JPS61118637A - Apparatus for detecting internal pressure of cylinder of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the generation of lowering in torque or the deterioration of stability caused by erroneous judgment, by detecting a cylinder internal pressure max. crank angle to allow an abnormality judge means to judge whether the output of a cylinder internal pressure sensor is abnormal. CONSTITUTION:A microcomputer 20 detects a cylinder internal pressure ax. crank angle at every one combustion cycle on the basis of the pressure data based on the signal from a cylinder internal pressure sensor 1 and the reference position pulse and unit angle pulse from a crank angle sensor 2 and further judges the abnormality of the output of the cylinder internal pressure sensor 1 on the basis said max. crank angle value. In this case, MBT control is stopped to output an ignition signal S7 at the fundamental ignition period corresponding to the number of rotations of an engine or at the ignition period calculated by performing correction due to a factor other than the cylinder internal pressure max. crank angle to said fundamental ignition period.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cylinder internal pressure detection device for an internal combustion engine.
In particular, the present invention relates to a cylinder pressure detection device for detecting the cylinder pressure maximum crank angle used for optimal control of ignition timing, etc.

[Conventional technology]

As an ignition timing control method for an internal combustion engine, for example, as seen in Japanese Patent Application Laid-Open No. 58-82074, the pressure inside the cylinder (combustion chamber) of the engine is detected, and the crank angle (e pmax) at which the pressure is maximum is determined. There is a method to control the ignition timing so that it matches the target value.

Although there are some differences depending on the engine, as shown in Fig. 10, the crank angle θ at which the cylinder internal pressure reaches the maximum Pmax is
If the ignition timing 00 is controlled so that pmax is at a position of 10" to 20 degrees after TDC (compression top dead center), the generated torque of the engine can be maximized.

Ignition timing control using this method is called MBT control, and in order to perform this MBT control, it is necessary to detect the cylinder internal pressure maximum crank angle (hereinafter abbreviated as "θρmaxi").

Therefore, conventional cylinder internal pressure detection devices detect the cylinder internal pressure by attaching a cylinder internal pressure sensor to the cylinder head of an internal combustion engine, and detect the rotation angle of the crankshaft with a crank angle sensor. ), the output of the cylinder internal pressure sensor is successively compared for each cycle, and e pmax is detected within the entire crank angle range of the - combustion cycle (4 cycles for a 4-cycle engine, 2 cycles for a 2-cycle engine). Ta.

[Problem that the invention seeks to solve]

However, with such conventional cylinder internal pressure detection devices, even if the cylinder internal pressure sensor fails and no longer outputs a signal corresponding to accurate cylinder internal pressure,
Since an incorrect crank angle is detected as θpmax, if the MBT control of the ignition timing is performed as described above, the ignition timing will deviate from the optimum timing.
There have been problems in that it causes a decrease in torque, deterioration in stability, and an increase in harmful exhaust gas.

The object of the present invention is to solve the problems in the conventional cylinder internal pressure detection device for an internal combustion engine.

[Means for solving problems]

The cylinder internal pressure detection device for an internal combustion engine according to the present invention, as shown in FIG. Cylinder internal pressure maximum crank angle detection means (B
pmax detection means) 3 and 8 detected by it.
It is provided with an abnormality determining means 4 for determining an abnormality in the output of the cylinder internal pressure sensor 1 based on the value of pmax.

According to the first invention, the abnormality determining means 4
For example, as shown in FIG. 2, it consists of a comparator 41 and a crank angle range setter 42,
It is configured to determine whether or not the output of the cylinder internal pressure sensor 1 is abnormal depending on whether Q pmax detected by is within a preset crank angle range 01 to 02.

According to the second invention, the abnormality determining means 4 shown in FIG. 1 includes, for example, a difference detector 43, a memory 44, a comparator 45, and a comparison value setter 46 as shown in FIG.
(O newly detected by lpmax detection means B)
The cylinder internal pressure sensor 1 is determined depending on whether the difference ΔO between pmax and O pmax detected in the previous one combustion cycle and stored in the memory 44 is smaller than a predetermined value (set by the comparison value setter 46). The device is configured to determine an abnormality in the output.

