JPH03275918A - Active muffler system for sound-arresting exhaust sound of internal combustion engine - Google Patents

Abstract

PURPOSE:To simplify circuit constitution and improve reliability by installing a pressure wave generating means which is driven by the output of an A.C. power generator which generates the A.C. voltage having a plurality of explo sion order components corresponding to the number of times of explosion of an engine and generates the pressure wave for sound-arresting the exhaust sound in an exhaust pipe. CONSTITUTION:An A.C. power generator 3 which is connected with the rotary shaft 2 of an engine 1 and revolves in synchronization with the engine 1 and generates the A.C. voltage having a plurality of explosion order components corresponding to the number of times of explosion of the engine 1 is installed. Then, a pressure wave generating means 5 is driven by the output of the A.C. power generator 3, and the pressure waves are generated, and the exhaust sound of an exhaust pipe 6 is sound-arrested.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a system for muffling the exhaust noise of an internal combustion engine, and more particularly to an active muffling system without a feedback loop.

[Conventional technology]

As shown in Fig. 3, the active silencing system that muffles the exhaust noise of an internal combustion engine generates pressure waves inside the device that are in opposite phase and have the same sound pressure as the exhaust pressure waves detected by a microphone 3 installed in the exhaust pipe 2 of the engine 1. is calculated and generated electronically, and output into the exhaust pipe to mute the sound by interference between both pressure waves.Another microphone 4 detects the muted state, feeds it back to the electronic circuit 5 of the device, makes corrections, and outputs the sound to the speaker 6. It was outputting from. The electronic circuit 5 includes an arithmetic circuit that performs calculations so that the residual error detected by the microphone 4 is small, and an amplification circuit that drives the speaker 6.

In the prior art shown in FIG. 3 above, there is an adverse effect due to the feedback of additional sound from the speaker 6 to the microphone 3, so in order to counteract this adverse effect, an active noise reduction system is also available in which a second speaker 7 is provided as shown in FIG. It is well known (for example, see Japanese Patent Laid-Open No. 1156/1983).

These conventional technologies use repeated feedback to track changes in exhaust sound due to changes in engine operating conditions and perform a muffling effect, reducing the exhaust pressure loss, reflected waves, standing waves, and smoothness of muffler-type exhaust systems. It has the advantage of being free from disadvantages such as efficiency.

(Problem to be solved by the invention) In an internal combustion engine such as an automobile engine, the operating conditions such as rotation speed and load change from moment to moment, and there is almost no steady state.
According to the above-mentioned active silencing system using feedback, the time lag of the feedback system adversely affects the followability of the active silencing system. The factors contributing to the time lag are the distance A from the engine 1 to the first microphone 3, the distance B between both microphones 3 and 4, and the calculation processing speed of the electronic circuit 5. Furthermore, due to the structure of the speaker, an active silencing system using such feedback cannot deal with high frequency components.

In order to improve the followability and accuracy of the feedback system, it is necessary to increase the adaptive processing speed, which makes the equipment more complex and sophisticated, which leads to a vicious cycle in which the time lag of the equipment is exacerbated, resulting in decreased reliability and There was a problem of increased costs.

In view of the above, it is an object of the present invention to provide an active silencing system that does not have the above-mentioned disadvantages found in feedback systems.

[Means to solve the problem]

In order to achieve the above object, an active silencing system for silencing the exhaust noise of an internal combustion engine according to the present invention provides a
an alternating current generator (3) connected to the rotating shaft (2) of the engine (1), which rotates in synchronization with the engine (1) and generates alternating voltage of a plurality of explosion order components corresponding to the number of explosions of the engine (1);
It is equipped with a pressure wave generating means (5) which is driven by the output of the alternator and generates a pressure wave that cancels out the exhaust noise from the exhaust pipe.

