JPS5831458B2 - engine over run - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a type of vehicle that automatically controls the carburetor throttle valve opening degree in relation to the engine rotational speed, which is currently commonly used in vehicles powered by a two-stroke engine that uses mixed fuel. It is an object of the present invention to provide an overrun control method in which the use of a speed governor is preferable in terms of vehicle maneuverability and is suitable for cases where it is necessary to control engine overrun.

For example, in a vehicle, favorable maneuverability is generally obtained by the operator arbitrarily operating the throttle valve of the carburetor. If a speed governor is used that automatically controls the engine speed in relation to the engine speed, the operator will have less freedom in controlling the engine speed because the throttle valve operation will be restricted. becomes worse.

Conventionally devised overrun control methods to avoid the above problems include a method that prevents overruns by grounding the ignition system when the engine speed reaches a set value, thereby preventing sparks from being generated at the ignition plug. However, with this method, a considerable amount of unburned air-fuel mixture is discharged into the exhaust system during the period when no spark is generated, which may cause an explosion within the exhaust system, which limits its practical use. .

The present invention is aimed at solving the above-mentioned conventional problems.In a two-stroke engine using mixed fuel, while the engine speed is above a set value, air is passed from the intake port through the carburetor to the crankcase. It is characterized by adding an appropriate amount of excess fuel for rotation suppression to any part of the intake passage leading to the scavenging passage.

That is, the present invention was inspired by the fact that engine overrun can be suppressed by setting the carburetor to increase the fuel flow rate.

In the case of a carburetor, it must be set to the optimum air-fuel ratio within the operating speed range, and if it is set so that the fuel is rich enough to control overrun, the engine output within the operating range will decrease significantly. However, according to the method of the present invention, combustion is achieved by injecting an appropriate amount of fuel into the intake system and supplying a rich mixture to the combustion chamber while the engine speed is above the set value. Since the condition is controlled and the engine is thereby prevented from overrunning, an explosion in the exhaust system due to the discharge of unburned air-fuel mixture does not occur, and overrun can be safely controlled.

In particular, overrun control using this method is useful for two-stroke engines with preloaded crank chambers that use mixed fuel.
Since lubricating oil is supplied along with the injected fuel, it is extremely effective in preventing seizures in various parts of the engine that tend to occur at high engine speeds that exceed the practical range.

The details of the present invention will be described below with reference to Examples.

Figures 1a and 1s show examples using solenoid valves,
Figure 1a shows a system in which fuel is supplied directly from a fuel source to a solenoid valve, and Figure 1a shows a system in which return fuel from a circulation type carburetor is supplied to a solenoid valve.

In both figures, A is a generator that operates in conjunction with the rotating shaft of the engine, and B is a generated power control device, the details of which will be described later in connection with FIG. 3.

C is the fuel supply source, which is a powered tank or fuel pump, C1
is a fuel supply line from fuel source C to carburetor 1, C2 is a fuel supply line from fuel source C to solenoid valve 3, C3 is a return fuel line from circulation type carburetor 1 to solenoid valve 3, and C4 is a fuel supply line from fuel source C to carburetor 1; is a return fuel line from the solenoid valve 3 to the fuel source C.

Further, 2 is an intake pipe that communicates with an intake air intake port (not shown) via the carburetor 1, 4 is a crankcase, 5 is a crankshaft, 6 is a connecting rod, 7 is a piston, and 8
is the cylinder, 9 is the cylinder head, 10 is the exhaust pipe, 11
indicates a spark plug.

Also, a scavenging passage that communicates the combustion chamber in the upper part of the cylinder 8 with the crank chamber for fuel prepressurization is not shown.

2a and 2a show details of the solenoid valve 3, and the second
Figure a shows the fuel source C directly supplying fuel to the solenoid valve 3, and Figure 2 shows the fuel source C directly supplying fuel to the solenoid valve 3. It returns fuel to

In both figures, 31 is a fuel inlet, 32 is a solenoid, and 3
3 is a valve spring (compression spring), 34 is a valve, 3
5 is a fuel discharge port, and 36 is a return fuel outlet to the fuel tank C.

The lead wire to the solenoid 32 is not shown in FIGS. 2a and 2b.

Figure 3 shows the wiring of the solenoid valve control system.

