JPS58173590A - Control apparatus of sewing machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sewing machine control device that starts and stops a sewing machine or performs variable speed control according to the position of an adjusting means for setting the sewing machine speed.

Conventionally, the sewing machine control device has mainly adopted a method in which the position of the adjustment means is converted into an analog signal, the analog signal is used as a speed setting signal, and the speed control section is configured by analog calculation processing centered on an op-amp circuit. It had been.

However, in recent years, there has been a remarkable development of digital ICs, especially microcomputers (hereinafter referred to as microcomputers), and even speed control parts are becoming digital due to their cost and reliability advantages. Currently, this is being steadily carried out. In this case, the detection signal of the adjustment means must of course be digitized, and when a sewing machine pedal is used as the adjustment means, a coat switch with a built-in several-bit switch may be used as the digitization means. A device that is linked to a pedal, or a shield plate with holes arranged between several bits of light-emitting/light-receiving elements so that the combined signal of the several bits changes in conjunction with the pedal, or a magnet. Various methods have been adopted, such as one in which a change in distance or a change in the direction of magnetic flux is detected by a Hall element or a magnetoresistive element by interlocking the pedal with the pedal, and then the analog signal is A/D converted to obtain a digital signal. has been done.

Here, common to the above various methods, in the digital method, there is always a boundary where the signal changes, and when the pedal is positioned at the boundary, two adjacent signals may be caused by vibrations of the sewing machine etc. It has the fatal disadvantage that it cannot be used practically because the speed of the sewing machine fluctuates greatly because the sewing machine speed varies between values.

The present invention eliminates the above-mentioned drawbacks, and provides a sewing machine control device in which the speed setting is smoothly switched according to the adjustment means, and stable speed rotation is performed unaffected by sewing machine vibration. It is.

FIG. 1 shows a block diagram of an application example of the present invention, and a description will be added below with reference to the same figure.

Reference numeral 1 designates a pedal position detection circuit, which converts the amount of depression of a foot pedal (not shown) from a reference position into an electrical signal. A method is used in which magnets are arranged and interlocked, and the rotation angle of the magnets is detected and amplified by a magnetoresistive element.

Therefore, the output signal PA is output as an analog signal. 2 is an A7Dg converter, which converts the analog signal PA output from the pedal position detection circuit 1 into a 4-bit digital signal Pp; 3 is a microcomputer constituting a control means for controlling the sewing machine; It is the central part of the sewing machine's control.

4 and 5 are clutch coil 6 and brake coil 7
Indicates the driver. Here, the motor (not shown) transmits the rotational force of the main body of the motor, which is constantly rotating at high speed, to the output shaft through the magnetic circuit by excitation of the clutch coil 6, and depending on the magnitude of the excitation current. A so-called electromagnetic coupling structure is used in which speed control is performed by changing the sliding speed between the rotating part of the motor body, and on the other hand, the output shaft is stopped through the magnetic circuit by excitation of the brake coil 7. It is something that we have. Reference numeral 8 indicates a sewing machine, which is usually connected to the output shaft of the motor via a pulley and a belt. Reference numeral 9 denotes a needle position detection circuit, which adjusts a magnet piece attached to the shaft end of the sewing machine to correspond to the needle top position, rotates it in synchronization with the rotation of the sewing machine shaft, and detects a stationary position opposite to the magnet piece. The needle up position is detected by a Hall IC placed in the needle up position and a needle up signal NU is output. Reference numeral 1o denotes a frequency generator, which is usually attached to the end of the sewing machine shaft and outputs a signal with a period that changes depending on the rotational speed of the sewing machine. Reference numeral 11 denotes a waveform shaping circuit, which is composed of a circuit centered on a comparator, and is a circuit that shapes the signal into a rectangular pulse signal FGK, and the pulse signal FG is input to the interrupt terminal iNT of the microcomputer 3. .

The operation configured as above will be described below.

First, when the pedal is depressed from the reference position, the amount of movement thereof is detected by the pedal position detection circuit 1, and an analog signal PA is output. The analog signal PA is converted into a setting position signal P which is a 4-bit digital value by the A/D converter 2.
The signal is converted to D and output to the microcomputer 3.

