Vehicle attitude angle detection device

Abstract

To provide a vehicle attitude angle detection device which can suppress cost at cheap price as the whole vehicle while making it possible to detect a vehicle attitude angle as accurately as conventional vehicle height sensor type and G sensor type detection devices.SOLUTION: A front part of a vehicle 2 is attached with front G sensors 11L, 11R which detect acceleration along a longitudinal direction and a vertical direction of the vehicle 2 as a detection axis. In addition, a rear part of the vehicle 2 is attached with C-pillar G sensors 13L, 13R which detect acceleration along a lateral direction and the vertical direction of the vehicle 2 as a detection axis. To detect a vehicle attitude angle of the vehicle 2, double integral value of the acceleration in the vertical direction which is detected by the front G sensors 11L, 11R and double integral value of the acceleration in the vertical direction which is detected by the C-pillar G sensors 13L, 13R are determined. Then, the vehicle attitude angle is calculated from these double integral values.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a device for detecting a vehicle attitude angle, which is the attitude angle in the pitch direction of a vehicle. [Background technology]

[0002] BACKGROUND ART Conventionally, auto-leveling control is known that automatically adjusts the optical axis of a headlamp in accordance with the vehicle attitude angle (inclination angle around an axis extending in the left-right direction).

[0003] Auto-leveling control requires the detection of the vehicle attitude angle. Methods for detecting the vehicle attitude angle include vehicle height sensor and G sensor methods. With the vehicle height sensor method, for example, vehicle height sensors attached to the front and rear suspensions detect the vertical displacement (sinking amount) of the front and rear suspensions, and the vehicle attitude angle is calculated from these displacement amounts. With the G sensor method, a G sensor attached to the vehicle body detects vector changes in the longitudinal and vertical directions of gravitational acceleration, and the vehicle attitude angle is calculated from these vector changes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-116201 Summary of the Invention [Problem to be solved by the invention]

[0005] The vehicle height sensor type has good detection accuracy for vehicle attitude angle, but has the problem that the vehicle height sensor is heavy and expensive.On the other hand, to improve the detection accuracy of the vehicle attitude angle, the G sensor type needs to correct the error (offset) in the installation position of the G sensor and its sensitivity, and as a means for doing so, a G sensor with detection axes in the left-right direction in addition to the front-back and up-down directions is required, which increases the cost.

[0006] An object of the present invention is to provide a vehicle attitude angle detection device that can detect a vehicle attitude angle with the same accuracy as conventional vehicle height sensor and G sensor types, while keeping the cost of the entire vehicle low. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, a vehicle attitude angle detection device according to the present invention is a device for detecting a vehicle attitude angle, which is an attitude angle in a pitch direction of a vehicle, and includes: a front acceleration sensor attached to the front of the vehicle and detecting acceleration with the longitudinal and vertical directions of the vehicle as detection axes; a rear acceleration sensor attached to the rear of the vehicle and detecting acceleration with the lateral and vertical directions of the vehicle as detection axes; and a calculation unit that calculates the vehicle attitude angle from the difference between a double integral value of the vertical acceleration detected by the front acceleration sensor and a double integral value of the vertical acceleration detected by the rear acceleration sensor.

[0008] According to this configuration, a front acceleration sensor is attached to the front of the vehicle to detect acceleration with the longitudinal and vertical directions of the vehicle as detection axes, and a rear acceleration sensor is attached to the rear of the vehicle to detect acceleration with the lateral and vertical directions of the vehicle as detection axes.

[0009] The double integral value of the vertical acceleration detected by the front acceleration sensor and the double integral value of the vertical acceleration detected by the rear acceleration sensor are calculated. The double integral value of the acceleration corresponds to the amount of displacement. Therefore, the double integral value of the vertical acceleration detected by the front acceleration sensor corresponds to the amount of vertical displacement at the mounting position of the front acceleration sensor. Furthermore, the double integral value of the vertical acceleration detected by the rear acceleration sensor corresponds to the amount of vertical displacement at the mounting position of the rear acceleration sensor. Therefore, the vehicle attitude angle can be calculated from the double integral value of the vertical acceleration detected by the front acceleration sensor and the double integral value of the vertical acceleration detected by the rear acceleration sensor.

[0010] By providing the front acceleration sensor and rear acceleration sensor on the left and right sides, respectively, it is possible to detect the amount of vertical displacement at each mounting position of the front acceleration sensor and rear acceleration sensor, thereby making it possible to detect the vehicle attitude angle with the same accuracy as conventional vehicle height sensor and G sensor types.

