JP3497321B2 - Multiplex communication circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an occupant protection device including a plurality of airbags for protecting an occupant in the event of a vehicle collision, for example. -Abbreviation of network). Prior to the description of a multiplex communication circuit according to the present invention, a general occupant protection apparatus before multiplex communication is applied will be described with reference to FIG. 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. When the collision determination function of the microcomputer 11 determines that a serious collision has occurred based on the acceleration signal supplied from the acceleration sensor 10, the charged charge is turned on by the switch circuit 7. 8. Discharge is performed in series through a mechanical acceleration switch 9 (in this case, in an on state, usually in an off state), and a primer (not shown) is ignited by a primer 8,
The airbag is deployed. The mechanical acceleration switch 9 has a structure disclosed in Japanese Patent Application No. 5-351470 filed by the present applicant. The microcomputer 11 has a failure diagnosis function. For example, when the capacity of the backup capacitor 5 is diagnosed, the switching transistor 13 is turned on for a predetermined time, and the electric charge charged in the backup capacitor 5 is transferred via the resistor 12. It discharges, reads the amount of change in the terminal voltage of the backup capacitor 5 at that time, diagnoses the capacitance, and when it is determined that the capacitance is different from the specified value and is abnormal, an alarm device such as a lamp (not shown) is used. Inform the crew. Further, the microcomputer 11 inputs the respective terminal voltages of the primer 8 and the voltage difference thereof, and when the disconnection or short circuit of the primer 8 is diagnosed and judged as abnormal, an alarm device such as a lamp not shown is used. Inform the crew. [0004] However, recently, there has been a demand for protecting an occupant against a collision from the front and rear of the vehicle and protecting the occupant also from a collision from the left and right. As a method for responding to the demand, for example, the occupant protection device shown in FIG. 4 is arranged near the center console so as to cope with a collision from the front of the vehicle, and the same occupant protection device as the occupant protection device is used. It is conceivable to arrange the occupant protection devices near the door so as to be able to cope with a collision from the left and right directions of the vehicle. Had to arrange a plurality of long harnesses, and there was a risk that costs would increase. In addition, the use of a plurality of harnesses necessitates the use of expensive connectors, which may increase costs. Accordingly, the present invention has been made in view of the above problems, and a power supply line is commonly used as a signal line without greatly impairing the voltage stability of the power supply line.
The purpose is to reduce costs. According to a first aspect of the present invention, there is provided a multiplex communication circuit having a first resistor having one end connected to an output side of a DC power supply, and one end connected to the other end of the first resistor. Connected second
A resistor, a first switch circuit having one end connected to the other end of the second resistor and the other end grounded, and a first switch circuit turned on;
A main communication control circuit that outputs a request signal to be turned off and inputs a response signal corresponding to the request signal from the other end of the first resistor; and a power supply line connected to the other end of the first resistor. A constant voltage circuit supplied from a DC power supply; a third resistor having one end connected to the input side of the constant voltage circuit; a second switch circuit having one end connected to the other end of the third resistor and the other end grounded And a failure diagnosis function of performing a failure diagnosis of each circuit unit, when a request signal of the main communication control circuit is input from one end of the third resistor, and a failure is generated by the failure diagnosis function,
A sub-communication control circuit that controls the second switch circuit to be turned on and off and outputs a response signal corresponding to the request signal each time the request signal is received a plurality of times. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Embodiment 1 of the present invention will be described with reference to FIG. First, the main occupant protection device 35 will be described. That is, reference numeral 21 denotes a booster circuit, which boosts an input voltage from the battery 1 supplied through the ignition switch 2 to charge the backup capacitor 23 through the resistor 22, and switches the switch circuit 32, the resistor 34,
The boosted voltage is supplied to the auxiliary occupant protection device 45 via the power supply line 36 in series. Reference numeral 24 denotes a longitudinal acceleration sensor for detecting an acceleration generated in the longitudinal direction of the vehicle.
