Vehicle sound generating device

Abstract

To enable an occupant to feel the comfortableness of vehicle acceleration.SOLUTION: A sound generation apparatus for a vehicle includes: a sound control unit 12 for generating a sound signal representing a sound; a speaker 20 for outputting a sound according to the sound signal; an acceleration state detection unit 13 for detecting that a vehicle 2 is in an acceleration state; a target speed estimation unit 14 for estimating a target speed of the vehicle in the acceleration state; and an acceleration time estimation unit 15 for estimating an acceleration time required for the vehicle to reach the target speed. When it is detected that the vehicle is in the acceleration state, the sound control unit sets a time transition of a parameter of the sound signal and generates the sound signal on the basis of the time transition of the parameter. The time transition of the parameter includes a repeat of a first trend and a second trend. Each time interval obtained by dividing the acceleration time is set as a time until the first trend changes to the second trend for the first time after it is detected that the vehicle is in the acceleration state, and as a time interval between each change timing at which the first trend changes to the second trend and the next change timing.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a sound generating device for a vehicle, and more particularly to a sound generating device for a vehicle that outputs a predetermined sound while the vehicle is running. [Background technology]

[0002] Conventionally, there are known technologies that output simulated engine sounds or motor sounds to the driver in response to vehicle operating conditions such as vehicle speed and driver operation such as accelerator pedal depression. For example, a vehicle sound generating device described in Patent Document 1 outputs a synthesized sound containing multiple frequencies set to be proportional to the rotation speed of an electric motor, and sets the increase in the output of low-frequency sounds to be greater than the increase in the output of high-frequency sounds in response to an increase in motor torque value. This allows the driver to easily recognize the strength of the vehicle's acceleration in response to accelerator operation, promoting accurate accelerator operation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-32972 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the technology in the above-mentioned patent documents can encourage drivers to operate the accelerator accurately, it is not possible to output a sound that allows occupants to fully feel the pleasantness of the vehicle's acceleration when the accelerator pedal is pressed hard to accelerate the vehicle (for example, when merging onto a highway).

[0005] The present invention has been made to solve such problems, and has an object to provide a sound generating device for a vehicle that allows the occupants to feel the pleasantness of the acceleration of the vehicle. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a vehicle sound generation device mounted on a vehicle that runs using an electric motor as a power source, the device comprising: a sound control unit configured to generate a sound signal representing a sound; a sound output unit that outputs a sound corresponding to the sound signal generated by the sound control unit; an acceleration state detection unit that detects whether the vehicle is in an accelerating state; a target speed estimation unit that, when it is detected that the vehicle is in an accelerating state, estimates a target speed of the vehicle in the accelerating state; and an acceleration time estimation unit that, when it is detected that the vehicle is in an accelerating state, estimates an acceleration time required for the vehicle to reach the target speed. When it is detected that the vehicle is in an accelerating state, the sound control unit sets a time transition of a parameter of the sound signal and generates the sound signal based on the time transition of the parameter, the time transition of the parameter includes a repetition of a first trend and a second trend following the first trend, and each time interval obtained by dividing the acceleration time is set as the time from when it is detected that the vehicle is in an accelerating state until the first trend first changes to the second trend, and as the time interval of each change timing at which the first trend changes to the second trend. The parameter includes one or both of frequency and sound pressure, the first trend is a trend in which the parameter increases over time, and the second trend is a trend in which the parameter decreases over time. do.

[0007] According to the present invention configured in this manner, the timings at which the first trend changes to the second trend in the time transition of the sound signal parameters are determined by the time intervals into which the acceleration time required for the vehicle to reach the target speed is divided, so that the time transition of each parameter of the sound signal can be set so that the sound is changed at appropriate timing according to the acceleration time. This makes it possible to change the output sound at a timing that appropriately reflects the acceleration of the vehicle, allowing the occupants to feel the pleasantness of the vehicle's acceleration. Furthermore, the changes in sound over time can be clearly recognized by the occupants, making the acceleration of the vehicle feel even more pleasant.

[0009] Also, in the present invention, preferably, the vehicle sound generating device has a motor rotation speed sensor that detects the rotation speed of the electric motor, and the sound control unit generates a sound signal based on at least the rotation speed of the electric motor when it is not detected that the vehicle is in an accelerating state. According to the present invention configured in this manner, the time progression of the sound output when it is detected that the vehicle is in an accelerating state can be made to stand out in contrast to the sound based on the motor rotation speed, allowing the occupants to feel an even more pleasant sensation of the vehicle's acceleration.

[0010] In the present invention, preferably, the target speed estimation unit acquires a speed limit ahead in the traveling direction of the vehicle in an accelerating state, and estimates that speed limit to be the target speed. With this configuration, the target speed can be more accurately estimated based on the speed limit ahead of the vehicle in the direction of travel. This allows the output sound to be changed at a timing that more appropriately reflects the vehicle's acceleration, allowing occupants to feel an even more pleasant sensation of vehicle acceleration.

[0011] In the present invention, preferably, the target speed estimation unit acquires the speed of a nearby vehicle traveling in the same direction as the vehicle in an accelerating state, and estimates that the speed of the nearby vehicle is the target speed. With this configuration, the target speed can be more accurately estimated based on the speed of surrounding vehicles, which allows the output sound to be changed at a timing that more appropriately reflects the vehicle's acceleration, allowing the occupants to feel an even more pleasant acceleration of the vehicle.

