JP3410302B2 - Communication device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device which is mounted on an automobile and reduces erroneous communication operation in a noise environment of a noise electromagnetic field.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an outline of the main configuration of a conventional communication device. Reference numeral 1 is a sub-computer, which is composed of a sub-microprocessor 5 and a transistor Tr1 etc.
And the signal output thereof is input to the base of the transistor Tr1 and is output to the wires a and c of the wire harness 2 through the transistor Tr1 and the load resistor R1 and the like.

A wire harness 2 is composed of three insulated electric wires (three-wire type) and a connector. A data signal input from the sub computer 1 is output to the center computer 3 via the wire harness 2. It Also,
DC power is supplied from the DC power supply terminal 4 of the center computer 3.
Is supplied to one terminal of the resistor R1 in the sub computer 1 and the sub microprocessor 5 through one of the three electric wires (b).

The other wire (c) of the wire harness 2 is for grounding, and is configured to be used both for the signal and for the negative side of the DC power supply. The wire harness 2 is constructed such that the three electric wires are covered with a net-like shield coating, and the upper layer of the wire harness 2 is covered with an insulating jacket, and the end of the net-like shield portion is grounded to the frame of the mounted vehicle. This protects the computer from malfunction due to pulsed electrical noise generated from the electronic ignition system of the engine and various switches.

A center computer 3 is composed of an OP amplifier 6, a main microprocessor 7, a stabilized DC power source B and the like. 4 is a DC power supply terminal, which is one terminal of a connector set in the center computer 3,
The positive side of the stabilized DC power source B is connected (the negative side is grounded), and a bypass capacitor on the output side of the DC power source B not shown in the figure causes a ground potential (zero potential) for the data signal frequency. ).

Reference numeral 5 denotes a sub-microprocessor, which is composed of a semiconductor including a memory and an arithmetic unit and its peripheral circuits,
Signal processing is performed based on the programmed criteria with the required signal input from the sensor, and the data signal is output. 6
Is an operational amplifier, which is composed of a differential amplifier and peripheral circuits such as a threshold voltage supply circuit for its operation. The data signal from the sub-computer 1 is input to the inverting input terminal of the operational amplifier 6.

Reference numeral 7 is a main microprocessor, which is a ROM,
It is composed of a semiconductor and its peripheral circuits that consist of a RAM and a computing unit such as a register, and signal processing is performed based on the programmed criteria by the data signal input from the OP amplifier 6
The required control signal is output. With the above configuration, the DC power required for the operation of the sub computer 1 is supplied from the center computer 3 side via the wires b and c of the wire harness 2, and the data signal output from the sub computer 1 is the wire. It is input to the center computer 3 via a and the wire c and is comprehensively processed to obtain a target output.

[0008]

By the way, this three-wire type wiring harness has a problem that a shield wire structure for noise prevention is required, resulting in high cost and a wide wiring space at the time of mounting. It was It is an object to realize a signal communication device that solves these problems.

[0009]

According to the present invention, there are provided a first communication means and a second communication means which are supplied with power and perform a communication process, and the first communication means and the second communication means. A communication line connected between the first communication means and the communication signal indicating the result of processing by the first communication means, the communication signal being sent to the second processing means via the communication line. Comprises a power supply line to which a power level is applied and a quasi-floating ground line to which a quasi-floating ground level is applied. The input / output terminals of the second communication means to which the communication line is connected are balanced. Type comparing circuit is connected through the input / output circuit, and the comparing means performs a sensitive operation when signals of opposite phases appear at the two input terminals, and signals of the same phase appear at the two input terminals. If you do Characterized in that it is one that does not take place.

In the balanced type input / output circuit, a first resistance means connected between a power source and an output terminal to the first communication means, a ground and a first communication means are provided. Between the second resistance means connected to the input terminal, the third and fourth resistance means connected in series between the output terminal and the ground, and between the input terminal and the power supply And a fifth and sixth resistance means connected in series to the inverting input terminal of the comparison means is connected to a connection point of the third and fourth resistance means, and a non-inverting input terminal of the comparison means is connected to the connection point of the third and fourth resistance means. It is characterized in that it is connected to the connection point of the fifth and sixth resistance means.

