JPS61241667A - Engine speed detecting device for diesel car - Google Patents

Abstract

PURPOSE:To improve accuracy of detection of engine speed by correcting engine speed by the output signal of an alternator when calculating engine speed from the output signal of the alternator. CONSTITUTION:The oscillation signal of an engine block corresponding to engine speed of idling stage is converted to an electric signal by a piezo-electric sensor 1 and outputted. An alternator (ACG) 4, quantity of power generation of which is controlled by a voltage regulator 3, outputs three-phase full wave rectifier output from an A terminal and charges a battery 5. At the same time, A terminal output is made to pulsating current by smoothing effect of the battery 5. A detecting device 7 extracts minute ripple component corresponding to the engine rotation signal from the output signal of the sensor 1 and output signal of the A terminal and inputs a waveform shaped pulse signal. This is processed and calculated by a microcomputer 9 and rotational frequency of the engine is calculated, and finally, corrected engine speed is displayed in a display section 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an engine rotation speed detection device for an automobile, and more particularly to a diesel vehicle engine rotation speed detection device suitable for detecting the engine rotation speed of a diesel vehicle.

[Background of the invention]

Since diesel cars do not have an ignition system unlike gasoline cars, a variety of methods have been proposed for conventional engine speed detection devices for diesel cars.
Most methods, as described in Japanese Patent No. 7-22113, detect the engine vibration signal using a detection device attached to the surface of the engine block to determine the engine rotation speed. However, with this type of conventional device, even if a vibration signal proportional to the engine rotation signal can be converted into an electrical signal,
Since it is difficult to obtain a good 8/N ratio particularly in a high rotation range, there is a problem in that it is difficult to obtain a stable engine rotation speed signal over a wide rotation range.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above and to provide an engine speed detection device for a diesel vehicle that can stably detect engine speed over a wide range of engine speeds.

[Summary of the invention]

The present invention provides a pulse signal obtained by converting a minute ripple component signal at the power output terminal of an alternator whose frequency is proportional to the engine rotation signal by a comparator circuit. At times, the ratio between the output signal of the piezoelectric sensor mounted on the outer surface of the engine block and the calculated engine speed is determined as a correction coefficient, and then the pulse signal of the minute ripple component signal of the alternator is used. This is an engine rotation speed detection device for a diesel vehicle that enables stable and highly accurate engine rotation speed detection over a wide range of engine rotation ranges by correcting the calculated engine/engine rotation speed using the above correction coefficient.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

FIG. 1 is a system configuration diagram showing an embodiment of an engine rotation speed detection device for a diesel vehicle according to the present invention. In Fig. 1, 1 is a piezoelectric sensor mounted on the outer surface of the engine block to detect vibrations generated on the surface of the engine block when the vehicle's engine is operating. Converts the signal into an electrical signal and outputs it. 2 is the vehicle charging system,
As is well known, the alternator 4 whose power generation amount is controlled by the voltage regulator 3 of the electric system 2 outputs a three-phase full-wave rectified output from the A terminal (power output terminal), and connects the cough A terminal to the battery 5.
The battery 5 is charged by connecting it to the positive terminal of the battery 5, but at the same time, due to the smoothing capacitor effect of the battery 5, the output of the terminal A becomes a pulsating signal containing a minute ripple component corresponding to the engine rotation signal. Furthermore, the output of the A terminal of the alternator 4 also supplies power to the load 6. 7 is a detection device (main body), 8 is its interface circuit, 9 is a microcomputer, and 10 is a display section. The detection device 7 inputs the output signal of the piezoelectric sensor 1 and the output signal of the A terminal of the alternator 4, and outputs a waveform-shaped signal of the output signal of the piezoelectric sensor 1 and the A terminal via the interface circuit 8. A minute ripple component corresponding to the engine rotation signal is extracted from the output signal of the terminal, a waveform-shaped pulse signal is obtained, and the engine rotation speed is calculated by performing multiple processing and calculations on the microcomputer 9, and is finally corrected. Display section 1 shows the engine rotation speed.
Display at 0.

FIG. 2 is a block diagram of a piezoelectric sensor processing circuit section (first processing circuit section) for waveform shaping the output signal of the piezoelectric sensor 1 of the interface circuit 8 of FIG. 1. Second
In the figure, reference numeral 11 denotes a bandpass filter circuit with a hole for extracting signal components in a necessary frequency band from the output signal of the piezoelectric sensor 1, and a circuit 1 for detecting the output signal 11a of the bandpass filter circuit 11.
2 is a detection circuit, and 13 is a comparison circuit that shapes the waveform of the output signal 12b of the detection circuit 12. Note that FIG. 3 is a waveform diagram of each processed signal of the piezoelectric sensor signal of FIG. 2.