[0012] Also, in the present invention, preferably, the target speed estimation unit acquires a speed corresponding to the type of road on which the vehicle is traveling in an accelerating state from among speeds previously associated with road types, and estimates that the acquired speed is the target speed. With this configuration, the present invention can more accurately estimate the target speed based on the type of road the vehicle is traveling on. This allows the output sound to be changed at a timing that more appropriately reflects the vehicle's acceleration, allowing the occupants to feel an even more pleasant sensation of vehicle acceleration.

[0013] Also, in the present invention, preferably, the acceleration time estimation unit acquires the acceleration of the vehicle when it is detected that the vehicle is in an accelerating state, and estimates the acceleration time by dividing the difference between the target speed and the vehicle speed by the acceleration. With this configuration, the present invention can more accurately estimate the acceleration time required for the vehicle to reach the target speed, thereby changing the output sound at a timing that more appropriately reflects the vehicle's acceleration, allowing the occupants to feel an even more pleasant acceleration of the vehicle. [Effects of the Invention]

[0014] The vehicle sound generating device of the present invention can make the occupants feel the pleasant sensation of vehicle acceleration. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an explanatory diagram of a vehicle sound generating device according to an embodiment of the present invention; [Figure 2] 1 is a configuration diagram of a vehicle sound generating device according to an embodiment of the present invention. [Figure 3] 1A and 1B are conceptual diagrams illustrating situations in which a vehicle's target speed is estimated. (a) illustrates acceleration due to an increase in the speed limit ahead in the direction of travel, (b) illustrates acceleration due to overtaking, and (c) illustrates acceleration to catch up with traffic. [Figure 4] 1 is a flowchart of a sound generation process according to an embodiment of the present invention. [Figure 5A] 1 is a frequency map that defines the relationship between the motor rotation speed and frequency according to an embodiment of the present invention. [Figure 5B] 1 is a sound pressure map that defines the relationship between the motor rotation speed and sound pressure according to an embodiment of the present invention. [Figure 6] 10 is a flowchart of a target speed estimation process according to an embodiment of the present invention. [Figure 7A] 10 is a frequency map defining the time transition of frequency when a vehicle is in an accelerating state according to an embodiment of the present invention. [Figure 7B]10 is a sound pressure map that defines the time transition of sound pressure when a vehicle is accelerating according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0017] <Configuration of vehicle sound generation device> First, the configuration of a sound generation device for a vehicle of the present invention will be described with reference to Figures 1 and 2. Figure 1 is an explanatory diagram of a sound generation device for a vehicle, and Figure 2 is a diagram of the configuration of the sound generation device for a vehicle.

[0018] 1 and 2, a vehicle sound generation device 1 of this embodiment includes a sound control device 10 mounted on a vehicle 2, a speaker 20 that outputs a predetermined sound to the driver in the vehicle cabin, and an in-vehicle device group 30 that includes various sensors that detect the state of the vehicle 2 and various devices that output information related to the driving conditions of the vehicle 2. The vehicle 2 is an electric vehicle (EV) equipped with an electric motor 3 as a rotational power source.

[0019] The sound control device 10 is a well-known computer-based controller that includes circuits. The sound control device 10 includes one or more processors as a central processing unit (CPU) that executes programs, a memory (storage unit 16) that is configured, for example, with RAM (Random Access Memory) or ROM (Read Only Memory) and stores various programs and databases, and a data input / output device that inputs and outputs electrical signals.

[0020] Various maps used to generate sound signals are stored in a database in the memory unit 16. The sound control device 10 is communicably connected to other in-vehicle devices via an in-vehicle communication line. The sound control device 10 is configured so that the processor executes a program based on various information from the in-vehicle equipment group 30, thereby outputting a sound signal Ss to the speaker 20. In this case, the processor of the sound control device 10 functions as a sound control unit 12, an acceleration state detection unit 13, a target speed estimation unit 14, and an acceleration time estimation unit 15, as will be described later.

[0021] The speaker 20 is a sound output unit equipped with an amplifier. The speaker 20 receives a sound signal Ss from the sound control device 10, amplifies the sound signal Ss by a predetermined amplification factor, and outputs a sound (typically a synthesized sound) SC based on the sound signal Ss. The speaker 20 does not have to be provided inside the vehicle cabin as long as the driver can recognize the sound SC generated by the speaker 20.

[0022] The in-vehicle device group 30 includes a rotation speed sensor 31 that detects the rotation speed of the electric motor 3, an accelerator pedal position sensor 32 that detects the accelerator position corresponding to the amount of accelerator pedal operation of the vehicle 2, a motor torque sensor 33 that detects the motor torque of the electric motor 3, a vehicle speed sensor 34 that detects the speed of the vehicle 2, an acceleration sensor 35 that detects the acceleration of the vehicle 2, a navigation device 36 that provides position information of the vehicle 2 obtained from a GPS receiver or a gyro sensor and map information obtained from a map information database, a camera 37 that captures images of the surroundings of the vehicle 2, a radar 38 that measures the position and speed of objects around the vehicle 2, and a turn signal (directional indicator) 39 that indicates the traveling direction of the vehicle 2 in response to operation by the driver. These in-vehicle devices 30 transmit signals S31 to S39 that indicate the detected vehicle state and acquired information via an in-vehicle communication line. The sound control device 10 can receive various signals from the in-vehicle device group 30 via the in-vehicle communication line.

