JPH0777989A - Engine noise reduction device - Google Patents

Abstract

(57) [Summary] [Purpose] To reliably reduce engine noise. [Structure] An engine 1 is provided with a rotation speed detector 11 for detecting an engine rotation speed and a speaker 12 is attached thereto. The electronic control means 13 is the rotation speed detector 1 described above.
1 based on the rotation speed detection signal detected by the speaker 1.
2 is configured to output a secondary sound signal. Engine 1
During operation, the secondary sound having a phase opposite to the noise generated from the engine is generated from the speaker 12. Then, these two sounds overlap and cancel each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for reducing noise generated by an engine by the action of active noise reduction.

[0002]

2. Description of the Related Art The inventor of the present invention knows, as a conventional technique utilizing this type of active noise reduction, a technique of reducing the noise of a passenger car. This is a technology in which a microphone for detecting a squeaking noise is provided in the passenger compartment of a passenger car, and a muffling speaker is provided under the seat to generate a secondary sound having a phase opposite to the noise detected by the microphone from the speaker. Is.

[0003]

The above-mentioned prior art is excellent in that these two sounds can be canceled by superimposing the secondary sound of the speaker on the sound of the car interior. However, when trying to reduce the noise of the engine itself by using the above-mentioned conventional technique, there are the following problems.

The microphone receives not only engine noise but also noise such as reflected sound of the engine noise, so that the detection accuracy is poor. Further, the noise generated by the engine takes a little time to propagate to the microphone, so that the generation of the secondary sound is delayed accordingly. Therefore, the engine noise and the secondary sound are likely to be out of phase with each other, and the noise remains. Further, since the speaker is provided at a position distant from the engine, the place where the phases of the engine noise and the secondary sound overlap each other is limited. From the above, engine noise cannot be reliably reduced. An object of the present invention is to reliably reduce engine noise.

[0005]

In order to achieve the above object, the present invention provides a device for reducing engine noise, for example, as shown in FIG.
As shown in FIG. A rotation speed detector 11 for detecting the rotation speed of the engine 1, a secondary sound generator 12 for generating a sound having a phase opposite to the noise of the engine 1, and a rotation speed detection signal for the rotation speed detector 11 are provided. The secondary sound generator 12 is provided with the control means 13 for outputting a secondary sound signal to the secondary sound generator 12, and the secondary sound generator 12 is attached to the engine 1.

[0006]

The present invention operates as follows, for example, as shown in FIG. When the engine 1 is in operation, the control means 13
Based on the rotation speed detection signal of the rotation speed detector 11, for example, a secondary sound conversion signal having a phase opposite to the engine noise such as intake sound is output to the secondary sound generator 12 such as a speaker. Then, the secondary sound generator 12 generates a secondary sound for active silencing, and the secondary sound is propagated radially concentrically with the engine noise.

[0007]

The present invention has the following effects because it is configured and operates as described above. Unlike the conventional example, since the noise detecting microphone is not used, it is possible to prevent noise from being input to the control means. Further, since the secondary sound for active muffling is controlled by the engine speed, and there is almost no time delay in detecting the engine speed, the phase shift of the secondary sound can be prevented. Further, since the secondary sound generator is attached to the engine, the secondary sound and the engine noise can be superposed substantially concentrically. As described above, the engine noise can be surely reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.
The engine 1 is formed in a vertical shape, and has a cylinder block 3 on which a cylinder head 3 and a head cover 4 are mounted and fixed in order. Reference numeral 5 is a crankshaft, reference numeral 6 is a flywheel, and reference numeral 7 is an intake manifold.

A top dead center position detector 11 for detecting that a piston (not shown) in the cylinder block 2 has reached a top dead center position is opposed to the flywheel 6.
The top dead center position detector 11 can calculate the rotation speed of the crankshaft 5 by counting the number of times the piston reaches the top dead center position within a fixed time.

A speaker 12 for producing a sound having a phase opposite to the intake sound radiated from the intake manifold 7 is attached to the engine 1 so as to face the intake manifold 7 above. The speaker 12 constitutes a secondary sound generator. Electronic control means 13 is provided for outputting a secondary sound signal to the speaker 12 based on the rotation speed detection signal detected by the top dead center position detector 11. This control means 1
Reference numeral 3 denotes a secondary sound converter 14 and a power amplifier 1 that output a waveform having a phase opposite to that of the intake noise according to the rotation speed detection signal.
5 and 5.

The above embodiment can be modified as follows. An engine load detecting means for detecting the temperature of the engine cooling water or the exhaust gas temperature of the engine 1 is provided,
The secondary sound signal is output to the speaker 12 based on the load detection signal of the load detection means and the rotation speed detection signal of the top dead center position detector 11. According to this configuration, the operating state of the engine can be grasped in multiple ways, so that the engine noise can be reduced more reliably according to the operating state.

As the engine speed, the speed of the crankshaft 5 may be directly detected. The secondary sound converter 14 may output a waveform having an opposite phase with respect to other types of noise such as exhaust sound. The speaker 12 may be attached to the cylinder block 2 or the head cover 4. The secondary sound generator is not limited to the speaker, but may be another type of sound generator.

[Brief description of drawings]

FIG. 1 is a control block diagram of an engine noise reduction device according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 11 ... Rotation speed detector (top dead center position detector), 12 ... Secondary sound generator (speaker), 13 ... Control means, 14 ... Secondary sound converter, 15 ... Amplifier.

Claims (2)

[Claims] 1. A rotation speed detector (11) for detecting the rotation speed of the engine (1), and a secondary sound generator (12) for generating a sound having a phase opposite to the noise of the engine (1). And a control means (13) for outputting a secondary sound signal to the secondary sound generator (12) based on the rotation speed detection signal of the rotation speed detector (11). A device for reducing engine noise, characterized in that a device (12) is attached to the engine (1). 2. The engine noise reducing device according to claim 1, further comprising a load detecting means for detecting a load of the engine (1), wherein the control means (13) controls the load of the load detecting means. A structure capable of outputting the secondary sound signal based on the detection signal and the rotation speed detection signal of the rotation speed detector (11).