現(xiàn)場(chǎng)車削提升機(jī)制動(dòng)盤裝置以及工藝設(shè)計(jì),現(xiàn)場(chǎng)車削提升機(jī)制動(dòng)盤裝置以及工藝設(shè)計(jì),現(xiàn)場(chǎng),車削,提升,晉升,機(jī)制,裝置,以及,工藝,設(shè)計(jì) 河南理工大學(xué)萬方科技學(xué)院本科畢業(yè)論文 本科畢業(yè)設(shè)計(jì)（論文） 中英文對(duì)照翻譯 院（系部） 萬方科技學(xué)院機(jī)械與動(dòng)力工程系 專業(yè)名稱 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 年級(jí)班級(jí)　 機(jī)設(shè)08-2班 學(xué)生姓名 梁 利 彎 指導(dǎo)老師 牛 振 華 2012年5月 ENGINE MECHANICAL Operation Main Components and Classification of the Engine The automotive engine is essentially a heat mobiles are internal combustion engines. Princiole of Operation The spark-ignition engine is an internal-combustion engine with externally supplied in ignition .The gasoline engine is a kind of spark-ignition engines. The four-stroke-cycle gasoline engine cycle is spread over four pistion strokes. The first stroke in your engine is called the intake stroke. Instead of opening the intake valve after you have drawn the poston down . you will find it better to open the intake valve as the piston starts down . This allows the air to draw fuel in the entire time the piston is moving down. Remember , the intake stroke starts with the piston at the top of the cylinder(intake valve open and exhaust valve closed)and stops with the piston at the bottom of its travel . This requires one half turn of the crankshaft. As the crankshaft continues to move , the piston is forced up through the cylinder . If you keep both valves closed , the fuel mixture will be squeezed , or compressed , as the piston reaches the top .This is called the compression stroke . It , too , requires a half turn of the crankshaft . The compression stroke serves to break up the fule into even smaller particles . This happens due to the the sudden swelling and churning of the mixture as it is compressed . When the air fule mixture is subjected to a sudden sharp compression force . its temperature rises .This increase in temperature makes the mixture easier to ignite and causes it to explode with greater force , As the piston reaches the top of its travel on the compression sroke , it has returned to the pro[er position to be pushed back down by the explosion. Remember , the compression stroke starts with the piston at the bottom of the cylinder(both valves closed)and the stops with the piston at the top of the cylinder . This requires an additional half turn of crankshaft . As the piston reaches the top the compression stroke ,the mixture is broken into tiny particles and heated up . when ignited , it will explode with great force . This is the right time to explode the mixture . A spark plug provides a spark inside the combustion chamber ,The spark produced at the plug is formed by the ignition system. Just imagine that a hot spark has been provided in the fuel mixture . The mixture will explode and , in turn , force the piston down into the cylinder . This gives the crankshaft a quick and forceful push . This is the power stroke , Both valves must be kept closed during the power stroke or the pressure of the burning fuel will squirt out through the valve ports . Remenber , the power storke starts with the piston at the top of ylinder(both valves closed) and stops with the piston at the botton of the cylinder , T his requires another half turn of the crankshaft . When the piston reaches the bottom of the power stroke .the exhaust valve opens . The spinning crankshaft forces the piston up through the cylinder , pushing burned gases out . This is the exhaust stroke . Remenber , the exhaust stroke starts with the piston at the bottom of the cylinder (exhaust valve open and intake valve closed) . It stops with the piston at the top of the cylinder . This requires one more half turn of the crankshaft . If you count the number of half turns in the intake , compression , power , and exhaust storkes , You will find you have a total of four , This gives you two complete turns , or revolutions ,of the crankshaft . When the crankshaft is turning around twice ,it is receiving power only during one half turn , or one fourth of the time . As soon as the piston reaches the top of the exhaust stroke , it starts down on another intake , compression , power ,and exhaust cycle , this cycle is repeated over and over ,Each complete cycle consists of four strokes of the piston , hence the name four-storke cycle. Main Engine Componennts Engine Block The engine block serves as a rigid metal foundation for all parts of engine . It contains the cylinders and supports the crankshaft and camshaft . In older engines ,the valve seats , ports ,and guides are built into the block ,Accessry unis and the clutch housing are boled to it . Blocks are made of either cast iron or aluninum ,The lighter the block(providing it has sufficient strength), the better ,The modern thin-wall casting proces controls core size and