Automobile maintenance is a major sector of the industry of automobile and also a major income. Nowadays, Internal Combustion engine maintenance can be a very important area in automobile maintenance and valve lapping process which is subjected here, is done during IC engine maintenance. The current methods used for most automobile maintenance, valve lapping process are not effective and consume a lot of working hours. ‘Valve lapping Machine for Internal Combustion Engines’ is a machine designed to overcome these problems by optimising the human involvement in the process.
The thesis consist of the background in designing the machine, methodologies used, results obtained by data analysis in order to optimize the design and design of the valve lapping machine. Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine. This can take two forms. The first type of lapping involves rubbing a brittle material as glass against a surface such as iron or glass itself using an abrasive such as aluminum oxide, jeweler’s rouge, optician rouge, emery, silicon carbide, diamond, etc.
This produces microscopic conchoidal fractures as the abrasive rolls about between the two surfaces and removes material from both. The other form of lapping involves a softer material such as pitch or a ceramic for the lap, which is “charged” with the abrasive. The lap is then used to cut a harder material ” the work piece. The abrasive embeds within the softer material, holding it and permitting it to score across and cut the harder material. Taken to a finer limit, producing a polished surface such as with a polish cloth on an automobile, or polishing pitch upon glass or steel. Taking to the ultimate limit, with the aid of accurate interferometry and specialized polishing machines or skilled hand polishing, lens makers produces surfaces that are flat to better than 30 nanometers. This is one twentieth of the wavelength of light from the commonly used 632.8 nm helium neon laser light source. Surfaces, this flat can be molecularly bonded by bringing them under the right conditions. Keywords :- Valve lapping; Engine valves; Cylinder head 1. INTRODUCTIONValve lapping or the process of creating a good seat between engine valves and the corresponding valve seat area in the IC engine head is a task which have to be done very accurately. The importance of obtaining a good seat is for the air/fuel mixture or air is prevented from flowing in to the combustion chamber, same as the exhaust gas is prevented from flowing to the exhaust manifold from the combustion chamber until the right time. And also a good seat prevents compression leaks. The engine will lose its efficiency by huge percentages if any of the situations explained above happens. So as this is a very important task in IC engine maintenance, extra attention is given to this particular task by technicians. This process of valve lapping is typically done using a valve lapping stick or a power tool. As both of this tools are not very effective, these tools can be replaced by the ‘ Valve Lapping Machine for Internal Combustion Engines’, specifically designed for the process of engine valve lapping. The machine employs a fully mechanical system which performs two different motions in two directions previously performed by hand when using valve lapping stick and power tool. Comparatively the valve lapping machine is very effective because the human involvement is very limited in the process.A valve job is an operation which is performed on any four stroke cycle, internal combustion engine, the purpose of which is to resurface the mating surfaces of the poppet valves and their respective valve seats that control the intake and exhaust of the air/fuel mixture that powers the motion of the pistons after the start cycle.In the earliest automotive engines, the valves needed to be removed and the sealing surfaces sanded, ground or lapped multiple times during the life of a typical engine. As the decades passed, however, engines ran cleaner and the addition of tetraethyl lead in gasoline meant that such maintenance became more frequent. Today, valve jobs are done on passenger cars for the purpose of maintenance, although they are still quite common with high-performance cars. Some reasons that may induce the need for a valve job in a modern passenger include: excessive RPM, high mileage, overheating, material failure, and foreign object damage (FOD). 1.1. What is Valve Lapping In the process of valve lapping in an internal combustion engine cylinder head, the goal is to achieve a good seat between valve seating area of an engine valve and the valve seat area of cylinder head in order to avoid the compression leaks through the seating from the combustion chamber and to avoid air/fuel-air mixture leaking in to the combustion chamber through the seating. The internal combustion engine operates by achieving a certain compression ratio which is differing from engine to engine and combusting an air-fuel mixture which is compressed to a certain volume decided by the compression ratio. And if the air-fuel mixture leaks through the seating, the volume of the air- fuel mixture will change and combustion process will not be accurate resulting a reduction in productivity of the engine. Therefore it is vital to have a fully sealed combustion chamber i.e. the valve seating is very important in acquiring a fully sealed combustion chamber. Fig 1 : Effect of Lapping 1.1.1 Lapping process While the valve lapping process, we have to observe the valve seat area time to time by the naked eye. It’s the normal way to conclude whether the valve seat is good or further valve lapping is needed. Figure shows a lapped valve and a non-lapped valve. After the valve lapping process, the most common way to observe the seating of valves is a technique using petrol. After the valve job is done, the mechanic or technician place the precise valve in the precise spot in the cylinder head and pour petrol to the stem of the valve which he have to observe. This poured petrol then reaches the seating area of the valve. Then it is observed if petrol leaks through the seat. If petrol leaks through the valve seat it concludes that the valve job is not successful and if petrol does not leaks through the valve seat it concludes that the valve has acquired a good seat, so recommending to assemble the engine using the valve. Fig 2 : Need for Lapping of Valves. 