JPH0562202B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for monitoring a blow-by phenomenon in an intake valve or an exhaust valve of an internal combustion engine.

[Prior art]

FIG. 1 shows the structure around the combustion chamber of an internal combustion engine as seen from the exhaust valve side. In FIG. 1, the combustion chamber is comprised of a cylinder lid 10 and a liner 12. An exhaust valve housing 18 is attached to the cylinder lid 10, and an exhaust valve 16 is installed in the housing so as to be slidable in the vertical direction. An exhaust branch pipe 20 is connected to the exhaust valve housing 18, and an exhaust pipe 22 is further connected thereto.

As shown in FIG. 2, the blow-through phenomenon of the exhaust valve 16 occurs when a part of the face portion 16a of the exhaust valve 16 is corroded at high temperature by combustion gas, and a concave hole 24 is formed. , exhaust valve 16
The face portion 16a and the seat surface 1 of the exhaust valve housing 18
This is a phenomenon in which the combustion gas 25 during the explosion stroke leaks from the blow-through hole 24 due to poor airtightness with the blow-through hole 24. Once this blow-through phenomenon occurs,
Due to the erosion caused by the blow-through, the blow-through hole 24 becomes larger and larger, resulting in a decrease in output, so early detection is desired.

A conventional method for detecting the blow-by phenomenon of an exhaust valve is to install a thermometer 26 inside the exhaust branch pipe 20, and to detect this by utilizing the fact that an abnormally high temperature is measured when combustion gas blows through. However, with this method, detection is impossible unless the blow-through hole 24 of the exhaust valve 16 becomes considerably large and the heat capacity of the blow-through gas 25 becomes large.

In addition, the blow-by phenomenon of the intake valve is caused by the cylinder lid 1
This is a phenomenon in which 0 is subjected to low-temperature corrosion, creating concave holes, through which combustion gas blows. Once this phenomenon occurs, combustion gas blows through the blow-through hole, causing further corrosion, and holes also form on the face of the intake valve.

A conventional method for detecting the blow-by phenomenon of an intake valve is to detect the temperature of the intake pipe by utilizing the heating of the intake pipe due to the blow-by of combustion gas. However, even in this case, it was impossible to detect the hole unless it became considerably large.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a blow-through monitoring device that can detect a blow-through phenomenon of an intake valve or an exhaust valve at an early stage.

[Structure of the invention]

This invention makes it possible to detect a blow-by phenomenon even at an early stage by detecting the flame light of blow-by gas at an intake port or an exhaust port behind an intake valve or an exhaust valve. Flames observed at the intake port or exhaust port include flames observed when a valve opens during a normal intake stroke or exhaust stroke, in addition to those caused by blow-by gas. For example, as shown in the following example, By controlling the detection timing by the crank angle, flame caused by blow-by gas can be detected.

〔Example〕

FIG. 3 shows an embodiment in which the present invention is applied to an exhaust valve of a four-stroke internal combustion engine.

In FIG. 3, an exhaust valve housing 18 is attached to the cylinder lid 10, and an exhaust valve 16 is attached therein so as to be slidable in the vertical direction. A hole 30 is formed through the exhaust valve housing 18 and the cylinder housing 10, into which a heat-resistant optical fiber 32 is inserted and fixed. The tip of the optical fiber 32 is connected to the face portion 16 of the exhaust valve 16.
It faces the exhaust port 33 formed behind the cylinder a, so that the flame of the blow-by gas 25 flowing out from inside the cylinder to the exhaust port 33 can be detected.

The light detected by the optical fiber 32 is guided to an optical power meter 34. The optical power meter 34 is
It converts input light into an electrical signal of a magnitude corresponding to the amount of light, and is composed of optical sensors such as photodiodes and phototransistors.
The output signal of the optical power meter 34 is input to the control device 36.

The crank angle detection sensor 38 detects the crank angle and instructs the timing to detect the blow-through phenomenon in order to prevent the flame of combustion gas during normal exhaust from being mistakenly detected as being due to the blow-through phenomenon. . That is, as shown in FIG. 4a, for example, the range of angle θ from the compression stroke to the explosion stroke, from when the intake valve closes until the exhaust valve 16 opens, is designated as the timing for detecting the blow-through phenomenon. This crank angle detection sensor 38 can be detected, for example, by attaching a marking to the flywheel 42 attached to the crankshaft 40 and detecting it with an optical sensor (however, it is detected once every two rotations of the crankshaft 40). ), the above angle θ
Detection is performed.

