I. Award speech
He looks ugly compared to the merchandise on the counter in the store; but he is not inferior to the transistor invented by Shockley. He is not a product yet, he only represents a new technology is being born; maybe in the future, he will also enter the museum of history like the transistor invented by Shockley. He was born not to show people his beauty and beauty, but to benefit mankind. The technology of the "electronic treatment device for automobile exhaust" of the present invention will enable people to get rid of and suffer from the pollution of air from automobile exhaust.
2. A problem that humanity urgently needs to solve
As of March 2010, the number of motor vehicles in the country was approximately 192 million, of which more than 70 million were vehicles, and continued to maintain a rapid growth momentum. It is estimated that by the end of 2010, it will exceed 75 million, with an average annual increase of 17%. While the number of cars is growing strongly, China's annual gasoline consumption has reached 55 million tons. After gasoline is burned in car engines, most of the substances are converted into toxic gases and discharged into the air, making air pollution more and more serious.
Vehicle exhaust pollutants mainly include: carbon monoxide, hydrocarbons, nitrogen oxides, sulfur dioxide, soot particles (some heavy metal compounds, lead compounds, black smoke and oil mist), odor (formaldehyde, etc.). At present, automobile exhaust has become the "culprit" of urban air pollution. In some cities, automobile exhaust pollution already accounts for 80% of air pollution sources. Due to automobile exhaust pollution, many cities have become unbearable. People can no longer see the blue sky. The turbid air makes the daytime visibility less than 200 meters. Not only does the increase of traffic accidents, but also makes people feel depressed and breathe Difficulties and the proliferation of various diseases have seriously affected people's health.
For human health, solving the problem of automobile exhaust pollution, that is, the problem of automobile exhaust purification treatment, has become an urgent problem that humans need to solve.
The purpose of my participation in the Hangsheng Cup automotive electronics application program competition is to show all people who are concerned about the problem of automobile exhaust pollution-a technical idea that can realize the purification of automobile exhaust, or a kind of automobile exhaust Purification device.
3. An electronic purification device for automobile exhaust
At present, there are many forms of automobile exhaust purification devices, such as: the three-way catalyst purifier currently commonly used, as well as multiple catalyst purifiers, and ozone purifiers, ozone plus water gas purifiers, ozone plus catalyst purifiers.
However, these existing technologies have their own shortcomings. Although the three-way catalyst purifier and the multi-catalyst purifier play a certain role in the absorption of hydrocarbons, carbon monoxide and nitrogen oxides, they have little effect on other dust particles. Moreover, the service life of the catalyst is generally very short, requiring frequent replacement and high cost; in addition, the catalyst generally contains rare heavy metals, and the active heavy metals are toxic to the human body. Therefore, the recovery of toxic substances after the catalyst is used is also a troublesome matter. Ozone plus water gas purifier has a complicated structure and is bulky, and the water needs to be replaced frequently, which is costly and inconvenient to use. The technical performance of the ozone plus catalyst purifier and the three-way catalyst purifier has not increased significantly, but the cost has increased a lot, and there are also many shortcomings.
In view of the shortcomings of the current automobile exhaust purification device, the electronic purification device for automobile exhaust of the present invention not only avoids the technical deficiencies of many of the above automobile exhaust purification devices, but also further enhances the automobile exhaust purification treatment capacity.
The automobile exhaust purification device (patent application No. 3) of the present invention uses high-voltage static electricity to ionize and charge the soot particles in the automobile exhaust (exhaust gas), and then to attract and collect the charged soot particles through a strong electric field Car exhaust electronic purification device. Because the electric field force can penetrate the atomic structure of the substance, the strong electric field can ionize or polarize the molecules, thereby destroying the molecular structure of the substance, so that the molecular structure or mixture of harmful gas substances in the exhaust gas of the car is cracked by the limbs, making it Into non-toxic substances.
Using this electronic purification device for automobile exhaust, it can very effectively attract and collect harmful gases and soot particles in automobile exhaust gas, and also convert carbon monoxide in exhaust gas into carbon dioxide, and then decompose carbon dioxide into oxygen and carbon substances. The harmful soot particles in the automobile exhaust gas are firmly adsorbed and solidified on the soot collection board in the automobile exhaust electronic purification device, and then after the harmful soot waste collected on the soot collection board is accumulated to a certain thickness, the strong electric field force Under the action of inter-polar fire, the harmful smoke dust waste that has been solidified on the smoke dust collection plate is shed and discharged, thereby reducing the pollution of the exhaust gas and purifying the environment, which is beneficial to human health.
