WO2011132347A1 - A simulated engine sound generating apparatus - Google Patents

A simulated engine sound generating apparatus Download PDF

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Publication number
WO2011132347A1
WO2011132347A1 PCT/JP2011/000209 JP2011000209W WO2011132347A1 WO 2011132347 A1 WO2011132347 A1 WO 2011132347A1 JP 2011000209 W JP2011000209 W JP 2011000209W WO 2011132347 A1 WO2011132347 A1 WO 2011132347A1
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WO
WIPO (PCT)
Prior art keywords
sound
vehicle speed
engine sound
storage means
signal
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PCT/JP2011/000209
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French (fr)
Inventor
Shinya Odama
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Koyama Kogyo Co., Ltd.
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Publication of WO2011132347A1 publication Critical patent/WO2011132347A1/en

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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K15/00—Acoustics not otherwise provided for
    • G10K15/02—Synthesis of acoustic waves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
    • B60Q5/00—Arrangement or adaptation of acoustic signal devices
    • B60Q5/005—Arrangement or adaptation of acoustic signal devices automatically actuated
    • B60Q5/008—Arrangement or adaptation of acoustic signal devices automatically actuated for signaling silent vehicles, e.g. for warning that a hybrid or electric vehicle is approaching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2200/00—Type of vehicles
    • B60L2200/12—Bikes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2270/00—Problem solutions or means not otherwise provided for
    • B60L2270/42—Means to improve acoustic vehicle detection by humans

