JPH03265404A - Data transmission system - Google Patents

Abstract

PURPOSE:To protect a data signal on a transmission line against adverse influence by employing a transmission transformer in the communication of data signal for the purpose of isolation between a transmitter and the transmission line and grounding the neutral point of the transformer winding on the transmission line side to the body in each transmitter. CONSTITUTION:When high speed digital transmission is carried out between transmitters 1, 2, a digital signal is transmitted from the transmitter 1 through a transmission transformer 3 on a transmission line 7 to a transmission transformer 4 and received by the transmitter 2. When such a transmission system is applied on a train, an in-phase noise voltage wave induced in the transmission line 7 from a noise source 8 during data transmission is discharged through the neutral points 5, 9 of the winding of closer or both transmission transformers 3, 4 on the transmission line side to ground points 6, 10. Consequently, influence of noise can be eliminated in shorter time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a data transmission system, and in particular, to a data transmission system that uses an ordinary lead-through without noise countermeasures such as shielding. Regarding transmission systems.

[Conventional technology] In recent years, demand for on-board multiplex transmission systems to meet the increasing demand for on-board data transmission, such as monitoring of various train equipment and various information services, has been limited to specific new vehicles. This is also increasing on existing trains.

However, it is extremely difficult to add new cables to vehicles that are already in operation due to the cost of construction and the time constraints of train operation4. If a drop-in line made of

In fact, in some cases, transmission is carried out using spare pull-through lines (usually several pull-through lines are prepared as spares during manufacturing).

On the other hand, even in the case of a newly built car, if it is possible to use conventional pull-through wires rather than using optical fibers, twisted pair wires, etc. as transmission line cables, the structure of the jumper coupler between the car bodies can be left as is. This also has the advantage that increases in costs can be suppressed and there is no need to change the handling method during train connection work.

However, trains are equipped with many devices that generate large amounts of electromagnetic noise, and these devices also use other through lines included in the same bundle to transmit data. The service lead-through will receive significant induced noise from the parallel lead-throughs of other equipment.

, two, this type of data transmission method according to the prior art is
The data transmission speed is kept lower than that of normal wired transmission lines,
Measures are being taken to increase the transmission signal voltage.

However, it is certain that the amount of information that must be handled by data transmission on trains will continue to increase in the future.9 To cope with this, data transmission speeds must be increased, but as long as through lines are used, It is difficult to improve transmission speed with conventional noise countermeasure methods.

By the way, as a conventional technology for countering common mode noise in transmission transformer circuits, there is no technology for data transmission equipment on trains.
New Noise Countermeasures, 11 Written by Henly-W-OTT, a technique described in Japan Technology and Economic Center (published February 1977) and widely used is known.

Hereinafter, a data transmission method according to the prior art will be explained with reference to the drawings.

FIG. 11 is a diagram showing the prior art.9 In FIG. 11, 51 is a microphone, 52 is an audio signal device, 53 and 54 are transmission transformers, and 57 is a transmission line.

In the prior art shown in FIG. 11, an audio signal captured through a microphone 51 in the studio is transmitted!・The 7 transmission lines 57 that are sent out to the transmission lines 57 via the lances 53 connect the studio and the adjustment room, and are 50m-□100m.
It has a length of m. The audio signal sent onto this transmission path is input to the audio signal device 52 via the transmission transformer 54. At this time, in-phase noise is added to the two cables of the transmission line 57 from the noise source 58.9 As is well known, in the case of differential transmission shown in FIG. , is discharged from the middle point 55 of the winding of the transmission transformer 53 to the ground point 56. ′:′ causes galvanization in the winding, and no voltage is induced inside the device due to noise.

[Problems to be Solved by the Invention] However, the above-mentioned conventional technology is different in circumstances and is used in multiplex transmission of digital signals, which is the object of the present invention, especially when high-speed transmission is to be performed. It is something that cannot be done.

That is, in the prior art, since the signal targeted for common-mode noise countermeasures is an audio signal, the frequency is much lower than the frequency of transmission data for high-speed transmission, and voltage is induced between the ground and the transmission line 57. Since the induced noise caused by the noise is absorbed by the grounding point 56 earlier than the audio signal is transmitted from the microphone 51 to the audio signal device 52, the noise in the audio signal can be reduced.

By the way, in higher-speed transmission, the time width of the data signal becomes narrower, so it is preferable in terms of signal reliability to make the residual time of the noise voltage on the transmission path as short as possible. However, in the conventional technique, when common-mode noise is added to the transmission line 57 in the vicinity of the transmission transformer 54, it takes time to drain the noise to the apogee, and there is a possibility that the noise remains for a long time. According to the conventional technology, the transmission line 5
The problem is that the data on the 7 is destroyed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a data transmission system capable of solving the problems of the prior art and performing high-speed data transmission with resistance to noise.

