JPH0331039A - Device for reducing noise in car room - Google Patents

Abstract

PURPOSE:To efficiently reduce noise in a car room by using unbalanced inertia force and combustion vibratory excitation force of an engine to obtain a phase delay for a crank angle and using a crank angle signal, delayed by the amount of this phase delay, as a synchronous signal at the time of generating a secondary sound. CONSTITUTION:A crank angle in an engine is detected by a sensor 11, while being based on this detection signal, unbalanced inertia force in proportion to the square of an engine speed is calculated in a means 12. While a load of the engine is detected by a sensor 13, while being based on this detection signal, combustion vibratory excitation force is calculated in a means 14. Further being based on the unbalanced inertia force and the combustion vibratory excitation force, a phase delay for the crank angle is calculated in a means 15. While, a crank angle signal, delayed by the amount of the phase delay, is generated by a means 16 as a synchronized signal which is a phase reference value of secondary sound. By using the synchronous signal, a secondary sound signal is generated by a means 17 while it is output to a secondary sound source 19 in a car room by a means 18.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to reduction of vehicle interior noise vcrIi, particularly to a synchronization signal used as a reference value for the phase of secondary sound.

(Prior Art) As a vehicle interior noise reduction device, for example, there is a device as shown in FIG.
(See Publication No. 2).

This reduces vehicle interior noise by generating two loud sounds S from the speaker (secondary sound source) 8 that have the same amplitude and opposite phase to the noise P from the noise source 1 received by the microphone 2. This is what I am trying to do. In addition, 4 and 6
is a 7-lier converter, 3 and 7 are Komi 1 cheaters, and 5 is a processor.

(Problem M to be solved by the invention) By the way, in such a device, the phase of the secondary sound must be corrected at any time by feedback control in response to the change in the phase of the noise inside the vehicle. If there is a sudden change in phase, it becomes impossible to follow the change, and in that case, it becomes impossible to sufficiently reduce the noise inside the vehicle.

However, using a high-speed processor to improve the followability of feedback control will increase costs.

This invention was made with a focus on such conventional problems, and uses the unbalanced inertia force and combustion inertia force determined by the engine speed and load to reduce the phase lag of noise in the passenger compartment with respect to the crank angle. It is an object of the present invention to provide a device that can cope with phase fluctuations in vehicle interior noise during transient periods by determining a crank angle signal delayed by this phase delay and using it as a synchronization signal.

(Means for Solving the Problems) As shown in FIG. 1, the present invention includes a sensor 11 that detects the crank angle of an engine, and an unbalanced inertia that is proportional to the engine speed based on the crank angle signal. Means 12 for calculating force and sensor 1 for detecting engine load
3, a means 14 for calculating a combustion excitation force according to the second engine load, and a means 15 for calculating a phase delay with respect to the crank angle from this combustion excitation force and the unbalanced inertia force.
and delays the crank angle signal by this phase delay,
means 16 for generating synchronization (No. 3) using this delayed crank angle signal as a reference value for the phase of the secondary sound, and means 17 for generating a secondary sound signal using this synchronization signal;
Means 18 is provided for outputting this secondary sound signal to a secondary sound source 19 disposed within the vehicle interior.

(Function) When the phase of engine vibration and torque fluctuations relative to the crank angle changes due to changes in engine speed and load, the phase of cabin noise (directly the engine rotation two-wave component) relative to the crank angle changes according to this change. changes.

In this case, according to the present invention, the phase lag of the noise inside the vehicle with respect to the crank angle is determined using the unbalanced inertia force and combustion excitation force determined by the rotational speed and load at that time. For example, when the load suddenly increases, the phase of the noise in the vehicle interior relative to the crank angle will be delayed by a large amount, but the phase of the secondary sound will be significantly delayed in response to this large delay in the phase of the noise in the vehicle interior. In addition, when the phase of vehicle interior noise relative to the crank angle is significantly delayed due to a sudden decrease in rotational speed, the phase of secondary sounds is also significantly delayed. The phase of the secondary sound closely follows the change.

(Embodiment) FIG. 2 is a system diagram showing an embodiment applied to a four-cylinder engine equipped with a fuel injection device.

