Data processing: measuring – calibrating – or testing – Measurement system – Speed
Reexamination Certificate
1999-11-12
2004-03-02
Nghiem, Michael (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Speed
Reexamination Certificate
active
06701275
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an rpm (revolution per minute) calculating apparatus for calculating an rpm of an engine on the basis of a detection pulse derived from a rotary sensor used to control the engine. More specifically, the present invention is directed to such an rpm calculating apparatus for controlling an engine, capable of expanding a high rpm region calculable in an easy process operation without deteriorating a calculation capability with respect to a low rpm region while a calculation period is not changed.
2. Description of the Related Art
Conventionally, rpm calculating apparatuses for controlling engines are known in the field, in which rpms (revolution per minute) of engines are calculated based upon detection pulses derived from rotary sensors. For example, this type of rpm calculating apparatus is utilized in the transmission control apparatus described in Japanese Patent Application Laid-open No. Hei 6-81940.
Referring now to
FIG. 6
to
FIG. 9
, the conventional rpm calculating apparatus for controlling the engine will be explained.
FIG. 6
is a block structural diagram for schematically showing the conventional rpm calculating apparatus for controlling the engine.
FIG. 7
is an explanatory diagram for explaining a waveform of a detection pulse “P” derived from a rotary sensor, and also calculation timing.
FIG. 8
is a flow chart for describing a pulse detection interrupt routine.
FIG. 9
is a flow chart for describing an rpm calculation interrupt routine.
In
FIG. 6
, a rotary member
1
coupled to an engine (not shown) is provided in an integral manner with, for example, a crank shaft, and either an input shaft or an output shaft of an engine transmission for gear change purposes. A plurality of teeth
2
are formed along an outer peripheral portion of the rotary member
1
with a constant interval.
A rotary sensor
3
constructed of an electromagnetic pick-up and the like is positioned opposite to the teeth
2
of the rotary member
1
, and produces a detection pulse “P” in response to an rpm of the rotary member
1
. It is now assumed that the rotary sensor
3
contains a waveform shaping circuit used to produce such a detection pulse “P”.
A microcomputer
10
calculates an rpm of an engine on the basis of the detection pulse “P” so as to control this engine. The microcomputer
10
constitutes a main body of this conventional rpm calculating apparatus for controlling the engine.
As indicated in
FIG. 7
, only timing (namely, detection time instant “ti”) of one edge (for example, rising edge) of the detection pulse “P” derived from the rotary sensor
3
is guaranteed.
As a result, the microcomputer
10
detects only the rising edge of the detection pulse “P” as the pulse detection time instant “ti” and the pulse number, and then calculates an rpm “Ne” of the engine.
The rpm calculation is executed by the microcomputer
10
at calculation timing “Ti” every constant calculation period as indicated in FIG.
7
.
For instance, as time instant information acquired at calculation timing T
2
, such pulse detection time instants “t1” and “t2” are used which have been stored immediately before the respective calculation timings “T1” and “T2”.
Next, a pulse detecting operation executed by the microcomputer
10
will now be described with reference to FIG.
8
.
The pulse detection interrupt routine of
FIG. 8
is executed every time the rising edge of the detection pulse P is detected.
In other words, in
FIG. 8
, the microcomputer
10
stores the latest pulse detection time instant “ti” every time the rising edge of the detection pulse P is detected while sequentially updating the latest pulse detection time instant “ti” (step S
1
).
Subsequently, a counter value “Ci” for counting a pulse number is incremented (step S
2
), and then the pulse detection interrupt routine shown in
FIG. 8
is ended by the microcomputer
10
.
As a result, both the latest pulse detection time instant “ti” and the pulse number “Ci” counted from the preceding calculation timing are stored into a RAM of the microcomputer
10
.
Referring now to
FIG. 9
, an rpm calculating operation of the microcomputer
10
will be described.
The rpm calculation interrupt routine of
FIG. 9
is executed at calculation timing “Ti” every calculation time period “T”.
That is, in
FIG. 9
, the microcomputer
10
executes the rpm calculation every predetermined calculation timing Ti (step S
11
).
For example, the rpm Ne at calculation timing “T2” indicated in
FIG. 7
is calculated based upon the following equation (1):
Ne
=(
Np/M
)×{(60×10
6
)/
T
12} (1).
It should be noted that in the above equation (1), symbol “Np” denotes a pulse number which is detected within the calculation time period “T” (namely, time period defined from the pulse detection time instants “ti” to “t2”); symbol “M”, shows a pulse number (tooth number of the rotary member
1
) which is detected while the rotary member
1
is rotated by 1 turn; and symbol “T12” denotes time defined from the pulse detection time instants “t1” to “t2”. In this case, the time T
12
is counted in unit of (10
−6
) second.
Subsequently, the microcomputer
10
stores the latest pulse detection time instant “t2” at the present calculation timing T
2
(step S
12
), and then clears the counter value Ci for counting the pulse (step S
13
). Thereafter, the rpm calculation interrupt routine shown in
FIG. 9
is accomplished. As a result, the latest pulse detection time instant “ti” is updated every time the rpm calculation is carried out, and also the counter value Ci indicative of the pulse number is cleared as “0”.
As previously explained, the microcomputer
10
stores the latest pulse detection time instant “ti”, and counts the detection pulse number “Np” (see FIG.
8
), and furthermore measures the time lapse “T12” (sec) of the pulse detection time instant within the calculation time period and the pulse number “Np”. As a result, the microcomputer
10
can calculate the rpm “Ne” based upon the above-described equation (1) (see FIG.
9
).
Generally speaking, in order to improve calculation precision of the rpm “Ne”, it is preferable to detect a large quantity of pulse numbers “Np” as many as possible in the calculation time period “T” if the calculation process range is defined within the range for the calculation process capability of the microcomputer
10
.
In the case that the rpm calculation is carried out based only on the rising edge of the detection pulse “P”, for example, since the calculation time period “T” is set to a long time period, the low rpm region which can be calculated in high precision can be expanded up to the detection limit of the rotary sensor
3
.
However, when the calculation time period T is set to such a long time period, since the detection pulse number Np in the calculation time period T within the high rpm region is increased, the total number of the respective process operations indicated in FIG.
8
and
FIG. 9
is increased, so that the calculation loads of the microcomputer
10
are increased. As a result, the calculable high rpm region is narrowed within the processing capability of the microcomputer
10
.
On the other hand, another solution is conceivable. For example, the calculation time period “T” may be set to be a short time period within the high rpm region. That is, the calculation timeperiod “T” may be switched in response to the rpm “Ne”. However, the calculation control program is made complex.
In particular, when this solution method is applied to the transmission control of the engine, the control time period of the duty solenoid for driving a clutch is exclusively set, and the rpm calculation time period “T” is set identical to this control time period. As a consequence, it is practically difficult to switch the calculation time period “T”.
As previously explained, in the conventional rpm calculating apparatus for controlling the engine, since the pulse number “Np” is counted in response to only
Mitsubishi Denki & Kabushiki Kaisha
Nghiem Michael
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