Development and design of electric hair dryer
Hair dryer is mainly used for hair drying and shaping, but it can also be used for local drying, heating and physiotherapy in laboratories, physiotherapy rooms, industrial production and art works.
1、 Scheme and principle of electric hair dryer
1. Working principle of hair dryer
The hair dryer is mainly used for drying hair and shaping, as well as for drying food and clothes. When the electric hair dryer is powered on, the motor drives the fan blade 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. In addition, with appropriate switch setting and temperature control protection, it outputs air flows with different temperatures and different flow rates.
2. Types of hair dryers
Hair dryers are divided into three categories according to different purposes: professional, household and travel hair dryers. Among them, professional hair dryers generally use AC motor to drive blades, with high power, sufficient air volume and long service life; Household hair dryers generally use DC motors with low power; The travel hair dryer has small shape, can be folded and collected, and is easy to carry. Generally, the power is small. It mostly adopts double voltage design, which is convenient for travel.
3. Structural accessories of hair dryer
The main parts of the electric hair dryer include power cord, switch, air inlet net, anti-skid glue, protective wire sleeve, combination of motor and fan blade, heating wire frame, air outlet net and heat insulation cylinder. Common accessories include diffusers and nozzles.
2、 Design method of electric hair dryer
1. Design idea of hair dryer
Firstly, according to the customer's requirements, the shape meeting the customer's requirements is designed; Then the internal structure meeting the requirements is designed according to the shape, including the combination of motor and fan blade and heating wire frame; Design circuit diagram and hot wire layout scheme, and select parts; Test the design sample, send it to the certification authority for testing, and carry out production after passing the certification test. The design focuses on the shape and heating wire frame.
2. Design principles of hair dryer
Appearance design principle: ergonomic factors shall be considered for the appearance of the hair dryer. The handle must be suitable for one hand operation of all functions, with light weight, which is convenient for the operator to use it alone for a long time. The center of gravity of the product is basically in the center of the palm when holding it. When the hair dryer is placed on the desktop, it must be stable, not overturned or moved.
Basic design scheme of appearance: according to the design scheme of its shell, the hair dryer can be divided into two schemes: front / rear shell and left / right shell. In the first scheme, the shell is matched with buckle connection and fastened with screws at the handle. The advantage is that it is not easy to break when falling, but the appearance will be limited by the direction of mold output, The front / rear shell interface is the position of the maximum diameter size: in the second scheme, in addition to the fastening of the shell, the front end is generally fixed with metal buckle or cylinder. The advantage is that the shape is changeable, but the shell is easy to break. These two schemes have their own advantages and disadvantages. They are adopted flexibly according to the needs of customers. As long as they can meet the needs of customers and strengthen the design in weak links, they can design qualified products.
Main criteria for part design: ① the size of air outlet and inlet mesh must meet the test requirements in the safety standard. When the distance from the charged body cannot meet the requirements of safety standards, plastic materials must be used. ② the switch can be designed at any position on the handle, based on the principle that the finger can operate when holding the product alone. The cold air switch is designed on the upper part of the handle for pressing with the index finger. The pressure regulating switch is designed at the lower part of the handle. It cannot be twisted or pushed by fingers alone. It must only be operated with special tools. ③ The anti-skid glue is designed on both sides of the hair dryer and uses soft and elastic plastic materials, such as PVC. ④ The protective wire is sleeved at the end of the handle. Pay attention to the hardness of the material, especially when used with the power cord, it shall meet the tortuous test required in the safety standard. The principle is "thin is hard, thick is soft". PVC materials are generally used. ⑤ The combination of motor and blade directly affects the wind speed, air flow, noise, product life, etc. The main material of motor frame and fan blade is PC, which has the characteristics of relatively stable size and better mechanical strength. The fan blade of silent series hair dryer shall be made of P material, and its light weight characteristics shall be taken to reduce the motor load. The speed of the motor is generally 15000-20000 rpm, and the service life is difficult to guarantee when the speed is too high. When designing the hair dryer of DC motor, if there is cold air function, 24-28v motor shall be considered, because the current required by high-voltage motor is relatively small, and the outlet temperature can be lower under the cold air gear. In addition to special customer requirements, when the service life of DC motor of hair dryer is ≥ 200 d~ hours, the service life of AC motor is ≥ 500 hours. The ideal motor is: high speed, high efficiency, low spark and low noise. ⑥ The common heating wires of hair dryer include iron chromium resistance wire and nickel chromium resistance wire. Iron chromium resistance wire has the characteristics of high resistivity, small resistance temperature coefficient and high service temperature, but it is easy to oxidize. Nickel chromium resistance wire has high resistivity, good surface oxidation resistance, high strength at high temperature, good processability and weldability, and relatively high cost. The shape of the heating wire is mainly wavy and spiral. The spiral wire can use a hard heating wire, and the wavy wire must use a soft wire, otherwise the wire will be broken during winding. The wavy wire is beautiful, but the processing cost is high. ⑦ In addition to being the insulation part of the front of the hair dryer and the hot wire frame, the heat insulation cylinder is also mainly used to correct the airflow turbulence caused by the shape of the hair dryer. ⑧ When designing accessories, the area of air outlet shall not be less than that of hair dryer as far as possible, otherwise the temperature of accessories will rise and deform after long-term use. ⑨ Select the power cord with corresponding certification mark and meet the requirements of safety standards of the sales country. The plug must have the certification mark of the country of sale and meet the maximum current of the hair dryer.
