INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2017-011335 filed on Jan. 25, 2017 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to an occupant protection device for a vehicle and an occupant protection method for a vehicle that protect an occupant of the vehicle.

2. Description of Related Art

In the related art, an occupant protection device for a vehicle that detects a collision of an object with the vehicle to protect an occupant has been suggested.

For example, a collision determination device including wall side acceleration sensors provided in both walls of a vehicle and a central side acceleration sensor provided in a central portion of a vehicle is known (for example, see Japanese Unexamined Patent Application Publication No. 11-180249 (JP 11-180249 A)). In the above-described collision determination device, an acceleration detected by the wall side acceleration sensors and the central side acceleration sensor is integrated, and when the integral value exceeds a threshold, a comparator generates a comparison output. An occupant protection device is started based on the comparison output.

Furthermore, an occupant protection device including a side collision prediction sensor configured to predict a collision with a side surface of a vehicle and a side collision sensor configured to detect a collision with the side surface of the vehicle is known (for example, see Japanese Unexamined Patent Application Publication No. 2007-253720 (JP 2007-253720 A)). In the above-described occupant protection device, a collision with the side surface of the vehicle is predicted by the side collision prediction sensor, and when determination is made that the collision with the side surface of the vehicle occurs based on an impact on the side surface of the vehicle detected by the side collision sensor, the occupant protection device is started.

SUMMARY

However, in order to suppress an erroneous operation of the occupant protection device, in a case where a threshold for starting the occupant protection device is set with respect to a detection value of the side collision sensor, when a collision having a detection value smaller than the set threshold occurs, there is a possibility that the occupant protection device is not started. For example, in a case where the magnitude of a collision with a side surface of a vehicle cabin is set as a threshold for starting the occupant protection device, a side collision with a front fender has a detection value smaller than that of the collision with the side surface of the vehicle cabin, and the occupant protection device is not started.

In a case where an object, such as another vehicle, approaches at a high speed and collides with a side of a host vehicle, a timing at which the occupant protection device should be started is made in a shorter time when a relative speed of the host vehicle and the object, such as another vehicle, becomes higher. When the threshold set for suppressing an erroneous operation of the occupant protection device becomes large, a time until the threshold at the time of the collision is reached is extended, and the timing at which the occupant protection device is started is delayed. For this reason, there is a possibility that the occupant protection device is not started at the timing, at which the occupant protection device should be started, due to the relative speed of the host vehicle and the object. Accordingly, there is room for improvement on a technique for protecting an occupant from the collision of the object approaching the side of the host vehicle.

The present disclosure has been accomplished in consideration of the above-described fact, and provides an occupant protection device for a vehicle and an occupant protection method for a vehicle capable of improving occupant protection performance from a collision on a side of a vehicle with a simple configuration.

A first aspect of the present disclosure relates to an occupant protection device for a vehicle. The occupant protection device includes a side collision prediction device, a physical quantity detection device, an airbag device, and an electronic control unit. The side collision prediction device is configured to predict a collision with a side of a host vehicle and output a prediction result including determination about whether or not the predicted collision is an inevitable collision. The physical quantity detection device is configured to detect a physical quantity related to the collision with the side of the host vehicle and output a detection value of the physical quantity. The airbag device is configured to expand to protect an occupant of the vehicle when the airbag device is operated. The electronic control unit is configured to, in a case where the detection value of the physical quantity exceeds a first threshold, perform first control for operating the airbag device, and in a case where the detection value of the physical quantity exceeds a second threshold for a predetermined time from when the side collision prediction device determines that the collision is an inevitable collision, perform second control for operating the airbag device. The second threshold is a value smaller than the first threshold.

According to the first aspect of the present disclosure, the collision with the side of the host vehicle is predicted, and in a case where the detection value of the physical quantity exceeds the second threshold for the predetermined time after determination is made that the predicted collision is an inevitable collision, the airbag device is operated. With this, in the physical quantity detection device, such as a sensor for a side surface collision, even in a case where the physical quantity that is smaller than a threshold usually determined is detected, it is possible to operate the airbag device at an optimum timing with respect to the collision with the side of the host vehicle while suppressing an erroneous operation of the airbag device.

In the occupant protection device according to the first aspect of the present disclosure, the predetermined time may be a time that is determined as a time until the collision in which the airbag device has to be operated occurs from when determination is made that the collision is the inevitable collision. With this, in performing control for operating the airbag device, it is possible to make a time using a threshold having a value smaller than the threshold usually determined be a short time, and to further suppress an erroneous operation of the airbag device. For example, in a case where a collision prediction time to a collision with the host vehicle can be predicted, the side collision prediction device determines the predicted collision prediction time as a predetermined time, whereby it is possible to perform control using a threshold having a small value for a short time.

In the occupant protection device according to the first aspect of the present disclosure, the side collision prediction device may be configured to output a prediction result including a predicted collision position in a case where the collision is the inevitable collision. The physical quantity detection device may be configured to detect a lateral acceleration in a vehicle part according to the predicted collision position as the physical quantity and outputs the detection value.