Supplied to The microcomputer 25 has a collision judging function. When the microcomputer 25 judges that a serious collision has occurred based on the acceleration signal supplied from the longitudinal acceleration sensor 24, the microcomputer 25 is charged with the backup capacitor 23 by turning on the switch circuit 26. The electric charge is discharged through a discharge diode 27, and an ignition current is passed in series to a primer 28 and a mechanical acceleration switch (which is normally in an off state, but is in an on state at the time of a collision) 29, and an air bag or the like is discharged. Let it unfold. Since the longitudinal acceleration sensor 24 is provided on the front side of the vehicle, it is difficult to detect the acceleration from the rear of the vehicle. The microcomputer 25 has a function of diagnosing the failure of the backup capacitor 23, the primer 28, and the like. In the capacity diagnosis of the backup capacitor 23, the signal line Y is connected immediately after the ignition switch 2 is turned on. The switch circuit 32 is turned off through the switch circuit 32 so that the charge of the backup capacitor 23 is not discharged as a dark current of each circuit of the auxiliary occupant protection device 45, that is, the auxiliary occupant protection device 45 described later loads the backup capacitor 23 with a load. Microcomputer 25 after the relationship acting as
Turns on the switching transistor 31 and discharges the charge sufficiently charged in the backup capacitor 23 through the resistor 30 for a predetermined time, and the microcomputer 25 determines the amount of change in the terminal voltage of the backup capacitor 23 at that time. The capacity is diagnosed by reading and calculating the capacitance, and when it is determined that the capacity is abnormal, the occupant is notified using an alarm device such as a lamp (not shown). The microcomputer 25 judges the disconnection of the primer 28 based on the terminal voltage of the primer 28 and its voltage difference. Notify the occupants using the warning device. When the microcomputer 25 determines that a serious collision has occurred based on the acceleration signal from the longitudinal acceleration sensor 24, the microcomputer 25 turns on the switch circuit 26, turns on the primer 28, and deploys the airbag provided on the steering wheel. In response to the acceleration information from the auxiliary occupant protection device 45 described later via the signal line Z, the switch circuit 26 'is turned on as necessary to turn on the primer 28', and the airbag provided on the seat or the like is deployed. . Further, the microcomputer 25 sends a request signal for requesting the auxiliary occupant protection device 45 to supply various diagnostic signals (response signals) via the signal line X and the first communication circuit 33 at regular intervals T. (See FIG. 3A), while the auxiliary occupant protection device 45 is connected via the signal line Z.
(See FIGS. 3B and 3C), and the alarm device such as a lamp is activated as described above according to the type (contents) of the response signal. Reference numeral 34 in the figure denotes a resistor inserted in the power supply line 36 between the switch circuit 32 and the input / output terminal (power supply terminal) B of the main occupant protection device 35. The switching transistor 41 is equivalent to a switching transistor 41 'to be described later. The switching transistor 41 is turned on and off by the first communication circuit 33 to output a request signal, and the resistor 42 is equivalent to the resistor 42'. Thus, these series circuits are interposed between the power supply line 36 and the switching transistor 41, and have the same function as each other, and constitute the same circuit. Next, the auxiliary occupant protection device 45 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-right direction of the vehicle, and outputs an acceleration signal as a detection output. This is a lateral acceleration sensor supplied to the computer 25 '. The microcomputer 25 'has a collision determination function similar to that of the microcomputer 25, and is 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 magnitude of the collision from the side of the vehicle is determined, and if it is determined that the collision is a serious collision, the collision information is transmitted to the second communication circuit 33 ′,
Power supply line 3 via switching transistor 41 '
6 is output. The microcomputer 25 'has a diagnostic function similar to the microcomputer 25. The diagnostic function diagnoses a failure of the left-right acceleration sensor 24' and the acceleration switch 40, for example. When it is determined that there is no abnormality, the first communication circuit 33 connects the power supply line 36 via the power line 36 until the abnormality is determined.
