JPS6340711B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention supplies power to various switch devices placed on the pad of a steering wheel of an automobile, and transmits signals from the devices to the vehicle body. The present invention relates to a signal transmission device, and particularly relates to a signal transmission device for a steering wheel that uses two lines as both a power supply line and a signal transmission line to supply power and transmit signals.

<Prior art> For example, in an automobile steering wheel in which a planetary gear or the like is used to hold the pad of the steering wheel in a stationary state and various switches are arranged on the pad, a large number of signal transmission lines from the pad are connected. This requires a large number of slip rings and brushes to be used for moving parts, making it structurally impossible. A method has been proposed in which a signal current is superimposed on the power supply current using a transmission line, and the signal is transmitted from the pad (transmitter) side to the vehicle body (receiver) side.

<Problems to be Solved by the Invention> However, the signal superimposition method on the power supply line modulates the signal on the pad side using a predetermined transmission mode, and then superimposes this AC modulated signal on the power supply current via coupling. This signal is then demodulated and detected in the receiving section on the car body side and extracted as signals for various switches from the pads, so noise generated by power supply voltage fluctuations, external electric fields, and external magnetic fields such as when starting the engine, etc. However, there was a problem in that accurate signal transmission could not be performed, causing various devices to malfunction.

This invention was made in consideration of the above points, and uses a signal transmission line also as a power supply line,
The time for power supply and signal transmission is divided periodically, and while power is supplied to the transmitter installed on the steering wheel in a predetermined half cycle, the power is supplied from the transmitter to the receiver installed on the vehicle body side in the next half cycle. To provide a signal transmission device for a steering wheel that can eliminate the influence of noise and accurately transmit signals by transmitting signals, and eliminates the need for a dedicated line for signal transmission.

<Means for Solving the Problems> In order to achieve the above object, the steering wheel signal transmission device of the present invention supplies power from a receiving section provided on the vehicle body side to a transmitting section provided on the steering wheel. , and a transmission line for transmitting a signal from the transmitting section to the receiving section is connected between the receiving section and the transmitting section, and the receiving section is connected to the transmission line when power is supplied and signal transmission is alternately and periodically time-shared. The transmitter is equipped with a circuit that sends the power supply voltage to the transmitter through the transmission line, and a circuit that inputs the signal transmitted from the transmitter through the transmission line during signal transmission cycles, and the transmitter charges the power supply current supplied from the receiver. It is equipped with a charging power supply section that discharges during signal transmission, a timing detector that detects the timing of power supply and signal transmission, and a circuit that outputs a signal at the period of signal transmission and transmits it to the receiving section through a transmission line. configured.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

Fig. 1 shows a power supply from a transmitter 2 placed on the steering wheel pad of a car to a receiver 1 installed on the vehicle body, and a ground wire and a transmission line 12 connected between the transmitter 2 and the receiver 1. 1 shows a block diagram of a device that performs transmission by sharing supply and signal transmission. Reference numeral 3 denotes a power supply section for the receiving section 1, which uses a battery B as a power source to generate a constant voltage V _DD for the receiving section 1 and a constant voltage V _CC to be supplied to the transmitting section 2 via a power supply switch 4. It is configured. Reference numeral 5 denotes an oscillator for generating a clock pulse signal, which outputs a clock pulse signal to the reception control section 6. The reception control section 6 is configured to send a predetermined timing pulse signal to each circuit of the reception section 1 to control each circuit, and sends a transmission/reception pulse signal a to the power supply switch 4 and an inverter 10 to the reception switch 11. It operates to send an inverted pulse signal of the pulse signal a to the latch 8, a latch pulse signal h and an initial reset pulse signal to the latch 8, and a shift pulse signal i to the shift register 7. The shift register 7 outputs the received signal input via the reception switch 11 as data to the latch 8, and the data input to the latch 8 is latched by the latch pulse signal h and sent from the transmitter 2 via the buffer 9. Connected configured to obtain data. The output side of the power supply switch 4 and the input side of the reception switch 11 are connected to a transmission line 12 for both power supply and signal transmission.

On the other hand, the transmitter 2 includes a timing detector 13 that sends a transmission/reception detection pulse signal C detected by the difference in voltage between power supply and data transmission in the transmission line 12 to the transmission controller 16, a charging capacitor, and a constant voltage. A charging power supply section 14 equipped with a circuit, an oscillator 15 for clock pulse signals, a transmission control section 16,
It is composed of a multiplexer 17 and a transmission switch 18. The charging power supply unit 14 is connected to the transmission line 12
The capacitor is charged with the power supply current that is time-divided and periodically inputted from the transmitter 2, and operates to stably supply each circuit of the transmitter 2 with a constant voltage _VDD that is sufficiently lower than the supplied power supply voltage _VCC . The transmission control unit 16
Input the clock pulse signal from the oscillator 15,
The transmitting pulse signal d having the same period as the transmitting/receiving pulse signal a formed in the receiving section 1 is outputted to the transmitting switch 18 , and the channel selection signal is further sent to the multiplexer 17 . The multiplexer 17 inputs signals from various switches arranged on the pad of the steering wheel.
The configuration and connection are such that this signal is sent to the transmission line 12b via the transmission switch 18 as an output signal e while being controlled by a channel selection signal from the transmission control section 16.

Next, with reference to the timing chart of FIG. 2, the operation of the signal transmission apparatus having the above configuration will be explained, as well as the signal transmission method.

