JPH09295551A - Multiplex communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a power supply line also as a signal line so as to surely transmit a multiplex signal with a large pulse duration by adding a function of rapidly charging a capacitor of a constant-voltage circuit of a sub-control device simultaneously with the end of transmitting the header of a request signal to a main control device. SOLUTION: When an IG switch 2 is turned on, and a microcomputer 25 of a driver's seat air bag system 35 starts operating to perform an electrostatic capacity diagnosis, immediately after turning off a switch circuit 32 through a signal line Y, the microcomputer 25 turns on a switching transistor 31 for designated time to discharge a backup capacitor 23 through a resistance 30. At this time, the microcomputer reads the terminal voltage to obtain the voltage change amount, and decides whether the electrostatic capacity is a regulated value or not, and if abnormal, a warning device is operated. After that, the switch circuit 32 is turned on to start feeding to the driver's seat air bag system through a communication circuit 33 and a power supply line 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex communication device adaptable to an occupant protection device provided with a plurality of airbags for protecting an occupant in the event of a front and side collision of a vehicle. is there.

[0002]

2. Description of the Related Art A conventional multiplex communication device of this type will be described with reference to an occupant protection device shown in FIG. First, the driver's seat airbag system (main occupant protection device) surrounded by the broken line 16
Will be described below. The booster circuit 3 boosts the input voltage from the battery 1 supplied via the ignition switch 2 and charges the backup capacitor 5 via the resistor 4. The charged electric charge is turned on by the switch circuit 7 when the microcomputer 11 determines a serious collision based on the acceleration signal supplied from the longitudinal acceleration sensor 10, and the detonator 8 passes through the discharge diode 6, The mechanical acceleration switch 9 (which is in the on state at this time, but is normally in the off state) is discharged in series, and the detonator 8 ignites an explosive (not shown),
The airbag is deployed. The mechanical acceleration switch 9 has a structure disclosed in Japanese Patent Application No. 5-351470 by the present applicant.

The microcomputer 11 has a failure diagnosis function. When diagnosing the capacity of the backup capacitor 5, the microcomputer 13 turns on the transistor 13 for a predetermined time and discharges the charge in the backup capacitor 5 via the resistor 12. The amount of change in the terminal voltage of the backup capacitor 5 at that time is read and the backup capacitor 5 is read.
Diagnose whether the capacitance of is within the specified range,
If it is determined to be abnormal (out of the specified value range), an alarm device (not shown) such as a lamp is driven to notify the occupant. The microcomputer 11 alternately and repeatedly executes the failure diagnosis function and the collision determination function in a very short time.

Further, the microcomputer 11 also activates the alarm device based on the failure diagnosis information of the driver side airbag system (sub-occupant protection device) 19 supplied from the first communication circuit 17 described later. First communication circuit 17
When a request signal is supplied from the microcomputer 11 at a constant cycle, the microcomputer 11 supplies the request signal to the second communication circuit 20 of the driver side airbag system 19, and vice versa. When supplied,
It is supplied to the microcomputer 11.

Next, the driver side air bag system 19 which is activated in the event of a collision from the side of the vehicle will be described below. The driver side airbag system 19 is composed of a switch circuit 7 ', a detonator 8', a mechanical acceleration switch 9 ', a lateral acceleration sensor 10', a microcomputer 11 ', a second communication circuit 20 and a constant voltage circuit 21. In order to protect an occupant against a collision from the side of the vehicle, the power source thereof is a power line (harness) indicated by reference numeral 18 for the driver seat airbag system 1
It is connected so as to be supplied from the backup capacitor 5 (or the booster circuit 3) of 6. Further, a request signal transmitted from the microcomputer 11 at regular intervals is taken into the microcomputer 11 'via the second communication circuit 20, and a response signal (diagnosis result) to the request signal is supplied every time the request signal is supplied. Is transmitted to the microcomputer 11 via the second communication circuit 20.

