JP4583897B2 - In-vehicle bus branch wiring harness - Google Patents

Description

The present invention relates to a vehicle mounting the bus branch for wire harness scan.

  In an automobile, in order to reduce in-vehicle wiring (wire harness), a communication system in which a large number of electrical units composed of a control device and a sensor / actuator group are connected through a multiplex communication line is constructed. In low-speed multiplex communication, a communication system is constructed from a communication circuit using a single signal line and body, whereas in high-speed multiplex communication of several tens of kbps to 10 Mbps, twisted pair wires (twisted pair wires) are used. Used as a communication path (bus). And the communication part (node) of an electrical equipment unit drives a communication path using a vehicle-mounted bus drive device (transceiver).

  As a typical method of such multiplex communication, there is CAN (Control Area Network) communication. As for the physical layer of this CAN communication protocol, signal level, electric wire characteristics, and wiring topology are defined in ISO / DIS11898, SAE-J2284, and the like.

  The in-vehicle bus drive device used for CAN drives CAN_H and CAN_L bus drive lines with a pair of transistors. Further, in-vehicle devices use these on-vehicle bus drive devices with a protection circuit.

  In general, in an automobile, an electrical unit (ECU) that is operated with power supplied even when the key is removed, and an electrical unit that operates only when power is supplied by turning the key to the position of an accessory or ignition Are mixed on the same in-vehicle bus.

  Such an in-vehicle bus drive device used for an in-vehicle bus needs to set an input impedance high in order to make it difficult to affect the in-vehicle bus when de-energized.

  On the other hand, the output impedance viewed from the vehicle-mounted bus is designed as low as possible. This is because it is necessary to quickly charge and discharge the charge of the capacitive component connected to the in-vehicle bus and drive it at a normal signal level. Numerically, the value is about 30Ω, which is the output impedance of a CMOS transistor having a large TTL or driving capability.

  Summarizing the above prior art, there is an intentional connection between the final drive stage transistor in the in-vehicle bus driving device of a node and the in-vehicle bus driving device of the other node connected to the end of the in-vehicle bus or the in-vehicle bus. The resistance component was not added to the. The same applies to high-speed in-vehicle multiplex communication of several tens of kbps to 10 Mbps using twisted pair wires other than CAN.

  In general, when a communication line is square-wave driven, the waveform is as shown in FIG. That is, in the communication line, ringing 1 and 3 as shown in FIG. 18 occurs due to reflection of the line due to impedance mismatch. In FIG. 18, reference numeral 6 indicates overshoot and reference numeral 5 indicates undershoot.

  On the other hand, in the case of an in-vehicle bus that transmits a differential signal using a twisted pair wire, there are two signals. For example, in the case of a CAN that is a typical example of an in-vehicle bus, the signal waveform is as shown in FIG.

  Hereinafter, the waveform on one side (CAN_H signal) of the differential signal will be described.

  The CAN_H signal is directly driven by the output stage transistor, and the output impedance is set low as described above.

  On the other hand, the characteristic impedance of the twisted pair wire is slightly high, about 120Ω. For this reason, impedance mismatch has already occurred.

  Here, it is assumed that the wiring topology of the CAN bus is expressed as shown in FIG. In FIG. 20, reference numerals 6a and 6b are nodes having the longest inter-node distance L, reference numerals 6c to 6e are CAN nodes connected to the branch line 8 drawn from the trunk line 7, and reference numeral λ is the length of the branch line 8 (cable stub). (Long) and d indicate the minimum distance between nodes.

  In CAN, the cable stub length λ is recommended to be a maximum of 0.3 m in ISO / DIS11898, which is an international standard, and 1 m is recommended in the Society of Automotive Engineers (SAE) -J2284, which is a standard of the American Automobile Engineering Association. . However, in an actual automobile, since the space for wiring is narrow, the cable stub length λ may inevitably become longer than the recommended dimension. For this reason, ringing due to signal reflection out of phase is difficult to settle.

