JPH0642799B2 - Stepping motor start-up circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a starter circuit for starting a step motor, and more particularly to a starter circuit capable of surely restarting even if rotation is stopped due to overload. .

<Prior Art> Step motors have characteristics of self-starting frequency (frequency that can be started by themselves) and maximum response frequency, which are determined by the size of the load. Therefore, in order to rotate the step motor at high speed, if the load torque is heavy, first input the drive pulse for driving the motor at a frequency that enables self-starting, and then rotate the step motor in synchronization with the drive pulse. The frequency is gradually increased to obtain the rotation speed of the target frequency. In addition, when the step motor is stopped and the speed is changed from high speed to low speed rapidly, if the load inertia is large, the motor is rotated by the load and the drive pulse frequency and rotation speed become out of synchronization. Also, the drive pulse frequency must be gradually reduced according to the inertia of the load. Furthermore, when it is desired to reduce the influence on the load when starting and stopping the step motor, the drive pulse frequency is sequentially controlled.

When the step motor is drive-controlled in this way, it is necessary to sequentially increase / decrease the drive pulse frequency at the time of start / stop.
The oscillation frequency of the oscillator is controlled by varying the control voltage, or an oscillator that applies the charging / discharging time constant of the capacitor is used to detect the charging voltage of this capacitor and vary the threshold of the detection circuit to control the oscillation frequency. ing.

<Problems to be Solved by the Invention> However, in the above-mentioned conventional apparatus, if vibration or impact is applied during rotation of the step motor, rotation stop occurs due to modulation or overload. In such a case, in order to rotate the step motor, it is necessary to detect that the rotation has stopped and restart it.

The present invention has been made in view of the above problems, and an object of the present invention is to automatically and surely restart even when modulation or rotation stop occurs.

<Means for Solving Problems> A configuration of the present invention for solving the above problems is a stepping motor starting circuit that outputs a voltage signal as driving frequency information, wherein the starting circuit is a reference voltage source. (VF), starting means, a switch for switching between the two, and the switch control section, which is a circuit having a voltage output time constant according to an increase in drive frequency at the time of starting the starting means. The switch control unit includes a rotation stop detection unit, an activation unit operation end detection unit, and a flip-flop that switches the switch in response to outputs from both of them. The rotation stop detection unit includes a rotation detector and the rotation detector. It is composed of a comparator for comparing the output with a predetermined value, and outputs a significant signal when the step motor is in an abnormal stop state.
The start-up operation end detection unit is composed of a hysteresis comparator that compares the output voltage of the start-up means with a reference voltage (VF) equivalent voltage (Vt), and outputs a significant signal when the start-up operation ends. The flip-flop inputs the output signal of the logic circuit to which the output signal of the rotation stop detection unit and the output signal of the activation means operation end detection unit are input, and outputs the inverted signal from the activation means operation end detection unit. A signal is input to the reset input and outputs a signal for arranging the switch to the moving means side when the motor is abnormally stopped and to the reference voltage source (VF) side when the start-up means ends the operation.

<Embodiment> FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG., + V _F is a first reference voltage determined rotational speed of the step motor, this voltage is connected to the input side of the voltage-frequency converter 2 via a resistor R (V _F
in). The output side of the voltage / frequency converter 2 is connected to the input side of the motor drive circuit 3, and the step motor 4 is rotated by the output from the motor drive circuit. Reference numeral 5 denotes an encoder for detecting the rotation speed of the step motor. The output from the encoder 5 is connected to the frequency / voltage converter 6, and the output (V _FS ) of the frequency / voltage converter 6 is one of the first comparator 7. Is connected to the input side of. A second reference voltage (voltage Vr for determining the rotation speed of the step motor) is input to the other input side of the first comparator 7. The output (Vc) of the first comparator 7 is connected to one input side of the logic circuit 8. Reference numeral 9 is an RS flip-flop, and the output side of the RS flip-flop 9 is connected to the control terminal of the switch 11. The common terminal side of the switch 11 is grounded via the capacitor C, one terminal side of the other two terminals is grounded, and the other side is connected to the input terminal of the voltage / frequency converter. The voltage (Vi) on the common terminal side of the switch 11 is connected to one input side of the second comparator 10, and the third reference voltage (charging and discharging of the capacitor C is applied to the other input side of the second comparator 10). The voltage Vt) for determining is input. The output (Vo) of the second comparator 10 is connected to the RS flip-flop 9 and the other input side of the logic circuit 8.

2A to 2G are time charts of waveforms of respective parts at the time of starting and restarting the step motor in the above configuration.
It will be as shown in. That is, immediately after the power is turned on, the motor rotation speed f _s = 0, V
_{With Fs} = 0, Vc = high level, Vi = 0, Vo = high level, the RS flip-flop and the switch are in the set (S) state. Therefore, a voltage of Vi = 0 is applied to the voltage / frequency converter 2. Thereafter, rises from 0 at constant tau = CR when the voltage V _F in which is applied to the voltage / frequency converter 2 resistor R and capacitor C, the rotation speed of the stepping motor with a rise in the voltage V _F in the case that It rises according to a constant. As a result, the output frequency of the encoder 5 increases, and at the same time, the output V _{F of the} frequency / voltage converter 6 increases.
Although s also rises, the output (Vc) of the first comparator 7 becomes low level when the voltage becomes the same as the second reference voltage (Vr).

