JPH0666824A - Control system and air bag system using acceleration sensor - Google Patents

Abstract

PURPOSE:To provide a control system using acceleration sensors, which is prevented from malfunction resulting from the sensors and has a satisfactory failure diagnosing function. CONSTITUTION:For a control system using acceleration sensors, the acceleration sensors 2, 3 are mounted in the same package 1. One acceleration sensor 2 is of a servo control type to allow intentional operation of the system through a failure diagnosing signal from a control section 4. Another acceleration sensor 3 is of a non-servo type to allow operation of the system on condition that necessary output for control is given from both sensors 2, 3. These acceleration sensors nap may be formed with sensors having different properties against obstruction arising from the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system using an acceleration sensor.

[0002]

2. Description of the Related Art In automobiles, airbag systems, suspension control, four-wheel torque control, etc.
The target physical displacement amount is detected by the acceleration sensor. As the acceleration sensor, various types such as a pressure type, a resistance strain type, and a capacitance type have been proposed and developed.

As a prior art relating to this type of acceleration sensor, for example, Sensors and Actuators, A. 21-23 (1990) pp. 316-319 (Sensors and Actuators).
, A21-23 (1990) 316-319).

By the way, some acceleration sensors of this type are required to have extremely high reliability, since some of them are inoperative or malfunctioning such as an airbag system, which may affect human life.

Therefore, as the acceleration sensor, a servo control type that can respond by applying a failure diagnosis signal is used.
There is proposed a method of diagnosing a failure of the detecting section and each part of the system by applying a force to intentionally actuate the movable section (the mass section that is displaced in response to acceleration) of the acceleration sensor based on the failure diagnosis signal. ing.

In order to prevent malfunctions, two acceleration sensors for detecting acceleration of the same purpose are mounted, and the system is activated when both acceleration sensors output an acceleration detection signal of a predetermined level or higher. There has been proposed such a method (for example, Japanese Patent Laid-Open No. 3-20674).

[0007]

By the way, such a servo control type acceleration sensor uses a high-sensitivity detection section because it is necessary to perform servo control, and therefore, an acceleration smaller than the collision acceleration is detected in actual acceleration detection. Even if you do, there is a risk that you may react accidentally, and it is necessary to take precautions.

On the other hand, in the case of 1, since the same type of acceleration sensor is used, there is the same fault acceptance characteristic with respect to external disturbances (eg, electromagnetic waves, temperature, humidity, etc.), and both accelerations are Therefore, it is possible that a malfunction occurs due to the influence of an external failure.

The present invention has been made in view of the above points, and a first object thereof is to provide a control system satisfying both conditions of a failure diagnosis function of an acceleration sensor and a sensor malfunction prevention. Secondly, it is to provide a control system that can reliably prevent malfunctions, particularly against external obstacles.

[0010]

In order to achieve the above object, the present invention basically proposes the following as an acceleration sensor used for system control.

First, in a control system using an acceleration sensor, a plurality of acceleration sensors are mounted in the same package, and one of these acceleration sensors is intentionally driven by a failure diagnosis signal from a failure diagnosis system of the system. A servo control type acceleration sensor which can be operated, and the other is composed of a non-servo type acceleration sensor, and the system is operated on condition that the outputs required for control are made from both of these acceleration sensors. It was set (this is the first invention).

The other is to mount a plurality of acceleration sensors in the same package as described above, but these acceleration sensors are composed of sensors having different characteristics with respect to externally applied obstacles, and The system is set to operate on condition that outputs required for control are provided from both acceleration sensors of the above (this is the second invention).

[0013]

Operation of the first invention: With such a structure, a plurality of acceleration sensors are mounted in the same package, so that accelerations of the same purpose can be detected at the same position. Moreover, one of these acceleration sensors is a servo control type acceleration sensor and can be connected to the failure diagnosis system of the system, so that a failure diagnosis signal is applied to the detection section of the acceleration sensor to add a deliberate actuation force. By doing so, the functions of the sensor and each part of the system can be checked and failure diagnosis can be performed.

As described above, such a servo control type acceleration sensor has a high sensitivity for enabling servo control, but on the other hand, the acceleration level actually aimed at by the hypersensitivity reaction (for example, in the case of an airbag system). The system may operate erroneously even if it receives a smaller acceleration than the collision acceleration.

However, according to the present invention, it is set to operate the system on condition that outputs required for control are provided from both the servo control type acceleration sensor and the non-servo type acceleration sensor mounted in the same package. Therefore, the above problems can be solved. In other words, one non-servo type acceleration sensor is not required to have sensitivity as high as servo control, and structurally does not make the movable part of the detection part (the mass part that is displaced in response to acceleration) sensitive to the target acceleration. Since the support structure of the movable part can be easily set so that the range can be narrowed down and responded, even if the servo control type acceleration sensor outputs erroneously, the non-servo type acceleration sensor does not output or It is possible to prevent malfunction by not generating the output required for system operation.

