JPH02246793A - Pulse motor driving method - Google Patents

Abstract

PURPOSE:To reduce noise, caused by rotary vibration of shaft system due to excessive output torque, by measuring the magnitude and duration of peak current flowing through each driving phase then determining the duration and the magnitude of current of a phase, to be excited next, according to thus measured peak current and duration thereof. CONSTITUTION:A control section 3 reads out current value data from a current measuring section then reads out exciting condition of a phase, to be excited next, from a table contained in a memory 4 and controls a pulse motor driver 5. Upon increase of load torque due to some cause, e.g. when the current increases from a peak value Ip3 to Ip5, the control section 3 immediately reads out ON time Ton4 for the phase to be excited next from the table and controls the pulse motor driver 5 such that the ON time for the phase to be excited next will be Ton4. Consequently, peak current Ip7 flows through a motor to increase allowable load torque so as to compensate for increase of load torque.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a pulse motor, and particularly to a method for driving a pulse motor suitable when the load of the pulse motor varies greatly.

[Conventional technology]

As a conventional pulse motor drive method, the basics and applications of stepping motors (1986, Sogo Electronic Publishing Co., Ltd.)
As described in P. 15B, a so-called constant voltage drive method or constant current drive method is adopted.

Control of the phase current value of the pulse motor has been performed only when changing the drive pulse rate of the pulse motor (during so-called slewing or when driving at a plurality of pulse rates).

[Problem to be solved by the invention]

The above-mentioned conventional technology does not give consideration to reducing the amount of heat generated by the motor when the load fluctuation of the pulse motor is large, or to reducing the power consumption of the device. Particularly with respect to the load of the pulse motor, if the peak load torque is larger than the steady load torque, there is a problem in that the power supply for the pulse motor and the device must be large-sized.

In addition, since the pulse motor and other devices are large-sized and have a structure that constantly generates peak load torque, there is a problem in that excessive torque causes rotational vibration in the shaft system, resulting in large noise.

- For boat fishing, the permissible load torque of a pulse motor is limited by the current value at which the temperature rise due to heat generation does not exceed the heat resistance temperature of the winding insulation. However, if the use is for a short time and the temperature rise can be ignored, the allowable load torque can be further increased by increasing the current value.

The purpose of the present invention is to reduce the amount of heat generated by flowing a large current to generate a large torque when the load torque becomes large (when the load torque becomes large), and by suppressing the current value to a small value when the load torque is small. The purpose is to reduce noise by making the device smaller, suppressing temperature rise, making it possible to use a small pulse motor, and keeping the power consumption of the device to a low level.

[Means to solve the problem]

The pulse motor driving method of the present invention measures the peak current value and current flow time flowing through each phase of the pulse motor being driven, and the current flow for the next excitation is determined according to the measured peak current value and current flow time. It is characterized by determining the time and current value.

[Effect]

According to this invention, the current value flowing through each phase of the pulse motor being driven and the current flow time (on time) are measured,
Based on this, the current flow time of the current value of the next excitation is determined. Therefore, when the load torque is small, the pulse motor is driven with a small current value, and when the load torque is large, the pulse motor is driven with a large current value.

Next, the principle of the present invention will be explained using a 1-2 phase excitation compolar drive as an example. Figure 2(a) is 1-
The excitation sequence of each phase in two-phase excitation compolar drive is shown. Each phase A, B, A, B4! is controlled so that it is excited for three steps and de-energized for five steps.

) in Fig. 2 shows the excitation method for one phase A. Normally, in order to simplify the control system, the on-time Ton is synchronized with the phase advance.
and an off time ↑off are provided, and the peak value Ip of the current is controlled by this time ratio.

Fig. 3 shows the relationship between the load torque Tr and the above peak current value Ip as the on-time ratio t −Ton / (Ton + Toff
) is shown as a parameter. In Fig. 3, when the relationship between the load torque T' and the peak current !p falls below the straight line BB', the pulse motor loses synchronization. When the load torque Tr is O, the peak current Ip indicated by the operating point A' flows.As the load torque Tr increases, the operating point changes along the straight line A'B'.
The peak current ip also gradually increases along the straight line A'B'. When the load torque Tr exceeds point B', the operating point B
B", the pulse motor loses synchronization.

Furthermore, in FIG. 3, when ε=1.0, the peak current 1p changes along straight lines A' and B' depending on the load. Also, the load torque Tr at the operating point B''
raax indicates the maximum torque that the pulse motor of this example can generate.

In FIG. 3, there is a section in which load torque Tr', which is much smaller than maximum load torque Trtaax, is considered, and ε
When driven under the condition of =0.4, the peak current Iρ has a value at the operating point C'. Further, when driven under the conditions of ε-1, 0, the peak current rp becomes the value at the operating point C because it is the same as the load torque Tr' of the pulse motor. Therefore, the peak current 1p will increase significantly.

That is, when the maximum value of the load torque Tr is less than or equal to Tr', it is sufficient to drive under the condition of ε=0.4, but when the maximum value of the load torque Tr becomes large such as Tr'',
It is necessary to drive under the condition of ε=1.0.

However, in a normal example, the load torque Tr is the maximum value Tr.
' is a very small amount of time out of the total operating time of the pulse motor, and most of the time the steady load torque Tr' is lower. However, in the prior art, considering that the load torque Tr is the maximum value Tr, the drive is performed under the condition of ε=1.0, so the peak current ■ρ is at the operating point C This results in an unspecified value, resulting in large power consumption and heat generation.

