WO2002034579A1

WO2002034579A1 - Control circuit for at least one occupant protection means and corresponding test method

Info

Publication number: WO2002034579A1
Application number: PCT/DE2000/003796
Authority: WO
Inventors: Ernst Futterlieb; Claus Schmidt
Original assignee: Siemens Aktiengesellschaft
Priority date: 2000-10-25
Filing date: 2000-10-25
Publication date: 2002-05-02

Abstract

The invention relates to a control circuit for at least one occupant protection means (8) in a motor vehicle. Said control circuit comprises several sensors (1, 2, 3) that each detect a state quantity of the motor vehicle, a first evaluation unit (5), which is connected to the sensors (1, 2, 3) on the input side and which is provided for generating a first firing signal (FIRE1) for activating the occupant protection means (8) according to the detected state quantities, and comprises a second evaluation unit (6), which is connected to the sensors (1, 2, 3) on the input side and which is provided for generating a second firing signal (FIRE2) for activating the occupant protection means (8) according to the detected state quantities. The first evaluation unit (5) and the second evaluation unit (6) are connected to the occupant protection means (8) on the output side via a logic circuit (11), which triggers the occupant protection means (8) when both the first firing signal (FIRE1) as well as the second firing signal (FIRE2) are present.

Description

description

Control circuit for at least one occupant protection device and associated test method

The invention relates to a control circuit for at least one occupant protection means in a motor vehicle according to the preamble of claim 1 and an associated test method according to claim 8.

In modern motor vehicles, occupant protection means such as airbags, sidebags or belt tensioners are used to reduce the severity of injuries to the occupants that occur in the event of an accident. The occupant protection means are triggered here by a plurality of acceleration sensors, which are located in the

Motor vehicle are arranged and measure the acceleration occurring in an accident in each case in a predetermined direction. Since the individual acceleration sensors have different spatial orientations, both the direction and the magnitude of the acceleration can be calculated from the output signals of the acceleration sensors, the occupant protection means being activated when the magnitude of the acceleration exceeds a predetermined limit value (e.g. 10 g).

A control circuit is known from German published patent application DE 196 45 952 A1 which evaluates the ess signals of a plurality of acceleration sensors in order to recognize an accident in the motor vehicle and activates the occupant protection means as a function of the measurement signals. Furthermore, it is known from this document to subject the measurement signals of the various acceleration sensors to a plausibility test in order to detect a malfunction of individual sensors or the control circuit. If the various acceleration sensors are arranged in a star shape in one plane, for example, the sum of the positive and negative accelerations measured by the acceleration sensors must be be zero. If the sum signal of the acceleration sensors deviates from this value, then there is a malfunction of one or more of the sensors or also of the control unit itself. The known plausibility check of the measurement signals generated by the acceleration sensors described above thus advantageously enables the detection of a malfunction of the sensors or the evaluation unit analyzing the measurement signals of the acceleration sensors for accident detection.

However, the known plausibility check only enables a test on the sensor side of the evaluation unit, whereas errors on the actuator side of the evaluation unit remain undetected. For example, it is possible that an ignition switch for an occupant protection device is defective, so that the occupant protection device is not ignited in the event of an accident, although the evaluation unit detects an accident on the basis of the sensor signals. Another possible error on the actuator side is that the data transmission from the evaluation unit for the sensors to the ignition switches of the occupant protection means is disturbed. In the event of an accident, this can result in the occupant protection means not triggering, even though the evaluation unit emits an ignition signal for the sensors. In addition, if the data transmission between the evaluation unit and the ignition switches for the occupant protection means is disturbed, there is a risk of an occupant protection means being incorrectly triggered.

The invention is therefore based on the object of providing a control circuit for occupant protection means in a motor vehicle which offers increased security against errors on the actuator side.

The invention is based on the known control circuit described above according to the preamble of claim 1, by the characterizing features of claim 1 and. - With regard to a self-test procedure - solved by the features of claim 8.

The invention includes the general technical teaching for triggering the occupant protection means provide two inde ^{¬-independent} evaluation units from each other, each generating an OFF solvent signal, wherein the trigger signals generated by the two evaluation units are linked by a logic circuit in such a manner that the occupant protection means only trigger when both trigger signals are present. In this way, it is largely prevented that disruptions in the data transmission from the evaluation units to the occupant protection means lead to incorrect triggering of the occupant protection means, since it is extremely unlikely that a corresponding disturbance will occur simultaneously in both evaluation units.

