JPH04105687A - Cloth-feeding device of sewing-machine - Google Patents

Abstract

PURPOSE:To prevent the generation of motor noise even in the range of a low speed, by providing both a speed-detecting means and a control means whereby the energizing system of a step motor is shifted stepwise so that the step angle thereof is made small as the rotary speed of an arm shaft or of a member synchronizing with the arm shaft, which is detected by the speed- detecting means, is made slow, and a feed-driving means is controlled according to data for the amount of feeding. CONSTITUTION:To an I/O interface 11, a control means 29 is connected, which switches the energization of a step motor 76 for feeding stepwise, and controls a driving circuit 21 for the motor 76. That is to say, this control means 29 shifts the exitation of the step motor 76 stepwise so that the step angle thereof is made small according that the rotary speed of an arm shaft 28 or of a member synchronizing with the arm shaft 28, which is detected by a speed detector 84, is made slow, and controls the driving circuit 21 according to data for the amount of feeding in pattern data stored in a ROM 25. In this way, sewing work can be done with much the same touch as a usual mechanical drive type cloth-feeding.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sewing machine in which a cloth feeding mechanism is directly driven by a stepping motor.

The present invention relates to a cloth feeding device that can perform sewing with a feeling similar to that of conventional mechanically driven cloth feeding even when the rotational speed of the upper shaft of a sewing machine is slow, and can suppress motor noise quietly.

Conventional technology In sewing machines that perform straight stitches, zigzag stitches, and various other pattern stitches, the cloth feed mechanism that moves the feed dog back and forth to feed the workpiece cloth in the desired direction is powered by a stepping motor that is separate from the main shaft drive motor. A driving sewing machine has been proposed. For example, in Japanese Unexamined Patent Application Publication No. 139694/1989, which is a previous application filed by the present applicant, the upper 'F movement mechanism of the feed dog is driven by a motor for driving the main shaft, and the forward and backward movement mechanism of the feed dog is driven by an independent stepping mechanism. A configuration in which the device is driven by a motor is disclosed.

In such sewing machines in which the cloth feeding mechanism is directly driven by a stepping motor, the following two methods are known as methods for driving the stepping motor. One method is to rotate a stepping motor at a constant frequency, regardless of the rotation speed of the upper shaft of the sewing machine. The latter one is
This method changes the driving frequency of the stepping motor in response to the rotation speed of the upper shaft of the sewing machine.

Problems to be Solved by the Invention As mentioned earlier, when the stepping motor is rotated at a constant driving frequency and sewing is performed at medium or high speeds, the feed of the workpiece cloth is Tracks relatively well. However, when the sewing speed becomes low, it would be ideal for the feed speed of the work cloth to follow suit, but since the cloth feed mechanism is driven at a constant speed, the feed speed of the work cloth is reduced. Rather than being held in place, it feels as if it is being pulled. For this reason, an operator who has been using a conventional sewing machine that mechanically drives the forward and backward movement of a feed dog feels uncomfortable and has an operational feeling that is difficult to use.

Therefore, the above-mentioned method has been proposed in which the driving frequency of the stepping motor is varied with respect to the rotational speed of the upper shaft of the sewing machine. According to this, when the rotational speed of the upper shaft decreases, the feed speed of the work cloth also decreases accordingly, so that an operational feeling similar to that of conventional mechanical feed can be obtained. However, when the drive frequency is changed, the drive frequency in the low speed range also becomes lower, which has another drawback in that a large motor noise is generated due to the characteristics of the stepping motor.

OBJECTS OF THE INVENTION The present invention has been proposed in order to suitably solve the drawbacks inherent in the conventional sewing machines in which cloth feed is directly driven by the stepping motor described above. It is an object of the present invention to provide a cloth feeding device that can follow the rotational speed of an upper shaft, give an operational feeling similar to mechanical feeding, and can prevent the generation of motor noise even in a low speed range.

1dlI! Means for Solving I In order to overcome the above-mentioned problems and achieve the intended purpose, the present invention provides a needle bar that is provided with a sewing needle and that is reciprocated up and down by the drive of an upper shaft by a sewing machine motor; a feeding mechanism for transporting the work cloth in a desired direction when approximately adjusted; a feeding stepping motor for driving the feeding mechanism; a data generating means for generating feeding amount data regarding at least one stitch pattern; In a sewing machine comprising a feed drive means for driving the feed stepping motor based on feed amount data from a data generation means, the rotational speed of the upper shaft or a member rotating in synchronization with the upper shaft is detected. and speed detection means.