1.1.2 Engine valvesThere are two kinds of engine valves, intake/inlet valves and exhaust/outlet valves. These valves could be identified easily in a cylinder head. Inlet valves are usually bigger than exhaust valves. Although more than one inlet valve and exhaust valve can be present for a single cylinder. There are different designs for inlet valves and exhaust valves. The most commonly used valve design is poppet valve design. Then there are sodium valves used in some turbo-charges engines. And mask valves, mushroom valves, tulip valves could be observed in different situations. The following figure shows a detailed diagram of a valve. Fig 3 : Detailed View of ValveAs you can see in the figure the seat angle is the most important thing in the valve lapping process. Seat angle is normally 45° and 30° in most of valves. The other important factor of designing the valve lapping machine is the stem diameter of the valve. The valve is to be fixed to the valve lapping machine in order to start the lapping process by the stem of the valve. The dimensions from the collected data of valves are analyzed in order to acquire three categories of stem diameters. These analyzed data is used for the specifications of valve holding pieces of the machine to be built. Overall length of the valve is also a important factor to consider when adjusting the machines before starting the valve lapping process. Valve lapping stick and hand motion Valve lapping sticks are the tools that we use to lap valves by hand movement. The valve is attached to the sucker at the tip of the stick and lapping compound is applied before the process begins. This is a very hard process to undergo and it will take approximately half an hour to lap one valve of a 3.0 L engine. Following figures shows the valve lapping sticks and the hand movement used to lap valves.Fig 4 : Commonly used valve lapping sticks Fig 5 : Hand movement while lapping of valvesWhile lapping valves as shown in figure , the technician have to decide whether to apply compound from observing the valve seat area time to time. This method is still used in basic garages.1.1.3 Valve lapping power toolUsing the valve lapping power tool is much more efficient than the valve lapping by hand movement. It will take less than 15 minutes to lap a valve using the power tool. But still we have to hold the power tool in position for lapping process, which is somewhat hard labor to undergo. Power tools work using an electric motor or pneumatically using compressed air. Fig 6 : Valve lapping using a power tool 1.1.4 Lapping compoundLapping compound is applied to the valve seat before beginning of the process. Lapping compound wears surfaces of the valve and the valve seat of the cylinder block smoothing both surfaces and creating a good seat. A lapping compound tube usually has two types of compound available in the top end and bottom end separately. The two types named as fine and coarse. Technician decides which type of compound has to be used by observing the valve seat. If the valve seat has rough edges, coarse compound is used. Otherwise fine compound is used obtain a smooth surface. Fig 7 : Application of Lapping Compound on Valve.1.1.5 Cylinder headCylinder head is the casting which seals the combustion end of the cylinder block and the inlet and exhaust valves and their ports are positioned in the cylinder head for air/fuel mixture intake and exhaust of the combustion products. Cylinder head also facilitate overhead cam shafts if present and otherwise it facilitates rocker arms and valve springs. 1.1.6 Cam systemAs a cam system is implemented in the machine, it is better to have a idea about cam systems. A cam , follower, follower system and a drive are the four basic parts of a cam system. Clyde H. Moon, P.E. states that “A cam is a mechanical part which imparts a prescribed motion to another part by direct contact. It may remain stationary, translate or rotate”. Follower is directly contacting the cam while the follower system receives a specific motion through the follower given by the cam. Drive is the element which transmits motion to the cam or to the follower system.Fig 8 : Cam And Follower 1.2. PROBLEM STATEMENT:The main purpose of the project is to minimize the human effort with excellent machines with precision although the time required for the process is the same for manual as well as the machine but, if we use a machine instead of the person the person can do another job by this time. Also the efforts which are given by employee will be reduced1.3. OBJECTIVES 1. The main goal of this project is to design a machine both efficient and effective than previously used methods for valve lapping and to reduce the labor cost by reducing the human involvement in the process. The objectives that had to be achieved in order to achieve the main goal were designing the basic model of the machine designing the valve lapping mechanism:2. Assembly of the whole machine by designing the parts needed, calculating and designing the cam needed, analyzing data and categorizing them in order to design five valve holding pieces, analyzing data to obtain the specifications of the machine, obtaining two high torque dc motors that has specific RPM(revolutions per minute) values and deciding what materials must be used in order for the design to be durable and economical.3. Lapping and cleaning of valves needs to be carried out simultaneously to reduce the lead time of an Engine. In order to attain this objective, a mechanism needs to be developed.1.4. SCOPEThe scope of the project is multi-fold; the study encompasses material study, component study, and finally system study. On the material level, the study-focus is put on PCM property characterization. On the component level, a combination of heat transfer modeling, storage design and experimental validation is performed. On the system level, the study is centered on techno-economic feasibility evaluation of system.1.5. METHODOLOGYSEMESTER I1. We started our work with literature survey.2. Preliminary model was estimated.3. Numerical Analysis was carried out.4. Cad model was designed in Catia v5.5. Material Selection.SEMESTER II1. We will complete calculations of remaining parts.2. We will purchase standard components from market.3. We will be done a rough 3D model of our project.4. Manufacturing will be done.5. Assemble will be done.