[0023] In this embodiment, the motor torque is detected by the motor torque sensor 33, but this is not limiting, and the motor torque may be a requested motor torque value for the electric motor 3. Alternatively, the sound control device 10 may calculate the motor torque from the accelerator opening degree, etc., using an acceleration characteristics map, etc.

[0024] <Control by vehicle sound generation device> Next, the basic concept of control by the vehicle sound generation device 1 of this embodiment will be described. Simply outputting a synthetic sound containing a frequency set to be proportional to the motor's rotation speed, as in the conventional technology described above, does not allow the occupant to fully appreciate the pleasantness of vehicle acceleration when accelerating the vehicle by pressing the accelerator pedal hard. The inventors of the present invention therefore investigated what kind of sound would make the occupant feel the pleasantness of vehicle acceleration. As a result, they found that if the occupant perceives the output sound as having a "rhythmic" quality, the occupant will perceive the pleasantness of vehicle acceleration from the output sound. Furthermore, when a sound that changes over time is output while the vehicle is accelerating, the occupant will perceive the output sound as having a "rhythmic" quality if the occupant receives high ratings without bias in three subjective evaluation items: (1) the sense of rhythm perceived from the time progression of the sound; (2) the degree of correspondence between the occupant's expectation of the time progression of the sound and the actual time progression of the sound; and (3) the degree of correspondence between the time progression of the sound and the scenery that changes as the vehicle accelerates.

[0025] Therefore, the inventors conducted an experiment in which subjects boarded a vehicle simulator, reproduced the changing scenery when the vehicle was accelerating, and output sounds with various time transition patterns, and had the subjects evaluate the scores of the three subjective evaluation items. Specifically, time transitions of two parameters representing the sound, namely the frequency and sound pressure of a sound signal, were set, and sounds corresponding to the sound signals generated based on the time transitions of the set parameters were output. The time transitions of each parameter included a first trend in which each parameter increased over time, and a second trend in which each parameter decreased over time following the first trend. The sounds were output under multiple conditions in which the time intervals at which the first trend changed to the second trend were varied, and the subjects evaluated the scores of the three subjective evaluation items under each condition.

[0026] As a result, it was found that the time interval between each change in the timing when the first trend changes to the second trend has the greatest effect on the score for each evaluation item. More specifically, it was found that when the time from when the vehicle enters an accelerating state to when the first trend first changes to the second trend (i.e., until the first change), and the time interval between each change, are equal within the range of 1000 milliseconds to 2000 milliseconds, each evaluation item will receive a high score without bias.

[0027] Therefore, in this embodiment, the vehicle sound generating device 1 outputs a sound corresponding to a sound signal in which the time transition of each parameter is set so that the time from when the vehicle 2 enters an accelerating state to the first change timing and the time interval between each change timing are 1000 milliseconds to 2000 milliseconds. This allows the occupant to recognize that the output sound has a "sense of rhythm" and makes the acceleration of the vehicle 2 feel pleasant.

[0028] Furthermore, in this embodiment, when the vehicle 2 enters an accelerating state, a target speed of the vehicle 2 in the accelerating state is estimated, and an acceleration time required for the vehicle 2 to reach the target speed is estimated. Then, time intervals obtained by dividing the estimated acceleration time are set as the time from when the vehicle 2 enters the accelerating state to the first change timing, and as the time intervals between each change timing. This makes it possible to set the time transition of each parameter so that the sound is changed at an appropriate timing according to the time required for acceleration to reach the target speed, allowing the occupants to feel a pleasant acceleration of the vehicle 2.

[0029] The target speed used to estimate the acceleration time is estimated by the target speed estimation unit 14 based on the driving conditions of the vehicle 2 and the surrounding traffic environment. FIG. 3 is a conceptual diagram illustrating an example of a situation in which the target speed of the vehicle 2 is estimated. The example of FIG. 3(a) shows a situation in which the host vehicle (vehicle 2) is about to accelerate to enter an expressway from an ordinary road, and the speed limit ahead in the traveling direction increases to 100 km / h. In such a situation, the target speed estimation unit 14 acquires the speed limit ahead in the traveling direction based on information acquired from the navigation device 36 and the camera 37, and estimates that this speed limit is the target speed of the host vehicle.

[0030] 3(b) shows a situation in which the host vehicle (vehicle 2) is changing lanes into an adjacent lane to accelerate in order to overtake another vehicle 5 traveling ahead, and has its blinker 39 turned on in the direction of the adjacent lane. Also, in the example of FIG. 3(b), another vehicle 6 is traveling ahead in the adjacent lane. In such a situation, the target speed estimation unit 14 acquires the speed of the other vehicle 6 traveling ahead in the adjacent lane in the direction indicated by the blinker 39 based on information acquired from the radar 38, and estimates that the speed of the other vehicle 6 is the target speed.

