JP2015040480A - Additive supply device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an additive supply device for an internal combustion engine, capable of reducing the consumption of additive.SOLUTION: An additive supply device includes: a urea addition valve for injecting urea water into an exhaust passage of the engine; a NOx eliminating catalyst for eliminating NOx using additive added from the urea addition valve; and a control device for executing the injection of the additive from the urea addition valve when the temperature of exhaust gas in an area of the exhaust passage at its further upstream side in the flowing direction of the exhaust gas than the urea addition valve is a predetermined temperature or higher. The urea addition valve has a radiation fin to be heat-exchanged with outside air to radiate heat. The control device keeps the injection amount of the urea water (a target cooling injection amount TQc) smaller as an outside air temperature Thout is lower (S102, S106).

Description

  The present invention relates to an additive supply device for an internal combustion engine.

  In order to purify the exhaust of an internal combustion engine, an apparatus for supplying an additive to an exhaust passage is known. For example, in the apparatus described in Patent Document 1, urea water is supplied into the exhaust passage in order to reduce and purify nitrogen oxide (NOx) in the exhaust with a catalyst.

  Moreover, in the apparatus of patent document 1, in order to protect an addition valve from the heat damage by high temperature exhaust, the additive is supplied into the inside of the addition valve. In this apparatus, since the additive is vaporized inside the addition valve and the supply passage for supplying the additive to the addition valve, the addition valve is cooled using the heat of vaporization.

JP 2009-103013 A

  In the apparatus of Patent Document 1, it is necessary to inject the additive from the addition valve when the addition valve is cooled. In the injection of the additive for cooling the addition valve, the amount of addition is not necessarily an amount suitable for the purification of NOx in the catalyst, and the additive may be injected in a situation not suitable for the purification of NOx. is there. In this case, the injection of the additive for cooling the addition valve is a cause of an increase in the consumption of the additive.

  This invention is made | formed in view of such a situation, The objective is to provide the additive supply apparatus of the internal combustion engine which can reduce the consumption of an additive.

  Hereinafter, an additive supply device for an internal combustion engine for achieving the above-described problem is provided with an addition valve for injecting an additive into an exhaust passage of the internal combustion engine, and on the downstream side in the exhaust flow direction of the addition valve in the exhaust passage NOx purification catalyst for purifying NOx by addition of additive from the addition valve, and addition from the addition valve when the exhaust temperature in the exhaust passage upstream of the addition valve in the exhaust passage is equal to or higher than a predetermined temperature And a control unit that executes injection of the agent. The addition valve has a radiation fin that dissipates heat by heat exchange with the outside air, and the control unit decreases the amount of the additive injected as the outside air temperature is lower.

  According to the above apparatus, although the temperature of the addition valve is increased by receiving heat from the exhaust gas of the internal combustion engine, the addition valve is cooled by heat exchange with the outside air in the radiating fin. Can be suppressed. Moreover, in the above apparatus, the exhaust temperature of the upstream portion of the exhaust passage in the exhaust flow direction from the addition valve in the exhaust passage is lower as the outside air temperature is lower, that is, as the temperature of the addition valve is lower due to a larger amount of heat exchange in the radiating fin. The injection amount of the additive when the temperature is equal to or higher than the predetermined temperature can be reduced, whereby the injection amount of the additive for cooling the addition valve can be reduced. Therefore, the additive consumption can be reduced while suppressing the temperature increase of the addition valve.

In the above apparatus, it is preferable that the internal combustion engine is mounted on a vehicle, and the control unit decreases the injection amount of the additive as the traveling speed of the vehicle increases.
In the above apparatus, the higher the traveling speed of the vehicle, the greater the amount of traveling wind, so the amount of heat exchange in the radiating fins increases and the temperature of the addition valve decreases. According to the above apparatus, the amount of additive consumed can be reduced because the amount of injection of the additive for cooling the addition valve can be reduced in accordance with the relationship between the traveling speed of the vehicle and the heat exchange amount in the radiating fin. Can be suitably reduced.

In the above apparatus, it is preferable that the control unit decreases the injection amount of the additive as the temperature of the exhaust gas from the internal combustion engine is lower.
The lower the temperature of the exhaust gas from the internal combustion engine, the lower the amount of heat received by the addition valve from the exhaust gas. According to the above apparatus, the amount of additive injection for cooling the addition valve can be reduced as the exhaust temperature is lower and the temperature of the addition valve tends to be lower. Can be reduced.

In the above apparatus, it is preferable that the control unit decreases the injection amount of the additive as the flow rate of the exhaust gas in the exhaust passage decreases.
The smaller the flow rate of the exhaust gas from the internal combustion engine, the lower the amount of heat received by the addition valve from the exhaust gas, so the temperature of the addition valve tends to decrease. According to the above apparatus, as the exhaust flow rate is small and the temperature of the addition valve tends to be lower, the amount of additive injection for cooling the addition valve can be reduced. Can be reduced.

  In the above apparatus, the control unit calculates a first additive injection amount for cooling the addition valve and a second additive injection amount for purifying NOx in the NOx purification catalyst, When the first additive injection amount is larger than the second additive injection amount, the additive is injected from the addition valve based on the first additive injection amount, and the first additive is injected. When the injection amount is equal to or less than the second additive injection amount, it is preferable to execute injection of the additive from the addition valve based on the second additive injection amount.