On the other hand, the output (Vo) moth momentarily low level of the second comparator 10 at the time the voltage reaches a level similar to the reference voltage of the voltage of the capacitor C is also increased at a fixed time constant (Vi = V _F in) , Then RS flip-flop 9
A reset signal is output from the switch 11, the switch 11 is in a reset state, the charge stored in the capacitor C is discharged, and the first reference voltage V is input to the voltage / frequency converter 2.
_F is applied. As a result, the output of the second comparator 10 becomes high level again. As the second comparator 10, for example, a hysteresis comparator having the characteristics shown in FIG. 1 (b) is used.
If i) is between _O~V L ~L _H is output (Vo) is at a high level, the output at the time beyond the _{V H} (Vo) becomes the low level.

This state (Vc = low level, Vi = O, Vo = high level and RS flip-flop and switch reset) is maintained during normal rotation.

Now, assume that the motor is overloaded due to shock or vibration, and the motor rotation slows or stops. As a result, the output V _{F s} of a frequency / voltage converter 6 becomes the reference voltage (Vr) hereinafter, emits signals via the RS flip-flop from the logic circuit 8 outputs of the first comparator 7 becomes a high level, The switch 11 is located on the set (S) side. As a result, V _Fin once becomes zero potential, and the voltage rises with the time constant of RC. Therefore, the step motor 4 can gradually start rotating from the self-starting frequency, and each unit maintains the same state as the above-described operation.

In the above embodiment, the step motor is configured to start exponentially with the CR time constant, but in such a case, it may not start properly because the initial rise at the start is rapid. In such a case, the CR circuit may be replaced by an integrating circuit as shown in FIG. 3 (a).

FIG. 3 (a) shows only the integrating circuit portion in the overall configuration diagram shown in FIG. 1 (a), and the same elements as those in FIG. 1 (a) are denoted by the same reference numerals. In this example, the signal from the RS flip-flop 9 is connected to the two switches 11a and 11a.
When the switch is set to the reset (R) side, the output of the amplifier 20 becomes zero, and when the switch is set to the (S) side, the output rises linearly as shown in FIG. 3 (b). . Therefore, compared with the configuration shown in FIG. 1 (a), the rising can be made gentler and more reliable starting can be performed.

In this embodiment, an example in which an encoder and a frequency / voltage converter are used as the rotation speed detecting means has been described, but the present invention is not limited to this example, and a tacho generator may be used, for example.

<Effects of the Invention> As described above in detail with the embodiments, according to the present invention, the rotation of the step motor can be automatically continued even when the rotation of the step motor is stopped due to impact or vibration. By monitoring the rotation during steady operation in real time and using a comparator with hysteresis as the second comparator, it is possible to realize fine control without reacting to slight rotation abnormalities during steady operation. .

[Brief description of drawings]

FIG. 1 (a) is a structural explanatory view showing an embodiment of the present invention, FIG. 1 (b) is an explanatory view showing an output state of a second comparator, and FIG. 2 is a step motor starting and restarting. FIG. 3 is a time chart showing waveforms of respective parts of FIG. 3, and FIG. 3 is a configuration explanatory view showing another embodiment. 2 ... Voltage / frequency converter, 3 ... Motor drive circuit, 4 ... Step motor, 5 ... Encoder, 6 ... Frequency / voltage converter, 7 ... First comparator, 8 ... Logic circuit, 9 ... RS
Flip-flop, 10 ... Second comparator, 11 ...
Switch, + V F _... first reference voltage, Vr ... second reference voltage, Vt ... third reference voltage.

Claims (1)

[Claims] 1. A starter circuit for a step motor that outputs a voltage signal as drive frequency information, wherein the starter circuit includes a reference voltage source (VF), a starter, a switch for switching between the two, and the switch. A starter means is a circuit having a voltage output time constant corresponding to an increase in the drive frequency at the time of start-up, and the switch controller has a rotation stop detecting portion and a starter operation end detecting portion. , A flip-flop that receives the outputs of both of them and switches the switch, and the rotation stop detection unit is composed of a rotation detector and a comparator that compares the output of the rotation detector with a predetermined value. A significant signal is issued in a stopped state, and the activation means operation end detection section compares the output voltage of the activation means with a reference voltage (VF) equivalent voltage (Vt). The flip-flop is a logic circuit to which the output signal of the rotation stop detector and the output signal of the starter operation end detector are input. Is input to the set input and the inverted signal from the start-up operation end detection unit is input to the reset input, the switch is set to the start-up means side when the motor is abnormally stopped, and the reference voltage source ( A starter circuit for the step motor that outputs a signal to place a switch on the (VF) side.