JP2000009598A - Knock detection device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent a noise spike from being caused by a surge voltage of a relay and to make knock detection erroneous. A knock sensor output is set to a first reference value Vth.
1 (a), and when it exceeds this, a high voltage is output to charge the capacitor (b), and while the charging voltage exceeds the second reference value Vth2, a high voltage is output to operate the filter ( c) Rectifying and integrating the passed frequency components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a knock detection device for an internal combustion engine.

[0002]

2. Description of the Related Art As a knock detection technique for an internal combustion engine, for example, a technique described in Japanese Patent Application Laid-Open No. 58-28641 is known. This prior art includes a buffer filter that inputs a knock sensor output, a rectifying and integrating circuit, a maximum value detection circuit, a minimum value detection circuit, and a microcomputer that inputs a maximum value detection circuit and a minimum value detection circuit output. .

That is, in this prior art, a knock frequency component that has passed through a buffer filter is rectified and integrated by a rectifying and integrating circuit and sent to a maximum value detecting circuit and a minimum value detecting circuit. The maximum value detection circuit detects the maximum value of the input value, and the minimum value detection circuit detects the minimum value of the input value.

The microcomputer generates a knock determination level based on the detected minimum value, compares the generated knock determination level with the output of the maximum value detection circuit during the knock detection period, and detects the knock determination level. Is exceeded, it is determined that knock (abnormal combustion) has occurred in the engine combustion chamber.

[0005]

By the way, various electric components such as relays are mounted on the internal combustion engine of a vehicle, and noise generated due to a surge voltage when the relay is turned on and off is output to the knock sensor output. If mixed, the maximum value may be erroneously detected.

A description will be given with reference to FIG.

In the figure, S1 indicates a signal (knocking signal) caused by knocking, and S2 indicates a seating sound of the intake / exhaust valve (background signal described above). Although the noise shown in FIGS. 5A and 5B is a spike signal of several μsec or less, the rectifying and integrating circuit integrates the noise signal as well (C). It is detected as a value (d, e). As a result, the knock detection may be erroneously performed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the above-mentioned disadvantages, and to provide a knock detection apparatus for an internal combustion engine which can reliably remove noise mixed in the output of a knock sensor so that knock detection is not erroneous. To provide.

[0009]

According to a first aspect of the present invention, there is provided a knock sensor which is disposed near a combustion chamber of an internal combustion engine and outputs a signal corresponding to vibration of the internal combustion engine. A filter means for inputting and filtering the output of the knock sensor and outputting a knock frequency component, and generating a knock determination value from an input value by inputting the output of the filter means and comparing the input value with the input value. A knock detection device for an internal combustion engine including a knock detection device for detecting a knock generated in a combustion chamber of an internal combustion engine, wherein a filtering section setting means for inputting an output of the knock sensor and setting a filtering section of the filter means is provided. The knock detection means performs the knock detection by inputting the output of the filter means in the set filtering section. It was constructed as. The "filter means" filters the knock sensor output,
The output of the knock sensor is appropriately amplified. The “filtering section” may be set by time or by angle.

Accordingly, even if noise or the like generated due to a surge voltage when the relay is turned on / off is mixed in the knock sensor output, the noise can be reliably removed, and knock detection is not mistaken.

According to a second aspect of the present invention, the filtering section setting means inputs the knock sensor output and compares it with a first reference value. When the sensor output exceeds the first reference value, a high voltage is output. A first comparison circuit that outputs
A holding circuit that inputs and holds the output of the comparing circuit, and compares the output of the holding circuit with a second reference value, and outputs a signal when the output of the holding circuit exceeds the second reference value. And a second comparison circuit for setting the filtering section.

Thus, even if noise or the like generated due to a surge voltage when the relay is turned on / off is mixed in the knock sensor output, it can be more reliably removed, and knock detection is not erroneously performed.

[0013]

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

FIG. 1 is a schematic diagram showing an overall knock detection device for an internal combustion engine according to the present invention.