In the preferred embodiment, the evaluation units do not control the occupant protection means directly, but via a controllable switching element, the controllable one

Switching element for feedback of the respective switching state is connected to the first evaluation unit and / or the second evaluation unit. This enables a self-test of the control circuit on the actuator side. For this purpose, one evaluation unit generates a trigger signal for the occupant protection means independently of the sensor signals, while the other evaluation unit blocks the release of a trigger signal independently of the sensor signals. Due to the AND linkage of the trigger signals generated by the two evaluation units, there is no triggering of the occupant protection means on the actuator side during the self-test. The switching state of the switching elements between the evaluation units and the occupant protection means is then queried and checked during the self-test. In this way, malfunctions in the data transmission from the evaluation units to the controllable switching elements for controlling the occupant protection means can be determined. Other advantageous further developments are characterized in the Unteransprü ^¬ or are explained in greater detail below together with the description of the preferred embodiment with reference to FIGS. Show it:

1 shows a control circuit according to the invention for occupant protection means in a motor vehicle as a block diagram, and FIGS. 2a-2d show a self-test method according to the invention

Flowchart as well

Figure 3 shows the arrangement of the acceleration sensors in a motor vehicle.

The control circuit shown in FIG. 1 has a plurality of acceleration sensors 1, 2, 3, which are arranged in a motor vehicle 4 in a horizontal plane at different angles to the longitudinal axis U of the motor vehicle 4, as can be seen from FIG. 3.

The acceleration sensors 1, 2, 3 are connected on the output side to two evaluation units 5, 6 which, from the measurement signals a _x , a _y , a _{z of} the acceleration sensors 1, 2, 3, produce the acceleration values a _u and a _v in the vehicle longitudinal direction U and in the vehicle transverse direction Calculate V according to the following formulas:

+ a _γ "cosZ (U, Y) + a _z 'cosZ (U, Z) a _v = a _χ -cosZ (V, X) + a _γ ' cosZ (V, Y) + a _z 'cos (V, Z)

The two evaluation units 5, 6 enable the triggering of a plurality of occupant protection devices via the associated ignition electronics, only one assembly 7 with an airbag 8 as the occupant protection device being shown in dashed lines in FIG. 1. The evaluation units 5, 6 can, however, independently of this, further assemblies with further occupant protection means such as, for example, sidebags, windowbags or control belt tensioners that are not shown for the sake of simplicity.

To activate the airbag 8, the assembly 7 has two controllable ignition switches 9, 10, which are controlled by the evaluation units 5 and 6 via a trigger signal FIRE1 and FIRE2, respectively, and connected on the output side to the airbag 8 via an AND element 11 are. The airbag 8 is only triggered when both the evaluation unit 5 and the evaluation unit 6 emit a trigger signal FIRE1 or FIRE2 to the ignition switches 9, 10. The AND combination of the two trigger signals FIRE1, FIRE2 offers the advantage that malfunctions in the data transmission between the evaluation units 5, 6 and the ignition switches 9, 10 do not lead to incorrect triggering. In addition, the AND linkage of the trigger signals FIRE1, FIRE2 prevents a malfunction in one of the two evaluation units 5, 6 from causing the airbag 8 to trigger incorrectly.

In addition, the circuit shown in FIG. 1 enables a self-test on the sensor side, as will be described below and is shown in FIGS. 2a and 2b. For this purpose, the control circuit 3 has excitation elements 12, 13, 14, each of which is assigned to one of the acceleration sensors 1, 2, 3 and enables separate mechanical excitation of the acceleration sensors 1, 2, 3 in order to simulate a malfunction of the remaining acceleration sensors. When the excitation element 12 is excited alone, only the acceleration sensor 1 detects an acceleration, whereas the acceleration sensors 2 and 3 do not detect any acceleration. The evaluation units 5 and 6 internally carry out a plausibility check in which it is checked whether the acceleration values a _x , a _y , a ₂ measured by the acceleration sensors 1, 2, 3 are consistent.

