JP4332840B2 - Reducing agent injector for exhaust gas purification - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reducing agent injector used in an exhaust gas purifying apparatus for decomposing and detoxifying NOX (nitrogen oxide) contained in exhaust gas with a reducing agent and a reducing catalyst.
[0002]
[Prior art]
In order to prevent air pollution caused by exhaust gas discharged from machinery and equipment such as diesel engines, boilers, gas turbines, and coke ovens, removal and reduction of NOx in exhaust gas has been widely practiced. As a denitration means, it is common to use an aqueous solution of ammonia or urea as a reducing agent and spray and add it to the exhaust gas and then contact it with the reduction catalyst.
[0003]
When spraying the reducing agent into the exhaust gas, in particular, if the urea aqueous solution remains liquid, it generates a solid compound derived from the reducing agent, and adheres to and accumulates on the reduction catalyst and the exhaust pipe, causing functional problems such as clogging. There is a problem of causing. Therefore, as means for vaporizing the reducing agent, Japanese Patent Application Laid-Open No. 5-31327 proposes means for spraying the reducing agent directly into the exhaust gas and vaporizing it with the heat of the exhaust gas, and Japanese Patent Application Laid-Open No. 2-207119 discloses a reducing agent. Has been proposed which is sprayed into compressed air, mixed with exhaust gas, and vaporized by the heat of exhaust gas. Japanese Patent Application Laid-Open No. 5-57146 proposes means for spraying a vaporized gas obtained by spraying a reducing agent into superheated steam of an exhaust gas boiler, and Japanese Patent Application Laid-Open No. 5-220342 discloses an electric device. There has been proposed means for injecting, into the exhaust gas, a vapor obtained by spraying a reducing agent into air heated by a heater.
[0004]
The means for vaporizing the reducing agent using the heat of the exhaust gas described above does not require special heat generation means for vaporization, but if the exhaust gas temperature is lower than the vaporizing temperature of the reducing agent, the solid compound Inconveniences such as generation and mass release of NOX into the atmosphere occur.
Moreover, the means for vaporizing the reducing agent using the heat of the superheated steam of the exhaust gas boiler is a means in a very limited specific field, and is not widely available.
[0005]
Furthermore, the means for using the heat generated by the electric heater is easy to achieve the purpose of removing and reducing NOx even when the exhaust gas temperature is low, as in the technology using the heat of superheated steam, but consumes a large amount of power. In particular, when using electric power obtained with a generator attached to a diesel engine for automobiles, there arises a problem that reduction in fuel consumption and increase in capacity of the generator are inevitable. In addition, this means does not consider adjusting the amount of the reducing agent according to the NOx concentration in the exhaust gas, as in the other means described above, and it is possible to remove and reduce NOx sufficiently due to excess and deficiency. In addition to being unable to do so, there is a concern that excess reducing agent is wasted into the atmosphere, as well as causing further pollution of the atmosphere. In particular, it is impossible to always spray an appropriate amount of reducing agent in response to the NOX concentration that varies greatly as in the case of an automobile diesel engine whose operating conditions change significantly and frequently.
[0006]
On the other hand, the inventor of the present application and the patent applicant previously referred to Japanese Patent Application No. 2002-298498, in addition to making the reducing agent high pressure with a pump and heating it to a temperature slightly lower than the boiling point with a heater, We proposed an exhaust gas purification device that efficiently removes NOX by injecting it into the exhaust gas passage with an injector while controlling the pressurization and heating state with an electronic control device.
[0007]
This prior application technology uses an electronic control device to control the reducing agent injection amount in accordance with the NOx concentration, and also to control the reducing agent heating temperature in accordance with the temperature of the reducing agent and exhaust gas. It is highly useful in that it does not cause excess or deficiency and can be reliably vaporized when sprayed into the exhaust gas passage.
[0008]
Here, since the injector used in the prior application technique requires high-precision and sharp flow control from a small flow rate to a large flow rate, an electromagnetically driven fuel injection valve used for fuel supply of an automobile internal combustion engine and The same is preferably used.
[0009]
However, since such an injector is exposed to a high-temperature reducing agent, the reliability of the heat resistance of the Nichrome wire coating of the electromagnetic coil, the resin part of the connector, the airtight O-ring, etc. is low, and troubles are likely to occur. There's a problem.
