Dual motor drive system for injection molding machines

Abstract

An electric-motor-powered screw drive system (10) provides increased output torque within a predetermined space envelope. A pair of electric motors (30, 32) are disposed in end-to-end relationship with their respective output drive shafts (34, 36) in opposed, coaxial relationship. A coupling member (38) extends between the respective motor output shafts (34, 36) to mechanically couple them together for joint rotation in the same direction of rotation and at the same rotational speed. The control circuit for one of the motors includes an inverter (52) to cause the output shaft of the one motor to rotate in the opposite direction from that of the other motor so that torque at the output of the combined motors (30, 32) at the coupling member (38) is the sum of the torques of each of the individual motors.

Description

technical field [0001] This invention relates to a drive motor for powering the operation of an injection molding machine and, more particularly, to a motor drive system utilizing two motors that are mechanically coupled together. Background technique [0002] For many years, injection molding machines for molding plastic parts were operated hydraulically. The hydraulic machine includes a linear hydraulic actuator providing linear motion and a rotary hydraulic motor providing rotary motion. As the positioning accuracy requirements of the various components of the machine during the operating cycle are increasing, due to the compressibility of the hydraulic fluid and the volume change of the fluid with temperature changes, the positioning accuracy of the hydraulic components is obviously limited. Therefore, the use of electric motors in the mechanical transmission system of such machines began several years ago. The main reason is that more precise position control can be ob...

AI Technical Summary

Problems solved by technology

[0004] One disadvantage of electric motors is that when higher power output is required, electric motors are larger in size, weight and cost than hydraulic motors

However, the maximum output torque of AC servo motors sold on the market has a certain limit

Therefore, the capacity of an injection molding machine powered by such an AC servo motor is limited by the output torque of a commercially available motor

Although two such motors can be connected by a belt or gears to provide a combined motor torque output, the system takes up a lot of space and is relatively complex

In addition, other mechanical elements need to be added to the system which reduce the accuracy of the output control of the combined motor due to the effects of belt stretch, mechanical wear and the like inherent in mechanical transmission elements

Images