JPH08123435A - Active noise control unit for automobile - Google Patents

Abstract

PURPOSE: To easily generate sound energy which is large enough to absorb an air suction noise under noise reduction control which generates a sound wave interfering with the air suction noise in an air suction system. CONSTITUTION: A frequency component of suction pulsation is extracted based on the output of an air flow meter (S1 and S2), and phase processing is performed for the frequency component (S3). Then a cycle (f) and an amplitude Pw that a sound wave outputted from a speaker is expected to have are calculated based on the extraction result (S4). The cycle (f) and amplitude Pw are converted into the cycle fp and duty ratio Duty of a pulse signal used for electric feeding control over a voice coil respectively (S5). Here, the pulse having the cycle fp and duty ratio Duty is generated through the clocking of a timer (S6) and the power supply to the voice coil is controlled with the pulse signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise control system for an automobile, and more specifically, to reduce noise in an automobile.
The present invention relates to a device that positively reduces interference due to sound waves separately generated.

[0002]

2. Description of the Related Art In recent years, a technique called active noise control has been proposed as a technique for ensuring the quietness of an automobile. In view of the fact that the sound is a kind of wave phenomenon in which a change in the density of air propagates in the air, the active noise control is based on, for example, noise (primary sound) in a vehicle and another sound wave (two The primary sound is canceled by interfering with the secondary sound).

[0003]

By the way, in order to reduce the intake system noise generated due to the intake pulsation of the engine by the active noise control, a speaker is installed in the intake system which is a noise source. As a result, intake noise can be efficiently reduced. In this case, in order to absorb the amplitude energy of the intake pulsation in the intake system, acoustic energy of about 150 dB is required in the intake system, and it is necessary to output about 30 to 50 W of energy from the amplifier to the speaker. .

However, since the power supply voltage (battery voltage) in an ordinary automobile is about 12 V, it is difficult to obtain the output of the amplifier, and the amount of heat generated to obtain the output in the power amplification of the amplifier is large. There was a problem of becoming. Further, if the amplifier output is kept constant, it is necessary to lower the impedance of the speaker in order to secure acoustic energy, which causes a problem that the speaker design is difficult.

The present invention has been made in view of the above problems, and acoustic energy for absorbing the amplitude energy of vehicle noise can be secured by a vehicle-mounted power source and a general speaker, and a large amount of heat is generated. The purpose is to be able to secure without accompanying.

[0006]

Therefore, in the active noise control system for an automobile according to the invention of claim 1, the noise detecting means detects the noise propagating in the vehicle interior of the automobile, while the noise reducing control means: A device for causing another sound wave for canceling the detected noise to be generated from the sound wave generating means and interfering with the noise, wherein drive control of the sound wave generating means by the noise reduction control means is performed by a pulse signal. The frequency of the sound wave is adjusted by the cycle of the pulse signal, and the sound pressure of the sound wave is adjusted by the duty ratio of the pulse signal.

In the vehicle active noise control system according to the invention of claim 2, the noise propagating in the vehicle compartment detected by the noise detecting means is the intake sound of the engine mounted in the vehicle, and the sound wave generation is performed. The means is configured to generate a sound wave in the intake system of the engine. In the automobile active noise control device according to the invention of claim 3, the generation of the pulse signal in the noise reduction control means is based on the data of the cycle and the duty ratio set based on the noise detected by the noise detection means. It is configured to be performed by measuring time.

In the automobile active noise control device according to the invention of claim 4, the sound wave generating means is constituted by attaching a movable diaphragm to a voice coil whose energization is controlled by a pulse signal from the noise reducing control means. ,And,
The movable diaphragm strokes only in the direction in which the voice coil moves when the pulse signal is turned on.

In the active noise control system for an automobile according to a fifth aspect of the invention, the sound wave generating means is constituted by attaching a movable diaphragm to a voice coil whose energization is controlled by a pulse signal from the noise reducing control means. Meanwhile,
A pulse correction for directly supporting a sound wave converting means for converting a sound wave into an electric signal to the voice coil and correcting the pulse signal based on a comparison between a waveform of the electric signal from the sound wave converting means and a predetermined expected output waveform. A means is provided.

