JPH07213774A - Vibration control device for sewing machine - Google Patents

Abstract

PURPOSE:To provide a vibration control device for a sewing machine capable of actively reducing the vibration of the sewing machine generated on a bed by the rotation of an arm shaft and the vertical reciprocation of a needle bar without reducing the mechanical strength of the sewing machine and without introducing a complex mechanical design. CONSTITUTION:The control signal interfering with the detected vibration is generated by a controller 101 so that the detection value of a vibration detecting sensor 82 is minimized based on the synchronization signal detected by a synchronization signal generating device 60 generating the synchronization signal synchronized with the rotation of the arm shaft of a sewing machine, the detection signal of the vibration detecting sensor 82 detecting the vibration on a bed portion, and the transfer function set by the controller 101. A piezoelectric actuator 74 is operated based on the control signal to generate the control vibration, and the detected vibration can be actively reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration control device for a sewing machine, which actively reduces vibrations on the sewing machine main body caused by rotation of the upper shaft of the sewing machine, vertical reciprocating motion of a needle bar, and the like. Is.

[0002]

2. Description of the Related Art Conventionally, various contrivances have been made in sewing machines in order to suppress the occurrence of vibration. Specific examples thereof will be described with reference to FIG. 9 showing an internal configuration of a main body of a conventional sewing machine.

First, the mass of the entire structure of the needle bar 40 and the accompanying needle bar holder 46 that reciprocates vertically is reduced, and the vibration itself generated by the vertical reciprocation of the needle bar 40 is reduced. It was done. For example, the needle bar 40
In the prior art, a round bar-shaped steel material was conventionally used as the material, but the weight thereof is reduced by changing to a hollow aluminum material.

Secondly, the vibration generated by the vertical reciprocating motion of the needle bar 40, the vibration generated by the swing motion of the balance 36,
Also, the vibration generated by the movement of the parts associated with the needle bar 40 and the balance 36 is canceled by the vibration generated by the rotational movement of the balance crank 34 also associated with the needle bar 40 and the balance 36. , The material of each part, dimensions,
And the arrangement etc. are determined.

Thirdly, the thickness of the member of the arm 22 is increased,
There is one in which generation of vibration is suppressed by increasing the rigidity of the arm 22.

Fourthly, there is also a simple device that generates a waveform having a phase opposite to that of the vibration generated by the vertical reciprocating motion of the needle bar 40 and suppresses the vibration of the sewing machine by using the waveform having the opposite phase.

[0007]

However, according to the above-mentioned first prior art, the mechanical strength of the entire mechanism is lowered, so that there is a limit to the reduction of mass, and the vibration is reduced accordingly. There is also a limit.

Further, according to the second conventional technique, the needle bar 40, the balance 36, and the parts such as the balance crank 34 which are moving in association therewith, make complicated mutual movements, Moreover, since the mutual movements are high-speed movements, it is very difficult to design each part in a balanced manner so as to reduce vibrations.

Further, according to the third conventional technique, the cost of parts is increased, and the rigidity of the arm 22 is increased to increase the weight of the entire sewing machine and reduce the weight of the sewing machine. This is outside the design intent of facilitating operator handling.

Further, according to the fourth prior art, it is very difficult to accurately make the vibration of the upper shaft of the sewing machine have the same amplitude and opposite phase with respect to the vibration generated by the high speed rotation. In addition, in reality, it is considered that it is impossible to suppress the vibration while following the vibration, because the vibration affects the vibration and the time delay of the vibration transmission system.

The present invention has been made to solve the above-mentioned problems, and does not reduce the mechanical strength of the sewing machine and does not introduce a complicated design.
An object of the present invention is to provide a vibration control device for a sewing machine that actively reduces vibration on the sewing machine main body caused by rotation of the upper shaft of the sewing machine, vertical reciprocating motion of a needle bar, and the like.

[0012]

In order to achieve the above-mentioned object, a vibration control device for a sewing machine according to the present invention comprises a synchronization signal generating means for generating a synchronization signal in synchronization with the rotation of the upper shaft of the sewing machine, and the upper shaft. Vibration detection means for detecting the vibration generated on the sewing machine main body due to the rotation and the vertical reciprocating motion of the needle bar, and the control vibration generation means capable of generating the control vibration for canceling the vibration generated on the sewing machine main body, Transfer function setting means for presetting a transfer function indicating the characteristics of the mechanical parts of the sewing machine, electric parts for control, etc., a synchronization signal generated from the synchronization signal generating means, and a transfer set by the transfer function setting means. And a vibration control means for controlling the control vibration generating means so that the vibration detected by the vibration detecting means is minimized based on the function and the detection signal of the vibration detecting means.

Further, the synchronizing signal generating means and the control vibration generating means may be provided in the bed portion of the sewing machine main body.

