JP2006332973A - Connection structure of multiplex communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the distortion of a multiplex signal waveform without altering a substrate of an electronic control unit. <P>SOLUTION: Three or more electronic control units 11 and 16 which are connected through multiplex communication are mounted on a vehicle. The two electronic control units 11 and 12 are connected to both terminals of a trunk line 17 constituting a communication line 19, the other electronic control unit 13 is connected to a branch line 18 branching off from the trunk line 17, and an electric conductor 20 for an open stub whose tip is made open is intermediately connected to a branch line 18 on a position side of connection with the electronic control unit 13 for prevention against distortion of the multiplex signal waveform. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a connection structure for a multiplex communication device, and more specifically, in a multiplex communication device in which a large number of electronic control units are connected via a branch line using a wire harness as a transmission path, distortion of a signal waveform generated on the branch line side during communication is reduced. It is an improvement.

  In recent automobiles, there are an increasing number of cases where a plurality of electronic control units (ECUs) control each other in cooperation with each other in order to achieve high functionality and environmental support due to advances in IT technology. When connecting a plurality of electronic control units in this way, the electric wires of the wire harness are used as signal lines, the electronic control units are connected to both ends of the main wires and the branch control terminals branching from the main wires are electronically controlled. In many cases, units are connected, and an increase in the number of electric wires is suppressed by connecting each electronic control unit with a signal line such as a twisted pair line and performing multiplex communication (Japanese Patent Laid-Open No. 2002-368766). .

However, an increase in the amount of information to be communicated and an increase in the number of connected electronic control units may distort the waveform of the multiplexed signal transmitted / received on the signal line, resulting in a communication error, particularly distortion in the signal waveform on the branch line. Is likely to occur.
In order to eliminate this signal distortion, means such as reducing the communication speed, reducing the number of electronic control units to be connected, and shortening the length of the signal line can be considered. However, it is impossible to reduce the communication speed or reduce the number of electronic control units in order to maintain the high functionality of the automobile. For this reason, the circuit wiring of the wire harness has become very difficult.

In general, the interface circuit for multiplex communication is often defined by specifications, and it is difficult to mount signal waveform improving means on the board of the electronic control unit. Even if it is possible to cope with waveform improvement in the substrate of the electronic control unit, it is useless if the design of the substrate is changed once the electronic control unit is manufactured.
JP 2002-368766 A

  The present invention has been made in view of the above problems, and an object thereof is to improve the distortion of a multiplexed signal waveform without changing the substrate of the electronic control unit.

  In order to solve the above-described problems, the present invention is such that three or more electronic control units connected by multiplex communication are mounted on a vehicle, and two of these electronic control units are connected to both main terminals constituting the communication line. In addition, another electronic control unit is connected to a branch line branched from the main line, and an open stub electric wire with an open end is used to prevent distortion of multiple signal waveforms on a branch line on the connection position side with the electronic control unit A connection structure for a multiplex communication device is provided, characterized in that the intermediate connections are intermediately connected.

With the above configuration, since the open stub wire is connected to the middle of the branch line constituting the communication line and impedance matching on the branch line is achieved, disturbance of the signal waveform caused by signal reflection can be reduced. . Therefore, it is possible to improve the distortion of the multiple signal waveform without reducing the communication speed, reducing the number of electronic control units, or shortening the length of the communication line.
In addition, since the open stub wire is not provided on the substrate of the electronic control unit, but only connected to the communication line later, the waveform can be improved on the communication line side and the electronic control unit side is not affected. Therefore, even if a reception failure or the like occurs due to signal waveform distortion after all the designs are completed, it is only necessary to retrofit and connect an open stub wire to a necessary place, thereby improving the flexibility of design work.

  It is preferable that the trunk line and the branch line are made of twisted pair electric wires, and the open stub electric wire intermediately connected to the twisted pair electric wires is also made of twisted pair electric wires.

The open stub wire is preferably set to a length matching impedance.
The above-described configuration has an advantage that the tuning operation is simplified because it is only necessary to adjust the length of the wire when impedance matching is performed so that signal reflection does not occur.

Alternatively, it is preferable that impedance is matched to the open stub wire without depending on the length of the wire by interposing an inductance or a capacitance.
If it is the said structure, since impedance matching can be aimed only by adjusting an inductance and a capacitance, it can prevent that the electric wire for open stubs becomes long.

