JPS62157268A - Choke valve drive device of 2-cycle engine of crank case pre-compression type - Google Patents

Abstract

PURPOSE:To improve ease of starting an engine of crank case pre-compression type by actuating to open a choke of a carburetor with a pressure in the crank case so that the choke is securely opened to a specified opening ratio at a first combustion when the engine is started. CONSTITUTION:In an engine 1 in which mixture is compressed in a crank case 2, each crank case is communicated to a carburetor 15, with a choke valve arranged on the upstream side of the carburetor 15. When the engine is at rest, the choke valve 18 is closed with a spring 31 arranged in an actuator 30. If a first combustion occurs when the engine is started, pressure in the crank case 7 becomes high which is led to the actuator 30 to open the choke valve 18 till its projection 28a comes into contact with a stoppe 35. Thereafter the choke valve 18 is actuated to open according to a thermowax 23.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a choke valve provided in the intake passage of a two-stroke engine with precompression in the crank chamber, and particularly to a drive device for opening the choke valve. .

(Prior art) As a conventional technology, a choke valve for restricting the amount of intake air is provided in the intake passage of a two-stroke engine with precompression in the crank chamber, a thermal expansion member is connected to the choke valve, and the thermal expansion member is connected to the choke valve. Some engines have a structure in which the choke valve is opened by controlling heating with a heater that is energized according to the rise in engine temperature.

(Problems to be Solved by the Invention) The above-mentioned conventional device cannot instantaneously control the heating of the thermal expansion member to a predetermined value, and especially immediately after starting the engine, it is difficult to control the temperature rise of the engine. The opening degree of the valve will be delayed.

For this reason, immediately after the engine is started, the concentration of the mixture of air and fuel generated in the carburetor becomes higher than necessary, resulting in an unauthorized explosion and a disadvantage that warm-up of the engine becomes unsmooth.

SUMMARY OF THE INVENTION An object of the present invention is to obtain a new choke valve drive device for a rank chamber precompression type two-stroke engine that eliminates the above-mentioned drawbacks.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a choke valve for limiting the amount of intake air in the intake passage of a two-stroke engine with precompression in the crank chamber. In this choke valve drive device, the choke valve is operated to open in response to a rise in temperature of the engine, and the choke valve is preferentially operated at a low opening due to the negative pressure in the crank chamber generated when the engine is started.

(Function) Since the present invention has the above configuration, when the engine starts, large positive and negative pressures are immediately generated in the crank chamber.

Then, the choke valve is immediately operated at a low opening to a predetermined value by the negative pressure generated in the crank chamber, and as a result, the air/fuel mixture generated in the carburetor is mixed by 11III degrees, that is,
The concentration of the mixture will drop to a predetermined value.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 is an explanatory diagram of a horizontal multi-cylinder two-stroke engine for outboard motors to which the present invention is applied, Fig. 2 is a side view of the carburetor attached to the engine, and Fig. 3 is the opening of the choke valve. FIG. 3 is a characteristic diagram showing characteristics.

In Fig. 1, 1 is an engine, which connects six cylinders to V
It consists of a two-stroke engine with precompression scavenging in the crank chamber placed in a mold.

The engine 1 has a crankcase 2 and a cylinder block 3 connected in the left-right direction, and a crankshaft 4 vertically supported by the crankcase 2 and a piston 5 fitted in the cylinder block 3 are connected by a connecting rod 6.

Further, a carburetor 15 is connected to an intake passage 7a connected to the left side of the crankcase 2, and a reed valve 8 is provided downstream of the carburetor 15 to allow air flow only in the direction of the crank chamber 7.

The reciprocating movement of the piston 5 as the crankshaft 4 rotates generates positive and negative pressure in the crank chamber 7, and when the pressure is negative, a mixture of fuel and air is sucked from the carburetor 15 through the reed valve 8, and positive pressure is generated. Sometimes, this air-fuel mixture is supplied from the crank chamber 7 to the combustion chamber 9 through a scavenging passage (illustrator C) formed in the cylinder block 3, and is ignited by the ignition plug 10 when the piston 5 is compressed. There is.

In the figure, reference numeral 11 denotes a drive shaft connected to the lower part of the crankshaft, and a propeller holder 14 to which a propeller 13 is fixed is connected to the lower part of the drive shaft 11 via a gear mechanism 12.

The carburetor 15 has a throttle valve 17 and a choke valve 18 on the downstream side of the venturi 16 and the second stream side, and is connected to the crank chamber 7 of each cylinder via a reed valve 8. There is.

The choke valve 18 of each carburetor 15 is connected to the link mechanism 1
They are synchronously connected together by 9.

For example, in the figure, the upper end of an actuating rod 22 is connected to the valve shaft 20 of the choke valve 18a at the center via an arm 21, and the lower end of this actuating rod 22 is connected to a thermal expansion member 23 made of thermowax.

