JP2002033740A - Multiplex communication circuit and passenger protection device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiplex communication circuit that is simplified, reducing the number of components. SOLUTION: In the multiplex communication circuit where a main control section and sub control sections conduct multiplex communication by using a power supply line for a signal line, communication input output ports of the main control section consist of a reception port, a transmission port, and control ports that can be set to a high impedance mode. When the main control section makes communication with specific selected sub control sections among the sub control sections, the high-impedance mode of the control ports sets communication lines of the other sub control sections that are not selected to a communication disabled state and the main control section makes communication with the selected communication available sub control sections.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multiplex communication circuit,
For example, 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.

[0002]

2. Description of the Related Art A conventional multiplex communication circuit and an occupant protection device of this type include, for example, one disclosed in Japanese Patent Application Laid-Open No. H11-255066, which will be described with reference to FIG. That is, in FIG. 4, the driver's seat side airbag unit 2 is
The passenger side airbag unit 3 is connected by sharing the signal lines A and B as power supply lines, and the booster circuit 6 of the front collision airbag unit 1
And boosts the output voltage supplied via the ignition switch 5 to charge the backup capacitor 7. The microcomputer 8 has a communication function, a collision determination function, and a diagnosis function. The microcomputer 8 inputs an acceleration signal from the longitudinal acceleration sensor 9 when a collision occurs, and determines whether the acceleration signal is a serious collision. If it is determined that the backup circuit 7 is turned on, the charge stored in the backup capacitor 7 is transferred to the detonator 11 and the mechanical acceleration switch 12.
To deploy an airbag or the like (not shown).

When the program for the diagnostic function of the microcomputer 8 is operated, the request signal created by the microcomputer 8 is simultaneously supplied to the first and second transmission switching transistors 40 and 44. The request signal is supplied to both the driver side airbag unit 2 and the passenger side airbag unit 3 via the signal lines A and B, and the driver side airbag unit 2 and the passenger side airbag unit 2 are supplied. Each of the bag units 3 generates a response signal in accordance with the supplied request signal, and transmits the response signal to a communication circuit (the third airbag unit 2 for the driver side airbag unit 2).
The signal is supplied to both signal lines A and B via the communication circuit 37).

When the low level state of the signal forming the response signal is generated, the negative potential sides Y and Y 'of the resistors 18 and 19 become low level, and a potential difference is generated between both terminals of the resistors 18 and 19. I do. At this time, the microcomputer 8
Since the selection prohibition signal is alternately supplied from the fourth communication circuit 13c to the comparison circuits 41 and 45 (FIG. 5A,
For example, when one comparison circuit 41 is supplied with the selection prohibition signal from the fourth communication circuit 13c of the microcomputer 8, the reference value of the comparison circuit 41 is at the 0 level. Although the output of the comparator 41 is maintained at the high level, the selection inhibit signal is not supplied to the other comparator 45, so that the output of the comparator 45 is in the high level or the low level by the voltage between the terminals of the resistor 18. The state becomes the level state (see FIG. 5D).

[0005] The selection prohibition signals to both of the comparison circuits 41 and 45 are alternately repeated as shown in FIGS. 5A and 5B, so that both of the comparison circuits 41 and 45 transmit the fourth communication circuit. 13c is supplied to a multiplexer (see FIG. 5 (D)), and the diagnosis function of the microcomputer 8 diagnoses both the side airbag units 2 and 3 for failure. If necessary, an alarm lamp or the like (not shown) Is driven to emit a failure notification. In the figure, the multiplex communication is performed by the fourth communication circuit 13c of the front airbag unit 1.
And a portion formed by a broken line frame portion indicated by reference symbol T and a portion formed by the third communication circuit 37, the switching transistor 38, and the resistor 39 of the driver side airbag unit 2. The same applies to the passenger side airbag unit 3. In the figure, 32 is a microcomputer, 33 is a lateral acceleration sensor, 37
Is a third communication circuit. The microcomputer 32 makes a collision judgment based on the acceleration from the left-right acceleration sensor 33. If it judges that a serious collision has occurred, the microcomputer 32 connects the third communication circuit 37, the switching transistor 38, and the signal line A. The microcomputer 8 supplies an ignition signal to a side impact detonator (not shown) to deploy the airbag. The same applies to the side airbag unit 3 for the passenger seat.

