JPH06332467A - Muffling device for belt transmission part - Google Patents

Abstract

PURPOSE:To provide the compact muffling device for belt transmission part equipped with satisfactory sound absorbing performance for suppressing the external leakage of sounds generated by engaging a timing belt and a timing pulley. CONSTITUTION:This muffling device for belt transmission part can always present a high sound absorbing performance even when the rotating speed is changed, since a control means outputs a control signal to a pulse motor 20 while calculating the position of a shield panel 16 from the rotating speed of a timing pulley 4 detected by a tacometer 22 so that the frequency of the engaging sound of a timing belt 6 with the timing pulley 4 can be matched with the resonance frequency of porous panel structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silencer for a belt transmission section using a timing belt.

[0002]

2. Description of the Related Art Conventionally, a belt transmission unit is composed of a drive source such as a motor, a driven body such as a timing pulley, and a timing belt suspended between the two. The power from the drive source is transmitted through the timing belt to the timing pulley. Was to be transmitted to. Further, in the belt transmission part, in order to prevent the meshing sound of the timing belt and the timing pulley from leaking to the outside, the timing belt and the timing pulley may be covered with a sound deadening cover having a sound absorbing material stuck inside. there were.

Here, the frequency of the meshing sound between the two is expressed by the following equation.

[0004]

[Equation 1]

The noise level at the frequency Fm of the meshing sound becomes higher as the transmission energy is larger, and all the meshing sounds generated at the individual teeth are in synchronism, so that harmonics with respect to the meshing frequency Fm are likely to occur. It was

[0006]

However, in the conventional sound deadening device for the belt transmission section as described above, in order to increase the sound absorbing performance of the sound absorbing material, the sound absorbing material is thickened, or
Alternatively, since it is necessary to take a large amount of air layer behind the sound absorbing material, the sound deadening cover becomes large in size, which not only increases cost, but also impairs the original function of the product.

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to provide a silencer for a belt transmission section which is small in size and has excellent sound absorbing performance.

[0008]

To achieve this object, a muffler for a belt transmission according to the present invention suppresses the sound generated between a meshing timing belt and a timing pulley from leaking to the outside. A silencer for a belt transmission, comprising a cover configured to cover the timing belt and the timing pulley, a perforated plate having a large number of holes disposed inside the cover, and the perforated plate. A shield plate that forms an air layer behind the plate, an actuator that moves the shield plate to change the thickness of the air layer, a rotation speed detection unit that detects the rotation speed of the timing pulley, and And a control means for controlling the actuator by calculating the movement amount of the shielding plate from the output signal of the rotation speed detection means.

[0009]

According to the muffler of the belt transmission section of the present invention having the above-described structure, since the air layer is formed behind the perforated plate by the shielding plate, when the sound is incident, the air in the hole is blown. Starts to vibrate according to the frequency of sound, and energy is lost due to friction between the hole and the tube wall, and the sound is absorbed.
In particular, the absorption efficiency becomes very high when the resonance frequency determined by the thickness of the air layer, the plate thickness of the perforated plate, the hole diameter, and the aperture ratio coincides with the frequency of the incident sound. Since the shield plate is moved by the actuator and the thickness of the air layer can be changed, the resonance frequency of the perforated plate sound absorbing structure can be changed.

On the other hand, the frequency of the meshing sound between the timing belt and the timing pulley changes depending on the number of rotations of the timing pulley as expressed by the equation (1).

The control means calculates the position of the shield plate from the rotation speed of the timing pulley detected by the rotation speed detection means so that the resonance frequency of the perforated plate structure and the frequency of the meshing sound match, and a control signal is sent to the actuator. By outputting, the control is performed so that the sound absorption performance is always high even if the rotation speed changes.

[0012]

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

As shown in FIGS. 1 and 2, the belt transmission portion provided with the muffler in this embodiment rotates a drive pulley (not shown) axially mounted on a drive motor (not shown) which is a drive source. In order to transmit the rotation of the driven pulley 4 mounted on the shaft 2 to the rotary shaft 2,
It is composed of a timing belt 6 suspended between a drive pulley and a driven pulley 4, and further covers 8 and 10 which are divided into left and right so as to cover the driven pulley 4 and the timing belt 6. Has been. Inside the cover 10, a guide groove 1 of a shield plate 16 described later is provided.
A protrusion 10a that fits with 6b is formed.

