JPS6143961Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a knocking prevention device for an internal combustion engine, and is particularly suitable for use in a premixed high-compression gasoline internal combustion engine with a compression ratio of 10 to 14, in which a homogeneous mixture is taken in through an intake pipe. The present invention relates to a suitable knocking prevention device for an internal combustion engine.

Generally, in a conventional gasoline internal combustion engine with a compression ratio of about 8 to 9, the air-fuel ratio is set to around the output air-fuel ratio of, for example, 12 to 13 at around full load when the throttle valve is fully open. On the other hand, regarding ignition timing, the minimum advance angle (hereinafter referred to as
Generally, as shown in Figure 1, near full load, the MBT ignition timing (solid line A) is set to the knocking limit (solid line B).
As the state progresses further and knocking occurs, use a knocking sensor, etc. to detect knocking, and if knocking occurs at point C on the MBT ignition timing, adjust the ignition timing to point D near the knocking limit. The ignition timing is set using feedback control.

On the other hand, in recent years, research has been conducted on high-compression gasoline internal combustion engines with significantly increased compression ratios, mainly in order to improve fuel efficiency in the partial load range. In order to prevent knocking in the load range, it is necessary to significantly delay the ignition timing in the entire load range, resulting in a significant drop in output, deterioration of fuel efficiency, increase in torque fluctuation, and furthermore, an excessive rise in exhaust temperature. This causes the engine to become unusable. On the other hand, instead of retarding the ignition timing, it is possible to enrich the air-fuel ratio to the region shown at point E in Figure 1 to prevent knocking, but this would require a significant enrichment of the air-fuel ratio and the output However, in terms of fuel efficiency, smoldering spark plugs, torque fluctuations, etc., it is still not a practical engine.

The present invention has been devised to eliminate the above-mentioned conventional drawbacks, and aims to put into practical use a high-compression gasoline internal combustion engine that does not suffer from the above-mentioned drawbacks.

In order to achieve the above objectives, this invention has a compression ratio of 10
A knocking sensor that detects knocking in ~14 premixed high-compression gasoline internal combustion engines,
means for detecting that the engine is under high load;
An air-fuel ratio control means capable of making the air-fuel ratio of the air-fuel mixture leaner than the stoichiometric air-fuel ratio is provided, and when knocking is detected when the engine is under high load, the air-fuel ratio control means controls the air-fuel ratio of the air-fuel mixture. The air-fuel ratio is set to be leaner than the stoichiometric air-fuel ratio to prevent knocking.

In addition, in the above-mentioned high load state, the intake pipe negative pressure is 100
This is when the temperature is below mmHg.

Further, the air-fuel ratio control means is a fuel flow rate reduction mechanism disposed in the carburetor.

Alternatively, the air-fuel ratio control means is an air bleed air amount increasing mechanism disposed in the carburetor.

Alternatively, the air-fuel ratio control means is an electronically controlled fuel injection device.

The principle of the present invention will be explained below. Generally, the relationship between the air-fuel ratio, MBT ignition timing, and knocking limit in a gasoline internal combustion engine is considered to be as shown in Figure 1. Therefore, in a high compression gasoline internal combustion engine with a compression ratio of about 10 or more, It was thought that it would be difficult to put it into practical use because the ignition timing would have to be significantly delayed. However, the inventors and others proposed a compression ratio of 10 to 14, in which a homogeneous air-fuel mixture is inhaled through the intake pipe.
When we investigated the relationship between the air-fuel ratio, MBT ignition timing (solid line A), and knocking limit (solid line B) for a premixed high-compression gasoline internal combustion engine, we found that the relationship is as shown in Figure 2. . That is, unlike an engine with a normal compression ratio, there is a region F in which knocking does not occur even at an ignition timing near MBT in an air-fuel ratio region even leaner than the stoichiometric air-fuel ratio. Therefore, by using point G within this region F, it is possible to operate at the MBT ignition timing without knocking, even near full load. This point G only in high compression gasoline internal combustion engines
The reason why can be used is that in high compression gasoline internal combustion engines,
The knocking limit becomes extremely sensitive to the air-fuel ratio in the lean air-fuel ratio range, and conversely becomes insensitive to the ignition timing. Stable combustion cannot be obtained with a compression ratio, and with a lean air-fuel ratio, the absolute amount of fuel supplied to the engine is lower than the output air-fuel ratio, resulting in a decrease in output. The decrease in output can be considerably compensated for by the efficiency improvement due to the compression ratio improvement and the efficiency improvement due to stable combustion at the lean air-fuel ratio, so even if operated at point G, the low compression ratio internal combustion engine This is because there is less reduction in output compared to (point D in FIG. 1). In addition, when the compression ratio is about 14 or more,
Furthermore, the knocking becomes more severe and the point G in FIG. 2 moves further toward the lean side, making it impossible to obtain stable combustion. The present invention was made based on the experimental results of the inventors.