Therefore, when the load torque Tr is the maximum value Tr", ε=1
．． 0, and the load torque Tr is always the load torque Tr
', if you drive with ε=0.4, the constant load torque T
The peak current ■ρ at the time r' can be reduced to the value shown at the operating point C'.

Therefore, this invention focuses on the above-mentioned points, and since the peak current 1p of a pulse motor is determined by the driving conditions and load torque as shown in FIG. By determining the time and the load torque Tr at that time, it is possible to determine the driving conditions for the next excitation phase to match the load torque Tr. If this is done one after another for each phase advance, even if the load torque Tr fluctuates, it is possible to always maintain optimal drive conditions, reduce power consumption, and reduce the amount of heat generated by the pulse motor. .

〔Example〕

The present invention will be described in more detail below with reference to embodiments shown in the accompanying drawings. The following explanation will be made regarding a 1-2 phase excitation unipolar drive system of a 4-phase pulse motor, but it goes without saying that the present invention can be applied even if the number of phases and excitation methods are different.

FIG. 1 is a diagram showing a control system of a pulse motor to which the present invention is applied. In FIG. 1, switching transistors Ql to Q4 are connected to each phase of a pulse motor 1, and the emitters of each switching transistor Ql to Q4 are connected to each other.
Resistors R1 to R4 for current measurement are connected.

The current flowing through each phase A, A, B, and B of the pulse motor is converted into voltage by resistors R1 to R4, and is input to the current measuring section 2.

The control unit 3 reads the current value data (on time and peak current value) output from the current measurement unit 2, and determines the cause of the next excitation phase from the table stored in the memory 4. An example is shown.

For example, if the on-time is Ton 2 when driving the steady load torque Tr', and the peak current value at this time is Ip Hiro 3, the control section 3 determines the next excitation phase from the table shown in Fig. Ton2 is always read out as the excitation time, and steady driving is performed.

Here, if the load torque increases for some reason, for example, if the peak current value increases from Ip3 to Ip5, the control unit 3 immediately reads the on-time Ton4 of the next excitation phase from the table shown in Figure 3, and pulses it. The motor driver 5 is controlled so that the on-time of the next excitation phase becomes Ton4.

As a result, the peak current 1p7 flows through the pulse motor, the allowable load torque increases, and the increase in the load torque can be compensated for.

Also, when the load torque returns to the steady value ↑r',
The peak current value decreases to lp5, and the control unit 3 reads the on-time Ton2 of the next excitation phase from the table shown in FIG. 2, and returns to the steady state.

Therefore, in the conventional driving method, the on-time must always be Ton4, and the peak current value is Ip5 even under a steady load, whereas according to this embodiment, the peak current value under a steady load is The value can be kept to Ip3, and the heat generation of the pulse motor and the power consumption of the device can be kept low.

FIG. 3 is a diagram showing a specific example in which the pulse motor driving method of the present invention is applied to a sheet separation mechanism.

The paper sheet separation mechanism shown in FIG. do. However, depending on the condition of the paper sheet 8,
Two or three sheets of paper may be caught between the feed roller 6 and the gate roller 7, and the torque for driving the feed roller 6 may be several times that in a steady state. Conventionally, the pulse motor and its control system were constructed so that the pulse motor always generated a load torque commensurate with this torque, resulting in a large device and large power consumption. However, by adopting the present invention, a small pulse motor can be used and power consumption can also be reduced.

The paper sheet separation mechanism shown in Fig. 3 is often used as a banknote separation mechanism in the banknote processing mechanism of an automatic cash takeout device. In such a case, the torque fluctuation for driving the feed roller 6 is large, and the present invention can be particularly effective.

[Effects of the Invention] As is clear from the above description, according to the present invention, when a load with large load fluctuations is driven by a pulse motor, a small pulse motor can be used and the power consumption can be reduced. .

In addition, when the load torque is small, the output torque of the pulse motor can be reduced, and the output torque of the pulse motor can be increased only when the load torque is large. Noise caused by rotational vibration of the system can be reduced.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a pulse motor control system to which the present invention is applied, and Fig. 2 (a) is a diagram showing the excitation sequence of each phase when the pulse motor is driven by a 1-2 phase excitation comparator drive system. , Fig. 2 (b) is a diagram showing an example of one-phase excitation current when a pulse motor is driven by the 1-2 phase excitation compolar drive method 2, and Fig. 3 is a diagram showing the relationship between load torque and peak current. , FIG. 4 is a diagram showing an example of a table stored in the memory shown in FIG. 1, and FIG. 5 is an explanatory diagram showing a paper sheet classification mechanism. 1...Pulse motor, 2...Current measuring section, 3...
Control unit, 4...Table, 5...Pulse motor driver, 6...Feed roller, 7...Gate roller, 8...Paper sheet. Agent Patent Attorney Tadashi Akimoto Figure 1 Figure 2 (a) (b) b Shotukan layer 11-Rukugoi Funeral map

Claims (2)

[Claims] 1. The feature is that the peak current value and current flow time flowing through each phase of the pulse motor being driven are measured, and the current flow time and current value for the next excitation are determined according to the measured peak current value and current flow time. A method of driving a pulse motor. 2. 2. The method for driving a pulse motor according to claim 1, further comprising reading out a peak current value and current flow time of next excitation from a predetermined table based on the measured peak current value and current flow time.