placement much more accuratcely than the older casting process .This permits casting the block walls much thinner , reducing the weight of the block .Since the bolck wall thickness is more uniform , block distortion during service less severe . Cylinders The cylinder is a aroud hole formed in the block .It forms a guide guide for the piston and acts as a containner for taking in , compressing ,firing , and the exhausting the air-fuel chareg , Cylinder have been made of both steel and cast iron .Cast iron is by far the most popular. When steel cylinders are desired in an aluminum block, they are installed in the form of cylinder sleeves(round , pipe-like liners ), These sleeves may be eiher cast or pressed into the block ,Some engines use removable cylinder sleeves . When the cylinde becomes won The old sleeves can be pulled out and new sleeves can be pressed in . The sleeves are pressed into oversize cylinder holes ,Cylinder sleeves are widely used in heavy-duty truck and industrial engines ,Sleeves can also be used to be repair a won or cracked cylinder in a cast iron block . Pistons The piston must move down through the cylinder to the cylinder to produce a vacuum to draw a fuel charge into the cylinder . It then travels up in the cylinder and compresses the mixture ,When the mixture is fired , the pressure of the expanding gas is transmitted to the top of piston . This drives the piston back down through the cylinder with great force , transmitting the expanding gas to the crankshaft ,The piston then then travels up through the cylinder and exhaust the burned fuel charge. Pistons are usually made of aluminum . Often ,aluminum piston are tin-plated to allow proper break-in when the engine is stared ,Aluminum pistons can be forged ,but they are more commonly cast .Cast iron is a good material for pistons used m a slow-speed engine .It has excellent wear characteristics and will provide good performance . Connecting Rods As the name implies , connecting rods are used to connect protons to the crankshaft .The upper end of the rod oscillates(swings back and forth), while the lower ,or big end ,bearing rotates(turns). Because there is very little bearing movement in the upper end , the bearing area can be reasonably small . The lower end rotates very fast , and the crankshaft bearing journal turns inside the connecting rod . This rotational speed tends to produce heat and wear .To make the rod wear well, a larger bearing area is required. The upper end of the rod has a hole through it for the piston pin ,The botton of the large end of the connecting red must be removed SO the rod can be installed on the crankshaft journal .The section that is removed is called the connecting rod cap. Connecting rods are normally made of alloy steel .They are drop-forged shape and then machined . Crankshaft The engine crankshaft provides a constant turning force to the wheels ,it has through to which connecting rods are attached ,and its function to change the reciprocating motion of the piston to a rotary motion to drive the wheels . Crankshaft are made of alloy steel or cast iron. The crankshaft is held in position by a series of main bearings ,The maximum mumber of main bearings for a crankshaft is one more than the munber of cylinders. It may have fewer main bearings than cylinder .Most engines use pressman insert bearings that are constructed like the connecting rod bearings, But are somewhat larger .In addition to supporting the crankshaft , one of the main bearings must control the forward and backward movement. Flywheel A heavy flywheel is attached to the rear of the crankshaft with bolts ,The function of the flywheel is to smooth out engine speed and keep the crankshaft spinning between power strokes . in some engines , the flywheel also serves as a mounting ,surface for the clutch . The outer rim of the flywheel has a large ring attached with gear teeth cut into it , The teeth of the starter motor engine these teeth and spin the flywheel to crank the engine . When all automatic transmission is used ,the torque converter assembly works with the flywheel. Camshaft The camshaft is used to open and close the valves . There is one cam on the camshaft for each valve in the engine ,Generally only one camshaft is used in most engines . Newer engines are increasingly equipped with two or more camshaft. Valves Each engine cylinder ordinarily has two valves . However , modern engines often use four valves per cylinder(two intake and two exhaust), A few engines used in smaller vehicles have three intake valves per cylinder : two intake valves and one exhaust valves or three intake valves and two exhaust valves . Because the head of an exhaust valve operates at temperatures up to 1300C(704C) ,valves are made of heat-resistant metal . In order to prevent burning ,the valve