As the rotational speed of the upper shaft or a member rotating in synchronization with the upper shaft detected by the speed detection means becomes slower, the step angle of the feeding stepping motor is gradually switched to an excitation method that decreases the step angle, and A control means for controlling the feed drive means according to the feed amount data.

According to the present invention, as the rotational speed of the upper shaft of the sewing machine becomes slower, the step angle of the feeding stepping motor can be switched to an excitation method that gradually decreases the step angle.

Embodiment Next, a preferred embodiment of the cloth feeding device for a sewing machine according to the present invention will be described below with reference to the accompanying drawings. In FIG. 2, reference numeral 10 indicates an electronically controlled zigzag sewing machine, and a pedestal section 14 erected from the right end of the bed section 12 is provided with an arm 16 extending horizontally to the left from the upper end. . A head 18 provided at the left end of the arm 16 is provided with a needle bar 22 having a sewing needle 20 attached to its tip.

The needle bar 22 is vertically movably mounted on a support 26 which is pivotally supported on the machine frame through a pin 24 so as to be swingable by a required central angle left and right. A sewing machine upper shaft 28 is horizontally supported on the arm 16, and a crank 30 provided at the left end of the top #128 is connected to a needle bar holder 32 provided on the needle bar 22. A pulley 34 is provided at the right end of the upper shaft 28 of the sewing machine, and the rotation of a sewing machine motor 36 disposed on the pillar portion 14 is transmitted to the upper shaft 28 via a belt 38 and the pulley 34. . Therefore, when the sewing machine motor 36 is driven, the upper shaft 28 rotates in a required direction, and the needle bar 22 is given vertical movement via the crank 30.

Further, a sector gear 40 is vertically pivotally supported on the pillar portion 14, and this sector gear 40 meshes with a pinion 44 provided on a stepping motor 42 for swinging the needle bar, so that it can swing left and right at a required central angle. It looks like this. The support body 26 of the needle bar 22 and the sector gear 40 are connected by a connecting rod 46 extending horizontally inside the arm 16.

Therefore, if the stepping motor 42 for swinging the needle bar is rotated in the forward and reverse directions, the supporting body 26 will move as the sector gear 40 swings.
is driven to swing left and right via a connecting rod 46. As a result, the needle bar 22 is given a left-right swinging motion for zigzag stitching.

In the slit 50 formed in the needle plate 48 of the bed portion 12,
A feed dog 52 for feeding the work cloth (not shown) in the vertical and longitudinal directions is provided, and the feed dog 52 is connected to a feed mechanism 54 that operates approximately in synchronization with the needle bar 22. The feed mechanism 54 includes a feed base 56 that supports the feed dog 52;
It basically consists of a vertical feed shaft 58 that gives the feed table 56 vertical movement, and a horizontal feed 60 that gives the feed table 56 back and forth movement. That is, the feed table 56 supporting the feed dog 52 is horizontally arranged in the front-rear direction on the bed portion 12, and has a fork 56a and a straight-line portion 56b formed at its front and rear ends, respectively.

A vertical feed shaft 58 is horizontally supported on the front side of the bed portion 12 so as to be able to swing freely around -.
The fork 56a is fitted through a pin 63. Further, on the rear side of the bed portion 12, a horizontal feed shaft 60 is horizontally supported so as to be able to swing freely around the axis, and two arms 64 and 64 extending from the feed 60 in a perpendicular direction are attached to the feed base. 56 is pivotally mounted.

A swinging wheel 66 that can freely swing around the shaft is disposed on the rear side of the vertical feed shaft 58, and a cam 68 fixed to the swinging shaft 66 is attached to a bifurcated ring provided perpendicularly to the vertical feed shaft 58. Arm 7
0 is engaged. This swing 466 is connected to a crank portion 28a formed on the upper shaft 28 via a rod 72. Therefore, when the sewing machine motor 36 is driven, the upper shelf 28 rotates and gives vertical motion to the needle bar 22, and the swing shaft 66 swings and rotates via the rod 72, causing the cam 6
The feed dog 52 is driven up and down along the path 8→bifurcated arm 70→vertical feed shaft 58→feed table 56.

Further, a sector gear 74 is fixed to the right end portion of the horizontal feed shaft 60, and this sector gear 74 is engaged with the pinion 3I of a feed stepping motor 76 provided on the pillar portion 14. By driving the feeding stepping motor 76 in synchronization with the vertical movement of the teeth 52, the feeding teeth 52 are driven forward and backward in their raised and lowered positions, respectively.

