Structural characteristics of the hottest cah212 c

Structural characteristics of cah212 carburetor

cah2l2 carburetor is a double cavity down suction diaphragm transfer carburetor introduced from Pierburg company in Germany. The carburetor is composed of an upper body, a lower body, an automatic air blocking body and an automatic air blocking cover in the working process. Because cah112 carburetor is made of aluminum alloy, the weight of carburetor assembly is greatly reduced. In addition, many important structural partners are replaced by engineering plastics. Therefore, cah212 carburetor has the characteristics of more compact structure and lighter weight compared with H200, as shown in figure 3-l18

(L) starting system

it includes choke, automatic choke, blaster, fast idle mechanism and choke forced opening mechanism. The starting system is semi-automatic

① automatic air blocking The automatic air choke is a bimetallic torsion spring type, using engine cooling cycle

figure: cah212 carburetor structure

1- main control throttle; 2-idle oil outlet; 3-adjusting screw of idle mixer; 4-transition hole; 5-lower body; 6-sealing gasket; 7-upper body; 8-main chamber small throat; 9-choke; 10 idle air orifice; 11 main chamber main air orifice and foam tube; 12 main air measuring hole and foam pipe of auxiliary chamber; 13 full load enrichment pipe; 14 auxiliary chamber transition system oil intake pipe; 15 - auxiliary cavity small throat; 16. The clamping length of the secondary cavity transition air test is short, and the correct application method of the clamping of the tensile testing machine should be the measuring hole; 17 - auxiliary chamber throttle; 18 vacuum air intake pipe; 19 auxiliary cavity transition hole; 20 - transition oil measuring hole of auxiliary chamber; 21 main oil measuring hole of auxiliary chamber; 22 main oil measuring hole of main chamber; 23 balance pipe; 24 needle valve; 25 oil inlet filter; 26 needle valve fork; 27 float; 28 sealing gasket; 29 flange; 30 partial load enrichment valve; 31 bonnet; 32 compression spring; 33 diaphragm; 34 acceleration pump cam; 35 mushroom head valve; 36 acceleration pump spring; 37 accelerating pump diaphragm; 38 acceleration pump rocker arm; 39 acceleration pump tappet; 40 pump cover; 41 oil return hole; 42 ball valve; 43 accelerating pump nozzle; 44 temperature time valve air intake; 45； The function of the common heating method of water and electric heating wire is to use the bimetallic torsion spring to twist with the change of temperature

② blaster: it is a two-stage type, and its function is to assist the automatic choke mechanism to control the two openings of the choke under specific two working conditions, so that the engine can maintain operation and warm the engine economically after cold start

③ fast idle mechanism: so as to minimize the impact of temperature drift. See figure 3-l19 for the basic composition and structure. The function of the fast idle mechanism is to adjust the opening of the throttle valve through the fast idle cam and adjusting screw during the warm-up process, so as to control the mixed air volume supplied by the carburetor to the engine. Since the deflection of the fast idle cam is controlled by the bimetallic torsion spring with automatic air blocking, the fast idle mechanism can reasonably control the warm-up speed according to the thermal state of the engine. The fast idle cam has five steps, the highest of which is the cold start stage. During cold start, the choke is closed, and the throttle screw must fall on this cold start stage to open the throttle at a large angle to ensure the smooth start of the engine. The steps after the second step are all required for fast idle warm-up. When the driver steps on and releases the throttle, the throttle screw falls on the one step higher than the idle cam. When the adjusting screw finally disengages the fast idle cam, the engine can run at the normal idle speed only when it reaches the normal operating temperature

figure: fast idle mechanism

1-throttle longitudinal frame; 2-fast idle speed adjusting screw; 3-fast idle cam; 4-follow-up rocker arm; 5-choke

figure: choke forced opening mechanism

1-throttle rocker arm; 2-fast idle speed adjusting screw; 3-cam; 4-follow-up rocker arm; 5-connecting rod; 6-choke rocker arm; 7-choke; 8-throttle limit screw; 9-throttle

④ choke forced opening mechanism: this mechanism is a linkage mechanism of throttle and choke, as shown in figure 3-l20. When the engine is in a cold state, that is, when the choke opening is still small, and it needs to drive cold, with the throttle opening larger, this mechanism will force the choke to open larger to prevent excessive mixture

(2) idle system

the idle system includes idle oil orifice, air orifice, idle shut-off valve, idle adjusting screw and idle oil needle. Its function is to ensure that the engine supplies appropriate mixture when idling. The idle shut-off valve shown in figure 3-l2l is an electric

magnetic valve assembled on the idle oil circuit. Its function is to open or cut off the idle oil circuit with the opening and closing of the ignition lock, which can effectively ensure the engine shutdown

(3) main oil supply system

it is composed of main chamber small throat, main chamber throttle, main air orifice of main chamber, main oil orifice of main chamber, etc. Its function is to supply enough combustible mixture to the main chamber when the throttle is opened wider

