JP2001004653A - Acceleration detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration detector with excellent reliability by using a simplified satellite sensor unit. SOLUTION: A central unit (hereinafter referred to as ECU) 210 and a satellite sensor unit (hereinafter referred to as satellite) 220 are connected by two wire harnesses 203, 204, and power is supplied from the ECU to the satellite. A voltage signal indicating an acceleration detected by a G sensor 221, or indicating the result of a failure diagnosis of the G sensor 221 is converted into a current signal by a voltage-current converting circuit 222, inputted into the ECU 210 side through the wire harness 203, and converted into the voltage signal again by a current-voltage converting circuit 215. A microcomputer 212 conducts development control of an airbag (not illustrated) or the failure diagnosis of the G sensor 221 based on the voltage signal after conversion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration detection device, and more particularly to an acceleration detection device suitable for application to impact detection of an airbag system mounted on a vehicle such as an automobile.

[0002]

2. Description of the Related Art Conventionally, an automobile, which is a typical vehicle, is equipped with an airbag system for protecting an occupant from a generated shock.

[0003] Generally, an airbag system is provided with an acceleration (G) sensor for detecting the acceleration of the generated shock, and it is determined whether or not the airbag should be deployed based on the detection result of the G sensor. .

[0004] In such an airbag system, a quick deployment operation when an impact occurs is required,
From the viewpoints of safety and reduction of repair cost, it is required to accurately determine the operation according to various conditions such as the physique of the occupant to be protected, whether or not the child seat is mounted on the seat, and the mounting direction. .

Therefore, in recent years, it is possible to detect such various states and adjust the deployment timing, deployment strength, or multi-stage deployment of the airbag according to the detection results.
A so-called smart airbag system has been proposed.

In such a smart airbag system, SPS (Single Point Sensing), in which the generated impact is detected by a G sensor mounted in the vehicle interior, is generally employed. When an impact such as an offset collision occurs, the timing at which the G sensor outputs an output signal indicating the impact may be delayed. In this case, even if the ECU (central unit) that controls the deployment of the airbag performs the multistage deployment of the airbag based on the detected acceleration, it is difficult to deploy the airbag at the most effective timing. In some cases. In order to deal with such a problem, a technology for responding to various impacts has been proposed by remotely arranging a satellite sensor unit including a G sensor near the end of the vehicle in addition to the G sensor provided in the vehicle interior. Have been.

[0007]

However, the smart airbag system having the above-mentioned satellite sensor unit has the following problems.

FIGS. 6 to 11 are system configuration diagrams showing a configuration of an acceleration detection function including a central unit and a satellite sensor unit in a conventional smart airbag system.

Among these detection modes, FIGS. 6 to 8
Is a system configuration in which power is supplied to the satellite sensor unit from a vehicle power supply supplied directly from a battery or via an ignition switch (IG_SW).

In the system configuration shown in FIG. 6, a satellite sensor unit 120A includes a constant voltage power supply for generating a constant voltage power supply (for example, a 5V power supply) for ECU internal logic from a system power supply (for example, a 12V power supply) supplied from a vehicle power supply. The circuit includes a circuit 101, an acceleration sensor 102 for detecting acceleration when an impact occurs, and a microcomputer (hereinafter, microcomputer) 103 capable of diagnosing failure of the acceleration sensor 102. Then, the satellite sensor unit 120
A is a wiring harness for external connection, which is a total of four wiring harnesses 151 to 154 for system power supply, system ground (GND), acceleration sensor failure diagnosis signal transmission, and acceleration sensor output signal transmission. Having.

In the system configuration shown in FIG. 7, the switching element 1 that shuts off the output signal of the acceleration sensor 102 when the sensor is abnormal based on the failure diagnosis result of the acceleration sensor 102 by the microcomputer 103
6, the wire harness 15 for sharing the acceleration sensor output signal transmission wire harness and the acceleration sensor failure diagnosis signal transmission wire harness in the plurality of wire harnesses of the system of FIG.
5 is an example in which the required wire harness is reduced by one.

