With the continuous growth of people's demand for personalized automotive products, the design and production of automobiles and their internal components have also shown diversified functional characteristics. Comfort is one of the core goals of car seat design optimization. At present, the design of car seats not only needs to follow the laws of ergonomics and ensure reasonable structure, but also take into account the relief of driving fatigue and the promotion of human health, and continuously enrich and enhance the functional value of seats. The introduction of graphene materials has a significant positive impact on improving the heating performance of car seats.

1 Analysis of the development trend of car seats

As a car product component that directly contacts the human body, car seats need to have good safety, comfort and environmental protection. With the continuous improvement of the personalized needs of the automobile user group, giving play to the role of intelligent technology and meeting users' requirements for car seat heating, massage, ventilation, etc. has gradually become the main direction and trend of current car seat product research and development design.

2 Overview of graphene materials

2.1 Features Graphene material is a honeycomb structure composed of carbon hexagonal materials. It is an emerging lightweight material with good functional characteristics in recent years. Graphene atoms have the characteristics of consistent structural distribution and present stable and firm properties. Since graphene materials are characterized by a single-layer structure and are both thin, light and flexible, they have good application advantages at both the physical and chemical levels and have high application value. From the perspective of conductivity, the electrons inside graphene will not be disturbed too much by external environmental factors during movement, and the conductivity is good. The thermal conductivity is similar to that of carbon materials. It can be used as a new experimental material and applied in multiple industries and fields.

2.2 Advantages

(1) Ultra-thinness. In the process of preparing graphene materials by chemical vapor deposition and redox methods, by optimizing the performance of the prepared graphene materials, the prepared graphene sheets can show a significant light, thin and light-transmitting effect.

(2) Toughness. Graphene materials have good toughness and elasticity. In the experiment, the stretched size of graphene materials can reach about 20% of their actual size.

(3) Conductivity. Affected by the single-layer atomic structure of graphene materials, the movement of electrons is confined to this layer of plane, thus giving graphene unique electrical properties. The study found that the combination of graphene materials with electronic components and equipment can significantly improve the power storage capacity of electronic products.

3 Comparison of heating performance of graphene and resistance wire

Based on the excellent performance of graphene materials, this paper mainly studies the application of graphene materials in seat heating performance. The study compares the traditional resistance wire heating method with the heating technology using graphene materials to evaluate their application effects.

3.1 Power comparison The comparative experiment of heating performance of graphene materials and resistance wire materials adopts the following steps.

(1) Heating pads are made of graphene materials and resistance wire materials respectively, and they are installed on two car seats.

(2) Temperature sensors are arranged at key positions on the seat surface to monitor temperature changes.

(3) The car seat equipped with the heating pad is placed in a high and low temperature test chamber, and the test chamber temperature is set to -10 ℃. After the temperature of each part of the seat is stabilized at -10 ℃, the indicators related to heating performance are tested, including heating efficiency, heating speed and temperature distribution uniformity.

The power of the heating pads using the two materials was compared. According to the standard of every 1 minute, the change of the current value after the heating pad was started was measured, and the corresponding power value was calculated to obtain the power change curve of the heating pads of the two materials. After obtaining the comparison results, it was found that the average power of the graphene heating pad was maintained at 55.8 W in the first 7 minutes, and dropped to 40 W after 7 minutes. In the subsequent detection process, its power has been maintained at 40 W. The average power of the resistance wire heating pad was maintained at 73 W in the first 13 minutes, and it dropped to 50 W after 14 minutes. It can be seen that the power used by the heating pad mainly based on graphene material is significantly less than that of the resistance wire heating pad.

3.2 Comparison of heating speed From the analysis of the heating speed of the heating pads using the two materials, in the actual test, the programmable linear DC power supply provides power supply for the two heating pads, and the voltage of 13.5 V is connected to the two samples respectively, and the change of the surface temperature of the car seat is detected and recorded. The test found that the temperature of the graphene heating pad can reach 40 ℃ when heated for 6 minutes and maintain around this temperature value. The temperature of the resistance wire heating pad only reached 40 ℃ when heated for 13 minutes. From the perspective of the temperature change range, within 2 minutes of starting heating, the surface temperature of the car seat equipped with the graphene heating pad can rise from -10 ℃ to 21 ℃, while the surface temperature of the car seat equipped with the resistance wire heating pad can only rise from -10 ℃ to 11 ℃. The test results confirm that the graphene material has a better heating performance than the resistance wire.