Definitions

  • the present invention relates to a simulated engine sound generating apparatus for usein an electric vehicle which is mounted on an electric motorcycle limited in speed and generates a simulated engine sound, especially as basic waveform for reproducing the stimulated engine sound by using either one of an idling engine sound, 3sound components and an artificial down-converted sound.
  • Electric vehicles particularly electric motorcycles are expected to reduce environmental pollution.
  • more than half of motorcycles are an electric type.
  • the electric motorcycle runs silently near the sidewalk, it is difficult to notify in advance a walker of the approach of the electric motorcycle, which is dangerous.
  • An apparatus which generates this type of simulated engine sound generally employs a configuration which repeatedly reproduces sound data stored in advance as a digital signal obtained by recording an engine sound of a vehicle during normal driving for several seconds while changing the pitch (frequency (sound height))or volume (sound pressure (sound size)) ofthe sound data according to driving states of an engine (rotation speed or accelerator manipulation).
  • the pitch is increased in proportion when the rotation speed of the engine is increased, and is decreased when the rotation speed of the engine is decreased.
  • the volume is increased as a driver presses on the accelerator, and is decreased as the driver eases off the accelerator.
  • an object of the present invention is to provide a cheaper apparatus which generates an engine sound simply and correctly.
  • the present inventors have found that in a normal idling state of an electric vehicle,it is difficult to reproduce an engine sound at the time of idling in which an electric motor does not rotate when a simulated engine sound is to be reproduced on the basis of a vehicle speed which is calculated from a driving signal such as a pulse generated by the electric motor with the electric motor being stopped, but it is effective for reproduction of the engine sound that an actual sound is formed using an idling sound as a basic waveform in an electric vehicle which typically runs at low speed considering that recognition of the idling state is important to a driver in view of mental preparation.
  • a high frequency engine sound componentand a low frequency engine sound component are not changed uniformly according to a vehicle speed, but the proportion of the low frequency engine sound component is high at a low speedof 20 to 30km/h or less and the proportion of the high frequency engine sound component is high at a high speed of 30km, and a base sound such as a machine vibration is combined therewith in addition thereto, to thereby form the actual engine sound.
  • an object of a first embodiment of the present invention is to provide a simulated engine sound generating apparatus which is capable of reproducing an idling sound, although a motor does not rotate, at the time of idling and approximately correctly reproducing an actual engine sound at the time of running, by using sound at the time of idling as a basic sound pressure waveform and by overlapping and adjusting frequency and sound pressure in consideration of the basic sound pressure waveform and a motor rotation number, and which has low costs.
  • a second embodiment of the present invention it has been found that by dividingcomponents forming a simulated engine sound into a high frequency engine sound component anda low frequency engine sound component and by overlapping these components with a base soundsuch as a machine vibration at a specific ratio, it is possible to cover a range from idlingto low-speed running and from low-speed running to high-speed running by changing the reproduction rate of a single actual engine sound in an electric motorcycle of 45km/h or less, andit is an object to provide a simulated engine sound generating apparatus which is yet closerto the actual engine sound, based on these findings.
  • a third embodiment of the present invention based on the finding that when an actual engine sound at the time of running is used as a basic waveform, it is desirable that an artificial sound is firstly created on the basis of the actual sound, and a sampling cycle is rapidly increased at the time of accelerating, instead of being linearly changed according to the vehicle speed corresponding to the amount of wheel rotations, to thereby allow the apparatus to be close to the actual sound, it is an object to provide a simulated engine sound generating apparatus which generates an engine sound close to an actual sensation at a low cost.
  • a simulated engine sound generating apparatus 200 for use in an electric vehicle which reproduces a simulated engine sound predicted from waveform data from an actual engine sound according to a vehicle speed on thebasis of a motor rotation number of the electric vehicle and generates the simulated engine sound, including: vehicle speed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal determining a sampling cycle according to the vehicle speed and a sound pressure signal determining a volume gain according to the vehicle speed, on the basis of a pulse signal; first storage means 221 which stores an actual engine sound at the time of idling within a predetermined time as data on a basis sound pressure waveform; second storage means 222 which temporarily stores the basic sound pressure waveform data read from the first storage means as a base engine sound waveform; a memory controller 224 which receives the sampling signal according to the vehicle speed from the vehicle speed detection means and transmits a signal changing the sampling cycle (reproduction rate)
  • a simulated engine sound generating apparatus 200 for use in an electric vehicle which reproduces a simulated engine sound predicted from waveform data from an actual engine sound according to a speed of the electric vehicle and generates the simulated engine sound, including: first storage means 221 which stores data on a sound pressure waveform of the actual engine sound within a predetermined time; second storage means 222 which temporarily stores an engine sound from the sound pressure waveform data read from the first storage means; third storage means 223 which temporarily stores a base sound of a machine vibration system from the sound pressure waveform data read from the first storage means; a frequency divider 225 which divides an engine sound waveform read from the second storage means at a reproduction rate determined according to the vehicle speed into a high frequency band engine sound waveform component and a low frequency band engine sound waveform component; vehicle speed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal determining a sampling cycle according to the vehicle speed
  • the frequency divide may be used.
  • the first storage means may contain the basic waveform of the 3 components and the second storage means is used for the high frequency waveform and the third storage means is used for a basic sound waveform component B of machine vibration system and the fourth storage means is used for a low frequency waveform L.
  • a simulated engine sound generating apparatus 200 for use in an electric vehicle which reproduces a simulated engine sound predictedfrom waveform data from an actual engine sound according to a vehicle speed on the basis of a motor rotation number of the electric vehicle and generates the simulated engine sound, including: vehicle speed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal determining a sampling cycle according to the vehicle speed and a sound pressure signal determining a volume gain according to the vehicle speed, on the basis of a pulse signal; first storage means 221 which stores, as data on a basic sound pressure waveform, an artificial sound obtained by down-converting an actual engine sound at the time of running within a predetermined time using a Gaussian smoothing technique; second storage means 222 which temporarily stores the basic sound pressure waveform data read from the first storage means as a base engine sound waveform; a memory controller 224 which receives the sampling signal according to the vehicle speed from the vehicle speed detection means and transmits
  • the first storage means stores, as data on a basic sound waveform, an artificial sound obtained by down-converting an actual engine sound at the time of running within a predetermined time and smoothing by a Weighted Moving Average Method, especially a Gaussian smoothing method which is well known method in a field of Image processing.
  • the mixer 226 which receives the sound pressure signal linearly changed according to the vehicle speed from the vehicle speed detection means 210, transmits data on a sound pressure waveform from the second storage means at the sampling cycle rapidly changed at the time of accelerating, and stops or decreases the sound pressure waveform data transmitted from the second storage means atthe limit speed or higher.
  • the first embodiment it is possible to generate an idling sound even at the time of idling in which a motor does not rotate even in the case of an electric vehicle which measures a vehicle speed by a number of rotations of the electric motor by using an engine sound waveform at the time of idling as a basic waveform, and to nearly completely reproduce a simulated sound of an actual engine sound at a low speed range allowed by the electric vehicle by adjusting the frequency and sound pressure thereof even in a case where the engine sound waveform at the time of idling is used as the basic waveform, thereby generating an effective simulated engine sound from idling to the low speed range.
  • a predetermined actual engine sound waveform as a basic waveform, by dividing it into a high frequency engine sound component, a low frequency engine sound component and a base component such as a machine vibration, and by adjusting a reproduction rate according to the vehicle speed for these components and adjusting sound pressures of these three components and a mixing ratio according to the vehicle speed, it is possible to reproduce a simulated engine sound close to the actual engine sound according to the vehicle speed without preparing a map which stores the actual engine sound according to the vehicle speed.
  • the third embodiment it is possible to simplify the apparatus by using an actual engine sound at the time of running as a basic waveform and by using an artificial sound obtained by down-converting the basic waveform using a Gaussian smoothing technique, and to reliably prevent deviation from the actual sound by rapidly changing a sampling cycle at the time of accelerating at this time so that the sampling cycle is not linearly changed according to the vehicle speed which is the amount of wheel rotations.
  • the base sound component such as a machine vibration is included as one basic waveform
  • the sound generation means as a voice coil in a resonance section formed in a seat of the electric vehicle, it is possible to provide asimulated engine sound generating apparatus for use in an electric vehicle which vibrates the seat of the electric motorcycle and generates sound by reproducing vibrations of an enginemotorcycle.
  • the actual engine sound waveform data stored in the first storage means employs an actual engine sound at the time of idling of 1,000 to 1,500rpm. Further, when the actual engine sound at the time of running is used,for simplification of the apparatus, the actual sound is down-converted from a digital audio standard frequency (48kHz) using a Gaussian smoothing technique. In this case, it is desirable to use frequency of10kHz or higher to reduce deviation from the actual sound.
  • Fig. 1 is a diagram illustrating a configuration of an electric motorcycle including a simulated engine sound generating apparatus according to the present invention.
  • Fig. 2 is a block diagram illustrating a control system of an electric motorcycle according to the present invention.
  • Fig. 3 is a block diagram illustrating a configuration of a vehicle simulated engine soundgenerating apparatus according to a first embodiment of the invention.
  • Fig. 4 is a graph illustrating an example of a program adjusting a sampling cycle and gain from a vehicle speed according to a first embodiment of the invention.
  • Fig. 5(a) is a diagram illustrating an actual engine sound waveform at the time of idling, and Fig.
  • FIG. 5(b) is a diagram illustrating a simulated engine sound waveform having twice the gain and twice the frequency at a vehicle speed of 30km/h.
  • Fig. 6 is a block diagram illustrating a configuration of a vehicle simulated engine sound generating apparatus according to a second embodiment of the invention.
  • Fig. 7 is a block diagram illustrating a configuration of a vehicle simulated engine sound generating apparatus according to a third embodiment of the invention.
  • Fig. 8 is a waveform diagram when a basic actual engine sound (a) is divided into a high frequency engine sound component (b) and a low frequency engine sound component (c).
  • Fig. 9 is a program which determines a mixing ratio of respective waveforms to a vehicle speed.
  • FIG. 10 is a graph illustrating an example of a program adjusting a vehicle speed, a sampling cycle and gain when an artificial sound down-converted from an actual engine sound at the time of bike running is used as a basic waveform, according to a first embodiment of the invention.
  • an electric tricycle 100 includes a vehicle body 110 in which a seat 111 is installed and a handle apparatus 120 is installed in a front section of the vehicle body 110.
  • a seating switch 112 and an engine sound generator 200 are installed in the seat 111, and a power supply 113 is embedded in a lower section thereof.
  • the electric tricycle 100 can drive a driving motor 116 installed in a vehiclewheel 115 through a controller 114 (not shown).
  • the handle apparatus 120 includes a right accelerator grip 121, a left grip 122 and a left brake arm 123.
  • a parking device 130 is installed in the left brake arm 123 .
  • the left brake arm 123 can mainly allow a rear wheel to be in a brake state.
  • a reference numeral 124 is a driving switch, and a reference numeral 125is a reversing switch.
  • a front panel 126 is installed in the center of the handle apparatus 120, and the driving switch 124 is installed at a lower section thereof.
  • the seating switch 112 which is a boarding detection means of a driver (not shown)is installed in the seat 111, and detects seating (boarding) and non-seating (non-boarding) of the driver.
  • the seating switch may include an infrared light switch or a limit switch. If the driver sits in the seat 111, the switch turns on to be in a boarding detection state. This is transmitted to the controller 114 as a seating signal S2. Further, if the driver moves away from the seat 111, the switch turns off to be in a non-boarding detection state.
  • a limit switch can detect weight of the driver and if a person having a weight of 30 to60 kg or more, in view of the weight of an adult, sits in the seat 111, the seating signal S2 is firstly transmitted.
  • the safety apparatus includes the seating switch 112 which works with the driving switch;the parking device 130 which works with the hand brake arm 123; a parking switch 131 installed in the parking device 130; and a motor sound generating apparatus 200 which works with the electric motor 116.
  • the driving switch 124 turns on, the driving signal S1 is transmitted to the control means 114.
  • the seating switch 112 detects the weight of the passenger. If the weight is 30 kg or more,the seating signal S2 is transmitted to the control means 114.
  • the control means 114 is in a driving preparation state in which electric power from the power supply can be transmittedto the driving motor 116 by an AND signal of the driving signal S1and the seating signal S2.
  • the driving signal S1 is also transmitted to the engine sound generating apparatus 200, and an idling sound can be generated from the engine sound generating apparatus 200.
  • a release signal S3 is transmitted to the control means 114.
  • the control means 114 supplies electric power to the electric motor 116from the power supply 113.
  • the amount of electric power to the electric motor gives play tothe accelerator means 121.
  • An accelerator signal S4 corresponding to a desired speed is transmitted to the control means 114 according to the rotation aperture.
  • the driving speed can be switched between a high speed drivable state and a low speed drivable state by a switch 127.
  • a simulated engine sound is generated from the engine sound generating apparatus 200 according to the driving amount of the electric motor 114.
  • a reversing signal S5 is transmitted to the control means, and the electric motor 116 is rotated backwards by the accelerator means 121 to be able to go backwards at low speed.