In the system configuration shown in FIG. 8, the microcomputer 103 is deleted from the satellite sensor unit 120A shown in FIG.
Transmits a signal for failure diagnosis of the acceleration sensor 102 to the satellite sensor unit 120C, and receives the output signal of the acceleration sensor 102 by the central unit 110C.

In each of the above-described system configurations shown in FIGS. 6 to 8, power is supplied from the vehicle power supply to the satellite sensor unit.
A surge absorbing element (for example, a power zener diode, etc.) 105 for protecting the satellite sensor unit from alternator load dump surge, which is generated when an electrical load is suddenly cut off from the alternator, may be necessary, and this is an obstacle to reducing material costs. Becomes

Therefore, in the system configuration shown in FIGS. 9 to 11, the power supply to the satellite sensor units 120D to 120F is not directly supplied from a battery or the like, but to the central units 110D to 110F.
A system configuration in which a constant voltage power supply (for example, a 5V power supply) (not shown) provided at 0F is provided. According to the system configurations shown in FIGS. 9 to 11, compared to the system configurations shown in FIGS. 6 to 8, the constant voltage power supply circuit 101,
Although the surge absorbing element 105 can be eliminated, a wire harness for power supply and a wire harness for the ground line thereof, and a wire harness for acceleration signal transmission and the like are required, and this becomes a new obstacle to reducing the member cost, and The increased wire disconnection of the wire harness, poor contact at the connector portion, and the like may cause a higher failure rate.

Accordingly, an object of the present invention is to provide a highly reliable acceleration detection device using a simplified satellite sensor unit.

[0016]

In order to achieve the above object, an acceleration detecting device according to the present invention has the following configuration.

That is, the impact of an airbag system of a vehicle, comprising a satellite sensor unit including an acceleration sensor and a central unit to which an acceleration signal output from the satellite sensor unit is input and diagnoses a failure of the acceleration sensor. An acceleration detection device suitable for use as detection means, wherein the satellite sensor unit and the central unit are connected by two signal lines, and the central unit is connected to the satellite sensor unit via those signal lines. And the acceleration signal is input from the satellite sensor unit to the central unit.

Preferably, the satellite sensor unit converts an output voltage of the acceleration sensor into a current, and superimposes the current signal on the power supply voltage applied to the signal line as the acceleration signal. The central unit may include a current / voltage conversion circuit that separates a current signal input as the acceleration signal from the power supply voltage and converts the separated current signal into a voltage signal.

Also, for example, the satellite sensor unit includes a diagnosis control circuit that outputs a predetermined signal for performing a fault diagnosis to the acceleration sensor at a timing when power supply is started, and indicates a fault diagnosis result of the acceleration sensor. An output cutoff circuit that cuts off an output voltage of the sensor in response to a signal, while the central unit includes:
When a predetermined voltage signal is output from the current / voltage conversion circuit when power supply to the satellite sensor unit is started, or as a result of the output cutoff circuit cutting off the output voltage of the acceleration sensor,・ When the voltage signal from the voltage conversion circuit is no longer output
It is preferable to include a failure diagnosis unit that determines that the acceleration sensor has failed.

When an offset due to the current consumption of the satellite sensor unit occurs in the acceleration signal input to the central unit, in order to prevent the offset component from affecting the acceleration detection accuracy.
In the satellite sensor unit, a method of mounting the acceleration sensor in a direction opposite to an original acceleration direction to be detected by the acceleration sensor when an impact occurs, the method being inversely proportional to a change in a detection voltage input from the acceleration sensor. A method of providing a means for outputting a current signal having a relation to the voltage / current conversion circuit, or a method of generating a voltage signal which is in inverse proportion to a change in a current signal inputted from the satellite sensor unit in the central unit. It is preferable to adopt a method of providing output means in the current / voltage conversion circuit.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the acceleration detecting device according to the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a diagram showing a system configuration of an acceleration detection device according to a first embodiment, and shows a circuit portion corresponding to an impact detection function in an airbag system.

