Airbag control device

Abstract

To perform operation control of an airbag accurately.SOLUTION: An airbag control device 10 mounted on a vehicle includes an operation determination part, an output part, a direction determination part, and a change part. The operation determination part compares a first detection value with an operation threshold value to generate a deployment signal for deploying the airbag 52 on the basis of a comparison result. The output part outputs the deployment signal when predetermined output conditions are satisfied. The direction determination part determines, on the basis of a second detection value, a direction of an impact acting on a vehicle body in a vertical direction. When the direction of the impact acting on the vehicle body is determined to be a downward direction, the change part changes the operation threshold value to a direction in which the airbag is deployed more easily than when the direction is not determined to be the downward direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to operation control of an airbag installed in a vehicle. [Background technology]

[0002] An airbag control device installed in a vehicle detects an impact acting on the vehicle body using an acceleration sensor or the like, and activates an airbag by detecting, for example, the acceleration in the front-rear direction that occurs during a collision. However, since the acceleration in the front-rear direction is also detected when the vehicle runs over a road or a curb, or when the vehicle is traveling on a rough road, there is a problem that the airbag may be erroneously activated in a situation that is not a collision.

[0003] The following Patent Document 1 proposes a technique for preventing the airbag from being accidentally activated when the vehicle is traveling on rough roads or the like, in which the airbag is activated when the acceleration applied in the vertical direction exceeds a threshold value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-108820 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the technology of the above-mentioned Patent Document 1, the threshold value is changed to a high value only depending on the magnitude of the vertical impact, regardless of whether the impact is in the vertical direction or the vertical direction. Therefore, for example, when a vehicle is subjected to a downward impact by going under a large vehicle such as a truck due to a collision, the threshold value is set high even though the airbag should be deployed, making it difficult to deploy the airbag. In other words, it is difficult to accurately control the deployment of the airbag.

[0006] One aspect of the present disclosure is to perform airbag deployment control with precision. [Means for solving the problem]

[0007] One aspect of the present disclosure is an airbag control device mounted on a vehicle, comprising an activation determination unit, an output unit, a direction determination unit, and a change unit. The activation determination unit is configured to compare the first detection value with a predetermined activation threshold based on a detection value by a first detection device or a first detection value based on the detection value, and generate a deployment signal for deploying the airbag based on the comparison result. The first detection device detects an impact in a predetermined direction among impacts acting on the vehicle body. The output unit is configured to output the deployment signal when a predetermined output condition is satisfied. The direction determination unit is configured to determine the direction of the impact acting on the vehicle body in the up-down direction based on a detection value by a second detection device or a second detection value based on the detection value. The second detection device is a detection device different from the first detection device, and detects an impact in the up-down direction among impacts acting on the vehicle body. The change unit is configured to change the activation threshold to a direction in which the airbag is more likely to deploy when the direction determination unit determines that the direction of the impact acting on the vehicle body is downward than when the direction determination unit does not determine that the impact is downward.

[0008] With this configuration, when a relatively large downward impact occurs to the vehicle body, such as when getting under a large vehicle such as a truck, the activation threshold is changed so as to facilitate the deployment of the airbag. This makes it possible to facilitate the deployment of the airbag in a situation where the airbag should be deployed, such as when getting under a large vehicle. As a result, the operation of the airbag can be controlled with high accuracy. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a block diagram showing the configuration of an airbag system. [Diagram 2] FIG. 2 is an explanatory diagram for explaining a coordinate system of a vehicle. [Diagram 3]FIG. 2 is a block diagram illustrating the functions of a CPU. [Figure 4] 4 is a flowchart showing a process according to the first embodiment. [Diagram 5] 13 is a flowchart of a situation determination process. [Figure 6] Fig. 6a is an explanatory diagram for explaining operation when running over a obstacle, Fig. 6b is an explanatory diagram showing an example of a detection value Gz when running over a obstacle, Fig. 6c is an explanatory diagram showing an example of a detection value Gz after signal processing when running over a obstacle, and Fig. 6d is an explanatory diagram for explaining a change in the operation threshold when running over a obstacle. [Figure 7] Fig. 7a is an explanatory diagram explaining the operation when diving in. Fig. 7b is an explanatory diagram showing an example of the detection value Gz when diving in, Fig. 7c is an explanatory diagram showing an example of the detection value Gz after signal processing when diving in, and Fig. 7d is an explanatory diagram explaining the change of the operation threshold when diving in. [Figure 8] 11 is an explanatory diagram illustrating an example in which the direction in which an impact exceeding a judgment value first occurred is erroneously judged when only a directional threshold value is used; FIG. [Figure 9] FIG. 11 is an explanatory diagram for explaining a change in deployment timing. [Figure 10] 10 is a flowchart showing a process according to a modified example of the first embodiment. [Figure 11] 11A is a diagram illustrating the resultant acceleration and the impact angle in the second embodiment, and FIG 11B is a diagram illustrating the rearward impact range, FIG 11C is a diagram illustrating the upward impact range, and FIG 11D is a diagram illustrating the downward impact range. [Figure 12] FIG. 11 is an explanatory diagram for explaining a determination map according to the second embodiment. [Figure 13] 10 is a flowchart showing a process according to a second embodiment. [Figure 14] FIG. 13 is an explanatory diagram for explaining a determination map according to a modified example 2-2 of the second embodiment. [Figure 15] FIG. 13 is an explanatory diagram for explaining a determination map according to a modified example 2-3 of the second embodiment. [Figure 16]FIG. 13 is an explanatory diagram for explaining a determination map according to a modified example 2-4 of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following, "behind" does not necessarily mean behind in the strict sense, and does not have to mean exactly behind (i.e. directly behind) as long as the same effect is achieved. The same applies to "front," "right," "left," etc.

[0011] [1. First embodiment] [1-1. Configuration] The airbag system 1 shown in Fig. 1 is a system mounted on a vehicle. In the following, as shown in Figs. 2a and 2b, the traveling direction of the vehicle (i.e., the front-rear direction) may be described as the x-axis, the width direction of the vehicle (i.e., the left-right direction) as the y-axis, and the vertical direction (i.e., the up-down direction) as the z-axis. The front-rear direction, left-right direction, and up-down direction are mutually perpendicular. The positive and negative directions of each axis are as shown in Figs. 2a and 2b.

[0012] The airbag system 1 includes an airbag ECU 10. The airbag system 1 may also include a first acceleration sensor 11, a second acceleration sensor 12, a safing sensor 13, an object detection sensor 14, and an airbag activation device 15. The airbag activation device 15 may include a drive circuit 51 for driving the airbag 52, and the airbag 52.

[0013] The airbag ECU 10 is an electronic control device for controlling the operation of the airbag 52. ECU is an abbreviation for Electronic Control Unit. The airbag operating device 15 includes an airbag 52, an inflator (not shown) for inflating the airbag 52, a drive circuit 51 for operating the inflator, and the like. In this embodiment, the airbag 52 is a frontal collision airbag that is deployed in the event of a frontal collision of the vehicle and is positioned between an occupant and on-board components. The airbag 52 is accommodated inside a steering wheel, an instrument panel, or the like (not shown). In the event of a collision, the airbag 52 deploys rearward in the fore-and-aft direction (hereinafter also referred to as the rearward direction). Hereinafter, the direction in which the airbag 52 deploys is also referred to as the deployment target direction.

[0014] The first acceleration sensor 11, the second acceleration sensor 12, and the safing sensor 13 are acceleration sensors that detect an impact acting on the vehicle body. The first acceleration sensor 11 detects a forward / rearward impact acting on the vehicle body. As described above, in this embodiment, the target deployment direction is the rearward direction. The detection direction of the first acceleration sensor 11 (i.e., the forward / rearward direction) includes the target deployment direction. Although not shown, the first acceleration sensor 11 is disposed, for example, inside the airbag ECU 10 and detects a forward / rearward impact acting on the vehicle body. For example, in this embodiment, the first acceleration sensor 11 indicates a forward impact, i.e., an impact when a force is applied from the rear, with a detection value having a positive sign, and indicates a rearward impact, i.e., an impact when a force is applied from the front, with a detection value having a negative sign.

[0015] The second acceleration sensor 12 detects a vertical impact acting on the vehicle body. The second acceleration sensor 12 may be disposed in the same position as the first acceleration sensor 11, or may be disposed in a different position. For example, the second acceleration sensor 12 may be disposed under the hood to easily detect an impact from above. Alternatively, the second acceleration sensor 12 may be disposed at the bottom of the vehicle body near the front wheels to easily detect an impact from below. For example, in this embodiment, the second acceleration sensor 12 indicates an impact in the upward direction, i.e., an impact when a force acts from below, with a detection value having a positive sign, and indicates an impact in the downward direction, i.e., an impact when a force acts from above, with a detection value having a negative sign.

[0016] The safing sensor 13 is an acceleration sensor that detects a front-rear impact acting on the vehicle body in the same manner as the first acceleration sensor 11, but is different from the first acceleration sensor 11. The safing sensor 13 is disposed, for example, inside the airbag ECU 10 (not shown) and detects a front-rear impact acting on the vehicle body. For example, in this embodiment, the safing sensor 13 indicates a forward impact, i.e., an impact when a force acts from behind, with a detection value having a positive sign, and indicates a rearward impact, i.e., an impact when a force acts from the front, with a detection value having a negative sign.

[0017] The first acceleration sensor 11, the second acceleration sensor 12, and the safing sensor 13 are not limited to the above-mentioned positions, and may be installed at any position on the vehicle body, such as at the front of the vehicle body (engine room, bumper, etc.).

[0018] The object detection sensor 14 is a sensor for detecting objects around the vehicle and identifying an object that collides with the vehicle (hereinafter also referred to as a collision object), and although not shown, is disposed on the vehicle so as to be able to detect objects in front of, behind, and on the left and right sides of the vehicle. The object may be, for example, a vehicle, a pedestrian, or a fixed object. The object detection sensor 14 may detect an object that collides with the vehicle and output a detection result. The detection result may include at least the shape of the object. The detection result may include the distance from the vehicle to the object, the orientation of the object based on the traveling direction of the vehicle, the relative speed, etc.