The first and second resistance means have the same resistance value. Further, the first and second resistance means serve as both resistance means for power consumption current to the first communication means and resistance means for signal detection. Further, the comparison means is composed of an operational amplifier, and the voltage division ratio of the third and fourth resistance means and the voltage division ratio of the fifth and sixth resistance means are the first or second resistance means. It is characterized in that the output from the operational amplifier is set not to be inverted by the voltage change of only one of the above.

The first communication means is a side control unit which is provided on the side of the vehicle and detects a collision on the side of the vehicle and transmits the processing result as a collision detection signal via the communication line. The second communication means is provided on the center side of the vehicle, receives the collision detection signal through the communication line, processes the collision detection signal, and deploys an airbag provided in the vehicle when a collision is determined. It is a main side control unit.

[0013]

EXAMPLES Next, examples of the present invention will be described. In this example, a sub computer 1 (satellite side unit) having an acceleration sensor (not shown) provided on a side surface of a vehicle is involved in communication in a side collision detection type airbag system.
And a communication with a center computer 3 (main unit) that receives a side collision signal transmitted from the sub computer 1 and performs airbag deployment processing, but is not particularly limited to this and general first control It is applicable as long as it is communication between the unit and the second control unit.

The sub-computer 1 and the center computer 3 are also known as sub-ECU 1 (Electronic Control).
Unit), and is also referred to as the main ECU 3. FIG. 1 is a configuration diagram showing a circuit configuration of an embodiment of the present invention. Incidentally, FIG.
The same numbers are given to the same configurations as those shown in, and the detailed description is omitted.

Reference numeral 1 denotes a sub-computer, which is composed of a microprocessor 5 and its peripheral circuits, and has a common data signal output line output from the sub-computer 1 and a DC power supply line for supplying DC power consumed by the computer. Terminal a1 of the wire harness 2 which is composed of terminals
And a3. This microprocessor 5 processes a detection output (acceleration) from a G sensor (not shown) and outputs a rectangular wave data signal indicating that the ignition should not be or should be ignited in accordance with the acceleration. Power supply side communication line 21 by turning Tr1 on and off
Vary the amplitude level of the voltage.

The transistor Tr1 as the output stage is interposed (connected) between the power supply side communication line 21 and the quasi-floating ground line 22. A wire harness 2 is composed of two insulated and twisted electric wires (twisted pair) and their connectors. Reference numeral 3 denotes a center computer, which includes the OP amplifier 6 and resistors R2, R3, R4, R5, R6, R7, and the main microprocessor 7 which form a resistor network for bias voltage formation, signal transmission, and DC power supply. Composed.

The main microprocessor 7 determines whether or not to ignite a squib (not shown) based on the data signal output from the OP amplifier 6, and controls the deployment of the airbag. Reference numeral 6 denotes an OP amplifier, which is composed of a differential amplifier having two balanced input terminals and a peripheral circuit thereof, which operates in response to an input of a signal having an opposite phase with respect to the ground line, and has a signal (noise) of the same phase. It is configured so that no sensitive operation is performed in response to an input.

More specifically, the voltage dividing ratio (R4 / R5) of the voltage dividing resistors R4 and R5 for inputting the potential at the point B seen from the point D side to the OP amplifier 6 and C seen from the point A side. OP of potential at point
The voltage division ratio of the voltage dividing resistors R6 and R7 (R6
/ R7) is set so that the OP amplifier 6 is not inverted by a voltage change of one of the resistors R2 and R3. Next, the operation will be described.

First, the data signal output from the sub-computer 1 is output as a ground-balanced output to the terminals a1 and a3 of the wire harness 2 consisting of two electric wires, and passes through the terminals a2 and a4 of the wire harness 2. , Is input to the inverting input terminal and the non-inverting input terminal of the OP amplifier 6 via the resistors R4 and R7 in the center computer 3, respectively, and the output of the OP amplifier 6 is supplied to the main microprocessor 7 as an unbalanced output to ground. This signal is output, signal processing is performed based on the programmed criteria at this signal input, and the necessary control signal is output.

