Green manufacturing of the hottest camshaft

The camshaft is an important part of the automobile engine. Its main function is to promote the opening and closing of the intake and exhaust valves according to certain laws, and cooperate with the piston to complete the intake and exhaust work of the engine. Camshaft is a high-speed and high-precision mechanism, which needs to bear a lot of torque at the same time. Therefore, the design and manufacture of camshaft directly affects the power, movement and environmental protection characteristics of the engine

1 structure of camshaft

automotive engine camshaft mainly includes cam, journal and shaft. Each part has different functions and different requirements. The structural forms of camshaft in engine mainly include bottom mounted type and top mounted type

bottom mounted camshaft, the so-called OHV (over head valve), its valve is located on the top of the engine, the camshaft is located on the crankcase side, and the valve is controlled by the valve distribution device. This method has the advantages of simple structure, easy maintenance, good transmission torque and low-speed performance, but the speed is slow, the transmission is poor, and the output power is low. This form of camshaft has been eliminated in cars now

due to the short distance between the upper camshaft and the valve, the energy consumption is reduced, and the speed and running stability are improved. Therefore, a large number of cars use overhead camshaft

top mounted camshaft can be divided into single camshaft and double camshaft according to its development and structure, namely SOHC (single over head CAM) and DOHC (double over head CAM)

a single camshaft has only 1 camshaft, so each cylinder can only have 2 ~ 3 valves, generally 2 or 1 inlet and 1 outlet

the double camshaft has two camshafts, one to control the intake valve and one to control the exhaust valve. In this way, 4 ~ 5 valves can be achieved for each cylinder, generally 2 or 3 inlets and 2 hills. Double camshaft can realize high-speed operation and better cooperate with the combustion of the engine, so it is widely used now

2 connotation and system of green manufacturing

Green Manufacturing GM (green manufacturing) is the American Association of manufacturing engineers at the end of last century (s) sitishan's advanced manufacturing mode that comprehensively considers environmental impact and resource utilization efficiency. The introduction of green manufacturing into automotive engine manufacturing is not only the internal need of the development of the automotive industry, but also the external requirement of society, environment and law for the development of the automotive industry.

green manufacturing includes the whole life cycle from design, material selection, manufacturing, packaging, transportation, use, remanufacture and scrap disposal, including the basic principles of green manufacturing Theory, key technology of green manufacturing and supporting technology of green manufacturing constitute a complete green manufacturing system

3 green design of camshaft

3.1 structural form of camshaft

structural form of camshaft design, there are mainly two kinds: integral type and assembly type

integral type is a relatively traditional structural form, and the structure and manufacturing of its cam, shaft and journal are all integrated

assembly type is to separate the three parts, and then assemble them together after each part completes manufacturing. According to different connection modes, assembly type includes material connection mode, sintering connection mode and mechanical connection mode

(1) integral type. Through casting or forging, the integrated blank is obtained. After corresponding machining and heat treatment, the camshaft with required performance is obtained

(2) material connection. The material connection mode is to use other materials as the intermediary to realize the connection between the cam and the shaft. The method is to manufacture the cam and the shaft separately, and then connect the cam and the shaft according to the positioning requirements

the common method is to use welding to fix the inverted or partial arc segment at the joint. This method is usually used in steel because it is easy to show deformation and cracks. Now there are also powder metallurgy cams that have been grinded and shafts that have been machined are cast into the mold. The static load testing machine of plastic sleepers is installed and debugged successfully, and the connection is realized after cooling. This form can realize lightweight

(3) sintering type. The assembly method of sintered assembly camshaft is relatively special. Insert the shaft into the powder metallurgy cam, and then put it into the sintering furnace together. The sintering is completed at high temperature, and the shaft and cam are closely connected with the shaft

(4) mechanical connection. There are many methods of mechanical connection, such as hot sleeve method, internal high-pressure forming method, rolling expansion method in pipe and cam pressure sleeve positioning method

hot sleeve method is a relatively simple method. When machining cams and shafts, the outer diameter of the shaft is slightly larger than the inner diameter of the cam to form an interference fit. Heat the cam to expand, so that the inner diameter of the cam is larger than the outer diameter of the shaft for a short time. At this time, put the cam into the shaft, and the cam and the shaft will be closely connected after cooling

internal hydroforming, i.e. Ihu. The method is to use a special equipment to put the processed cam rim with equal wall thickness into the hydraulic press with Ihu tool. The shape of the die cavity of Ihu tool is completely consistent with the shape of the blank shaft. The shaft is made of Ningxin steel pipe, and then the liquid medium is added to the shaft pipe, and the two ends of the shaft pipe are sealed. The pressure in the pipe is increased to 300 MPa. The shaft pipe will undergo plastic deformation under the action of pressure, and finally it will fully fit on the Ihu tool, so as to realize the close connection between the shaft pipe and the cam wall, and finally achieve the connection between the shaft and the cam. The axial positioning of the cam and the shaft is achieved by pressing the pipe at the side of the cam outward to a certain height, which is generally about 0.1 mm

