JP6264048B2 - Injection control device - Google Patents

Description

  The present invention relates to an injection control device, and more particularly, to an injection control device for an injection valve that injects an additive upstream of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine.

  Conventionally, as an exhaust purification catalyst provided in an exhaust passage of a diesel engine or the like, ammonia compound (hereinafter referred to as NH3) hydrolyzed from urea water is selectively used as a reducing agent, and nitrogen compounds (hereinafter referred to as NOx) in exhaust gas are selectively used. A selective reduction catalyst (hereinafter referred to as SCR) for reducing and purifying is known. In such an exhaust purification device including an SCR, a urea addition valve that injects urea water is provided on the exhaust upstream side of the SCR.

  The urea addition valve may be damaged due to heat damage at high exhaust temperature. For this reason, there is known a technique for preventing the urea addition valve from being damaged due to heat damage by performing an appropriate amount of urea injection and cooling when the exhaust temperature exceeds the heat resistance of the urea addition valve (for example, patents). Reference 1).

JP 2010-248925 A

  By the way, there is an upper limit on the amount of NH3 adsorbed by the SCR, and when urea water is excessively injected from the urea addition valve, NH3 slipped from the SCR is released to the atmosphere, which is not preferable. For this reason, conventionally, when a failure or the like causing excessive injection occurs in the urea addition valve, the urea injection is completely stopped. However, if urea injection is stopped while exhaust temperature is high, such as during forced regeneration of a diesel particulate filter (Diesel Particulate Filter: DPF), the urea addition valve will be affected by heat damage. There is a possibility of damage.

  The objective of this invention is providing the injection control apparatus which can prevent the damage by the heat damage of a urea addition valve effectively.

  In order to achieve the above object, an injection control device of the present invention is an injection control device for an injection valve that injects an additive to an exhaust upstream side of an exhaust purification catalyst arranged in an exhaust passage of an internal combustion engine, An over-injection determination unit that determines whether or not the additive injection of the injection valve is over-injection, and an intermittent injection to the injection valve when the over-injection determination unit determines that the injection valve is over-injection Injection instructing means for instructing.

  In the case where the injection valve further includes an open adhesion determination unit that determines whether or not the injection valve is in a valve open fixed state, and the injection instruction unit determines that the open valve determination unit determines that the injection valve is in a valve open fixed state Alternatively, intermittent injection may be instructed to the injection valve.

  The injection instruction means determines that the over-injection determination means determines that the injection valve is over-injected, and the open sticking judgment means determines that the injection valve is not in the valve open sticking state. Instructing the first intermittent injection at a predetermined injection interval, the over-injection determining means determines that the injection valve is over-injected, and the open adhesion determining means determines that the injection valve is in the valve open fixed state In this case, the injection valve may be instructed to perform second intermittent injection having an injection interval longer than the first intermittent injection.

  The injection instruction means causes the injection valve to execute the first intermittent injection, and then determines that the excess injection determination means does not cause the injection valve to become excessive injection, or if the injection valve causes the second intermittent injection to the injection valve. When the open sticking determination means determines that the injection valve is not in the valve open sticking state and the excessive injection determination means determines that the injection valve does not become excessive injection, the injection valve Alternatively, an injection amount corresponding to the operating state of the internal combustion engine may be instructed.

  The injection amount of the first intermittent injection may be set to be larger as the internal combustion engine becomes higher in load, and the injection amount of the second intermittent injection may be set to be smaller than the injection amount of the first intermittent injection.

  The injection valve injects urea water as an additive, and the exhaust purification catalyst is a selective reduction catalyst that purifies nitrogen compounds in exhaust gas using ammonia generated by hydrolysis from urea water as a reducing agent. May be.

  According to the injection control device of the present invention, it is possible to effectively prevent the urea addition valve from being damaged due to heat damage.

It is a typical whole block diagram which shows the injection control apparatus which concerns on one Embodiment of this invention. It is a functional block diagram which shows ECU of this embodiment. It is a time chart figure which compared the injection quantity and injection interval of the 1st intermittent injection mode of this embodiment, and the 2nd intermittent injection mode. It is a flowchart which shows an example of the control content by the injection control apparatus of this embodiment.

