JPH0335612B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an abnormality detection device for a knocking detection device, and in particular to a device for detecting an abnormality in a knocking detection device, which is used to delay the ignition timing by a predetermined angle to prevent the occurrence of knocking when knocking occurs. The present invention relates to a device for detecting an abnormality.

It is well known that the so-called knocking phenomenon occurs when an abnormal knocking sound occurs inside the engine while the vehicle is running. Strong knocking occurs when the ignition timing is too advanced in a high load range above a certain value. . This kind of knocking causes unpleasant noise, and if the knocking is severe enough, strong air column vibrations occur inside the cylinder, which can cause abnormal high temperatures in some parts of the cylinder, which can damage the engine. become. However, if the knocking is slight, even if knocking occurs by advancing the ignition timing, it is possible to improve the fuel efficiency of the vehicle by increasing the combustion efficiency of the engine. From this point of view, it is preferable to allow a moderate amount of knocking in order to obtain an operating state with optimal engine efficiency. Therefore, in order to optimize the operating efficiency of the engine and keep the knocking sound level below a predetermined level, knocking control is performed in accordance with various conditions.

Such knocking control involves attaching a knocking sensor such as a microphone to the engine body that detects knocking sound and outputs it as an electrical signal, and when the level of this electrical signal exceeds a predetermined level in a high load region, the ignition timing is delayed and the electrical When the signal level is below a predetermined level, the ignition timing is controlled to advance to the maximum advance angle that does not exceed knocking.

However, if an abnormality occurs in the knocking sensor that detects knocking, such as disconnection, sensor deterioration, poor contact, or superimposition of electrical noise on the sensor wire harness, the knocking state cannot be detected. An electrical signal of a predetermined level or higher is not output even though the engine is knocking, or an electrical signal of a predetermined level or higher is output even though the engine is not knocking. In particular, if it is determined that there is no knocking even though the engine is causing knocking, the ignition timing will advance to the maximum advance state, causing severe knocking or plague in the engine, and in the worst case, the ignition timing will advance to the maximum advance state. Problems arise in that the plug or piston may melt and damage the engine, such as the gasket blowing out.

Conventionally, in order to solve this problem, as shown in FIG. 1, the average (background) level of the electrical signal output from the knocking sensor is determined, and this average level is set as a predetermined level.
A method has been used in which the knocking detection device is determined to be abnormal when the value falls below ₀ . However, with such conventional methods, it is possible to detect abnormalities such as sensor deterioration, wire breakage, poor contact, etc. in which the average level of the electrical signal output from the knocking sensor decreases, but electrical noise Do not overlap the wire harness of the sensor,
There has been a problem in that it is not possible to detect an abnormal mode in which the sensor output is abnormally high, which occurs due to voltage being applied to the sensor for some reason.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an abnormality detection device for a knocking detection device that can detect even an abnormal mode in which the sensor output becomes high.

In order to achieve the above object, the present invention, as shown in FIG. a detecting means; a starting state detecting means for detecting whether the engine is in a starting state; and a starting state detecting means for detecting whether the engine is in a starting state; abnormality determination means for determining that the knocking detection means is abnormal when the output of the knocking detection means is equal to or higher than a second predetermined level higher than the first predetermined level when the output of the knocking detection means is below the predetermined value; The present invention proposes an abnormality detection device for a knocking detection means, which is equipped with an abnormality determination invalidation means that substantially invalidates the abnormality determination.

Generally, as the engine speed increases, the average level of the knocking sensor output also increases.

Therefore, in the present invention, even if the engine speed exceeds a predetermined value, if the output of the knocking detection means is below the first predetermined level, disconnection, sensor deterioration, or contact failure occurs in the knocking sensor, etc., and the output is It is determined in the conventional manner that an abnormal state has occurred in which the condition cannot be obtained.

On the other hand, when the engine speed is below the predetermined value and the output of the knocking detection means is above the second predetermined level, which is higher than the first predetermined level, it is not the signal from the knocking sensor itself that is input, but noise. It is determined that an abnormal voltage from the other system is applied to the knocking detection means and an abnormal state has occurred.

When the engine is started, especially during a cold start, the engine vibrations are large, so the average level of the output of the knocking detection means is high, so even if the knocking sensor etc. is normal, there is a high risk of misjudging it as abnormal. , substantially invalidates abnormality determination.

As described above, in the present invention, the abnormality determination mode of the knocking detection device is finely switched depending on whether the engine is in a starting state or not, and whether the engine speed exceeds a predetermined value after starting. Abnormalities in the knocking detection means can be detected accurately and reliably.