  FIG. 21 is a diagram illustrating a particularly bad waveform example of the differential signal of the in-vehicle CAN bus. The differential threshold voltage value in CAN communication has a lower limit value of 0.5V and an upper limit value of 0.9V. Each in-vehicle bus driving device compares the differential voltage of CAN_H and CAN_L with the differential threshold voltage value, and determines that the signal line is dominant when the voltage on the signal line is higher than 0.9V. If the upper voltage is lower than 0.5V, it is determined to be recessive.

  In FIG. 21, when the change from recessive to dominant (2) occurs, the convergence of ringing is fast and the threshold voltage of 0.9 V is not interrupted, but when the change from dominant to recessive (3) occurs, the convergence is very poor . This is because the dominant voltage is actively maintained by the transistor, whereas the recessive voltage is passively maintained, so that the ringing 1 due to the signal reflection is difficult to be settled. A time difference Δt (= T2−T1) occurs between time T1 when the dominant state actually ends and time T2 at which the reception side can determine the start of recessive. Such a long time difference Δt causes a communication error.

  For this reason, in order to maintain the necessary communication speed, efforts are made to reduce the cause of ringing by reducing the number n of connected nodes, shortening the bus length L, or shortening the inter-node distance d. Although this was necessary, this was a major limitation in the on-board bus topology design, which made it difficult to design the entire network of the vehicle, and depending on the scale, it was necessary to divide the bus at the gateway, causing cost increases. It was.

Accordingly, an object of the present invention is to increase the degree of freedom of network design of the entire vehicle and increase the bus scale that increases the cost while maintaining the communication speed of the in-vehicle bus by speeding up the ringing convergence of the bus. It is to provide a car mounting bus branch line for the wire harness scan that.

In order to solve the above-mentioned problem, the invention described in claim 1 is connected to an in-vehicle bus trunk having a characteristic impedance Z ₀ , and a differential voltage V _BUS of a signal on the in-vehicle bus trunk is a predetermined dominant differential threshold. In-vehicle bus drive for transmitting and receiving signals on the in-vehicle bus trunk line while distinguishing between the active state (dominant) and passive state (recessive) of data compared with the hold voltage value V _DT and the recessive differential threshold value V _RT A wire harness for in-vehicle bus branch lines for connecting a device to the in-vehicle bus trunk line, comprising a resistor connected in series between the in-vehicle bus drive device and the in-vehicle bus trunk line.

The invention according to claim 2 is the wire harness for the in-vehicle bus branch line according to claim 1 , wherein the resistor has a differential voltage from the in-vehicle bus main line and the dominant differential threshold voltage value V _DT. A predetermined calculation formula from the recessive differential threshold value V _RT , the dominant output voltage V _D of the in-vehicle bus drive device, the recessive output voltage V _R, and the characteristic impedance Z ₀ of the in-vehicle bus main line. It is set to a value in the range obtained.

The invention according to claim 3 is the wire harness for in-vehicle bus branch according to any one of claims 1 and 2, wherein the resistor is molded with a transparent resin .

In the present invention, even if the branch line length becomes long, the amount of reflection can be attenuated by inserting a resistor in the communication line from the in-vehicle bus branch line to the junction portion with the in-vehicle bus trunk line. Therefore, ringing of the communication line can be reduced. In this case, since only a resistor needs to be inserted, there is an advantage that the cost for the countermeasure can be reduced.

Further, only when optional Device connection, wire well harness only using a dedicated ones, as it can use the circuit-device already designed as electrical unit. Moreover, since the number of parts is small, it is small and inexpensive, and it can be used by attaching only to the necessary branch lines, which is advantageous in terms of cost. As for the method of fixing the resistance portion, simple fixing such as tape fixing to the wire harness can be performed, and it is easy to adopt a waterproof structure.

  Moreover, since only the bus branch line is changed, it is possible to make an emergency use such as exchanging the wire harness of the electrical unit, particularly for only the electrical unit having severe ringing.