  • the driving signal S1 is transmitted to the engine sound generating apparatus 200 when the driving switch 124 is turned on, the rotation of the motor 116 remains stopped, but the idling sound is generated. If the number of motor rotations is increased, asimulated engine driving sound suitable for an actual engine sound is generated according tothe vehicle speed, and a gasoline engine sound can be reproduced. Alternatively, an alarm sound providing notification of the backward movement may be generated by the reversing switch 125.
  • Fig. 3 is a block diagram illustrating the engine sound generating apparatus 200 according to a first embodiment of the present invention.
  • the engine sound generating apparatus 200 includes speed detection means 210 which calculates a vehicle speed from a rotation speedof an electric motor M; engine sound reproduction means 220 which generates a simulated engine sound according to the vehicle speed according to a vehicle speed signal Vs from the speed detection means 210; and engine sound generation device 230 which generates the simulated engine sound from the reproduction means 220, and reproduces an idling sound which is a basic waveform so that a sampling cycle (reproduction rate) and a sound pressure intensity are changed according to the vehicle speed.
  • speed detection means 210 which calculates a vehicle speed from a rotation speedof an electric motor M
  • engine sound reproduction means 220 which generates a simulated engine sound according to the vehicle speed according to a vehicle speed signal Vs from the speed detection means 210
  • engine sound generation device 230 which generates the simulated engine sound from the reproduction means 220, and reproduces an id
  • the engine sound generating apparatus 200 includes vehicle speed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal which determines a sampling cycle according to the vehicle speed on the basis of a pulse signal and a sound pressure signal which determines a volume gain according to the vehicle speed;first storage means 221 which stores an actual engine sound at the time of idling within a predetermined time as data on a basic sound pressure waveform;second storage means 222 which temporarily stores the basic sound pressure waveform data read from the first storage means as abase engine sound waveform; a memory controller 224 which receives the vehicle speed signal according to the vehicle speed from the vehicle speed detection means and transmits a sampling signal changing the sampling cycle (reproduction rate)which is a reading speed to the second storage means; a mixer 226 which receives the sound pressure signal according to the vehicle speed from the vehicle speed detection means 224, transmits a basic sound pressure waveform from the second storage means at the time of idling, and ampl
  • the vehicle speed detection means 210 includes a pulse detector 211 which detects rotation of the electric motor M as pulses of the three-phase motor; an amplifier means 212whichdigitalizes the pulse signal for transmission; and a calculator 213 which calculates the vehicle speed from the digital signal.
  • the vehicle speed detection means 210 transmits a sampling signal fsam according to the vehicle speed from the calculator 213 to the memory controller 224 of the simulated engine sound generation means 220, and also transmits a sound pressure signal G according to the vehicle speed to the mixer 226.
  • a sampling signal Ssam according to the vehicle speed and the gain (sound pressure) signal G according to the vehicle speed are adjusted as shown in Fig. 4.
  • a following method may be adopted to make a preferred another base sound in place of using the above actualengine sound during running as a base sound.
  • an actual engine sound is recorded in a mode of digital audio standard (48kHz) or a CD standard frequency (44.1 kHz) and down-converted to a lower suitable frequency (for example 10 kHz) where the actual sound waveform is subjected to a smoothing process and finally reproduced in a style of the quadratic function or the same function including a more rapidly change part.
  • the actual engine sound recorded in the digital mode of 48 kHz is down-converted up to a suitable frequency for simplicity of apparatus construction. For example, it has been found that 10kHz is a critical frequency in a down-converted case from 48 kHz because reproductionaccuracy becomes very different between more than 10 kHz and less than 10 kHz in case of thesimulated engine sound from the down-converted frequency sound waveform.
  • the actual sound waveform to be down-converted is subjected to a smoothing method for eliminating a mechanical sound contained in the actual engine sound. Many of the smoothing method are well known in an Image processing field.
  • Gaussian Smoothing Method is more suitable to make a base sound from the actual engine sound used for reproduction of the simulated sound.
  • the other Gaussian filter coefficient can be used for reproduction of the simulated sound in the present invention.
  • a weight when an average value is calculated,is increased as it approached a waveform target pixel and is decreased when it moves away from target pixel, and the down-converted actual sound is smoothed to a base sound waveform by the Weighted moving Average Method, especially the Gaussian Smoothing Method.
  • the down-converted waveform is sampled in a rapidly changed sampling cycle mode like the quadratic function or the same function in order to reproduce a stimulated sound having an increasing tempo because it has been found that such a quadratic function sampling mode including a rapidly changed sampling cycle is better than a constant linear function sampling mode for reproducing an acceleration sound.
  • the sampling cycle and gain (sound pressure) corresponding to the vehicle speed had better be adjusted in a manner as shown in Fig.10.
  • the reproduction rate may be adjusted considering the base sound property in order to make a simulated engine sound more approaching to the actual engine sound.
  • the reproduction rate (sampling cycle)should bechanged at the three divisions of the slow running state, the acceleration state and the constant running state respectively.
  • the sampling cycle is better to be changed in a manner of at least 3 steps such as slow running state, accelerating state and constant running state.
  • the gain (sound pressure) had better be programmed to be increased with a constant gradient from the idling state 0 km/h and rapidly decreased or dropped at 25 km/h and then be stopped or maintainedsmall up to 40 km/h,whereby even if the vehicle speed would be calculated according to the rotation speed of the electric motor and the sampling cycle is determined by the calculated vehicle speed, the stimulated engine sound will not be overlapped with the rotation sound of wheel, resulted in no interruption caused by the rotation sound. That means, blend with noise due to the wheel rotation, which causes an undesirable result.
  • Fig. 6 is a block diagram illustrating an engine sound generating apparatus 200 according to a second embodiment of the present invention.
  • the engine sound generating apparatus 200 includes speed detection means 210 which calculates a vehicle speed from a rotation speed of an electric motor M; engine sound reproduction means 220 which generates a simulated engine sound according to a vehicle speed by a vehicle speed signal Vs from the speed detection means 210; and an engine sound generation device230 which generates the simulated engine sound from the reproduction means 220.
  • the engine sound which is a basic waveform is divided into a high frequency engine sound component, a low frequency engine sound component and a base sound component such as a machine vibration and is reproduced so that a sampling cycle (reproduction rate) and a sound pressure intensity are changed according to the vehicle speed, and a mixing ratio of the three components is adjusted according to the vehicle speed.
  • the simulated engine sound generating apparatus 200 for use in an electric vehicle which reproduces a simulated engine sound predicted from waveform data from an actual engine sound according to a speed of the electric vehicle and generates the simulated engine sound, includes first storage means 221 which stores data on a sound pressure waveform of the actual engine sound within a predetermined time; second storage means 222 which temporarily stores an engine sound from the sound pressure waveform data read from the first storage means; third storage means 223 which temporarily stores a base sound of a machine vibration system from thesound pressure waveform data read from the first storage means; a frequency divider 225 which divides an engine sound waveform read from the second storage means at a sampling cycle (reproduction rate) determined according to the vehicle speed into a high frequency band engine sound waveform component and a low frequency band engine sound waveform component; vehiclespeed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal determining a samplingcycle according to the vehicle speed, a
  • the engine sound reproduction means 220 includes the memory controller 224 which receives a vehicle speed signal SV output from the vehicle detection means 210 and generates a sampling signal Sc which controls a sound generation sampling cycle reproduction rate); the first storage means 221 including a flash memory which stores sound pressure waveform data of the actual engine sound; the second storage means 222 including a DRAM which generates a sound pressure signal of the simulated engine sound on the basis of a sound generation reproduction rate control signal Sc generated by the memory controller 224 and the sound pressure waveform data read from the first storage means 221; the third storage means 223 including a DRAM which generates a simulated base sound at a predetermined sampling cycle on the basis ofthe sampling signal Sc generated by the memory controller 224 and the sound pressure waveform data read from the first storage means 221; the frequency divider 225 which divides the engine sound waveform read at the sampling cycle (reproduction rate) determined according to the vehicle speed from the second storage means 222 into the high frequency band engine soundwaveform component H and the low frequency band engine sound waveform component L; the
  • the first storage means 221 stores an actual engine sound for a predetermined time corresponding to two rotations of a crank shaft (one combustion cycle of the engine), and transmits the actual engine sound to the second and third storage means by a driving signal.
  • Theactual engine sound of 500 to 1000rpm in an idling state is generally recorded.
  • the actual engine sound signal is sound waveform data and includes the high frequency engine sound component H of the actual engine sound, the low frequency engine sound component L of the actual engine sound, and the base sound component B such as a machine vibration.
  • a basic waveform (a) shown in Fig. 7 can be divided into a high frequency component waveform(b) and a low frequency component waveform (c).
  • the above-described three types of signals are slightly changed ateach sampling cycle (reproduction rate) based on a vehicle speed SV transmitted by the memory controller 221.
  • the first storage means 222 records the sound pressure waveform data obtained by converting the actual engine sound into digital data as an engine sound corresponding to one engine combustion cycle, in the idling running state.
  • the second storage means 223 transmits the engine sound pressure waveform data of the frequency according to the vehicle speed on the basis of the sampling signal transmitted by the memory controller 221.
  • the third storage means 224 transmits the basesound pressure waveform data of the frequency according to the vehicle speed on the basis ofthe sampling signal transmitted by the memory controller 221.
  • the memory controller 224 changes the frequency of the simulated engine sound on the basis of a speed ratio of the engine rotation speed, when the engine sound which is the base of the sound pressure waveform data is recorded, to the engine rotation speed detected by the engine rotation speed detection means 210.
  • the basic sound pressure waveform data is generated by recordingan engine sound in a state where the engine rotation number is 2000rpm
  • it is adjusted as follows in a state where the engine rotation number is 3600rpm.
  • the time required for the crank shaft to rotate twice is 60msec in the state of 2000rpm, and is about 33msec in the stateof 3600rpm.
  • the sampling cycle (reproduction rate) of the simulated engine sound is changed.
  • the simulated engine sound generating apparatus 200 stores the sound pressure waveform data corresponding to two rotations of the crank shaft of the engine sound in the first storage means 222, and generates the simulated engine sound using the sound pressure waveform data read from the first storage means 222, the simulated engine sound is generated to correspond to the vehicle speed.
  • the driver of the vehicle can hear the natural simulated engine sound.
  • the sound pressure waveform data uses sound data including the engine sound and the base sound such as a machine vibration, the engine sound is divided into the high frequency component and the low frequency component, and the mixing ratio of the respective components is changed according to the vehicle speed, to generate the simulated engine sound.
  • the simulated engine sound is constantly changed even though driving is performed at a constant speed, and becomes a sound which is similar to the engine sound having variations in explosion.
  • the actual engine sound is divided into the high frequency engine sound waveform, the low frequency engine sound waveform, and the base sound waveform, and the relationships between the vehicle speed and the high frequency engine sound waveform, the low frequency engine sound waveform and the base sound waveform are shown inFig.7.
  • the mixing ratio signal is obtained in consideration of the sound pressure ratio, but may be obtained by combination of the sound pressure signal and the mixing ratio.
  • the sound pressure waveform data corresponding to one combustion cycle of the engine is adjusted at the reproduction rate according to the vehiclespeed, the engine sound pressure waveform data is transmitted from the second storage means 222, and the base sound pressure waveform data is transmitted from the third storage means 223. Then, the engine sound pressure waveform data is divided into the high frequency enginesound component and the low frequency engine sound component by the frequency divider 226. Further, on the basis of the vehicle speed signal, for example, the base sound component is mixed with the high frequency engine sound component and the low frequency engine sound component at the ratio shown in Fig. 8. Then,this result is amplified by the amplifier, to thereby perform reproduction and sound generation using a microphone. The reproduction time of the simulated engine sound corresponding to one piece of sound pressure waveform data is changed according to the rotation speed of the engine, and thus, the simulated engine sound is naturally changed.
  • a simulated engine sound generating apparatus 200 for use in an electricvehicle data on a sound pressure waveform of an actual engine sound within a predetermined time is not divided using a frequency divider 226, but is inadvance stored in the first storage means 221 as a high frequency engine sound waveform component, a low frequency engine sound waveform component and a base sound waveform component such as a machine vibration.
  • the simulated engine sound generating apparatus 200 for use in an electric vehicle includes second storage means 222 which temporarily stores the high frequency engine sound component read from the first storage means; fourth storage means 227which temporarily stores the lower frequency engine sound component read from the first storage means; and third storage means 223 which temporarily stores the base sound component of the machine vibration system read from the first storage means.
  • the frequencydivider 226 is not used, this configuration is the same as in the second embodiment in Fig. 6. Thus,like elements are given like reference numerals, and thus are not further described.
  • the third embodiment since the sound pressure waveform data is not divided into the high frequency and the low frequency by the frequency divider 226 as in the second embodiment,a crossover frequency which is a branch point cannot be changed by the software. However, since the crossover frequency is considered when being stored in the first storage means 221,this does not cause any problem.
  • the simulated engine sound corresponding to the vehicle speed is generated, it is possible to generate an effective simulated engine sound according to a running state.
  • a driver can hear a natural simulated engine sound, and also can recognize driving information of his or her vehicle such as a motor rotation speed by his or her sense of hearing without using an indicator.