[0019] In this embodiment, the object detection sensor 14 includes an image sensor. The image sensor captures an image of the periphery of the vehicle and detects an object by a known image recognition technique based on image data representing the captured image. Note that the object detection sensor 14 may be a millimeter wave radar, LiDAR, or the like.

[0020] The airbag ECU 10 includes a microcomputer (hereinafter, referred to as microcomputer 30) including a CPU 31 and a memory 32 such as a ROM 33 and a RAM 34. The airbag ECU 10 may further include an input interface circuit 20, signal processing units 21 to 23, and an output interface circuit 24.

[0021] The input interface circuit 20 is a circuit for inputting signals from the first acceleration sensor 11, the second acceleration sensor 12, and the safing sensor 13. The output interface circuit 24 is a circuit for outputting an activation signal to the airbag activation device 15.

[0022] The signal processing units 21, 22, and 23 are connected to the first acceleration sensor 11, the second acceleration sensor 12, and the safing sensor 13, respectively, and function as LPFs (i.e., low-pass filters). The signal processing units 21, 22, and 23 smooth signals indicating detection values ​​by the first acceleration sensor 11, the second acceleration sensor 12, and the safing sensor 13, respectively. The signal processing units 21, 22, and 23 may be analog circuits or digital circuits using a DSP or the like. Hereinafter, the detection value by the first acceleration sensor 11 after signal processing by the signal processing unit 21 is referred to as a detection value Gx. Also, the detection value by the second acceleration sensor 12 after signal processing by the signal processing unit 22 is referred to as a detection value Gz. The detection value by the safing sensor 13 after signal processing by the signal processing unit 23 is referred to as a detection value Sx.

[0023] Various functions of the microcomputer 30 are realized by the CPU 31 executing a program 41 stored in the ROM 33. Furthermore, the execution of this program 41 executes a method corresponding to the program 41. Note that some or all of the functions executed by the CPU 31 may be configured as hardware using one or more ICs, etc. Furthermore, some or all of the functions executed as hardware using one or more ICs, etc. may be configured as some or all of the functions executed by the CPU 31. Furthermore, the number of microcomputers constituting the airbag ECU 10 may be one or more.

[0024] 3, in the airbag ECU 10, the CPU 31 has a function as a deployment signal unit 35 and a function as an output generation unit 36. In a flowchart described later, steps S10 to S120 correspond to the processing performed by the deployment signal unit 35, and steps S130 to S160 correspond to the processing performed by the output generation unit 36.

[0025] The deployment signal unit 35 generates a deployment signal when the detection value Sx in the forward / backward direction by the safing sensor 13 exceeds a predetermined safing threshold Thxc and the detection value Gx in the forward / backward direction by the first acceleration sensor 11 exceeds an activation threshold Thxa. The deployment signal is a signal that permits the deployment of the airbag 52. The deployment signal can also be said to be a signal that determines whether the airbag 52 is needed. The activation threshold Thxa is a threshold for determining whether the airbag 52 is needed.

[0026] The determination by the safing sensor 13 is intended to increase the accuracy of the determination by the first acceleration sensor 11. The safing threshold Thxc is set so that the absolute value of the safing threshold Thxc is smaller than the absolute value of the activation threshold Thxa so that it is easier to exceed the safing threshold Thxc than to exceed the activation threshold Thxa. In addition, the deployment signal unit 35 changes the timing of outputting the generated deployment signal to the airbag activation device 15.

[0027] The output generating unit 36 ​​determines whether or not a predetermined output condition is satisfied based on the detection result by the object detection sensor 14, and when it is determined that the output condition is satisfied, permits output of a deployment signal to the airbag activation device 15. In other words, even if a deployment signal is generated, when it is determined that the output condition is not satisfied, the generated deployment signal is not output to the airbag activation device 15.

[0028] [1-2. Processing] Next, the process executed by the microcomputer 30 will be specifically described with reference to the flowchart of FIG. 4. The process shown in FIG. 4 is repeatedly executed at a predetermined execution cycle. It is desirable that the airbag 52 is deployed without delay after a relatively large impact that requires the deployment of the airbag 52 occurs. For this reason, the execution cycle of the process in FIG. 4 may be set to a period of, for example, several hundred μsec to several tens of msec. Note that the execution cycle is not limited to the above-mentioned period, and may be set to any period.

[0029] First, in step (hereinafter, S) 10, the CPU 31 obtains the detection values ​​Gx, Gz, and Sx. In the next step S20, the CPU 31 determines whether or not an impact has been detected in the target deployment direction (i.e., the rearward direction in this embodiment). As described above, the detection value Gx has a positive sign when an impact in the forward direction has been detected. The CPU 31 determines that an impact in the rearward direction has been detected when the sign of the detection value Gx is negative. The CPU 31 shifts the process to S30 when it is determined that an impact in the rearward direction has been detected, and ends this process when it is not determined that an impact in the rearward direction has been detected.

[0030] In steps S30 to S100, the CPU 31 identifies the vertical direction in which an impact exceeding a predetermined judgment value T first occurred, and changes various parameters such as the activation threshold Thxa and the safing threshold Thxc based on the identified direction and the magnitude of the impact. The identified direction here is either the upward or downward direction. The magnitude of the impact is the absolute value of the detection value of the impact by various sensors such as the detection value Gx, the detection value Gz, the detection value Gc, etc. The judgment value T is a threshold for distinguishing between a relatively large impact that may require the deployment of the airbag 52 and a relatively small impact that clearly does not require the deployment of the airbag 52.

[0031] First, in S30, the CPU 31 preliminarily determines whether the rearward impact acting on the vehicle body is upward or downward based on the detection value Gz. Specifically, when the detection value Gz exceeds a predetermined directional threshold value Tz, the CPU 31 preliminarily determines that the impact is upward if the sign of the detection value Gz is positive, and that the impact is downward if the sign is negative.

[0032] As described above, since the detection value Gz has a positive or negative sign depending on the direction of the impact, the direction threshold Tz is also expressed as a positive upward direction threshold Tzu (i.e., upward direction threshold Tzu>0) and a negative downward direction threshold Tzd (i.e., downward direction threshold Tzd<0) as shown in Figs. 6 to 8 described later. The absolute value of the upward direction threshold Tzu may be equal to the absolute value of the downward direction threshold Tzd, or the absolute value of the upward direction threshold Tzu may not be equal to the absolute value of the downward direction threshold Tzd. In the following, for example, the absolute value of x may be indicated using a sign, such as |x|.

[0033] The CPU 31 determines that the detection value Gz exceeds the directional threshold Tz when the detection value Gz<the lower directional threshold Tzd<0, or when 0<the upper directional threshold Tzu<the detection value Gz. That is, the CPU 31 determines that the detection value Gz exceeds the directional threshold Tz when |Gz|>|Tzd| (where the detection value Gz<0), or |Tzu|<|Gz| (where 0<the detection value Gz). Hereinafter, for example, when it is stated that a parameter y having a sign exceeds a threshold z, this means that the absolute value of the parameter y exceeds the absolute value of the threshold z having the same sign as the parameter y (i.e., |y|>|z|).

[0034] The absolute value of the direction threshold Tz (i.e., the absolute value of the upward direction threshold Tzu or the absolute value of the downward direction threshold Tzd) is set smaller than the absolute value of the judgment value T (i.e., the absolute value of the upward judgment value Tu or the absolute value of the downward judgment value Td). In other words, |Tzu|<|Tu| and |Tzd|<|Td|.

[0035] The CPU 31 shifts the process to S40 when the absolute value of the detection value Gz exceeds the absolute value of the directional threshold Tz of the same sign as the detection value Gz, and shifts the process to S100 when the absolute value of the detection value Gz does not exceed the absolute value of the directional threshold Tz of the same sign as the detection value Gz. In other words, the CPU 31 shifts the process to S100 when it is determined that a relatively large impact requiring the airbag 25 has not occurred first in the upward direction, and that a relatively large impact requiring the airbag 25 has not occurred first in the downward direction.

[0036] In S40, the CPU 31 acquires the elapsed time. The elapsed time indicates the time that has elapsed since it was determined in S30 that the detection value Gz has exceeded the direction threshold value Tz. For example, the CPU 31 may count the elapsed time using a free-running timer or the like that the CPU 31 has in another process (hereinafter also referred to as a counting process) different from this process. In the counting process, the CPU 31 may reset the elapsed time when it is determined in S30 that the detection value Gz has exceeded the direction threshold value Tz, and start counting the elapsed time from when it was determined in S30 that the detection value Gz has exceeded the direction threshold value Tz.

[0037] In the next step S50, the CPU 31 determines whether the time elapsed since it was determined in S30 that the detection value Gx exceeded the direction threshold Tz is equal to or shorter than a predetermined direction determination time. The direction determination time may be, for example, a time shorter than the execution cycle of the process shown in FIG. 4. If the elapsed time is equal to or shorter than the direction determination time, the CPU 31 shifts the process to S60, and if the elapsed time exceeds the direction determination time, the CPU 31 shifts the process to S100. In this embodiment, the memory 32 stores the most recently acquired detection values ​​Gx, Gz, and Sx. The detection values ​​Gx, Gz, and Sx may be overwritten each time they are acquired.

[0038] In S60, the CPU 31 judges whether the direction in which a relatively large impact that may require the deployment of the airbag 52 first acts on the vehicle body is the upward direction. Specifically, when the CPU 31 judges that the detection value Gz detected within a predetermined direction judgment time after the detection value Gz exceeds the direction threshold value Tz in S30 (i.e., after the sign of the detection value Gz is positive and the absolute value of Gz>the absolute value of Tzu) is the upward direction (i.e., the sign is positive) and the detection value Gz exceeds the predetermined judgment value T, the CPU 31 judges that the direction in which a relatively large impact that may require the deployment of the airbag 52 first acts on the vehicle body is the upward direction. Here, when the CPU 31 judges that the direction is the upward direction (i.e., a positive judgment), the CPU 31 shifts the process to S70, and when the CPU 31 judges that the direction is not the upward direction (i.e., a negative judgment), the CPU 31 shifts the process to S80.