With proper functioning of the acceleration sensors 1, 2, 3 uss an excitation of a single acceleration Position sensor 1, 2 or 3 therefore lead to an incorrect plausibility check. The individual acceleration sensors 1, 2, 3 are therefore individually excited one after the other by the associated excitation elements 12, 13, 14, as shown in FIGS. 2a and 2b. Here lead the

Evaluation units 5, 6 each carry out a plausibility check in order to check whether the respective acceleration sensor 1, 2 or 3 is working correctly. If all acceleration sensors 1, 2, 3 are functioning properly, the plausibility check must show that the acceleration values a _x , a _y , a _z measured by the acceleration sensors 1, 2, 3 are not consistent.

In addition, the control circuit shown in FIG. 1 also enables testing on the actuator side, which is shown in the form of a flow chart in FIGS. 2c and 2d. For this purpose, the ignition switch 9 is connected to the evaluation unit 6 in order to enable feedback of the switching state of the ignition switch 9. Furthermore, the ignition switch 10 is connected to the evaluation unit 5 in order to transmit to the evaluation unit 5 a feedback signal FEEDBACK2 for the switching state of the ignition switch 10. At the beginning of the self-test for the actuator side of the control circuit, the evaluation unit 5 first transmits a control signal to the evaluation unit 6, so that the latter blocks the trigger signal FIRE2 so that the airbag 8 is prevented from being triggered during the self-test. The evaluation unit 5 then generates the trigger signal FIRE1 in order to switch on the ignition switch 9. The evaluation unit 6 then queries the feedback signal FEEDBACK1 from the ignition switch 9, which reflects the switching state of the ignition switch 9. The evaluation unit 6 then transmits the feedback signal FEEDBACK1 to the evaluation unit 5, which checks it. In the event of an error-free data transmission from the evaluation unit 5 to the ignition switch 9, the feedback signal must

FEEDBACKl indicate that the ignition switch 9 has ignited. In the event of incorrect data transmission from the evaluation 5 unit to the ignition switch 9 or in the event of a malfunction of the ignition switch 9, the feedback signal FEEDBACK1 indicates that the ignition switch 9 has not ignited.

After the test of the data transmission between the evaluation unit 5 and the ignition switch 9 described above, the data transmission between the evaluation unit 6 and the ignition switch 10 is then checked, which is shown in FIG. 2d in the form of a flow chart.

For this purpose, the evaluation unit 5 first blocks the release of the trigger signal FIRE1. The evaluation unit 5 then controls the evaluation unit 6 so that it generates the trigger signal FIRE2. The evaluation unit 5 then queries the feedback signal FEEDBACK2 from the ignition switch 10 and checks it. In the event of a correct data transmission between the evaluation unit 6 and the ignition switch 10, the feedback signal FEEDBACK2 must indicate that the ignition switch 10 has switched through. In the event of incorrect data transmission from the evaluation unit 6 to the ignition switch 10 or in the event of a malfunction of the ignition switch 10, the feedback signal FEEDBACK2, on the other hand, indicates that the ignition switch 10 has not switched through.

Finally, the two evaluation units are also connected to a configuration controller and peripheral sensors 15, for example to block an airbag deployment when a person is at a short distance in front of the airbag in order to prevent an occupant injury from an airbag deployment.

The invention is not restricted to the preferred exemplary embodiment described above. Rather, a multitude of variants and modifications are conceivable that make use of the inventive idea and therefore also fall within the scope of protection.

Claims

claims

1. Control circuit for at least one occupant protection means (8) in a motor vehicle (4), with

a plurality of sensors (1-3) each for detecting a state variable of the motor vehicle (4),

a first evaluation unit (5) connected on the input side to the sensors (1-3) for generating a first trigger signal (FIRE1) for activating the occupant protection device (8) as a function of the detected state variables {a _; , a _y , a _z ),

marked by

a second evaluation unit (6) connected on the input side to the sensors (1-3) for generating a second trigger signal (FIRE2) for activating the occupant protection means (8) as a function of the detected state variables

The first evaluation unit (5) and the second evaluation unit (6) are connected on the output side via a logic circuit (11) to the occupant protection means (8) which triggers the occupant protection means (8) when both the first trigger signal (FIRE1) and the second trigger signal (FIRE2) is present.

2. Control circuit according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the logic circuit is an AND gate (11).

3. Control circuit according to claim 1 or 2, characterized in that between the first evaluation unit (5) and the logic circuit (11) a controllable first switching element (9) is arranged to control the logic circuit (11), the first switching element (9) being connected to the first evaluation unit (5) and / or the second evaluation unit (6) for reporting the switching state.

