JPH0350558B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a sewing pattern forming device in an electronically controlled sewing machine, and in particular, a stepping motor driven by open-loop control is used as a driving section for driving the sewing pattern forming device. This relates to a safety device for the control mechanism for the needle drop position in the event of a needle drop position.

(Purpose) The present invention is an electronically controlled sewing machine in which a control signal for electronically controlling the motion of a seam forming mechanism is stored in a storage unit, and a stepping motor that controls and drives the needle amplitude corresponds to the maximum amplitude of the needle. By providing a guide section that moves the needle further than the angle and sets the initial position based on a position outside the maximum amplitude range of the sewing pattern, and guides the needle so that the falling position is always within the maximum amplitude range of the sewing pattern. To prevent the operation of a sewing machine from being stopped or damage to a throat plate etc. due to a needle falling outside the maximum amplitude range of a sewing pattern, and to ensure smooth operation.

(Prior art) In conventional electronically controlled sewing machines, the stitch position of the sewing pattern is controlled using a linear motor drive device based on closed loop control or a stepping motor drive device based on open loop control. Lube control requires a feed pack circuit, which complicates the circuit configuration accordingly, and open loop control has its own drawbacks, such as the inability to guarantee the control position.

(Structure) The present invention was invented to eliminate the drawbacks of the above-mentioned prior art, and one embodiment thereof will be described below.

Reference numeral 1 designates a sewing machine frame, and a pulse motor mounting plate 2 is fixed to the machine frame with tightening screws 3, 3 as shown in FIG. A motor output shaft 5 to which a driving motor, that is, a stepping motor 4 is fixed, protrudes from the mounting plate 2.
A cam body 8 in which a cam portion 6 and a gear portion 7 are integrated is fixed to. Further, a gear shaft 9 is fixed to the mounting plate 2 and protrudes parallel to the motor output shaft 5, and the gear portion 7 of the cam body 8 is attached to the gear shaft.
An operating gear body 11 forming an operating gear 10 that meshes with the
is pivotally mounted to be movable within the position range of two stopper pins 13, 13 provided at appropriate positions on the mounting plate 2.

An arm portion 15 fixed to one end of the amplitude rod 14 is rotatably fitted into a shaft portion 12 fixed to an arm portion provided on the operating gear body 11, and an arm portion 15 fixed to one end of the amplitude rod 14 is rotatably fitted. An arm 18 of a needle bar support 17 is connected to the fixed arm 16.

The needle bar support body has a shaft portion 19 inserted through it approximately in the center.
The needle bar 20 is pivotally attached to the sewing machine frame 1 so as to be pivotable about the sewing machine frame 1, and a needle bar 20 that can reciprocate in the vertical direction is supported at a position opposite to the arm portion 18.

A needle 21 is attached to the lower end of the needle bar, and a needle bar holder 22 is fixed approximately at the center of the needle bar. (not shown) allows the needle bar 20 to reciprocate in the vertical direction.

23 is a base plate fixed to the sewing machine frame 1, and a rectangular through hole 24 is formed in the middle of the base plate at a position corresponding to the upper part of the vertical movement range S of the needle bar holder 22. A slipper cam plate 25, which faces the needle bar side from the through hole 24 and faces the end of the needle bar cover 22, is attached to the base plate 23 so that its mounting position can be adjusted in the vertical direction. There is. As shown in FIG. 3, the stopper cam plate has a stopper 26 protruding from the vicinity of the bottom of the through hole 24, the stopper 26 being inclined upwardly.

The mounting position of the stopper is slightly smaller than the distance from the top dead center of the needle until the tip of the needle comes into contact with the upper surface of the presser foot 27 which has been raised and stopped by the presser foot lifting lever. The position is lowered by a small distance P.

Reference numeral 28 denotes a contact type position detector, ie, a micro switch, for detecting the lateral position of the needle 21, which is held in a switch case 29 and fixed to the stepping motor mounting plate 2 with screws 20.

The micro switch 28 is actuated by a cam body 8 fixed to the motor shaft 5 when the stepping motor 4 rotates and causes the needle to oscillate more than the rotation angle corresponding to the maximum amplitude range of the sewing pattern. It's getting old.

The stepping motor 4 includes a rotor RT and windings A and B, as shown in FIG. It is controlled by turning on and off the current and changing the direction of the current.