[For production]

Therefore, in any invention, θpm in FIG.
Since the abnormality determining means 4 determines whether the output of the cylinder internal pressure sensor 1 is abnormal or not based on the value of O pmax detected by the ax detecting means 3, the determination signal S is normally used to adjust the ignition timing according to θpmax. By inputting it to the ignition advance control circuit 5 that controls the MBT, when the abnormality determining means 4 determines that there is an abnormality in the sensor output, the MBT
Control can be stopped.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 4 is a system configuration diagram showing the main parts of an internal combustion engine to which the cylinder internal pressure detection device according to the present invention is applied.
Parts corresponding to those in the figure are designated by the same reference numerals as E1.

In FIG. 4, 6 is an air cleaner that removes dirt and dust from the intake air, 7 is an air flow meter that measures the flow rate of the intake air, and 8 is a throttle valve that is opened and closed by an accelerator pedal (not shown).

The air that flows into the intake pipe through these is mixed with the fuel injected from the injector 10 in the intake manifold S, becomes an air-fuel mixture, and is sucked into the combustion chamber 11.
It is ignited by the spark plaque 12 and burns, and the piston 1
Drive 3.

Then, the exhaust gas after combustion is discharged to the outside through the exhaust manifold 14. That Exis 1~
- Several 02 sensors 15 are installed in the manifold 14 to detect the air-fuel ratio of the combustion mixture.

16 is a water temperature sensor attached to the cylinder block 17A, which detects the temperature of engine cooling water.

A distributor 18 has a built-in crank angle sensor 2, and distributes the ignition pulses generated in an ignition coil per day to the ignition plugs 12 attached to each cylinder.

The crank angle sensor 2 detects the crank angle at every reference position of the crank angle (every 180° for a 4-cylinder engine, every 6
For cylinder engines, a reference position pulse is output every 120°,
A negative pulse is output for every unit angle (for example, 2 degrees).

The crank angle at that point in time can be determined by counting the number of unit angle pulses after the reference position pulse is input from the crank angle sensor 2 in the control unit 20, which will be described later. Furthermore, the rotational speed of the engine can be determined by measuring the frequency or period of the unit angular pulse.

The cylinder internal pressure sensor 1 is attached to the cylinder head 17B to also serve as a washer for the spark plug 12, and outputs an electric signal according to the pressure inside the cylinder (combustion chamber 11). Note that the details will be described later.
The I control unit 20 outputs a signal S1 from the cylinder internal pressure sensor 1, a signal S2 from the water temperature sensor 16, a signal S3 from the air flow meter 7, a signal S4+ from the crank angle sensor 2, and 0.
This device inputs a signal Ss from two sensors 15 and outputs a signal S6 for driving the injector 10 and an ignition signal S7 for the ignition coil IS to control fuel injection timing, injection amount, and ignition timing.

Further, this control unit 20 corresponds to 13 in the cylinder internal pressure detection device according to the present invention shown in FIG.
It also functions as pmax detection means 3 and abnormality determination means 4.

By the way, the cylinder internal pressure sensor 1 is as shown in FIG.
As shown in B), a pair of piezoelectric elements 1a, both formed in a ring shape, are sandwiched between a pair of outer electrodes 1b and one output electrode 1c, and the inner and outer peripheries are covered with a plastic mold 1d to insulate the output electrodes. A shielded wire 1e is connected to 1c, forming the washer type of a spark plug.

The cylinder internal pressure sensor 1 is fastened to the outer recess of the cylinder head 17B in place of the washer 81 of the spark plug 12, as shown in FIG.

Next, details of the control unit 20 in FIG. 2 will be explained with reference to FIG. 7.

This control unit 1 to 20 is a multiplexer 2
1, a latch circuit 22, an A/D converter 23, a microcomputer 24 and its external memory 25, and output circuits 26 and 27.

