JPH029361B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed setting device for a sewing machine in which a driving speed can be set in relation to a digital code stored in advance in a storage circuit of a microcomputer (hereinafter referred to as microcomputer).

Conventionally, in the above-mentioned sewing machines, a rotation detection means consisting of a magnet and a coil is arranged in relation to the main shaft, and a sine wave generated in the rotation detection means by the rotation of the main shaft is integrated and output as an analog output. D/A (digital/analog) digital code stored in advance in the memory circuit of
Conventionally, the drive speed of the sewing machine motor was controlled by converting it into an analog value using a converter and comparing this analog value with the analog output from the rotation detecting means. Due to the complexity of the circuit configuration and the non-uniform arrangement of the magnets and coils of the rotation detection means, variations in the analog output values of multiple rotation detection means are unavoidable. In this case, there were differences in the setting speed for each machine, resulting in a decline in product quality and reliability.

The object of the present invention is to eliminate the above-mentioned conventional drawbacks with a simple configuration.

To explain an embodiment of this invention with reference to the drawings, a sewing machine 2 placed on a table 1 is equipped with a microcomputer MC.
(Fig. 2) enables automatic sewing, and a pulley 3 fixed to a main shaft (not shown) is connected via a belt 6 to a drive pulley 5 of a motor 4 fixed below the table 1. . The motor 4 is a well-known electromagnetic clutch motor equipped with a brake solenoid BS and a clutch solenoid CS (FIG. 2). TG is a magnet (not shown) with m poles fixed to the outer peripheral surface of the main shaft.
and an electromagnetic coil (not shown) disposed close to the magnet, which generates m sinusoidal rotation signals per rotation of the main shaft. Reference numeral 7 denotes a control box that houses an electric circuit (FIG. 2) and is electrically connected to the motor 4.

Next, to explain the electric circuit of this embodiment, in Fig. 2, MC is a well-known microcomputer with memory, calculation, and input/output functions, and stores various stitch information, speed setting information, sewing process information, etc. in advance. , the drive of the sewing machine 2 is controlled via a control means (not shown) by sequentially reading out various information based on the sewing process information, and the digital code (A4A3A2A1) shown in FIG. 3 is generated based on the speed setting information.
Output. CNT is a division counter, and the rotation detection means
One period of the sinusoidal rotation signal from the TG is counted as one, and one output signal is generated for every input of n rotation signals.
Generate Ein. FVC is a conversion circuit, and as shown in Figure 4, it consists of resistors R3 and R4 and a capacitor C.
1, C2, diode D, Darlington connected transistors Tr1 and Tr2, and operational amplifier CP
A constant DC voltage +Vc is applied to the in-phase input terminal of the comparator CP3, and an operating signal Vs is generated from the output terminal of the operational amplifier CP4. When the output signal Ein of the division counter CNT has a height E and a pulse interval Δt as shown in FIG. ≫△t) Also, the time constant determined by the capacitor C2 and the resistor R4 is set to be sufficiently larger than △t (C2R4≫△t).
The output signal Ein is differentiated by a capacitor C1, a resistor R3, and an operational amplifier CP3 in the circuit shown in FIG.
Rectified by diode D, transistor Tr1,
After being amplified by Tr2, capacitor C2 and resistor R
4 and the operational amplifier CP4 to become a DC operating signal Vs. At this time, if the time average value of the current flowing through the capacitor C1 is taken as the time average value, then the charge stored in the capacitor C1 at time Δt is expressed as ΔQ. Then, since C1R3≪△t, △Q=EC1=△t.
This current is linearly amplified by transistors Tr1 and Tr2 and flows to resistor R4, so Vs becomes
Proportional to R4. However, f = 1/△t holds true for the frequency of the output signal Ein, and if we apply it to EC1 = △t, then = EC1f, and therefore the voltage Vs is
Proportional to EC1R4f. When the pulse height E of the output signal Ein is constant, since EC1R4 is constant, it can be expressed as Vs = kf by a predetermined constant K, that is, the operating voltage Vs is generated at the frequency of the output signal Ein, that is, per unit time. Proportional to the number of output signals Ein.
MDR is a motor control circuit, resistors R1 and R2
, operational amplifiers CP1, CP2, brake solenoid BS, and clutch solenoid CS.
A constant DC voltage Vo is applied to the in-phase input terminal of the operational amplifier CP1, and a voltage VoR2/(R1+R2), which is obtained by dividing the constant DC voltage Vo by resistors R1 and R2, is applied to the negative-phase input terminal of the operational amplifier CP2. . At this time R1<
The reason for this is set as R2, which will be explained later. When the operating signal Vs of the frequency-to-voltage conversion circuit FVC is applied to the negative phase input terminal of the operational amplifier CP1 and the in-phase input terminal of the operational amplifier CP2, as shown in Fig. 6, Vo
<Brake solenoid BS operates in relation to Vs, and VoR2/(R1+R2) = determined in relation to Vo.
Clutch solenoid CS operates in relation to V1>V2.