In addition, this injector is a system in which a valve body (needle valve) is directly driven via a plunger by the suction force of an electromagnetic coil. However, when the injection pressure is high, it is necessary to increase the suction force accordingly. For this reason, it is necessary to increase the voltage of the current flowing through the electromagnetic coil or to use an electromagnetic coil having a low resistance value through which a large current flows.
[0010]
Furthermore, in the technique of heating the above-described reducing agent and then injecting it into the exhaust gas, a heater such as a heat exchanger or an electric heater using waste heat of the exhaust gas is used. The reducing agent pipe is provided, and at the time of engine start when the reducing agent in the pipe is in a low temperature state, the reducing agent in the downstream of the heater and in the injector remains at a low temperature. Therefore, if it is directly injected into the exhaust gas, the exhaust gas at the time of start-up may be at a low temperature, so that the reducing agent is not sufficiently vaporized, causing a problem of solid compound adhesion / deposition.
[0011]
[Problems to be solved by the invention]
The present invention is intended to solve the above-described problems, and for the reducing agent injector used in the exhaust gas purifying apparatus, it is possible to prevent a failure even when exposed to a high temperature reducing agent, Minimize the driving force of the solenoid valve required for injection quantity control. Furthermore, when the reducing agent immediately before injection is in a low temperature state or when the operating state of the exhaust gas generating machine / equipment changes transiently However, it is an object to realize reliable vaporization in the exhaust gas passage.
[0012]
[Means for Solving the Problems]
Therefore, the present invention is to inject a high-pressure and high-temperature reducing agent into an exhaust gas passage extending from an exhaust gas generating machine / equipment and provided with a denitration reactor to bring the reducing agent into contact with the reduction catalyst of the denitration reactor in a vaporized state. The reducing agent injector used in the exhaust gas purifying apparatus for decomposing NOX in the exhaust gas thereby has an injection hole and a valve body and an injection reducing agent passage for introducing the high-pressure and high-temperature reducing agent into the injection hole. A drive unit having an injection unit, a reducing agent passage for cooling through which a reducing agent at high pressure and room temperature passes, a pressure chamber for driving a valve body provided in the middle thereof, and an electromagnetic valve for controlling the reducing agent pressure in the pressure chamber The drive unit is cooled by the passage of the high-pressure / normal-temperature reducing agent, and the solenoid valve opens the outlet of the pressure chamber by a drive signal generated by an electronic control device in accordance with the NOx concentration in the exhaust gas. Open and close The valve body opens the injection hole by injecting the pressure in the pressure chamber when opened, and injects the high-pressure and high-temperature reducing agent, and the pressure in the pressure chamber increases by closing to close the valve body. The fact that the injection hole is closed is the first means for solving the problem.
[0013]
This makes it possible to use an aqueous urea solution that is harmless to the reducing agent and is easy to handle. In addition to the high-pressure / high-temperature reducing agent supplied to the injection unit, a high-pressure / normal-temperature reducing agent is introduced into the electromagnetic drive unit. In particular, by cooling the solenoid valve portion, it is possible to easily prevent the low heat resistant parts used in the drive unit from being thermally damaged by the high temperature reducing agent for injection. Moreover, since the valve body of the injection unit is driven using the high pressure of the reducing agent introduced into the driving unit, the suction force of the electromagnetic coil is sufficient to open and close the outlet of the pressure chamber. Therefore, it is possible to easily cope with high-pressure injection with a small-sized electromagnetic valve with low power consumption. In the present invention, the high-temperature reducing agent refers to a reducing agent that is heated to a temperature slightly lower than the vaporization temperature, and the high-pressure reducing agent is sufficiently atomized and injected into the pressure chamber when injected from the injection unit. It refers to a reducing agent that has been pressurized to a pressure that can provide a force to drive the valve body.
[0014]
Further, as a second means for solving the above problem, in addition to the first means, an electric heater for heating the reducing agent in the injection reducing agent passage is provided in the injection unit, and the electric heater includes a reducing agent. When the temperature is lower than the temperature that can be vaporized when injected, the reducing agent is heated to a temperature at which vaporization can be performed according to a command from the electronic control device. This makes it possible to perform precise temperature control during the injection of the reducing agent. In particular, the inconvenience that the low-temperature reducing agent is injected into the exhaust gas passage at the time of starting or the like is eliminated, and the inside of the exhaust gas passage is eliminated. Sufficient vaporization can always be realized.
