JPH07227489A - Vibration proofing device for sewing machine - Google Patents

Abstract

PURPOSE:To sufficiently reduce the vibrations and noises in the arm of a sewing machine frame. CONSTITUTION:A dynamic vibration absorber 60 is attached to the top end part of an arm 30a of a sewing machine frame 30. That dynamic vibration absorber 60 is composed of a coil spring 60b having the vertical axial line of a coil, and a weight 60a having fixed weight. The coil spring 60b is linked in the state of being supported inside the arm 30a at one upper side end part thereof and of hanging the weight 60a at the other lower side end part. Therefore, when the vibrations or the like are applied to that dynamic vibration absorber 60, the weight 60a is vertically fluctuated while vertically bending the coil spring 60b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration preventing device for a sewing machine, which damps vibrations generated in the arm of a sewing machine frame, especially when the sewing machine is operated.

[0002]

2. Description of the Related Art A sewing machine generally found in the past has a mechanism for reciprocating or swinging a needle bar 28, a balance 20, etc., as shown in FIG. Further, it has at least one motor 10 as a drive source for driving the needle bar 28 and other mechanisms. A timing belt 12 is provided between the drive shaft of the motor 10 and the upper pulley 14.
Is stretched. Further, the upper shaft pulley 14 is fixed to the right end of the upper shaft 16, and the timing belt 1
By the driving force transmitted by 2, it can rotate together with the upper shaft 16.

Further, the upper shaft 16 is rotatably attached to a frame 30 shown in FIG. A balance crank 18 is fixed to the left end of the upper shaft 16 as shown in FIG. 6, and the balance crank 18 has
One end of the balance 20 is rotatably attached. Further, the balance crank 18 has a needle bar crank 2
2 is fixed, and one end of a connecting rod 24 is rotatably attached to the needle bar crank 22. A needle bar holder 26 is rotatably attached to the other end of the connecting rod 24, and a needle bar 28 is fixed to the needle bar holder 26.

In the above structure, when the motor 10 is started, its power is transmitted by the transmission belt 12 and the upper pulley 1.
4, upper shaft 16, balance crank 18, needle bar crank 22,
It is transmitted to the needle bar 28 via the connecting rod 24 and the needle bar holder 26, whereby the needle bar 28 reciprocates in the vertical direction. Further, the rotation of the upper shaft 16 is transmitted to the balance 20 via the balance crank 18, and the balance 20 reciprocally swings up and down.

The inertial force due to the reciprocating and swinging motions of the respective mechanisms becomes a vibrating force for vibrating the sewing machine frame 30 via the bearing of the upper shaft 16, and vibration and noise are generated in the arm 30a of the sewing machine frame 30. Had occurred.

In order to reduce the vibration and noise, in the conventional sewing machine, the balance crank 18 is provided with an unbalance amount corresponding to the inertial force, and acts as an eccentric weight to balance the inertial force. You can see what you did.

[0007]

However, the round trip,
It is theoretically impossible to perfectly balance the inertial force due to the oscillating motion by the eccentric weight, and when the sewing machine is operated at a high speed, a large vibration force is generated on the upper shaft 16. . Further, the sewing machine frame 30 is manufactured in a structure as shown in FIG. 7, and because of its structure, the resonance of the mode in which the arm 30a vibrates in the vertical or front-back direction has an eigenvalue at a relatively low frequency. For example, when an operating sewing machine has a wide range of rotational speeds, it is generally difficult to avoid resonance. For this reason, in the conventional sewing machine, when operating at a high speed, resonance occurs in the arm 30a, and vibration and noise increase, which causes the user to feel uncomfortable.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a vibration preventing device for a sewing machine, which can sufficiently reduce the vibration and noise of the arm of the sewing machine frame. It is a thing.

[0009]

To achieve this object, in the vibration preventing device for a sewing machine of the present invention, the tip end portion of the arm of the sewing machine frame is provided with a natural frequency substantially equal to the natural frequency of the arm. It has a dynamic vibration absorbing means.

The dynamic vibration absorbing means can be composed of an elastic body which is elastically displaceable at least in the vertical direction and a weight which is connected to the elastic body.