  In the above apparatus, an injection amount (first additive injection amount) required for cooling the addition valve and an injection amount (second additive injection amount) required for NOx purification in the NOx purification catalyst are obtained. While being calculated separately, injection of the additive from the addition valve is executed based on the larger one of the injection amounts. Thereby, when the first additive injection amount is larger than the second additive injection amount, the temperature of the addition valve cannot be suppressed only by injecting the amount of additive necessary for NOx purification. The amount of additive necessary for cooling of the additional valve more than this is injected. Therefore, at this time, an amount of additive sufficient for purifying NOx and suitable for cooling the addition valve can be injected. Moreover, when the first additive injection amount is equal to or less than the second additive injection amount, the temperature of the addition valve can be suppressed by injecting an amount of additive necessary for NOx purification. The amount of additive required for NOx purification is injected. At this time, an appropriate amount for the purification of NOx and a sufficient amount of additive for cooling the addition valve can be injected from the addition valve. Therefore, according to the above apparatus, it is possible to reduce the consumption of the additive while satisfying both the function of cooling the addition valve and the function of purifying NOx.

  In the above apparatus, the control unit sets the second additive injection amount to a positive value when the execution condition of the additive injection for purifying the NOx is satisfied, and the execution condition is not satisfied. Sometimes, the second additive injection amount can be set to “0”.

  In the above apparatus, when the execution condition is satisfied, the second additive injection amount is used to inject the additive from the addition valve. When the execution condition is not satisfied, the second additive injection amount is used. Without injection, injection of the additive from the addition valve is executed based on the first additive injection amount. Thus, according to the said apparatus, the injection of the additive from an addition valve can be performed according to the necessity of the injection of the additive for NOx purification | cleaning.

Schematic which shows schematic structure of one Embodiment of the additive supply apparatus of an internal combustion engine. The flowchart which shows the execution procedure of the injection quantity calculation process. The conceptual diagram which shows the relationship between outside temperature and correction value A1. The conceptual diagram which shows the relationship between vehicle speed and correction value B1. The conceptual diagram which shows the relationship between 2nd exhaust temperature and correction value C1. The conceptual diagram which shows the relationship between exhaust flow volume and the correction value D1. The conceptual diagram which shows the relationship between an engine load, an engine speed, and a base cooling injection quantity. The conceptual diagram which shows the relationship between an engine load, an engine speed, and target purification injection quantity.

Hereinafter, an embodiment embodying an additive supply device for an internal combustion engine will be described.
FIG. 1 shows a schematic configuration diagram showing a diesel engine (hereinafter simply referred to as “engine”) to which the additive supply device of the present embodiment is applied, and the peripheral configuration thereof.

  The engine 1 is provided with a plurality of cylinders # 1 to # 4. A plurality of fuel injection valves 4 a to 4 d are attached to the cylinder head 2. These fuel injection valves 4a to 4d inject fuel into the combustion chambers of the cylinders # 1 to # 4. Also, the cylinder head 2 is provided with intake ports for introducing fresh air into the cylinders and exhaust ports 6a to 6d for discharging combustion gas to the outside of the cylinders corresponding to the respective cylinders # 1 to # 4. It has been.

  The fuel injection valves 4a to 4d are connected to a common rail 9 that accumulates high-pressure fuel. The common rail 9 is connected to the supply pump 10. The supply pump 10 sucks fuel in the fuel tank and supplies high-pressure fuel to the common rail 9. The high-pressure fuel supplied to the common rail 9 is injected into the cylinder from the fuel injection valves 4a to 4d when the fuel injection valves 4a to 4d are opened.

  An intake manifold 7 is connected to the intake port. The intake manifold 7 is connected to the intake passage 3. An intake throttle valve 16 for adjusting the intake air amount is provided in the intake passage 3.

An exhaust manifold 8 is connected to the exhaust ports 6a to 6d. The exhaust manifold 8 is connected to the exhaust passage 26.
In the middle of the exhaust passage 26, there is provided a turbocharger 11 that supercharges intake air introduced into the cylinder using exhaust pressure. An intercooler 18 is provided in the intake passage 3 between the intake side compressor of the turbocharger 11 and the intake throttle valve 16. The intercooler 18 cools the intake air whose temperature has risen due to supercharging of the turbocharger 11.

  A first purification member 30 for purifying exhaust gas is provided in the middle of the exhaust passage 26 and downstream of the exhaust side turbine of the turbocharger 11. Inside the first purification member 30, an oxidation catalyst 31 and a filter 32 are arranged in series with respect to the flow direction of the exhaust gas.

  The oxidation catalyst 31 carries a catalyst for oxidizing HC in the exhaust. The filter 32 is a member that collects PM (particulate matter) in the exhaust gas, and is made of porous ceramic. The filter 32 carries a catalyst for promoting the oxidation of PM, and the PM in the exhaust gas is collected when passing through the porous wall of the filter 32.