[0015]
Further, in the first or second means, a temperature sensor is provided in the injection reducing agent passage of the injection unit, and the electronic control unit is configured to perform the electric control based on the temperature of the reducing agent immediately before injection detected by the temperature sensor. The third means is to control the heater. This makes it possible to precisely control the temperature of the reducing agent immediately before injection, and further ensures the vaporization of the reducing agent injected into the exhaust gas passage.
[0016]
Furthermore, in the first, second or third means, the high-pressure / high-temperature reducing agent is pressurized with a pump, then heated with a heater, and sent to the injection unit. The reducing agent is a fourth means in which the reducing agent pressurized by the pump is diverted in front of the heater, passed through the drive unit, and returned to the suction side of the pump. As a result, the reducing agent pressurized by the pump is heated to be suitable for vaporization and sent to the injection unit, and the route to be fed to the drive unit at room temperature without being heated to be suitable for cooling. Since the reducing agent that has been reliably diverted and sent to the drive unit passes through the drive unit while cooling, it is returned to the suction side of the pump, so that it can be effectively reused.
[0017]
In addition, in the first, second, third, or fourth means, the injection unit and the driving unit are arranged with a thin cylindrical body that restricts heat conduction interposed therebetween. The fifth means. As a result, a large amount of heat is prevented from being conducted from the injection unit to the drive unit, and the temperature of the injection unit is lowered by the cooling action from the drive unit, and the reducing agent temperature at the time of injection is reduced. Can be prevented.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that, even in different embodiments, the same components are described with the same reference numerals. The reducing agent used in the present embodiment is an aqueous urea solution from the viewpoint of safety and ease of handling.
[0019]
First, the configuration and operation of the exhaust gas purification apparatus 50 in which the injector of the present invention is arranged will be described with reference to FIG. In the present embodiment, the exhaust gas generating machine / equipment is an automobile diesel engine 1, the exhaust gas passage is an exhaust pipe 2, and an injection unit 20A and a drive unit 30A shown in FIG. A container 6A is used.
[0020]
The reducing agent stored in the tank 9 is sent to the injector 6A through the pipe 12, and a low pressure pump 8, a high pressure pump 15, a heater 14, and an electric heater 13 are provided in the path. The reducing agent guided by the pipe 12 extending from the tank 9 is pressurized by the low pressure pump 8 and then further pressurized by the high pressure pump 15. The pressure of the reducing agent is adjusted by the pressure regulator 7 a on the discharge side of the low-pressure pump 8, and the pressure is adjusted by the pressure regulator 7 b on the discharge side of the high-pressure pump 15. The reducing agent injection by the injector 6A is controlled by the electronic control device 10, and is built in the drive unit 30A of the injector 6A by an operation command (duty cycle signal) from the electronic control device 10. The electromagnetic valve is repeatedly opened and closed to adjust the injection amount from the injection unit 20A.
[0021]
In general, when a liquid is heated and vaporized, the liquid is more easily vaporized as the pressure is lower, and the vaporization is more difficult as the pressure is increased. Therefore, if the reducing agent in a liquid state is heated to a high pressure and then heated, it can be heated to a high temperature while being in a liquid state. It is being done. Therefore, in this embodiment also, the reducing agent is pressurized before heating. Then, the high-pressure reducing agent is heated to a vaporization temperature, that is, a temperature slightly lower than the boiling point, by the heater 14 and the electric heater 13, so that it is kept in a liquid state and can be completely vaporized when jetted. It becomes possible. In addition, in the present embodiment, the pump is made in two stages and the discharge pressures are adjusted to be constant. As a result, the pressure fluctuates and the reducing agent boils in the heater 14 and the electric heater 13. It is possible to eliminate the concern that bubbles are generated in the pipe and solid compounds are generated. Further, by preventing bubbles from being included in the reducing agent to be injected, the amount of reducing agent injected from the injector 6A can be made accurate and the exhaust gas purification efficiency can be increased.
[0022]
The pipe 12 is branched between the high-pressure pump 15 and the heater 14 into an injection reducing agent pipe 12a toward the injection section 20A of the injector 6A and a cooling reducing agent pipe 12b toward the driving section 30A of the injector 6A. The
The high pressure / normal temperature reducing agent that has entered the injection reducing agent pipe 12 a is heated by the heat of the pipe wall of the exhaust pipe 2 by the heater 14 controlled by the temperature control device 16. The pipe wall of the exhaust pipe 2 is heated by the conduction heat from the diesel engine 1 and the heat of the exhaust gas flowing through the exhaust pipe 2 and enables the reducing agent to be heated to a high temperature.