Further, the elastic body is constituted by a coil spring whose coil axis is vertical, and one of the upper and lower ends of the coil spring is supported by the arm and the other end is connected to the weight. It may be configured.

Further, the elastic body is constituted by an elastic beam having a base end supported by the arm, a tip protruding substantially horizontally, and elastically displaceable in a direction orthogonal to the protruding direction. The weight may be connected to the tip of the elastic beam.

[0013]

According to the vibration preventing device for a sewing machine of the present invention having the above-mentioned structure, when the sewing machine is operated at a rotation frequency close to the natural frequency of the arm, a natural frequency almost equal to the natural frequency of the arm is generated. The dynamic vibration absorbing means that it has damps the resonance of the arm in the vertical and longitudinal directions. This significantly reduces the vibration of the arm and consequently also the noise radiated by the arm.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment embodying the present invention will be described with reference to FIGS.

In FIG. 1, an arm 30a of the sewing machine includes a needle bar mechanism, a balance mechanism and an upper shaft 16 for driving them.
Etc. are provided. The upper shaft 16 includes a pair of left and right bearings 44.
Is rotatably supported by a motor 10 via a timing belt 12 hung on a pulley 14 at one end thereof.
It is designed to be driven to rotate by. The upper shaft 16
Rotation of the lower shaft 48 via the connecting rod 46.
And the inner hook 50 is driven.
The lower shaft 48, the inner hook 50, and the like are provided inside the lower bed 30b. The arm 30a and the bed 30b form a sewing machine frame 30.

A dynamic vibration reducer 60 as a dynamic vibration absorbing means is provided at the tip of the arm 30a. The dynamic vibration reducer 60 includes a coil spring (elastic body) 60b whose coil axis is in the vertical direction, and a weight 60a having a constant weight. One end of the coil spring 60b is supported inside the arm 30a, and the other end of the coil spring 60b is connected to the weight 60a in a suspended state. Therefore, if vibration or the like is applied to the dynamic vibration reducer 60, the coil spring 60b bends in the vertical direction and the weight 60a
Fluctuates vertically. In addition, the mass of the weight 60a is M,
When the spring constant of the coil spring 60b is K and the resonance frequency of the vertical bending of the arm 30a is Pa,

[0018]

[Equation 1]

The values of K and M are set so that

When the dynamic vibration reducer 60 is not provided, the rotation frequency of the upper shaft 16 or an integral multiple of the rotation frequency is the arm 30a.
When it is close to the vertical resonance frequency Pa, the arm 30a resonates and the arm tip vibrates greatly. In the sewing machine of this embodiment to which the dynamic vibration reducer 60 is attached,
The vertical resonance of the arm 30a is absorbed by the dynamic vibration absorber 60, and at the vertical resonance frequency Pa of the arm 30a, the vibration of the arm 30a is reduced and the noise is also reduced.

Now, the principle of the dynamic vibration reducer will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, when another system (m ₂ , k ₂ , c ₂ ) which is a dynamic vibration absorber is added to the main system (m ₁ , k ₁ , c ₁ ) that vibrates under the force of force, The equation of motion is expressed by the following equation.

[0022]

[Equation 2]

[0023]

[Equation 3]

The solutions of these simultaneous equations are as follows.

[0025]

[Equation 4]

[0026]

[Equation 5]

However,

[0028]

[Equation 6]

[0029]

[Equation 7]

[0030]

[Equation 8]

[0031]

[Equation 9]

[0032]

[Equation 10]

[0033]

[Equation 11]

[0034]

[Equation 12]

[0035]

[Equation 13]

[0036]

[Equation 14]

[0037]

[Equation 15]

[0038]

[Equation 16]

[0039]

[Equation 17]

Further, ω is the frequency of the exciting force acting on the main system m ₁ . Focusing on the amplitude of the main system m ₁ , m = 1/20,
When β _{1 is} 1.0 and h ₁ = 0.02, and X ₁ is calculated using h ₂ as a parameter, it becomes as shown in FIG. Even with a dynamic vibration absorber having a mass ratio of 1/20 of the main system, the coupling of the two significantly reduces the amplitude in the resonance region of the main system. The dynamic vibration reducer utilizes this principle.

