JP6561776B2 - Urea water injection device - Google Patents

Description

  The present invention relates to a urea water injection device that injects urea water into exhaust gas in an exhaust passage in an exhaust purification device that reduces NOx contained in exhaust flowing through the exhaust passage.

  As a conventional urea water injection device, for example, one described in Patent Document 1 is known. In the urea water injection device (urea water addition device) of Patent Document 1, a urea water tank that stores urea water is provided, and an injector provided in the exhaust pipe portion of the internal combustion engine is used for exhaust flowing through the arrangement passage in the exhaust pipe portion. The urea water in the urea water tank is injected (added).

  The urea water may freeze depending on the temperature environment of the outside air. Therefore, in patent document 1, it is made to thaw the frozen urea water by providing heating parts, such as a heater, in the outer surface of the urea water pipe part which connects a urea water tank and an injector.

  Alternatively, a hot water passage through which a part of the cooling water (hot water) of the radiator for the internal combustion engine flows is added, and this hot water passage is disposed in the urea water tank, and on the outer surface of a part of the urea water pipe portion. I try to contact them. Then, the warm water of the radiator flowing through the warm water passage is used to keep the urea water warm so as to suppress the freezing of the urea water, or to perform thawing when frozen.

JP 2010-84694 A

  However, in the urea water injection device disclosed in Patent Document 1, the number of components increases and the configuration becomes complicated with the addition of a heating unit and a hot water passage. Further, in the case of using the hot water passage, immediately after the internal combustion engine is started, the temperature of the cooling water of the radiator is low, and an immediate effect cannot be obtained for keeping the temperature of the urea water or performing thawing. Moreover, since the cooling water of a radiator becomes the expected temperature accompanying the temperature rise of an internal combustion engine, the temperature control for heat retention or defrosting is difficult.

  In view of the above problems, an object of the present invention is to provide a urea water injection device that enables effective thawing of urea water with a simple configuration.

  In order to achieve the above object, the present invention employs the following technical means.

In the present invention, the valve body (122) that opens and closes the nozzle hole (121a) provided at the tip and the coil (123a) that drives the valve body by generating a magnetic attractive force by energization from the DC power supply (131) And an injector (120) having a nozzle hole disposed in the exhaust pipe (11) of the internal combustion engine,
In a urea water injection device comprising: a control unit (150) that opens and closes an injection hole by a valve body and injects urea water into exhaust gas in an exhaust pipe unit by controlling a state of energization from a DC power supply unit to a coil ,
An AC power supply (132) for supplying AC power to the coil;
A temperature detector (140) for detecting the temperature of the urea water,
When the temperature obtained from the temperature detection unit is lower than the freezing determination temperature for determining freezing of urea water, the control unit operates the coil as a heater by energizing the coil from the AC power supply unit,
When the temperature obtained from the temperature detection unit is equal to or higher than the freezing judgment temperature, the coil is opened and closed by energizing the coil from the DC power supply unit ,
When the temperature obtained from the temperature detection unit is lower than the freezing determination temperature, the cycle of the AC power is increased as the temperature is lower .

  According to this invention, when the temperature obtained from the temperature detection unit is lower than the freezing determination temperature, it can be estimated that the urea water is frozen. In this case, when the coil is energized from the AC power supply unit, the current flow direction in the coil is repeatedly reversed, and the magnetic attraction force by the original DC power supply unit is not generated. Then, the coil generates heat by the alternating current, and operates as a heater, so that the frozen urea water can be thawed.

  Therefore, the coil can be used as a heater without adding a dedicated heater, and a urea water injection device that enables effective thawing of urea water with a simple configuration can be provided.

  When the temperature obtained from the temperature detection unit is equal to or higher than the freezing determination temperature, it can be estimated that the urea water will not freeze, and by energizing the coil from the DC power supply unit, a magnetic attraction force is generated, The valve body can be opened and closed.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows a corresponding relationship with the specific means of embodiment description mentioned later.

It is explanatory drawing which shows the whole structure of a urea water injection apparatus (exhaust gas purification system). It is a flowchart which shows the control content with respect to the DC power supply part of 1st Embodiment, and an AC power supply part. It is a flowchart which shows the control content with respect to the DC power supply part of 2nd Embodiment, and an AC power supply part.

