Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1988-02-26
1989-07-11
Silbaugh, Jan H.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
364476, 425151, 425166, B29C 4576
Patent
active
048470236
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control method for an injection motor of an injection-molding machine, and more particularly, to a method for controlling an injection motor having an overheat preventing function, whereby injection-molding conditions are set securely such that the injection motor is prevented from overheating.
2. Description of the Related Art
In an injection-molding machine, as is generally known, a synchronous motor (hereinafter referred to as an injection motor) is used as a drive source for an injection unit. Processes of injection, hold, and application of back pressure for metering are executed by means of the injection motor. In the injection-molding machine of this type, the output torque of the injection motor is small, so that a very small driving current flows through the injection motor, during the injection process or when the back pressure is applied. In the hold process, a great output torque must be produced, so that a very great driving current flows. Meanwhile, the injection motor is selected in consideration of various design conditions, such as economical efficiency. It is uncommon, therefore, to use, as the injection motor, a large-capacity motor such that its continuous rated current is never exceeded by the driving current. As a result, the driving current during the hold process may possibly exceed the continuous rated current by a large margin, so that the average value of the driving current flowing through the injection motor during one injection-molding cycle may sometimes exceed the continuous rated current. In such a case, the injection motor may suffer from overheating or some other problems.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a control method for an injection motor of an injection-molding machine, which solves the aforementioned problems associated with prior art methods of injection motor control wherein the average injection motor driving current exceeded the continuous rated current, thus tending to cause overheating. Thus, an object is to provide a method in which whether the injection motor can overheat before completing the execution of an injection-molding cycle under injection-molding conditions, newly inputted and set, is easily ascertained in advance, thereby preventing the injection motor from overheating.
In order to achieve the above object and other objects of the invention, method for controlling an injection motor to prevent overheating according to the present invention, comprises steps of: previously determining whether an overheating state can be produced such that the integral of the amount of heat, produced by an injection motor driving current for one injection-molding cycle, exceeds the allowable integral of the heat amount obtained when a continuous rated current flows, in accordance with new set values of injection-molding conditions, before executing the injection-molding cycle under the new set injection-molding conditions; and delivering a warning output if it is concluded that the overheating state can be produced.
According to the present invention, as described above, whether the overheating state can be produced such that the integral of the amount of heat, produced by the injection motor driving current for one injection-molding cycle, exceeds the allowable integral of the heat amount obtained when the continuous rated current flows, is previously determined in accordance with set input values of injection-molding conditions before executing the injection-molding cycle under the new set injection-molding conditions; and the warning output is delivered when it is concluded that the overheating state can be produced. Thus, when the injection-molding conditions are inputted for setting, during the execution of the injection-molding cycle or the period of suspension thereof, whether the injection motor can overheat is easily ascertained in advance, so that the injection motor can be prevented from overheating.
BRIEF DESCRIPTION OF
REFERENCES:
patent: 4695237 (1987-09-01), Inaba
patent: 4696632 (1987-09-01), Inaba
patent: 4759705 (1988-07-01), Otake et al.
Fanuc Ltd.
Heitbrink Jill L.
Silbaugh Jan H.
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