JPH0838777A - Vibration control device for sewing machine - Google Patents

Abstract

PURPOSE:To actively reduce the vibrations of a sewing machine on a bed generated by the rotation of an arm shaft and the vertical reciprocating motion of a needle bar without reducing the mechanical strength of the sewing machine and without introducing a complex design. CONSTITUTION:Control signals interfering with detected vibrations are generated by a controller so that the detected values of vibration detecting sensors 82a, 82b are made minimum 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 31 of a sewing machine, detection signals of vibration detecting sensors 82a, 82b detecting the vibrations on a bed portion, and the transfer function set by the controller. Control vibrations are generated when piezoelectric actuators 74a, 74b are operated based on the control signals, and multiple detected vibrations 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. 7, which shows 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.

Fifthly, Japanese Patent Application No. 6-11569 discloses a vibration control device for a sewing machine in which an actuator, a spring and a weight are provided only below the needle plate.

[0008]

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 prior art, the needle bar 40, the balance 36, and the components 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.

According to the fourth conventional technique, it is very difficult to accurately set the same amplitude and opposite phase to the vibration generated by the high speed rotation of the upper shaft of the sewing machine.
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.

Further, according to the fifth conventional technique, since the bed of the sewing machine is not a rigid body, suppressing the vibration at one place on the bed does not always reduce the vibration of the entire bed.

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, in which 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, etc. is actively reduced at a plurality of locations at the same time.

[0014]

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 simultaneously detecting vibrations generated at multiple points on the sewing machine body due to rotation of the sewing machine and vertical reciprocating motion of the needle bar, and control vibrations for canceling vibrations generated at the multiple points on the sewing machine body at the same time. A plurality of control vibration generating means, a transfer function setting means for presetting a transfer function indicating characteristics or mutual interference characteristics of the mechanical system parts of the sewing machine, electric parts for control, etc., and the synchronization signal generating means. A plurality of vibrations detected by each of the vibration detecting means at the same time based on a synchronization signal generated from the above, a transfer function set by the transfer function setting means, and a plurality of detection signals detected by the vibration detecting means. And a plurality of vibration control means for controlling said respective control vibration generating means so as to minimize.

Further, the synchronizing signal generating means, each vibration detecting means and each control vibration generating means may be provided in a 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 respective control vibration generating means are a lower surface of the bed portion and a weight elastically urged toward the lower surface thereof. It may be configured to be press-fitted between the two.

[0017]

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 by the above, and the vibration is detected by a plurality of vibration detecting means. Then, based on the synchronization signal, the detection signal of each vibration detection unit, and the transfer function set by the transfer function setting unit, each vibration detected by each vibration detection unit is minimized at the same time. By controlling each of the control vibration generating means by each of the vibration control means, the control vibration generated from each of the control vibration generating means works to cancel a plurality of vibrations on the sewing machine bed. Vibration can be actively reduced.

By providing the synchronizing signal generating means and each control vibration generating means in the bed portion of the sewing machine main body, the vibration of the bed portion in which the vibration is generated is canceled out, and the vibration of the entire sewing machine main body is effective. Can be reduced to

Further, while the synchronizing signal generating means is supported on the upper surface of the bed portion, the respective control vibration generating means are a lower surface of the bed portion and a weight elastically urged toward the lower surface thereof. By virtue of the press-fitting arrangement between them, the vibration of the bed portion can be canceled more effectively.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described in detail below with reference to the drawings. Further, for convenience of explanation, the vibration detection means and the vibration control means are respectively set to two channels.

In FIG. 6 showing the outer 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 main body 16 has a lower bed portion 20 in contact with the oil pan 12 and an upper arm 22.
And is constituted by.

The internal construction of the sewing machine 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 shown in FIG.
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, there is provided a synchronizing signal generator 60 as a synchronizing signal generating means for generating a synchronizing signal in synchronization with the rotation of the upper shaft 31, and
A needle plate 70 and a sliding plate 72 are provided on the left side of the bed portion 20.

