Development and design of electric hair dryer
The hair dryer is mainly used for hair drying and styling, but it can also be used for local drying, heating and physiotherapy in laboratories, physiotherapy rooms, industrial production, and arts.
1. Scheme principle of hair dryer
1. Working principle of hair dryer
The electric hair dryer is mainly used for drying hair and shaping, and can also be used for drying food and clothing. When the hair dryer is connected to the power supply, the motor drives the fan blades to rotate, sucks the air from the air inlet, heats it through the electric heating element, and blows out the hot air from the air outlet, plus appropriate switch settings and temperature control protection, output different temperatures and Air flow at different flow rates.
2. The type of hair dryer
Hair dryers are divided into three categories according to different uses: professional, household and travel hair dryers. Among them, professional hair dryers generally use AC motors to drive the wind blades, which have large power, sufficient air volume, and long service life; household hair dryers generally use DC motors, which have low power; travel hair dryers have small shapes, can be folded and stored, and are easy to carry and general power. On the small side, the dual-voltage design is mostly used to facilitate travel.
3. Structural accessories of hair dryer
The main parts of the hair dryer are power cord, switch, air inlet network, non-slip rubber, wire protection sleeve, motor and fan blade combination, heating wire rack, air outlet network, heat insulation cylinder. Commonly used accessories include diffusers and air nozzles.
Second, the design method of the hair dryer program
1. Design idea of hair dryer
First of all, according to the customer's requirements, design the shape that meets the customer's requirements; then design the internal structure that meets the requirements according to the shape, including the combination of the motor and the fan blade, and the heating wire frame; design the circuit diagram and heating wire layout plan, and select parts; Carry out the test and send it to the certification body for testing. Production will be carried out after the certification test is passed. The focus of the design is the shape and heating wire frame part.
2. Design principles of hair dryer
Appearance design principle: The appearance of the hair dryer needs to consider ergonomic factors. The handle must be suitable for one-handed operation of all functions. The weight is lighter and it is convenient for the operator to use it for a long time. The center of gravity of the product is basically in the center of the palm when the hand is held. The hair dryer is placed in The desktop must be stable, not flipped, or moved.
Basic shape design scheme: The hair dryer can be divided into two schemes according to its outer casing design: front/rear casing and left/right casing. The casing of the first scheme adopts snap connection and screws in the handle part The advantage of tightening is that it is not easy to break when dropped, but the shape will be limited by the direction of the mold out. The front/rear shell interface is the largest diameter size position: the second scheme of the shell cooperates with the buckle tightening For external fixation, metal buckles or cylinders are generally used for auxiliary fixation at the front end. The advantage is that the shape is changeable, but the shell is easily broken. These two schemes have their own advantages and disadvantages. They can be flexibly adopted according to the needs of customers. As long as they can meet the needs of customers and strengthen the design in the weak links, qualified products can be designed.
The main criteria for part design: ① The size of the outlet and inlet meshes must meet the test requirements in the safety standards. When the size of the charged body cannot meet the requirements of the safety standards, plastic materials must be used. The switch can be designed at any position on the handle. The principle can be operated by fingers when holding the product in one hand. The cold air switch is designed on the upper part of the handle so that the index finger can be pressed. The pressure regulating switch is designed at the lower part of the handle. It cannot be twisted or pushed with fingers alone, and must only be operated with special tools. ③ The non-slip rubber is designed on both sides of the hair dryer, using soft and elastic plastic materials, such as PVC. ④ The wire protection sleeve is at the end of the handle, pay attention to the hardness of the material, especially when used in conjunction with the power cord, it should meet the tortuous test required by the safety standards. The principle is "thin is hard, thick is soft". PVC materials are generally used. ⑤ The combination of motor and fan blade directly affects the wind speed and air flow, noise, product life, etc. The main material of the electric frame and the wind blade is PC, which is characterized by its relatively stable size and better mechanical strength. The wind blades of the mute series hair dryers need to use PP materials, and their light weight characteristics make the motor load smaller. The speed of the motor is generally between 15000 and 20000rpm, and the service life is difficult to guarantee when the speed is too high. When designing a DC motor hair dryer, if there is a cold wind function, you should consider using a 24-28 volt motor, because the relatively high current required by the high-voltage motor is relatively low, and the temperature of the wind can be lower in the cold wind gear. Except for special customer requirements, when the DC motor life of the hair dryer is ≥200 d~, the AC motor life is ≥500 hours. The ideal motor is: high speed, high efficiency, low spark, low noise. ⑥ Commonly used heating wires for hair dryers include iron-chromium resistance wire and nickel-chromium resistance wire. The iron-chromium resistance wire has the characteristics of high resistivity, small temperature coefficient of resistance, and high use temperature, but it is easy to oxidize. The nickel-chromium resistance wire has higher resistivity, good surface oxidation resistance, and has higher strength at higher temperature , Has good processing performance and solderability, relatively high cost. The shape of the heating wire is mainly wavy and spiral. The spiral wire can use a harder heating wire, and the wavy wire must use a softer wire, otherwise the wire will be broken during winding, the wavy wire is beautiful but the processing cost is higher . ⑦Insulation tube is not only used as the insulation part of the front part of the hair dryer and the heating wire frame, its other main function is to correct the turbulence of the air flow caused by the shape of the hair dryer. ⑧ When designing accessories, it is necessary to consider that the area of the air outlet should not be less than the area of the air outlet of the hair dryer, otherwise the temperature of the accessories will rise and deform when used for a long time. ⑨Select the power cord with the corresponding certification mark and meet the safety standards of the country of sale. The plug must have the certification mark of the country of sale and meet the maximum current of the hair dryer.
