JPH0493633A - Cylinder internal pressure detection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To accurately detect he internal pressure of each cylinder by sensing the predetermined piston position before firing in the compression stroke of each cylinder, and correcting the detected value of internal pressure of each cylinder on the basis of the predetermined correction value therefor. CONSTITUTION:Cylinder internal pressure sensors 12a to 12d are provided as cylinder internal pressure detecting means for separately sensing the internal pressure of cylinders Nos. 1 to 4. Also the camshaft of an internal combustion engine 1 is fitted with a crank angle sensor 13 as a means for detecting the predetermined piston position. This sensor 13 outputs a reference angle signal REF and a unit angle signal POS, respectively. Signals detected with the sensors 12a to 12d on the basis of the signals REF and POS are inputted to a control unit 11, according to the firing order of each cylinder. The control unit 11 uses a correction result available from the detected values of the sensors 12a to 12d multiplied with a corresponding correction value as a final detection value, thereby diagnosing a misfire, calculating means effective pressure Pi, and further detecting or otherwise engine output torque and an intake air am ount.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a cylinder pressure detection device for an internal combustion engine.
The present invention relates to a device capable of compensating for variations in detection characteristics of in-cylinder pressure detection means provided for each cylinder.

<Prior art> A commonly used method for understanding the combustion state of an internal combustion engine is to detect the pressure inside the combustion chamber (in-cylinder pressure).
As means for this purpose, for example, as disclosed in Japanese Patent Publication No. 41-5154, SAE Technical Page/<-750883, etc., there are devices configured to detect cylinder pressure using piezoelectric sensors, and devices using strain gauges. There are devices that use sensors to detect cylinder pressure.

Then, a misfire is determined for each cylinder based on the cylinder pressure detected by the cylinder pressure detection device, and the average effective pressure Pi is calculated for each cylinder based on the cylinder pressure. The ignition timing and EGR amount can be modified based on the surge torque detected from fluctuations in Pi, and furthermore, as disclosed in Japanese Utility Model Application Publication No. 62-132252, the amount of fuel supplied can be adjusted for each cylinder based on the average effective pressure. Corrections are being made to improve air-fuel ratio variations between cylinders.

<Problem to be solved by the invention> However, it is unavoidable that the various sensors used in the cylinder pressure detection device will have 8-force characteristic variations during manufacturing, and if a sensor is provided for each cylinder. Second, surge torque control requires a highly accurate cylinder pressure detection value because the accuracy of the cylinder pressure detected by the sensor varies between cylinders.

Even if fuel supply correction control is attempted, there is a problem in that it is difficult to ensure desired accuracy.

The present invention was developed in view of the above-mentioned problems, and an object of the present invention is to provide a device that absorbs variations in the characteristics of cylinder pressure sensors and can accurately detect cylinder pressure between cylinders.

<Means for Solving the Problems> Therefore, a cylinder pressure detection device for an internal combustion engine according to the present invention is configured as shown in FIG.

In FIG. 1, cylinder-specific in-cylinder pressure detection means are provided for each cylinder of an internal combustion engine and detect the in-cylinder pressure of each cylinder, respectively.

On the other hand, the predetermined piston position detection means detects a predetermined piston position before ignition in the compression stroke of each cylinder.

The cylinder-by-cylinder in-cylinder pressure sampling means detects the in-cylinder pressure detection value of the cylinder by the cylinder divided cylinder pressure detection means when the predetermined piston position detection means detects a predetermined piston position before ignition in the compression stroke of each cylinder. sample,
The cylinder-by-cylinder correction value setting means sets a correction value for the detected cylinder pressure value for each cylinder so that the cylinder-by-cylinder pressures sampled by the cylinder-by-cylinder cylinder pressure sampling means are uniform under the same operating conditions.

The cylinder pressure detection value correction means corrects the cylinder pressure detection value of the cylinder-specific cylinder pressure detection means for each cylinder based on the correction value set for each cylinder by the cylinder-specific correction value setting means, and uses the correction result as a cylinder pressure detection value. Output as the final detected value.