The driver side air bag system 19
Is a unit that is attached to the door of the vehicle or in the vicinity thereof.
0 ′, which is the same as the longitudinal acceleration sensor 10. The difference from the acceleration sensor 10 is that the detection direction is changed and the acceleration sensor 10 is attached to the vehicle so that the acceleration from the lateral direction of the vehicle can be detected.

Reference numeral 11 'denotes a microcomputer having a collision judgment function equivalent to that of the microcomputer 11,
The collision is judged based on the acceleration signal from the lateral acceleration sensor 10 'which detects the acceleration signal generated in the lateral direction of the vehicle, and when it is judged to be a serious collision, the switch circuit 7'is turned on. Reference numeral 20 is a second communication circuit, which is the first
The request signal from the communication circuit 17 is sent to the microcomputer 1
1 ', and the response signal from the microcomputer 11' is transmitted to the first communication circuit 17. Reference numeral 21 is a constant voltage circuit, which naturally has a large-capacity capacitor (having a smaller electrostatic capacity than the backup capacitor 5) for voltage stabilization on the input side, and is connected from the booster circuit 3 (or the backup capacitor 5) to the power supply line. Electric power is supplied via 18 to make it a constant voltage to supply electric power to each circuit portion of the driver side airbag system 19.

As a result, the driver side airbag system 19 operates from the booster circuit 3 of the driver airbag system 16 or the backup capacitor 5 to the power supply line 1.
In addition to receiving the boosted voltage via 8, the driver's side airbag system 19 detects the acceleration due to the collision from the side of the vehicle by the lateral acceleration sensor 10 ', and the microcomputer 11' collides based on the detection signal. When the judgment function judges that the accident is a serious accident, the switch circuit 7'is turned on to cause the electric power charged in the backup capacitor 5 of the driver airbag system 16 to flow in series to the detonator 8 and the mechanical acceleration switch 9 to ignite the explosive charge. And deploy the airbag.

Further, the failure diagnosis function of the microcomputer 11 'carries out failure diagnosis of the detonator 8'and the like, and a request signal from the driver airbag system 16 is sent to the first and second signals.
Every time the request signal is supplied periodically via the communication circuits 17 and 20, and the request signal is supplied, the microcomputer 11 ′ of the driver side airbag system 19 outputs the diagnosis result from the second communication circuit 20 as a response signal. First communication circuit 17
When it is determined that the abnormal condition data has been supplied, the microcomputer 11 drives the alarm device.

[0010]

However, the multiplex communication system shown in FIG. 4 has a problem that a power supply line and a signal line are required as a harness, and the cost is not reduced.

Therefore, the present invention has been made in view of the above-mentioned problems, and the power supply line is also used as a signal line, and the pulse is surely transmitted even if the pulse width of the multiple signal is large. The purpose is to

[0012]

According to a first aspect of the present invention relating to a multiplex communication apparatus, a first control signal is generated on the basis of a detection signal from a first sensor, which is fed by a DC power source, and each circuit section is formed. A main controller having a function of monitoring the voltage and performing a fault diagnosis, a constant voltage circuit having a voltage stabilizing capacitor and being fed from the DC power source through a harness, and a second sensor The second control signal is generated based on the detection signal, and at least one sub control device having a function of monitoring each circuit unit is provided, and the main control device includes the harness for the sub control device. A multiplex communication in which a request signal including a header, a code, and the like is supplied via the controller, and the sub-control circuit returns a response signal including at least a monitoring result of each circuit unit to the main control circuit in response to the request signal. A location, the main control unit, at the same time as the transmission end of the header of the request signals, rapidly charging a voltage stabilizing capacitor of the constant voltage circuit of the sub-control unit.