Further, while the synchronizing signal generating means is supported on the upper surface of the bed portion, the control vibration generating means is disposed between the lower surface of the bed portion and a weight elastically urged toward the lower surface. It may be arranged to be press-fitted.

[0015]

According to the vibration control device for a sewing machine of the present invention having the above-mentioned structure, when the sewing machine is operated, a synchronizing signal is generated from the synchronizing signal generating means, the upper shaft thereof is rotated, and the needle bar is vertically reciprocated. Vibration is generated on the main body of the sewing machine, and the vibration is detected by the vibration detecting means. Then, the synchronization signal, the detection signal of the vibration detection means,
Based on the transfer function set by the transfer function setting means, the vibration control means controls the control vibration generating means so that the vibration detected by the vibration detecting means becomes minimum, thereby controlling the control vibration. The control vibration generated from the generating means acts to cancel the vibration on the sewing machine main body, so that the vibration can be actively reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 7 showing the external appearance of the sewing machine, the sewing machine main body 16 is installed on the oil pan 12 fixed to the table 10 with a vibration isolating rubber 14 interposed therebetween.
It is adapted to be driven by a motor 18 fixed to the lower part of 0.

The sewing machine body 16 has a lower bed portion 20 in contact with the oil pan 12 and an upper arm 22.
It is composed of and.

The internal structure of the sewing machine main body 16 is shown in FIG. The pulley 30 is fixed to one end of an upper shaft 31 installed in the arm 22, and the pulley 30 and the pulley 30 are connected to each other.
The motor 18 therein is connected by a belt 32.
The driving force of the motor 18 is transmitted to the upper shaft 31 via the belt 32 and the pulley 30.

A balance crank 34 is fixed to the other end of the upper shaft 31, and the balance crank 34 rotates as the upper shaft 31 rotates. The balance 36 is connected to the balance crank 34 and swings up and down as the upper shaft 31 rotates. The needle bar 40 includes a needle bar crank 42 and a needle bar connecting rod 4.
4, and is connected to the balance 36 via the rod holder 46,
As the upper shaft 31 rotates, it reciprocates up and down while being guided by the needle bar metal 50 and the needle bar metal 52 fixed to the arm 22. Hereinafter, the pulley 30 side is the right side and the needle bar 40 side is the left side.

At the right end of the upper shaft 31, a synchronizing signal generator 6 for generating a synchronizing signal in synchronization with the rotation of the upper shaft 31.
0 is provided, a needle plate 70 and a slide plate 72 are provided on the left side of the bed portion 20, and a piezoelectric actuator 7 for constituting a control vibration generating unit is provided below the needle plate 70 and the slide plate 72.
4, a pair of coiled springs 76, and a weight 78 are provided. The springs 76 are fixed to the lower part of the bed portion 20 in front of and behind the sliding plate 72, and the weights 78 are fixed to the lower ends of the springs 76 and always spring to the lower surface side of the bed portion 20. It is energized. Therefore, the piezoelectric actuator 74 is press-fitted between the lower surface of the bed portion 20 and the upper surface of the weight 78 by the pulling force of the spring 76.

The control box 80 in FIG.
It is fixed adjacent to 8.

A vibration control system for such a sewing machine is shown in FIG.
As shown in FIG. 4, a vibration detection sensor (vibration detection means) 8 for detecting residual vibration on the upper surface of the bed portion 20 of the sewing machine.
2, a synchronizing signal generator (synchronizing signal generating means) 60 for generating a synchronizing signal synchronized with the rotation of the upper shaft 31, and the piezoelectric actuator 74 for generating control vibration for canceling the vibration generated in the bed portion 20. Connected to. The control unit mainly includes an amplifier 108, an A / D conversion unit 104, a D / A conversion unit 106, a filter LPF 105 for removing high frequency components, and a filter H for removing DC components.
The vibration detected by the vibration detection sensor 82 is composed of the PF 107, the adaptive filter 103, and the control unit 101, and based on the detection signal of the vibration detection sensor 82, the synchronization signal synchronized with the rotation of the upper shaft 31, and the transfer function described later. In order to minimize the
The drive control signal is output to 4.

That is, when a synchronizing signal synchronizing with the rotation of the upper shaft 31 is generated from the synchronizing signal generator 60, the synchronizing signal is passed through the amplifier 108, the filter LPF 105 and the A / D converter 104, and the adaptive filter 103 and the controller. 101 are input respectively. On the other hand, the vibration of the bed portion 20 is detected by the vibration detection sensor 82, and the detection signals are detected by the amplifier 108, the filter HPF 107, and the filter LPF1.
05 and the A / D conversion unit 104 to the control unit 101. The control unit 101 obtains transfer functions indicating these characteristics in consideration of changes in the transfer characteristics due to disturbance in the vibration path and changes in the characteristics of each electric component or mechanical system component, and based on these transfer functions. The vibration suppression effect, that is, the detection signal of the vibration detection sensor 82 for detecting the interference state between the vibration generated in the bed portion 20 and the control vibration generated by the piezoelectric actuator 74 should be applied to the adaptive filter 103. A transfer function is determined, and a control parameter for specifying the transfer function is set in the adaptive filter 103.

