JP7737571B2 - Information transmission device - Google Patents

Description

The present invention relates to an information transmission device that transmits information regarding vehicle behavior to vehicle occupants.

As a technology relating to outputting audio to occupants in vehicles such as automobiles depending on the state of the vehicle, for example, Patent Document 1 describes a driving assistance device that provides an easily recognizable steering angle and steering direction, in which the steering amount of the steering wheel is indicated by a sound that changes in conjunction with the steering amount.
Specifically, it describes controlling the tone so that the tone gets higher as the steering amount increases, and changing the volume, pitch, tone, sound pressure, frequency, position of the sound image, etc. to indicate the steering amount of the steering wheel.
Patent document 2 describes a music generation device for a vehicle that easily generates music that reflects the vehicle's behavior and the driver's operations, and includes a memory unit that stores multiple sound source loop patterns that each correspond to information based on the vehicle driver's operations or the vehicle's behavior, and a control unit that selects a specific sound source loop pattern from the multiple sound source loop patterns in accordance with the information and controls output or output stop.

Japanese Patent Application Laid-Open No. 2007-62706 JP 2016-66912 A

Since there is a time response delay between the start of steering the vehicle and the actual occurrence of vehicle body behavior, such as lateral acceleration, yaw rate, and roll angle, depending on the steering situation, occupants may feel that lateral acceleration, etc. has occurred suddenly, and may experience discomfort or anxiety due to being unable to properly support their body.
To address this, possible measures include, for example, lowering the yaw rate gain relative to the steering angle of the vehicle, or improving the ability of the seat or the like to hold the occupant.
However, lowering the yaw rate gain slows down the vehicle's response, impairing its performance and marketability. Furthermore, seat-based measures are difficult to adapt to various occupant sizes.
In view of the above-mentioned problems, an object of the present invention is to provide an information transmission device that improves the predictability of a driver's ability to predict behavior caused by steering of a vehicle.

In order to solve the above-mentioned problems, an information transmission device according to one aspect of the present invention is an information transmission device provided in a vehicle having a steering device for steering wheels, and is characterized by comprising a parameter detection unit that detects a parameter correlated with the steering amount of the steering device, an excitation waveform generation unit that generates an excitation waveform, an excitation unit that uses the excitation waveform to vibrate the air around the occupant, and a gain adjustment unit that increases the output gain of the excitation waveform in accordance with an increase in the absolute value of the differential value of the parameter.
According to this, by generating a sound whose sound pressure increases in accordance with an increase in the absolute value of the differential value of a parameter correlated with the steering amount of the steering device (so-called steering speed), the sound can predict to the occupants the behavior that will occur at the beginning of steering, before the lateral acceleration, yaw rate, roll angle, etc. actually occur in the vehicle.
This improves the occupant's predictability of vehicle behavior, and prevents the occupant from feeling abrupt about the vehicle behavior.

In the present invention, the excitation waveform may have a dominant frequency included in a frequency band of 100 to 400 Hz.
This makes it possible to use Pacinian corpuscles, which are highly sensitive in the audible range and in the cutaneous sense, and improves the occupant's ability to sense sound and recognize it through their cutaneous senses, thereby enabling more reliable transmission of information to the occupant.
Here, more preferably, by setting the dominant frequency in the frequency band of 150 to 300 Hz, the region of receptors with better sensitivity can be used, and the above-mentioned effect can be promoted.

In the present invention, the rate of increase of the output gain with respect to an increase in the absolute value of the differential value in the gain adjustment unit can be configured to be maximum in a region where the absolute value of the differential value is minute, and to decrease as the absolute value of the differential value increases.
This makes it possible to set a large output gain even in a region where the absolute value of the differential value is relatively small, and makes it possible to properly convey information to the occupant even in the early stage of steering when the steering angle and steering speed are small.
Furthermore, in a region where the absolute value of the differential value is large, the output gain can be prevented from becoming excessively large.
For example, the output gain can be set based on a logarithmic function of the absolute value of the derivative.