(4) main chamber transition system

the main chamber transition oil outlet is a fine slit, which is located above the idle oil outlet. Its function is to ensure the smooth transition from idle speed system to main oil supply system and good operation under partial load. However, at this time, the valve of the auxiliary chamber is still locked, in the closed state, and has not yet participated in the work. When the relative humidity of the vehicle driving environment exceeds 95% and the temperature is lower than 0 ℃, ice is easy to appear in the carburetor

the reason for icing is that the high-speed flowing gas and a large amount of evaporated fuel take away a lot of heat. When the ignition switch is turned on, the heating element starts to heat, so as to prevent the carburetor body from supercooling. When the temperature of the heating element itself exceeds the conversion temperature, its resistance suddenly becomes infinite, making the heating function stop naturally

(5) partial load and enrichment system

cah212 carburetor's partial load enrichment is completed by the enrichment valve, and the enrichment I valve is a diaphragm control valve. The inner chamber of the valve cover behind the diaphragm is in contact with the mixing chamber through an air circuit. When the load is low, due to the small opening of the throttle valve, the vacuum behind the throttle valve is very high, so that the diaphragm is sucked, and the valve core is pulled to the valve seat against the tension of the spring, thus blocking the enrichment system oil circuit. When the throttle valve is opened large and the load is high, the vacuum degree at the air intake hole will drop, and the suction of the diaphragm is not enough to overcome the spring force, so the valve core will be pushed open. The fuel flows into the main oil well of the main chamber from the enrichment system oil circuit, mixes with the main oil system fuel, and then injects into the chamber from the main oil outlet, so as to enrich the mixture

with the partial load enrichment valve, the main oil orifice in the main chamber can be selected smaller, which improves the low load economy. When the load is large or accelerating, with the opening of the throttle, the enrichment valve immediately compensates for the oil supply, thus ensuring the responsiveness and acceleration of the carburetor

(6) the acceleration of the carburetor of the shading system

is completed by the acceleration pump, which is a diaphragm type, and its oil volume and injection law depend on the stroke and motion law of the diaphragm, and are controlled by the initial position of the cam

(7) auxiliary chamber transition system

cah2l2 carburetor adopts transfer capsule or auxiliary chamber control mechanism, and is equipped with main and auxiliary chamber linkage locking mechanism. The function of setting auxiliary chamber transition system is Counteract the dilution trend of the mixture caused by the sudden increase of air intake when the secondary chamber throttle starts to open. The throttle valve of the auxiliary chamber is not opened at will, and the following two conditions must be met,

① the engine speed and load are large enough, that is, the air intake reaches a certain value

② the throttle opening of the main chamber is enough to make the two locking cams out of the self-locking range

only when these two conditions are met at the same time, the vacuum degree of the main and auxiliary cavities can suck the diaphragm. The structure of the auxiliary cavity transfer case is shown in ring 3-l22. The sucked diaphragm makes the diaphragm pull rod pull the throttle valve of the auxiliary chamber open. However, the opening law of the auxiliary chamber is still limited by the locking cam, that is to say, the throttle valve of the auxiliary chamber can only be opened according to the structural design law. In addition, when the throttle valve of the main chamber is closed, the mechanism will force the throttle valve of the auxiliary chamber to close accordingly, which is a safety measure

figure: sub chamber transfer case

1- main chamber throttle; 2-throttle limit screw; 3-cam; 4-throttle rocker arm; 5-fast idle speed adjusting screw is people-oriented; 6-auxiliary chamber throttle valve; 7-auxiliary chamber throttle rocker arm; 8-transfer capsule valve; 9-transfer capsule; 10 torsion spring; 11 follow up fork; 12 - sub chamber throttle limit screw

(8) full load system

in order to ensure the inflation of the engine under full load high-speed working conditions, the air supply and fuel supply are further compensated, which not only opens the sub chamber working system, but also adds a full load enrichment pipe to meet the requirements of the engine. In addition to the above systems, cah2l2 carburetor is equipped with some additional devices, including idle shut-off valve, PTC heater, oil vapor separator, throttle buffer, idle load compensator, etc. the first several have been introduced, and the idle load compensator is introduced below

idle load compensator is composed of vacuum capsule, electromagnetic change-over valve and air intake pipe, as shown in figure. When the electrical appliances with large power consumption of the whole vehicle (such as automatic transformer, steering booster or air brake, etc.) work under idle working conditions, the electromagnetic conversion valve on the load compensator opens the vacuum path, so that the vacuum degree of the intake pipe acts on the diaphragm in the diaphragm box, and the diaphragm is sucked. Pull up the diaphragm pull rod, so that the load compensation rocker arm pulls up the throttle rocker arm, and the throttle valve then opens an angle, so as to increase the inflation of the engine and make up for the power consumed by the electrical appliances, Thus, the idle speed of the engine is no longer affected by the vehicle power, and always idles at the specified speed. (end)