The working principle of the soot collection plate is very similar to the working principle of electro-flocculation or electroplating, except that the dielectric between the two electrodes in the electro-flocculation or electroplating tank is the electrolyte, and the dielectric between the soot collection plates is charged exhaust particles, Under the effect of a strong electric field, the charged exhaust particles will conduct electricity like the electrolyte, but the difference in conductivity and potential gradient between the two is relatively large. When current flows through the electrolyte, the positively charged electrolyte will run toward the negative plate, and the negatively charged electrolyte will run toward the positive plate. Therefore, electroflocculation or electroplating is a process of ion deposition. The electrode passes current to attach the metal to the surface of the object.
According to this principle, in the soot collection plate, the charged soot material will be easily deposited and attached to the surface of the charged soot collection plate under the action of a strong electric field. Therefore, compared with other automobile exhaust gas purifiers, this automobile exhaust gas purification device has a simple structure and is very effective for automobile exhaust gas purification treatment.
An electronic purification device for automobile exhaust gas of the present invention is mainly composed of a bar grid structure or a grid structure with high-voltage positively charged anode plates, a group of insulated dust collection plates with high-voltage positive and negative charges, and a high-voltage power supply, etc. It consists of three parts; the grid electrode or grid structure with high voltage positive electric anode plate is installed in front of the smoke collection plate, and is fixed in a shell with the smoke collection plate with insulating material, the anode electrode in the smoke collection plate The plate and the cathode plate are also insulated with insulating materials and fixed in the same casing; the high-voltage power supply has two sets of high-voltage electrical output, and one set is used for the anode plate of the grid structure or grid structure. The other group is used for the soot collection plate. The negative poles of the two sets of high-voltage electrical output are connected together and connected to the cathode electrode plate in the soot collection plate; the anode electrode plate with high voltage positive electricity in the grid structure or grid structure is called It is the first high-voltage anode plate, and a group of high-voltage positive poles connected to the high-voltage power source is called the first high-voltage anode, and the anode plate in the soot collection plate is called the second high-voltage anode plate. High voltage power supply Another group of high voltage positive electrode is called a second ultor.
Figure 1, Figure 2, and Figure 3 are the structural diagram, electrical connection diagram, and electrical schematic diagram of a high-voltage switching power supply, respectively, for a car exhaust electronic purification device. In Figures 1, 2, and 3, "1" is the first high-voltage anode plate, which is connected to the first high-voltage anode (HV1) in the DC switching high-voltage power supply of Figure 3 and is insulated from other components. "200" is the soot collecting plate assembly, which is composed of multiple cathode plates and multiple anode plates, and "21" is the cathode plate in the soot collecting plate assembly, which is connected to the cathode in the DC switching high-voltage power supply of Fig. 3 "22" is the anode plate in the soot collection plate assembly, also known as the second high-voltage anode plate, which is connected to the second high-voltage anode (HV2) in the DC switching high-voltage power supply of FIG. 3.
When exhaust gas is discharged from the exhaust pipe of the car, because the exhaust gas is basically uncharged, that is, "0" potential, the uncharged exhaust gas is driven by the pressure difference, first from the grid of the first high-pressure anode plate Passing in the middle of the grid, the first high-voltage anode plate is a positively charged plate, and there is a very strong electric field around it. When an object approaches it, a corona discharge will be generated. At this time, the object will face the anode plate Emitting electrons makes the object positively charged, especially under high temperature environment, the work function of the object emitting electrons is much smaller than that under normal temperature conditions, which greatly enhances the ability of the object to emit electrons to the first high voltage anode plate. Some objects that are not easy to emit electrons will also be polarized and charged under the action of a strong electric field force, that is, the charge in the object should also be redistributed, so that the end of the object near the first high-voltage anode plate is negatively charged and the other Positively charged.
Oxygen is easily charged by polarization or ionization in a strong electric field. After emitting oxygen, oxygen will be positively charged (become O + 2). Positively charged oxygen is easily recombined with polarized and charged oxygen. Ozone (O3), which is easily combined with carbon monoxide (CO) to produce carbon dioxide (CO2), making it a non-toxic gas.
When the charged gas or charged exhaust particles pass through the soot collection plate, due to the strong electric field between the anode and cathode plates of the soot collection plate, the positively charged gas or positively charged exhaust particles are very It is easy to be attracted to the cathode plate, and the negatively charged gas or negatively charged exhaust particles will also be easily attracted to the anode plate, so that the anode and cathode plates of the soot collection plate are coated with a layer to be discharged by automobile exhaust A viscous substance produced by a substance.
