Chain saw carburetor main classification and basic
1. Classification of chain saw carburetor Carburetor is divided into simple carburetor and complex carburetor. Carburetors can also be divided into down suction and flat suction. The carburetor is divided into throttle type, rotary type and lifting type. A rotary throttle is a disc-shaped throttle that rotates around an axis between the carburetor throat and the intake pipe to change the flow area of ??the intake passage. The structure of the lift throttle is a bucket-shaped plate throttle, which moves up and down at the throat, and changes the passage area at the throat. This method is mostly used for motorcycle carburetor. There is also a carburetor that is a hybrid of the two. It uses a person to control a rotary throttle and a diaphragm to control a lifting throttle. This is also commonly used on motorcycles and is called the CV type. 2. Structure of chain saw carburetor The complex carburetor is composed of three parts: upper, middle and lower. The upper part has an air inlet and a float chamber, the two ends have throats, measuring holes and nozzles, and the lower part has a throttle valve. The float chamber is a moment descriptor, which stores gasoline from the gasoline pump. There is a float outside the container. The height of the float (oil surface) should be used to control the amount of oil. The oil inlet of one end of the nozzle in the middle communicates with the measuring hole of the float chamber, and the oil outlet of the other end is at the throat of the throat. The larynx is in the shape of a waist of a bee, with two large ends in the middle and a small cross section at its throat. When the initiator starts, the piston descends and suction occurs. When the inhaled airflow passes through the throat, the velocity is the highest, but the static pressure is the lowest. Therefore, the pressure of the throat is less than the atmospheric pressure, that is, a pressure difference occurs between the throat of the throat and the float chamber. That is, with the 'vacuum degree' that people often say, the greater the pressure difference, the greater the vacuum degree. Gasoline is ejected from the nozzle outlet under the effect of vacuum. Because the air flow rate at the throat of the throat is 25 times that of the gasoline, the oil flow from the nozzle is washed away by the high-speed air flow, forming a size Uneven fog particles, that is, 'fog'. The initially atomized oil particles are mixed with air to decompose 'mixed gas', and enter the extinguishing chamber of the cylinder through the throttle valve, intake duct and intake valve. Here, the opening of the throttle and the speed of the engine determine the vacuum at the throat, and the change in the opening of the throttle indirectly affects the proportion of the mixture. These are important reasons for the operation of the engine. A concept of 'air-fuel ratio' is touched here. The so-called air-fuel ratio refers to the ratio of air quality to fuel quality. Superstitious believes that 1 kg of gasoline needs about 14.7 kg of air to be completely extinguished, that is, the air-fuel ratio is 14.7:1. The mixed gas is called the standard mixed gas. Because this value is difficult to complete in theory, it is also called the 'actual mixed gas'. The air-fuel ratio greater than the standard mixture is called lean mixture, and the one less than the standard mixture is called rich mixture. Because the concentration change of the mixed gas is closely related to the load change of the engine under various operating conditions, Complex carburetor can't meet this kind of changing requirement at any time, so people often add new installations on complex carburetor to adjust the carburetor's task form. Starting from tomorrow, it constitutes a carburetor with various auxiliary installations, followed by idle speed, enrichment, deceleration and start-up installation. At present, the rare carburetor of the 4-cylinder engine is a double-chamber split carburetor, which has two throats, which can be distinguished according to different working conditions of the engine or at the same time. The rare carburetor of the 6-cylinder engine is a dual-cavity parallel carburetor. It is actually two single-cavity carburetors and together, each cavity serves as the mixed gas supply for half the number of cylinders. There are also multi-cavity carburetor, which is usually disassembled on the higher power engine. Among the various functions of the carburetor installation, the main fuel supply installation is the fuel supply installation required by the engine in other working conditions except idle speed, which is the basic fuel supply structure of the carburetor. Idle speed installation is the installation that provides little and rich mixture during idle operation to maintain the minimum speed of the engine fluctuation. Enrichment installation is the installation of rated oil supply when the engine is under heavy load to compensate for the lack of main oil supply. Deceleration installation is the installation of rated fuel supply when the throttle opening suddenly increases when the car decelerates, so that the engine speed and power can increase rapidly. The start-up installation is an installation that provides a very rich mixture when the engine is cold-started. A rare way is to install a choke valve behind the throat to control the intake air volume. In particular, idling should be mentioned here. Idle speed is the most commonly used engine operating condition, which is used to initiate the engine's hot start process and stop without shutting down. The driving function of the car has very important significance, especially when driving in the city. The idling situation often determines the fuel consumption and pollution level of the car. The idling speed of the engine is usually only 600-800 rpm, and the throttle is nearly closed. The vacuum of the throat caused by such a speed cannot smoothly draw gasoline from the float chamber, but the vacuum in front of the throttle is very high. Therefore, it is only necessary to set up another idle oil passage on the base of the complex carburetor, and the injection hole is set after the throttle valve, and the results are solved. Because the idling demand is low and the mixture is rich, it is more sensitive to the operation of the engine. To complete the idling mode that requires both fluctuation and minimum speed, it is necessary to stop the adjustment of the fuel quantity control and the adjustment of the minimum opening of the throttle valve. Today's carburetor is equipped with two adjustment screws at idle speed to distinguish the adjustment oil quantity and throttle opening. At the same time, in order to avoid the situation that the engine is still closed when the ignition switch is closed, there is also an idling solenoid valve in the idling oil passage of the carburetor, which is dedicated to the old and cut-off idling oil passage to ensure that the engine can quickly shut down.