[0006]

However, for example, in recent electric components of vehicles, there is a demand for further miniaturization in terms of mounting space and a reduction in cost. Given such a multiplex communication circuit and an occupant protection device using the multiplex communication circuit, it is necessary to delete at least one electronic component such as a semiconductor component which has a particularly high unit cost. Is done.

Therefore, the present invention has been made in view of the above problems, and has as its object to reduce the number of parts and simplify the communication circuit.

[0008]

According to a first aspect of the present invention, a main control unit supplied with power from a vehicle-mounted battery and a plurality of sub-control units are connected via communication input / output ports provided respectively. Multiplex communication for supplying power to each of the plurality of sub-control units from the vehicle-mounted battery via the main control unit and performing multiplex communication between the main and the plurality of sub-control units via the communication input / output port In the circuit, the communication port of the main control unit, for reception, for transmission, and configured for low-level mode, high-level mode, or control for switching to high-impedance mode, the main control unit, When performing communication with a specific sub-control unit selected from among a plurality of sub-control units, the communication lines of the other non-selected sub-control units are switched to the control port in a high-level mode. Therefore The disabled state, is characterized in that communication is performed between the selected and via the available communication port sub-control unit.

The communication input / output port of the main control unit according to the second invention is connected to a communication line via a transmission circuit and a reception circuit, and the transmission port of the main control unit is connected to the plurality of transmission circuits. And commonly connected to a control port of the main control unit, and outputs of a plurality of receiving circuits and a reception port of the main control unit are commonly connected.

According to a third aspect of the present invention, a transmission circuit connected to the communication line is commonly connected to a transmission port of the main control unit, and input lines of the plurality of reception circuits are connected to a control port of the main control unit. And the outputs of a plurality of receiving circuits and the receiving port of the main control unit are commonly connected.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. In FIG. 1, the same configuration as FIG.
Or, the equivalent components are denoted by the same reference numerals and the detailed description thereof will be omitted, and only different portions, that is, the communication interface circuit T will be described below. The basic difference is that, first, the selection prohibition signal output from the fourth communication circuit 13c of the microcomputer 8 in FIG. 4 is a low-level or high-level logic signal. The microcomputer 8 '(main control unit) switches the ports connected to the base terminals of the transmission switching transistors 40 and 44 to output ports, in other words, to high impedance mode.

For example, when performing multiplex communication with the side airbag 2 for the driver's seat, as shown in FIGS. 2C and 2D, a port connected to the base terminal of the transmission switching transistor 44 (hereinafter referred to as control). Port)
Similarly, when switching from a low level state (also referred to as an output low level) to a high impedance state (FIG. 2C) and performing multiplex communication with the passenger side airbag unit 3, the base of the transmission switching transistor 40 is also used. The port connected to the terminal is switched from the low level state to the high impedance state (FIG. 2D).

More specifically, between the negative potential side Y of the resistor 18 inserted in the multiplex signal line A and the ground, a resistor 21 and a transmission switching transistor 44 connected in series are inserted. A resistor 23 and a transmission switching transistor 40 connected in series are interposed between the negative potential side Y ′ of the resistor 19 inserted in the multiplex signal line B and the ground, and these transmission switching transistors are connected. The base terminals of the transistors 40 and 44 are connected to the collector terminal of the transmission switching transistor 50 via resistors 51 and 52 respectively connected thereto, and are also grounded via the resistor 53.

A second difference is that there is no signal line connected from the fourth communication circuit 13c on the input side of the comparison circuits 41 and 45 in FIG.