  Further, a fuel addition valve 5 for supplying fuel as an additive to the oxidation catalyst 31 and the filter 32 is provided in the vicinity of the collecting portion of the exhaust manifold 8. The fuel addition valve 5 is connected to the supply pump 10 through a fuel supply pipe 27. The position of the fuel addition valve 5 may be changed as appropriate as long as it is in the exhaust system and upstream of the first purification member 30.

  When the amount of PM collected by the filter 32 exceeds a predetermined value, the regeneration process of the filter 32 is started, and fuel is injected from the fuel addition valve 5 into the exhaust manifold 8. The fuel injected from the fuel addition valve 5 is combusted when it reaches the oxidation catalyst 31, thereby increasing the exhaust temperature. The exhaust gas whose temperature has been raised by the oxidation catalyst 31 flows into the filter 32, whereby the temperature of the filter 32 is raised, whereby the PM deposited on the filter 32 is oxidized and the filter 32 is regenerated.

  A second purification member 40 that purifies the exhaust gas is provided downstream of the first purification member 30 in the middle of the exhaust passage 26. A selective reduction type NOx catalyst (hereinafter referred to as SCR catalyst) 41 that reduces and purifies NOx in the exhaust using a reducing agent is disposed inside the second purification member 40.

  Further, a third purification member 50 that purifies the exhaust gas is provided in the middle of the exhaust passage 26 and downstream of the second purification member 40. Inside the third purification member 50, an ammonia oxidation catalyst 51 for purifying ammonia in the exhaust is disposed.

  The engine 1 is provided with a urea water supply mechanism 200 that supplies a reducing agent to the SCR catalyst 41. The urea water supply mechanism 200 includes a tank 210 that stores urea water, a urea addition valve 230 that injects urea water into the exhaust passage 26, a supply passage 240 that connects the urea addition valve 230 and the tank 210, and a supply passage 240. The pump 220 is provided in the middle.

  The urea addition valve 230 is provided in the exhaust passage 26 between the first purification member 30 and the second purification member 40, and its injection hole is directed to the SCR catalyst 41. When the urea addition valve 230 is opened, urea water is injected and supplied into the exhaust passage 26 via the supply passage 240.

  The urea addition valve 230 is attached to the exhaust passage 26 via the heat radiating member 231. A plurality of heat radiating fins 232 are integrally formed on the outer surface of the heat radiating member 231. Since such a heat radiating member 231 is provided, heat exchange between the urea addition valve 230 and the outside air is promoted, and the urea addition valve 230 is cooled. When injecting urea water from the urea addition valve 230, the urea addition valve 230 is cooled by heat exchange with the relatively low temperature urea water supplied from the tank 210.

  The pump 220 is an electric pump, and at the time of forward rotation, the urea water is fed from the tank 210 toward the urea addition valve 230. On the other hand, during reverse rotation, urea water is sent from the urea addition valve 230 toward the tank 210. That is, during reverse rotation of the pump 220, urea water is collected from the urea addition valve 230 and the supply passage 240 and returned to the tank 210.

  A dispersion plate 60 is provided in the exhaust passage 26 between the urea addition valve 230 and the SCR catalyst 41 to promote atomization of the urea water by dispersing the urea water injected from the urea addition valve 230. It has been.

  The urea water injected from the urea addition valve 230 is hydrolyzed by the heat of the exhaust to become ammonia. The ammonia is supplied to the SCR catalyst 41 as a NOx reducing agent. Ammonia supplied to the SCR catalyst 41 is occluded by the SCR catalyst 41 and used for NOx reduction. A part of the hydrolyzed ammonia is directly used for NOx reduction before being occluded by the SCR catalyst 41.

  In addition, the engine 1 is provided with an exhaust gas recirculation device (hereinafter referred to as an EGR device). This EGR device is a device that reduces the combustion temperature in a cylinder by introducing a part of exhaust gas (so-called EGR gas) into intake air, thereby reducing the amount of NOx generated. The EGR device includes an EGR passage 13 that communicates the intake passage 3 and the exhaust manifold 8, an EGR valve 15 provided in the EGR passage 13, an EGR cooler 14, and the like. By adjusting the opening degree of the EGR valve 15, the exhaust gas recirculation amount introduced into the intake passage 3 from the exhaust passage 26, that is, the EGR amount is adjusted. Further, the temperature of the exhaust gas flowing through the EGR passage 13 is lowered by the EGR cooler 14. In this embodiment, the introduction of EGR gas by the EGR device is an engine operation in which the engine load KL (in this embodiment, the fuel injection amount from the fuel injection valves 4a to 4d) is relatively small and the engine rotational speed NE is relatively low. It is executed only in the area. That is, in the engine operation region where the engine load KL is large and the engine operation region where the engine rotational speed NE is high, the EGR gas is not introduced by the EGR device.

  Various sensors for detecting the engine operation state are attached to the engine 1. For example, the air flow meter 19 detects the intake air amount GA in the intake passage 3. The throttle valve opening sensor 20 detects the opening of the intake throttle valve 16. The engine rotation speed sensor 21 detects the rotation speed of the crankshaft, that is, the engine rotation speed NE. The accelerator sensor 22 detects an accelerator pedal depression amount, that is, an accelerator operation amount ACCP. The outside air temperature sensor 23 detects the outside air temperature THout. The vehicle speed sensor 24 detects the traveling speed of the vehicle on which the engine 1 is mounted, that is, the vehicle speed SPD. The ignition switch 25 detects a start operation and a stop operation of the engine 1 by a vehicle driver.

