JP2552754B2 - Internal combustion engine combustion detection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for detecting a combustion state of an internal combustion engine based on an ion current generated between gaps of spark plugs, and particularly to a device for detecting a combustion state of the internal combustion engine. The present invention relates to an internal combustion engine combustion detection device whose reliability is improved by changing a threshold level.

[Prior Art] In general, an internal combustion engine used for an automobile gasoline engine or the like is driven by a plurality of cylinders (for example, four cylinders) in four cycles of intake, compression, explosion, and exhaust. In order to optimally control the ignition timing by the igniter, the fuel injection sequence by the injector, etc., electronic calculation is performed by a microcomputer.
Therefore, in addition to various operating conditions, the microcomputer takes in a reference position signal for each cylinder synchronized with the rotation of the internal combustion engine, a cylinder identification signal corresponding to a specific cylinder, and the like, and identifies the operating position for each cylinder. Control is performed at the optimum timing. A rotation signal generator that detects rotation of the camshaft or crankshaft of the internal combustion engine and generates a synchronization signal is used as a means for generating the reference position signal and the cylinder identification signal.

For example, in the ignition control of each cylinder, it is necessary to burn sparks with an ignition plug in the air-fuel mixture compressed by the piston. However, depending on the fuel condition, spark plug condition, etc., the ignition-controlled cylinder may not be able to combust, and if such a condition occurs, an abnormal load is applied to other cylinders, which may lead to engine damage. There is. Therefore, in order to maintain the safety of the engine, it is necessary to detect whether or not combustion has been reliably performed in each cylinder for each ignition cycle, and conventionally, the ion current generated between the gaps of the spark plugs is detected. An apparatus has been proposed that determines the combustion state.

FIG. 2 is a configuration diagram showing a conventional internal combustion engine combustion detection device.

In the figure, (1) is a crankshaft serving as a drive shaft of an internal combustion engine, which is connected to pistons of a plurality of cylinders (not shown) and is rotationally driven. (2) is a cam shaft that rotates in synchronization with the crank shaft (1), and (3) is a timing belt that connects the crank shaft (1) and the cam shaft (2).

In the case of a general four-cycle engine, intake, compression, explosion and exhaust are performed for two revolutions of the crankshaft (1), so that one camshaft (2) for every two revolutions of the crankshaft (1). The cam shaft (2) rotates and makes one rotation in synchronization with one cycle of four-cycle operation of each cylinder. Therefore, in the case of a 4-cylinder engine, the operating position of each cylinder is 1/2 cycle (1 cycle) of the crankshaft (1).
80 °) out of phase with the camshaft (2) by 1/4 cycle out of phase.

Reference numeral (4) is a rotary shaft of a rotary signal generator connected to the cam shaft (2), and reference numeral (5) is a rotary disc for detecting a reference position provided at one end of the rotary shaft (4). (6) is a rotating disk (5)
Is a slit-shaped window formed on the cylinder, and is provided so as to correspond to the reference position (predetermined rotation angle) for each cylinder.
Further, the rotary disc (5) is provided with a cylinder identification window (not shown) corresponding to a specific cylinder as required.

Reference numeral (8) is a fixed plate which is arranged so as to face a part of the rotary disc (5). The fixed plate (8) is provided with a photocoupler sensor (not shown) facing the window (6) so as to generate a reference position signal L for each cylinder.
Here, one end on the front side in the rotational direction of (6) corresponds to the first reference position of each cylinder, and one end on the rear side in the rotational direction corresponds to the second reference position of each cylinder. L is
The pulse waveform has a rising edge at the first reference position and a falling edge at the second reference position.

(10) is a microcomputer (hereinafter referred to as an ECU) that constitutes an electronic control unit, and based on a reference position signal L and operation state signals from various sensors (not shown),
Fuel control and ignition control of each cylinder are performed. The ECU (10) includes a distribution unit that controls each cylinder according to the determined cylinder order.

(11) is a grounded emitter power transistor driven by the ECU (10), (12) is an ignition coil whose primary coil side is connected to the power transistor (11), and (13) is a secondary coil of the ignition coil (12). A spark plug connected to the side, (14) is a backflow prevention diode inserted between the ignition coil (12) and the spark plug (13), and these (11) to (14) are ignition parts. I am configuring. Although the ignition unit is provided for each cylinder, only the ignition unit for one cylinder is shown here as a representative.

