Abnormality detection device for injection molding machine

Patent metadata

Field	Value
Publication number	US-11858190-B2
Application number	US-201715461799-A
Country	US
Kind code	B2
Filing date	Mar 17, 2017
Priority date	Mar 25, 2016
Publication date	Jan 2, 2024
Grant date	Jan 2, 2024

Abstract

An abnormality detection device includes a servo CPU; a physical quantity detection unit which detects a physical quantity such as a load applied on a servo motor which operates a movable part included in an injection molding machine. The abnormality detection device further includes a first storage unit directly readable/writable by the servo CPU; and a second storage unit not directly readable/writable by the servo CPU. A reference physical quantity is stored in the first and second storage units. The servo CPU outputs an instruction for stopping or decelerating the movable part in response to a first physical quantity deviation, which is a deviation between a reference physical quantity read from the first storage unit and a current physical quantity, or a second physical quantity deviation, which is a deviation between a reference physical quantity read from the second storage unit and a current physical quantity, exceeds a threshold value.

First claim

The invention claimed is:

1. An abnormality detection device for an injection molding machine, the abnormality detection device comprising:
a servo CPU;
a driving unit which drives and controls a servo motor based on an instruction from the servo CPU so as to drive a movable part;
a physical quantity detection unit which detects any one of a load applied on the servo motor, a speed of the servo motor, a current flowing in the servo motor, and a position deviation of the servo motor, as a physical quantity; and
first and second storage units which store a physical quantity in such a manner as to associate the physical quantity with the time that has elapsed during the operation of the movable part or the position of the movable part in the operation of the movable part, as a reference physical quantity, wherein
the reference physical quantities which are stored in the first and second storage units, respectively, are sequentially compared with a physical quantity which is currently detected in such a manner that the reference and currently detected physical quantities are associated with the time that has elapsed during the operation of the movable part or the position of the movable part in the operation of the movable part, and thus, first and second physical quantity deviations are found so that an abnormality can be detected in the case where any physical quantity deviation exceeds a threshold value,
the first storage unit is directly readable/writable by the servo CPU,
the second storage unit is not directly readable/writable by the servo CPU, and
the servo CPU outputs an instruction to stop or decelerate the movable part in the case where either a first physical quantity deviation which is a deviation between a reference physical quantity read from the first storage unit and a current physical quantity or a second physical quantity deviation which is a deviation between a reference physical quantity read from the second storage unit and a current physical quantity exceeds a threshold value.

2. The abnormality detection device according to claim 1 ,
wherein the first storage unit has a smaller storage capacity or costs higher per unit storage capacity than the second storage unit.

3. The abnormality detection device according to claim 1 ,
wherein the first storage unit is an internal RAM of the servo CPU or an external RAM which is connected with the servo CPU through a memory bus.

4. The abnormality detection device according to claim 1 , wherein
the first storage unit is configured to store the physical quantity detected by the physical quantity detection unit from a start of the operation of the movable part to a maximum storage time, and
the second storage unit is configured to store the physical quantity detected by the physical quantity detection unit after the maximum storage time until an end of the operation of the movable part.

5. The abnormality detection device according to claim 1 , further comprising:
a CNC (Computer Numerical Control) CPU configured to control the injection molding machine in accordance with an automatic operation program; and
a PMC (Programmable Machine Control) CPU configured to control a sequence operation of the injection molding machine,
wherein the servo CPU is configured to read/write on the second storage unit through the CNC CPU or the PMC CPU.

6. The abnormality detection device according to claim 1 , wherein
the servo CPU is configured to calculate the first physical quantity deviation based on the reference physical quantity stored in the first storage unit to detect the abnormality with no substantial delay from an occurrence of the abnormality, and
the abnormality is detected, based on the second physical quantity deviation, with a delay from the occurrence of the abnormality.

7. The abnormality detection device according to claim 1 , further comprising: a first abnormality detection unit and a second abnormality detection unit,
wherein
the first abnormality detection unit is configured to compare the current physical quantity notified from the physical quantity detection unit with the reference physical quantity read from the first storage unit in a manner that the current and reference physical quantities are associated with the time that has elapsed during the operation of the movable part or the position of the movable part in the operation of the movable part, to obtain the first physical quantity deviation, and
the second abnormality detection unit is configured to compare the current physical quantity notified from the physical quantity detection unit with the reference physical quantity read from the second storage unit in a manner that the current and reference physical quantities are associated with the time that has elapsed during the operation of the movable part or the position of the movable part in the operation of the movable part, to obtain the second physical quantity deviation,
the second abnormality detection unit is configured to notify the first abnormality detection unit of abnormality in response to the second physical quantity deviation exceeding the threshold value, and
the first abnormality detection unit is configured to notify the servo amplifier of the instruction to stop or decelerate the movable part in response to any of (i) the first abnormality detection unit being notified of abnormality from the second abnormality detection unit and (ii) the first physical quantity deviation exceeding the threshold value.

Assignees

• Fanuc Corp

Inventors

• Maruyama Junpei

Classifications

• B29C45/768 Primary

  Detecting defective moulding conditions (B29C45/84 takes precedence) · CPC title

• B29C2945/76006

  Pressure · CPC title

• B29C2945/7611

  Velocity · CPC title

• B29C2945/76033

  Electric current or voltage · CPC title

• B29C2945/76096

  Distance · CPC title