WO2000037284A1

WO2000037284A1 - Device for controlling an occupant protection means of a vehicle

Info

Publication number: WO2000037284A1
Application number: PCT/DE1999/004002
Authority: WO
Inventors: Thomas Stierle; Gerd Winkler; Lorenz Pfau; Michael Feser
Original assignee: Siemens Aktiengesellschaft
Priority date: 1998-12-18
Filing date: 1999-12-16
Publication date: 2000-06-29
Also published as: DE19858760A1

Abstract

The invention relates to a device for controlling an occupant protection means of a vehicle, comprising a pressure-sensitive sensor (1) for recognizing an impact-induced pressure change in a chamber arranged at the side of the vehicle as well as an acceleration sensor (2), also arranged at the side of the vehicle, for recording a transverse vehicle acceleration (g). An evaluation unit (3) evaluates the recorded pressure (p) and the recorded transverse acceleration (g). A firing unit (4) controls the occupant protection means (5) in accordance with the evaluated pressure (p) and acceleration (g).

Description

description

Device for controlling an occupant protection device of a vehicle

The invention relates to a device for controlling a vehicle occupant protection means according to the preamble of patent claim 1.

A known device (WO 94/11223) contains a pressure-sensitive sensor in a chamber arranged on the side of the vehicle to detect a pressure change in the chamber caused by an impact, and an evaluation unit for evaluating the pressure taken up.

The object of the invention is to achieve a rapid triggering of the occupant protection device in the event of a sufficiently strong impact and to prevent false triggering.

The object is achieved by the features of patent claim 1. An acceleration sensor for recording a vehicle lateral acceleration is arranged on the vehicle edge. To detect a side impact, the pressure-sensitive sensor is provided with a further sensor that detects an impact, but which detects an impact on the basis of another physical measurement principle. This minimizes the risk of false triggering if one of the two sensors fails. The associated occupant protection means are only triggered regularly if both sensors deliver impact-significant sensor signals. The occupant protection means is therefore not triggered if, for example, the vehicle side door is deformed greatly when it is opened and the pressure sensor therefore detects a change in pressure in the 'vehicle door' chamber. However, the lateral acceleration of the vehicle is so low that an evaluation unit provided for evaluation cannot determine any impact state information from the lateral acceleration Triggering, for example, a side airbag would justify. Another important advantage of the invention is that individual types of crash can now trigger the associated occupant protection means more quickly. For example, if a pile hits the B-pillar arranged between the front and rear doors of the vehicle, there is only a relatively small deformation of the side door. Accordingly, only a pressure signal with a correspondingly low amplitude can be received, which only reaches its maximum at relatively late times and thus fulfills a trigger criterion. In this case, the acceleration sensor will detect a strong, significant acceleration impact signal at relatively earlier times from the start of the impact, so that inflation of the side airbag can now be initiated much earlier. For different

Impact types, a combination of pressure detection and acceleration detection in the event of a side impact, provide the best possible protection for the occupant through extremely early impact detection as well as through the detection of a sensor defect and the subsequent blocking of an airbag trigger. An impact of a pile against a side door only causes a weak lateral acceleration signal in the vehicle center due to the low penetrating mass and the less stiffened vehicle body. With this type of impact, however, the pressure-sensitive sensor detects a significant impact to trigger within an extremely short time from the start of the impact. Due to the arrangement of the acceleration sensor on the side of the vehicle, i.e. preferably at / close to a vehicle side part, however, even in the event of such an impact, a signal — albeit only a weak one — is recognized at an early point in time, which signal can subsequently be used as confirmation for the impact-significant pressure signal.

An advantageous further development of the invention provides that the evaluation unit carries out the following classification when evaluating the recorded pressure and the recorded lateral acceleration: On the basis of the evaluation of the pressure and the -

3 Acceleration signal, the impact is classified into the following three classes for each signal:

1. No impact 2. Impact detected, but no statement as to whether the

Impact is sufficiently severe to trigger the occupant protection means (safing function) and 3. A sufficiently strong impact is detected to trigger.