  The first exhaust temperature sensor 100 provided upstream of the oxidation catalyst 31 detects the first exhaust temperature TH1 that is the exhaust temperature before flowing into the oxidation catalyst 31. The differential pressure sensor 110 detects a pressure difference ΔP between the exhaust pressure upstream and the exhaust downstream of the filter 32.

  A second exhaust temperature sensor 120 and a first NOx sensor 130 are provided in the exhaust passage 26 between the first purification member 30 and the second purification member 40, and upstream of the urea addition valve 230. The second exhaust temperature sensor 120 detects a second exhaust temperature TH2, which is the exhaust temperature before flowing into the SCR catalyst 41. The first NOx sensor 130 detects a first NOx concentration N1, which is the NOx concentration in the exhaust before flowing into the SCR catalyst 41.

  A second NOx sensor 140 that detects a second NOx concentration N2 that is the NOx concentration of the exhaust gas purified by the SCR catalyst 41 is provided in the exhaust passage 26 downstream of the third purification member 50.

  Outputs from these various sensors are input to the control device 80. The control device 80 includes a central processing control device (CPU), a read-only memory (ROM) that stores various programs and maps in advance, a random access memory (RAM) that temporarily stores CPU calculation results, an input interface, and an output. It is mainly composed of a microcomputer equipped with an interface. Note that power is supplied from the battery to the CPU and the various sensors described above.

  Then, the controller 80 controls, for example, the fuel injection amount control / fuel injection timing control of the fuel injection valves 4a to 4d and the fuel addition valve 5, the discharge pressure control of the supply pump 10, and the drive amount of the actuator 17 that opens and closes the intake throttle valve 16. Various controls of the engine 1 such as control and opening control of the EGR valve 15 are performed. The exhaust gas purification control such as the regeneration process for burning the PM collected by the filter 32 is also performed by the controller 80.

  Further, the control device 80 performs additive addition control by the urea addition valve 230 as one of exhaust purification control. In this addition control, injection of urea water for purifying NOx in the SCR catalyst 41 (hereinafter referred to as purification injection) and injection of urea water for cooling the urea addition valve 230 (hereinafter referred to as cooling injection) are performed. Executed.

  The cleaning injection is basically executed as follows. That is, based on the engine operating state (engine load KL and engine speed NE), a urea water injection amount (target purification injection amount TQn) that is sufficient to reduce NOx discharged from the engine 1 is calculated. The Then, the open state of the urea addition valve 230 is controlled so that the same amount of urea water as the target purification injection amount TQn is injected from the urea addition valve 230. In the present embodiment, the target purification injection amount TQn corresponds to the second additive injection amount.

  Further, the cooling injection is basically executed as follows. That is, based on the engine operating state (engine load KL and engine speed NE), urea water injection without excess or deficiency in order to keep the temperature of the urea addition valve 230 exposed to high-temperature exhaust gas below the upper limit temperature in the temperature compensation range. An amount (target cooling injection amount TQc) is calculated. Then, the open state of the urea addition valve 230 is controlled such that the same amount of urea water as the target cooling injection amount TQc is injected from the urea addition valve 230. In the present embodiment, this target cooling injection amount TQc corresponds to the first additive injection amount. The fact that the injection of urea water from the urea addition valve 230 contributes to the cooling of the urea addition valve 230 is that the second exhaust temperature TH2 is a predetermined temperature (specifically, the nozzle hole of the urea addition valve 230). The temperature can be determined by determining that the temperature in the vicinity is equal to or higher than the boiling point of urea water. In this case, since the urea water is vaporized inside the urea addition valve 230, the urea addition valve 230 is cooled by the heat of vaporization. Further, when the second exhaust temperature TH2 is equal to or higher than a predetermined temperature, the NOx concentration (first NOx concentration N1) in the exhaust before flowing into the SCR catalyst 41 and the NOx concentration (first NOx) of the exhaust purified by the SCR catalyst 41 are increased. When the 2NOx concentration N2) does not change so much, it can be said that the urea water hardly contributes to the purification of NOx, and the urea water injection contributes to the cooling of the urea addition valve 230.

  By the way, in the cooling injection, the injection amount is not necessarily an amount suitable for NOx purification in the SCR catalyst 41, but is not suitable for NOx purification, for example, when the bed temperature of the SCR catalyst 41 is excessively high. In this case, urea water may be injected. In such a case, the cooling injection becomes a cause of increasing the consumption of urea water.

  Thus, in the present embodiment, a value corrected based on the outside air temperature THout, the vehicle speed SPD, the second exhaust gas temperature TH2, and the exhaust gas flow rate is calculated as the target cooling injection amount TQc.

  Hereinafter, the execution procedure of the process (injection amount calculation process) for calculating the urea water injection amount from the urea addition valve 230, including the process for calculating the target cooling injection amount TQc as described above, will be described in detail. .