Next, the operation of the above configuration will be described below with reference to FIG. When the front airbag unit 1 performs multiplex communication with the driver's seat side airbag unit 2, the control port connected to the base terminal of the transmission switching transistor 44 is connected via the signal line C to the control port.
By switching from the low level state to the high impedance state (FIG. 2C), the second transmission switching transistor 44 becomes operable. When performing multiplex communication with the passenger side airbag unit 3, the port connected to the base terminal of the transmission switching transistor 40 is switched from a low level state to a high impedance state via the signal line D (see FIG. )), The first transmission switching transistor 40
Becomes operable. For example, as shown in FIGS. 2C and 2D, the first high impedance mode section performs multiplex communication with the driver side airbag unit 2, and the next high impedance mode section performs the passenger seat section. Multiplex communication with the side airbag unit 3.

First, communication with the driver side airbag unit 2 will be described below, and then communication with the passenger side airbag unit 3 will be described, and this communication will be repeated alternately. Things. The low-level signal (section L in FIG. 2B) created by the microcomputer 8 'is supplied from the output port Tx to the base of the third transmission switching transistor 50 to be turned on.
The second transmission switching transistor 44 is made operable. When a transmission signal is supplied from the fourth communication circuit 13c to the operable second transmission switching transistor 44 via the signal line C, the second transmission switching transistor 44 is turned on and off by the transmission signal. Thus, the transmission signal is superimposed on the signal line (power supply line) A and supplied to the driver side airbag unit 2. At this time, the transmission signal is also received by the comparison circuit 45 via the signal line A and supplied to the microcomputer 8 ′. However, the microcomputer 8 ′ is output to the signal line A because the transmission signal is transmitted. Confirm that the transmitted signal is
The received transmission signal is discarded.

On the other hand, the driver side airbag unit 2, which receives the transmission signal when the transmission signal superimposed on the signal line A is detected by the comparison circuit 55, generates a response signal in accordance with the supplied transmission signal. Then, the response signal is superimposed on the signal line A via the switching transistors 50 and 54 (section L 'in FIG. 2F), whereby the response signal is detected by the comparison circuit 45 and the microcomputer 8' It is supplied to the fourth communication circuit 13c. Then, the diagnosis function of the microcomputer 8 'performs a failure diagnosis of the driver side airbag unit 2, and if necessary, drives an alarm lamp or the like (not shown) to drive the failure to notify the failure.

At this time, the response signal is also received by the comparison circuit 55 via the signal line A and supplied to the third communication circuit 37 of the microcomputer 32, but the microcomputer (sub-controller) 32 transmits the response signal. Since the response signal is output to the signal line A, the received response signal is discarded.

Next, the passenger side airbag unit 3
In the case of performing communication between the first transmission switching transistor 40 and the base station, the output port connected to the base terminal of the first transmission switching transistor 40 is switched from the low level state to the high impedance state via the signal line D (FIG. 2 (D)). The first transmission switching transistor 44 is enabled.

Thereafter, the low-level signal (section L in FIG. 2B) generated by the microcomputer 8 'is transmitted to the third
The power is supplied to the base of the transmission switching transistor 50 to be turned on, and the first transmission switching transistor 40 is made operable. The signal is supplied from the operable first transmission switching transistor 40 to the passenger side airbag unit 3 via the signal line B. At this time, the request signal is also received by the comparison circuit 41 via the signal line B. Although supplied to the microcomputer 8 ', the microcomputer 8' confirms that the request signal has been output to the signal line B because it is a transmitted request signal, and discards the received request signal.

On the other hand, the transmission signal superimposed on the signal line B is received in the same manner as the driver side airbag unit 2, and a response signal is created in accordance with the received transmission signal and output to the signal line B. , The response signal is detected by the comparison circuit 41, and the fourth signal of the microcomputer 8 '
It is supplied to the communication circuit 13c. Then, the diagnosis function of the microcomputer 8 'diagnoses the failure of the side airbag unit 3 for the passenger's seat, and turns on an alarm lamp or the like (not shown) to drive the alarm if necessary, thereby notifying the failure.

Embodiment 2 FIG. Embodiment 2 will be described with reference to FIG. 3, but what is shown in Embodiment 1 is 2
Although the two control ports are connected to the respective base terminals of the first and second transmission switching transistors 40 and 44, in the present embodiment, the two control ports are connected to the respective comparison circuits 41 and 45. It is connected to the non-inverting input terminal.