Embodiments of the present invention will be described in detail below with reference to the drawings. In the first embodiment of the present invention, as shown in FIG. 3, a homogeneous air-fuel mixture formed by a carburetor 14 is sucked through an intake pipe 12. In a premixed high-compression gasoline internal combustion engine 10 with a compression ratio of 10 to 14, a knocking sensor 16 is provided in the main body of the gasoline internal combustion engine 10 and converts vibrations of the engine main body or sound waves generated by this vibration into electrical signals. and,
A knocking detection circuit 17 that detects the presence or absence of knocking based on the output of the knocking sensor 16, and a fuel flow reduction device disposed in the carburetor 14 that can make the air-fuel ratio of the air-fuel mixture leaner than the stoichiometric air-fuel ratio. Based on the outputs of the mechanism 18, the intake negative pressure sensor 20 that detects the negative pressure in the intake pipe 12, the knocking detection circuit 17, and the intake negative pressure sensor 20, the knocking sensor 16 detects when the intake pipe negative pressure is 100 mmHg or less. If knocking is detected in the high load range,
A control circuit 22 is provided which drives the fuel flow rate mechanism 18 to make the air-fuel ratio of the air-fuel mixture leaner than the stoichiometric air-fuel ratio.

In the figure, 24 is an air cleaner, and 26 is an exhaust pipe.

As shown in detail in FIG. 4, the fuel flow rate reduction mechanism 18 includes a fuel passage 14d that leads the fuel in the carburetor float chamber 14c to a nozzle 14b for discharging gasoline into the bench lily 14a of the carburetor 14.
A valve body 18a that is disposed at one of the fuel inlets 14e and 14f and can close the fuel inlet 14f.
and a solenoid valve 18b that drives the valve body 18a to close the fuel inlet 14f. In the figure, 14g and 14h are fuel jets, 14
i is an air bleed passage, 14j is an air jet,
14k is a float, and 14l is a throttle valve.

The action will be explained below. The output signal of the knocking sensor 16 is input to the knocking detection circuit 17, and when the output level of the knocking sensor 16 is equal to or higher than a predetermined value, it is determined that knocking has occurred, and the knocking detection circuit 17 detects the knocking. The signal is input to control circuit 22 . On the other hand, the intake negative pressure in the intake pipe 12 is detected by the intake negative pressure sensor 20.
0 is turned off, and the output signal from the control circuit 22 is stopped. Therefore, during this partial load, the solenoid valve 18b is always closed, and the air-fuel ratio is equal to the fuel inlet 1.
The air-fuel ratio range is determined by the flow rate of fuel flowing in from 4e, and is set in a lean air-fuel ratio region in which knocking does not occur as in the conventional case, and is set in consideration of fuel efficiency, for example. On the other hand, the intake negative pressure in the intake pipe 12 is, for example, 100
When it approaches zero than mmHg, the intake negative pressure sensor 20
is turned on, and a signal instructing the solenoid valve 18b to open or close is sent from the control circuit 22. Therefore, the solenoid valve 18b starts operating in response to this signal, and the valve body 18
When the engine a closes the fuel inlet 14f, the flow rate of fuel flowing into the fuel passage 14d decreases, so that the air-fuel ratio is diluted as in the case of partial load, and knocking is prevented. On the other hand, when knocking no longer occurs, the solenoid valve 18b opens and the fuel inlet 14f opens.
is opened, the flow rate of fuel flowing from the float chamber 14c into the fuel passage 14d increases, resulting in an over-enriched air-fuel ratio. Therefore, by repeating this process, it is possible to maintain the air-fuel ratio just below the knocking limit. This air-fuel ratio control is performed by changing the duty ratio of the control signal. In this way, the full-load air-fuel ratio can be brought close to the rich side until the knocking limit is reached, so that although the air-fuel ratio is lean, the reduction in output can be kept to a minimum.

