From the point of view of humanized design of products, using the knowledge of ergonomics, the method of measurement and model was used to analyze the relationship between the various components of the office chair in the sedentary state. Research how to in new product development and design of the correct use of ergonomics theory to ensure the design to adapt to the degree related technical problems, and for the "chair family" -- sit crowd to use the health office chair of humanized design content, method and performance evaluation are studied and summarized.
Key words: human centered ergonomics health office chair
introduction
Entering the information age, more and more people are long time fixed in front of the computer table, every day for several hours or even more than ten hours working at his desk, learning, entertainment has become a normal life. With the deepening of the thought of "people first", the health of these people has been more and more valued by the public. In recent years, the rapid development of Ergonomics (or human for engineering, ergonomics science, ergonomics, etc.) is the interaction of people and machines, environment and rational combination of make the design of machine and environment system suitable for human physiological and psychological characteristics, reached in the production of high efficiency, safety, health and comfort to a science.
First, the seat of the ergonomic analysis
(a) the chair of history and culture
Human are sat on the floor (squatting, kneeling, lying, or "happy go lucky" one stone, wood, hide, before the invention of the chair. Research shows that humans began to use the seat (seat) is a symbol of power and status, the function of sitting is secondary. Throughout China from sat on the seats to pedal and sit chair this long process, in addition to the Ming style chair has simple concept of ergonomics, the rest of the basically is almost perpendicular to the back, sit not comfortable. Form the unique style of chair in China is subject to the influence of traditional Chinese culture: the culture of Confucian ritual requirements people sat, to conform to the Confucian "straight" logical requirements; legalist school in order to maintain the rule more further the Confucian etiquette strengthen, must comply with the relationship between the level of strengthening the chair as a symbol of identity, the status of the; Taoist culture shaping the chair's inner temperament, form or elegant or dignified, pursuit of natural texture decoration, reflecting the harmony between man and nature, the idea of a ". With the development of productive forces and relations of production change, the relationship between people and chair also changed, but seat status symbol meaning still exist.
(two) chair and human health
Today, people know that sitting can not only reduce the labor intensity, improve work efficiency, but also with the health of people have a close relationship.
1 physiological characteristics of the human body sitting posture
When a person is changed into a sitting position, 60% of the body's bending comes from the hip rotation, and the other 30% is from the curve of the lumbar spine. The person sitting in the straight waist, thigh and torso at right angles to, by maintaining the spine's natural S-shaped, intradiscal pressure than bending over. However, for a long time sitting will naturally relax the body, hip joint bends are formed. At this time thigh anterior and posterior muscles are in a relaxed state, can relieve the load on the back muscles, making the entire body feel comfortable.
Orthopedic experts measured people in different posture and sitting disc internal pressure changes, it was found that body posture is the main factor to determine the intradiscal pressure, intradiscal pressure is too high is the direct cause of damage to the disc. Sitting straight waist is conducive to reducing intradiscal pressure, but the muscle load increases; bent over sitting conducive to relax the muscles, but increase the internal pressure of the intervertebral disc. Study found that, if the spine is not a long-term lack of support, then the waist will because the arch bending caused by the load of the vertebrae, the intervertebral disc, the tendon, leading to chronic muscle fatigue and soreness; if disc pressure too easily lead to intervertebral disc protrusion; if the nerve compression and is prone to paralysis of the phenomenon. At the same time, the respiratory system, digestive system, as well as the eyesight of the eyes and so on will also be changed and even the disease because of the sitting posture.
2 working and living environment analysis
The 2009 China city health status survey "and" China town "white-collar elite" population health white paper "the study shows that Chinese enterprises white-collar staff 86% age 22-45 years old between, but inflammation of the eye and visual acuity decreased 80%, 30% of abnormal cervical vertebra and lumbar vertebra, urinary tract abnormalities 23.5%, proportion of sub-health up to 76%. There are 58% of white-collar "daily sedentary office 8 - 5 hours", more 25% of people "daily sedentary office 12 - 8 hours", become a veritable "chair"".
With the concept of people-oriented and staff self-protection awareness of the enhancement, the domestic company for employee health related to the office environment, software and hardware facilities, and gradually pay attention to. At present, pay attention to the point of view tend to be concentrated in environmental design style, air quality, lighting, heating refrigeration and even provide entertainment area; and related to the quality supervision departments for the office environment and office furniture inspection tend to be concentrated in of home with the strength, stability, formaldehyde release amount, heavy metal content, soft hard cladding, physical and chemical properties; for the ergonomics design of the special chair for the office, in China there is no unified, scientific and rigid testing standards.