[0031] 3(c) shows a situation in which the host vehicle (vehicle 2) is trying to accelerate in order to catch up with another vehicle 4 traveling ahead of the host vehicle in the same lane as the host vehicle. In such a situation, the target speed estimation unit 14 acquires the speed of the other vehicle 4 traveling ahead of the host vehicle based on information acquired from the radar 38, and estimates that the speed of the other vehicle 4 is the target speed.

[0032] Furthermore, when the vehicle 2 enters an accelerating state in a situation that does not correspond to any of Figures 3(a) to (c), the target speed estimation unit 14 identifies the type of road on which the vehicle 2 is traveling based on information obtained from the navigation device 36, obtains the speed that is previously stored in the memory unit 16 in association with that road type, and estimates that the obtained speed is the target speed of the vehicle 2.

[0033] <Sound generation processing> Next, the flow of sound generation processing by the vehicle sound generation device 1 of this embodiment will be described with reference to Figures 4 to 7B. Figure 4 is a flowchart of the sound generation processing according to this embodiment, Figures 5A and 5B are maps that define the relationship between the motor rotation speed and sound signal parameters according to this embodiment, Figure 6 is a flowchart of the target speed estimation processing according to this embodiment, and Figures 7A and 7B are maps that set the time transition of the sound signal parameters when the vehicle is accelerating according to this embodiment.

[0034] The sound generation process shown in FIG. 4 is repeatedly executed at a predetermined cycle by the vehicle sound generation device 1 (mainly the sound control device 10 and the speaker 20).

[0035] First, in step S1, the sound control device 10 acquires various information from the in-vehicle device group 30. Specifically, the sound control device 10 acquires the motor rotation speed detected by the motor rotation speed sensor 31, the accelerator opening detected by the accelerator opening sensor 32, the motor torque detected by the motor torque sensor 33, the speed of the vehicle 2 detected by the vehicle speed sensor 34, the acceleration of the vehicle 2 detected by the acceleration sensor 35, the position information and map information of the vehicle 2 acquired by the navigation device 36 (including the type of road on which the vehicle is traveling, the planned driving route, and the speed limits of the road on which the vehicle is traveling and the planned driving route), an image of the surroundings of the vehicle 2 acquired by the camera 37, the positions and speeds of objects present around the vehicle 2 measured by the radar 38, and the indication direction of the turn signal (direction indicator) 39 in response to the driver's operation.

[0036] Next, in step S2, the sound control device 10 (more specifically, the acceleration state detection unit 13) determines whether the vehicle 2 is in an accelerating state based on the information acquired in step S1. Specifically, when the accelerator opening increases (for example, when the rate of increase in accelerator opening is 20% / sec or more), the sound control device 10 determines that the vehicle 2 is in an accelerating state if the increase in accelerator opening from the start to the end of the increase is a predetermined amount (for example, 30%) or more, and the accelerator opening at the end of the increase is a predetermined amount (for example, 40%) or more.

[0037] Alternatively, instead of the accelerator opening, the sound control device 10 may determine whether the vehicle 2 is accelerating based on the motor torque. For example, when the motor torque increases, the sound control device 10 may determine that the vehicle 2 is accelerating if the increase in motor torque from the start to the end of the increase is equal to or greater than a predetermined amount, and if the motor torque at the end of the increase is equal to or greater than a predetermined value.

[0038] If the result of step S2 is that it is not determined that the vehicle 2 is in an accelerating state (step S2: No), that is, if the acceleration state detection unit 13 does not detect that the vehicle 2 is in an accelerating state, the process proceeds to step S3, and the sound control device 10 (more specifically, the sound control unit 12) sets the frequency F1 of the sound signal based on the motor rotation speed of the electric motor 3.

[0039] Specifically, a frequency map that defines the relationship between the motor rotation speed R and the frequency F1 is referenced to set the frequency F1 according to the motor rotation speed R. Fig. 5A shows the frequency map that defines the relationship between the motor rotation speed R and the frequency F1. The frequency map shown in Fig. 5A defines that the frequency F1 of the sound signal increases as the motor rotation speed R increases.

[0040] Next, in step S4, the sound control device 10 (more specifically, the sound control unit 12) sets the sound pressure P1 of the sound signal based on the motor rotation speed of the electric motor 3.

[0041] Specifically, a sound pressure map that defines the relationship between the motor rotation speed R and the sound pressure P1 is referenced to set the sound pressure P1 according to the motor rotation speed R. Figure 5B shows the sound pressure map that defines the relationship between the motor rotation speed R and the sound pressure P1. The sound pressure map shown in Figure 5B defines that the sound pressure P1 of the sound signal increases as the motor rotation speed R increases.

[0042] On the other hand, if it is determined in step S2 that the vehicle 2 is in an accelerating state (step S2: Yes), that is, if the acceleration state detection unit 13 detects that the vehicle 2 is in an accelerating state, the sound control device 10 (more specifically, the sound control unit 12) sets the time trends of the sound signal parameters, frequency F2 and sound pressure P2. As described above, the time trends of frequency F2 and sound pressure P2 include a repetition of a first trend in which each parameter increases over time, and a second trend in which each parameter decreases over time following the first trend.