The cases where the current IA flows in the direction of the arrow in Fig. 5 and the opposite direction in the winding A are called A-phase excitation and phase excitation, respectively, and the case where the current IB flows in the winding B as well
If the flow in the direction of the arrow in the figure and in the opposite direction are respectively referred to as B-phase excitation and phase excitation, in this embodiment, after the phase adjustment of the amplitude control mechanism, the stepping motor 4 is in each excitation state and in each of these excitation states. The resulting needle drop and needle amplitude are as shown in FIG. That is, the needle amplitude control range of the stepping motor 4 during operation of the sewing machine is based on the initially set middle baseline position M point (the state shown in FIG. 6) and the left baseline position where the operating gear 10 is controlled to rotate clockwise. This is the range between the stretch point (the solid line state in FIG. 7) and the R point (the plumb line state in FIG. 7) at the right base line position whose rotation is controlled in the counterclockwise direction. There is an interval of one pulse between the operating gear 10 that has reached the position R and the stopper pin B.

(Operations and Effects) Since the present invention has the above configuration, it functions as follows. That is, when setting the initial position, the operating phase of the microswitch 28 is 5 pulses from a position outside the maximum amplitude range of the needle, that is, the left baseline position L point, and the operating gear 10 is rotated clockwise from the state shown by the solid line in FIG. In this state (FIG. 8), the stepping motor 4 further rotates in the same direction by four pulses and reaches the phase. In this state, operating gear 10
There is an interval of one pulse between the stopper pin 13 and the stopper pin 13. After this, the position rotated by 8n pulses in the opposite direction is the needle position of the middle base line M point shown in FIG.
This is the initial setting position.

The phase of the output shaft 5 of the stepping motor 4 before the power is turned on is undefined and may be out of step. Therefore, the initial setting control is automatically performed in the above-mentioned order when the power is turned on, so that the correct position is always set.

In the configuration according to the above embodiment of the present invention, the initial position setting of the stepping motor is automatically and correctly performed each time it is used, and the switch for initial setting is provided outside the maximum amplitude range of the needle bar. Since overuse of the switch can be avoided, the life of the switch can be significantly extended.

However, since the swinging movement of the needle bar in the amplitude direction is possible beyond the maximum amplitude range of the sewing pattern, when modulation occurs in the signal storage unit that stores the signals sent to the stepping motor, or the needle If an unexpected external force is applied to the rod amplitude transmission mechanism, and the amplitude movement of the needle bar goes beyond the planned range, the needle will not fall into the planned needle drop and will collide with the throat plate or fabric presser. However, in the present invention, before such a situation occurs, the sewing machine is swung out of the planned range by Q. The needle bar fixed to the needle bar is lowered while contacting the inclined part of the stopper formed on the stopper cam plate, so that the needle is within the planned range as shown by arrow F of the plumb line in Figure 3. This is extremely effective in practice because it can prevent accidents as described above.

[Brief explanation of drawings]

The drawings illustrate one embodiment of the present invention.
The figure is an exploded perspective view showing a part of the structure of the present invention, FIG. 2 is a side view showing a part of the invention, FIG. 3 is a sectional view taken from FIG. 2, and FIG. 4 is a main part of the invention. 5 is a principle diagram of the pulse motor, FIGS. 6 to 8 are plan views showing each state of the main parts of the present invention, and FIG. 9 is a relationship between the excitation state of the pulse motor and the needle drop position. 4 is a diagram showing a stepping motor, and 6 is a diagram showing a stepping motor.
20 is a cam portion, 20 is a needle bar, 22 is a needle bar cover, 25 is a stopper cam plate, and 28 is a switch.

Claims (1)

[Claims] 1. In an electronically controlled sewing machine equipped with a mechanism for storing sewing pattern control signals in a storage section and controlling a stepping motor using the control signals to form a sewing pattern, A switch is provided which is actuated by a cam fixed to the drive shaft of the motor when the motor is angularly rotated outside the maximum amplitude range of the sewing pattern, and a switch is provided on the needle bar disposed in the mechanism for forming the sewing pattern. The present invention is characterized in that a stopper cam plate is provided, the end of which comes into contact with a position opposite to the end of the fixed needle bar, and guides the needle bar from a position outside the maximum amplitude range of the sewing pattern to within the maximum amplitude range. Needle bar drive safety device for electronically controlled sewing machines.