FIG. 2 shows an execution procedure of the injection amount calculation process. A series of processes shown in the flowchart of FIG. 2 is executed by the control device 80 as an interrupt process at predetermined intervals.
As shown in FIG. 2, in this process, it is first determined whether or not the following addition conditions are satisfied (step S101).

[Addition conditions] The bed temperature of the SCR catalyst 41 is equal to or higher than the activation temperature. Specifically, the second exhaust temperature TH2 is equal to or higher than a predetermined temperature (for example, 200 ° C.).
When this addition condition is not satisfied (step S101: NO), this process is temporarily terminated without executing the following process.

When the addition condition is satisfied (step S101: YES), the correction value A1 is calculated based on the outside air temperature THout (step S102).
FIG. 3 shows the relationship between the outside air temperature THout and the correction value A1. As shown in FIG. 3, the smaller the outside air temperature THout, the smaller the correction value A1 (where 0 <A1 ≦ “1.0”) is calculated. The correction value A1 is a value that decreases the target cooling injection amount TQc as the value decreases. Therefore, in this process, the target cooling injection amount TQc decreases as the outside air temperature THout decreases.

  In the present embodiment, although the temperature of the urea addition valve 230 is increased by receiving heat from the exhaust, the urea addition valve 230 is cooled by heat exchange with the outside air in the radiating fins 232, and accordingly, the urea addition valve 230 is correspondingly cooled. Temperature rise is suppressed. Moreover, the target cooling injection amount TQc can be reduced as the outside air temperature THout is lower, that is, as the temperature of the urea addition valve 230 is lower because the heat exchange amount (heat radiation amount) in the heat radiation fin 232 is larger. Therefore, by executing the cooling injection based on the target cooling injection amount TQc, it is possible to reduce the consumption of urea water while appropriately suppressing the temperature increase of the urea addition valve 230.

Further, a correction value B1 is calculated based on the vehicle speed SPD (step S103 in FIG. 2).
FIG. 4 shows the relationship between the vehicle speed SPD and the correction value B1. As shown in FIG. 4, as the vehicle speed SPD is higher, a smaller value is calculated as the correction value B1 (where 0 <B1 ≦ “1.0”). The correction value B1 is a value that decreases the target cooling injection amount TQc as the value decreases. Therefore, the target cooling injection amount TQc decreases as the vehicle speed SPD increases.

  As the vehicle speed SPD is higher, the amount of traveling wind increases, so the amount of heat exchange (heat dissipation amount) in the radiating fins 232 increases and the temperature of the urea addition valve 230 decreases. In this process, the target cooling injection amount TQc can be reduced when the vehicle speed SPD is high, in accordance with the relationship between the vehicle speed SPD and the heat exchange amount in the radiating fins 232. Therefore, by executing the cooling injection based on the target cooling injection amount TQc, it is possible to reduce the consumption of urea water while appropriately suppressing the temperature increase of the urea addition valve 230.

Further, a correction value C1 is calculated based on the second exhaust temperature TH2 (step S104 in FIG. 2).
FIG. 5 shows the relationship between the second exhaust temperature TH2 and the correction value C1. As shown in FIG. 5, the smaller the second exhaust temperature TH2, the smaller the correction value C1 (where 0 <C1 ≦ “1.0”) is calculated. The correction value C1 is a value that decreases the target cooling injection amount TQc as the value is smaller. Therefore, the target cooling injection amount TQc decreases as the second exhaust temperature TH2 decreases.

  As the exhaust temperature of the engine 1 is lower, the amount of heat received by the urea addition valve 230 from the exhaust is smaller, so the temperature of the urea addition valve 230 tends to be lower. In this process, the target cooling injection amount TQc can be decreased as the second exhaust temperature TH2 is lower and the temperature of the urea addition valve 230 is likely to be lower. Therefore, by executing the cooling injection based on the target cooling injection amount TQc, it is possible to reduce the consumption of urea water while appropriately suppressing the temperature increase of the urea addition valve 230.

Further, the correction value D1 is calculated based on the exhaust flow rate of the engine 1 (specifically, the intake air amount GA that is the index value) (step S105 in FIG. 2).
FIG. 6 shows the relationship between the exhaust gas flow rate and the correction value D1. As shown in FIG. 6, the smaller the exhaust flow rate, the smaller the correction value D1 (where 0 <D1 ≦ “1/0”) is calculated. The smaller the correction value D1 is, the smaller the target cooling injection amount TQc is. Therefore, the target cooling injection amount TQc decreases as the exhaust flow rate decreases.

  The smaller the exhaust gas flow rate, the lower the amount of heat received by the urea addition valve 230 from the exhaust gas, so the temperature of the urea addition valve 230 tends to decrease. In this process, the target cooling injection amount TQc can be reduced as the exhaust flow rate of the engine 1 is small and the temperature of the urea addition valve 230 tends to be low. Therefore, by executing the cooling injection based on the target cooling injection amount TQc, it is possible to reduce the consumption of urea water while appropriately suppressing the temperature increase of the urea addition valve 230.