In FIG. 1, reference numeral 10 denotes a four-cylinder, four-cycle internal combustion engine (hereinafter referred to as "engine"). A throttle valve 14 is arranged in the intake pipe 12 connected to the main body 10a of the engine 10. A throttle opening sensor 16 is connected to the throttle valve 14, outputs an electric signal corresponding to the opening θTH of the throttle valve 14, and sends it to an electronic control unit (hereinafter referred to as “ECU”) 20.

The above-described intake pipe 12 forms an intake manifold (not shown) downstream of the position where the throttle valve is disposed. In the intake manifold, a fuel injection valve (not shown) is provided upstream of an intake valve (not shown) of each cylinder. An injector 22 is provided for each cylinder.

The fuel injection valve 22 is a fuel pump (not shown)
Is mechanically connected to the fuel pump to
U20 is electrically connected to control the valve opening time,
While the valve is opened, the pumped fuel is injected (supplied) into the cylinder.

In the intake pipe 12, a throttle valve 14
A pressure sensor 26 is mounted downstream of the intake pipe 12 via a branch pipe 24.
An electric signal corresponding to the PBA is output.

An intake air temperature sensor 30 is mounted downstream of the engine, and outputs an electric signal corresponding to the intake air temperature TA. A water temperature sensor 32 is disposed near a cooling water passage of the engine body 10a. An electric signal corresponding to the water temperature TW is output.

In the internal combustion engine 10, a cylinder discrimination sensor 34 is attached near a camshaft or a crankshaft (both not shown), and outputs and outputs a cylinder discrimination signal CYL for each piston position of a predetermined cylinder.

Similarly, a crank angle sensor 36 is mounted near a camshaft or a crankshaft (both not shown), and for each crank angle (for example, BTDC 10 degrees) related to the TDC position of a piston (not shown). And outputs a CRK signal pulse at a crank angle (30 degrees) cycle shorter than the cycle of the TDC signal pulse.

In the exhaust system of the internal combustion engine 10, an exhaust pipe 4 connected to an exhaust manifold (not shown) is provided.
An air-fuel ratio sensor (O ₂ sensor) 42 is provided at an appropriate position of 0, outputs a signal corresponding to the oxygen concentration O ₂ in the exhaust gas, and a three-way catalyst 44 is provided downstream thereof. , HC, CO, and NOx components.

Further, a combustion chamber (not shown) of the internal combustion engine 10 is provided.
A spark plug 48 is arranged at the bottom. The ignition plug 48 is electrically connected to the ECU 20 via an igniter 50.

Further, a knock sensor 52 is arranged on a cylinder head (not shown) of the engine body 10a, and outputs a signal corresponding to the vibration of the engine 10.

The outputs of these sensors are also sent to the ECU 20.

FIG. 2 is a block diagram showing details of the ECU 20.

As shown, the ECU 20 includes a microcomputer (hereinafter referred to as "CPU") 60. The outputs of the cylinder discrimination sensor 34 and the crank angle sensor 36 are subjected to waveform shaping by waveform shaping circuits 62 and 64, and the CPU 6 executes the processing.
Input to 0. The CPU 60 counts the output of the waveform shaping circuit 62 and detects the engine speed NE.

The output of the absolute pressure sensor 26 and the like is A /
It is converted to a digital value via a D conversion circuit 66 and
60 is input. The CPU 60 detects an operating state such as an engine load (intake pipe absolute pressure PBA) other than the engine speed NE based on the input values, and calculates a basic ignition timing from the engine speed NE and the intake pipe absolute pressure PBA. The ignition timing is determined by correcting the basic ignition timing from the water temperature TW or the like, and is sent to the igniter 50 via the driver 68 to ignite the ignition plug 48.

Here, the output of the knock sensor 52 is input to a buffer filter (filter means) 70, where the output of the knock sensor is amplified so as to be inverted around about 5 V, and the knock frequency (for example, 5 kHz to 12 kHz).
kHz) (passing (filtering)).

The output of the buffer filter 70 is sent to a rectifying / integrating circuit 72 where the knock frequency component is rectified and integrated. The output of the rectifying and integrating circuit 72 is sent to a maximum value detection circuit 76 and a minimum value detection circuit 78. Maximum value detection circuit 76
, The maximum value of the input value is detected, and the minimum value detection circuit 78 detects the minimum value of the input value.