In the first embodiment, the fuel flow rate reduction mechanism was a solenoid valve disposed in the carburetor for reducing the amount of fuel flowing into the fuel passage, but the fuel flow rate reduction mechanism is limited to this. not. For example, when an electronically controlled fuel injection device is used as a fuel supply system, the air-fuel ratio of the mixture can be lowered from the stoichiometric air-fuel ratio by reducing the opening time of the fuel injection valves installed in the intake manifold. Of course, it is also possible to set it on the dilute side.

A second embodiment of the present invention is shown in FIG. In this embodiment, as the air-fuel ratio control means, an air bleed air amount increasing mechanism 30 is used, which includes a valve body 30a that controls the opening and closing of the air bleed passage 14i of the carburetor 14, and a solenoid valve 30b that drives the valve body 30a. It is something. The other points are the same as those of the first embodiment, so the explanation will be omitted.

In this embodiment, the knocking detection circuit 17
Based on the output signal of the intake negative pressure sensor 20, if knocking occurs in a high load range, the time during which the air bleed passage 14i is open by the solenoid valve 30b increases, and the air-fuel ratio becomes lower than the stoichiometric air-fuel ratio. It is considered to be on the thin side. On the other hand, if knocking does not occur even in a low load range or a high load range, the time during which the air bleed passage 14i is closed by the solenoid valve 30b becomes longer, and the air-fuel ratio becomes closer to the stoichiometric air-fuel ratio or the output air-fuel ratio. Controlled by fuel ratio.

As explained above, according to the present invention, it is possible to prevent knocking of a high-compression gasoline internal combustion engine at high loads, resulting in less reduction in output compared to conventional low-compression gasoline internal combustion engines, and significantly improving fuel efficiency. After that, stable operation can be performed. In addition, by controlling the air-fuel ratio according to knocking only in the high-load range, during partial-load operation, the air-fuel ratio can be adjusted for a different purpose than in the high-load range, such as setting an even leaner air-fuel ratio to improve fuel efficiency. It has excellent effects such as making it possible to set the

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the air-fuel ratio near full load, MBT ignition timing, and knocking limit in a conventional low-compression gasoline internal combustion engine.
Diagram 3 showing the relationship between the air-fuel ratio near full load, MBT ignition timing, and knocking limit in a high-compression gasoline internal combustion engine to explain the principle of the present invention.
4 is a schematic diagram showing the configuration of a premixed high-compression gasoline internal combustion engine equipped with the knocking prevention device for an internal combustion engine according to the present invention, and FIG. 4 shows the fuel flow reduction mechanism in the first embodiment. FIG. 5 is an enlarged sectional view showing the carburetor installed therein, and FIG. It is a sectional view showing a container. 10...Gasoline internal combustion engine, 12...Intake pipe,
14... Carburetor, 16... Notking sensor, 1
7...Knocking detection circuit, 18...Fuel flow rate increase mechanism, 20...Intake negative pressure sensor, 22...Control circuit, 30...Air bleed air amount increase mechanism.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A knocking sensor for detecting knocking in a premixed high-compression gasoline internal combustion engine with a compression ratio of 10 to 14, and means for detecting that the engine is in a high load state; An air-fuel ratio control means capable of making the air-fuel ratio of the air-fuel mixture leaner than the stoichiometric air-fuel ratio is provided, and when knocking is detected when the engine is under high load, the air-fuel ratio control means controls the air-fuel ratio of the air-fuel mixture. A knocking prevention device for an internal combustion engine, characterized in that the air-fuel ratio is made leaner than the stoichiometric air-fuel ratio to prevent the occurrence of knocking. (2) The high load range state detection means detects intake pipe negative pressure and determines that the high load state is present when the intake pipe negative pressure is 100 mm/Hg or less.Claim 1 of the Utility Model Registration Claim The knocking prevention device for an internal combustion engine described in . (3) The knocking prevention device for an internal combustion engine according to claim 1 or 2, wherein the air-fuel ratio control means is a fuel flow reduction mechanism disposed in a carburetor. (4) The knocking prevention device for an internal combustion engine according to claim 1 or 2, wherein the air-fuel ratio control means is an air bleed air amount increasing mechanism disposed in a carburetor. (5) The knocking prevention device for an internal combustion engine according to claim 1 or 2, wherein the air-fuel ratio control means is an electronically controlled fuel injection device.