Action of the second invention: Since each acceleration sensor mounted in the package has different characteristics with respect to a failure, when one acceleration sensor mounted in the package reacts to a failure. However, it is possible to increase the probability that the other acceleration sensor does not react to the above-mentioned obstacle, and therefore, if the system is set to operate when signals are output from both acceleration sensors, Therefore, it is possible to reliably prevent malfunction of system control and improve reliability.

[0017]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a control system according to an embodiment of the present invention, FIG. 2 is a view showing a package mounting mode of an acceleration sensor of the control system, and FIGS. 3 and 4 are accelerations used in the control system. It is a sensor.

In FIG. 1, reference numeral 1 denotes a package of an acceleration sensor, and two acceleration sensors 2 and 3 are mounted inside the package. The acceleration sensor 2 is an electronic acceleration sensor that outputs acceleration as an electric signal corresponding to the displacement amount. For example, the acceleration sensor 2 is an electrostatic servo control type capacitive acceleration sensor, and the acceleration sensor 3 is A non-servo capacitive accelerometer is used.

A specific example of the servo control type acceleration sensor 2 will be described with reference to FIG. 3, and a specific example of the non-servo type acceleration sensor 3 will be described with reference to FIG.

In FIG. 3, the acceleration sensor 2 is a detection unit 2
The detection unit 2a includes an upper and lower glass substrate 20 having fixed electrodes 23 and 24, and a movable electrode (mass part) 22 that is disposed between the fixed electrodes 23 and 24 with a minute gap therebetween. The movable electrode 22 is elastically supported by the beam 21.

Capacitances C1 and C2 exist between the fixed electrodes 23 and 24 and the movable electrode 22, and the capacitance differences C1 and C2 are present.
The difference ΔC of 2 is given to the conversion circuit 2b. Conversion circuit 2b
Is composed of at least a ΔC detector 25, a pulse width modulator 26, a knot circuit 27 and a filter 28, and these elements 25, 26, 27 and the detector 2a form an electrostatic servo system.

That is, when the acceleration G is applied to the detecting portion 2a, the movable electrode 22 moves due to the inertial force based on the acceleration. Therefore, the distance between the movable electrode and each fixed electrode changes, and the electrostatic capacitances C1 and C2 change. ΔC detector 25 is C
The difference ΔC between 1-C2 is detected, and the voltage ΔVc proportional to ΔC
The pulse voltage V _E having a pulse width proportional to the value of V is given to the fixed electrode 23 and, at the same time, inverted by the knot circuit 27 to be V _E ′ and given to the fixed electrode 24.

With the above circuit configuration, the inertial force due to the acceleration G and the electrostatic force due to the pulse voltages V _E and V _E ′ (V _E
The movable electrode 22 is servo-controlled to a position (reference position) at which (depending on the pulse width of), and the pulse width of the pulse V _E is taken out at the output terminal 29 of the filter 28, so that the voltage V _O proportional to the acceleration G obtain.

Next, the acceleration sensor 3 will be described.

As shown in FIG. 4, the acceleration sensor 3 has the same structure as the detection unit 2a of the acceleration sensor 2 with respect to the detection unit 3a, and the conversion circuit 3b is composed of a ΔC detector 25 and a filter 30. It

The detecting unit 3a detects the acceleration G as in the detecting unit 2a of FIG. 3, supplies this signal to the ΔC detector 25, and outputs it as an output signal through the filter 30 and the terminal 31.
In this case, since the signal processing system is not a servo system but an open system, the rigidity of the beam 21 is increased and the movable electrode 22 can respond at a target acceleration level.
The sensitivity is lower than that of the servo-controlled acceleration sensor so that it does not react excessively.

Next, a package mounting mode of the acceleration sensors 2 and 3 will be described with reference to FIG.

FIG. 3A shows a state in which the cap is attached,
(B) shows a state in which the cap is removed. Package 1
Is composed of a housing 1A for accommodating the sensor and a cap 1B for covering the same. The housing 1A is provided with mounting bolt insertion holes 6 and 7 and an output pin terminal 8.

In the package 1, the detecting section 2a of the acceleration sensor 2 and the conversion circuit 2b, and the detecting section 3a of the acceleration sensor 3 are included.
And the conversion circuit 3b are mounted. It is desirable that the package 1 be shielded to prevent radio interference. For example, the entire package is composed of a shield member and this is grounded. In addition, from the sensors 2 and 3 to the control unit 4 described below.
It is desirable to shield the signal lines up to.

