Electricity: motive power systems – Constant motor current – load and/or torque control
Reexamination Certificate
2000-01-24
2001-02-27
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Constant motor current, load and/or torque control
C318S563000, C388S903000, C388S907500
Reexamination Certificate
active
06194856
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to an electric motor driver for driving an electric motor, and more particularly to an electric motor driver which includes in the inside thereof a current control loop, with which an electric motor current is detected to form the feedback control unit, and which is suitable for controlling a position, velocity, a current, a torque and the like.
As the microprocessors have advanced, in the electric motor control apparatuses as well for use in the general industrial machines, the conventional analog control has been changed into the digital control employing the micro-controller. The devices and components which are used in the printed circuit boards have also been changed from the transistors to the IC (Integrated Circuit) and further to the MSI (Medium Scale Integrated Circuit), the LSI (Large Scale Integrated Circuit) and the VLSI (Very Large Scale Integrated Circuit) so that the ASIC (Application Specific IC), the dedicated customs LSI which is ordered by the customer, the gate arrays and the like have been used. Thus, the miniatulization of the controllers have advanced. Also, the ministulization of the package of the digital IC has further advanced by adopting the technique of mounting them to the surface of the printed circuit board. In addition, as the high density integration of the ICs has advanced, the number of lead terminals of the IC chip (the number of pins) has exceeded
100
, and along with this, instead of the conventional IC including the lead terminals which have the pitch of 2.54 mm, the IC chip including the lead terminals which have the pitch of 1.27 mm called the half pitch, and further the IC chip including the lead terminals which have 1.00 mm, 0.8 mm or 0.75 mm pitch have been used. In addition, in recent years, the lead package having the pitch of 0.5 mm has also been used. In correspondence thereto, for the conductor pattern spacing of the printed circuit board, in recent years, the design has been advanced from the construction in which one conductor pattern is passed through the space defined between the adjacent lead terminals having the pitch of 2.54 mm to the construction in which three conductor patterns or three or more conductor patterns are passed through the space defined between the adjacent lead terminals having the pitch of 2.54 mm. Thus, the high density mounting for the printed circuit board has advanced.
On the other hand, with respect to the power source for subjecting the general industrial machine to the variable speed running, the vector control without any of velocity sensors with which the induction motor as the A.C. motor is driven by the inverter, and the vector control with a velocity sensor are adopted, and also the A.C. servo motor, which self-contains a position sensor and a velocity sensor, for use in the machine tools, the metal processing machines, the assembly machines, the spinning machines, the weaving machines, the robots, or the like has been actively used, from the request for the automation and the labor saving, in the processing/assembling field or the like. The basic control thereof is the position, velocity, current and torque control. From the request for the promotion of the high speed for the line velocity and the promotion of the high speed for a tact time in recent years, in the vector control for the induction motor, the high speed current control is carried out in such a way that the current of the motor is separated into the current component for the torque which is in proportion to the torque and another current component for the magnetic flux which intersects perpendicularly the current component for the torque. In addition, in the case of the A.C. servo motor, for the revolving-field type synchronous motor employing the permanent magnet as the rotor, the position of the permanent magnet is detected by the magnetic pole positions detector (rotor position detector) in order to carry out the high speed current control. In any case, the instantaneous value of the current is controlled.
The place where each of those A.C. motor controllers is installed is located within the control board which is installed in the vicinity of the motor in the assemble field or the processing field, and hence in the environment in the periphery of the control board, the scrap metal which has been generated by the cutting and the cutting oil are floated in the air, and in the case of the tire processing factory, the dust containing therein carbon particles which has been generated in processing rubber is floated in the air, and also in the case of the textile factory or the spinning machine factory, the cotton dust is floated in the air. Those carbon dust and cotton dust are adhered little by little to the printed circuit board provided within the controller. In addition, in the weaving machine factory, in the water jet style wherein the weft yarns of the automatic weaving machine for knitting the warps and the weft yeans are blown by the water, since the water is treated, the humidity in the periphery thereof is increased, and the dew condensation is generated on the printed circuit board of the motor control circuit as the temperature falls gradually. The ICs are mounted on the printed circuit board and the above-mentioned devices having the small lead pitch are mounted thereon. For this reason, the leads of the ICs will be covered with the dust containing carbon or the cotton dust which have been adhered to the printed circuit board with lapse of time.
When the running of the A.C. motor is started in the morning everyday, upon the start of the running, the temperature in the control board rises, and then when the running of the A.C. motor is stopped in the night, the temperature in the control board falls and the external air temperature also falls. For this reason, the humidity of the air, within the control board, which is heated in the daytime is increased and when it becomes the night, the dew condensation occurs on the circuit board with the dust containing carbon and the cotton dust at the temperature equal to or lower than the critical temperature. Then, if at the time when starting the running in the morning on the next day, the supply of the electric power to the circuit board is started, then the electrical short circuit may occur between the adjacent leads of the ICs in some cases. While this electrical short circuit is apt to occur in the rainy season. In the case of the weaving machine of the water jet style in which the water is used, the electrical short circuit occurs irrespective of any of the seasons. For this reason, the operation of the motor control circuit may lead to the malfunction, and the semiconductor devices in the inverter main circuit may be broken down in some cases.
Next, the description will hereinafter be described in detail with respect to the influences in the case where the adjacent leads are electrically short circuited resulting from that the dust and the cotton dust have been adhered to the lead terminals of the ICs mounted on the printed circuit board of the A.C. servo motor control circuit for controlling the position, velocity, current and torque, and also the moisture is bedewed together with the dust and the cotton dust.
FIG. 1
is a control block diagram, partly in circuit diagram, showing a configuration of an A.C. servo motor as a conventional one example. In the figure, reference numeral
1
designates a servo motor, and reference numeral
2
designates an encoder which includes complexly a magnetic pole positions sensor
2
-
1
for detecting the magnetic pole positions of a rotor of the A.C servo motor and a rotational speed and position sensor
2
-
2
for detecting the rotational speed and position of the A.C. servo motor, and also which is self-contained in the A.C. servo motor. Reference numeral
3
designates a position control unit, reference numeral
5
designates a velocity control unit, reference numeral
7
designates a current control unit, and reference numeral
8
designates a PWM (Pulse Wid
Kobayashi Sumio
Ninomiya Hisakazu
Takase Makoto
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Ro Bentsu
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