  For example, in CAN communication, which is a typical example of a communication system for an in-vehicle bus, in the case of changing from dominant to recessive in FIG. 21 (3), if the convergence of ringing is accelerated, from the time T1 when the dominant state actually ends. Δt (= T2−T1) is shortened until time T2 when the reception side determines the start of recessive, and communication errors are less likely to occur. Conversely, there is a design margin for increasing the number of nodes and extending the branch line length.

  Therefore, in one embodiment of the present invention, several Ω (around 1 Ω) between the on-vehicle bus branch line and the junction portion between the on-vehicle bus trunk line, such as from the transistor output of the bus drive stage to the communication line or on the communication line. A resistor of several tens of Ω was provided in series. FIG. 21 is before countermeasures and FIG. 1 is after countermeasures. From the viewpoint of impedance matching, the location where the resistor is mounted is preferably close to the in-vehicle bus driving stage transistor. This resistor functions as a so-called damping resistor that suppresses overshoot, undershoot, and reflected wave amplitude.

  Generally, in a LAN (Local Area Network) in a building or a wide area communication WAN (Wide Area Network), the conductor resistance of the communication line cannot be ignored because the signal line is long. Therefore, in order to avoid a decrease in signal voltage, there has been no provision of a series resistor that serves as a damping resistor on the communication path.

  For example, when a resistor is inserted in series in the communication line, the signal amplitude H in the communication line decreases. Actually, the amplitude of 2V in FIG. 21 is reduced to a little less than 1.5V in FIG.

  However, in the in-vehicle bus, the longest distance L between the nodes (FIG. 20) is at most 10 m or less and is relatively short, so the conductor resistance of the communication line can be almost ignored. Therefore, if the damping resistance is such that an amplitude of 1.4 V (= 0.9 V + 0.5 V) corresponding to the determination margin on the recessive side (threshold voltage 0.5 V with respect to 0 V) can be secured in advance, it is put in series with the communication line. There is no effect on the overall noise margin.

  By the way, by inserting a resistor in series in the communication line, a negative phenomenon of signal rise / fall time delay also occurs. However, since a communication speed of about 1 Mbps or less is applied in the in-vehicle communication, the delay of the rise / fall time of the signal hardly becomes a problem. This is because, in the case of communication of 1 Mbps or less, the pulse width of 1 bit is 1 μs or more, and when the resistance value inserted in series in the communication line is in the range of several Ω to several tens Ω, the signal rises / falls. This is because the influence is several ns to several tens ns or less, and hardly affects the communication.

  As described above, inserting a resistor in series in a communication line is a problem in a LAN (Local Area Network) in a building or a WAN (Wide Area Network) in a wide area communication. In communication of 1 Mbps or less, there is almost no problem as long as the resistance value is appropriately selected. The effect is the same as that of the damping resistor. As shown in FIG. 21 → FIG. 1, the convergence of ringing 1 is accelerated, and from the time T1 when the dominant is actually ended to the time T2 when the reception side determines the start of recessive. The time difference Δt can be reduced. Therefore, restrictions on bus topology design are eased while maintaining communication quality.

FIG. 7 shows the state of the communication line when viewed with a differential voltage. Here, 41 is a transmission side electrical unit, 42 is its bus drive (output impedance Z _S ), 43 is a resistor (resistance value R) attached according to the present invention, 44 is a reception side electrical unit, and 45 is its bus drive ( (Receiving state), 46 is a resistance (resistance value R) attached according to the present invention, 47 is a communication line (characteristic impedance Z ₀ ) serving as a trunk line, and 48 is a termination of the trunk line. Assuming that the amplitude at which the bus driving device 42 drives the output dominantly is V, the differential amplitude V _D applied to the communication cable 47 by the Z _S , R, Z ₀ voltage division ratio is
V _D = Z ₀ V / (Z ₀ + 2R + Z _S ) (1)
It becomes. The differential amplitude applied to the input of the bus driving device 45 is also V _D. The resistor 46 is not affected because the bus driver 45 is in a receiving state and the input impedance is extremely high.

