JPH07124361A - Sewing machine - Google Patents

Abstract

PURPOSE:To reduce vibration of a sewing machine by reducing a vertical 'exciting force following an up-down movement of a needle bar and also by solving a horizontal exciting force. CONSTITUTION:When an arm shaft 2 rotates. a needle bar 12 vertically reciprocates through a needle bar crank; at the same time, a first balancer 20 and a second balancer 26 rotate at equal velocity and in reverse to the rotation of the arm shaft 2. The needle bar crank 6 as well as both the balancers 20, 26 have their centers of gravity respectively at positions eccentric from the centers of rotation, and are fixed such that their centers of gravity are positioned right above (below) their centers of rotation when the needle bar 12 is at its lowest (top) point. By placing the rotation axes of the needle bar crank 6 as well as both the balancers 20, 26 respectively parallel and on the same plane, the centrifugal force of both the balancers 20, 26 and the inertia force of the needle bar 12 compensate each other, so that the vertical exciting force is reduced and the horizontal exciting force is not generated, and further, no inertia couple is caused around the arm shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine in which vibration generated by the vertical movement of a needle bar is reduced.

[0002]

2. Description of the Related Art Conventionally, in this type of sewing machine, FIG.
In order to cancel out the inertial force generated with the vertical movement of the needle bar 170, the centrifugal force of the needle bar crank 172, whose center of gravity is located eccentric from the axis of the upper shaft 174, is used as shown in FIG. Are known. This centrifugal force is the needle bar 1
When 70 is at the highest point or the lowest point, it works only in the vertical direction and cancels out the inertial force of the needle bar 170.
Also works horizontally when is between the highest and lowest points. Therefore, even if the eccentric mass of the needle bar crank 172 is determined so as to minimize the vertical and horizontal components of the force (excitation force) that acts on the sewing machine body and causes vibration, the force is sufficiently small. I won't.

Further, as a mechanism for reducing the vibrating force acting on the sewing machine main body to prevent the vibration, there is a practical use method, Sho 60-19277.
The vibration prevention mechanism described in Japanese Patent No. 4 is known. In the vibration prevention mechanism described in this publication, as shown in FIG. 4, an upper shaft 174 is rotatably supported by a sewing machine frame 176, and a needle bar crank 172 rotates on the upper shaft 174 together with the upper shaft 174. Is fixed as. Further, the connecting rod 17 is attached to the needle bar crank 172.
One end of 8 is rotatably supported, and a needle bar 170 is connected to the other end of the connecting rod 178. The needle bar 170 is supported so as to be vertically movable with respect to the sewing machine frame 176. . At this time, the needle bar crank 1
The center of gravity G1 of 72 is eccentric from the axis C1 of the upper shaft 174, and when the needle bar 170 is located at the lowest point, the needle bar crank 1
The center of gravity G1 of 72 is determined to be located right above the axis C1.

Further, the balancer shaft 1 is provided above the upper shaft 174.
80 is rotatably supported by the sewing machine frame 176. When the upper shaft 174 rotates, the balancer shaft 180 rotates via the gears 182a and 182b having the same number of teeth meshing with each other, and the balancer 184 fixed to the balancer shaft 180 also rotates. When the needle bar 170 is located at the lowest point, the center of gravity G4 of the balancer 184 causes the balancer shaft 18 to move.
It is determined to be located directly above the axis C4 of 0.

Next, the force acting on the upper shaft mechanism will be described with reference to FIGS. 4 and 5.

G1 is the center of gravity of the needle bar crank 172, and G2 is the needle bar 170, the needle bar holder 171, and the connecting rod 1.
It is the composite center of gravity of 78 and the mass of the needle bar crank 172 is M
1, the total mass of the needle bar, etc. is M2, the distance between the axis C1 and G1 of the upper shaft 174 is L1, and the axis C of the upper shaft 174 is C from the point of supporting the connecting rod 178 of the needle bar crank 172.
The distance to 1 is L2, the distance between the supporting points of the connecting rod 178 is L3, and the crank ratio is λ (= L2 / L3).
And Also, the mass of the balancer 184 is M4, and the distance between the axis C4 of the balancer shaft 180 and the center of gravity G4 of the balancer is L.
Set to 4.

When the upper shaft 174 of the sewing machine having the above structure is rotated at the rotational angular velocity ω, the sewing machine frame 176 is provided.
The horizontal and vertical exciting forces Fx and Fy acting on the main body of the sewing machine via the can be expressed by the following equations.

[0008]

[Equation 1]

[0009]

[Equation 2]

Here, M4 L4 = M1 L1, M2 L
If 2 = 2M1 L1, the following equation is obtained.