Here, a detected value sampling permission means is provided for permitting the cylinder-by-cylinder in-cylinder pressure sampling means to sample cylinder pressure detection values for each cylinder only when the steady-state operation detection means detects whether the engine is in a steady-state operating state. That's preferable.

<Operation> According to this configuration, the detected cylinder pressure value is sampled for each cylinder at a predetermined screw position before ignition in the compression stroke of each cylinder, so the sampled value is independent of the air-fuel ratio and ignition timing of each cylinder. It is unaffected and changes only by the amount of intake air.

Therefore, the variation in the sampling values directly indicates the variation in the detection characteristics between the cylinders of the in-cylinder pressure detection means for each cylinder.If a correction value is set for each cylinder to eliminate such variation, It is possible to absorb variations in the detection characteristics of the provided in-cylinder pressure detection means for each cylinder.

Also, during transient engine operation, the amount of intake air may be unstable.
Even if the cylinder pressure detection value is sampled at a predetermined piston position, the detection value may not be sampled under the same conditions between cylinders, so sample the cylinder pressure detection value for each cylinder only during steady engine operation. It is good to configure it like this.

<Example> The present invention will be explained in detail below.

In FIG. 2 showing one embodiment, a 4-stroke, 4-cylinder internal combustion engine 1 includes an air cleaner 2. Throttle chamber 3.
Air is sucked in through the intake manifold 4. The combustion exhaust gas is then transferred to the exhaust manifold 5. Exhaust duct 6, three-way catalyst 7. It is discharged into the atmosphere via the muffler 8.

The throttle chamber 3 is provided with a throttle valve 9 that opens and closes in conjunction with an accelerator pedal (not shown), and the intake air amount of the engine 1 is controlled by the throttle valve 9.

Further, each branch portion of the intake manifold 4 is provided with an electromagnetic fuel injection valve 10a for injecting and supplying fuel to each cylinder.
~10d are installed, respectively, and are controlled to open independently according to injection pulse signals from a control unit 11 containing a microcomputer. The electromagnetic fuel injection valves 10a to 10d are supplied with fuel that is pressure-fed from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator, and the opening time of the fuel injection valves 10a to 10d is The amount of fuel injection should be adjusted accordingly.

Furthermore, cylinder pressure sensors 12a-12d serve as cylinder-specific cylinder pressure detection means for detecting the cylinder pressure for each cylinder (#1 to #4).
This is provided.

Incidentally, the cylinder pressure sensors 12a to 12d are manufactured by U.S. Pat.
It may be a piezoelectric type that is installed as a washer for a spark plug, as disclosed in Publication No. 17432, etc.
It is more preferable to use a type of sensor that detects the in-cylinder pressure as an absolute pressure by having the sensor section directly facing into the combustion chamber.

Further, a crank angle sensor 13 is provided on the camshaft (not shown) of the engine 1 as a predetermined piston position detection means for detecting the crank angle through rotation of the camshaft, and corresponds to the stroke phase difference between the pistons. A reference angle signal REF for every 180 degrees of crank angle (for example, every 70 degrees BTDC) and a unit angle signal PO3 for every unit crank angle are output, respectively. Incidentally, among the reference angle signals REF, for example, a signal corresponding to the #l cylinder can be distinguished from the others, so that the reference angle signal REF can be made to correspond to each cylinder.

Further, the throttle valve 9 is provided with a potentiometer-type throttle sensor 14 for detecting the opening degree TV○ of the throttle valve 9.

The control unit 11 controls the amount of fuel injected by the fuel injection valves 10a to 10d as described above, and also performs misfire diagnosis, surge torque detection, etc. for each cylinder based on the detection signals from the cylinder pressure sensors 12a to 12d, respectively. In order to detect the average effective pressure, etc., as shown in the flowchart of FIG.
v-HO34a v is set, and the correction value HO3 for each cylinder is
Each cylinder pressure sensor 12 based on 1a v-HO34aV
The detected values a to 12d are corrected and set.

In this embodiment, the functions of cylinder-specific cylinder pressure sampling means, cylinder-specific correction value setting means, cylinder pressure detection value correction means, and detection value sampling permission means are provided by the control unit 11 or software, and the functions are provided by the control unit 11 or software. The driving detection means is composed of a throttle sensor 14 and a crank angle sensor 13, as will be described later.