  After the correction values A1, B1, C1, and D1 are calculated in this manner (steps S102 to S105 in FIG. 2), the injection amount of the cooling injection is controlled based on the engine load KL and the engine speed NE. A basic value (base cooling injection amount Qcb) is calculated (step S106).

  The exhaust temperature increases as the engine load KL increases, and the exhaust flow rate increases as the engine speed NE increases. Therefore, the amount of heat received from the exhaust of the urea addition valve 230 increases and the temperature of the urea addition valve 230 increases. Tends to be high. In this process, in order to keep the temperature of the urea addition valve 230 below the upper limit temperature of the temperature compensation range in accordance with such a tendency, the relationship among the engine load KL, the engine rotational speed NE, and the base cooling injection amount Qcb is determined and controlled. It is stored in the device 80. In the process of step S106, as shown in FIG. 7, a larger amount is calculated as the base cooling injection amount Qcb as the engine load KL is larger and as the engine rotational speed NE is higher.

  A value (Qcb × A1 × B1 × C1 × D1) obtained by multiplying the base cooling injection amount Qcb by the correction values A1, B1, C1, and D1 is calculated as the target cooling injection amount TQc (step S107 in FIG. 2). ).

Thereafter, based on the engine load KL and the engine speed NE, the urea water injection amount (the target purification injection amount TQn) in the purification injection is calculated (step S108).
FIG. 8 shows the relationship among the engine load KL, the engine rotational speed NE, and the target purified injection amount TQn. As shown in FIG. 8, in the engine operation region (EGR region) where the introduction of EGR gas by the EGR device is executed, a “positive value” is set as the target purified injection amount TQn. In the present embodiment, purifying injection is executed in the EGR region, assuming that the purifying injection execution condition is satisfied. In this EGR region, the larger the engine load KL and the higher the engine rotational speed NE, the greater the amount of NOx in the exhaust gas, so a larger amount is calculated as the target purified injection amount TQn. On the other hand, “0” is set as the target purification injection amount TQn in the engine operation region (non-EGR region) where the introduction of EGR gas by the EGR device is not executed. In this non-EGR region, the injection is not executed on the assumption that the execution condition of the purification injection is not satisfied. 7 and 8 indicate a boundary between the EGR region and the non-EGR region.

  Thereafter, the target cooling injection amount TQc and the target purified injection amount TQn are compared, and the larger one of these injection amounts is calculated as the final injection amount Qf (step S109 in FIG. 2), and then this process is temporarily terminated. Is done.

In addition, in the addition control of the present embodiment, the valve opening state of the urea addition valve 230 is controlled so that the same amount of urea water as the final injection amount Qf is injected from the urea addition valve 230.
Hereinafter, an operation by calculating the final injection amount Qf in this way will be described.

  In the present embodiment, the injection amount (target cooling injection amount TQc) necessary for cooling the urea addition valve 230 and the injection amount (target purification injection amount TQn) necessary for purifying NOx in the SCR catalyst 41 are different. While being calculated separately, the urea water injection from the urea addition valve 230 is executed based on the larger one of these injection amounts (final injection amount Qf).

  Thereby, when the target cooling injection amount TQc is larger than the target purification injection amount TQn, the temperature of the urea addition valve 230 can be appropriately suppressed only by injecting a sufficient amount of urea water to reduce NOx. If it is not possible, an amount of urea water larger than this, that is, a sufficient amount of urea water is injected to keep the temperature of the urea addition valve 230 below the upper limit temperature. Therefore, at this time, an amount of urea water that is sufficient for purifying NOx in the SCR catalyst 41 and that is sufficient to keep the temperature of the urea addition valve 230 below the upper limit temperature can be injected. .

  In addition, when the target cooling injection amount TQc is equal to or less than the target purification injection amount TQn, the temperature of the urea addition valve 230 can be appropriately suppressed by injecting a sufficient amount of urea water to reduce NOx. As much as possible, an amount of urea water required for NOx purification is injected based on the target purification injection amount TQn. At this time, a sufficient amount of additive for cooling the urea addition valve 230 can be injected from the urea addition valve 230 in order to reduce NOx.

  Therefore, according to the present embodiment, the urea addition valve 230 is used both when the target cooling injection amount TQc is larger than the target purification injection amount TQn and when the target cooling injection amount TQc is equal to or less than the target purification injection amount TQn. Both the function of cooling the catalyst and the function of purifying NOx in the SCR catalyst 41 are preferably satisfied.

  In the present embodiment, the target cooling injection amount TQc and the target purification injection amount TQn are calculated separately. Therefore, without correcting the target purification injection amount TQn unnecessarily, the heat dissipation amount of the urea addition valve 230 by the heat dissipation fin 232 (specifically, the outside air temperature THout and the vehicle speed SPD that are the index values) and the urea addition valve 230 from the exhaust gas. The target cooling injection amount TQc can be accurately corrected according to the amount of heat received (specifically, the second exhaust temperature TH2, which is the index value, and the exhaust flow rate). Thereby, in order to reduce the NOx discharged from the engine 1, the urea water injection amount without excess or deficiency can be accurately calculated as the target purified injection amount TQn, and the temperature of the urea addition valve 230 can be calculated within the temperature compensation range. Therefore, the urea water injection amount without excess or deficiency can be accurately calculated as the target cooling injection amount TQc. Therefore, the injection amount of urea water can be appropriately reduced in accordance with the heat radiation amount of the urea addition valve 230 by the heat radiation fins 232 and the heat reception amount of the urea addition valve 230 from the exhaust, and the consumption amount of urea water is preferable. Can be reduced.