Next, the supply of DC power to the sub computer 1 and the application of a bias (threshold) voltage to the OP amplifier 6 will be described. The inverting input terminal of the OP amplifier 6 is
It is connected to the connection point of the resistor R4 and the resistor R5, the other end of the resistor R5 is grounded, the other end of the resistor R4 is connected to the resistor R2, and the other end of the resistor R2 is connected to the DC power supply terminal 4. As a result, a bias (threshold) voltage is applied to this inverting input terminal.

The connection point between the resistor R2 and the resistor R4 is the supply point on the power supply side of the DC power, the supply voltage is the power supply level via R2, and is connected to the terminal a2 of the wire harness 2, One conductive path on which the power supply and the data signal are superimposed is formed. The non-inverting input terminal of this differential amplifier is connected to the connection point between resistors R7 and R6,
The other end of R6 is connected to the DC power supply terminal 4, the other end of the resistor R7 is connected to the resistor R3, and the other end of the resistor R3 is grounded, so that the non-inverting input terminal has a bias (threshold) voltage. Given.

The connection point between the resistor R3 and the resistor R7 is a supply point close to the ground side of the DC power, and the supply voltage is a quasi-floating ground level via R3 (potential slightly floating than the ground).
That is, the other conductive path that is connected to the terminal a4 of the wire harness 2 and on which the DC power supply and the data signal are superimposed is formed. In addition, about the value of resistance R2 and resistance R3, R2 = R3
Since the direct current loop that flows through these resistors becomes the resistor R3 from the round trip of the wire harness 2 (including the sub computer 1) via the resistor R2, the voltage drop across each resistor is the same value. Becomes

This is because the input terminals of the center computer 3 (the connection points between the resistors R2 and R4 and the connection points between the resistors R3 and R7) to which the terminals a2 and a4 of the wire harness 2 are connected are grounded. This is a balanced input / output circuit that exhibits the same input / output impedance with respect to the line both in terms of direct current and in terms of frequency of the data signal, and is configured to exhibit the effect of noise elimination described below. .

The resistors R2 and R3 are choke coils each having a small DC resistance (balanced circuit having the same inductance) when a higher impedance is required for the data signal or when the DC power consumption of the computer 1 is larger. From the viewpoint of configuring
You can change to. Therefore, the electric noise sources of automobiles are ignition noise and cranking noise of starter,
There are various types such as pulsating current components of alternator, switching noise of reactors such as various solenoid coils, etc.The propagation path of these noises is transmitted through various wire harnesses or radiated from the harnesses through space and guided to various electronic devices. Some items are picked up and picked up.

Now, referring to FIG. 2, FIG. 2 is a signal waveform diagram showing the operation of FIG. 1, where the horizontal axis is the time axis and the vertical axis is the voltage axis. Point D in FIG. 1 is the ground potential (0 V), point A indicates the power supply voltage (for example, 5 V), and relates to the signal consumed and output by the sub computer 1 that operates in response to a collision signal from a sensor (not shown). The voltage v1 is the voltage drop of the resistors R2 and R3 due to the current flowing through the CPU 5,
The voltage v2 is each voltage drop in the resistors R2 and R3 due to the current flowing in the transistor Tr1.

At the point B, the voltage drop (V1
+ V2) appears as a downward waveform, and the voltage divided by the resistors R4 and R5 is applied to the inverting input terminal of the OP amplifier 6. On the other hand, at point C, the voltage drop (V1 + V2) of the resistor R3 is upward waveform. The voltage divided by the resistor R6 and the resistor R7 is applied to the non-inverting input terminal of the OP amplifier 6, and the OP amplifier is driven by the signal voltage appearing at these points B and C, that is, when viewed from the power supply side. One drive voltage V3 (between points A and C) and the other drive voltage V4 (between points D and B) viewed from the ground side are intermediate voltages of the power supply voltage (shown by a chain line, for example, 2.5 V). ), The op-amp gives the optimum response operation to the collision signal.

The noise picked up by the wire harness 2 appears as noise N1 at the point B and noise N2 at the point C with the same polarity and phase. Therefore, as will be described later, these noises are generated by the OP amplifier. OP is suppressed by 6
No output from the amplifier 6. In this embodiment, the sub computer 1 itself and the center computer 3 itself are provided with an electrical shield (not shown) so as not to pick up the electrical noise.