By connecting in this manner, the transmission signal generated by the microcomputer 8 '(FIG. 2B)
Is supplied to the third transmission switching transistor 50 from the output port Tx, the transmission signal becomes
The first transmission switching transistor 40 (or the second transmission switching transistor 44) is turned on and off to overlap the respective signal lines A (or B), and the driver side airbag unit 2 (or the passenger seat). It is simultaneously supplied to the side airbag unit 3). As a result, the driver side airbag unit 2 (or the passenger side airbag unit 3) generates a response signal to the transmission signal, and superimposes the response signal on the signal lines A and B connected to the transmission signal. , Return.

That is, these response signals are supplied to comparison circuits 41, 45 connected to the respective signal lines A, B, and the microcomputer 8 'is connected to, for example, the side airbag unit 2 for the driver's seat. When the multiplex communication is selected, the control port connected to the non-inverting input terminal of the comparing circuit 41 goes high through the signal line, and the control port connected to the non-inverting input terminal of the comparing circuit 45. Is set to the high impedance mode via the signal line, only the response signal supplied to the comparison circuit 45 is supplied to the microcomputer 8 ′,
The diagnosis function of the microcomputer 8 'diagnoses the failure of the driver's side airbag unit 2 and turns on an alarm lamp or the like (not shown) as necessary to notify the failure.

On the other hand, when the microcomputer 8 'selects, for example, multiplex communication with the passenger side airbag unit 3, the control port connected to the non-inverting input terminal of the comparison circuit 45 goes high. Since the control port connected to the non-inverting input terminal of the comparison circuit 41 is set to the high impedance mode, only the response signal supplied to the comparison circuit 41 is supplied to the microcomputer 8 ' The diagnosis function 8 'diagnoses the failure of the driver's side airbag unit 2 and turns on an alarm lamp or the like (not shown) as necessary to notify the failure.

[0026]

As described above, according to the present invention,
The number of components of the multiplex communication circuit can be reduced, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of Embodiment 1 of a multiplex communication circuit and an occupant protection device using the same according to the present invention.

FIG. 2 is an operation explanatory timing chart for explaining the operation of FIG. 1;

FIG. 3 is a circuit block diagram of Embodiment 2 of a multiplex communication circuit and an occupant protection device using the same according to the present invention.

FIG. 4 is a circuit block diagram of a conventional multiplex communication circuit and an occupant protection device using the same.

FIG. 5 is an operation explanatory timing chart for explaining the operation of FIG. 4;

[Explanation of symbols]

13c, 37 Communication circuit 18, 19, 21, 23, 51, 52 Resistance 40, 44, 50, 54 Transmission switching transistor 41, 45, 55 Comparison circuit

Claims (3)

[Claims] 1. A main control unit supplied with power from a vehicle-mounted battery and a plurality of sub-control units are connected via communication input / output ports provided respectively, and the main control unit is connected to the main control unit via the main control unit. A multiplex communication circuit that supplies power from the vehicle-mounted battery to each of the plurality of sub-control units and performs multiplex communication between the main and the plurality of sub-control units via the communication input / output port; The port is for receiving, for transmitting,
Low-level mode, high-level mode, or control for switching to high-impedance mode, the main control unit communicates with a specific sub-control unit selected from the plurality of sub-control units. When performing, the communication line of the other non-selected sub-control unit is set to the communication disabled state by switching the control port to a high level mode, and the sub-control is performed through the selected and communicable communication port. A multiplex communication circuit for performing communication with a unit. 2. The communication input / output port of the main control unit,
Connected to a communication line via a transmission circuit and a reception circuit,
The transmission port of the main control unit is commonly connected to the plurality of transmission circuits, and is separately connected to the control port of the main control unit, and further includes outputs of a plurality of reception circuits and reception ports of the main control unit. 2. The multiplex communication circuit according to claim 1, wherein the port and the port are connected in common. 3. A transmission circuit connected to the communication line is commonly connected to a transmission port of the main control unit, and input lines of the plurality of reception circuits are separately connected to a control port of the main control unit. 3. The multiplex communication circuit according to claim 1, wherein outputs of the plurality of reception circuits and a reception port of the main control unit are commonly connected.