In the present invention, the gain adjustment unit can be configured to set the output gain so that the sound pressure generated by the vibration of the vibration unit does not dominate the background noise when the vehicle is running, at the ear of at least one occupant.
This prevents the sound generated by the vibration of the vibration unit from being buried in the background noise of the vehicle, causing the occupants to feel uncomfortable, and also allows information to be transmitted appropriately.

In the present invention, the parameters may include at least one of a steering angle of the steering device, an input torque to the steering device, an actuation amount of an actuator that steers the wheels, and an output command value to the actuator.
This allows the steering amount of the steering device to be properly grasped using parameters that can be easily detected in a typical vehicle.

As described above, the present invention provides an information transmission device that improves occupants' predictability of behavior caused by steering the vehicle.

1 is a diagram schematically illustrating the configuration of an electric power steering device for a vehicle having an embodiment of an information transmission device to which the present invention is applied. 1 is a diagram illustrating a system configuration of an information transmission device according to a first embodiment; FIG. 3 is a diagram schematically illustrating an example of an excitation waveform in the first embodiment. FIG. 1 is a diagram showing the timing of electrical pulses emitted by receptors when stimulated. FIG. 1 shows the frequency sensitivity distribution of Pacinian corpuscles and Meissner corpuscles. FIG. 4 is a diagram schematically illustrating an example of gain adjustment in a first gain adjuster of the first embodiment. FIG. 4 is a diagram schematically illustrating an example of an output history of a microphone in the first embodiment. FIG. 4 is a diagram illustrating an example of a correlation between the sound pressure of background noise and frequency in the first embodiment. FIG. 4 is a diagram schematically illustrating an example of gain adjustment in a second gain adjustment unit according to the first embodiment. 1 is a diagram schematically illustrating an arrangement in a vehicle cabin of a vehicle in which an information transmission device according to a first embodiment is provided; FIG. 10 is a diagram schematically illustrating the configuration of an automatic driving system for a vehicle equipped with a second embodiment of an information transmission device to which the present invention is applied.

First Embodiment
A first embodiment of an information transmission device to which the present invention is applied will be described below.
The information transmission device according to the embodiment is provided in a four-wheel vehicle (for example, an automobile such as a passenger car) in which the two front wheels are steered (turned).
A vehicle is equipped with an electric power steering device that uses an electric motor to provide a steering assist force to a steering device that steers the front wheels.

FIG. 1 is a diagram schematically showing the configuration of an electric power steering device for a vehicle according to a first embodiment.
The electric power steering device 1 is composed of a steering wheel 10, a steering shaft 20, an intermediate shaft 21, a pinion shaft 22, a rack shaft 30, a rack housing 40, a tie rod 50, a housing 60, a steering angle sensor 71, a torque sensor 72, an actuator unit 80, an electric power steering control unit (EPS control unit) 90, etc.

The steering wheel 10 is, for example, a circular ring-shaped operating member that is turned by the driver to input a steering operation.
The steering wheel 10 is disposed in the vehicle interior facing the driver's seat.
The occupant (driver) senses the steering feeling of the vehicle from the sensation (tactile sensation) transmitted from the steering wheel 10 to the fingers.

The steering shaft 20 is a rotating shaft with one end attached to the steering wheel 10, and transmits the rotational movement of the steering wheel 10 to a rack and pinion mechanism that converts it into translational movement in the vehicle width direction.
An intermediate shaft 21 and a pinion shaft 22 are connected in this order to the end of the steering shaft 20 opposite to the steering wheel 10 side.

Universal joints (Cardan joints) 23, 24 are provided between the steering shaft 20 and the intermediate shaft 21, and between the intermediate shaft 21 and the pinion shaft 22, respectively, so that rotation can be transmitted when the shafts are bent.
A pinion gear is formed at the tip of the pinion shaft 22 to mesh with a rack gear 31 of the rack shaft 30 and drive the rack shaft 30 .

The rack shaft 30 is a columnar member arranged so that its longitudinal direction (axial direction) is aligned with the vehicle width direction.
The rack shaft 30 is supported so as to be able to translate in the vehicle width direction relative to the vehicle body.
A rack gear 31 that meshes with the pinion gear of the pinion shaft 22 is formed on a part of the rack shaft 30 .
In response to the rotation of the steering shaft 20, the rack gear 31 of the rack shaft 30 is driven by the pinion gear, and the rack shaft 30 moves in a translational (straight) direction along the vehicle width direction.
The rack gear 31 is disposed offset to either the left or right side (usually the driver's seat side) in the vehicle width direction.
For example, if the vehicle is a so-called right-hand drive vehicle in which the driver's seat is located on the right front seat, the rack gear 31 is positioned offset to the right of the center when in neutral.