As shown in FIG. 1, the acceleration detecting device according to the present embodiment includes a central unit 210 disposed at a position near a dashboard in a vehicle interior and a vicinity of an end of the vehicle (inside a bumper, an engine room, etc.). And a wire harness 203 for supplying power from the central unit 210 to the satellite sensor unit 220 and transmitting a detection signal from the satellite sensor unit 220 to the central unit 210. It is electrically connected to the ground line 204.

The central unit 210 is supplied with power from the battery 201 mounted on the vehicle via the IG_SW 202 or directly. Reference numeral 211 denotes a constant voltage power supply circuit that supplies a predetermined voltage (for example, 5 V) stabilized by a voltage supplied from the battery 201 to each unit of the central unit 210. Reference numeral 212 denotes a general single-chip microcomputer (microcomputer), which operates on the power supply voltage supplied from the constant voltage power supply circuit 211. The microcomputer 212 detects output signals of the acceleration sensor 213 provided in the central unit 210 and the acceleration sensor 221 provided in the satellite sensor unit 220, performs predetermined arithmetic processing based on the detected signals, and performs In addition to performing deployment control of the illustrated airbag (explosion control of the inflator), failure diagnosis of the G sensor 221 and the like is performed.

Further, the central unit 210 is provided with a switching element 214 such as a transistor for supplying a predetermined constant voltage to the satellite sensor unit 220, and the wiring harness 20 of the switching element 214 is provided.
3 or the current flowing to the constant voltage power supply circuit 211 side,
A general current / voltage (IV) conversion circuit 215 that detects an acceleration sensor output signal from the satellite sensor unit 220 and converts the detected current into a voltage is provided.

In this embodiment, the power supply to the satellite sensor unit 220 by the central unit 210 is performed by using the constant voltage power supply circuit 211 and the switching element 214 for turning on / off the output of the power supply circuit. The power supplied from the battery 201 to the central unit 210 is not limited to
A switching element 217 to be turned off and a constant voltage power supply circuit 216 for generating a predetermined constant voltage power supply to be supplied to the satellite sensor unit 220 from the power supply voltage turned on and off by the switching element 217 may be used.

The satellite sensor unit 220 is operated by a predetermined constant voltage power supply supplied from the central unit 210, and detects an acceleration (G) sensor 221 for detecting an acceleration when an impact occurs, and a voltage signal which is an output signal of the acceleration sensor 221. A general voltage / current (VI) conversion circuit 222 for converting (an analog signal or a digital signal) into a current signal, and a circuit for causing the acceleration sensor 221 to perform a predetermined failure diagnosis using power supply from the central unit 210 as a trigger 223, and a transistor 2 that shuts off an output signal of the acceleration sensor 221 when a failure occurs in the sensor.
24. Here, when the product specification for the failure diagnosis of the acceleration sensor 221 is started, for example, when a predetermined one pulse is input, as a specific configuration of the circuit 223, the power supply from the central unit 210 starts. Then, a one-shot pulse generation circuit that outputs the predetermined pulse signal only once may be used.

The detailed operation of the acceleration detecting device according to the present embodiment having the above-described system configuration will be described below.

The impact applied to the vehicle is detected by the acceleration sensor 2
21, a voltage signal corresponding to the detected impact is output from the sensor (at this time, the impact is also detected by the acceleration sensor 213 with a slight time delay). The output voltage of the acceleration sensor 221 is
The voltage / current conversion circuit 222 converts the current signal into a current signal.
Are superimposed on the power supply voltage applied during the transmission and transmitted to the central unit 210 via these wire harnesses.

The central unit 210 converts a change in current of a constant voltage power supply supplied to the satellite sensor unit 220 into a voltage signal by a current / voltage conversion circuit 215, and converts the voltage signal into the satellite sensor unit 220.
Is input to the microcomputer 212 as the acceleration signal detected in step (1). The microcomputer 212 performs predetermined arithmetic processing based on the input acceleration signal, and performs deployment control of an airbag (not shown) (explosion control of an inflator).