[0043] In detail, first, in step S5, the sound control device 10 (specifically, the target speed estimation unit 14) executes a target speed estimation process for estimating the target speed of the vehicle 2.

[0044] Fig. 6 is a flowchart of the target speed estimation process. As shown in Fig. 6, first, in step S11, the sound control device 10 (more specifically, the target speed estimation unit 14) determines whether or not the speed limit will increase ahead in the traveling direction of the vehicle 2. Specifically, the sound control device 10 acquires the speed limit for the current position and the speed limit ahead in the traveling direction based on the position information and map information acquired by the navigation device 36 in step S1, and the surrounding images acquired by the camera 37, etc. Then, it determines whether or not the speed limit ahead in the traveling direction will increase from the speed limit for the current position.

[0045] If, as a result of step S11, it is determined that the speed limit will increase ahead in the direction of travel of the vehicle 2 (step S11: Yes), that is, in the case of a situation such as that illustrated in Figure 3(a), the process proceeds to step S12, and the sound control device 10 (more specifically, the target speed estimation unit 14) estimates that the speed limit ahead in the direction of travel is the target speed.

[0046] On the other hand, if it is not determined in step S11 that the speed limit will increase ahead in the traveling direction of the vehicle 2 (step S11: No), the process proceeds to step S13, where the sound control device 10 (more specifically, the target speed estimation unit 14) determines whether or not the turn signal (direction indicator) 39 is operating. Specifically, the sound control device 10 determines whether or not the turn signal (direction indicator) 39 is operating based on the information acquired from the turn signal (direction indicator) 39 in step S1.

[0047] As a result of step S13, if it is determined that the turn signal (direction indicator) 39 is operating (step S13: Yes), the process proceeds to step S14, where the sound control device 10 (more specifically, the target speed estimation unit 14) determines whether there is an adjacent lane in the direction indicated by the turn signal (direction indicator) 39 and whether there is another vehicle traveling in the same direction as the vehicle 2 on that adjacent lane. Specifically, the sound control device 10 identifies the direction indicated by the turn signal (direction indicator) 39 based on the information acquired from the turn signal (direction indicator) 39 in step S1, and determines whether there is an adjacent lane in the direction indicated by the turn signal 39 based on the position information and map information acquired by the navigation device 36, the surrounding image acquired by the camera 37, etc. in step S1. If there is an adjacent lane in the direction indicated by the turn signal 39, then it determines whether there is another vehicle traveling in the same direction as the vehicle 2 on that adjacent lane based on the positions and speeds of objects present around the vehicle 2 measured by the radar 38.

[0048] If it is determined as a result of step S14 that there is an adjacent lane in the direction indicated by the turn signal (directional indicator) 39 and that there is another vehicle traveling in the adjacent lane in the same direction as vehicle 2 (step S14: Yes), that is, in the case of a situation such as that illustrated in FIG. 3(b), the process proceeds to step S15, and the sound control device 10 (more specifically, the target speed estimation unit 14) estimates that the speed of the other vehicle traveling in the adjacent lane in the same direction as vehicle 2 is the target speed. Specifically, the sound control device 10 estimates that the speed of the other vehicle is the target speed based on the position and speed of the other vehicle in the adjacent lane measured by radar 38.

[0049] On the other hand, as a result of step S13, if it is not determined that the blinkers (directional indicators) 39 are operating (step S13: No), that is, if the blinkers 39 are not operating, the process proceeds to step S16, where the sound control device 10 (more specifically, the target speed estimation unit 14) determines whether or not there are other vehicles (for example, a preceding vehicle or a vehicle running alongside) traveling in the same direction around the vehicle 2. Specifically, the sound control device 10 determines whether or not there are other vehicles traveling in the same direction around the vehicle 2 based on the positions and speeds of objects present around the vehicle 2 measured by the radar 38.

[0050] If it is determined in step S16 that there is another vehicle traveling in the same direction as vehicle 2 around it (step S16: Yes), that is, in the case of a situation such as that illustrated in Figure 3(c), the process proceeds to step S17, and the sound control device 10 (more specifically, the target speed estimation unit 14) estimates that the speed of the other vehicle traveling in the same direction as vehicle 2 is the target speed. Specifically, the sound control device 10 estimates that the speed of the other vehicle is the target speed based on the position and speed of the other vehicle around vehicle 2 measured by radar 38.

[0051] On the other hand, if the result of step S14 is that there is an adjacent lane in the direction indicated by the turn signal (directional indicator) 39 and it is not determined that there is another vehicle traveling in the same direction as vehicle 2 on that adjacent lane (step S14: No), that is, if there is no adjacent lane in the direction indicated by the turn signal 39 or there is no other vehicle in the adjacent lane in the direction indicated by the turn signal 39, or if the result of step S16 is that it is not determined that there is another vehicle traveling in the same direction around vehicle 2 (step S16: No), the process proceeds to step S18, and the sound control device 10 (more specifically, the target speed estimation unit 14) estimates that the speed associated with the type of road on which vehicle 2 is traveling is the target speed. Specifically, a speed table that associates each type of road (for example, an ordinary road, an expressway, etc.) with a speed is stored in advance in the storage unit 16. The sound control device 10 identifies the type of road on which the vehicle 2 is traveling based on the position information and map information acquired by the navigation device 36 in step S1, and acquires the speed associated with that road type by referring to the speed table. The acquired speed is then estimated to be the target speed.