In the automobile active noise control device according to the invention of claim 6, the sound wave generating means is constructed by attaching a movable diaphragm to a voice coil whose energization is controlled by a pulse signal from the noise reducing control means. Meanwhile,
The pulse signal is corrected based on a current detection unit that detects a current flowing in the sound wave generation unit by the energization control by the pulse signal, and a waveform of the current detected by the current detection unit and a predetermined expected output waveform. And a pulse correction means for performing the correction.

[0011]

According to the active noise control device for an automobile of the present invention, in the construction for reducing the noise by interfering with the acoustic wave generated separately with respect to the noise of the automobile, the acoustic wave generating the acoustic wave is generated. Since the means is driven and controlled by the pulse signal, the frequency and the sound pressure of the generated sound wave are adjusted, so that a large amount of heat is not generated and a high output is obtained based on the power supply mounted on the vehicle. Is possible.

According to the vehicle active noise control system of the second aspect of the present invention, the intake sound of the engine is detected and the sound wave for interfering with the intake sound is generated in the intake system. Here, in order to generate sound waves in the intake system and reduce intake noise, particularly large acoustic energy is required, but the required energy can be secured by the pulse control.

According to the active noise control device for an automobile of the third aspect of the invention, the ON / OF of the pulse signal for controlling the sound wave generation is controlled based on the cycle and the duty ratio.
It is generated by time control of F timing. Claim 4
According to the vehicle active noise control device of the present invention, in the configuration using the dynamic speaker including the voice coil and the movable diaphragm as the sound wave generating means, the movable diaphragm is moved only in the direction in which the voice coil moves when the pulse signal is turned on. By making a stroke
A large amount of movement of the movable diaphragm due to ON / OFF of the pulse signal is secured, and thus necessary acoustic energy can be secured.

According to the active noise control device for an automobile of the fifth aspect, the desired sound wave is generated by pulse control by directly supporting the sound wave converting means for converting a sound wave into an electric signal to the voice coil. It is determined whether or not the sound wave is generated, and the result of the determination is fed back to the pulse signal applied to the sound wave generation means to correctly generate the sound wave required for noise reduction.

According to the active noise control system for an automobile of the sixth aspect, the current flowing through the voice coil is detected by the pulse control, and the waveform of the current shows the output waveform corresponding to the desired sound wave. It is determined whether or not there is a sound wave, and the result of this determination is fed back to the pulse signal to be given to the sound wave generation means to correctly generate the sound wave required for noise reduction.

[0016]

Embodiments of the present invention will be described below. Figure 1
1 shows a system configuration of an engine mounted on an automobile in an embodiment, in which air is sucked into an engine 1 through an air cleaner 2, an intake duct 3, a throttle chamber 4, an intake collector 5, and an intake manifold 6.

The throttle chamber 4 is provided with a throttle valve 7 interlocking with an accelerator pedal (not shown) to adjust the intake air amount of the engine 1. An electromagnetic fuel injection valve 8 is provided for each cylinder in a branch portion of the intake manifold 6, and fuel injected from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator is injected into the intake manifold 6. Supply.

The fuel injection valve 8 is intermittently driven to open according to an injection pulse signal sent from a control unit 9 having a built-in microcomputer, and according to the pulse width of the injection pulse signal calculated by the control unit 9. The fuel injection amount is controlled. Intake duct 3 upstream of the throttle chamber 4
Is provided with an air flow meter 10 for detecting the intake air amount Q of the engine 1.

Here, the air flow meter 10 detects the intake air amount Q of the engine as a mass flow rate based on a change in the resistance value of the heat-sensitive resistance arranged in the intake duct, for example, and intake pulsation occurs. Then, the output changes according to the intake pulsation. When intake pulsation is generated in the intake system of the engine 1, intake noise is generated along with the intake pulsation. Therefore, the intake pulsation noise can be detected by the air flow meter 10, and the intake pulsation noise will be described later. In the present embodiment for performing control for reducing pulsation (intake pulsation noise), the air flow meter 10 corresponds to noise detecting means.