Since the wire harness 2 has two insulated electric wires twisted in a rope shape, the noise voltage induced in the two twisted pairs is grounded in an environment in which the lines of electromagnetic force of noise are parallel to each other. The same noise voltage is induced between the line and the terminal a2 and between the ground line and the terminal a4, and noise is not picked up against the noise magnetic field between the twisted pair, that is, between the terminals a2 and a4. A noise voltage of the same phase is induced with respect to the noise field (cancellation by twist).

This in-phase noise voltage is input from the terminals a2 and a4 to the balanced input circuit of the center computer 3, so that the phase and amplitude of the noise voltage are disturbed with respect to the ground line due to the same input impedance. Without OP
The amplifier 6 cancels this noise voltage. More resistance
Since R2 and R3 are also used as the power supply current consumption resistor of the CPU 5 and the signal detecting (noise canceling) resistor, the cost can be reduced.

As described above, according to the present embodiment, when an inexpensive twisted pair consisting of only two wires sharing a power supply line and a communication line is used and signals and DC power are superposed and transmitted, each conductor of the twisted pair is connected. Since the circuit is configured so that the power supply impedance to ground for each terminal is the same,
It is possible to provide a low-cost signal communication device with reduced noise interference, less malfunction, and low cost.

[0031]

As described above in detail, according to the present invention, not only the power supply line and the communication line can be shared to reduce the cost, but also the signal and the DC power are superposed on the two-wire type signal communication device. A low-cost signal communication device that is less likely to malfunction due to noise interference by configuring a balanced circuit that uses the bias (threshold) voltage forming circuit part of the signal input circuit and the DC power supply circuit in common for transmission. Can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is a signal waveform diagram showing the operation of FIG.

FIG. 3 is a configuration diagram showing a conventional signal communication circuit configuration.

[Explanation of symbols]

1-Sub computer 2 ... Wire harness 3 ... Center computer 4 ... DC power supply terminal 5 ... Sub-microprocessor 6 ... OP amplifier 7: Main microprocessor

Claims (6)

(57) [Claims] 1. A first communication means and a second communication means that are supplied with power and perform communication processing, and a communication line connected between the first communication means and the second communication means. And a communication signal indicating a result of processing by the first communication means is sent to the second processing means via the communication line, wherein the communication line has a power supply level as a power supply line. And a quasi-floating ground level is applied as a quasi-floating ground line, and the input / output terminal to which the communication line in the second communication means is connected is compared via a balanced type input / output circuit. Means is connected, the comparing means performs a sensitive operation when signals of opposite phases appear at the two input terminals, and performs a sensitive operation when signals of the same phase appear at the two input terminals. It ’s not something And a communication device. 2. The balanced input / output circuit comprises: a first resistance means connected between a power source and an output terminal to the first communication means; and a ground and a first resistance means connected to the first communication means. A second resistance means connected between the input terminal and a third resistance means connected in series between the output terminal and the ground;
A fourth resistor means, and a fifth resistor connected in series between the input terminal and the power source,
A sixth resistance means, the inverting input terminal of the comparison means is connected to the connection point of the third and fourth resistance means, and the non-inverting input terminal of the comparison means is the fifth resistance means.
2. The communication device according to claim 1, wherein the communication device is connected to a connection point of the sixth resistance means. 3. The communication device according to claim 2, wherein the first and second resistance means have the same resistance value. 4. The first and second resistance means serve as both resistance means for power consumption current to the first communication means and resistance means for signal detection. Two
Alternatively, the communication device according to item 3. 5. The comparison means comprises an operational amplifier, and a voltage division ratio between the third and fourth resistance means and the fifth division means.
3. The voltage division ratio between the first resistance means and the sixth resistance means is set so that the output from the operational amplifier is not inverted by a voltage change of only one of the first or second resistance means. The communication device according to any one of claims 1 to 4. 6. The first communication means is a side control unit which is provided on a side of a vehicle and detects a collision on the side of the vehicle and transmits the processing result as a collision detection signal via a communication line. The second communication means is provided in the center of the vehicle, receives the collision detection signal through the communication line, processes the collision detection signal, and deploys the airbag provided in the vehicle when a collision is determined. The communication device according to claim 1, wherein the communication device is a main side control unit.