The condition that the noise margin of dominant and recessive is not biased is V _D −V _DT ≧ V _RT −V _R (2)
It is. This is because in the case of CAN, the right side of equation (2) is a fixed value and only V _D is variable. Here, V _DT represents a dominant differential threshold voltage value, V _RT represents a recessive differential threshold value, and V _R represents a recessive output voltage (0 V in CAN).

Substituting Equation (1) into Equation (2) and arranging for R, and taking R> 0 into consideration, the calculated equation 0 <R ≦ Z ₀ (V / (V _DT + V _RT ) −1) / 2−Z _S (3)
Is obtained.

  In equation (3), it can be seen that V must be set so that the right side does not become negative, and the range of R at that time is obtained.

For example, in the case of CAN, V is normally 2 V. Therefore, if V _DT = 0.9 V, V _RT = 0.5 V, Z ₀ = 120 Ω, and Z _S is sufficiently small, equation (3) is 0 <R ≦ 25.7.

  When V becomes 1.5 V, 0 <R ≦ 8.57, and there is a possibility that a value of R that can sufficiently shorten the convergence time of ringing cannot be selected. For this reason, it is desirable to set the output voltage amplitude V of the in-vehicle bus drive device high. The output voltage amplitude of the in-vehicle bus driving device is determined by the forward voltage by the diodes 15a and 15b in FIG. Therefore, by managing the process so that this parameter becomes small, an in-vehicle bus drive device having an output voltage amplitude capable of ensuring a noise margin with a predetermined damping resistor inserted can be produced.

<First embodiment>
FIG. 2 is a block diagram showing the in-vehicle bus drive device 11 according to the first embodiment. As shown in FIG. 2, the in-vehicle bus drive device 11 is a CAN controller IC that controls CAN communication, and includes a pair of transistors 13a and 13b for outputting a pair of differential signals (CAN_H signal and CAN_L signal). The signal transmission circuit unit 13 includes diodes 15a and 15b for defining the direction of voltage application to the transistors 13a and 13b, and resistors 17a and 17b connected in series to the output sides of the diodes 15a and 15b, respectively. .

  One transistor 13a of the pair of transistors 13a and 13b of the signal transmission circuit unit 13 is a high-side transistor for outputting a CAN_H signal, and one end is connected to the power supply Vcc and the other end is an anode of the diode 15a. And is turned on / off according to a gate signal given from the transmission circuit 14 of a predetermined electrical unit. The other transistor 13b is a low-side transistor for outputting a CAN_L signal. One end of the transistor 13b is connected to the cathode of the diode 15b, the other end is grounded (GND), and a gate signal is supplied from a predetermined electrical unit. Turns on and off according to

  The diodes 15a and 15b are interposed between the twisted pair cable 21 serving as a communication line and the transistors 13a and 13b of the signal transmission circuit unit 13 in order to prevent backflow of current.

  Each of the resistors 17a and 17b is a damping resistor for suppressing the amplitude, overshoot, undershoot, etc. of the ringing 1 due to signal reflection or the like. In particular, the resistors 17a and 17b are received from the twisted pair cable 21 by the receiving circuit 22 of the communication partner. The resistance value R (for example, several Ω to several tens Ω) is set so that the convergence time of the ringing 1 in the recessive state of the signal is within the intended time.

  The connection of the predetermined electrical unit to the receiving circuit 22 is drawn from the connection point between the diodes 15a and 15b and the resistors 17a and 17b. As a result, the signal received from the twisted pair cable 21 that is a communication line is divided by the resistors 17 a and 17 b and then input to the receiving circuit 22.

  The in-vehicle bus drive device 11 is connected to the board-side connector 23 via a predetermined protection circuit 24, and the board-side connector 23 is detachably connected to the harness-side connector 25 on the twisted pair cable 21 side. Yes.

