JPH06300121A - Noise suppressing cover for belt transmission device - Google Patents

Abstract

PURPOSE:To provide a noise suppressing cover for belt transmission device which is excellent in noise absorbing performance, low in cost, and small in size. CONSTITUTION:A noise suppressing cover 14 for belt transmission device is formed so that it covers a toothed belt 9 and a toothed pulley 8 meshed with each other to suppress noise caused between them from leaking to the outside. Also it is provided with a perforated plate 15, in which multiple holes are formed along the external periphery of the toothed belt 9 engaged with the toothed pulley 8, and a cavity part 16, which is formed on the outside of the perforated plate and connected to the holes, inside the cover. The resonance frequency produced by them is aligned to the frequency of noise produced between the toothed belt and the toothed pulley. Thus the engagement noise produced inside the cover enters from an intermediate wall to the cavity part, loses its energy by friction with the hole wall surfaces, etc., and absorbed, therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soundproof cover for a belt transmission using a toothed belt.

[0002]

2. Description of the Related Art Conventionally, a belt transmission device is composed of a drive source such as a motor, a driven body such as a toothed pulley, and a toothed belt suspended between the two. Was transmitted to the toothed pulley via the toothed belt.

Further, in the belt transmission device, a sound is generated due to the meshing of the toothed belt and the toothed pulley, which is generally generated when the both teeth collide with each other. The frequency f of the sound can be obtained by the formula f = number of pulley teeth × pulley rotation number / 60, but actually, a frequency nf (n: integer) that is an integral multiple thereof is also generated. FIG. 6 shows this example, and is a measurement result of frequency analysis of the meshing sound when the number of pulley teeth is 80 and the pulley rotation speed is 720 rpm. In the figure, (a)
Is the primary meshing frequency f = 80 × 720/60 = 96
It shows the sound of 0Hz, (b), (c), (d),
(E) is secondary (1920Hz) and tertiary (2880H)
z), fourth order (3840 Hz), and fifth order (4800 Hz) frequencies.

According to this, the meshing sound has a high-frequency component, which is a very offensive sound, thus impairing the working environment. Therefore, in order to eliminate this,
In some belt transmission devices, the toothed belt and the toothed pulley are covered with a sound deadening cover having a sound absorbing material attached inside in order to prevent the meshing sound from leaking to the outside.

[0005]

However, the sound deadening cover of the conventional belt transmission as described above has poor sound absorbing performance, and a method for improving it is to increase the thickness of the cover itself or the sound absorbing material. However, this not only increases the cost of the cover due to its large size, but also impairs the original function of the device.

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to provide an inexpensive muffler cover for a belt transmission which has a good sound absorbing performance, is inexpensive.

[0007]

In order to achieve this object, the sound deadening cover of the belt transmission according to the present invention suppresses the sound generated between the meshing toothed belt and the toothed pulley from leaking to the outside. In order to cover both of them, an intermediate wall having a large number of holes is formed inside the cover along the outer peripheral surface of the toothed belt that meshes with the toothed pulley, and an intermediate wall between them. It has a cavity formed outside the wall and communicates with the hole, and is configured so that the resonance frequency by them and the frequency of the sound generated between the toothed belt and the toothed pulley match. There is.

[0008]

In the muffler cover of the belt transmission device of the present invention having the above-described structure, the meshing sound generated therein enters through the hole of the intermediate wall into the hollow portion, and at that time, due to friction with the wall surface of the hole or the like. It is absorbed by causing energy loss.

[0009]

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

FIG. 1 is a diagram showing a mechanical structure of a main part of a sewing machine to which the present invention is applied. To explain the outline of the structure, a bearing 11 is provided in the machine frame of the sewing machine, and the bearing 11 is provided. A main shaft 3 is rotatably supported by. The balance crank 1 is fixed to one end of the main shaft 3, and the toothed pulley 8 is fixed to the other end. A toothed belt 9 is suspended between the toothed pulley 8 and a motor 10 which is a drive source. With the above configuration, as the motor 10 rotates, its power is transmitted to the toothed pulley 8 via the toothed belt 9 so that the main shaft 3 rotates.

Further, the toothed pulley 8 and the toothed belt 9 are provided with teeth at their engaging portions, and the motor 1
The driving force of 0 is sufficiently transmitted to the spindle 3. A crank pin (not shown) is provided on the balance crank 1.
Is fixed, and a balance 2 having a thread insertion hole for inserting an upper thread is rotatably connected to the crank pin. The balance 2 is rotatably connected to the other end of a link (not shown) whose one end is rotatably supported by the sewing machine frame. Thereby, the balance 2 is rotated along with the rotation of the main shaft 3.
The thread insertion hole of oscillates.

