JPH0318654A - Knock detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve detection accuracy by selecting only the input with gain corresponding to the output level of a knock sensor among plural inputs to perform A/D conversion and detecting whether or not knock is generated on the basis of the A/D conversion value. CONSTITUTION:The output from a knock sensor 37 is inputted into a peak hold circuit 54 through the band-pass filter (approximately 7kHz) 52 and gate switch 53 of a signal processing circuit 38, potential-divided at the resistances R1, R2 of a level converting circuit 55 and inputted into an A/D converter 56. These input signal levels V1, V2 become high accompanied by the increase of the engine speed. The A/D converter 56 has such a conversion characteristic that the detection accuracy is rough when the level is low and the accuracy is heightened as the level becomes higher, so that only the input level V1 or V2 selected by the input selection signal, corresponding to the gain, from a processing circuit 43 is inputted into the A/D converter 56, and whether or not knock is generated is detected at the processing circuit 43 by this A/D conversion value. The detection accuracy can be thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a knock detection device suitably used in an ignition timing control device for an internal combustion engine. In conventional ignition timing control devices for internal combustion engines, the ignition timing is advanced by a predetermined unit advance amount at predetermined time intervals, and when a knock occurs, retard control is performed in accordance with the knock intensity. In this way, the advance angle amount is configured to converge around the basic advance angle amount determined based on, for example, the intake air pressure and the rotational speed of the internal combustion engine. A knock detection device generally used in such a configuration holds the maximum value of the output from a knock sensor realized by an acceleration sensor, etc., that is, performs a so-called peak hold, and detects the output within a predetermined time. The maximum value of is converted into a digital signal via an analog/digital converter and inputted to a control device realized by, for example, a microcomputer (for example, Japanese Patent Laid-Open No. 58-25577). Problems to be Solved by the Invention In the prior art as described above, control devices and analog/digital converters that are generally realized by microcomputers etc. have a power supply voltage of, for example, 5V, whereas the peak hold voltage is, for example, 5V. The output from the knock sensor that is inputted increases as the rotational speed of the internal combustion engine increases, and exceeds the power supply voltage of 5V at about 4800 rpm, for example. Therefore, above 4800 rpm, the output of the knock detection device becomes saturated. Therefore, in order to make measurements possible even in the high rotation range of an internal combustion engine, a voltage of, for example, about 8 cm is required as a reference voltage for analog/digital conversion. However, with such an ellipse, a separate power source is required to generate the 8V reference voltage, making the ellipse complicated. In order to prevent such problems, one conceivable method is to compress the output from the knock sensor using, for example, a voltage dividing resistor and input it to the analog/digital converter. , the detection accuracy in the low speed range of the internal combustion engine deteriorates. An object of the present invention is to provide a knock detection device for an internal combustion engine that can detect the output from a knock sensor over a wide range and with high accuracy using a relatively simple horizontal control. Means for Solving the Problems The present invention includes: a knock sensor that detects knock of an internal combustion engine; a level converter that outputs the output of the knock sensor at a plurality of different levels; and a plurality of inputs, each input having a an analog/digital converter to which output signals from the level converting means are respectively input and converts the input signals from analog to digital; and an analog/digital converter for deriving an input selection signal to the analog/digital converter; a detection means for reading conversion data of a signal to an input of an analog/digital converter selected in the above, and detecting the presence or absence of occurrence of knock based on the read data. It is a detection device. Operation According to the present invention, knock in the internal combustion engine is detected by a knock sensor, and the detection output is given to the level conversion means. This level conversion means converts the output of the knock sensor into a plurality of different levels and outputs the converted levels. The plurality of output signals from the level conversion means are input to corresponding inputs of the analog/digital converter. This analog/digital converter performs analog/digital conversion processing on the signal to the input selected by the input selection signal from the detection means, and outputs the signal to the detection means. The detection means reads the digital conversion data of the signal to the input of the analog/digital converter selected by the input selection signal, and detects the presence or absence of knocking based on the read data.