In FIG. 3, %lla is the output signal of the bandpass filter circuit 11, 12a corresponding to the same reference numerals as in FIG.

12b is each detection signal and output signal of the detection circuit 12, 13a
indicates the waveform of the output signal (waveform shaping signal) of the comparison circuit 13. In other words, the output signal (
The electrical signal) is passed through the bandpass filter circuit 11 to obtain an output signal 11a having the waveform shown in FIG. 3 having a signal component in a necessary frequency band (7 to 10 kHz), and the frequency component of the engine rotation signal is extracted. Then, by detecting the output signal 11a with the detection circuit 12, a detection signal 1 having the waveform shown in FIG. 3 is obtained.
2a1 output signal 12b is obtained, and the maximum amplitude value of output signal 11a is extracted. Furthermore, by shaping the output signal 12b in the comparator circuit 13 and converting it into a pulse signal,
An output signal 13a of a pulse signal (waveform shaping signal) having the waveform shown in FIG. 3 is output.

FIG. 4 is a block diagram of an alternator output signal processing circuit section (second processing circuit section) for extracting minute ripple components from the output signal of the alternator 3 in the interface circuit 8 of FIG. 1 and shaping the waveform. be. In FIG. 4, 14 is a first low-pass filter circuit that removes extra high frequency components from the output signal of the A terminal of the alternator 3;
Reference numeral 5 denotes a second Q low-pass filter circuit having an integrating circuit that attenuates minute ripple components of the output signal 14a of the low-pass filter circuit 14; 16 inputs the two types of output signals 14a and 15a of the filter circuits 14 and 15 and outputs the same phase. 17 is an amplifier circuit that amplifies the output signal 16a of the differential amplifier circuit 16, and 18 is a comparison circuit that shapes the waveform of the output signal 17a of the amplifier circuit 17. Note that the circuit portion for extracting minute ripple components from the alternator output signal in FIG.
It is known from the publication no. Note that FIG. 5 is a waveform diagram of each processed signal of the alternator output signal of FIG. 4. In FIG. 5, 14a corresponds to the same reference numerals as in FIG. The output signal 18a indicates the waveform of the output signal (waveform shaping signal) of the comparator circuit 18. That is, first, according to the above-mentioned known example, the output signal of the alternator 30A terminal (power output terminal) of the charging system 2 of the vehicle is passed through the first low-pass filter circuit 14 to remove excess high frequency components other than the necessary minute ripple components. By removing the pulsating flow signal, the output signal 14a of the pulsating flow signal containing only the minute ripple component of the waveform shown in FIG.
The output signal 14a is then passed through the second low-pass filter circuit 15 to attenuate and remove the minute ripple components, resulting in an output signal 15 of the pulsating current signal having the waveform shown in FIG.
a is obtained, and two further output signals 14a.

15a is input to the differential amplifier circuit 16, and by removing the pulsating current signal of the in-phase input component, an output signal 16a in which only the minute ripple component of the waveform shown in FIG. 5 is extracted is obtained. Next, by amplifying the output signal 16a of the minute ripple component obtained in the above-mentioned known example in the amplifier circuit 17, an amplified output signal 17a having the waveform shown in FIG. 5 is obtained, and the output signal 17a is further compared. The waveform is shaped by circuit 18.]
The signal 16a of the minute ripple component of the fifth waveform is converted into an output signal 18a of a pulse signal (waveform shaping signal) and output.

Next, nine piezoelectric sensors are obtained by the piezoelectric sensor processing circuit section (first processing circuit) and the alternator output signal processing circuit section (second processing circuit section) of the interface circuit 8 in FIGS. 2 and 4. The microcomputer 7 processes the output signal 13a of the waveform shaping signal (pulse signal) of the alternator 1 and the output signal 18a of the waveform shaping signal (pulse signal) of the minute ripple component of the A terminal output signal of the alternator 3.
Through the calculation, the engine rotation speed is calculated and displayed on the display unit 10. FIG. 6 schematically shows a processing procedure 70 mainly performed by the microcomputer 9 in the system shown in FIG. −
It is a chart. That is, first, in the initial stage SO, the vehicle is brought into an idle state in step S1. In step S2, the output signal of the piezoelectric sensor 1 that has detected the vibration signal of the engine block corresponding to the engine rotation signal during idling is transmitted to the first processing circuit section (the second processing circuit section) of the interface circuit 8.
The engine rotation speed N is calculated from the output signal 13a of the pulse signal whose waveform has been shaped as shown in FIG. In addition, in step S3, the output signal of the alternator (ACG) 40A terminal is processed in the second processing circuit section (FIG. 4) of the interface circuit 8, and the output signal 18a of the waveform shaping signal (pulse signal) of the minute ripple component is similarly processed. Calculate engine rotation speed Nm. At this time, the engine speed N is generally determined by the number of poles P of the alternator 4, the minute ripple component signal of the A terminal output signal, that is, the frequency f of the pulse signal 18a, and the engine crankshaft and alternator 30 rotation ratio, that is, the pulley ratio R.
It can be calculated using the following formula.