[0023]
An example of the configuration of the heater 14 and the temperature control device 16 is shown in detail in an enlarged view within a dashed line in the lower part of FIG. That is, the temperature control device 16 attaches the pedestal 16c to the pipe wall of the exhaust pipe 2, fixes the heater 14 to the pedestal 16c with the heat insulating material 16d interposed therebetween, and allows the heat transfer member 16b to slide on the pedestal 16c. The heat transfer member 16b is coupled to a rod 16f extending from the solenoid 16a so as to come into contact with or away from the heater 14. The pedestal 16c and the heat transfer member 16b are made of a metal excellent in heat conduction. Further, the heater 14 is formed by forming a heat transfer path 14b inside a solid body 14a which is also made of a metal having high heat conductivity, and a temperature sensor 17a is installed at an outlet portion of the heat transfer path 14b. Yes.
[0024]
The high pressure / high temperature reducing agent heated by the heater 14 is further heated by the electric heater 13 and then supplied to the injection unit 20A of the injector 6A in a high pressure / high temperature state. Here, the reducing agent whose boiling point has been raised by pressurization is heated to such an extent that it cannot be vaporized, so that it can be instantly vaporized when injected into the exhaust pipe 2 at substantially atmospheric pressure. Further, in addition to the heating by the heater 14, the heating by the electric heater 13 generates a relatively low temperature waste heat unlike a boiler or a gas turbine that generates a relatively high temperature waste heat. This is because sufficient and appropriate heating is performed in response to the characteristics of the diesel engine, which is easy and the temperature change of the waste heat is large. Since the heater 14 heats the reducing agent using waste heat from the exhaust pipe 2 and the electric heater 13 is an auxiliary heating, it is newly required to heat the reducing agent. The consumption of electric power, which is assumed to be energy, is small.
[0025]
In addition to the temperature sensor 17a being arranged in the heater 14, a temperature sensor 17b is also arranged at the outlet portion of the electric heater 13, and the temperature sensor 5 is also arranged in the exhaust pipe 2. NOx sensors 4a and 4b are respectively arranged before and after the denitration reactor 3 in the exhaust pipe 2. Then, based on the values detected by these temperature sensors 17a, 17b, 5, NOX sensors 4a, 4b, the electronic control device 10 issues an operation command to the temperature adjusting device 16, the electric heater 13, and the injector 6A. The temperature control of the reducing agent corresponding to the exhaust gas temperature and the injection amount control according to the NOX concentration in the exhaust gas can be performed. In addition, by controlling the heater 14, the injector 6A, and the electric heater 13 with the electronic control device 10 in this way, the temperature of the reducing agent is precisely controlled and completely vaporized in the exhaust pipe 2, and the exhaust gas is exhausted. It is possible to instantly respond to changes in the exhaust gas state in the pipe 2.
[0026]
As described above, in the path until the reducing agent is injected by the injector 6A, the pressure and temperature are appropriately controlled and managed so as not to vaporize the solid matter when the reducing agent is an aqueous urea solution. In addition to not generating it, it is extremely significant in that it can reliably prevent the problem that the reducing agent pressure fluctuates by generating the gas phase and the injection of the gas phase part causes a fluctuation in the reducing agent injection amount. It is.
[0027]
Next, the injector 6A will be described in detail with reference to FIG.
The injector 6A is not limited to the case where it is used in the exhaust gas purifying device 50 of the diesel engine 1 described above, and is capable of highly accurate flow control from a small flow rate to a large flow rate so that it can be widely used. The configuration is the same as that of an electromagnetically driven fuel injection valve used for fuel supply of an automobile internal combustion engine.
[0028]
The injector 6A has a substantially cylindrical shape and is provided with a drive unit 30A on the base end side (upper part) of the metal main body case 18 and an injection part 20A on the distal end side (injection nozzle side). The main body case 18 includes an upper main body case 18a that forms the drive section 30A, a lower main body case 18b that forms the injection section 20A, and a thin cylindrical body 18c that restricts heat transfer at a substantially central position sandwiched between them. It consists of
[0029]
20 A of injection parts have the nozzle 20a provided with the nozzle chamber 22 and the injection hole 21, and have the reducing agent inlet 25 for injection in the side surface near the cylindrical body 18c. In the nozzle chamber 22, a needle-like valve element 19 having a pointed tip is movably inserted in the vertical direction in the drawing, and the tip closes or opens the injection hole 21 by vertical movement.
