JPH0510915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sewing machine control device having a so-called variable speed function, which drives the sewing machine at a predetermined speed according to the amount of pedal depression.

Configuration of conventional example and its problems Conventionally, this type of control device has been used for a long period of time. The so-called analog speed control is performed by comparing the signal, or even the signal smoothed by an RC circuit, with an appropriate reference voltage for the clutch or brake to activate or de-energize the clutch/brake coil and perform speed control. Control systems have been adopted, for example, as seen in Japanese Patent Publication No. 47-28376 and US Pat. No. 3,407,910.

However, in recent years, with the development of semiconductor control devices such as microcomputers, digital control methods have been developed, and so-called so-called Digital speed control has come into use.

Although the digital speed control described above has various advantages, it is not yet perfect, and especially in the case of a control method that changes the rotational speed of the sewing machine in stages according to the amount of pedal depression, A method has been adopted in which the lowest speed of the sewing machine is used as a reference speed, and a speed that is approximately an integral multiple of the reference speed is obtained by frequency-dividing the speed signal from a speed generator (Japanese Patent Laid-Open No. 56-63393). .

For example, if the above standard speed is 200 rpm, the maximum speed of this conventional system is 6000 rpm.
For the above-mentioned high-speed sewing machines, the rotational speed that is an integer multiple of approximately 200rpm according to the pedal depression (the speed difference between each stage is at least 200rpm) is not of much concern.
For low speed sewing machines such as a maximum of 600 rpm or less,
The sewing machine was originally intended for delicate sewing work at low speeds, and therefore had the disadvantage that at a minimum speed of 200 rpm, the speed changed too suddenly, making it difficult to perform sewing work.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks and to provide a sewing machine control device with good workability for either high-speed sewing machines or low-speed sewing machines.

Composition of the Invention The present invention provides a method for changing the frequency of a clock pulse from a variable frequency oscillator to extend the period of a pulse signal from the speed generator divided by a frequency divider in accordance with a command from the speed setting device. By changing the count value of the clock pulse even if it is a constant cycle, substituting the count value into a predetermined calculation formula and controlling the drive control section of the motor, a constant speed can be achieved. Even if the number of divisions is the same, the speed can be varied by changing the frequency of the clock pulse from the oscillator, and the change curve of the rotational speed of the sewing machine relative to the amount of pedal depression is created. can be made variable, as described above.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the block diagram of FIG.

In the figure, numeral 1 represents a sewing machine driven by a motor (not shown), and is a part that performs sewing work. A speed generator 2 is attached to the sewing machine 1, and the speed generator 2 generates a plurality of equally spaced pulse signals at fixed angles per rotation of the sewing machine. The waveform shaping circuit 3 is composed of simple control elements such as an OP amplifier or an IC in order to shape the pulse signal into a rectangular wave. The frequency divider 4 is an IC circuit that can switch the frequency division ratio according to the speed setting signal from the speed setting device 5. The speed setting device 5 is a part that outputs a stepped position signal corresponding to the depression position of the sewing machine pedal as a speed setting signal,
For example, it is composed of a shielding plate linked to the pedal and several pairs of light emitting/light receiving elements arranged at corresponding positions. Reference numeral 6 indicates a counter, and reference numeral 7 indicates a variable frequency oscillator, which is composed of a variable resistor, a capacitor, and an IC, and is capable of continuously changing the frequency of the clock pulse according to changes in the variable resistor. Reference numeral 8 indicates a latch, 9 an arithmetic unit, and 10 a timer, all of which are constructed from IC circuits, and in particular can be easily constructed using a one-chip microcomputer that incorporates all of these functions. Driver 1
The clutch/brake coil 12, which constitutes the drive control section of the motor, is located in the electromagnetic clutch/brake coupling section of the motor, and transmits the rotational force of the motor to the output shaft via the magnetic circuit/lining section. is configured to be transmitted. The output shaft of the motor has a pulley attached to its end, and is linked to the sewing machine 1 via the pulley and belt.