The second invention is AC power generation 1! (3) and the pressure wave generating means (5) is provided with an operating circuit (8) that operates the power and phase for each explosion order component, and also operates the operating circuit according to the engine speed and throttle opening. configured to control.

In the third invention, the phase is further controlled for each explosion order component in accordance with the exhaust temperature.

[Operation] The alternator rotates in synchronization with the engine and generates alternating current voltages of multiple explosion order components. This alternating current voltage drives the pressure wave generating means to generate pressure waves and cancel out the exhaust noise.

In the second aspect of the invention, the power and phase applied to the pressure wave generating means are controlled by the operating circuit for each explosion order component in accordance with the engine rotational speed and throttle opening degree, thereby performing fine noise reduction.

In the third invention, the phase is further manipulated in accordance with the exhaust temperature, so that it is possible to muffle the exhaust sound more precisely in accordance with the change in the sound speed of the exhaust sound due to the temperature change.

"Embodiment" In the embodiment shown in FIGS. 1(a) to (C), 1 is an engine, 2 is its rotating shaft, 3 is an alternator, and a toothed belt 4
The rotating shaft 2 and the alternator are connected to each other so as not to deviate in timing, and the alternating current generator 3 rotates in synchronization with the engine. The alternating current generator 3 includes a first generator 3a that generates a sine wave alternating current of the same frequency in synchronization with the explosion pulse of the engine 1, and a second generator 3b that generates a sine wave alternating current of twice the frequency. and a third generator 3c that generates a sine wave alternating current of three times the frequency are arranged in tandem and integrated as shown in Fig. 1).

The rotors of these three generators are arranged on one rotating shaft. Stator coils 3a', 3b', and 3c+ of these three generators 3a, 3b, and 3c generate alternating current voltages having frequencies of primary, secondary, and tertiary explosion order components, respectively. 5 is a pressure wave generating means such as a speaker or a piston horn, which is connected in series with the three stator coils 3a'+3b' and 3c' of the alternator 3, and the generated pressure wave is transmitted to the exhaust pipe (6). It is attached to the exhaust pipe so that it can be injected. Since the phase of the exhaust sound in the exhaust pipe 6 is delayed in accordance with the time it takes to transmit from the engine 1 to the installation position of the pressure wave generating means 5, the phase of the pressure wave injected from the pressure wave generating means 5 into the exhaust pipe is Taking this into consideration, it is necessary to make the phase opposite to each order component of the exhaust sound by 180 degrees, and in order to satisfy this phase condition, the generators 3a, 3b, 3c are
The generated voltage is determined. Specifically, the generators 3a, 3b, 3c is selected, and the angular position of, for example, the rotor or stator of each generator is determined so as to generate the AC voltage of that phase.

For example, if engine 1 has 6 cylinders and 4 cycles,
When the rotation speed is 3,000 r, p, m, the number of explosions is 1.
That's 9,000 times per minute. Therefore, the frequency of one blow component is 100 Hz, the frequency of two blow components is 200 Hz, and the frequency of three blow components is 300 Hz.

Reference numeral 7 denotes a sub-muffler installed downstream of the exhaust pipe 6, which removes high-frequency components unsuitable for generating electricity with the alternator 3 (for example, LKH
A well-known sub-muffler using a sound-absorbing material such as glass wool is used to muffle the sound of noise (above z) with this sub-muffler. Low frequency components are muted by a combination of an alternator 3 and a pressure wave generating means 5.

In the above embodiment, since the alternating current voltage of each order of the alternator 3 is proportional to the engine rotation speed, the pressure wave converting means 5
The power of the pressure waves injected into the exhaust pipe 6 from the exhaust pipe 6 (in the opposite phase to the exhaust sound) increases as the engine speed increases, which is advantageous for muffling the exhaust sound.