3、 Precautions for design and development of hair dryer
1. Provisions on electrical safety distance
The distance between all live parts of the hair dryer (such as hot wire, rivet, copper wire, etc.) and the air outlet network shall be at least 8RA m, but if the opening of the air outlet network is greater than 3m, the distance shall be 15m. Except for the product, there shall be no other holes on the machine body, and the parts with holes must meet the test requirements of test fingers and test needles corresponding to safety standards. If the safety distance between the overlap of the product shell and all live parts in the fuselage is not enough, it must be separated by supplementary insulation. The distance between the charged body and the charged body inside the product is usually designed as 100V / LM M. in the actual design, it is generally designed as the minimum spacing of 3M m, and the spacing of > 3M M can be designed according to the size of the space. The minimum climbing distance and clearance distance meet the specific requirements of national safety standards.
2. Requirements for switches and circuit boards
The switch used by the hair dryer shall have corresponding certification marks, and the rated current and voltage of the switch must be greater than the rated current and voltage of the hair dryer. In the design of circuit board, the distance between ij N poles is 3.2m. Others must be designed according to 100V / LM M. The switch of the hair dryer has many gears, which can cause high and low wind speed and power. In order to achieve this effect, one or more diodes are generally used in series on the line to make the current half waveguide pass, so as to reduce the power and micro motor speed. However, when designing products with European and Chinese specifications, attention should be paid to the harmonic test of E M C in the safety standard. The current through each diode in the design circuit shall not exceed 3a. If the current exceeds the standard, it can be neutralized by using two diodes to reverse control different heating wires.
3. Selection of electronic components
Temperature controller is the main component for safety protection of electric hair dryer. Temperature controller with certificate shall be selected. The temperature of the temperature controller should not be set too low to prevent the problem of automatic triggering of the temperature controller during shutdown. Generally, the temperature of the commonly used temperature controller is 9O ℃ to 140 ~ C. Temperature fuse is the last barrier for safety protection of hair dryer. Generally, temperature fuse supported by relevant certification certificate is used. Its main performance is that the maximum passing current meets the requirements and the rated temperature control temperature is stable. The selection temperature of the temperature fuse is generally about 30 ~ C higher than that of the thermostat to prevent the disconnection of the temperature fuse from being triggered earlier than that of the thermostat. The EMC pressing parts in the hair dryer are composed of safety gauge capacitors connected to the positive and negative poles of the power supply, ceramic capacitors welded on the micro motor, single stone capacitors, electrolytic capacitors and inductors. Different parts have different effects on the interference of various parts of EMC. For example, the capacitance of the capacitance needs to be adjusted in the low-frequency part of EMV and the inductance of the inductance needs to be adjusted in the high-frequency part of EMV. As for the harmonic part, the line design needs to be changed. The above parts shall be adjusted according to the test conditions of the designed products.
4. Process requirements of heating wire frame design
The stamping copper rivet at the terminal shall be provided with a washer in the way of "sandwich". Except for the elements with obvious plane such as temperature controller pin and lead connector, other elements must be provided with a copper washer during connection to ensure that the connection point in the circuit has sufficient contact area and prevent fusing elements. The bent leg size of the temperature fuse must be larger than its minimum size, otherwise the temperature fuse will be damaged. The wiring terminals at both ends of the wave heating wire and the intermediate tap terminals must be clamped to prevent poor contact. After the heating wire is wound, it is required that the spacing of the heating wire shall be uniform, and there shall be no wire collision, distortion, small wave or multi wave phenomenon; All exposed copper wires shall not collide with each other, contact other electrical components, and reduce the safety distance; There is no obvious damage to the hot wire. The distance between the output lead of the negative ion generator and the air outlet shall meet the requirements of safety regulations, and the distance from other charged bodies shall not be less than 32mm.