Therefore, when the output from the knock sensor is small, the analog/
Among the plurality of inputs of the digital converter, an input corresponding to an output with a high gain is selected from among the outputs derived from the level converting means. On the other hand, when the output from the knock sensor is strong, the input of the analog/digital converter is selected based on the input selection signal, which corresponds to the output of the level conversion means with a small gain. Embodiment FIG. 1 is a block diagram showing a control device 1 for an internal combustion engine including a knock detection device 40 according to an embodiment of the present invention and related elliptical commands. Combustion air introduced through the intake port 2 is purified by an air cleaner 3, and after its inflow amount is adjusted by a throttle valve 5 interposed in the intake pipe 4, it flows into a surge tank 6. ．． Combustion air flowing out of the surge tank 6 is mixed with fuel injected from a fuel injection valve 8 disposed in an intake pipe 7, and is supplied to a combustion chamber l1 of an internal combustion engine 10 via an intake valve 9. Combustion chamber 11
is provided with a spark plug 12, and this combustion chamber 11
The combustion exhaust gas from the engine is discharged through the exhaust valve 13, and is discharged into the atmosphere from the exhaust pipe 14 through the three-way catalyst 15. The intake pipe 4 is provided with an intake air temperature detector 21 for detecting the temperature of intake air, the throttle valve 5 is provided with a throttle valve opening detector 22, and the surge tank 6 is provided with an intake pressure detector 23. It will be established. Further, in the vicinity of the combustion chamber 11, a cooling water temperature detector 24 and a knock sensor 37 implemented by, for example, an acceleration sensor are provided. The output from the knock sensor 37 is input to the control device 1 via a signal processing circuit 38. Knock sensor 3
7 and the signal processing circuit 38 constitute a knock detection device 40 according to the present invention. In the exhaust pipe 14, the three-way catalyst 1
An oxygen concentration detector 25 is provided upstream of the three-way catalyst 15, and an exhaust temperature detector 26 is provided downstream of the three-way catalyst 15. The rotational speed of the internal combustion engine 10 is detected by the crank angle detector 27
Detected by. In addition to the respective detectors 21 to 27, the control device 1 includes a vehicle speed detector 28, a start detector 29 that detects whether or not a starter motor 33 that starts the internal combustion engine 10 is started, and an air conditioner. Air conditioning detector 3 that detects
0 and the detection result from the neutral detector 31 that detects whether the gear stage of the automatic transmission is in the neutral position when the automobile in which the internal combustion engine 10 is mounted has an automatic transmission of size f. is input.

Furthermore, this control device 1 is powered by a battery 34, and the control device 1 is connected to each of the detectors 21 to
31 and the power supply voltage of the battery 34 detected by the voltage detector 20, the fuel injection amount, ignition timing, etc. are calculated, and the fuel injection valve 8, spark plug 12, etc. are controlled. The intake pipe 4 is also formed with a side passage 35 that bypasses the upstream and downstream sides of the throttle valve 5, and this side passage 35 is provided with a flow rate control valve 36. The flow rate control valve 36 adjusts and controls the flow rate of combustion air during idling when the throttle valve 5 is substantially fully closed, based on the output from the control device W1. The control device if also drives the fuel pump 32 when the internal combustion engine 10 is operating. FIG. 2 is a block diagram showing specific horizontal commands of the control device 1. The detection results of the detectors 20 to 25 are supplied from an input ink face circuit 41 to a processing circuit 43 via an analog/digital converter 42. In addition, the detector 2
2. The detection results of 27 to 31 are provided to the processing circuit 43 via the input interface circuit 44. Furthermore, the processing circuit 43 is supplied with the output of the knock sensor 37 via the signal processing circuit 38. Processing circuit 4
3 is provided with a memory 45 for storing various control maps and learning values, and this processing circuit 43 is provided with a memory 45 for storing various control maps and learning values.
6. The control output from the processing circuit 43 is derived via an output interface circuit 47, and is applied to the fuel injection valve 8 to control the fuel injection amount, and is also applied to the ignition plug 12 via the igniter 48 to control the ignition. The timing is controlled and also applied to the flow control valve 36 to control the flow rate of incoming air through the bypass 35 during idle. Processing circuit 43 also derives a control output for driving fuel pump 32. The detection result of the exhaust temperature detector 26 is determined by the exhaust temperature detection circuit 4 in the control device 1.
