JP2555677B2 - Knock detection device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a knocking detection device for an internal combustion engine, and more particularly to a knocking detection device having a knock sensor abnormality detection function.

[Prior Art] Conventionally, as one of knocking detection devices for an internal combustion engine, when an abnormality occurs in a knock sensor and knocking of the internal combustion engine cannot be detected, the ignition timing control device causes knocking in the internal combustion engine. In order to prevent the ignition timing from being advanced, it is possible to self-determine the abnormality of the knock sensor. The abnormality determination of the knock sensor is made based on the output signal level from the knock sensor. In other words, when an abnormality occurs in the knock sensor, the detection sensitivity of the knock sensor to the vibration of the internal combustion engine decreases, and the output signal level becomes lower than usual.Therefore, when determining the abnormality of the knock sensor, the output signal level from the knock sensor is normal. It depends on whether it is smaller or smaller.

By the way, since the knock sensor generates an AC signal that changes between positive and negative depending on the vibration of the internal combustion engine, when actually determining the abnormality of the knock sensor, the AC signal from the knock sensor is processed and its amplitude is processed. It is necessary to generate a voltage signal for detecting a sensor abnormality corresponding to the level. However, in order to generate the voltage signal for detecting the abnormality of the knock sensor in this way, a special signal processing circuit for generating the abnormality detection signal is required, which is costly.

Therefore, conventionally, for example, as described in JP-A-56-38563, a knock determination voltage (noise) generated based on an output signal from a knock sensor for determining whether or not knocking has occurred in an internal combustion engine. When the signal level) falls below a predetermined value, an abnormality of the knock sensor is detected, or as described in JP-A-58-206877, the deviation of the knock determination voltage generated under two operating conditions of the internal combustion engine. It is considered that an abnormality of the knock sensor is detected when is less than or equal to a preset reference value. That is, by using the knock determination voltage generated for knocking detection to detect the abnormality of the knock sensor, the signal processing circuit for generating the abnormality detection signal is unnecessary.

[Problems to be Solved by the Invention] However, when the former technique is applied to an actual knocking detection device to detect an abnormality of the knock sensor,
There is a problem that the abnormality detection accuracy is reduced.

That is, first, the knocking of the internal combustion engine is detected when the knock determination voltage and the output signal from the knock sensor are compared in magnitude, and the output signal exceeds the knock determination voltage, but as described above, the output signal from the knock sensor is detected. Is an AC signal that is inverted between positive and negative depending on the vibration of the internal combustion engine.To compare the positive and negative input voltages with the knock determination voltage, an expensive circuit capable of processing the negative input voltage must be used in the comparison circuit. I have to. So, in the actual knocking detection circuit,
A knock determination voltage is generated by applying a reference voltage to the AC signal from the knock sensor by applying processing such as rectification, integration, and amplification, and a positive voltage signal is generated by adding the reference voltage to the output signal from the knock sensor. Is converted into a value, and the respective voltage values are compared in magnitude to perform knock determination. Therefore, if the knock determination voltage is used as it is to detect the abnormality of the knock sensor as described above, the accuracy of knock sensor abnormality detection decreases due to the tolerance of the reference voltage applied when the knock determination voltage is generated. Occasionally, an abnormality of the knock sensor is erroneously detected.

On the other hand, when the abnormality of the knock sensor is detected based on the deviation of the knock determination voltages generated under the two operating conditions of the internal combustion engine as in the latter case, even if the reference voltage fluctuates, both knock determination voltages are Since it changes, the deviation is not affected by the fluctuation of the reference voltage, and the abnormality detection accuracy of the knock sensor does not decrease. However, in this case, since the abnormality of the knock sensor can be detected only when the internal combustion engine is operated under two predetermined operating conditions, there is a problem that it takes time to detect the abnormality of the knock sensor and the responsiveness is poor.

Therefore, the present invention has been made for the purpose of providing a knocking detection device capable of detecting abnormality of a knock sensor with a simple circuit configuration, with high accuracy and without response delay.

[Means for Solving the Problems] That is, the present invention made to achieve the above object is
As illustrated in the figure, a knock sensor M1 for detecting the vibration of the internal combustion engine, an output signal from the knock sensor M1 is integrated, a reference voltage is added, and a knock determination voltage corresponding to the amplitude level of the output signal is output. A knock determination voltage creating means M2 that applies a reference voltage to the output signal from the knock sensor M1, and a knock detection means M3 that detects knocking of the internal combustion engine when the voltage value exceeds the knock determination voltage. In the knocking detection device for the internal heat engine equipped, a pressure reducing means M4 for subtracting the reference voltage from the knock determination voltage
And a knocking detection device for an internal combustion engine, comprising: an abnormality detection unit M5 that detects an abnormality of the knock sensor based on the pressure reduction result of the pressure reduction unit M4.