As shown in FIG. 5, piezoelectric actuators 74a and 74b for constituting control vibration generating means, a pair of coiled springs 76a and 76b, and a weight are provided on the left side and the center of the bed 20 below. 78a and 78b are provided. The springs 76 are fixed to the lower portion of the bed portion 20 at two positions, and the weights 78a and 78b are fixed to the lower ends of the springs 76 and are always elastically urged toward the lower surface of the bed portion 20. There is. Therefore, each of the piezoelectric actuators 74 includes a lower surface of the bed portion 20 and a weight 78.
It is press-fitted and arranged by the pulling force of each spring 76 between itself and the upper surface. Further, vibration sensors 82a and 82b for detecting residual vibration are arranged on the bed, respectively. The respective vibration detection sensors 82a and 82b constitute vibration detection means.

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

As shown in FIG. 4, the vibration control system 80 of the sewing machine has vibration detection sensors 82a and 82b for detecting residual vibration on the upper surface of the bed portion 20 of the sewing machine.
, A synchronizing signal generator 60 for generating a synchronizing signal synchronized with the rotation of the sewing machine, and the piezoelectric actuators 74a, 74b for generating control vibration for canceling the vibration generated in the bed portion 20. Control system 8
0 is configured as shown in FIG.
/ D converter 104, D / A converter 106, filter LPF 105 for removing high frequency components, adaptive filter 10
3, the digital filter and the control unit 101, each vibration detection sensor 82 based on the detection signal of each vibration detection sensor 82, the synchronization signal synchronized with the rotation of the upper shaft 31 of the sewing machine, and the transfer function described later. The control unit 101 outputs a drive control signal to each piezoelectric actuator 74 so as to simultaneously minimize the detection vibration of the above.

That is, when a synchronizing signal which is synchronized with the rotation of the sewing machine is generated from the synchronizing signal generator 60, the synchronizing signal is input to the adaptive filter 103 and the digital filter 102 via the filter LPF 105 and the A / D converter 104, respectively. . The digital filter generates reference signals considering mutual interference and inputs them to the control unit 101.

On the other hand, the vibration of the bed portion 20 is detected by each vibration detection sensor 82, and the detection signals thereof are amplified by the amplifier 108, the filter LPF 105 and the A / D converter 10.
4 is input to the control unit 101. The control unit 101 adjusts the coefficient of the adaptive filter 103 in consideration of the change of the transfer characteristic due to the disturbance in the vibration path, the characteristic change of each electric component or the mechanical component itself, the mutual interference, etc. To 103. The output of the adaptive filter 103 drives each actuator. That is, the two-channel adaptive filter 103 is provided so that the detection signals of the respective vibration detection sensors 82 for detecting the interference state between the vibration generated in the bed portion 20 and the control vibration generated by each piezoelectric actuator 74 are simultaneously minimized. The control parameter for determining the power transfer function and specifying the transfer function is set to 2
The channel adaptive filter 103 is set.

The control unit 101 always corrects the control parameters according to the change of the vibration transmission path and the change of the characteristic 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 its input signal is a digital signal having a predetermined amplitude characteristic and phase characteristic based on the transfer function given from the control unit 101 by the two-channel adaptive filter 103. Converted to a signal. The digital signal is D / A
The signals are D / A converted and amplified by the converter 106 and the amplifier 108, and applied as a drive signal for each piezoelectric actuator 74, and each piezoelectric actuator 74 generates control vibration for canceling vibration on the bed portion 20 of the sewing machine. It As a result, vibrations due to the rotation of the upper shaft 31 and the vertical movement of the needle bar 40 are damped at the installation position of each vibration detection sensor 82.

FIG. 2 shows a conceptual diagram of a sync signal generator 60 for generating a sync signal in synchronization with the rotation of the sewing machine. Since it is known from the frequency analysis of the vibration that the vibration on the bed portion 20 consists of an integral multiple of the rotation frequency of the sewing machine, by passing a synchronization signal synchronized with the rotation frequency through the same transmission system, It is thought that the vibration of can be generated. Therefore, in FIG. 2, when the 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 sewing machine.

Further, in order to synthesize the control vibration for driving each piezoelectric actuator 74 from the signal synchronized with the rotation of the sewing machine, it is easy to give an arbitrary characteristic,
The 2-channel adaptive filter 103 in FIG. 3 is composed of a finite impulse response filter (also called FIR filter).

Here, a method of controlling vibration in the control unit 101 will be described.