[0030]
The injection reducing agent inlet 25 is connected to the nozzle chamber 22 via an injection reducing agent passage 24 directed toward the injection port 21. The nozzle chamber 22 is a substantially cylindrical space in which the base end portion is enlarged and the injection hole 21 is opened at the distal end portion, and the distal end portion of the valve body 19 is inserted into the nozzle chamber 22. The valve body 19 is linearly connected via a piston rod 27a to a piston 27 fitted in a cylinder hole 38 constituting a pressure chamber 38a, which will be described later, in the drive unit 30A, and is injected by a spring 23. The tip 21 is biased in the direction of pressing (closing) the hole 21.
[0031]
On the other hand, the drive unit 30A has a cooling reductant outlet 35 at the upper end, and incorporates an electromagnetic valve 41A including an electromagnetic coil 31, a valve 29a, an electromagnetic valve spring 36, and a valve seat 30a in the center. There is provided a support member 30d having a cylinder hole 38 near the cylindrical body 18c and fitted with a piston 27 so as to be slidable up and down. The space on the side opposite to the piston of the cylinder hole 38 constitutes a pressure chamber 38 a, and an outlet orifice 38 b provided substantially at the center of the ceiling of the pressure chamber 38 a communicates with the cooling reductant outlet 35.
[0032]
A cooling reducing agent inlet 32 is opened on the outer peripheral side surface of the upper body case 18a in the vicinity of the cylinder hole 38, and this cooling reducing agent inlet 32 is opened to the side wall of the pressure chamber 38a via the reducing agent inflow passage 33a. An inlet orifice 37 is connected.
[0033]
The valve seat 30a is formed in the upper opening of the outlet orifice 38b. The valve 29a has a short shaft shape, and a flange-like movable iron core 29f is fixed to the base end. The conical tip portion is urged by the electromagnetic valve spring 36 in a direction in contact with the valve seat 30a, and is supported by the support member 30f so as to be slidable in the vertical direction. An electromagnetic coil 31 controlled by the electronic control device 10 is disposed above the valve 29a, and the movable iron core 29f is attracted by the magnetic force generated during energization to resist the urging force of the electromagnetic valve spring 36. To pull up.
[0034]
The outlet orifice 38b passes through the inside of the electromagnetic valve spring 36 via the through hole 34a provided in the support member 30f and the hole provided in the flange portion of the valve 29a, and communicates with the cooling reducing agent outlet 35. ing.
[0035]
FIG. 2 shows a reducing agent injector 6A using a two-way solenoid valve 41A as the solenoid valve. FIG. 2A shows that the electromagnetic coil 31 is not energized and the injection hole 21 is the valve element 19. 2B shows a state in which the electromagnetic coil 31 is energized, the valve body 19 is retracted, the injection hole 21 is opened, and the reducing agent is injected. Show.
[0036]
At the time of non-energization shown in FIG. 2A, the high pressure / normal temperature reducing agent pressurized by the high pressure pump 15 and supplied to the cooling reducing agent inlet 32 through the cooling reducing agent pipe 12b is the reducing agent. It is introduced into the pressure chamber 38a from the inlet orifice 37 via the inflow passage 33a. At this time, since the electromagnetic coil 31 is not energized, the tip of the valve 29a is pressed against the valve seat 30a by the urging force of the electromagnetic valve spring 36 to close the outlet orifice 38b of the pressure chamber 38a. Therefore, the piston 27 is pressed and moved downward by the reducing agent at high pressure and room temperature in the pressure chamber 38a.
[0037]
On the other hand, in the injection unit 20A, the reducing agent supplied to the injection reducing agent inlet 25 through the injection reducing agent pipe 12a is in a high pressure / high temperature state, and passes through the injection reducing agent passage 24 to the nozzle chamber 22. To be introduced. At this time, the valve element 19 has a force acting in the valve closing direction, which is the sum of the spring load of the spring 23 and the reducing agent pressure of the pressure chamber 38 a, due to the reducing agent supplied to the nozzle chamber 22. Since it is larger than the force acting in the valve opening direction received by the annular valve body pressure receiving portion 19b in the large side diameter portion, the injection port 21 is closed.