must give off heat to the valve seat and to the valve guide . The valve must be make good contact with seat and must run with minimum clearance in the guide . Valve Lifters Mechanical valve lifters are usually made of cast iron , The bottom Dart that contacts the camshaft is hardened .Some lifters are hollow to reduce weight .Most valve trains that contain mechanical lifters have some provision for adjusting clearance . Mechanical valve lifters were used in older engines . Hydraulic valve lifters perform the same job as mechanical lifters , However ,hydraulic lifters are self-adjusting , operate with no lifte-to –rocker arm clearance . and uses engine oil under pressure to operate ,Hydraulic lifters are quite in operration . Engine Classification Cycle Classification Engines are often classified according to cycle . Most internal combustion piston engines use a two-or four –stroke cycle .All modern automobile engines use the four stroke cycle engine . The two-stroke cycle engine performs the intake , compression , firing , and exhaust sequence in one revolution of the crankshaft. Cylinder Classification The inline engine has its cylinders arranged one after the other in a straight line , They are in a vertical , or near vertical position . Most modern inline engines are four cylinders . A V-type engine places two banks or rows of cylinders at an angle to each other-genre-ally at 60or 90 ,The V-type engine has several advantages: short length , extra block rigidity , a short , heavy crankshaft , and low profile that is conducive to low hood lines , The shorter block permits a reduction in vehicle length with riot sacrifice in passenger room . The horizontal opposed engine is like a V-type engine , except that both banks lie in a horizontal plane . The advantage here is all extrmely low overall height .Which makes this engine ideally suited installations where space is limited . Cooling Classification As you have learned ,engines are either liquid-collde or air-colled . Most vehicles use liquid-colled engines .Air-colled engines are used in limited numbers modern vehicles . Fuel Classification Automobile engines can use gasoline , diesel fule , gasohol(mixture of gasoline and alcohol), alcohol , LNG(liquefied natural gas) ,CNG(compressed natural gas) ,or LPG(liquefied propane gas ) .Gasoline powers the majority of vehicles , but diesel fule is used in some vehicles .Gosohol ,LNG ,CNG ,and LPG are beginning to see wider use .One of the principle differences in these engines is in method of fuel delivery and carburction .Gasoline ,LNG ,CNG ,and LPG utilize the same basic type of engine , but LNG ,CNG ,and LPG utilize a slightly different fule delivery setup .Diesel engines do not use a carburetor or all ignition system . Valve System Operation of Valve system You have seen that the intake valve stroke .Both valves must remain closed during the compression and power stroke ,and the eshaust valve opens during the exhaust stroke , The designer must design a device to open and close the valves at the proper times . The shaft will have an egg-shaped bump called a cam lobe .The cam lobe is machined as an integral part of the shaft .This shaft is called a camshaft . The distance the valve will be raised , how long it will stay open , and how fast it opens and closes can all be controlled by the height and shape of the hole . As you will see later , it is impractical to have the cam lobe contact the end of valve stem . When the camshaft is turn ,the lobes will not even touch the valve stem ,The lifter is installed between the cam lobe and the valve stem . The upper end rides on the lobe and the lower and almost touches the valve stem . The lifter slides up and down in a a hole bored in the head metal that separates the valve stem from the camshaft . You have developed a method of opening and closing the valves .The next problem is how and at what speed to turn the camshafts , Each valve must be open for one storke .The intake valve is open during the intake storke and remains closed during the compression ,power ,and exhaust stroke .This would indicate that the cam lobe must be turn fast enough to raise the valve erery fourth stroke . You can see that it takes one complete revolution of the cam lobe four strokes of the piston . Remember that four srokes of the piston require two revolutions of the crankshaft , the cam shaft must be once , If you are speaking of the speed of the camshaft ,you can say that the camshaft must turn at one-half crankshaft speed . If the crankshaft is turning and the camshaft must turn at one-half crankshaft speed , it seems logical to use the spinning crankshaft to turn the camshaft ,One very simple way to drive the camshaft would be by means of gears and a belt . One gear is fastened on the end of the crankshaft ,and the other is