According to a second aspect of the present invention, a resistor is connected to an end of the harness on the main controller side, and a switch circuit is connected in parallel to the resistor, and the main control circuit uses the switch circuit to stabilize the voltage. It instantly switches to the ON state when the chemical capacitor is rapidly charged.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. The first embodiment according to the present invention will be described with reference to FIG. First, the driver's seat airbag system 35, which is a main occupant protection device, will be described. Ie 2
Reference numeral 1 is a booster circuit, which boosts an input voltage from the battery 1 supplied via the ignition switch 2 to generate a resistor 22.
The backup circuit 23 is charged via the switch circuit 3 and is serially inserted in the power supply line 36.
2. The boosted voltage is supplied to the driver side airbag system 46, which is the auxiliary occupant protection device, via the resistor 34.
Reference numeral 24 denotes a longitudinal acceleration sensor for detecting acceleration generated in the longitudinal direction of the vehicle. An acceleration signal as a detection signal is supplied to a microcomputer 25 described later.

The microcomputer 25 has a collision judging function, and when it judges a serious collision based on the acceleration signal supplied from the longitudinal acceleration sensor 24, the switch circuit 26 is turned on to cause the backup capacitor 23 to operate. Charged charge is discharged by diode 2
Discharge through 7, detonator 28, mechanical acceleration switch 2
An ignition current is flown in series with 9 to deploy the airbag attached to the handle. It goes without saying that the mechanical acceleration switch 29 is turned on at this time.

Further, the microcomputer 25 has a function of diagnosing the backup capacitor 23, the detonators 28, 28 ', the mechanical acceleration switch 29, and the like, and in the capacity diagnosis of the backup capacitor 23, the ignition switch 2 is turned on. Immediately after the operation, the switching circuit 32 is turned off via the signal line Y to prevent the charge stored in the backup capacitor 23 from being discharged as a dark current of each circuit of the driver side airbag system 46, and then the switching transistor 31. Is turned on, the charge charged in the backup capacitor 23 is discharged through the resistor 30, and the microcomputer 25 reads the amount of change in the terminal voltage of the backup capacitor 23 at that time during a predetermined time.
Thereby, the capacitance is calculated to perform the capacitance diagnosis, and when it is determined that the capacitance value is abnormal, the occupant is notified by using an alarm device such as a lamp.

The microcomputer 25 determines the disconnection diagnosis of the detonators 28, 28 'and the mechanical acceleration switch 29 based on the respective terminal voltages of the detonators 28, 28' mechanical acceleration switch 29 and the voltage difference between them. However, if it is determined that there is a disconnection or the like, the occupant is notified using an alarm device such as a lamp as in the above. Further, the microcomputer 25 supplies the request signal to the driver side airbag system 46 via the signal line X and the first communication circuit 33, and the driver side airbag system 46 responds to the request signal. Then, response signals such as various diagnostic signals are input to perform the same diagnosis as described above.

The request signal (FIG. 3 (A)) is sent by the microcomputer 25 to the switching transistor 4
Turn on / off 1 and the other side microcomputer 2
5 ', but at this time, a header having a larger pulse width than a pulse for data (or code) (Td section in FIG. 3) such as a header (indicated by section Th in FIG. 3A). When the low level signal T1 (FIG. 3 (D)) is supplied from the microcomputer 25 to the switch circuit 32 ′ in synchronization with the rising edge which is the end of the rising edge, as shown in FIG. The constant becomes very small.
That is, when the switch circuit 32 ′ is turned on, the voltage stabilizing capacitor 44 a provided on the input side of the constant voltage circuit 44 causes the booster circuit 21 and the backup capacitor 2 to operate.
3 by being rapidly charged by the output of FIG.
As shown in (E), there is no time constant at rising.

Incidentally, when the switch circuit 32 'is not connected, the transmitted waveform has a large time constant in the rising waveform at the end of the header as shown in FIG. 3 (B). . That is, the pulse width of the header is larger than the pulse width of the data (or code). Therefore, when the header is supplied, the booster circuit 21 and the backup capacitor 23 of the driver airbag system 35 are connected to the driver side. The power supply to the input side voltage stabilizing capacitor 44a of the constant voltage circuit 44 of the airbag system 46 is reduced, and the electric charge of the voltage stabilizing capacitor 44a in the constant voltage concave path is consumed during that time, and the request signal Figure 3 shows the rise of the pulse width of the pulse.
As shown in (B), the pulse width becomes blunt, and when read by the microcomputer 25 of the driver side airbag system 46, the pulse width increases by T0 (FIG. 3 (C)), and the type of signal is determined. You may not be able to.

