GB2054037A

GB2054037A - Detonation suppression in i.c. engines by supply of anti-knock fluids

Info

Publication number: GB2054037A
Application number: GB8021601A
Authority: GB
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1979-07-12
Filing date: 1980-07-02
Publication date: 1981-02-11
Also published as: FR2461102A1; GB2054037B; DE3026206A1; JPS5612043A; FR2461102B1

Abstract

Exhaust gas, water or alcohol is supplied to the engine intake 2 in response to a detonation vibration sensor 11. <IMAGE>

Description

SPECIFICATION Detonation or knocking avoidance device The present invention relates to a device for avoiding or suppressing detonation in an engine by lowering the combustion gas temperature as a result of introducing exhaust gas, or water, into the intake air.

It is known that continuous severe detonation of an engine detrimentally affects the durability and other characteristics of the engine. There is a correlation between the occurrence of detonation and the ignition timing. In general the occurrence of detonation increases by advancing the ignition timing.

There is known a device in which the ignition timing is retarded in response to severe detonation in an engine so as to avoid such detonation.

However, in such a device, the engine output is lowered by an amount corresponding to the degree of retardation of the ignition timing from the "minimum advance for best torque" (MBT) and also there is an increase in the fuel cost.

When the combustion gas temperature is lowered by the mixing of exhaust gas, or water, with the intake air, detonation can be suppressed.

But in this arrangement the deterioration of the engine output and the fuel cost characteristics is smaller in comparison with the above arrangement in which the ignition timing is retarded.

The present invention has for its object to provide a device, in which the fuel cost and/or the engine output characteristics can be improved compared with the conventional device by mixing an exhaust gas, or water or other fluid into the intake air when severe detonation occurs while always maintaining the ignition timing near the minimum advance for best torque (MBT).

The invention will now be described in greater detail with reference to the accompanying drawings, wherein: Fig. 1 is a simplified schematic diagram showing a first embodiment of the present invention; Fig. 2 is also a simplified schematic diagram showing a second embodiment of the present invention; and Fig. 3 is a third embodiment of the same.

Fig. 1 is a first embodiment of the present invention and it shows only the essential portion of the engine and the device.

In this figure, 1 represents the engine block, 2 is an intake conduit, 3 an exhaust conduit, 4 a throttle conduit, and 6 an exhaust gas recirculating valve means.

A three-way electromagnetic valve 7 is provided. Under non-detonating conditions, this valve 7 communicates a passageway 8a having an opening end upstream and adjacent the throttle valve 4 with a passageway 8b having an opening end in an operating chamber 6a of the exhaust gas recirculating valve means 6. The valve 6 opens or closes according to the vacuum negative pressure in the chamber 6a the same as in the conventional device.

On the other hand, under a detonating condition, the three-way electromagnetic valve 7 operates to communicate the passageway 8b with a passageway 8c having its open end connected to a vacuum tank 10 which accumulates the intake negative pressure through a check valve 9 so as to introduce the negative pressure into the operating chamber 6a thus forcibly opening the valve means 6 so that the exhaust gas is introduced into the intake air.

A detonation sensor 11, a detonation judging circuit 12, a monostable multivibrator 13, and an operating circuit 14 constitute a control system for detecting the detonation condition and switching the three-way electromagnetic valve 7.

It is known that a vibration component of a particular frequency increases in respect to the vibration of the engine block 1 when detonation occurs. For detecting the occurrence of detonation, by using this phenomena, the sensor 11 converts the abovementioned vibration component of the particular frequency into an electrical signal.

The detonation judging circuit 12 detects the relative variation of the output signal of the sensor 1 for instance, the output signal of the sensor 11 is compared with the mean value of the same signal and an assessment of the engine detonation is made when the number of occurrence of peak values of the output signal of the sensor 11 exceeding the mean value thereof, reaches or exceeds a certain standard number with respect to a predetermined crank angle and the circuit 12 delivers a detonation detection pulse.

Upon delivery of this detonation detection pulse, the operating circuit 14 operates to energize and to switch over the three-way electromagnetic valve 7 to connect the passageway 8c in place of the passageway 8a with the passageway Bb for a minimum required period defined by the monostable multivibrator 13, thus opening the valve means 6 to mix the exhaust gas with the intake air.

