JPS58210368A - Electronic engine control device - Google Patents

Abstract

PURPOSE:To enable abnormality of a sensor to be surely detected in the ignition timing control device of an internal-combustion engine provided with a knocking feed-back control device, by carrying out fail-safe operation when the intensity of a knocking sensor output signal becomes out of a predetermined range. CONSTITUTION:At the step 103 a judgement is made for determining whether a knocking sensor signal VSP is within a range between -alpha and +beta which is a possible automatic gain control range with respect to a sensor signal VAS on the sensor sensing, that is, VAS-alpha>VA>VAS+beta, or not. If it is ''No'', at the step 104 the previous spark retardation compensating amount thetaKN is selected. If it is ''Yes'', at the step 105 a spark retardation compensating amount is computed. Thereby, abnormality of the knocking sensor may be surely detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine control device, and particularly to an electronic engine control device equipped with a fail-safe function.

Various test drives have been conducted to improve fuel economy, and among them, lean mixture combustion and increasing the engine's compression ratio are considered to be effective. However, under these conditions, the engine is susceptible to knocking, which may lead to a reduction in driving performance, a reduction in engine output due to generation of reverse torque, or damage to the engine due to overheating. The knock that occurs in this engine has a strong relationship with the ignition timing, and due to the characteristics of the engine, it is known that engine output can be maximized by setting the ignition timing, including the ignition advance, just before the knock. There is. Therefore, reducing the ignition advance angle in order to avoid the occurrence of knock will conversely reduce the engine output, so it is necessary to control the ignition timing immediately before the occurrence of knock. Especially with a turbocharger
Engines have high compression ratios and require optimal ignition timing to maintain maximum efficiency. That is, knock control is employed in which the state of knock is detected and the ignition timing is corrected.

Such a knock control device uses a method of masking the ignition noise caused by the ignition among the signals from the knock sensor, detecting the knock signal, and retarding the engine by a certain amount based on the knock signal.

In other words, it retards a certain amount (for example, 0.4 degrees) due to the knock that occurs during the ignition timing, and determines whether or not to retard depending on whether there is a knock signal, and if there is a knock, it retards in steps by a certain amount. A so-called step retard method is adopted.

In this knock control, the role of the sensor that detects knocking is important. However, the sensor has a drawback that there are large variations during manufacturing, and a large amount of expense is required to reduce the variations in manufacturing control. In addition, changes over time are likely to be affected by external factors such as the operating conditions of the engine or the installation environment, resulting in the disadvantage that the original knock control function is lost.

In conventional electronic engine control devices, the output from the knock sensor is synchronized with the spark timing to cut ignition noise, and the signal from the knock sensor is passed through a band-pass filter. An automatic gain control circuit jib (
AGC circuit) and the average value of this amplified signal are obtained at the background level (BGL)' and
Compared to GL, a knock signal is obtained. The AGC circuit in this conventional device utilizes the characteristic that the impedance changes depending on the gate-source voltage of the FET.

However, this PET has very poor temperature characteristics,
In addition, there are many variations in the product, and it may change over time, so it is not always possible to obtain consistent performance.

Furthermore, conventionally, fail-safe operation in the event of knock sensor disconnection or short circuit has been performed after processing the vibration wave that is the knock signal, which has the disadvantage of being susceptible to the effects of level fluctuations such as noise and offset voltage between elements. Moreover, in order to prevent this, the number of elements has to be increased and the circuit configuration has to be complicated.

Additionally, in the past, fail-safe processing was performed in the event of a disconnection or short circuit in the sensor and input system. For example, the effects of fluctuations in the sensor signal due to changes in the sensor over time were almost ignored, and knock control corresponding to the engine status was performed. There were other drawbacks such as not being carried out.

The object of the present invention is to prevent disconnection and disconnection of knock sensors and connection systems.
It is an object of the present invention to provide an electronic engine control device that can accurately detect a short circuit or an abnormality caused by a change in knock sensor over time (change in sensor sensitivity! III) with a simple configuration.

The present invention monitors the vibration signal of a knock sensor during a predetermined operation of the engine, compares the vibration signal value with a predetermined value, and performs a fail-safe operation when the deviation between the two is outside a predetermined range. Difference in Yojinoku sensor and connection system 1g
, the aim is to detect them accurately.

Examples of the present invention will be described below.

In FIG. 1, one side of the invention is shown.

