JPS62180235A - In-cylinder pressure measuring instrument - Google Patents

Abstract

PURPOSE:To reduce the cost of a system and to mount it on even an engine in operation by detecting a start period of exhaustion from variation in in- cylinder pressure and finding a crank position on the basis of it. CONSTITUTION:A signal outputted from an in-cylinder sensor 2 is differentiated 4 to find the rate of variation in in-cylinder pressure, and the output result has two plus-side and minus-side peaks. The latter minus-side peak is generated on the basis of the start period of exhaustion as a start point and an exhaustion start period calculation device 5 detects it for >=2 turns of the engine. The elapsed time between those two peaks is measured by a frequency divider 6 to obtain a time T. When the top dead center (TDC) of the engine is 120 deg. before the exhaustion start period, the TDC is TX240/360sec after the point (A). At the same time, the elapsed time from the point (A), i.e. T/360sec is obtained as in-cylinder pressure data of every crank angle 1 deg.. Thus, the TDC and time of every crank angle are found and displayed 7 having the time information on a lateral axis and in-cylinder pressure on a longitudinal axis, thereby measuring variation in pressure to the crank angle.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a cylinder pressure measuring device for an internal combustion engine.

[Conventional technology]

FIG. 3 shows an example of a conventional cylinder pressure measuring device for an internal combustion engine.

In the figure, 1 is an internal combustion engine, 2 is a cylinder pressure sensor installed to continuously measure the explosion pressure in the cylinder of the internal combustion engine 1, and 3 is the top dead center (TDC) and crank angle ( In other words, a crank position sensor is attached to the end of the crankshaft to detect the piston position of the internal combustion engine 1.

7 is a display device.

The display device 7 displays the cylinder pressure from the cylinder pressure sensor 2 with the crank angle from the crank position sensor as the horizontal axis.

[Problem that the invention seeks to solve]

However, in the conventional type, it was necessary to install a crank position sensor 3 in order to correlate the cylinder pressure signal with the crank position.

This causes the following problems.

(7) In order to install the crank position sensor 3, it is necessary to modify or change the design of the internal combustion engine (hereinafter referred to as the engine). For this reason, the cylinder pressure measurement system becomes extremely expensive.

(b) Since it is difficult to modify an engine while it is in operation,
Adding a cylinder pressure measurement system to this would be extremely difficult.

The present invention has been made in view of the above, and an object of the present invention is to provide a cylinder pressure measuring device that does not require a crank position sensor and has exactly the same functions as a conventional cylinder pressure measuring system by using only a signal from a cylinder pressure sensor. With the goal.

[Means for solving problems]

In general, the in-cylinder pressure changes depending on the strokes of the internal combustion engine, such as compression, explosion, expansion, and exhaust.

This pressure tends to drop rapidly when evacuation begins (ie, when the evacuation valve or boat opens).

This exhaust start timing is determined at a predetermined position on the crankshaft and is mechanically fixed.

It does not change.

The present invention focuses on the above-mentioned phenomenon, detects the exhaust start timing from changes in cylinder pressure, and determines the crank position, that is, the piston position based on the exhaust start timing, thereby eliminating the need for a crank position sensor. shall be.

[Effect]

By having the above-mentioned configuration, the present invention can process the output signal of the cylinder pressure sensor with a differentiator, determine the rate of change in the cylinder pressure, and determine the exhaust start timing from this result.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Reference numeral 1 denotes an internal combustion engine, 2 a cylinder pressure sensor for detecting the cylinder pressure of the internal combustion engine l, and 7 a cylinder pressure sensor for detecting the cylinder pressure. It is a display device for displaying images.

4 is a differentiator for differentiating the cylinder pressure detection signal from the cylinder pressure sensor 2 to obtain the rate of change in cylinder pressure; 5 is an exhaust start for determining the exhaust start timing from the output signal from the differentiator 4; The timing calculator 6 is a frequency divider that calculates the elapsed time between one cycle of the exhaust start timing from the output signal from the exhaust start timing calculator 5.

The operation of the cylinder pressure measuring device having the above configuration will be explained.

The cylinder pressure sensor 2 outputs the signal shown in graph 1 of FIG. When this signal is processed by the differentiator 4, the rate of change in the cylinder pressure is determined, and graph 2 in FIG. 2 is obtained. As shown in graph 2, the output result from the differentiator 4 of the in-cylinder pressure has two peaks on the plus (±) side and two peaks on the minus (-) side.

The latter portion of this negative mountain occurs starting from the exhaust start time.

Therefore, the exhaust start timing calculator 5 detects the latter peak on the negative side for two or more revolutions of the engine. The elapsed time between these two peaks is measured by the frequency divider 6, and the measurement result is defined as the time T (seconds) in FIG.

Here, assuming that the top dead center (TDC) of the engine is 1200 minutes before the exhaust start time, the top dead center (TDC) is T x 240/360 = Ti (
seconds) later.

If it is desired to obtain cylinder pressure data for each crank angle of 1° at the same time, the time T (seconds) is divided into 360 equal parts, and the elapsed time from the point corresponding to each crank angle is obtained.

The time at top dead center (TDC) and the time for each crank angle are determined by the frequency divider 6 using the method described above.

The time information for each crank angle has the same function as the conventional crank position sensor 3 shown in FIG.

Therefore, in the display device 7, if the X-axis (horizontal axis) is the time information obtained by the frequency divider, and the cylinder pressure measured at the same time as this time is displayed on the Y-axis (vertical axis), as shown in FIG. This results in the same display results as the conventional system shown in .

〔Effect of the invention〕

The present invention is constructed as described above, and according to the present invention, changes in cylinder pressure relative to crank angle can be measured simply by detecting changes in cylinder pressure, and a rank position sensor is not required unlike conventional ones. Become. As a result, the cost of the in-cylinder pressure measurement system becomes low, and the system can be easily installed on an engine that is in operation.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing one embodiment of a cylinder pressure measuring device according to the present invention, and FIG. 2 is a diagram for explaining the present invention in detail. FIG. 3 is a system diagram showing an example of a conventional cylinder pressure measuring device. ■... Internal combustion engine, 2... Cylinder pressure sensor, 4...
Differentiator, 5... Exhaust start time calculator, 6... Frequency divider, 7... Display. 1 person Sakama Akigoto etc. Figure 1 ``) Ward 3

Claims (1)

[Claims] In a device that detects the cylinder pressure of an internal combustion engine using a cylinder pressure sensor and displays it on a display device, there is a differentiator for determining the rate of change in the cylinder pressure output from the cylinder pressure sensor, and an output signal from the differentiator. Cylinder pressure measurement characterized by comprising: an exhaust timing calculator that calculates the exhaust start timing; and a frequency divider that calculates the elapsed time from the cylinder pressure detection signal to the exhaust start timing between cycles of the engine. Device.