The rack housing 40 is a substantially cylindrical member that accommodates and supports the rack shaft 30 so that the rack shaft 30 can be relatively displaced along the vehicle width direction.
Rack boots 41 are provided on both ends of the rack housing 40 .
The rack boot 41 is a member that prevents foreign matter such as dust from entering the rack housing 40 while allowing the tie rod 50 to move relative to the rack housing 40 .
The rack boot 41 is made of a resin material such as elastomer and has a flexible bellows-like shape.

The tie rod 50 is an axial interlocking member that connects the end of the rack shaft 30 and the knuckle arm 61 of the housing 60, and rotates the housing 60 around the kingpin axis in conjunction with the translational movement of the rack shaft 30.
The inner end of the tie rod 50 in the vehicle width direction is swingably connected to the end of the rack shaft 30 via a ball joint 51 .
The outer end of the tie rod 50 in the vehicle width direction is connected to a knuckle arm 61 of a housing 60 via a ball joint 52 .

The housing (knuckle) 60 is a member that accommodates a hub bearing that supports the wheel W rotatably around the axle.
The housing 60 has a knuckle arm 61 formed to protrude forward or rearward relative to the axle.
The housing 60 is supported so as to be rotatable around a kingpin axis, which is a predetermined rotational center axis.
For example, if the vehicle's front suspension is a McPherson strut type, the kingpin axis is an imaginary axis connecting the bearing center of the strut top mount and the center of the ball joint that connects the lower part of the housing 60 and the transverse link (lower arm).
The housing 60 is pushed and pulled in the vehicle width direction by the rack shaft 30 via the tie rod 50, thereby rotating about the kingpin axis and steering the wheels W.

The steering angle sensor 71 is an angle encoder that detects the rotational angle position of the pinion shaft 22 .
The output of the steering angle sensor 71 is transmitted to an electric power steering control unit 90 .
The electric power steering control unit 90 is capable of calculating the steering angle θ of the wheels W (the toe change angle associated with steering) based on the output of the steering angle sensor 71 .

The torque sensor 72 is a sensor that detects the torque acting on the pinion shaft 22 (mainly the steering force exerted by the driver).
The torque sensor 72 is provided on the pinion shaft 22 at a portion closer to the intermediate shaft 21 than the actuator unit 80 .
The output of the torque sensor 72 is transmitted to an electric power steering control unit 90 .

The actuator unit 80 is a drive device that rotates the pinion shaft 22 to provide power assistance during manual driving and to perform steering operations during automatic driving.
The actuator unit 80 includes a motor 81, a gear box 82, and the like.
The motor 81 is an electric actuator that generates a driving force to be applied to the steering shaft 20 .
The rotation direction and output torque of the motor 81 are controlled by an electric power steering control unit 90 .
The gear box 82 includes a reduction gear train that reduces the speed (torque amplification) of the rotational output of the motor 81 and transmits it to the pinion shaft 22 .

The electric power steering (EPS) control unit 90 is a control device (motor control unit) that provides the motor 81 with a current command value that controls the rotation direction and output torque.
The electric power steering control unit 90 can be configured as a microcomputer having, for example, an information processing unit such as a CPU, a storage unit such as a RAM or a ROM, an input/output interface, and a bus connecting these.
The electric power steering control unit 90 is capable of acquiring information such as the outputs of the steering angle sensor 71 and torque sensor 72, the vehicle's running speed (vehicle speed), and the operating status of other on-board electronic devices, either directly or via an on-board LAN such as a CAN communication system.

When the vehicle is being manually driven, the electric power steering control unit 90 sets a current command value to be given to the motor 81 based on the torque input direction and detected torque value of the torque sensor 72 .
The electric power steering control unit 90 includes a power supply device that supplies electric power of a current value and a voltage value according to a current command value to the motor 81 via a signal line.