The present invention has the above configuration, and next, the speed setting operation will be explained. When the number of rotations of the main shaft is F, the number of rotation signals from the rotation detecting means TG is proportional to F, and is expressed as mF by the number m of magnetic poles of the magnet of the rotation detecting means TG. Division counter CNT
The setting value n is determined in relation to the speed setting information stored in advance in the microcomputer MC, and the number of output signals Ein becomes f=mF/n. Substituting this into Vs=kf gives Vs=kmF/n, and the It can be seen that the rotational speed F is proportional to the operating voltage Vs of the conversion circuit FVC.
In addition, as mentioned above, when the operating voltage Vs becomes larger than Vo, the brake solenoid BS is activated, which reduces the rotation speed F of the main shaft, and the operating voltage Vs
When becomes smaller than V1, the clutch solenoid operates and the rotation speed F of the main shaft increases, so servo control of the rotation speed F of the main shaft is established, and the electric circuit shown in Figure 2 is configured so that V1<Vs<Vo. Controls the motor 4. However, the resistances R1 and R2
It is set so that R1<R2, and Vo−
Since V1=VoR1(R1+R2)<Vo, approximately
Considering Vs=Vo, that is, Vo≒kmF/n, and by transforming this, we obtain the relationship that the rotational speed of the main shaft F≒Von/km.

Therefore, the rotation speed F of the main shaft of the sewing machine is determined by the microcomputer.
It is proportional to the numerical value n set in the division counter CNT by the digital code (A4A3A2A1) of the MC and the constant DC voltage Vo applied to the operational amplifiers CP1 and CP2 of the motor control circuit MDR. When the set value n of the division counter CNT is 1, that is, the minimum rotation speed F = Vo/km of the main shaft is, for example, 200 rotations/min, which is necessary for thread cutting.
If you set the value of n=1 to 16, the set speed will be 200, 400, 600, ...3200 revolutions/min, and thus the constant DC voltage Vo will be set based on the speed setting information stored in advance in the microcontroller MC. It is set how many times the speed should be set relative to the minimum speed determined in relation to.

Next, to explain the stability of the set speed while the spindle is rotating, F≒Von/km, V1<Vs
<From the formula of Vo, maximum rotation speed Fu = Von/km, minimum rotation speed FD = V1n/km = VoR2n/km (R1 + R2),
Therefore, the fluctuation of the set speed corresponding to the set value n is
Fu-FD=VoR1n/km (R1+R2), which is proportional to the set value n of the division counter. That is, as shown in FIG. 7, when n=1, the fluctuation in the set speed is small, but as shown in FIG. 8, as n increases and the set speed increases, the fluctuation also increases. At first glance, this
It seems that the rotation of the spindle becomes more unstable as the set speed increases, but the fluctuation rate of the set speed (Fu−
When calculating FD)/F, it becomes R1/(R1+
R2), and therefore the stability can be considered to be constant regardless of the magnitude of the set speed.

As described above, according to the present invention, the sine wave output of the rotation detection means is treated as a digital quantity by counting the number of its wave packets. By making it possible to directly control the output of the rotation detection means using digital values, a D/A converter is not required and the circuit configuration becomes simpler. There is no variation in the output of the sewing machine, and therefore uniform speed setting is possible for sewing machines of the same model, which has the effect of improving the quality and reliability of the sewing machines.

In addition, for example, in a sewing machine operated by a pedal, the digital code in the above embodiment is used to control the amount of pedal depression by A/D (analog/digital).
Alternatively, a digital switch may be used which individually generates a plurality of different digital codes by manual operation.

Further, in the above embodiment, the rotation detecting means is composed of a magnet and a coil, but is not limited to this, and various other means such as a magnet and a Hall element, a photo sensor, etc. can be used.

Furthermore, the drive motor of the sewing machine is not limited to an electromagnetic clutch motor; for example, a DC motor may be controlled by an SCR (silicon control) method in relation to changes in the operating voltage of the conversion circuit in the above embodiment. .

[Brief explanation of drawings]

Figure 1 is a front view of the sewing machine, Figure 2 is a block diagram of the electric circuit, Figure 3 is a diagram showing the correspondence between the digital code of the microcomputer and the setting value of the division counter, and Figure 4 is the circuit of the conversion circuit. 5 shows the output signal of the division counter, FIG. 6 shows the operation of the clutch solenoid and brake solenoid, and FIGS. 7 and 8 show the stability of the set speed. In the figure, TG is a rotation detection means, MC is a microcomputer, CNT is a division counter, and FVC
is a conversion circuit. MDR is a drive circuit.

Claims (1)

[Scope of Claims] 1. An electromagnetic clutch motor having a clutch solenoid that accelerates the sewing machine when energized and a brake solenoid that decelerates the sewing machine when energized; a rotation detecting means arranged in relation to the main shaft so as to generate the rotation speed; a setting means capable of generating a separate setting signal to set an appropriate motor speed for each specific seam formation; A storage circuit that stores in advance a plurality of digital codes set to correspondingly different values and can selectively read out the digital codes in relation to the setting signals, and a storage circuit that stores a number of rotation signals corresponding to the read digital code values. A frequency divider circuit that generates an output signal every time a signal is generated, a conversion circuit that generates an operating voltage that is directly proportional to the number of output signals that occur within a unit time, and a reference voltage that is set in advance with a certain magnitude and is adjusted to the reference voltage. A first control circuit that energizes the clutch solenoid in response to a decrease in the operating voltage; and a reference voltage having a constant magnitude lower than the reference voltage of the first control circuit is set in advance, and the operating voltage is adjusted relative to the reference voltage. a second control circuit for energizing a brake solenoid as the speed increases.