JPH0270961A - Indicated average effective pressure computing device for engine - Google Patents

Abstract

PURPOSE:To simplify a computing method by a method wherein a change amount of a cylinder internal pressure at a given crank angle is determined, and the change amount is corrected by means of a correction factor responding to a change in a stroke volume during an explosion stroke to compute an indicated average effective pressure. CONSTITUTION:By means of signals from a cylinder internal pressure sensor 2 and a crank angle sensor 3, a cylinder internal pressure detecting circuit 4 detects a cylinder internal pressure at each given crank angle, for example, 30 deg.CA. A factor computing circuit 5 computes a correction factor by means of which a cylinder internal pressure at a crank angle symmetrical to a compression top dead center TDC is corrected to output it to a deviation computing circuit 6. The deviation computing circuit 6 computes a deviation between cylinder internal pressures at respective given crank angles to output a computing result to a total sum circuit 7. The total sum circuit 7 computes a total sum at a given crank angle section of computing results, inputted from the deviation computing circuit 6, as a current indicated average effective pressure (torque). As a result, an indicated average effective pressure in a conventional computer for controlling an engine can be computed, and a cost can be reduced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an indicated mean effective pressure calculation device for an engine such as an automobile, and more specifically, it simplifies the method for calculating the indicated mean effective pressure and shortens the calculation time. related to a device for

(Prior Art) In recent years, various electronic control technologies for engines have rapidly developed and become popular. Torque control often plays an important role in the electronic control of such rotary power engines.

In other words, torque is one of the most basic and important parameters when controlling a rotational drive system, and when information on torque and rotation speed is obtained, the product of them is proportional to horsepower, so it is difficult to determine the state of power generation and transmission. It becomes possible to grasp the status.

As a conventional indicated mean effective pressure calculation device for this type of engine, for example, the rcB-210 engine Pi meter J
(@Ono side layer, published September 1987). In this device, a cylinder model as shown in FIG. 5 is set, where 21 indicates a piston, 22 indicates a connecting rod, and 23 indicates a crankshaft. In FIG. 5, when the stroke length is S and the connecting rod length is 2, let us calculate the rotational driving force transmitted from the piston 21 to the crankshaft 23 via the connecting rod 22, that is, the indicated mean effective pressure Pi in the cylinder. That is. Specifically, as shown in FIG. 6, one stroke is divided into A to D, and the indicated mean effective pressure Pi is calculated by a dedicated computer according to the following equations (1) to (2).

Here, ΔX(θ)=X(θ)−X(θ+2)...■ Also, X(θ) is the stroke length S1 connecting rod length l,
The offset value Δγ is calculated according to the following equation.

ΔX(θ) is calculated every two degrees when the stroke length S1 stove throat length l and offset value γ are input.

(Problem to be Solved by the Invention) However, in such a conventional indicated mean effective pressure calculation device for an engine, the indicated mean is calculated by the above-mentioned calculation method every 2 degrees of crank angle. Therefore, there was a problem that the calculation took time and required a dedicated computer, and the calculation could not be performed by the engine control computer. Additionally, installing a dedicated computer leads to high costs.

(Objective of the Invention) Therefore, the present invention calculates the amount of change in cylinder pressure at a predetermined crank angle that is symmetrical with respect to compression top dead center in the compression/explosion stroke, and converts these changes into changes in stroke volume in the explosion stroke. An object of the present invention is to simplify the calculation method by calculating the indicated mean effective pressure by correcting it with a correction coefficient corresponding to , and to provide an engine indicated mean effective pressure calculation device that can be realized at low cost.