[0039] Since the detection value Gz has a positive or negative sign depending on the direction of the impact, the judgment value T also includes an upper judgment value Tu (i.e., upper judgment value Tu>0) and a lower judgment value Td (i.e., lower judgment value Td<0). The CPU 31 judges that the detection value Gz has exceeded the judgment value T when the detection value Gz<lower judgment value Td<0, or 0<upper judgment value Tu<detection value Gz. That is, the CPU 31 judges that the detection value Gz has exceeded the judgment value T when the absolute value of the detection value Gz has exceeded the absolute value of the judgment value T (i.e., |Gz|>|Td|, or |Tu|<|Gz|). In this step, the CPU 31 judges that the detection value Gz has exceeded the judgment value T when |Tu|<|Gz|.

[0040] In the next S70, the CPU 31 changes the activation threshold Thxa in a direction that makes it difficult for the airbag 52 to deploy. Changing the activation threshold Thxa in a direction that makes it difficult for the airbag 52 to deploy means changing the activation threshold Thxa in a direction that increases the absolute value. Specifically, the CPU 31 sets the upper activation threshold Thxau as the activation threshold Thxa. At least, the absolute value of the upper activation threshold Thxau is greater than the absolute value of the lower activation threshold Thxad. The lower activation threshold Thxad will be described later.

[0041] Furthermore, the CPU 31 changes the safing threshold Thxc in a direction that makes it difficult for the airbag 52 to deploy. Specifically, the CPU 31 sets the upper safing threshold Thxcu as the safing threshold Thxc. At least, the absolute value of the lower safing threshold Thxcd is smaller than the absolute value of the upper safing threshold Thxcu.

[0042] Moreover, the CPU 31 sets the upper timing period DTu as the deployment timing period DT. The deployment timing period DT is a parameter for changing the timing of outputting the generated deployment signal to the airbag activation device 15. Moreover, the CPU 31 sets the upward direction flag and resets the downward direction flag. When the upward direction flag is set, it indicates that the direction in which a relatively large impact that may require the deployment of the airbag 52 on the vehicle body first acts is the upward direction, and when it is reset, it indicates that the direction is not the upward direction. When the downward direction flag is set, it indicates that the direction in which a relatively large impact that may require the deployment of the airbag 52 on the vehicle body first acts is the downward direction, and when it is reset, it indicates that the direction is not the downward direction. Then, the CPU 31 shifts the process to S110.

[0043] In S80, the CPU 31 judges whether the direction in which a relatively large impact that may require the deployment of the airbag 52 first acts on the vehicle body is the downward direction. Specifically, when the CPU 31 judges that the detection value Gz detected within the above-mentioned direction judgment time after the detection value Gz exceeds the direction threshold value Tz in S30 (i.e., after the sign of the detection value Gz is negative and the absolute value of Gz>Tzd) is the downward direction (i.e., the sign is negative) and the absolute value of the detection value Gz exceeds the absolute value of a predetermined judgment value T, the CPU 31 judges that the direction in which a relatively large impact that may require the deployment of the airbag 52 first acts on the vehicle body is the downward direction. Here, when the CPU 31 judges that the direction is the downward direction (i.e., a positive judgment), the CPU 31 shifts the process to S90, and when the CPU 31 judges that the direction is not the downward direction (i.e., a negative judgment), the CPU 31 shifts the process to S100.

[0044] As described above, the judgment value T includes an upper judgment value Tu (i.e., upper judgment value Tu>0) and a lower judgment value Td (i.e., lower judgment value Td<0). The CPU 31 judges that the detection value Gz exceeds the judgment value Tz when the detection value Gz<lower judgment value Td<0, in other words, when |Gz|>|Td|.

[0045] In the next S90, the CPU 31 changes the activation threshold Thxa in a direction that makes it easier for the airbag 52 to deploy. Changing the activation threshold Thxa in a direction that makes it easier for the airbag 52 to deploy means changing the activation threshold Thxa in a direction that reduces the absolute value. Specifically, the CPU 31 sets the lower activation threshold Thxad as the activation threshold Thxa. At least, the absolute value of the lower activation threshold Thxad is less than the absolute value of the upper activation threshold Thxau. Furthermore, the absolute value of the lower activation threshold Thxad may be less than the absolute value of the standard activation threshold Thxan. The absolute value of the standard activation threshold Thxan will be described later.

[0046] Furthermore, the CPU 31 changes the safing threshold Thxc in a direction in which the airbag 52 is easily deployed. Specifically, the CPU 31 sets the lower safing threshold Thxcd as the safing threshold Thxc. At least, the absolute value of the lower safing threshold Thxcd is less than the absolute value of the upper safing threshold Thxcu. Furthermore, the absolute value of the lower safing threshold Thxcd may be less than the absolute value of the standard safing threshold Thxcn. The standard safing threshold Thxcn will be described later.

[0047] Furthermore, the CPU 31 sets the lower timing period DTd as the development timing period DT. The CPU 31 also sets the downward direction flag and resets the upward direction flag. Then, the CPU 31 shifts the process to S110.

[0048] In S100, the activation threshold Thxa is changed to an initial value. The initial value is, for example, a value for appropriately deploying the airbag 52 in the event of a frontal collision in front of the vehicle. Specifically, the CPU 31 sets the standard activation threshold Thxan as the activation threshold Thxa. The CPU 31 also changes the safing threshold Thxc to the initial value. Specifically, the CPU 31 sets the standard safing threshold Thxcn as the safing threshold Thxc.

[0049] Furthermore, the CPU 31 changes the deployment timing period DT to an initial value. Specifically, the CPU 31 sets the standard timing period DTn as the deployment timing period DT. In this manner, the CPU 31 sets various parameters to their initial values, and resets the downward direction flag and the upward direction flag. The CPU 31 may also reset the elapsed time measured by the timer. Then, the CPU 31 shifts the process to S110.

[0050] In S110, the CPU 31 determines whether the magnitude of the component of the impact acting on the vehicle body in the target direction of deployment is relatively large enough to require the generation of a deployment signal for deploying the airbag 52. The CPU 31 generates the deployment signal based on a comparison result between the acquired detection value Gx and the activation threshold value Thxa. In this embodiment, the CPU 31 determines that the magnitude of the component of the impact acting on the vehicle body in the target direction of deployment is relatively large when the acquired detection value Sx exceeds the safing threshold value Thxc (i.e., the absolute value of Sx>the absolute value of Thxc) and the acquired detection value Gx exceeds the activation threshold value Thxa (i.e., the absolute value of Gx>the absolute value of Thxa).

[0051] The acquired detection value Gx here refers to the most recently acquired detection value Gx. The activation threshold value Thxa and the safing threshold value Thxc here refer to the activation threshold value Thxa and the safing threshold value Thxc set most recently (for example, in S70, S90, or S100).

[0052] When the absolute value of the detection value Sx is greater than the absolute value of the safing threshold Thxc and the absolute value of the detection value Gx is greater than the absolute value of the activation threshold Thxa, the CPU 31 determines that the magnitude of the component of the impact acting on the vehicle body in the target direction is relatively large. If the determination is affirmative, the CPU 31 shifts the process to S130, and if the determination is negative, the CPU 31 shifts the process to S10 and repeats the process from S10 onward.

[0053] In step S120, the CPU 31 generates a deployment signal. Note that, in this step, the deployment signal is not output to the outside of the airbag ECU 10. At S130, the CPU 31 executes a situation determination process. The situation determination process determines whether or not a predetermined output condition is satisfied. The CPU 31 sets or resets an output condition flag as a determination result. The output condition flag is information generated in the situation determination process, and is set when the current situation is a situation in which the airbag 52 should be deployed, and is reset when the current situation is a situation in which the airbag 52 should not be deployed. The CPU 31 may execute the situation determination process as a process separate from this process.

[0054] In S140, the CPU 31 obtains the output condition flag. In the next step S150, the CPU 31 determines whether the output condition is satisfied in the current situation based on the output condition flag. If the CPU 31 determines that the output condition is satisfied, the CPU 31 shifts the process to S160. On the other hand, if the CPU 31 determines that the output condition is not satisfied, the CPU 31 ends the process.

[0055] In S160, the CPU 31 outputs a deployment signal to the airbag actuation device 15 (i.e., specifically, the drive circuit 51) at a timing according to the deployment timing period DT set most recently (for example, in S70, S90, or S100). For example, the CPU 31 may output the deployment signal after the deployment timing period DT has elapsed since the deployment signal was generated. The CPU 31 then ends this process.

[0056] Next, the situation determination process executed by the CPU 31 in S130 will be described with reference to the flowchart of FIG. In S200, the CPU 31 acquires a detection result from the object detection sensor 14. As described above, the detection result may include information indicating the distance to the object, the direction, the relative speed, the shape of the object, and the like.

[0057] In the next step S210, the CPU 31 detects a collision object. For example, the CPU 31 may repeatedly acquire images and monitor objects around the vehicle by a process separate from this situation determination process, and recognize an object whose relative speed is detected as 0 as a collision object. In this step, the CPU 31 may identify the type of the recognized collision object by pattern matching or the like. The CPU 31 is to at least identify whether or not it is a person.

[0058] In S220, the CPU 31 acquires no-deployment information. The no-deployment information is information for prohibiting the deployment of the airbag 52 when an impact occurs in a predetermined direction (hereinafter, symmetric direction) caused by a predetermined object (hereinafter, target object), and is information in which the target object and the target direction are associated with each other. The no-deployment information may be stored in the memory 32. For example, in the no-deployment information, a person as the target object is associated with the downward direction as the target direction.

