JPS6120233B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive device for an electric sewing machine, and more particularly to a safety device that prevents malfunctions.

In recent years, sewing machine drive devices have been increasingly equipped with electronic circuits and ICs that require complex operations. However, the power supply for the IC of a sewing machine driving device using a conventional semiconductor IC generally does not include the low voltage detection circuit SC as shown by the broken line in FIG. Therefore, when the power switch SW is turned on,
Since the input voltage of the voltage regulator AVR is as shown by the broken line in Figure 7, the voltage Vs applied to the IC gradually rises as shown in the solid line in Figure 7, and from the time the power is turned on until _t1 .
The power supply voltage of the IC is lower than the operating voltage Vs of the IC. Furthermore, when the power switch SW is turned off, the IC power supply voltage is maintained at Vs from _t2 when the power is turned off until a certain time _t3 , but the voltage drops after _t3 . Since the minimum operating voltage of TTL, CMOS, etc. commonly used as semiconductor ICs is suppressed, there is a risk that the IC may malfunction during the low voltage when the power is turned on or off as described above. . If the IC malfunctions, the sewing machine shaft controlled by it may rotate, or in sewing machines with an automatic thread trimmer, the thread trimmer may malfunction and the needle may move unexpectedly.
This is extremely dangerous as the needle may break or fly off.

Similarly, if the current and voltage drop significantly during operation, the IC will malfunction in the same manner as above, which is dangerous, and if the load is heavy, the motor may lock up and burn out.

SUMMARY OF THE INVENTION An object of the present invention is to provide a safe sewing machine driving device by preventing dangers due to malfunction of an IC due to a drop in the power supply for the IC.

The present invention detects the magnitude of the input voltage of a voltage regulator of an IC power supply, and applies the output voltage of the voltage regulator to the IC only when this voltage exceeds a certain reference value, thereby preventing malfunction of the IC. This is how it was done.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the structure of the present invention will be described below with reference to FIGS. 1 to 6 for an electromagnetic clutch sewing machine with a fixed needle in the upper position. Figure 1 shows the sewing machine drive section, where the clutch friction plate CLM is directly connected to the motor MO.
Opposed to this is a clutch plate CLB that is directly connected to the pulley PUL. The clutch plate CLB further faces a brake friction plate BRM. A clutch coil CL and a brake coil BR are placed near the clutch plate CLB, and the clutch plate CLB, which energizes the clutch coil CL, is connected to the clutch friction plate CLM.
The clutch plate CLB rotates together with the motor MO. Next, when the brake coil BR is energized, the clutch plate CLB contacts the brake friction plate BRM and the brake is applied to stop the vehicle. Since the sewing machine shaft is driven by a belt (not shown) placed around the pulley PUL, the driving of the sewing machine shaft is stopped by the above operation.

FIG. 2 shows an example of a control circuit for a sewing machine with a needle stop in the upper position. DD is a lower position detection circuit that detects the lower position of the sewing machine needle, and this output is the IC
Enters logic AND circuit AND input 1. Input 2 of this AND circuit AND is a resistor with one end grounded.
It is connected to _R1 and the flat contact N of the foot switch FSW. The output of the AND circuit AND is connected to input 1 of the OR circuit OR and input 1 of the NOR circuit NOR. Input 2 of the NOR circuit NOR and OR circuit OR is a resistor R ₂ with one end grounded and a foot switch FSW.
It is connected to the front contact point L of. The output of the OR circuit OR is passed through the resistor _R3 , and the collector of the transistor _T1 is connected to the clutch coil CL, whose one end is connected to the power supply _V2 .
, the emitsuta is grounded. The output of the NOR circuit NOR is connected to the base of the transistor T ₂ through the monostable multi-MM and the resistor R ₄ . transistor
The collector of T ₂ is connected to the brake coil BR, which has one end connected to the power supply V ₂ , and its emitter is grounded. The operation of this circuit is that when the foot switch FSW is set to front L, the OR circuit OR and the NOR circuit NOR
Since the input 2 of the input 2 becomes H level, the output of the OR circuit becomes H regardless of the value of the input 1, the transistor _T1 becomes conductive, and the sewing machine shaft is driven as explained in FIG. The output of the NOR circuit NOR is at L level and the monostable multi-MM does not operate. If you want to stop next time, set foot switch FSW to flat pedal N. The input 2 of the OR circuit OR and the NOR circuit NOR goes to L level, and the input 2 of the AND circuit AND goes to H level. If the needle position is at a position other than the bottom and input 1 is also at H level, the output of AND is at H level and the sewing machine shaft continues to rotate, and when the needle position reaches the bottom, the bottom position detection circuit
Since the output of DD becomes L level and the inputs 1 and 2 of the OR circuit OR become L level, the power supply to the clutch coil is stopped. At the same time, the input 1 of the NOR circuit NOR changes from H to L, the output changes from L to H, and the monostable multi-MM operates for a certain period of time, turning on transistor _T2 for a certain period of time, energizing the brake coil BR. to stop the sewing machine shaft in the lower position.