[0052] After step S12, S15, S17 or S18, the sound control device 10 ends the target speed estimation process and returns to the main routine.

[0053] 4, after executing the target speed estimation process in step S5, the process proceeds to step S6, where the sound control device 10 (more specifically, the acceleration time estimation unit 15) estimates the acceleration time required for the vehicle 2 to reach the target speed. Specifically, the sound control device 10 estimates the acceleration time by dividing the difference between the target speed estimated in step S5 and the speed of the vehicle 2 detected by the vehicle speed sensor 34 in step S1 by the acceleration of the vehicle 2 detected by the acceleration sensor 35 in step S1.

[0054] Next, in step S7, the sound control device 10 (more specifically, the sound control unit 12) sets the time T from when it is detected that the vehicle 2 is in an accelerating state until the first change from the first trend to the second trend (i.e., until the first change timing), and T, which is the time interval between each change timing.

[0055] Specifically, the sound control device 10 sets the time interval obtained by equally dividing the acceleration time estimated in step S6 as the time interval T. At this time, the time interval T is specified to be equal to or greater than 1000 milliseconds and equal to or less than 2000 milliseconds. Furthermore, if there are multiple candidates for time intervals obtained by equally dividing the acceleration time that fall within the range of equal to or greater than 1000 milliseconds and equal to or less than 2000 milliseconds, the time interval T is specified to be shorter the greater the accelerator opening at the end of the increase in accelerator opening when it is determined that the vehicle 2 is in an accelerating state (or the greater the motor torque at the end of the increase in motor torque). For example, if the acceleration time estimated in step S6 is 5000 milliseconds, the candidates for the time interval T that fall within the range of equal to or greater than 1000 milliseconds and equal to or less than 2000 milliseconds as a result of equally dividing this acceleration time are 1000 milliseconds, 1250 milliseconds, and 1667 milliseconds. In this case, if the accelerator opening at the end of the increase in accelerator opening is between 40% and 55%, the time interval T is set to 1667 milliseconds, if the accelerator opening is between 55% and 70%, the time interval T is set to 1250 milliseconds, and if the accelerator opening is 70% or more, the time interval T is set to 1000 milliseconds. In this way, by setting the time interval T shorter as the accelerator opening at the end of the increase in accelerator opening is larger, the period of the sound change over time becomes shorter, so that the occupants can feel the strength of the acceleration of the vehicle 2 corresponding to the magnitude of the accelerator opening. Note that if the accelerator opening at the end of the increase in accelerator opening is less than a predetermined opening (for example, 40%), it is not detected that the vehicle 2 is accelerating, so the time interval T is not specified.

[0056] Next, in step S8, the sound control device 10 sets the time transition of the frequency F2 of the sound signal based on the time interval T set in step S7.

[0057] Specifically, the frequency F2 corresponding to the elapsed time t is set by referring to a frequency map that defines the relationship between the time t elapsed since it was detected that the vehicle 2 is in an accelerating state and the frequency F2 (i.e., the time transition of the frequency F2 when the vehicle 2 is in an accelerating state). Fig. 7A is a frequency map that defines the time transition of the frequency F2 when the vehicle 2 is in an accelerating state.

[0058] 7A, the time transition of the frequency F2 includes a repetition of a first trend in which the frequency F2 increases over time and a second trend in which the frequency F2 decreases over time following the first trend. The time transition is specified so that the time T from when it is detected that the vehicle 2 is accelerating to when the first trend first changes to the second trend, and the time interval T between each change, are between 1000 milliseconds and 2000 milliseconds.

[0059] Furthermore, the time intervals ΔT from each change timing until the second trend changes to the first trend are set equal to each other and shorter than T.

[0060] Furthermore, the maximum values ​​of the frequency F2 at each change timing when the first trend changes to the second trend are defined to be approximately equal.

[0061] Next, in step S9, the sound control device 10 sets the time transition of the sound pressure P2 of the sound signal based on the time interval T set in step S7.

[0062] Specifically, the sound pressure P2 corresponding to the elapsed time t is set by referring to a sound pressure map that defines the relationship between the time t elapsed since it was detected that the vehicle 2 is accelerating and the sound pressure P2 (i.e., the time transition of the sound pressure P2 when the vehicle 2 is accelerating). Fig. 7B is a sound pressure map that defines the time transition of the sound pressure P2 when the vehicle 2 is accelerating.

[0063] 7B, the time transition of the sound pressure P2, like the time transition of the frequency F2, includes a repetition of a first trend in which the sound pressure P2 increases over time and a second trend in which the sound pressure P2 decreases over time following the first trend. Furthermore, the time T from when it is detected that the vehicle 2 is accelerating to when the first trend first changes to the second trend, and the time interval T between each change timing at which the first trend changes to the second trend, are the same as the time interval T in the time transition of the frequency F2. Similarly, the time interval ΔT from each change timing to when the second trend changes to the first trend is also the same as the time interval ΔT in the time transition of the frequency F2.