In the figure, in the intake process of an engine 1, there is a sensor 2 that detects the amount of intake air, and a throttle valve 3 that adjusts the amount of intake air.
A control valve 9 is provided in the middle of a pipe that communicates between the upstream and downstream of the throttle valve 3.

Further, in the exhaust process, an exhaust purification device 11 and an exhaust gas sensor 6 etc. are provided in the middle, and a part of the exhaust gas is passed through the control valve 1.
0 to return to the intake stroke. The engine 1 is also provided with a cooling water temperature sensor 4, a knock sensor 7 that detects vibrations of the engine, an angle sensor 5 that also serves as an ignition device and detects the rotation angle of the engine, a fuel control device 8, etc. The module 12 is configured to input signals from the sensors described above, process them, and operate the fuel control device 8, ignition device 5, and control valves 9 and 10 to operate the engine 1. In particular, the knock sensor 7 converts engine vibration into an electrical signal, and this output is extracted in a frequency range of around 7 KHz by a band pass filter (BPF) of the module 12, and is converted into a predetermined reference signal (VREF). is compared with the comparator (COM') and a knock signal (rectangular wave) is obtained.

It has a function of performing calculation processing in the RAM and Ilo, and operating the ignition device 5 via the drive circuit (PW) to control the ignition timing. Also, a part of the output from the BPF' is passed through the integrator (INTI) to the A of the MPU.
It is input to the /D terminal.

The operation of the lock control device will be explained with reference to FIG.

The filter BPF in FIG. 1 has a knock occurrence area of, for example, 7K.
This is a type of Sallen-Key type filter that has the function of passing the frequency region around H2, and outputs the knowledge signal shown in (■) in FIG. 2(B). The signal ■ output from this filter BPP is compared with a predetermined reference voltage VRKF shown in ■ in FIG. 2 (B) by a comparator COM, and when the BPF output voltage exceeds the reference voltage VRKF Figure 2 (C
) A Q-Cruz sequence, which is output No. 18 (2), is output.

The output signal ■ from the comparator COM processed in this way is expressed as a count value Ilo as shown in FIG. 2(f)l.
The rotation angle signal measured at 2 and shown in FIG. The retardation correction amount θKN corresponding to
The engine is ignited as shown in Fig. 2 (P) at the final ignition timing as shown in Fig. After that, the engine is gradually advanced at a predetermined advance angle, moment by moment, until knock occurs again.
Correct the ignition timing. As a result, the engine can be operated at the optimum position for output characteristics.

Next, FIG. 3 shows the operation of the integrator (INT).

This will be explained using FIG.

The output of the knock sensor 7 is input to the module 12 via the connection 413.14 and a signal (
a), a part of which is connected to an integrator (INT) consisting of a resistor r1 and a capacitor C. A signal VA at the midpoint between the resistor R and the capacitor C is connected to the MPU (I10+).

FIG. 4 is an output characteristic diagram of the knock sensor 7, and under load condition LA, its output voltage increases almost proportionally to the engine speed N. The output voltage then moves as shown in the figure in response to the sensitivity of the knock sensor 7. here,
The output voltage of NA during the specified operation of the engine is VA when the sensor sensitivity is high! [, When the sensor sensitivity is small, V A L is obtained. On the other hand, on the control side, when the voltage VA is higher than V A H during the predetermined operation, or VA) I
At smaller times, areas that are difficult to control occur. Therefore, this voltage VA under the same conditions is the A/fi of the MPU.
Monitor VA>VAII, VA<VALk test-
It is determined that aL and te are out of order, and the above-mentioned θxN''k is set to the preset correction value θE, leading to a fail-safe operation in which correction control is performed to the ignition timing below the occurrence of knock.

That is, the N1 point is a point at which the engine is kept in a non-knocking state, for example, the idle speed, and the sensor signal Va indicates the engine's inherent vibration VAO (background level). In the figure, A indicates high sensor sensitivity, B indicates medium sensitivity, and C indicates low sensor sensitivity. The slope is decreasing and it is moving upwards to the right. Therefore, the sensor signal VA in the desired operating state NA changes from A, where the sensor sensitivity is high, to C, where the sensor sensitivity is low, as VAI(,V's).

It has changed greatly from VAL. Further, as the sensor changes over time, the sensor sensitivity may decrease as shown in FIG. 4.

For these reasons, the above-mentioned knock detection value is greatly influenced by sensor sensitivity even at the same knock intensity.

Therefore, in an arbitrary driving state, for example, an idling state where knocking cannot occur, the fourth
Signal value ■ of the corresponding sensor under the same conditions based on the signal value VAS shown in figure B. Sensor sensitivity can be detected by the deviation of

Next, the ignition timing correction control will be explained using the flowcharts shown in FIGS. 5 and 6.