The control circuit 36 receives the flame detection signal outputted from the optical power meter 34 and the crank angle detection signal outputted from the crank angle detection sensor 38, and detects the blow-through phenomenon. That is, the control circuit 36 inputs the flame detection signal to the gate circuit (analog switch) 44, turns on the gate circuit 44 during the period in which the crank angle detection sensor 38 detects the angle θ, and outputs the flame detection signal. Output. As shown in FIG. 4b, the flame detection signal input to the gate circuit 44 includes those caused by the blow-through phenomenon (indicated by) and those caused by normal exhaust (indicated by); The gate circuit 44 is judged here.
As shown in FIG. 4d, only the output due to the blow-through phenomenon is output.

The output of the gate circuit 44 is smoothed in a smoothing circuit 46 as shown in FIG. 4d. This smoothing circuit 46 prevents erroneous detection of sudden blowholes due to causes other than the blowhole 24, and calculates the amount of light, that is, the approximate size of the blowhole 24 by averaging the signals. used for The output of the smoothing circuit 46 is sent as it is to the display device 48 to display the amount of light, and is also input to the comparator 50, and if it exceeds the set level Vr, it is determined that a blow-through phenomenon has occurred, and the comparator The output of 50 is shown in Figure 4 e.
As shown in FIG. 2, the signal becomes "1" and the alarm 52 issues an alarm.

[Example of change]

[] In the above embodiment, by detecting the crank angle and controlling the timing of flame detection, flames caused by the blow-through phenomenon are determined from among all the flames observed at the exhaust port 33. In addition to this method, the following methods can be considered, for example.

(b) Method of determination based on level difference As shown in Figure 4b, there is a level difference between the flame intensity during normal exhaust and the flame intensity due to the blow-through phenomenon, so it is determined that the flame is during normal exhaust. By setting a level and excluding anything above that level, it is possible to determine the flame caused by the blow-through phenomenon.

(b) Method of determining by checking the number of flames detected during one cycle As shown in Figure 4b, when the blow-through phenomenon occurs, flames occur twice during one cycle from intake to exhaust. When no blow-by occurs, only flames caused by normal exhaust gas are detected, so the flames caused by the blow-by phenomenon can be determined from the number of flames detected during one cycle.

(c) Method of determining by waveform When a blow-through phenomenon occurs, the flame detection signal has a waveform as shown in Figure 4b.
By detecting this pattern, it is possible to identify flames caused by the blow-through phenomenon.

[] In the above embodiment, the present invention was applied to a 4-stroke internal combustion engine, but in the case of a 2-stroke internal combustion engine, the detection timing is set to the crankshaft, excluding the exhaust stroke, as shown in FIG. Detection may be performed in the same manner by setting the angle within the range of angle θ'.

[] In the above embodiment, the case where the present invention is applied to an exhaust valve is shown, but when the present invention is applied to an intake valve, the blow-through phenomenon can be detected with the same configuration as shown in FIG. 3.

[] In the above embodiment, the light from the exhaust port 33 is guided to the optical sensor (optical power meter 34) via the optical fiber 32, but if a heat-resistant optical sensor is used, this can be directly guided to the exhaust port. It is also possible to install it in 33.

〔Effect of the invention〕

As explained above, according to the present invention, the blow-by phenomenon is detected by detecting the light from the intake port and exhaust port behind the valve, so that it is possible to detect the blow-by phenomenon even at the very early stage. Become.

In addition, as shown in the example, detecting via an optical fiber requires less space for installing the optical sensor at the intake port or exhaust port, which is advantageous in terms of design. The device can be moved away from the room, increasing the reliability of the device.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure around the combustion chamber of an internal combustion engine as seen from the exhaust valve side, FIG. 2 is a view showing the blow-through phenomenon in the exhaust valve 16, and FIG. 3 is a view showing an embodiment of the present invention. 4 is an explanatory diagram of the operation of the control system in FIG. 3, and FIG. 5 is a diagram showing the crank angle for detecting the blow-through phenomenon in a two-stroke internal combustion engine. FIG. 3 is a diagram showing an example of timing. 10...Cylinder lid, 12...Liner, 16...
...Exhaust valve, 16a...Exhaust valve face part, 18...
...Exhaust valve housing, 18a...Exhaust valve housing seal portion, 20
...Exhaust branch pipe, 22...Exhaust pipe, 24...Blowout pipe, 25...Blowout gas, 26...Thermometer,
32...Optical fiber, 33...Exhaust port, 3
8...Crank angle detection sensor, 40...Crankshaft, 42...Flywheel,...Flame detection signal due to exhaust gas,...Flame detection signal due to blow-through phenomenon.

Claims (1)

[Claims] 1. In an internal combustion engine equipped with a means for detecting the flame light of blow-through gas flowing from inside the cylinder to the intake port or exhaust port behind the intake valve or exhaust valve. Air blow-by monitoring device for intake or exhaust valves.