  Further, in the present embodiment, “positive value” is set as the target purification injection amount TQn in the EGR region and the purification injection is executed, while “0” is set as the target purification injection amount TQn in the non-EGR region. Purification injection is not executed. Thus, when the execution condition is satisfied, the target purification injection amount TQn is used to inject urea water from the urea addition valve 230, and when the execution condition is not satisfied, the target purification injection amount TQn is not used. The urea water injection from the urea addition valve 230 is executed based on the target cooling injection amount TQc. As described above, according to this embodiment, it is possible to execute the injection of urea water from the urea addition valve 230 according to whether or not the purification injection is necessary.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The heat radiation fin 232 is provided in the urea addition valve 230, and the target cooling injection amount TQc is decreased as the outside air temperature THout is lower. Therefore, the target cooling injection amount TQc can be reduced in accordance with the heat dissipation amount in the radiation fins 232, and the temperature of the urea addition valve 230 can be reduced by executing the cooling injection based on the target cooling injection amount TQc. The consumption of urea water can be reduced while appropriately suppressing the increase.

  (2) The target cooling injection amount TQc is decreased as the vehicle speed SPD is higher. Therefore, in accordance with the relationship between the vehicle speed SPD and the heat exchange amount in the radiating fins 232, it is possible to suitably reduce the consumption of urea water while appropriately suppressing the temperature increase of the urea addition valve 230.

  (3) The target cooling injection amount TQc is decreased as the second exhaust temperature TH2 is lower. As a result, the target cooling injection amount TQc can be reduced in accordance with the relationship between the exhaust temperature of the engine 1 and the amount of heat received by the urea addition valve 230, so that the temperature increase of the urea addition valve 230 is appropriately suppressed, The consumption of urea water can be suitably reduced.

  (4) The target cooling injection amount TQc is decreased as the exhaust flow rate is smaller. As a result, the target cooling injection amount TQc can be reduced in accordance with the relationship between the exhaust gas flow rate and the amount of heat received by the urea addition valve 230 from the exhaust gas, while appropriately suppressing the temperature increase of the urea addition valve 230. The consumption of urea water can be reduced.

  (5) The target cooling injection amount TQc and the target purified injection amount TQn are calculated separately, and the larger one of these injection amounts is set as the final injection amount Qf, and the urea addition valve 230 is controlled based on the final injection amount Qf. The injection of urea water was performed. Therefore, both the function of cooling the urea addition valve 230 and the function of purifying NOx in the SCR catalyst 41 can be suitably satisfied. Moreover, since the urea water injection amount without excess or deficiency can be accurately calculated as the target cooling injection amount TQc in order to keep the temperature of the urea addition valve 230 below the upper limit temperature in the temperature compensation range, the consumption amount of urea water can be reduced. It can reduce suitably.

  (6) While a positive value is set as the target purification injection amount TQn in the EGR region where the purification injection execution condition is satisfied, the target purification injection amount TQn is set in the non-EGR region where the execution condition is not satisfied. “0” was set. Therefore, the urea water injection from the urea addition valve 230 can be executed according to whether or not the purification injection is necessary.

The above embodiment may be modified as follows.
As the engine load KL, instead of using the fuel injection amount from the fuel injection valves 4a to 4d, a value obtained by dividing the fuel injection amount by the engine speed NE (fuel injection amount / NE), accelerator operation amount ACCP, etc. Any value can be used.

  As the correction values A1, B1, C1, and D1 in the injection amount calculation process (FIG. 2), not only the value that is multiplied by the base cooling injection amount Qcb but also the value that is divided by the base cooling injection amount Qcb or addition A value to be subtracted or a value to be subtracted may be calculated.

  Processing for calculating the correction value A1 (step S102), processing for calculating the correction value B1 (step S103), processing for calculating the correction value C1 (step S104), and correction value D1 Any one, any two, or any three of the processes (step S105) for calculating the value may be omitted.

  If it is an index value of the heat release amount of the urea addition valve 230 by the heat release fins 232, the base cooling injection amount Qcb can be corrected using values other than the outside air temperature THout and the vehicle speed SPD (intake air temperature, etc.) as correction parameters. it can. In such an apparatus, a value that decreases the target cooling injection amount TQc may be calculated as a correction value as the heat radiation amount by the heat radiation fins 232 increases.

  If it is an index value of the amount of heat received from the exhaust, the base cooling injection amount Qcb can be corrected using values other than the second exhaust temperature TH2 and the exhaust flow rate (such as the first exhaust temperature TH1) as correction parameters. . In such an apparatus, the smaller the amount of heat received by the urea addition valve 230 from the exhaust, the smaller the target cooling injection amount TQc may be calculated as the correction value.

