JPH04132341A - Multiplex transmission system - Google Patents

Abstract

PURPOSE:To easily discriminate the fault of a multiplex unit main body and the disconnection fault of a branch line interconnecting a multiplex unit and a bus line by providing a disconnection detection line arranged between each branch connector and each multiplex unit and a disconnection line detection section provided to each branch connector to the system. CONSTITUTION:When a disconnection takes place in a branch line 9a of a multiplex unit An, a disconnection detection line 10a is simultaneously broken, an oscillation circuit 17 in a branch connector 5 is oscillated and an oscillation signal is sent to a bus line 9 via a diode 16. Thus, it is discriminated that a disconnection takes place in the branch line 9a of the multiplex unit An. On the other hand, while no signal is sent from the oscillation circuit 17 to the bus line 9, when message transmission reception is not implemented between the multiplex unit An connecting to the branch connector 5 having the oscillation circuit 17 and all other multiplex units Bn-Dn, it is discriminated that the multiplex unit An is faulty. Thus, whether the multiplex unit main body An is faulty or a disconnection exists in the branch line 9a is discriminated.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to a multiplex transmission system mainly installed in automobiles, etc., and in particular, to prevent failure of a multiplex unit and a branch line connecting the multiplex unit and a bus line. The present invention relates to a multiplex transmission system that can easily determine whether a wire is disconnected or not.

"Prior Art" As a type of bus applied to multiplex transmission systems, a multidrop ring in which both ends of a multidrop bus are short-circuited has been developed by the present applicant (Japanese Patent Application No. 6:3-1).
49346).

This multi-drop ring (hereinafter referred to as a bus line) is made of a single wire, a pair wire, a twisted pair wire, a knoll break wire, a coaxial cable, etc.

FIG. 4 is a schematic configuration diagram showing a multiplex transmission system using this bus line. Note that this multiplex transmission system is applied to automobiles.

In this figure, bus line l includes branch bus line 1a.
= Multiplex units A-1-( are connected via Ih. These multiplex units A-H control various devices such as lamps, wipers, and washers, and receive switch signals from various devices. As shown in the schematic diagram of FIG. 5, each unit has a communication section 2 that exchanges messages with other multiplex units, and a control section 3 that controls this communication section 2 and various devices not shown. It is composed of

In such a configuration, each of the multiplex units A to H controls various devices by exchanging messages with each other via the bus line l. For example, if a stop lamp switch is connected to multiplex unit 8 and a stop lamp is connected to multiplex unit D, when the driver depresses the brake pedal, multiplex unit A sends a switch signal to turn on the stop lamp. The containing message is sent via bus line l towards multiplex unit D. The multiplex unit D reads the received message (message) and supplies power to the stop lamp based on the switch signal included in the message, thereby lighting the lamp.

``Problems to be Solved by the Invention'' By the way, in the conventional multiplex transmission system described above, when a multiplex unit does not respond, it is assumed that the multiplex unit itself is malfunctioning or that the multiplex unit and the bus line
In order to determine whether the branch line connecting the line was broken, the branch line was pulled out and inspected. However, since this inspection requires a large number of man-hours, there is a problem in that maintainability is very poor.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a multiplex transmission system that can easily distinguish between a failure in a multiplex unit main body and a disconnection in a branch line connecting the multiplex unit and a bus line. It is an object.

[Means for Solving the Problems] The invention according to claim 1 includes a bus line, a plurality of branch connectors connected to the bus line, and a branch line connected to each of the branch connectors. , a multiplex transmission system comprising a plurality of multiplex units connected to each of the branch lines, a disconnection detection line disposed along the branch line between each of the branch connectors and each of the multiplex units; The invention according to claim 2, further comprising: a disconnection detection unit provided in each of the branch connectors and configured to send a signal indicating a disconnection to the bus line when the disconnection detection line is disconnected. In a multiplex transmission system comprising a bus line consisting of at least two electric wires and a plurality of multiplex units connected to each of a plurality of branch lines connected to this bus line, A feature is that a resonant circuit is provided in a portion drawn into the multiplex unit.

"Function" According to the configuration described in claim 1, when the disconnection detection line disposed along the branch line between the branch connector and the multiplex unit is disconnected, this disconnection is detected as a disconnection in the branch connector. The detection unit detects the disconnection and sends a signal indicating the disconnection to the bus line.