When this collected viscous substance accumulates to a certain thickness on the soot collecting plate, a spark discharge will occur between the anode and cathode plates, and a strong instantaneous current will collect on the anode plate and the cathode The object on the polar plate swelled and fell off, and a crackling discharge sound was emitted. Because there is a distributed capacitance of thousands of P between the anode plate and the cathode plate, a fully charged capacitor will generate a large current during discharge, and the current will cause the discharge gas to explode and make a popping sound.
4. Working principle of high-voltage power supply for automobile exhaust electronic purification device
Figure 3 is the working principle diagram of the DC switching high-voltage power supply. Its input voltage is 12V (it can also be 24 volts), because cars are generally powered by 12V storage batteries. DC switching high-voltage power supply is a push-pull switching power supply, because in low-voltage switching power supply, push-pull switching power supply has the highest working efficiency.
In addition, there are some differences between the push-pull switching power supply in Figure 3 and the general push-pull switching power supply, that is, when the two push-pull tubes work alternately, the alternating time is not equal to zero, but a delay (or Staggered) for a certain period of time (the duty cycle of the two push-pull tubes is only about 48%). The purpose is to prevent the moment when the two push-pull tubes work alternately, when the previous tube is not completely turned off, the latter tube will start to conduct, so that the on and off times of the two tubes overlap each other and increase The loss of the switch tube reduces the working efficiency of the DC high-voltage switching power supply.
Choose IR2155 as the driving circuit in Fig. 3. IR2155 is generally used in energy-saving lamps as a half-bridge switch tube drive circuit. The difference between the half-bridge drive and the push-pull drive is relatively large in circuit structure, so in Figure 3, the original circuit used for the half-bridge switch drive in IR2155 is used. For major changes, connect pin 6 directly to ground (originally connected to the half-bridge output) and pin 8 directly to the power supply (originally connected to the bootstrap capacitor).
In addition, the normal operating voltage of IR2155 is 15.6V, but the input voltage in Figure 3 is only 12V. Obviously this voltage cannot make IR2155 normal. In order to improve the working voltage of IR2155, the back electromotive force generated by the primary coil of the switching transformer T1 is rectified by using rectifier diodes D2 and D4 in Figure 3, and then superimposed with a 12V power supply (which becomes 24V), and then powers U1 (IR2155) through the resistor R1. To ensure that the operating voltage of IR2155 is 15.6V.
Under normal working conditions, the output power of the DC switch high-voltage power supply in Figure 3 is not large (less than 20W), but when the soot collection board is in a fire, its output power is very large, which can reach more than 100W. The operating voltage of each push-pull tube Q5, Q6 is relatively low, so the operating current is relatively large, so Q5, Q6 must choose a field effect tube with a relatively large drain current, or an IBGT tube with a relatively large collector current.
The output power of IR2155 is very small, and it cannot be used to directly drive push-pull tubes Q5 and Q6. Especially when Q5 and Q6 work at low voltage and high current, the output signal of IR2155 must be amplified. Group push-pull follower amplifier circuits (Q1, Q2 and Q3, Q4) respectively amplify the two sets of output signals of IR2155 to ensure that two push-pull tubes Q5 and Q6 provide sufficient drive current at the moment of turn-on and turn-off, Reduce the switching losses generated when Q5 and Q6 are turned on and off. C5, R5 and C6 and R6 are differential circuits, which have a certain effect on accelerating the turn-on and turn-off time of Q5 and Q6.
C1 is an energy storage filter capacitor, but its main function is to demagnetize the core of the switching transformer. At the moment when the power switch is turned off, the charge stored in C1 can maintain the switching power supply to continue to work for a period of time, making the primary coil of the switching transformer The operating voltage gradually drops to zero. This process ensures that the magnetization curve of the core of the switching transformer can return to the origin of the coordinates every time the power is turned off, that is, the core is completely demagnetized, which prevents magnetic saturation due to the magnetization of the transformer core when the switching power supply is working again. If there is no effect of C1, when the power switch is turned off, the magnetization curve of the core of the switching transformer will be stopped at a point with a non-zero value. It is easy for the transformer to saturate the next time it is turned on, causing the two push-pull tubes to pass The stream burned out.
D21, D22, D23, D24 and C21, C22, C23, C24 form a voltage doubler rectifier circuit. The output voltage of HV1 is generally higher than 10,000 volts, while the output voltage of HV2 is higher than 5 kV.