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Abstract

This invention related to a simulated engine sound generating apparatus 200 for use in an electric vehicle which reproduces a simulated engine sound predicted from modified waveform data of an actual engine sound according to a vehicle speed on the basis of a motor rotation number of the electric vehicle and generates the simulated engine sound, including: vehicle speed detection means 210,first storage means 221, second storage means 222, memory controller 224 for deciding the sampling cycle corresponding the vehicle speed, mixer 226 which receives the basic sound pressure waveform from the second storage means 222and amplifies the basic sound pressure waveform according to the vehicle speed transmitted from the second storage means 222 at a programmed ratio and sound generation means 230 as shown Fig.1.

Description

A SIMULATED ENGINE SOUND GENERATING APPARATUS

The present invention relates to a simulated engine sound generating apparatus for usein an electric vehicle which is mounted on an electric motorcycle limited in speed and generates a simulated engine sound, especially as basic waveform for reproducing the stimulated engine sound by using either one of an idling engine sound, 3sound components and an artificial down-converted sound.

Electric vehicles, particularly electric motorcycles are expected to reduce environmental pollution. In China,more than half of motorcycles are an electric type. However, sincethe electric motorcycle runs silently near the sidewalk, it is difficult to notify in advance a walker of the approach of the electric motorcycle, which is dangerous. Furthermore, it is difficult for a driver to feel excited without an engine sound during running, which is unsatisfactory.

An apparatus which generates this type of simulated engine sound generally employs a configuration which repeatedly reproduces sound data stored in advance as a digital signal obtained by recording an engine sound of a vehicle during normal driving for several seconds while changing the pitch (frequency (sound height))or volume (sound pressure (sound size)) ofthe sound data according to driving states of an engine (rotation speed or accelerator manipulation). Here, the pitch is increased in proportion when the rotation speed of the engine is increased, and is decreased when the rotation speed of the engine is decreased. On the other hand, the volume is increased as a driver presses on the accelerator, and is decreased as the driver eases off the accelerator.

However, if the simulated engine sound is matched with an actual rotation speed of theengine or an actual accelerator manipulation, a motor does not rotate at the time of idling,which causes a perfect silence. Thus, a driver must confirm driving information such as a rotation speed of the motor through an indicator or the like while driving a vehicle. In addition, when the vehicle is in a transitional state where the rotation speed of the engine or the accelerator manipulation is changed, there is a problem that the simulated engine sound becomes unnatural.

Thus, there has been proposed a system which forms a simulated engine sound corresponding to a rotation speed of a power unit or acceleration manipulation in a complicated mannerby preparing a map formed by allocating sound pressure waveform data of an engine sound within a predetermined time to the rotation speed and the accelerator manipulation, by arrangingin the map a plurality of unit areas each having a specific width in the rotation speed and the accelerator manipulation, and by storing the sound pressure waveform data of driving states of the engine in each unit area (refer to PTLT 1).

Patent2000-1142

However, if a configuration of a simulated sound is complicated, even though a correctresponse is achieved, the cost is undesirably increased. Accordingly, an object of the present invention is to provide a cheaper apparatus which generates an engine sound simply and correctly.

The present inventors have found that in a normal idling state of an electric vehicle,it is difficult to reproduce an engine sound at the time of idling in which an electric motor does not rotate when a simulated engine sound is to be reproduced on the basis of a vehicle speed which is calculated from a driving signal such as a pulse generated by the electric motor with the electric motor being stopped, but it is effective for reproduction of the engine sound that an actual sound is formed using an idling sound as a basic waveform in an electric vehicle which typically runs at low speed considering that recognition of the idling state is important to a driver in view of mental preparation. Further, it has been found that when an actual engine sound is carefully observed, a high frequency engine sound componentand a low frequency engine sound component are not changed uniformly according to a vehicle speed, but the proportion of the low frequency engine sound component is high at a low speedof 20 to 30km/h or less and the proportion of the high frequency engine sound component is high at a high speed of 30km, and a base sound such as a machine vibration is combined therewith in addition thereto, to thereby form the actual engine sound. Furthermore, it has been found that when an actual sound at the time of running is used as a basic waveform as it is,the capacity of the apparatus is increased, and thus, it is desirable to create an artificial sound which is down-converted using a weighted Moving Average Method, especially a Gaussian smoothing technique, but if a sampling cycle is linearly changed according to the vehicle speed when the number of wheel rotations is used as the vehicle speed, such an artificial sound is easily blended with noise due to the wheel rotation, which causes an undesirable result.

Based on these findings and careful and repeated researches, an object of a first embodiment of the present invention is to provide a simulated engine sound generating apparatus which is capable of reproducing an idling sound, although a motor does not rotate, at the time of idling and approximately correctly reproducing an actual engine sound at the time of running, by using sound at the time of idling as a basic sound pressure waveform and by overlapping and adjusting frequency and sound pressure in consideration of the basic sound pressure waveform and a motor rotation number, and which has low costs.

Further, in a second embodiment of the present invention, it has been found that by dividingcomponents forming a simulated engine sound into a high frequency engine sound component anda low frequency engine sound component and by overlapping these components with a base soundsuch as a machine vibration at a specific ratio, it is possible to cover a range from idlingto low-speed running and from low-speed running to high-speed running by changing the reproduction rate of a single actual engine sound in an electric motorcycle of 45km/h or less, andit is an object to provide a simulated engine sound generating apparatus which is yet closerto the actual engine sound, based on these findings.

Further, in a third embodiment of the present invention, based on the finding that when an actual engine sound at the time of running is used as a basic waveform, it is desirable that an artificial sound is firstly created on the basis of the actual sound, and a sampling cycle is rapidly increased at the time of accelerating, instead of being linearly changed according to the vehicle speed corresponding to the amount of wheel rotations, to thereby allow the apparatus to be close to the actual sound, it is an object to provide a simulated engine sound generating apparatus which generates an engine sound close to an actual sensation at a low cost.

That is, according to the first embodiment, there is provided a simulated engine sound generating apparatus 200for use in an electric vehicle which reproduces a simulated engine sound predicted from waveform data from an actual engine sound according to a vehicle speed on thebasis of a motor rotation number of the electric vehicle and generates the simulated engine sound, including:

vehicle speed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal determining a sampling cycle according to the vehicle speed and a sound pressure signal determining a volume gain according to the vehicle speed, on the basis of a pulse signal;

first storage means 221 which stores an actual engine sound at the time of idling within a predetermined time as data on a basis sound pressure waveform;

second storage means 222 which temporarily stores the basic sound pressure waveform data read from the first storage means as a base engine sound waveform;

a memory controller 224 which receives the sampling signal according to the vehicle speed from the vehicle speed detection means and transmits a signal changing the sampling cycle (reproduction rate) which is a reading speed to the second storage means;

a mixer 226 which receives the sound pressure signal according to the vehicle speed from the vehicle speed detection means 210, transmits the basic sound pressure waveform from the second storage means at the time of idling, and amplifies data on a sound pressure waveform adjusted to a frequency according to the vehicle speed transmitted from the second storage means at a predetermined ratio by the sound pressure signal at the time of running other than idling;and

sound generation means 230 which receives a sound pressure waveform signal from the mixer 226,generates an idling sound at the time of idling, and generates a simulated engine sound adjusted to a frequency and sound pressure according to the vehicle speed at the time ofrunning other than idling.