Now, the vibration signal detected by the l-th vibration sensor 82 is _{el (n)} , and the l-th vibration sensor 82a, 8b when there is no control vibration from the actuators 74a, 74b.
The vibration signal detected by 2b is d _l (n), the m-th actuators 74a and 74b, and the l-th vibration sensor 82a and 82b.
The j-th term of the transfer function with b is c _lmj , and the synchronization signal x
(n), the synchronization signal x (n) is input and the mth actuator 7
If the i-th coefficient of each filter for each output channel in the adaptive filter 103 that drives 4a and 74b is w _mi ,

[0036]

[Equation 1]

Is satisfied. Here, the term with (n) is a sample value at the sampling time, L is the number of vibration sensors (two in this embodiment), M is the number of actuators (two in this embodiment), I is the number of taps of the transfer function c _lm expressed by the FIR digital filter, and J is the number of taps of the adaptive filter 103.

In the above equation (1), the term in parentheses on the right side represents the output when the synchronizing signal is input to the filter (coefficient w _m ) for each output channel in the adaptive filter 103, and the term in parentheses on the right side. In the term obtained by multiplying the term by the transfer function, the signal energy input to the m-th actuator 74a, 74b is output as the vibration energy from the actuator 74a, 74b, and the vibration transfer function c _lm on the bed is obtained.
Represents the signal when reaching the l-th vibration sensor 82a, 82b via the, and the entire right side after "-" is l
Since the arrival signals to the 1st vibration sensors 82a and 82b are added up for all the actuators, the sum of the secondary vibrations that reach the 1st vibration sensors 82a and 82b is shown.

Then, the evaluation function J _e is

[0040]

[Equation 2]

Let us say that.

In order to find the filter coefficient w _m that minimizes the evaluation function J _e , the LMS adaptive algorithm is used in this embodiment. That is, the filter function w _mi is an instantaneous gradient value obtained by approximating the evaluation function J _e with each filter coefficient w _{m i.}
To update.

Therefore, from equation (2),

[0044]

(Equation 3)

From equation (1),

[0046]

[Equation 4]

Therefore, the right side of this equation (4) is r _lm (n
-i), the filter coefficient rewriting formula is given by the following formula (5).

[0048]

(Equation 5)

Here, μ is a constant called a step size, and is a parameter that influences the convergence speed and convergence accuracy of the adaptive filter.

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. 3 to generate output digital signals y ₁ (n) and y ₂ (n). The digital signal y ₁
(n), y ₂ (n) is D / A converted and amplified by the D / A converter 106 and the amplifier 108, and the piezoelectric actuator 74a,
A control vibration for canceling the vibration on the bed portion 20 caused by the rotation of the upper shaft 31 of the sewing machine is generated from each piezoelectric actuator 74.

The coefficient c _lmj of the digital filter 102 shown in FIG. 3 is obtained in advance. An electric circuit,
The mutual transfer function from each control actuator including the vibration detection sensor 82 and the piezoelectric actuator 74 to each vibration detection sensor 82 that reduces vibration is obtained. An FIR filter is mainly used as the digital filter 102.

Next, the operation of the embodiment will be described.

When the motor is started, the encoder output and the timing pulse are input to the synchronizing signal generator 60, and the synchronizing signal x is output and supplied to the control system 80.

In the control system 80, the synchronizing signal x is supplied to the digital filter 102 and the adaptive filter 103 via the filter LPF 105 and the A / D converter 104. Of these, the digital filter 102 uses the input synchronizing signal x to calculate the filtered synchronizing signal r _{lm according} to the equation (4) in correspondence with the transfer function c _lm between the sensor and the actuator, and The signal r _lm is output to the control unit 101.

On the other hand, the vibration sensors 82a and 82b detect the vibration remaining at that position and output error signals e ₁ and e ₂ corresponding to the vibration to the control system 80. In the control system 80, the input error signals e ₁ and e ₂ are input to the amplifier 10
8, low-pass filter LPF105, A / D converter 10
4 to the control unit 101.