The control unit 101 corrects the control parameters as needed according to changes in the vibration transmission path and changes in the characteristics of the control system. As a result, the synchronization signal generator 60
The sync signal detected by the
It is input to the adaptive filter 103 via the PF 105 and the A / D conversion unit 104, and the input signal is the adaptive filter 10
The signal is converted into a digital signal having predetermined amplitude characteristics and phase characteristics on the basis of the transfer function given by the control unit 101. The digital signal is the D / A conversion unit 106.
Also, the signal is D / A converted and amplified by the amplifier 108 and applied as a drive signal for the piezoelectric actuator 74, and the piezoelectric actuator 74 generates control vibration for canceling the vibration on the bed portion 20 of the sewing machine. As a result,
At the installation position of the vibration detection sensor 82, the vibration due to the rotation of the upper shaft 31 and the vertical movement of the needle bar 40 is damped.

FIG. 3 is a conceptual diagram of a sync signal generator 60 for generating a sync signal in synchronization with the rotation of the upper shaft 31 shown in FIG. Since it is known from the frequency analysis of the vibration that the vibration on the bed portion 20 is an integral multiple of the rotation frequency of the upper shaft 31, it is possible to pass the synchronization signal synchronized with the rotation frequency of the upper shaft 31 through the same transmission system. It is believed that vibration can be generated on the bed portion 20. Therefore, FIG.
Then, when a known encoder signal and timing signal are input, the output of the synchronization signal generator 60 is a pulse signal that is synchronized with the rotation of the upper shaft 31.

Further, in order to synthesize the control vibration for driving the piezoelectric actuator 74 from the signal synchronized with the rotation of the upper shaft 31, it is easy to give an arbitrary characteristic, so that
The adaptive filter 103 in FIG. 2 is composed of a finite impulse response filter (also called FIR filter) as shown in FIG. The input signal x (n) 300 is the generator output signal (hereinafter referred to as the synchronization signal) in FIG.
01 is a delay element, and w _0n , w _1n , w _2n , ..., W of symbol 303
_Mn is a variable filter coefficient transmitted from the control unit 101 in FIG. 2, symbol 302 is an adder, and symbol 306 is the number of filter taps. That is, the output y (n) 30 of the adaptive filter 103
5 is given by the following formula y (n) = w _0n x (n) + w _1n x (n-1) + w _2n x (n-2) + ・ ・ ・ + w _Mn x (n-
M) Variable filter coefficients w _1n , w _2n , ..., w _Mn are used as
This is because changes in the transfer characteristics due to disturbances in the vibration path and changes in the characteristics of each electric component or mechanical component itself converge to the optimum filter coefficient value while following them.

The control unit 101 of FIG. 2 is configured to sequentially estimate such a moving coefficient. FIG. 5 shows the configuration of the control unit 101. Here, the reference signal c (n) is generated by passing the synchronization signal x (n) through the delay filter 402. This reference signal
c (n) and the detection signal e (n) of the vibration sensor are adaptive algorithm 4
01 is input to the movable filter coefficients w _1n , w _2n , ...
Updating w _Mn w (n) = W (n-1) + μe (n) C (n) where W (n) = [w _1n w _2n ... w _Mn ] ^t C (n ) = [c (n) c (n-1) ・ ・ ・ c (nM)] ^t c (n) = h ₀ x (n) + h ₁ x (n-1) + ・ ・ ・ + h _p x (np) The parameter μ in the above equation is a constant called a step size, which is a parameter that affects the convergence speed and convergence accuracy of the filter coefficient W (n).

That is, in order to pursue the convergence speed, it is sufficient to increase the parameter μ within a converging range, but in consideration of the accuracy after convergence, it is necessary to comprehensively select the parameter μ. In particular, with respect to the vibration due to the reciprocating rotary motion of the sewing machine, it is necessary to suppress the vibration in a short time, and therefore it is considered that the convergence speed is required.

As described above, the estimated filter coefficient w _1n
w _2n ... W _Mn are transmitted to the adaptive filter of FIG. 4 to generate the output digital signal y (n) 305. The digital signal y (n)
Is D / A converted and amplified by the D / A converter 106 and the amplifier 108, and applied as a drive signal for the piezoelectric actuator 74. From the piezoelectric actuator 74, on the bed portion 20 caused by rotation of the upper shaft 31 of the sewing machine or the like. A control vibration is generated to cancel the vibration.