(20) is an ion current detector inserted between one end of the spark plug (13) and the ECU (10).
Diode (21) for preventing backflow connected to one end of 3)
, A load resistor (22) connected to the cathode of the diode (21), a DC power source (23) connected in series with the load resistor (22) and connected to the anode, a load resistor (22) and a DC power source The voltage dividing resistors (24) and (25) connected in parallel to the series circuit composed of (23), and the capacitor (26) inserted at the connection point of the load resistor (22) and the voltage dividing resistor (24). And the connection point of the voltage dividing resistors (24) and (25) is the comparison input terminal (-).
Threshold value TH from the intermediate connection point to the reference input terminal (+) of the comparator (27) connected in series between the power supply and the ground, and the comparator (27) whose output terminal is connected to the ECU (10). And voltage dividing resistors (28) and (29) for inputting.

Further, the voltage dividing resistors (24) and (25) constitute voltage generating means for generating a voltage V corresponding to the ion current I, and the voltage dividing resistors (28) and (29) serve as a combustion determination reference. Which constitutes a threshold generation means for generating the threshold TH.

The ion current detector (20) having the following configuration is provided only on the spark plug (13) of a specific cylinder or on the spark plug (13) of each cylinder as necessary.

Next, the operation of the conventional internal combustion engine combustion detection device shown in FIG. 2 will be described.

When the rotating disc (5) is rotated by the cam shaft (2) that is interlocked with the crank shaft (1), the photocoupler sensor on the fixed plate (8) outputs the reference position signal L corresponding to the window (6). To be done. The reference position signal L rises at, for example, the first reference position B75 ° of each cylinder, and the second reference position B5
It becomes a waveform that falls at °. The first reference position B75 ° is T
This is the crank angle position 75 ° before DC (top dead center), which corresponds to the control reference and initial energization angle. The second reference position B5 ° is a position 5 ° before TDC, and corresponds to the initial ignition angle during cranking. Further, another cylinder identification signal (which may be included in the reference position signal L) is output when the reference position signal L corresponding to the specific cylinder (for example, # 1 cylinder) is generated. Reference position signal L thus obtained
Is input to the microcomputer (10) together with the operation status signal. As the operation state signal, for example, the engine (crank) rotation speed and the load state (accelerator opening degree) are input.

The microcomputer (10) distributes an ignition control signal to each cylinder identified based on the reference position signal L, and the power transistor (11), the # 3 cylinder, the # 4 cylinder, and the # 2 cylinder in this order. ) Is turned on. Then, after the primary coil current of the ignition coil (12) is supplied for the required time, the power transistor (11) is cut off, the secondary coil side of the ignition coil (12) is driven, and the spark plug (13) is sparked. generate. At this time, the power supply voltage applied to the ignition coil (12) is a high negative voltage, but the spark plug (13)
It is cut off after being discharged at.

When this discharge causes an explosion (combustion) around the spark plug (13), immediately after that, a large amount of cations are generated in the gap of the spark plug (13). This cation becomes an ion current I, and from the gap of the spark plug (13),
The diode (21) is pulled by the negative voltage of the DC power supply (23).
And through the load resistor (22).

This ionic current I becomes a voltage across the load resistor (22), is further converted into a voltage V by the voltage dividing resistors (24) and (25), and is input to the comparator (27) at the comparison input terminal (- ) Is entered. This voltage V corresponds to the ion current I, and has a high value if an explosion occurs, and a low value if an explosion does not occur. On the other hand, the threshold TH preset in advance by the voltage dividing resistors (28) and (29) is input to the reference input terminal (+) of the comparator (27).

Therefore, the comparator (27) detects that the voltage V is the threshold TH.
If it is smaller, the output signal is turned off, if the voltage value V is equal to or higher than the threshold TH, the output signal is turned on, and the on signal is generated from the output terminal only when the ion current I is detected and input to the ECU (10).

The ECU (10) confirms, based on the cylinder identified from the reference position signal L and the voltage V corresponding to the ion current I, that combustion is normally performed in the ignition-controlled cylinder.

If the ignition-controlled cylinder is normal, the spark plug (13) discharges, causing an explosion, and the spark plug (13)
Many cations are generated during the period, but if no explosion occurs due to some trouble, almost no cations are generated. This makes it possible to determine the combustion state of the cylinder.

