This application is based on and claims priority under 35 U.S.C § 119 with respect to Japanese Patent Application 2006-302832, filed on Nov. 8, 2006, the entire content of which is incorporated herein by reference.
This invention relates to an active vibration reduction system, in particular, the invention relates to an active vibration reduction system which provides vibrations to a vibration source such as a vehicle engine to actively suppress vibrations from the vibration source.
An active vibration reduction system actively suppresses vibrations occurring when an engine, a motor or the like provided at a vehicle vibrates by providing vibrations, which has a substantially opposite phase of the vibrations of a vibration source, and thus improving comfort and quietness in the vehicle. For example, in an active vibration reduction system disclosed in JP 2001-14097A, an electromagnetic actuator (coil) is driven by controlling an H bridge circuit being synchronized with a rotational pulse signal of an engine, i.e. the vibration source, to generate the vibrations. The vibrations from the vibration source are suppressed by a counter-force of the generated vibrations.
In the active vibration reduction system, an enhanced vibration suppression performance is expected for upgrading the quietness of the vehicle. However, it becomes difficult for pedestrians and the like to perceive the approach of the vehicle in exchange for improvement of the vibration suppression performance. In order to resolve the issue, a car horn may be used. However, if the car horn is sounded while the vehicle is being driven in an urban area or a residential area, other issues such as a noise issue may occur.
A need exists for an active vibration suppression system which is not susceptible to the drawback mentioned above.
According to an aspect of the present invention, an active vibration reduction system for a vehicle for suppressing a vibration from a vibration source includes a vibration suppression signal generating unit for generating a vibration suppression signal having a frequency being synchronous with the vibration from the vibration source, a sensible signal generating unit for generating a sensible signal having a frequency being asynchronous with the vibration from the vibration source, a magnetic pole forming magnetic flux, a coil provided in a manner that intersects the magnetic flux, and a coil driving circuit relatively vibrating the magnetic pole and the coil by controlling an energized state of the coil based on the vibration suppression signal and the sensible signal.
The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:
Hereinafter, embodiments of the present invention will be described with reference to drawings.
The magnetic pole 6 is provided with a south pole 7 and north poles 8, and the coil 9 is movably inserted into a cylindrical space defined between the south pole 7 and the north poles 8. The coil 9 is held by a cylindrical coil holding member 11, and the coil holding member 11 is fixed to an engine sub-flame 10 which is provided at a body 100 via rubber mounts 12. Further, the engine 2 is provided via the engine sub-frame 10 and the engine mounts 13. Thus, the magnetic pole 6 is vibrated by the magnetic field formed by flowing current into the coil 9. As just described, the coil 9 is vibrated by a signal having a frequency being synchronous with the vibrations from the engine 2 and thereby suppressing the vibrations from the engine 2.
The estimation of the engine speed is calculated by using the moving average method as shown in
T=(AVR/(AVR−1))*(T−1)
Further, the engine speed and the frequency of the engine 2 are determined by the estimated time period. Specifically, assume that AVR−1 is 66 milliseconds, AVR is 60 milliseconds, and T−1 is 20 milliseconds. In this case, T is calculated to be approximately 18.18 milliseconds. Hence, it is estimated that the engine speed of the engine 2 maintained until the next interruption is approximately 1100 rpm and the frequency is 55 Hz. As just described, the engine speed and the frequency are calculated with higher accuracy by using the moving average method based on Feed forward control.
The control unit 20 is provided with a vibration suppression signal generating unit 25, which generates a vibration suppression signal, and a sensible signal generating unit 26 which generates a sensible signal. The frequency analysis is performed based on the engine speed of the engine 2, which is estimated in the processing unit 22 as described above, in the vibration suppression signal generating unit 25 to generate the vibration suppression signal having the frequency synchronized with the vibrations from the engine 2. In the active vibration reduction system according to the embodiments of the present invention, the coil 9, which is provided at the active vibration reduction system 1, is used for generating both the vibration suppression signal and the sensible signal, and the system does not include two separate coils for generating the respective signals. Thus, these signals need to be combined in advance. The signal synthesis is conducted in a signal synthesizing unit 27, and an example of the signal synthesis is shown in
The sensible signal has the frequency being asynchronous with the vibrations from the engine 2. The data of the sensible signal may be created in advance, and the data is stored in a recording unit 24. The processing unit 22 reads in the data from the recording unit 24 as needed to output the data to the sensible signal generating unit 26. Although one kind of the sensible signal, which is stored in the recording unit 24, may be sufficient, but plural kinds of sensible signals may be stored therein. As for the storing process, the data of the sensible signals may be stored in the recording unit 24 during the manufacturing process of the control unit 20. In addition, a communication unit 23 provided at the control unit 20 communicates with external facilities via an antenna, and the signal data may be rewritten and be added in accordance with the user's preference.
The synthesized signal, which is synthesized in the signal synthesizing unit 27, is input to a coil driving circuit 31. The coil driving circuit 31 controls an energized state of the coil 9 provided at the active vibration reduction system 1.
Meanwhile, an amplitude value of the synthesized signal output from the signal synthesizing unit 27 is converted by a register R1 and a register R2 to be input to a buffer IC2. The output of the buffer IC2 is input to the controller IC1 via a coupling capacitor C3. The controller IC1 controls the current flowing into the coil 9 in accordance with the synthesized signal and thereby vibrating the magnetic pole 6 and the coil 9 relatively. In
The first and second embodiments are described referring to a flowchart.
