JPS6042749B2 - sewing machine control device - Google Patents

Description

[Detailed Description of the Invention] The present invention changes the frequency division ratio of the pulse signal from the speed generator according to the amount of pedal depression, and controls the frequency of the pulse signal after frequency division to be constant. The present invention relates to a sewing machine control device based on the idea of performing right-handed variable speed control according to the pedal position.

Conventionally, such a speed setting method uses a combination of a magnet interlocked with the pedal and a magnetic sensor placed opposite the magnet, and changes the distance between the magnet and the magnetic sensor as the pedal is depressed. There is a stepless speed setting method that outputs a speed setting signal, or a stepped speed setting method that turns on and off microswitches in conjunction with the pedal. The speed detection signal from the generator and the above-mentioned speed setting signal are analog quantities, and the control section is also processed as analog quantities.The speed generator or speed setting section is expensive due to its configuration, and the speed The control circuit also has a configuration with a large number of parts.

In addition to speed control as described above, sewing machine control functions generally include complex controls such as timing control of various solenoids attached to the sewing machine based on various switch inputs, or a function of stopping the sewing machine needle at a fixed position. Recently, there are cases in which the main part of these controls is configured with a single-chip microcomputer, but in all of these cases, the speed control part must handle analog signals as described above, so the above-mentioned It cannot be controlled by a single-chip microcomputer and is usually configured with a separate circuit.

Therefore, an object of the present invention is to simplify the generation section of each signal and reduce the cost by making the speed detection signal or the speed setting signal a digital quantity.
By digitizing the processing in the speed control section, we have made it possible to use the one-chip microcomputer mentioned above.
The aim is to achieve higher reliability or lower costs by reducing the number of parts.

According to the present invention, the above-mentioned object is that the speed generator only needs to supply pulse signals in which the intervals between the generated pulses are evenly spaced in terms of position, and therefore an inexpensive construction is possible. For example, a speed setting device that generates a speed setting signal may include a shielding plate linked to a pedal and several pairs of light emitting devices.
By combining only the light-receiving elements, a simple configuration is possible in which a combined digital signal is extracted from the several sets of light-receiving elements and used as a speed setting signal, and furthermore, the control circuit can be handled without the need for special conversion. All the signals that are transmitted are unified as digital signals, so the frequency divider,
By assigning the functions of each control element such as a period measuring device, latch, arithmetic unit, and timer to a recently developed control element such as a microcomputer, it is possible to significantly reduce the number of parts, and it is also possible to reduce the cost. A circuit can be implemented.

Furthermore, in the present invention, the number of steps required for speed setting can be easily accommodated by increasing the number of the light emitting/light receiving elements, and the relationship between the pedal depression position and the rotational speed of the sewing machine can be determined, for example, by increasing the number of the light emitting/light receiving elements. If a transparent type is used as the shield plate, it is possible to prepare several types of shield plates in which the hole position dimensions of the shield plates are adjusted in the direction of pedal movement, and to replace them. It has the advantage of being easy to handle.

Other features and advantages of the invention will become apparent from the following description of specific examples.

An application example of the present invention will be described below according to the block diagram of FIG.

Reference numeral 1 represents a sewing machine head, which is usually attached to a sewing machine stand and is used for sewing work.

A speed generator 2 is attached to the sewing machine head 1, and the speed generator 2 has a structure that generates a plurality of pulse signals at equal intervals in position and angle per one rotation of the sewing machine. The waveform shaping circuit 3 is composed of a simple control element such as an OP amplifier or other 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, and as described above, it is composed of a shield plate linked to the pedal and several pairs of light emitting and light receiving elements. be done. The period measuring device 6 is composed of a timer. The latch 7 is composed of an IC, the arithmetic unit 8 is a 1C circuit for calculation, and the timer 9 is composed of an IC. Here, the above-mentioned frequency divider period measuring device 6, latch 7, arithmetic unit 8 and timer 9 can be easily constructed by a one-chip microcomputer incorporating all these functions.