[0011] Since the front acceleration sensor can detect acceleration in the front-rear direction, it can also be used as a G sensor for controlling airbag deployment in the event of a frontal collision of the vehicle. In other words, the G sensor for controlling airbag deployment in the event of a frontal collision of the vehicle can also be used as a front acceleration sensor.

[0012] In addition, since the rear acceleration sensor can detect acceleration in the left and right direction, it can also be used as a G sensor for controlling airbag deployment in the event of a side collision of the vehicle. In other words, the G sensor for controlling airbag deployment in the event of a side collision of the vehicle can also be used as a rear acceleration sensor.

[0013] Therefore, even if the vehicle attitude detection device is installed in the vehicle, the cost of the entire vehicle can be kept low.

[0014] It is preferable that the calculation unit continues the double integral calculation of the vertical acceleration detected by the front acceleration sensor and the rear acceleration sensor until a certain time has elapsed from the start of the double integral calculation, and calculates the vehicle attitude angle from each double integral value at the time when the certain time has elapsed.

[0015] This allows the vertical displacement of the front acceleration sensor and the rear acceleration sensor to be detected at their respective mounting positions after the vertical displacement of the vehicle has settled down when a person gets in or luggage is loaded onto the vehicle, thereby enabling the vehicle attitude angle to be detected with high accuracy. [Effects of the Invention]

[0016] According to the present invention, the vehicle attitude angle can be detected with the same accuracy as conventional vehicle height sensor and G sensor types, while the cost of the entire vehicle can be kept low. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram showing the configuration of an airbag system having the function of a vehicle attitude angle detection device according to an embodiment of the present invention, and also shows a plan view of a vehicle equipped with the airbag system. FIG. [Figure 2] FIG. [Figure 3] 10 is a flowchart showing a flow of a vehicle attitude angle detection process. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0019] <Vehicle main components> Fig. 1 is a block diagram showing the configuration of an airbag system 1 having the function of a vehicle attitude angle detection device according to one embodiment of the present invention, along with a plan view of a vehicle 2 equipped with the airbag system 1. Fig. 2 is a side view of the vehicle 2.

[0020] The airbag system 1 is mounted on a vehicle 2 and is a system for protecting an occupant from an impact when the vehicle 2 is subjected to an impact due to a collision.

[0021] Front door openings and rear door openings are formed at the front and rear of the left and right side surfaces of the vehicle 2. Also, on the left and right side surfaces of the vehicle 2, front doors 3L, 3R are provided so as to be able to open and close the left and right front door openings, respectively, and rear doors 4L, 4R are provided so as to be able to open and close the left and right rear door openings, respectively.

[0022] As part of its framework, the vehicle 2 has A-pillars 6L, 6R between the windshield 5 and the left and right front door openings, B-pillars 7L, 7R between the left and right front door openings and the rear door openings, and C-pillars 8L, 8R along the rear ends of the left and right rear door openings.

[0023] Front G sensors 11L and 11R are disposed at the left and right front portions of the vehicle 2. The front G sensors 11L and 11R are biaxial acceleration sensors that detect acceleration with the longitudinal direction and the vertical direction as detection axes. Because the front G sensors 11L and 11R use the longitudinal direction as their detection axis, they can detect longitudinal acceleration in the event of a frontal collision of the vehicle 2.

[0024] B-pillar G-sensors 12L, 12R are disposed at the bottom of the left and right B-pillars 7L, 7R, respectively. The B-pillar G-sensors 12L, 12R are uniaxial acceleration sensors that detect acceleration with the left-right (lateral) direction as their detection axis. Because the B-pillar G-sensors 12L, 12R use the left-right direction as their detection axis, they can detect lateral acceleration in the event of a side collision of the vehicle 2.

[0025] C-pillar G-sensors 13L, 13R are disposed at the bottom of the left and right C-pillars 8L, 8R, respectively. The C-pillar G-sensors 13L, 13R are biaxial acceleration sensors that detect acceleration using the left-right and up-down directions as their detection axes. Because the C-pillar G-sensors 13L, 13R use the left-right direction as their detection axis, they can detect lateral acceleration during a side collision of the vehicle 2.

[0026] The airbag system 1 includes an airbag control unit 14. The airbag control unit 14 includes a microcomputer (microcontroller unit), which includes, for example, a CPU, a nonvolatile memory such as a flash memory, and a volatile memory such as a DRAM (Dynamic Random Access Memory).