  Hereinafter, based on an accompanying drawing, the injection control device concerning one embodiment of the present invention is explained. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  As shown in FIG. 1, an exhaust manifold 10b of a diesel engine (hereinafter simply referred to as an engine) 10 is connected to an exhaust passage 11 that leads exhaust gas to the atmosphere. The exhaust passage 11 is provided with an exhaust flow rate sensor 20, a pre-stage post-treatment device 30, an exhaust temperature sensor 21, a post-stage post-treatment device 40, a NOx sensor 27, and the like in order from the exhaust upstream side. In FIG. 1, reference numeral 22 denotes an engine rotation sensor, reference numeral 23 denotes an accelerator opening sensor, reference numeral 24 denotes a vehicle speed sensor, reference numeral 25 denotes an outside air temperature sensor, and reference numeral 26 denotes a cooling water temperature sensor.

  The pre-stage post-treatment device 30 is configured by sequentially arranging an oxidation catalyst (Diesel Oxidation Catalyst: DOC) 31 and a DPF 32 in the catalyst case 30a from the upstream side. A fuel addition valve 33 is provided in the exhaust passage 11 upstream of the DOC 31.

  The fuel addition valve 33 injects unburned fuel (mainly HC) into the exhaust passage 11 in response to an instruction signal input from an electronic control unit (hereinafter, ECU) 50. In addition, when using the post injection by the multistage injection of the engine 10, this fuel addition valve 33 may be omitted.

  The DOC 31 is formed, for example, by supporting a catalyst component on the surface of a ceramic carrier such as a cordierite honeycomb structure. When HC is supplied by the fuel addition valve 33 or post injection, the DOC 31 oxidizes this and raises the exhaust temperature.

  The DPF 32 is formed, for example, by arranging a large number of cells partitioned by porous partition walls along the flow direction of the exhaust gas and alternately plugging the upstream side and the downstream side of these cells. The DPF 32 collects PM in the exhaust gas in the pores and surfaces of the partition walls, and when the amount of accumulated PM reaches a predetermined amount, so-called forced regeneration is performed to remove the PM. The forced regeneration is performed by supplying unburned fuel (HC) to the DOC 31 by the fuel addition valve 33 or post injection, and raising the exhaust temperature flowing into the DPF 32 to the PM combustion temperature (for example, about 500 to 600 ° C.). Is called.

  The post-stage post-processing device 40 includes an SCR 41 accommodated in the case 40a. A urea addition valve 42 is provided in the exhaust passage 11 upstream of the SCR 41.

  The urea addition valve 42 is, for example, a known electromagnetic valve, and opens and closes in response to an instruction signal input from the ECU 50, so that the urea addition valve 42 enters the exhaust passage 11 upstream from the SCR 41 and enters the urea water tank 43 from the urea water tank 43. The urea water pumped by the water pump 44 is injected. The injected urea water is hydrolyzed by exhaust heat to be generated as NH3, and is supplied as a reducing agent to the SCR 41 on the downstream side.

  The SCR 41 is formed, for example, by supporting zeolite or the like on the surface of a ceramic carrier such as a honeycomb structure, and includes a large number of cells partitioned by porous partition walls. The SCR 41 adsorbs NH3 supplied as a reducing agent and selectively reduces and purifies NOx from the exhaust gas passing through the adsorbed NH3.

  The ECU 50 controls the engine 10, the fuel addition valve 33, the urea addition valve 42, and the like, and includes a known CPU, ROM, RAM, input port, output port, and the like. In order to perform these various controls, sensor signals of the various sensors 20 to 27 are input to the ECU 50.

  Further, as shown in FIG. 2, the ECU 50 includes a normal-time injection control unit 51, a urea excess injection determination unit 52, a valve-open sticking determination unit 53, an intermittent injection control unit 54, and a failure determination unit 55. As a functional element. Each of these functional elements will be described as being included in the ECU 50 which is an integral hardware, but any one of these may be provided in separate hardware.