  A plurality of modes for carrying out the present invention will be described below with reference to the drawings. In each embodiment, parts corresponding to the matters described in the preceding embodiment may be denoted by the same reference numerals, and redundant description may be omitted. When only a part of the configuration is described in each mode, the other modes described above can be applied to the other parts of the configuration. Not only combinations of parts that clearly indicate that the combination is possible in each embodiment, but also a combination of the embodiments even if they are not clearly specified unless there is a problem with the combination. It is also possible.

(First embodiment)
1 and 2 show a urea water injection device 100 according to a first embodiment of the present invention. A urea water injection device 100 according to the first embodiment is provided in an exhaust pipe portion 11 of an internal combustion engine (engine) of a vehicle to constitute an exhaust purification system 10. The exhaust purification system 10 is a device that decomposes NOx contained in the exhaust gas flowing through the exhaust pipe section 11. The internal combustion engine is, for example, a diesel engine.

  The exhaust pipe portion 11 is a cylindrical pipe, and an exhaust passage 11a is formed therein. One end of the exhaust pipe portion 11 is connected to the internal combustion engine, and the other end is open to the atmosphere. Exhaust gas discharged from the internal combustion engine flows through the exhaust passage 11a. In the exhaust passage 11a, a DPF (Diesel Particulate Filter), an oxidation catalyst, an SCR catalyst, an ammonia slip catalyst, and the like are provided in order from the internal combustion engine side.

  The DPF and the oxidation catalyst are integrally formed. The DPF is a filter that collects minute carbon particles contained in the exhaust gas. The oxidation catalyst is a catalyst that promotes the oxidation of HC and CO contained in exhaust gas to water and carbon dioxide. The SCR catalyst is a catalyst that promotes reduction of NOx contained in the exhaust gas with urea water. The ammonia slip catalyst is a catalyst that promotes oxidation of excess ammonia contained in the exhaust gas that has passed through the SCR catalyst.

  A urea water injection device (hereinafter referred to as an injection device) 100 includes a urea water supply unit 110, an injector 120, a power supply unit 130, a temperature sensor 140, a control unit 150, and the like.

  The urea water supply unit 110 includes a urea water tank 111, a urea water pump 112, a pressure adjustment unit 113, a urea water pipe unit 114, and the like. The urea water tank 111 is a container for storing urea water, that is, an aqueous solution of urea. The urea water pump 112 is a pump that supplies urea water stored in the urea water tank 111 to the injector 120. The pressure adjusting unit 113 is a device that adjusts the pressure of urea water supplied to the injector 120 by the urea water pump 112. The urea water pump 112 and the pressure adjustment unit 113 are controlled by a control unit 150 described later.

  The urea water pipe portion 114 is a pipe that connects the urea water tank 111 and the injector 120. The urea water pipe portion 114 forms a urea water passage through which the urea water flows between the urea water tank 111 and the injector 120.

  The injector 120 injects urea water in the urea water tank 111 into the exhaust passage 11a. The injector 120 includes a body 121, a needle valve 122, an electromagnetic drive unit 123, and the like.

  The body 121 is a cylindrical member, and accommodates a needle valve 122 and an electromagnetic drive unit 123 therein. The front end portion of the body 121 on the injection side is obliquely inserted into the exhaust pipe portion 11 so as to face the downstream side of the exhaust, and an injection hole 121a is formed at the front end portion. A valve seat 121b on which the seal portion 122b of the needle valve 122 is seated is formed on the inner peripheral surface of the nozzle hole 121a.

  The needle valve 122 is a needle-like valve body that is accommodated inside the body 121 so as to be movable in the longitudinal direction. The distal end side of the needle valve 122 is an enlarged head portion 122a. A seal portion 122b that can be seated on the valve seat 121b of the body 121 is formed on the outer periphery of the head portion 122a. In addition, a urea water passage 122c that connects between the urea water pipe portion 114 and the injection hole 121a is formed in the needle valve 122 (center portion). Furthermore, a flange 122d that expands in a flat plate shape is formed at the end of the needle valve 122 opposite to the head 122a.

  The seal part 122b is configured to open and close the nozzle hole 121a by being seated on or separated from the valve seat 121b of the body 121. Here, when the needle valve 122 moves to the side opposite to the nozzle hole 121a (the urea water pipe part 114 side), the seal part 122b is seated on the valve seat 121b, and conversely, the needle valve 122 moves to the nozzle hole 121a side. The seal portion 122b moves away from the valve seat 121b.