In Figure 3, B1 is a rectifier, B2 is a Zener diode,
The Zener diode B2 has a characteristic of becoming conductive at the voltage generated by the generator A when the engine rotation reaches the maximum set rotation speed.

When the engine is operated within the practical rotational speed range, the solenoid valve 3 is in a closed state, and the engine is operated only with the fuel supplied from the carburetor 1.

When the vehicle jumps and spins, the engine speed increases beyond the practical range, causing the voltage generated by generator A to increase to the conduction voltage (Zener voltage) of Zener diode B2.
When the current is reached, current flows through the Zener diode B2, the solenoid valve 3 is operated in an open state, and the fuel is transferred from the fuel discharge port 35 to the intake pipe 2, so as to keep the speed on the same side of the engine within a safe range.
A regulated flow rate of fuel is provided by calibrating the fuel outlet 35 either directly or indirectly by metering jet attachment.

That is, when the engine rotation reaches the preset maximum rotation speed, excess fuel is immediately added to the intake passage.
Furthermore, if excess fuel is continuously added while the rotational speed further increases beyond the above-mentioned set value, the combustion speed decreases as the air-fuel mixture concentration increases, and overrun is effectively suppressed.

When the vehicle returns to its normal state and the rotational speed of the engine drops to within a practical range, the voltage generated by the generator A naturally also drops.

As a characteristic of Zener diode B2, the applied voltage decreases to the Zener voltage at which current started flowing first,
When the current decreases further, the current stops flowing, so the solenoid valve 3 returns to the closed state, and fuel is normally supplied only from the carburetor 1.

As explained above, according to the present invention, two types of mixed fuel are used.
In a cycle engine, while the engine speed exceeds a set value, an appropriate amount of rotation suppressing material is applied to any part of the intake passage from the intake air intake, through the carburetor 1, to the crankcase 4, and to the scavenging passage. Since excess fuel is added, the following effects can be expected.

(a) Since the arbitrariness of throttle valve operation is not restricted, maneuverability does not deteriorate due to a reduction in the degree of freedom in engine speed, and overruns can be effectively suppressed. .

(b) In the present invention, since fuel is added above the set rotation speed, the rotation speed begins to drop immediately, resulting in a quick response (for example, in a small boat with a water jet propulsion system, the engine When overrun to 10,000 rpm III, 3 Asec due to addition of excess fuel, internal 8,000 rpm
It has been confirmed that the deceleration rate is up to rpIII).

However, contrary to the present invention, in the method of controlling the fuel by throttling the fuel during overrun, the air-fuel ratio during normal operation is generally smaller (richer) than the theoretical value, so the air-fuel ratio is temporarily reduced while throttling the fuel. The fuel ratio will pass through the theoretical value, and at that time the rotational speed will increase, causing a delay in overrun control.

In addition, in a two-stroke engine that uses mixed fuel, if the fuel is throttled, seizure is likely to occur, and this tendency is particularly noticeable during overrun, so it is not preferable to throttle the fuel to prevent overrun.

(c) There is no risk that a large amount of unburned air-fuel mixture will be discharged into the exhaust system and explode therein.

(d) Since the carburetor 1 may be a simple single-throttle valve type conventionally used, a compact and inexpensive overrun control method can be obtained.

(e) Since extra lubricating oil is supplied together with fuel during overrun into a two-stroke engine that uses mixed fuel, seizure can be reliably prevented.

Note that the location for adding excess fuel may be selected from within the intake system from the air intake port to the intake valve as shown in the figure, or from the crank chamber.

In addition to detecting the engine speed using the generator output as shown in the figure, it may also be detected from centrifugal force, fan wind pressure, or pump discharge pressure.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention, and FIG.
The vertical sectional view of the solenoid valve in the figure, and FIG. 3 is a wiring diagram of the solenoid valve control system. 1... Carburetor, 2... Intake pipe, 3...
...Solenoid valve for adding excess fuel, 4...Crankcase.

Claims (1)

[Claims] 1. In a two-stroke engine using mixed fuel, while the engine speed is above the set value, apply an appropriate amount to any part of the intake passage from the intake air intake through the carburetor to the crankcase and scavenging passage. An engine overrun control method characterized by adding excess fuel to suppress rotation of an engine.