Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2001-11-30
2003-07-15
Kwon, John (Department: 3754)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S609000, C123S643000
Reexamination Certificate
active
06591810
ABSTRACT:
This application is based on Application No. 2001-182989, filed in Japan on Jun. 18, 2001, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control system for an internal combustion engine, and in particular to ignition timing control of such a control system.
2. Description of the Related Art
FIG. 12
is a view schematically illustrating the construction of this kind of known control system for an internal combustion engine. In this figure, the known control system includes an internal combustion engine control unit (ECU)
1
, a reference signal generator
3
for generating a reference signal representative of a reference position of the rotational position of an engine, and an ignition (IG) coil
8
connected with a spark plug
9
. The ECU
1
includes a CPU
2
acting as an arithmetic processing section, a reference signal input I/F circuit
5
, an IG coil drive output I/F circuit
7
connected with the ignition (IG) coil
8
, and a RAM
11
acting as a temporary storage device. The CPU
2
includes a timer TM
1
which is constituted by software. Here, note that the output side of the CPU
2
in
FIG. 12
illustrates the configuration for one cylinder.
FIG. 13
is a time chart of signals at respective portions of the system of FIG.
12
.
In the past, the ECU
1
has an ignition timing control function as one of its various control functions. For a control method of an ignition system, there is known a full transistor method in which energization start timing and energization cut-off timing to an IG coil are controlled to accumulate energy therein, and these timing are generally controlled by a CPU. In addition, these timing are important items for engine power and the stability thereof, and hence accurate control and high control accuracy are required.
As such a concrete full transistor control method, there is used a predetermined single timer to which the timing for starting energization is set with a predetermined timing signal (i.e., signal representative of a reference angle position of the rotational position of the engine) taken as a reference. Then, after start of energization, the timing of cutting off an energizing current is set to this timer. Ignition timing is the timing at which a high voltage is developed in an IG coil thereby to generate a spark in a spark plug connected therewith, and hence the timing of cutting off the energizing current is the ignition timing. That is, two timing (i.e., the timing of energization and the timing of cutting off the energization) is controlled by the single timer.
Now, the concrete content of such control will be described below. In the known system configuration of
FIG. 12
, connected with the ECU
1
are the reference signal generator
3
, the IG coil
8
and the spark plug
9
for supplying an optimum amount of ignition energy to an internal combustion engine (hereinafter sometimes simply referred to as an engine) at optimal timing.
The reference signal input I/F circuit
5
of the ECU
1
serves to detect a signal from the reference signal generator
3
, and upon detection of a reference signal, the reference signal input I/F circuit
5
converts it into a signal which can be controlled by the CPU
2
, and supplies it to the CPU
2
as reference timing. The CPU
2
calculates optimal energization timing and optimal cut-off timing to the IG coil
8
based on the reference timing, and supplies a control output to the IG coil drive output I/F circuit
7
, thereby driving the IG coil
8
.
FIG. 13
illustrates signal waveforms at respective portions of FIG.
12
. A signal from the reference signal generator
3
is passed through the reference signal input I/F circuit
5
, so that the waveform of the signal S
1
input to the CPU
2
is converted into a reference signal of a rectangular waveform of a high (H) level representative of reference timing for control of ignition timing such as, for example, BTDC 70° (i.e., a position of a crank angle of 70° before top dead center). The CPU
2
calculates the rotational speed of the engine from the reference timing, and optimal ignition timing and optimal energization time based on information from various sensors. Based on the results of these calculations, the CPU
2
controls energization start timing T
1
and ignition (energization cut-off) timing T
2
to the IG coil
8
, for example, by using the timer TM
1
of a predetermined time resolution, which is operated by clock pulses of a predetermined time resolution in the CPU
2
.
Specifically, at a time point of the reference signal (BTDC 70°), the energization start timing T
1
is set to the timer TM
1
, and the timer TM
1
is driven to start operation. At the same time, the ignition (cut-of timing T
2
is stored at a predetermined position of the RAM
11
. When the timer TM
1
performs counting and reaches the energization start timing T
1
previously set, an interrupt is generated so that the output signal S
2
from the CPU
2
to the IG coil drive output I/F circuit
7
is changed from the L level to the H level, whereby the IG coil
8
starts to be energized, as illustrated at a waveform S
3
in
FIG. 13
, thus accumulating energy therein.
Subsequently, the ignition (cut-off) timing T
2
previously stored in the RAM
11
is set to the timer TM
1
, and the timer TM
1
is driven to start counting. When the timer TM
1
reaches the ignition (cut-oft) timing T
2
thus set, an interrupt is generated so that the output signal S
2
from the CPU
2
to the IG coil drive output I/F circuit
7
is changed from the H level to the L level, thereby causing the IG coil
8
to generate an ignition output from its secondary side to the spark plug
9
as illustrated at waveforms S
3
and S
4
in FIG.
13
. Thereafter, each time the reference timing (reference signal S
1
) is generated and input to the CPU
2
, the CPU
2
performs control and output in the same way as described above, whereby the engine is controlled in a stable manner.
In general, in a four-cycle engine having four cylinders, the ECU controls four or two ignition coils, and in a four-cycle engine having six cylinders, the ECU controls six or three ignition coils. In contrast to this, in two-cycle engines, it is necessary to control IG coils corresponding in number to cylinders according to the configuration and control processes of the engine, and hence in a two-cycle engine having four cylinders, four ignition coils must be controlled, and in a two-cycle engine having six cylinders, six ignition coils must be controlled. That is, in the case of two-cycle engines, the CPU is required to have timers corresponding in number to engine cylinders (i.e., the number of IG coils) in order to perform ignition timing control.
FIG. 14
illustrates a concrete example of the configuration of a known control system for an internal combustion engine;
FIG. 15
illustrates a time chart of signals at respective portions of the system of
FIG. 14
; and
FIGS. 16 through 18
illustrate the operation of the system of FIG.
14
. In these figures, the same or corresponding parts as those of
FIGS. 12 and 13
are identified by the same symbols.
Now, the operation of this known control system will be described below with reference to these figures. As described above, in the case of two-cycle engines, IG coils
8
corresponding in number to the cylinders must be controlled and driven independently of one another, and hence in a two-cycle engine having n cylinders for instance, the reference signal generator
3
generates n reference signals so that reference timing (reference signal S
1
) is input to the CPU
2
via the reference signal input I/F circuit
5
. When the reference timing is input to the CPU
2
, a reference signal interrupt is generated (step S
100
of FIG.
16
), and a check is made as to which cylinder generates the current interrupt (step S
101
), and then respective cylinders are processed as described below (step S
103
).
In the case where the cylinder having generated the current i
Kwon John
Mitsubishi Denki & Kabushiki Kaisha
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