Further, the upper shaft 28 of the sewing machine is provided with a speed detector 84 consisting of a disk 80 having a large number of radially formed slits and a photointerrupter 82. This speed detector 8
4 detects the light transmitted through the slit of the disk 80, and the first
It supplies a signal regarding the rotational speed of the upper shaft 28 to a later-described CPU 86 shown in the figure. Speed detector 8 in the illustrated example
4 detects the rotational speed of the upper shaft 28, but the rotational speed of a member rotating in synchronization with the upper shaft 28 may also be detected.

Further, the upper shaft 28 of the sewing machine is provided with a phase detector 88 that detects the rotational phase of the upper shaft 28 and determines the timing of cloth feeding. That is, the upper shaft 28 is provided with a disk 9o coaxially with the slit disk 80 and having one slit formed in the radial direction, and a photointerrupter 92 is disposed with the slit disk 90 in between. . This photointerrupter 92 has a slit disk 90 and an upper 41128
When the rotational phase of the slit is about 360 degrees, the light passing through the slit is detected and a cloth feed reference signal is supplied to the CPU 86 shown in FIG. In addition, in Fig. 2.

Detailed illustrations and explanations of the driving mechanism of the top #81, the linking mechanism of the presser foot 83, etc. attached to the sewing machine 10 will be omitted.

Next, the control system of the sewing machine 10 will be explained with reference to the block diagram shown in FIG. The I10 interface 11 of the control circuit C includes a pattern selection switch 13 for selecting a desired pattern, a start/stop switch 15 for selectively instructing start/stop of the sewing machine 10, and a speed switch for detecting the rotational speed of the upper shaft 28. A detector 84 detects the rotational phase of the upper shaft 28,
The phase detector 8 generates a cloth feed reference timing signal.
8 are connected. Further, the sewing machine motor 36 is connected to the drive circuit 17, and the needle bar swinging stepping motor 42 is connected to the drive circuit 1.
9. The feeding stepping motors 76 are each connected to the I10 interface 11 via the drive circuit 21. Note that the I10 interface 11 has a sewing machine 10.
Other elements necessary to operate the machine are provided, such as a volume for adjusting the amount of swing of the needle bar, a volume for adjusting the feed rate of the work cloth, and a clock pulse generating means for synchronizing each movable part. , illustration and description are omitted.

The I10 interface 11 is connected to the CPU 86, ROM 25, RAM 27, etc. via the bus 23. This ROM 25 stores pattern data in which needle position data, that is, feed amount data and needle swing data for each sewing operation is stored for each of a large number of patterns such as one character or symbol, and also stores selected stitch pattern data. A control program is stored that controls the feeding stepping motor 76 based on the feeding amount data when reading and receiving a feeding start signal. The ROM 25 also stores a control program for controlling the driving of the sewing machine motor 36, a control program for controlling the start of the feed operation for determining the start timing of the cloth feed operation based on the feed amount data and the speed signal, and the like. Further, the RAM 27 includes various types of memories that temporarily store the results of calculations performed by the CPU 86.

Furthermore, a control means 29 is connected to the machine/circle interface 11 for changing the excitation method of the feeding stepping motor 76 in stages and for controlling the drive circuit 21 (feed driving means) of the motor 76. That is, this control means 29 controls the upper shaft 2 detected by the speed detector 84.
8 (or a member that rotates in synchronization with the upper shaft 28), the excitation method is changed in stages to reduce the step angle of the feeding stepping motor 76. The drive circuit 21 is controlled according to the feed amount data in the pattern data.

In the present application, the emphasis is placed on the stepwise switching to the excitation method that reduces the step angle of the feeding stepping motor 76 as the rotational speed of the upper shelf 28 becomes slower.
An outline of this excitation method will be explained. A stepping motor applies a direct current that changes stepwise to the stator winding, and by sequentially switching this current, continues the stepwise rotation by a constant angle θ determined by the structure and excitation method. Various methods are known for excitation of the motor, depending on the number of phases of the motor and the number of phases to be excited simultaneously. Regarding 2-phase or 3-phase stepping motors, the 1-phase excitation force type always excites only one phase, but because there is no braking force when the rotor steps, it vibrates heavily and tends to cause disturbances. . In reality, one phase is not excited one by one, but a method is adopted in which two adjacent phases are simultaneously excited, or three phases are simultaneously excited.