Next, the driver side air bag system 4
6 will be described. Reference numeral 24 'denotes the same acceleration sensor as the longitudinal acceleration sensor 24, which has a different detection direction from the longitudinal acceleration sensor 24, is mounted so as to detect the acceleration in the left and right direction of the vehicle, and outputs an acceleration signal as a detection output. Supply to computer 25 '. The microcomputer 25 'is the microcomputer 2
As in the case of No. 5, it has a collision determination function, and based on an acceleration signal supplied from the lateral acceleration sensor 24 'and a switch signal supplied from an acceleration switch 40 described later, the scale of a collision from the side of the vehicle is determined. The second communication circuit 3 determines the result of the determination as a response signal together with the result of the diagnosis described later.
Output through 3 '.

The microcomputer 25 'has a diagnostic function similar to that of the microcomputer 25 and performs a failure diagnosis of the lateral acceleration sensor 24' and the acceleration switch 40, and the first communication circuit 33 via the power supply line 36. Each time a request signal is supplied, the driver airbag system through the second communication circuit 33 '(the same as the first communication circuit 33), the power supply line 36, and the signal line Z, using the diagnosis result as a response signal. 35 to the microcomputer 25.

The acceleration switch 40 is composed of a semiconductor acceleration sensor and a comparison circuit for inputting the detection output thereof, and outputs a switch signal when the output from the semiconductor acceleration sensor exceeds the reference value of the comparison circuit. To do.

Reference numeral 41 'is a switching transistor such as a field effect transistor, which is on / off controlled by the output signal of the second communication circuit 33' and outputs a response signal formed from a signal indicating a collision, various diagnostic signals, and the like. . 42 '
Is the switching transistor 41 'and the power supply line 3
When the switching transistor 41 or 41 ′ is turned on when the voltage on the anode side of the backflow prevention diode 43 is turned on by a resistor inserted between the resistor 6 and the resistor 34, which is connected in series with the resistor 34 via the power supply line 36. The output voltage of the constant voltage circuit 44 is maintained at a constant voltage by preventing the charging voltage level of the voltage stabilizing capacitor 44a on the input side of the constant voltage circuit 44 from becoming 0 level (see FIG. 2). The reference voltage is always supplied to the constant voltage circuit 44 described later. The constant voltage circuit 44
Always receives an input voltage and supplies electric power to each circuit constituting the driver side airbag system 46.

The power line 36 has a voltage waveform as shown in FIG. 2 when communication is performed between the driver airbag system 35 and the driver side airbag system 46. That is, in FIG. 2, the voltage V1 is a value obtained by resistance-dividing the output voltage V3 of the booster circuit 21 when the switching transistors 41 and 41 ′ are turned on by the resistors 34 and 42 ′, and the voltage V2 is the switching transistor 41 (or 41). ') Is the voltage when turned off, the resistance 3
Determined by the value of 4.

Next, the operation of the above configuration will be described. (1) When the diagnostic function operates, the ignition switch 2 is turned on, the microcomputer 25 of the driver seat airbag system 35 starts to operate, and when performing the capacitance diagnosis, the microcomputer 25 passes through the signal line Y. Immediately after the switch circuit 32 is turned off, the switching transistor 31 is turned on for a predetermined time to discharge the sufficiently charged backup capacitor 23 through the resistor 30, and the terminal voltage of the backup capacitor 23 at that time is set to a micro value. When the computer 25 reads it, the microcomputer 25 obtains the voltage change amount of the terminal voltage of the backup capacitor 23, and then determines whether the electrostatic capacitance has a specified value or not, and activates an alarm device when an abnormality occurs. Let me know. In addition, the alarm device is activated even if the breakage of the detonators 28 and 28 'is diagnosed and it is determined that there is a failure.