  In the in-vehicle bus drive device 11 having such a configuration, a gate signal is given to the transistors 13a and 13b of the signal transmission circuit unit 13 from the transmission circuit 14 of the electrical unit.

  As for the CAN_H signal, when one transistor 13a is turned on in response to the gate signal from the transmission circuit 14 of the electrical unit, the power supply Vcc is turned on by the transistor 13a and the diode 15a, the resistor 17a, the protection circuit 24, the board side connector 23, and the harness. It is sent to the twisted pair cable 21 through the side connector 25.

  At this time, in the other electrical unit, the voltage supplied from the twisted pair cable 21 is input to the receiving circuit 22 through the harness side connector 25, the board side connector 23, the protection circuit 24, and the resistor 17a.

That is, since there is no series resistance in the connector and the protection circuit, the output voltage of the transmission-side in-vehicle bus drive device is multiplied by Z ₀ / (Z ₀ + 2 * 17a) and transmitted to the reception circuit in the reception-side in-vehicle bus drive device. .

  The CAN_L signal is the same as that of the CAN_H signal except that the power supply Vcc and the ground GND are different.

  In the present embodiment, since the resistors 17a and 17b are incorporated in the in-vehicle bus drive device 11, there is no need to add parts to the circuit of the electrical unit, and there is no need to redesign the printed wiring board. There is an advantage not accompanied by much.

<Second embodiment>
This second embodiment differs from the first embodiment in that resistors 17a and 17b are incorporated in the protection circuit 24 as shown in FIG. Other configurations are the same as those of the first embodiment.

  Here, a circuit between the pin of the in-vehicle bus drive device 11 and the board-side connector 23 is called a protection circuit.

  The second embodiment is similar to the first embodiment in that the resistors 17a and 17b are inserted in series in the communication line, and thus has the same advantages as the first embodiment.

  Further, since only two resistors are added on the printed circuit board, the design can be easily changed and the cost is hardly increased.

<Third embodiment>
As shown in FIG. 4, the third embodiment differs from the first and second embodiments in that resistors 17a and 17b are incorporated in the harness-side connector 25. Other configurations are the same as those of the first and second embodiments.

  The third embodiment is similar to the first and second embodiments in that the resistors 17a and 17b are inserted in series in the communication line, and thus has the same advantages as the first embodiment. There is.

  Further, since only the harness side connector is changed, there is an advantage that the conventional electrical unit can be used as it is. In particular, it can be dealt with only for the terrible electrical unit with ringing 1, which is convenient.

<Fourth embodiment>
In the fourth embodiment, as shown in FIG. 5, the first embodiment to the third embodiment are configured in that resistors 17 a and 17 b are interposed between the harness-side connector 25 and the twisted pair cable 21. Make it different. Other configurations are the same as those in the first to third embodiments.

  The fourth embodiment is similar to the first to third embodiments in that the resistors 17a and 17b are inserted in series in the communication line, and thus has the same advantages as the first embodiment. There is.

  Since the present embodiment can be applied without changing any of the IC, the printed circuit board, and the connector, it is convenient for emergency.

<Fifth embodiment>
This fifth embodiment differs from the first to fourth embodiments in that resistors 17a and 17b are incorporated in the board-side connector 23 as shown in FIG. Other configurations are the same as those in the first to fourth embodiments.

  The fifth embodiment is the same as the first to fourth embodiments in that the resistors 17a and 17b are inserted in series in the communication line, and thus has the same advantages as the first embodiment. There is.

  Further, since it can be applied only by changing the board connector 23, the change of the printed board is almost unnecessary, and the application is easy.

<Sixth embodiment>
In the first to fifth embodiments, the resistors 17a and 17b are provided in series in the connector, the in-vehicle bus drive device or the protection circuit between the transistor output of the bus drive stage and the communication line. The mounting location of 17b may not be limited between the transistor output of the bus drive stage and the communication line. As one example of this, the sixth example is such that resistors 17a and 17b of several Ω (including around 1Ω) to several tens of Ω are provided in series on a communication line (vehicle bus).

