JPS631487Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is an in-vehicle electronic device that suppresses noise generated by multiple control devices (control computers, etc.) mounted on the same vehicle and that interferes with reception of communication equipment such as in-vehicle radios. Regarding a control device.

In recent years, with the spread of microcomputers, technology is being adopted in automobiles in which one or more microcomputers are used to control engines and various electrical components.

Figure 1 shows an example of the schematic configuration of a microcomputer used in an in-vehicle electronic control system.
1 is a microprocessor, 2 is a clock oscillator using a crystal resonator;
uses an internal circuit to shape the waveform of the oscillation output of the crystal resonator, and the rise and fall times are each several nanoseconds.
A rectangular clock pulse of ~ several tens of ns is obtained. 3 is a memory, 4 _A to 4 _D are control circuits, 5 _A to 5 _D are A/D converters and D/A for transmitting and receiving signals with external circuits.
This is an input/output interface group containing various circuits such as a converter and a sensor amplifier, and these memory, control circuits, and interface group are connected to the clock pulse or memory control signal and the clock pulse in order to synchronize with the microprocessor 1. A logical product signal is supplied. The digital block 6 consisting of the above parts is housed in a metal case 8 together with a power supply section 7.
It is stored in 9 _A to 9 _D are input/output signal lines, 1
0 is the power line.

As shown in Fig. 2, the case 8 is installed in a place where the environmental conditions such as temperature and humidity are relatively favorable inside the vehicle, such as under the instrument panel or the seat, and is connected to the input/output signal line _9A. ~9 _D uses input/output signals of the digital block 6, that is, input signals from various sensors for calculating control parameters, and digitally processes these signals to control operations of the engine, various electrical components, actuators, etc. Transmitting control output signals.

The frequencies of the signals originally transmitted by these input/output signal lines are from 0 to several tens of kHz, and these signal lines and power lines are made of ordinary vinyl-coated wires, bundled together with the harnesses of other electrical equipment, and It is normal for the wiring to be concentrated. Due to this wiring condition, the input/output signal lines of the microcomputer and the harnesses of other electrical components, such as the in-vehicle radio 11 and the antennas (glass antennas embedded in the windshield and rear glass) 12, 13,
It can be said that the harnesses 14 and 15 connecting between the two are extremely tightly coupled in terms of high frequency through induction, electromagnetic radiation, and the like. Further, since the microcomputer and the in-vehicle radio are powered by the same in-vehicle battery 16 and also use the vehicle body 17 as a common ground, they are also directly conductively coupled through these power lines and ground lines.

By the way, square wave clock pulses of several hundred kHz to several MHz, which are used as synchronization control signals for microcomputers, consist of a high-level (several volts) fundamental wave and its harmonic components, and its frequency covers a wide radio frequency band. Range i.e. AM band to FM,
Since it is distributed over the TV band, it can be regarded as a type of noise source, and if the noise component leaks to the input/output signal lines 9 _A to 9 _D and the power line 10, it will cause damage to these input/output signal lines and the power line. Direct or indirect coupling with the radio harness or antenna may cause interference with vehicle radio reception.

In particular, when multiple microcomputers are mounted on the same vehicle and the frequencies of the harmonic components of the clock pulses used for each of them are close to each other within the FM broadcasting frequency band, the multiple microcomputers can be operated simultaneously. When the harmonic components of the clock pulses generated by them mutually interfere with each other, the in-vehicle radio generates extremely loud noise (interference noise) compared to when they are operated individually.
It has become clear from the experimental results of the inventors that this occurs.

In order to prevent noise components that cause reception interference from leaking into the input/output signal lines and power supply lines, it is necessary to distinguish between parts of the microcomputer that operate on clock pulses and those that do not (input/output interfaces, power supplies, etc.). ) must be completely separated in terms of high frequency, which is technically and economically unfeasible.

In addition, to prevent the coupling of signal lines with leaked noise components due to clock pulses to radio harnesses and antennas, (a) Use shielded wires such as coaxial cables as signal lines, or shield the entire signal line.

(b) Route the signal line as far away from the radio harness and antenna as possible.

There are methods such as the following, but none of them are practical when there are a large number of signal lines, the wiring of the signal lines is complex, and the terminals are located at various locations within the vehicle.

The present invention has been developed in view of the above-mentioned problems, and when an in-vehicle electronic control device is configured using a plurality of control devices such as microcomputers that are synchronously controlled by clock pulses, at least one of the control devices is A common clock signal generation circuit is provided for two or more of the control devices, and a clock signal generated from the clock signal generation circuit is transmitted to each of the control devices in a sine wave or a waveform close to a sine wave with few harmonic components, and the clock signal is transmitted to each of the control devices. By shaping the pulse waveform into a pulse waveform in each control device, or dividing the frequency after shaping and using it as a clock pulse for synchronous control of each control device, the fundamental wave or harmonics of the clock pulse used in at least two or more control devices can be generated. To provide an in-vehicle electronic control device that can easily and reliably prevent reception interference of an in-vehicle radio or the like due to mutual interference of fundamental wave components or harmonic components of these clock pulses by accurately matching wave spectrum frequencies. .