3.3 Comparison of thermal uniformity Taking thermal uniformity as the main content of the test, the thermal imaging of the surface of the car seat is mainly collected by infrared thermal imager. The test found that the surface temperature of the car seat with the graphene heating pad is more uniform, and the temperature of the car seat near the resistance wire with the resistance wire heating pad is significantly higher than other areas. It can be concluded that the graphene heating pad has better thermal uniformity.

4　Analysis of the application of graphene heating pads in car seats After verifying the superiority of graphene heating pads in car seats, combined with the actual application environment of car seats and the personalized needs of users, the combination of graphene heating pads and the functions of car seats themselves can better play the role of graphene heating pads.

4.1　Ventilation From the perspective of the heating function of car seats, the current car seats are mainly covered with heating pads with fabric or leather materials. Although the application of these materials can save the production cost of car seats, most of the materials have high density and are difficult to ventilate. Under the relatively closed and narrow space restrictions inside the car, the heating function of the heating pad can easily have a negative impact on the ventilation function of the car and the use effect of the car seat. To address this issue, the ventilation system of the seat must be carefully considered to ensure that the installation position of the graphene heating pad will not hinder the suction or blowing function, so as to play its heating role without sacrificing the ventilation effect.

4.2　Heating The application of graphene heating pads in car seats mainly heats the back, buttocks and other positions of the driver and passengers, helping the human body to relieve fatigue and improve the comfort of the car environment. The resistance wire heating pad used in the past only has a single heating function and is prone to uneven heating. The graphene heating pad can provide three-speed temperature control adjustment modes of high, medium and low by combining temperature sensors and heating controllers, effectively avoiding the problems of single heating function and uneven heating. In the design and production process, the power size and specifications of the heating pad must be fully considered to match the adaptability of the car seat to the selected heating pad type and the size and shape of the seat, so as to avoid the risk of fire caused by short circuit faults due to mismatch of model specifications. Therefore, when designing and producing heating pads, the specifications of car seats circulating in the market should be used as a reference to ensure that the specifications and types of the heating pads are compatible with the seats, and to ensure the quality and safety of the heating pad application.

4.3 Physiotherapy The application of graphene heating pads in car seat physiotherapy mainly starts from the massage function of car seats. After the graphene heating pad is powered on, the wavelength of the far-infrared waves generated by the graphene heating is concentrated between 6 and 14 µm. The far-infrared waves in this range are very close to the wavelength of the far-infrared waves generated by the human body itself, so in actual heating, the phenomenon of same-frequency resonance can be produced. In this case, the far infrared waves generated by graphene are more easily absorbed by the human body, thereby effectively improving human blood circulation, enhancing metabolism, and improving human immunity. Based on this effect, the use of graphene heating pads for car seat design can conform to the concept of healthy seats and play an important role in improving the functional value of car seats.

5 Design and Verification

In order to further play the role and value of the application of graphene heating pads in car seats, combined with the actual product structure of car seats, this paper designs and analyzes the graphene heating pads used for car seats to ensure that the advantages and characteristics of graphene can play a role in helping to improve the functions of car seats. The design and effect verification of graphene heating pads are mainly achieved from the following aspects.

5.1 Heating pad design When designing a heating pad based on graphene materials, it is required to combine the basic structure of car seats and traditional resistance wire heating pads, and determine that the graphene heating pad is mainly composed of breathable non-woven fabrics, breathable foam, base film, current collector, heating coating, and hot melt adhesive covering film. On the premise of clarifying the shape and size standards of conventional foam for car seats, the graphene heating pad is designed mainly with a curved structure, fillets are applied to the corners of the heating pad structure, flat cables are applied to the transition part, and circular riveting is used to connect the connection interface. In order to manually adjust and control the temperature of the heating pad, a temperature sensor needs to be installed at the head of the heating pad to collect the temperature. In order to give full play to the thermal conductivity of graphene materials, the breathable sponge is used as the main carrier of the heating pad, the heating pad is fixed on the breathable sponge, and then the combined device is fixed on the foam of the car seat.