FIG. 2 is a diagram illustrating a system configuration of the information transmission device according to the first embodiment.
The information transmission device 100 vibrates the air around the ears of the occupants using a speaker 170 disposed in the vehicle cabin, thereby alerting the occupants to an impending vehicle behavior by means of an acoustic signal.
The information transmission device 100 includes a waveform generation unit 110, a differential calculation unit 120, a first gain adjustment unit 130, a microphone 140, a sensing value calculation unit 150, a second gain adjustment unit 160, a speaker 170, and the like.

The waveform generating unit 110 generates an excitation waveform, which is the waveform of the acoustic signal generated by the speaker 170 .
FIG. 3 is a diagram schematically illustrating an example of an excitation waveform in the first embodiment.
In FIG. 3, the horizontal axis represents time, and the vertical axis represents voltage (amplitude).
For example, as shown in FIG. 3(a), the excitation waveform can be a sine wave.
Furthermore, as shown in FIG. 3B, for example, the excitation waveform can be a waveform in which a plurality of sine waves with different wavelengths are superimposed (combined).
Furthermore, the excitation waveform is not limited to these and can be changed as appropriate.
For example, various waveforms such as a rectangular wave, a triangular wave, or a waveform simulating the sound of a vehicle running can be used as the excitation waveform, either alone or in combination with other waveforms.

In the first embodiment, the frequency of the vibration waveform can be set to have a dominant frequency in the range of, for example, 100 to 400 Hz, more preferably, 150 to 300 Hz.
The reason for this will be explained below.
When the air around the passenger is vibrated, sensory receptors that detect the vibrations include Merkel cells, Meissner's corpuscles, and Pacinian corpuscles.
FIG. 4 is a diagram showing the timing of an electrical pulse emitted by a receptor when stimulated.
In FIG. 4, the horizontal axis represents time, and the vertical axis represents, from the top down, pressure and the electrical pulse generation states of Merkel cells, Meissner's corpuscles, and Pacinian corpuscles.

Merkel cells have a relatively slow response and respond to direct current components.
Meissner's corpuscles correspond to when a rate of change (velocity) of contact pressure occurs.
Pacinian corpuscles respond to moments of transient change and are said to be the most sensitive of these receptors.
It is believed that the Pacinian corpuscles are the most sensitive receptors for passengers to sense minute vibrations as combined auditory and tactile information.

FIG. 5 is a diagram showing the frequency sensitivity distribution of Pacinian corpuscles and Meissner corpuscles.
In FIG. 5, the horizontal axis indicates frequency and the vertical axis indicates amplitude above the threshold, with smaller values indicating better sensitivity.
As shown in FIG. 5, the Pacinian corpuscles exhibit good sensitivity in the region around 100 to 400 Hz, and even better sensitivity in the region around 150 to 300 Hz.
Such a range is generally included in the range of 20 Hz to 20 kHz, which is the range of human hearing.
The dominant frequency of the excitation waveform can be set to 250 Hz, for example.

The differential calculation section 120 acquires information on the steering angle θ of the wheels W detected by the steering angle sensor 71 from the electric power steering control unit 90, and calculates a differential value Δθ by time differentiation.
The differential calculation unit 120 sequentially transmits the calculated differential value Δθ to the first gain adjustment unit 130 .

The first gain adjustment section 130 performs a first gain adjustment, which will be described below, on the fundamental wave of the excitation waveform generated by the waveform generation section 110 .
The first gain adjustment changes the gain G1, which is the output gain multiplied by the voltage of the excitation waveform, according to the differential value (rate of change per time) of the steering angle θ of the steering device (a parameter correlated with the steering amount).

FIG. 6 is a diagram schematically illustrating an example of gain adjustment in the first gain adjustment unit.
In FIG. 6, the horizontal axis indicates the absolute value of the differential value Δθ of the steering angle θ of the wheel FW, and the vertical axis indicates the gain G1 by which the voltage of the vibration waveform is multiplied.
The gain G1 can be configured to increase in accordance with an increase in the absolute value of the differential value Δθ.
Furthermore, the rate of increase of the gain G1 in response to an increase in the absolute value of the differential value Δθ in the first gain adjustment unit 130 can be configured to be maximum in a region where the absolute value of the differential value Δθ is small, and to decrease as the absolute value of the differential value Δθ increases.