FIG. 2 shows the relationship between the rotational speed of the sewing machine and the vertical vibration acceleration of the tip of the arm 30a. Without the dynamic vibration reducer 60, a large resonance occurs near the upper limit of the rotation speed of the sewing machine. When the dynamic vibration reducer 60 is attached, the resonance peak becomes smaller,
The frequency will also be lower.

By the way, as shown in FIG. 4, when the dynamic vibration reducer 60 is attached, there is a peak on both sides of the resonance frequency Pa, and resonance does not completely disappear. Therefore, the present invention works very effectively in the case where the resonance frequency is close to the upper limit of the rotation speed as shown in FIG. 2, but if not,
It is relatively easy to suppress the two peaks by adding appropriate damping to the dynamic vibration reducer 60.

In the dynamic vibration reducer 60 of this embodiment, the upper end of the coil spring 60b is supported by the arm 30a, and the weight 60a is connected to the lower end of the coil spring 60b.
The lower end of the weight may be supported by the arm 30a, and the weight 60a may be connected and supported by the upper end thereof. Also in this case, the same effect as the above can be obtained.

The second embodiment of the present invention will be described below with reference to FIG.

In the present embodiment, a dynamic vibration reducer 70, which is a dynamic vibration absorbing means composed of a spherical weight 70a and an elastic beam 70b, is attached inside the tip of the arm 30a. The elastic beam 70b has its base end fixed to the inside of the arm 30a, its tip protruding substantially horizontally to the left, and the weight 70a fixed to its tip. The tip of the elastic beam 70b to which the weight 70a is fixed can be elastically displaced in a direction orthogonal to the protruding direction. The spring constant of the elastic beam 70b is set so that the natural frequencies of the dynamic vibration reducer 70 in the up, down, front, and rear directions are close to the natural frequencies of the arms 30a in the respective directions. As a result, the vibration reducing effect can be obtained not only in the vertical direction of the arm 30a but also in the longitudinal resonance.

The present invention is not limited to the embodiments described in detail above, and various modifications can be made without departing from the spirit of the invention. For example, in each of the above-described embodiments, the case of translational vibration in the vertical and longitudinal directions has been described in detail, but the present invention is also applicable to the case of torsional vibration of the arm.

[0047]

As is apparent from the above description, according to the vibration preventing device for a sewing machine of the present invention, the vibration generated in the arm of the sewing machine frame and the noise caused by the vibration can be sufficiently reduced.

[Brief description of drawings]

FIG. 1 is a schematic view of a sewing machine according to a first embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the rotation speed of the sewing machine and the vertical acceleration level of the arm tip.

FIG. 3 is a model diagram showing a configuration of a dynamic vibration reducer.

FIG. 4 is a graph showing the effect of a dynamic vibration reducer.

FIG. 5 is a schematic view of a sewing machine according to a second embodiment of the present invention.

FIG. 6 is a mechanism diagram showing a needle bar mechanism, a balance mechanism, and the like of a conventional sewing machine.

FIG. 7 is a diagram showing a conventional sewing machine frame.

[Explanation of symbols]

 30 Sewing machine frame 30a Arm 60 Dynamic vibration absorber 60a Weight 60b Coil spring 70 Dynamic vibration absorber 70a Weight 70b Elastic beam

Claims (4)

[Claims] 1. A tip portion of an arm of a sewing machine frame,
A vibration preventing device for a sewing machine, comprising a dynamic vibration absorbing means having a natural frequency substantially equal to a natural frequency of the arm. 2. The dynamic vibration absorbing means comprises an elastic body that is elastically displaceable at least in the vertical direction and a weight connected to the elastic body.
The vibration prevention device for the sewing machine according to. 3. The elastic body is constituted by a coil spring whose coil axis is a vertical direction, and one of the upper and lower ends of the coil spring is supported by the arm and the other end is connected to the weight. The anti-vibration device for a sewing machine according to claim 2, wherein: 4. The elastic body is constituted by an elastic beam having a base end supported by the arm, a tip protruding substantially horizontally, and elastically displaceable in a direction orthogonal to the protruding direction. The vibration preventing device for a sewing machine according to claim 2, wherein the weight is connected to a tip portion of the elastic beam.