JPH02306842A - Device for reducing indoor stuffy noise - Google Patents

Abstract

PURPOSE:To reduce stuffy noise in consideration of engine load by synchronizing a sinusoidal wave signal with the rotation of an engine, and processing the sinusoidal wave signal on the basis of the phase control quantity and sound pressure control quantity preliminarily stored in response to a determined rotation order component and load. CONSTITUTION:A condition judging part 62 introduces a determined rotation order component forming a generation source of stuffy noise, its TDC, and an engine load from a sensor 4, and controls an oscillator 7 in such a manner that the sinusoidal wave signal generated from the oscillator 7 is synchronized with the determined rotation order component of the engine. Optimum phase control quantity phi and sound pressure control quantity G corresponding to the existing engine speed and engine load are selected and read from ROM 63. The above control quantities phi and G process the sinusoidal wave signal from the oscillator 7 synchronized with the engine rotation (TDC) in a phase control part 64 and a sound pressure control part 65, respectively, to delay the phase by the portion of a determined value, so that the sinusoidal wave signal is passed through a band-pass filter 66 with an original waveform as reducing sound pressure to the maximum extent.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a device for reducing muffled noise in a vehicle interior, and in particular actively reduces low-frequency muffled sound in a closed space such as a car that has a surrounding sound source. This relates to a device for

(Prior art) The muffled sound inside the cabin of a car is caused by the resonance phenomenon that occurs in the cabin, which forms a closed space, under certain conditions. It is thought that this is due to the ingredients.

The measures that were initially taken to reduce such muffled noise were passive, for example, adding '+t' to the engine system, which is the source of vibration, to improve the coupling rigidity and improving the transmission system. To counter this, each mount was tuned, the panel rigidity was increased for the sounding element inside the vehicle, and mass dampers, dynamic dampers, etc. were installed in the resonant parts as countermeasures against resonance.

Such aggressive measures lead to increased costs and heavy slippage, and their effects are not fully satisfactory.

For this reason, JP-A-48-82304 and JP-A-59
A device that can actively reduce muffled sound has been proposed in Japanese Patent No. 9699 and the like.

In particular, the latter Japanese Patent Application Laid-Open No. 59-9699 describes a four-cylinder vehicle in which muffled noise is a problem. Process the signal in various ways,
By separately adding sound from a speaker that is in the opposite phase to each frequency component (rotational order component) of the muffled sound observed at the driver's listening point in the vehicle and has the same magnitude as the muffled sound component, the interference effect can be improved. This reduces the muffled sound pressure level at the listening point.

[Problem to be solved by the invention]

In the above conventional example, since the information stored in the fixed storage device does not include the continuous load state of the engine as a parameter, the information stored in the fixed storage device is based on the premise of a constant load. For example, as shown in Fig. 3(a), if the memory information for performing the above active control is obtained by experiment when the throttle closing degree is 1/4 of the fully open state as load information, then as the load increases, hand,
It was found that when active control n is not applied (indicated by a dotted line), the value gradually approaches and the effect of active control decreases.

Therefore, it is an object of the present invention to reduce muffled noise in a vehicle by considering the engine load.

[Failure to solve the problem]

In order to achieve the above object, the vehicle interior muffled sound reduction device according to the present invention includes a means for detecting a predetermined rotational order component such as a muffled sound generation source of the engine, a load detecting means for the engine, and a sine wave signal. The generated oscillation 23 and the sine wave signal are synchronized with the rotation of the engine, and the sine wave signal is processed based on the phase control term and sound pressure control amount stored in advance in correspondence with the rotational order component and the ft load. It includes a control means and an amplifier that drives a speaker using the output of the control means.

[For production]

Figure 8 is an Oak-Fall diagram showing the sound pressure level of the 1st to 8th order components of rotation caused by an explosion in a four-cylinder engine. In the case of this 4-cylinder engine, the component is a rotational secondary component based on the inertial force of the piston and the explosive force in the cylinder (the primary explosion component with 2 explosions per engine revolution), and similarly for the 6-cylinder engine. In this case, it becomes a rotational third-order component.

Therefore, the ignition point of the engine that causes such a rotational order component is determined, and the delay time 11 (see Fig. 9 (a)) from this ignition point to the ear, which is the listening point, is calculated in advance. If the phase of the sine wave signal from the oscillator is determined and synchronized with the ignition timing, the muffled sound component of the engine can be reduced.