(Means for Solving the Problems) In order to achieve the above object, the indicated mean effective pressure calculation device for an engine according to the present invention includes a pressure detection means for detecting the cylinder pressure of the engine, and a crank angle detection means for detecting the crank angle of the engine. correction coefficient setting means for setting a correction coefficient corresponding to a change in stroke volume at every predetermined crank angle when the engine is in the explosion stroke; calculating means for detecting the amount of change in the cylinder pressure at a predetermined crank angle symmetrical with respect to the compression top dead center, and correcting the amount of change using the correction coefficient to calculate the indicated mean effective pressure; It is equipped with

(Function) In the present invention, cylinder low pressure is detected at every predetermined crank angle during the compression/explosion stroke, and the amount of change in the crank angle at the rank angle is symmetrical with respect to the compression top dead center during the explosion stroke. The indicated mean effective pressure is calculated by being corrected with a correction coefficient corresponding to the change in volume.

Therefore, the method of calculating the indicated mean effective pressure is simplified,
The calculation time is significantly reduced.

(Example) Hereinafter, the present invention will be explained based on the drawings.

1 to 4 are diagrams showing an embodiment of the indicated mean effective pressure calculation device for an engine according to the present invention.

First, the configuration will be explained. FIG. 1 is a block diagram showing the overall configuration of the indicated mean effective pressure calculating device.

In FIG. 1, l is an indicated mean effective pressure calculation device,
The illustrated average effective pressure calculation device l includes a cylinder internal pressure sensor (pressure detection means) 2, a crank angle sensor (crank angle detection means) 3, a cylinder internal pressure detection circuit 4, a coefficient calculation circuit (correction coefficient setting means) 5, and a deviation calculation circuit 6. FIG. 2 shows the mounting position of the sensor when this device is applied to an engine. In FIG. 2, 11 is an engine, and the engine 11 has a cylinder 12.
A piston 13 is slidably housed therein, and the vertical movement of the piston 13 is transmitted to the crankshaft 15 via a connecting rod 14 as rotational driving force. During the intake stroke, the engine 11 moves from the intake manifold 16 to the intake valve 17.
During the compression stroke, when the piston 13 reaches a predetermined crank angle BTDC before the compression top dead center TDC, the spark plug 18 is ignited and the explosion/swelling stroke begins. At this time, the combustion pressure within the cylinder 12 pushes down the piston 13 and transmits rotational driving force to the crankshaft 15. Thereafter, the piston 13 moves up and enters the exhaust stroke, exhausting the exhaust gas in the cylinder 12 from the exhaust valve (path shown) to the exhaust pipe (path shown), completing one stroke.

Returning to FIG. 1 again, the cylinder internal pressure sensor 2 is attached to the cylinder part 12 of the engine 11 as shown in FIG.
The piezoelectric element converts the cylinder pressure (hereinafter referred to as cylinder internal pressure) into an electrical signal, and outputs this electrical signal to the cylinder internal pressure detection circuit 4. The crank angle sensor 3 is installed to detect the position (crank angle) of the crankshaft 15 as shown in FIG.
The compression top dead center (TD) of each cylinder is adjusted every 120" crank angle for a 6-cylinder engine and 180" for a 4-cylinder engine.
C) At a previous predetermined position, e.g. B T D C70° (H
) level pulse, and outputs (H
) is outputted to the cylinder internal pressure detection circuit 4 and the coefficient calculation circuit 5.

The cylinder internal pressure detection circuit 4, deviation calculation circuit 6, and summation circuit 7 have a function as calculation means 8, and are constituted by a microcomputer. Cylinder internal pressure detection circuit 4
detects the in-cylinder pressure at every predetermined crank angle (for example, 30° CA), and the detection signals Pcomb -i, Pc
Output omp-i to the deviation calculation circuit. Coefficient calculation circuit 5
calculates a correction coefficient f (i) for correcting the in-cylinder pressure at a crank angle that is symmetrical with respect to the compression top dead center TDC, and outputs it to the deviation calculation circuit 6. The deviation calculation circuit 6 calculates the deviation of the cylinder pressure at every predetermined crank angle based on the detection signals P comb·i and Pcomp-i and the correction coefficient f (i), and outputs the calculation result to the summation circuit 7 . The summation circuit 7 calculates the sum of the calculation results manually inputted from the deviation calculation circuit 6 over a predetermined crank angle section into the indicated mean effective pressure (
Torque) is calculated as Pi.