The gain G1 in the first gain adjustment unit 130 can be calculated, for example, from the absolute value of the differential value Δθ of the steering angle θ using a logarithmic function.
The gain G1 is expressed by, for example, the following equation 1.

Gain G1=log(absolute value of steering angle differential value Δθ×coefficient k) (Equation 1)

The coefficient k can be a value set, for example, at the development stage of the vehicle, in accordance with the characteristics of the vehicle (for example, the yaw gain relative to the steering angle θ, the position of the center of gravity, etc.).

The microphone 140 is a sound collecting device that is provided inside the vehicle cabin and collects background noise inside the vehicle cabin.
The microphone 140 is preferably disposed in a position close to the ear of the occupant, and may be provided, for example, in the headrest portion of the seat.
The output of the microphone 140 is transmitted to the sensing value calculation unit 150 .

The sensing value calculation unit 150 extracts components of a predetermined frequency band from the background noise of the vehicle acquired by the microphone 140, and transmits the sound pressure of the extracted components to the second gain adjustment unit 160 as a sensing value.
FIG. 7 is a diagram schematically illustrating an example of an output history of a microphone.
In FIG. 7, the horizontal axis indicates time, and the vertical axis indicates the sound pressure of the background noise acquired by the microphone 140 .

The sensing value calculation unit 150 performs a fast Fourier transform (FFT) process on the acoustic signal of background noise acquired by the microphone 140 to convert it into the frequency domain, and then performs a band-pass filter process to extract components in a predetermined frequency band.
The frequency band to be extracted is set so as to include the dominant frequency of the excitation waveform output by the waveform generating unit 110 .
The sensing value calculation unit 150 sets the average sound pressure of the extracted frequency band as the sensing value to be used for the second gain adjustment.

FIG. 8 is a diagram showing an example of the correlation between the sound pressure of background noise and frequency.
In FIG. 8, the horizontal axis represents frequency and the vertical axis represents sound pressure.
The band-pass filter can be configured to extract a frequency band near the dominant frequency (for example, 250 Hz) of the excitation waveform in the waveform generating unit 110, for example.
The sound pressure in the extracted frequency band (for example, the average value of the frequency band) is provided to the second gain adjuster 160 as a sensing value.

The second gain adjustment section 160 further performs a second gain adjustment, which will be described below, on the vibration waveform after the first gain adjustment.
The second gain adjustment changes the gain of the excitation waveform according to the sensing value of the noise inside the vehicle in order to adjust the output amplitude of the excitation waveform according to changes in background noise (drivetrain noise, aerodynamic noise, road noise, etc.) while the vehicle is running.
The second gain adjustment section 160 performs second gain adjustment based on the output of the sensing value calculation section 150 .

The second gain adjustment section 160 sets the gain G2 based on the sensing value output by the sensing value calculation section 150 .
FIG. 9 is a diagram illustrating an example of gain adjustment in the second gain adjustment unit.
In FIG. 9, the horizontal axis represents the sensing value, and the vertical axis represents the gain G2 by which the voltage of the vibration waveform is multiplied.
The gain G2 can be configured to increase as the sensing value increases.
The gain G2 is set so that the sound pressure of the sound generated by the excitation amplitude output from the speaker 170 does not dominate over the sound pressure of background noise near the ears of the passengers.
Preferably, the gain G2 is set so that the sound generated by the excitation amplitude is hidden in the background noise of the vehicle and reaches a sound pressure level that can be heard unconsciously by the occupants.

The output value (voltage) A of the vibration waveform after the first gain adjustment and second gain adjustment described above is expressed by Equation 2.

Output value A = waveform generating unit output value × gain G1 × gain G2
= Waveform generating unit output value × log (absolute value of steering angle differential value Δθ × coefficient k)
× Gain G2 (Equation 2)

The speaker 170 is a vibration device that is arranged in the vehicle cabin and uses the output value A to vibrate the air around the passengers in the vehicle cabin, thereby generating sound.
The placement of the speaker 170 will be described in detail later.
The speaker 170 may be configured to be shared with a speaker used for audio reproduction in an in-car audio device, for example.
Furthermore, a dedicated speaker 170 may be provided for the information transmission device 100 .