On the other hand, the time α from the top dead center (hereinafter referred to as TDC) to the ear, which is the listening point, for the rotational order component shown in FIG. 9(a) is the transmission of nonlinear characteristics from engine mount → cab → cabin space. It depends on the route and is considered to be an approximately constant time.

Therefore, to what extent should the phase of the sine wave signal from the oscillator synchronized with the engine rotation (TDC) be advanced to cause ignition?
It is sufficient to measure in advance whether the muffled sound is reduced at the time tl-α from the time point to TDC.

In this case, ti becomes thicker (becomes) as the engine load increases, as shown in Ll and [2] in Figures (b) and (C).
(The injection point is delayed and the ignition point is delayed).

This is because, for example, in a diesel engine, advance angle correction is normally performed using a load timer.

In other words, when the load increases, emphasis is placed on increasing the output, and the figure (
This is because the injection time is advanced as shown in C1, and as the load decreases, the injection time is delayed with emphasis on noise as shown in Figure (b).Therefore, when controlling the phase of muffled noise, the i-load Control that takes this into consideration is required.

In addition, in order to optimally reduce muffled sound, it is necessary not only to control the phase but also to perform sound pressure control (reverse phase control) that corresponds to the sound pressure of muffled sound, and this sound pressure is also affected by load changes. receive.

That is, as the load increases, the in-cylinder pressure increases with the increase in fuel, and as described above, emphasis is placed on output and noise is neglected, so the noise increases without being suppressed.

In order to reduce muffled noise, it is necessary to control the phase and sound pressure in accordance with load changes. (Explosion) How to process the phase amount and sound pressure amount of a sine wave signal synchronized with the TDC of the engine rotation according to the rotational order component (rotation speed) and engine load in response to the engine rotation speed. is determined in advance and stored in the control means.

Then, by reading out the phase amount and sound pressure amount corresponding to the actually detected predetermined rotation order component (rotation speed) and engine load, and processing the sine wave signal from the oscillator synchronized with TDC, the muffled sound can be optimized. can be reduced.

(Example of implementation) Fig. 1 shows the overall configuration of a device for reducing muffled noise in a vehicle interior according to the present invention, in which 1 is a car, 2 is an engine of the car 1, and 3 is a crank angle sensor of the engine 2. , 4 is a control lever angle sensor as an engine load detection means installed on the fuel injection pump 5 (in the case of a diesel engine) of the engine 2; 6 is a controller as a control means for performing predetermined calculations based on the outputs of the sensors 3 and 4; 7 is an oscillator that is built into the controller 6 and outputs a sine wave signal synchronized with the engine rotation (TDC), and 8 is an amplifier for driving the speaker 9. In this embodiment, the engine is a 4-cylinder engine. As shown in FIG. 2, the crank angle sensor 3 includes, for example, two protrusions provided at an interval of 180' on the circumference of a Gff disc 13 provided coaxially with the crankshaft 12, corresponding to the TDC. The unit 14 constitutes a means for detecting an engine rotation two-dimensional component (first-order explosion component) which generates an output pulse twice during one rotation of the engine and is a source of muffled noise. In addition, as the load detection means, an accelerator pedal depression amount sensor, a throttle closing sensor (in the case of a gasoline engine), etc. can be used.

FIG. 2 specifically shows the controller 6 in the vehicle interior noise reduction device shown in FIG. 1 as a functional block.
a counter unit 61 that counts the engine rotation speed), and a condition determination unit 6 that manually determines various conditions based on the engine rotation 2 component, its TDC, and the engine load from the sensor 4.
2, a ROM 63 that outputs the phase control φ and the sound pressure control amount G according to the conditions (engine speed, load) from the condition determination unit 62, and a ROM 63 that outputs the phase of the sine wave output signal from the oscillator 7. A phase control unit 64 processes the sound pressure of the sine wave output signal from the oscillator 7 using the sound pressure control amount G from the ROM 63, and a sound pressure control unit 65 processes the sound pressure of the sine wave output signal from the oscillator 7 using the sound pressure control amount G from the ROM 63. The bandpass filter 66 passes only a desired frequency component of the sine wave output signal of the oscillator 7 and sends it to the amplifier 8.

Next, the operation of the embodiment of the present invention will be explained with reference to FIG.

First, the counter section 61 counts the second-order component pulse (corresponding to TDC) of the engine rotation speed from the crank angle sensor 3 and supplies it to the condition determination section 62. The oscillator 7 is controlled so that the signal is synchronized with the engine rotation, that is, the TDC of the rotational second-order component. Furthermore, the condition determining unit 62 determines whether the input engine speed falls within a control target range determined experimentally in advance.