For example, in the two-phase excitation force type, the two coils of phase A and phase B are excited at the same time, and even when switching phases, the other phase is always excited, so the energy during the step is transferred to the two coils. The line Ii is rapidly consumed and braking is applied.

Therefore, disturbance is reduced and it can be used in a wide frequency range. Furthermore, a method in which two adjacent phases are combined and excited while sequentially shifting to the next phase is called a 2-2 phase excitation force method. For example, in a stepping motor that has four phases clockwise: A, B, C, and D, a pair of A and B phases → a pair of B and C phases → a pair of C and D phases → D In this case, the pairs of phase and A phase are excited in this order.

Furthermore, an excitation method that alternately combines one-phase excitation and two-phase excitation is called a 1-2 phase excitation force method. For example, in the 4-phase stepping motor mentioned above, a combination of A and B phases → B phase alone → B phase and C
This is a method in which the excitation of two adjacent phases and the excitation of the next single phase are sequentially shifted, such as from a set of phases to C phase alone, and so on. In addition, by halving the phase currents flowing in the A and B phases and adding an intermediate step in which the magnetic field strength is halved, the 1-2 phase excitation described above is doubled. This is called the phase excitation magnetic force type. In this way, even though the structure of the stepping motor is the same, various excitation methods can be used to change the order of the current flowing through each phase, or to divide the level of the phase current value to change the strength of the magnetic field in each phase. By doing so, a minute step angle can be obtained. In other words, the step angle θ of the rotor gradually decreases in the order of description.

The moment of inertia of the rotor when stepping is reduced,
The rotational sound is quiet, but the rotational speed also decreases in this order.

In addition, the step angle θ, which is determined by the mechanical structure and number of phases of the stepping motor, is electrically subdivided and driven to reduce motor shaft vibration, noise, and overshoot during starting and stopping. Control using a step drive method is also possible.

Operation of the Embodiment Next, the actual use of the cloth feeding device of the sewing machine according to the present embodiment will be explained. In the embodiment, the excitation method of the feeding stepping motor 76 is set to one of the following depending on the rotational speed of the upper shelf 28: ■ 2-2 phase excitation method, ■ 1-2 phase excitation method, and ■ Double 1-2 phase excitation method. The switch shall be made in stages.

In the flowchart in Figure 3, the startup and
When the stop switch 15 is operated and a start signal is input to the CPU 86, control of the sewing machine 10 is started, and initial settings are made in step 1.

Accordingly, the sewing machine motor 36 is driven and the upper shaft 28 is rotated according to the control program stored in the ROM 25.

In step 2, it is confirmed whether the upper shaft 28 is rotating, and if the answer is negative (NO), the process returns to step 2 to reconfirm, and if the answer is yes (YES), the process moves to step 3. In step 3, the rotational speed of the upper shaft 28 detected by the speed detector 84 is, for example, 500 R, P, M.
, check whether it is greater than or equal to. Here, the rotation speed is 500
R, P, M.

If the above relatively high speed is affirmed (YES).

Proceeding to step 6, the 2-2 phase excitation force formula is selected.

Also, if it is denied (No) as not more than 500 R, P, M, the process moves to the next step 5, and the upper axis 28
It is confirmed whether the rotational speed is, for example, 200 R, P, M or more. If it is affirmed (YES) that the rotation speed is a medium speed of 200 R, P, M or more (and 500 R, P, M or less), the process moves to step 7 and the 1-2 phase excitation force is An expression is selected. In step 5, 200 R,
If the result is negative (NO), the process moves to step 8 and the double 1-2 phase excitation force formula is selected.

In this way, the rotational speed of the upper shaft 28 is 500R, P, M,
High speed above or 500 R, P, M, 20 OR below
,P,M, medium speed or higher, 20OR,P,M.

Stepping motor 76 for feeding at low speed or below
The excitation method is selected in stages. However, until the cloth feed command is issued from the phase detection l1188, the motor 76
is not driven, and the operations from steps 3 to 8 are repeated. That is, after any of the excitation methods is selected, it is checked in step 9 whether or not a cloth feed command is issued from the phase detector 88, and its timing. This step 9
If the cloth feed command is denied (NO), the process returns to step 3 and is reconfirmed, and if the cloth feed command is affirmed (YES), the process moves to step 10. In this step 10, the feeding stepping motor 76 is driven via the drive circuit 21 in FIG. 1 according to the excitation method selected at that time.