Hereinafter, the present invention will be described in detail with reference to FIG. 3 and subsequent drawings.

Figure 3 shows that the electronic control unit 20 in the same vehicle is a control unit A consisting of three microcomputers;
A conventional example is shown in which the digital blocks 21 _A , 21 _B , 21 of these control devices are configured with B and C.
_C are clock oscillators 22 _A , 22 _B , 2, respectively.
It is synchronously controlled by clock pulses Φ _A , Φ _B , and Φ _C created by waveform shaping the signal from 2 _C.

FIG. 4a shows the clock pulses Φ _A , Φ B , Φ C used in each of the controllers A, _B , and _C in this case.
shows the spectrum of harmonic components within the FM broadcast frequency band, and each clock frequency is set to 1MHz.
When the frequency band is set to 1MHz, these high-order harmonics appear at 1MHz intervals as shown in this figure.

As shown in the enlarged figure b, if the harmonic spectrum frequencies of the clock pulses Φ _A and Φ _C of the control device A and the control device C are located with a slight frequency difference on the order of an audible frequency (such as This is because even if the frequency specs of the crystal oscillators and ceramic oscillators that make up the clock oscillator are set to be the same, the clock oscillation frequencies of each are not completely the same and there is a slight frequency error. (This can occur with a relatively high probability), when these control devices A and C are operated simultaneously while mounted on a vehicle, extremely loud noise (interference noise) is generated in the vehicle radio compared to when they are operated individually.

FIG. 5 shows, as an example, two unmodulated wave signals S1,
S2 (frequency difference 1kHz, level 15dBμV) is synthesized by a signal mixer, and the test radio (vehicle FM/AM
The absolute level of the beat noise volume when measuring two-signal interference noise by directly applying it to the antenna terminal of a radio (for example, Clarion RN391i) is shown in the S/N characteristic diagram of the car radio.
When the speaker output voltage 0.775V when a Hz, 30% modulated wave is applied at an antenna terminal level of 80 dBμV is 0 dB, S+N is 400 Hz, the speaker terminal voltage level relative to the input voltage of a 30% modulated wave, and N is the input of an unmodulated wave. The speaker terminal voltage level with respect to the voltage, a, is
The level of beat noise when two signals S ₁ and S ₂ of 15 dBμV are input at the same time, and a' indicates the noise level when only one signal of 15 dBμV is input.

As shown in Figure 5, when two signals with close frequencies are received at the same time, even when an extremely weak unmodulated signal is received, a beat noise sound with approximately the same level as the modulated wave is generated at the speaker output, and the beat noise volume level is This is about 20 dB higher than the noise volume level when only one unmodulated signal is received.

On the other hand, if the clock frequencies of the clock pulses Φ _A and Φ B of the control devices A and _B are almost completely the same, then the clock pulses Φ A and Φ B of the control devices A and B
It has been found that even when the two systems are operated simultaneously in a vehicle, noise is suppressed to the same extent as when they are operated individually. This means that if the frequencies of the two signals S ₁ and S ₂ generated from the control device and mixed into the car radio are exactly the same, the period T = 2π/( ω ₂ −
ω ₁ ) becomes infinite (fundamental wave frequency 0Hz),
This is because it will no longer be played on the radio.
(ω ₁ and ω ₂ are the angular frequencies of the signals S ₁ and S _2. ) Based on this, the present invention aims to match the fundamental wave or harmonic spectrum frequencies of the clock pulses used in multiple control devices in the same vehicle. An example of this is shown in FIG.

In this embodiment, an on-vehicle electronic control device 20 is constructed using control devices A, B, and C consisting of three microcomputers, where 23 is a clock signal generation circuit common to all the control devices, and 24 is a low-pass filter. In this embodiment, these are built into the control device A. 25 _A , 25 _B , and 25 _C are waveform shaping circuits, and 26 _A , 26 _C are frequency dividing circuits.

Specifically, the clock signal generation circuit 23 is made of a crystal resonator, a ceramic resonator, or a
It consists of an oscillation circuit using CR circuits, etc.
The clock signal generated from this clock signal generation circuit 23 is transmitted to the digital block 21 of the control device A.
The clock pulse is input to _A , is shaped into a square wave pulse by the waveform shaping circuit _25A built in the digital block _21A , and is then changed to the required clock frequency by the frequency dividing circuit _26A , which synchronously controls the digital block _21A . used as.

The output of the waveform shaping circuit 25 _{A (} or frequency dividing circuit 26 _A ) taken out from the clock output terminal of the digital block 21 A is sent to the low pass filter 24, which attenuates the harmonic components of the square wave pulse. , is removed and converted into a waveform close to a sine wave. This low-pass filter output signal is output from control device A, and transmitted to other control devices B and C via a clock signal transmission line 27 connecting the control devices.
The signals are sent to waveform shaping circuits _25B and _25C built in the . The clock signal is again shaped into a square wave pulse by the waveform shaping circuits _25B and _25C , and then either the repetition frequency remains unchanged or the repetition frequency is lowered by the frequency dividing circuit _26C , and then the clock signal is output to the digital block 2.
It is applied to the clock input terminals of _1B and _21C .

