When the engine is working, there is always a portion of the combustible mixture and exhaust gas passing through the piston ring to the crankcase. After the vapor of gasoline vaporizing into the crankcase will condense, the oil will become thinner and the performance deteriorates. The exhaust gas contains water vapor and sulfur dioxide. The water vapor condenses in the oil to form a foam which destroys the oil supply. This phenomenon is especially severe in winter; sulfur dioxide generates sulfite when it encounters water, and sulfite meets the oxygen in the air to generate sulfuric acid. These acidic substances The appearance of not only deterioration of oil, but also make parts corroded. Due to the flammable gas mixture and exhaust to the crankcase, the pressure inside the crankcase will increase, oil will leak from the crankshaft oil seal, crankcase liner, etc. and loss. Oil vapor lost to the atmosphere can increase the engine's atmospheric pollution. Engine equipped with crankcase ventilation can avoid or reduce the above-mentioned phenomenon, therefore, the role of engine crankcase ventilation is: 1. Prevent oil deterioration: 2. To prevent crankshaft oil seal, crankcase liner leakage; 3. To prevent a variety of Oil vapor pollutes the atmosphere. Second, the form and characteristics of crankcase ventilation 1. Natural ventilation The gas drawn from the crankcase can be directly introduced into the atmosphere, this ventilation is called natural ventilation. The ventilation structure is simple and easy to use, but the introduction of the combustible mixture of air and oil vapor easily pollutes the atmosphere, therefore, the use of modern engines is not much. According to the way into the atmosphere of natural ventilation with ordinary and respirator-style. (1) The oil vapor inside the ordinary crankcase is directly communicated with the atmosphere through the fuel filler opening of the oil pipe. This ventilation does not require specialized mechanical parts, all kinds of oil vapor directly into the atmosphere to the pollution of the atmosphere, it is not suitable for some rural areas on the tractor with a small internal combustion engine. (2) Respirator type crankcase oil vapor through a respirator-type device and the atmosphere. This respirator device is a filtering device that absorbs harmful gases and prevents the atmosphere from being polluted. Figure l for the Nanjing Yuejin Group and Italy joint venture production Iveco light passenger car engine breathing apparatus. The respirator is bolted to one side of the cylinder block with an air inlet on the side of the bottom communicating with the crankcase and the upper air outlet connected to the atmosphere through two rubber tubes. Inside the respirator, there are two layers of strainer filled with plated wire to separate oil mist and gas. Engine work, fleeing into the crankcase gas from the breathing apparatus inlet; into the respirator, filtered through the filter, separation, the last clean air from the outlet through the rubber tube. Because there are two layers of filters, oil mist is rarely discharged, both to ensure the pressure balance within the crankcase, but also to prevent the crankcase oil and gas pollution on the atmosphere. 2. Forced ventilation Use the suction of the engine intake system to suck the gas inside the crankcase, this ventilation is called forced ventilation. This kind of ventilation is somewhat complicated in structure, but it can be used in modern automobile engines because it can recover the combustible mixture and exhaust gas that flee into the crankcase, not only help to improve the economy of the engine, but also reduce the emission pollution of the engine . Press suction crankcase gas forced ventilation in the form of general, one-way valve, oil and gas separation and integrated. (1) The general style is just to use the rubber tube to connect the crankcase and intake pipe ventilation mode for the general forced ventilation. The ventilation structure is relatively simple, just the pipe connection, the middle does not require other components connected, suitable for some small engines. Gasoline crankcase general forced air device. An air intake hose is provided in the upper part of the air cleaner for opening into the valve cover. An outlet pipe of the tappet cover is connected to the inlet of the carburetor. Engine work, the crankcase gas into the carburetor through the outlet pipe, the fresh air filtered by the air filter through the intake hose, valve cover added to the crankcase. (2) One-way valve Connect a check valve in the pipe connecting the crankcase to the intake pipe to prevent the oil in the crankcase from being sucked out. Suitable for vehicle gasoline engine such as EQ6100Q, Japan Mitsubishi Pajero (Cheetah) car engine Wait. Gasoline one-way valve crankcase forced ventilation device. A small air cleaner is fitted to the valve housing and is connected by an exhaust pipe between the crankcase and the intake pipe and a check valve is provided at the connection pipe before entering the intake pipe. When the engine is working, the steam in the crankcase is drawn into the cylinder through the outlet pipe and check valve, and the fresh air enters the crankcase through the small air cleaner on the valve cover. The function of the check valve is to prevent the suction of the engine oil from the crankcase when the engine vacuum is too high at low speed and light load. Crankcase ventilation check valve, mainly by the valve, valve body, seat and spring composition. When the engine is idling, the intake pipe has a large degree of vacuum, the one-way valve is sucked in the valve seat, and the exhaust gas in the crankcase enters the intake pipe through the small hole in the valve. As the engine load increases, the vacuum degree of the intake pipe decreases, Under the action of force to open to the outside, then the ventilation gradually increased; engine load, the valve is fully open, the maximum ventilation, which play a role in updating the crankcase air. (3) Oil-air separator type Connect an oil-gas separator in the pipe connecting the crankcase to the intake pipe to separate the oil and gas sucked from the crankcase so that the liquid oil flows back to the crankcase and the gaseous gas Inhalation of the intake pipe, this can reduce the oil consumption. Steyr engine oil separator, which is mounted on the front of the engine cylinder head. Engine work, fleeing into the crankcase oil and gas pipe into the oil and gas separator, due to the oil and gas separator volume under the plane is inclined, so the liquid oil along the slope, the return pipe back to the crankcase, and the gas through the gas Connect the tube into the air intake. (4) The integrated type is not only connected with a check valve in the pipe connecting the crankcase and the intake pipe, but also connected with an oil-gas separator, which greatly reduces oil consumption and ensures engine oil lubrication stability under various working conditions. Gasoline engine crankcase integrated forced ventilation device. Install the crankcase ventilation inlet air cleaner on the cylinder head front cover, install the crankcase ventilation air outlet filter on the cylinder cover rear cover, there is oil-gas separation in the filter, so it is also called oil-gas separation Device.