The evaluation unit delivers the evaluation of the present pressure and / or acceleration signal in the form of an impact state information to the assigned ignition unit. The ignition unit advantageously triggers the assigned occupant protection means if an impact was recognized either on the basis of the evaluation of the acceleration, which justifies triggering the occupant protection means and at the same time allows the pressure signal to indicate an existing impact. Alternatively, the occupant protection means is triggered if the pressure signal suggests an impact that is sufficiently strong to trigger and at the same time at least one impact is recognized on the basis of the acceleration signal. This type of sensor signal processing keeps open which of the two impact sensors ultimately makes the actual triggering decision. The other sensor must then take over the function of a safing sensor in order to trigger it and see a minimum strength in its signal which speaks at least for the presence of an impact. This free trigger design alone enables all different types of side impact to be recognized quickly and leads to the occupant protection device being triggered at an early stage.

It is necessary that the acceleration sensor is arranged on the vehicle edge. This means that an acceleration, albeit with a low signal amplitude, is recognized in the case of strongly invasive types of impact with a small penetration area, so that the acceleration sensor at least as a safing sensor can be used and provides a signal early. On the other hand, the acceleration sensor will provide a significant signal at early times, especially in the case of impact hits with only a slight overlap of the vehicle door, i.e. in the case of impact hits on rigid body components such as pillars and cross members, which can then initiate a triggering of the occupant protection means. Nevertheless, with these types of impacts, the pressure sensor delivers a pressure rise signal at an early point in time, albeit with a low amplitude, which is, however, sufficient in any case for the pressure sensor to be used as a safing sensor. The invention increases protection for the occupant with regard to short triggering times and safe triggering decisions in the case of many different types of impact, while at the same time avoiding the risk of incorrect triggering due to failure of a sensor or the incorrect evaluation of a single sensor signal.

Further advantageous developments of the invention are characterized by the subclaims.

The invention and its developments are explained in more detail with reference to exemplary embodiments in the drawing. Show it:

1 shows a block diagram of the device according to the invention, FIG. 2 shows a spatial arrangement of the sensors used in the invention in a motor vehicle, and FIG. 3 shows an ignition unit,

Figure 4, 5 acceleration and pressure waveforms with different types of impact.

FIG. 1 shows a block diagram of the invention with a pressure sensor 1, an acceleration sensor 2, an evaluation unit 3, an ignition unit 4, an occupant protection device 5 and a data line 6. The pressure sensor 1 delivers Pressure signal p to the evaluation unit 3. The acceleration sensor 2 supplies an acceleration signal g to the evaluation unit 3. The pressure sensor 1 is preferably designed as an air pressure sensor and arranged in an air-filled chamber on the vehicle side. The pressure sensor 1 is preferably arranged in a vehicle side part, such as the vehicle door. The space between the inner door panel and the outer skin can serve as a chamber. It is essential for the arrangement of the pressure sensor 1 that the medium in which it is arranged is significant in the event of a side impact

Changes in pressure. It is not necessary for the chamber to be hermetically sealed. Rather, slow pressure changes, e.g. caused by temperature fluctuation allowed inside the chamber. The pressure changes must not, however, be in the millisecond range that the

Represents time range for a significant impact signal to be compensated. The chamber can also be filled with a medium other than air, for example with a liquid, etc. It is essential that the chamber experiences a deformation in the event of a side impact and this deformation manifests itself in a pressure increase in the internal chamber pressure.

