JPH01187346A - Output sensitivity compensator for combustion pressure sensor - Google Patents

Abstract

PURPOSE:To make accurate pressure detectable all the time by calculating the torque value and its between-combustion-cycle variation, on the basis of output of a combustion pressure sensor comparing this variation with a reference value, and compensating sensitivity of the pressure sensor. CONSTITUTION:A cylinder internal pressure sensor (fuel pressure sensor) 38 is set up in a combustion chamber 20, and torque, an engine generates, is calculated by a control circuit 50 from cylinder internal pressure being detecting in a combustion stroke. In addition, a fuel injection quantity to be sprayed to the inside of an intake pipe 30 from an injector 36 is controlled according to a difference between the calculated torque and desired torque, and thereby an air-fuel ratio is controlled within a specified range. In a suchlike controller, a combustion cycle intervariation of the above calculated torque is calculated, and this combustion cycle intervariation is compared with a reference value whereby sensitivity of the pressure sensor 38 is compensated. With this constitution, any influence of sensitivity change in the pressure sensor 38 is eliminated, and thus accurate pressure is made detectable all the time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sensitivity correction device for a combustion pressure sensor in an internal combustion engine equipped with a combustion pressure sensor.

[Conventional technology]

It is known that a combustion pressure sensor is disposed in a combustion chamber of an internal combustion engine, and an operation control factor of the internal combustion engine, such as an air-fuel ratio, is controlled by a combustion pressure signal from the combustion pressure sensor. That is, the torque generated by the engine can be determined from the cylinder pressure detected during the combustion stroke. On the other hand, the relationship between the engine generated torque and the intake air amount is constant as long as the air-fuel ratio is within the range. Therefore, by controlling the fuel injection amount according to the difference between the torque calculated from the detected value of the combustion pressure sensor and the target torque, the air-fuel ratio can be controlled within a certain range. For example, JP-A-60-2496
See No. 47. Then, by looking at the fluctuations in torque, the amount of fuel injection is reduced as long as the fluctuation value is within an allowable range (thereby, lean combustion can be performed within the limit range of torque fluctuations).

In the above system, the measured value of the pressure sensor is multiplied by a certain coefficient (sensitivity) in order to know the combustion pressure.

In this case, the sensitivity of the pressure sensor fluctuates over time or due to the opening of the individual lid, which causes errors in the pressure measurement value and, by extension, the torque measurement value.

Therefore, in JP-A No. 59-206648, constant operating conditions (for example, ignition timing, EG
It takes advantage of the fact that there is a certain relationship between the cylinder pressure value and the intake air amount value when the R ratio and air-fuel ratio are fixed. In other words, the cylinder pressure and the amount of intake air measured with an air flow meter are measured, the actual correspondence between the two is compared with the standard correspondence, and the cylinder pressure is corrected by the error from the standard value. .

[Problem to be solved by the invention]

In the prior art, the measurement value of a sensor that measures the amount of intake air (or its equivalent value) is used as a reference for pressure correction. However,
There are also variations in characteristics in the sensor (air flow meter or intake pipe pressure sensor) that measures the intake air amount as a reference. Therefore, there is a problem that an error occurs in the correction value.

An object of this invention is to enable sensitivity to be detected without using a sensor to form a reference value for comparison.

[Means to solve the problem]

As shown in FIG. 1, the combustion pressure sensor sensitivity correction device of the present invention calculates torque based on the combustion pressure signal from the combustion pressure sensor l in an internal combustion engine equipped with a combustion pressure sensor l for detecting the combustion pressure of the internal combustion engine. means 2; means 3 for calculating inter-combustion cycle fluctuations in the calculated torque;
and means 4 for correcting the sensitivity of the pressure sensor by comparing the calculated inter-combustion cycle variation with a reference value.