U2 is a voltage comparator (TL431). A reference comparison voltage (approximately 2.5V) has been set in it. The other input comparison voltage is obtained by dividing R24 and R9, and R9 is a sampling resistor. During normal operation, because the sampling output voltage of R9 is relatively high, that is, the input voltage of U2 is relatively high, U2 is in the on state, that is, the output voltage of U2 is 2.5V. The function of U2 is mainly used to control the turn-on or turn-off of another voltage comparator Q7. During normal operation, because the voltage (2.5V) applied to the Zener diode DZ3 is lower than the breakdown voltage, Q7 is in the off state.
The output voltage of U2 or the input voltage of Q7 is input by diode D5, and the input signal of D5 is obtained through sampling resistor R10. Since one end of R10 is connected to the cathode plate of the soot collecting plate, the current flowing through the cathode plate will also flow through R10, and a voltage drop will occur on R10. This voltage is the sampling voltage of sampling resistor R10. Or called sampling output voltage. During normal operation, the sampling voltage of R10 is very small, and when U2 is turned on, the sampling voltage of R10 is bypassed by U2 after D5 (it is embedded at 2.5V). Therefore, the sampling voltage of R10 cannot make the Zener diode DZ3 is on, and Q7 is off at this time.
When there is a fire between the soot collection plates, due to the sudden increase in the output current, first the HV2 high-voltage output voltage should be reduced, because the voltage drop generated by R23 will increase, so that the HV2 high-voltage output voltage will be reduced, thus sampling The sampling voltage output by resistor R9 should also be reduced. After the sampling voltage output by R9 undergoes C7 integration delay, U2 will change from on to off, and its output voltage will be greater than 2.5V. At this time, the sampling voltage of R10 passes through D5, and then integrates through integrating circuits C8, R7, and C9, so that the phase of the sampling signal is delayed. The delayed sampling signal passes through the Zener diode DZ3 and is finally added to the input of Q7. Terminal to turn on Q7.
After Q7 is turned on, the output signal of the sawtooth oscillator of U1 is bypassed through R8, U1 stops working, and no drive signal is output, so that the two push-pull tubes Q5 and Q6 also stop working, so that the switching power supply has no high voltage output. After C8 and C9 in the integration circuit are fully discharged, Q7 will return to the previous cut-off state, after which, the DC switching power supply starts to work normally again. Therefore, there is intermittent flashing between the smoke and dust collecting plates, and the DC switching power supply must be turned off once for each flashing to protect the safety of the DC switching power supply.
In addition, the threshold for ignition protection can also be changed. Changing the size of the sampling resistors R9 and R10 can change the threshold for ignition protection. For some small ignitions, as long as the power loss does not exceed the maximum output power of the DC high-voltage switching power supply, the DC high-voltage switching power supply does not need to be protected, but instead it can improve the working efficiency of the automobile exhaust electronic purification device. Therefore, the threshold of ignition protection and the length of continuous ignition time can be determined according to the use effect.
The length of the ignition time is mainly determined by the time constants of C7 and C8, R7, C9 and the time constant of C10 in the integration circuit. The larger the time constant, the longer the ignition time and the longer the intermittent time. As before, U2 and Q7 belong to the sampling amplifier circuit, U2 belongs to the power supply output voltage sampling, and Q7 belongs to the power supply output current sampling, but the phase of the input signal of the two sampling amplifier circuits must be delayed. Equivalent to two delay times in series, but when the integrating circuit is discharged, it is not in series in time, so that the charging and discharging time of the integrating circuit can be adjusted separately to make the ignition duration as long as possible, and the recovery time as much as possible Shorter to improve work efficiency.
DZ1 is the limiting diode of the output voltage of the sampling resistor R9. When the sampling output voltage exceeds a certain voltage value, the limiting diode DZ1 will be turned on to prevent U2 from being damaged due to the excessive input voltage. DZ2 is also a limiting diode. When the sampled output voltage of R10 exceeds the voltage regulation value of the Zener diode, DZ2 is turned on to prevent U2 from being damaged due to the high operating voltage.
The circuit in Figure 3 can also be powered by a 24V DC power supply, but the circuit needs some changes: the diode D1 is replaced by a resistor, the resistor R1 and the diodes D2 and D4 are removed, the diode D3 is short-circuited, and the number of turns of the primary coil of the switching transformer is also increased.
The automobile exhaust electronic purification device of the present invention is estimated to cost between 100 yuan and 200 yuan. I believe that this kind of automobile exhaust electronic purification device will have a very broad market in the future.
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