Another object of the present invention is to provide a data transmission system that solves the problems of the prior art and is capable of high-speed data transmission using ordinary lead-through lines.

[Means for Solving the Problems] According to the present invention, the above object is to insulate between a transmission device and a transmission line by using a transmission transformer for transmitting and receiving data signals,
In order to reduce the common mode noise transmitted through the transmission line, this is achieved by using a differential system in which the midpoint of the transmission line side winding of the transmission transformer is grounded to the vehicle body in each transmission device.

In addition, this can be achieved by inserting a capacitor between the ground point and the midpoint.

[Operation] Since the midpoint of the transmission line side winding of each transmission transformer is grounded, the noise voltage waves transmitted from the noise source in both the transmitting and receiving directions are discharged from each transmission transformer to the grounding point. This makes it possible to prevent the noise signal from disappearing in a short time and adversely affecting the data signal on the transmission path.Also, since it is grounded via a capacitor, it is possible to prevent the noise signal from dissipating in a short period of time and adversely affecting the data signal on the transmission path. Unnecessary current (described later) flowing from the ground can be blocked by the capacitor.

[Embodiments] Hereinafter, embodiments of the data transmission system according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention. In Figure 1, 1 and 2 are transmission devices, 3.4 is a transmission transformer, 5.9 is a midpoint, 6.1o is a grounding point, 7 is a transmission line, and 8
is a noise source.

A first embodiment of the present invention shown in FIG. 1 is a transmission system that performs high-speed transmission of digital signals using an ordinary lead-through line.

In the first embodiment of the present invention, when performing digital high-speed transmission between the transmission device 1 and the transmission device 2, for example,
The digital signal output from the transmission device 1 is input to the transmission transformer 4 through the transmission transformer 3 and the transmission path 7, and is received by the transmission device 2.

When such a transmission system is applied to trains,
The transmission path length of the transmission path 7 ranges from 350 m to 400 m. Through this transmission line, the in-phase noise voltage wave added to the transmission line 7 by the noise source 8 during data transmission is transmitted to the nearest
Alternatively, it is discharged to the ground points 6, 10 via the midpoints 5, 9 of the transmission line side windings of both transmission transformers 3.4. Therefore, the illustrated first embodiment of the present invention can eliminate the effects of noise in a shorter time.

By the way, in a differential transmission system, it is assumed that the in-phase nature of the noise is high. There is no extreme variation in characteristic impedance between sets of books.

Therefore, as mentioned above, within a short period of time where the signal transmission time becomes an issue, the side receiving the noise, that is,
When viewed from the train throughline, the noise source 8 behaves as if it were a signal source with a constant internal impedance. Therefore, the noise voltage waves induced in the two cables that make up the transmission line have sufficient in-phase, and the differential method can work effectively.

Next, we will explain how to deal with the potential difference between the car body and the ground, which is a problem unique to trains.

In electric railways, a potential difference is created in the longitudinal direction of the train (11 in Figure 1) due to the current returning from own or other vehicles to the substation.
occurs. This potential difference is 50 to 60V during power
It also becomes. For this reason, contact at two or more points of force! ! Based on this potential difference, a current flows into the above-mentioned differential transmission circuit configured as follows. Although this current is magnetically canceled by the differential operation of the transmission transformer and does not become noise, it causes the winding of the transmission transformer, which has a small current capacity, to generate heat.

Next, the present invention that can solve this problem will be explained in detail.

FIG. 2 is a diagram showing the configuration of a second embodiment of the present invention.

In FIG. 2, 12 is a capacitor, and other symbols are the same as in FIG. 1.

The second embodiment of the present invention shown in FIG.
Alternatively, paying attention to the fact that it is an alternating current at a commercial frequency (low frequency), the inflow current from the ground is recut to the capacitor 12.

In this embodiment, by selecting a sufficiently high transmission signal frequency for the data signal transmitted on the transmission line 7, the reactance of the inserted capacitor is made small with respect to the data signal.
On the other hand, it is designed to have a large value with respect to the frequency of the overhead wire.

According to the second embodiment of the present invention having such a configuration, the same effect as the first embodiment of the present invention described above can be achieved without being affected by the potential difference described above, that is, high-speed data signals can be processed. It is possible to achieve the effect of achieving both stable transmission and protection of the transmission transformer.

FIG. 3 is a diagram showing the configuration of a third embodiment of the present invention in which the present invention is actually applied to a train. In Figure 3, 21~
23 is a transmission device, 25 to 27 are transmission transformers, 28 is a connecting portion, and 29 is a vehicle body; other symbols are the same as in FIG. 2.