4、 Safe use method of electric hair dryer in use
The hair dryer is a high-power household appliance (the power can reach 1000 watts), which has a certain risk of leakage. Because the environment in which it is used is humid or there is a great chance of obvious water volume, it should use the power socket of the standard group. It is necessary to pull out the plug after the use of the hair dryer. On the one hand, if the plug is not pulled out, there will be a certain electric energy consumption. On the other hand, it is easy to burn the electrical appliances in the case of unstable voltage. When pulling out the socket head, hold the plug and pull it out, which is not only to prevent the plug from being damaged when pulling the wire, but also to prevent the risk of accidental electric shock without force.
If the power cord or plug is damaged or heated during the use of the hair dryer, it should be stopped immediately. This is because first of all, the damage of the line will lead to the risk of electric leakage and increase the possibility of electric shock; Second, the line voltage may be unstable. If the voltage is too high, the current will increase, resulting in line heating and the risk of damaging electrical appliances; Third, it should be avoided to use the hair dryer for a long time.
When the electric hair dryer is turned on, it will produce electric sparks. Electric spark is a normal physical phenomenon, but it is easy to cause fire and personal and property losses. 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 civil electrical appliance, its rated voltage is very harmful to people. If it is damaged, it should be sent to the designated professional maintenance Office for maintenance or replacement in time. This is because, on the one hand, in order to avoid unnecessary harm to customers, on the other hand, to protect the service life of the hair dryer, it is easy to cause damage to the internal structure of the hair dryer under unprofessional removal or maintenance, so as to reduce the service life of the hair dryer, and there is also a risk of direct damage to the hair dryer.
5、 Electromagnetic radiation of hair dryer
We know that for all kinds of household appliances, the problem of electromagnetic radiation will exist.
First, let's talk about some basic knowledge: as long as the voltage is connected at both ends of the appliance, there will be an electric field; As long as there is current flowing in the electric appliance, there must be a magnetic field around the current; The voltage and current in electrical appliances often change. The changing electric field will produce a magnetic field, and the changing magnetic field will also produce an electric field. Therefore, household appliances, large or small, whether hair dryers, rice cookers, electric washing machines, compressed household refrigerators, air conditioners, automatic washing machines, computers, televisions, microwave ovens and other household appliances, as long as they are related to electricity, they will more or less radiate electromagnetic fields.
As one of the electrical appliances, hair dryer is no exception. Every time you enjoy the gentle warm wind after washing your hair, you may not have thought that the power consumption of this small appliance per second is actually very large, and the power can reach 1000 watts, even higher than the working power of a giant such as a refrigerator. Compared with mobile phones that rely on a small battery to work at milliwatt power, or compared with microwave ovens whose doors are closed to shield radiation at work, it is not surprising that the electromagnetic field intensity radiated by the hair dryer, a high-power electrical appliance, exceeds these "key suspected objects of radiation". However, the greater the intensity of the electromagnetic field radiated by the hair dryer does not mean that it does great harm to human health.
Firstly, we compare the electromagnetic radiation of household appliances with X-ray: X-ray is an ionizing radiation, and the electromagnetic field radiated by household appliances is non ionizing radiation. X-ray radiation is similar to nuclear radiation. It can cause molecular bond breakage of cells in the human body. It is possible to cause cancer. It must not be underestimated. It is very important to control the dose in use. Non ionizing radiation has no such ability.
In addition, although the radiation emitted by electrical appliances belongs to non ionizing radiation and mostly belongs to the radio wave band in the electromagnetic wave, the electromagnetic fields radiated by different electrical appliances are different if their frequencies are different. For the hair dryer, the AC with frequency of 50Hz is used. Accordingly, the frequency of electromagnetic wave generated around the hair dryer is also about 50Hz. The frequency of electromagnetic wave emitted by mobile phone for communication is in the range of 0.8ghz to 2GHz. The microwave in the microwave oven is also roughly this frequency, while the circuit working frequency in the computer CPU is several GHz, and the frequency of the radiated electromagnetic field is also roughly in this range. In terms of the value of frequency alone, it can be seen that the radiation frequency of hair dryer is much lower than that of other household appliances. The mechanism of their influence on human body is different due to the different frequency. After being absorbed by the human body, the RF electromagnetic field will be transformed into the energy of rapid movement of molecules in the body. Friction will occur between fast-moving molecules and the temperature will rise. The microwave oven uses this thermal effect to heat food. The electromagnetic field energy is relatively large (such as the electromagnetic field intensity inside the microwave oven), which is enough to pose a real threat to the human body. The low-frequency electromagnetic field (i.e. such as hair dryer) will not have the heating effect of RF electromagnetic field.