The program shown in the flowchart of FIG. 3 is interrupted and executed at the BTDC50' position during the compression stroke of each cylinder, and in this embodiment, the ignition timing range is set to BT
Assuming that the DCO is ~40', the flowchart in FIG. 3 is executed before ignition during the compression stroke.

First, step 1 (indicated as Sl in the figure).

(Similarly below), the detection signals of the cylinder pressure sensors 12a to 12d provided in the cylinder whose compression is B TDC500 this time are A/D converted and input. That is, the detection signals of the cylinder pressure sensors 12a to 12d are sequentially inputted according to the ignition type at each sampling timing of every 180 degrees detected based on the reference angle signal REF and the unit angle signal PO8.

In the next step 2, it is determined whether the engine 1 is in transient operation. Specifically, for example, the throttle sensor 14
The opening degree TVO of the throttle valve 9 detected is approximately constant,
When the engine rotational speed N calculated based on the detection signal from the crank angle sensor 13 is approximately constant, the engine 1
In other cases, it is assumed to be a steady operating state.

When it is determined that the operation is transient, the process proceeds to step 3, and assuming that the cylinder pressure P sampled this time is a common detection value for each cylinder, P1 to P1 indicating the cylinder pressure for each cylinder are
The current detection value P is set for each of P4, so that the upper hooks 12a to 12d are apparently treated as having no variation in detection characteristics.

On the other hand, engine 1 that was determined not to be in transient operation in step 2
In the steady operating state, the process proceeds to step 4, where it is determined based on the reference angle signal REF from the crank angle sensor 13 which cylinder the current compression BTDC 50° corresponds to.

For example, this compression B T D C50' or #4
If it is from the cylinder, proceed to step 5 and set the current sampling value P to P4, and set the sampling value P to the current compression BTDC50° or the cylinder pressure data PI-P4 of the corresponding cylinder. Set (Step 5 to Step 8). Therefore, if the engine 1 continues to operate in a steady state, the cylinder pressure data P1 to P4 become the data detected by the corresponding cylinder pressure sensors 12a to 12d, respectively.

In the next step 9, the average value of the in-cylinder pressures P1 to P4 sampled at compression BTDC 50 degrees for each cylinder in the steady operating state as described above is determined, and the average value is set to Avp.

Immediately after the transition, since P1 to P4 = P are set during the transient operation, it becomes P Avp, but the data actually detected for each cylinder during steady operation is PI-P.
4, the variations in the detection characteristics of the cylinder pressure sensors 12a to 12d appear as variations in Pi-P4.

That is, during steady operation, in other words, when the intake air amount of the engine l is approximately constant, the piston position before ignition during the compression stroke (in this example, the compression BTDC 50
The in-cylinder pressures in the cylinders (°) should be approximately equal in each cylinder without being affected by the air-fuel ratio or ignition timing, or in reality there may be variations in the characteristics of each cylinder pressure sensor 12a to 12d during manufacturing. The detected values may not be equal,
The detection characteristics of the cylinder pressure sensors 12a to 12d are likely to be due to variations in the cylinder pressures PI-P4 sampled for each cylinder at a compression BTDC of 50° during steady operation.

Therefore, the correction values for each cylinder are set as follows so that the values detected by each cylinder pressure sensor 12a to 12d or the compression BTDC 50° under the same operating conditions are uniform (the above average value Avp). By setting the correction value for the difference, variations in the characteristics of the cylinder pressure sensors 12a to 12d are absorbed, and the cylinder pressure detection values between the cylinders can be compared with high accuracy.

In step 10, a value obtained by dividing the average value Avp by the current sampling value P is set as a correction value HO3.

Therefore, by multiplying the detected cylinder pressure value by this correction value HO3, the cylinder pressure P sampled this time becomes the average value A V
By doing so, it is possible to correct the variation between cylinders in the cylinder pressure detected at the compression BTDC of 50° (variation in the detection characteristics of the cylinder pressure sensors 12a to 12d).