N ('fLPM) = (20Xf)/C'f%XP)
(1) Since the frequency f is uniquely determined here, the number of poles P and the pulley ratio R will be considered. First, the number of poles P is set to P=12 since most major vehicles, from light vehicles to large vehicles, have 12 poles. Further, the pulley ratio R is determined to be 2.2 since it was found from actual measurements of many car models that R=2.1 to 2.3. In this case, due to the error in the pulley ratio R (the error in the engine speed N11 in equation 11 is about ±5%. Therefore, by substituting P' = 12 and R = 2.2 in equation (1), it is expanded to the following equation. can.

0.758xf in NB (RPM)... (2) Here, in step S4, the error in the engine rotation speed Nm calculated from the frequency f of the minute ripple component signal of the alternator output signal is corrected according to equation (2). Therefore, the ratio of the engine rotation speed Nm calculated from the output signal of the piezoelectric sensor 1 in step S2 and the engine rotation speed Nm calculated in step S3, that is, the correction coefficient is calculated as =Nm/Nm. . Based on the results of the processing and calculations in the initial process SO, in step S5, the product of the engine rotation speed N1 calculated from the minute ripple component signal of the alternator 30A terminal output signal and the correction coefficient is calculated and corrected accurately. The corrected engine rotation speed N = K x N m can be calculated, and the corrected engine rotation speed N is displayed on the display unit 10 in step S6.

〔Effect of the invention〕

As described above, according to the present invention, when calculating the engine rotation speed of a diesel vehicle from the output signal of the alternator, a piezoelectric sensor detects the vibration signal of the engine block corresponding to the engine rotation signal once in the idling state. Since the engine speed is corrected based on the output signal of the alternator, it is possible to detect the engine speed stably and accurately over a wide range of engine speeds.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram showing an embodiment of the engine speed detection device for a diesel vehicle according to the present invention, and FIG.
A block diagram of the piezoelectric sensor processing circuit section (first processing circuit section) of the interface circuit 8 shown in the figure, FIG. 3 shows each processed signal waveform diagram of FIG. 2, and FIG. A block diagram of the processing circuit for output signals of 8 (second processing circuit), FIG. 5 is a waveform diagram of each processed signal in FIG. 4, and FIG. 6 is a flowchart of the processing procedure in FIG. 1. 1...Piezoelectric sensor, 2...Vehicle charging system, 3...
・Voltage regulator, 4...Alternator (ACG)
, 5... Battery, 6... Load, 7... Detection device (main body), 8... Interface circuit including first and second processing circuit units, 9... Microcomputer,
1o...Display section, 11...Band filter circuit, 12
...Detection circuit 1.13...Comparison circuit, 14...Filter circuit, 15...Filter circuit, 16...Differential amplifier circuit, 17...Amplification circuit, 18...Comparison circuit .

Claims (1)

[Claims] 1. A sensor that detects engine block vibration corresponding to an engine rotation signal generated during operation of a vehicle engine and converts it into an electrical signal, a band filter circuit that extracts a frequency component of the engine rotation signal from the output signal of the sensor, and a band filter circuit that extracts the frequency component of the engine rotation signal from the output signal of the sensor. A first processing circuit section consisting of a detection circuit that extracts the maximum amplitude value of the output signal of the circuit, a first comparison circuit that converts the output signal of the detection circuit into a pulse signal, and a power output terminal of the alternator of the vehicle. A first filter circuit that removes unnecessary high-frequency signal components from a pulsating current signal containing minute ripple components to be output; an output signal of the first filter circuit; and a second filter circuit that filters the output signal of the first filter circuit A differential amplifier circuit extracts the above-mentioned ripple component signal of a frequency corresponding to the engine rotation signal by using two inputs of the output signal passed through the circuit and removes the in-phase component, and converts the output signal of the differential amplifier circuit into a pulse signal. A second processing circuit comprising a second comparison circuit and a pulse signal output from the first comparison circuit when the sensor detects engine block vibration corresponding to the engine rotation signal when the vehicle is idling. Calculating, as a correction coefficient, the ratio of the value calculated for the rotation speed and the value calculated for the engine rotation speed based on the pulse signal output from the second comparison circuit based on the output signal of the power output terminal of the alternator;
Detection of engine rotation speed of a diesel vehicle, comprising a processing calculation means for correcting a value obtained by calculating the engine rotation speed using only the pulse signal outputted from the second comparison circuit using the output signal of the alternator, using the correction coefficient. Device.