On the basis of clarifying the basic structure of the graphene heating pad, the basic functions of the graphene heating pad also need to be considered. Combined with the analysis of the application of graphene heating pads in car seats, the graphene heating pad should have the functions of ventilation, massage and heating at the same time. The ventilation and heating functions are clearly introduced in the previous article. The massage function mainly emphasizes that when installing the graphene heating pad, the massage air cushions are arranged in groups at the position of the seat back, so that the graphene heating pad corresponds to the area where the massage air cushion is set. To achieve this goal, the graphene heating pad should be in the form of a flexible strip structure with an arc structure at the corner to cooperate with the movement of the massage airbag. In this way, the massage air cushion will not be damaged due to the deformation of the heating pad, and the massage function of the car seat can be effectively realized.

5.2 Heating pad verification In order to verify the application effect of the graphene heating pad in the car seat, the use function and performance of the graphene heating pad are verified in combination with the production quality standard requirements of automobile products. According to the current technical requirements and test methods for automobile seat heating pads in my country's automobile industry standard documents, the quality performance and application effect of the graphene heating pad are verified, mainly involving the four basic indicators of the graphene heating pad in terms of heating function, kneeling endurance, load capacity and ventilation capacity.

(1) The heating function test is specifically divided into two aspects: heating uniformity and temperature rise test. Referring to the test principles of 3.2 and 3.3 of this article, it is clear that in the test of heating function, the temperature difference between each temperature measuring point on the surface of the car seat and the set temperature value is within 1.5℃ as the standard for the inspection of heating uniformity; the temperature rise test requires that the temperature rise rate of multiple temperature measuring points on the surface of the car seat meets the requirements of relevant verification standards.

(2) The kneeling endurance test includes two aspects: sitting simulation test and swing and bounce test. The sitting simulation test requires the mechanical device of the heating pad to rotate outward and return at an angle of α along the Z axis. Under a load pressure of 900 N, 12,000 cycles are required for each angle. The swing and bounce test mainly simulates the impact of the human body on the backrest of the car seat when the car rotates and slides. According to the general human force standard, a force of 450 N is applied to the backrest of the car seat. Under the action of the force, the heating pad rotates 5° left and right with the x-axis as the center. After four repetitions, the downward sliding distance along the Z axis is based on 150 mm. The test is required to be repeated 50,000 times.

(3) The load capacity test is mainly based on the kneeling test. In the actual test, it is necessary to apply 0 N, 1,000 N, and 0 N test forces at the selected test points in turn, and the loading process cycle of this force is controlled to be about 4 s. Then the power of the graphene heating pad is turned on for 3 minutes and then turned off for 7 minutes. According to this operation, each test point was tested 7,500 times.

(4) The ventilation capacity verification is mainly carried out by ventilation test. Under normal air density, a 70 kg dummy is used to simulate the actual load of the car seat. This process requires the measured air volume to be above 130 L/min. According to the above test standards and methods, the performance and application effect of the graphene heating pad are tested. The results show that the application of this type of heating pad meets the relevant functional requirements of the car seat and can play an important role in improving the quality of car seat products.

The application experiment of the graphene heating pad proves that it has better performance than the traditional resistance wire heating pad, can meet the optimization design requirements of the car seat, and has good application and development prospects. As a new type of nanomaterial, the application of graphene heating pads must also consider the issue of production cost. In the future development of the automotive industry, we should further strengthen the optimization and development of graphene materials and production process technology, reduce costs, and let the graphene heating pad play a role in car seats, so as to effectively improve the overall quality of automotive products.

6 Conclusion

Applying graphene heating pads to the optimization design of car seats can effectively improve the comfort of car seats, enhance the overall value of car seats, and promote the improvement of the overall quality of automobile products. Car seat design based on graphene materials should combine the heating function of graphene heating pads with the functions of car seats themselves on the basis of clarifying the properties of graphene materials themselves. Verification results show that graphene heating pads can effectively improve the design level of car seats.