First, as an example, the value of the constant voltage V _CC created by the power supply section 3 is set to 8.2V, V _DD is set to 5V,
The output voltage _VDD of the charging power supply unit 14 is also set to 5V, and the oscillation frequencies of the oscillators 5 and 15 are both 145K.
Set to Hz. When the power is turned on, an initial reset signal is first output from the reception control section 6 to the latch 8, and the output contents of the latch 8 are cleared. At the same time, the reception control section 6 operates, and as shown in the output signal a of the timing chart, a high-level pulse signal with a width of approximately 7 ms set by the built-in time counter is output to the power supply switch 4, and this switch is activated. The circuit is closed for a time corresponding to this pulse width, and the power supply voltage V _CC is supplied from the power supply switch 4 to the charging power supply section 14 of the transmitting section 2 via the transmission line 12 . In the charging power supply unit 14, the current of the voltage V _CC is used for the power supply time.
It charges during T ₁ and discharges during the next signal transmission time T ₂ to create a constant voltage V _DD using a stabilizing circuit that is considerably lower than the charging voltage V _CC as shown in the charging voltage waveform f in the timing chart. and is supplied to each circuit of the transmitting section 2. Timing detector 13 detects voltage V _CC
Set the threshold voltage between and the voltage V _DD ,
The voltage of the transmission line 12 is detected and compared with this threshold voltage, and if this voltage is higher than the threshold voltage V _CC , a high level signal is generated, and if the voltage is lower than the threshold voltage V _DD , a high level signal is generated. The transmission control unit 16 converts the low level signal into a transmission/reception detection pulse signal C as shown in the timing chart of FIG.
send to The transmission control section 16, which has received the high level signal of the transmission/reception detection pulse, stops sending the channel switching signal to the multiplexer 17, sets the transmission pulse signal d to a low level, and opens the transmission switch 18, as shown in the timing chart. Therefore,
Data signals for various switches are not transmitted from the transmitter 2 during the power supply time _T1 . On the other hand, when the transmission/reception pulse signal a becomes low level due to the timed operation of the time counter in the reception control section 6, the power supply switch 4 is opened and the power supply to the transmission section 2 is stopped. At the same time, a high level signal is input to the reception switch 11 via the inverter 10, the reception switch 11 is closed, an input signal g is input from the transmission line 12 to the data input side of the shift register, and a shift pulse signal i is input from the reception control section 6. is output to the shift register 7. Further, in the transmitting section 2, the timing detector 13 detects that the supplied power supply voltage V _CC disappears, changes the transmission/reception detection pulse signal C to a low level, and applies it to the transmission control section 16. Then, the transmission control section 16 changes the transmission pulse signal d to a high level and applies it to the transmission switch 18 to close it, and at the same time outputs a channel selection signal from the time counter to the multiplexer 17. Parallel data signals from various switches inputted to the multiplexer 17 are outputted serially by inputting a channel selection signal, and transmitted from the transmitting switch 18 to the receiving section 1 via the transmission line 12. Note that the shift pulse signal of the receiving section 1 and the channel selection signal of the transmitting section 2 are synchronized. Therefore, the transmitted data signal is serially input from the reception switch 11 to the shift register 7, and when the signal transmission time _T2 of the data signal ends, the latch signal h is input from the reception control section 6 to the latch 8.
The output data of the shift register 7 is latched as is, and the data signals sent from the various switches of the transmitter 2 are taken out in parallel via the buffer 9. In this way, the above operations are repeated during the time-divided power supply time T ₁ and signal transmission time T ₂ , and power supply and signal transmission are performed by the transmission line signal b that shares the transmission line 12 .

Note that a part of the transmitter/receiver used in the above embodiment can also be configured using a microcomputer.

<Structure of the Invention> As explained above, according to the steering wheel signal transmission device of the present invention, power is supplied from the receiving section provided on the vehicle body side to the transmitting section provided on the steering wheel, and from the transmitting section to the receiving section. The signal transmission is carried out by sharing the transmission line connected between them, and the power supply time and the signal transmission time are set alternately by time division, and the power supply and signal transmission are repeated at regular intervals. Therefore, compared to the conventional method of transmitting an AC modulated signal by superimposing it on a power supply line, it is possible to transmit an accurate signal without introducing noise.

In addition, the transmission line between the steering wheel transmitter and the receiver on the vehicle body side can be made into a single line by using a common ground for the vehicle body, and connecting parts such as slip rings and brushes required for the connection line. The space for providing it can be reduced.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, with FIG. 1 being a block diagram of a signal transmission device, and FIG. 2 being a timing chart during operation of the same device. 1... Receiving section, 2... Transmitting section, 12... Transmission line, 13... Timing detector, 14... Charging power supply section.

Claims (1)

[Claims] 1. A transmission line that supplies power from a receiving section provided on the vehicle body side to a transmitting section provided on the steering wheel, and transmits a signal from the transmitting section to the receiving section, connects the receiving section and the transmitting section. The receiving section includes a circuit that sends a power supply voltage to the transmitting section through the transmission line during power supply in which power supply and signal transmission are alternately and periodically time-shared; a circuit that periodically inputs a signal transmitted from the transmitting section through the transmission line; the transmitting section includes a charging power supply section that charges the power supply current supplied from the receiving section and discharges it during signal transmission; A steering wheel comprising: a timing detector that detects the timing of power supply and signal transmission; and a circuit that outputs a signal at the period of the signal transmission and transmits the signal to the receiving section through the transmission line. signal transmission equipment.