FIG. 10 is a diagram showing a schematic layout of the interior of a vehicle in which the information transmission device of the first embodiment is provided.
Inside the vehicle interior 200, a driver's seat 210, a passenger seat 220, a rear seat 230, an instrument panel 240, etc. are provided.

The driver's seat 210 and the passenger seat 220 are front seats provided at the front of the vehicle compartment.
The driver's seat 210 and the passenger seat 220 are arranged side by side in the vehicle width direction.
In the example shown in FIG. 10, the vehicle is a so-called right-hand drive vehicle, with the driver's seat 210 located on the right side and the passenger seat 220 on the left side relative to the center of the vehicle body.
The driver's seat 210 and the passenger seat 220 each have a cushion portion on which the occupant's buttocks and thighs are placed, a seatback portion disposed behind the occupant's back, and a headrest portion disposed behind the occupant's head.

The rear seat 230 is a bench-like seat located behind the driver's seat 210 and the passenger seat 220 .
The rear seat 230 can accommodate, for example, two passengers sitting side by side.
The rear seat 230 has a cushion portion on which the occupant's buttocks and thighs are placed, a seatback portion disposed behind the occupant's back, and a headrest portion disposed behind the occupant's head.
The right seating portion of rear seat 230 is disposed behind driver's seat 210 , and the left seating portion is disposed behind passenger seat 220 .

The instrument panel 240 is provided near the front end of the vehicle interior 200 and is a member that houses, for example, an instrument panel, a ventilation/air-conditioning/heating system, an infotainment system, and the like.
The instrument panel 240 is disposed so as to face the occupants seated in the driver's seat 210 and the passenger seat 220 .

In the example shown in FIG. 10, for example, four speakers 170 are provided at intervals on the front, rear, left and right sides of the vehicle interior 200.
In the following description, the reference numerals of the speakers 170 are given subscripts corresponding to their positions.

The right front speaker 170FR is disposed near the right end of the instrument panel 240.
The speaker 170FR is a directional speaker that is directed toward the head (ears) of a passenger seated in the driver's seat 210.
The left front speaker 170FL is disposed near the left end of the instrument panel 240.
Speaker 170FL is a directional speaker that is directed toward the head (ears) of an occupant seated in passenger seat 220.

The right rear speaker 170RR is disposed in the headrest portion of the driver's seat 210.
Speaker 170RR is a directional speaker that is directed toward the head (ear) of an occupant seated on the right side of rear seat 230.
The left rear speaker 170RL is disposed in the headrest of the passenger seat 220.
Speaker 170RL is a directional speaker that is directed toward the head (ear) of an occupant seated on the left side of rear seat 230.

In the first embodiment, with the above configuration, when the driver performs a steering operation and the steering angle θ of the wheels W changes, the speaker 170 emits a sound to the occupants with an amplitude corresponding to the differential value Δθ of the steering angle θ.
This sound is masked by the sound of the vehicle running (background noise), making it difficult for occupants to consciously recognize it as sound, but it can subconsciously alert occupants to the occurrence of vehicle behavior accompanied by lateral acceleration and yaw rate.