[0059] In S230, the CPU 31 determines whether a predetermined output condition is satisfied based on the unexpanding information. The output condition here means that it is determined that the collision object detected in S210 matches the target object in the unexpanding information, and the direction of the impact by the collision object matches the target direction in the unexpanding information. In other words, if the collision object matches the target object, and the direction of the impact by the collision object matches the target direction, the output condition is not satisfied. In other words, in this embodiment, if the collision object is a person, and the impact direction is downward, the output condition is not satisfied.

[0060] If it is determined that the output condition is satisfied, the CPU 31 shifts the process to S240. Then, in S240, the CPU 31 sets an output condition flag, and ends this situation determination process. The output condition flag is a flag that is set when the output condition is satisfied.

[0061] On the other hand, if it is determined that the output condition is not satisfied, the CPU 31 shifts the process to S250. Then, in S250, the CPU 31 resets the output condition flag, and ends this situation determination process.

[0062] [1-3. Operation] <Impacts caused by driving over bumps or rough roads, etc.> For example, assume that an impact (i.e., an upward impact) occurs due to climbing over a step or driving on a rough road, as shown in Fig. 6a. In this case, the airbag ECU 10 smoothes the output of the second acceleration sensor 12 (e.g., Fig. 6b) by the signal processor 22 as shown in Fig. 6c.

[0063] Then, based on the smoothed detection value Gz, if a newly acquired detection value Gz exceeds the judgment value T with the same sign as the sign when the detection value Gz exceeded the directional threshold value Tz within the direction judgment time (for example, from time t11) after the smoothed detection value Gz exceeded the directional threshold value Tz, the airbag ECU 10 judges that a relatively large impact in the vertical direction first occurred in the direction indicated by the sign.

[0064] In the example shown in Fig. 6d, when the detection value Gz exceeds the upper threshold value Tzu and exceeds the upper determination value Tu with the same positive sign as the sign of the upper threshold value Tzu within the direction determination time after exceeding the upper threshold value Tzu (for example, at time t12), the activation threshold value Thxa is changed to a direction in which the airbag 52 is less likely to be deployed. That is, the activation threshold value Thxa is changed to the upper activation threshold value Thxau.

[0065] In this embodiment, although not shown, the safing threshold value Thxc is also changed to the upper safing threshold value Thxcu. This prevents the airbag 52 from being erroneously deployed when an impact occurs due to climbing over a step, driving on a rough road, or the like.

[0066] <Impact from diving> For example, assume that an impact due to submersion occurs as shown in Fig. 7a. In this case, the airbag ECU 10 smoothes the output (e.g., Fig. 7b) by the second acceleration sensor 12 using the signal processor 22 as shown in Fig. 7c. Then, based on the smoothed detection value Gz, if a newly acquired detection value Gz exceeds the determination value T with the same sign as the sign when the detection value Gz exceeded the direction threshold Tz within the direction determination time (e.g., from time t21), the airbag ECU 10 determines that a relatively large impact in the vertical direction first occurred in the direction indicated by the sign.

[0067] 7d, when the detection value Gz exceeds the downward threshold Tzd (for example, at time t21) and exceeds a lower determination value Tud having the same negative sign as the sign of the detection value Gz exceeding the downward threshold Tzd within the direction determination time after exceeding the downward threshold Tzd (for example, at time t23), the activation threshold Thxa is changed to a direction in which the airbag 52 is likely to be deployed. That is, the activation threshold Thxa is changed to a lower activation threshold Thxad.

[0068] In this embodiment, although not shown, the safing threshold Thxc is also changed to the lower safing threshold Thxcd. This prevents the airbag 52 from being inflated by mistake when the vehicle is getting underway. In other words, the airbag 52 is appropriately inflated when the vehicle is getting underway.

[0069] [1-4. Effects] According to the first embodiment described above in detail, the following effects are achieved. (1a) When it is determined that the direction in which a relatively large impact in the vertical direction first occurs is downward, the airbag ECU 10 changes the activation threshold value Thxa so that the airbag 52 is more likely to deploy than when it is not determined that the impact is downward. Specifically, the airbag ECU 10 changes the activation threshold value Thxa so as to reduce the absolute value. This makes it possible to make the airbag 52 more likely to deploy when, for example, a relatively large impact in the downward direction first occurs on the vehicle body due to the vehicle getting under a large vehicle such as a truck. As a result, the operation of the airbag 52 can be controlled with high accuracy.

[0070] Furthermore, when it is determined that the direction in which a relatively large impact first occurs in the vertical direction is the upward direction, the airbag ECU 10 changes the activation threshold value Thxa so that the airbag 52 is less likely to deploy than when it is not determined that the impact is the upward direction. Specifically, the activation threshold value Thxa is changed so as to have a larger absolute value. This makes it possible to suppress erroneous deployment of the airbag 52 when, for example, a relatively large impact first occurs in the upward direction due to running up a vehicle, driving on a rough road, or the like. As a result, the operation of the airbag 52 can be controlled with high accuracy.

[0071] (1b) When the detection value Gz exceeds the determination value T for the first time, the airbag ECU 10 identifies the direction based on the detection value Gz as the vertical direction of the impact acting on the vehicle body. Specifically, the airbag ECU 10 determines whether the detection value Gz exceeds a direction threshold value Tz having an absolute value smaller than the determination value T, and determines that the detection value Gz has exceeded the determination value T for the first time when the detection value Gz exceeds the direction threshold value Tz within a predetermined direction determination time.

[0072] As described above, the airbag ECU 10 identifies the direction of the impact when the detection value Gz exceeds the direction threshold Tz and exceeds the determination value T on the same side (i.e., with the same sign) as the side on which the direction threshold Tz was exceeded within the direction determination time from when the detection value Gz exceeded the direction threshold Tz. For example, as shown in Fig. 8, if the detection value Gz is determined based only on the determination value T, the impact acting on the vehicle body is applied in the upward direction, but if the detection value Gz exceeds the downward determination value Td without exceeding the upward determination value Tu, the direction of the impact acting on the vehicle body initially is in the upward direction, but is in fact in the upward direction.

[0073] In this embodiment, two thresholds are provided: a direction threshold Tz and a judgment value T. In addition, a time limit is set such that the judgment value T must be exceeded within a direction judgment time after the direction threshold Tz is exceeded. This allows the direction in which a relatively large impact that exceeds the judgment value T first occurs to be identified with high accuracy. The direction judgment time may be appropriately determined through experiments, etc.

[0074] (1c) The first acceleration sensor 11 detects an impact in at least one of the front-rear and left-right directions perpendicular to the up-down direction. In addition, one of the directions detected by the first acceleration sensor 11 (i.e., the front-rear direction) (e.g., the rear direction) is included in the target deployment direction. Since the target deployment direction is included in the direction detected by the first acceleration sensor 11, it is possible to accurately determine whether or not the airbag 52 needs to be deployed based on the detection value Gx of the first acceleration sensor 11.

[0075] (1d) When the airbag ECU 10 determines in S20 that the first detection value is a detection value in the target deployment direction, the airbag ECU 10 determines the direction of the impact acting on the vehicle body in the vertical direction in S60 and S80. When the airbag ECU 10 determines in S20 that the first detection value is not a detection value in the target deployment direction, the airbag ECU 10 does not determine the direction of the impact in S60 and S80. This allows the determination to be performed only when necessary, thereby reducing the processing load.

[0076] Furthermore, when it is determined in S20 that the first detection value is not the detection value in the deployment target direction, the airbag ECU 10 does not change the activation threshold value Thxa based on the determined impact direction in S70, S90, and S100. This allows the activation threshold value to be changed only when necessary, thereby reducing the processing load.

[0077] (1e) In S210, the airbag ECU 10 detects a colliding object based on the detection result by the object detection sensor 14, and acquires no-deployment information in S220. The no-deployment information is information for prohibiting the deployment of the airbag 52 when an impact occurs in a predetermined symmetrical direction by a predetermined target object, and is information in which at least the target object and the target direction are associated with each other. In S150, the airbag ECU 10 determines whether or not the output condition is satisfied based on the no-deployment information, with the output condition being a negative determination that the colliding object matches the target object and that the direction of the impact by the colliding object matches the target direction. In S160, the airbag ECU 10 outputs a deployment signal when the output condition is satisfied, and does not output a deployment signal when the output condition is not satisfied. As a result, even if a deployment signal is generated, it is possible to prohibit the output of the generated deployment signal depending on the situation of the collision.

[0078] In addition, in the no-deployment information, a person is set as a target object, and a downward direction is set as a target direction, and a person and a downward direction are associated with each other. This makes it possible to prohibit the deployment of the airbag 52, for example, in a case where a person collides with a vehicle and rides up onto the vehicle body, causing a downward impact. Note that the target object and the target direction associated in the no-deployment information may be set arbitrarily. This makes it possible to deploy or prohibit the deployment of the airbag 52, depending on the type of object, for example, in a case where an object falls onto the hood of the vehicle.

[0079] (1f) In S70, S90, and S100, the airbag ECU 10 generates a deployment timing period DT for changing the timing of outputting a deployment signal to the airbag actuator 15 (i.e., the drive circuit 51) based on the direction of the impact acting on the vehicle body determined in S60 and S80. The airbag ECU 10 outputs the deployment signal based on the deployment timing period DT. The airbag ECU 10 may output the deployment signal, for example, after the deployment timing period DT has elapsed since the deployment signal was generated, by timer control or the like.

[0080] As shown in Fig. 9, the appropriate length of the period from the time when a collision is determined to have occurred (i.e., the time when the deployment signal is generated) to the time when the airbag 52 is deployed differs between a normal collision and a collision due to the vehicle getting under a truck. In this embodiment, for example, when it is determined that the direction of a relatively large impact acting on the vehicle body is downward, it is determined to be a collision due to the vehicle getting under a truck or the like, and a deployment timing period DT (i.e., a lower timing period DTd) different from the deployment timing period DT (i.e., a standard timing period DTn) in a normal collision in the front direction is set. This allows the deployment signal to be output at the appropriate timing, and the airbag 52 to be deployed at the appropriate timing.