-The apparatus of the said embodiment is applicable also to the apparatus in which purification injection is performed in an EGR area | region.
Processing for calculating the target purification injection amount TQn in the injection amount calculation processing (FIG. 2) (step S108), and processing for calculating the larger one of the target cooling injection amount TQc and the target purification injection amount TQn as the final injection amount Qf (Step S109) may be omitted. In this device, the urea addition valve 230 is opened so that the same amount of urea water as the target cooling injection amount TQc is injected from the urea addition valve 230 on condition that the cooling injection execution condition is satisfied. What is necessary is just to control a valve state. Even with such a device, compared with a device in which correction based on the outside air temperature THout, the vehicle speed SPD, the second exhaust gas temperature TH2, and the exhaust gas flow rate is not executed, the temperature increase of the urea addition valve 230 is appropriately suppressed and the consumption of urea water is reduced. The amount can be reduced. Note that whether or not the cooling injection execution condition is satisfied is determined based on, for example, the engine operation region (engine load KL and engine speed NE) or when the second exhaust temperature TH2 is equal to or higher than a predetermined temperature. It can be determined that the temperature of the urea addition valve 230 is equal to or higher than a predetermined temperature. The temperature of the urea addition valve 230 is not only directly detected by a temperature sensor, but also based on the vehicle operation state (fuel injection amount, intake air amount GA, engine rotational speed NE, exhaust temperature, outside air temperature THout, vehicle speed SPD, etc.). It can also be estimated.

  -Although urea water was used as an additive, you may make it use this other additive.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder head, 3 ... Intake passage, 4a-4d ... Fuel injection valve, 5 ... Fuel addition valve, 6a-6d ... Exhaust port, 7 ... Intake manifold, 8 ... Exhaust manifold, 9 ... Common rail, DESCRIPTION OF SYMBOLS 10 ... Supply pump, 11 ... Turbocharger, 13 ... EGR passage, 14 ... EGR cooler, 15 ... EGR valve, 16 ... Intake throttle valve, 17 ... Actuator, 18 ... Intercooler, 19 ... Air flow meter, 20 ... Throttle valve opening Degree sensor, 21 ... Engine rotation speed sensor, 22 ... Accelerator sensor, 23 ... Outside air temperature sensor, 24 ... Vehicle speed sensor, 25 ... Ignition switch, 26 ... Exhaust passage, 27 ... Fuel supply pipe, 30 ... First purification member, 31 ... oxidation catalyst, 32 ... filter, 40 ... second purification member, 41 ... NOx purification catalyst (selective reduction type NOx catalyst: SCR) Medium), 50 ... third purification member, 51 ... ammonia oxidation catalyst, 60 ... dispersion plate, 80 ... control device as control unit, 100 ... first exhaust temperature sensor, 110 ... differential pressure sensor, 120 ... second exhaust temperature Sensors: 130 ... first NOx sensor, 140 ... second NOx sensor, 200 ... urea water supply mechanism, 210 ... tank, 220 ... pump, 230 ... urea addition valve, 231 ... radiation member, 232 ... radiation fin, 240 ... supply passage.

Claims (6)

An addition valve that injects an additive into the exhaust passage of the internal combustion engine; and a NOx purification catalyst that is provided downstream of the addition valve in the exhaust passage in the exhaust flow direction and purifies NOx by addition of the additive from the addition valve. An additive supply device for an internal combustion engine, comprising: a control unit that performs injection of the additive from the addition valve when the exhaust temperature in the exhaust flow direction upstream side of the addition valve in the exhaust passage is equal to or higher than a predetermined temperature Because
The addition valve has a radiating fin that radiates heat by heat exchange with outside air,
An additive supply apparatus for an internal combustion engine, wherein the controller reduces the injection amount of the additive as the outside air temperature is lower. The additive supply device for an internal combustion engine according to claim 1,
The internal combustion engine is mounted on a vehicle;
The additive supply device for an internal combustion engine, wherein the control unit decreases the injection amount of the additive as the traveling speed of the vehicle increases. The additive supply device for an internal combustion engine according to claim 1 or 2,
The additive supply apparatus for an internal combustion engine, wherein the control unit decreases the injection amount of the additive as the temperature of the exhaust gas of the internal combustion engine is lower. The additive supply device for an internal combustion engine according to any one of claims 1 to 3,
The additive supply device for an internal combustion engine, wherein the control unit reduces the injection amount of the additive as the flow rate of the exhaust gas in the exhaust passage decreases. In the internal combustion engine additive supply apparatus according to any one of claims 1 to 4,
The control unit calculates a first additive injection amount for cooling the addition valve and a second additive injection amount for NOx purification by the NOx purification catalyst, and the first additive injection amount. When the additive injection amount is larger than the second additive injection amount, the additive injection from the addition valve is executed based on the first additive injection amount, and the first additive injection amount is An additive supply device for an internal combustion engine, which performs injection of an additive from the addition valve based on the second additive injection amount when it is equal to or less than a second additive injection amount. The additive supply device for an internal combustion engine according to claim 5,
The controller sets the second additive injection amount to a positive value when an additive injection execution condition for purifying the NOx is satisfied, and when the execution condition is not satisfied, the second injection amount. An additive supply device for an internal combustion engine, wherein the additive injection amount of the engine is set to “0”.