JPS6348297B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring intake air pressure necessary for engine control, and relates to an improved method for measuring intake air pressure so as to eliminate measurement errors due to intake pulsation.

The intake pressure measurement technique itself is known, in which the intake pressure in the intake pipe is sampled under certain conditions in synchronization with engine rotation.

When measuring the intake pressure using conventional technology, it is necessary to set a throttle at the pressure outlet to sufficiently suppress the intake pulsation, to smooth the input pressure signal using a circuit and average it, or to measure the intake pressure by adjusting the engine crank angle. There was a method of collecting samples within a certain angle range of the axis.

The above method of dulling the pressure or pressure signal has the disadvantage that the response is significantly delayed during transitions when the intake pressure fluctuates, and when sampling within a certain range of crank angle positions, the engine speed,
Accurate measurement was difficult because the pressure waveform of the intake pulsation varied greatly depending on the load condition and pressure extraction specifications.

An object of the present invention is to provide a method for accurately measuring the average value of intake air pressure without impairing responsiveness and without being affected by intake pulsation, and this method is based on the following principles. There is.

Intake air pressure decreases during the intake stroke of the engine and increases during other strokes, so it has a pressure change that is synchronized with the intake stroke, ie, intake pulsation. If sufficient attention is paid to the detection position of the intake pressure, this intake pulsation waveform can be approximated by a sine wave. Therefore, if the average value of the intake pressure is f(t) (here, t is time), the intake pressure P(t) can be expressed by the following equation.

P(t)=f(t)+a(t)sin(2πt/τ) where a(t): Amplitude of intake pulsation τ: Intake pulsation period π: Pi What we want to measure is the average pressure f(t ), so
It is sufficient to remove the influence of a(t) sin (2πt/τ), which is a pulsation term. Therefore, if we choose the first pressure sampling point as t ₁ and the next pressure sampling point as t ₂ = t ₁ + τ/2, then sin(2π(t ₁ + τ/2)/τ) = sin(2πt ₁ /τ+
Since π) = -sin(2πt ₁ /τ), the sum of the pressures at two points is P(t ₁ ) + P(t ₂ ) = f(t ₁ ) + f(t ₂ ) + (a(t ₁ ) −a(t ₂ )) sin(2πt ₁ /τ). Inspiratory pulsation amplitude a during half period τ/2
Since the change a(t ₁ )−a(t ₂ ) in (t) is small and can be ignored compared to f(t), P(t ₁ )+P(t ₂ )≒f(t ₁ )+f(t ₂ ). . In other words, if the intake pressures P(t ₁ ) and P(t ₂ ) at two points t ₁ and t ₂ (=t ₁ +τ/2) are measured and the average is calculated, the average intake pressure (f(t ₁ ) +f
(t ₂ ))/2 can be obtained.

At this time, even if the engine speed is changing, that is, the intake pulsation period is changing, the intake pulsation period can be determined from certain crankshaft rotation angles θ ₁ and θ ₁ obtained from the engine crankshaft rotation angle detection device as the pressure signal collection timing. By selecting a crankshaft rotation angle θ ₂ that corresponds to 1/2 period after , the influence of intake pulsation can be removed.

The method of the present invention includes an engine crankshaft rotation angle detection device, a pressure transducer or a detector provided between the throttle valve and the cylinder inlet, and a measurement timing based on the engine crankshaft rotation angle position. This can be carried out by an intake pressure measuring device constituted by a device for storing and arithmetic processing the obtained pressure signal.

The present invention will be explained below with reference to embodiments shown in the drawings. FIG. 1 is a block diagram of a device for carrying out the method of the present invention, in which 1 is an engine, 2 is a converter or detector for detecting its intake pressure, 3 is a device for detecting a crankshaft rotation angle, and 4 is a device for detecting a crankshaft rotation angle. is an arithmetic circuit equipped with a microcomputer, which inputs signals from the crankshaft rotation angle detection device 3 and the intake pressure detector 2, and calculates the average intake pressure according to a predetermined program.

FIG. 2 shows the processing procedure in the arithmetic circuit 4. A signal 403 is received from the crankshaft rotation angle detection device 3 every half period τ/2 of the intake pulsation, and a signal 402 from the pressure detector 2 is collected. At this time, if the intake pressure is not stored in the storage device, this sampled signal 404 is stored as the intake pressure a. When the next signal after τ/2 is collected, it is set as the intake pressure signal b that was collected this time, and the intake pressure signal a stored in the storage device is
The pressure signal b is stored in the storage device as the pressure signal a, and the average pressure is output from 408. The above process is repeated every half period τ/2.