A crank angle sensor 11 for extracting a rotation signal of the engine 1 from a crank shaft or a cam shaft is provided, and the engine rotation is performed based on a detection signal output from the crank angle sensor 11 at every predetermined crank angle. Speed Ne
Can be calculated. Further, a throttle sensor 12 for detecting the opening TVO of the throttle valve 7, a water temperature sensor 13 for detecting the engine cooling water temperature Tw, etc. are provided.

The control unit 9 calculates the basic injection pulse width Tp based on the intake air amount Qa detected by the air flow meter 10 and the engine rotation speed Ne calculated based on the detection signal from the crank angle sensor 11. At the same time, the basic injection pulse width Tp is set to the cooling water temperature Tw.
The final injection pulse width T is corrected according to operating conditions such as
i is set, and an injection pulse signal having the injection pulse width Ti is output to the fuel injection valve 8.

Here, the control unit 9 is
As well as functioning as the fuel injection control unit as described above, it also functions as an active noise control unit for reducing intake noise of the engine 1 as noise propagating in the vehicle interior of the automobile. In the present embodiment, a speaker 15 (sound wave generating means) for separately generating a sound wave for interfering with the intake noise is provided near the air cleaner 2 (inside the intake system) for the active noise control.
The control unit 9 as noise reduction control means
Is to generate a sound wave from the speaker 15 based on the intake pulsation detected by the air flow meter 10, and to cancel the sound wave by interfering with the intake noise (intake pulsation),
It is designed to reduce intake pulsation noise.

The speaker 15 is a so-called dynamic speaker in which a voice coil is attached to a movable diaphragm.
Here, the drive control system of the speaker 15 is configured as shown in FIG. In FIG. 2, the control unit 9 receives an intake air amount detection signal Q from the air flow meter 10 and a correction information signal, which will be described later, which is A / D converted by an A / D converter 16 and read. The converted data is processed by a digital signal processor (DSP) 17 to generate a pulse signal for driving and controlling the speaker 15.

The pulse signal is an ON / OFF control signal for the transistor 21 that switches the energization of the voice coil 19 of the speaker 15, and when the pulse signal is at a high level (ON), the transistor 21 is turned on.
Is turned on and a current flows through the voice coil 19 connected to the vehicle-mounted battery voltage VB. With this configuration, the frequency of the sound wave generated from the speaker 15 is adjusted by the cycle fp of the pulse signal,
Duty ratio (ON time ratio) Dut of the pulse signal
The sound pressure of the sound wave is adjusted by y (see FIG. 3).

Next, the driving control of the speaker 15 will be described in detail with reference to the flowchart of FIG. In the flowchart of FIG. 4, in step 1 (denoted as S1 in the figure. The same applies hereinafter), the data of the intake air amount Q read by A / D conversion is time-sequentially data MQn.
It is stored as (n = 1, 2, 3, ...).

In step 2, a predetermined low frequency component (intake pulsation component) is extracted from the stored time-series data MQn of the intake air amount Q by digital filtering. In step 3, a phase rotation process is performed to shift the phase of the extracted frequency component by a predetermined angle.

In step 4, the sound wave (expected signal) to be output from the speaker to cancel the intake sound (intake pulsation noise) based on the frequency component subjected to the phase rotation processing.
The amplitude Pw and the period f are calculated (see FIG. 5). In step 5, the amplitude Pw is set to the duty ratio D of the drive pulse signal of the speaker 15 by using a preset conversion table.
In addition to converting into the duty, the period f is converted into the period fp of the drive pulse signal of the speaker 15.

In step 6, the duty ratio Duty and the period fp obtained by the conversion are set in a timer (not shown) having a memory for storing these data, and the ON / OFF timing of the pulse signal is set by the timer. The time is measured, and a pulse signal having the duty ratio Duty and the period fp is generated from the timer.
With such a configuration, if the speaker 15 is not digitally controlled by analog control but is digitally controlled by a pulse signal, in the case where a large acoustic energy is required to absorb the intake pulsation as in the present embodiment. Even so,
It is possible to generate the required acoustic energy without causing a large amount of heat generated by the amplifier due to the voltage of the vehicle battery.