[0027] Airbags 15 are also provided in the passenger compartment of the vehicle 2. The airbags 15 include a driver's seat airbag that protects the head and chest of a person sitting in the driver's seat in the event of a frontal collision of the vehicle 2, a passenger's seat airbag that protects the head and chest of a person sitting in the passenger seat in the event of a frontal collision of the vehicle 2, and side airbags that protect the chest and abdomen of people sitting in the driver's seat, passenger seat, and rear seats in the event of a side collision of the vehicle 2.

[0028] The airbag control unit 14 controls the deployment of the airbag 15 based on detection signals input from the front G sensors 11L, 11R, the B-pillar G sensors 12L, 12R, and the C-pillar G sensors 13L, 13R. The airbag 15 is equipped with an inflator. The inflator is equipped with a squib (ignition device) and a drive circuit that drives the squib. An ignition control signal is output from the airbag control unit 14 to the drive circuit. When the squib ignites in accordance with the ignition control signal, high-pressure gas is generated by ignition of a gas generating agent, and the airbag 15 is instantly inflated (deployed).

[0029] The airbag control unit 14 incorporates the function of a vehicle attitude angle detection device that detects the attitude angle of the vehicle 2 in the pitch direction, that is, the vehicle attitude angle which is the tilt angle around an axis extending in the left-right direction.

[0030] A headlamp unit 16 is also connected to the airbag control unit 14. The headlamp unit 16 includes a headlamp (headlight) provided at the front of the vehicle 2, a headlamp lighting circuit, a leveling mechanism that adjusts the optical axis of the headlamp, and a controller that controls the leveling mechanism.

[0031] <Vehicle attitude angle detection processing> FIG. 3 is a flowchart showing the flow of the vehicle attitude angle detection process.

[0032] In order to detect the vehicle attitude angle of the vehicle 2, the airbag control unit 14 performs a vehicle attitude angle detection process.

[0033] The detection of the vehicle attitude angle of the vehicle 2 is performed when the vehicle 2 is stopped. Therefore, if the vehicle 2 is not stopped (NO in step S1), the vehicle attitude angle detection process does not proceed to the next step. Vehicle speed information is input to the airbag control unit 14, and it is determined whether the vehicle 2 is stopped or not based on the vehicle speed information.

[0034] When the vehicle 2 is stopped (YES in step S1), when the airbag control unit 14 receives a detection signal of vertical acceleration (vertical G) from at least one of the front G sensors 11L, 11R and the C-pillar G sensors 13L, 13R, the airbag control unit 14 starts calculating the double integral of the detected vertical acceleration (step S2).

[0035] Thereafter, it is determined whether a certain time has elapsed since the start of the double integral calculation (step S3). Until the certain time has elapsed since the start of the double integral calculation, the double integral calculation of the vertical acceleration detected by the front G sensors 11L, 11R and the C-pillar G sensors 13L, 13R continues.

[0036] When a certain time has elapsed since the start of the double integral calculation (YES in step S3), the difference between the double integral value of the vertical acceleration detected by the front G sensors 11L, 11R and the double integral value of the vertical acceleration detected by the C-pillar G sensors 13L, 13R is calculated. In calculating this difference, for example, the difference between the average value of the double integral values ​​of the vertical acceleration detected by the left and right front G sensors 11L, 11R and the average value of the double integral values ​​of the vertical acceleration detected by the left and right C-pillar G sensors 13L, 13R is obtained. Then, from the relationship between the calculated difference and the wheelbase (known) of the vehicle 2, the vehicle attitude angle, which is the attitude angle in the pitch direction of the vehicle 2, is calculated (step S4).

[0037] Then, the airbag control unit 14 transmits the vehicle attitude angle to the headlamp unit 16 as vehicle tilt angle information for optical axis control (step S5), and the vehicle attitude angle detection process ends. When the headlamp unit 16 receives the vehicle tilt angle information, a controller provided in the headlamp unit 16 controls a leveling mechanism, and the optical axis of the headlamp is automatically adjusted according to the vehicle tilt angle.

[0038] <Action and effect> As described above, the front G sensors 11L, 11R are attached to the front of the vehicle 2 to detect acceleration with the longitudinal and vertical directions of the vehicle 2 as detection axes. In addition, the C-pillar G sensors 13L, 13R are attached to the rear of the vehicle 2 to detect acceleration with the lateral and vertical directions of the vehicle 2 as detection axes.