[Operation] In the knocking detection device of the present invention configured as described above, the knocking determination voltage generating means M2 generates the knocking determination voltage by adding the reference voltage to the value obtained by integrating the output signal from the knock sensor M1. And knock detection means M3
However, the knock determination is performed depending on whether the value obtained by adding the reference voltage to the output signal from the knock sensor M1 exceeds the knock determination voltage. The knock sensor M1 abnormality is detected by pressure reducing means.
The operation of M4 and the abnormality detection means M5 is performed based on the voltage signal obtained by subtracting the reference voltage from the knock determination voltage.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 2 is a schematic configuration diagram showing an ignition timing control device for an internal combustion engine including a knocking detection device, which controls the ignition timing of the internal combustion engine using an output signal from a knock sensor as one parameter.

As shown in the figure, the ignition timing control device includes a knock sensor 2 for detecting vibration of the internal combustion engine, a rotation speed sensor 4 for detecting the rotation speed of the internal combustion engine, an intake pressure sensor 6 for detecting the intake pipe pressure, and the like of the internal combustion engine. It is composed of various sensors for detecting the operating state and an electronic control unit 10 for driving and controlling the ignition device 8 by obtaining an optimum ignition timing according to the operating state of the internal combustion engine based on output signals from these sensors. There is.

The electronic control unit 10 includes a CPU 11 for executing various kinds of arithmetic processing for performing ignition timing control, a control program for executing arithmetic processing in the CPU 11 and various data stored in advance.
M12, RAM13 for temporarily storing various data for executing arithmetic processing in the CPU11, input / output port 14 for inputting output signals from the above-mentioned sensors and outputting control signals for the ignition device 8, and these parts The data bus 15 and the like are connected to form a logical operation circuit. Also an electronic control unit
Reference numeral 10 denotes a signal processing circuit 16a, 16b, 16c ... Processing an output signal from each sensor and converting it into a digital signal, and a drive circuit driving the ignition device 8 based on a control signal output from the input / output port 14. 17, a power supply circuit 18 for supplying power to each of the above parts, and the like are also provided.

In the ignition timing control device configured as described above, first, the basic ignition timing corresponding to the load of the internal combustion engine is obtained based on the output signals from the rotation speed sensor 4 and the intake pressure sensor 6, and is output from the signal processing circuit 16a. The basic ignition timing is corrected on the basis of the knock determination pulse to control the internal combustion engine to the knock generation limit (knocking control), or when the internal combustion engine is idle, the rotational speed sensor 4 is input through the signal processing circuit 16b. Various known ignition timing controls are executed, such as advancing the basic ignition timing based on the output signal to stabilize the idle rotation of the internal combustion engine (idle control).

Next, FIG. 3 shows a signal processing circuit 16a for processing an output signal from the knock sensor 2 which is a main part of the present invention.

As shown in the figure, in the signal processing circuit 16a, first, the output signal from the knock sensor 2 is a bandpass filter (BPF) 2
Entered in 0. The BPF20 is for extracting knock frequency components in the output signal from the knock sensor 2 and removing other noise frequency components. The signal from which the noise frequency components have been removed by the BPF20 (hereinafter referred to as knock sensor signal) ) Vs is coupled via the coupling capacitor C1 to the half-wave rectifying / integrating amplifier 22 as the knock determination voltage creating means M2.
Is input to

The half-wave rectifying / integrating amplifier 22 is for processing the knock sensor signal Vs from the BPF 20 to create the knock determination voltage Vk. As shown in FIG. 4 (a), first, the knock sensor signal is half-wave rectified and The average level Vi of the half-wave rectified value is obtained by integration, the average level Vi is amplified K times, and then the reference voltage Vo output from the reference voltage generating circuit 24 is added to create the knock determination voltage Vk. Then, the knock determination voltage Vk thus created is input to the inverting input terminal of the operational amplifier 26 as the knock detecting means M3 that functions as a comparator.

On the other hand, the knock sensor signal Vs from the BPF 20 is also input to the non-inverting input terminal of the operational amplifier 26 via the coupling capacitor C2. The virtual ground voltage Vg output from the reference voltage generating circuit 24 is also applied to the non-inverting input terminal of the operational amplifier 26, and the potential of the non-inverting input terminal is from the BPF 20 as shown in FIG. 4 (a). It is a value obtained by adding the virtual ground voltage Vg to the knock sensor signal Vs that is output.