FIG. 5 shows a flowchart of ignition timing correction control using rotational angle interruption.

First, when there is a rotation angle interruption in step 100, it is determined in step 101 whether or not the engine condition is within a range where knock does not occur, such as whether the engine cooling water temperature is at a predetermined value or not. If it is determined in step 101 that the knock determination conditions are met, then in step 102 it is determined whether or not the knock sensor determination conditions are met, that is, the idle position. If the knock determination conditions are not satisfied in step 101, the process returns. Also, step 1
In step 02, if it is determined that the knock sensor determination conditions are met, step 103 determines whether the sensor signal VF12 is within the range of 1α and 10β, which is the range in which automatic gain control is possible, that is, VAII−α>V a>V
A 8+β . . . Determine whether (1) is satisfied.

If it is determined in step 102 that the knock sensor determination condition is not met, in step 104 the previous retardation correction amount θ is determined.
Select l[N k. Also, in step 103,
If it is determined as YES, the retard angle correction amount θt is determined in step 105.
N table is selected for θ as the value of H, and step 10
Move on to 6. If the determination in step 103 is NO, then in step 105, the abnormality correction value θE is output as the correct value of θKN.

Next, in step 106, the knock detection value is loaded. Thereafter, in step 107, the knock detection value is reset.

Next, in step 108, it is determined whether the knock detection value is larger than the specified value, and if it is determined to be larger, step 1
09, the proportion (θKN
1 Search k tables. Next, in step 110, the knock control amount θKN is calculated, and in step 111, the correction limit value of θKN is processed.
In step 113, the retardation correction amount θKN is added to the ignition timing θ(N, L) calculated based on the engine operating state to calculate the final ignition timing θit, and in step 113, θ1. Set it in the wo register.

Next, the ignition task flow will be explained using FIG. 6.

First, in step 200, the ignition timing θIN,L)
is calculated, and in step 201 it is determined whether or not the knock control condition is satisfied. If NO, in step 205, the corrected ignition timing θKN is output.

If it is determined in step 201 that the knock control conditions are correct, then in step 202 the integral (advanced speed) is fully calculated, and in step 203 the integral is corrected (table searched) and the ignition Add to time θKN. With this value, step 20
4, maximum advance angle value processing for knock control is performed.

Therefore, according to the non-embodiment, it is possible to realize abnormality detection in the event of an abnormality such as a fluctuation in the output voltage due to a change in the knock sensor over time or a disconnection or short circuit in the input signal system including the knock sensor, and also with a simple configuration. This has the effect of improving the reliability of safe operation.

In addition, as another example, the method for determining abnormal voltage is V A B
-α) VA) VA s+β It goes without saying that similar results can be obtained and the same effect as in the previous embodiment can be obtained.

As described above, according to the present invention, it is possible to accurately detect disconnections and short circuits in the knock sensor and the connection system, or abnormalities due to changes in the knock sensor over time (variations in sensor sensitivity) with a simple configuration.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is a time chart of each part, Fig. 3 is a partial detailed diagram of the abnormality detection circuit of the knock sensor system, Fig. 4 is an output characteristic diagram of the knock sensor, and Fig. 5 is a diagram showing the output characteristics of the knock sensor. FIG. 6 is a control flowchart. 5... Ignition device, 7... Knock sensor, 12...
Module, COM... comparator, INT... integrator. ,4. m - Agent Patent attorney Akira Takahashi (Saw Figure 1 Z concave (A) Kitakata Fu (C) U, ---, -11-, -2--, n
1lIL-1---11,,-Figure 3/4 47th IJ41 Figure C

Claims (1)

[Claims] 1. A knock sensor, a first means for removing ignition noise at the time of ignition from a sensor output detected by the knock sensor, and a bandpass filter that converts the signal from which the ignition noise has been removed into a frequency band of a knock occurrence region. , a second means for comparing the knock signal outputted from the bandpass filter with a predetermined reference signal and outputting a pulse signal; a third means for totally integrating the signal outputted from the filter; a fourth means for counting the pulse signal outputted by the second means; a fifth means for calculating a retard amount from the count value in the fourth means; and an output from the fifth means. The present invention is characterized by comprising: a sixth means for retarding the ignition timing based on the above, and a seventh means for determining the abnormality of the 7-length period based on whether the output from the third means is larger than a predetermined value. Electronic engine control device.