Then, cylinder internal pressure sensor 1. Each signal S+ from the water temperature sensor 16, air flow meter 7, and 02 sensor 15
,S2,S,1. S5 is input to multiplexer 21.

Note that the output of the cylinder internal pressure sensor 1 is converted into a voltage signal by a known charge amplifier and inputted, but is not shown here.

This multiplexer 21 switches these inputs and outputs them to the A/D converter 23 at the timing when the latch circuit 22 inputting the signal S4 of the crank angle sensor 2 is generated.

Each signal converted into a digital signal by the A/D converter 23 is sequentially read into the microcomputer 24.

The microcomputer 20 detects θpmax for each combustion cycle based on pressure data based on the signal from the cylinder internal pressure sensor 1 and the reference position pulse and unit angle pulse from the crank angle sensor 2, and further detects θpmax (J p
An abnormality in the output of the cylinder internal pressure sensor 1 is determined based on the value of max.

Further, it determines the fuel injection timing and injection amount, and outputs a signal S6 that drives the injector 10 via the output circuit 26, and also determines the ignition timing and ignites the ignition coil on the 1st via the output circuit 27. A signal S7 is output, and MBT control is normally performed so that θpmax is at a predetermined position.

However, when it is determined that the output of the cylinder internal pressure sensor 1 is abnormal, the MBT control is stopped and the ignition signal is sent to the basic ignition timing according to the engine speed, or to the ignition timing corrected by factors other than θpmax. Output S7.

Next, the functions of this microcomputer 24, which correspond to the first embodiment of the invention, will be explained using flowcharts 1 to 1 in FIG.

First, in step 1, the crank angle O is measured from the signal of the crank angle sensor 2, and in step 2, the cylinder internal pressure P is measured from the signal of the cylinder internal pressure sensor 1.

Next, in step 3, it is determined whether this crank angle 0 is the crank angle at suction bottom dead center.

If YES, in step 4 the cylinder internal pressure maximum value P
The cylinder internal pressure P BDC at the suction bottom dead center is set as max, and in step 5, the crank angle θBDC at the suction bottom dead center is set as (J pmay.

If No in step 3, in step 6 the maximum cylinder internal pressure Pmax up to now is compared with the cylinder internal pressure P measured in step 2, and if P)Pmax, proceed to step 7 and change P to Pmax. max and 0 as e pmax
Change each memory as follows.

If No in step 6 and the process in step 5, 7
．． 7-Two j1□□411 Tsuuga□. Determine whether the crank angle is at bottom dead center for 71 shots.

If No in step 8, the θpmaxill fixed range in the current combustion cycle has not ended, so the process returns to step 1 and repeats the routine up to step 8.

If YES in step 8, the measurement range of Opmax in the current combustion cycle has ended, so the process proceeds to step 9.

In step 9, it is determined whether the detected O pmax is within a preset crank angle range (a predetermined range, for example, 20 degrees before compression top dead center to 40 degrees after compression top dead center).

If YES here, the output of the cylinder internal pressure sensor 1 is assumed to be normal and the process proceeds to step 10 to perform MBT control; if No, the output of the cylinder internal pressure sensor 1 is assumed to be abnormal and the process proceeds to step 11 to perform the MBT control. do not have.

Then, in step 12, set the crank angle at the bottom dead center of the explosion to θp.
In step 13, the cylinder internal pressure P at the bottom dead center of the explosion is set as the initial value of Pmax, and the process returns to step 1 to detect θpmax in the next combustion cycle.

Next, the functions of the microcomputer 24 shown in FIG. 7, which correspond to the second embodiment of the invention, will be explained with reference to the flowchart shown in FIG.

In this flowchart, the steps other than step 9 are the same as each step in the flowchart of FIG. means i-
1 means the value in the previous combustion cycle, and i+1 means the value in the next combustion cycle.

Then, in step 9, the cylinder internal pressure maximum crank angle θpmaxj detected in the current combustion cycle and the cylinder internal pressure maximum crank angle detected in the previous combustion cycle are calculated.
An abnormality in the output of the cylinder internal pressure sensor 1 is determined based on whether the absolute value of the difference from θpmaxi-1 is smaller than a predetermined value set in advance.