This control target range is shown in Figure 8, which shows:
This is a three-dimensional graph (waterfall diagram) that shows what kind of frequency spectrum is shown for each rotation order component of the engine.The vertical axis shows the engine speed (rpm) against the frequency (+12) on the horizontal axis. The protruding part indicates the sound pressure level of the muffled sound.

Since this example deals with the case of a four-cylinder engine, the main component of the muffled sound is the second-order component of engine rotation, and among these,
If the engine speed belongs to any of the control target ranges (2), (2), and (2) where the muffled sound level is large, such as parts A, B, and C shown in the figure, the following control is executed.

Therefore, when the condition determination unit 62 recognizes that the engine speed belongs to any of the control target ranges ■, ■, and ■, the condition determining unit 62 selects the current engine speed and engine load from the ROM 63 The optimum phase control amount φ and sound pressure control amount G corresponding to the above are selected and read out.

Here, to explain the ROM63, this ROM6
As explained in connection with FIG. 9, the data stored in 3 (shown in hexadecimal in FIG. 2) is used for phase control to offset the deviation in ignition timing depending on the engine load using TDC as the reference timing. The amount φ and the sound pressure side 71151tC for canceling out the sound pressure level change of the muffled sound according to the engine load were experimentally measured in correspondence with the engine rotation speed.

That is, regarding the phase, the above control target range ■, ■, ■
(for example, the engine rotational speed at every 10100 rpm (engine rotational speed with T'DC as the reference timing for the rotational secondary component due to the protrusion 14 shown in FIG. 2) and at every predetermined interval (lever angle). By conducting experiments with respect to the engine load and sequentially determining the phase control amount that reduces the muffled sound most at the listening point, it is possible to form phase control ROM data for various engine temperatures.

Similarly, regarding the sound pressure G, the control target range ■,
The sound pressure control 211 ROM data can be created by conducting experiments for the engine speeds and engine loads that fall in (1) and (2) and sequentially determining the sound pressure that will reduce the muffled sound the most at the listening point.

In this way, the ROM'! The phase control amount ψ and the sound pressure control amount G (reverse position (11) read from -3 are the same as the engine rotation (T'DC) in the phase control section → 4 and the sound pressure control section y5, respectively. The sine wave signal from the oscillator 7 is processed, its phase is delayed by a predetermined value, and the original waveform that reduces the sound pressure to the maximum is applied to the amplifier 1i 38 via the bandpass filter 66. The incoming signal is made to have an optimum volume and is output from a speaker 9.

The results of controlling the muffled noise according to the engine load in this way are shown in Figure 3 (b), and in Figure 3 (a).
It can be seen that, compared to the case where the phase/sound pressure control is performed based on the 1/4 negative time shown in 1, when the load becomes large, the effect of the active control is fully exerted as shown by the shaded area. In other words, α represents the sound pressure in the vehicle interior when phase and sound pressure control is performed at 1/4 load, and β represents the sound pressure in the vehicle interior when phase and sound pressure control is performed at 7/8 load. It shows the sound pressure,
It can be seen that when the load increases, α<β, and the muffled noise inside the vehicle is reduced.

In the above embodiments, the muffled noise is controlled only by the load and engine speed, regardless of the engine temperature, but it is known that as the engine temperature increases, the ignition point is delayed.

This is because when the temperature decreases, it takes time to atomize the fuel necessary from the time of injection to ignition and to raise the temperature of the combustion chamber.

Therefore, when controlling the phase of the muffled sound, it is preferable to perform control that takes temperature into consideration.

In addition, in order to optimally reduce muffled sound, it is necessary not only to control the phase, but also to control the sound pressure side '4n (reverse phase control) corresponding to the sound pressure of muffled sound. be influenced by.

In other words, when the engine temperature is low (warming up from a cold state), the sound pressure of the muffled sound due to diesel knock increases, but as the engine warms up and the engine gradually warms up, the diesel knock decreases. The sound pressure of the levering sound becomes smaller.

After warming up, as the engine temperature increases, the viscosity of the fuel decreases due to the increase in the temperature of the fuel itself and the temperature F of the fuel pipe, and the fuel injection amount decreases. For this reason, the amount of fuel is normally increased to compensate for the decrease in output, but this increases too much, causing the cylinder pressure to rise and the sound pressure of the muffled noise to increase.

In order to reduce muffled noise, the engine temperature (detected by a coolant temperature sensor or fuel temperature sensor installed in the engine) is detected as shown by the dotted line in Figure 2.
It is preferable to control the phase and sound pressure in accordance with this temperature change.