Figure 3 shows ICs such as AND circuit AND and OR circuit OR.
1 is an example of a power supply device according to the invention for a logic circuit; Commercial power AC is connected to the primary side TR ₁ of the transformer through a switch SW. trance 2
One end of the next coil TR ₂ is grounded, and the other end is connected through a diode D ₁ to one end of a capacitor C ₁ , the emitter of a transistor T ₂ , and one end of a resistor R ₁ . The other end of resistor _R1 is a constant voltage element
It is connected to the base of transistor T ₂ through ZD. The emitter of transistor _T2 and the other end of the capacitor are grounded. The base of transistor T ₁ is connected to the collector of transistor T ₂ through a resistor R ₂ . The collector of transistor T ₁ is connected to the input of the voltage regulator AVR. A voltage regulator AVR keeps the output voltage constant even if the input voltage changes within a certain range. In this configuration, the SC surrounded by a broken line is called a low voltage detection circuit. Further, the resistor R _{1 ,} the constant voltage element ZD, and the transistor T ₂ are a voltage detection section that detects the level of the voltage Vc appearing on the capacitor C ₁ . The resistor R ₂ and the transistor T ₁ are a switch section that switches the output of the constant voltage device into conduction or non-conduction. The present invention configured as described above operates as follows. When the power switch SW is turned on, the secondary side of the transformer
Voltage is generated on TR ₂ . This voltage is connected to diode D ₁
It is rectified by , and smoothed by capacitor _C1 . Therefore, the terminal voltage Vc of the capacitor rises as shown by the broken line in FIG. If the Vz of the constant voltage element ZD in Fig. 3 is selected to be higher than the voltage at which the voltage regulator AVR operates normally, the voltage detection section does not operate from t ₀ to t ₁ in Fig. 7, and the base current of the transistor T ₂ decreases. does not flow and transistor _T2 is "off". Therefore, the switch part _T1 is also "off" and the voltage regulator AVR
Since no voltage is applied to the input of , the output Vs is also zero. When the capacitor terminal voltage Vc exceeds the voltage Vz of the constant voltage element after t ₁ , the voltage detection section operates and current flows through the constant voltage element ZD, and the transistor T ₂
is energized. As a result, _T1 of the switch section becomes conductive and voltage is applied to the voltage regulator AVR, so that the output voltage Vs of the voltage regulator rises instantaneously. Also, when the power switch SW is turned off, capacitor C ₁
The terminal voltage Vc is the voltage of the constant voltage element that gradually decreases.
Below Vz, the voltage detection section does not operate and the transistor
T ₂ is "off" and transistor T ₁ in the switch section
is in the "off" state, so the input voltage of the voltage regulator becomes zero, and the output voltage also suddenly drops from Vs to zero at _t3 .
As described above, the circuit shown in Figure 3 detects the terminal voltage Vc of capacitor C ₁ and turns the input voltage of the voltage regulator AVR "on" and "off", so that the voltage of the AND circuit AND and the OR circuit OR is always normal. to prevent malfunction. In addition, since the terminal voltage of capacitor _C1 is proportional to the voltage of the commercial power supply AC, when the voltage of the commercial power supply AC drops significantly, the AND circuit is also activated.
It can cut the voltage of logic circuits such as AND and OR circuits to stop their operation and prevent malfunctions.