[0011]

[Equation 3]

[0012]

[Equation 4]

From these equations, it can be understood that the horizontal exciting force Fx can be theoretically set to 0 as compared with the case where the balancer 184 is not used. It should be noted that the smaller the crank ratio λ, the smaller the vertical exciting force Fy.

[0014]

However, as shown in FIG. 5, the above sewing machine has a horizontal sum of the centrifugal force of the balancer 184 and the centrifugal force of the needle bar crank 172 when θ = 90 °. Becomes 0, but both generate a force (inertial couple) Mz that tries to rotate about the upper axis.

[0015]

[Equation 5]

This L6 is the distance between the axis C1 of the upper shaft 174 and the axis C4 of the balancer 184. The sewing machine frame 176 is vibrated by the inertia couple, and vibration is generated.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to reduce the vertical direction exciting force, not to generate the horizontal direction exciting force, and to further rotate around the upper axis. The purpose of the present invention is to provide a sewing machine with reduced vibration by not generating the inertia couple.

[0018]

In order to achieve this object, the sewing machine of the present invention is one in which the needle bar reciprocates up and down by the rotation of the upper shaft, and at the same speed as the upper shaft and in the reverse direction. The center of gravity of the rotating first balancer and second balancer and the needle bar crank, the first balancer, and the second balancer when the needle bar is at the uppermost point are directly below the respective rotation centers, and the needle bar is at the lowest point. In some cases, the center of gravity of the needle bar crank, the first balancer, and the second balancer are arranged directly above their respective rotation centers, and they are arranged in parallel and on the same plane, respectively, and the needle bar crank, the first balancer, and And a rotating shaft of the second balancer.

[0019]

In the sewing machine of the present invention having the above-described structure, when the upper shaft rotates, the needle bar reciprocates up and down, and at the same time, the first balancer and the second balancer rotate at the same speed as the upper shaft and reversely rotate. Needle bar crank, the first balancer and the second
The rotation axes of the balancers are arranged in parallel and on the same plane, and when the needle bar is at the uppermost point, the center of gravity of the needle bar crank, the first balancer, and the second balancer are directly below the respective rotation centers, and the needle bar is Needle bar crank, when at the lowest point,
Since the center of gravity of the first balancer and the center of gravity of the second balancer are arranged directly above the respective rotation centers, the centrifugal force of the needle bar crank, both balancers, and the inertial force of the needle bar cancel each other out, and the horizontal direction The vertical direction exciting force is reduced without generating not only an exciting force but also an inertial couple about the upper axis.

[0020]

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

FIG. 1 is a perspective view of the upper shaft mechanism of the present invention.

The upper shaft 2 is rotatably attached to the sewing machine frame 4. A needle bar crank 6 is fixed to the left end of the upper shaft 2, one end of a connecting rod 8 is rotatably attached to the needle bar crank 6, and the other end of the connecting rod 8 holds the needle bar. 10 is rotatably attached, and a needle bar 12 is fixed to the needle bar holder 10. The needle bar 12 is supported so as to be vertically movable with respect to the sewing machine frame 4, and this mechanism causes the needle bar 12 to reciprocate up and down as the upper shaft 2 rotates. The needle bar crank 6 has a center of gravity G1 at a position eccentric from the axis C1 of the upper shaft 2 by a distance L1.

Further, a first balancer shaft 14 is rotatably attached to the sewing machine frame 4 so as to be parallel to the upper shaft 2, and is attached to the gear 16 fixed to the upper shaft 2 and the first balancer shaft 14. The rotation of the upper shaft 2 is transmitted to the first balancer shaft 14 by the meshing of the gear 18 formed therein. Since the gears 16 and 18 have the same number of teeth, the first balancer shaft 14 rotates at the same speed as the upper shaft 2 and in the opposite direction. A first balancer 20 having a center of gravity G2 is fixed to the first balancer shaft 14 at a position eccentric from the axis C2 by a distance L2.

Further, the second balancer shaft 2 is positioned so as to be parallel to and coplanar with the first balancer shaft 14 and the upper shaft 2.
2 is rotatably attached to the sewing machine frame 4, and a gear 16 fixed to the upper shaft 2 and a gear 24 fixed to the second balancer shaft 22 mesh with each other, whereby the rotation of the upper shaft 2 is prevented. It is transmitted to the shaft 22. Both gears 16, 24
The second balancer shaft 22 has the same number of teeth as the upper shaft 2
Rotates at the same speed and in the opposite direction. This second balancer shaft 2
2 has a center of gravity G at a position eccentric from the axis C3 by a distance L3.
The second balancer 26 having 3 is fixed.

Both balancers 20 and 26 have needle bar 12
Is at the lowest point, the centers of gravity G2 and G3 are located directly above the respective centers of rotation C2 and C3, and when the needle bar 12 is at the highest point, the centers of gravity G2 and G3 are located directly below the respective centers of rotation C2 and C3. Are fixed so that they are located.