Therefore, if a signal indicating a disconnection is sent from the disconnection detector to the bus line, it can be determined that a disconnection has occurred in the branch line connected to the branch connector having the disconnection detector. On the other hand, when a signal indicating a disconnection is not sent from the disconnection detection unit to the bus line, signals are exchanged between the multiplex unit connected to the branch line of the branch connector having this disconnection detection unit and all other multiplex units. If this is not done, it can be determined that the main body of the multiplex unit is malfunctioning.

According to the second aspect of the present invention, the presence of each resonant circuit can be detected by using an absorption frequency meter or the like and adjusting its oscillation frequency to the resonant frequency of the resonant circuit of each multiplex unit.

Therefore, if a resonance point cannot be obtained even if the oscillation frequency is matched to the resonant frequency of the resonant circuit provided in a certain multiplex unit, there is a disconnection in the branch line that connects the multiplex unit and the bus line. I understand. On the other hand, if signals are not exchanged between the multiplex unit and all other multiplex units even if a resonance point is obtained, it can be determined that the multiplex unit main body is malfunctioning.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic configuration diagram showing a multiplex transmission system according to a first embodiment of the present invention. Note that this multiplex transmission system is applied to automobiles as described above. In this figure, branch connectors 5 to 8 are connected to the bus line 9, respectively.

Further, these branch connectors 5 to 8 have branch lines 98 to 98.
A multiplex unit An=I)n is also connected via 9d. Furthermore, branch connectors 5 to 8 and multiplex unit An=
A disconnection detection line 1oa-IOd is provided along the branch lines 98-9d. Each of the multiplex units Δn=Dn described above has the same configuration as each of the multiplex units A-1-1 described above except that the connector type is different. Further, the above-mentioned bus line 9 is composed of at least two electric wires.

FIG. 1 is a diagram that does not show the internal structure of the branch connector 5 and the connection state between the branch connector 5 and the multiplex unit 80. The branch connector 5 has a transistor 1 as shown in the figure.
3a, I3b, capacitors 14a, I4b, 1° resistor 15a-15d, and diode 16.
7 is provided.

The remaining elements of this oscillation circuit 17 except for the diode 16 constitute a so-called astable multivibrator.

In this case, the time constants of the astable multi-by-breaks arranged in each branch connector 5 to 8 are determined to have different oscillation frequencies.

The diode 16 has an anode connected to the transistor +
3a collector, one end of capacitor 14a, and resistor +5a
are commonly connected to one end of the bus line 9, and have their cathodes connected to one line of the bus line 9.

This diode 16 sends the oscillation signal of the astable multivibrator to the bus line 9.

The above-mentioned disconnection detection line IOa is connected between the emitters of the transistors 13a and 13b and the base of the transistor 13a. When the disconnection detection line IOa is not disconnected, the emitter and base of the transistor 13a are at the same potential, so the astable multi-vib break does not go into an oscillation state.

In a multiplex transmission system having such a configuration, for example, when the branch line 9a of the multiplex unit Δn is disconnected, the disconnection detection line IOa is also disconnected at the same time, and the oscillation circuit 17 in the branch connector 5 oscillates. As a result, the oscillation signal is sent to the bus line 9 via the diode 16. By detecting this sent signal, it is found that a break has occurred in the branch line 9a of the multiplex unit 80. On the other hand, in a state where no signal is sent from the oscillation circuit 17 to the bus line 9, between the multiplex unit 80 connected to the branch connector 5 having this oscillation circuit 17 and all the other multiplex units Bn=Dn. If messages (signals) are not being exchanged, it can be seen that this multiplex unit An is out of order. Therefore, it is possible to easily determine whether there is a failure in the main body of the multiplex unit An or a break in the branch line 9a.