Now the operation of the system will be explained in more detail. When detonation occurs in an engine, the vibration component of the aforementioned particular frequency in the vibration of the engine block suddenly increases and the output signal of the sensor 11 detecting the vibration increases very rapidly at the same time.

The detonation judging circuit 12 judges the detonating condition and delivers a detonating detection pulse output.

Based on this detonation detection pulse, output, the operating circuit 14 energizes and switches the three-way electromagnetic valve 7 to connect the passageway 8c (instead of 8a) with the passageway Bb for a period defined by the monostable multivibrator 1 3.

Under this condition, a high negative pressure is introduced into the operating chamber 6a of the valve means 6 which opens (or its degree of opening is increased) so that a large amount of exhaust gas, much larger than under the normal vacuum negative pressure, is introduced into the intake air.

By this increase of the amount of exhaust gas into the intake air, the combustion gas temperature is relatively lowered resulting in the suppression or avoidance of the detonation.

When comparing the known system of delaying the ignition timing, the practice of the present invention to avoid detonation by mixing the exhaust gas with the intake air is advantageous in the engine output and fuel cost characteristics.

According to the present invention, the ignition timing can always be kept near the minimum advance for best torque (MBT) so that the output and the fuel cost characteristics can be improved compared with the conventional system.

In the embodiment shown in Fig. 2, there are provided a water tank 1 5, a passageway 8dfor communicating the water tank 1 5 with the intake air tube 2 downstream of the throttle valve 4 and an electromagnetic valve 7' for closing or opening the passageway 8d. When the detonation occurs, the electromagnetic valve 7 is opened and water flows through the passageway 8d and restricted orifice 1 6 to be mixed with the intake air. Thus the combustion gas temperature is lowered and the detonation is suppressed or terminated. The other components are the same as those in Fig. 1 and designated by the same reference numerals, but the detailed explanation thereof is omitted. This embodiment produces the same effect as that shown in Fig. 1.

The same effect can be obtained by introducing tertiary buthyl alcohol (TBA), methyl tertiary buthyl alcohol, Gasohol, ethyl alcohol, etc instead of water.

Fig. 3 shows the third embodiment of the present invention in a simplified form. In this embodiment, a by-passbpassageway 17 is connected to the exhaust conduit 3 and a portion of the exhaust gas is introduced into a condenser 19 cooled by cooling fins 18 to extract the moisture component in the exhaust gas by condensation. This water is introduced into the intake air through the passageway 8dand other components the same as shown in Fig. 1. By this embodiment, the difficulty of maintaining a water reservoir for feeding water into the intake air is avoided.

Components similar to those of Fig. 1 have the same reference numerals and this embodiment produces the same effect as that of Fig. 2.

As has been explained in the foregoing, according to the present invention, the occurrence of detonation is suppressed or avoided by mixing exhaust gas, or water, or other suitable fluid into the intake air and by lowering the combustion temperature so that the ignition timing can be kept near the minimum advance for best torque (MBT), which results in greatly improved characteristics compared with the conventional device using the principle of delaying the ignition timing.

Claims

1. A detonation suppression or avoidance device comprising means for detecting occurrence of detonation based on the resultant vibration of an engine, and means for introducing a fluid into the intake air for lowering the combustion gas temperature upon the occurrence of detonation in response to the detected output signal of said detecting means.

2. A detonation suppression or avoidance device as claimed in claim 1, wherein the introducing means introduces at least one of exhaust gas, water, tertiary butyl alcohol, methyl tertiary butyl alcohol, Gashol, or ethyl alcohol.

3. A detonation suppression or avoidance device as claimed in claim 1 or 2, wherein said introducing means includes an electromagnetic valve having control means comprising a detonation sensor mounted on the engine, a detonation judging circuit and a monostable multivibrator.

4. A detonation suppression or avoidance device as claimed in claim 3, wherein said electromagnetic valve controls the flow of exhaust gas into the engine air intake at a point downstream of the throttle valve by means of a vacuum-operated valve.

5. A detonation suppression or avoidance device as claimed in claim 3, wherein said electromagnetic valve controls the flow of water from a reservoir into the engine air intake at a point downstream of the throttle valve.

6. A detonation suppression or avoidance device as claimed in claim 5, wherein said reservoir comprises a condenser which extracts the water content from a portion of the exhaust gas.

7. A detonation suppression or avoidance device substantially as described with reference to, and as illustrated in, Fig. 1, or Fig. 2, or Fig. 3 of the accompanying drawings.