JPH05157138A - Torque fluctuation reducing mechanism - Google Patents

Abstract

PURPOSE:To reduce production of a fluctuation in torque exerted on an upper shaft by a method wherein planetary gears arranged symmetrically about the upper shaft are revolved and rotated around the upper shaft through rotation of the upper shaft and torque is generated by means of a centrifugal force exerted on an eccentric mass attached to the planetary gear. CONSTITUTION:A rotary arm 11 is rotated through rotation of an upper shaft 20 and planetary gears 12 and 12' are revolve around an upper shaft 10 through a rotary arm 11. Further, the planetary gears 12 and 12' are arranged concentrically to the shaft 20 and also rotated to be geared with a fixed gear 10 fixed to a machine frame. Since eccentric masses 13 and 13' are arranged symmetrically about the rotation center of the upper shaft 20, torque is exerted on the rotary arm 11 by means of an inertia force generated through acceleration movement of the eccentric mass. By changing a ratio between the radii of the pitch circles of the gears 10 and 12, the frequency of generated torque is changed and the magnitude of torque is regulatable by means of the masses of the eccentric masses 13 and 13' and an eccentric amount of the eccentric mass 13. This mechanism erases torque of the upper shaft 20 generated by an inertia force with torque generated by the mechanism.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque fluctuation reducing mechanism for a shaft of a rotary machine.

[0002]

2. Description of the Related Art Conventionally, for example, an upper shaft mechanism of a sewing machine is shown in FIG.
As shown in FIG. 3, the needle bar 22 includes a needle bar mechanism, a needle bar crank rod 24, a needle bar crank 25, and a balance mechanism composed of a balance 27, a balance support 28, and a balance crank 29. The torque acting on the upper shaft 20 fluctuates as shown in FIG. 7 due to the inertial force accompanying the reciprocating motion of the balance 27. The horizontal axis represents the upper axis rotation angle with the needle bar highest point as a reference. From this figure, it can be seen that the torque largely fluctuates before and after the lowest point of the needle bar (rotational angle 180 °). Also,
It can also be seen that the torque fluctuation of the upper shaft 20 of the sewing machine can be represented mainly by a combination of two times and three times the upper shaft rotation frequency. The load acting on the motor also fluctuates as the upper shaft torque fluctuates, so that vibration and noise generated from the motor increase.

As a device for reducing the torque fluctuation of the shaft, Japanese Patent Publication No. 2-14573 discloses a torque transmission gear driven by a rotating shaft and a shaft arranged by the torque transmission gear concentrically with the shaft. A ring gear that is rotationally driven in the opposite direction, a pair of rotating bodies that are pivotally supported by the ring gear so as to be symmetrically positioned with respect to the rotation center of the shaft, and that are rotationally driven by the shaft, and the pair of rotating bodies, respectively. A shaft type torsional vibration isolator has been proposed which is characterized by comprising an attached eccentric mass. This device uses a set of gear systems to control the rotation frequency of the shaft.

[0004]

[Equation 1]

The torque of (1) is damped. Here, R is the pitch circle radius of the main gear 32, r is the pitch circle radius of the rotating bodies 35 and 35 ', and x is the distance from the rotation centers c and c'of the rotating bodies 35 and 35' to the pitch circle q of the ring gear. .

[0006]

However, in order to use the above-mentioned device to absorb the torque that fluctuates at the frequency twice or three times the rotational frequency of the shaft, two gear devices are required. As a result, the number of parts is large and the device cannot be manufactured at low cost, and the size of the entire device is large, and it is difficult to store the device in a narrow space in the sewing machine frame.

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to realize a mechanism for reducing fluctuations in the axial torque of a rotary machine with a small number of parts.

[0008]

To achieve this object, a torque fluctuation reducing mechanism of the present invention comprises a fixed gear arranged concentrically with a shaft and fixed to a frame, and a rotary arm fixed to the shaft. , A set of planetary gears rotatably supported by the rotary arm, meshing with the fixed gear and symmetrically arranged with respect to the rotation center of the shaft, and an eccentric mass fixed to the planetary gear.

[0009]

In the torque fluctuation reducing mechanism of the present invention having the above-described structure, the rotation of the shaft causes the rotating arm fixed to the shaft to rotate, and the planetary gear rotatably supported by the rotating arm rotates about the shaft. Revolve around. Further, since the planetary gear is arranged concentrically with the shaft and meshes with a fixed gear fixed to the frame, the planetary gear also rotates.

[0010]

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

FIG. 1 shows an embodiment in which the torque fluctuation reducing mechanism of the present invention is added to the upper shaft mechanism of the sewing machine, and FIG. 2 shows a detailed view of the torque fluctuation reducing mechanism. The same members as those of the conventional technique are designated by the same reference numerals, and detailed description thereof will be omitted.

The upper shaft mechanism of the sewing machine comprises a needle bar mechanism composed of a needle bar 22, a needle bar crank rod 24 and a needle bar crank 25, and a balance mechanism composed of a balance 27, a balance support 28 and a balance crank 29. By rotating the upper shaft 20, the needle bar 22 and the balance 27 reciprocate.

The torque fluctuation reducing mechanism is arranged concentrically with the upper shaft 20, and has a fixed gear 10 fixed to the sewing machine frame 30, a rotating arm 11 fixed to the upper shaft 20, and a rotating arm 11. A set of planetary gears 12, 12 'which are freely supported, mesh with the fixed gear 10, and are symmetrically arranged with respect to the center of rotation of the upper shaft 20, and the planetary gears 12,
It consists of an eccentric mass 13, 13 'fixed to 12'.