That is, when the speaker 15 is analog-controlled, a voltage corresponding to the required sound pressure is required, but in the pulse control, the sound pressure is adjusted by the duty ratio of the pulse signal. It becomes possible to secure the required sound pressure by the voltage of the battery mounted on the vehicle. Further, as described above, if the pulse signal is generated by timing the ON / OFF timing of the pulse signal by the timer, the D / A converter required for analog control can be omitted.

If the speaker 15 has a structure in which the movable diaphragm strokes only in the direction in which the voice coil 19 moves when the pulse signal is turned on, the movable diaphragm is switched by turning the pulse signal on and off. The stroke can be maximized, and thus it becomes easy to secure a large acoustic energy. In the above embodiment, the duty ratio Dut of the pulse signal that produces the expected sound wave is obtained.
Although the pulse signals of y and the period fp are set by using the preset conversion table, the actual sound wave output of the speaker 15 is monitored as shown in the flowchart of FIG. 6, and based on the monitor result. The duty ratio Du
A configuration in which the pulse signals of ty and the period fp are corrected and set may be used.

Steps in the flowchart of FIG.
Since the processing from 11 to step 14 is exactly the same as the above-described steps 1 to 4 of the flowchart of FIG. 4, the description will be given from step 15. In step 15, the monitor signal of the actual sound wave output of the speaker 15 is A / D converted and read. The monitor signal is, for example, as shown in FIG.
The configuration may be such that the current waveform flowing in the voice coil 19 of the speaker 15 is read by pulse control (current detecting means), or, as shown in FIG. 8, a microphone 31 (sound converting means) for converting sound waves into electric signals. May be directly connected to and supported by the voice coil 19, and the movement of the diaphragm of the microphone 31 caused by displacement of the microphone 31 with the vibration of the voice coil 19 (movable diaphragm) may be read as an electric signal.

In step 16, from the waveform of the voice coil current read by the A / D conversion or the output current (correction information signal) of the microphone 31, the amplitude Pw 'and the cycle f'of the actual sound wave output of the speaker 15 are obtained. To calculate. In step 17, the calculated actual amplitude Pw ′ is compared with the expected amplitude value Pw calculated in step 4. Then, when the actual amplitude Pw 'is smaller than the expected value Pw, the routine proceeds to step 18, where the duty ratio Du of the pulse signal Du
If the actual amplitude Pw 'is larger than the expected value Pw, on the other hand, the routine proceeds to step 19, where the duty ratio Duty is changed to the predetermined value ΔDu.
The actual amplitude Pw ′ is reduced by ty and the expected value Pw is obtained.
Try to get closer to.

In step 20, the calculated actual cycle f'is compared with the expected value f of the cycle calculated in step 4. Then, when the actual period f ′ is shorter than the expected value f, the process proceeds to step 21 and the period fp of the pulse signal.
Is increased by a predetermined value Δfp, and conversely, the actual cycle f ′ is
Is longer than the expected value f, the routine proceeds to step 22, where the cycle fp is corrected by a decrease by a predetermined value Δfp so that the actual cycle f ′ approaches the expected value f.

If the configuration is such that the cycle fp of the pulse signal and the duty ratio Duty are corrected and set as described above,
Even with a configuration in which the speaker 15 is pulse-controlled, it is possible to generate a highly accurate expected sound wave. The functions of steps 16 to 22 correspond to the pulse correction means in this embodiment.

A microphone is installed in the intake system on the upstream side of the air cleaner 2 and
A configuration may be adopted in which the cancellation result of the intake pulsation is detected and the cycle and duty ratio of the pulse signal are corrected based on the detection result. Further, in the present embodiment, the intake air pulsation noise is indirectly detected by the air flow meter 10 as the noise detection means, but the intake noise (intake pulsation noise) is directly detected by the microphone as the noise detection means. It may be configured.

[0036]

As described above, according to the active noise control device for an automobile according to the invention of claim 1, since the sound wave generation is pulse-controlled, it does not generate a large amount of heat and is mounted on the vehicle. It becomes possible to obtain a high output based on the power source, and even if a large amount of acoustic energy is required for noise reduction, it is possible to easily secure the required energy.