The failure diagnosis of the satellite sensor unit 220 performed by the central unit 210 includes an initial diagnosis at the start of the system and a constant diagnosis during the operation of the system. The failure diagnosis function generally provided in the acceleration sensor 221 is provided. It is performed using.

That is, the initial diagnosis is performed by the central unit 2
The operation is started by inputting a predetermined signal output from a circuit 223 for generating a predetermined failure diagnosis signal to the acceleration sensor 221 with the start of power supply from the apparatus as a trigger. In a normal state, a predetermined voltage signal is output from the acceleration sensor 221 in accordance with the input of the predetermined signal for failure diagnosis, and a current signal corresponding to the voltage signal is transmitted via the wire harness 203 as described above. Is converted again into a voltage signal, and the central unit 210 performs a failure diagnosis based on the voltage signal.

Further, the constant diagnosis during the operation of the system is performed by a circuit configuration in which a signal output from the acceleration sensor 221 is input to the input side of the switching element 224 when a failure occurs.
When the switch 24 is turned on, the detection signal of the G sensor 221 is blocked from being input to the VI conversion circuit 222, and this abnormal state may be detected by the microcomputer 212 of the central unit 210. .

As described above, according to the acceleration detecting device of the present embodiment, the satellite sensor unit 220 having a simplified circuit configuration and the central unit 21
0 can be supplied to the satellite sensor unit 220 and the acceleration signal from the G sensor 221 can be transmitted to the central unit 210 only by connecting the two wire harnesses 203 and 204 to each other. Based on this, when a predetermined acceleration signal cannot be detected at the time of initial diagnosis, or when an acceleration signal cannot be detected during operation of the system, it is determined that a failure has occurred, so that a failure diagnosis result of the sensor can be recognized.

Therefore, according to the acceleration detecting device according to the present embodiment, the required wire harness can be reduced as compared with the system configuration described as the conventional example,
The cost of the entire system can be reduced, the rate of disconnection can be reduced in accordance with the reduction of the wire harness, and the number of connectors used to connect each unit to the wire harness can be reduced. It is possible to reduce the rate of occurrence of failures due to poor contact or the like in portions, and to improve reliability.

[Second Embodiment] Next, a second embodiment based on the acceleration detecting device according to the above-described first embodiment will be described. In the following description, the same configuration as that of the first embodiment will not be described repeatedly, and the description will focus on the characteristic portions of the present embodiment.

According to the acceleration detecting device of the first embodiment, the system configuration can be simplified.
The reliability against failure can be improved. However, since the power supply to the satellite sensor unit 220 and the transmission of the acceleration signal to the central unit 210 are performed by the two wire harnesses 203 and 204, the satellite sensor unit 22
Since the current consumed by the acceleration sensor 221 and its peripheral circuits within 0 is superimposed on the acceleration signal output to the central unit 210, the acceleration signal is subjected to current / voltage conversion by the central unit 210. The offset corresponding to the current consumption occurs in the voltage signal after the reset (see FIG. 2). This offset voltage is applied to the satellite sensor unit 22 even when the detection signal from the acceleration sensor 221 is not actually output.
It always occurs during the operation of 0. Therefore, the acceleration sensor 2
Among the predetermined acceleration detection ranges (spans) that are set equally in the forward (+) direction and the reverse (−) direction on the central unit 210 side according to the product specifications of 21, the side on which the offset voltage is generated There is a problem that the acceleration detection range is substantially reduced.

In the present embodiment, in order to prevent the offset from affecting the acceleration detection accuracy, the mounting direction of the acceleration sensor relative to the original acceleration direction to be detected by the acceleration sensor 221 when an impact occurs. Is mounted in the opposite direction, so that the acceleration sensor outputs a detection signal that is inverted from the case where the sensor is mounted in the forward direction (see FIG. 3).

