JPH05340801A - Knocking controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To detect the abnormality of the signals of a plurality of knocking sensors without making the circuit configuration of the sensors complicated. CONSTITUTION:Resistors R1 and R2 are respectively incorporated in a plurality of knocking sensors 11 and 12 which detect the knocking generated in an internal combustion engine and the signals of the sensors 11 and 12 are inputted to a multiplexer 13. In addition, a common pull-up resistor R5 is connected to the sensors 11 and 12 on the output side of the multiplexer 13. At the normal time, knocking detection is performed by respectively connecting switches 14 and 17 to their E and G sides and, at the time of executing abnormality detection, abnormality is detected from the outputs of the sensors 11 and 12 pulled up by means of the resistor R5 by respectively connecting the switches 14 and 17 to their D and F sides.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, which detects knocking due to vibration or noise of the internal combustion engine and has a function of retarding ignition timing or rich air-fuel ratio when knocking is detected. Is.

[0002]

2. Description of the Related Art In recent years, a so-called knock control system (hereinafter referred to as KCS) has been studied, which detects knocking occurring in an internal combustion engine to advance or retard the ignition timing.

There are also several methods for detecting the failure of the knock sensor, one of which is to incorporate a resistor in the sensor and pull up in the inner circuit to detect the voltage value. (For example, JP-A-60-100021). However, in the case of having a plurality of knock sensors, fail detection circuits for the number of sensors are required, and the circuit becomes complicated.

For example, in the case of using a plurality of sensors in Japanese Patent Laid-Open No. 60-100021, it is necessary to provide comparators and pull-up resistors for the number of sensors. In addition, pull-up voltage is A
An A / D conversion port corresponding to the number of sensors and a pull-up resistor are required in the case of performing D / D conversion and determining a fail based on the voltage value.

[0005]

SUMMARY OF THE INVENTION In view of the problems of the prior art, the present invention detects abnormalities in a plurality of knock sensor signals, and its object is to detect the abnormalities without complicating the circuit configuration. is there.

[0006]

Therefore, according to the present invention, knock determination is made in accordance with outputs from a plurality of knock sensors for detecting knocking occurring in an internal combustion engine, and signals are pulled up by the knock sensors each having a built-in resistor. In the case of detecting more than each of the knock sensors by the voltage thereof, each of the sensor signals is input to a multiplexer, and an internal combustion engine in which a pull-up resistor common to the knock sensors is connected to the output side of the multiplexer. A knocking control device for an engine is provided.

[0007]

As a result, one of a plurality of knock sensor signals is
One is selected by the multiplexer, and the selected knock sensor signal is pulled up by a pull-up resistor common to each sensor.

[0008]

EXAMPLES The present invention will be described below with reference to examples shown in the drawings. FIG. 1 is a block diagram showing an embodiment. Reference numerals 11 and 12 are knock sensors with built-in resistors R1 and R2. Reference numeral 13 is a multiplexer (hereinafter MPX) for selecting one of the knock sensor signals and the adjustment resistors R3 and R4 voltage. R5 is MP.
It is one pull-up resistor common to the knock sensors 11 and 12 connected between the output side of X13 and the 5V power supply.

Reference numeral 15 is a bandpass filter for selecting only knock frequency components, 16 is a peak hold circuit for detecting the maximum value of the knock sensor signal, and 14 and 17 are filters 15.
And a switch for bypassing the hold circuit 16,
Reference numeral 18 is an A / D converter for A / D converting the peak hold signal, knock sensor signal, and adjust voltage, and 19 is a microcomputer for performing knock determination calculation.

FIG. 2 shows a flowchart executed by the microcomputer 19. Main routine 210
At the knock determination section start timing (step 211)
Or the end timing (step 212).

At the start timing, the processing 220 of the open timing routine shown in FIG. 3 is performed. First, the knock determination section is opened (step 221) and the peak hold circuit 16 starts the peak hold of the knock sensor signal (step 222). At this time, MPX 13 is preselected with A or B, and switches 14 and 17 are set to E and
Of course, G is selected.

At the end timing, the processing 230 of the close timing routine shown in FIG. 4 is performed. First, the peak hold value of the knock sensor signal is A / D converted (step 231), and knock determination is performed according to the value (step 232). Various knock determination methods are well known as the determination method, and a description thereof will be omitted here.