Next, the force acting on the upper shaft mechanism will be described with reference to FIG.

G4 is a combined center of gravity of the needle bar 12, the needle bar holder 10 and the connecting rod 8. The mass of the needle bar crank 6 is M1, the mass of the first balancer 20 is M2, the second
The mass of the balancer 26 is M3, the total mass of the needle bar, etc. is M4,
The distance from the supporting point of the connecting rod 8 of the needle bar crank 6 to the axis C1 of the upper shaft 2 is L4, the distance between the supporting points of the connecting rod 8 is L5, and the crank ratio is λ.
(= L4 / L5). In addition, the horizontal distance between the axis C1 of the upper shaft 2 and the axis C2 of the first balancer shaft 14 is L
7. Let L8 be the horizontal distance from the axis C3 of the second balancer shaft 22.

When the upper shaft 2 of the sewing machine having the above structure is rotated at the rotational angular velocity ω, the horizontal and vertical exciting force F acting on the sewing machine body through the sewing machine frame 4 is applied.
x and Fy and the inertial couple Mz about the upper axis can be expressed by the following equations.

[0029]

[Equation 6]

[0030]

[Equation 7]

[0031]

[Equation 8]

Here, (M2 L2 + M3 L3) = M
1 L1, M4 L4 = 2 M1 L1, M2 L2 L7 =
If M3 L3 L8, then the following equation is obtained.

[0033]

[Equation 9]

[0034]

[Equation 10]

[0035]

[Equation 11]

As an example, M2 = M3, L2 = L3, M
The above equation holds even when 1 L1 = 2M2 L2 and L7 = L8.

From these equations, by decreasing the crank ratio λ, the vertical exciting force Fy is reduced, the horizontal exciting force Fx is not generated, and the inertia couple Mz about the upper axis is further reduced.
It turns out that does not occur. In this embodiment, the first balancer shaft 14 and the second balancer shaft 22 are provided on both ends of the upper shaft 2.
The couples are arranged so as to fit on the horizontal plane to eliminate the couple.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention. For example, in the above-described embodiment, the gear is used as a means for transmitting the rotation of the upper shaft to the balancer shaft, but a toothed belt may be used as another means.

In the present embodiment, the upper shaft 2, the first balancer shaft 14 and the second balancer shaft 22 are arranged so as to fit on a horizontal plane, but the three shafts 2, 14, 22 are in one plane. If it fits, the plane does not need to be a horizontal plane, and may be a plane inclined depending on the internal structure of the sewing machine.

In the present embodiment, the first balancer shaft 14 and the second balancer shaft 22 are arranged on both sides of the upper shaft 2 so as to fit on a horizontal plane to eliminate the couple. If it fits in the plane, an even number of intermediate gears may be provided in accordance with the internal structure of the sewing machine and the positions of the shafts 14 and 22 may be separated from the upper shaft 2.

In the present embodiment, the first balancer 20 and the gear 18 are fixed to the first balancer shaft 14, and the second balancer 26 and the gear 24 are fixed to the second balancer shaft 22, which are integrated. Although the gear and the balancer are integrally molded, the integrally molded product may be rotatably attached to the rotary shaft, and the rotary shaft may be fixed.

[0042]

As is apparent from the above description,
According to the sewing machine of the present invention, the vertical exciting force is reduced, the horizontal exciting force is not generated, and the inertia couple around the upper shaft is not generated. Therefore, the vibration is reduced, and the sewing machine is quiet and accurate. Is possible.

[Brief description of drawings]

FIG. 1 is a perspective view of an upper shaft mechanism of the present invention.

FIG. 2 is an explanatory diagram of a mechanical model of the upper shaft mechanism of the present invention.

FIG. 3 is a perspective view of an upper shaft mechanism of a conventional sewing machine.

FIG. 4 is a perspective view of an upper shaft mechanism of a conventional sewing machine.

FIG. 5 is an explanatory diagram of a mechanical model of an upper shaft mechanism of a conventional sewing machine.

[Explanation of symbols]

 2 Upper shaft 10 Needle bar 20 1st balancer 26 2nd balancer

Claims (1)

[Claims] 1. A sewing machine in which a needle bar reciprocates up and down by the rotation of an upper shaft, comprising a first and a second balancer rotating at a constant speed and in reverse with the upper shaft, the needle bar crank, and the first balancer. And the rotation axes of the second balancer are arranged in parallel and in the same plane,
When the needle bar is at the uppermost point, the needle bar crank, the first
When the center of gravity of the balancer and the second balancer are directly below the respective centers of rotation, and when the needle bar is at the lowest point, the centers of gravity of the needle bar crank, the first balancer and the second balancer are the centers of their respective centers of rotation. A sewing machine characterized in that it is arranged so as to be on the top.