JPH07150948A - Two cycle gasoline engine - Google Patents

Abstract

PURPOSE:To enable self-ignition running even in a low rotation and low load region unsuitable for self-ignition running, in a two cycle gasoline engine performing self-ignition running in at least a certain load region. CONSTITUTION:The load of a generator 16 driven by an engine 1 is increased in the given low rotation and low load region of the engine by a load control device 19 provided on a circuit 17. Consequently unburnt hydrocarbon quantity in exhaust gas is also reduced to improve a running condition in a low rotation and low load region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stroke gasoline engine in which an air-fuel mixture in a combustion chamber is burned by self-ignition in at least a certain load range.

[0002]

2. Description of the Related Art An exhaust port and a scavenging port that are opened and closed by a piston are formed on the inner peripheral surface of a cylinder hole, and fresh air prepressed in the crank chamber is sent from the scavenging port into the cylinder chamber, and burned gas is discharged from the exhaust port. However, in a two-cycle gasoline engine (hereinafter, referred to as a two-cycle engine or simply an engine) in which fresh air compressed in the cylinder chamber is ignited by a spark plug, irregular combustion due to misfire easily occurs in a low and medium load range, As a result, problems such as abnormal vibration of the engine and an increase in the amount of unburned hydrocarbons in the exhaust gas and thus an increase in fuel consumption occur.

So-called active radical combustion has hitherto been proposed as a method for solving this problem. This active radical combustion activates the fresh air by the heat energy contained in the residual gas of the previous cycle to make it very easy to ignite, and self-ignites at the end of compression to achieve good combustion even in the low and medium load regions. It is something to be obtained, for example,
Japanese Patent Laid-Open No. 56-38766 discloses a two-cycle engine utilizing such active radical combustion (active heat atmosphere combustion).

[0004]

According to the research results of the present inventors, the load range in which the active radical combustion is stably maintained in the two-cycle engine is limited by the scavenging efficiency, the engine speed, and the like, and depends on the engine speed Ne. The load range in which active radical combustion is possible is the range shaded in FIG.

That is, in FIG. 1, the curve a is the upper limit value of the load capable of stably sustaining the active radical combustion at each engine speed Ne, and the curve b is the lower limit value.
Therefore, the area surrounded by both curves a and b (the shaded area)
In the high load region above the curve a (curve c indicates the full load), the normal ignition operation by the spark plug etc. It is possible to effectively prevent the release of hydrocarbons and the occurrence of irregular combustion.

The problem here is the area D below the curve b.
Is. The region D is a region corresponding to low speed, low load idle operation. In this region, it is difficult to cause the self-ignition combustion because the load is too small, and even if the ignition operation is performed, the irregular combustion due to the misfire easily occurs,
This leads to an increase in hydrocarbon emissions and combustion consumption.

Therefore, the present invention is intended to provide a two-stroke engine which solves the above problem in the area D.

[0008]

According to the present invention, in a two-cycle gasoline engine which operates by self-ignition in at least a certain load range, the load of an auxiliary machine such as a generator driven by the engine is It is increased in a predetermined low rotation and low load range of the engine.

According to the present invention, in the low rotation and low load region corresponding to the region D, the engine load increases due to the increase in the auxiliary machine load, and the region where the self-ignition operation is possible is reached beyond the curve b. Therefore, low rotation, low load operation such as idle operation can be performed by self-ignition operation to suppress irregular combustion, hydrocarbon emission, etc., and for this purpose, special control means is not required.

[0010]

[Examples] FIG. 2 is a schematic diagram showing an example of an engine in which self-ignition operation is performed by utilizing active radical combustion. 1 is an engine, 2 is a crankcase, 3 is a cylinder, and 4 is a piston. The engine 1 has an exhaust control valve 6 at an exhaust port 5.

The exhaust control valve 6 is driven by a servo motor 7, and the amount of drive thereof is determined by a drive signal Δθe sent from the CPU 8 to the servo motor 7. The opening ratio of the exhaust port 5 by the exhaust control valve 6 obtained as a result of driving, that is, the exhaust opening ratio θe is fed back from the servo motor 7 to the CPU 8.

Reference numeral 9 denotes a throttle valve provided in an intake pipe 11 connected to an intake port 10. The opening degree θ _th of the throttle valve is detected by a throttle valve opening sensor 12 composed of a potentiometer or the like and input to the CPU 8.