According to the first embodiment described above, the following effects can be obtained.
(1) By generating a sound whose sound pressure increases in accordance with an increase in the absolute value of the differential value Δθ of the steering angle θ of the wheel W by the steering device, the sound can give the occupants a preview of the behavior that will occur in the vehicle at the beginning of steering, before the lateral acceleration, yaw rate, roll angle, etc. actually occur in the vehicle.
This improves the occupant's predictability of vehicle behavior, and prevents the occupant from feeling abrupt about the vehicle behavior.
This allows the occupant to prepare for the occurrence of acceleration or the like by, for example, applying force to the body, thereby preventing the occupant from unintentionally losing his/her seated position.
(2) By making the excitation waveform have a dominant frequency in the frequency band of 100 to 400 Hz, more preferably 150 to 300 Hz, it becomes possible to use Pacinian corpuscles, which are in the audible range and highly sensitive to skin sensation, and improves the occupant's perception of sound and cutaneous sensation. As a result, information can be transmitted more reliably to the occupant.
(3) By setting the gain G1 using a logarithmic function from the absolute value of the differential value Δθ of the steering angle θ, it is possible to set a large gain G1 even in an area where the absolute value of the differential value Δθ is relatively small, and information can be appropriately conveyed to the occupant even in the initial stage of steering when the steering angle θ and the differential value (steering speed) Δθ are small.
Furthermore, in a region where the absolute value of the differential value Δθ is large, the output gain can be prevented from becoming excessively large.
(4) By setting the gain G2 so that the sound pressure generated by the vibration of the speaker 170 does not predominate at the ear of at least one occupant compared to the background noise while the vehicle is moving, it is possible to prevent the sound generated by the vibration of the speaker 170 from being drowned out by the background noise of the vehicle and being perceived as harsh by the occupants, and to properly convey information.
(5) By using the steering angle θ of the wheels W as a parameter correlated with the steering amount of the steering device, the parameter can be easily and appropriately acquired using a steering angle sensor that is normally provided in a typical vehicle.

Second Embodiment
Next, a second embodiment of an information transmission device to which the present invention is applied will be described.
In the second embodiment, the vehicle is provided with an automatic driving function that performs steering operations, acceleration/deceleration operations, etc. independently without relying on the driving operations of the driver.

FIG. 11 is a diagram illustrating a schematic configuration of an automatic driving system for a vehicle in which an information transmission device according to the second embodiment is provided.
In addition to the electric power steering control unit 90 described above, the autonomous driving system 300 further includes an autonomous driving control unit 310, an engine control unit 320, a transmission control unit 330, a brake control unit 340, and the like.
Each of these units includes a microcomputer having an information processing unit such as a CPU, a storage unit such as a RAM or a ROM, an input/output interface, and a bus connecting these.
Furthermore, the units are connected to each other via an in-vehicle LAN such as a CAN communication system or directly, and are capable of communicating with each other.

The autonomous driving control unit 310 recognizes the environment around the vehicle using various sensors such as a stereo camera device, a millimeter wave radar device, a laser scanner device, and a high-precision 3D map.
The autonomous driving control unit 310 generates an autonomous driving scenario based on the recognized environment, including information regarding the vehicle's driving line, speed, etc.
The autonomous driving control unit 310 issues instructions to the electric power steering control unit 90, engine control unit 320, transmission control unit 330, and brake control unit 340 based on the autonomous driving scenario, and controls the steering and acceleration/deceleration of the vehicle.

Instead of steering input from the driver as in the first embodiment, the electric power steering control unit 90 controls the actuator unit 80 in accordance with the required steering angle instructed by the automatic driving control unit 310, and steers the wheels W.

The engine control unit 320 comprehensively controls the engine, which is the power source for running the vehicle, and its accessories.
The engine control unit 320 controls the output of the engine so that the torque actually generated by the engine matches the required torque instructed by the automatic driving control unit 310 .

The transmission control unit 330 comprehensively controls the transmission, which changes the speed (speeds down or speeds up) of the rotation of the output shaft of the engine, and its accessories.
In response to instructions from the automatic driving control unit 310, the transmission control unit 330 switches between the driving range and the non-driving range, switches between forward and reverse travel, and changes gears (changes the gear ratio) when traveling forward.

The brake control unit 340 controls the braking force of the hydraulic service brakes provided on each wheel of the vehicle.
The brake control unit 340 adjusts the brake fluid pressure supplied to the wheel cylinders of each wheel in accordance with the required braking force instructed by the automatic driving control unit 310, thereby generating the required braking force.

In the second embodiment, even during autonomous driving where the driver does not generally perform steering operations, the requested steering angle transmitted from the autonomous driving control unit 310 to the electric power steering control unit 90 is used as an input to the information transmission device 100 (a parameter correlated with the steering angle of the steering device), and the first gain adjustment is performed based on its differential value.
According to the second embodiment described above, even in an automatically driven vehicle, when steering due to automatic driving control begins, a sound is generated according to the absolute value of the differential value of the steering angle, making it possible for occupants to foresee the occurrence of vehicle behavior involving the occurrence of lateral acceleration, yaw rate, roll angle, etc., and preventing occupants from feeling abrupt about the vehicle behavior.