Thus, the zero level of the predetermined acceleration detection range is reduced by the offset voltage generated by the circuit current consumption of the satellite sensor unit 220 to the side of the acceleration direction having a low influence on the airbag deployment determination logic. And the original acceleration detection range in the acceleration direction having a high influence on the airbag deployment determination logic can be secured, so that the generated acceleration can be more accurately compared with the first embodiment. Can be detected.

[Third Embodiment] In the present embodiment, the second
By using a method different from the method described in the above embodiments, it is possible to prevent the above-described offset voltage from being generated in the current / voltage conversion circuit 215, thereby preventing the acceleration accuracy from being affected.
Acceleration is detected more accurately as in the second embodiment.

In this embodiment, the voltage / current conversion circuit 222 in the satellite sensor unit 220 is used to prevent the offset voltage from affecting the acceleration detection accuracy.
Is configured to output a current that is in inverse proportion to a change in the output voltage of the acceleration sensor 221 that is input (see FIG. 4). That is, when the output voltage of the acceleration sensor 221 increases, the current signal output from the voltage / current conversion circuit 222 decreases in accordance with the increase in the voltage, and conversely,
The circuit is configured such that when the output voltage of the acceleration sensor 221 decreases, the current signal output from the voltage / current conversion circuit 222 increases in accordance with the increase in the voltage. Specifically, the voltage / current conversion circuit 222 may be provided with, for example, a circuit to which a general non-inverting amplifier circuit is applied.

According to the present embodiment, as in the second embodiment, the acceleration can be detected more accurately.

[Fourth Embodiment] In the present embodiment, the second
The above-described offset voltage is applied to the current / voltage conversion circuit 21 by a method different from the method described in the third embodiment.
5 prevents the acceleration from affecting the detection accuracy of the acceleration, and detects the acceleration more accurately as in the second embodiment.

In the present embodiment, in order to prevent the offset voltage from affecting the acceleration detection accuracy, the current / voltage conversion circuit 215 in the central unit 210 is set to be in inverse proportion to the change in the input current signal. (See FIG. 5). That is, when the current signal input from the satellite sensor unit 220 increases, the voltage signal output from the current / voltage conversion circuit 215 decreases according to the increase in the current, and conversely, the voltage signal input from the satellite sensor unit 220 increases. The circuit is configured such that when the current signal decreases, the voltage signal output from the current / voltage conversion circuit 215 increases in accordance with the increase in the current. Specifically, the current / voltage conversion circuit 2
For example, a circuit to which a general differential amplifier circuit is applied may be provided in 15.

According to the present embodiment, the acceleration can be detected more accurately as in the second embodiment.

[0046]

As described above, according to the present invention,
Thus, it is possible to provide an acceleration detection device that uses a simplified satellite sensor unit and has excellent reliability.

In other words, according to the first aspect of the present invention, the satellite sensor unit is provided with a voltage / current conversion circuit, and the central unit is provided with a current / voltage conversion circuit (claim 2). The power supply and the transmission of the acceleration signal can be realized only by connecting the satellite sensor unit and the central unit with a line, and the magnitude of the acceleration signal (when the acceleration signal cannot be detected or reaches a predetermined value: Claim Based on the item 3), a failure diagnosis result of the acceleration sensor can also be transmitted.

According to the present invention, even if an offset due to the current consumption of the satellite sensor unit occurs in the acceleration signal input to the central unit, the acceleration is detected by the offset. The influence on accuracy can be prevented, and more accurate acceleration detection can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a system configuration of an acceleration detection device according to a first embodiment.

FIG. 2 is a diagram illustrating an offset voltage generated by current consumption of a satellite sensor unit.

FIG. 3 is a diagram illustrating a method for solving an offset voltage according to a second embodiment.

FIG. 4 is a diagram illustrating a method of solving an offset voltage according to a third embodiment.

FIG. 5 is a diagram illustrating a method for solving an offset voltage according to a fourth embodiment.