Next, the peak temperature is reset (step 233). Next, in order to A / D-convert the adjustment voltage (step 236), MPX13 is selected to C or H (step 234), and the switches 14 and 1 for bypassing the filter 15 and the peak hold circuit 16 are selected.
7 is selected as D or F (step 235).

Next, in order to A / D convert the knock sensor signal pulled up by the pull-up resistor R5 which is the fail determination level (step 238), the MPX 13 is knocked by the knock sensor signal A or which corresponds to the cylinder to be knocked next. Select B (step 237). This A / D converted value is within a predetermined range (L and M are predetermined values, for example, 0.5V,
4.5V) determines normal, and otherwise determines abnormal. (Steps 239, 240). For example, it can be determined from the fact that the knock sensor ground short is 0 V, the power supply short is 5 V, and the open is 5 V.

Next, in order to perform a normal knock determination, the switches 14 and 17 are selected to E and G so as to be input to the filter 15 and the peak hold circuit 16 (step 241). FIG. 5 shows a timing chart when the knock sensor 11 or 12 is ground-shorted on the way.

In the knock determination section, the MPX 13 and the bypass switches 14 and 17 are selected so that the peak hold value of the knock sensor 11 or 12 is input to the A / D converter 18. MPX 13, bypass switches 14 and 1 so that the adjusted and pulled-up knock sensor raw signal is input to the AD converter 18 when it is outside the knock determination section.
7 is selected.

When the knock sensors 11 and 12 are normal, the knock sensor signal has a predetermined voltage (for example, pull-up power supply 5).
If V, R1 = R2 = R5, it is pulled up to 2.5V). When the knock sensor 11 or 12 is short-circuited to the ground, it is not pulled up and the knock sensor signal becomes almost OV as shown in the figure, and the fail can be detected by the A / D conversion value.

Noise may occur when the MPX 13 and the switches 14 and 17 are switched. In particular, when the switches 14, 17 are switched from D, F to E, G, noise may be tailed depending on the time constant of the filter 15, and depending on the switching timing, noise may enter the next knock determination section. It may happen. Therefore, MP
It is preferable to switch X13 and the switches 14 and 17 immediately after the knock determination section ends.

Next, the adjustment will be described. The adjust is for adjusting the ROM constant in the microcomputer with an external resistor. For example, the knock determination level RO
The M constant is corrected based on the A / D conversion value of the voltage value created by the external dividing resistor.

Conventionally, when there are a plurality of adjusts, each resistor is realized by forming a dividing resistor as shown in FIG. 6A, but as described above, pull-up is performed as shown in FIG. 6B. It can be shared by the resistor R5 and therefore the resistor can be saved.

Further, in FIG. 1, the number of ports of the A / D converter 18 is saved by bypassing the filter 15 and the peak hold circuit 16 with the switches 14 and 17, but there is a margin in the number of ports. Then, the switch may be eliminated and the knock sensor pull-up signal may be directly connected to another port of the A / D converter 18.

[0022]

As described above, according to the present invention, the knock sensor signal selected by the multiplexer can detect the abnormality of the plurality of knock sensors by the pull-up resistor common to each sensor. It has an excellent effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a device of the present invention.

FIG. 2 is a flowchart of a knock determination routine used to explain the operation of the above embodiment.

FIG. 3 is a flowchart of an open timing processing routine used to explain the operation of the above embodiment.

FIG. 4 is a flowchart of a close timing processing routine used for explaining the operation of the above embodiment.

FIG. 5 is a waveform chart of each part provided for explaining the operation of the above embodiment.

FIG. 6 is an electric circuit diagram for explaining the adjustment.

[Explanation of symbols]

 11 knock sensor 12 knock sensor 13 multiplexer R1 resistor R2 resistor R3 adjust resistor R4 adjust resistor R5 pull-up resistor

Claims (2)

[Claims] 1. A knock determination is made according to outputs from a plurality of knock sensors for detecting knocking generated in an internal combustion engine, and a signal is pulled up by each of the knock sensors with a built-in resistor, and the voltage of each knock sensor is used to pull up the signal. The above-mentioned knocking control device for an internal combustion engine, wherein each of the sensor signals is input to a multiplexer, and a common pull-up resistor is connected to the knock sensor on the output side of the multiplexer. 2. An internal combustion engine in which one of a plurality of knock sensors or a plurality of adjusting resistors is selected by a multiplexer, and the selection switching tamming of the multiplexer or the adjusting resistor is performed immediately after the end of the knock determination section. Knocking control device for engines.