Method of estimating a life of ball screw included in...

Measuring and testing – Toothed gear

Reexamination Certificate

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

Reexamination Certificate

active

06332355

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of estimating a life of a ball screw for moving an injection screw included in an electric injection molding machine and generating an alarm or the like, and a life estimating system for carrying out the method.
2. Description of the Related Art
In an electric injection machine, an injection screw is reciprocated axially by rotating a ball screw by an electric motor. Therefore, the greatest load is exerted on the ball screw during an injection molding operation. If the ball screw is damaged during a long period of use, it is expected that the operation of the injection molding machine must instantly be stopped. If such a situation takes place, the broken ball screw must immediately be replaced with a new one, which interrupts the operation of the associated production line, adversely affecting the stability of the quality of moldings and may possibly cause damage in component parts associated with the ball screw.
To avid such a situation it is desired to estimate time when the condition of the ball screw is close to a condition that causes damage to the ball screw, i.e., to estimate the life of the ball screw, and to replace the ball screw with a new one before the same is broken.
Generally, it has been a general practice to decide the life of the ball screw by the intuition of an operator skilled in the operation of the injection molding machine and to change the ball screw when the operator decided that the life of the ball screw has almost terminated. It is difficult to estimate the life of the ball screw accurately only by the operator's intuition. The usable ball screw is thrown away and time and labor is wasted for the unnecessary change of the usable ball screw if the usable ball screw is changed too early. The ball screw will be broken and serious damage will be made to the associated component parts if the time for changing the ball screw is delayed excessively.
From such a point of view, a life estimating apparatus for estimating the life of a rotary member included in an injection molding machine or the like proposed in JP-A No. Hei 6-91683 is capable of accurately estimating, on the basis of a recognition that bearings supporting the ball screw is a most heavily loaded member, the life of a rotary member, such as a bearing or a ball screw.
This previously proposed life estimating apparatus comprises a revolution counter for directly or indirectly counting the number of revolutions of a rotary member driven for rotation by a driving motor, an arithmetic unit capable of calculating a fatigue life of the rotary member on the basis of the number of revolutions of the rotary member and torque required to rotate the rotary member, and a comparator for comparing the total number of revolutions of the rotary member counted by the revolution counter and fatigue life of the rotary member calculated by the arithmetic unit, and provides a warning when the total number of revolutions of the rotary member approaches or arrives at the fatigue life to prompt the operator to replace the rotary member with a new one.
The foregoing prior art life estimating apparatus for estimating the life of a rotary member included in an injection molding machine or the like compares a numerical value indicating the counted total number of revolutions of the rotary member, and a numerical value representing the fatigue life calculated on the basis of the torque of the driving motor required to drive the rotary member for rotation, and uses a condition where the difference between those numerical values is practically naught as a criterion for deciding the life of the rotary member. Particularly, an arithmetic procedure for calculating the fatigue life on the basis of the torque is very complicated and, if the life of the bearing is used for life estimation, many parameters in addition to the torque of the driving motor are necessary and the arithmetic procedure becomes further complicated.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method of estimating a life of a ball screw included in an electric injection molding machine, capable of appropriately and surely estimating the life of a ball screw by a simple arithmetic procedure, and to provide a life estimating apparatus capable of estimating the life of a ball screw by a simple arithmetic procedure, having a simple configuration and capable of being manufactured at a low cost.
The present invention provide, a method of estimating a life of a ball screw included in an electric injection molding machine comprising an injection unit having a heating barrel and an injection screw placed for rotation in the heating barrel, and an electric motor connected to the injection screw by the ball screw; said method comprising the steps of determining a total energy value indicating an amount of total energy supplied to the ball screw on the basis of operating conditions of the ball screw and the electric motor and deciding whether or not the life of a ball screw has terminated by comparing a predetermined life energy value for the ball screw determined on the basis of force generated by the ball screw and moving speed of the ball screw, and the total energy value.
The present invention provides a life estimating apparatus for estimating a life of a ball screw included in an electric injection molding machine comprising an injection unit having a heating barrel and an injection screw placed for rotation in the heating barrel, and an electric motor connected to the injection unit by the ball screw, said life estimating apparatus comprising an encoder connected to the electric motor an arithmetic-and-storage means for multiplying a moving speed of the ball screw in a unit time measured by the encoder, and an operating current supplied to the electric motor together during this time, and accumulating products, each formed by multiplying the moving speed of the ball screw and the operating current supplied to the electric motor in the unit time, and storing the accumulated products as cumulative data and a life deciding means for determining a total energy value indicating an amount of total energy supplied to the ball screw on the basis of the cumulative data stored in the arithmetic-and-storage means, and comparing the total energy value, and a predetermined life energy value for the ball screw determined on the basis of force generated by the ball screw and the moving speed of the ball screw to decide whether or not the life of a ball screw has terminated.
The present invention provides a life estimating apparatus for estimating a life of a ball screw included in an electric injection molding machine comprising an injection unit having a heating barrel and an injection screw placed for rotation in the heating barrel, and an electric motor connected to the injection screw by the ball screw, said life estimating apparatus comprising an encoder connected to the electric motor a torque meter interposed between the ball screw and the electric motor an arithmetic-and-storage means for multiplying a moving speed of the ball screw in a unit time measured by the encoder and a torque of the ball screw during this time measured by the torque meter together, and accumulating products, each formed by multiplying the moving speed of the ball screw and the torque of the ball screw in the unit time, and storing the accumulated products as cumulative data and a life deciding means for determining a total energy value indicating an amount of total energy supplied to the ball screw on the basis of the cumulative data stored in the arithmetic-and-storage means, and comparing the total energy value, and a predetermined life energy value for the ball screw determined on the basis of force generated by the ball screw and the moving speed of the ball screw to decide whether or not the life of a ball screw has terminated.


REFERENCES:
patent: 4733361 (1988-03-01), Krieser et al.
patent: 5749265 (1998-05-01), Namimatsu et al.
patent: 608

LandOfFree

Say what you really think

Search LandOfFree.com for the USA inventors and patents. Rate them and share your experience with other people.

Rating

Method of estimating a life of ball screw included in... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of estimating a life of ball screw included in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of estimating a life of ball screw included in... will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFUS-PAI-O-2583553

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.