  The electromagnetic drive unit 123 includes a coil 123a and an elastic member 123b. The coil 123 a is formed by winding a conductive wire, and is disposed so as to surround the needle valve 122 on the urea water pipe portion 114 side of the body 121. The coil 123 a is connected to the control unit 150 via the power supply unit 130. The controller 150 controls the energization of the coil 123a. The coil 123a generates a magnetic field (magnetic attractive force) when supplied with power from the DC power supply unit 131 in the power supply unit 130, and generates heat when supplied with power from the AC power supply unit 132. ing.

  The core wire of the coil 123a is formed from carbon nanotubes (CNT). A carbon nanotube is a six-membered ring network (graphene sheet) made of carbon in a single-layer or multilayer coaxial tube. Moreover, the coating material of the coil 123a is made of a fluororesin. The fluororesin is polytetrafluoroethylene and is known by the Teflon trade name.

  The elastic member 123b is configured by, for example, a coil spring or the like, and one end portion in the axial direction is in contact with the intermediate position in the longitudinal direction of the body 121, and the other end portion is in contact with the flange portion 122d of the needle valve 122. The elastic member 123b has a force in the direction in which the entire length extends. Therefore, the needle valve 122 receives an urging force in the direction in which the seal portion 122b is seated on the valve seat 121b by the elastic member 123b.

  That is, when the coil 123a is not energized, the needle valve 122 receives a force from the elastic member 123b and the seal portion 122b is seated on the valve seat 121b as described above. On the other hand, when energization from the DC power source 131 to the coil 123a is performed, a magnetic attractive force generated from the coil 123a is applied to the needle valve 122. The direction of the magnetic attractive force is opposite to the direction of the urging force by the elastic member 123b. Therefore, when the magnetic attractive force applied to the needle valve 122 becomes larger than the biasing force received from the elastic member 123b, the needle valve 122 moves to the side that opens the nozzle hole 121a.

  The power supply unit 130 supplies power to the coil 123a, and includes a DC power supply unit 131 for DC and an AC power supply unit 132 for AC. Each of the power supply units 131 and 132 is selectively controlled by a control unit 150 to be described later, and supplies power to the coil 123a in order to thaw frozen urea water or to open / close the normal nozzle hole 121a.

  The temperature sensor 140 is a temperature detection unit that directly or indirectly detects the temperature of the urea water. Here, the temperature sensor 140 is provided on the outer peripheral portion of the body 121 so as to correspond to the position of the coil 123a, and indirectly detects the temperature of the urea water in the injector 120 via the body 121. ing. The temperature signal (urea water temperature) detected by the temperature sensor 140 is output to the control unit 150 described later.

  The control unit 150 includes a microcomputer that includes a CPU, a ROM, a RAM, and the like. The control unit 150 is connected to, for example, an accelerator opening sensor or a rotational speed sensor provided in the vehicle, and detects an operating state of the internal combustion engine based on signals output from the accelerator opening sensor or the rotational speed sensor. It is supposed to be. The control unit 150 controls the urea water pump 112, the pressure adjustment unit 113, and the DC power supply unit 131 based on the detected operating state of the internal combustion engine. In addition, the control unit 150 determines whether the urea water is frozen from the temperature signal obtained from the temperature sensor 140, and selects the AC power source unit 132 when determining that the urea water is frozen. It is to be controlled (details will be described later).

  Next, the operation of the injection device 100 based on the above configuration will be described with reference to FIG.

  When the internal combustion engine (engine) is started, the control unit 150 starts control of the injection device 100 based on the flowchart of FIG.

  First, in step S <b> 100, the control unit 150 performs temperature detection by the temperature sensor 140. That is, a temperature signal is acquired from the temperature sensor 140 at predetermined time intervals. As described above, the temperature signal obtained from the temperature sensor 140 corresponds to the temperature of the urea water in the injector 120, and is hereinafter referred to as the urea water temperature.

  In step S110, the control unit 150 determines the urea water temperature. That is, the control unit 150 is provided with a freezing determination temperature as a threshold for determining whether or not the urea water is frozen, and the urea water temperature obtained from the temperature sensor 140 is equal to or higher than the freezing determination temperature. It is determined whether or not. The freezing judgment temperature is, for example, a temperature of about minus 11 to 14 ° C. at which urea water reaches freezing.