If the frequency falls out of a predetermined frequency range, that is, when the engine speed is slow as in an idling state and the frequency is low, or when the engine speed is high as in an acceleration state and the frequency is high (Step #03:Yes), the vibration suppression signal generating unit 25 reads the phase and amplitude data, which corresponds to the determined frequency, from the amplitude and phase table to generate the vibration suppression signal (Step #04). Next, the sensible signal generating unit 26 reads the music scale data stored in the recording unit 24 to generate the sensible signal based on the music scale data (Step #05).
The vibration suppression signal generating unit 25 and the sensible signal generating unit 26 output the vibration suppression signal and the sensible signal respectively to the signal synthesizing unit 27 (Step #06). The signal synthesizing unit 27 generates the synthesized signal based on the respective signals (Step# 07), and the coil 9 is energized by the coil driving circuit 31 (Step #08). The energization of the coil 9 continues until the phrase playing time elapses (Step #09:No). When the phrase playing time elapses, the energization of the coil 9 is terminated (Step #09:Yes).
If the frequency, which is calculated using the TACH signal, is in the predetermined frequency range, for example, when the vehicle is running on a highway or when the electric-hybrid vehicle is driven by the motor (Step #03:No), the output of the vibration suppression signal generating unit 25 is terminated because the vibrations from the engine 2 is imperceptible (Step #10). If the switch of the output switching unit 28 is not on (Step #11:NO), the sensible signal generating unit 26 reads the melody registered in a melody table stored in the recording unit 24 to generate the sensible signal (Step #12). At this time, the output from the vibration suppression signal generating unit 25 is terminated, and thus the sensible signal is output to the coil driving circuit 31 without being combined with the vibration suppression signal (Step #13) and the coil 9 is energized (Step #08). The energization of the coil 9 continues until the phrase playing time elapses (Step #9:No). When the phrase playing time elapses, the energization of the coil 9 is terminated (Step #9:Yes).
On the other hand, if the switch of the output switching unit 28 is on (Step #11:Yes), the sound source is output from the audio equipment 30 to the coil driving circuit 31 via the lowpass filter 29 (Step #14). The coil 9 is energized by the coil driving circuit 31 based on the signal of the sound source (Step #08). The energization of the coil 9 continues until the phrase playing time elapses (Step #09:NO). When the phrase playing time elapses, the energization of the coil 9 is terminated (Step #09:Yes).
In the aforementioned embodiments, each component of the control unit 20 is described. These components may be mounted on a chip by employing a microcomputer and an ASIC (Application Specific Integrated Circuit). Further, the control unit 20 and the coil driving circuit 31 may be mounted on one chip. So configured, the size of the active vibration reduction system is reduced and thus enabling the system to save space.
In the aforementioned embodiments, the signal in the audible frequency range is used as the sensible signal. However, the sensible signal is not limited to this kind of signal. For example, the sensible signal may be used as a warning signal in case that the driver falls asleep at the wheel, and vibrations are generated to wake up the driver.
In the first embodiment, the sensible signal is generated by multiplying the vibration suppression signal by 8, but the number of times is not limited to 8. The number of times may be set to any number.
In the first embodiment, the sensible signal is stored in the recording unit 24 or may be rewritten or added by the communication unit 23 which communicates with the external facilities via the antenna. However, the sensible signal is not limited to these examples. For instance, the vehicle may communicate with a predetermined base station or other systems by using CAN (Controller Area Network) to alert the driver about abnormality of the vehicle or road construction by melodies.
In the second embodiment, the synthesized signal, which is synthesized from the vibration suppression signal and the sensible signal, and the audio signal input from the audio equipment are switched in the output switching unit 28 to transmit the signal to the coil driving circuit 31. However, the transmission of the audio signal is not limited to the above-described example. A signal may be synthesized from the vibration suppression signal and the audio signal to be transmitted to the coil driving circuit 31. Further, the vibrations may be suppressed based on the audio signal alone.
The structure of the active vibration reduction system 1 allows the vibration suppression signal to suppress the vibrations from the vibration source. In addition, a signal having a frequency being asynchronous with the vibrations from the vibration source is synthesized, and the coil 9 is vibrated based on the synthesized signal. Thus, the sensible signal is output while suppressing the vibrations from the vibration source.
According to the above-described structure of the active vibration reduction system 1, the sensible signal may be in the audible frequency range. Further, the signal generated based on the sensible signal may serve as a warning device. This structure allows the vehicle to run in the urban area and the residential area playing the music, and thereby alerting the pedestrians of the approach of the vehicle without sounding the car horn. Thus, accidents, possibly leading to physical injuries, become avoidable.
According to the above-described structure of the active vibration reduction system 1, the audio signal transmitted from the audio equipment 30 via the lowpass filter 29 may be used as the sensible signal, and the magnetic pole 6 and the coil 9 are relatively vibrated based on the audio signal.
The structure allows the user to use the audio signal from the exterior portion of the system as the sound source. Thus, melodies are sounded without adding new speakers. Further, since the audio signal is transmitted via the lowpass filter 29, the speaker function is preformed stressing bass sounds. Therefore, a surround-sound system, which stresses the bass sounds, is built.
The principles, of the preferred embodiments and mode of operation of the present invention have been described in the foregoing specification. However, the invention, which is intended to be protected, is not to be construed as limited to the particular embodiment disclosed. Further, the embodiment described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents that fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.
Number | Date | Country | Kind |
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2006-302832 | Nov 2006 | JP | national |