JPH04265698A - Step motor drive - Google Patents

Abstract

PURPOSE:To achieve a good driving state without causing trouble such as excessive torque by feeding a step motor with an optimal exciting current for each operating characteristic of slow-up, constant speed and slow down. CONSTITUTION:A timing table 21 being set with exciting phase data and exciting current switching timing for each operational characteristic of slow-up, constant speed and slow-down and a current value table 22 being set with exciting current values for producing optimal torques are provided. An exciting current control means 19 comprising current detecting detectors 13AC, 13BD, an enable gate 14 and comparators 16AC, 16BD then sets the current flowing into the step motor 11 according to the tables thus suppressing excessive torque.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor drive device for driving a stepping motor used for driving a carriage of a serial printer with acceleration, constant speed, and deceleration operating characteristics.

0003

2. Description of the Related Art Generally, stepping motors are widely used to drive the carriages of serial printers. This stepping motor is designed to suppress vibrations as much as possible during driving, and to drive with response characteristics unique to each stepping motor, that is, to drive at high speeds beyond the motor's self-starting range, as shown in Figure 3. It is operated with such characteristics.

That is, a slow-up area a is provided to perform acceleration, and after the speed has increased, printing is performed in a constant-speed area b, and after printing is completed, the stepping motor is decelerated in a slow-down area c, and the stepping motor is stopped. let In addition, at the bottom of the same figure, the above-mentioned regions (hereinafter referred to as operating characteristics) a, b, and c are shown.
It shows the required torque at . As is clear from this, in the constant speed driving characteristic b, the slow-up driving characteristic a
The required torque is less than .

Furthermore, as a driving method for a stepping motor, a microstep method is considered for the purpose of reducing vibration noise during driving, and is described in, for example, Japanese Patent Laid-Open No. 1-152996. This microstep method is
While the conventional drive signal is a rectangular wave, this is a method in which the drive signal is changed stepwise by microsteps, and the waveform is approximated to a sine wave or the like.

[0006] By the microstep method, each of the slow-up, constant speed, and slow-down operating characteristics a and b
, c will be described with reference to FIG. 4.

In FIG. 4, A, B, C, and D represent the excitation phases of the stepping motor, and the operating characteristics a,
It shows the excitation phase switching timing in b and c.

[0008] The slow-up operation characteristic a is when the stepping motor is started up, and a large torque is required for acceleration. Since the torque of the stepping motor is proportional to the magnitude of the excitation current, the peak value of the excitation current is set so as to satisfy the required torque for the operating characteristic a. The peak value of this excitation current is preset in a control microcomputer or the like, and as shown in the figure, the other characteristics b and c are also driven by the excitation current set to this peak value.

However, as mentioned above, the constant speed driving characteristic b
Since this requires less torque than the slow-up operation characteristic a, driving with the excitation current results in operation with excessive torque, which generates vibrations and noise.

0010

[Problem to be solved by the invention] As described above, since the setting value of the excitation current is common to each characteristic, the torque in constant speed operation characteristic b becomes excessive, which causes vibration and noise. .

An object of the present invention is to provide a stepping motor drive device that can obtain a good driving condition without causing problems such as excessive torque by supplying the optimum excitation current for each characteristic. It is in.

[Configuration of the invention]

[0013]

[Means for Solving the Problems] The present invention provides a stepping motor drive device for driving a stepping motor with acceleration, constant speed, and deceleration operating characteristics. , a timing table in which the excitation phase data and excitation current switching timing for obtaining each of these operating characteristics are set, and the optimum excitation current value for each of the acceleration, constant speed, and deceleration operating characteristics. switching means for sequentially exciting the excitation phase circuit of the stepping motor by switching the excitation phase circuit of the stepping motor according to the excitation phase data and its excitation current switching timing based on a set current value table and a clock signal; Output means for outputting the optimum excitation current value set in the current value table for each operating characteristic as a reference value, and detecting the excitation phase current of the stepping motor and matching this value with the reference value of the output means. and excitation current control means for controlling the current.