Next, the effect will be explained.

In this example, as shown in Fig. 3, the explosion stroke (0
The cylinder pressure PCOllb-1 of the compression stroke (0° to -180°) and the cylinder pressure Pcomp-i of the compression stroke (0° to -180°) are detected by the cylinder pressure detection circuit 4, and Correction coefficient f (t) (i = Q.

30°, 60° . . . 180°) are calculated by the coefficient calculation circuit 5. In the deviation calculation circuit 6, Pcomb-i
s Pc.

Deviation for every 30° crank angle based on mp-i and [(i) ((Pcomb-i, Pcomp-i)
X f (i) ) is calculated, and the summation circuit 7 calculates the following formula ■
The indicated average effective Pi is calculated according to:

= (Pcomb・o −Pcomp・@)
X f (0) + (Pcomb, .-pcO
mp'-30) X f (30)+ (Pcomb
・ha -Pcomp--bo X f (60)
・・−・＋ (Pcomb−+eo −Pco
mp--+go) It is calculated and set, and the above 30°
This is to make the accuracy of the deviation of the cylinder pressure calculated every 2 degrees equal to the accuracy of the conventional calculation performed every 2 degrees.

Therefore, if the indicated mean effective pressure Pi is calculated by the above calculation method, the calculation formula can be simplified and the calculation time can be significantly shortened. ......■ It becomes possible to perform calculations using a computer for engine control, and it can be realized at low cost.

Note that the correction coefficient f (i) may be calculated in advance according to the crank angle and stored in a predetermined memory as a table value.

(Effects) According to the present invention, the amount of change in cylinder pressure for each predetermined crank angle that is symmetrical with respect to the compression top dead center in the compression/explosion stroke is determined, and these changes are calculated as the amount of change in the stroke volume in the explosion stroke. Since the indicated mean effective pressure is calculated by correcting it with a correction coefficient corresponding to the change, the method for calculating the indicated mean effective pressure can be simplified and the calculation time can be significantly shortened. As a result, it becomes possible to calculate the indicated mean effective pressure in a conventional engine control computer, and it is possible to realize an indicated mean effective pressure calculation device for an engine at low cost.

[Brief explanation of the drawing]

1 to 4 are diagrams showing an embodiment of the indicated mean effective pressure calculating device for an engine according to the present invention, in which FIG. 1 shows the overall configuration thereof, and FIG. 2 shows the mounting position of the sensor. Figure 3 is a diagram showing the relationship between cylinder pressure and crank angle to explain the calculation method, Figure 4 is a diagram showing the relationship between the correction coefficient and crank angle, and Figure 5.6 is a diagram showing the relationship between the correction coefficient and crank angle. 5 is a diagram showing a conventional indicated mean effective pressure calculation device for an engine, FIG. 5 is a diagram showing an engine model for calculating the engine torque, and FIG. 6 is a diagram for explaining the calculation method. 1... Indicated mean effective pressure calculation device, 2...
・Cylinder internal pressure sensor (pressure detection means), 3...
・Crank angle sensor (crank angle detection means), 5...
...Coefficient calculation circuit (correction coefficient setting means), 8...
...Calculation means.

Claims (1)

[Claims] A pressure detection means for detecting the cylinder pressure of the engine, a crank angle detection means for detecting the crank angle of the engine, and a correction coefficient corresponding to the change in stroke volume at each predetermined crank angle when the engine is in the explosion stroke. a correction coefficient setting means for detecting the in-cylinder pressure during the compression/explosion stroke at each predetermined crank angle, and determining the amount of change in the in-cylinder pressure at a predetermined crank angle symmetrical to the compression top dead center; An indicated mean effective pressure computing device for an engine, comprising computing means for computing indicated mean effective pressure by capturing these changes using the correction coefficient.