The possible threat to human health mainly lies in: low-frequency electric field and low-frequency magnetic field will generate or induce current in the human body. If the current is large enough, it can stimulate nerves and muscles. However, to generate such stimulation, the energy of the electromagnetic field itself must be large enough. In conclusion, although the working power of the hair dryer is relatively large, it can indeed radiate a certain electromagnetic field. However, the radiation of hair dryer belongs to low-frequency electromagnetic field, but it is far lower than the intensity that will harm 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. Motor does not rotate: this fault is the most common. During maintenance, first check whether the electric heating wire eh1 (warm wind electric heating wire) and Eh2 can burn red (you can observe it from the hair dryer, and pay attention to set the power switch to the "hot air" position). If EHI cannot burn red, the fault is generally in the power plug, power line, power switch or corresponding power line. As long as the universal meter is used to measure one by one, the fault can be found quickly. In general, the power line is most commonly desoldered, broken and the power switch is damaged. If eh1 can be burned red, it indicates that 220V power supply has been normally connected to the hair dryer. The fault is generally on the motor power supply circuit or the motor and its blades. For this, first extend the screwdriver into the manhole at the back of the hair dryer and gently pull the fan blade. If it can be pulled out, it indicates that the fault is in the motor itself or the power supply circuit. Unscrew the screw on the handle, disassemble the hair dryer and measure whether there is working voltage at both ends of the motor (generally, the voltage of hair dryer permanent magnet motor is 10-18v, or check whether EHI and di-d4 are normal). If the motor power supply circuit fault can be eliminated through this inspection, it indicates that the motor itself is poor. See article 4 below for the inspection method. Most motor power supply circuit failures occur near the joints at both ends of EHI. After reconnection, pay attention to tightening the compression screws at the joint. If the blade cannot be moved or jammed, it indicates that the fault is on the blade and other parts, mainly caused by the change of blade position or blade deformation. The fault can be eliminated after readjusting the blade (motor) position or correcting the blade shape.
2. No hot air: the motor rotates and no hot air is sent out, which is caused by the lack of heat in Eh2. During maintenance, mainly check whether the connector leads at both ends of Eh2 are broken, desoldered or in poor contact. Because Eh2 is connected with the lead wire with solder chips and compression screws, it is easy to loose and short crack. After reconnecting the broken end, tighten the compression screw. In a few cases, EHI broken wire fault will also occur. The broken head can be sanded and twisted for connection.
3. No cool air: the hot air block is normal without cool air. The fault is in the power switch, which is generally caused by the deformation of the switch reed or serious oxidation and singeing of the contact. Carefully disassemble the power switch, correct the reed shape with tweezers or grind away the oxidation dirt on the relevant contacts with sandpaper.
4. Motor flying and loud noise: this fault is caused by poor motor. Its main manifestations are: the motor speed is significantly higher than the normal speed when starting up or working, and the noise increases greatly; Some motors stop running after flying for a while and can't be started again. During maintenance, after removing the hair dryer, it can be seen that the carbon brush or commutator of the motor is seriously worn and stained with more dirt. In this regard, first wipe away the dirt such as carbon powder with absolute alcohol or carbon tetroxide, and then properly grind the head of the carbon brush to keep it in good contact with the commutator without too much pressure. If the spring is loose, the carbon powder pressure is small, which is easy to cause poor contact failure. The spring can be lengthened appropriately. If the carbon brush is excessively worn, consider replacing it with a new one.
5. Insufficient air volume: it is generally caused by the low speed of the motor. If there is no problem with the carbon brush pressure and resistance of the motor according to the above methods, the fault is usually caused by serious wear of the motor bearing or lack of oil. The bearing, motor or lubricating oil can be replaced.
6. Low or high and low air temperature: mainly caused by poor Eh2 contact. The resistance value of Eh2 of 450 ~ 600W hair dryer at room temperature shall be 100 ~ 120 Ω. If the measured value is greater than this value, the fault can be confirmed. Poor contact usually occurs at the contact of both ends of Eh2.