One end of a needle bar crank rod 4 is rotatably connected to the crank pin, and the other end of the needle bar crank rod 4 is rotatably connected to a needle bar 7. . The needle bar 7 is vertically movably supported by a bearing 12 provided on a needle bar base 6 supported by the machine frame. Then, in order to match the timing of the vertical reciprocating movement of the thread insertion hole of the balance 2 and the vertical reciprocating movement of the needle bar 7, the vertical plane including the axis of the needle bar 7 is set to the vertical plane including the axis of the main shaft 3. The needle bar 7 is arranged so as to be parallel with a sufficient distance in the horizontal direction. At the lower end of the needle bar 7, a needle 13 for penetrating a material to be sewn and performing sewing is supported.

FIG. 2 is an external view showing a state in which the sound deadening cover is mounted, and FIG. 3 is a sectional view around the sound deadening cover.

The sound deadening cover 14 which covers the periphery of the portion where the toothed pulley 8 and the toothed belt 9 mesh with each other has a perforated plate 15 and a cavity 16 formed behind it. The perforated plate 15 is provided along the outer peripheral surface of the toothed belt 9, and the hole portion faces the outer peripheral surface of the toothed belt 9. The cavity 16 is a cavity formed by being partitioned by the outer peripheral surface of the perforated plate 15 and the cover housing 17 portion, and communicates with the holes of the perforated plate 15.

With the above structure, when a sound is generated by meshing between the toothed pulley 8 and the toothed belt 9, the sound is incident on the perforated plate 15, and the air in the hole corresponds to the frequency of the sound. Vibration starts, which causes the air inside the cavity 16 behind to vibrate. In this case, energy loss occurs due to friction with the tube wall of the hole that can be regarded as a thin short tube, and sound is absorbed. At this time, the frequency of the meshing sound (fk)
Is the resonance frequency (f0) of the perforated plate sound absorbing structure of the cover 14 (the vibration system consisting of the perforated plate 15 and the cavity 16 behind).
When it coincides with, the energy loss increases and the sound absorption efficiency increases. Resonance frequency of the perforated plate sound absorbing structure (f
0) is calculated by the following equation.

[0016]

[Equation 1]

Here, c: sound velocity in air (m / s) t: plate thickness (m) d: hole diameter (m) H: cavity thickness (m) h: aperture ratio of perforated plate (Πd2 / 4W2) W: Hole spacing (m) Therefore, each dimension of the perforated plate sound absorbing structure (see FIG. 4) is determined so as to satisfy the condition of fk = f0. Figure 5
The cover 14 including the perforated plate sound absorbing structure is provided with the toothed pulley 8
It is the result of frequency analysis of the noise level of the sewing machine when the meshing portion between the toothed belt 9 and the toothed belt 9 is covered. According to this, it can be seen that there is no noise peak at the first meshing frequency (f) and its integral multiple, and the noise is absorbed by the cover 14.

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 cover 14 is composed of the perforated plate 15 and the hollow portion 16 behind, but it is also possible to fill the hollow portion with a sound absorbing material or the like. The sound absorption performance can be improved.

[0019]

As is clear from the above description, the soundproof cover of the belt transmission according to the present invention has the following structure:
Along the outer peripheral surface of the toothed belt that meshes with the toothed pulley, there is provided an intermediate wall having a large number of holes and a cavity formed outside the intermediate wall and communicating with the holes. Since the resonance frequency and the frequency of the sound generated between the toothed belt and the toothed pulley are configured to coincide with each other, the meshing sound generated in the cover is transmitted from the hole in the intermediate wall to the cavity. Since the light enters and is absorbed by the friction with the wall surface of the hole and the like, the sound absorption performance is better than before, and the cost and the size can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a power transmission mechanism of a sewing machine to which the present invention is applied.

FIG. 2 is a view showing a state in which a sound deadening cover is attached to the power transmission mechanism of the sewing machine shown in FIG.

FIG. 3 is a cross-sectional view showing a configuration around a sound deadening cover shown in FIG.

FIG. 4 is a diagram for explaining a sound absorbing structure of a sound deadening cover.

FIG. 5 is a frequency analysis diagram of noise absorbed by the sound deadening cover.

FIG. 6 is a frequency analysis diagram of noise generated from a conventional belt transmission device.

[Explanation of symbols]

 8 Toothed pulley 9 Toothed belt 10 Motor 14 Cover 15 Perforated plate 16 Cavity

Claims (1)

[Claims] 1. A sound deadening cover for a belt transmission, which is configured to cover both of the meshed toothed belt and the toothed pulley so as to prevent the sound generated between the toothed pulley and the toothed pulley from leaking to the outside. Has an intermediate wall formed with a number of holes along the outer peripheral surface of the toothed belt that meshes with the toothed pulley, and a cavity formed outside the intermediate wall and communicating with the holes. A soundproof cover for a belt transmission, characterized in that the resonance frequency by them and the frequency of the sound generated between the toothed belt and the toothed pulley are matched.