In the in-vehicle electronic control device of the present invention configured in this manner, the frequencies of the clock pulses of each control device, which are the fundamental frequency of the noise radio waves, are exactly equal or have a multiple relationship. The spectral frequencies of the two will also match exactly. As a result, even if noise radio waves from a plurality of control devices are simultaneously received by the antenna of the in-vehicle radio, the generation of interference noise can be completely eliminated.

Furthermore, since the clock signal on the clock signal transmission line 27 is transmitted in the form of a sine wave or a waveform close to the sine wave with harmonic components removed by the low-pass filter 24, the noise radio waves radiated from the transmission line 27 are transmitted at the fundamental wave frequency of the clock signal. You can think of it as just the ingredients,
By setting this frequency so that it does not overlap with the AM broadcast frequency band, it is possible to avoid interference with the car radio by the clock signal on the transmission line.

FIG. 7 is a diagram showing another embodiment of the present invention, and FIG.
The difference from the figure is that a clock signal generation circuit 23 and a low-pass filter 24 are provided separately from the control devices A, B, and C. The oscillation waveform of the clock signal generation circuit 23 does not include many high-order harmonic components,
If the waveform is close to a sine wave, the low-pass filter 24 may be omitted. The output signal of the clock signal generation circuit 23 is transmitted to each of the control devices A, B, and C via the clock signal transmission line 27, and is input to the waveform shaping circuits _25A , _25B , and _25C . in this case,
In the control devices A, B, and C, waveform shaping circuits 25 _A , 2
The square wave pulse shaped by the waveform shaping circuit _25C is input to the digital blocks _21A and _21B as a clock pulse as it is, and the square wave pulse shaped by the waveform shaping circuit _25C is input to the frequency dividing circuit _26C in the control device C.
After lowering the clock frequency, it is input to digital block _21C .

It is clear that the configuration of this embodiment also provides the same effects as the embodiment of FIG. 6.

In the above embodiment, the clock signal generation circuit is common to all the control devices included in the in-vehicle electronic control device, but the clock signal generation circuit is not limited to this. By providing a common signal generation circuit, the effect of noise suppression can be obtained.

As explained above, according to the present invention, a plurality of control devices that are synchronously controlled by clock pulses are mounted on the same vehicle (for example, a clock using a crystal oscillator and a microcomputer control the amount of fuel supplied to the engine, the ignition timing, Devices that control EGR, idle speed, etc., or devices that calculate and display travel distance, travel time, fuel consumption, required travel time to destination, etc.), even if they operate simultaneously, the fundamental wave of their clock pulses It is possible to prevent the occurrence of large noise due to mutual interference of components or harmonic components, and because only the fundamental wave component or harmonic component of each clock pulse is affected, interference noise can reduce the marketability of in-vehicle radios, etc. It is possible to easily solve the problem of the prior art, which is that it is severely damaged.

Furthermore, according to the present invention, only one clock signal generation circuit is required for multiple control devices, which reduces the number of oscillation crystal oscillators, ceramic oscillators, etc., and reduces costs. It will be advantageous.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of the configuration of an on-vehicle microcomputer, Figure 2 is a wiring system diagram of a vehicle equipped with a microcomputer, and Figure 3 is a concept showing a conventional example of an on-vehicle electronic control unit using multiple microcomputers. Figure 4a shows the spectrum of clock harmonic components within the FM broadcast frequency band, Figure b shows a partially enlarged view, and Figure 5 shows the absolute level of beat noise along with the S/N characteristics of the car radio. The actual measurement diagrams, FIGS. 6 and 7, are block diagrams showing embodiments of the present invention. 20... Vehicle electronic control device, A, B, C... Control device consisting of a microcomputer, 21 _A ,
21 _B , 21 _C ...Digital block, 23...
Clock signal generation circuit, 24...Low pass filter, 25 _A , 25 _B , 25 _C ... Waveform shaping circuit, 2
6 _A , 26 _C ... Frequency dividing circuit, 27... Clock signal transmission line.

Claims (1)

[Scope of utility model registration request] In an in-vehicle electronic control device configured using a plurality of control devices that are synchronously controlled by clock pulses, a common clock signal generation circuit is provided for at least two or more of the control devices, and a clock signal is generated from the clock signal generation circuit. A clock signal is transmitted to each of the control devices in the form of a sine wave or a waveform similar to a sine wave with few harmonic components, and the clock signal is shaped into a pulse waveform within each control device, or after being shaped, the clock signal is frequency-divided and sent to each control device. An in-vehicle electronic control device configured to be used as a clock pulse for synchronous control, and characterized in that the spectrum frequencies of the fundamental wave or harmonics of the clock pulse used in at least two or more control devices are made equal to each other. Device.