Therefore, depending on the engine temperature, the oscillator 7
The phase and sound pressure of the sine wave signal from Is it possible to obtain the desired phase control amount and sound pressure by giving the engine speed? 111 are sent to the phase control section 64 and the sound pressure control section 65, respectively, and the muffled sound is reduced in the same manner as described above.

However, when the engine temperature changes from low temperature to normal temperature to high temperature, normally the water temperature does not rise at normal temperature after warming up, so when low temperature → normal temperature, the fl is controlled by water temperature, and when normal temperature → high temperature, the fuel temperature is controlled. It is necessary to perform control 'n. Note that it is also possible to perform control using the intake air temperature during the switching from water temperature to fuel temperature.

By performing phase and sound pressure control based on temperature changes, for example, compared to performing only muffled sound control determined at room temperature for all temperatures, in water temperature control mode, as the temperature decreases, The effect of reducing muffled noise becomes greater, and in the fuel (intake temperature) control mode, the effect of reducing muffled sound becomes more noticeable as the temperature rises above room temperature.

Furthermore, it is more preferable to directly detect the engine ignition timing, which is the main cause of muffled engine noise, and process the phase and sound pressure without actually measuring the engine temperature.

Therefore, in the embodiment shown in FIG. 4, in the case of a diesel engine, an ignition (ignition) sensor 80, which is installed singly or in plural numbers to eliminate variations, is used as shown in FIG. 6(a)), and the condition determining unit 62 which receives this ignition output waveform detects the engine rotational speed based on this signal and sends a reference signal of the shaped waveform (■ in the same figure) to the oscillator 7. (In addition, since the condition determination unit 62 detects the engine rotation speed based on the ignition output waveform, in this case, the rank angle sensor is not necessary as shown in FIG. 2.) The oscillator 7 that receives the reference signal outputs a sine wave. (Same figure (C))
This sine wave output is stored in the ROM 63 as the phase side of the rotational secondary component according to the engine speed and engine load. 2
More accurate phase and
Sound pressure can be controlled.

When forming a map of the ROM 63 used here, T
Waveform (d) is obtained by processing the phase and sound pressure of the sine wave output waveform (C) in the same way as in the case of Figure 2 (engine temperature is not required) using the sensor output waveform (a) as the engine reference timing pulse instead of DCO. It is sufficient to measure the control amount for generating this by experiment.

FIG. 7 shows the case where the ignition sensor 80 is used and the case where the fixed reference point (T
DC), and shows that as the temperature rises in the cable portion, the volume reduction decreases.

If the ignition sensor is used in this way, control that takes into account at least the transmission characteristics of the engine mount system will suffice.

〔Effect of the invention〕

As described above, the vehicle interior muffled sound reduction device according to the present invention detects a predetermined rotational order component that is a source of engine muffled noise, and generates an oscillator corresponding to the rotational order component and the engine load at that time. The engine's output sine wave signal is processed to drive a speaker to reduce muffled noise. It is possible to generate a sound that offsets the muffled noise in the vehicle cabin caused by the eight-shot engine under any load condition of the engine.

[Brief explanation of drawings]

FIG. 1 is a conceptual configuration diagram showing an embodiment of a vehicle interior muffled sound reduction device according to the present invention; FIG. 2 is a block diagram functionally showing a controller in the embodiment of the present invention; The figure shows a comparison of the effect of reducing the sound pressure in the vehicle interior between the conventional example and the present invention. Figure 4 shows an example using an ignition sensor. Figure 5 shows the arrangement of the ignition sensor. Figure 6 is a waveform diagram when the output waveform of the ignition sensor is used as the reference timing, Figure 7 is a graph diagram showing the effect when using the ignition sensor, and Figure 8 is the book. FIG. 9 is a three-dimensional graph diagram showing the tilting of the controlled object with respect to the engine speed according to the invention. FIG. 9 is a graph diagram showing changes in ignition timing due to changes in engine load. In FIG. 1, 1 is an automobile, 2 is an engine, 3 is a crank angle sensor, 4 is a control lever angle sensor, 6 is a controller, 7 is an oscillator, 8 is an amplifier, and 9 is a speaker. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] means for detecting a predetermined rotational order component that is a source of engine muffled noise; a load detection means for the engine; an oscillator that generates a sine wave signal; It is characterized by comprising a control means for processing the sine wave signal based on a phase control amount and a sound pressure control amount stored in advance in correspondence with the component and load, and an amplifier for driving a speaker with the output of the control means. A device for reducing muffled noise inside the vehicle.