JPS62293990A - Overload protective system of servo motor - Google Patents

Abstract

PURPOSE:To evacuate a machine for which is used a servo motor under a safe condition without deteriorating the system, bi changing over the time-limit characteristic to g peculiarity curve on rigorous condition when the temperature of the servo motor exceeds the allowable value. CONSTITUTION:A time-limit characteristic curve generation circuit 6 outputs a time-limit characteristic curve A on lenient condition when a thermister 5 does not actuates. The current-time characteristic of a servo motor is restricted by this time-limit characteristic A. If the servo motor actuates when its temperature is in excess of the allowable value, an alarm signal is outputted in response to that signal. On the other hand, the output is changed from the time-limit characteristic curve A to the time-limit characteristic curve B of rigid condition. Because of this, a machine where the servo motor is used on safe condition is evacuated so that the servo motor may not be damaged and other smiconductor devices destructed.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an overload protection system for a servo motor used in an automatic guided vehicle (AGV), etc. This invention relates to a servo motor overload protection system that has two levels of restriction.

[Conventional technology]

When protecting servo motors and related equipment,
In particular, for servo motors, a protection method has been adopted in which a thermostat or thermistor is installed inside the servo motor (mainly in the windings) to stop the servo motor when an alarm occurs.

[Problem that the invention seeks to solve]

However, when controlling automatic guided vehicles (AGV) etc. with servo motors, if the servo motors are stopped at the same time as an alarm occurs, the automated guided vehicles (AGV)
The problem is that the entire line can be brought down due to the failure of one automatic guided vehicle (AGV).

On the other hand, automatic guided vehicles (AGVs) that ignored alarms and broke down
), there is a risk of damage to the servo motor and other driving semiconductor devices.

The purpose of the present invention is to solve the above-mentioned problems and provide a safe servo motor overload protection system that can prevent the line from going down and prevent damage to the servo motor, etc. even when an alarm occurs. be.

[Means for solving problems]

In order to solve the above problems, the present invention generates two time-limiting characteristic curves in a servo motor overload protection system that protects the servo motor from overload using a time-limiting characteristic curve for a predetermined one-hour current. It has a time-limited characteristic curve generation circuit, and during normal operation, the servo motor's current one-hour characteristic is limited by the first time-limited characteristic curve, which has gentle conditions, and it detects when the servo motor's temperature exceeds the allowable value. After that, we adopted a servo motor overload protection system that is configured to limit the servo motor's current one-hour characteristic using a second time-limited characteristic curve with strict conditions. [Function] If the temperature of the servo motor does not exceed the allowable value, the servo motor's current one-hour characteristic is limited by the first time-limiting characteristic curve with gentle conditions, and if the temperature of the servo motor exceeds the allowable value, Since the servo motor's current one-hour characteristic is limited by the second time-limited characteristic curve, which has strict conditions, the servo motor can only be operated under low load conditions, and equipment using the servo motor cannot be moved outside the line. , can be evacuated.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows a block diagram of an embodiment of the present invention. In the figure, l is an amplifier which receives a speed command signal from a control device (not shown), amplifies it, and outputs it. 2
is a power amplifier, which is composed of power transistors, SIRIS, etc., and receives the output signal from amplifier 1,
Amplifies and converts the C input to drive the servo motor. 3 is a servo motor, which is driven by a power amplifier 2;
Loads not shown, e.g. automated guided vehicles (AGV)
etc. 4 is a current detector, and servo motor 3
The load current is detected and the detected signal is sent to the comparator. A thermistor 5 operates when the temperature of the servo motor exceeds a permissible value, and its output is connected to a time-limited characteristic curve generation circuit 6. Reference numeral 6 denotes a time-limit characteristic curve generating circuit, which has a time-limit characteristic curve A with gentle conditions and a time-limit characteristic curve B with strict conditions. Thermistor 5
When the servo motor is not operating, the time-limiting characteristic curve 6 outputs a time-limiting characteristic curve A with gentle conditions, and the current one-hour characteristic of the servo motor is limited by this time-limiting characteristic curve A. When the temperature of the servo motor exceeds the allowable value, the servo motor receives this signal and outputs an alarm signal, while changing the output from the time-limit characteristic curve A to the time-limit characteristic curve B, which has stricter conditions.

Reference numeral 7 denotes a characteristic limiting circuit, which inputs the time-limited characteristic curve output from the time-limited characteristic curve generating circuit 6 and the current of the servo motor, and controls the power amplifier 6 so that the current one-hour characteristic of the servo motor does not exceed the time-limited characteristic curve. do.

FIG. 2 shows a time limit characteristic curve A and a time limit characteristic curve B. In the figure, the vertical axis represents the current value of the servo motor, and the horizontal axis represents time. The characteristic limiting circuit 7 controls the servo motor current so that it does not reach the upper right of the time limit characteristic curves A and B. For example, when the current is I, the time limit characteristic curve A is limited by a time T1, but the time limit characteristic curve B is more severe than this, and the current 1 is limited by a short time T. Note that the current I is the continuous allowable current of the servo motor.

In this way, if the temperature of the servo motor exceeds the allowable value,
An alarm signal is output and the time limit characteristic curve A changes to the more severe time limit characteristic curve B. If the operator sees this alarm signal and operates the servo motor within this condition, for example at a low speed, the automatic guided vehicle (AGV) etc. can be safely evacuated.

In the above embodiment, the time limit curve is switched when the servo motor exceeds the allowable value, but when the temperature of the transistor of power amplifier 2 is detected and this temperature exceeds the allowable value. It can also be configured to switch the time-limiting characteristic curve.

〔Effect of the invention〕

As explained above, in the present invention, two time-limiting characteristic curves are used, and when the temperature of the servo motor exceeds the allowable value, the first time-limiting characteristic curve with gentle conditions is changed to the second time-limiting characteristic curve with strict conditions. Since the configuration is configured to switch to the time-limited characteristic curve, the servo motor can be operated under safe conditions without shutting down the system using the servo motor, and without damaging the servo motor or other semiconductor devices. equipment that is being used can be evacuated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a time characteristic curve of the embodiment. 3-- Servo motor 4-- Current detector 5-- Thermistor 6-- Time-limited characteristic curve generation circuit 7--
Characteristic limiting circuit Figure 1 Figure 2

Claims (1)

[Claims] (1) In a servo motor overload protection system that protects the servo motor from overload using a predetermined current-time characteristic curve, it has a time-limit characteristic curve generation circuit that generates two time-limit characteristic curves, During operation, the current-time characteristic of the servo motor is limited by the first time limit characteristic curve, which has gentle conditions, and after it is detected that the servo motor temperature has exceeded the allowable limit, it is limited by the second time limit characteristic curve, which has strict conditions. An overload protection method for a servo motor, characterized in that the current-time characteristic of the servo motor is configured to be limited by a characteristic curve.