9, and when the detection result is that the temperature is abnormally high, a warning light 51 is turned on via the drive circuit 50. FIG. 3 is a block diagram showing a specific configuration of the signal processing circuit 38. The output from the knock sensor 37 is input to a band pass filter 52 of the signal processing circuit 38. The center frequency of this bandpass filter 52 is, for example, approximately 7
kHz, and the bandpass filter 52
The output from the . The gate switch 53 is controlled to open or close in response to a gate opening/closing signal from a terminal G1 of the processing circuit 43 led out to a line l1. The peak hold circuit 54 also resets the hold value in response to a reset signal from the terminal G2 of the processing circuit 43 that is led out to the line 12.

The output from the peak hold circuit 54 is input to an analog/digital converter 56 via a level conversion circuit 55. The level conversion circuit 55 is connected to the resistors Rl and R2, and the output from the peak hold circuit 11854 is inputted to the input terminal CHI of the analog/digital converter 56 via the line e3.
The voltage is divided by l and R2, and the input terminal CH2 is input from line l4.
is input.

This analog/digital converter 56 selects the input terminals CHl and CH2 in response to the input selection signal from the output terminal G3 of the processing circuit 43 inputted via the line l5, and selects the input terminals CHl and CH2, and the input signal levels V1 and v2 are is converted from analog to digital and output to the input terminal G4 of the processing circuit 43 via line l6. The processing circuit 43 also includes a timer 57 for setting the derivation timing of the gate opening/closing signal and the reset signal, and an analog/digital converter 5.
register 58 for storing conversion data from 6;
59 are provided. The peak hold circuit 54 includes a bandpass filter 5
When the output from the knock sensor 37 via 2 is indicated by reference numeral lll in FIG. Output. Furthermore, the input signal levels Vl and V2 of the analog/digital converter 56/\ increase as the rotational speed NE of the internal combustion engine leap 10 increases, as shown in FIG. If the resistance values of the resistors Rl and R2 are selected to be the same, for example, when the input signal level ■1 of the input terminal CH1/\ is indicated by the symbol ffil3 in FIG. 5, the input terminal C
The input signal level v2 to H2 is 1/2 of the input signal level ■1, as indicated by reference numeral l14. On the other hand, as shown in FIG. 6, the conversion characteristics of the analog/digital converter 56 are such that when the input signal levels Vl and V2 are relatively small, the detection accuracy is rough;
The accuracy improves as l, V2 increases. FIG. 7 is a timing chart for explaining the knock detection operation. When the processing circuit 43 detects a falling pulse of the top dead center signal as shown at time t1 from the output of the crank angle detector 27 shown in FIG. As shown in (3), derive a reset signal to release the reset state. In addition,
At time t2, which is earlier than time t1 when the top dead center signal is detected, an ignition signal is derived to the igniter 48 as shown in FIG. 7(2). At time t3, when a predetermined time W1 has elapsed from time t1 when the top dead center signal was detected, a gate opening/closing signal for making the gate switch 53 conductive is derived, as shown in FIG. 7 (4>). As a result, the output from the knock sensor 37 via the bandpass filter 52 shown in FIG. 7(5) is held at its maximum value in the peak hold circuit 54 as shown in FIG. 7(6). When a predetermined time W2 has elapsed from the time t3, the elapsed time t4
As shown in FIG. 7(4), a gate opening/closing signal for cutting off the gate switch 53 is derived, and as shown in FIG. 7(7), the analog/digital converter 56 outputs a peak hold signal. The voltage level held in circuit 54 is converted from analog to digital.