〔Example〕

In FIG. 2, 10 is a cylinder block, 12 is a piston, 14 is a connecting rod, 16 is a crankshaft, 18 is a cylinder spatula, 20 is a combustion chamber, 22 is an intake valve, 24 is an intake boat, 26 is an exhaust valve, 28 is an exhaust boat, 30 is an intake pipe, 32 is a throttle valve, and 34 is an intake pipe pressure sensor. A fuel injector 36 is installed in the intake pipe 30 near the intake boat 24. A cylinder pressure sensor 38, such as a piezoelectric type, is attached to the cylinder head 18, and can detect the pressure inside the cylinder bore. Cylinder pressure sensor 3
Reference numeral 8 is provided to determine a value corresponding to the torque generated by the engine using a well-known method from the detected cylinder pressure. The crank angle sensor 40.42 is connected to a crankshaft 1 such as a distribution shaft (not shown) of a distributor connected to the crankshaft 16.
6 is provided to generate a pulse signal corresponding to the rotation of the rotating shaft 44 that rotates in conjunction with the rotating shaft 44. The first crank angle sensor 40 is for confirming the reference position and generates a pulse signal every crank angle corresponding to one cycle of the engine, that is, every 720° CA. On the other hand, the second crank angle sensor 4
2, for example, generates a pulse signal every 1 degree of the crank angle, and serves as a start signal for interrupt processing to calculate torque based on fuel injection and cylinder pressure, and also determines the engine rotation speed NB from the pulse interval. be able to.

The control circuit 50 is configured as a microcomputer system and is used to execute air-fuel ratio control according to the present invention. The control circuit 50 includes a microprocessing unit (MPU) 52, a memory 54, and an input port 5.
6, an output port 58, and a bus 60 that connects these. Input port 56
is connected to each sensor, and operating condition signals are input. That is, a signal corresponding to the intake pipe pressure PM is input from the intake pipe pressure sensor 34. A signal corresponding to the cylinder pressure is input from the cylinder pressure sensor 38. Also, the crank angle sensor 40
, 42 input pulse signals corresponding to the crank angle. Reference numeral 63 denotes an air-fuel ratio sensor, such as an 02 sensor or a lean sensor, which generates an air-fuel ratio signal. MPL 152 performs calculations according to programs and data stored in memory 54 to form fuel injection signals. Output port 5
2 is connected to a fuel injector 36 and a fuel injection signal is applied thereto.

The sensitivity correction of the pressure sensor in this invention is based on the following principle. Engine torque can be calculated as the effective area of the combustion pressure curve shown in Figure 3, and is expressed as the combustion pressure at the rank angle shown by ■ before top dead center TDC. This is the total value obtained by multiplying the pressure difference by each weighting coefficient. That is, the cylinder pressure sensor 3
The torque when the sensitivity of 8 is the reference value (1, 0) is P
TI? If OB, then PTRQ, = α+(P+ Po) +
αz (Pg Po) + α3 (h l'o)
+α4 (P a P o) ...+11. α1. α2. α3. α4 is a weighting coefficient. The torque fluctuation generated in each combustion stroke, that is, the variance σ8, is expressed by, where PTRQeM--- is the average value,
Represented by Here, n is the number of samples. If the sensor to be calibrated has zero times the sensitivity of the sensor exerting the reference pressure, its torque VTRQA is: PTRQ, -C(α+(P+Po)+αz
(Pg-po) + α, (P, -PO) + α4 (P,
−P, ) )=CxPTRQl
・ ・ ・(4), the average value PTI? [1
, , , is PTR(laa*aa = (C×
ΣPTR口@H)/n=CXPTRQ++s+em
, ...(5), and the variance σ is -CXσ, ...(6), that is, the equation (6) is the current variance value σ, and the standard variance value σ.
, which means that the sensitivity can be measured from the ratio of . On the other hand, in Figure 4, which shows the relationship between the dispersion σ and the air-fuel ratio, it can be seen that σ is maintained almost constant when the air-fuel ratio is in the range of 13 to 17 (load and rotational speed are maintained constant).
. Figure 5 shows engine speed and intake pipe pressure (equivalent to load)
The results of measuring the dispersion when changing various values are shown. As can be seen from the figure, the dispersion is not affected by these within a certain range of load and rotational speed. Therefore, it is possible to measure the variance values representing combustion fluctuations in these operating ranges and calculate the sensitivity of the sensor using equation (6). Then, by multiplying the actual measurement value by this sensitivity, the accurate cylinder pressure can be determined.

FIG. 6 shows a flowchart of a routine for correcting the combustion pressure sensor sensitivity based on the above principle.

This routine is executed every time a signal of a constant crank angle (for example, every l'cA) arrives from the crank angle sensor 42. In step 78, it is determined whether or not the current crank angle is at the crank angle position 2 in FIG. 3, which is just before the compression top dead center TDC.