Next, FIG. 2 shows a schematic diagram of an engine equipped with a knocking control device to which the present invention is applied. As shown in the figure, this engine is equipped with an air flow meter 2 as an intake air amount sensor provided downstream of an air cleaner (not shown). The air flow meter 2 includes a compensation plate 2 rotatably provided within the damping chamber.
A and a potentiometer 2B that detects the opening degree of the compensation plate 2A. Therefore, the amount of intake air is determined by potentiometer 2.
It is detected as the voltage output from B. Also,
An intake air temperature sensor 4 is provided near the air flow meter 2 to detect the temperature of intake air.

A throttle valve 6 is arranged downstream of the air flow meter 2, and downstream of the throttle valve 6,
A surge tank 8 is provided. An intake manifold 10 is connected to the surge tank 8, and a fuel injection device 12 is disposed protruding into the intake manifold 10.
The intake manifold 10 is the engine body 1
A catalytic converter (not shown) is connected to the combustion chamber 14A of the engine No.
It is connected to the. The engine body 14 is provided with a knocking sensor 18 that detects engine knocking and is configured with a microphone or the like. Note that 20 is a spark plug, 22 is an O ₂ sensor for controlling the air-fuel mixture to near the stoichiometric air-fuel ratio, 24 is a cold/hot water temperature sensor that detects the engine cooling water temperature, and 33 is a starter.

The spark plug 20 of the engine body 14 is connected to a distributor 26, and the distributor 26 is connected to an igniter 28. The distributor 26 is provided with a cylinder discrimination sensor 30 and an engine rotation speed sensor 32, which are comprised of a pickup and a signal rotor fixed to the distributor shaft.
This cylinder discrimination sensor 30 is configured to detect, for example, a crank angle.
A cylinder discrimination signal is output to the electronic control circuit 34 every 720 degrees, and the engine rotation speed sensor 32 outputs a crank angle reference position signal to the electronic control circuit 34, for example, every 30 degrees of the crank angle.

The electronic control circuit 34 includes a random access memory (RAM) 36, a read-only memory (ROM) 38, a central processing unit (CPU) 40, and a first input/output circuit, as shown in FIG. It is configured to include a port 42, a second input/output port 44, a first output port 46, and a second output port 48, and includes a RAM 36, a ROM 38, a CPU 40,
First input/output port 42, second input/output port 4
4. The first output port 46 and the second input/output port 48 are connected by a bus 50. The first input/output port 42 includes buffers 52A, 5
2B, 52C, a multiplexer 54, and an analog-digital (A/D) converter 56, an air flow meter 2, a cooling water temperature sensor 24, and an intake air temperature sensor 4 are connected. The multiplexer 54 and A/D converter 56 are controlled by a signal output from the first input/output port 42. The second input/output port 44 includes a starter 33
are connected, buffer 60 and comparator 6
₂ , a cylinder discrimination sensor 30 and an engine rotation speed sensor 32 are connected via a waveform shaping circuit 64, and a knocking sensor 30 is connected via an input circuit 66 and an A/D converter 68. A sensor 18 is connected. The input circuit 66 and A/D converter 68 are controlled by the signal output from the second input/output port 44, and take in the electric signal output from the knocking sensor at predetermined time intervals. Further, the first output port 46 is connected to the igniter 28 via the drive circuit 70,
Second output port 48 is connected to fuel injector 12 via drive circuit 72 .

The ROM 38 of the electronic control circuit 34 stores in advance a map of the basic ignition advance angle expressed by the engine speed and intake air amount, the basic fuel injection amount, etc., and the signal from the air flow meter 2 and the engine speed sensor. 32, the basic ignition advance angle and basic fuel injection amount are read out, and various signals including signals from the cooling water temperature sensor 24 and intake temperature sensor 4 read out the basic ignition advance angle and basic fuel injection amount. A corrected ignition advance angle and a corrected fuel injection amount are added to control the igniter 28 and the fuel injection device 12. _O2 sensor 2
The air-fuel ratio signal output from 2 is used for air-fuel ratio control to control the air-fuel ratio of the mixer to near the stoichiometric air-fuel ratio. Furthermore, when the level of the electrical signal output from the knocking sensor 18 exceeds a predetermined level set in advance, it is determined that knocking has occurred, and the igniter 28 is controlled to delay the ignition timing. Conversely, when the level of the electrical signal output from the knocking sensor 18 is below a predetermined level, it is determined that knocking does not occur, and the ignition timing is controlled to the maximum advance angle that does not cause knocking. Ru.