  If NO in step S110, that is, if it is determined that the urea water temperature is lower than the freezing determination temperature, it can be estimated that the urea water is frozen, and the control unit 150 receives AC power from the AC power supply unit 132 in step S120. Is supplied to the coil 123a.

  Here, it is presumed that the needle valve 122 is locked with respect to the body 121 due to the freezing of urea water. In such a state, when the coil 123a is energized from the DC power source 131 as usual, a magnetic attraction force acts on the side that opens the nozzle hole 121a, even though the needle valve 122 is locked by freezing. There is a possibility that the operation of the injector 120 may be hindered.

  Therefore, as described above, when AC power is supplied from the AC power supply unit 132 to the coil 123a, the current flow direction is repeatedly reversed in the coil 123a, and the magnetic attraction force by the original DC power supply unit 131 is generated. It becomes a form that does not. The coil 123a generates heat due to the alternating current, and operates as a heater, so that the frozen urea water can be thawed. After step S120, step S100 and step S110 are repeated.

  On the other hand, if the determination in step S110 is affirmative, that is, if the urea water temperature is determined to be equal to or higher than the freezing determination temperature, it can be estimated that the urea water is not frozen, and the control unit 150 in step S130, the DC power supply unit 131 is estimated. The normal opening / closing control of the needle valve 122 is performed using

  That is, the control unit 150 operates the urea water pump 112 and the pressure adjustment unit 113 in accordance with the operation state of the internal combustion engine obtained from the accelerator opening sensor and the rotation speed sensor. In addition, the controller 150 supplies DC power to the coil 123a from the DC power source 131, thereby generating a magnetic attractive force for the needle valve 122 to open the nozzle hole 121a and to the exhaust flowing through the exhaust passage 11a. And inject urea water. Alternatively, by stopping energization of the coil 123a, the nozzle hole 121a is closed and the urea water injection is stopped.

  As described above, when the urea water is expected to be frozen, the coil 123a can be operated as a heater by energizing the coil 123a from the AC power supply unit 132. Therefore, the coil 123a can also be used as a heater without adding a dedicated heater, and the injection device 100 that enables effective thawing of urea water with a simple configuration can be obtained.

  In the present embodiment, the core wire of the coil 123a is formed of carbon nanotubes. Carbon nanotubes are, for example, chemically stable materials compared to ordinary copper wires, and also have high corrosion resistance in an alkaline environment (urea aqueous environment), so a complex structure for improving corrosion resistance, etc. As unnecessary, corrosion resistance can be improved at low cost.

  In addition, the carbon nanotube has a higher tensile strength than, for example, a normal copper wire, and a smaller size can be set as a winding material of the coil 123a. As a result, the number of turns can be increased to increase the generated magnetic attractive force, and the reliability in the opening / closing operation of the needle valve 122 can be increased.

  Further, the coating material of the coil 123a is made of a fluororesin. The fluororesin has high heat resistance and can suppress thermal deterioration even in a high temperature environment where exhaust is handled. As a result, it is possible to prevent moisture from entering from the thermally deteriorated portion into the internal core wire, and to improve the corrosion resistance of the coil 123a together with the use of the carbon nanotube.

(Second Embodiment)
A second embodiment is shown in FIG. In the second embodiment, the basic configuration of the injection device 100 of the first embodiment is the same, and the control content by the control unit 150 is changed. The flowchart shown in FIG. 3 is obtained by changing step S110 to step S110A and changing step S120 to step S120A and step S120B with respect to the flowchart described in FIG.

  After step S100, control unit 150 determines in step S110A that the urea water temperature is lower than the freezing determination temperature by dividing it into “large” and “small”. Here, for the sake of convenience, the freezing determination temperature described in the first embodiment is set as the first freezing determination temperature, and the second freezing determination temperature is set to a side lower than the first freezing determination temperature.

  When the urea water temperature obtained from the temperature sensor 140 is lower than the second freezing determination temperature, the degree lower than the freezing determination temperature (first freezing determination temperature) is set to “large”, and the urea water temperature is When the temperature is between the second freezing determination temperature and the first freezing determination temperature, the degree lower than the freezing determination temperature (first freezing determination temperature) is set to “small”.

  Therefore, if it is determined in step S110A that the degree lower than the freezing determination temperature is “large”, the control unit 150 determines the cycle of AC power (AC current) supplied from the AC power supply unit 132 to the coil 123a in step S120A. , And a predetermined long cycle.