The CPU 60 generates a knock determination level based on the detected minimum value, compares the generated knock determination level with the maximum value detection circuit output during the knock detection period,
When the detected maximum value exceeds the knock determination level, it is determined that knock (abnormal combustion) has occurred in the engine combustion chamber, and the determined ignition timing is retarded by a predetermined amount.

The present invention is characterized in that a filtering section setting means 80 for inputting a knock sensor output and setting a filtering section of the filter means is provided, and an output of the filter means in the set filtering section is input. And knock detection is performed. The filtering section setting means 80 includes a first comparing circuit 82, a holding circuit 84, and a second comparing circuit 86
Consists of

FIG. 3 is a circuit diagram showing the details thereof.

As shown, the first comparison circuit 82 includes a comparator 82a, the non-inverting input terminal of which is connected to the knock sensor 52, and the inverting input terminal of which is connected between the microcomputer operating voltage and ground. The reference value Vth1 is input to a voltage dividing circuit.

The holding circuit 84 includes a capacitor 84a and a resistor 8
4b, the capacitor 84a is connected to the comparator 80a and is charged and held when a high voltage is input.

The second comparison circuit 86 includes a comparator 86a. The non-inverting input terminal of the second comparing circuit 86 is connected to the holding circuit 84 to input the charging voltage of the capacitor 84a. The reference voltage Vth2 is input to a voltage dividing circuit between the computer operating voltage and the ground, and outputs a high voltage when the charging voltage exceeds the reference value Vth2.

Next, referring to the time chart of FIG.
The operation of the filtering section setting means 80 will be described.

In the first comparison circuit 82, the comparator 82
a outputs a high voltage when the sensor input exceeds the reference value Vth1, as shown in FIG. The output high voltage is sent to the holding circuit 84, and the capacitor 84a is charged and held as shown in FIG.

When the charging voltage exceeds the reference value Vth2 as shown in FIG. 4B, the second comparison circuit 86 performs the period (the filtering section described above; tf in FIG. 4B).
A high voltage is output and sent to the buffer filter 70, and as shown in FIG. 4C, the operation is performed for a time (or an angle) corresponding to the filtering section to pass the knock frequency component of the sensor output.

The knock frequency component passed through the buffer filter 70 is sent to a rectifying / integrating circuit 72, where the input value is rectified and integrated as shown in FIG. The signal is sent to the circuit 78.

Here, as shown in FIG. 4A, a noise spike generated due to a surge voltage or the like when the relay is turned on / off may be mixed into the knock sensor output. The period tn of the noise generated due to the surge voltage when the relay is turned on and off is several μsec as described above.
Is less than.

Therefore, in this embodiment, the characteristics of the capacitor 84a of the holding circuit 84 and the reference values Vth1 and Vth2 of the first and second comparing circuits 82 and 84 are appropriately set to output the second comparing circuit output. , 1 / of the noise period tn
The filtering section tf exceeding 2 is set.

As a result, regarding the noise spike, the charging voltage of the capacitor of the holding circuit 84 becomes equal to the second reference value Vt.
Since it does not exceed h2, the comparator 86a does not output a high voltage, and does not operate the buffer filter 70 to pass the knock frequency component.

That is, as shown by the broken lines in FIGS. 4C and 4D, the frequency component caused by the noise is
It is not output from 0 and is not input to the rectifying and integrating circuit 72. Although the sensor output is shown as a sine wave in FIG. 4 for convenience of understanding, the sensor output actually has a waveform as shown in FIG.

As described above, since no filtering section is set for noise and the sensor output is not passed, the maximum value detection circuit 76 and the minimum value detection circuit 78 remove the frequency component caused by the noise. It is not mistaken for the maximum value or the minimum value.
The PU 60 does not erroneously detect knock.