Each time a request signal (supplied at a constant period T) shown in FIG. 3A is received a plurality of times, a response signal (see FIG.
If it is determined that there is any abnormality in the diagnosis result, a response signal indicating the abnormality (see FIG.
The main occupant protection device 3 is connected via a communication circuit 33 ′ (same as the first communication circuit 33), the power line 36, and the signal line Z.
5 to the microcomputer 25. The acceleration switch 40 includes a semiconductor acceleration sensor and a comparison circuit that inputs a detection signal from the acceleration sensor.
A switch signal is output when a detection output from the semiconductor acceleration sensor exceeds a reference value of the comparison circuit. Reference numeral 41 'denotes a switching transistor such as a field effect transistor, which is turned on and off by an output signal of the second communication circuit 33'. Reference numeral 42 'denotes a resistor inserted in a line (an extension line of the power supply line 36) between the switching transistor 41' and the input / output terminal (also a power supply terminal) of the auxiliary occupant protection device 45.
2 ′ is connected in series with the resistor 34 via the power supply line 36, and applies a voltage generated on the anode side of the backflow prevention diode 43 when the switching transistor 41 ′ is turned on (or when the first communication circuit 33 Even when the switching transistor 41 formed on the output side is turned on, the minimum voltage level is kept at a constant voltage other than 0 level, so that the input voltage can be always supplied to the constant voltage circuit 44 described later. The constant voltage circuit 4
Reference numeral 4 always receives an input voltage and supplies power to each circuit constituting the auxiliary occupant protection device 45. The power line 36 is connected to the main occupant protection device 3.
When the communication is performed between the vehicle 5 and the auxiliary occupant protection device 45, the voltage waveform is as shown in FIG. That is, in FIG. 2, the voltage V1 is the switching transistor 41, 4
Step-up circuit 2 when one of 1 'is turned on
The output voltage V3 of 1 is connected to the resistors 34 and 42 (or 42 ').
The voltage V2 is the voltage when the switching transistor 41 is turned off, and is determined by the value of the resistor 34. Next, the operation of the above configuration will be described. When the ignition switch 2 is turned on when the diagnostic function operates and the microcomputer 25 of the main occupant protection device 35 starts operating,
The microcomputer 25 turns off the switch circuit 32 via the signal line Y. Immediately thereafter, the microcomputer 25 turns on the switching transistor 31 for a certain period of time, and switches the backup capacitor 23
By discharging the voltage via the resistor 30 and inputting the terminal voltage of the backup capacitor 23 to the microcomputer 25 at that time, the microcomputer 25 determines whether or not the capacitance is a regular value based on the voltage change of the terminal voltage of the backup capacitor 23. The alarm is activated to notify the operator when an abnormality is detected. Thereafter, the microcomputer 25 diagnoses the disconnection and short-circuit abnormality of each part of the main occupant protection device 35, for example, the primers 28 and 28 '. When the diagnosis is completed, the microcomputer 25 turns on the switch circuit 32 and switches the first communication circuit. 33,
A request signal for obtaining a diagnosis result performed by the microcomputer 25 'is output to the microcomputer 25' of the auxiliary occupant protection device 45 via the power line 36 at regular intervals T. The microcomputer 25 'that has received the request signal (FIG. 3A) performs a failure diagnosis of each part in the auxiliary occupant protection device 45, for example, the lateral acceleration sensor 24', the acceleration switch 40, and the like, and there is no abnormality in the diagnosis result. While the determination is made, a response signal (FIG. 3B) indicating that there is no abnormality until the request signal is received a predetermined number of times, and the request signal is determined when the diagnosis result is determined to be abnormal. Each time is supplied, a response signal indicating an abnormality is output (FIG. 3
(C)). Also, by the output of the second communication circuit 33 ',
ON / OFF control of the switching transistor 41 ′,