In the control section 101, the filter coefficient update calculation is performed based on the equation (5) using each input signal. That is, the evaluation function, that is, each vibration sensor 82, is _{added to the} filter coefficient w _mi (n) at the current sampling time n.
The error signal e _l (n) corresponding to the residual vibration from a and 82b is calculated for each filter coefficient in the direction in which the root mean square becomes the minimum, and the filter coefficient w _mi (which should be set at the sampling time (n + 1)) n + 1) is obtained. Therefore, the control unit 10
1 outputs a control signal corresponding to the calculated value w _mi (n + 1) to the adaptive filter 103. Therefore, the coefficient of each filter in the adaptive filter 103 is updated to the newly calculated filter coefficient w _mi at the sampling time (n + 1).
In this way, the control unit 101 repeats the update of the filter coefficient every predetermined sampling time so as to minimize the evaluation function J _e .

Then, each filter in the adaptive filter 103 performs vector operation of the input synchronizing signals x and w _mi by the filter coefficient set at that time to obtain output values y ₁ and y ₂ , This value is used as a drive signal for D /
It outputs to the actuators 74a and 74b via the A converter 106, the low pass filter LPF 105, and the amplifier 108, respectively.

As a result, each actuator 74a,
Since 74b generates control vibrations according to the input signals y ₁ and y ₂ , the generated vibration output propagates on the bed corresponding to the transfer function c _lm estimated in advance and forms vibrations. Therefore, after the control is converged, the vibration in the local range on the bed of the arranged vibration sensor and the control vibration interfere with each other and are almost cancelled, and the residual vibration is significantly reduced. At this time, even if a change in vibration occurs due to the rotation of the motor, the change is reliably detected by the synchronization signal x, so that the above-mentioned vibration is reliably reduced.

The vibration sensor for vibration evaluation shown in FIG. 5 may move on the bed regardless of the fixed type.

In the above embodiment, the case where two actuators and two vibration sensors are provided as control vibration sources has been described. However, the invention is not necessarily limited to this. For example, three actuators and three vibration sensors may be used. A configuration can also be adopted.

[0062]

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 values of the plurality of vibration detection means, and the mutual interference transfer function set by the transfer function setting means, the detection values of each vibration detection means, that is, the vibrations at a plurality of points on the sewing machine main body are simultaneously detected. It is possible to activate a plurality of control vibration generating means for generating control vibration so as to minimize the vibration, and 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 an electrical control configuration of the present invention.

FIG. 2 is a configuration diagram of a circuit that generates a synchronization signal.

FIG. 3 is a block diagram showing a configuration of a vibration control system.

FIG. 4 is a schematic configuration diagram showing an embodiment.

FIG. 5 is an internal configuration diagram of a sewing machine main body according to the present invention.

FIG. 6 is an external view of a sewing machine.

FIG. 7 is an internal configuration diagram of a conventional sewing machine main body.

[Explanation of symbols]

 31 upper shaft 60 synchronization signal detecting device 74 piezoelectric actuator 76 spring 78 weight 80 control box 82 vibration detection sensor 101 control unit

Claims (3)

[Claims] 1. A synchronization signal generating means for generating a synchronization signal in synchronization with the rotation of the upper shaft of the sewing machine, and vibration generated at a plurality of points on the main body of the sewing machine due to the rotation of the upper shaft and the vertical reciprocating motion of the needle bar. A plurality of vibration detection means for detecting at the same time, a plurality of control vibration generating means capable of generating a control vibration for canceling the vibration generated at a plurality of locations on the sewing machine main body at the same time, for the mechanical system parts and control of the sewing machine Transfer function setting means for presetting a transfer function indicating characteristics of electric parts or mutual interference characteristics, a synchronization signal generated from the synchronization signal generating means, a transfer function set by the transfer function setting means, and each of the vibration detections. A plurality of vibration control means for controlling each of the control vibration generating means based on a plurality of detection signals detected by the means so that the plurality of vibrations detected by each of the vibration detecting means are simultaneously minimized; Vibration control device of the sewing machine, characterized in that it includes. 2. The vibration control device for a sewing machine according to claim 1, wherein the synchronization signal generating means, each vibration detecting means and each control vibration generating means are provided in a bed portion of the sewing machine main body. 3. The synchronizing signal generating means is supported on the upper surface of the bed portion, while the respective control vibration generating means are respectively a lower surface of the bed portion and a weight elastically urged toward the lower surface thereof. The vibration control device for a sewing machine according to claim 2, wherein the vibration control device is press-fitted between the two.