Further, the reference voltage generating circuit 24 is composed of three resistors R1 to R3 connected in series. Each of the resistors R1 to R3 divides the power source voltage Vcc from the power source circuit 18 to obtain the reference voltage V3.
The o and the virtual ground voltage Vg are generated by the following equation.

Vg = Vcc ・ R3 / (R1 + R2 + R3) Vo = Vcc ・ (R2 + R3) / (R1 + R2 + R3) Therefore, the knock determination voltage Vk is the half-wave rectified integral amplification value Vi ・ K of the knock sensor signal Vs, and the virtual ground voltage Vg and resistance. Voltage Vf (= Vcc ・ R2 / (R1
+ R2 + R3)) is added.

Then, the operational amplifier 26 compares the respective input terminal voltages, and when the knock sensor signal Vs to which the virtual ground voltage Vg is added exceeds the knock determination voltage Vk, determines that knocking has occurred in the internal combustion engine, A knock determination pulse as shown in FIG. 4 (b) is output to the input / output port 14.

When generating the knock determination voltage Vk, adding the offset voltage Vf together with the virtual ground voltage Vg to the half-wave rectified integral amplification value ViK of the knock sensor signal is to improve the knock detection performance during low rotation operation of the internal combustion engine. This is to ensure.

That is, during low speed operation of the internal combustion engine, the vibration of the internal combustion engine is small, and the half-wave rectification integral amplification value ViK of the knock sensor signal is generated.
Therefore, by simply adding the virtual ground voltage Vg, the difference from the knock sensor signal Vs to which the virtual ground voltage Vg is added becomes small, and even if the engine vibration is small, the operational amplifier 26 produces a small electromagnetic field. Knock determination may be erroneously performed due to static noise. Therefore, in this embodiment,
By adding the offset voltage Vf as described above, such a problem at the time of low engine speed is solved.

Further, next, in the signal processing circuit 16a, a pressure reducing means for generating a sensor abnormality signal Ve for making an abnormality determination of the knock sensor 2 based on the knock determination voltage Vk and the reference voltage Vo.
Abnormal signal generation circuit 28 as M4 and A / D that converts the sensor abnormal signal Ve into a digital signal and outputs it to the input / output port 14.
A converter 30 is provided.

The abnormal signal generation circuit 28 includes an operational amplifier OP1 and resistors R4 to R4.
It is configured as a differential amplifier circuit by 7 and the deviation (Vk−Vo) between the knock determination voltage Vk and the reference voltage Vo in order to reduce the LSB (Least Significant Bit) error of the A / D converter 30 as much as possible. The signal is amplified by a predetermined factor to generate a sensor abnormality signal Ve as shown in FIG. 4 (c). A zener diode ZD1 is provided in the signal output section of the abnormal signal generation circuit 28 in order to suppress the input voltage to the A / D converter 30 to the rated value (that is, to protect the A / D converter 30). Has been.

Then, the sensor abnormality signal Ve which is A / D converted by the A / D converter 30
Are taken into the CPU 11 via the input / output port 14 and used to determine the abnormality of the knock sensor 2.

That is, when an abnormality occurs in the knock sensor 2 and the vibration of the internal combustion engine cannot be satisfactorily detected, the signal level of the knock sensor signal Vs decreases, and even if knocking occurs in the internal combustion engine, if the signal level is high. However, the knock determination pulse is no longer output from the comparator (operational amplifier) 26. Even in such a case, if the CPU 11 side executes the knocking control, the knocking occurs in the internal combustion engine. Assuming that the internal combustion engine is not knocked, the basic ignition timing is advanced and corrected, resulting in further knocking. Therefore, in the present embodiment, the CPU 11 side executes the sensor abnormality determination process as shown in FIG. 5, detects the abnormality of the knock sensor 2 based on the sensor abnormality signal Ve, and prohibits the knocking control. .

The sensor abnormality determination processing corresponds to the above-described abnormality detection means M5, and as shown in FIG. 5, first, at step 100, a predetermined sensor abnormality determination execution condition such that the internal combustion engine is at a predetermined rotation speed or higher is satisfied. If it is determined that the execution condition is satisfied, the process proceeds to step 110 to determine whether or not the sensor abnormality signal Ve is lower than a preset reference level Veo, and Ve <Ve
If it is o, it is determined that an abnormality has occurred in the knock sensor 2, and the sensor abnormality flag Fe is set in step 120, and execution of the knocking control process (not shown) is prohibited by this sensor abnormality flag.