The coefficient h _{0 of} the delay filter 402 shown in FIG. 5,
h ₁ , ... H _p are obtained in advance. FIG. 6 shows a setting sequence before performing vibration control in order to obtain these. That is, the transfer function from the control actuator including the electric circuit, the vibration detection sensor 82, and the piezoelectric actuator 74 to the vibration detection sensor 82 that reduces vibration is obtained. An adaptive FIR filter using the LMS adaptive algorithm is mainly used as the adaptive filter 501. The signal generation source 502 can provide a periodic signal or a random signal, but in this embodiment, a periodic signal similar to the vibration of the sewing machine is used.

Regarding the overall operation of FIG. 6, a periodic digital signal is generated from the signal generation source, and this drives the piezoelectric actuator 74 via the D / A conversion unit 106, the low pass filter LPF 105 and the amplification amplifier 108. Then, control vibration is generated. On the other hand, a periodic digital signal is input to the adaptive filter 501 from a signal generation source and an output is generated. In the adder 503, the vibration signal picked up by the vibration detection sensor 82 and passed through the amplifier 108, the low pass filter LPF 105 and the amplification amplifier 108 and the adaptive filter 50.
The output of 1 is added and the error e (n) 504 is obtained. The adaptive filter 501 sequentially modifies the coefficient of the adaptive filter 501 so as to minimize the error e (n) 504. Finally, this convergence value is used as the filter coefficients h ₀ , h ₁ , ... H _p in FIG.

As described above, since the vibration control device for the sewing machine of the above-described embodiment is configured by using the conventionally used parts without adding many new parts or incorporating a complicated design. , Without lowering the mechanical strength of the sewing machine, maintaining the manufacturing cost of the conventional sewing machine main body, and actively reducing the vibration on the bed caused by the rotation of the upper shaft of the sewing machine and the vertical movement of the needle bar. A control device can be provided.

In the vibration control system of the sewing machine shown in FIG. 2, the vibration sensor for vibration evaluation may move on the bed regardless of the fixed type.

[0035]

As is apparent from the above description, in the vibration control device for a sewing machine of the present invention, the power transmission device such as a motor operates to transmit power, thereby rotating the upper shaft and vertically reciprocating the needle bar. When vibration occurs on the body of the sewing machine due to movement, etc.,
Using the generated synchronization signal, the detection value of the vibration detection means, and the transfer function set by the transfer function setting means, the control vibration is generated so that the detection value of the vibration detection means, that is, the vibration on the sewing machine main body is minimized. The control vibration generating means can be operated to actively reduce the vibration on the sewing machine main body. Further, when the rotation of the upper shaft of the sewing machine is constant, even if the vibration on the main body of the sewing machine changes due to a thermal phenomenon or a disturbance, it is possible to accurately follow the vibration of this variable system and reduce the vibration. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a configuration diagram of a vibration control system of a sewing machine.

FIG. 3 is a configuration diagram of a circuit that generates a synchronization signal.

FIG. 4 is a configuration diagram of an adaptive filter.

FIG. 5 is a configuration diagram of a control unit of the control system of the sewing machine.

FIG. 6 is a configuration diagram showing a setting sequence for vibration control of the sewing machine.

FIG. 7 is an external view of a sewing machine.

FIG. 8 is an internal configuration diagram of the sewing machine main body.

FIG. 9 is an internal configuration diagram of a conventional sewing machine main body.

[Explanation of symbols]

 31 Upper Axis 60 Synchronous Signal Detection Device 74 Piezoelectric Actuator 76 Spring 78 Weight 80 Control Box 82 Vibration Detection Sensor 101 Control Unit 502 Signal Generation Source

Claims (3)

[Claims] 1. A synchronization signal generating means for generating a synchronization signal in synchronization with the rotation of the upper shaft of a sewing machine, and a vibration for detecting a vibration generated on the main body of the sewing machine due to the rotation of the upper shaft, the vertical reciprocating motion of a needle bar and the like. Detecting means, control vibration generating means capable of generating control vibration for canceling vibration generated on the sewing machine main body, and preset transfer function indicating characteristics of the mechanical system parts of the sewing machine, electrical parts for control, etc. Based on the transfer function setting means, the synchronization signal generated from the synchronization signal generating means, the transfer function set by the transfer function setting means, and the detection signal of the vibration detection means, the vibration detected by the vibration detection means is minimum. A vibration control device for a sewing machine, comprising: 2. The vibration control device for a sewing machine according to claim 1, wherein the synchronization signal generating means and the control vibration generating means are provided in a bed portion of the sewing machine main body. 3. The control signal generating means is supported between the lower surface of the bed portion and a weight elastically urged toward the lower surface while supporting the synchronizing signal generating means on the upper surface of the bed portion. The vibration control device for a sewing machine according to claim 2, wherein the vibration control device is press-fitted.