|Title of Invention
METHOD TO DETERMINE THE PHASE OF A FOUR-STROKE COMBUSTION ENGINE
|Methods are specified for determining the phase angle in a four-stroke internal combustion engine with an odd number of cylinders and without a camshaft sensor, in which the phase angle is detected by virtue of the fact that the relationship of a first signal, which is emitted. by a crankshaft angle sensor and has a singularity, with a second signal, which is, for example, a rotational- speed signal or the output signal of an inlet-manifold air-pressure sensor, is determined, and the characteristic of the second signal in the region of the singularity of the first signal is evaluated. Since this signal characteristic is different depending on whether the crankshaft is in its first or second r~volution, the. phase angle can be uniquely determined.
Method for determining the phase angle in a four-stroke internal combustion engine
The invention proceeds from a method for determining the phase angle in a four-stroke internal combustion engine with an odd number of cylinders according to thet generic type of the main claim.
In a multi-cylinder internal combustion engine with a crankshaft and at least one camshaft, the control, unit of the internal combustion engine calculates, in accordance with the synchronization as a function of the detected position of the crankshaft or camshaft, at what instant for which cylinder fuel is to be injected and when in which cylinder ignition is to be triggered. In conventional internal combustion engines, it is customary to determine the angular position of the crankshaft with the aid of a sensor which scans a disk, which is connected to the crankshaft and has a characteristic surface, for example with a multiplicity of identical angle marks and a reference mark, and emits a corres-ponding signal to the control unit.
Since the crankshaft rotates twice within a working cycle of a four-stroke internal combustion engine, while the camshaft rotates only once, the phase angle of the internal combustion engine cannot pe determined uniquely from the crankshaft sensor signal alone, for'which reason it is customary also to determine the camshaft position with the aid of a dedicated sensor, a so-called phase sensor, this phase sensor scanning;a disk which is connected to the camshaft and has a Single marking. The signal produced, which has one- pulse per camshaft revolution, unit.
International application WO 87/05971 has disclosed a device for cylinder detection or for detecting the power stroke of an internal combustion engine with an odd number of cylinders, whiqh manages without a camshaft sensor. For this puirpose, the relationship of the signal which is supplied by a crankshaft sensor and has one pulse per crankshaft revolution, that is to say two pulses per camshaft revolution, with a second signal is determined in the control unit of the internal combustion engine, said second signal being, for example, a signal fluctuating periodically in the power stroke of the internal combustion engine. This periodically fluctuating signal is either the output signal of a rotational-speed sensor or the output signal of an inlet-manifold air-pressure sensor. Using the conditions prevailing in an internal combustion engine with an odd number of cylinders and the fixed phase relationship between the crankshaft and camshaft, it is possible to detect the power cycle with the aid of a simple logical combination of the crankshaft signal and the second signal, since in one crankshaft revolution the periodically fluctuating second signal must be "high", while it must be " low" in the other revolution of the crankshaft. Thus, in the known device the power cycle is detected with the aid of a simple logical combination of two signals. However, evaluation of a signal characteristic is not proposed.
Advantages of the invention
The method according to the invention for determining the phase angle in a four-stroke internal combustion engine and having the features of Claim 1 has the advantage that it is possible to synchronize an engine without detecting the camshaft position. This also holds for systems in which a phase relationship between the crankshaft and camshaft can be varied. This advantage is achieved by virtue of the fact that in order to determine the phase angle the relationship of the signal, which is supplied by the crankshaft angl* pehsor and has
a singularity, with a second signal, which fluctuates in the combustion cycle and has cylinder-specific characteristics is determined, the characteristic of the second signal being examined during the occurrence of the singularity of the first signal in order to determine the phase angle. Since the method relates exclusively to internal combustion engines with an odd number of cylinders, upon the occurrence of the singularity of the first signal th Further advantages of the invention follow from the measures specified in the subclaims. Here, it has proved to be particularly advantageous that phase shifts between the first and second rotational-speed signals are not a problem in determining the phase angle, since the relationship of the characteristic of the second signal, and not of the occurrence of a minimum or maximum of the second signal, with the singularity of the first signal is determined.
It is particularly advantageous that the method for determining the phase angle can already be carried out during the starting operation, that is to say in advance of the first firing of a cylinder. This early determination of the phase angle is possible because the different strokes have different effects on the rotational speed or the inlet-manifold air-pressure even ■ without firing.
