JPH0246195A - Driving control for stepping motor - Google Patents

Abstract

PURPOSE:To let the output torque of a motor be appropriate in an ordinary temperature environment and in a low temperature environment and to avoid waste of power by varying motor drive current in accordance with the change of environmental temperature. CONSTITUTION:A bimetal 8 detects an ambient temperature of a carriage driving mechanism, a load of a stepping motor. By the command of a control circuit 5 when a reference voltage generation circuit 7 receives the output of the bimetal 8, the reference voltage is set from the predetermined judgement criterion and the circuit 7 outputs the reference voltage to a 'negative' terminal of a comparator 4. When the ambient temperature grows higher, the reference voltage is raised to increase the driving current of the stepping motor. On the other hand, when the ambient temperature becomes low, with the reference voltage reduced the driving current of the stepping motor is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a drive control method for a stepping motor driven by a drive control circuit using a constant current chopper type drive method.

[Technical Background of the Invention] Conventionally, when a certain load is connected to a stepping motor and driven, large load fluctuations occur depending on whether the environmental temperature in which the load is used is high or low.

In particular, when used at an environmental temperature of less than 0°C, the stepping motor that drives the load increases its output torque by the increase in the load, compared to when used in a room temperature environment or a high temperature environment. There must be.

In order to control a stepping motor under these conditions, it is necessary to use a drive element with an appropriate rating because it is easy to apply rated power to the stepping motor, has good start-up characteristics, and has a set current value. A constant current control drive method called the constant current control drive method is used.

[Prior Art of the Invention] Conventionally, when a stepping motor driven by a constant current chopper drive method is used in a low temperature environment below 0°C, the output torque specification of the stepping motor is It was set based on the load.

However, with these specifications, when the stepping motor is used in a room temperature environment or a high temperature environment,
There is a disadvantage that the output torque of the stepping motor becomes excessive, and that amount of power is wasted.Especially, when used in a high temperature environment, the temperature of the stepping motor and the drive element increases, causing If the heat resistance rating is exceeded, there is a risk of damage, so it is necessary to provide cooling means such as a heat sink or a cooling fan to take cooling measures, which has the disadvantage of being expensive.

[Purpose of the Invention] The present invention has been made in view of the above-mentioned drawbacks.The output torque of the stepping motor is appropriate in a normal temperature environment and a high temperature environment, so there is no wastage of power, and drive efficiency is high. The purpose is to provide a low-cost stepping motor that does not require any countermeasures.

[Summary of the Invention] In a drive control system for a stepping motor driven by a constant current chopper drive system, the present invention measures the ambient temperature of a load connected to the stepping motor using a temperature sensor, and measures the ambient temperature according to changes in the ambient temperature. The above object is achieved by changing the driving current of the stepping motor accordingly.

[Embodiments of the invention] Hereinafter, the present invention will be explained in detail based on one embodiment.

FIG. 1 shows an example of a drive control circuit according to the stepping motor drive control method of the present invention.

In national isolation, 1 is a winding of a stepping motor, and the current flowing through the winding is controlled by transistors 2 and 3.

The former transistor 2 is switched by the output signal of the comparator 4, and the latter transistor 3 is switched by the excitation sequence control signal output from the control circuit 5.

The "+" input terminal of the comparator 4 receives the voltage Ves due to the voltage drop across the resistor 6 for detecting the current flowing through the winding 1, and the "-" input terminal receives the voltage Ves from the reference voltage generation circuit 7. The output reference voltage Vs is input.

When the excitation sequence signal is not output, the reference voltage generation circuit 7 detects the output of the bimetal 8, which is a temperature sensor, and outputs a predetermined reference voltage Vs.

The contact of the bimetal 8 turns ON when the temperature falls below a predetermined temperature t°C, and turns OFF when the temperature rises above t°C.

In addition, 9 is a diode for current circulation, and 10 is the corresponding wire 1.
This is a DC power supply supplied to the

The operation of the drive control circuit will be explained.

First, when the winding 1 is excited, the transistor 3 is turned on by the drive timing signal from the control circuit 5, but since the transistor 2 is OFF, no current flows through the winding 1, and the voltage drop across the resistor 6 is It is OV. Therefore, the input voltage at the "10" terminal of the comparator 4 is OV, while the reference voltage Vs is input from the reference voltage generation circuit to the "-" terminal, so the output of the comparator is the transistor 2. It works to turn on.

When the transistor 2 is turned on, a current 11 flows from the power supply 1o to the transistor 2, the transistor 3, and the resistor 6, and as the current 1 increases, the resistor 6
The voltage drop vRs gradually increases.