3. Matters needing attention in the design and development of hair dryer
1. Regulations for electrical safety distance
The distance between all live parts of the hair dryer (such as heating wires, rivets, copper wires, etc.) and the air outlet network must be at least 8ra m, but if the opening of the air outlet network is greater than 3m m, the distance is required to be 15m m. In addition to product requirements, there should be no other openings in the fuselage, and the openings must meet the test requirements of test fingers and test pins corresponding to the safety standards. If the safety distance between the coincidence of the product shell and all live parts in the fuselage is not enough, it must be separated by supplementary insulation. The product is usually designed with a distance of 100V/lm m between the charged body and the charged body. In actual design, it is generally designed with a minimum distance of 3mm. Depending on the size of the space, it can be designed with a distance of >3mm. The minimum climbing distance and clearance distance meet the specific requirements of the national safety standards for sales.
2. Requirements for switches and circuit boards
The switch used by the hair dryer should have the corresponding certification mark, and the rated current and voltage of the switch must be greater than the rated current and voltage of the hair dryer. The design of the circuit board, the distance between the IJ N pole is 3.2mm. Others must be designed according to 100V/lm m. The switch of the hair dryer has many gears, which can cause the wind speed and power to be different. In order to achieve this effect during design, one or more diodes are generally used in series on the line, causing a current half-waveguide to pass through to reduce power and micro-motor speed. However, when designing products of European and Chinese specifications, it is necessary to pay attention to the harmonic test of E M C in safety standards. In the design circuit, the current of each diode cannot exceed 3A. If the current exceeds the standard, two diodes can be used to reverse the control of different heating lines.
3. Selection of electronic components
The thermostat is the main component for the safety protection of the hair dryer, and a thermostat with a certificate should be selected. The temperature of the thermostat cannot be set too low to prevent the thermostat from automatically triggering during shutdown. The temperature of the commonly used thermostat is 9O℃ to 140~C. The temperature fuse is the last barrier for the safety protection of the hair dryer. Generally, the temperature fuse supported by the relevant certification is used. Its main performance is that the maximum passing current meets the requirements and the rated temperature control temperature requirements are stable. The selection temperature of the temperature fuse is generally about 30~C higher than that of the thermostat to prevent the problem that the temperature fuse is disconnected earlier than the thermostat triggers. The EMC pressed parts in the hair dryer are composed of safety capacitors connected to the positive and negative poles of the power supply, ceramic capacitors welded to the micromotor, monolithic capacitors, electrolytic capacitors and inductors. Different parts have different effects on the interference of each part of EMC, such as The low frequency part of EMV needs to adjust the capacitance value of the capacitor, and the high frequency part needs to adjust the inductance value of the inductor. As for the harmonic (HARMONIC) part, the circuit design needs to be changed. The above parts should be adjusted according to the test conditions of the designed products.
4. Technological requirements for the design of heating wire racks
The terminal stamping copper rivets need to be added as a "sandwich" method with gaskets. Except for the thermostat feet and lead connectors and other components with obvious planes, other components must be added with copper gaskets when connecting to ensure that there are connection points in the circuit Sufficient contact area to prevent fusing of components. The bent foot size of the thermal fuse must be larger than its minimum size, otherwise it will damage the thermal fuse. The wiring terminals at both ends of the wave heating wire and the middle tap terminal must be clamped to prevent poor contact. After the heating wire is wound, it is required that the heating wire is evenly spaced, without touching, twisting, low-wave or multi-wave phenomenon; all exposed copper wires should not collide with each other, other electrical components, and the safety distance cannot be reduced; the heating wire has no obvious damage. The distance between the output lead of the negative ion generator and the air outlet meets the safety requirements, and the distance to other charged objects cannot be less than 32mm.