The rotation of the upper shaft 20 causes the upper shaft 20 to rotate.
The rotating arm 11 fixed to the rotation rotates, and the planetary gears 12, 1 rotatably supported by the supporting shaft 14 with respect to the rotating arm 11.
2'revolves around the upper shaft 10. Furthermore, the planetary gears 12,
The reference numeral 12 ′ is arranged concentrically with the shaft 20 and meshes with the fixed gear 10 fixed to the sewing machine frame 30 so that it also rotates.

The torque generated by the torque fluctuation reducing mechanism constructed as described above will be described with reference to FIG. The position of the center of gravity of the eccentric mass 13 is represented by coordinate values (X, Y) in an XY coordinate system fixed in space with the upper axis as the origin.

[0016]

[Equation 2]

[0017] Here, Θ: rotation angle of the upper shaft 20 θ: rotation angle of the planetary gear 12 with respect to the rotating arm 11 α: angle of the planetary gear 12 with respect to the rotating arm 11 at the initial position (Θ = 0) R: of the fixed gear 11 Pitch circle radius r: Pitch circle radius of the planetary gear 12 e: Eccentricity of the eccentric mass 13. Next, with the axis of the upper shaft as the origin, x fixed to the upper shaft
Acceleration of the center of gravity of the eccentric mass 13 in the -y coordinate system (a _x, a _y) is expressed by the following equation.

[0018]

[Equation 3]

Where Ω: rotational angular velocity of the upper shaft 20, Ω = dΘ / dt n: ratio of pitch circle radii of the fixed gear 11 and the planetary gear 12,
n = R / r. Since the eccentric masses 13 and 13 'are arranged symmetrically with respect to the center of rotation of the upper shaft 20, the component in the x direction is canceled out and the component in the y direction is canceled out of the inertial force generated by the acceleration motion of the eccentric mass. Applies a couple to the rotating arm 11.
This couple T is expressed by the following equation.

[0020]

[Equation 4]

Here, m is the mass of the eccentric masses 13 and 13 '. As can be seen from the above equation, the frequency of the generated torque can be changed by changing the value of n. For example, if n = 2, the torque having a frequency twice the upper shaft rotation frequency is generated. Further, the magnitude of the torque can be adjusted by the values of m and e from the equation (6). By symmetrically arranging multiple sets of planetary gears with different pitch circle radii,
A single device can generate torque at multiple frequencies.

Values of R, n, e, m and eccentric mass 13, 1
By properly selecting the initial position α of 3 ′, the upper shaft torque generated by the inertial force associated with the reciprocating motion of the needle bar 22 and the balance 27 can be canceled by the torque generated by the mechanism described above.

As a second embodiment, a fixed gear 11 having a pitch circle radius R = 12 mm and a pitch circle radius r ₁ = 6 mm as shown in FIG.
Planet gears 15a, 15b, eccentric masses 16a, 16b with eccentricity e ₁ = 2 mm and mass m ₁ = 18 g, planetary gears 15c, 15d with pitch circle radius r ₂ = 4 mm, and eccentricity e ₂ =
FIG. 5 shows the analysis result of the fluctuation of the upper shaft torque when the upper shaft torque fluctuation reducing mechanism is configured using the eccentric masses 16c and 16d having the mass of ₂ mm and the mass m _{2 of} 12 g. The horizontal axis represents the upper shaft rotation angle from the needle bar uppermost point, and the vertical axis represents the upper shaft torque. The broken line shows the analysis result by the upper shaft mechanism without the torque fluctuation reducing device. The masses of the needle bar, needle bar crank, balance, and balance support used in the analysis are 54.5, 7.1, 11.1, and 5.
The rotation speed of the upper shaft is 1 g and the rotation speed is 710 rpm. In this example,
The difference between the maximum value and the minimum value of the upper shaft torque can be reduced from 21.5 kgfmm to 4.4 kgfmm without the torque fluctuation reducing mechanism, which is about 80% reduction.

[0024]

As is apparent from the above description, the torque fluctuation reducing mechanism of the present invention can significantly reduce the shaft torque fluctuation with a small number of parts.

[Brief description of drawings]

FIG. 1 is an upper shaft mechanism diagram of a sewing machine according to a first embodiment.

FIG. 2a is a front view of a torque fluctuation reducing mechanism according to the first embodiment. 2b is a side view of the torque fluctuation reducing mechanism according to the first embodiment. FIG.

FIG. 3 is an explanatory diagram used for calculating a generated torque according to the first embodiment.

FIG. 4 is a torque fluctuation reduction mechanism diagram of the second embodiment.

FIG. 5 is a diagram of results of upper shaft torque analysis of the second embodiment.

FIG. 6 is an upper shaft mechanism diagram of a conventional sewing machine.

FIG. 7 is a diagram showing a conventional upper shaft torque analysis result.

FIG. 8 is an explanatory diagram used to calculate an angular velocity of a rotating body of a conventional shaft type torsional vibration damper.

[Explanation of symbols]

 10 Fixed Gear 11 Rotating Arm 12, 12 'Planetary Gear 13, 13' Eccentric Mass 20 Upper Shaft 30 Sewing Machine Frame

Claims (1)

[Claims] 1. A fixed gear arranged concentrically with the shaft and fixed to a frame, a rotary arm fixed to the shaft, a rotary gear rotatably supported by the rotary arm and meshing with the fixed gear, A torque fluctuation reducing mechanism including a set of planetary gears arranged symmetrically with respect to a rotation center and an eccentric mass fixed to the planetary gears.