Can not be denied, as a good performance of the office chair, to meet the basic functions of the chair one one sit under the premise of protecting people's health should be the primary consideration. Media, known as "China design knocking at the gate of the world" Tsinghua University Associate Professor Shi Zhenyu urged: "employees every day about 60% of the time is spent in the office chair chair bear protecting employees' health problems, so the concept of health must be on the agenda. In Europe and the United States some big companies to hire people, some will be written for the employees seat for the brand, model and so on, each of the chairs have been scientific health certificate, the out their health of employees is very responsible.
(three) the analysis of the man machine environment system of the office chair
Office chair is usually composed of a seat frame, elastic material, fixed parts, skin (armor), accessories (regulation, moving parts) etc.. Based on the theory of ergonomics to design put a chair in the office is used for a long time, it is necessary to take the seat to bring users convenience and comfort, reduce sedentary fatigue, improve work efficiency, materials are energy saving and environmental protection and other factors. These are related to the user's physiological experience, psychological experience, health and safety and its impact on product evaluation and purchase desire. For chair design, need to use to measure science, physiology, psychology, mechanics, materials science, aesthetics, mechanical engineering, and marketing science related discipline knowledge, so that the product design really reflect on people, respect and concern to the natural environment, is combination of people and products, environment of perfect harmony.
Two, office chair ergonomic design
The comfort of the office seat usually includes: elastic comfort, sitting comfort, mobile convenience, operating comfort, etc.. Elastic comfort is generally not only by the size parameters to ensure. Sitting comfort, mobile convenience, and operation comfort can be guaranteed by the structure and size parameters of the seat, the measurement of the human body size in a sitting position.
(two) the comfortable sitting posture and the chair scale
Reasonable chair design can make different size can obtain the reasonable support at the pose varied, as far as possible to keep the spine's natural bent, thus reducing the pressure on the back muscles and lumbar, such sedentary people wouldn't feel too tired. The head and neck can not be too forward so as not to cause cervical deformation; there must be a reasonable supporting waist, waist down pressure etc.. The chair seat height control can make people stand up at the foot force most convenient. The height of the seat is measured when the height of the seat is measured by the height of the seat. In fact, the most important factor to determine the height of the seat is the need to consider the position and angle of the elbow on the work table. So the seat height should be determined according to the working face height. The arm of the chair to a reasonable height so that the light on the elbow, wrist movement feel more comfortable. Shen Liming, Hou Jianjun think the job to keep the level of the arm or down is the best principle of office desktop design. At the same time through the VDT experimental operation, Li Li, Wang Sheng and other found that the forearm and the level of 0. When the angle, the EMG integral value is minimum, at this time the muscle load is the smallest. The stability of the body can also be achieved through the hand, if you need to arm support, you can put the arm on the table. For armrest of chair and armrest height from seat more than 200mm check for appropriate, should be to make arms hanging naturally highly, the armrest is too high is error in the design.
The solution to these problems is closely related to the size of the human body. Although different body size differences in body size, but the angle of the human body sitting joint angle is approximately the same, this is our product design needs to focus on the reference. After calculating, the human body's sitting posture can be characterized by a set of joint angle of the sitting posture, the comfortable range of the joint angle of the sitting posture.
From the perspective of the lower body, comfortable sitting posture is to keep close to the level of the feet and thighs supported by the ground. In order to avoid excessive pressure at the front of the thigh knee popliteal position, the front seat to ground or foot height should not be more than the soles of the feet distance to the popliteal position. Due to the work surface height needs may chair height caused by some human foot is not up to the ground, then should use the Ottomans, and other support. Of course, with the rotating shaft can be adjusted height of the chair is the most ideal choice. The rotating shaft of the working chair can make the chair to be adapted to the height difference, the posture change or the movement of the human body by rotation. Swivel chair also increased the sit to reach for the scope of, to sit with the easy access to or away from the object, and does not require before and after move the chair. With the roller is also the most of the work of the work of one of the design of the contents of the.
Shi Zhenyu designed this health office chair in the structural consideration to allow the chair family in the seat of the joint angle of the comfort range can be relaxed and free activities. In the back of a chair near the waist position slightly lordosis, thus facilitating lumbar support to keep the back curve, lighten the burden of the waist and abdomen muscle; back at the top near the neck position backward tilt, convenient support cervical to reduce the burden of the blood supply to the head system; try to keep parallel to the thigh and arm posture in the chair surface, knees, elbows, hips and tries to achieve the right angle.