The system is configured as described above, and its operation will be explained below.

First, while the sewing machine 1 is rotating, the speed generator 2 outputs a signal with a frequency proportional to the rotation speed of the sewing machine, and the waveform shaping circuit 3 shapes the signal into a pulse as a rectangular wave. Outputs a signal string. This pulse signal train is divided by the frequency divider 4 according to the set amount from the speed setter 5, for example, if the set amount is doubled, it will be divided into 1/2, and if the set amount is 4 times, it will be divided into 1/4. A frequency-divided pulse train P _D is output. A counter 6 counts the clock pulses from the variable frequency oscillator 7 over one cycle period of the frequency-divided pulse train _PD ,
The latch 8 latches the actually measured period of the section immediately before the pulse section to be controlled, and outputs the actually measured period T _P to the arithmetic unit 9. The arithmetic unit 9 calculates the excitation time of the clutch coil or brake coil by substituting the measured period T _P into a predetermined arithmetic expression, sets the arithmetic result value T _BC in the timer 10, and then calculates the excitation time through the driver 11. The clutch/brake coil 12 is energized for the calculated time to control the pulse section, which is the control target range, and by repeating the above, the averaged rotational force is transmitted to the sewing machine head, and the sewing machine uses the speed setting device. The vehicle will be driven at the speed determined by 5.

Here, when the frequency of the clock pulse of the variable frequency oscillator 7 is changed, the counter 6
The output value changes even if the period of the frequency-divided pulse train P _D is constant, and therefore the result of substituting into the predetermined calculation formula also changes, making it possible to shift the sewing machine speed to a new stable speed. becomes.

Next, a specific example of calculation by the arithmetic unit 9 in the block diagram of FIG. 1 will be described with reference to FIG. In this example, the calculation curve is represented by the simplest straight line, but all other calculation possible curves may be used.

The equation of the straight line is expressed by the following equation.

T _CB = AT _P −B However, T _CB ; Clutch/brake excitation time A, B; Constant T _P ; Actual measurement period In Fig. 2, the The actual measurement cycle is represented, and the Y-axis represents the clutch current application time (in the case of positive) or the brake current application time (in the negative case) in the above-mentioned control target section, and the constants A and B are fixed in the curve.

For example, when the clock pulse from the variable frequency oscillator 7 has a predetermined period, the calculation formula shown in the same figure is adopted, and as shown by point α, the period is only the time T _CB1 of T _P1 . The clutch coil is energized at the duty cycle when the clutch is engaged, and operates to absorb the sewing machine load and maintain a constant speed.

For example, when the load becomes heavier than normal constant speed operation with a load, the actual measurement period becomes longer as the sewing machine rotational speed decreases, and the clutch current application rate increases, and these factors increase the load. When they match, constant speed operation is performed. On the other hand, when the load becomes lighter, the rate of application of the clutch current decreases to try to lower the rotational speed, and when these are balanced, constant speed operation is performed. Furthermore, if the rotational speed extremely exceeds the set value due to some kind of disturbance or transient speed overshoot, the calculation result will be negative and the speed will be reduced quickly by applying brake current. is running.

Here, the coefficient A in the above equation determines the gain of the system, and is arbitrarily determined in consideration of the responsiveness, stability, etc. of the system. Also,
Constant B is determined by the clutch current application rate required to maintain the set speed under normal sewing machine load conditions.

The frequency of the clock pulse is then changed;
For example, if the period becomes smaller,
The count value by the counter 6 increases, and as shown in the figure, the counter value changes to T _P2 , and the calculation result of the clutch engagement time is T _CB2 (point β).
Since the Y-axis shows real time, the duty cycle of clutch engagement temporarily increases, rapidly accelerates, and stabilizes at a speed higher than the conventional stable speed, and conversely, the above-mentioned As the period of the clock pulse increases, the count value by the counter 6 becomes smaller, and the clutch transition temporarily shifts to point δ, where the clutch engagement duty cycle is reduced and decelerated, and becomes stable at a speed lower than the conventional stable speed. Become.