If the value of the set position signal PD is greater than or equal to a specified value, the microcomputer 3 converts the set position signal PD to R as described below.
According to the OM table, the pulse signal FGO is converted into a value indicating the number of times it is divided into a speed setting signal S, and is set in the built-in RAM (RAM1) as the number of times the frequency is divided, as well as the signal C.
L is output, the clutch coil 6 is excited via the driver 4, and the sewing machine 8 is driven.

As described above, when the machine y8 accelerates, the pulse signal FG is outputted to the interrupt input terminal NT of the microcomputer 3 through the frequency generator 10 and the waveform shaping circuit 11, and the microcomputer 3 input to the above RA
The frequency is divided by the number of times stored in M1, the divided period is actually measured, and the calculation is performed by substituting it into the calculation formula described later, and the next pulse signal FG is calculated.
The excitation time of the clutch and brake in the section is controlled, and speed control is performed while repeating actual measurement and control in this way.

As described above, the sewing machine 8 is operated at a speed according to the analog signal PA detected and output by the pedal position detection circuit 1.

Next, when the pedal is returned to the reference position and the set position signal PD becomes smaller than the specified value, a low speed is first set, and the brake coil 7 is energized via the driver 5, and the sewing machine 8 is operated at a low speed. to rapidly decelerate. When the sewing machine reaches a low speed, the clutch coil 6 is turned off when the needle up signal Nu is output from the needle position detection circuit 9, and the brake coil 7 is energized for a certain period of time, so that the needle is in the up position. will be suspended.

In this way, a series of operations are carried out in which the sewing item is finished, replaced with a new sewing item, and the next sewing starts. The above is an outline of the operation, and the features of the present invention will be explained in more detail below. The explanation will be explained according to the figures after Figure 2.

FIGS. 2 and 3 are diagrams showing the principle of speed control, and the explanation will be given below with reference to the figures.

The equation shown in Figure 2 uses a linear equation to simplify the calculation, and A is a constant corresponding to the gain of the normal system.
In addition, B is a constant that allows fine adjustment of the speed, and it improves the stability of the system.
Determined by considering responsiveness.

In the same figure, the actually measured period TP of the pulse signal FG after the frequency division is first measured and substituted into the arithmetic expression. Control is continued to excite the period after frequency division of the next pulse signal FGO for the time determined by the calculation result.

That is, when the actual measured period TP changes to a smaller value, that is, when the sewing machine changes to a higher speed side, the on-duty of the clutch is reduced, and in some cases, (TP2
If the actual measured period TP changes to a larger direction, that is, to a lower speed, the clutch on-duty increases and the speed increases. In this way, stable operation is performed at the α point (actual measurement period TP1, clutch-on time Tc1) which is exactly balanced with the sewing machine load.

The above stable state is shown in FIG. The figure shows a stable operating state at low speed Np, and the pulse signal F
For the period TP1 of G, the clutch coil excitation signal CL
Stable operation is performed with a duty such that only Tc1 is output.

Here, when the frequency of the pulse signal FG is divided inside the microcomputer 3 as described above, the actually measured period TP increases rapidly, and therefore the engagement ratio of the clutch increases and the sewing machine accelerates and rises. Assuming that the load torque of the sewing machine does not change much at different speeds, the final clutch on date will be similar to that during the low speed NP operation, and the sewing machine will operate at about 6 points. That is, for example, if the number of frequency divisions is 1, it will be operated at twice the speed of the low speed NP.

An example of the structure of the ROM table for converting the setting position signal PD to the speed setting signal S (frequency division value) is shown in the table below.

Note that the speed setting signal marked with * in the table above) is required only when transitioning from drive to stop, and 0.1.2 of the setting position signal PD corresponding to the part marked with * is a stop command by a separate program. It is distinguished as an area.

The relationship between the setting position signal PD and the sewing machine speed based on the speed setting signal SK converted as shown in the above table is shown in a graph in FIG.

The sewing machine speed NM shown here can be approximately expressed by the following formula based on the above-mentioned principle. Particularly in the range 3 or more of the set position signal PD (drive command range), for example, at the boundary between 6 and 6 or 7 and 8, the sewing machine speed will suddenly change by one step of the reference speed NP, and if the pedal If the sewing machine is located at the boundary, vibrations of the sewing machine or slight fluctuations in the power supply voltage will cause a fairly large speed fluctuation of the reference speed Np. FIG. 6 is a flowchart showing an embodiment of countermeasures against the speed fluctuation using a timer, which is one of the features of the present invention.