4. Control circuit according to at least one of the preceding claims, characterized in that a controllable second switching element (10) for controlling the logic circuit (11) is arranged between the second evaluation unit (6) and the logic circuit (11), the second switching element ( 10) is connected to the first evaluation unit (5) and / or the second evaluation unit (6) for feedback of the switching state.

5. Control circuit according to at least one of the preceding claims, that the first evaluation unit (5) is connected to the second evaluation unit (6) in order to transmit control data.

6. Control circuit according to at least one of the preceding claims, that the first evaluation unit (5) and / or the second one

Evaluation unit (6) is connected to a control unit (15).

, Control circuit according to at least one of the preceding claims, characterized in that at least one excitation element (12-14) is provided to simulate a malfunction of one of the sensors (1-3), each of which only a single sensor (1-3) or only a part of the Excites sensors (1-3) and thereby simulates a malfunction of the other sensors (1-3), the excitation element (12-14) being triggered with the first evaluation unit. unit (5) and / or with the second evaluation unit (6).

8. Test method for a control circuit according to one of the preceding claims, with the following steps:

- Blocking the first trigger signal (FIRE1) by the first evaluation unit (5) or the second trigger signal (FIRE2) by the second evaluation unit (6) regardless of the state variables (a _x , a _y ) detected by the sensors (1-3) , a _z ) of the motor vehicle (4)

- Generation of either the second trigger signal (FIRE2) by the second evaluation unit (6) or the first trigger signal (FIRE1) by the first evaluation unit (5) independently of the state variables (a _x , a.) Detected by the sensors (1-3) _y , a _z ) of the motor vehicle (4)

- Detection and checking of the switching state of the first switching element (9) and / or the second switching element (10) by the first evaluation unit (5) and / or the second evaluation unit (6).

9. Test method according to claim 8, characterized in that the first evaluation unit (5) the first Auslόsungs- signal (FIRE1) independently of the state variables (a _x , a _y , a _z ) detected by the sensors (1-3) ( 4) blocks, while the second evaluation unit (6) generates the second trigger signal (FIRE2) independently of the state variables (a _x , a _y , a _z ) of the motor vehicle (4) detected by the sensors (1-3), the first Evaluation unit (5) controls the second evaluation unit (6) to generate the second trigger signal (FIRE2).

10. Test method according to claim 8, characterized in that the first evaluation unit (5) the first trigger signal (FIRE1) independently of the state variables (a, a _y , a _z ) detected by the sensors (1-3) of the motor vehicle (4) blocks while the second evaluation unit (6) generates the second trigger signal (FIRE2) independently of the state variables (a _x , a _y , a _z ) of the motor vehicle (4) detected by the sensors (1-3), the second evaluation unit ( 6) controls the first evaluation unit (5) to block the first trigger signal (FIRE1).

11. Test method according to claim 8, characterized in that the second evaluation unit (6) the second trigger signal (FIRE1) independently of the state variables (a _x , a _y , a _z ) detected by the sensors (1-3) ( 4) blocks, while the first evaluation unit (5) generates the first trigger signal (FIRE1) independently of the state variables (a _x , a _y , a _z ) of the motor vehicle (4) detected by the sensors (1-3), wherein the first evaluation unit (5) controls the second evaluation unit (6) to block the second trigger signal (FIRE2).

12. Test method according to claim 8, characterized in that the second evaluation unit (6) the second trigger signal (FIRE2) independently of the state variables (a _x , a _y , a _z ) detected by the sensors (1-3) of the motor vehicle (4) blocks while the first evaluation unit (5) the first

Trigger signal (FIRE1) is generated independently of the state variables (a _x , a _y , a _z ) of the motor vehicle (4) detected by the sensors (1-3), the second evaluation unit (6) generating the first evaluation unit (5) first trigger signal (FIRE1).

13. Test method according to at least one of claims 8 to 12, that the first evaluation unit (5) and / or the second one

Evaluation unit (6) excite a single sensor (1-3) or a part of the sensors (1-3) in order to malfunction the to simulate other sensors (1-3), the first evaluation unit (5) and / or the second evaluation unit (6) performing a plausibility check of the state variables (a _x , a _y , a _z ) detected by the sensors (1-3) ,