On the other hand, as described above, the system operates so that the period of the frequency-divided pulse signal P _D from the frequency divider 4 is always constant, and therefore, for example, the frequency division ratio is changed from 1 to 1/2 by the speed setting device 5. In such a case, the actually measured cycle is first doubled, but the cycle is kept constant as described above, and therefore the final sewing machine rotational speed is stabilized at approximately double. In this way, the speed setting is changed in stages, and when the dividing ratio becomes 1/n, the setting speed is n compared to the reference setting speed when it is 1.
It can take double the value. (However, n=1, 2,...) Here, as mentioned above, the frequency-divided pulse signal
Since the period of P _D is expressed by the count value of the clock pulse, the count value can be continuously varied by adjusting the variable frequency oscillator 7. Therefore, by adjusting the variable frequency oscillator 7, it is possible to change the count value according to the pedal depression stroke. It becomes possible to vary the set speed under a predetermined number of frequency divisions.

Next, referring to FIG. 3, the relationship between the depression stroke and the sewing machine rotation speed based on the application of the present invention will be described.

In the figure, the numbers in parentheses indicate the frequency division ratio, and the frequency division ratio is 1/n, and the reference rotation speed is
If N ₁ [rpm], the rotation speed of the sewing machine is N ₁ ×n
Calculated in [rpm].

The curves (solid line), (dashed line), and (two-dot chain line) shown in the figure correspond to the case where the frequency of the clock pulse is normal, lowered, and higher, respectively, and therefore the frequency of the variable frequency oscillator is It is clear that by adjustment the set speed for the pedal depression stroke can be selected continuously and arbitrarily.

Effects of the Invention An embodiment of the present invention has been described above, and as is clear from this, the present invention can convert the pulse signal indicating the actual speed from the speed generator using a frequency divider.
By dividing the frequency by a frequency division ratio determined based on a speed setting signal from a speed setting device corresponding to the amount of pedal depression, stepped speed switching is performed, and the clock pulse output from the variable frequency oscillator is The present invention attempts to obtain a predetermined speed change curve by changing the ratio of the set speed of each gear to the pedal depression according to the frequency setting. Depending on the type of low-speed sewing machine, etc., the speed difference between each stage can be continuously changed by adjusting the variable frequency oscillator, thereby making it possible to realize a sewing machine control device that facilitates sewing work and has good workability.

[Brief explanation of drawings]

FIG. 1 is a block diagram as an example of application of the present invention, FIG. 2 is a diagram showing a calculation curve, and FIG. 3 is a diagram showing the relationship between the pedal depression stroke and the rotational speed of the sewing machine. 1... Sewing machine, 2... Speed generator, 4... Frequency divider, 5... Speed setter, 6... Counter, 7...
Variable frequency oscillator, 9... Arithmetic unit, 12... Clutch/brake coil (drive control section).

Claims (1)

[Claims] 1. A motor that drives the sewing machine, a speed generator that generates a plurality of pulse signals each time the sewing machine rotates, a speed setting device that generates a speed setting signal according to the amount of movement of the pedal, and the speed generator. The motor comprises a frequency divider for frequency-dividing the pulse signal from the oscillator, a counter for counting clock pulses from the oscillator over one cycle period of the pulse signal after the frequency division, an arithmetic unit, and a drive control section for the motor. , by changing the frequency division ratio of the frequency divider according to the speed setting signal, a reference pulse according to the frequency division ratio is obtained as an output of the frequency divider, and further, the arithmetic unit is configured to obtain a reference pulse according to the frequency division ratio by changing the frequency division ratio of the frequency divider according to the speed setting signal; substituting into a predetermined arithmetic expression based on the count value for one period of the reference pulse,
Controlling the drive control unit so that the period of the reference pulse is constant, performs stepped variable speed control on the motor according to the amount of movement of the pedal, and the oscillator is configured with a variable frequency oscillator, A sewing machine control device in which the frequency of the clock pulse is made variable to enable speed adjustment.