23 is attached to the crank pongee 22 of the engine 21,
The crank angle sensor outputs a pulse signal (crank angle signal) every 180 degrees of crank angle, and this crank angle signal is input to the engine control unit 24 and to the rectangular wave generator 25 . Note that instead of the above-mentioned crank angle signal, a signal obtained by adding ignition advance angle information to the ignition signal and making the signal essentially equivalent to the crank angle signal may be used.

The rectangular wave generator 25 (also the rectangular wave generator 27 to be described later) is a circuit that shapes the input waveform containing some disturbance as shown in FIG. 3 into a clean rectangular wave as shown in FIG. 4. , the rectangular wave signal from the rectangular wave generator 25 is input to the synchronization signal generator 28.

The rectangular wave signal is also input to the frequency-voltage converter 26, and the voltage signal from the frequency-voltage converter 26 is input to the synchronization signal generator 28 as engine rotation speed information. This is because if a rectangular wave signal is also captured as the number of rectangular waves per predetermined time, it represents the frequency (engine speed), so the voltage value of the voltage signal corresponds to the engine speed.

A mixture ratio control signal is sent from the engine control unit 24 to which the crank angle signal is inputted to an injector (not shown).
It is input to the synchronization signal generator 28 via 7.

The mixture ratio control signal is a pulse signal having a substantially rectangular wave, and the length of the rectangular wave at a high level corresponds to the fuel injection amount. In other words, according to the intermittent injection method, if the fuel pressure applied to the injector is kept constant, the fuel injection amount is controlled depending on the length of the injector at a high level. Here, the mixture ratio control signal is employed as engine load information. Note that instead of the mixture ratio control signal, the output of a sensor that detects knocking (correlated with combustion torque) may be used.

The synchronization signal generator 28 calculates the phase delay with respect to the crank angle according to the voltage value of the voltage signal and the length of the high level of the mixture ratio control signal, that is, according to the engine speed and load information. Square wave generator 2 for the phase delay
Delays the crank angle signal from 5.

The above phase delay is calculated by calculating the unbalanced inertia force from the voltage value from the frequency-voltage converter 26 and the combustion excitation force from the high level of the mixture ratio control signal, as shown in the ff$5 diagram. Obtain it by synthesizing the components. In addition, in FIG. 5, each operation performed by the rectangular wave generator 25, 27, frequency-voltage converter 26, and synchronization signal generator 28 is shown as a flowchart.

FIG. 6 shows a specific configuration example for realizing each function of the synchronization signal generator 28 shown in FIG. 5.

Reference numeral 29 denotes an amplifier circuit that outputs a voltage value proportional to the square of the input voltage value, and a voltage signal proportional to the engine rotation speed from the frequency-voltage converter 26 is input to this amplifier circuit 29. Here, since the unbalanced inertial force is proportional to the square of the engine speed, the output from this amplifier circuit 29 corresponds to the unbalanced inertial force.

This is a part that performs the function of the unbalanced inertial force calculation means 12 shown in FIG.

30 is an amplifier circuit that outputs a voltage value proportional to the length of the input, and a mixing ratio control signal is input to this amplifier circuit 30.

This amplifier circuit 30 outputs an output according to the length of the high level, and this output represents the engine load.

31 is a normal amplifier circuit that outputs a voltage value proportional to the input voltage value, and the output from the amplifier circuit 30 is input to this amplifier circuit 31. Since the combustion excitation force is approximately proportional to the engine load, the output from the amplifier circuit 31 corresponds to the combustion excitation force. Here, the two Je width circuits 30 and 31 function as the combustion excitation force calculation means 14 in FIG.

In the phase delay arithmetic operation circuit 32 to which respective equivalent amounts of the combustion excitation force and the unbalanced inertial force are input, the ratio of the output voltage value from the amplifier circuit 31 to the output voltage value from the amplifier circuit 29 is set to 8. Then, the phase delay θ with respect to the input A is calculated by the following equation.

θ= Lan-I(A-sin(φ)/(1+A-
cos (φ)) However, in the open equation, φ is the phase difference between the unbalanced inertial force and the combustion excitation force, and according to the open equation, the phase θ of the wave that is a combination of two sine waves with different amplitudes and phases It means that is found. This is a part that performs the function of the phase delay calculation means 15 shown in FIG.

Note that the phase delay arithmetic operation circuit 32 does not have to strictly implement the above equation. In other words, I don't mind using approximations instead of trigonometric functions.