In this embodiment, as described above, the knock sensor 52 is disposed near the combustion chamber of the internal combustion engine (engine 10) and outputs a signal corresponding to the vibration of the internal combustion engine, and receives the output of the knock sensor. Filter means (buffer filter 70) for filtering and outputting a knock frequency component, generating a knock determination value from an input value by inputting the output of the filter means, and comparing the input value with the knock value to determine the combustion of the internal combustion engine. Knock detection means (rectifier / integration circuit 72, maximum value detection circuit 7)
6. A knock detection device for an internal combustion engine provided with a minimum value detection circuit 78 and a CPU 60).
Is set, and the knock detection means is configured to perform the knock detection by inputting the output of the filter means in the set filtering section.

Further, the filtering section setting means receives the knock sensor output and receives a first reference value Vt.
h1; a first comparing circuit 82 for outputting a high voltage when the sensor output exceeds the first reference value; a holding circuit 84 for inputting and holding the output of the first comparing circuit; The output of the circuit is compared with a second reference value Vth2, and when the output of the holding circuit exceeds the second reference value, a second comparison circuit 86 that outputs a signal to set the filtering section is provided. Configured.

In the above description, the output of the comparator 84a is sent to the buffer filter 70 to pass the knock frequency component of the sensor output for a period (or angle) corresponding to the filtering section. The output may be input to the CPU 60 to mask the buffer filter output during a period (or angle) other than the filtering section.

Further, the filtering section setting means 80
A filter may be provided in front of the filter to capture only the knock frequency component.

[0050]

According to the first aspect of the present invention, when the relay is turned on and off,
Even if noise or the like generated due to the surge voltage at the time of off enters the output of the knock sensor, it can be reliably removed, and there is no mistake in knock detection.

According to the second aspect, even if noise or the like generated due to a surge voltage when the relay is turned on / off is mixed in the knock sensor output, it can be more reliably removed. There is no mistake.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an overall knock detection device for an internal combustion engine according to the present invention.

FIG. 2 is a block diagram showing details of an electronic control unit (ECU) of the apparatus shown in FIG. 1;

FIG. 3 is a circuit diagram showing details of a gate setting means of a buffer filter in the block diagram of FIG. 2;

FIG. 4 is a time chart showing the operation of the gate setting means of FIG. 3;

FIG. 5 is a time chart similar to FIG. 4, illustrating the operation of the prior art.

[Explanation of symbols]

 Reference Signs List 10 internal combustion engine (engine) 20 ECU (electronic control unit) 52 knock sensor 60 microcomputer (CPU) 70 buffer filter (filter means) 72 rectifying and integrating circuit 76 maximum value detection circuit 78 minimum value detection circuit 80 filtering section setting means 82 1st comparison circuit 84 holding circuit 86 second comparison circuit

Continued on front page F term (reference) 2G064 AC03 AC21 AC42 AC48 AC53 AC60 CC13 CC29 CC33 CC53 CC54 DD28 2G087 AA13 BB12 CC34 EE21 EE23 FF04 FF23 FF32 3G084 DA04 DA20 DA27 EA01 EA05 EA07 EA11 EB22 EC03 FA25

Claims (2)

[Claims] 1. A method comprising: a. A knock sensor that is arranged near a combustion chamber of an internal combustion engine and outputs a signal corresponding to vibration of the internal combustion engine; b. Filter means for inputting and filtering the output of the knock sensor and outputting a knock frequency component; c. A knock detection unit configured to generate a knock determination value from an input value by inputting an output of the filter unit and detect a knock generated in a combustion chamber of the internal combustion engine by comparing the input value with the input value. A knock detection device, d. Filtering section setting means for inputting an output of the knock sensor to set a filtering section of the filter means, wherein the knock detecting means inputs the output of the filter means in the set filtering section and sets the knock A knock detection device for an internal combustion engine, which performs detection. 2. The method according to claim 1, wherein the filtering section setting means includes: e. A first comparison circuit that inputs the knock sensor output and compares it with a first reference value, and outputs a high voltage when the sensor output exceeds the first reference value; f. A holding circuit that receives and holds the output of the first comparison circuit; and g. A second comparing circuit that compares an output of the holding circuit with a second reference value, and outputs a signal to set the filtering section when the output of the holding circuit exceeds the second reference value. The knock detection device for an internal combustion engine according to claim 1, wherein: