JPS5857628B2 - engine carburetor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carburetor for an engine equipped with an auto-choke mechanism, and particularly to its fast idle cam mechanism.

Conventionally known carburetors with auto choke mechanisms include a bimetal mechanism that controls the opening of the choke valve according to the outside temperature, and a fast idle cam mechanism that sets the opening of the throttle valve in response to the opening of the choke valve. It is also equipped with a complete explosion diaphragm mechanism, etc. to maintain continuous operation after the engine is started (see, for example, Japanese Utility Model Application No. 50-26221).
.

That is, as shown in FIG. 1, a choke lever 4 is fixed to a choke shaft 3 that supports a choke valve 2 provided in a carburetor intake passage 1, and a bimetallic (
The bimetal allows the choke valve 2 to respond to the outside temperature by supporting one end of the bimetal (not shown), while the unloader 6, which is rotatably mounted on the shaft 5 of the carburetor body, is connected to the choke lever 4. A fast idle cam 8 is rotatably attached to the shaft 5 and connected via a rod 7, and the first idle cam 8 is attached by a spring 9 so as to rotate counterclockwise in the figure with respect to the unloader 6. The first idle cam 8 is configured to engage with a locking portion 6a provided on the unloader 6 to stop its rotation in the counterclockwise direction, and the first idle cam 8 has a stepped cam portion 8.
a, 8b, 8c, and 8d, and the throttle valve 10 is held at a predetermined opening degree by bringing the tip of a throttle valve lever 11, which rotates together with the throttle valve 10, into contact with the cam portions 8a to 8d. , the throttle valve 10 is choked by bringing the throttle valve lever 11 into contact with any of the cam parts 8a to 8d of the fast idle cam 8 in accordance with the opening degree of the choke valve 2 according to the outside temperature during a cold start. The engine is started by holding the valve Iζ open at a predetermined opening corresponding to the opening of the valve 2.

However, in the conventional device described above, the choke valve 2 is fully closed to throttle the intake air for engine starting and to ensure the supply of a large amount of fuel, and the purpose is to fully close the choke valve 2 when the outside temperature is below a certain temperature (usually 10 to 20 degrees Fahrenheit). ℃ or below), it is necessary to fully close the choke valve 2. In this case, the throttle valve 10 is opened to a predetermined opening degree with its throttle valve lever 11 coming into contact with the cam portion 8a of the first idle cam 8 at the maximum opening degree. After the engine starts, the choke valve 2 is released from the fully closed state by the complete explosion diaphragm mechanism and is opened to a predetermined opening degree to ensure continued operation of the engine, whereas the throttle valve 10 is opened by its return spring. Since it is in contact with the first idle cam 8 due to spring force, even if the choke valve 2 is opened, it does not return to the idle opening position, and this first idle cam 8 and throttle valve 10
The engaged state will not be released unless the accelerator pedal is pressed even after the engine has started.

This also applies to the first idle cam 8 in which the cam portions 88 to 8d of the first idle cam 8 are formed in stages, as shown in FIG. 1, as well as those in which a continuous smooth cam portion is formed.

Therefore, if the first idle cam 8 is set with the assumption that the engine will be started at extremely low temperatures (for example, -15°C) and the throttle valve 10 is left wide open, then at normal low temperatures when the choke valve 2 is completely off (for example, 10'C) After the engine is started, the throttle valve 10 opens to a degree greater than that required for stable engine rotation, which causes the engine rotation to rise, causing noise and heat damage to the exhaust gas purification device.

Also, if the fast idle cam 8 is set at a normal low temperature (for example, 100G) and the throttle valve 10 is opened to a predetermined opening, the engine may not start or may not start at extremely low temperatures (for example, -15℃). Due to the low temperature, especially in engines equipped with automatic transmissions, the viscous resistance of the oil is high, so the engine stops immediately.

In other words, with the conventional fast idle cam mechanism,
The opening degree of the throttle valve 10 is uniquely determined when the choke valve 2 is fully closed, and it is not possible to control the throttle valve opening degree below the fully closing temperature of the choke valve 2, causing the above-mentioned problem. was.

The present invention has been made in view of this problem, and includes a first idle cam in an auto choke mechanism, in which a cryogenic cam part is provided in addition to a low temperature cam part when the choke valve is fully closed, and both are kept at outside temperature. It is an object of the present invention to provide an engine carburetor that can appropriately set a fast idle cam in response to normal low temperatures and extremely low temperatures by selectively using the carburetor.

That is, the present invention provides a carburetor for an engine equipped with a fast idle cam having a cam part that sets the opening degree of a throttle valve in accordance with the opening degree of a choke valve. The present invention is characterized in that the cam portion is multi-staged, and the cam portion is configured to be used selectively depending on the outside temperature.

Hereinafter, the present invention will be explained in detail based on embodiments shown in FIG. 2 and the following figures.

Incidentally, the same parts as in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted.

FIG. 2 shows a first embodiment of the present invention, in which a conventional fast idle cam 8 has a cam portion 8a at the highest position as a low temperature cam portion corresponding to the choke valve 2 being fully open at normal low temperatures (for example, 10° C.). In addition to setting it so that
One end of the bimetal 12, which switches 0N-OFF at about 10'C), is fixed near the shaft 5 of the fast idle cam 8 with a pin 13, and the cryogenic cam part 14 is attached to the other end of the low-temperature cam part 8a. The top is slidably attached,
At normal low temperatures (for example, 10°C), the cryogenic cam part 14
is located away from the low temperature cam part 8a as shown by the solid line, and the throttle valve lever 11 comes into contact with the low temperature cam part 8a to hold the throttle valve 10 at a predetermined opening degree. For example, at -10°C), the bimetal 12 switches,
As shown by the imaginary line, the cryogenic cam part 14 slides on the low-temperature cam part 8a and is located protruding above the low-temperature cam part 8a, and the throttle valve lever 11 is attached to the cryogenic cam part 14. The throttle valve 10 is held at a larger opening degree than when the temperature is normally low.

Further, FIG. 3 shows a second embodiment of the present invention, in which a fast idle cam 8' is formed with stepped cam parts 8'a to 8'f, and the highest of the cam parts 8'a to 8'f is Cam part 8 at position
/a is the cryogenic cam part, and the next highest cam part &'
b is a low-temperature cam part, and the conventional unloader 6
The locking part 6a of the
Using a bimetal 15 that switches in a 0N () FF manner at 10℃), connect one end of the bimetal 15 to the unloader 6 with pin
6, and the other end is brought into contact with the first idle cam 8' to prevent counterclockwise rotation by the spring 9 of the first idle cam. At normal low temperatures, the bimetal 15 is shown in the imaginary line. By stopping the rotation of the first idle cam 8' at the position shown, the throttle valve lever 11 comes into contact with the low-temperature cam part B/b, and the maximum opening corresponding to the choke valve of the throttle valve 10 being fully opened is maintained. On the other hand, at extremely low temperatures, the bimetal 15 is switched to the position shown by the solid line, and the first idle cam 8'
By changing the stopping position for the throttle valve lever 11
is in contact with the cryogenic cam portion &'a to maintain the throttle valve 10 at a larger opening.

Furthermore, FIGS. 4 and 5 show a third embodiment of the present invention, in which similarly stepped cam portions 17a to 17a are provided on the back surface of a conventional fast idle cam 8 set for normal low temperature use.
The cryogenic first idle cam 17 having a diameter of 17d is overlapped with its cam parts 17a to 17d protruding from the cam parts 8a to 8d of the low temperature fast idle cam 8,
Both first idle cams 8 and 17 are urged by a spring 18 to slide in the axial direction on the shaft 5, while an extremely low temperature (about -10°C) is applied to the opposite side of the spring 18.
The dish-shaped bimetal 19 is provided to restrict the sliding movement of the springs 18 of both the first idle cams 8, 17, and the dish-shaped bimetal 19 switches between the two first idle cams 8, 17 as shown by the imaginary line at normal low temperatures.
5, the throttle valve lever 11 comes into contact with the cam portions 8a to 8d of the low-temperature first idle cam 8, and the choke When the valve is fully closed, the throttle valve 10 is held at a predetermined opening degree by contacting the cam portion 8a at its highest position, while at extremely low temperatures, the dish-shaped bimetal 19 switches between both first idle cams 8 as shown by the solid line. By reversing the convex shape with respect to °17 and setting the sliding restriction position of both first idle cams 8, 17 to the left, the throttle valve lever 11 is brought into contact with the cam portions 17a to 17d of the first idle cam 17 for cryogenic use. When the choke valve is fully closed, the throttle valve 10 is held at a larger opening by coming into contact with the cam portion 17a at its highest position.

In each of the above embodiments, the low-temperature and extremely low-temperature cam parts corresponding to fully opening the choke valve of the first idle cam are selectively switched using a bimetal according to the outside temperature, but instead of this bimetal, a wax pellet or the like is used. Although it is of course possible to use a means that responds to the temperature, bimetal is preferable because it is suitable for ON-OFF switching and has the advantage of being inexpensive.

Further, in each of the above embodiments, the cam part of the first idle cam is formed in steps, but the present invention can also be applied to a cam part in which the cam part is formed continuously and smoothly. It is sufficient to use one that continuously changes the amount of deformation depending on the outside temperature.

Furthermore, in the above explanation, the case where the cam part corresponding to the full opening of the choke valve of the first idle cam is made into two stages, one for low temperature and one for extremely low temperature, has been described. 0℃) and cryogenic temperatures (e.g. -1
It goes without saying that the technical idea of the present invention also includes the provision of three or more stages of cam portions (5° C.).

As explained above, according to the present invention, in a carburetor for an engine equipped with an auto-choke mechanism, the cam portion corresponding to fully opening the choke valve of the first idle cam is multi-staged, and the cam portion is adjusted in accordance with the outside temperature. By configuring the throttle valve to be used selectively when starting the engine, the opening degree of the throttle valve can be set to an appropriate opening degree depending on the outside temperature. It is possible to improve engine startability by preventing noise caused by the rise and heat damage to the exhaust gas purification device.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional example, FIGS. 2 to 5 illustrate embodiments of the present invention, FIG. 2 is a schematic diagram of a main part showing Embodiment 1, and FIG. FIG. 4 is a schematic view of the main part showing the third embodiment, and FIG. 5 is a sectional view taken along the line v--v in FIG. 4. 1... Carburetor intake passage, 2... Choke valve, 3... Choke shaft, 4... Choke lever, 5... Shaft , 6... Unloader, 6a... Locking part, 7... Rondo, 8, 8'... First idle cam, 8a
~8d, 8'a~8'f...Cam section, 9...
...Spring, 10... Throttle valve, 11...
... Throttle valve lever 12 ... Bimetal, 13.
...Pin, 14...Cryogenic cam part, 1
5... Bimetal, 16... Pin, 1
7... First idle cam for cryogenic temperatures, 17
a to 17d...Cam portion, 18...Spring, 19...Dish-shaped bimetal.

Claims (1)

[Claims] 1. In a carburetor for an engine equipped with a fast idle cam that has a cam part that sets the opening degree of the throttle valve according to the opening degree of the choke valve, the cam part corresponding to fully closing the choke valve of the first idle cam is multistaged. Also, a carburetor for an engine, characterized in that the cam portion is configured to be used selectively depending on outside temperature.