JPS61272425A - Engine brake actuating device of 2-cycle engine - Google Patents

Abstract

PURPOSE:To produce an engine brake force being highmost efficiency responding to the number of revolutions of an engine, by a method wherein two valves are located in a passage through which a combustion chamber is communicated to the open air, and are opened and closed according to an accel position and the number of revolutions of an engine. CONSTITUTION:A first valve 14 is situated to the one end of a communicating passage 12 having the one end open to a combustion chamber 7 and the other end open to the open air side, and a second valve 23 is situated to the intermediate of the passage 12. The first valve 14 is coupled to accel mechanisms 20-22, and the first valve 14 is opened in a given position passing an idle position toward a direction in which a valve is closed. The opening area of the second valve 23 is regulated according to the number of revolutions of an engine. This enables an engine brake to be actuated with high efficiency depending upon the number of revolutions of an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine brake actuation device for a two-stroke engine.

(Prior art and its problems) Generally, two-stroke engines installed in small motorcycles apply engine braking by operating the accelerator mechanism and closing the throttle valve of the capretor near the idle position. However, the braking force is theoretically very small compared to that of a 4-cycle engine.

In order to solve this problem, for example, Utility Model Application No. 56-569
As disclosed in Publication No. 45, a pressure reducing valve (decompression) provided to facilitate cranking when starting the engine and improve startability is linked to the accelerator mechanism, and the accelerator is activated when descending or decelerating. The pressure reducing valve is opened near the idle position of the mechanism to communicate the combustion chamber with the atmosphere, and the resistance caused by compressible gas flowing in and out of the combustion chamber and cylinder chamber as the piston moves up and down is utilized. There is a known method for increasing the braking force of engine braking.

However, in such conventional examples, since the pressure reducing valve is simply opened when descending or decelerating, the effect of the braking force differs depending on the speed of the engine when braking by the engine brake starts, and the effect of the braking force varies over a wide range of engine speeds. There was a problem in that it was difficult to obtain the best braking force for the number of brakes.

(Object of the Invention) The present invention was made in view of the above circumstances, and an object of the present invention is to provide an engine brake actuation device for a two-stroke engine that can obtain good braking force over a wide range of engine speeds. do.

(Summary of the Invention) In order to achieve the above object, the present invention includes a first valve disposed at the one end opening of a communication passage whose one end opens into the combustion chamber and whose other end opens to the atmosphere side; a second valve disposed in the middle of the engine; a first valve operating mechanism that opens the first valve at a predetermined position beyond the idle position in the valve closing direction in conjunction with the accelerator mechanism; The second valve operating mechanism controls the opening of the second valve in accordance with the rotational speed to change the opening area of the communication passage.

(Example of the invention) An embodiment of the present invention will be described below based on the accompanying drawings.

FIG. 1 shows a cross section of a main part of a two-stroke engine to which the engine brake actuating device according to the present invention is applied. A combustion chamber 7 is formed above the cylinder chamber 2 . , at a predetermined location on one side wall of the lower part of the combustion chamber 7, one end is attached to the combustion chamber 7.
An exhaust pipe 8 is formed at the other end of which communicates with the atmosphere, while an intake port 9 is formed at a predetermined location on one side wall of the lower part of the cylinder chamber 2 to communicate with a carburetor (not shown). . A reed valve 10 is attached to the open end of the suction port 9, and the reed valve 1''0 introduces the mixed gas from the carburetor into the crankcase 1, so that the gas in the crankcase 1 flows back toward the carburetor. It is designed not to.

A communication passage 12 is provided at substantially the top of the combustion chamber 7. One end 12a opens facing the combustion chamber 7, and the other end 12b communicates with and opens to the downstream side of the exhaust pipe 8. Opening end 1 of this communication path 12
A first valve 14 for communicating or blocking communication between the communication passage 12 and the combustion chamber 7 is attached to 2a. This first valve 14
is a poppet valve, for example, and includes a valve body 15 and a valve body 15.
The valve element 15 is opened and closed by a first valve operating mechanism 17.

This first valve operating mechanism 17 is, for example, a link mechanism, and is composed of a pressing member 19 rotatably supported approximately at the center on a shaft 18 and a wire 20, and one end of the pressing member 19 is connected to the valve body 15.
The valve shaft 15a is brought into contact with one end of the valve shaft 15a, and one end of a wire 20 is connected to the other end. The other end of this wire 20 is connected, for example, to one end 21a of a grip 21 of a handle (not shown).

One end 21a of this grip 21 is connected to one end of a wire 22 constituting an accelerator mechanism, and the other end of the wire 22 is connected to a rotating shaft (both not shown) of a throttle valve.
The throttle valve is continuously controlled to open from a fully closed position (idle position) to a fully open position in response to rotation of the grip 21.

The first valve operating mechanism 17 closes the poppet valve 14 in the rotational range of the grip 21 from the fully open position to the fully closed (idle) position of the throttle valve.
As shown in the figure, the wire 20 is pulled in the direction of arrow A at a position where the grip 21 is rotated by a predetermined angle θ in the valve closing direction from the idle position, and the pressing member 19 is accordingly rotated counterclockwise. The valve body 15 is moved against the spring force of the spring 16 to press the valve body 15 and open the valve.