Further, according to the second embodiment of the present invention, there is provided a simulated engine sound generating apparatus 200 for use in an electric vehicle which reproduces a simulated engine sound predicted from waveform data from an actual engine sound according to a speed of the electric vehicle and generates the simulated engine sound, including:

first storage means 221 which stores data on a sound pressure waveform of the actual engine sound within a predetermined time;

second storage means 222 which temporarily stores an engine sound from the sound pressure waveform data read from the first storage means;

third storage means 223 which temporarily stores a base sound of a machine vibration system from the sound pressure waveform data read from the first storage means;

a frequency divider 225 which divides an engine sound waveform read from the second storage means at a reproduction rate determined according to the vehicle speed into a high frequency band engine sound waveform component and a low frequency band engine sound waveform component;

vehicle speed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal determining a sampling cycle according to the vehicle speed, a sound pressure signal determining a volume gain according to the vehicle speed, and a mixing ratio signal of the high frequency engine sound component, the low frequency engine sound component and a base sound component according to the vehicle speed, on the basis of a calculated vehicle speed signal;

a memory controller 224 which receives the sampling signal according to the vehicle speed from the vehicle speed detection means and transmits a signal changing the sampling cycle (reproduction rate) which is a reading speed according to the vehicle speed to the second storage means and the third storage means;

a mixer 226 which mixes three components of a base sound waveform component B, a high frequency band engine sound waveform component H and a low frequency band engine sound waveform component L read from the third storage means 203 at a reproduction rate determined according to the vehicle speed, at a predetermined ratio according to the vehicle speed on the basis of the mixing ratio signal; and

sound generation means 230 which generates a simulated engine sound mixed according tothe vehicle speed. In order to make the 3 component waveform from the actual engine sound, the frequency divide may be used. In place of the frequency divider, the first storage means may contain the basic waveform of the 3 components and the second storage means is used for the high frequency waveform and the third storage means is used for a basic sound waveform component B of machine vibration system and the fourth storage means is used for a low frequency waveform L.

According to the third embodiment,there is provided a simulated engine sound generating apparatus 200 for use in an electric vehicle which reproduces a simulated engine sound predictedfrom waveform data from an actual engine sound according to a vehicle speed on the basis of a motor rotation number of the electric vehicle and generates the simulated engine sound, including:

vehicle speed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal determining a sampling cycle according to the vehicle speed and a sound pressure signal determining a volume gain according to the vehicle speed, on the basis of a pulse signal;

first storage means 221 which stores, as data on a basic sound pressure waveform, an artificial sound obtained by down-converting an actual engine sound at the time of running within a predetermined time using a Gaussian smoothing technique;

second storage means 222 which temporarily stores the basic sound pressure waveform data read from the first storage means as a base engine sound waveform;

a memory controller 224 which receives the sampling signal according to the vehicle speed from the vehicle speed detection means and transmits a signal rapidly changing the sampling cycle (reproduction rate) which is a reading speed at the time of accelerating at 5km ormore and a limit speed or less, to the second storage means;

a mixer 226 which receives the sound pressure signal linearly changed according to thevehicle speed from the vehicle speed detection means 210, transmits data on a sound pressurewaveform from the second storage means at the sampling cycle rapidly changed at the time of accelerating, and stops or decreases the sound pressure waveform data transmitted from the second storage means at the limit speed or higher;and

sound generation means 230 which receives a sound pressure waveform signal from the mixer 226,and generates a simulated engine sound adjusted to a frequency and sound pressure according to the vehicle speed at the time of accelerating.

In a preferred embodiment of the simulated engine sound generating apparatus according to the present invention, the first storage means stores, as data on a basic sound waveform, an artificial sound obtained by down-converting an actual engine sound at the time of running within a predetermined time and smoothing by a Weighted Moving Average Method, especially a Gaussian smoothing method which is well known method in a field of Image processing. The Gaussian Smoothing Method may be carried out with B(Gaussian distribution function)=1.3 and primary Gaussian filter coefficient (1,6,15,20,15,6,1). In this case, the memory controller 224 which receives the sampling signal according to the vehicle speed from the vehicle speed detection means 210 may be programmed in a manner to transmit a signal rapidly changing the sampling cycle (reproduction rate) such as a quadratic function or the similar function including a rapidly changing part and may be programmed in a manner that 1)the sampling signal starts from the position where the idling sound is reproduced at the vehicle speed of 0km/h, then2) the reproduction rate (sampling cycle) changes at states of at least three division including with A(gradient)=0.5 to 1 (on the condition of y= Ax)at a slow running time up to 5 km/h, and A=1.5 to 3 at an acceleration time between 5 to 15 km/h or more, and A=0 to 0.5 at a constant running time between 15 to 25 km/h or more. On the other hand, the mixer 226 which receives the sound pressure signal linearly changed according to the vehicle speed from the vehicle speed detection means 210, transmits data on a sound pressure waveform from the second storage means at the sampling cycle rapidly changed at the time of accelerating, and stops or decreases the sound pressure waveform data transmitted from the second storage means atthe limit speed or higher.


 Advantageous Effects of the Invention

According to the first embodiment, it is possible to generate an idling sound even at the time of idling in which a motor does not rotate even in the case of an electric vehicle which measures a vehicle speed by a number of rotations of the electric motor by using an engine sound waveform at the time of idling as a basic waveform, and to nearly completely reproduce a simulated sound of an actual engine sound at a low speed range allowed by the electric vehicle by adjusting the frequency and sound pressure thereof even in a case where the engine sound waveform at the time of idling is used as the basic waveform, thereby generating an effective simulated engine sound from idling to the low speed range. Further, according to the second embodiment, by storing a predetermined actual engine sound waveform as a basic waveform, by dividing it into a high frequency engine sound component, a low frequency engine sound component and a base component such as a machine vibration, and by adjusting a reproduction rate according to the vehicle speed for these components and adjusting sound pressures of these three components and a mixing ratio according to the vehicle speed, it is possible to reproduce a simulated engine sound close to the actual engine sound according to the vehicle speed without preparing a map which stores the actual engine sound according to the vehicle speed. Further, according to the third embodiment, it is possible to simplify the apparatus by using an actual engine sound at the time of running as a basic waveform and by using an artificial sound obtained by down-converting the basic waveform using a Gaussian smoothing technique, and to reliably prevent deviation from the actual sound by rapidly changing a sampling cycle at the time of accelerating at this time so that the sampling cycle is not linearly changed according to the vehicle speed which is the amount of wheel rotations.

According to the embodiments, as the base sound component such as a machine vibration is included as one basic waveform, by installing the sound generation means as a voice coil in a resonance section formed in a seat of the electric vehicle, it is possible to provide asimulated engine sound generating apparatus for use in an electric vehicle which vibrates the seat of the electric motorcycle and generates sound by reproducing vibrations of an enginemotorcycle.

According to the embodiments, since the high frequency engine sound component, the lowfrequency engine sound component and the base sound component are adjusted according to the vehicle speed, it is desirable that the actual engine sound waveform data stored in the first storage means employs an actual engine sound at the time of idling of 1,000 to 1,500rpm. Further, when the actual engine sound at the time of running is used,for simplification of the apparatus, the actual sound is down-converted from a digital audio standard frequency (48kHz) using a Gaussian smoothing technique. In this case, it is desirable to use frequency of10kHz or higher to reduce deviation from the actual sound.

Fig. 1 is a diagram illustrating a configuration of an electric motorcycle including a simulated engine sound generating apparatus according to the present invention. Fig. 2 is a block diagram illustrating a control system of an electric motorcycle according to the present invention. Fig. 3 is a block diagram illustrating a configuration of a vehicle simulated engine soundgenerating apparatus according to a first embodiment of the invention. Fig. 4 is a graph illustrating an example of a program adjusting a sampling cycle and gain from a vehicle speed according to a first embodiment of the invention. Fig. 5(a) is a diagram illustrating an actual engine sound waveform at the time of idling, and Fig. 5(b) is a diagram illustrating a simulated engine sound waveform having twice the gain and twice the frequency at a vehicle speed of 30km/h. Fig. 6 is a block diagram illustrating a configuration of a vehicle simulated engine sound generating apparatus according to a second embodiment of the invention. Fig. 7 is a block diagram illustrating a configuration of a vehicle simulated engine sound generating apparatus according to a third embodiment of the invention. Fig. 8 is a waveform diagram when a basic actual engine sound (a) is divided into a high frequency engine sound component (b) and a low frequency engine sound component (c). Fig. 9 is a program which determines a mixing ratio of respective waveforms to a vehicle speed. Fig. 10 is a graph illustrating an example of a program adjusting a vehicle speed, a sampling cycle and gain when an artificial sound down-converted from an actual engine sound at the time of bike running is used as a basic waveform, according to a first embodiment of the invention.

Hereinafter, an embodiment of a vehicle simulated engine sound generating apparatus according to the present invention will be described in detail with reference to the accompanying drawings. An embodiment of an electric tricycle of the present invention will be described.

As shown in Fig.1, an electric tricycle 100 according to the present embodiment includes a vehicle body 110 in which a seat 111 is installed and a handle apparatus 120 is installed in a front section of the vehicle body 110. A seating switch 112 and an engine sound generator 200 are installed in the seat 111, and a power supply 113 is embedded in a lower section thereof. The electric tricycle 100 can drive a driving motor 116 installed in a vehiclewheel 115 through a controller 114 (not shown).

On the other hand, the handle apparatus 120 includes a right accelerator grip 121, a left grip 122 and a left brake arm 123. In the left brake arm 123 a parking device 130 is installed. The left brake arm 123 can mainly allow a rear wheel to be in a brake state. A reference numeral 124 is a driving switch, and a reference numeral 125is a reversing switch.

A front panel 126is installed in the center of the handle apparatus 120, and the driving switch 124 is installed at a lower section thereof.