  FIG. 8 is a block diagram showing a sixth example of this embodiment, and FIG. 9 is a diagram showing an internal configuration of an adapter 29 used in the sixth example.

  In the sixth embodiment, as shown in FIG. 8, an adapter 29 is installed in the vicinity of the harness side connector 25 on a twisted pair cable 21 as a communication line (vehicle-mounted bus), and resistors 17 a and 17 b are incorporated in the adapter 29. Therefore, the configuration is different from that of the first to fifth embodiments. Other configurations are the same as those in the first to fifth embodiments.

  The connection method between the adapter 29 and the twisted pair cable 21 may be a connector connection or a pressure contact connection, or other methods may be employed. The adapter 29 may be a pigtail type.

  The sixth embodiment is similar to the first to fifth embodiments in that the resistors 17a and 17b are inserted in series in the communication line, and thus has the same advantages as the first embodiment. There is.

  Moreover, since the adapter 29 can be used to achieve a very small size and light weight, it can be bundled with other electric wires and fixed with a simple binding tool such as a tape.

  Furthermore, since the adapter 29 can be retrofitted, it can be manufactured easily.

  Further, there is an advantage that the adapter 29 can be easily attached and used only at a necessary portion of the twisted pair cable 21.

<Seventh embodiment>
FIG. 10 is a block diagram showing an example of the in-vehicle bus branch wire harness 30 according to the seventh example of this embodiment. In each of the above-described embodiments, the resistors 17a and 17b are provided as damping resistors for suppressing the ringing 1 amplitude, overshoot, undershoot, and the like. However, for example, at a frequency of about CAN, only the ringing voltage amplitude attenuation is effective. large. In this embodiment, attention is paid only to the ringing voltage amplitude attenuation.

  In other words, in this embodiment, the in-vehicle bus branch wire harness 30 includes a twisted pair wire 21 as a branch line forming a multiplex communication path, a resistance portion 31 and connectors 25 and 32 as shown in FIG. They are bundled with electric wires and separated into individual connectors at a predetermined length according to the vehicle type.

  The resistor unit 31 is a damping resistor for suppressing the amplitude of the ringing 1 (FIG. 1) due to signal reflection or the like, and in particular, a recessive state of a signal received from the twisted pair cable 21 by the receiving circuit 22 of the communication partner. Is set to a resistance value R (for example, several Ω (including around 1 Ω) to several tens Ω) such that the convergence time of ringing 1 is within an intended time.

  Reference numeral 7 denotes a main line, reference numeral 11a denotes an electronic control unit (ECU), reference numeral 32 denotes a connector, and reference numeral 33 denotes a junction connector (JC) for connecting the connector 32 to the main line 7. Other configurations are the same as those in the first to sixth embodiments.

  According to this embodiment, since the resistance portion 31 is incorporated in the in-vehicle bus branch wire harness 30, there is no need to add parts to the circuit of the electrical unit, and there is no need to redesign the printed wiring board. There is an advantage not accompanied by a rise.

<Eighth embodiment>
FIG. 11 is a block diagram showing an eighth example of this embodiment. In this embodiment, as shown in FIG. 11, the in-vehicle bus branch line 21 is directly spliced to the in-vehicle bus trunk line 7 without using a junction connector (JC). Other configurations are the same as those of the seventh embodiment, and resistors 17a and 17b are provided in the communication line within the resistor portion 31.

  The eighth embodiment is similar to the seventh embodiment in that the resistors 17a and 17b are inserted in series in the communication line, and thus has the same advantages as the seventh embodiment.

<Ninth embodiment>
FIG. 12 is a block diagram showing a ninth example of this embodiment. In this embodiment, as shown in FIG. 12, a connector 35 is provided for connecting the in-vehicle bus branch line 21 to a junction connector (JC) 33, and resistors 17 a and 17 b are provided in the connector 35. Other configurations are the same as those of the seventh and eighth embodiments.

