The topic of vehicle weight reduction has been discussed more and more frequently. This shows that lighter weight is increasingly important for cars. In the following, combined with the practice of lightweight electric bus, share its lightweight experience.
1. Lightweight understanding
The lightweight design of vehicles is based on the purpose of low fuel consumption and exhaust pollutants. When the overall performance of the vehicle is up to the standard, the vehicle's service quality is made lighter as much as possible, making the vehicle more convenient for acceleration and rapid cornering.
1Comprehensive performance standards refer to indicators related to automobile safety, and cannot be reduced by lightweight design. Otherwise, its lightweight technology is not advocated;
2 After the lightweight design, the implementation process should be mature, and the batch production capacity of the production line cannot be reduced; otherwise, its lightweight technology is not advocated;
3 After the lightweight design, the cost principle of the product can be decreased rather than increased; otherwise, its lightweight technology is not advocated;
4 After lightweight design, product maintenance is more convenient, otherwise, its lightweight technology is not advocated.
2. The goal of lightweighting
The lightweight design is based on the purpose of low fuel consumption and exhaust pollutants. However, the implementation of the product design level, the goal of lightweight, must be clear and specific, there is no specific goal, should not go to lightweight design, such as parts and components, is the assembly, is the vehicle structure, is the decoration, must be specific. The clear meaning of the target is important for lightweight design. It cannot be lightweight for light weight, and it cannot blindly try new technologies and materials. Lightweight design must have market needs, such as:
1Electric bus, because the battery is too low in energy, one continuous mileage is too short. The basic goal of lightweight electric buses is to fit more batteries;
2 To install more batteries, the overall vehicle trim quality will be exceeded. The basic goal of lightweighting of electric buses cannot exceed the standard;
3 After requesting lightweight electric buses, more batteries can be installed, but their structural strength should be stronger and their toughness more flexible. Basic requirements: Must meet passenger car safety standards.
3. The basic way to reduce weight
The basic ways are:
(1) Lightweight organization
1 vehicle body; 2 chassis structure; 3 body structure; 4 assembly parts;
The main means is to apply value engineering methods and eliminate redundant functions through structural optimization.
(2) Adopt new materials and new processes
Under the premise of ensuring safety performance, the weight of the vehicle is lighter and the purpose of fuel saving is achieved. The main approach is to add lighter new materials (such as high-strength steels, aluminum alloys, carbon fibers, etc.) to replace ordinary steels. The use of new processes must be more scientific and reasonable, and it will certainly improve product quality and ensure production progress.
(3) Assembly of new materials
14mm thick side window glass, plastic steel glass;
2 aluminum steel wheels, aluminum drive motor housing;
3 pull aluminum shaped electrical enclosure;
4 less leaf spring steel plate;
5 other lightweight materials, such as engineering plastic parts.
4. Process changes caused by light weight
1 Aluminum alloy materials and high-strength steels, welding process has its own characteristics, and completely different from the steel welding process;
2 Aluminum alloy materials must use the matching welding and welding equipment and welding materials.
3 Aluminum alloy materials and steel welding, must adopt new processes, such as riveting, wedge.
However, the riveting process has resulted in a decrease in batch production capacity. The wedge-making process has resulted in too many profile specifications and a large number of forming dies. Basically, it is non-standard.
The changes in production processes that must be caused by light weight must have solutions.
5. The effectiveness of lightweighting
1 The safety of vehicles is basically guaranteed;
2 The curb quality of the whole vehicle can basically reach the standard at present, but the cost generally increases;
3 Some lightweight components of electric buses have achieved significant results.
6. Lightweight basic trend
The light weight of electric buses has obvious effects. The basic trend of light weight for electric buses is to use lightweight materials such as aluminum alloy materials, high-strength steels, and engineering plastics. High-strength steels are mainly used in chassis structure design; aluminum alloy materials are mainly used in body mechanisms; engineering plastics are mainly used in appearance components and humanized facilities.
(1) Basic trends in the application of metallic materials:
1Using aluminum alloy material, mainly with body skin and body upper structure,
2 High-strength steel is mainly used for chassis load-bearing parts.
(2) Basic trends in the application of glass materials:
34mm laminated glass, mainly used for front windshield;
4 Plastic steel glass is mainly used for side windows. At present, plastic steel glass can turn buses into almost panoramic and sightseeing vehicles.
(3) Basic trends in application of engineering plastic materials:
Mainly used for: automotive rearview mirror housing, automotive cooling fan, automotive air conditioning outlet, car handle (handrail), car battery box, passenger seat backrest, seat plate, passenger area floor and so on.
7. Lightweight examples
The basic idea is to advance the stamping process of passenger car production to the profile forming process. The profile forming process is completed by upstream professional manufacturers, which expands the depth and breadth of lightweight materials for aluminum, magnesium and titanium alloys. The traditional production process of passenger cars has been transformed, trying not to adopt mechanical connection technologies such as pressure welding, clamp riveting, self-piercing riveting, blind riveting and folding. The main approach:
1 The power battery is designed as a drawer type, placed in the chassis, the chassis structure is made of aluminum, magnesium, titanium alloy lightweight materials;
2 The car body skeleton is a gantry structure that is formed once, and is supplied by the upstream manufacturers. The main engine factory saves the welding process and can be assembled directly.
3 Other aspects Lightweight Use light-weight materials that are now familiar to everyone.
The author's understanding of the lightweight work of passenger cars is:
(1) The electric bus is a relatively good scene for the current lightweight, mainly because the price of the electric bus is relatively high, and there is room for cost reduction. The promotion of other passenger cars is lightweight, and the current digestion space is limited.
(2) Many experts propose that carbon fiber is the future trend of automobile lightweighting, and carbon fiber is more difficult in the lighter promotion process of passenger cars:
1 How to resolve carbon fiber parts (assembly parts)? There is no recognition that carbon fiber is an environmentally friendly material.
2 Carbon Fiber For large buses, the entire exterior molding is difficult, and if it is collided in the later period, how can it be repaired? There is no feasible way.
3 The carbon fiber molding process is relatively complicated at present, and the bus is more personalized and the batch size is relatively small, so the cost is relatively high.
(3) There will be more and more applications of engineering plastics. The main reason is that there are more and more humanized parts on buses. The use of engineering plastics is ideal.