The normal-time injection control unit 51 is an example of the injection instruction unit of the present invention, and controls urea injection of the urea addition valve 42 in the optimum basic injection mode _{Q_0} corresponding to the operating state of the engine 10. This basic injection mode _{Q_0} is selected during normal operation when the urea addition valve 42 is not over-injected or stuck open. Hereinafter, an example of the injection amount setting procedure in the basic injection mode _{Q_0} will be described.

  First, the amount of NOx discharged from the engine 10 is estimated based on the operating state of the engine 10 detected by the various sensors 20 to 23 and the like. When a NOx sensor (not shown) is arranged upstream of the SCR 41, the sensor value of this NOx sensor may be used directly.

Further, based on the estimated NOx emission amount of the engine 10 and the sensor value of the NOx sensor 27, the NH3 consumption amount corresponding to the NOx purification rate of the SCR 41 is estimated, and the current NH3 actual adsorption amount of the SCR 41 is calculated from this NH3 consumption amount. Is estimated. Further, the current NH 3 adsorptionable amount of the SCR 41 is estimated from the sensor value (SCR internal temperature) of the exhaust temperature sensor 21. Then, the NH3 target adsorption amount of the SCR 41 is set based on the NH3 actual adsorption amount and the NH3 adsorbable amount, and the urea supply amount necessary to achieve the NH3 target adsorption amount is set as the injection amount in the basic injection mode _{Q_0} . Set as.

The urea excessive injection determination unit 52 is an example of the excessive injection determination unit of the present invention, and determines whether or not urea injection of the urea addition valve 42 is excessive. Whether the urea injection is excessive, it can cause failure of the failure or engine 10 from various sensors 20 to 23 used to set the injection amount of the basic injection mode Q _{_0,} the excess injection fault code It is determined based on the occurrence or the like of

  The valve open adhesion determination unit 53 is an example of an open adhesion determination unit according to the present invention, and determines whether or not the urea addition valve 42 is in the valve open adhesion state. Whether or not the valve is stuck open is determined based on, for example, a change in an instruction signal (pulse current) output to the urea addition valve 42, an increase in the output of the urea water pump 44, or the like.

The intermittent injection control unit 54 is an example of the injection instruction unit of the present invention, and is optimal for protecting the urea addition valve 42 from heat damage when excessive injection or valve opening sticking occurs in the urea addition valve 42. The injection amount of the urea addition valve 42 is controlled by selectively using the first intermittent injection mode _{Q_1} or the second intermittent injection mode _{Q_2} .

More specifically, the first intermittent injection mode _{Q_1} is selected when there is a possibility that the urea addition valve 42 may cause excessive injection for reasons other than the valve opening stuck. Urea injection amount and injection interval of the first intermittent injection mode Q _{_1} is set based on sensor values of various sensors 20 to 26 indicating the operating state of the first map 54a and the engine 10 that is stored in advance in ECU 50. In the first map 54a, the urea injection amount is set so as to increase as the operating state of the engine 10 becomes higher.

In the state where the urea addition valve 42 causes excessive injection, it is difficult to accurately control the injection amount. Therefore, if a large amount of injection instruction is issued, NH3 slip may be caused. Thus, the first intermittent injection mode Q _{_1} is set in the injection amount that ensures sufficient margin for the current NH3 adsorption capacity of SCR41.

On the other hand, when the urea addition valve 42 is in the valve open fixed state, the second intermittent injection mode _{Q_2} is selected. The second intermittent injection mode _{Q_2} is urea injection for returning the urea addition valve 42 from the fixed valve open state, and the urea injection amount and the injection interval are stored in the second map 54b stored in the ECU 50 in advance. It is set based on the sensor values of various sensors 20 to 26 indicating the operating state of the engine 10.

In addition, when the valve is stuck open, urea water pumped by the urea water pump 44 may constantly flow out from the urea addition valve 42, and if the same amount of urea injection as the first intermittent injection mode _{Q_1} is instructed, a large amount May cause NH3 slip. Therefore, as shown in FIG. 3, the injection interval of the second intermittent injection mode Q _{_2} is set longer than the first discontinuous injection mode Q _{_1.} Preferably, the injection interval of the first intermittent injection mode _{Q_1} is set, for example, on the order of seconds to minutes, and the injection interval of the second intermittent injection mode _{Q_2} is set, for example, on the order of minutes. Further, as shown in FIG. 3, the urea injection amount of the second intermittent injection mode Q _{_2} is set smaller than the first intermittent injection mode Q _{_1.} In particular, the urea injection amount of the second intermittent injection mode _{Q_2} may be at least that which gives an instruction signal (pulse current) to the urea addition valve 42, and NH3 slip is also caused in urea injection when the urea addition valve is stuck open. It is set not to occur.