Next, FIG. 3 is a schematic diagram showing the main parts of a second embodiment of the present invention. As shown in this figure, a resonant circuit 20a in which a coil 18 and a capacitor 19 are connected in series is inserted in a portion of the branch line 9a drawn into the multiplex unit Ann. The resonant frequency of this resonant circuit 20a is unique to this circuit, and other multiplex units B nn-D n
The resonant frequencies of the resonant circuits 20b to 20d (not shown) provided in each of the resonant circuits 20b to 20d (not shown) are different from each other. In this case, each of the resonant circuits 201) to 20d also has a different resonant frequency from each other. Multiplex units Ann=Dnn can be specified by having mutually different resonance frequencies. By providing the resonant circuits 20a to 20d in each of the multiplex units Ann-Dnn in this way, it is possible to detect a disconnection in each of the branch lines 98 to 9d. For example, if a break occurs in the branch line 9d, if the absorption frequency meter 21 sequentially adjusts its oscillation frequency to the resonant frequencies of the resonant circuits 208 to 20d, the oscillation frequency will match the resonant frequency of the resonant circuit 20d. A resonance point cannot be obtained at t-.

This shows that a break has occurred in the branch line 9d. On the other hand, if messages are not exchanged with all of the other multiplex units Bnn=Dnn even though a resonance point is obtained, this multiplex unit A
It can be seen that nn is out of order. Therefore, it is possible to easily determine whether there is a failure in the main body of the multiplex unit Ann or a break in the branch line 9a.

In addition, the above 1. In the second embodiment, four multiplex units An=Dn, Ann-Dnn have been described, but this number is not limited.

Further, in the above embodiment, an astable multi-by-break is used for the oscillation circuit 17, but it goes without saying that the present invention is not limited to this, and that various oscillators can be used.

Also, the above 1. It goes without saying that the multiplex transmission system of the second embodiment can be applied to any vehicle that employs a multiplex transmission system, in addition to automobiles.

"Effects of the Invention" Since this invention is configured as explained above,
The effects described below are produced.

In the multiplex transmission system according to claim n, there is provided a disconnection detection line arranged along the branch line between each branch connector and each multiplex unit, and a disconnection detection line provided at each branch connector when the disconnection detection line is disconnected. Since we have installed a disconnection detection unit that sends a signal indicating a disconnection to the bus line when there is a disconnection, if a multiplex unit does not respond, it is possible that the multiplex unit itself is malfunctioning, or that the branch line connecting the multiplex unit and the bus line is connected. It can be easily determined whether the wire is disconnected or not.

Therefore, since these can be easily determined, there is no need to pull out and inspect the branch line in the event of a failure. As a result, the number of man-hours is reduced and maintainability is improved compared to the conventional method.

In the multiplex transmission system according to claim 2, since the resonant circuit is provided in the portion drawn into the multiplex unit of each of the plurality of branch lines connected to the bus line consisting of at least two electric wires, each resonance circuit is provided. By checking whether a resonance point can be obtained for the circuit, it is possible to easily determine whether there is a failure in the multiplex unit body or a break in the branch line connecting the multiplex unit and the bus line.

Therefore, the same effect as described in claim 1 described above can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a multiplex (4-transmission system) according to a first embodiment of the present invention, FIG. 2 is a circuit diagram showing the main parts of the same embodiment, and FIG. 3 is a diagram showing a second embodiment of the present invention. 4 and 5 are schematic configuration diagrams showing a conventional multiplex transmission system. 9a to 9d...branch lines, 10a=lOd... Disconnection detection line, 17...
...Oscillation circuit (disconnection detection section), 18 ... Coil, 19 ... Capacitor (18 and 19 constitute the resonance circuit 20a), 2 turtles ... Absorption type frequency meter, An=Dn...Multiple unit, A nnA+D
nn−°−°multiplex unit.

Claims (2)

[Claims] (1) A bus line, a plurality of branch connectors connected to the bus line, a branch line connected to each of the branch connectors, and a plurality of multiplex units connected to each of the branch lines. In a multiplex transmission system,
a disconnection detection line disposed along the branch line between each of the branch connectors and each of the multiplex units;
A multiplex transmission system comprising: a disconnection detection unit provided in each of the branch connectors and configured to send a signal indicating a disconnection to the bus line when the disconnection detection line is disconnected. (2) In a multiplex transmission system comprising a bus line consisting of at least two electric wires and a plurality of multiplex units connected to each of a plurality of branch lines connected to this bus line, each of the branch lines A multiplex transmission system characterized by providing a resonant circuit in a portion drawn into the multiplex unit.