  The ninth embodiment is similar to the seventh and eighth embodiments in that resistors 17a and 17b are inserted in series in the communication line, and therefore has the same advantages as the seventh and eighth embodiments. is there.

  Furthermore, since there are no parts in the middle of the wire harness 30, there is an advantage that the wiring harness 30 can be easily operated as compared with the seventh and eighth embodiments.

<Tenth embodiment>
FIG. 13 is a block diagram showing a tenth example of this embodiment. In this embodiment, as shown in FIG. 13, the in-vehicle bus branch line 21 is provided with resistors 17a and 17b inside a junction connector (dJC) 34 (not shown). Other configurations are the same as those of the seventh and eighth embodiments.

  The tenth embodiment is the same as the seventh and eighth embodiments in that resistors 17a and 17b are inserted in series in the communication line, and therefore has the same advantages as the seventh and eighth embodiments. is there.

  Furthermore, since there are no parts in the middle of the wire harness 30, there is an advantage that the wiring harness 30 can be easily operated as compared with the seventh and eighth embodiments.

<Eleventh embodiment>
FIG. 14 is a block diagram showing an eleventh example of this embodiment. In this embodiment, as shown in FIG. 14, a resistor portion 31 for inserting resistors 17a and 17b in series is molded integrally with a twisted pair cable 21 as a communication line, and the resistor portion 31 serves as a waveform shaping device. It is configured to function. In this embodiment, since welding or a pressure welding method can be used for electrical connection, a printed circuit board is not required and costs can be reduced. In addition, downsizing, weight reduction, and waterproofing can be easily realized. Furthermore, when the resistance part 31 of the twisted pair cable 21 is molded, if the mold resin is made transparent, the connection part between the resistance part 31 and the twisted pair cable 21 can be easily observed, which is convenient.

  Furthermore, a practical vehicle-mounted bus branch wire harness 30 can be realized by applying the molding method as in the eleventh embodiment to the configuration of the seventh and eighth embodiments.

  According to this embodiment, the present invention can be applied at low cost without changing any of the IC and the printed board of the on-vehicle electronic unit (ECU) 11a, the connectors 23, 25, 32, and the junction connector 33.

<Twelfth embodiment>
FIG. 15 is a block diagram showing a twelfth example of this embodiment. In this embodiment, as shown in FIG. 15, resistors 17 a and 17 b are built in a connector 35 for connecting a twisted pair cable 21 as a branch line to a junction connector 33. Reference numeral 36 in FIG. 15 indicates a contact portion (connection terminal).

  In this embodiment, welding or pressure welding can be used for electrical connection, but a printed circuit board may be used.

  Further, by applying the twelfth embodiment to the ninth embodiment, a practical on-vehicle bus branch wire harness 30 can be realized.

  According to this embodiment, the present invention can be applied at low cost without changing any of the IC and printed circuit board or junction connector 33 of the on-vehicle electronic unit (ECU) 11a.

<Thirteenth embodiment>
FIG. 16 is a schematic perspective view showing a junction connector 34 according to a thirteenth example of this embodiment, and FIG. 17 is a circuit block diagram thereof. In this embodiment, resistors 17a and 17b are built in the junction connector 34 as shown in FIG. Reference numerals (7), (8-1), (8-2)... (8-n) in FIGS. 16 and 17 indicate branch line numbers.

  Although not shown in FIGS. 16 and 17, circuit terminations and filters may be formed in the junction connector 34.

  This embodiment is the same as the seventh to ninth embodiments in that the resistors 17a and 17b are inserted in series in the communication line, and thus has the same advantages as the seventh to ninth embodiments.

  Furthermore, since it can be applied only by changing the junction connector 34, it can be applied at low cost without changing any of the IC and the printed circuit board of the in-vehicle electronic unit (ECU) 11a or the connector 35 for the junction connector 34. It is.

