JPS6223593B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a speed setting device for an industrial sewing machine. In recent years, in the field of sewing machine control, products that make full use of electronic components such as microcomputers (hereinafter referred to as microcomputers), memory, and ICs have been commercialized, and in the field of speed control in particular, products that make full use of the electronic components mentioned above are also being commercialized. A so-called digital control method has also begun to be developed, and the development of control technology is remarkable. However, complete digitalization of the speed control section using a microcomputer is accompanied by various difficulties and has not yet been realized, and it can be said that the current mainstream is still analog control. Conventionally, analog control has been the mainstream for speed control as described above, and therefore, a sewing machine speed setting device that outputs an analog value is the most desirable configuration and has actually been adopted. The present invention is intended to provide a sewing machine speed setting device that is simplest in structure when configured as a digital speed control system centered on control elements such as a microcomputer, and is highly reliable at a reasonable price. The speed control of a sewing machine is basically variable speed control according to the amount of depression of the sewing machine pedal. That is,
When the sewing machine is in the neutral position, the sewing machine is stopped, and when the pedal is pressed a little, it starts rotating at a low speed, and the deeper the pedal is pressed, the faster the speed becomes.Variable speed control is generally used. Therefore, the sewing machine rotates at maximum speed when the pedal is fully depressed. On the other hand, the above-mentioned maximum speed can be set easily depending on the skill level of the operator, or depending on the sewing process such as straight stitching or curved stitching, and also as a measure to prevent skipped stitches, puckering, and thread breakage due to needle heating. It is desired to be able to vary the The maximum speed adjustment described above requires an adjustable specified speed independent of the position of the pedal, and the present invention aims to provide the maximum speed setting device at low cost and with high reliability. Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a basic block diagram of the present invention, in which 1 is a speed setting mechanism, 2 is a speed control mechanism, 3 is a motor, and 4 is a speed setting mechanism.
5 is a sewing machine, and 6 is a speed detection mechanism attached to the sewing machine 5 to detect the speed of the sewing machine. are shown respectively. The operation is performed as follows. First, when a sewing machine pedal (not shown) is depressed, the speed setting mechanism 1 outputs a speed setting signal _{V s} based on the amount of pedal depression. The sewing machine 5 acts to transmit the rotational force to the sewing machine 5, and the sewing machine 5 starts rotating. Further, a speed detection mechanism 6 linked to the sewing machine 5 detects the rotational speed of the sewing machine 5, outputs a speed detection signal V _F , and in response to the speed setting signal V _s ,
The sewing machine 5 is operated at the speed when the speed detection signals V _F are balanced. Here, FIG. 2 shows a block diagram that is a more specific form of the basic block diagram mentioned above. In Figure 5, 7 is a sewing machine pedal (not shown)
8 is a microcomputer, and in this embodiment, it is a 4-bit 1-chip microcomputer that includes memory, I/O, etc. It shows the case. Reference numerals 9 and 10 indicate drivers for the clutch coil 11 and brake coil 12, which act to transmit the rotational force of the motor 3 to the sewing machine 5 via the magnetic circuit, lining, and belt, as described above. Further, a frequency generator 13 is fixed to the sewing machine shaft (not shown) of the sewing machine 5, and generates a pulse train having a frequency corresponding to the rotational speed of the sewing machine. The waveform shaping circuit 14 is composed of a Schmitt trigger circuit, and shapes the pulse train into a square wave. The maximum speed setting element 15 is composed of a switch and an interface circuit. The operation of the system configured as described above is performed as follows. First, as mentioned above, when the sewing machine pedal is depressed, a speed setting signal V corresponding to the amount of depression
_s is input from the variable speed setting element 7 to the microcomputer 8 as 4-bit digital data, and the microcomputer 8 confirms that the sewing machine pedal is depressed and excites the clutch coil 11 via the driver 9, thus As described above, the rotational force of the motor 3 is transmitted to the sewing machine 5 via the belt, and the sewing machine 5 is started. When the sewing machine 5 is started in this manner, the frequency generator 13 attached to the sewing machine shaft generates a pulse signal having a period according to the rotational speed of the sewing machine, and the waveform is further shaped into a square wave by the waveform shaping circuit 14. , an example pulse V _F having a period representing the sewing machine speed is fed back to the microcomputer 8. If the speed increases too much with respect to the speed setting signal _Vs , the brake coil 12 is energized via the driver 10, and the sewing machine 5 is decelerated.In this way, the clutch coil 11 or the brake By controlling the excitation of the coil 12, the sewing machine rotational speed according to the speed setting signal is maintained. Here, the speed control function based on the arithmetic expression of the microcomputer 8 will be described below with reference to FIGS. 3 to 5. In the case of minimum speed operation, the microcomputer performs calculations according to the following calculation formula, as shown in FIG. T _BC -aT _F -b (1) where a: gain constant b: constant T _BC : If the result is positive, it indicates the clutch-on time, and if it is negative, it indicates the brake-on time. T _F : Pulse train period of the frequency generator First, the pulse train section from the frequency generator 13 is actually measured, and after calculation is performed using equation (1), the time obtained by the calculation in the next pulse train section |T _B.C.