According to the first aspect of the present disclosure, the lateral acceleration is detected in the vehicle part according to the predicted collision position of the inevitable collision, whereby it is possible to detect an acceleration caused by the inevitable collision at an optimum position. Although a vehicle part where variation in the lateral acceleration appears changes according to a collision position, it is possible to obtain in advance a correspondence relationship between a collision position and a vehicle part where variation in acceleration appears due to a collision at the collision position. For this reason, a vehicle part optimum for detecting the acceleration is determined with the collision at the predicted collision position, and the lateral acceleration is detected in the vehicle part according to the predicted collision position, whereby it is possible to detect an optimum physical quantity.

In the occupant protection device according to the first aspect of the present disclosure, the physical quantity detection device may be configured to, in a case where the predicted collision position is a front fender portion of the host vehicle, detect the lateral acceleration in a central portion of the host vehicle. The physical quantity detection device may be configured to, in a case where the predicted collision position is a cabin portion of the host vehicle, detect the lateral acceleration in a side portion of the host vehicle.

According to the first aspect of the present disclosure, in a case where the predicted collision position of the inevitable collision is the front fender portion of the host vehicle, the lateral acceleration is detected in the central portion of the host vehicle. In a case of the collision with the front fender portion, for example, a detection value of the lateral acceleration in the central portion of the host vehicle is detected to be greater than a detection value of the lateral acceleration in a side portion near the cabin of the host vehicle. Accordingly, it is possible to obtain a detection value sufficient for performing control for operating the airbag device in a case of the collision with the front fender portion. In a case where the predicted collision position of the inevitable collision is the cabin portion of the host vehicle, the lateral acceleration of the host vehicle is detected in the side portion of the host vehicle. It is preferable that the side portion of the host vehicle is a side portion near the cabin. In a case of the collision with the cabin portion of the host vehicle, variation in the lateral acceleration of the host vehicle remarkably appears in the side portion of the host vehicle. Accordingly, it is possible to obtain a detection value sufficient for performing control for operating the airbag device in a case of the collision with the cabin portion. Then, the side portion near the cabin is determined as the vehicle part, whereby it is possible to obtain a more preferable detection value.

In the occupant protection device according to the first aspect of the present disclosure, the side collision prediction device may be configured to output a prediction result including a predicted relative speed of a collision prediction object and the host vehicle in a case where determination is made that the collision is the inevitable collision. The electronic control unit may be configured to perform the second control in a case where the predicted relative speed is equal to or higher than a predetermined speed determined in advance.

According to the first aspect of the present disclosure, as a condition of performing the control for operating the airbag device, a case where the predicted relative speed is equal to or higher than the predetermined speed determined in advance is added to the conditions. For this reason, it is possible to suppress an erroneous operation at the time of a minor collision or the like that is likely to occur in a case of operating the airbag device using a threshold having a small value.

In the occupant protection device according to the first aspect of the present disclosure, the side collision prediction device may be configured to output a prediction result including a predicted relative speed of a collision prediction object and the host vehicle in a case where determination is made that the collision is the inevitable collision. The electronic control unit may be configured to, in the second control, delay a timing of operating the airbag device by a delay time determined based on the predicted relative speed from when the detection value exceeds a value smaller than the second threshold.

According to the first aspect of the present disclosure, the timing of operating the airbag device is delayed by the delay time determined based on the predicted relative speed. For example, in a case where the operation timing is too early, the airbag device cannot obtain the internal pressure of the airbag effective for occupant protection. In a case where the operation timing is too late, sufficient airbag expansion cannot be obtained. Accordingly, the timing of operating the airbag device is adjusted according to the delay time determined based on the predicted relative speed, for example, is adjusted such that the higher the predicted relative speed, the shorter the delay time, whereby it is possible to operate the airbag device at a timing effective for occupant protection, and to improve occupant protection performance.

In the occupant protection device according to the first aspect of the present disclosure, the side collision prediction device may be configured to output information indicating that the side collision prediction device is operated normally. The electronic control unit may be configured to, in a case where the side collision prediction device is operated normally, perform control for operating the airbag device.

According to the first aspect of the present disclosure, a case where the side collision prediction device is operated normally is added to the conditions, and the control for operating the airbag device is performed. For this reason, it is possible to suppress an erroneous operation due to abnormal data or the like in a case where the side collision prediction device is not operated normally, for example, in a case where the side collision prediction device is stopped or abnormal.

A second aspect of the present disclosure relates to an occupant protection method for a vehicle. The occupant protection method includes, with an electronic control unit, predicting a collision with a side of a host vehicle and outputting a prediction result including determination about whether or not the predicted collision is an inevitable collision; detecting a physical quantity related to the collision with the side of the host vehicle and outputting a detection value; performing first control for operating an airbag device in a case where the detection value exceeds a first threshold, the airbag device being configured to expand to protect an occupant of the vehicle when the airbag device is operated; and in a case where determination is made that the prediction result is an inevitable collision, performing second control for operating the airbag device in a case where the detection value exceeds a second threshold for a predetermined time from the determination. The second threshold is smaller than the first threshold.

According to the second aspect of the present disclosure, in the physical quantity detection device, such as a sensor for a side surface collision, even in a case where the physical quantity that is smaller than a threshold usually determined is detected, it is possible to operate the airbag device at an optimum timing with respect to the collision with the side of the host vehicle while suppressing an erroneous operation of the airbag device.

As described above, according to the aspects of the present disclosure, it is possible to improve the occupant protection performance of a vehicle with a simple configuration.