However, the seating switch 112 which is a boarding detection means of a driver (not shown)is installed in the seat 111, and detects seating (boarding) and non-seating (non-boarding) of the driver. The seating switch may include an infrared light switch or a limit switch. If the driver sits in the seat 111, the switch turns on to be in a boarding detection state. This is transmitted to the controller 114 as a seating signal S2. Further, if the driver moves away from the seat 111, the switch turns off to be in a non-boarding detection state. A limit switch can detect weight of the driver and if a person having a weight of 30 to60 kg or more, in view of the weight of an adult, sits in the seat 111, the seating signal S2 is firstly transmitted.

Subsequently, a control system of a safety apparatus of the above-described electric tricycle 100 will be described with reference to Fig. 2. That is, the safety apparatus according to this embodiment includes the seating switch 112 which works with the driving switch;the parking device 130 which works with the hand brake arm 123; a parking switch 131 installed in the parking device 130; and a motor sound generating apparatus 200 which works with the electric motor 116. As shown in Fig. 2, if the driving switch 124 turns on, the driving signal S1 is transmitted to the control means 114. Here, if the driver sits in the seat 111,the seating switch 112 detects the weight of the passenger. If the weight is 30 kg or more,the seating signal S2 is transmitted to the control means 114. The control means 114 is in a driving preparation state in which electric power from the power supply can be transmittedto the driving motor 116 by an AND signal of the driving signal S1and the seating signal S2. On the other hand, the driving signal S1 is also transmitted to the engine sound generating apparatus 200, and an idling sound can be generated from the engine sound generating apparatus 200.

Further, if the parking switch 131 turns off, a release signal S3 is transmitted to the control means 114. The control means 114supplies electric power to the electric motor 116from the power supply 113. The amount of electric power to the electric motor gives play tothe accelerator means 121. An accelerator signal S4 corresponding to a desired speed is transmitted to the control means 114 according to the rotation aperture. Thus, the electric motor 116 is driven to be gradually increased in speed. The driving speed can be switched between a high speed drivable state and a low speed drivable state by a switch 127. A simulated engine sound is generated from the engine sound generating apparatus 200 according to the driving amount of the electric motor 114.

Further, in this embodiment, if the reversing switch 125 turns on, a reversing signal S5 is transmitted to the control means, and the electric motor 116 is rotated backwards by the accelerator means 121 to be able to go backwards at low speed.

Accordingly,according to the above-described embodiment, while the driver does not sitin the seat 111, even though the driving switch 124 is in an ON state and even if the accelerator 121 is inadvertently operated, the rotation of the motor 116remains stopped. In a case where the driver sits and his or her weight exceeds a limit value (for example, 30kg), since the seating signal S2 is sent to the control means 114, if the accelerator means 121 is operated according to the AND signal of the driving signal S1 and the seating signal S2, the electric motor 116 rotates according to the accelerator signal S4, and the electric tricyclemoves forward. The forward speed can be switched between high speed and low speed by the switch 127. In the case of moving backwards, while the reversing switch 125 is pressed to transmit the reversing signal S5, low speed backing is performed by the manipulation of the accelerator means 121.

Further, since the driving signal S1 is transmitted to the engine sound generating apparatus 200 when the driving switch 124 is turned on, the rotation of the motor 116 remains stopped, but the idling sound is generated. If the number of motor rotations is increased, asimulated engine driving sound suitable for an actual engine sound is generated according tothe vehicle speed, and a gasoline engine sound can be reproduced. Alternatively, an alarm sound providing notification of the backward movement may be generated by the reversing switch 125.

Fig. 3 is a block diagram illustrating the engine sound generating apparatus 200 according to a first embodiment of the present invention. The engine sound generating apparatus 200 includes speed detection means 210 which calculates a vehicle speed from a rotation speedof an electric motor M; engine sound reproduction means 220 which generates a simulated engine sound according to the vehicle speed according to a vehicle speed signal Vs from the speed detection means 210; and engine sound generation device 230 which generates the simulated engine sound from the reproduction means 220, and reproduces an idling sound which is a basic waveform so that a sampling cycle (reproduction rate) and a sound pressure intensity are changed according to the vehicle speed. That is, the engine sound generating apparatus 200 includes vehicle speed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal which determines a sampling cycle according to the vehicle speed on the basis of a pulse signal and a sound pressure signal which determines a volume gain according to the vehicle speed;first storage means 221 which stores an actual engine sound at the time of idling within a predetermined time as data on a basic sound pressure waveform;second storage means 222 which temporarily stores the basic sound pressure waveform data read from the first storage means as abase engine sound waveform; a memory controller 224 which receives the vehicle speed signal according to the vehicle speed from the vehicle speed detection means and transmits a sampling signal changing the sampling cycle (reproduction rate)which is a reading speed to the second storage means; a mixer 226 which receives the sound pressure signal according to the vehicle speed from the vehicle speed detection means 224, transmits a basic sound pressure waveform from the second storage means at the time of idling, and amplifies data on a sound pressure waveform adjusted to a frequency according to the vehicle speed transmitted from the second storage means at a predetermined ratio by the sound pressure signal at the time of running other than idling; and sound generation means 230 which receives a sound pressure waveform signal from the mixer 226,generates an idling sound at the time of idling, and generates a simulated engine sound adjusted to a frequency and sound pressure according to the vehiclespeed at the time of running other than idling.

The vehicle speed detection means 210 includes a pulse detector 211 which detects rotation of the electric motor M as pulses of the three-phase motor; an amplifier means 212whichdigitalizes the pulse signal for transmission; and a calculator 213 which calculates the vehicle speed from the digital signal. The vehicle speed detection means 210transmits a sampling signal fsam according to the vehicle speed from the calculator 213 to the memory controller 224 of the simulated engine sound generation means 220, and also transmits a sound pressure signal G according to the vehicle speed to the mixer 226. Generally, a sampling signal Ssam according to the vehicle speed and the gain (sound pressure) signal G according to the vehicle speed are adjusted as shown in Fig. 4. That is, the sampling signal Ssam is programmed so that the sampling signal Ssam is started from a position where the idling sound is reproduced at a vehicle speed of (0km/h)according to an expression (Ssam = SV (vehicle speed signal) X constant number + idling constant number), and then is changed to linearly reduce thereproduction rate according to the vehicle speed. On the other hand, the gain (sound pressure) signal G is programmed so that the gain (sound pressure) signal G is increased accordingto a quadratic curve f(x) from 0km/h depending on an expression (G = f(x) + idling constant number), is flatly changed at 20km/h, rapidly drops from 30km/h, and then maintains a low state up to 40km/h therefrom. Accordingly,if the basic waveform (see Fig. 5(a)) which is the engine sound at the time of idling is controlled as shown in a program in Fig. 4, the enginesound shown in Fig. 5(b) is reproduced at a vehicle speed of about 30km/h.

In case of this preferred embodiment according to the present invention, in order to make a simpler and more costless apparatus for generating a simulated engine sound, a following method may be adopted to make a preferred another base sound in place of using the above actualengine sound during running as a base sound. First of all, an actual engine sound is recorded in a mode of digital audio standard (48kHz) or a CD standard frequency (44.1 kHz) and down-converted to a lower suitable frequency (for example 10 kHz) where the actual sound waveform is subjected to a smoothing process and finally reproduced in a style of the quadratic function or the same function including a more rapidly change part.

1) The actual engine sound recorded in the digital mode of 48 kHz is down-converted up to a suitable frequency for simplicity of apparatus construction. For example, it has been found that 10kHz is a critical frequency in a down-converted case from 48 kHz because reproductionaccuracy becomes very different between more than 10 kHz and less than 10 kHz in case of thesimulated engine sound from the down-converted frequency sound waveform.

2) The actual sound waveform to be down-converted is subjected to a smoothing method for eliminating a mechanical sound contained in the actual engine sound. Many of the smoothing method are well known in an Image processing field. Among them, it has been found that a Weighted Moving Average Method, especially a Gaussian Smoothing Method is more suitable to make a base sound from the actual engine sound used for reproduction of the simulated sound. In thiscase, Gaussian Smoothing Method is carried out with B(Gaussian distribution function)=1.3 and primary Gaussian filter coefficient (1,6,15,20,15,6,1). The other Gaussian filter coefficient can be used for reproduction of the simulated sound in the present invention.In the Gaussian Smoothing Method, a weight, when an average value is calculated,is increased as it approached a waveform target pixel and is decreased when it moves away from target pixel, and the down-converted actual sound is smoothed to a base sound waveform by the Weighted moving Average Method, especially the Gaussian Smoothing Method.