In the embodiment shown in FIGS. 2(a) and 2(b), an operating circuit 8 for controlling the power and phase for each explosion order component is provided between the alternator 3 and the pressure wave generating means 5, and the engine is rotated. The power and phase are controlled according to the engine speed, throttle opening, and exhaust temperature. A delay circuit can be used to manipulate the phase. 9 is the throttle opening sensor, 10! ,
? This is an exhaust temperature sensor.

The operation circuit 8 is an adjustment circuit 8a that adjusts the power and phase supplied from the primary, secondary, and tertiary stator coils 3a'+3b'', 30° of the alternating current generator 3 to the pressure wave generating means 5.
and a control circuit 8b that controls this adjustment circuit according to engine speed, throttle opening, and exhaust temperature. The control circuit 8b recognizes the rotational speed of the engine by inputting an alternating current signal from the stator coil 3a'. The control circuit 8b controls the adjustment circuit 8a based on the functional relationship between the engine speed, throttle opening, exhaust temperature, and the power and phase of each order component. The functional relationship at this time is grasped in advance by analyzing the engine exhaust sound using a tracking analyzer, etc.
By incorporating the function into the program of the control circuit 8b, it can be easily utilized. In this second embodiment, one phase of the electric power of each order component is controlled according to the rotational speed, throttle opening degree, and exhaust temperature, so that exhaust noise can be muffled more precisely.

In the embodiment shown in FIGS. 2(a) and 2(b), high-frequency components are also muffled by the sub-muffler 7, and low-frequency components are muffled by the alternator 3.
An active silencing system consisting of a pressure wave generating means 5 and an operating circuit 8 is responsible for this.

〔Effect of the invention〕

Since the present invention is configured as described above and does not have a feed bank loop, it is possible to realize an active silencing system with a simple circuit configuration, low cost, and high reliability. Furthermore, since there is no need for a microphone that has drawbacks in terms of characteristic correction for heat and deterioration due to heat, costs and reliability can be improved in this respect as well.

[Brief explanation of the drawing]

Figures 1 (a), (b), and (C) show the first embodiment of the present invention, in which (a) is an overall schematic diagram of the system, (i) is a perspective view of the alternator, and (C) is an electrical circuit diagram. , FIGS. 2(a) and 2(b) show a second embodiment of the present invention, and FIG. 2(a) is an overall schematic diagram of the system.
ω) is a schematic diagram of an electric circuit, and FIGS. 3 and 4 are overall schematic diagrams of different prior art systems. 1...engine, 2...rotating shaft, 3...alternator, 3a'+3b', 3c'...stator coil, 4...toothed belt, 5...pressure wave generation means, 6...exhaust pipe, 7...submuffler, 8...operation circuit, 9...throttle opening sensor, 10...exhaust temperature sensor

Claims (1)

[Claims] 1. An alternating current of a plurality of explosion order components that is connected to the rotating shaft (2) of the engine (1) and rotates in synchronization with the engine (1), and that corresponds to the number of explosions of the engine (1). Exhaust sound of an internal combustion engine comprising an alternator (3) that generates voltage and a pressure wave generating means (5) that is driven by the output of the alternator and generates a pressure wave that cancels the exhaust noise of the exhaust pipe. Active sound deadening system. 2. An operating circuit (8) is provided between the alternating current generator (3) and the pressure wave generating means (5) to control the power and phase for each explosion order component, and also to control the engine speed and throttle opening. 2. The active noise reduction system for suppressing exhaust noise of an internal combustion engine according to claim 1, wherein the active noise reduction system is configured to control the operating circuit in accordance with the above. 3. An active silencing system for silencing the exhaust noise of an internal combustion engine according to claim 2, wherein the active silencing system is configured to manipulate the phase for each explosion order component in accordance with the exhaust temperature. 4. The active sound silencing system according to claim 1, 2 or 3 is used in an exhaust system in which a sub-muffler (7) for high frequency attenuation made of a sound absorbing material such as glass wool is installed to perform the silencing of relatively low frequency components. Active noise reduction system that suppresses exhaust noise from internal combustion engines.