If the voltage regulation on the secondary side of the transformer is poor in the low voltage detection circuit SC shown in Figure 3, the terminal voltage Vc of the capacitor C ₁ will exceed the voltage Vz of the constant voltage element, and the transistors T ₂ and T ₁ will become conductive. When the voltage regulator AVR is energized, Vc drops to below the voltage Vz of the voltage regulator ZD and the transistor
4 and 5 can be considered as measures to prevent so-called hunting, in which T ₂ and T ₁ turn "off" again. FIG. 4 shows an example in which the voltage detection section is composed of a diode _D2 , a capacitor _C2 , a resistor _R1 , a constant voltage element ZD, and a transistor _T2 , and the switch section is composed of a resistor _R2 and a transistor _T1 . A method in which the part that detects the voltage by the constant voltage element ZD is configured with another diode D ₂ and the capacitor C ₂ , and the voltage Vc ₂ of the capacitor C ₂ is detected separately from the input of the voltage regulator AVR. It is.

In Figure 5, the voltage detection section consists of resistors R ₃ and R ₄ and a Schmitt circuit HC, and the switch section consists of a transistor.
This is an example configured with _T1 . This is a Schmitt circuit
This is an example in which a circuit with hysteresis characteristics such as HC is incorporated into a low voltage detection circuit to prevent the hunting.

Furthermore, if a capacitor or the like is used inside the voltage regulator AVR in Fig. 3, and the output voltage rises gradually even if the input voltage rises suddenly, the detection section should be regulated as shown in Fig. 6. A circuit may be used in which the voltage device is placed on the input side and the switch portion is placed on the output side. In other words, a transistor _T1 is provided on the output side of the voltage regulator AVR to adjust the voltage of the capacitor _C1 .
A method of detecting Vc and turning the output voltage Vs "on" and "off" can be considered.
It is possible to prevent malfunctions of logic circuits.

According to the present invention, when the power is turned on or off, the IC
It is possible to prevent the IC logic circuit from malfunctioning due to a drop in the logic circuit power supply voltage, thereby preventing dangers such as needle breakage due to unexpected rotation of the sewing machine shaft or malfunction of the automatic thread trimming mechanism. Additionally, malfunctions due to abnormal drops in commercial power supply voltage can also be prevented.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of an electromagnetic clutch type sewing machine drive mechanism, FIG. 2 is a circuit diagram of a driving circuit of the sewing machine with needles stopped at the upper position of the mechanism shown in FIG. 1, and FIG. 3 is a circuit diagram of a power supply device for the drive circuit according to the present invention. 4 to 6 are circuit diagrams showing other embodiments of the drive circuit power supply according to the present invention, and FIG. 7 is a diagram showing voltage rise and fall characteristics for explaining the present invention. be. MO...Motor, CL...Clutch coil,
CLM...clutch friction plate, CLB...clutch plate, BR...brake, BRM...brake friction plate, PUL...pulley, AND...and circuit,
NOR……Noah circuit, OR……OR circuit, MM……
Monostable multi, DD...lower position detector, T ₁ ~ _{T 2} ...
...transistor, _R1 to _R4 ...resistance, FSW...foot switch, L...front contact, N...flat contact,
AC... Commercial power supply, SW... Switch, D ₁ ... Diode, ZD... Constant voltage element, TR ₁ ... Transformer primary coil, TR ₂ ... Transformer secondary coil,
SC...Low voltage detection circuit, AVR... Constant voltage device,
Vs...Power supply for IC, HC...Schmitt circuit.

Claims (1)

[Claims] 1. A foot switch that gives an operation command to a sewing machine;
A needle position detection mechanism that detects the upper or lower position of the sewing machine needle, and an IC logic circuit that controls driving and stopping of the sewing machine in relation to the needle position signal of this needle position detection mechanism and the operation command signal of the foot switch. , the IC logic circuit is configured such that the power supply is provided by a rectifier/smoothing circuit that rectifies and smoothes the commercial power supply, and a constant voltage device connected to the latter stage of this circuit, wherein the rectifier/smoothing circuit A low voltage detection circuit consisting of a voltage detection section that includes a constant voltage element on the output side of the circuit, and a switch section that is operated by the output of this voltage detection section.
An SC is provided, of which the voltage detection section is connected between the rectification/smoothing circuit and the voltage regulator, while the switch section is selectively connected to the input side or output side of the voltage regulator, and the voltage detection section is connected between the rectifier/smoothing circuit and the voltage regulator. malfunction of an electric sewing machine, characterized in that when the input voltage of the low voltage detection circuit obtained from the above is less than a reference value determined by the constant voltage element, the switch section operated by the voltage detection section is made non-conductive. Prevention device.