However, the level of the threshold TH is set corresponding to the ion current I when the operating condition is stable, whereas the level of the ion current I differs depending on the operating condition. For example, when the engine speed is high or the load is large, noise is superimposed on the ionic current I, and the level of the ionic current I increases.
Therefore, when the voltage V is compared with the constant threshold TH, the comparator (27) may output an ON signal only with the noise level, and in reality, the combustion proceeds normally even if the combustion does not occur. It is determined that the engine has been broken, and as described above, the engine may be damaged.

[Problems to be Solved by the Invention] As described above, in the conventional internal combustion engine combustion detection apparatus, since the level of the threshold TH for combustion state determination is set to a constant level, the level of the ion current I changes depending on the operating state. In that case, the ion current I is not accurately determined,
There is a problem that it becomes difficult to detect combustion with high reliability.

The present invention has been made to solve the above problems, and an object thereof is to obtain an internal combustion engine combustion detection device that does not impair reliability even when the level of the ion current changes.

[Means for Solving the Problem] In the internal combustion engine combustion detection device according to the present invention, the threshold generation means is configured by a threshold level variable circuit that generates different thresholds according to the operating state of the internal combustion engine, and the operating state is steady. A low level threshold is generated in the state, and a high level threshold is generated if the operating state is higher than the steady state or in a high load state.

[Operation] In the internal combustion engine combustion detection apparatus according to the present invention, the threshold level is changed according to the operating state of the internal combustion engine, and the combustion state is accurately detected regardless of the level change of the ion current.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an internal combustion engine combustion detection apparatus according to an embodiment of the present invention, in which (1) to (27) are the same as those described above.

Reference numeral (30) is a threshold level variable circuit which serves as threshold generation means, and generates different thresholds according to the operating state of the internal combustion engine under the control of the ECU (10).

Further, a part of the program of the ECU (10) is changed, and the ECU (10) controls the threshold level variable circuit (30) according to the operating state.

Next, the operation of the embodiment of the present invention shown in FIG. 1 will be described.

Similarly to the above, the ECU (10) drives the power transistor (11) based on the reference position signal L corresponding to the crank angle of each cylinder, and the spark plug (1
3) Discharge. Then, the ion current detector (20)
Takes in the ion current I generated in the gap of the spark plug (13) immediately after the discharge, and the ECU (10) turns the comparator (2
It is determined from the output signal of 7) that the level of the ion current I is the combustion level.

At this time, the ECU (10) controls the threshold level variable circuit (30) according to the number of revolutions and the load state, and if the operating state of the internal combustion engine is in a steady state, it produces a low level threshold TH, A high level threshold TH is generated when the value is high or the load is large.

As a result, even if the level of the ion current I changes depending on the operating state, the combustion state can be reliably detected.

[Effects of the Invention] As described above, according to the present invention, a threshold level variable circuit that generates different thresholds according to the operating state of an internal combustion engine is provided, and if the operating state is a steady state, a low level threshold is generated. Since the high level threshold is generated when the operating state is higher than the steady state or in the high load state, it is possible to accurately detect the combustion state regardless of the level change of the ion current. There is an effect that a highly reliable internal combustion engine combustion detection device can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional internal combustion engine combustion detecting device. (10) …… ECU (13) …… Spark plug (20) …… Ion current detector (24), (25) …… Voltage divider resistor (voltage generator) (27) …… Comparator (30) ...... Threshold level variable circuit I ... Ion current, V ... Voltage TH ... Threshold In the drawings, the same reference numerals indicate the same or corresponding portions.

Claims (1)

(57) [Claims] 1. An ion current detector comprising: a plurality of cylinders whose ignition is controlled in synchronism with rotation of an internal combustion engine; and an ion current detector provided in an ignition plug of at least one of the cylinders. The detector is a voltage generation unit that generates a voltage corresponding to the level of the ionic current generated from the spark plug, a threshold generation unit that generates a threshold serving as a combustion determination reference, and compares the voltage with the threshold. In an internal combustion engine combustion detection device including a comparator that generates an output signal that represents a combustion state, the threshold generation means includes a threshold level variable circuit that generates a different threshold depending on the operating state of the internal combustion engine, and If the operating state is a steady state, a low level threshold is generated and the operating state is Engine combustion detecting apparatus characterized by generating a threshold if high levels of long high rpm condition or heavily loaded than normal state.