The acceleration sensor 2 can work according to different physical principles and can be designed as a piezoelectric, piezoresistive or capacitive acceleration sensor. The evaluation unit 3 is preferably a microprocessor and is also arranged on the vehicle edge. However, the evaluation unit 3 can also be designed as a circuit with preferably integrated components, etc. The acceleration sensor 2 and the evaluation unit 3 can be arranged in a common housing. The pressure sensor is preferably also arranged in this common housing, the housing then containing a pressure transmission element for the transmission of pressure changes to the pressure sensor. The evaluation unit 3 evaluates the delivered acceleration g and the supplied pressure p. If the evaluation unit 3 contains only a single processor, the algorithm Mixing evaluation of the sensor signals achieved by a quasi-parallel operation of this microprocessor. However, the evaluation unit can also contain two processors, one each for evaluating a single sensor signal. Each processor can then be connected to the ignition unit via its own data line or connected to a common data bus for connection to the ignition unit.

A low-pass filter for smoothing each sensor signal is preferably connected upstream of the microprocessor or implemented in the microprocessor as software. In the following, for the evaluation of the pressure signal p as well as for the evaluation of the acceleration signal g, an algorithmic processing rule is stored in the evaluation unit, which is carried out when a minimum pressure or a minimum acceleration is exceeded. The aim of each processing rule is to provide impact state information which states whether the pressure signal or the acceleration signal are designed in such a way that triggering of the associated occupant protection means is necessary. The processing instructions for the pressure and acceleration signals differ from each other since different physical quantities are measured, which behave differently in the same impact. The processing instructions lead e.g. Threshold value comparisons by or determine the steepness of the signal. In addition, the evaluation unit 3 contains further processing instructions which, as a result, provide collision status information which states whether there is an collision at all. These processing instructions result in a so-called safing function. The aim of this processing instruction is therefore not to identify an impact that is sufficiently strong to trigger and to indicate the best possible ignition timing, but rather to be able to state at an early point in time whether an impact of any kind that does not necessarily trigger the associated one

Protective agent must lead, is present or not. The low-pass filtered sensor signal is preferably used with a Threshold value compared and if the threshold value is exceeded, the corresponding impact state information is issued. Here, too, the processing instructions for the pressure signal differ from the processing instructions for the acceleration signal.

The evaluation unit 3 thus contains at least four processing instructions which differ from one another, the processing instructions for pressure and acceleration differing from one another, as well as the processing instructions for the triggering function and the safety function. As a result, the evaluation unit 3 can accordingly deliver four impact states AZF1 to AZF4. The evaluation unit 3 can, however, also deliver more than four impact state variables, provided that this is useful for the drawing of the occupant protection system.

According to FIG. 1, the evaluation unit 3 is connected to the ignition unit 4 via a data line 6. An ignition unit 4 is shown by way of example in FIG. 3. The ignition unit 4 contains a physical interface 41 and a logical interface 42 for decrypting the m coded form transmitted data signals AZF1 to AZF. The logical interface can also be designed as a microprocessor and can take over further processing routines. According to FIG. 3, an ignition element 51 assigned to the occupant protection means - for example a side airbag or a head airbag - is connected via lines and two power stages 43 and 44 to an energy source U _BA τ. The interface 42 controls the power stages 43 and 44 via ignition signals fl and f2 in the event of an impact. In this case, for example, the ignition signal fl is generated by the interface 42 when the second or fourth impact state information AZS2 or AZS4 is transmitted by the evaluation unit 3, that is to say those impact state information ÄZS which require the occupant protection means 5 to be ignited. The ignition signal f2 is always output as soon as the interface 42 the first or the receives third impact state information AZS 1 or AZS3 from the evaluation unit 3. This impact state information AZS states that at least one impact of any kind is recognized and results, for example, from a threshold value comparison of the recorded acceleration or the recorded pressure signal with a relatively low threshold value. The interface 42 is designed such that the ignition signal f2 must be based on a pressure evaluation if the ignition signal fl is based on an acceleration evaluation and vice versa. The ignition unit 4 can also be arranged together with the evaluation unit 3 on the vehicle edge, preferably in the same housing.