After that, the switch circuit 32 is turned on, and power is supplied to the driver side airbag system 46 through the first communication circuit 33 and the power supply line 36, so that the microcomputer 25 causes the microcomputer 25 '. , Supply diagnostic request signal,
In synchronization with the end of transmission of the header of the request signal, the switch circuit 32 ′ is turned on for a predetermined time before the next data is transmitted, and the constant voltage circuit 44 is supplied via the power supply line 36.
The voltage stabilizing capacitor 44a is rapidly charged.

Further, the microcomputer 25 'receiving the request signal is connected to the driver side air bag system 46.
Inside, for example, the terminal voltage of the lateral acceleration sensor 24 'and the like is read, and by the output of the second communication circuit 33',
By turning on / off the switching transistor 41 ', the signal line Z is sent to the microcomputer 25 of the driver airbag system 35 via the power supply line 36.
If it is determined that there is a failure as a result of the diagnosis by the microcomputer 25, the alarm device is activated in the same manner as above.

(2) When the collision determination function is activated When the vehicle has a frontal collision after the above-mentioned various diagnoses have been completed (or when it has not been executed), the mechanical acceleration switch 29 of the driver airbag system 35. Is turned on, and when the microcomputer 25 determines that there is a serious collision based on the acceleration signal from the longitudinal acceleration sensor 24, the microcomputer 25 turns on the switch circuit 26 ′ to discharge the charge stored in the backup capacitor 23. The detonator 28 is energized via the protection diode 27 to deploy an airbag or the like in the driver's seat to protect the occupant from a frontal collision.

On the other hand, the microcomputer 25 'of the driver side airbag system 46 has the acceleration switch 4
The switch signal from 0 and the lateral acceleration sensor 24 '
If it is judged to be a serious collision based on the acceleration signal from
The microcomputer 25 'is the microcomputer 2
5, the determination result is returned as a response signal, and the microcomputer 25 turns on the switch circuit 26 'to turn on the charge stored in the backup capacitor 23 through the power supply line 36 and the detonator 28. To protect the occupant from a side collision by deploying an airbag provided on the seat.

[0030]

As described above, according to the first aspect of the invention, the waveform of the multiplexed signal transmitted between the devices can be faithfully transmitted, and the effect that erroneous transmission is eliminated is exhibited.

According to the second aspect of the invention, even if the transmission line and the power supply line are shared and used, the effect that the signal can be surely transmitted while the electric power is transmitted is exhibited.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of an occupant protection device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram of a power supply line 36 in FIG.

FIG. 3 is a waveform explanatory diagram for explaining problems in the related art and points to be improved by the present invention.

FIG. 4 is a circuit diagram of a conventional example of the present invention.

[Explanation of symbols]

 24,24 'Accelerometer 25,25' Microcomputer 26,26 ', 32 Switch circuit 28,28' Detonator 33,33 'Communication circuit 34,42 Resistor 31,41 Switching transistor 40 Acceleration switch

Claims (2)

[Claims] 1. A main control device that is supplied with a direct current power supply and that has a function of creating a first control signal based on a detection signal from a first sensor and monitoring each circuit unit to perform a failure diagnosis. It has a constant voltage circuit having a voltage stabilizing capacitor and is fed from the DC power source through a harness, and creates a second control signal based on a detection signal from a second sensor, and each circuit unit. And at least one sub-control device having a function of monitoring, the main control device, through the harness to the sub-control device, while supplying a request signal consisting of a header, a cord, etc., In response to the request signal, the sub control circuit,
A multiplex communication device that returns a response signal including at least the monitoring result of each circuit unit to the main control circuit, wherein the main control device is a constant voltage of the sub-control device at the same time as the transmission of the header of the request signal is completed. A multiplex communication device characterized by rapidly charging a voltage stabilizing capacitor of a circuit. 2. A resistor is connected to an end of the harness on the main controller side, and a switch circuit is connected in parallel with the resistor, and the main control circuit connects the switch circuit to the voltage stabilizing capacitor. 2. The multiplex communication device according to claim 1, wherein the multiplex communication device is instantaneously switched to an ON state during quick charging.