The CPU 8 is further equipped with an engine speed sensor.
The engine speed Ne detected by 13, the suction pipe pressure P _i detected by the suction pipe pressure sensor 14, the cooling water temperature T _W detected by the water temperature gauge 15, and the like are also input.

The CPU 8 judges the operating state of the engine based on each of these input values and issues various control signals. In the operating region where active radical combustion is performed, the CPU 8 responds to the engine speed Ne and the throttle valve opening θ _th. The servo motor 7 operates according to a control map that defines the exhaust opening ratio θe, and outputs a drive signal Δθe that results in the exhaust opening ratio θe according to the map.
Send to. The exhaust opening ratio θe is set to such a value that the in-cylinder pressure regulated by this gives an optimum self-ignition timing, and therefore active radical combustion is stably maintained.

The engine 1 is provided with a generator, which is driven by the crankshaft of the engine, as in a normal engine. FIG. 3 shows the engine 1 in a more simplified manner, and a generator attached to the engine is designated by reference numeral 16
It is indicated by. Reference numeral 17 denotes an electric circuit connected to the output side of the generator 16, which is used to load electric equipment fed by the circuit.
It is shown as.

In addition to the load 18, a load control device 19 is inserted in the electric circuit 17, and the load control device 19 controls the engine speed Ne, the throttle valve opening θ _th , the cooling water temperature T _W, etc. In response to the input signal from the CPU 8, the load of the generator 16 is increased. The load control device 19 is shown in FIG.
The variable resistance device may be composed of a resistor 20 and a slider 21 as shown in FIG. 2, and in this case, the sliding amount s of the slider 21 is controlled by an input signal from the CPU 8 to load the generator 16. To the desired value.

As the load of the generator 16 increases, the load of the engine increases, but the load control device 19 operates when the load condition of the engine is within the region D of FIG. 1, and the engine load is at least at the curve b position. To ensure stable self-ignition operation.

Table 1 shows A of FIG. 1 for a certain engine.
When the operation is performed at the point B and the point B, that is, when no load operation is performed at the idle speed i (point B), the load is increased by α as described above at the idle speed i and the curve b is obtained. When the operation is performed at point A above, the indicated mean effective pressure (P _mi ), fuel consumption (FC),
Hydrocarbon emission amount (HC) and rotation fluctuation deviation value (δN
It is a comparison of e).

[0019]

[Table 1]

The values of FC, HC, and δNe are all lower in the operation at the point A than in the operation at the point B. From this, the irregular combustion is reduced by increasing the engine load in the low rotation and low load region. Therefore, it can be seen that the unburned hydrocarbon amount in the exhaust gas and the fuel consumption amount are also reduced, and the operating condition in this region is significantly improved.

Moreover, the engine load is increased by a simple means of increasing the load of the generator 16 and does not require any complicated and special control means. You may make it increase the load of auxiliary machines other than a generator in order to increase an engine load.

[0022]

EFFECTS OF THE INVENTION According to the present invention, in a two-cycle gasoline engine that performs self-ignition operation at least in a certain load range, it is possible to perform self-ignition operation even at low rotation and low load ranges that are unsuitable for self-ignition operation, and to perform irregular combustion. , Hydrocarbon emission, fuel consumption, etc. can be effectively suppressed, and no special control means is required for this purpose.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a load range in which a self-ignition operation is possible according to a rotation speed of an engine.

FIG. 2 is a schematic diagram showing an example of an engine configured to perform a self-ignition operation.

FIG. 3 is a diagram showing a load circuit of a generator.

FIG. 4 is a diagram showing an example of a load control device inserted in the same load circuit.

[Explanation of symbols]

1 ... Engine, 2 ... Crankcase, 3 ... Cylinder, 4
... Piston, 5 ... Exhaust port, 6 ... Exhaust control valve, 7 ... Servo motor, 8 ... CPU, 9 ... Throttle valve, 10 ... Intake port, 11
... intake pipe, 12 ... throttle valve opening sensor, 13 ... engine speed sensor, 14 ... intake pipe pressure sensor, 15 ... water temperature gauge, 16 ... generator, 17 ... electric circuit, 18 ... load, 19 ... load control device , 20 ...
Resistor, 21 ... Slider.

Claims (1)

[Claims] 1. In a two-stroke gasoline engine that operates by self-ignition in at least a certain load range, the load of an auxiliary machine such as a generator driven by the engine is set to a predetermined low rotation and low load range of the engine. A two-stroke gasoline engine, which is characterized in that it is designed to be increased.