The third embodiment of the present invention shown in FIG.
Data signals are transmitted and received through the terminals 5 to 27. Transmission transformers 25 to 25 of each transmission device 21 to 23
The midpoint of 27 on the transmission line side is grounded via a capacitor 12.

In this third embodiment of the present invention, each transmission device is grounded, and since the length of the train is 20 meters for boat fishing, grounding points are provided approximately every 25 meters. It will be done. Normally, when electric wires are bundled, the signal propagation speed of the electric wires is about 200,000 per second. Therefore, in the third embodiment of the present invention, noise is discharged in a little over 0.1 microseconds, for example. , the probability of error can be made small even with a high-speed data signal with a width of 1 microsecond.

FIG. 4 is a diagram showing the configuration of a fourth embodiment of the present invention.

In FIG. 4, 31 to 34 are transmission devices, 36 to 43 are transmission transformers, and other symbols are the same as in FIG. 3.

This fourth embodiment of the present invention is an application of the present invention to a loop type transmission system. In this way, the transmission device 31
In an embodiment of the invention in which .about.34 are placed alternately on either side of the loop, noise drainage points can be obtained every 50 meters.

In normal wired data transmission, relatively high speed 960
Taking a transmission rate of 0 bits per second as an example, the time width of one bit is approximately 104 microseconds.

On the other hand, the residence time of the influence of noise according to the embodiment of this book@Ming. According to the example,
High transmission reliability can be obtained.

Further, in the fourth embodiment of the present invention, the middle point of the transmission transformer is grounded at each position of the plurality of transmission devices, so that
Even if a failure occurs in which the ground is cut off at one point, there will be backup at other grounding points, improving system durability.

Next, we will discuss ways to further increase system durability.
Various examples will be described.

FIG. 5 is a diagram showing the configuration of a fifth embodiment of the present invention.

In FIG. 5, 45 is a resistor, and other symbols are second
This is the same as the case shown in the figure.

This fifth embodiment of the present invention is an example in which the midpoint grounding method is improved, and the midpoint of the transmission transformer is grounded by a series circuit of a capacitor 12 and a resistor 45.

According to the fifth embodiment of the present invention, by appropriately selecting the value of the resistor 45, strong surge current from a nearby noise source is suppressed and the capacitor 12 is protected.
This embodiment can exhibit the same effects as the fourth embodiment of the present invention, and is also preferable in terms of component reliability. Furthermore, even if the capacitor 12 is short-circuited, it is possible to suppress the inflow current due to the difference in mold size between the vehicle bodies, and it is possible to prevent a burnout accident of the transmission transformer.

FIG. 6 is a diagram showing the configuration of a sixth embodiment of the present invention,
The numbers in the figure are the same as in FIG.

The embodiment shown in FIG. 6 is an embodiment equipped with a means for protecting the transmission device from accidental contact with the lead-through wires.

Inside a train, DC 100V is normally used as a power source for various control devices. Therefore, in the unlikely event that a wiring accident occurs, a DC voltage will be applied between the windings of the transmission transformer, and in the worst case, this may lead to a burnout accident.

Therefore, the sixth embodiment of the present invention is constructed by providing a capacitor circuit in the connection between the lead-through line and the transmission transformer. The resistor 45 inserted in series achieves the same purpose as the fifth embodiment shown in FIG. 5, but only a capacitor may be used if the action of the resistor is not required. Although all the resistors 45 are the same, their values may be changed for manufacturing reasons only.

Furthermore, the capacitor 12 described above is effective in preventing unnecessary current from flowing in from the grounding point 6 described above, assisting the function of the capacitor 12 provided on the grounding side, and achieving a system effect of multiple safety. .

The method of connecting the transmission device to the transmission path shown in FIGS. 5 and 6 can be applied to both the multi-drop configuration shown in FIG. 3 and the loop configuration shown in FIG. 4. In this way, unifying the interfaces to the transmission paths of all transmission devices is effective in simplifying the manufacturing process.

All of the embodiments described above use dedicated electric wires. However, in the case of trains that are already in service, there are many cases in which there are few or no spare electric wires due to previous modifications.

An embodiment of a transmission system to which the present invention is applied in such a case will be described below.

FIG. 7(a) is a diagram showing the configuration of a seventh embodiment of the present invention. In FIG. 7(a), 60 is an in-vehicle device, 61 is a power line, 62 is an interface unit, and other symbols are the same as in FIG. 5.

In FIG. 7(a), one of the transmission lines is a dedicated line 7,
The other one is a power line 61 for another vehicle-mounted device 60. Further, in this figure, the transmission transformer, capacitor, and series resistor circuit are collectively shown as an interface unit 62.

In the seventh embodiment of the present invention, data transmission with low loss is possible by using a power supply fi [61 with high impedance to ground] by using appropriate equipment, for example, a brake lead-in line. It is.