According to the active noise control system for an automobile of the second aspect of the invention, in the structure for generating the sound wave for canceling the intake noise in the intake system, a large acoustic energy for canceling the intake noise is secured, Thus, there is an effect that the intake noise can be effectively reduced. According to the vehicle active noise control device of the third aspect, the pulse signal for controlling the sound wave generation is generated by the time control of the ON / OFF timing based on the cycle and the duty ratio. There is an effect that the system configuration can be simplified by omitting the A converter.

According to the active noise control device for an automobile of the fourth aspect of the present invention, when the movable diaphragm strokes only in the direction in which the voice coil moves when the pulse signal is turned on, the pulse signal is turned on and off. A large amount of movement of the movable diaphragm due to is secured, so that the necessary acoustic energy can be easily secured. According to the active noise control device for automobiles of the fifth and sixth aspects of the present invention, it is determined whether or not a desired sound wave is generated by pulse control, and the determination result is used as a pulse signal to be given to the sound wave generation means. There is an effect that the sound wave required for noise reduction can be correctly generated by feedback.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an engine in an embodiment.

FIG. 2 is a circuit diagram showing a speaker driving system in the embodiment.

FIG. 3 is a diagram showing a pulse signal given to a speaker in the embodiment.

FIG. 4 is a flowchart showing speaker drive control of the first embodiment.

FIG. 5 is a diagram showing a correlation between an intake pulsation signal and an expected output of a speaker.

FIG. 6 is a flowchart showing speaker drive control according to the second embodiment.

FIG. 7 is a circuit diagram showing a coil current monitor circuit according to a second embodiment.

FIG. 8 is a diagram showing an installed state of a microphone in the second embodiment.

[Explanation of symbols]

 1 engine 2 air cleaner 3 intake duct 4 throttle chamber 5 intake collector 6 intake manifold 7 throttle valve 9 control unit 10 air flow meter 11 crank angle sensor 15 speaker 16 A / D converter 17 DSP 19 voice coil 21 transistor 31 microphone 31

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G10K 11/16

Claims (6)

[Claims] 1. A noise detecting means for detecting noise propagating in the vehicle interior of an automobile, and another sound wave for canceling the noise detected by the noise detecting means is generated from the sound wave generating means to interfere with the noise. In a vehicle active noise control device including a noise reduction control unit, drive control of the sound wave generation unit by the noise reduction control unit is performed by a pulse signal, and a sound wave is generated by a cycle of the pulse signal. Adjust the frequency, and
An active noise control device for an automobile, wherein the sound pressure of a sound wave is adjusted according to the duty ratio of the pulse signal. 2. The noise propagating in the vehicle compartment detected by the noise detecting means is an intake sound of an engine mounted on an automobile, and the sound wave generating means generates a sound wave in an intake system of the engine. The active noise control device for an automobile according to claim 1, wherein 3. The noise reduction control means generates the pulse signal by time measurement based on data of a cycle and a duty ratio set based on noise detected by the noise detection means. The active noise control device for a vehicle according to claim 1 or 2. 4. The sound wave generating means is constituted by attaching a movable diaphragm to a voice coil whose energization is controlled by a pulse signal from the noise reduction control means, and the voice coil is turned on when the pulse signal is turned on. The active noise control device for a vehicle according to any one of claims 1 to 3, wherein the movable diaphragm makes a stroke only in a moving direction. 5. The sound wave generating means is constituted by attaching a movable diaphragm to a voice coil whose energization is controlled by a pulse signal from the noise reduction control means, while the sound wave converting means converts a sound wave into an electric signal. Is directly connected to and supported by the voice coil, and pulse correction means for correcting the pulse signal based on a comparison between the waveform of the electric signal from the sound wave conversion means and a predetermined expected output waveform is provided. Item 5. The active noise control device for an automobile according to any one of items 1 to 4. 6. The sound wave generating means is constituted by attaching a movable diaphragm to a voice coil whose energization is controlled by a pulse signal from the noise reduction control means, while the sound wave generating means energizes by the pulse signal. Current detection means for detecting the current flowing through the voice coil by control, and pulse correction means for correcting the pulse signal based on the comparison between the waveform of the current detected by the current detection means and a predetermined expected output waveform are provided. Claim 1 characterized by the above.
The active noise control device for a vehicle according to any one of items 1 to 4.