FIG. 2 shows a symbolically represented motor vehicle in a side view, from which the arrangement of sensors 1 and 2 can be seen. A pressure sensor 1 is arranged in each of the vehicle side doors. The acceleration sensors 2 are arranged on the vehicle sills of the A and B pillars. Each vehicle door is assigned its own evaluation unit. Each sensor combination of acceleration sensor and pressure sensor of a vehicle door is therefore responsible for triggering the occupant protection means assigned to this vehicle door or to this vehicle seat.

FIGS. 4 and 5 show exemplary signal profiles of a recorded pressure p and a recorded acceleration g over time, nominated to uniform reference values. FIG. 4 shows signal profiles resulting from a side impact with a high impact speed, FIG. 5 shows signal profiles resulting from a pole impact on the B-pillar. It is clear here that in the impact according to FIG. 4, the impact status information AZF1, that is to say the safing signal based on the acceleration evaluation, is supplied first, followed by the impact status information AZF2, which provides the triggering decision based on the pressure evaluation. In the impact according to FIG. A small increase in pressure is sufficient to provide the impact state information AZF3, i.e. the safing signal based on the pressure evaluation, whereas a short time later the impact state information AZF4 is delivered, which is based on the algorithmic acceleration evaluation and has classified the impact as sufficiently strong to trigger it . It is significant that, in the impact according to FIG. 4, a trigger decision based on the algorithmic evaluation of the acceleration would only have triggered at a much later point in time. In contrast, in the case of the impact according to FIG. 5, an algorithmic evaluation of the pressure signal, due to its low level, might not have triggered until a late point in time.

Claims

claims

1. Device for controlling an occupant protection means of a vehicle, - with a pressure-sensitive sensor (1) for detecting a pressure change caused by an impact in a chamber arranged on the vehicle edge, and

with an evaluation unit (3) for evaluating the recorded pressure (p), characterized in that - an acceleration sensor (2) for recording a lateral vehicle acceleration (g) is arranged on the vehicle side,

- That the evaluation unit (3) is designed for evaluating the transverse acceleration (g) recorded, and - that an ignition unit (4) is provided for controlling the occupant protection means (5) depending on the evaluated pressure (p) and the evaluated acceleration (g) .

2. Device according to claim 1, characterized in that the evaluation unit (3) is arranged on the vehicle edge.

3. Apparatus according to claim 1 or claim 2, characterized in that the evaluation unit (3) is designed to output a first impact state information (AZS1), which is provided when an acceleration change is detected, and a second impact state information (AZS2), which is delivered if a sufficient change in pressure to trigger the occupant protection means (5) is detected,

4. Device according to one of the preceding claims, characterized in that the evaluation unit (3) is designed for output third impact state information (AZS3), which is provided when a pressure change is detected, and fourth impact state information (AZS4), which is provided when an acceleration change sufficient to trigger the occupant protection means (5) is detected.

5. The device according to claim 3, characterized in that the ignition unit (4) is designed to trigger the occupant protection means (5) when the first and second impact state information (AZS1, AZS2) are present.

6. The device according to claim 4, characterized in that the ignition unit (4) is designed to trigger the occupant protection means (5) when the third and fourth impact state information (AZS3, AZS4) are present.

7. Device according to claims 3 to 6, characterized in that the ignition unit (4) is designed to trigger the occupant protection means (5) when the first and the second impact state information (AZS1, AZS2) or the third and fourth impact state information (AZS3 , AZS4) are available.

8. Device according to one of claims 2 to 7, characterized in that the ignition unit (5) is arranged at a distance from the evaluation unit (4), that the evaluation unit (4) via a data line (6) with the Ignition unit (5) is connected, and that the evaluation unit (4) is designed to transmit the impact state information (AZS) in coded form.

9. Device according to one of the preceding claims, characterized in that the pressure sensor (1), the acceleration sensor (2) and the evaluation unit (4) are arranged in a common housing.

10. Device according to one of the preceding claims, characterized in that a pressure sensor (1) and an acceleration sensor (2) are provided for each vehicle door.