FIG. 6 is a system configuration diagram showing a configuration of an acceleration detection function including a central unit and a satellite sensor unit in a conventional smart airbag system.

FIG. 7 is a system configuration diagram showing a configuration of an acceleration detection function including a central unit and a satellite sensor unit in a conventional smart airbag system.

FIG. 8 is a system configuration diagram showing a configuration of an acceleration detection function including a central unit and a satellite sensor unit in a conventional smart airbag system.

FIG. 9 is a system configuration diagram showing a configuration of an acceleration detection function including a central unit and a satellite sensor unit in a conventional smart airbag system.

FIG. 10 shows a conventional smart airbag system.
FIG. 2 is a system configuration diagram illustrating a configuration of an acceleration detection function including a central unit and a satellite sensor unit.

FIG. 11 shows a conventional smart airbag system.
FIG. 2 is a system configuration diagram illustrating a configuration of an acceleration detection function including a central unit and a satellite sensor unit.

[Explanation of symbols]

110A, 110B, 110C, 110D, 110E,
110F, 210: Central unit (ECU), 120A, 120B, 120C, 120D, 120E,
120F, 220: satellite sensor unit, 101, 211, 216: constant voltage power supply circuit, 102, 213, 221: acceleration sensor, 103, 111, 212: microcomputer, 104, 224: switching element for interrupting sensor output, 105 : Surge absorbing element, 151 to 168, 203, 204: wiring harness, 214, 217: switching element for power supply, 215: current / voltage conversion circuit, 222: voltage / current conversion circuit,

Claims (7)

[Claims] 1. An acceleration detecting device comprising: a satellite sensor unit including an acceleration sensor; and a central unit to which an acceleration signal output from the satellite sensor unit is input and which performs a failure diagnosis of the acceleration sensor. The satellite sensor unit and the central unit are connected by two signal lines, power is supplied from the central unit to the satellite sensor unit via the signal lines, and the acceleration signal is transmitted to the satellite sensor unit. An acceleration detecting device, which is inputted from a sensor unit to the central unit. 2. A voltage / current conversion circuit for converting the output voltage of the acceleration sensor into a current and superimposing the current signal on the power supply voltage applied to the signal line as the acceleration signal. The central unit includes a current / voltage conversion circuit that separates a current signal input as the acceleration signal from the power supply voltage and converts the separated current signal into a voltage signal. 2. The acceleration detection device according to 1. 3. A diagnostic control circuit for outputting a predetermined signal for performing a failure diagnosis of the acceleration sensor at a timing when power supply is started, and a signal representing a failure diagnosis result of the acceleration sensor. An output cutoff circuit that cuts off the output voltage of the sensor, wherein the central unit is configured to output a predetermined voltage signal from the current / voltage conversion circuit when power supply to the satellite sensor unit is started. When the output is not output, or when the output cutoff circuit cuts off the output voltage of the acceleration sensor and the voltage signal from the current / voltage conversion circuit is no longer output, it is determined that the acceleration sensor has failed. 3. The acceleration detection device according to claim 2, further comprising a failure diagnosis unit that performs the operation. 4. The satellite sensor unit according to claim 1, wherein the acceleration sensor is mounted in a direction opposite to an original acceleration direction to be detected by the acceleration sensor when an impact occurs. Item 3. The acceleration detection device according to Item 2. 5. The satellite sensor unit according to claim 1, wherein the voltage / current conversion circuit includes a unit that outputs a current signal that is inversely proportional to a change in a detection voltage input from the acceleration sensor. The acceleration detecting device according to claim 2, wherein 6. The central unit, wherein the current / voltage conversion circuit includes a unit that outputs a voltage signal that is in inverse proportion to a change in a current signal input from the satellite sensor unit. The acceleration detecting device according to claim 2, wherein 7. The acceleration detection device according to claim 1, wherein the acceleration detection device is an impact detection unit of an airbag system of a vehicle.