (literature B) discloses an example of a drive control for a stepping motor based on the mentioned leakage current detection method. The Japanese Patent Publication (unexamined) No. 99796/1995 titled “Drive for Stepping Motor” (literature AB) discloses an example of a drive control for a stepping motor employing both of the mentioned load current detection method and leakage current detection method.
On the other hand, publicly known abnormality detection means for a plurality of electrical loads are broadly classified into: an external hardware method, in which a result obtained by carrying out determination and synthesis with the use of a hardware (H/W) is fetched in a microprocessor; and an internal software (S/W) method in which a synthesized state signal is inputted to the microprocessor, and a determination processing is carried out inside of the microprocessor.
In the mentioned literature A, an external H/W method is disclosed, in which an abnormality as to four magnetic field coils of a stepping motor is delay-latched, and after AND-connection thereof, a result of synthesis abnormality determination is fetched in the microprocessor. In the mentioned literature B, an external H/W method is disclosed, in which a normal state signal as to four magnetic field coils in a stepping motor are OR-connected by means of a diode, an integral circuit is reset using an output signal from the diode, and an output from the integral circuit can be fetched in the microprocessor as a result of synthesis abnormality determination when required. In the mentioned literatures AB, an internal S/W method is disclosed, in which various state signals are logically connected and inputted to a microprocessor, and a period and a duty ratio of the inputted pulse train are monitored in the microprocessor, whereby detection of disconnection and short circuit is carried out.
As a further known art relating to this invention, the Japanese Patent Publication (examined) No. 92016/1995 titled “Failure Detection Circuit of Fuel Injection Valve Drive Circuit for Internal Combustion Engine” (literature C) discloses an example of a drive control of an electromagnetic coil for fuel injection valve drive based on the mentioned surge voltage detection method.
Furthermore, in the Japanese Patent Publication (unexamined) No. 18315/1993 titled “Automobile Engine Control Apparatus” (literature D), it is described that, in order to carry out initialization of an actuator which is drive-controlled by a microprocessor incorporated in an engine control apparatus, a power is fed to the engine control apparatus via a power supply relay driven by a power supply switch, operation of the mentioned power supply relay continues even after turning OFF the power supply switch, and the power supply relay is interrupted by ending the initialization.
Among the various conventional arts as described above, the external H/W method shown in the literature A or B has a disadvantage from the view points of dimensions and cost, whereas the internal S/W method as shown in the literature AB may be desired in such viewpoints. However, in the art disclosed by the literature AB, there is no concept of specifying which load system falls within an abnormality among a large number of electrical loads, eventually resulting in a disadvantage of making it difficult to carry out a maintenance work.
Moreover, it is certain that any abnormality in the magnetic field coils, the open/close elements, the wiring or the like can be detected in an overall manner when applying the surge voltage detection method disclosed in the literature C to multiphase magnetic field coils. A problem, however, exists in that when synthesizing surge voltages in multiphase magnetic field coils in parallel, it becomes difficult to extract and detect an abnormal phase as long as the stepping motor is driven at a high speed.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide an abnormality detector for motor drive system capable of making a maintenance work easy by using an individual state detection signal provided by a

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