in pipe rolling expansion method, which is a way to achieve the connection between cam and shaft through in pipe rolling expansion, and adopts the sliding rolling principle. This type of shaft still adopts thin-walled steel pipe. After passing through the inner hole of the cam, the rolling tool with rolling interference is used to pass through the thin-walled steel pipe, causing plastic deformation of the steel pipe. The inner hole of the cam at the rolling position is elastically deformed by the outward pushing force of the steel pipe. In this way, the outward plastic deformation and expansion of the steel pipe and the elastic rebound action with the inner hole of the cam will form a high pressure fit, so as to achieve the connection between the cam and the shaft. It should be noted that the joint needs a certain strength, which depends on the rolling diameter

in addition, different materials have different minimum rolling interference. Only when the minimum rolling interference is exceeded can the connection be realized, and the rolling interference has little effect on the joint strength. Finally, the rolling expansion method in the pipe has no strict tolerance requirements for the inner hole of the cam, so this method is a relatively simple processing technology

the positioning method of cam pressure suit is to roll the steel pipe surface of Zhongning to make it plastic deformation, so as to process the groove in the direction of circular play, while the shallow groove in the direction of circular play is processed on the inner hole surface of the cam, and then put the cam on the steel pipe at room temperature, and if the tensile test results show that the tensile strength of one specimen does not meet the requirements, press it axially. Because there is a certain amount of interference between the steel pipe and the inner hole of the cam, plastic deformation occurs when the cam is pressed in. At the same time, making a connection between the steel pipe surface and the inner hole of the cam is a special bite connection realized by processing based on the principle of plastic flow or cutting deformation

3.2 green design requirements

green design is an important part of green manufacturing and the basis for other parties of green manufacturing. The main requirements of green design are as follows:

(1) environmental attributes should be considered in design. Traditional design mainly considers the attributes of function, performance, quality and cost, but does not consider the environmental attributes of products

(2) green product structure. There are two main requirements for the greening of product structure: one is the simplification of product structure; the other is the disassembly of product structure

the simplification of product structure requires that when designing products, the structure should be as simple as possible, with the least parts, the lightest parts, and the optimal combination structure, that is, to realize the required functions with the simplest structure

the detachability of the product structure requires that the connection mode between various parts of the product be fully considered in the product design, and the detachable connection be adopted as far as possible. In addition, the disassembly between parts should be convenient and easy to avoid damaging disassembly

(3) it is conducive to recyclable design. That is, the product recycling and reuse should be considered in advance during the design. Traditional design mainly considers the structure and manufacturing of products, but less about the treatment at the end of product life. Green design requires that when designing, we should consider how to effectively recycle the product at the end of its service life, so as to reduce the damage to the environment, and obtain the recycling of resources to obtain better economic benefits

(4) green design for manufacturing. Breakthrough design only considers the traditional fields such as manufacturability, economy and convenience, and takes into account the environmental requirements of manufacturing, such as using blank with no or little allowance to reduce the processing process and reduce material and energy consumption; in cutting and grinding, dry or quasi dry processing methods are adopted to reduce the pollution to the environment, etc. by adopting green manufacturing process, Finally, green

3.3 camshaft green design analysis

(1) environmental attribute analysis of working process. In the working process of camshaft, the impact on environmental attributes mainly has two aspects: one is the loss of resources; the other is the impact on the environment

the loss of resources mainly includes the loss of materials and energy. This first requires that the camshaft has a better service life, less material consumption and less net mass. The material consumption of integral camshaft is large and its service life is short. At the same time, because the common integral cam adopts integrated production, its shafts are mostly solid shafts, with large net mass and high energy consumption. Now, some Zhongning shafts can reduce the net mass and reduce the consumption. In addition, in view of the two main parts of cam and vehicle, the requirements of cam and vehicle are different. The cam mainly requires wear resistance, and the shaft mainly requires better strength and stiffness. In order to realize the integration of materials, we can only increase the use of materials, so the overall camshaft material utilization is poor

material connection, sintering assembly and mechanical connection can reduce the consumption of materials. 2 The cable connecting the sensor and the host shall not have intermediate connector consumption. At the same time, due to the small net mass, energy consumption can be reduced. The reduction of energy consumption can also reduce the environmental pollution caused by engine exhaust

(2) green analysis of product structure. In order to simplify the product structure, the integral camshaft adopts an integrated structure, which does not need a special structure, and has obvious advantages. Camshaft connected by material, connected by plastic or welding, and sintered camshaft using powder metallurgy technology do not need special structure, so the structure is relatively simple. Mechanical connection has many special structures to complete the connection between cam and shaft, so the structure is more complex

on the removable side, the camshaft connected by material, whether through plastic connection or welding, is not removable. The sintered camshaft is also non removable. It is very difficult to disassemble these two kinds of camshafts and separate their parts. The camshaft with mechanical connection is also non detachable, but the difficulty of disassembly is low, and the parts can be easily separated. Therefore, the disassembly performance is better than the first two

(3) recoverability analysis. As an integral camshaft, its material is consistent and does not exist