In this way, the analog/digital conversion operation is performed, as shown in Fig. 7 (
At time t5 when the derivation of the ignition signal is stopped as shown in 2), a reset signal is derived to the peak hold circuit 54 as shown in FIG. 7(3), and thereby, as shown in FIG. As shown in , the holding operation of the peak hold circuit 54 is released. Further, over a predetermined time W3 from time t5, the processing circuit 43 performs a process of determining the detected knock intensity. FIG. 8 is a flowchart for explaining the ignition timing control movement ft'. In step n1, the rotational speed NE of the internal combustion engine 10 is calculated from the first equation based on the detection result from the crank angle detector 27. Note that in this first equation, the period T 1 (msee)
teeth,? As shown in FIG. 7 (1), this is the period of the top dead center signal, and when the internal combustion engine 10 is, for example, a 4 cylinder 4 cycle internal combustion engine, the top dead center signal is derived every 180 degrees of crank angle. , Therefore, the rotational speed NE can be determined from the first equation. In step n2, corresponding to the rotational speed NE and the intake air pressure detected by the intake pressure detector 23,
The optimum advance angle control amount S@^n, which is stored as a reserved two-dimensional map in the memory 45, is obtained by interpolation calculation. In step n3, based on the data read from the analog/digital converter 56, a retard control amount S1■ corresponding to the intensity of knock occurrence is determined. In step n4, the advance angle control amount S obtained in step n2 is determined. From (2), the retard control amount S Kllll+ determined in step 7 n 3 is subtracted, and furthermore, a correction control amount S IIIXX based on, for example, the temperature of the cooling water detected by the cooling water temperature detector 24 is added, In this way, the advance angle control amount S, ■ is corrected, and the actual advance angle control amount S TN? is calculated, and the process returns to step R51. FIG. 9 is a flowchart for explaining the knock detection timing setting operation, and as described above, when the internal combustion engine 10 is a 4-stroke @4-cycle internal combustion engine,
Interrupts are processed every 0 degrees of crank angle. step nil
Then, the period T1 of the top dead center signal is measured. In step nl2, the time W1 from time t1 when the top dead center signal is detected and the interrupt processing operation is started until the gate switch 53 is turned on is set. step n
In l3, a period W2 during which the gate switch 53 is conductive is determined based on the period T1 measured in the step nil.
is set. In step nl4, the time W1 set in step nl2 is added to the detection time t1 of the top dead center signal, and the conduction time t3 of the gate switch 53 is set. In step nl5, a timer 57 is set to output a gate opening/closing signal to the gate switch 53 at time t3 set in step nl4, and thereafter, when the timer 57 reaches this set time, the gate opening/closing signal is output. is derived. In step nl6, the time t
3 plus the conduction time W2 of the gate switch 53,
The cutoff time t4 of the gate switch 53 is set, and the operation returns to that shown in FIG. 8. FIG. 10 is a flowchart for explaining the knock detection operation, and the time measured by the timer 57 is the 911th
Each time the gate switch 53 is turned on/off at times t3 and t4 set by the processing operation shown in J, the processing operation is interrupted and performed. In step n 2 1, it is determined whether the timing for turning on the gate switch 53 indicated by time t3 has come, and if so, the process moves to step n 2 2, and in the same manner as in step n 1 6, the gate switch 53 is cut off. Time t4 is set. In step 023, the timer 57 is set so that a gate opening/closing signal for cutting off the gate switch 53 is derived at the time t4, and the processing operation shown in FIG. 8 is returned to. When the gate switch 53 is cut off at step n21, that is, at time t4, the process moves to step n24, where the analog/digital converter 56 converts the input signal level v1 from the input terminal CHI into analog/digital, and at step n25, the input signal level v1 from the input terminal CHI is converted from analog to digital. Converts the input signal level V2 from CH2 from analog to digital. In step n26, the converted data ADCHI in step n24 is stored in the register 58, and in step n27, the converted data ADC112 in step n25 is stored in the register 59. In step n28, a reset signal is derived from the output terminal G2 to the peak hold circuit 54.

In step n29, the rotational speed NE obtained in step n1 is set to a predetermined value, for example, 4500 rpm.
If it is not, that is, if the peak value of the output from the knock sensor 37 is used as it is, the conversion data A is determined in step n30.
DCHI is stored in accumulator A. Further, in step ri 2 9, the rotational speed NE is 450
When the speed is 0 rpm or more, that is, when the output from the knock sensor 37 is divided into 1/2 by the resistors Rl and R2 and used, the conversion data AD is changed in step r131.