The outputs of the acceleration sensors 2 and 3 are input to the control unit 4 as shown in FIG. The control unit 4 is composed of, for example, a microcomputer, and outputs a control signal necessary for system operation from a terminal 5 on condition that signals of a predetermined level or higher are input from both the acceleration sensors 2 and 3, and is illustrated. Drives and controls the actuators, etc. of a system that does not exist. It is set so that the system control signal is not output as an erroneous signal when only one of the acceleration sensors 2 and 3 outputs a predetermined level or higher.

Further, the control unit 4 outputs a failure diagnosis signal to the detection unit 2a of the servo control type acceleration sensor 2 periodically or at the time of starting operation, and the fixed diagnosis signal 2 of the detection unit 2a is output.
3 and 24 to intentionally actuate the movable electrode 22,
It has a failure diagnosing function that simulatively checks whether or not a normal output is made from the detection unit 2a and whether or not each unit of the system is in a normally operable state. In this case, the failure diagnosis function may actually operate each part of the system if there is no problem, but if the operation of each part of the system causes a problem in operation, do not operate each part of the system and drive it. This is done by checking if the control signal is actually sent to the circuit. As for the non-servo type acceleration sensor, it is possible to use a detection unit structure which is more robust than the servo type sensor and has an extremely low failure rate.

According to the present embodiment having the above-mentioned configuration, in addition to providing a failure diagnosis function, it is possible to check in advance whether or not there is an abnormality such as a malfunction due to disconnection or damage of the system. Since the system is operated based on the outputs of both acceleration sensors, malfunction can be prevented.
In the above embodiment, the acceleration sensors 2 and 3 use capacitance type acceleration sensors.
It is also possible to use various types of electronic acceleration sensors such as pressure type. In this case, when the acceleration sensor is servo-operated for failure diagnosis, the electrostatic electrode as described above is used for failure diagnosis. Alternatively, the mass portion of the acceleration detecting portion may be intentionally operated by an electromagnetic force.

FIG. 5 shows a second embodiment of the present invention.

In this embodiment, acceleration sensors 51 and 52 having different characteristics with respect to an externally applied obstacle are mounted in the same package 1. The acceleration sensor 51 is, for example, an electronic acceleration sensor such as a capacitance type, a resistance strain type, or a pressure type, and the acceleration sensor 52 is a mechanical acceleration that responds to acceleration when the acceleration exceeds a predetermined level and performs a switch operation. It uses a sensor. The detectors 51a and 52a of the sensors 51 and 52 and the conversion circuits 51b and 52b are mounted in the package 1.

Although the acceleration sensors 51 and 52 are of different types, their purpose is to detect the same acceleration.

The control unit 53 in the present embodiment further receives the switch-on signal from the mechanical acceleration sensor 52 (a signal generated when the mechanical switch is turned on when the acceleration is equal to or higher than a predetermined acceleration), and further the electronic acceleration When a signal of a predetermined level or higher is output from the sensor 51, a drive signal required for system control is output to each unit (not shown) of the system via a terminal 54.

According to this embodiment, the following effects can be obtained.

Since one mechanical acceleration sensor 52 is resistant to radio waves, heat, etc., the other one uses an electronic acceleration sensor 51 which is relatively weak against these failures. However, if the system is set to operate when signals are output from both acceleration sensors, malfunction of system control can be reliably prevented and reliability can be improved. On the contrary, even if water etc. adheres to the contacts of the mechanical acceleration sensor and the switch short-circuits and a switch signal is generated, if the electronic acceleration sensor has fault resistance characteristics against it, Similarly, malfunction of system control can be prevented.

The one electronic acceleration sensor 51 is
Since the displacement amount of the acceleration can be detected, if the output of the sensor 51 is taken in under the condition that the mechanical acceleration sensor 52 is switched on, the malfunction prevention and the degree of acceleration can be detected and the acceleration can be detected. System control becomes possible.

As the electronic acceleration sensor 51, a servo control type acceleration sensor having a failure diagnosis function as described in the first embodiment may be used.

FIG. 6 shows an example of an airbag system to which the above-mentioned first embodiment is applied.

