JPH0327158B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a multiplex signal transmission system for automobiles,
In particular, the present invention relates to a method for transmitting high-speed pulses such as vehicle speed pulses and ignition pulses in an automotive multiplex signal transmission device that time-division multiplexes and serially transmits switch signals and sensor signals.

[Prior art]

2. Description of the Related Art In recent years, wire harnesses, which are electrical wiring systems inside automobiles, have become more complex and enlarged, and various problems have arisen in the design, manufacture, and installation of the harnesses. In addition, there is a strong desire to expand the space inside the vehicle, and there is a limit to the pace at which harnesses can be installed.Furthermore, there is the problem that an increase in the weight of the harness must be suppressed as much as possible in order to reduce the weight of the vehicle body.

The most effective way to solve the above problems is to
“Automotive Technology, VOL.38, No.2, (Sho 59-2-1),
As disclosed in "P. 215 to 220," a multiplex signal transmission system for automobiles can be considered, which is configured to multiplex and serially transmit a large number of signals in a harness using several signal lines.

FIG. 2 is a block diagram showing the system configuration of the multiplex signal transmission system for automobiles. As shown in the figure, a plurality of terminal devices 1 to 4 arranged in a vehicle are connected in a loop through multiplex communication lines 5 to 8, and signals are multiplexed and transmitted between each terminal device 1 to 4 in a time-division manner.

FIG. 3 is a diagram showing the flow of information transmitted between each terminal device 1 to 4 through a multiplex communication line. As shown in the figure, the input information sampled by each of the terminal devices 1 to 4 is time-division multiplexed and transmitted on multiplex communication lines 5 to 8 with four frames as one cycle.

FIG. 4 is a diagram showing details of the signal frame structure of the terminal device 1. As shown in the figure, the information input by the terminal device 1 is composed of n bits, with a transmission address code SA composed of a plurality of bits provided at the front end, and an error verification code FCC composed of a plurality of bits at the rear end. The bits 1-1 to 1-n between the address code SA and the error verification code FCC are state (ON/OFF) signals corresponding to the switches and sensors input by the terminal device 1, respectively. Here, one switch state is transmitted to each terminal device 1 to 4 at one transmission cycle period t1.

[Problem that the invention seeks to solve]

By the way, the pulses output from automobile sensors include ignition pulses that are proportional to the engine speed, vehicle speed pulses that are proportional to the speed of the vehicle, etc.
Period of one transmission cycle (normal number + msec to several hundred m)
sec). Turn on/off such high-speed pulses in the same way as switch information
If the status is transmitted as is, one transmission cycle period
Changes in state below t1 cannot be tracked. Therefore, it is necessary to provide a line for transmitting such high-speed pulses separately from the multiplex communication lines 5 to 8, which is an obstacle to simplifying the wiring harness.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a multiple signal transmission system for automobiles that multiplexes and transmits high-speed pulses such as ignition pulses and vehicle speed pulses.

[Means for solving problems]

The present invention uses an automotive multiplex signal transmission method to transmit ignition pulses and vehicle speed pulse signals, since these high-speed pulse signals require instantaneous pulse signal status (ON/OFF) information. Rather, focusing on the fact that period information is required, the system is configured to detect the period of the high-speed pulse, code the period, and transmit the coded information.

[Effect]

By configuring as described above, it becomes possible to transmit a pulse signal faster than one transmission cycle of multiplex signal transmission through the multiplex communication line.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a terminal device used in the automotive multiplex signal transmission system according to the present invention, and FIG. 5 is a timing chart of ignition pulses and code information on the multiplex communication line. The terminal device 4 includes a single-chip microprocessor 11, a line driver/receiver unit 12 for sending and receiving signals to and from the multiplex communication line 5, an interface unit 13 including input/output signal drivers/receivers, etc., and a differential pulse generator for pulse signals. The interface section 14 includes a circuit.

Now, the transmission of the ignition pulse proportional to the engine speed will be explained. Although it varies depending on the type of vehicle, if the engine speed range is 100 to 7000 rpm, the period of the ignition pulse is several milliseconds to several hundred meters.
It will be about sec. In addition, devices that input ignition pulses include tachometers and automatic constant speed running devices, but these devices operate using the engine speed as a parameter, and in terms of response, one transmission cycle (usually One sample every few msec to several hundred msec is sufficient. Therefore, the terminal device 4 that inputs the ignition pulse calculates the pulse period, converts the unit to the engine speed, and converts the unit to the engine speed (coded). information) on a multiplex communication line.

The ignition pulse pl is input through the signal line 15, passes through the interface section 14, and causes the microprocessor 11 to generate an interrupt. After an interrupt occurs, the built-in timer is activated as a counter to determine the time until the next interrupt occurs, that is, the pulse interval t2. The rotation speed T (encoded information) that has been subjected to unit conversion processing from the obtained pulse interval t2 is saved in a predetermined area of the memory, and is saved every transmission cycle t1 as shown in Figure 5. The rotational speeds T1 and T2 thus obtained are transmitted onto the multiplex communication line 5. Terminal devices 1, 2, and 3 also have the same configuration as terminal device 4.

In the above embodiment, the transmission of an ignition pulse was explained as an example, but the period of a high-speed pulse such as a vehicle speed pulse may be determined, and the period may be converted into a unit, and vehicle speed information or the like may be transmitted for each transmission cycle.

〔Effect of the invention〕

As explained above, according to the present invention, the following excellent effects can be obtained.

(1) Among the high-speed pulse signals that are sensor signals, the period of the pulse signal that does not require the instantaneous state (ON/OFF) information of the pulse signal but requires period information is encoded and transmitted. Multiplex transmission of signals is possible via multiplex communication lines, helping to save labor on in-vehicle wiring.

(2) Furthermore, by incorporating high-speed pulse signals into automotive multiplex signal transmission, it becomes possible to easily improve the functionality of the automotive multiplex system.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of a terminal device used in the automotive multiplex signal transmission system according to the present invention, Figure 2 is a block diagram showing the system configuration of the automotive multiplex signal transmission system, and Figure 3 is a multiplex communication line. 4 is a diagram showing the details of the signal frame structure of the terminal device 1, and FIG. 5 is a timing chart showing the waveform of the ignition pulse and its coded information on the multiplex communication line. It is. In the figure, 1-4... terminal device, 5-8... multiplex communication line, 11... microprocessor, 12... line driver/receiver section, 13... interface section, 14... interface section.

Claims (1)

[Claims] 1. A plurality of terminal devices are distributed inside the vehicle, and the plurality of terminal devices are connected in a loop through multiplex communication lines, and switch signals and sensor signals input to the terminal devices are time-divisionally distributed. In an automotive multiplex signal transmission system that multiplexes and serially transmits, among the high-speed pulse signals that are the sensor signals,
A multiplex signal transmission for automobiles characterized by detecting the period of a pulse signal that does not require instantaneous state (ON/OFF) information of the pulse signal but requiring period information, and transmitting the period as a code. method.