As described above, in this embodiment, the sensor abnormality signal Ve for determining the abnormality of the knock sensor is generated by amplifying the deviation (Vk-Vo) between the knock determination voltage Vk and the reference voltage Vo. . Therefore, even if the reference voltage Vo changes with the fluctuation of the power supply voltage Vcc, the sensor abnormality signal Ve always has a value corresponding to the amplitude level of the knock sensor signal Vs, and the knock determination voltage Vk is used as it is to determine the abnormality of the knock sensor. It is possible to improve the accuracy of knock sensor abnormality determination as compared with a conventional device that performs the above. Further, since the sensor abnormality signal Ve is constantly generated based on the knock sensor signal Vs, compared to a device that determines the abnormality of the knock sensor based on the deviation of the knock determination voltage Vk generated under two kinds of operating conditions of the internal combustion engine. , It is possible to quickly detect the abnormality of the sensor.

Here, in the above embodiment, the sensor abnormality signal Ve is generated on the signal processing circuit 16a side, and the abnormality determination of the knock sensor is performed by the CPU 11
On the side, the sensor abnormality signal Ve and the reference level Veo are configured to be compared with each other. For example, as shown in FIG. 6, on the signal processing circuit 16a side, the knock determination voltage is detected by the A / D converter 30 '. Vk and reference voltage Vo are sequentially A / D converted, and CPU 11 side obtains deviation Ve ′ of each A / D converted value by sensor abnormality determination processing as shown in FIG. 7 (step 105). Deviation V calculated in step 110 ′
The sensor may be determined based on e '. In FIGS. 6 and 7, parts other than the above description are the same as those in the above-described embodiment, and therefore, those parts are denoted by the same numbers as in FIGS. 3 and 5, respectively, and will not be described. Is omitted.

Further, in the above embodiment, the knock determination voltage Vk is set to a value obtained by integrating and amplifying the half-wave rectified value of the knock sensor signal Vs, and the reference voltage Vo (= virtual ground voltage Vg + offset voltage Vf).
However, as is well known, the knock determination voltage may be set corresponding to the average amplitude level of the knock sensor signal Vs, so full-wave rectification of the knock sensor signal Vs is performed. It may be generated by adding a reference voltage composed only of the virtual ground voltage Vg to the value obtained by integrating and amplifying the value, or by adding the reference voltage Vo to the value obtained by integrating the peak of the knock sensor signal Vs. It may be configured as follows.

Further, in the above embodiment, the knock determination voltage Vk is the reference voltage Vo obtained by adding the offset voltage Vf to the virtual ground voltage Vg.
However, as described above, the reference voltage consisting of only the virtual ground voltage Vg is used to improve the knock detection characteristics during low-speed operation of the internal combustion engine. Even if added, knock determination can be performed. In this case, the sensor abnormality signal Ve may be set based on the deviation (Vk-Vg) between the knock determination voltage Vk and the virtual ground voltage Vg.

[Effects of the Invention] As described in detail above, in the knocking detection device of the present invention, the abnormality determination of the knock sensor is configured to be performed based on the voltage signal obtained by subtracting the reference voltage from the knock determination voltage. Can be detected accurately and quickly.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a schematic configuration diagram showing the overall configuration of an ignition timing control device of an embodiment, and FIG. 3 is a signal processing for processing an output signal from a knock sensor. Electrical circuit diagram showing the configuration of the circuit 16a, fourth
FIG. 6 is a time chart for explaining the operation of the signal processing circuit 16a, FIG. 5 is a flow chart showing an abnormality determination process executed by the CPU 11 for determining an abnormality of the knock sensor, and FIG.
FIG. 7 is an electric circuit diagram showing another configuration example of the signal processing circuit 16a, and FIG. 7 is a flow chart showing another example of the abnormality determination process. M1, 2 …… Knock sensor M2 …… Knock judgment voltage creating means (22 …… half-wave rectification integrating amplifier) M3 …… Knock detecting means (26 …… operational amplifier (comparator)) M4 …… pressure reducing means (28 …… Abnormal signal generation circuit) M5: Abnormality detection means, 11: CPU 12: ROM, 13: RAM 16a: Signal processing circuit, 24: Reference voltage generation circuit

Claims (1)

(57) [Claims] 1. A knock sensor for detecting vibration of an internal combustion engine, and a knock determination for outputting a knock determination voltage corresponding to the amplitude level of the output signal by integrating a signal output from the knock sensor and adding a reference voltage. Of the internal heat engine including a voltage generating means, a knock detection means for applying a reference voltage to the output signal from the knock sensor, and detecting knocking of the internal combustion engine when the voltage value exceeds the knock determination voltage. An internal combustion engine, comprising: a knocking detection device; pressure reduction means for reducing a reference voltage from the knock determination voltage; and abnormality detection means for detecting abnormality of the knock sensor based on a pressure reduction result of the pressure reduction means. Knocking detection device for engines.