[0064] Furthermore, the maximum value of the sound pressure P2 at each change timing when the first trend changes to the second trend is defined to be approximately the same at each change timing.

[0065] After step S4 or S9, the process proceeds to step S10, where the sound control device 10 (more specifically, the sound control unit 12) generates a sound signal and outputs the sound signal to the speaker 20.

[0066] In step S10, if the sound control device 10 does not detect that the vehicle 2 is accelerating in step S2 and has set the frequency F1 and sound pressure P1 based on the motor rotation speed in steps S3 and S4, the sound control device 10 generates a sound signal based on those frequency F1 and sound pressure P1. In other words, if it does not detect that the vehicle 2 is accelerating, the sound control device 10 sequentially generates sound signals based on the motor rotation speed and outputs them to the speaker 20.

[0067] On the other hand, if the time progression of the frequency F2 is set in step S8 and the time progression of the sound pressure P2 is set in step S9, the sound control device 10 generates a sound signal based on the time progression of the frequency F2 and the sound pressure P2. In other words, if it is detected that the vehicle 2 is accelerating, the sound control device 10 generates a sound signal in accordance with the time progression of the frequency F2 and the sound pressure P2 that were previously set in steps S8 and S9, and outputs it to the speaker 20.

[0068] Next, in step S11, the speaker 20 receives the sound signal and outputs a sound corresponding to this sound signal. After step S9, the vehicle sound generation device 1 ends the sound generation process and returns to step S1.

[0069] <Modification> In the above embodiment, if it is not detected in step S2 of the sound generation process that the vehicle 2 is in an accelerating state, a single frequency F1 is set based on the motor rotation speed in step S3. However, multiple frequencies F1 may be set here. In this case, in step S8, the sound control device 10 generates a sound signal that combines multiple frequencies.

[0070] Furthermore, in the above-described embodiment, when it is detected in step S2 of the sound generation processing that the vehicle 2 is in an accelerating state, an example has been described in which the time course of the frequency F2 is set in step S8 and the time course of the sound pressure P2 is set in step S9, but the frequency F2 may be set based on the motor rotation speed in step S8 (i.e., set in the same way as the frequency F1 in step S3), and the time course of the sound pressure P2 may be set in step S9. Alternatively, the time course of the frequency F2 may be set in step S8, and the sound pressure P2 may be set based on the motor rotation speed in step S9 (i.e., set in the same way as the sound pressure P1 in step S4).

[0071] In addition, in the above-described embodiment, an example was shown in which the first trend and the second trend are repeated three times using the frequency map of Figure 7A and the sound pressure map of Figure 7B, but this repetition may be more than three times (for example, four or five times).

[0072] In the above embodiment, an example was shown in which the target speed of the vehicle 2 in an accelerating state was estimated by the target speed estimation process shown in Fig. 6, but the target speed may be estimated by other methods. For example, the sound control device 10 may always estimate the speed associated with the type of road on which the vehicle 2 is traveling as the target speed.

[0073] In the above embodiment, the sound control device 10 sets the time interval T in step S7 of the sound generation processing as the time interval obtained by equally dividing the acceleration time estimated in step S6. However, time intervals obtained by dividing the acceleration time at a ratio other than equal division may be set as the time from when the vehicle 2 enters an accelerating state to when the first trend first changes to the second trend, and as the time intervals for each change timing. For example, a predetermined division ratio may be stored in the storage unit 16 in advance, and time intervals obtained by dividing the acceleration time at that division ratio may be set as the time from when the vehicle 2 enters an accelerating state to when the first trend first changes to the second trend, and as the time intervals for each change timing. In this case, the acceleration time may be divided into three parts, for example, T1, where T1 is the time from when the vehicle 2 enters an accelerating state to the first change timing, T2 is the time from the first change timing to the second change timing, and T3 is the time from the second change timing to the third change timing, so that T1:T2:T3 = 1:2:2.5.

[0074] <Action and effect> Next, the effects of the vehicle sound generation device 1 of this embodiment will be described.

[0075] When it is detected that the vehicle 2 is in an accelerating state, the vehicle sound generation device 1 of this embodiment sets a time transition of a parameter of a sound signal and generates a sound signal based on the time transition of the parameter. The time transition of the parameter includes a repetition of a first trend and a second trend following the first trend, and each time interval obtained by dividing the acceleration time required for the vehicle 2 to reach a target speed in an accelerating state is set as the time from when it is detected that the vehicle 2 is in an accelerating state until the first trend first changes to the second trend, and the time intervals at which the first trend changes to the second trend.

[0076] Therefore, the time transition of each parameter of the sound signal can be set so that the sound is changed at an appropriate timing according to the acceleration time. This allows the output sound to be changed at a timing that appropriately reflects the acceleration of the vehicle 2, allowing the occupants to feel the pleasantness of the acceleration of the vehicle 2.

[0077] Furthermore, the parameters of the sound signal include one or both of frequency and sound pressure, and the first trend is a trend in which the parameter increases over time, and the second trend is a trend in which the parameter decreases over time, so that the occupants can clearly recognize the change in sound over time, and can feel the acceleration of vehicle 2 even more pleasant.