  In the above-described embodiment and each example thereof, the CAN communication has been described as an example. However, the present invention is applicable to any bus that performs differential communication using a twisted pair line as a communication line. For example, FlexRay communication differs from CAN in signal level and communication speed, has two dominants (active state) representing O / 1, and has a recessive (passive state) corresponding to high impedance. Since this recessive state is a period between communication slots, it is necessary to quickly suppress ringing of the bus signal, but the present invention can contribute to this.

  Therefore, in the above embodiment and each of the examples, the final output stage of the CAN bus driving device is an example in which a pair of transistors and diodes are configured. However, in other communication systems, the final output stage circuit is suitable for it. Should be read as

It is a figure which shows the square wave and differential threshold voltage value ( _VDT , _VRT ) of in-vehicle communication in one Embodiment of this invention. It is a block diagram which shows 1st Example of this invention. It is a block diagram which shows 2nd Example of this invention. It is a block diagram which shows 3rd Example of this invention. It is a block diagram which shows 4th Example of this invention. It is a block diagram which shows 5th Example of this invention. It is a block diagram showing the mode of a communication line when it sees with a differential voltage. It is a block diagram which shows 6th Example of this invention. It is a figure which shows the adapter in 6th Example of this invention. It is a block diagram which shows 7th Example of this invention. It is a block diagram which shows 8th Example of this invention. It is a block diagram which shows 9th Example of this invention. It is a block diagram which shows 10th Example of this invention. It is a block diagram which shows 11th Example of this invention. It is a block diagram which shows 12th Example of this invention. It is a block diagram which shows 13th Example of this invention. It is a circuit block diagram which shows 13th Example of this invention. It is a figure which shows the square wave of the signal which flows into a communication line. It is a figure which shows the waveform of the signal which flows into the twisted pair line in the case of the vehicle-mounted bus which transmits a differential signal. It is a figure which shows the bus | bath topology in in-vehicle communication. It is a figure which shows the relationship between the differential threshold voltage value ( _VDT , _VRT ) and ringing in CAN communication.

Explanation of symbols

7 trunk line 8 branch line 11 vehicle-mounted bus drive device 13 signal transmission circuit unit 13a, 13b transistor 14 transmission circuit 15a, 15b diode 17a, 17b resistance 21 twisted pair cable 22 reception circuit 23 board side connector 24 protection circuit 25 harness side connector 29 adapter 30 Bus branch wire harness 31 Resistance section 32 Connector 33 Junction connector 34 Junction connector 35 Connector L Bus length d Distance between nodes

Claims (3)

The differential voltage V _BUS of the signal on the in-vehicle bus trunk line is compared with a predetermined dominant differential threshold voltage value V _DT and a recessive differential threshold value V _{RT while} being connected to the in-vehicle bus trunk line having the characteristic impedance Z _0. In- vehicle bus branch wire for connecting an in - vehicle bus drive device for transmitting and receiving signals on the in-vehicle bus trunk line while distinguishing between an active state (dominant) and a passive state (recessive) of data to the in-vehicle bus trunk line A harness ,
A wire harness for an in-vehicle bus branch line comprising a resistor connected in series between the in-vehicle bus drive device and the in-vehicle bus trunk line . It is a wire harness for in- vehicle bus branch lines according to claim 1,
The resistor includes a differential voltage from the vehicle bus trunk, and the dominant differential threshold voltage value V _DT, and the recessive differential threshold value V _RT, a dominant output voltage V _D of the vehicle bus driving device The in- vehicle bus branch wire harness is set to a value obtained from a recessive output voltage V _R and a characteristic impedance Z ₀ of the in-vehicle bus trunk line using a predetermined calculation formula. It is a wire harness for in-vehicle bus branch lines according to any one of claims 1 and 2 ,
The wire harness for on-vehicle bus branch lines, wherein the resistor is molded with a transparent resin .

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