Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2001-11-30
2003-05-06
Kwon, John (Department: 3754)
Internal-combustion engines
Spark ignition timing control
Electronic control
Reexamination Certificate
active
06557527
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a knock control apparatus for an internal combustion engine.
2. Description of the Related Art
FIG. 1
shows an example of a structure of a general internal combustion engine and peripheral equipment. In the drawing, reference numeral
18
designates an internal combustion engine (hereinafter referred to as an engine) mounted in a vehicle, and this engine
18
is connected to an intake pipe
15
and an exhaust pipe
16
. A downstream portion of the intake pipe
15
is constructed so as to branch to introduce intake air into respective cylinders of the engine
18
, and the exhaust pipe
16
is constructed by branch portions corresponding to the respective cylinders and a collecting portion where the branch portions are collected. A throttle valve operated by a driver is provided at an upstream side of the intake pipe
15
, and a throttle sensor
2
for outputting a signal proportional to an opening degree of the throttle valve is provided at a rotating shaft of the throttle valve. An ISC valve
17
is provided in a bypass parallel to the throttle valve, and an air cleaner
4
, an intake air temperature sensor
3
for outputting a signal proportional to an intake air temperature, and an air flow sensor
1
for outputting a signal proportional to an intake air amount are provided at an upstream side of the throttle valve. At an intermediate portion of the intake pipe
15
, as shown in the drawing, an EGR valve
8
is provided, and a bypass extending to the exhaust pipe
16
from the vicinity of the EGR valve
8
is provided. In the vicinity of the connection portion of the exhaust pipe
16
with the bypass, an O
2
sensor
6
for outputting a signal proportional to a residual oxygen concentration in exhaust gas is provided.
An injector
10
for fuel injection is provided at each of the branch portions of the downstream portion of the intake pipe
15
, and a predetermined amount of fuel sent through a delivery pipe
19
is injected into the engine
18
from the injector
10
. The engine
18
is provided with a water temperature sensor
14
for outputting a signal proportional to the temperature of cooling water for cooling the engine
18
and a knock sensor
13
for detecting knock. Further, the engine
18
is provided with an ignition coil
9
corresponding to each cylinder, and a crank angle sensor
5
for outputting a signal proportional to the revolution speed of the engine
18
. The signals of the respective sensors are inputted to an ECU
12
constituted of a microcomputer, and the ECU
12
carries out an operation for controlling the injector
10
, the igniter and the like on the basis of the input signals, and outputs control signals.
An operation thereof will be described. When a driver turns a key and switches on an ignition at the time of start of the engine, current starts flowing through the ECU
12
for controlling the engine, and various sensors and actuators fixed to the engine
18
as well. Thereafter, when the driver turns a start switch (SW)
7
, a stator is connected to a battery
11
, thereby cranking the engine
18
. When the engine
18
is cranked, the ECU
12
starts the fuel injection into the respective cylinders, and controls the engine
18
so that the respective cylinders are ignited.
FIG. 4
is a block diagram showing a structure of a conventional knock control apparatus for an internal combustion engine.
FIG. 5
is an explanatory view showing a variation of each value in the conventional apparatus of FIG.
4
. In
FIG. 4
, reference numerals
12
and
13
designate the ECU and the knock sensor shown in
FIG. 1
, respectively. The structure in the ECU
12
will be described. Reference numeral
20
designates a knock I/F circuit including a band pass filter
21
and a peak hold
22
, in which an output signal from the knock sensor
13
is inputted, only a knock intrinsic frequency component is extracted from the output signal of the knock sensor by the band pass filter
21
, and the output signal of the band pass filter in a predetermined period (B6° to A104°) of each cylinder is peak-held by the peak hold portion
22
. Reference numeral
24
designates an A/D conversion portion for A/D converting the peak hold signal outputted from the knock I/F circuit
20
. Reference numeral
25
designates a BGL including an averaging portion
26
and a threshold (BGL) calculation portion
27
, in which the A/D converted peak hold signal is averaged and amplified to obtain a threshold level (BGL) for a knock judgement. Reference numeral
28
designates a compare subtraction portion, which compares the peak hold signal with the BGL, judges the presence of occurrence of knock, and outputs a signal proportional to the intensity of knock. Reference numeral
29
designates an every one ignition delay angle amount calculation portion, which calculates a delay angle amount proportional to the intensity of knock for every one ignition from the knock judgement result of the compare subtraction portion
28
. Reference numeral
30
designates a knock delay angle amount calculation portion, which integrates the delay angle amount for every one ignition and calculates a knock correction amount of ignition timing, however, in the case where knock does not occur, an advance angle return is made. Reference numeral
31
designates an A/D conversion portion for A/D converting a knock sensor output signal outputted from the knock sensor
13
. Reference numeral
32
designates a knock sensor fail detection portion, which detects failure (disconnection, short circuit, etc.) of the knock sensor
13
on the basis of the A/D converted knock sensor output signal, and makes a predetermined amount delay angle correction.
An operation thereof will be described. A knock intrinsic frequency component is extracted from the output signal of the knock sensor
13
by the band pass filter
21
and is amplified. The signal after the processing is, as shown in
FIG. 5
, peak-held during a predetermined period (B6° (BTDC6° CA) to A104° (ATDC104° CA)) after ignition of each cylinder. The peak hold value is compared with a knock judgement level at that time, and a knock judgement is made. This knock judgement level is determined in such a manner that a prescribed averaging processing from the peak hold value is carried out, and the calculation from the averaged value (multiplying it by a coefficient and adding an offset thereof) is carried out. In this averaging processing, in view of the compatibility between stabilization of the knock judgement level (suppression of fluctuation due to the variation of knock sensor signal level for each cycle) and followingness to the change of an average signal level due to the change of an operating state, two-stage filter processing and a suitable filter averaging coefficient are set.
The conventional knock control apparatus is constructed as described above, and in general, in accordance with the change of the peak hold value (noise level), and the knock judgement level is also sequentially calculated to be updated to a level suitable for the operating state of the engine at that time (suitable for the knock judgement and causing no erroneous judgement). However, in the case where the noise level is rapidly changed (increased), there occurs a state where the calculation of the knock judgement level can not follow, there temporarily occurs a state where the knock judgement level is low with respect to the noise level, and there has been a problem in that a knock erroneous judgement due to noise can occur.
As examples of the knock erroneous judgement, for example, the following two examples can be enumerated.
(1) At the time of rapid change (increase) in a noise level by the rapid increase of engine revolution.
(2) In a GDI engine, at the time when the generation timing of mechanical noise at the time of injector operation is changed from a state where it is outside a knock control detection period of a knock sensor output signal to a state where it is within the detection period
Kwon John
Mitsubishi Denki & Kabushiki Kaisha
Sughrue & Mion, PLLC
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