[0081] In the above embodiment, the airbag ECU 10 corresponds to the airbag control device, and the microcomputer 30 corresponds to the operation determination unit, the output unit, the direction determination unit, the change unit, the collision object identification unit, the output condition unit, and the timing unit. S110 and S120 correspond to the process as the operation determination unit, S160 corresponds to the process as the output unit, and S60, S65, S80, and S85 correspond to the process as the direction determination unit. S90 corresponds to the process as the change unit, S210 corresponds to the process as the collision object identification unit, S220 corresponds to the process as the correspondence acquisition unit, S150 corresponds to the process as the output condition unit, and S70, S90, and S100 correspond to the process as the timing unit. The first acceleration sensor 11 corresponds to the first detection device, the second acceleration sensor 12 corresponds to the second detection device, the detection value Gx corresponds to the first detection value, and the detection value Gz corresponds to the second detection value. The comparison result between the detection value Gx and the activation threshold value Thxa corresponds to the comparison result. The deployment timing period DT corresponds to the timing instruction. The activation threshold value Thxa corresponds to the activation threshold value.

[0082] [1-5. Modifications] (Variation 1-1) In the above-described embodiment, the airbag ECU 10 (i.e., CPU 31) may determine that the second detection value has exceeded the judgment value for the first time if the differential value of the detection value Gz becomes 0 within a predetermined direction judgment time after the detection value Gz exceeds the direction threshold value, and the detection value Gz at the time the differential value becomes 0 exceeds the judgment value T.

[0083] In this case, as in the flowchart shown in Fig. 10, S35 described below may be added to the flowchart shown in Fig. 4. That is, in S35 to which the CPU 31 proceeds after a positive determination in S30, the CPU 31 may generate a differential value of the detection value Gz every time the detection value Gz is acquired, and determine whether the generated differential value is 0 or not. The CPU 31 may then repeatedly calculate the differential value until the differential value of the detection value Gz becomes 0, and when the differential value becomes 0, the process may proceed to S40.

[0084] [2. Second embodiment] [2-1. Differences from the first embodiment] The second embodiment has a basic configuration similar to that of the first embodiment, and therefore differences will be described below. Note that the same reference numerals as those in the first embodiment indicate the same configuration, and the preceding description will be referred to.

[0085] In the above-described first embodiment, the direction in which a relatively large impact first acts on the vehicle body in the vertical direction is identified based on the detection value Gz, and the activation threshold value Thxa is changed to a preset value according to the direction. In contrast, the second embodiment differs from the first embodiment in that the direction in which a relatively large impact first acts on the vehicle body in the vertical direction is identified based on a two-dimensional determination map 42.

[0086] The first acceleration sensor 11 detects an impact acting on the vehicle body in a first detection direction, which is a direction perpendicular to the up-down direction and is at least one of the front-rear direction and the left-right direction, as a first detection value. In this embodiment, the front-rear direction including the target deployment direction is the first detection direction. The detection value Gx corresponds to the first detection value. The second acceleration sensor 12 detects an impact acting on the vehicle body in the up-down direction, which is a second detection direction perpendicular to the first detection direction, as a second detection value. In this embodiment, the detection value Gz corresponds to the second detection value.

[0087] In accordance with the above-mentioned differences, the airbag ECU 10 detects at least one of the magnitude of the impact acting on the vehicle body and the magnitude of the first detection direction component of the impact acting on the vehicle body (i.e., the detection value Gx, which is the first detection value) based on the first detection value (i.e., the detection value Gx) and the second detection value (i.e., the detection value Gz), as shown in FIG. 11a.

[0088] In this embodiment, the airbag ECU 10 detects the magnitude of the impact acting on the vehicle body. Specifically, the resultant acceleration Gc of the detection values ​​Gx and Gz is detected as the magnitude of the impact acting on the vehicle body. As shown in FIG. 11a, the airbag ECU 10 detects an impact angle GΘ, which is an angle between the direction of the impact acting on the vehicle body and the first detection direction (i.e., the front-rear direction) on a detection plane having two axes, the first detection direction (i.e., the front-rear direction) and the second detection direction (i.e., the up-down direction). The impact angle GΘ is expressed as positive on the upward side in the up-down direction and negative on the downward side.

[0089] As will be described later in Modification 2-2, the airbag ECU 10 may determine that the direction of the impact that acted on the vehicle body in the vertical direction is downward based only on the impact angle GΘ when the impact angle GΘ is included in the downward impact range, as shown in Figures 11b, 11c, and 11d. In contrast, in this embodiment, the direction of the impact that acted on the vehicle body in the vertical direction is determined based on a determination map 42.

[0090] <Judgment map> The determination map 42 is a two-dimensional map with two axes of the impact angle GΘ and one of the resultant acceleration Gc, which is the magnitude of the impact, and the detection value Gx, which is the magnitude of the first detection direction component of the impact, and is a map for determining the direction of the impact acting on the vehicle body in the vertical direction. In this embodiment, as shown in Fig. 12, a two-dimensional map with the impact angle GΘ and the resultant acceleration Gc as the two axes is used as the determination map 42. The determination map 42 may be stored in the memory 32 in advance, or, if the airbag system 1 is equipped with a wireless notification device or a wired communication device, may be obtained from outside the airbag ECU 10 by wireless or wired communication.

[0091] A plurality of determination regions are set in the determination map 42. The plurality of determination regions include at least an upward region where the impact direction is determined to be upward, and a downward region where the impact direction is determined to be downward. The plurality of determination regions also include regions other than the upward region and the downward region where the impact direction is determined to be neither upward nor downward. The map that separates the upward region from the other regions is also referred to as the upper map Mu, and the map that separates the downward region from the other regions is also referred to as the lower map Md.

[0092] A predetermined activation threshold Thxa is associated with each of the upward region, the downward region, and the region other than the upward region and the downward region. The threshold correspondence information is information that stores each judgment region and a corresponding activation threshold. The threshold correspondence information may be stored in advance in the memory 32 together with the judgment map 42, or may be obtained from outside the airbag ECU 10 by wireless or wired communication.

[0093] [2-2. Processing] Next, the process executed by the CPU 31 in the second embodiment will be described with reference to the flowchart of Fig. 13. Note that the processes of S10-S20 and S110-S160 in Fig. 13 are similar to the processes of the same steps in Fig. 4.

[0094] In S35, to which the CPU 31 proceeds after a positive determination in S20, the CPU 31 calculates a resultant acceleration Gc and an impact angle GΘ based on the detection values ​​Gx and Gz acquired in S10, using equations (1) and (2), respectively. In this embodiment, the impact angle GΘ is expressed as an angle centered on the x-axis (i.e., 0°) in the xz plane in Fig. 2. The resultant acceleration Gc is expressed as a magnitude obtained by combining the detection values ​​Gx and Gz.

[0095] Gc = (Gx 2 + Gz 2 ) 1 / 2 (1) Formula GΘ=tan -1 (Gz / Gx) (2) formula In the next S45, after determining in S20 that the impact acting on the vehicle body is in the target deployment direction (i.e., rearward), the CPU 31 determines whether or not the impact acting on the vehicle body is within a predetermined angle range with respect to the direction along the target deployment direction (i.e., the front-rear direction as the first detection direction). In other words, it determines whether or not the impact is detected in a direction in which the impact is suppressed by the airbag 52. Hereinafter, the predetermined angle range with respect to the direction along the target deployment direction is also referred to as the target deployment range. If the CPU 31 determines that the direction of the impact acting on the vehicle body is within the target deployment range, the CPU 31 shifts the process to S100, and if it determines that the direction is outside the predetermined angle range, the CPU 31 shifts the process to S55.

[0096] Specifically, the CPU 31 determines whether the absolute value of the impact angle GΘ exceeds a predetermined target deployment angle α. When the absolute value of the impact angle GΘ is less than the target deployment angle α, the CPU 31 determines that the impact acting on the vehicle body is within a predetermined angle range with respect to the direction along the target deployment direction, and that the direction of the impact is such that the airbag 52 functions. When -α°≦impact angle GΘ≦+α°, the absolute value of the impact angle GΘ is determined to be less than the target deployment angle α. The target deployment angle α may be, for example, 30°, but is not limited thereto and may be set arbitrarily.

[0097] In S55, the CPU 31 obtains the determination map 42. In this embodiment, the determination map 42 is a two-dimensional map whose axes are the impact angle GΘ and the resultant acceleration Gc. Next, in S65, the CPU 31 determines whether or not the coordinates (GΘ, Gc) are included in the upward region in the determination map 42. In this embodiment, as shown in Fig. 12, in the determination map 42, a range in which the impact angle GΘ is positive and is indicated by diagonal lines is predetermined as the upward region.

[0098] Here, when the CPU 31 determines in the determination map 42 that the coordinates (GΘ, Gc) are included in the upward region, it shifts the process to S70. In the subsequent S70, similarly to the case in which it is determined in the above-described embodiment that the impact acting on the vehicle body was in the upward direction, it sets the activation threshold Thxa, the safing threshold Thxc, the deployment timing period DT, and various flags, and shifts the process to S110.

[0099] On the other hand, when it is determined in the determination map 42 that the coordinates (GΘ, Gc) are not included in the upward region, the CPU 31 shifts the process to S85. At S85, the CPU 31 determines whether or not the coordinates (GΘ, Gc) are included in the downward region in the determination map 42. In this embodiment, as shown in Fig. 12, in the determination map 42, a range in which the impact angle GΘ is negative and is indicated by diagonal lines is predefined as the downward region.

[0100] Here, when the CPU 31 determines in the determination map 42 that the coordinates (GΘ, Gc) are included in the downward region, it shifts the process to S90. In the subsequent S90, similarly to the case in which it is determined in the above-described embodiment that the impact acting on the vehicle body was downward, it sets the activation threshold Thxa, the safing threshold Thxc, the deployment timing period DT, and various flags, and shifts the process to S110.

[0101] Furthermore, the CPU 31 shifts the process to S100 when it is determined in the determination map 42 that the coordinates (GΘ, Gc) are not included in the upward or downward region. In S100, the CPU 31 sets the activation threshold Thxa, the safing threshold Thxc, the deployment timing period DT, and various flags, in the same manner as in the case where it is determined in the above-described embodiment that the impact acting on the vehicle body is neither upward nor downward, and shifts the process to S110.

[0102] Then, the CPU 31 executes the processes from S110 onwards, similarly to the above-described embodiment. [2-3. Operation] The following describes the operation of the airbag ECU 10 based on the determination map 42. In the following description, the magnitude of the impact angle GΘ refers to the magnitude of the absolute value of the impact angle GΘ.

[0103] (1) Scope 1 Range 1 is a range where GΘ of the coordinates (GΘ, Gc) is -α°≦impact angle GΘ≦+α°. In range 1, the direction of the impact acting on the vehicle body is determined to be rearward (i.e., neither upward nor downward), regardless of the magnitude of the resultant acceleration Gc. Note that in the above-mentioned process, the impact angle GΘ is determined to be within range 1 based on the magnitude of the impact angle GΘ without using the determination map 42.

[0104] When it is determined that the impact angle GΘ is within the range 1, it is determined that the direction of the impact acting on the vehicle body is neither upward nor downward. In other words, the activation threshold value Thxa is changed to a standard value (i.e., the standard activation threshold value Thxan). As a result, in the case of a normal collision, such as a collision with a vehicle ahead, the activation control of the airbag 52 is appropriately performed based on the standard activation threshold value Thxa.

[0105] (2) Range 2 Range 2 is a range where GΘ of the coordinates (GΘ, Gc) is positive and +α°<impact angle GΘ<+90°. Range 2 is estimated to include impacts caused by running over obstacles, driving on rough roads, etc. Also, the larger the impact angle GΘ, the more likely it is that the impact is caused by a collision that is not a normal front-rear collision, such as colliding with a vehicle ahead. These impacts are estimated to be impacts that require the activation threshold value Thxa to be changed in a direction that makes it difficult for the airbag 52 to deploy.

[0106] In the determination map 42, the lower end 421 of the upward direction region is set to decrease as the impact angle GΘ increases in the range of +α°<impact angle GΘ<+90°. The lower end of the upward direction region refers to the boundary on the side where the resultant acceleration Gc is smaller, among the boundaries that separate the upward direction region from other regions.

[0107] According to such a determination map 42, when the resultant acceleration Gc is equal to or smaller than a predetermined magnitude (for example, Gc1), the larger the impact angle GΘ, the more likely it is to be determined that the resultant acceleration is within the upward region, regardless of the magnitude of the resultant acceleration Gc.

[0108] That is, the activation threshold Thxa is changed in a direction that makes it difficult for the airbag 52 to deploy. For example, the activation threshold Thxa may be changed to a lower activation threshold Thxad. This makes it possible to prevent the airbag 52 from erroneously deploying when the magnitude of the detected impact angle GΘ is relatively large, compared to a comparative example in which a determination map is used in which the lower end of the upper region, such as the lower end 422, does not decrease with an increase in the impact angle GΘ but remains a constant value.

[0109] (3) Range 3 In range 3, GΘ in the coordinates (GΘ, Gc) is negative, and -α°>impact angle GΘ>-β° (i.e., |α|<|β|). Range 3 is estimated to include impacts caused by crawling under or a relatively large falling object (hereinafter, a large falling object). These impacts are assumed to be impacts that require the activation threshold Thxa to be changed in a direction that makes it easier for the airbag 52 to deploy.

[0110] In the determination map 42, the lower end 423 of the downward direction region is set to decrease with an increase in the magnitude of the impact angle GΘ in the range of -α°>impact angle GΘ>-β°. The lower end of the downward direction region refers to the boundary on the side where the resultant acceleration Gc is smaller, among the boundaries that separate the downward direction region from other regions.

[0111] According to such a judgment map 42, when the composite acceleration Gc is equal to or less than a predetermined magnitude (e.g., Gc2) and the impact angle GΘ is a negative value, the larger the absolute value of the impact angle GΘ, the more likely it is to be judged to be in the downward region, regardless of the magnitude of the composite acceleration Gc.

[0112] In other words, the activation threshold value Thxa is changed in a direction that makes it easier to deploy the airbag 52. As a result, the airbag 52 is more likely to deploy when the absolute value of the detected impact angle GΘ is relatively large than in a comparative example in which a determination map is used in which the lower end of the downward region, like the lower end 424, does not decrease as the absolute value of the impact angle GΘ, which is a negative value, increases but remains constant.

[0113] (4) Range 4 is a range where GΘ of the coordinates (GΘ, Gc) is negative and -β°>impact angle GΘ>-90°. In range 4, an impact caused by a falling object from above in the vertical direction is estimated. When the magnitude of the impact angle GΘ is greater than the magnitude of the predetermined angle β, it means that the rearward component of the impact caused by the falling object is relatively small. In other words, even if the frontal collision airbag 52, which has the effect of increasing the safety of the occupant against an impact in the rearward direction (i.e., the direction of the target for deployment), is activated, it is assumed that the effect is limited (i.e., reduced).

[0114] In the determination map 42 of the present embodiment, the lower end 425 of the downward region is set so as to rise with an increase in the absolute value of the impact angle GΘ in the range of -β°>impact angle GΘ>-90°.

[0115] According to such a determination map 42, when the impact angle GΘ is a negative value, the greater the absolute value of the impact angle GΘ, the more likely it is to be determined that the impact angle is not within the downward region, and the activation threshold Thxa is not changed in a direction in which the airbag 52 is more likely to be deployed. This makes it possible to prevent the airbag 52 from being unnecessarily deployed when the absolute value of the detected impact angle GΘ is relatively large, compared to a comparative example in which a determination map is used in which the lower end of the downward region is a constant value that does not decrease as the absolute value of the impact angle GΘ, which is a negative value, increases, such as the lower end 426. In other words, it is possible to prevent the airbag 52 from being erroneously deployed.

[0116] [2-4. Effects] According to the second embodiment described above in detail, in addition to the effect (1a) of the first embodiment described above, the following effect is further achieved.

[0117] (2a) The airbag ECU 10 determines the direction of the impact acting on the vehicle body in the vertical direction based on the detected impact angle GΘ and resultant acceleration Gc, using the determination map 42. As a result, the airbag ECU 10 accurately identifies the direction of the impact acting on the vehicle body in the vertical direction using the determination map 42 based on two-dimensional parameters, and can therefore accurately control the operation of the airbag 52 in various situations.

[0118] (2b) The airbag ECU 10 identifies a judgment area on the judgment map 42 based on the detected impact angle GΘ and resultant acceleration Gc, and when the identified judgment area is determined to be a downward area, determines that the direction of the impact acting on the vehicle body is downward. When the airbag ECU 10 determines that the direction of the impact acting on the vehicle body is downward, it changes the activation threshold value Thxa in a direction in which the airbag is more likely to deploy than when the direction is not determined to be downward. In other words, the airbag ECU 10 changes the activation threshold value Thxa in a direction that reduces the absolute value. This makes it possible to obtain the same effect as (2a).

[0119] The airbag ECU 10 may at least specify whether the area is a downward area and change the activation threshold value Thxa in a direction in which the airbag is likely to deploy when it is determined that the area is downward. Furthermore, the airbag ECU 10 may specify whether the area is an upward area and change the activation threshold value Thxa in a direction in which the airbag is unlikely to deploy when it is determined that the area is upward. Furthermore, the airbag ECU 10 may change the activation threshold value Thxa to a standard value or an initial value when it is determined that the area is other than the downward area and the upward area.

[0120] (2c) In S70, S90, and S100, the airbag ECU 10 may set the activation threshold value Thxa using the threshold value correspondence information based on the detected impact angle GΘ and resultant acceleration Gc. The threshold value correspondence information is information that associates each judgment region with a predetermined activation threshold value Thxa. In this embodiment, in the threshold value correspondence information, the activation threshold value Thxa associated with the downward region (for example, the lower activation threshold value Thxad) is set to a value that makes it easier for the airbag 52 to deploy than the activation threshold value Thxa associated with a judgment region other than the downward region (for example, the upper activation threshold value Thxau or the standard activation threshold value Thxan). The value that makes it easier for the airbag 52 to deploy means a value whose absolute value is relatively small. As a result, the airbag ECU 10 can arbitrarily set the activation threshold value Thxa according to each region of the judgment map 42 using the threshold value correspondence information, and therefore can perform accurate and precise operation control of the airbag 52 using the judgment map 42 and the threshold value correspondence information.

[0121] [2-4. Modifications] (Variation 2-1) In Modification 2-1, in the second embodiment, Range 1, i.e., the deployment target range, may be asymmetric with respect to the front-rear direction as the first detection direction. For example, in the determination map 42, αd° and αu° may be set as the deployment target angles instead of α°, and if -αd°≦impact angle GΘ≦+αu° (|αd|≠|αu|) is satisfied in S20, it may be determined that an impact has occurred in the deployment target direction (i.e., the rearward direction).