  As is clear from the above description, according to the present invention, impedance matching is achieved by the open stub wire, so that distortion of the multiplexed signal waveform can be improved. At that time, the open stub electric wire is not provided on the substrate of the electronic control unit, but is only retrofitted to the communication line, thereby improving the flexibility of the design work.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a multiplex communication system 10 mounted on a vehicle. Various electronic control units (multiplex communication devices) 11 to 16 are connected to a communication line 19, and the electronic control units 11 and 12 are trunk lines of the communication line 19. The other electronic control units 13 to 16 are connected to the branch line 18 branched from the main line 17 via connectors C3 to C6. In addition, the trunk line 17 and the branch line 18 of the communication line 19 are comprised by the twisted pair electric wire.

When the signal reflection occurs due to impedance mismatch at the connection portion of the branch line 18 to the electronic control unit 13 and there is distortion of the signal waveform, the branch line 18 on the connection position side with the electronic control unit 13 is opened at the tip. A stub wire 20 is intermediately connected. The open stub wire 20 is composed of a twisted pair wire, and the open end is insulated.
As shown in FIG. 2 (A), the open stub electric wire 20 has the ends of the pair of electric wires 20 connected to the pair of electric wires constituting the branch line 18 of the communication line 19 by soldering H, respectively.
As an alternative, as shown in FIG. 2 (B), the end portion of the open stub wire 20 ′ may be wound around the branch line 18 of the communication line 19 so as to form the splice portion S.
Further, the electric wire may be branched using a dedicated branch connector.

As shown in FIG. 2A, the length L of the open stub wire 20 is set to such a length that the impedance between the electronic control unit 13 and the branch line 18 is matched. This length L is separately calculated by computer simulation or the like.
In the final delivery form, the release stub electric wire 20 is wound around the branch line 18 and taped together so that it does not get in the way during transportation and wiring.

  With the above configuration, since the impedance matching is achieved by connecting the open stub wire 20 to the middle of the communication line 19, the disturbance of the signal waveform due to signal reflection can be reduced, and the multiple signal waveform Distortion improvement. Moreover, since the open stub wire 20 is not provided in the electronic control unit 13 but is simply connected to the communication line 19 later, the tuning work for improving the waveform does not affect the electronic control unit 13 side, and the design work Flexibility can be improved.

FIG. 3 shows a second embodiment.
The difference from the first embodiment is that an inductance or a capacitance is provided in the open stub wire 30.

The open stub wire 30 is a straight pair wire, and the open end is insulated. The pair of wire ends of the open stub wire 30 are connected to the pair of wires constituting the branch line 18 of the communication line 19 by soldering H, respectively. Note that, as in the first embodiment, they may be connected to each other by splice connection or connector connection.
The open stub wire 30 is provided with an inductor coil 31 serving as an inductance and a capacitor 32 serving as a capacitance. By adjusting these capacities and the like, the impedance is matched regardless of the length of the wire. Yes.
With the above configuration, impedance matching can be achieved only by adjusting the inductance and capacitance, so that there is an advantage that it is possible to prevent the open stub wire 30 from becoming long. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

1 is an overall view showing a connection structure of a multiplex communication apparatus according to a first embodiment of the present invention. (A) is a principal part enlarged view, (B) is a principal part enlarged view of a modification. It is a principal part enlarged view which shows 2nd Embodiment.

Explanation of symbols

11 to 16 Electronic control unit 17 Trunk line 18 Branch line 19 Communication lines 20 and 30 Open stub wire 31 Inductor coil 32 Capacitor C1 to C3 Connector H Solder S Splice part

Claims (4)

  Three or more electronic control units connected by multiplex communication are mounted on the vehicle, and two of the electronic control units are connected to both terminals of the main line constituting the communication line and are connected to branch lines branched from the main line. Another electronic control unit is connected, and an open stub wire having an open end is intermediately connected to a branch line on the connection position side with the electronic control unit for preventing distortion of a multiple signal waveform. Multiplex communication device connection structure.   The multiplex communication device connection structure according to claim 1, wherein the trunk line and the branch line are made of twisted pair electric wires, and the open stub electric wires that are intermediately connected to the twisted pair electric wires are also made of twisted pair electric wires.   The connection structure for a multiplex communication apparatus according to claim 1 or 2, wherein the open stub wire is set to a length for matching impedance.   The connection structure for a multiplex communication apparatus according to claim 1, wherein the open stub wire is provided with an inductance or a capacitance so that impedance is matched regardless of the length of the wire.

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