The signal from this phase delay arithmetic operation circuit 32 is transmitted to a delay circuit 33.
Here, the crank angle signal is delayed by the phase delay θ. This performs the function of the synchronization signal generating means 16 in FIG.

By combining the amplifier circuits 29 to 31 and the arithmetic circuit 32 as described above, the phase delay θ with respect to the crank angle is
Rather than calculating θ each time, the value of θ calculated in advance is stored in memory, and θ is calculated according to the engine speed and load.
It is also possible to read the value of . In this case, if the engine speed is constant, the load decreases as the load decreases, and as the engine speed increases, the maximum phase value at that speed (i.e., the phase value at maximum load) decreases. Set the value of θ so that Therefore, the value of θ becomes maximum when the engine is rotating at low speed and under maximum load. Note that if severe accuracy is not required, the value of θ may be roughly set to zero at high speed rotation and a constant value at low to medium speed rotation.

Returning to FIG. 2, the synchronization signal (crank angle signal delayed by the phase delay) generated by the synchronization signal generator 28 is sent to the processor unit 41 that performs arithmetic processing, and the processor unit 41 uses the synchronization signal Based on this, a secondary blind signal with the same amplitude and opposite phase as the vehicle interior noise is generated. This secondary sound signal is sent via a power amplifier 42 to a loudspeaker 43, where a secondary sound is generated. That is, the processor unit 41 is the secondary sound generating means 1 of FIG.
7 and output means 18 of 8! The power amplifier 42 and loudspeaker 43 function as the secondary sound source 19.

Note that a microphone may be provided in the vehicle interior and feedback control may be performed so that the noise in the vehicle interior is minimized. In Fig. 2, square wave generators 25 and 27 are used, but if the signals input to them have waveforms close to rectangular waves, they can be omitted. The functions of the amplifier circuit, arithmetic circuit, and delay circuit can also be taken over by the microprocessor unit 41.

Here, the operation of this embodiment will be explained.

In the case of a multi-cylinder engine, engine vibration and torque fluctuation, which are assumed to be the source of noise inside the cabin, are among the reciprocating inertia forces generated by the reciprocating movement of heavy objects such as pistons.
It is caused by the unbalanced inertial force that remains unbalanced between pistons with different phases of motion and the excitation force caused by combustion. In the case of the 4-cycle 4-cylinder engine, which is currently the most common type of engine for the 111, the frequency component twice the engine rotation (engine rotation 2 dog component) is the most dominant for both the unbalanced inertia force and the combustion excitation force. The unbalanced inertia force and the combustion excitation force are both synchronized with the crank angle 4y.

However, the unbalanced inertia force and the combustion excitation force have different phases (almost opposite phases), and under conditions of full throttle, the combustion excitation force, which is approximately proportional to the engine load, is at low speed and the engine rotation The unbalanced inertial force, which is proportional to the square of the number, becomes dominant at high speed rotation, so the engine rotation two-dog component of the excitation force, which is the combination of the combustion excitation force and the unbalanced inertia force, is generated at low speed rotation and high speed rotation. The phase is almost opposite. Figures 7 and 8 show the results of simulating the torque fluctuations when the accelerator is fully opened when the engine rotation is 2000 rpm and when the accelerator is fully opened when the engine rotation is 6000 rpm. It can be seen that even under the fully open accelerator condition, the combustion excitation force is dominant in the low speed rotation range shown in FIG. 7, and the unbalanced inertial force is dominant in the high speed rotation range shown in FIG.

Torque fluctuations are caused by the force applied to the piston changing into rotational moment via the crank mechanism, and are closely related to the engine's vertical unbalanced forces, including combustion power.

Therefore, the relationship between the rotational speed and load and the vibration of the engine itself is almost the same as the relationship between them and torque fluctuation. Therefore, as long as the source and transmission path of noise vibration do not change significantly depending on the rotation speed, if the phase of engine vibration or torque fluctuation with respect to the crank angle changes due to changes in rotation speed and load, the cabin noise will be affected accordingly. The phase with respect to the crank angle also varies.

In the conventional example, this phase fluctuation must be corrected as needed by feedback control, so if there is a sudden change in phase, it cannot be followed, and it is not possible to sufficiently reduce the noise inside the vehicle.