(two) seat body pressure distribution
The action of the gravity of human body on the cushion and backrest pressure distribution is called for body pressure distribution when a person is sitting on the chair, his body weight is not all in the hips, but concentrated in the two sciatic small-scale. Excellent design should allow the body to withstand the weight of the area around the area of the sciatic nodule. The elastic seat surface can increase the contact surface between the human and the chair, thereby reducing the inhomogeneity of the pressure distribution. But the elastic bearing chair has a degree of certainty, the seat is too soft easy to cause the body to balance and stability. To try to do the different weight of people sitting down there is a kind of chair in the slow deformation brought about by the stability of the comfortable feeling.
The angle of the seat is obviously affected by the pressure distribution data. Obtained through the analysis of the experimental results: inclination angle of a backrest for the backrest of the contact area is the most significant, had the greatest influence on the impact on the average back pressure, across the surface of the maximum pressure, average pressure gradient; seat surface height is main factors that influence the seat surface contact area of the and the maximum pressure gradient of the sea surface, and the average pressure has the greatest impact; the seat surface inclination angle has the greatest influence on the maximum back pressure value of. The results are: a high numerical sea surface pressure distribution data has a significant influence, seat surface inclination angle and the inclination angle of the backrest of significant change in back pressure distribution data from the variance analysis.
Reasonable seat seat should be high for the popliteal height value, the seat angle of 0. Dip angle of 20. In cannot change seat surface is elastic, material and the seat surface shape, can by changing the seat of seat height, seat angle and inclination angle of the backrest to achieve changes in the data distribution in the upper body seat pressure, resulting in a more comfortable seat. Different body pressure distribution indexes have different physical meanings, and should be chosen according to the functional requirements of the seat.
(three) simultaneous tilting
Ideal chair back should be adjusted in horizontal and vertical two directions. Good design is the seat backrest with the action of the spring, with the back of the human body and the corresponding movement in and out. Some seat backrest can support the shoulder, with higher height and is concave shape, can give a larger area of the whole back support. The seat with a back elastic called synchronized tilting. Now the flexibility of ordinary office chairs rely mainly on gas springs, air springs will make people sit up and feel good. Shi Zhenyu's chair is a new type of elastic support structure is a new type of glass fiber material, this material than steel flexible memory, basic does not exist fatigue problem. In addition, moisture, elasticity coefficient is relatively stable, tolerance is relatively good, no expansion and contraction. Its rough surface can be breathable, but also reduce the body's decline. Its material pollution is also relatively small, resource conservation, cost is also suitable for.
(four) the factors affecting the performance of office chairs
The hot phenomenon of close parts of the seat and body is also the factors that affect the comfort of the seat. Especially in the summer, although most of the office space, such as air conditioning cooling measures, but the problem still exists. In addition to the skin of the seat material to meet the requirements of a certain flexibility and texture performance, the elimination of hot and have the main function, to the skin fabric of the seat with moisture absorption and heat regulation. Plastic chair surface is airtight, the surface is too slippery, make the person sit to feel uncomfortable. From the relevant parameters, it is found that the wool fabric has not only good moisture absorption, heat insulation, but also rapid moisture diffusion. So it is the most appropriate to solve the hot problem of the skin of wool fabric. Similarly, the choice of cushion material to meet the ventilation and heat dissipation performance, the general general use of polyurethane foam, this is because it easily from the surface of the rapid dissemination of water vapor and good air permeability. If material cushion is simply the pursuit of good air permeability, is natural fiber and chemical fiber interlaced elastic polyurethane fibers. The latter has fibrous wall, also has a smooth ventilation environment, the performance is better than that of poly ammonia bubble.
conclusion
Seat design should be from the human body engineering research and improvement, Shi Zhenyu in the design process of the analysis methods and research methods used to provide us with a scientific design example. According to the principle of human centered design, following the scientific design and research methods, it is necessary to ensure that the office chair has a good elastic comfort, sitting comfort, mobile convenience, operating comfort and so on. With the further development of the concept of people-oriented unceasingly thorough popular feeling and the theory of man-machine engineering in the design research and practice will create more suitable for use in a chair family health seat, so that the overall efficiency of the man-machine system to achieve the best level.