fastened on the end of the camshaft .The large camshaft gear drives the smaller crankshaft gear through the belt . If ,for instance ,the small gear Oil the crankshaft has 10 teeth and the large gear on the camshaft has 20 teeth ,the crankshaft will truth the camshaft at exactly one-half crankshaft speed . VVT-Toyota`s Continuously Variable Valve Timing The most significant and satisfying changes to the Lexus GS line are in the area power train . In the case of GS300 , Lexus breathes new life into last year`s 3.0Lin-line six by introducing VVT-continuously variable valve timing syestem .On the dyne ,VVT shows up as only five additional horsepower and 10 lb-ft of torque . But in the car it meansfuel economy improvements of 1.6 mpg .smoother idle ,California TLEV (transitional tow-emissions vehicle )certification and zero-to 60 mph a half second quicker . Toyota eliminates the compromise of conventional valve timig with the introduction of VVT , By continuously varying intake valve timing (up to 60 crank angle degrees) , Toyota optimizes low-to mid-speed torque , improves fule economy and lowers emissions without having a negative impact on idle . In essence ,the system controls valve overlap ,which means it can climinate it completyly for a glass smooth idle . or maximize it to boost volumetric efficiency ang reduce pumping losses this translates into power ,economy and cleaner running at all engine speeds. The heart of the system is the intake cam pulley , which consists of an inner and outer section ,The inner portion is fixed to the camshaft and nests inside the belt-driven outer pulley via helical spline gears . An electronically controlled hydraulic piston moves the pully halves relative to one another ,causing the cam portion to rotate within the outer pulley. This rotation davances or retarda intake valve timing .A spool valve reacting to signals from the ECU controls hydraulic pressure . VTEC-Honda Variable Valve Timing and Lift Electronic Control By desiging a higher valve lift ,wider valve-timing ,and large valve valve diameter ,it is possible to obtain a higher volumetric efficienvy to copy with higer output engine speeds ,The VTEC is used to improve volumetric effiency from low engine speed to high engine speed .With VTEC, the valve timing and lift can be dajusted at low engine rotation to increase troque and prevent air from being forced back through the intake . VTEC Operation Fig.2-4 shows the VTEC mechanism while operating at low engine speeds . In the low-speed mode the 3 rocker arms are separated and use cams A&B only . At this time the mid rocker arm is in contact with the high speed cam due to the spring force in the lost motion mechanism .It is separated from the primary and secondary rocker arm and thus is not actuating the valve .Fig.2-5shows the VTEC mechanism while operating in the high speed mode . During high speed engine operation the 3 rocker arms are connected and move together due to the 2 hydraulic pistons which have moved over due to increased hydraulic presure. MIVEC-Mitsubishi Innovative Valve timing Elecctronnic Control system The MIVEC dual-intake valve canshaft enables changing betweeen low-speed and high-speed moders(Fig.2-6), resulting in easy operation from low to high rams ,improving the driving experience when staring from a stop light , merging on to the freeway ,or accelerating to overtake another car .In the pursuit of pure driving enjoyment,potentially incompatible goals like fuel economy ,environment-friendiness,and clean driving have all been achieved . Low-speed Mode The difference in the dual-intake valve lift(low lift and medium lift)and enhanced in-cylinder streaming further stabilize combustion without compromising fuel econmy ,emissions ,and torque . High-speed Mode Extending the injection valve opening time and expanding the valve lift range in ,creases intake air mass and achieves output close to best in class . The Grandis is equipped with the 2.4L MIVEC and the Colt is equipped with the 1.3 and 1.5L MIVEC . Electronic Valve Control System An electronic valve control (EVC) system replace the mechanical camshaft ,controling each valve with actuators for inpendent valve with actuators for independent valve timing .The EVC system control the opening and closing time and lift amout of each intake and exhaust valve with independent actuators on each valve .Changing from a mechanical camshaft driven valve into dependently controled actuator valves provide a huge amount of flexibility in engine control strategy .Vehicles utilizing EVC can realize several benefits including : 1) increase engine power and fuel economy. 2) Allows centralized and distributed EVC system to perform at their full potential. 3) Adapts to engines of varied cylinder counts . With all of improved efficiencies and consumer benefi