The structures of the acceleration sensors 2 and 3 in the package 1 and the control unit 4 are the same as those in the first embodiment. Here, the detection unit 3 of the non-servo type acceleration sensor 3 is used.
“A” is capable of responding to the acceleration (for example, ± 50 G) necessary for detecting a vehicle collision and higher, and the detection unit 2a of the servo-type acceleration sensor 2 is capable of responding even if the acceleration is lower than that and malfunctions. Even when a diagnostic signal is applied, it can respond. The collision signal 40 of the vehicle is detected by the detection unit 2
a, 3a. When a signal corresponding to the collision acceleration is output from both the acceleration sensors 2 and 3, the control unit 4 drives the inflator 41, which causes the thermal energy of the explosive to expand the airbag 42. In this embodiment, the output signal of the detection unit 3a is further input to the terminal 43.
And is used as another safety signal, for example, a seat belt fastening signal.

In such a security device, inactivity and malfunctions affect human life, so that applying a control system having the same effect as that of the first embodiment can greatly contribute to improving reliability. The malfunction can be prevented also when the control system of the second embodiment is applied as an airbag system.

Further, the control system of the present invention is useful for a security system, and can be applied to other than the airbag system.

[0046]

According to the first aspect of the present invention, by providing the above-described configuration and operation, it is possible to provide a control system that satisfies both the failure diagnosis function of the acceleration sensor and the sensor malfunction prevention. According to the invention, it is possible to provide a control system capable of surely preventing malfunction due to an external failure.

[Brief description of drawings]

FIG. 1 is a block configuration diagram according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a package mounting mode of the acceleration sensor used in the first embodiment.

FIG. 3 is a configuration diagram of one acceleration sensor used in the above embodiment.

FIG. 4 is a configuration diagram of the other acceleration sensor used in the above embodiment.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is a block configuration diagram of an airbag system according to a third embodiment of the present invention.

[Explanation of symbols]

1 ... Package, 2 ... Servo control type acceleration sensor, 3 ...
Non-servo type acceleration sensor, 2a, 3a ... Detection unit, 2b,
3b ... Conversion circuit, 4 ... Control unit, 51, 52 ... Acceleration sensor (electronic acceleration sensor, mechanical acceleration sensor), 53
… Control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Matsukura 2520 Takaba, Katsuta-shi, Ibaraki Pref., Automotive Equipment Division, Hitachi, Ltd. (72) Masanori Kubota 2520 Takaba, Katsuta-shi, Ibaraki Hitachi, Ltd. Mfg. Co., Ltd. Automotive Equipment Division (72) Inventor Keiji Hanzawa 2477 Kashima Yatsu Kashima, Katsuta City, Ibaraki Prefecture 3 Hitachi Automotive Engineering Co., Ltd.

Claims (7)

[Claims] 1. A control system using an acceleration sensor, wherein a plurality of acceleration sensors are mounted in the same package, and one of these acceleration sensors can be intentionally activated by a failure diagnosis signal from a failure diagnosis system of the system. A servo-control type acceleration sensor, the other is a non-servo type acceleration sensor, and the system is set to operate on the condition that both of these acceleration sensors have outputs required for control. A control system using an acceleration sensor. 2. The control system according to claim 1, wherein both of the acceleration sensors are of a capacitance type. 3. A control system using an acceleration sensor, wherein a plurality of acceleration sensors are mounted in the same package, and these acceleration sensors are composed of sensors having different characteristics with respect to an externally applied obstacle, A control system using an acceleration sensor, wherein the system is set to operate on the condition that outputs required for control are provided from both of these acceleration sensors. 4. The acceleration sensor according to claim 1, wherein one of the acceleration sensors is an electronic acceleration sensor that outputs an acceleration as an electric signal corresponding to a displacement amount of the acceleration sensor, and the other is an acceleration sensor. A control system using an acceleration sensor, comprising a mechanical acceleration sensor that performs a mechanical switch operation according to a displacement. 5. The package according to any one of claims 1 to 4, wherein the package includes therein an acceleration detection unit of each acceleration sensor and a conversion circuit that converts acceleration into an electric signal. A control system using an acceleration sensor. 6. An airbag system for detecting a collision acceleration of a vehicle and activating an airbag, wherein two sensors are used as acceleration sensors for detecting the collision acceleration, and one of these acceleration sensors is an airbag system. This is a servo control type acceleration sensor that can be connected to the fault diagnosis system, and the other is composed of a non-servo type acceleration sensor and mounted in the same package. Both of these acceleration sensors output a signal corresponding to the collision acceleration. An airbag system comprising a control unit for activating the airbag when the airbag is operated. 7. An airbag system for detecting a collision acceleration of a vehicle and activating an airbag, wherein two sensors are used as acceleration sensors for detecting the collision acceleration, and these acceleration sensors are used for obstacles applied from the outside. In contrast, it is equipped with a control unit that is configured with sensors having different characteristics and mounted in the same package, and that activates the airbag when signals corresponding to collision acceleration are output from both of these acceleration sensors. Airbag system to be.