In FIG. 5, first, at 12, the setting position signal PD1 is
is newly read, and in step 13 it is checked whether the stop command is within the stop command range of ◯ to 2. If the stop command is within the stop command range, the process proceeds to the stop processing routine, and if not, the sewing machine continues to be driven. Next, in step 14, the set position signal PD2 is compared with the previously read set position signal PD2, and if the values are not adjacent, or if the time T has elapsed even if the values are adjacent, the timer is stopped in step 16, and the newly read set position signal PD2 is compared. The set position signal PD1 is adopted, and if not, time T is preset to the timer at 17, the timer is activated, and the set position signal PD2 read last time is adopted. Note that after the above-mentioned timer is started, a separate timer interrupt processing routine (not shown) is executed.
When preset and activated, constant clock time is performed.

Furthermore, at 18, the set position signal PD adopted as described above is
1 or PD2 is converted into the speed setting signal S by the ROM table and the process proceeds to the next step.

The processing shown in the above flowchart is inserted into a part of the control processing loop during driving of the sewing machine, and therefore, the first point is that even if the newly read set position signal PD1 is a value adjacent to the conventional set position signal PD2, For example, the process is made valid only when the state continues for a period of time T or more, and otherwise it is made valid immediately.

If the time T is set too long, the response to the transition between the adjacent pedal positions will be delayed; however,
It is considered easy to set a time T that is not affected by instantaneous changes in the analog signal PA due to vibrations or power fluctuations during normal sewing machine operation, and in which response delay does not pose a problem. In normal sewing work that requires particularly high responsiveness, operations that cause the set position signal PDO value to change sharply are generally performed, and in such cases, the above-mentioned Since the time T can be ignored and an immediate response can be made, it is considered that the time T can be set to a sufficiently long time.

In the above, a case has been described in which a pedal is used as an adjusting means for setting the speed of the sewing machine, but for example, a variable volume for limiting the maximum speed of the sewing machine is used as the adjusting means, and the set position signal is further converted into an A/D signal. Of course, the present invention is also effective in cases where the setting position signal is obtained by a code switch, or in cases where the setting position signal is obtained directly by a code switch.

As is clear from the above description, according to the present invention,
In digital speed control, the present invention provides a sewing machine control device in which the sewing machine speed is not affected by fluctuations in the pedal position signal PA due to vibrations of the sewing machine or fluctuations in the power supply voltage. Even at the switching point, smooth speed switching 9 without speed fluctuation can be realized, and the effect is great.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a principle diagram of speed control, Fig. 3 is a time chart showing a low speed operation state, Fig. 4 is an explanatory diagram of sewing machine speed with respect to pedal position, and Fig. 5 is an illustration of the sewing machine speed. It is a flowchart which shows the speed setting process of this invention. 1...Pedal position detection circuit, 2...8/D converter, 3...Microcontroller, 6...
・・・Clutch coil, 7 ・Brake coil, 8...
・Middle insert, 9...Needle position detection circuit, 1o...
Frequency generator. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 4C Figure 2 Seki Figure 3

Claims (2)

[Claims] (1) An adjusting means for setting the sewing machine speed, a setting position detecting means for converting the position of the adjusting means into a setting position signal which is a digital value, and a speed converting means for converting the setting position signal into a speed setting signal; a motor whose speed is variable-speed controlled in accordance with the speed setting signal, a sewing machine driven by the motor, and a control means for controlling the sewing machine;
It consists of a timer that can be preset, and the transition condition from the speed setting signal S1 based on the arbitrary setting position signal P1 to the speed setting signal S2 based on the arbitrary setting position signal P2 is determined by the time T preset in the tie-7-.
The sewing machine control device is limited to only when the set position signal P2 continues throughout the period. (2) If the set position signals P1 and P2 are not in an adjacent positional relationship, the restriction is eliminated and the speed setting signal S2 based on the set position signal P2 can be immediately shifted to. The sewing machine control device described.