At this time, the drive circuit 21 is controlled by the control means 29 to
Control is performed according to the feed amount data stored in the OM 25.

That is, if the rotation speed of the upper shaft 28 is 1, for example, 500 R,
If the speed is higher than P or M, the workpiece cloth must be fed at a correspondingly high speed. According to this embodiment, the excitation method of the feeding stepping motor 76 is as follows.
Since the 2-2 phase excitation force type is selected because it can provide sufficient torque at a relatively high speed, it is possible to provide an operational feeling similar to that of the mechanical feed described above. Further, the rotation speed of the upper shaft 28 is 50
At medium speeds of 0R, P, M and below, 20 OR, P, M, or at low speeds of 20 OR, P, M and below, the workpiece cloth may be fed at a medium or low speed commensurate with the rotational speed. In the embodiment, a method is selected in which the step angle gradually decreases, such as a 1-2 phase excitation force type at medium speeds and a double 1-2 phase excitation force type at low speeds. Therefore.

The work cloth can be fed at a speed commensurate with the rotational speed of the upper shaft 28, and the noise generated by the feeding stepping motor 76 can also be suppressed.

In the example, a case will be explained in which, as the rotational speed of #28 on the sewing machine becomes slower, the selection is made in the order of 2-2 phase excitation force type → 1-2 phase excitation type → double 1-2 phase excitation force type. However, it goes without saying that other excitation methods can be suitably employed as long as they can be switched stepwise to an excitation method that gradually reduces the step angle. Although the speed detector 84 has been described as one that directly detects the rotational speed of the upper shaft 28 of the sewing machine, it may also be configured to detect the rotational speed of a member that rotates in synchronization with the upper shaft 28, for example. Good too.

DETAILED DESCRIPTION OF THE INVENTION According to the cloth feeding device according to the present invention, in a sewing machine in which the cloth feeding mechanism is directly driven by a stepping motor, when the rotational speed of the upper shaft of the sewing machine becomes slow, the cloth feeding device according to the present invention This is a stepwise switch to a motor excitation method in which the step angle of the rotor in the stepping motor gradually decreases. In this excitation method in which the step angle gradually decreases, the moment of inertia of the rotor during stepping is suppressed, so rotation is smooth and motor noise can be suppressed. In addition, the speed of the feeding stepping motor is controlled in synchronization with the speed of the upper shaft, so even if the speed of the upper shaft becomes slow, the workpiece cloth will not be pulled at a high speed as in the past. Therefore, there is an advantage that sewing can be performed with a feeling similar to that of conventional mechanically driven cloth feeding.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a control system of a sewing machine in which the present invention is preferably implemented, FIG. 2 is a schematic configuration diagram of a sewing machine according to an embodiment, and FIG. 3 is a flowchart diagram of a sewing machine according to an embodiment. It is. 76...Stepping motor for feeding 84...Speed detection means (speed detector) 88...Phase detection means (phase detector) Patent applicant Brother Industries, Ltd. Applicant's agent Patent attorney Yoshiku Yamamoto 0 ... Sewing machine 20 ... Sewing needle 1 ... Feed drive means (drive circuit) 2 ... Needle bar 5 ... Data generation means (ROM) 8 ... Upper shaft 29 ... Control means 6. ...Sewing machine motor 54...Feed mechanism FIG, 1 FIG, 3 (No rear drawing)

Claims (1)

[Claims] The upper shaft (with a sewing needle (20) and a sewing machine motor (36))
a needle bar (22) that is reciprocated up and down by the drive of the needle bar (28); a feeding mechanism (54) that transports the work cloth in a desired direction in approximately synchronization with the needle bar (22); 54); a data generating means (25) for generating feed amount data regarding at least one stitch pattern; In the sewing machine (10), the sewing machine (10) is equipped with a feed drive means (21) that drives the feed stepping motor (76), the upper shaft (28) or a member that rotates in synchronization with the upper shaft (28). Speed detection means (84) for detecting rotation speed
and the upper shaft (28) detected by the speed detection means (84).
) or its upper shaft (28), as the rotational speed of the member that rotates in synchronization with the upper shaft (28) decreases, the step angle of the feeding stepping motor (76) is changed stepwise to an excitation method that decreases the step angle. A cloth feeding device for a sewing machine, comprising: control means (29) for controlling the feeding drive means (21) according to data.