Figure 3 is a flowchart showing the above processing procedure, starting with the signal from the crankshaft rotation angle detection device, collecting the pressure signal Pi, and if this is the first sampling (K = 0), it is stored. If it is the second time or later (K=1), the average of the stored pressure Pi−1 and the pressure Pi sampled this time is calculated and output, and the pressure Pi sampled this time is used as the previous pressure.
Rewrite it as Pi-1 and store it.

Figure 4 shows an 1800c.c. 4-cylinder cycle gasoline engine with a rotation speed of 1000r.pm and negative intake pressure of -100mm.
This is the inspiratory pulsation during Hg. Normal intake pulsation period τ can be expressed as (360° x number of cycles)/2 x number of cylinders in terms of crankshaft rotation angle. In the case of the above engine, τ=180° CA (crankshaft rotation angle). The procedure for carrying out the method of the present invention in the case of the above-mentioned engine will be explained below, and the experimental results will be attached. In the figure, #4, #2, #1, #3 are cylinder numbers,
TDC indicates top dead center. First, pressure P1 is sampled and stored at T1, pressure P2 is sampled at T2, and the average (P1+P2)/2 thereof is output and P2 is stored. Next, pressure P3 is sampled at T3, and the average pressure (P2+P3)/2 is output and P3 is stored. The above process is then repeated one after another.

Figure 5 shows the experimental results. T1, T2, T3,
T4 is the timing at which the pressure signal is sampled, and here T1 is the crankshaft rotation angle of 45 degrees, and pressure signals are sampled every 90 degrees thereafter. The pressures at T1, T2, T3, and T4 are P1, P2, P3, and P4, respectively. These are the measurement results of Pm according to the method of the present invention.

In the above embodiment, the half cycle of the intake pulsation τ/
The pressure was sampled every 2 hours, and the average of the previous value and the current value was calculated. However, if you want to calculate the average of one engine revolution or the average of n engine revolutions, take the pressure of 2M intake pulsations that occur during that time. It is sufficient to collect the pressure signals, store them in a storage device, and calculate their average.

As is clear from the above explanation, in the present invention, pressure signals are collected at two points: a certain rotational angular position of the engine crankshaft and an angular position 1/2 period after the intake pulsation period from that angular position. The value of the pressure signal obtained is stored by replacing it with the value of the pressure signal collected last time, and the intake pressure is measured by instantly calculating the average of the values of these two pressure signals after the pressure signal is collected. , it is possible to instantaneously and accurately measure the average intake pressure without being affected by the magnitude of the amplitude of intake pulsation or phase shift, and without delay in response. Moreover, since the value of the newly measured pressure signal is replaced with the value of the previously measured pressure signal and stored, the storage device can be configured with one memory to implement this method, and the memory capacity is small. All you need is the necessary equipment, and pressure measurement can be carried out extremely easily.

Thus, when using the method of the present invention, in effect 1
By measuring the pressure at the same time (that is, the result of the previous pressure measurement is memorized), it is possible to detect the intake pressure at that time and control the engine, which is extremely useful for increasing the engine speed. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an apparatus for carrying out the method of the present invention, FIG. 2 is an explanatory diagram showing the signal flow of the arithmetic circuit in FIG. 1, and FIG. 3 is a diagram showing the signal flow of the arithmetic circuit in FIG. A flowchart showing the flow, Figure 4 shows the 4-cylinder 4
FIG. 5, a characteristic diagram showing the intake pulsation in a cycle engine, is a diagram showing the results of an experiment in which the intake pressure shown in FIG. 4 was measured by the method of the present invention. 1: Engine, 2: Pressure detector, 3: Crankshaft rotation angle detection device, 4: Arithmetic circuit.

Claims (1)

[Claims] 1 In a method for measuring intake pressure in an engine having an engine crankshaft rotation angle detection device and a pressure transducer or pressure detector located between a throttle valve and a cylinder inlet, a certain rotational angular position of the engine crankshaft and its angle Collect pressure signals at two points at the angular position after 1/2 period of the intake pulsation period from the position,
The value of the pressure signal collected this time is replaced with the value of the pressure signal collected last time and stored, and after the pressure signal is collected, the intake pressure is measured by instantly finding the average of the values of these two pressure signals. How to do it.