Next, an embodiment of the present invention for detecting whether or not a knocking sensor used in the engine as described above is abnormal will be described. FIG. 4 shows a flowchart of an interrupt routine performed at every predetermined crank angle when this embodiment is implemented by an electronic control circuit. First, in step 82, the electrical signals output from the knocking sensor 18 are averaged to obtain the average level B of the knocking sensor output, and the engine speed N is also taken based on the output of the engine speed sensor 32, and the RAM 36 to be memorized. Next, in step 94, it is determined whether the starter 33 has been turned on, that is, whether the engine has been started. Then, when the engine is started, no abnormality detection is performed in the knocking detection means, and in step 88, the ignition timing is controlled using a preset fixed advance angle at the time of starting. on the other hand,
If it is determined in step 94 that the engine has started, then in step 92 the engine speed N is set to a predetermined value R. (For example 1500r.p.
m.) is exceeded. step
If it is determined in step 92 that the engine speed N exceeds the predetermined value R ₀ , then in step 84 the average level B is compared with a first predetermined level _BL set in advance. Here, the average level B
exceeds the first predetermined level B _L , then
It is determined that the knocking sensor is normal, and in step 88, if knocking is detected, the ignition timing is delayed, and if knocking is not detected, the ignition timing is advanced, so that normal knocking control is performed. On the other hand, if the average level B is below the first predetermined level B _L , it is determined in step 90 that the knocking sensor is abnormal, and the ignition timing is controlled to the maximum retard angle that does not cause knocking, or the air-fuel ratio is adjusted. Perform fail-safe control to control the rich side.

On the other hand, if it is determined in step 92 that the engine speed N is below the predetermined value, then in step 86 a second predetermined level that is preset as the average level B and higher than the first predetermined level B _L is determined. B Compare with _H. Here, if the average level B is less than the second predetermined level _BH , the above-mentioned normal knocking control is performed in step 88. On the other hand, the average level B is a second predetermined level B _H
If the above is the case, it is determined in step 90 that the knocking sensor is abnormal, and the above-mentioned fail-safe control is performed.

Incidentally, the relationship between the average level of the sensor output and the engine rotation speed in the above embodiment is shown in FIG.
In the figure, A is the characteristic of a normal sensor, B is the characteristic of an abnormal sensor when the output decreases due to sensor deterioration, etc., and C is the characteristic of an abnormal sensor when the output increases due to the application of abnormal voltage, noise, etc. are shown respectively.

According to this embodiment, since the abnormality of the knocking sensor is detected by changing the predetermined level depending on the engine speed, it is possible to narrow the interval between the first predetermined level and the second predetermined level. , it is possible to improve the accuracy of abnormality detection.

According to the present invention, there is a disconnection in the knocking sensor, etc.
As in the case of sensor deterioration or poor contact,
If the output of the knocking detection means is below a predetermined level even if the engine speed exceeds a predetermined value, it is of course possible to detect an abnormality in the knocking detection device. It is also possible to detect an abnormality in the knocking detection device when the output becomes abnormally high, such as when an abnormal voltage is applied to the knocking detection device. Further, an excellent effect can be obtained in that erroneous detection at the time of starting the engine is prevented.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the average level and engine speed in a conventional abnormality detection method of a knocking detection device, FIG. 2 is a schematic diagram showing an example of an engine to which the present invention is applied, and FIG. 2 is a block diagram showing the electronic control circuit in FIG. 2, FIG. 4 is a flowchart for explaining an embodiment of the present invention, and FIG. 5 is a relationship between the average level and engine speed in the embodiment. FIG. 6 is a block diagram showing the system configuration of an abnormality detecting device for knocking detecting means according to the present invention. 18...Knocking sensor, 32...Engine speed sensor, 33...Starter, 34...Electronic control circuit.

Claims (1)

[Scope of Claims] 1 Knocking detection means including a knocking sensor that detects engine knocking and outputs an electrical signal; Engine speed detection means that detects engine speed; and whether or not the engine is in a starting state. starting state detection means for detecting whether the engine speed is above a predetermined value and the output of the knocking detection means is below a first predetermined level or when the engine speed is below the predetermined value; abnormality determination means for determining that the knocking detection means is abnormal when the knocking detection means is at or above a second predetermined level higher than the first predetermined level; and for determining that the abnormality determination is substantially invalid when the engine is in a starting state. An abnormality detecting device for a knocking detecting means, comprising: an abnormality determination invalidating means.