[0014]

[Operation] In the present invention, when driving a stepping motor with acceleration, constant speed, or deceleration operating characteristics, the timing table includes excitation phase data and data for each operating characteristic in order to obtain the optimum torque for each operating characteristic. Set the excitation current switching timing, set the optimum excitation current value in the current value table, set the reference value of the excitation current, match the reference value with the excitation current control means, and check if the driving state with constant speed characteristics is excessive. Always obtain good driving conditions without excessive torque.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a stepping motor 11 is used to drive a carriage of a serial printer (not shown). This stepping motor 11 has an excitation winding 11
a, 11b, and these excitation windings 11a, 1
The excitation windings 11a and 11b are connected to corresponding NPN transistors 12A, 12B, 12C, and 12D at both ends of the excitation windings 11a and 11b.
It is connected to the.

That is, one end of one excitation winding 11a is connected between the collector and emitter of the A-phase transistor 12A, and the other end is connected to the C-phase transistor 12C.
They are connected in common through the collector and emitter of the transistors, and are further connected to ground through a current detection resistor 13AC. One end of the other excitation winding 11b is connected to the B-phase transistor 12.
The other end of the D-phase transistor 12D is commonly connected through the collector and emitter of the D-phase transistor 12D, and is further connected to the ground through the current detection resistor 13BD.

At the base of each transistor 12A, 12B, 12C, 12D of the transistor array 12,
A corresponding AND gate 14A of the enable gate 14,
The output terminals of 14B, 14C, 14D are connected, and these AND gates 14A, 14B, 14C, 14D
An excitation phase switching signal is inputted via.

Here, the AND gates 14A, 14B
, 14C, 14D, corresponding phase data for excitation phase switching is inputted from the microcomputer 15 to one input terminal of each of them. Furthermore, output signals from the comparators 16AC and 16BD are input to each other input terminal.

The terminal voltage of the current detection resistor 13AC is input to the inverting input terminal of the comparator 16AC, and the reference voltage corresponding to the reference value of the excitation current, which will be described later, is input to the non-inverting input terminal. There is. therefore,
When the A-phase or C-phase current value rises to the excitation current reference value and the input voltage to the inverting input terminal exceeds the reference voltage applied to the non-inverting terminal, the output of the comparator 16AC inverts to L level. , corresponding AND gate 14A
Alternatively, the other input terminal of 14C is set to L level. Therefore, if the AND gate 14A or 14C is on, it is turned off, and the corresponding transistor 12A or 12C is turned off, thereby cutting off the phase current.

The function of the comparator 16BD is the same as that of the comparator 16AC, and when the B-phase or D-phase current value rises to the reference value of the excitation current, the output is inverted to L level, and the output of the corresponding AND gate 14B or AND gate 14D is When the other input terminal is set to L level and these AND gates 14B or 14D are on, the AND gates 14B or 14D are turned off, and the corresponding transistor 12B or 12D is turned off. and cut off the phase current.

Based on these functions, the transistor array 12 and enable gate 14 control the stepping motor 1 according to the excitation phase switching timing generated by the microcomputer 15 based on the clock signal, that is, the phase data output from the microcomputer 15.
This serves as a switching means 18 for switching one excitation phase circuit. Also,
The current detection resistors 13AC, 13BD, comparators 16AC, 16BD, and enable gate 14 are as follows:
The excitation current control means 19 detects the excitation phase current of the stepping motor 11 and makes this value match the reference value of the excitation current.

The microcomputer 15 has a timing table 21 and a current value table 22 in an internal ROM for driving the stepping motor 11.

The above-mentioned timing table 21 drives the stepping motor 11 with the respective operating characteristics a, b, and c of slow-up, constant speed, and slow-down shown in FIG. The excitation phase data A, B, C, and D shown in FIG. 2 to be obtained and the switching timing of the excitation phases (that is, the switching timing of the excitation current) are set.

In addition, the current value table 22 includes the aforementioned slow-up, constant speed, and slow-down operating characteristics a, b, and c.
For each case, the optimum excitation current value for these operating characteristics, that is,
Excitation current values for obtaining appropriate drive torque are set in accordance with each microstep phase, as shown in FIG. 2.