3) The down-converted waveform is sampled in a rapidly changed sampling cycle mode like the quadratic function or the same function in order to reproduce a stimulated sound having an increasing tempo because it has been found that such a quadratic function sampling mode including a rapidly changed sampling cycle is better than a constant linear function sampling mode for reproducing an acceleration sound. For example, the sampling cycle and gain (sound pressure) corresponding to the vehicle speed had better be adjusted in a manner as shown in Fig.10. In this case, the sampling cycle in the memory controller 221 is programmed in a mannerthat 1)the sampling signal starts from the position where the idling sound is reproduced at the vehicle speed of 0 km/h, then 2) the reproduction rate (sampling cycle)changes at A(gradient)=0.5 (under the condition of y=Ax) corresponding to the vehicle speed at a slow runningtime up to 5 km/h, and A=2 at an acceleration time between 5 to 15 km/h or more, and A=0.3 at a constant running time between 15 to 25 km/h or more. The reproduction rate may be adjusted considering the base sound property in order to make a simulated engine sound more approaching to the actual engine sound. Generally, the reproduction rate (sampling cycle)should bechanged at the three divisions of the slow running state, the acceleration state and the constant running state respectively. The sampling cycle is better to be changed in a manner of at least 3 steps such as slow running state, accelerating state and constant running state. On condition that A=1 shows a gradient concerning a linear function of y=Ax, it is recommended that the sampling cycle is A=0.5 to 1 at the slow running state, A=1.5 to 3 at the acceleration state and A=0 to 0.5 at the constant running state. On the other hand, the gain (sound pressure) had better be programmed to be increased with a constant gradient from the idling state 0 km/h and rapidly decreased or dropped at 25 km/h and then be stopped or maintainedsmall up to 40 km/h,whereby even if the vehicle speed would be calculated according to the rotation speed of the electric motor and the sampling cycle is determined by the calculated vehicle speed, the stimulated engine sound will not be overlapped with the rotation sound of wheel, resulted in no interruption caused by the rotation sound. That means, blend with noise due to the wheel rotation, which causes an undesirable result.

Fig. 6 is a block diagram illustrating an engine sound generating apparatus 200 according to a second embodiment of the present invention. In a similar way to the first embodiment, the engine sound generating apparatus 200 includes speed detection means 210 which calculates a vehicle speed from a rotation speed of an electric motor M; engine sound reproduction means 220 which generates a simulated engine sound according to a vehicle speed by a vehicle speed signal Vs from the speed detection means 210; and an engine sound generation device230 which generates the simulated engine sound from the reproduction means 220. Here, the engine sound which is a basic waveform is divided into a high frequency engine sound component, a low frequency engine sound component and a base sound component such as a machine vibration and is reproduced so that a sampling cycle (reproduction rate) and a sound pressure intensity are changed according to the vehicle speed, and a mixing ratio of the three components is adjusted according to the vehicle speed. That is, according to the second embodiment, the simulated engine sound generating apparatus 200 for use in an electric vehicle which reproduces a simulated engine sound predicted from waveform data from an actual engine sound according to a speed of the electric vehicle and generates the simulated engine sound, includes first storage means 221 which stores data on a sound pressure waveform of the actual engine sound within a predetermined time; second storage means 222 which temporarily stores an engine sound from the sound pressure waveform data read from the first storage means; third storage means 223 which temporarily stores a base sound of a machine vibration system from thesound pressure waveform data read from the first storage means; a frequency divider 225 which divides an engine sound waveform read from the second storage means at a sampling cycle (reproduction rate) determined according to the vehicle speed into a high frequency band engine sound waveform component and a low frequency band engine sound waveform component; vehiclespeed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal determining a samplingcycle according to the vehicle speed, a sound pressure signal determining a volume gain according to the vehicle speed, and a mixing ratio signal of the high frequency engine sound component, the low frequency engine sound component and a base sound component according to thevehicle speed, on the basis of a calculated vehicle speed signal; a memory controller 224 which receives the vehicle speed signal according to the vehicle speed from the vehicle speed detection means and transmits a sampling signal changing the sampling cycle (reproduction rate)which is a reading speed according to the vehicle speed to the second storage means and the third storage means; a mixer 226 which mixes three components of a base sound waveform component B, a high frequency band engine sound waveform component H and a low frequency band engine sound waveform component L read from the third storage means 203 at a sampling cycle (reproduction rate)determined according to the vehicle speed, at a predetermined ratio according to the vehicle speed on the basis of the mixing ratio signal; and sound generation means 230 which generates a simulated engine sound mixed according to the vehicle speed.

The engine sound reproduction means 220 includes the memory controller 224 which receives a vehicle speed signal SV output from the vehicle detection means 210 and generates a sampling signal Sc which controls a sound generation sampling cycle reproduction rate); the first storage means 221 including a flash memory which stores sound pressure waveform data of the actual engine sound; the second storage means 222 including a DRAM which generates a sound pressure signal of the simulated engine sound on the basis of a sound generation reproduction rate control signal Sc generated by the memory controller 224 and the sound pressure waveform data read from the first storage means 221; the third storage means 223 including a DRAM which generates a simulated base sound at a predetermined sampling cycle on the basis ofthe sampling signal Sc generated by the memory controller 224 and the sound pressure waveform data read from the first storage means 221; the frequency divider 225 which divides the engine sound waveform read at the sampling cycle (reproduction rate) determined according to the vehicle speed from the second storage means 222 into the high frequency band engine soundwaveform component H and the low frequency band engine sound waveform component L; the mixer226 which mixes the three components of the base sound waveform component B, the high frequency band engine sound waveform component H and the low frequency band engine sound waveform component L read from the third storage means 223 at the reproduction rate determined according to the vehicle speed, at the predetermined rate according to the vehicle speed,and transmits the signal mixed according to the vehicle speed to the generation means 230 which generates the simulated engine sound. The generation means 230 includes an amplifier 231 which amplifies the sound pressure signal and a speaker or a voice coil 232 which is connected to the amplifier 231.

The first storage means 221 stores an actual engine sound for a predetermined time corresponding to two rotations of a crank shaft (one combustion cycle of the engine), and transmits the actual engine sound to the second and third storage means by a driving signal. Theactual engine sound of 500 to 1000rpm in an idling state is generally recorded.

The actual engine sound signal is sound waveform data and includes the high frequency engine sound component H of the actual engine sound, the low frequency engine sound component L of the actual engine sound, and the base sound component B such as a machine vibration. A basic waveform (a) shown in Fig. 7 can be divided into a high frequency component waveform(b) and a low frequency component waveform (c).

In this embodiment, the above-described three types of signals are slightly changed ateach sampling cycle (reproduction rate) based on a vehicle speed SV transmitted by the memory controller 221.

The first storage means 222 records the sound pressure waveform data obtained by converting the actual engine sound into digital data as an engine sound corresponding to one engine combustion cycle, in the idling running state.

The second storage means 223 transmits the engine sound pressure waveform data of the frequency according to the vehicle speed on the basis of the sampling signal transmitted by the memory controller 221. On the other hand, the third storage means 224 transmits the basesound pressure waveform data of the frequency according to the vehicle speed on the basis ofthe sampling signal transmitted by the memory controller 221.

The memory controller 224 changes the frequency of the simulated engine sound on the basis of a speed ratio of the engine rotation speed, when the engine sound which is the base of the sound pressure waveform data is recorded, to the engine rotation speed detected by the engine rotation speed detection means 210.

Here, in a case where the basic sound pressure waveform data is generated by recordingan engine sound in a state where the engine rotation number is 2000rpm, it is adjusted as follows in a state where the engine rotation number is 3600rpm. The time required for the crank shaft to rotate twice is 60msec in the state of 2000rpm, and is about 33msec in the stateof 3600rpm. Thus, the sampling cycle (reproduction rate) of the simulated engine sound is changed.

If the engine rotation number is 3000rpm, with respect to the length of the simulated engine sound in the state of 2000rpm, 3000/2000 = 1.5 is obtained. Thus, the memory controller 221 reduces the sampling cycle (reproduction rate) by 34%, so that the length of the sound corresponding to the two rotations of the crank shaft becomes 40msec. Further, with respect to the length of the simulated engine sound in the state of 4000rpm, 4000/2000 = 2.0 is obtained. Thus, the memory controller 221 reduces the sampling cycle (reproduction rate) by50%, so that the length of the sound corresponding to two rotations of the crank shaft becomes 30msec. In this way, as the sampling cycle (reproduction rate) of the simulated engine sound is changed by the memory controller 221 in this way, it is possible to generate a natural simulated engine sound.

Accordingly,since the simulated engine sound generating apparatus 200 according to this embodiment stores the sound pressure waveform data corresponding to two rotations of the crank shaft of the engine sound in the first storage means 222, and generates the simulated engine sound using the sound pressure waveform data read from the first storage means 222, the simulated engine sound is generated to correspond to the vehicle speed. Thus, the driver of the vehicle can hear the natural simulated engine sound.

Further, in the present embodiment, the sound pressure waveform data uses sound data including the engine sound and the base sound such as a machine vibration, the engine sound is divided into the high frequency component and the low frequency component, and the mixing ratio of the respective components is changed according to the vehicle speed, to generate the simulated engine sound. Thus, the simulated engine sound is constantly changed even though driving is performed at a constant speed, and becomes a sound which is similar to the engine sound having variations in explosion. The actual engine sound is divided into the high frequency engine sound waveform, the low frequency engine sound waveform, and the base sound waveform, and the relationships between the vehicle speed and the high frequency engine sound waveform, the low frequency engine sound waveform and the base sound waveform are shown inFig.7. Here, the mixing ratio signal is obtained in consideration of the sound pressure ratio, but may be obtained by combination of the sound pressure signal and the mixing ratio.