At a predetermined position downstream of the poppet valve 14 in the communication passage 12, a second valve, for example, a repulp 23 is interposed. A rotation shaft (not shown) of the valve body 23a of the valve 23 is connected to a second valve operating mechanism, the rotation shaft 24a of which is connected to the crankshaft 5 and expands as the rotational speed of the engine increases. For example, it is connected to the governor 24 via a link mechanism (not shown). This governor 24 is set so that the engine speed operates within a predetermined speed range,
The opening area of the communication passage 12 is continuously controlled by rotating the rotating shaft 24a according to the engine speed.

(Function) Next, the function of the engine brake actuating device for the two-stroke engine having the above configuration will be explained.

When the handle grip 21 is returned to the idle position when exiting the vehicle or decelerating, the engine enters the idle operating state.
The engine brake begins to work and the vehicle speed begins to slow down.

As shown in FIG. 2, when the handle grip 21 is further rotated in the direction of closing the throttle valve by an angle θ from the idle position (fully open position), the valve 14 opens and the communication passage 12 and the combustion chamber 7 are connected. As the piston 3 moves up and down, the gas in the combustion chamber 7 flows into and out of the communication passage 12, and this inflow and outflow creates resistance in the engine.

On the other hand, the rotary valve 23 changes the opening area of the communication passage 12 according to the engine speed, and accordingly
The flow rate of gas flowing into and out of 2 is controlled. As a result,
Since the amount of gas corresponding to the engine speed flows in and out between the combustion chamber 7 and the atmosphere side, an optimum braking force corresponding to the engine speed can be obtained.

Note that the other end 12b of the communication passage 12 may be opened directly to the atmosphere without being connected to the exhaust pipe 8.

3 and 4 show second and third embodiments of the present invention,
In FIG. 3, one end of each of the communicating passages 30°35 is opened and communicated with the approximate top of the combustion chamber 7, and a first opening is provided at one end and midway of each communicating passage 30°35 in the same manner as in the first embodiment. A valve, for example a poppet valve 31.36, and a second valve, for example a rotary valve 32.37, are fitted and these poppet valves 31
．． This is an embodiment in which check valves 33 and 38 are provided between the valves 36 and 32 and 37, respectively. The check valve 33 is configured to open and close only in the exhaust direction, and the check valve 38 is configured to open and close only in the intake direction.
(not shown), while the other end of the communication passage 35 is open and communicated with the atmosphere. As a result, by discharging gas through the communication passage 30 and inhaling gas through the communication passage 35, the intake and exhaust directions can be restricted to one direction, and the efficiency of intake and exhaust can be more effectively achieved. ,
Braking power will improve accordingly.

Figure 4 shows the check valve 33°38 shown in Figure 3 (second embodiment).
This is an embodiment in which pressure valves 40 and 41, which also serve as check valves, are respectively installed instead. These pressure valves 40 and 41 are set to open at a predetermined pressure immediately before the end of the intake and exhaust strokes. Thereby, the pressure valves 40 and 41 are opened immediately before the end of the intake and exhaust strokes, and the braking force of the engine brake can be obtained more effectively.

Although this embodiment describes the case where the rotary valve 23 is controlled to open and close by the governor 24 according to the engine speed, the present invention is not limited to this, and the rotary valve 23 may be electrically controlled according to the engine speed. It's okay. Furthermore, the engine rotational speed region may be divided into a plurality of regions, and the degree of opening of the low-return valves 23, 32, 37, etc. may be controlled in stages for each region.

(Effects of the Invention) As detailed above, according to the present invention, the first valve disposed at the one end opening of the communication passage whose one end opens into the combustion chamber and the other end opens to the atmosphere side; a second valve disposed in the middle of the
a first valve operating mechanism that operates in conjunction with an accelerator mechanism to open the first valve at a predetermined position beyond the idle position in the valve closing direction; and a first valve operating mechanism that opens the second valve in accordance with the engine speed. Since it is equipped with a second valve operating mechanism that controls and changes the opening area of the communication passage, the most efficient braking force of the engine brake according to the engine speed can be obtained with a simple structure. effective.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part showing an embodiment of the engine brake actuation device for a two-stroke engine according to the present invention, and FIG. 2 is a graph showing the relationship between the throttle valve and the rotational position of the second valve and the grip. , FIG. 3 is a sectional view of a main part showing a second embodiment of the present invention, and FIG. 4 is a sectional view of a main part showing a third embodiment of the invention. 7... Combustion chamber, 12, 30.35... Communication passage, 14
゜31.36...first valve, 23,32.37...
Second valve.

Claims (1)

[Claims] 1. A first valve disposed at the opening of one end of a communication passage whose one end opens to the combustion chamber and the other end opens to the atmosphere, a second valve disposed in the middle of the passage, and an accelerator mechanism. a first valve operating mechanism that opens the first valve at a predetermined position beyond an idle position in a valve closing direction; an engine brake operating device for a two-stroke engine, comprising: a second valve operating mechanism that changes an opening area of the communication passage;