FIG. 7(b) is a diagram showing the configuration of an eighth embodiment of the present invention. In FIG. 7, 63 is an impedance matching device, and other symbols are the same as in FIG. 7(a).

This embodiment is based on the seventh embodiment of the present invention described above.
This embodiment is capable of achieving impedance matching between the leased line 7 side and the electric IKia 61 side when impedance matching cannot be achieved between them.

That is, in this embodiment, as shown in FIG. 7(a),
An impedance matching device 63 is inserted between the transmission lines and one of the transmission lines to maintain balance. The matching device 63 is suitably a resistor. This is because if the inductance is included, the digital signal will become dull, which will adversely affect the transmission of the digital signal.

FIG. 8 is a diagram showing the configuration of a ninth embodiment of the present invention.

In FIG. 8, 64 is the electric WA line of the transmission device itself, and other symbols are the same as in FIG. 7(a).

This ninth embodiment of the present invention has a power source 1i of the transmission device itself.
164 as a transmission line. In this case, an inductance can be inserted into the power supply line at the manufacturing stage of the transmission device to intentionally increase the high frequency impedance, and a power supply line 64 dedicated for transmission can be secured. This is an effective method when

FIGS. 9 and 10 are diagrams showing the configurations of tenth and eleventh embodiments of the present invention. In Figures 9 and 10, 65
．． Reference numeral 67 indicates a control signal line of the on-vehicle control device, 66 and 68 indicate the on-vehicle control device, and other symbols are the same as in the case of FIG. 7(a).

The tenth and eleventh embodiments of the present invention are embodiments in which there is no electric wire exclusively for transmission, and control signals 1a65. The control signal line 67 of another vehicle-mounted control device 68 is used as a signal power line, and the transmission signal voltage is superimposed on the electric wire already used for other purposes. By using such an embodiment, it is possible to install a multiplex transmission system on any type of train.

FIG. 10 shows an example of a system configuration in which none of the wires has a high impedance to ground.

In this embodiment, the power supply lines 61, 64, etc. are considered to be grounded because their potentials are stable, and are connected to the middle point of the transmission transformer.

Furthermore, if it is necessary to lower the impedance of the power supply line to ground at high frequencies, a capacitor 69 may be added between it and the ground point as shown in the figure.

It is desirable that the frequency of the power source of these power lines 61, 64, and 67 is low.

[Effects of the Invention] As explained above, according to the present invention, in an extremely noisy environment on a train, the
Data transmission with sufficiently high reliability can be performed at high speed using a lead-through line made of ordinary electric wires.

[Brief explanation of drawings]

Figures 1, 2, 3, 4, 5, 6, 7(a), 7(b), 8, 9, and 1O are , respectively, are diagrams showing the first to eleventh embodiments of the present invention, and FIG. 11 is a diagram showing the prior art. 1.2,21,22,23,31,32,33°34・
...Transmission device, 3.4.25-27.36-43
．． 53.54...Transmission transformer, 5.9...
...Middle point of transmission line side winding of transmission transformer, 6, lO...
...Grounding point, 7...Transmission line, 8...
・Noise source, 12... Capacitor, 45...
...Resistor, 62...Interface unit. Figure 1 Figure 2 Figure 5 Figure Figure Figure

Claims (1)

[Claims] 1. In a device in which a plurality of serial multiplex transmission devices are connected by a transmission line made of electric wire, the transmission device and the transmission line are connected via a transmission transformer, and each transmission transformer A data transmission system characterized by grounding the midpoint of the transmission line side winding. 2. The data transmission system according to claim 1, wherein the middle point of at least one of the transmission transformers is grounded via a first capacitor. 3. The data transmission system according to claim 2, characterized in that a first resistor is inserted in series with the first capacitor. 4. At least one of the transmission transformers and the transmission line electric wire are connected via second capacitors, respectively.
Data transmission system as described in Section. 5. The data transmission system according to claim 4, characterized in that a second resistor is inserted in series with the second capacitor. 6. Claim 1, wherein the transmission line electric wire is an electric wire that is not shielded or twisted.
The data transmission system described in one of paragraphs to 5. 7. In a system in which a plurality of series multiplex transmission devices on a train are connected by a transmission line made of electric wire, the transmission device and the transmission line are connected via a transmission transformer, and the transmission line side winding of each transmission transformer is The middle point of the line is grounded to the electric wire, and at least one of the electric wires whose middle point is grounded to the transmission line electric wire and the transmission transformer is an electric wire used for another purpose in the train. Train data transmission system. 8. The train data transmission system according to claim 7, characterized in that a third capacitor is connected between the electric wire connecting the midpoint of the transmission transformer and the train car body. 9. The train data transmission system according to claim 8, wherein the transmission line electric wire and the transmission transformer are connected through an impedance matching circuit.