When the dropped voltage vIIs becomes equal to or higher than the reference voltage Vs, the output of the comparator 4 acts to turn off the transistor 2, and as a result, the current 1 stops and the current 1, the transistor 3, and the current 1, winding 1, transistor 3. Circulating current ■2 that circulates through the resistor 6 and diode 9 begins to flow.

When the current (2) gradually decreases while being consumed by the winding 1, the voltage drop Vas also decreases accordingly, but when the voltage drop VR8 falls below the reference voltage Vs, the output of the comparator 4 turns on transistor 2 again
Work like you do.

In this way, by repeating the above operation, winding 1
An almost constant current flows through.

Therefore, by changing the setting of the reference voltage Vs input to the "-" terminal of the comparator 4, the current in the winding 1 can be easily varied.

Next, the operation will be explained using a timing chart shown in FIG. 2, taking as an example a case where a carriage drive mechanism for driving a printer carriage is connected to a stepping motor driven by the drive control circuit.

In this case, in order to detect the ambient temperature of the carriage drive mechanism, which is the load of the stepping motor, a bimetal 8 installed at a predetermined position in the printer detects 0FFL when the temperature exceeds t°C, and 0FFL when the temperature exceeds t'C. It is set to turn on.

First, as instructed by the control circuit 5, the reference voltage generation circuit 7 accepts the output of the bimetal 8, sets the reference voltage Vs based on a predetermined criterion, and applies the reference voltage Vs to the "-" terminal of the comparator 4. Outputs.

For example, when the ambient temperature T is t°C or higher, the bimetal 8 is 0F.
Settings are made so that when Ft, the reference voltage VsL is generated, and when the bimetal 8 is turned on below t°C, the reference voltage Vsu is generated.

When the reference voltage Vs is set at the "-" terminal of the comparator 4, an operation timing signal is output, and driving of the stepping motor is started.

If the ambient temperature T is t°C or higher, the bimetal 8 is turned off.
The "-" terminal of comparator 4 is connected to the reference voltage V.
Since SL is applied, the exciting current IL flows through the winding 1 of the stepping motor, but when the ambient temperature T gradually decreases to below t°C (point T), the bimetal 8 turns on. Since the reference voltage VSL changes to a higher voltage Vsll, the excitation current also changes to a larger current IN, and the stepping motor is driven.

Furthermore, the ambient temperature T rises to t°C or more (point T x)
When this happens, bimetal 8 turns OFF.

The change in the reference voltage Vt is 0N10FF of the bimetal 8.
However, if the reference voltage Vs changes while the stepping motor is being driven, rotational ripples will occur in the stepping motor, which will have a greater effect on the printing operation by the carriage mechanism. Do not change the reference voltage.

In other words, the reference voltage Vs is changed at times other than when the stepping motor is being driven so as not to affect the load during driving.

In this way, if the stepping motor is driven with a small load and the ambient temperature is t°C or higher, a small drive current (
When the load below t°C is large, by using a large drive current IN, the output torque of the stepping motor becomes appropriate due to changes in the environmental temperature, and the drive efficiency increases.

No more wasted electricity.

The present invention uses a so-called constant current chopper drive method.
It can be applied to drive a stepping motor with any number of phases, and any excitation method can be used.

Furthermore, the temperature sensor may be made of any material such as a bimetal or mister, and a plurality of temperature sensors may be used to provide a plurality of different reference voltages Vs for a plurality of different temperature settings.
By setting , the drive current may be varied in multiple stages.

Further, in order to accurately detect the ambient temperature of the load, the temperature sensor is preferably installed at a location where it is not affected by heat sources such as a power source or a heat generating element.

[Effects of the Invention] As described in detail above, the present invention adjusts the driving current of the stepping motor according to changes in the environmental temperature, thereby making the output torque of the stepping motor appropriate in a room temperature environment and a low temperature environment. , there is no waste of power, the drive efficiency is high, and there is no need for cooling measures in high-temperature environments, so it is possible to provide a low-cost stepping motor.

[Brief explanation of the drawing]

FIG. 1 is a drive control circuit diagram of the present invention, and FIG. 2 is a timing chart showing changes in drive current etc. due to temporal changes in ambient temperature. 1... Winding wire 2, 3... Transistor 4
... Comparator 6 ... Resistor 7 ... Reference voltage generation circuit 8 ... Bimetal patent applicant

Claims (1)

[Claims] In a drive control method for a stepping motor driven by a drive control circuit using a constant current chopper type drive control method, the drive control circuit detects an ambient temperature of a load connected to the stepping motor. a temperature sensor for detecting the temperature sensor output when the stepping motor is stopped, and a drive current that controls the stepping motor drive current to a predetermined current value when the output value reaches a predetermined temperature. 1. A stepping motor drive control method, comprising: a control means, wherein the drive current changes according to load fluctuations caused by changes in the ambient temperature of the load.