[0038]
At the time of energization shown in FIG. 2B, the movable iron core 29f is attracted against the urging force of the electromagnetic valve spring 36 by the generated magnetic force, and the distal end portion of the valve 29a is separated from the valve seat 30a, and the pressure chamber 38a. To the cooling reductant outlet 35 via the outlet orifice 38b. At this time, since the flow area of the inlet orifice 37 is made smaller than the flow area of the outlet orifice 38b, the pressure in the pressure chamber 38a rapidly decreases. For this reason, the force in the valve opening direction due to the high-pressure and high-temperature reducing agent received by the valve body pressure receiving portion 19b becomes larger than the force in the valve closing direction due to the pressure chamber 38a and the spring 23, and the valve body 19 moves upward and is injected. The hole 21 is opened and a reducing agent is injected. Therefore, since the electromagnetic coil 31 only needs to have an attractive force enough to drive the valve 29a, even when a high injection pressure is required at the time of reducing agent injection, the injection amount is controlled with a small amount of power consumption. be able to.
[0039]
Thus, when excitation and demagnetization by energizing / de-energizing the electromagnetic coil 31 is repeated for a long time, the temperature of the injection unit 20A exposed to the high temperature reducing agent gradually increases, and this heat passes through the main body case 18. Then, it is conducted to the drive unit 30A. Therefore, in addition to being heated by the electric resistance heat by energization in the electromagnetic valve 41A, the drive unit 30 is also heated by the heat from the injection unit 20A.
[0040]
However, each time the valve 29a is opened, the drive unit 30A is supplied with a reducing agent at room temperature, and passes through. Therefore, the inside of the drive unit 30A and the low heat-resistant components constituting it are continuously cooled. To prevent high temperatures. Accordingly, the injector 6A suffers a thermal failure because the portion having a problem with the heat resistance of the drive unit 30A on the base end side is sufficiently cooled even when the injection unit 20A on the front end side is exposed to a high temperature reducing agent. There is almost no worry. In the present embodiment, since the thin cylindrical body 18b is provided at a substantially intermediate portion of the main body case 18 that is a heat conduction path from the injection unit 20A to the drive unit 30A, heat conduction from the injection unit 20A. Is limited. Further, the cylindrical body 18b also has a function of preventing the temperature of the reducing agent to be injected from being lowered by suppressing the temperature drop of the injection unit 20A due to the cooling of the drive unit 30A.
[0041]
FIG. 3 shows a different embodiment of the injector. The injector 6B has the same drive unit 30A as the drive unit 30A of the injector 6A in FIG. 2, and the injection unit 20B has the injection shown in FIG. An electric heater 39 and a temperature sensor 40 are provided in the injection section 20A of the container 6A. The configuration and operation of the drive unit 30A are the same as those shown in FIG.
[0042]
For example, immediately after the diesel engine 1 is started in a cold state, the waste heat temperature is low, and even when heated by the electric heater 13, the temperature required for vaporization may not be reached. According to the present embodiment, when the temperature sensor 40 detects the temperature of the reducing agent immediately before injection, and based on the value, the electronic control device 10 determines that the temperature required for vaporization has not been reached, the electric heater 39 Is energized to heat the reducing agent to the required temperature. Thereby, the problem that the reducing agent with insufficient heating is injected into the exhaust pipe 2 and the solid compound adheres to the exhaust pipe 2 or the reduction catalyst without being sufficiently vaporized can be solved. Note that the heating by the heater 39 can be controlled by the temperature detected by the temperature sensors 17 a and 17 b provided in the heater 14 and the electric heater 13 without using the temperature sensor 40. However, the temperature control of the reducing agent to be injected can be made more accurate by detecting the reducing agent temperature just before the injection with the temperature sensor 40.
[0043]
4 and 5 show an injection having a drive unit 30B in which the electromagnetic valve 41A of the two-way valve structure in the drive unit 30A of the injector 6A of FIG. 2 or the injector 6B of FIG. FIG. Since the injector 6C has the same injection unit as the injection unit 20A or the injection unit 20B described above, only the driving unit 30B will be described with the illustration thereof omitted.