Thus, in the present invention, the sound pressure waveform data corresponding to one combustion cycle of the engine is adjusted at the reproduction rate according to the vehiclespeed, the engine sound pressure waveform data is transmitted from the second storage means 222, and the base sound pressure waveform data is transmitted from the third storage means 223. Then, the engine sound pressure waveform data is divided into the high frequency enginesound component and the low frequency engine sound component by the frequency divider 226. Further, on the basis of the vehicle speed signal, for example, the base sound component is mixed with the high frequency engine sound component and the low frequency engine sound component at the ratio shown in Fig. 8. Then,this result is amplified by the amplifier, to thereby perform reproduction and sound generation using a microphone. The reproduction time of the simulated engine sound corresponding to one piece of sound pressure waveform data is changed according to the rotation speed of the engine, and thus, the simulated engine sound is naturally changed.

In Fig. 7, in a simulated engine sound generating apparatus 200 for use in an electricvehicle according to a third embodiment, data on a sound pressure waveform of an actual engine sound within a predetermined time is not divided using a frequency divider 226, but is inadvance stored in the first storage means 221 as a high frequency engine sound waveform component, a low frequency engine sound waveform component and a base sound waveform component such as a machine vibration. Thus, the simulated engine sound generating apparatus 200 for use in an electric vehicle includes second storage means 222 which temporarily stores the high frequency engine sound component read from the first storage means; fourth storage means 227which temporarily stores the lower frequency engine sound component read from the first storage means; and third storage means 223 which temporarily stores the base sound component of the machine vibration system read from the first storage means. Except that the frequencydivider 226 is not used, this configuration is the same as in the second embodiment in Fig. 6. Thus,like elements are given like reference numerals, and thus are not further described. In the third embodiment,since the sound pressure waveform data is not divided into the high frequency and the low frequency by the frequency divider 226 as in the second embodiment,a crossover frequency which is a branch point cannot be changed by the software. However, since the crossover frequency is considered when being stored in the first storage means 221,this does not cause any problem.

According to the above-described embodiments of the present invention, since the simulated engine sound corresponding to the vehicle speed is generated, it is possible to generate an effective simulated engine sound according to a running state.

Accordingly, by mounting the simulated engine sound generating apparatus in the electric vehicle, a driver can hear a natural simulated engine sound, and also can recognize driving information of his or her vehicle such as a motor rotation speed by his or her sense of hearing without using an indicator.

200 stimulated engine sound generating apparatus

210 vehicle speed detection means

221 first storage means

222 second storage means

223 third storage means

224 memory controller

226 mixer

230 sound generation means

Claims (12)


  1. A simulated engine sound generating apparatus 200 for use in an electric vehicle which reproduces a simulated engine sound predicted from waveform data of an actual engine sound according to a vehicle speed on the basis of a motor rotation number of the electric vehicle and generates the simulated engine sound, including:

    vehicle speed detection means 210 which measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal determining a sampling cycle according to the vehicle speed and a sound pressure signal determining a volume gain according to the vehicle speed, on the basis of a pulse signal;

    first storage means 221 which stores an actual engine sound at the time of idling or lower speed within a predetermined time as data on a basis sound pressure waveform;

    second storage means 222 which temporarily stores the basic sound pressure waveform dataread from the first storage means 221 as a base engine sound waveform;

    a memory controller 224 which receives the sampling signal according to the vehicle speed from the vehicle speed detection means 210and transmits a signal changing the sampling cycle (reproduction rate) to the second storage means 222 as a reading out frequency of the basic sound pressure waveform from the second storage means 222;

    a mixer 226 which receives the sound pressure signal according to the vehicle speed fromthe vehicle speed detection means 210, transmits the basic sound pressure waveform from the second storage means 222 at the time of idling, and amplifies the basic sound pressure waveform on a sound pressure waveform adjusted to the reading out frequency according to the vehicle speed transmitted from the second storage means 222 at a predetermined ratio by the sound pressure signal at the time of running other than idling; and

    sound generation means 230 which receives a sound pressure waveform signal from the mixer 226, generates an idling sound at the time of idling, and generates a simulated engine sound adjusted to the frequency and the sound pressure according to the vehicle speed at the time of running other than idling.



  2. The simulated engine sound generating apparatus according to claim 1 further comprising:

    third storage means 223 which temporarily stores a base sound waveform component B of a machine vibration system from the sound pressure waveform data read from the first storage means 221;

    a frequency divider 225 which divides an engine sound waveform read from the second storage means 222 at a reproduction rate determined according to the vehicle speed into a high frequency band engine sound waveform component H and a low frequency band engine sound waveform component L.



  3. The simulated engine sound generating apparatus according to claim 2 wherein:

    the vehicle speed detection means 210 measures the vehicle speed on the basis of pulses of a three-phase motor of the electric vehicle and calculates a sampling signal determining a sampling cycle according to the vehicle speed, a sound pressure signal determining a volume gain according to the vehicle speed, and a mixing ratio signal of the high frequency engine sound component H,the low frequency engine sound component L and a base sound waveform component B according to the vehicle speed, on the basis of a calculated vehicle speed signal.



  4. The simulated engine sound generating apparatus according to claim 3 wherein:

    the memory controller 224receives the sampling signal according to the vehicle speed from the vehicle speed detection means 210 and transmits a signal changing the sampling cycle (reproduction rate) as a reading out frequency according to the vehicle speed to the second storage means 222and the third storage means 223;

    the mixer 226 mixes three components of the base sound waveform component B, the high frequency band engine sound waveform component H and the low frequency band engine sound waveform component L read from the third storage means 223 at a reproduction rate determined according to the vehicle speed, at a predetermined ratio according to the vehicle speed on the basis of the mixing ratio signal; and

    the sound generation means 230which generates a simulated engine sound mixed according to the vehicle speed.



  5. The simulated engine sound generating apparatus according to claim 1 further comprising:

    third storage means 223 and fourth storage means 227,

    wherein the second storage means 222 temporarily stores a high frequency band engine sound waveform component H from the sound pressure waveform data read from the first storage 221, the third storage means 223 temporarily stores a base waveform component B of a machine vibration system from the sound pressure waveform data read from the first storage means 221 and the fourth storage means 227 temporarily stores a low frequency band engine sound waveform component L from the sound pressure waveform data read from the first storage 221.



  6. The simulated engine sound generating apparatus according to claim 5,

    wherein the memory controller 224 receives the sampling signal according to the vehicle speed from the vehicle speed detection means 210 and transmits a signal changing the sampling cycle (reproduction rate) as a reading out frequency according to the vehicle speed to the second storage means 222 and the third storage means 223;

    the mixer 226 mixes three components of the base sound waveform component B, the high frequency band engine sound waveform component H and the low frequency band engine sound waveform component L read from the third storage means 223 at a reproduction rate determined according to the vehicle speed, at a predetermined ratio according to the vehicle speed on the basis of the mixing ratio signal; and

    the sound generation means 230which generates a simulated engine sound mixed according to the vehicle speed.



  7. The simulated engine sound generating apparatus according to claim 1 wherein the first storage means stores, as data on a basic sound waveform, an artificial sound obtained by down-converting an actual engine sound at the time of running within a predetermined time and smoothing by a Weighted Moving Average Method.



  8. The simulated engine sound generating apparatus according to claim 7 wherein the Weighted Moving Average Method is a Gaussian smoothing method.



  9. The simulated engine sound generating apparatus according to claim 8 wherein the Gaussian Smoothing Method is carried out with B(Gaussian distribution function)=1.3 and primary Gaussian filter coefficient (1,6,15,20,15,6,1).



  10. The simulated engine sound generating apparatus according to claim 8 wherein the memory controller 224 which receives the sampling signal according to the vehicle speed from the vehicle speed detection means 210 is programmed in a manner to transmit a signal rapidly changing the sampling cycle (reproduction rate) such as a quadratic function or the similar function including a rapidly changing part.



  11. The simulated engine sound generating apparatus according to claim 10 wherein the memory controller 224 is programmed in a manner that 1)the sampling signal starts from the position where the idling sound is reproduced at the vehicle speed of 0 km/h, then 2) the reproduction rate (sampling cycle) changes at states of at least three division including with A(gradient)=0.5 to 1 (on the condition of y= Ax)at a slow running time up to 5 km/h, and A=1.5 to 3 atan acceleration time between 5 to 15 km/h, and A=0 to 0.5 at a constant running time between15 to 25 km/h.



  12. The simulated engine sound generating apparatus according to claim 10 wherein the mixer 226 which receives the sound pressure signal linearly changed according to the vehicle speed from the vehicle speed detection means 224,transmits data on a sound pressure waveform from thesecond storage means at the sampling cycle rapidly changed at the time of accelerating, and stops or decreases the sound pressure waveform data transmitted from the second storage means at the limit speed or higher.
PCT/JP2011/000209 2010-04-19 2011-01-18 A simulated engine sound generating apparatus WO2011132347A1 (en)

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