JPH01227034A - Detecting apparatus of inner-cylinder pressure - Google Patents

Abstract

PURPOSE:To detect the state of combustion inside a cylinder, by detecting a peak position of a combustion pressure by means of a detection signal of a peak position detector, while detecting a timing value thereof. CONSTITUTION:A waveform of a combustion pressure inside a cylinder is once stored in a waveform memory 1. Starting at a time when a piston comes to a compression to dead center, subsequently, the waveform stored in the memory 1 is read out, and the waveform read out in a sequence reverse to the one in which it is inputted is inputted to one input of a subtracter 2. The same waveform as that inputted to the memory 1 is inputted to the other input of the subtracter 2 and a subtraction of waveforms is executed therein. From an output waveform therefrom, a timing value (thetapmax) is detected by a peak position detector 3. Meanwhile, a pressure peak value Pmax at the time of detection of a peak position is obtained from a latch circuit 4 which latches the waveform inputted to the memory 1. By detecting the peak value of the waveform and the timing value thereof in this way, the state of combustion inside the cylinder can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an in-cylinder pressure detection device that detects a peak value of combustion pressure in a cylinder of an internal combustion engine and a timing value of the peak of combustion pressure.

[Prior Art] FIG. 3 is a schematic diagram of a conventional cylinder pressure detection device. (
5) is a detector that detects the peak value (P, , ) of the waveform and its timing value (θ911@11) from the combustion pressure waveform in the cylinder detected by the cylinder pressure sensor (not shown).

Figure 4 shows the peak value of combustion pressure and motoring P1,8.
In Figure 0, which is a diagram showing the pressure waveform in the case of the magnitude relationship of
1. (b) shows the pressure waveform when the peak value of combustion pressure≦motoring P1.8.

[Problems to be Solved by the Invention] In the conventional cylinder pressure detection device as described above, as shown in FIG.
In the pressure waveform of , the peak value of the combustion pressure is larger than the motoring P, -, so the peak value of the combustion pressure can be easily detected.

When the combustion pressure peak is smaller than the motoring P1, 8 as in the case of Fig. 4(b), it is very difficult to detect the combustion pressure peak position and peak value, especially when there is no maximum value. The problem was that it was difficult to

This invention was made to solve this problem, and the peak value of combustion pressure ≦ motoring P sa
An object of the present invention is to obtain a cylinder pressure detection device that can detect a peak value of combustion pressure and a timing value of combustion pressure by simple subtraction processing even in the case of x.

[Means for Solving Problem M] The in-cylinder pressure detection device according to the present invention includes a waveform memory that stores a combustion pressure waveform in a cylinder for a predetermined period, and inputs the pressure waveform stored in this waveform memory. a subtracter that subtracts the input pressure waveform from a pressure waveform read out sequentially in reverse order; a peak position detector that detects the peak position of the output waveform from the subtractor; and a latch that latches the input pressure waveform value. It is equipped with a circuit.

[Operations] In this invention, the peak position of combustion pressure is detected by the detection signal of the peak value detector, and the combustion pressure value at the peak position is detected from the latch circuit based on this detection signal.

[Embodiment] Fig. 1 is a block diagram showing the configuration of a cylinder pressure detection device according to an embodiment of the present invention. In Fig. 6, (1) is a waveform memory in which combustion pressure waveforms are sequentially input and stored. Then, at the time of reading, a reading circuit (not shown) reads out the data in the reverse direction to the sequential input order. (2) is a subtracter that subtracts the waveform read from the waveform memory (1) and the waveform input to the waveform memory (1). (3
) is a peak position detector that detects the peak position of the output waveform from the subtracter (2), and (4) is a latch circuit that latches the combustion pressure input waveform.

FIG. 2 is a diagram showing operating waveforms of each part in FIG. 1.

In the cylinder pressure detection device configured as described above, the second
The combustion pressure waveform shown in figure (a) is stored in the waveform memory (
1) and is temporarily stored in the waveform memory (1). Next, the piston of engine 1 reaches compression top dead center (T D
From the period C) onwards, the waveforms stored in the waveform memory (1) are read out by a reading circuit (not shown) in the reverse order of input, and the waveforms are input to one side of the subtracter (2). Ru. Furthermore, the same waveform as the 6 waveforms applied to the input terminal of the waveform memory (1) is applied to the other input of the subtractor (2), and the waveforms are subtracted there, as shown in Fig. 2(b).
The output waveform shown in is obtained. From this output waveform, the peak position detector (3) detects the peak timing value (
θP@all > is detected. On the other hand, the waveform memory (1
) can obtain the pressure peak value (P, . . . ) at the peak position detection time from the latch circuit (4) which latches the waveform applied to the input terminal of the pressure sensor.

As mentioned above, the peak value (P,) of the combustion pressure waveform.

, ) and its timing value (θ2.8°), the combustion condition inside the cylinder can be detected.

[Effects of the Invention] As described above, the present invention includes a waveform memory that stores combustion pressure waveforms in a cylinder for a predetermined period.

A subtracter that subtracts the input pressure waveform from the pressure waveform that is read out sequentially in the reverse order of inputting the pressure waveform stored in the waveform memory, and a peak that detects the peak position of the output waveform from this subtracter. Since the engine is equipped with a position detector and a latch circuit that latches the input pressure waveform, the combustion state can be detected with high accuracy even when the engine is idling.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a cylinder pressure detection device according to an embodiment of the present invention, Fig. 2 is an operation waveform diagram of each part of Fig. 1, Fig. 3 is a schematic diagram of a conventional cylinder pressure detection device, and Fig. 4 is a pressure waveform diagram in the cylinder of the engine. In the figures, (1)... Waveform memory, (2)... Subtractor, (3)... Peak position detector, (4)... Figure 1, Figure 2, Figure 3, Broom, Figure 4. Procedural amendment August 3, 1986

Claims (1)

[Claims] a waveform storage means for storing a cylinder pressure waveform for a predetermined period; a subtraction means for subtracting the input pressure waveform from a pressure waveform sequentially read out in the reverse order of inputting the pressure waveforms stored in the waveform storage means; A peak position detection means for detecting the peak position of the output waveform of the subtraction means, and a latch means for latching the input pressure waveform at the time when the peak position detection means is detected by the peak position detection means, and the detection signal from the peak value detection means is provided. An in-cylinder pressure detection device characterized in that the peak position of combustion pressure in the cylinder is detected and the combustion pressure value at the peak position is detected from the latch means based on the detection signal.