Fourth, the safe use of electricity in the use of hair dryers
The hair dryer is a high-power household appliance (power can reach 1000 watts), there is a certain risk of leakage, because the environment of its use is humid or there is a significant chance of significant water, so you should use the standard group of power sockets. It is appropriate to pull out the plug after using the hair dryer. On the one hand, if the plug is not pulled out, there will be a certain amount of power consumption. On the other hand, in the case of unstable voltage, it is easy to burn the electrical appliance. When pulling out the socket head, you should pinch the plug to pull it out. This is to prevent damage to the plug when pulling the wire, and it is also to prevent the risk of accidental electric shock without force.
When the power cord or plug is damaged or becomes hot during the use of the hair dryer, it should be stopped immediately. This is firstly because the line damage will cause the risk of electric leakage, increasing the possibility of electric shock; second, the line voltage may be unstable, if the voltage is too high, the current will increase and cause the line to heat, and there will be a risk of damage to the electrical appliances; third, it should Avoid using the hair dryer for a long time.
The electric blower will generate electric sparks at the moment when the switch is turned on. Electric sparks are normal physical phenomena, but they can easily cause fires and cause personal and property damage. Pay special attention to the safety of electricity when using in places where dangerous goods exist. Otherwise, it is easy to increase the possibility of disaster.
Although the hair dryer is a civilian electrical appliance, its rated voltage is very harmful to the person. If there is any damage, it should be sent to the designated professional maintenance office for repair or replacement in time. This is because on the one hand, in order to avoid unnecessary damage to customers, on the other hand, in order to protect the service life of the hair dryer, under unprofessional dismantling or maintenance, it will easily cause damage to the internal structure of the hair dryer, thereby reducing the hair dryer The service life also has the risk of directly damaging the hair dryer.
5. Electromagnetic radiation of hair dryer
We know that for all kinds of household appliances, electromagnetic radiation problems will exist.
First, let’s talk about some basic knowledge: as long as voltage is connected to both ends of the appliance, there must be an electric field; as long as there is current flowing through the appliance, there must be a magnetic field around the current; and the voltage and current in the appliance are often Changing, changing electric fields will generate magnetic fields, and changing magnetic fields will also generate electric fields. Therefore, no matter the size of the household appliances, whether it is a hair dryer, rice cooker, electric washing machine, compressed household refrigerator, air conditioner, fully automatic washing machine or household appliances such as computers, TVs, microwave ovens, as long as it is related to electricity, When used, the electromagnetic field will be radiated more or less outwards.
As one of the electrical appliances, the hair dryer is naturally no exception. When you enjoy the gentle warm air after washing your hair, you may not have thought about it. This small electrical appliance consumes a lot of power per second, and the power can reach 1000 watts, even higher than the refrigerator. The working power of such a behemoth. Compared to a mobile phone that relies on a small battery to operate at milliwatt power, or compared to a microwave oven whose door is closed to shield radiation during operation, the intensity of the electromagnetic field radiated by this high-power electrical appliance when the hair dryer is working exceeds these. "Key suspects of radiation" are not surprising. However, the intensity of the electromagnetic field radiated by the hair dryer is greater, and it does not mean that it is harmful to human health.
First, we compare the electromagnetic radiation of household appliances with x-rays: x-ray is an ionizing radiation, and the electromagnetic fields radiated by household appliances are all non-ionizing radiation. X-ray radiation is similar to nuclear radiation, which can cause the molecular bonds of cells in the human body to be broken. There is a possibility of carcinogenesis, and it must not be underestimated. The dose control is very important in application. Non-ionizing radiation does not have this ability.
Furthermore, although the radiation emitted by electrical appliances belongs to non-ionizing radiation, and most of them belong to the radio wave band in electromagnetic waves, the electromagnetic fields radiated by different electrical appliances are different if the frequency is different. For the hair dryer, the alternating current with a frequency of 50 Hz is used. Correspondingly, the frequency of the electromagnetic waves generated around the hair dryer is also about 50 Hz. The frequency of electromagnetic waves sent by mobile phones for communication is in the range of 0.8GHz to 2GHz. The microwave in the microwave oven is roughly this frequency, and the circuit operating frequency in the computer CPU is several GHz, and the frequency of the radiated electromagnetic field is also roughly in this range. As far as the frequency value is concerned, it can be seen that the radiation frequency value of the hair dryer is much lower than that of other home appliances. The difference in frequency makes the mechanism of their impact on the human body different. After being absorbed by the human body, the electromagnetic field of radio frequency will be converted into the energy of fast-moving molecules in the body. The friction between the fast-moving molecules will increase the temperature. The microwave oven uses this thermal effect to heat food. The relatively large electromagnetic field energy (such as the strength of the electromagnetic field inside the microwave oven) is enough to pose a real threat to the human body. The low-frequency electromagnetic field (that is, such as a hair dryer) will not have the heating effect of the electromagnetic field of radio frequency.