If YES in step 9, it is considered normal, and step 1
0/\ and performs MBT control, and if NO, it is regarded as abnormal, and the process advances to step 11, where MBT control is not performed.

〔Effect of the invention〕

As described above, the cylinder internal pressure detection device according to the present invention includes a pressure sensor for detecting the cylinder internal pressure, a crank sensor for detecting the crank angle, and a means for detecting the cylinder internal pressure maximum crank angle (θpmax) from the signals of both. and whether or not the detected O pmax is within the preset crank angle range, or its θpmax
Since it is equipped with a means to determine whether the output of the cylinder pressure sensor is abnormal based on whether the difference from the previous detected value is less than a predetermined value, it can be used in the event that the pressure sensor malfunctions and generates an abnormal output. In this case, it is possible to determine that the sensor output is abnormal and stop the MBT control of the ignition timing, thereby preventing a decrease in torque, deterioration of stability, and an increase in harmful exhaust gas due to erroneous control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of the cylinder internal pressure detection device according to the present invention, FIG. 2 is a block diagram showing an example of the configuration of the abnormality determining means according to the first invention, and FIG. FIG. 4 is a block diagram showing a configuration example of the abnormality determination means according to the invention; FIG. 4 is a system configuration diagram showing the main parts of an internal combustion engine to which the cylinder internal pressure detection device according to the invention is applied; ) is a plan view of the washer-type cylinder internal pressure sensor used in the embodiment shown in Fig. 4 and its cross-sectional view taken along the line b-b, and Fig. 6 is the mounting state of the cylinder internal pressure sensor on the cylinder head. 7 is a block diagram showing the configuration of the controller 1-roll unit 20 in FIG. 4 and its input/output relationship. FIG. FIG. 9 is a flowchart of an operating program showing functions corresponding to the embodiment of the invention; FIG. 9 is a flowchart of an operating program showing functions corresponding to the second embodiment of the invention; FIG. FIG. 1...Cylinder internal pressure sensor 2...Crank angle sensor 3...Cylinder internal pressure maximum crank angle detection means 4...
・Abnormality determination means 5...Ignition advance control circuit 7...
・Air flow meter 10...Injector 11・
... Combustion chamber 12 ... Spark plug 15 ...
・02 sensor 16...Water temperature sensor 17A...
・Cylinder block 17B...Cylinder head 18...Distributor 1st...Ignition coil 2
0... Control unit 24... Microcomputer 16-D (1 ω

Claims (1)

[Scope of Claims] 1. A cylinder internal pressure sensor that detects the cylinder internal pressure of an internal combustion engine, a crank angle sensor that detects the rotation angle of the crankshaft, and a cylinder internal pressure maximum crank from each detection signal from the cylinder internal pressure sensor and the crank angle sensor. angle(
cylinder internal pressure maximum crank angle detection means for detecting the maximum crank angle (θpmax);
θpmax) is within a preset crank angle range, and an abnormality determination means for determining an abnormality in the output of the cylinder internal pressure sensor. Device. 2. The cylinder internal pressure detection device for an internal combustion engine according to claim 1, wherein the crank angle range is from 20 degrees before compression top dead center to 40 degrees after compression top dead center. 3. A cylinder internal pressure sensor that detects the cylinder internal pressure of the internal combustion engine, a crank angle sensor that detects the rotation angle of the crankshaft, and the cylinder internal pressure maximum crank angle (
A cylinder internal pressure maximum crank angle detection means for detecting the cylinder internal pressure maximum crank angle (θpmax) detects the difference between the crank angle (θpmax) newly detected by the means and the cylinder internal pressure maximum crank angle detected in one previous combustion cycle to a predetermined value. A cylinder internal pressure detection device for an internal combustion engine, comprising: abnormality determination means for determining abnormality in the output of the cylinder internal pressure sensor depending on whether the output of the cylinder internal pressure sensor is smaller.