[0044]
A cylindrical outer valve 29b having a through-hole 29e extending from the proximal end to the distal end and having a flange-shaped movable iron core 29g at the proximal end is inserted with a thin-shaft inner valve 29c from the proximal end side. The side is fitted to the support member 30e so as to be slidable up and down, and is biased by the electromagnetic valve spring 36 so that the tip thereof is pressed against the outer valve seat 30b. The solenoid valve spring 36 is also fixed so as not to move by pushing the base end of the inner valve 29c upward.
[0045]
An inner valve seat 30c that is closed by the tip of the inner valve 29c is provided near the tip of the outer valve 29b. Furthermore, an introduction hole 29d communicating with the reducing agent inlet 32 for cooling via the reducing agent inflow passage 33b provided in the support member 30e is provided on the wall surface of the outer valve 29b adjacent to the inner valve seat 30c. A reducing agent outflow passage 34b through which the reducing agent flows in the direction of the cooling reducing agent outlet 35 is provided on the side of the support member 30e close to the outer valve seat 30b. Further, below the outer valve seat 30b of the support member 30e, a pressure chamber 38c connected by an outlet orifice 38d and a piston 27 fitted in the cylinder hole 38 so as to be slidable up and down are arranged.
[0046]
As shown in FIG. 4, when the electromagnetic coil 31 is not energized, the outer valve 29b is pressed against the outer valve seat 30b by the electromagnetic valve spring 36, so that the high pressure / normal temperature reducing agent is discharged from the pressure chamber 38c. The possible routes are closed. At this time, the inner valve 29c is separated from the inner valve seat 30c, and the reducing agent inflow passage 33b is in communication with the pressure chamber 38c. For this reason, the pressure chamber 38c is in a high pressure state, and the valve element closes the injection hole 21 by overcoming the force in the valve opening direction at the injection portion.
[0047]
As shown in FIG. 5, when the electromagnetic coil 31 is energized, the movable iron core 39g is attracted by the magnetic force against the urging force of the electromagnetic valve spring 36, and the outer valve 29b is separated from the outer valve seat 30b. And the reducing agent outflow passage 34b are communicated with each other. At this time, the inner valve seat 30c in the outer valve 29b is in close contact with the tip of the inner valve 29c, the reducing agent inflow passage 33b is cut off from the pressure chamber 38c, and the pressure chamber 38c has a low pressure. Therefore, the force in the valve opening direction in the injection unit becomes larger than the force acting in the valve closing direction, and the injection hole is opened to inject the reducing agent.
[0048]
As described above, the electromagnetic valve 41B has a three-way valve structure, so that when the pressure chamber 38c communicates with the outlet-side reducing agent outflow passage 34b by energization of the electromagnetic coil 31, the inlet-side reducing agent inflow passage. Since the communication between the pressure chamber 38b and the pressure chamber 38c is completely closed, the pressure difference between the pressure in the pressure chamber 38c and the pressure of the reducing agent supplied to the injection unit becomes larger, so that the valve body can be driven easily. This ensures that the reducing agent is injected. This also enables finer control of the injection amount.
[0049]
【The invention's effect】
As described above, according to the injector of the present invention, it is possible to prevent a thermal failure from occurring in the drive unit even when exposed to a high temperature reducing agent. In addition, it is possible to minimize the driving force of the solenoid valve necessary for the injection amount control and to realize reliable vaporization in the exhaust gas passage.
[Brief description of the drawings]
FIG. 1 is a partial enlarged view showing an example of an exhaust gas purifying apparatus using an injector of the present invention.
FIGS. 2A and 2B are longitudinal sectional views showing different states of the embodiment of the present invention. FIGS.
FIG. 3 is a longitudinal sectional view of a different embodiment of the present invention.
FIG. 4 is a partial longitudinal sectional view of still another embodiment of the present invention.