CH2 is doubled and stored in accumulator A.
From steps n30 and n31, the process moves to step n32.
After the knock intensity is detected based on the data stored in the accumulator A, the process returns to the processing operation shown in FIG. 8. In this way, in the knock detection device 40 according to the present invention,
Using an analog/digital converter 56 having a plurality of input terminals CHI, CH2, each of the input terminals CHI, CH2
In this case, the output from the knock sensor 37 is inputted at different levels through the peak hold circuit 54, etc., and the analog/
The input signal level to the input terminal CHI or CH2 on the side corresponding to the conversion characteristics of the digital converter 56 is used as the output from the knock sensor 37. Therefore, when the rotational speed NE of the internal combustion engine 10 is small and the output from the knock sensor 37 is small, the input signal level v1 of the input terminal CH1 to which the output from the knock sensor 37 is directly input is used for knock detection. This allows for highly accurate detection operations. On the other hand, when the rotational speed NE of the internal combustion engine 10 exceeds the predetermined value of 4500 rpm, the relatively large output of the knock sensor 37 is divided by the resistors Rl and R2 and input to the input terminal CH2. input signal level V2
is used for knock detection, thereby expanding the measurement range. Furthermore, like the control device 1, the knock detection device 40 can be driven with a power supply voltage of, for example, 5V, and there is no need to provide a separate power supply as described in the prior art section, which is relatively simple. It can be demonstrated with the following precepts. In the above-described embodiment, the signal processing circuit 38 is configured separately from the control device 1; however, in another embodiment of the present invention, the signal processing circuit 38 may be built into the control device 1. Good too. Effects of the Invention As described above, according to the present invention, an analog/digital converter having a plurality of inputs is used, and each input of the analog/digital converter receives a different output from the knock sensor depending on the level conversion means. After converting it to a level, input each input, select only the input of the gain corresponding to the output level from the knock sensor with the input selection signal, perform analog/'digital conversion, and perform knocking based on the converted data. Since the presence or absence of the knock sensor is detected, the output from the knock sensor can be adjusted over a wide range of output levels without reducing detection accuracy using a relatively simple configuration using an analog/digital converter with multiple inputs. It can be detected across a wide range of areas.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a control device 1 for an internal combustion engine equipped with a knock detection device 40 according to an embodiment of the present invention and its related parts, and FIG. 2 is a block diagram showing specific functions of the control device 1. , FIG. 3 is a block diagram showing the specific configuration of the signal processing circuit 38, FIG. 4 is a waveform diagram for explaining the level holding operation of the peak hold circuit 54, and FIG. 5 shows the conversion characteristics of the level conversion circuit 55. The graph shown in Figure 6 is analog/
A graph showing the conversion characteristics of the digital conversion circuit 56, FIG. 7 is a timing chart for explaining knock detection operation, FIG. 8 is a flow chart for explaining ignition timing control operation, and FIG. 9 is a knock detection timing setting. Flowchart for explaining the operation. FIG. 10 is a flowchart for explaining the knock detection operation. 1... Control device, 10... Internal combustion engine, 20-31.
...Detector, 37... Knock sensor, 38... Signal processing circuit, 40... Knock detection device, 43... Processing circuit, 52... Bandpass filter, 53... Gate switch, 54...Peak hold circuit, 55...
・Level converter circuit, 56...Analog/digital converter 4 Figure 5 Figure 5 NE (rpm) Figure 6 λ77 Reheno Y (v) Figure 7 Figure T1 8 Figure 9

Claims (1)

[Scope of Claims] A knock sensor that detects knock of an internal combustion engine, a level conversion means that outputs the output of the knock sensor at a plurality of different levels, and a plurality of inputs, each input having the level conversion means. an analog/digital converter into which output signals from the input terminals are input, and which converts the input signals into analog/digital; A knock detection device for an internal combustion engine, comprising: a detection means for reading conversion data of a signal into an input of a digital converter, and detecting the presence or absence of occurrence of knock based on the read data.