Inside the joint portion between the cover 8 and the cover 10, a perforated plate 12 having a large number of holes is disposed adjacent to the driven pulley 4, and the cover 10 is further provided.
A shield plate 16 for partitioning and forming an air layer 14 inside the cover 10 between the plate and the perforated plate 12 is provided inside. The shielding plate 16 has a female screw portion 16 at the center thereof.
Also, a is formed on the peripheral portion of the cover 10 and a guide groove 16b is formed on the peripheral portion thereof so as to be fitted with the protrusion 10a of the cover 10. Further, as shown in FIG. 1, the left end of the shield plate shaft 18 having a male screw portion 18a that meshes with the female screw portion 16a of the shield plate 16 is rotatably supported at the center of the perforated plate 12. The right end of the shield plate shaft 18 is connected to the drive shaft of a pulse motor 20 as an actuator. Therefore, as the pulse motor 20 rotates, the shield 16
Is movable in the left-right direction on the shield plate shaft 18, and thereby the thickness of the air layer 14 changes.

A tachometer 22 for detecting the number of revolutions of the driven pulley 4 is connected to the rotary shaft 2, and an output signal from the tachometer 22 is inputted to a control means 24 composed of a well-known microprocessor or the like. ing. The control means 24 calculates the amount of movement of the shield plate 16 based on the number of rotations of the driven pulley 4 and controls the amount of rotation of the pulse motor 20, whereby the number of rotations of the driven pulley 4 is controlled. The volume of the air layer 14 is set. Therefore, the cover 8, 10, the perforated plate 12, the shield plate 16, the shield plate shaft 18, the pulse motor 20, the tachometer 22, the control means 24, etc. of the present invention are used. A silencer is configured.

Next, the operation of the muffler for the belt transmission section constructed as described above will be briefly described. First, when the drive motor rotates, the drive pulley mounted on the drive motor rotates, and the rotational force is transmitted to the driven pulley 4 via the timing belt 6, whereby the rotary shaft 2 rotates. Here, the power is transmitted by the teeth of the driven pulley 4 and the timing belt 6 meshing with each other, but at this time, a meshing sound is generated at the frequency Fm expressed by the above-mentioned formula 1.

When this meshing sound enters the perforated plate 12, the air in the hole begins to vibrate according to the frequency of sound, and energy loss occurs due to friction with the tube wall of the hole.
Sound is absorbed. In particular, the resonance frequency F determined by the thickness of the air layer 14, the plate thickness of the perforated plate 12, the hole diameter, and the aperture ratio.
When 0 and the frequency of the incident sound match, the absorption efficiency is very high. The resonance frequency F0 of the perforated plate sound absorbing structure is obtained by the following equation.

[0018]

[Equation 2]

The aperture ratio h of the perforated plate 12 is calculated by the following equation.

[0020]

[Equation 3]

Therefore, the air layer 14 is adjusted so that the resonance frequency F0 of the perforated plate structure and the frequency Fm of the meshing sound coincide with each other.
If the thickness H is changed, the absorption efficiency is always increased even if the rotation speed changes.

In this embodiment, the male screw portion 1 of the shield plate shaft 18 is used.
8a and the female screw portion 16a of the shield plate 16 mesh with each other, and the protrusion 10a of the cover 10 and the guide groove 16b of the shield plate 16
Due to the fact that the shielding plate 16 is fitted, the shielding plate 16 slides as the shielding plate shaft 18 rotates, and the thickness of the air layer 14 changes. The control means 24 calculates the position of the shielding plate 16 such that F0 and the frequency Fm of the meshing sound match from the number of revolutions of the timing pulley detected by the tachometer 22, and outputs a control signal to the pulse motor 20.

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, although the present embodiment is applied to the driven pulley, it may be applied to the drive pulley. Further, in this embodiment, the pulse motor is used as the actuator, but other motors, solenoids,
The shield plate may be moved by a hydraulic cylinder or the like. Further, in this embodiment, no work is performed on the air layer,
A sound absorbing material may be applied to the air layer to reduce high-frequency meshing noise.

[0024]

As is clear from the above description, the silencer of the belt transmission device of the present invention meshes with the frequency of the meshing sound of the timing belt with the timing pulley and the resonance frequency of the perforated plate structure. As described above, the control means controls the position of the shielding plate based on the rotation speed of the timing pulley, so that high sound absorbing performance can always be exhibited even if the rotation speed changes.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a belt transmission device including a muffling device of the present invention.

FIG. 2 is a perspective view showing a main part thereof.

[Explanation of reference numerals] 6 timing belt 4 driven pulley 8, 10 cover 12 perforated plate 14 air layer 16 shield plate 20 pulse motor 22 tachometer 24 control means

Claims (1)

[Claims] 1. A silencer for a belt transmission unit for suppressing the sound generated between a meshing timing belt and a timing pulley from leaking to the outside, which is configured to cover the timing belt and the timing pulley. A cover, a perforated plate having a large number of holes arranged inside the cover, a shield plate forming an air layer behind the perforated plate, and a thickness for changing the thickness of the air layer An actuator that moves the shield plate; a rotation speed detection unit that detects the rotation speed of the timing pulley; and a control unit that controls the actuator by calculating the movement amount of the shield plate from the output signal of the rotation speed detection unit. A silencer for the belt transmission unit.