On the other hand, according to this example, the phase delay of the noise inside the vehicle with respect to the crank angle is determined using the unbalanced inertia force and the combustion excitation force, which are determined by the rotational speed and load at that time. In other words, since the phase of the noise inside the vehicle relative to the crank angle varies in a certain relationship depending on the rotation speed and load, for example, when the load suddenly increases, the phase of the noise inside the vehicle relative to the crank angle changes. is greatly delayed. In this case, in response to the phase of the cabin noise that is significantly delayed,
The phase of the secondary sound is also significantly delayed.

Further, when the phase of the i7L indoor noise relative to the crank angle is significantly delayed due to a sudden decrease in the rotational speed, the phase of the secondary sound is also significantly delayed.

As a result, it is possible to sufficiently follow changes in the phase of vehicle interior noise even during transient periods when the phase changes significantly.
The effect of reducing vehicle interior WJL sound during transient periods is enhanced. Furthermore, if the same level of control accuracy as before is sufficient, a cheaper processor can be used.

Figure 9 and PItJio diagram are other examples, respectively.
This corresponds to Fig. 5. In this other embodiment, the phase delay amount θ with respect to the crank angle is calculated in the phase delay performance unit 51 (see FIG. 10), and the signal of this phase delay amount and the crank angle signal from the rectangular wave generator 25 are input. A synchronization signal is generated in the processor unit 52.

Further, the processor unit 52 here also performs feedback control based on the output from a microphone (not shown) installed in the vehicle interior to detect actual vehicle interior noise. In other words, the phase delay of the vehicle interior noise with respect to the crank angle is given by the sum of the value calculated by the phase delay calculation unit 51 and the feedback value. In this case, it goes without saying that the processor unit 52 generates a secondary sound signal having the same amplitude and opposite phase as the noise.

(Effect of the invention) This invention calculates a phase delay with respect to the crank angle using combustion excitation force and unbalanced inertia force determined by the engine speed and load, and delays the crank angle signal by this phase delay. Since this is used as a synchronizing signal when generating secondary sound, the noise inside the vehicle can be effectively reduced even if the operating conditions suddenly change.

[Brief explanation of drawings]

mi diagram is a claim correspondence diagram of this invention, Pt52 diagram is a system diagram of one embodiment, FIGS. 3 and 4 are diagrams showing the input waveform and output waveform to the rectangular wave generator, respectively, and FIG. 5 is a diagram showing the above implementation. A flowchart for explaining the control contents of the example, Fig. 6 is a specific circuit diagram of the synchronous No. 13 generator of the above example, Fig. f57 and Fig. 8 are respectively shown at full load when the engine rotation speed is 2000 times per minute. FIG. 4 is a waveform diagram showing torque fluctuations during two rotations of the engine when the engine rotates at 6,000 times per minute and at full load. Fig. Pt59 is a system diagram of another embodiment, Fig. tPJ10 is a flowchart for explaining the control contents of this other embodiment, and Fig. 11 is a block diagram of a conventional example. DESCRIPTION OF SYMBOLS 11... Crank angle sensor, 12... Unbalanced inertia force calculation means, 13... Engine load sensor, 14...
Combustion excitation force calculation means, 15... phase delay calculation means,
16... Synchronization signal generation means, 17... Secondary sound signal generation means, 18... Output means, 19... Secondary sound source, 2
1... Engine, 23... Crank angle sensor, 24
...Engine control unit, 25.27...Square wave generator, 26...Frequency voltage converter, 28...Synchronization signal generator, 29-31...Amplification circuit, 32...Phase Delay arithmetic circuit, 33... Delay circuit, 41... Processor unit, 43... Loudspeaker-51.
. . . Phase delay arithmetic unit, 52 . . . Processor unit 7. Figure 5 (To the processor unit) Figure 9 Figure 10 (To the processor unit)

Claims (1)

[Claims] a sensor for detecting an engine crank angle; a means for calculating an unbalanced inertia force proportional to the square of the engine speed based on the crank angle signal; a sensor for detecting an engine load; means for calculating a combustion excitation force; means for calculating a phase delay with respect to the crank angle from the combustion excitation force and the unbalanced inertia force; means for generating a crank angle signal as a synchronization signal for use as a reference value for the phase of a secondary sound; means for generating a secondary sound signal using the synchronization signal; and means for disposing the secondary sound signal in a vehicle interior. A vehicle interior noise reduction device comprising: means for outputting to a secondary sound source.