Patent Publication Number: US-6912454-B2

Title: Active noise control system with horn sound feature

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to U.S. Provisional Application No. 60/389,584, which was filed on Jun. 18, 2002. 

   BACKGROUND OF THE INVENTION 
   This invention generally relates to active noise control systems for vehicles. More particularly, this invention relates to operating an active noise control system to provide a horn sound when a vehicle is not running. 
   Most vehicles include a horn that is activated by pressing or more switches typically mounted on a steering wheel assembly. The horn is properly used to notify other drivers or pedestrians of a vehicle&#39;s presence or approach, for example. Typical horn assemblies include a physical horn component mounted within the engine compartment that emits the horn sound responsive to appropriate switch activation. 
   Active noise control systems are well known. On modern vehicles, active noise control systems operate to cancel out noises associated with air intake assemblies, for example. A noise control system typically includes a speaker that is driven to emit a sound that cancels out engine noise sounds that otherwise may be noticed by an individual within the passenger compartment. A controller drives the speaker to provide the necessary noise cancellation signal or sound to provide the desired effect. 
   With the advances available in electronics onboard vehicles, those skilled in the art are always striving to provide additional features and functions for the consumer. Further, there is always a need to strive for minimizing the expenses associated with supplying vehicle components to manufacturers. This invention takes advantage of the capabilities of an active noise control system and provides further capabilities that eliminates otherwise needed separate components such as a horn. 
   SUMMARY OF THE INVENTION 
   In general terms, this invention is an active noise control system that also provides a horn sound function even when the vehicle is not running. 
   One example system designed according to this invention includes a speaker. A controller drives the speaker to produce a desired sound. The controller operates in a normal mode while the vehicle is running and typically drives the speaker to produce a noise cancellation sound to cancel out noises associated with operation of the engine so that such noises are not noticeable within the vehicle passenger compartment. The controller also operates in a power saving mode when the vehicle is not running. The controller wakes up from the power saving mode responsive to a horn switch activation that occurs when the vehicle is not running. The controller then drives the speaker to emit a horn sound and returns to the power saving mode after the horn switch activation is complete. 
   In one example, the system includes an amplifier associated with the speaker. The controller mutes the amplifier in the power saving mode and unmutes the amplifier responsive to the horn switch activation so that the desired horn sound is produced. 
   The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of a currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  schematically illustrates an active noise control system designed according to this invention supported on an example vehicle. 
       FIG. 2  is a flow chart diagram illustrating an example method of controller operation designed according to this invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  schematically shows a vehicle  20  that includes an active noise control system  22 . A speaker  24  and an amplifier  26  are driven by a controller  28 . The speaker  24  is associated with, for example, the air intake manifold of the vehicle to cancel out noises associated with engine operation that would otherwise be noticeable within the vehicle passenger compartment. Known active noise cancellation techniques provide such results. 
   A steering wheel assembly  30  is supported within the vehicle passenger compartment. A horn switch  32 , which operates in a conventional manner, is supported on the steering wheel assembly  30 . In the example arrangement, the horn switch  32  does not activate a separate horn device supported within the engine compartment. Instead, the noise control system  22  provides the horn sound using the speaker  24 . The controller  28  responds to activation of the horn switch  32  by driving the amplifier  26  and speaker  24  to emit a preselected horn sound. 
   The controller  28  operates in a normal operation mode while the vehicle is running. The controller  28  normally provides active noise control in a conventional manner. In the event that the horn switch  32  is activated, the controller  28  detects a horn switch activation and interrupts the active noise control temporarily so that the speaker  24  can be used to provide the desired horn sound. 
   It is desirable to provide an individual the ability to activate the horn even when the vehicle is not running. The controller  28  enters a power saving, standby mode when the ignition is turned off and the vehicle is not running. The controller  28  interprets a horn switch activation as a wake up signal when the controller is in the power saving mode. The controller  28  then responds to the horn switch activation by appropriately driving the speaker  24  to emit the horn sound. 
     FIG. 2  illustrates an example control strategy in flow chart form. At  42  the controller  28  is in the power saving mode. A horn switch activation at  44  provides a wake up signal to the controller  28 . In one example, the horn switch activation produces a low digital signal (i.e., 0) that is interpreted by the controller  28  as a wake up signal. Once awakened, the controller  28  continues checking for a horn switch activation signal every ten milliseconds at  46 . The controller  28  unmutes the amplifier  26  at  48  and drives the speaker  24  to emit the desired horn sound at  50 . In the illustrated example, the horn sound is generated for 200 milliseconds. The controller  28  continues checking for horn switch activation and driving the speaker  24  to emit the horn sound as long as the signal is present. 
   Once the horn switch  32  is released, the determination at  46  is negative. The controller  28  then mutes the amplifier at  52  and returns to the power saving mode at  42 . 
   In one example, the controller  28  comprises a digital signal processor (DSP). The DSP wakes up responsive to the horn switch activation signal and then controls the amplifier  26  and speaker  24  as necessary to achieve the desired horn sound. In another example, the controller  28  includes a microprocessor portion and a DSP portion. In this example, the microprocessor portion is responsible for handling the horn activation when the controller is in the power saving mode. In this latter example, the DSP remains in shutdown mode during horn activation when the vehicle is not running. 
   Those skilled in the art who have the benefit of this description will realize how best to select and arrange the electronics to achieve the horn activation strategy that best suits their particular needs. 
   The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.