In particular, when applying the frequency divider 4 to a microcomputer, first connect the pulse signal from the speed generator to the external interrupt terminal of the microcomputer, and then divide the frequency divider according to the speed setting signal from the speed setting device 5. This is made possible by performing program processing so as to enable the interrupt terminal input for each number of revolutions. The driver 10 is composed of a transistor and a resistance element, and the clutch/brake coil 11 is located in the electromagnetic clutch/brake coupling section of the electric motor, and is configured so that the rotational force of the motor is transmitted to the output shaft via the magnetic circuit and lining section. has been done.

Note that the output shaft of the electric motor has a pulley attached to its shaft end, and is linked to the sewing machine head 1 via the pulley and a belt. The system is configured as described above, and the operation will be explained below.

First, while the sewing machine head 1 is rotating, the speed generator 2 outputs a signal with a frequency proportional to the rotational speed of the sewing machine, and the waveform shaping circuit 3 shapes the signal into a pulse as a rectangular wave. Output signal/column.

This pulse signal train is transmitted by the frequency divider 4 according to the set amount from the speed setter 5. For example, if the set amount is doubled, it becomes 112,
If it is multiplied by 4, the frequency is divided into 114, and a frequency-divided pulse train PD is output. The synchronous measuring device 6 receives the frequency-divided pulse train P.
Each cycle of D is measured and latched by a latch 7 as the actual measurement period of the section immediately before the pulse section to be controlled, and the actual measurement period Tp is output to the arithmetic unit 8, and the arithmetic unit 8 performs a certain calculation. By substituting the measured cycle Tp into the equation, the excitation time of the clutch coil or brake coil is calculated, the calculated result value TBC is set in the timer 9, and the driver 1
0, the clutch/brake coil 11 is excited for the calculated time to control the pulse section, which is the control target range, and by repeating the above process, the averaged rotational force is applied to the sewing machine head 1. Then, the sewing machine will operate at the speed determined by the speed setting device 5. Next, the arithmetic unit 8 in the block diagram of FIG.
A specific calculation example will be described with reference to FIG.

In this example, the calculation curve is expressed as a straight line, but any other calculation curve can be used. The equation of the straight line is expressed by the following equation.

However, TCB: clutch/brake excitation time A, . B:
Constant Tp: Actual measurement period In Figure 2, the X-axis represents the actual measurement period of the speed generator pulse train one section before the control object section, and the Y-axis represents the clutch current application time in the control object section (if positive). ), or the application time of the brake current (in the case of a negative value), and the curve is expressed in a more specific form by setting A=2 and B=4 in the above equation (1).

For example, if a speed generator that generates a number of pulses per revolution is used, the actual measurement period T, will be 5 ms at a stable rotation speed of 200 r'Pm, and therefore the clutch current application time will be 5 ms. From Figure 2, 2rr1. s
(point α).

Therefore, each. Period of pulse section 57T7. Among S,
The clutch coil is excited with a duty such that the clutch is engaged for 2rrLs, and operates to absorb the sewing machine load and maintain a constant speed (200 rpm).

The coefficient A in the arithmetic expression adopted here is an arbitrary value. By freely selecting the value and adjusting the coefficient A, the gain of the system can be easily set. Further, the constant B is necessary to maintain the set speed under normal sewing machine load conditions, and can be said to be determined from the latch current input rate. In other words, if constant B is changed in Figure 2, moving in the linear Y-axis direction and focusing on point α, the clutch engagement time to maintain a speed of 200 r'Pm will change. , Therefore, the above constant B is determined from the necessary latch closing time. For example, when the load becomes heavier than the normal constant speed operation under a normal load as described above, the actual measurement cycle becomes longer as the sewing machine rotation speed decreases, and the clutch current application rate increases. Constant speed operation is performed when the values are balanced.

On the other hand, when the load becomes lighter, the clutch current application rate decreases to try to lower the rotational speed, and when these are balanced, constant speed/speed operation is performed. moreover,
According to Figure 2, if the rotational speed extremely exceeds the set value due to some disturbance or transient speed overshoot, the rotational speed should be increased to 250r'Pm, for example.
If the speed exceeds the limit, brake current is applied to quickly reduce the speed. As mentioned above, the system uses a frequency-divided pulse signal P from a frequency divider.

operates so that the period of Therefore, the final sewing machine rotation speed is stabilized to approximately double. In this way, the speed setting is switched in stages, and if the dividing ratio is 1/n, the setting speed will be n times the setting speed when it is 1. obtain(
However, n=1, 2, ...ri. Next, FIG. 3 shows an example of the relationship between the depression stroke and the rotational speed of the sewing machine based on the application of the present invention, and the explanation will be added below according to the same figure. In this example, the maximum pedal stroke is 14Tfr! ! t, the number of steps is 1, and the standard rotational speed (rotational speed with frequency division ratio = 1) is 200r''P.
m.