The initial expansion amount of the thermal expansion member 23 is set according to the temperature i of the engine 1 itself, and the heating is further controlled by the PCT heater 25. A PCT heater 25 is connected to a power generation coil that generates power by the rotation of the shaft 4, and this PCT heater 25 is
The amount of current flowing to the CT heater 25 is controlled by an auto choke control circuit 24.

As a result, each choke valve 18 is opened at a predetermined rate as the temperature of the engine 1 increases.

Further, in FIG. 1, the upper end of an operating rod 28 is connected to the valve shaft 26 of the lower choke valve 18b via an arm 27, and the lower end of this operating rod 28 is connected to a diaphragm 29.

This diaphragm 29 is connected to a case 30 formed into a tip shape.
It is hermetically installed on the open side of the Then, a spring 31 provided inside or outside the case 30 causes the actuation rod 2 to
8 is elastically biased upward, and the stop valve 18b (18) is biased to close via the arm 27.

Further, the case 3o is connected to the crank chamber 7 through a hose 32, and a check valve 33 is provided in the middle of the hose 32 to allow air flow only in the direction from the case 30 to the crank chamber 7.

Note that 34 in the figure is a battery.

Here, the link mechanism 19 described above is elastically operated in one direction so that each choke valve 18 is biased to close by a spring member (not shown).

The operating rod 22 and the arm 21 and the operating rod 28 and the arm 27 are set to engage only in the direction of opening the choke valves 18a and 18b.

In addition, the amount of downward movement of the operating iron 28, that is, the choke: j
r・, JJ is moved in the direction in which it is opened until the opening degree of the choke valve 18b reaches approximately 20 degrees, and when this opening degree is reached, the stopper 28a provided on the operating rod 28 closes the regulating body. 35 to prevent further downward movement of the actuation iron 28.

Next, the operation mode of the above embodiment will be explained.

When starting engine 1 (during cranking),
Since the crankshaft 4 does not rotate by itself, its rotational speed is slow, and the positive and negative pressures generated in the crank chamber 7 are weak. Therefore, the choke valve 18 is in a closed state as shown in FIG. 3(A).

Therefore, when starting the engine 1, a highly concentrated air-fuel mixture is generated in the carburetor 15 and supplied to the engine 1, thereby starting the engine 1.

When the engine 1 is started and reaches a complete explosion, the rotational speed of the crankshaft 14 and the reciprocating speed of the piston 5 increase, and the positive and negative pressures generated in the crank chamber 7 become stronger.

Then, the negative pressure inside the case 30 increases and the operating iron 2
8 is immediately lowered to open the choke valve 18b. In this case, when the operating rod 28 descends by a predetermined amount, the stopper 28a collides with the regulating body 35 and prevents further descent, so that the opening degree of the choke valve 18b is set to the third degree.
The angle is approximately 20 degrees as shown in Figure (A).

The two choke valves 18b are synchronously connected to the choke valves 18 of each cylinder by a link mechanism 19, and both are opened at the same opening degree.

Therefore, when the engine 1 is started, the concentration of the air-fuel mixture in the carburetor 15 is immediately reduced to a predetermined value and is supplied to the engine 1, and the engine 1 continues to operate in this state.

On the other hand, the thermal expansion member 23
The PCT heater 2S is heated by the PCT heater 2S whose energization is controlled by the PCT heater 2S, and its expansion amount gradually increases over time. As shown in the figure, each choke valve 18 is opened.

(Effects of the Invention) As is clear from the above description, according to the present invention, the choke valve is preferentially operated at a low opening by the negative pressure in the crank chamber generated when the engine is started.
Immediately after the engine is started, a mixture having a concentration reduced to a predetermined value is immediately supplied to the engine.

Therefore, the present invention has the advantage that the engine can be started and warmed up smoothly.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a horizontal multi-cylinder two-stroke engine to which the present invention is applied, Fig. 2 is a side view of the carburetor installed in the engine, and Fig. 3 is the opening degree characteristic of the choke valve of the carburetor. FIG. 1: engine, 2: crank case, 3 cylinder block, 4: crankshaft, 5: piston, 7: crank chamber, 7a: intake passage, 8: reed valve, 15: carburetor, 16
: Venturi, 17: Throttle Ben, 18 (18a
・18b): Choke valve, 19: Link mechanism, 23: Thermal expansion member, 24 Nio-tochi yoke control circuit, 25: PC
T heater, 26: Arm, 27: Valve shaft, 28: Operating rod, 28a: Stopper, 29: Diaphragm, 30: Case, 31: Spring, 32: Hose, 33: Check valve, 34
: Regulatory body. Application agent Hisashi Matsumoto

Claims (1)

[Claims] 1. A choke valve drive device in which a choke valve for limiting the amount of intake air is provided in the intake passage of a two-stroke engine with precompression in the crank chamber, and the choke valve is opened in response to a rise in engine temperature. A choke valve drive device for a two-stroke engine with precompression in the crank chamber, characterized in that the choke valve is preferentially operated at a low opening by the negative pressure in the crank chamber generated at the time of starting the engine.