[0039] To detect the vehicle attitude angle of the vehicle 2, a double integral value of the vertical acceleration detected by the front G sensors 11L, 11R and a double integral value of the vertical acceleration detected by the C-pillar G sensors 13L, 13R are calculated. The double integral value of the acceleration corresponds to the amount of displacement. Therefore, the double integral value of the vertical acceleration detected by the front G sensors 11L, 11R corresponds to the amount of vertical displacement at the mounting positions of the front G sensors 11L, 11R. Furthermore, the double integral value of the vertical acceleration detected by the C-pillar G sensors 13L, 13R corresponds to the amount of vertical displacement at the mounting positions of the C-pillar G sensors 13L, 13R. Therefore, the vehicle attitude angle can be calculated from the double integral value of the vertical acceleration detected by the front G sensors 11L, 11R and the double integral value of the vertical acceleration detected by the C-pillar G sensors 13L, 13R.

[0040] By providing the front G sensors 11L, 11R and the C-pillar G sensors 13L, 13R on the left and right sides, respectively, it is possible to detect the amount of vertical displacement at each mounting position of the front G sensors 11L, 11R and the C-pillar G sensors 13L, 13R, and therefore it is possible to detect the vehicle attitude angle with the same accuracy as conventional vehicle height sensor and G sensor types.

[0041] The front G sensors 11L, 11R are used as acceleration sensors for detecting the vehicle attitude angle, and because they can detect acceleration in the longitudinal direction, they are also used as G sensors for controlling airbag deployment in the event of a frontal collision of the vehicle 2. In other words, the front G sensors 11L, 11R are G sensors for controlling airbag deployment in the event of a frontal collision of the vehicle 2, and because they can detect acceleration in the vertical direction, they are also used as acceleration sensors for detecting the vehicle attitude angle.

[0042] Furthermore, the C-pillar G-sensors 13L, 13R are used as acceleration sensors for detecting the vehicle attitude angle, and because they can detect acceleration in the left-right direction, they are also used as G-sensors for controlling airbag deployment in the event of a side collision of the vehicle 2. In other words, the C-pillar G-sensors 13L, 13R are G-sensors for controlling airbag deployment in the event of a side collision of the vehicle 2, and because they can detect acceleration in the up-down direction, they are also used as acceleration sensors for detecting the vehicle attitude angle.

[0043] Therefore, even if the vehicle attitude detection device is installed in the vehicle 2, the cost of the vehicle 2 as a whole can be kept low.

[0044] The airbag control unit 14 continues the double integral calculation of the vertical acceleration detected by the front G sensors 11L, 11R and the C-pillar G sensors 13L, 13R until a certain time has elapsed from the start of the double integral calculation, and calculates the vehicle attitude angle from each double integral value at the time the certain time has elapsed.

[0045] As a result, when a person gets in or luggage is loaded into the vehicle 2, the amount of vertical displacement at each mounting position of the front G sensors 11L, 11R and the C-pillar G sensors 13L, 13R can be detected after the vertical displacement of the vehicle 2 has settled, thereby enabling the vehicle attitude angle to be detected with high accuracy.

[0046] <Modification> Although one embodiment of the present invention has been described above, the present invention can be embodied in other forms.

[0047] For example, the acceleration sensors (front acceleration sensors, rear acceleration sensors) for detecting the vehicle attitude angle are not limited to the front G sensors 11L, 11R and the C-pillar G sensors 13L, 13R, as long as they are acceleration sensors attached near the front, rear, left and right suspensions of the vehicle 2 and can detect acceleration in the vertical direction.

[0048] In addition, various design modifications can be made to the above-described configuration within the scope of the claims. [Explanation of symbols]

[0049] 2: Vehicle 11L, 11R: Front G sensor (front acceleration sensor) 13L, 13R: C-pillar G sensor (rear acceleration sensor) 14: Airbag control unit (vehicle attitude angle detection device, calculation unit)

Claims

1. A device for detecting a vehicle attitude angle, which is an attitude angle in a pitch direction of a vehicle, a front acceleration sensor attached to a front portion of the vehicle and detecting acceleration with a longitudinal direction and a vertical direction of the vehicle as detection axes; a rear acceleration sensor attached to a rear portion of the vehicle, for detecting acceleration with detection axes in the left-right direction and the up-down direction of the vehicle; a calculation unit that calculates the vehicle attitude angle from a difference between a double integral value of the acceleration in the vertical direction detected by the front acceleration sensor and a double integral value of the acceleration in the vertical direction detected by the rear acceleration sensor when the vehicle is stopped.

2. 2. The vehicle attitude angle detection device according to claim 1, wherein the calculation unit continues the double integral calculation of the vertical accelerations detected by the front acceleration sensor and the rear acceleration sensor until a predetermined time has elapsed from the start of the double integral calculation, and calculates the vehicle attitude angle from each double integral value at a time point when the predetermined time has elapsed.

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