In a system without a camshaft senior, it is possible to economize on the sensor together with electronics, the camshaft gear wheel and the corres¬ponding cabling. Three plug pins as well as the condi¬tioning circuit for the sensor and a computer port pin can be economized on the engine control unit. The printed circuit board area can likewise be reduced. In the absence of a camshaft sensor, it is possible to dispense with its diagnosis and with error handling measures for this sensor, the result being to enhance the availability of the overall system. These savings can be achieved without disadvantageous effects on how the' internal combustion engine p>erforms in terms of exhaust qas or WLai Liny. i I a J tfu [Jiuvow Lo be at.lv alii a*jrat *uw I ha I t ha
claimed methods cause no additional load on the runtime of the control unit software, since the synchronization is concluded before the actual engine operation, and thus does not constitute a runtime limitation for the computer resources.
# An exemplary embodiment of the invention is represented in the drawing and explained in more detail in the following description.
The components of the control system of atf internal combustion engine which are necessary to explain the invention are represented diagrammatically in Figure l. In this case, 10 denotes a sensor disk which is rigidly connected to the crankshaft 11 of the internal combustion engine and has on its circumference a multiplicity of identical angle marks 12 r
addition to these identical angle marks 12 is a reference mark 13 which is realized, for example, by two missipg angle marks.
The sensor disk 10 is scanned by a pick-up 14, for example an inductive pick-up or a Hall sensor. The voltage pulses of the signal SI, which are generated in
the pick-up when the angle marks are passing by> are conditioned in ci suitable way and further processed in t ha ''ml ml unit I '» ' »f Mm i lit »M IIH I r ' In addition to a crankshaft 11, an internal
combustion engine normally also has at least one cam¬
shaft, which is denoted in Figure 1 by 25 and usually has
a fixed relationship with the crankshaft 11. This rel¬
ationship is symbolized by the line 16. The angular
position of the camshaft 15 is not detected in the case
of the control system of an internal combustion engine
represented in Figure 1. A second signal, which
fluctuates periodically in the combustion cycle, is
processed in the control unit for the purpose of
synchronizing the relationship between the crankshaft 11
and camshaft 25. This second signal S2 is obtained with-
the aid of a sensor 17. The sensor 17 is, for example, a
sensor which measures the pressure in the inlet manifold
of the internal combustion engine. A different variable
which fluctuates in the combustion cycle could also be
evaluated, in principle. G' '
The control . unit 15 can also be supplied with further* input variables required to control or regulate the internal combustion engine; only the input variable of "ignition on" is further represented in Figure 1 as a signal which is supplied upon closure of the ignition switch 18 by the terminal K115 of the ignition lock and indicates to the control unit 15 that the internal combustion engine has been taken into use.
The control unit 15 itself comprises at least one central computer unit 19 and memory 20. Control signals for injection and ignition for appropriate components of the" internal combustion engine which are not denoted in more detail are formed in the control unit 15. ! These signals are emitted via the outputs 21 and 22 of the control unit 15. The control unit is supplied with voltage in the usual way from the battery 23 via a switch 24, which is closed during operation of the internal combustion engine as well as, if appropriate, during a running-on phase. The signal processing and evaluation
described below are performed in the control unit 15.
The control system represented in Figure 1 can be used to detect the angular position of the crankshaft 11 at any time during operation of the internal combustion engine. Upon starting, a singularity in the signal SI, which corresponds to the reference mark of the crankshaft, occurs at the latest after one revolution of the crankshaft 11. Since the assignment between the crankshaft 11 and camshaft 25 is normally known in the same way as the assignment between the position of the camshaft and the position of the individual cylinders of the internal combustion engine, synchronization can be performed after detection of the reference mark, but only if a niqnal whi.cn LB characteristic of the phane anqle in
In the system according to the invention, which
is intended to manage without a phase sensor or without
a camshaft sensor, that is to say thus without a sensor
which determines the position of the camshaft 25, there
is the problem that the reference mark signal supplied by
the crankshaft sensor is ambiguous, since the crankshaft
rotates* twice within a working cycle, while the camshaft
25 rotates only once. Consequently, .in addition to the
•signal SI, the signal S2, which is, for example, a
rotational-speed signal or the output signal of an inlet-
manifold air-pressure sensor and which has characteristic
properties for the position of the cylinder is evaluated
in the control unit 15. The relationship of this signal.
S2 or of the characteristic properties of this signal
with the signal SI is determined and, in particular, the
characteristic of the signal S2 during the occurrence of
the- reference mark or of the singularity of the signal J51
is evaluated. Such an evaluation i© possible sinoe in internal combustion engines with an odd number of cylinders the same conditions do not prevail for each crankshaft revolution. In internal combustion engines, in one engine position, abbreviated,below as Ml, there is a different number of cylinders in "specific strokes than in the
second possible engine position M2. This can be
illustrated as follows with the aid of a three-cylinder
Re the engine pualtion Ml, tui «xc*mple.
Cylinder 1 is in the compression cycle,
Cylinder 2 is in the intake cycle, and
Cylinder 3 is in the exhaust cycle.
By contrast, re the engine position M2: Cylinder 1 is in the exhaust cycle, Cylinder 2 is in the power cycle, and Cylinder 3 is in the intake cycle.