Furthermore, the microcomputer 15 includes a digital/analog converter (D/A converter) 23 as an output means for outputting a reference value of an excitation current value that matches the phase of each microstep with the clock signal as a reference. have That is, this D/A converter 23
converts the 8-bit digital signal set in the current value table into an analog signal (voltage value), and uses the comparator 16AC, 16BD as the reference value of the excitation current.
Output to the non-inverting terminal of

In the above configuration, the microcomputer 15 sets excitation phase data A, B, C, and D of FIG. 2 corresponding to the stopped state of the stepping motor 11 to the output port. Further, current values corresponding to the slow-up characteristic and matching the phase of the microstep are set in the D/A converter 23 and outputted respectively. Due to this operation, the enable gate 14 has its AND gate 14A,
Among 14B, 14C, and 14D, excitation phase data A and B
, C, and D, those at H level are turned on (at this time, the outputs of comparators 16AC and 16BD are both at H level), and transistor 12A of transistor array 12
, 12B, 12C, 12D are turned on, and the excitation windings 11a, 11b of the stepping motor 11 are turned on.
Excite and drive the corresponding phase of.

This excitation current value is determined by the current value detection resistor 13A.
Detected by corresponding ones of comparators 16AC and 16BD,
It is compared with the current value set by the D/A converter 23, and based on the result, the AND gates 14A, 1
4B, 14C, and 14D, and also controls the transistors 12 of the transistor array 12.
Turn on the corresponding ones of A, 12B, 12C, and 12D.
Control off. That is, the stepping motor 11 is driven by a chopper.

Here, as described above, the stepping motor 11 is driven with the respective operating characteristics a, b, and c of slow-up, constant speed, and slow-down, but the D/A converter 2
The current value set in 3 is switched to the optimum value for each operating characteristic a, b, c, so the current value set in
The optimum excitation current at c, that is, the excitation current that does not cause excess or deficiency of torque, is applied to the excitation windings 11a and 11b.
flows to Therefore, vibration and noise caused by excessive torque are reduced.
A good driving condition can be obtained.

[0030]

As described above, according to the present invention, the excitation phase data and excitation current switching timing are set in the timing table for each operating characteristic so that the optimum torque for each operating characteristic can be obtained, and the current value By setting the optimum excitation current value in the table, setting the reference value of the excitation current, and matching the reference value with the excitation current control means, the stepping motor can be operated at various speeds such as slow-up, constant speed, and slow-down. Since an excitation current that generates a torque corresponding to the characteristics is passed, vibration and noise caused by excessive torque can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a stepping motor drive device according to the present invention.

FIG. 2 is an operation explanatory diagram showing the switching timing of excitation phase data and the waveform of an excitation phase current in correspondence with each other in the apparatus of FIG. 1;

FIG. 3 is a characteristic diagram showing the relationship between each operating characteristic of a stepping motor and required torque.

FIG. 4 is an operation explanatory diagram showing the switching timing of excitation phase data and the waveform of an excitation phase current in correspondence with each other in a conventional device.

[Explanation of symbols]

11 Stepping motor 18 Switching means 19 Excitation current control means 21 Timing table 22 Current value table 23 Digital/analog converter (D/A converter) as output means

Claims (1)

[Claims] 1. A stepping motor drive device for driving a stepping motor with operating characteristics of acceleration, constant speed, and deceleration, for obtaining each of the operating characteristics for each of the acceleration, constant speed, and deceleration operating characteristics. a timing table in which excitation phase data and excitation current switching timing are respectively set; and a current value table in which excitation current values optimal for the operating characteristics are set for each of the acceleration, constant speed, and deceleration operating characteristics. , switching the excitation phase circuit of the stepping motor according to the excitation phase data and its excitation current switching timing based on a clock signal;
a switching means for sequentially exciting; an output means for outputting, as a reference value, an optimum excitation current value set in the current value table for each of the acceleration, constant speed, and deceleration operating characteristics; and an excitation phase current of the stepping motor. 1. A stepping motor drive device comprising: excitation current control means for detecting the value and controlling the detected value to match a reference value of the output means.