JPH0411238B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a thread tensioning device for a sewing machine.

(Prior art) There are two types of thread tension devices for sewing machines: a regular type that presses the thread between thread tension discs and applies tension through frictional resistance between the thread and the thread tension disc, and a radial spoke of a rotating spinning wheel. There is a method in which a thread is bent and wound between the parts, and when the thread is pulled, a spinning wheel is rotated, and control is controlled by pressing felt or the like against the side of the spinning wheel. Regarding automation, in the former case, there are methods such as adjusting the clamping force of the thread tension plate using an electromagnetic solenoid, or rotating the thread tension knob using a motor, but there are difficulties in making delicate adjustments. There is also the problem that the thread is damaged due to friction with the thread tension disc. The latter method has a problem in that the spinning wheel rotates inertia more than necessary, so it is not put into practical use except in special sewing machines, and there are not many proposals for its automation.

(Objective and Solution) The present invention provides a thread tension device that can be easily finely adjusted by electrical control and is suitable for automation. This solves the problem of inertial rotation of the spinning wheel by connecting it to a spinning wheel and controlling the braking force electrically to adjust the thread tension.In addition, a microcomputer, etc. can be used for electrical control as necessary. This allows for automatic and highly accurate adjustment.

(Example) Examples of the present invention will be described below based on the drawings. In FIG. 1, the spinning wheel 1 is connected to each spinning wheel body 2, 2'.
Arc-shaped spoke portions 3, 3' arranged in a radial manner are engaged with each other, and an upper thread (not shown) is received in the engaged portion 4, and a second thread is inserted into the second thread.
As shown in the figure, the upper thread 5 is fed out from the bobbin 6 and reaches the thread take-up spring 7, and the needle 8 is connected to a cloth (not shown).
When the upper thread 5 passes through the spinning wheel 1 due to the operation of the thread take-up 9, it rotates according to the amount of movement thereof. The stator 11 of the braking device 10 has a field core 12, as shown in FIG. 14a is the coil holder. The rotor 15 has an iron core 16 having 50 teeth 16, and the teeth 13 and 17 are at the same pitch angle. Therefore, when the teeth 13 and 17 of the poles that are symmetrical to each other with respect to the axis 18 are in the same rotational position relationship, the teeth of the other poles are arranged so that their rotational positions are shifted from each other. Spinning wheel 1 has shaft 18
The rotor 15 rotates at the same time as the rotor 15.
The electric coil 14 is DC excited by a control power supply circuit DV. When the teeth 13 and teeth 17 of either pole reach a rotational position where they coincide with each other, the magnetic flux through the air gap 19 becomes maximum, and the rotating spinning wheel 1 is pulled into this rotational position and becomes stable. It acts as a braking force when escaping from a position.

FIG. 4 is obtained by plotting the maximum value of the control torque T, that is, the braking torque in the stable state, with respect to the excitation current I of the electric coil 14, and the braking torque increases as the excitation current increases. In addition,
This braking torque is generated every time the teeth 13 and 17 match, but the number of teeth 13 and 17 is adjusted so that this braking torque is always present when the thread take-up lever 9 moves up to tighten and unwind the thread. It has been set.

In the above configuration, when the current I of the electric coil 14 is adjusted by the control current supply circuit DV, the braking torque T of the spinning wheel 1 is adjusted, and therefore, the braking torque T of the spinning wheel 1 is adjusted with respect to the unwinding of the upper thread 5 in response to the operation of the thread take-up 9. The force for preventing or limiting this is adjusted, and during the period of blocking or limiting, the thread is tightened in cooperation with the thread take-up spring 7.

FIG. 5 shows a braking device 10 in place of the braking device 10 in FIG. The coil 23 is DC-excited to alternately form N and S poles, thereby forming multiple poles on the circumference facing the rotor 24 with a gap 25 in between. The tooth pole 26 and the electric coil 27 have the same structure, and the tooth pole 26 is the same as the tooth pole 22.
This creates an intermediate position between the north pole and the south pole, and doubles the total number of poles. The rotor 24 has its axis 1
The spinning wheel 1 is fixed to 8', and the magnet 28
N poles and S poles are arranged alternately on the circumference. The excitation current is similarly controlled by the control current supply circuit DV shown in FIG.

FIG. 6 shows yet another embodiment of the braking device, in which the braking device 29 has a rotor 30 made of a magnet, and a stator 31 equipped with an excitation coil 32 excited by a DC power source E. , a secondary coil 33 that generates an induced voltage by the rotation of the rotor 30.
The induced voltage of the secondary coil 33 is adjusted by a variable resistor R. The excitation coil 32 generates a braking torque similar to that shown in FIG. 1 or 5, and the secondary coil 33 performs electrical braking to absorb the inertial force of the spinning wheel 1. The DC power supply E and the variable resistor R are the second
It is electrically controlled externally by a control circuit similar to the control current supply circuit DV shown in the figure.

FIG. 7 is a control block diagram, and the read-only storage device ROM stores the speed control signal of the sewing machine motor SM, each setting signal of the excitation current of the braking device 10 or 20, each program control signal, etc. . The central processing unit CPU works together with read-only storage ROM and temporary storage RAM,
The speed of the sewing machine motor SM is controlled via the input/output port I/O and the speed control device CONT, and the speed detector
The SD detects its speed and the central processing unit
The CPU controls the excitation current by the control current supply circuit DV according to the speed. The external adjustment device VR is for manually adjusting the braking force of the spinning wheel 1, and the central processing unit CPU similarly controls the excitation current according to the adjustment.

(Effects) As described above, according to the present invention, since the thread adjustment is electrically controlled, fine adjustment is possible, and since the rotation of the spinning wheel is braked from time to time, the problem of inertia is also solved. If necessary, it is also possible to automatically adjust using a microcomputer or the like as shown in FIG.

[Brief explanation of drawings]

Fig. 1 is an overall structural diagram of a spinning wheel and a braking device showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of a thread tension system, Fig. 3 is a sectional view in the direction of Fig. 1, and Fig. 4 is a diagram of Fig. 1. FIGS. 5 and 6 are diagrams showing other embodiments of the braking device, and FIG. 7 is a control block diagram. In the figure, 1 is a spinning wheel, 11, 21, 31 are stators,
15, 24, and 30 are rotors, and DV is a control current supply circuit.

Claims (1)

[Claims] 1. The field core consists of a stator that is composed of multiple poles, each of which is wrapped with an electric coil, and a rotor that generates braking force by receiving magnetic flux from the stator through an air gap. a spinning wheel that is interposed in the thread supply path of the sewing machine and rotates integrally with the rotor against the braking force as the thread moves; and a control for adjusting the braking force on one of the electric coils. An electromagnetic thread tensioning device for a sewing machine, which is provided with a control current supply circuit for supplying current.