  By supplying a long-period alternating current to the coil 123a, the time during which the coil 123a is continuously heated becomes longer. Therefore, the amount of heat given to the coil 123a is increased, that is, the heating rate is increased, and the urea water can be thawed in a short time. After step S120A, step S100 and step S110A are repeated.

  On the other hand, when it is determined in step S110A that the degree lower than the freezing determination temperature is “small”, in step S120B, the control unit 150 sets the cycle of AC power (AC current) supplied from the AC power supply unit 132 to the coil 123a. , And a predetermined short cycle. The predetermined short period is a period shorter than the predetermined high period described above.

  By supplying the short-period alternating current to the coil 123a, the time during which the coil 123a is continuously heated is shorter than in the case of step S120A. Further, the amount of heat given to the coil 123a is reduced, and the heating rate is reduced. Therefore, when the urea water temperature reaches the freezing determination temperature (first freezing determination temperature), it becomes possible to stop the heating control at a faster timing than in the case of the long cycle, and the urea water is heated too much. In addition, the transition operation from heating to heating stop can be performed smoothly. After step S120B, step S100 and step S110A are repeated.

  In step S110A, if the urea water temperature is equal to or higher than the first freezing determination temperature, the control unit 150 executes step S130 as in the first embodiment.

  As described above, in this embodiment, when the urea water temperature obtained from the temperature sensor 140 is lower than the freezing determination temperature, the control unit 150 increases the AC power cycle as the urea water temperature is lower. The thawing according to the frozen state is possible.

(Other embodiments)
In each of the above embodiments, the temperature sensor 140 is provided on the outer periphery of the injector 120, but may be provided inside. Further, the temperature sensor 140 is not limited to the injector 120, and may be provided in other parts such as the urea water pipe portion 114.

  Moreover, in each said embodiment, although the carbon nanotube was used as a core material of the coil 123a, it is not limited to this, It is good also as another copper wire, an iron wire, etc.

  Moreover, in each said embodiment, although the fluororesin was used as a coating | coated material of the coil 123a, it is not limited to this, It is good also as another polyacetal resin, polyphenylene sulfide resin, etc. The combination of the material of the core material of the coil 123a and the covering material may be arbitrary.

  Further, in the second embodiment, the first freezing determination temperature and the second freezing determination temperature are used to determine the degree to which the urea water temperature is lower than the freezing determination temperature. However, the present invention is not limited to this. In addition, more freezing determination temperatures may be provided, and heating control may be performed at a period of alternating current corresponding to each of three or more temperature regions.

  Moreover, although the urea water injection device 100 of each said embodiment was demonstrated as what is applied to the exhaust gas purification system 10 in a diesel engine, it is good also as what is applied to the exhaust gas purification system in a gasoline engine, a turbine engine, etc.

DESCRIPTION OF SYMBOLS 10 Exhaust purification system 11 Exhaust pipe part 100 Urea water injection apparatus 120 Injector 121a Injection hole 122 Needle valve (valve body)
123a Coil 131 DC power supply unit 132 AC power supply unit 140 Temperature sensor (temperature detection unit)
150 Control unit

Claims (3)

There is a valve body (122) for opening and closing the nozzle hole (121a) provided at the tip, and a coil (123a) for driving the valve body by generating a magnetic attractive force by energization from the DC power supply section (131). An injector (120) in which the nozzle hole is disposed in the exhaust pipe (11) of the internal combustion engine;
A control unit (150) for controlling the energization state of the coil from the DC power supply unit to open and close the nozzle hole by the valve body and injecting urea water into the exhaust gas in the exhaust pipe unit. In the urea water injection device,
An AC power supply unit (132) for supplying AC power to the coil;
A temperature detector (140) for detecting the temperature of the urea water,
When the temperature obtained from the temperature detection unit is lower than the freezing determination temperature for determining freezing of the urea water, the control unit heats the coil by energizing the coil from the AC power supply unit. And act as
When the temperature obtained from the temperature detection unit is equal to or higher than the freezing determination temperature, the coil is opened and closed by energizing the coil from the DC power supply unit ,
When the temperature obtained from the temperature detection unit is lower than the freezing determination temperature, the urea water injection device increases the period of the AC power as the temperature is lower . The urea water injection device according to claim 1 , wherein the core wire of the coil is formed of carbon nanotubes. The urea water injection device according to claim 1 or 2 , wherein the coating material of the coil is formed of a fluororesin.

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