The possible threats to human health are mainly: low-frequency electric fields and low-frequency magnetic fields will generate or induce currents in the human body. If the currents are large enough, they can stimulate nerves and muscles. However, to produce this kind of stimulus, the energy of the electromagnetic field itself must be large enough to be summed up. Although the working power of the hair dryer is relatively large, it can indeed radiate a certain electromagnetic field. But because the radiation of the hair dryer belongs to a low-frequency electromagnetic field, it is far below the intensity that will harm the human body. Therefore, as long as we use the hair dryer correctly, the radiation of the hair dryer will not cause damage to our health.
6. Common faults and maintenance of hair dryer
1. The motor does not rotate: this kind of fault is the most common. When overhauling, first check whether the electric heating wire EH1 (warm air heating wire) and EH2 can be red (can be observed from the air outlet, and pay attention to set the power switch to the "hot air" position). If EHI can not be red, the fault is generally in the power plug, power cord, power switch or corresponding power line. As long as the multimeter is used to measure one by one, the fault can be quickly found. Usually the power cord is unsoldered, broken and the power switch is damaged most often. If the EH1 can be red, it means that the 220V power supply has entered the hair dryer normally. The fault is generally on the motor power supply circuit or the motor and its fan blades. In this regard, you can first use a screwdriver to extend the back of the hair dryer into the manhole and gently dial the fan blade. If it can be pulled, the fault is in the motor itself or the power supply circuit. Unscrew the screw on the handle, disassemble the hair dryer to measure the working voltage at both ends of the motor (generally the voltage of the permanent magnet motor of the hair dryer is 10-18V, or check whether the EHI and DI-D4 are normal), if this check can be excluded If the power supply circuit of the motor is faulty, it means that the motor itself is bad. For the inspection method, please refer to Article 4 below. Most of the motor power supply circuit failures occur near the connectors at both ends of the EHI. After reconnecting, pay attention to tighten the compression screws at the connectors. If the fan blade cannot be toggled or stuck, it indicates that the fault is on the fan blade and other mechanical parts, mainly caused by the change in the position of the fan blade or the deformation of the fan blade. After the position of the fan blade (motor) is readjusted or the shape of the fan blade is corrected Troubleshoot.
2. No hot air: the motor rotates without hot air, which is caused by EH2 not being hot. Mainly check whether the joint leads at both ends of EH2 are broken, unsoldered or poorly contacted during maintenance. Because the EH2 is connected to the lead wires with solder tabs and compression screws, loosening and short cracks are more likely to occur. After reconnecting the broken head, tighten the clamping screw. In a few cases, EHI wire breakage faults can also occur, and the broken ends can be sanded and twisted.
3. No cool wind: The hot windshield is normal and no cool wind. The fault is in the power switch, which is usually caused by the deformation of the switch reed or the severe oxidation of the contacts and burning. Carefully disassemble the power switch, use tweezers to correct the shape of the reed or use sandpaper to remove the oxidized dirt on the relevant contacts to eliminate the fault.
4. The motor rotates rapidly and makes a lot of noise: this kind of failure is caused by the bad motor. Its performance is mainly: when the motor is turned on or during operation, the motor speed is significantly higher than the normal speed, and the noise is greatly increased; some motors stop after a while. It can't be started again. During maintenance, the carbon brush or commutator of the motor can be seen to be severely worn and stained with dirt. In this regard, first clean the dirt such as carbon powder with absolute alcohol or carbon tetraoxide, then smooth the head of the carbon brush properly to keep it in good contact with the commutator and the pressure is not too large. When the spring is loose, the pressure of the carbon powder is small, and it is easy to cause poor contact failure. The spring can be elongated appropriately. If the carbon brush is excessively worn, you should consider replacing it with a new one.
5. Insufficient air volume: generally caused by the motor speed is too low, if the motor carbon brush pressure and resistance are checked according to the above method, the fault is usually caused by severe wear or oil shortage of the motor bearing, the bearing, motor or lubricant can be replaced .
6. Low wind temperature or low time: mainly due to poor EH2 contact. The resistance value of EH2 of 450~600W hair dryer at normal temperature should be 100~120 ohms. The actual measured value is greater than this value to confirm the fault. Poor contact generally occurs at the contact between the two ends of EH2.