| only acts to excite the clutch or brake coil, and speed control is achieved by repeating this in sequential order. Normally, in stable operation where the sewing machine load is constant, the sewing machine is driven at point α in the figure.
The state of the current flowing through the clutch coil 11 at this time is shown by a solid line in FIG. Here, the gain constant a in equation (1) determines the gain of the system. That is, when a becomes large, even a slight variation in the period T _F causes a large change in the engagement ratio of the clutch (or brake) coil, and therefore the gain of the system increases. Further, the speed can be adjusted by changing the size of the constant b. That is, when |b| becomes smaller (as shown by the broken line in Figure 3), the engagement ratio of the clutch increases and attempts to move to point β, but at the same time the speed increases and the clutch engagement ratio decreases to a predetermined value. The operation is performed so as to stabilize at a point. The state of the current flowing through the clutch coil 11 at this time is shown by the broken line in FIG. In this way, constant speed control is performed at the lowest speed. On the other hand, medium speed to high speed operation is performed by dividing the pulse train of the frequency generator 13 by the software of the microcomputer 8. That is, the minimum speed obtained as described above is S ₁
If the frequency division ratio is 1/N and the gain of the system is high enough to ignore sewing machine load fluctuations due to changes in the rotational speed, the speed S can be expressed by the following equation. S=NS ₁ ......(2) (However, N=1, 2, 3...) Here, N in equation (2) is switched according to the speed setting signal _Vs from the variable speed setting element 7 in Fig. 2. By doing so, the speed S can be switched in stages. That is, the speed setting signal V _s is 4
When input as bit data to the microcomputer 8, the microcomputer 8 converts the above 4-bit data to N in equation (2) according to the contents of a so-called ROM table preset in the internal ROM, and divides the frequency. act as if it were to be done. Therefore, it can be said that by appropriately configuring the ROM, various speed curves such as those shown in "" or "" in FIG. 5 can be selected. The above is the normal control according to the speed setting signal V _s from the variable speed setting element 7. Next, regarding the specified speed setting element 15 in FIG.
Explain according to the diagram. The specified speed setting element 15 is constituted by a circuit including speed selection means using a 4-bit code switch, as will be described later, and its operation is performed as follows. First, when the maximum speed setting signal V _H from the specified speed setting element 15 is inputted to the microcomputer 8 as a 4-bit signal by a code switch described later, the 4-bit variable speed setting signal V _s from the variable speed setting element 7 is inputted to the microcomputer 8 as a 4-bit signal. Accordingly, the data indicating the N value in the ROM table built into the microcomputer, which is specified in advance, is selected in accordance with the specified speed setting signal _VH , and the speed control is performed as described above using the N value. becomes. That is, even if the variable speed setting signal _Vs according to the sewing machine pedal position is constant, the N value, that is, the speed setting value can be selected according to the code switch, and the maximum speed at the deepest depression position of the sewing machine pedal can be adjusted. Furthermore, the relationship between the sewing machine speed and the depression position of the pedal can be adjusted at an intermediate position of the sewing machine pedal. As described above, variable speed control is performed according to the amount of depression of the sewing machine pedal by the variable speed setting element 7, or speed control is performed according to the command from the specified speed setting element 15. Here, the variable speed setting element 7 detects the amount of depression of the sewing machine pedal and converts it into a 4-bit variable speed setting signal, and its configuration is firstly a rotary encoder with several bit switches, or a rotary encoder with several sets of switches. A light-emitting/light-receiving element and a shielding plate that passes between them and changes the signal from the light-receiving element according to the movement of the sewing machine pedal, or a magnet that moves according to the movement of the sewing machine pedal, Various configurations are conceivable, such as one in which this amount of movement is detected by a magnetically sensitive element and further converted into a several-bit signal by an A/D conversion circuit. Further, the specified speed setting element 15 and the N value built in the microcomputer are used for conversion to the N value.
A more specific example of the configuration of the ROM table section is shown in FIG. In Fig. 6, S indicates a code switch, which is switched by rotating, but in this case, unexpected data may be generated at the boundary between each switch, causing the speed setting to fluctuate abnormally. Table 1 below shows an example of the configuration of a gray code code switch in which only one of the switches corresponding to each bit changes and switches at the boundary in order to eliminate the problem. R indicates a resistance for pulling up to + _Xcc when the code switch is off, and the inverter
It is input to microcomputer 8 via IC. ROM ₀ ~
ROM ₁₅ indicates a ROM table for conversion to the N value, and its address and data structure are shown in Table 2 below. Addresses are indicated by 4 bits from A ₀ to _{A 15} , and data is allocated to each address as 4-bit data indicating the N value from N ₀ to N ₁₅ . Further, 16 indicates a decoder built into the one-chip microcomputer 8, and its output is connected to each select terminal of ROM ₀ to ROM ₁₅ of the ROM table.