[0122] (Variation 2-2) In the modified example 2-2, a determination map 42a shown in FIG. 14 may be used instead of the determination map 42 in the second embodiment. Range 1 is a range where GΘ of the coordinates (GΘ, Gc) is -α°≦impact angle GΘ≦+α° (hereinafter, rearward impact range). Range 2 is a range where GΘ of the coordinates (GΘ, Gc) is +α°<impact angle GΘ<+90° (hereinafter, upward impact range). Range 5 is a range where GΘ of the coordinates (GΘ, Gc) is -90°<impact angle GΘ<-α° (hereinafter, downward impact range). For example, when the coordinates (GΘ, Gc) are included in the downward impact range, the airbag ECU 10 may determine that the impact acting on the vehicle body is downward. The airbag ECU 10 may further determine that the impact that acted on the vehicle body was in an upward direction when the coordinates (GΘ, Gc) are included in an upward impact range, and may determine that the impact that acted on the vehicle body was in a rearward direction (i.e., in the direction of the target deployment) when the coordinates (GΘ, Gc) are included in a rearward impact range.

[0123] (Variation 2-3) In the modified example 2-3, a determination map 42b shown in FIG. 15 is used instead of the determination map 42 shown in FIG. 12. The determination map 42b is a two-dimensional map with two axes: the impact angle GΘ and the detection value Gx, which is the magnitude of the first detection direction component of the magnitude of the impact. In this embodiment, for example, in S65 to S100 of the flowchart in FIG. 13, the resultant acceleration Gc may be replaced with the detection value Gx. Also, the calculation of the resultant acceleration Gc in S35 may be omitted.

[0124] The operation of the airbag ECU 10 based on the determination map 42b will be described below. Note that, hereinafter, the detected value Gx is also referred to as the rearward acceleration Gx. (1) Scope 1 Range 1 is a range in which GΘ at coordinates (GΘ, Gx) is -α°≦impact angle GΘ≦+α°, similar to the determination map 42. In range 1, the direction of the impact acting on the vehicle body is determined to be in the rearward direction (i.e., neither upward nor downward), regardless of the magnitude of the rearward acceleration Gx. Note that in the above-described process, the impact angle GΘ is determined to be within range 1 based on the magnitude of the impact angle GΘ, without using the determination map 42.

[0125] If it is determined that the impact angle GΘ is within range 1, the direction of the impact acting on the vehicle body is determined to be neither upward nor downward. In other words, the activation threshold value Thxa is changed to a standard value (for example, the standard activation threshold value Thxan).

[0126] (2) Range 2 Range 2 is a range where GΘ of the coordinates (GΘ, Gx) is positive and +α°<impact angle GΘ<+90°. Range 2 is estimated to include impacts caused by running over a road or driving on a rough road. The larger the impact angle GΘ, the less likely the collision is to occur in the front-rear direction. In other words, it is estimated to be a collision in which the activation threshold value Thxa should be changed in a direction that makes it difficult for the airbag 52 to deploy, such as running over a road or driving on a rough road.

[0127] In the determination map 42b of the present embodiment, in range 2, similarly to the determination map 42, the lower end 431 of the upward region is set to decrease as the impact angle GΘ increases in the range of +α°<impact angle GΘ<+90°. As a result, when the magnitude of the detected impact angle GΘ is relatively large, it is more likely to be determined that the impact angle is within the upward region than in a comparative example in which a determination map is used in which the lower end of the upward region does not decrease as the impact angle GΘ increases but remains constant, such as the lower end 432. In other words, the activation threshold value Thxa is more likely to be changed in a direction that makes it difficult for the airbag 52 to deploy. As a result, erroneous activation of the airbag 52 is suppressed.

[0128] (3) Range 5 In range 5, GΘ in the coordinates (GΘ, Gx) is negative, and -α°>impact angle GΘ>-90°. Range 5 is estimated to include impacts caused by submersion or large falling objects. However, as the magnitude of the impact angle GΘ increases, the magnitude of the front-rear component of the impact acting on the vehicle body (i.e., specifically, the rearward component) becomes relatively smaller, making it difficult for the first acceleration sensor 11 to detect a collision.

[0129] In the determination map 42b, the lower end 433 of the downward region is set to descend as the magnitude of the impact angle GΘ increases within the range where -α° > impact angle GΘ > -90°. According to such a determination map 42b, when the rearward acceleration Gx is equal to or less than a predetermined magnitude (for example, Gx2), if the impact angle GΘ is a negative value, the larger the absolute value of the impact angle GΘ, regardless of the magnitude of the rearward acceleration Gx, it is more likely to be determined that it is within the downward region. That is, the operation threshold Thxa is more likely to be changed in the direction in which the airbag 52 is likely to deploy.

[0130] As a result, even if the lower end of the downward region, like the lower end 434, does not descend but remains a constant value as the absolute value of the impact angle GΘ with a negative value increases, compared with a comparative example using a determination map, when the absolute value of the detected impact angle GΘ is relatively large, the airbag 52 is more likely to be deployed.

[0131] Note that in the determination map 42b, a lower limit value Gxmin for the rearward acceleration Gx is set in the downward map. Thereby, in the case of an impact of a light falling object or the like where the airbag 52 should not operate (for example, an impact where the detected value Gx < Gxmin), the airbag 52 is suppressed from operating excessively.

[0132] (Modification 2-4) In Modification 2-4, instead of the determination map 42b shown in FIG. 16, the determination map 42c shown in FIG. 16 is used. The determination map 42c is a two-dimensional map with the impact angle GΘ and the detected value Gx as two axes, similar to the determination map 42b. In the determination map 42c, at least one determination region may include a plurality of divided regions. In the present embodiment, the upward region includes divided regions 1 to 3, and the downward region includes divided regions 4 to 6.

[0133] The threshold correspondence information associates each divided region with a predetermined activation threshold Thxa. For example, in the threshold correspondence information, the activation threshold Thxa associated with the divided regions 4 to 6 included in the downward region is set to a value at which the airbag 52 is more likely to be deployed than the activation threshold Thxa associated with the divided regions 1 to 3 included in the upward region.

[0134] In the threshold correspondence information, the activation threshold Thxa corresponding to each of the divided regions 1 to 3 included in the upward region may be different for each divided region. This allows the activation threshold Thxa to be set precisely according to the situation of the upward impact. Note that the activation threshold Thxa corresponding to each of the divided regions 1 to 3 may be set to any value.

[0135] In the threshold correspondence information, the activation threshold Thxa associated with each of the divided regions 4 to 6 included in the downward region may be different for each divided region. This allows the activation threshold Thxa to be set precisely according to the state of the downward impact. The activation threshold Thxa associated with each of the divided regions 4 to 6 may be set to any value.

[0136] (Variation 2-5) In the above embodiment, the threshold correspondence information is information that associates the judgment region or the divided region with the predetermined activation threshold Thxa, but the threshold correspondence information may be information that associates an activation threshold for each coordinate. That is, the threshold correspondence information may be information that associates each coordinate (GΘ, Gc) with the predetermined activation threshold Thxa. Or, the threshold correspondence information may be information that associates each coordinate (GΘ, Gx) with the predetermined activation threshold Thxa. This allows the activation threshold Thxa to be set more precisely depending on the impact situation.

[0137] (Variation 2-6) In the above embodiment, the threshold correspondence information may be information that associates each coordinate (GΘ, Gc) with a correction value for a predetermined actuation threshold Thxa (for example, any predetermined value such as a standard actuation threshold Thxan). The correction value may be an absolute value or a value that represents a ratio.

[0138] 3. Other embodiments Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0139] (3a) In the above-described embodiment, in the airbag ECU 10, the signal processing units 21 to 23 were circuits external to the microcomputer 30. However, they may be circuits internal to the microcomputer 30, or may be executed by a program 41 executed by the CPU 31 in the microcomputer 30.

[0140] (3b) In the above embodiment, the signal processors 21 to 23 are LPFs, but the signal processors 21 to 23 may be ones that perform first-order integration or second-order integration. Instead of the above-mentioned detection value Gx and the above-mentioned detection value Gz after the LPF processing, the CPU 31 may perform processing using the first-order integral value (i.e., speed) of the detection value of the first acceleration sensor 11 and the second acceleration sensor 12, or the second-order integral value (i.e., travel distance) of the detection value of the first acceleration sensor 11 and the second acceleration sensor 12. In this case, the first-order integral value or the second-order integral value of the detection value of the first acceleration sensor 11 corresponds to a value based on the first detection value. Also, the first-order integral value or the second-order integral value of the detection value of the second acceleration sensor 12 corresponds to a value based on the second detection value.

[0141] (3c) In the above-described embodiment, the airbag ECU 10 may not change the deployment timing period DT and may always use a predetermined fixed value as the deployment timing period DT. For example, the airbag ECU 10 may set the deployment timing period DT to 0 so that the deployment signal is output immediately when the output condition is satisfied.

[0142] (3d) In the above-described embodiment, the airbag ECU 10 may identify the direction of the impact acting on the vehicle body based on the ratio between the detection value Gx as the first detection value and the detection value Gz as the second detection value.

[0143] (3e) In the above-described embodiment, the airbag ECU 10 may detect an approaching object that is approaching the vehicle and may become a collision object, for example, by the object detection sensor 14, and may change the activation threshold value Thxa by identifying the type of the approaching object based on the detection result of the approaching object. The detection result may include at least the distance, direction, and relative speed of the object. The detection result may also include data indicating the shape, size, and image.

[0144] The airbag ECU 10 may, for example, identify an object whose relative distance between the vehicle and the object is shortening over time as an approaching object based on the detection result of the approaching object. The airbag ECU 10 may, for example, identify the characteristics of the approaching object, such as whether it is a person or not, whether it is an animal or not, whether it is a predetermined object or not, its shape, its size, etc., based on the detection result of the approaching object, and set the activation threshold value Thxa based on one or a combination of a plurality of these characteristics.

[0145] In this case, for example, in the flowchart shown in FIG. 4, after a positive determination is made in S20, the airbag ECU 10 may obtain the detection result by the object detection sensor 14, determine whether or not an approaching object exists within a predetermined distance from the vehicle, and, if it is determined that an approaching object exists, change the standard activation threshold Thxan, the upper activation threshold Thxau, and the lower activation threshold Thxad based on the characteristics of the approaching object. The airbag ECU 10 may overwrite the standard activation threshold Thxan, the upper activation threshold Thxau, and the lower activation threshold Thxad and store them in the memory 32 or the like. The airbag ECU 10 may then shift the process to S60. Thereby, in the following steps S70, S90, and S100, the standard activation threshold Thxan, the upper activation threshold Thxau, and the lower activation threshold Thxad based on the detection result of the approaching object are set as the activation threshold Thxa.