(Modification)
The present invention is not limited to the above-described embodiment, and various modifications and variations are possible, and these are also within the technical scope of the present invention.
(1) The configurations of the information transmission device and the vehicle are not limited to those of the above-described embodiments, and may be modified as appropriate.
For example, the hardware configuration of the information transmission device and the specific method of adjusting the gain of the excitation waveform are not limited to the configurations of the respective embodiments and can be modified as appropriate.
(2) In each embodiment, a parameter correlated with the steering amount of the steering device is, for example, a steering angle (actual steering angle detected by a steering angle sensor or a required steering angle in automatic driving control), but the parameter is not limited to this and can be changed as appropriate.
For example, the configuration can include at least one of the steering torque (input torque) input from the driver, the operating amount of the actuator that steers the wheels (for example, the rotation amount of the motor), and the output instruction value to the actuator.
(3) The present invention is not limited to vehicles in which an operating member such as a steering wheel is mechanically connected to a steering mechanism such as a steering gear box, as in the respective embodiments, but can also be applied to vehicles having a steer-by-wire steering device in which the steering mechanism is not mechanically connected to the steering wheel, etc. In this case, the actual steering angle of the front wheels and the state of the steering mechanism (for example, the rotational angle position of the pinion gear, the amount of movement of the rack shaft, etc.) can be used as parameters correlated with the steering amount of the steering device.
(4) In each embodiment, the level of background noise of the vehicle is obtained by a microphone as an example, but this is not limiting and the level of background noise may be obtained by other methods. For example, the level of background noise may be estimated based on the acceleration of the unsprung part of the vehicle, which correlates with input from the road surface, or the output value of a torque sensor of the steering device (torsion bar torque).

REFERENCE SIGNS LIST 1 Electric power steering device W Wheel 10 Steering wheel 20 Steering shaft 21 Intermediate shaft 22 Pinion shaft 23, 24 Universal joint 30 Rack shaft 31 Rack gear 40 Rack housing 41 Rack boot 50 Tie rod 51, 52 Ball joint 60 Housing 71 Steering angle sensor 72 Torque sensor 80 Actuator unit 81 Motor 82 Gear box 90 Electric power steering control unit 100 Information transmission device 110 Waveform generation unit 120 Differential calculation unit 130 First gain adjustment unit 140 Microphone 150 Sensing value calculation unit 160 Second gain adjustment unit 170 (170FR, 170FL, 170RR, 170RL) Speaker 200 Vehicle interior 210 Driver's seat 220 Passenger seat 230 Rear seat 240 Instrument panel 300 Automated driving system 310 Automated driving control unit 320 Engine control unit 330 Transmission control unit 340 Brake control unit

Claims (5)

An information transmission device provided in a vehicle having a steering device for steering wheels,
a parameter detection unit that detects a parameter correlated with a steering amount of the steering device;
an excitation waveform generating unit that generates an excitation waveform;
a vibration unit that vibrates the air around the occupant using the vibration waveform;
and a gain adjustment unit that increases an output gain of the excitation waveform in accordance with an increase in the absolute value of the differential value of the parameter. 2. The information transmission device according to claim 1, wherein the excitation waveform has a dominant frequency within a frequency band of 100 to 400 Hz. 3. The information transmission device according to claim 1, wherein an increase rate of the output gain with respect to an increase in the absolute value of the differential value in the gain adjustment unit is maximum in a region where the absolute value of the differential value is small, and decreases as the absolute value of the differential value increases. 3. The information transmission device according to claim 1, wherein the gain adjustment unit sets the output gain so that the sound pressure generated by the excitation of the excitation unit does not dominate background noise when the vehicle is running, at the ear of at least one occupant. 3. The information transmission device according to claim 1, wherein the parameters include at least one of a steering angle of the steering device, an input torque to the steering device, an actuation amount of an actuator that steers the wheels, and an output instruction value to the actuator.