【table】

【table】

[Table] The operation of the N-value conversion section configured as described above is performed as follows. First, when the sewing machine pedal is at an appropriate depression position, the variable speed setting signal _Vs is sent to the decoder 1 as 4-bit data.
6, decodes the data, and outputs
One of _O1 to _O15 is set to "H", and the ROM table connected to the output of the "H" is activated. For example, if the decoder 16 indicates that _O15 becomes "H" when the pedal is depressed to its maximum depth, ROM ₁₅ will be selected. Furthermore, the specified speed setting signal V _H from the code switch S is applied as an address input to the ROM table, is converted to the N value, and speed control is performed as described above. For example, as mentioned above, by the maximum depression of the pedal,
If ROM ₁₅ is selected and the fixed speed setting signal V _H by the code switch indicates A ₀ , then N
The operation is such that "N ₀ " is selected as the value. In this manner, as shown in FIG. 7, it is possible to adjust the maximum speed and select the sewing machine speed relative to the amount of pedal depression. Said ROM ₀ ~
It can be said that by appropriately configuring the data contents of the ROM ₁₅ , the speed steps shown in FIG. 7 can be set freely. Although the above embodiment describes the case where a 4-bit microcontroller is used, it goes without saying that 8-bit microcontroller is used.
The present invention is also effective when using other microcomputers such as 16-bit and 16-bit microcomputers. Further, the ROM part, which is a means for converting input data to the microcomputer from the variable or specified speed setting element into valid data, is not built-in but is provided outside the microcomputer, or the frequency dividing means and the above-mentioned frequency dividing means are provided outside the microcomputer. The present invention is effective in both cases. Furthermore, although a configuration using a code switch is shown in the embodiment as the speed selection means for the specified speed setting element 15, the oscillator is also provided, the frequency of the oscillator is made variable, and the oscillation frequency is actually measured by the microcomputer, The present invention is effective in both a configuration configured to process the pulse width, or a configuration in which the pulse width is made variable by a monostable multi-circuit, and the pulse width is actually measured and processed by the microcomputer. As is clear from the above explanation, according to the present invention, digital control by a control element such as a microcomputer is performed with a very simple configuration, and therefore reliability is improved and a low cost product is realized. The effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the present invention.
Fig. 2 is a detailed block diagram showing the configuration of the present invention, Fig. 3 is a diagram showing the principle of speed control, Fig. 4 is a diagram showing the clutch current waveform in constant speed operation, and Fig. 5 is a diagram showing the clutch current waveform in constant speed operation.
The figure shows an example of the configuration of a curve of sewing machine rotational speed with respect to the amount of depression of the sewing machine pedal. Figure 6 is a block diagram showing the details of the specified speed setting elements and the configuration of the converter to the speed control data "N" value. FIG. 7 is a diagram showing an example of the configuration of a curve of sewing machine speed versus pedal depression amount according to the present invention. 1...Speed setting mechanism, 2...Speed control mechanism, 3
...Motor, 4...Drive mechanism, 5...Sewing machine, 6
... Speed detection mechanism, 7 ... Variable speed setting element, 8
...Microcomputer, 13...Frequency generator, 15...
Specified speed setting element.

Claims (1)

[Claims] 1. A drive mechanism that drives a sewing machine by a motor;
a speed detection mechanism that detects the speed of the sewing machine shaft; a speed setting mechanism that commands the speed of the sewing machine shaft; and a speed that controls the rotation of the sewing machine shaft by comparing the output of the speed detection mechanism and the output of the speed setting mechanism. and a control mechanism, the speed detection mechanism is configured with a frequency generator that generates a plurality of equally spaced pulses for each revolution of the sewing machine or motor, and the speed setting mechanism corresponds to the movement of the sewing machine pedal. a variable speed setting element for outputting a pedal position signal, a specified speed setting element including a speed selection means unrelated to the movement of the sewing machine pedal, and a conversion means, the conversion means converting the pedal position signal into a speed command. A sewing machine speed setting device which converts the speed command signal into a signal, further limits the maximum speed of the sewing machine by the speed selection means, and at the same time switches the speed command signal according to the maximum speed limit. 2. The sewing machine speed setting device according to claim 1, wherein the converter is constituted by a ROM. 3. The pedal position signal from the variable speed setting element has a pedal position signal that uniquely changes according to the movement of the pedal, and is output from the converter by the specified speed setting element including the speed selection means. The sewing machine speed setting device according to claim 1, wherein any one of a plurality of variable speed curves can be selected. 4. The sewing machine speed setting device according to claim 1, wherein the speed selection means includes a code switch.