In this example, the number of steps is 1, so the speed setting device is linked to the pedal and has four sets of light emitting and
It is constructed by arranging light-receiving elements, and it is sufficient to use one of the obtained one-day combination speed setting signals. In the figure, the numbers in parentheses indicate the frequency division ratio, and the rotation speed of the sewing machine is calculated as 200r1 [Rpm] as described above, assuming that the frequency division ratio is 1/n.

The figure shows a relationship in which the amount of change in sewing machine rotation speed with respect to the tread stroke is small at low speeds and large at high speeds, but this relationship can be set freely by selecting the division ratio, and It can be said that it is possible to achieve a nearly stepless configuration by reducing the speed and increasing the number of stages. In addition, MA in the same figure
The rotational speed of x represents the rotational speed determined by the ratio of the motor pulley to the sewing machine pulley when the clutch coil is simply fully excited, regardless of the speed control according to the calculation curve described above.

One embodiment of the present invention has been described above, and as is clear from this, the present invention uses a frequency divider to set the pulse signal indicating the actual speed from the speed generator to set the speed according to the amount of pedal depression. By dividing only the frequency division ratio determined based on the speed setting signal from the device, stepped speed switching is attempted. The measured period of the pulse section one pulse section before the pulse section is substituted for the calculation formula determined based on the optimal design of the system, and the clutch coil is operated only for the determined time in the pulse section to be controlled based on the calculation result. Alternatively, it is based on the idea that the brake coil is excited and the brake coil is finally operated with a slight deviation from a predetermined set pulse cycle.

As mentioned above, in the present invention, the number of steps required for speed setting can be easily accommodated by increasing the number of light emitting/light receiving elements in the first half, and the relationship between the pedal depression stroke and the rotational speed of the sewing machine is determined by the pedal stroke. It can be freely selected by changing the frequency division ratio corresponding to the depression position.
For example, if a transmissive type is used as the light-emitting/light-receiving element, several types of replaceable shielding plates are prepared in advance, with the hole position dimensions of the shielding plates adjusted in the direction of movement according to the pedal depression. It has the advantage that it can be easily handled by preparing them and replacing them.

Note that, as described above, a motor having an electromagnetic crack brake structure is taken as an example, but the present invention can also be applied to a DC motor or other motors.

As is clear from the above explanation, the present invention is an epoch-making method that realizes digital speed control, which is different from the conventional speed control method using analog quantities. is possible, and its configuration is therefore extremely simplified.
It is clear that the reduction in the number of parts will result in higher reliability or lower costs, which will have great effects.

[Brief explanation of the drawing]

Fig. 1 is a block diagram as an application example of the present invention, Fig. 2 is a diagram showing a specific example of a calculation curve, and Fig. 3 is a diagram showing the relationship between the tread stroke and sewing machine rotation speed based on the application of the present invention. FIG. 1... Sewing machine head, 2... Speed generator, 4... Frequency divider, 5... Speed setter,
10...driver, 11...clutch/brake coil.

Claims (1)

[Claims] 1 A sewing machine having at least a sewing machine head for sewing, a motor for driving the sewing machine head, a control device, and a speed generator that generates a plurality of pulse signals every time the sewing machine head rotates once. In the drive device, the control device includes at least a speed setter that generates a speed setting signal according to the amount of pedal depression, a frequency divider that divides the frequency of the pulse signal from the speed generator, and a drive for the motor. and a control section, and is configured to change the frequency division ratio of the frequency divider according to the speed setting signal to obtain a reference pulse according to the frequency division ratio as an output of the frequency divider. and a sewing machine configured to perform stepped variable speed control on the motor according to the amount of pedal depression by controlling the drive control unit so that the period of the reference pulse is constant. Control device.