5 is a partial longitudinal sectional view showing a state different from FIG. 4 in the embodiment of FIG. 4;
[Explanation of symbols]
1 diesel engine, 2 exhaust pipe, 3 denitration reactor, 4a, 4b NOX sensor, 5, 17a, 17b temperature sensor, 6A, 6B, 6C injector, 7a, 7b pressure regulator, 8 low pressure pump, 9 tank, 10 Electronic control device, 12 piping, 12a injection reducing agent piping, 12b cooling reducing agent piping, 13, 39 electric heater, 14 heater, 14a fuselage, 14b heat transfer path, 15 high pressure pump, 16 temperature control device, 16a Solenoid, 16b heat transfer member, 16c base, 16d heat insulating material, 16e return spring, 16f rod, 18 body case, 18a upper body case, 18b lower body case, 18c cylindrical body, 19 valve body, 19b valve body pressure receiving portion, 20A, 20B injection part, 20a nozzle, 21 injection hole, 22 nozzle chamber, 23 spring, 24 reducing agent passage for injection, 25 injection Reducing agent inlet, 27 piston, 27a piston rod, 29a valve, 29b outer valve, 29c inner valve, 29d introduction hole, 29e through hole, 29f, 29g movable iron core, 30A, 30B drive unit, 30a valve seat, 30b outer valve seat, 30c Inner valve seat, 30d, 30e, 30f Support member, 31 Electromagnetic coil, 32 Cooling reducing agent inlet, 33a, 33b Reducing agent inflow passage, 34a Through hole, 34b Reducing agent outflow passage, 35 Cooling reducing agent outlet, 36 Solenoid valve spring, 37 inlet orifice, 38 cylinder hole, 38a, 38c pressure chamber, 38b outlet orifice, 40 temperature sensor, 41A, 41B solenoid valve, 50 exhaust gas purification device

Claims (7)

NOx in the exhaust gas by injecting a reducing agent of high pressure and high temperature into the exhaust gas passage extending from the exhaust gas generating machine / equipment and installing the denitration reactor and bringing the reducing agent into contact with the reduction catalyst of the denitration reactor in a vaporized state A reductant injector used in an exhaust gas purification device for decomposing
An injection part having an injection hole and a valve body and an injection reducing agent passage for introducing the high pressure / high temperature reducing agent into the injection hole, a cooling reducing agent passage through which the high pressure / normal temperature reducing agent passes, and in the middle thereof A drive unit having a pressure chamber for driving the provided valve body and an electromagnetic valve for controlling the reducing agent pressure of the pressure chamber;
The drive unit is cooled by the passage of the high pressure / normal temperature reducing agent, and the solenoid valve opens and closes the outlet of the pressure chamber by a drive signal generated by an electronic control device in accordance with the NOx concentration in the exhaust gas. When the pressure in the pressure chamber decreases, the valve body opens the injection hole to inject the high temperature / high pressure reducing agent, and when the valve body is closed, the pressure in the pressure chamber increases to inject the valve body. It is supposed to close the hole,
A reducing agent injector for exhaust gas purification. The injector of claim 1, wherein
The injection unit includes an electric heater that heats the reducing agent in the injection reducing agent passage, and the electric heater has a temperature lower than a temperature that can be vaporized when the reducing agent is injected. It is assumed that the reducing agent is heated to a temperature at which vaporization can be performed according to the command of the type control device.
A reducing agent injector for exhaust gas purification. A temperature sensor is provided in the injection reducing agent passage of the injection unit, and the electronic control unit controls the electric heater based on the temperature of the reducing agent immediately before injection detected by the temperature sensor. The reducing agent injector for exhaust gas purification according to claim 2. The high-pressure / high-temperature reducing agent is pressurized with a pump, then heated with a heater and fed into the injection unit, and the high-pressure / normal-temperature reducing agent is supplied with the reducing agent pressurized with the pump. The reducing agent injector for exhaust gas purification according to claim 1, 2 or 3, wherein the reductant is diverted before and passes through the drive unit and returns to the suction side of the pump. The reducing agent injector for exhaust gas purification according to claim 1, 2, 3, or 4, wherein the injection unit and the drive unit are arranged with a thin cylindrical body that restricts heat conduction interposed therebetween. The said solenoid valve is a two-way valve which raises the pressure of the said pressure chamber when it is a valve closing state, and reduces the pressure of the said pressure chamber when it is a valve opening state. Reducing agent injector for exhaust gas purification. The solenoid valve includes an outer valve that opens and closes a reducing agent discharge side of the pressure chamber, and an inner valve that is slidably inserted into the outer valve and opens and closes a reducing agent inflow side. When the outer valve is in a closed state, the inner valve 2 is a three-way valve that opens to increase the pressure in the pressure chamber, and when the outer valve is in the open state, the inner valve is closed to decrease the pressure in the pressure chamber. , 2, 3, 4 or 5. Reductant injector for exhaust gas purification.

Images