This compilation makes it plain that in both engine positions Ml and M2 one cylinder each is in the intake or exhaust cycle, whereas a third cylinder is either in the power cycle or in the compi*ession cycle, depending on the engine position. Whereas the influence of the compression cycle is to retard the; rotational speed, the power cycle leads to an increase in rotational speed. Thus, the rotational-speed characteristic and the characteristic of the inlet-manifold air-pressure differ in the first revolution of the crankshaft in a characteristic way from the characteristics in th« second crankshaft revolution. Consequently, the rotational-speed characteristic and the characteristic of the inlet-manifold air-pressure in the vicinity of the reference mark or in the vicinity of the singularity of the signal SI represent a criterion for the engine position, and can be used as a substitute for the camshaft signal, a detection signal which specifies the engine position Ml or M2 being generated.
Depending on the number of cylinders and pn the valve timings of the engine, a decision is made bot|h when evaluating the rotational-speed characteristic and when evaluating the pressure signal as to whether the sign
reversal of the gradient of the second signal1 or' a minimum/maximum evaluation of the second signal in tlhe vicinity of the reference mark or the singularity of the signal SI is the best method for detecting the phase angle. In order to determine the sign reversal or for the
minimum/maximum evaluation, the second signals are differentiated with respect to time, gradients and/or maximum/minimum values being obtained thereby. The precise measuring points for detecting the rotational speed or the inlet-manifold air-pressure are determined in an engine-specific fashion.
As verified by measurements, upon atarting the internal combustion engine both the rotat ional-speed
characteristic and the inlet-manifold air-pressure
characteristic can be used as signals S2 for synchronization immediately after the control unit has detected that the starter has been actuated. The evaluation can be performed in this case immediately after the engine starts to rotate in unfired operation even before the first injections or ignitions are trig¬gered. During the first revolutions without firing, both the rotational-speed characteristic and the inlet-mani¬fold air-pressure characteristic are typical of the first or second crankshaft revolution. After the start of normal engine operation, in particular at high engine revolutions or changes in rotational speed, the rotational-speed characteristic can possibly no longer be used to determine the engine position. If synchronization is to be carried out during operation, it must be performed by means of evaluating the inlet-manifold air-pressure signal.
If the methods according to the invention are used in systems with a camshaft sensor, they can always be used for operation in emergency conditions whenever a defect is detected in the camshaft sensor.
Also possible is a combination in which a method according to the invention is run immediately after the start, and^ during normal operation the output signal of a camshaft sensor is used to determine the phase angle.
1. Method for determining the phase angle in a* four-
stroke internal combustion engine with an odd number of
cylinders, in which there is formed a first signal, which
has a singularity, which can be assigned to a
prescribable crankshaft angle, and whose relationship
with a second signal, which is formed from * an output
signal of a rotational-speed sensor and/or the output
signal of an inlet-manifold air-pressure sensor, is
determined, and a detection signal is formed by
evaluating the second signal in the region of the
singularity of the first signal, characterized in that
the characteristic of the second signal, which is
respectively typical of a first revolution of the crank¬
shaft and a second revolution of the crankshaft, is
examined in the region of the singularity.
2. . Method for determining the phase angle according
to Claim 1, characterized in that the method is carried
out at the start, before the first firing in one of the
cylinders of the internal combustion engine.
3. Method according to Claim 1 or 2, characterized in that the evaluation of the second signal (S2) comprises the detection of a sign reversal in the gradient of the signal or a minimum/maximum evaluation in the vicinity of the singularity of the first signal (SI) .
4. Method according to Claim 3, characterized in that the control unit decides as a function of the number of cylinders and/or the valve timings of the internal combustion engine whether the evaluation is performed with the aid of the gradient of the second signal or with the aid of the minimum/maximum evaluation. '
5. Method according to one of the preceding claims, characterized in that the measuring points for detecting the rotational speed and/or the inlet-manifold air-
pressure are determined in an engine-specific fashion. 6. Method according to one of the preceding claims, characterized in that during operation further determinations or checks of the phase angle are performed
at prescribable times or under prescribable conditions, only the output signal of the inlet-manifold air-pressure sensor being evaluated in the determinations during
characterized in that in the case of an internal combustion engine with a phase sensor it is carried out in order to conduct emergency operation if tfhe control unit detects a defect in the phase sensor or the ■ associated signal conditioning circuit.
8. Method for determining the phase angle in a four-stroke internal combustion engine, substantially as herein described with reference to the accompanying drawings.
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|M/S. ROBERT BOSCH GMBH
|POSTFACH 30 02 20, D-70442 STUTTGART
|PCT International Classification Number
|F 02 P 07/077
|PCT International Application Number
|PCT International Filing date