[0078] Furthermore, when it is not detected that the vehicle 2 is in an accelerating state, the vehicle sound generating device 1 generates a sound signal based on at least the rotation speed of the electric motor. Therefore, the time progression of the sound output when it is detected that the vehicle 2 is in an accelerating state can be made to stand out in contrast to the sound based on the motor rotation speed, allowing the occupants to feel an even more pleasant acceleration of the vehicle 2.

[0079] Furthermore, the target speed estimation unit 14 acquires the speed limit ahead in the traveling direction of the vehicle 2 in an accelerating state and estimates that speed limit to be the target speed, so that the target speed can be more accurately estimated based on the speed limit ahead in the traveling direction of the vehicle 2. This makes it possible to change the output sound at a timing that more appropriately reflects the acceleration of the vehicle 2, allowing the occupants to feel an even more pleasant acceleration of the vehicle 2.

[0080] Furthermore, the target speed estimation unit 14 acquires the speeds of surrounding vehicles traveling in the same direction as the vehicle 2 while accelerating, and estimates that the speeds of the surrounding vehicles are the target speed, so that the target speed can be more accurately estimated based on the speeds of the surrounding vehicles. This allows the output sound to be changed at a timing that more appropriately reflects the acceleration of the vehicle 2, allowing the occupants to feel an even more pleasant acceleration of the vehicle 2.

[0081] Furthermore, the target speed estimation unit 14 acquires the speed corresponding to the type of road on which the vehicle 2 is traveling in an accelerating state from among speeds previously associated with road types, and estimates that the acquired speed is the target speed, so that the target speed can be more accurately estimated based on the type of road on which the vehicle 2 is traveling. This allows the output sound to be changed at a timing that more appropriately reflects the acceleration of the vehicle 2, allowing the occupants to feel an even more pleasant acceleration of the vehicle 2.

[0082] Furthermore, the acceleration time estimation unit 15 obtains the acceleration of the vehicle 2 when it is detected that the vehicle 2 is in an accelerating state, and estimates the acceleration time by dividing the difference between the target speed and the speed of the vehicle 2 by the acceleration, so that it is possible to more accurately estimate the acceleration time required for the vehicle 2 to reach the target speed. This makes it possible to change the output sound at a timing that more appropriately reflects the acceleration of the vehicle 2, allowing the occupants to feel an even more pleasant acceleration of the vehicle 2. [Explanation of symbols]

[0083] 1 Vehicle sound generation device 2 vehicles 3 Electric motor 10 Sound control device 12 Sound control section 13 Acceleration state detection unit 14 Target speed estimation section 15 Acceleration time estimation unit 16 Memory section 20 speakers 30 In-vehicle equipment group 31 Motor rotation speed sensor 32 Accelerator opening sensor 33 Motor torque sensor 34 Vehicle speed sensor 35 Acceleration sensor 36 Navigation devices 37 Camera 38 Radar 39 Turn signal

Claims

1. A vehicle sound generating device mounted on a vehicle that runs using an electric motor as a power source, a sound control unit configured to generate a sound signal representative of a sound; a sound output unit that outputs a sound corresponding to the sound signal generated by the sound control unit; an acceleration state detection unit that detects whether the vehicle is in an accelerating state; a target speed estimation unit that, when it is detected that the vehicle is in an accelerating state, estimates a target speed of the vehicle in the accelerating state; an acceleration time estimation unit that, when it is detected that the vehicle is in an accelerating state, estimates an acceleration time required for the vehicle to reach the target speed, when it is detected that the vehicle is in an accelerating state, the sound control unit sets a time transition of a parameter of the sound signal, and generates the sound signal based on the time transition of the parameter; the time transition of the parameter includes a repetition of a first trend and a second trend following the first trend, and each time interval into which the acceleration time is divided is set as a time from when it is detected that the vehicle is in an accelerating state until the first trend first changes to the second trend, and as a time interval between each change timing at which the first trend changes to the second trend; the parameters include one or both of frequency and sound pressure; The first trend is a trend in which the parameter increases over time, and the second trend is a trend in which the parameter decreases over time. Vehicle sound generating device.

2. a motor rotation speed sensor for detecting the rotation speed of the electric motor; When it is not detected that the vehicle is in an accelerating state, the sound control unit generates the sound signal based on at least the rotation speed of the electric motor. The vehicle sound generating device according to claim 1 .

3. The sound generation device for a vehicle according to claim 1 , wherein the target speed estimation unit acquires a speed limit ahead in the traveling direction of the vehicle in the accelerating state, and estimates that the speed limit is the target speed.

4. 3. The sound generation device for a vehicle according to claim 1, wherein the target speed estimation unit acquires a speed of a nearby vehicle traveling in the same direction as the vehicle in the accelerating state, and estimates that the speed of the nearby vehicle is the target speed.

5. 3. The sound generation device for a vehicle according to claim 1, wherein the target speed estimation unit acquires a speed corresponding to the type of road on which the vehicle is traveling in the accelerating state from among speeds previously associated with road types, and estimates that the acquired speed is the target speed.

6. 3. The sound generation device for a vehicle according to claim 1, wherein the acceleration time estimation unit acquires an acceleration of the vehicle when it is detected that the vehicle is in an accelerating state, and estimates the acceleration time by dividing a difference between the target speed and the speed of the vehicle by the acceleration.

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