That is, the signal is transmitted via the signal line Z to the microcomputer 25 of the main occupant protection device 35 via the power supply line 36 by multiplex communication, and the microcomputer 25 performs diagnosis. When the collision judging function is activated, after the above-mentioned various diagnoses have been completed (or not performed), when a forward collision such as a rear-end collision with the vehicle ahead occurs, the mechanical acceleration switch 29 of the main occupant protection device 35 Turns on,
Further, when the microcomputer 25 determines that a serious collision has occurred based on the acceleration signal from the longitudinal acceleration sensor 24, the microcomputer 25 controls the switch circuit 26 to turn on and transfers the electric charge charged in the backup capacitor 23 via the discharging diode 27. To energize the primer 28,
Deploy an airbag to protect occupants from a forward collision. However, at this time, since the acceleration acts in the front-rear direction of the vehicle, no signal is output from the left-right acceleration sensor 24 ′ of the auxiliary occupant protection device 45 and the acceleration switch 40, and the ignition current flows from the backup capacitor 23 to the primer 28 ′. Is not supplied. When the vehicle is collided from the side,
Since the mechanical acceleration switch 29 of the main occupant protection device 35 is not turned on and the front-rear direction acceleration sensor 24 does not output an acceleration signal having a magnitude corresponding to the acceleration signal associated with the frontal collision, the primer 28 is ignited. No current is supplied. On the other hand, the microcomputer 25 'of the auxiliary occupant protection device 45 determines that a serious collision has occurred based on the switch signal from the acceleration switch 40 and the acceleration signal from the lateral acceleration sensor 24'. Turns on the switch circuit 26 'in response to a request signal from the microcomputer 25 of the main occupant protection device 35 immediately thereafter, and sends a response signal for supplying an ignition current to the primer 28' to the second communication circuit 33 '. The microcomputer 25 controls the switch circuit 26 ′ to turn on and transfers the electric charge charged in the backup capacitor 23 to the primer 2.
8 'to deploy the airbag to protect the occupant from side impact. As described above, according to the present invention,
It is possible to reduce the number of times a response signal is issued in multiplex communication, thereby minimizing fluctuations in current consumption and voltage of the power supply line, and reduce costs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit block diagram of a first embodiment according to the present invention. FIG. 2 is a waveform diagram for explaining voltage fluctuation of a power supply line in FIG. FIG. 3 is an explanatory waveform diagram for explaining the operation of FIG. 1; FIG. 4 is a circuit diagram of a conventional example of the present invention. [Description of Signs] 24, 24 'Acceleration Sensor 25, 25' Microcomputer 26, 26 ', 32 Switch Circuit 28, 28' Primer 33, 33 'Communication Circuit 34, 42, 42' Resistance 31, 41, 41 'Switching Transistor 40 Acceleration switch

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichi Hashimoto 2-1910 Nisshin-cho, Omiya-shi, Saitama Prefecture Kansei Corporation (56) References B2) Patent 2773486 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01D 21/00 B60R 21/32 G01P 15/00 H04L 5/00 H04L 25/02

Claims (1)

(1) A first resistor having one end connected to the output side of the DC power supply, a second resistor having one end connected to the other end of the first resistor, and a second resistor. A first switch circuit having one end connected to the other end of the first resistor and the other end grounded, and a request signal for controlling ON / OFF of the first switch circuit, and outputting a response signal corresponding to the request signal to the first resistor. A main communication control circuit input from the other end, a constant voltage circuit fed from the DC power supply via a power line connected to the other end of the first resistor, and one end connected to the input side of the constant voltage circuit A third resistor, one end of which is connected to the other end of the third resistor and the other end of which is grounded; and a failure diagnosis function for performing failure diagnosis of each circuit portion. When the request signal of the main communication control circuit is input from and a failure occurs by the failure diagnosis function,
A multiplex communication circuit, comprising: a sub-communication control circuit that controls on / off of a second switch circuit and outputs a response signal corresponding to the request signal each time the request signal is received a plurality of times.