In step 11, similarly to step 4, it is determined whether the cylinder pressure P input in this step corresponds to the same cylinder. For example, when the cylinder pressure P of #4 cylinder is input, Proceed to step 12, this time step 10
The correction value HO3 set by
Set it to 34.

In the next step 13, the correction value HO34 set in step 12 and the weighted average value HO34a of the correction value HO34 are
v, and the weighted average value is newly calculated as Ho34
Set to av.

Similarly, in step 10, either the correction value HO3 set based on the detected value for each cylinder or the correction value HO3 of the corresponding cylinder.
1-Ho34, each correction value Ho5t-HO
The final correction value HO3 is calculated by weighted average for each cylinder.
1a v-Ho34 av is obtained (steps 14 to 19).

As mentioned above, the reason why the correction values HO3I-HO34 are weighted and averaged is to prevent the correction values HO31-H, O34 from greatly varying depending on the operating conditions.

The control unit 11 includes each cylinder pressure sensor 12a-
12d, the corresponding correction value HO31a v
-The correction result obtained by multiplying by HO34a v is used as the final detected value to diagnose misfires, calculate the average effective pressure Pi,
Furthermore, it also detects engine output torque and intake air amount.

Here, as mentioned above, the correction value HO31a v-HO34a may be due to variations in the detection characteristics of the cylinder pressure sensors 12a to 12d.
Since it is absorbed by the correction using v, the cylinder pressure detection values for each cylinder can be compared with high accuracy, and in particular, the air-fuel ratio correction control for each cylinder and the detection accuracy of surge torque are improved.

In this example, in a 4-cylinder engine, compression BTDC5
Although the cylinder pressure was sampled at 0°, it is clear that this does not limit the number of cylinders or the sampling timing, and the correction value HO31a v-HO34
a vi: Therefore, there are no limitations on how the corrected cylinder pressure can be used.

<Effects of the Invention> As explained above, according to the present invention, when detecting the in-cylinder pressure of each cylinder, it is possible to absorb detection characteristic variations between cylinders. This has the effect of improving the accuracy of controls such as air-fuel ratio correction for each cylinder and surge torque detection using internal pressure detection values.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG. 2 is a system I! showing an embodiment of the present invention. tff18 and FIG. 3 are flowcharts showing how to set a correction value for a detected cylinder pressure value in the above embodiment. 1... Internal combustion engine 9... Throttle valve 11.
...Control unit 12a-12d...i
Internal pressure sensor 13... Crank angle sensor 14...
Throttle sensor patent applicant Japan Electronics Co., Ltd. Patent attorney Fujio Sasashima

Claims (2)

[Claims] (1) Cylinder-specific in-cylinder pressure detection means provided for each cylinder of an internal combustion engine to detect the in-cylinder pressure of each cylinder, and a predetermined piston position detection means to detect a predetermined piston position before ignition in the compression stroke of each cylinder. and a cylinder-specific cylinder pressure for sampling the cylinder pressure detection value of the cylinder by the cylinder-specific cylinder pressure detection means when the predetermined piston position detection means detects a predetermined piston position before ignition in the compression stroke of each cylinder. sampling means; cylinder-specific correction value setting means for setting a correction value for the detected cylinder pressure value for each cylinder so that the cylinder pressures of each cylinder sampled by the cylinder-specific cylinder pressure sampling means are uniform under the same operating conditions; and a cylinder that corrects the cylinder pressure detection value of the cylinder-specific cylinder pressure detection means for each cylinder based on the correction value set for each cylinder by the correction value setting means, and outputs the correction result as a final detection value of the cylinder pressure. 1. A cylinder pressure detection device for an internal combustion engine, comprising: internal pressure detection value correction means. (2) Steady-state operation detection means for detecting a steady-state operating state of the engine; and only when the steady-state operating state of the engine is detected by the steady-state operation detecting means, cylinder-by-cylinder pressure detection values are detected by the cylinder-by-cylinder in-cylinder pressure sampling means. 2. The in-cylinder pressure detecting device for an internal combustion engine according to claim 1, further comprising a detected value sampling permission means for permitting sampling of the detected value.