[0146] (3f) In the above-described embodiment, the airbag ECU 10 may obtain a detection value Gy as a third detection value by a third detection device (for example, an acceleration sensor) that detects a left-right impact among impacts acting on the vehicle body, and may use the detection value Gy to control the airbag 52. Note that, instead of the first acceleration sensor 11, the second acceleration sensor 12, and the third detection device, a three-axis acceleration sensor that detects acceleration in three axes, with the front-rear direction as the x-axis, the left-right direction as the y-axis, and the up-down direction as the z-axis, may be used.

[0147] The airbag system 1 may include a side-impact airbag that inflates to fill the gap between the door and the occupant when an impact is received from the side of the vehicle (i.e., from the left or right direction). The side-impact airbag may include a driver's airbag arranged on the driver's side and a passenger's airbag arranged on the passenger's side.

[0148] When a vehicle is traveling on a curved road and collides into the rear of a truck or the like with a high loading platform traveling ahead, the vehicle body may receive impacts in the left-right direction in addition to the downward and front-rear directions, and a side-impact airbag may need to be deployed. In such a case, the airbag ECU 10 may execute deployment control of the side-impact airbag according to the direction and magnitude of the impact in the left-right direction.

[0149] In this case, for example, after a positive determination is made in S80 in the flowchart shown in Fig. 4, the airbag ECU 10 may acquire the detection value Gy and identify the direction of the impact acting on the vehicle in the left-right direction. The magnitude may also be identified along with the direction. Then, the airbag ECU 10 may change the activation threshold for deploying one of the driver's and passenger's airbags, which has the identified target deployment direction, to a value that makes it easier for the airbag to deploy, and change the activation threshold for deploying the other airbag to a value that makes it harder for the airbag to deploy, and proceed to S90.

[0150] In other words, when the vehicle body is subjected to an impact from the driver's side in the left-right direction while driving on a curved road as described above, the airbag ECU 10 changes the activation threshold for deploying the driver's airbag to a value that makes it easier for the airbag to deploy, and changes the activation threshold for deploying the passenger airbag to a value that makes it difficult for the airbag to deploy. This allows the driver's airbag to be deployed quickly, while suppressing the deployment of the passenger airbag, making it easier to escape from the vehicle through the passenger door.

[0151] (3g) In the above-described embodiment, the relationship between the direction of impact and the sign of the detected value of the first acceleration sensor 11, the second acceleration sensor 12, and the safing sensor 13 is not limited to the above-described relationship and may be determined appropriately. In the above-described embodiment, instead of the acceleration sensor, a stress detection sensor may be used as the first acceleration sensor 11 and the second acceleration sensor 12. The stress detection sensor may use a strain gauge to output a stress signal according to the magnitude of the impact acting in the front-back or up-down direction. Alternatively, a piezoelectric film may be used instead of the acceleration sensor. The piezoelectric film converts the force acting on the film into a voltage or strain.

[0152] (3h) The airbag ECU 10 and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the airbag ECU 10 and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the airbag ECU 10 and the method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. Also, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer. The method for realizing the functions of each unit included in the airbag ECU 10 does not necessarily need to include software, and all of the functions may be realized using one or more hardware.

[0153] (3i) Multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Also, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0154] (3j) In addition to the airbag ECU 10 or microcomputer 30 described above, the present disclosure can also be realized in various forms, such as a system including the airbag ECU 10 as a component, a program for causing the airbag ECU 10 or the microcomputer 30 to function, a semiconductor memory on which this program is recorded, and a method for controlling the operation of an airbag. [Explanation of symbols]

[0155] 1...airbag system, 10...airbag ECU, 11...first acceleration sensor, 12...second acceleration sensor, 14...object detection sensor, 15...airbag activation device, 30...microcomputer, 31...CPU, 52...airbag.

Claims

1. An airbag control device (10) mounted on a vehicle, an activation determination unit (S120) configured to compare a detection value by a first detection device that detects an impact in a predetermined direction among impacts acting on a vehicle body or a first detection value as a value based on the detection value with a predetermined activation threshold value, and to generate a deployment signal for deploying the airbag based on the comparison result; an output unit (S160) configured to output the deployment signal when a predetermined output condition is satisfied; a direction determination unit (S60, S65, S80, S85) configured to determine the direction of an impact acting on the vehicle body in the vertical direction based on a detection value by a second detection device that is a detection device different from the first detection device and detects an impact in the vertical direction among the impacts acting on the vehicle body, or a second detection value that is a value based on the detection value; a change unit (S90) configured to change the activation threshold value in a direction in which the airbag is more likely to deploy when the direction determination unit determines that the direction of the impact acting on the vehicle body is a downward direction than when the direction determination unit does not determine that the impact is a downward direction; An airbag control device comprising:

2. 2. The airbag control device according to claim 1, The change unit changes the activation threshold in a direction to reduce an absolute value of the activation threshold.

3. 3. The airbag control device according to claim 1, The direction determination unit, when the second detection value exceeds a predetermined determination value for the first time, identifies a direction based on the second detection value as the direction of an impact acting on the vehicle body in the vertical direction.

4. 4. The airbag control device according to claim 3, The direction determination unit determines whether the second detection value exceeds a predetermined direction threshold having an absolute value smaller than the determination value, and determines that the second detection value has exceeded the determination value for the first time when the second detection value exceeds the direction threshold within a predetermined direction determination time after the second detection value exceeds the direction threshold.

5. 4. The airbag control device according to claim 3, the direction determination unit determines whether the second detection value has exceeded a predetermined direction threshold having an absolute value smaller than the determination value, and determines that the second detection value has exceeded the determination value for the first time if a differential value of the second detection value becomes 0 within a predetermined direction determination time after the second detection value has exceeded the direction threshold, and the second detection value at the time the differential value became 0 exceeds the determination value.

6. 3. The airbag control device according to claim 1, wherein the first detection device detects an impact in at least one of a front-rear direction and a left-right direction perpendicular to a top-bottom direction.

7. 3. The airbag control device according to claim 1, The first detection device detects an impact acting on the vehicle body in a first detection direction, the first detection direction being a direction perpendicular to a vertical direction and including at least one of a front-rear direction and a left-right direction; The second detection device detects an impact acting on the vehicle body in a second detection direction that is a vertical direction and perpendicular to the first detection direction, The direction determination unit detects, based on the first detection value and the second detection value, one of the magnitude of the impact acting on the vehicle body and the magnitude of the first detection direction component of the impact acting on the vehicle body, and an impact angle, which is the angle that the direction of the impact acting on the vehicle body makes with respect to the first detection direction on a plane having the first detection direction and the second detection direction as its two axes, obtains a determination map, which is a two-dimensional map having the impact angle and one of the magnitude of the impact and the magnitude of the first detection direction component of the impact as its two axes, for determining the direction of the impact acting on the vehicle body in the vertical direction, and determines the direction of the impact acting on the vehicle body in at least the vertical direction using the determination map based on the detected impact angle and one of the magnitude of the impact and the magnitude of the first directional component of the impact.

8. 8. The airbag control device according to claim 7, the determination map has a plurality of divided determination regions, the plurality of determination regions including at least an upward direction region in which the impact direction is classified as an upward direction, and a downward direction region in which the impact direction is classified as a downward direction, The direction determination unit identifies a corresponding determination area on the determination map based on the detected impact angle and one of the magnitude of the impact and the magnitude of the first directional component of the impact, and when the identified determination area is determined to be the downward area, determines that the direction of the impact acting on the vehicle body is downward.

9. 9. The airbag control device according to claim 8, the change unit acquires threshold correspondence information that associates each of the determination regions with a predetermined activation threshold, and sets the activation threshold using the threshold correspondence information based on the detected angle of the impact and one of the magnitude of the impact and the first detection value; In the threshold correspondence information, an activation threshold associated with a downward region is set to a value that makes it easier for the airbag to deploy than an activation threshold associated with a determination region other than the downward region.

10. The airbag control device according to claim 1 or 2, An airbag control device, wherein one of the directions detected by the first detection device is included in a target deployment direction in which the airbag will deploy.

11. The airbag control device according to claim 10, The direction determination unit does not determine a direction of an impact acting on the vehicle body in a vertical direction when it is determined that the first detection value is not a detection value in the target deployment direction.

12. The airbag control device according to claim 10, The change unit does not change the activation threshold when it is determined that the first detection value is not a detection value in the target deployment direction.

13. 3. The airbag control device according to claim 1, a collision object identification unit (S210) configured to detect a collision object colliding with the vehicle body based on a detection result by an object detection sensor (14) for detecting objects around the vehicle; a correspondence acquisition unit (S220) configured to acquire non-deployment information, which is information for prohibiting the deployment of the airbag when an impact occurs in a predetermined symmetrical direction by a predetermined target object, and is information in which at least the target object and the target direction are associated with each other; an output condition unit (S150) configured to determine whether or not the output condition is satisfied, based on the no-expansion information, on the condition that it is determined that the colliding object coincides with the target object and that the direction of the impact by the colliding object coincides with the target direction; Further comprising: The output unit outputs the deployment signal when the output condition is satisfied based on the determination by the output condition unit, and does not output the deployment signal when the output condition is not satisfied.

14. 14. The airbag control device according to claim 13, In the no-deployment information, a person is defined as the target object, a downward direction is defined as the target direction, and the person and the downward direction are associated with each other.

15. 3. The airbag control device according to claim 1, A timing unit (S70, S90, S100) configured to generate a timing period for changing a timing for outputting the deployment signal based on a direction of an impact acting on the vehicle body determined by the direction determination unit, The output unit outputs the deployment signal based on the timing period.

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