If Yes, proceed to step 79, and in-cylinder pressure sensor 3
The measured value of 8 is stored in the Po area. If the answer in step 78 is No, the process proceeds to step 80, where it is determined whether the current crank angle is at point 2 in FIG. 3, which is somewhat past the compression top dead center TDC. If Yes, the process proceeds to step 82, where the cylinder internal pressure P at that time is input, and the process proceeds to step 84.
Then, the first term T in the torque calculation formula (formula (4)) is
It is calculated by T, = α, xCx (P+ P o). Similarly, in steps 86-90, the second term T2 in the torque calculation formula is T2=α2XcX (P2 P
Calculated by (1). In steps 92-96, the third term T in the torque calculation formula is calculated by T's=α, x CX (P3P o). In step 98-102, the fourth term T4 in the torque calculation formula is calculated by T4-αa x c x (P4 PO).

In step 104, the current torque PTRGA is calculated as PTR
It is calculated by QA=T I+T2 +'l', +'l'4. Step 106 is a sensitivity calculation routine, the details of which are shown in FIG. That is, this routine is executed every revolution (720° CA) of the engine. Step 1
At 10, the intake pipe pressure value PM and rotation NE are input. In step 112, it is determined whether the intake pipe pressure and rotational speed are within the range of Pl≦PM≦P2NE, ≦NE≦NE2. As shown in FIG. 5, this range is a region in which inter-cycle combustion fluctuations (=dispersion) have little fluctuation.

If the determination is Yes in step 112, step 11
4, the current torque value PTRQA calculated in step 106 is stored in PTRQAi. Step 116
Then i is incremented, and in step 118, i becomes n.
Determine whether or not it has been reached. If i≧n, step 1
In step 20, the torque average value PTR(IA,, □7 and variance σ1 are calculated according to equations (5) and (6). In step 122, the sensitivity C is calculated as C-σA/σB.σ, is a reference variance value, which value has been determined in advance through experiments and is stored in memory.In step 124, i is initialized to 1, and the same process is repeated.

〔Effect of the invention〕

According to this invention, the sensitivity of the in-cylinder pressure sensor is known by detecting combustion fluctuation factors by dispersion or the like and comparing this with a reference value of combustion fluctuation. Therefore, changes in the sensitivity of the cylinder pressure sensor can be corrected without using the output value of the sensor that measures the intake air amount as a reference value, eliminating the effects of changes in the sensor's sensitivity, allowing accurate pressure detection. shall be.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the present invention. FIG. 2 is a diagram showing the configuration of an embodiment of the invention. FIG. 3 is a graph showing the relationship between crank angle and cylinder pressure. FIG. 4 is a graph showing the relationship between air-fuel ratio and dispersion. FIG. 5 is a graph showing the relationship between intake pipe pressure and dispersion when the rotational speed is fixed. 6 and 7 are flowcharts showing a combustion pressure sensor sensitivity correction routine according to the present invention. 12... Piston, 16... Crankshaft, 20... Combustion chamber, 30... Intake pipe, 34... Intake pipe pressure sensor, 36... Fuel injector, 38... In-cylinder pressure Sensor, 40.42... Crank angle sensor, 50... Control circuit, 63... Air-fuel ratio sensor. Procedural amendment (voluntary) May 0, 1988 Kunio Ogawa, Commissioner of the Patent Office 1, Indication of the case, Patent Application No. 7607 of 1988 2, Name of the invention: Combustion pressure sensor output sensitivity correction device 3 , Relationship to the person making the amendment Patent applicant name (320) Toyota Motor Corporation 4, Agent address 5-8-10 Toranomon-chome, Minato-ku, Tokyo 105
In column 6 of "Detailed Description of the Invention" of the specification to be amended, insert a line break and insert the following sentence after "is done." on page 11, line 18 of the specification of contents of the amendment. Note that the sensitivity coefficient of the pressure sensor 38 is α. When the cylinder pressure is P, the output voltage V of the pressure sensor 38 is expressed as (2)=α,P. Here, when the sensitivity coefficient changes to α2 due to a change in the state of the pressure sensor, if the sensitivity correction coefficient is set as D=α1/α2, then by determining whether or not this sensitivity correction coefficient falls within a predetermined range, , an abnormality in the pressure sensor 38 can be detected. "that's all

Claims (1)

[Claims] 1. In an internal combustion engine equipped with a combustion pressure sensor that detects combustion pressure of the internal combustion engine, means for calculating torque based on a combustion pressure signal from the combustion pressure sensor, and means for calculating inter-combustion cycle fluctuations in the calculated torque. and means for correcting the sensitivity of the pressure sensor by comparing the calculated inter-combustion cycle variation with a reference value.