Even when the failure determination unit 55 executes the first intermittent injection mode _{Q_1} or the second intermittent injection mode _{Q_2} , the excessive injection of the urea addition valve 42 and the valve open sticking are not resolved (when it is not a temporary failure). In addition, it is determined that the urea addition valve 42 is completely broken. The determination result of complete failure is displayed on a display device in a driver's cab (not shown) to inform the driver.

Next, based on FIG. 4, the control flow by the injection control apparatus of this embodiment is demonstrated. In the flow of FIG. 4, the flag F ₁ is a determination flag indicating the excessive injection of the urea addition valve 42, and is turned on (F ₁ = 1) when there is a possibility of excessive injection, and there is a possibility of excessive injection. If not, it is turned off (F ₁ = 0). The flag F ₂ is a determination flag indicating that the urea addition valve 42 is stuck open, and is turned on when the valve is stuck (F ₂ = 1), and is turned off when the valve is stuck (F ₂ ). ₂ = 0).

In step (hereinafter, step is simply referred to as S) 100, urea injection of the urea addition valve 42 is controlled in the basic injection mode _{Q_0} . In S110, it is determined whether or not the urea addition valve 42 is over-injected. When there is a possibility of excessive injection (Yes), the process proceeds to S120, and the flag F ₁ is set to ON (F ₁ = 1). On the other hand, if not excessive injection (No), together with the flag F ₁ is set to OFF (F ₁ = 0) at S130, it returns to S100 to maintain the basic injection mode Q _{_0.}

In S140, it is determined whether or not the urea addition valve 42 is in the valve open fixed state. If not in the valve opening stuck state (No), together with the flag F ₂ is set to OFF (F ₂ = 0) at S150, the urea injection of the urea addition valve 42 at S160 the control in the first intermittent injection mode Q _{_1} Thereafter, this control is returned to S130.

In S140 described above, when the urea addition valve 42 is determined to be in the valve opening stuck state (Yes), with a flag F ₂ is set to ON (F ₂ = 1) in S200, the urea addition valve in S210 42 urea injection is controlled in the second intermittent injection mode _{Q_2} .

In S220, it is determined again whether or not the urea addition valve 42 is in the valve open fixed state. If the valve stuck open by the execution of the second intermittent injection mode Q _{_2} is resolved (No), the flag F ₂ in S230 is returned to S110 is set to OFF (F ₂ = 0). On the other hand, if the valve opening sticking has not been resolved (Yes), the process proceeds to S240.

In S240, it is determined whether or not a predetermined time has elapsed since the execution of the second intermittent injection mode _{Q_2} . If the predetermined time has elapsed (Yes), it is unlikely that the valve-opening sticking can be resolved even if the second intermittent injection mode _{Q_2} is continued, and thus the urea addition valve 42 is determined to be completely failed in S250. If the predetermined time has not elapsed (No), the process _returns to S210 to continue the second intermittent injection mode _{Q_2} . Thereafter, each control step from S100 to S250 described above is repeatedly executed until the ignition key of the engine 10 is turned off.

  Next, the effect of the injection control apparatus according to the present embodiment will be described.

  In the conventional device, when a mechanical failure such as excessive injection or valve opening sticking occurs in the urea addition valve 42, urea injection of the urea addition valve 42 is completely stopped to prevent NH3 slip from the SCR 41. Therefore, there is a problem that the urea addition valve 42 is damaged under the influence of heat damage at the time of high exhaust temperature, such as during forced regeneration of the DPF 32.

On the other hand, the injection control device of the present embodiment is also capable of the first intermittent injection mode Q even when excessive injection or valve opening sticking occurs in the urea addition valve 42 under high exhaust temperature conditions, such as during forced regeneration of the DPF 32. By executing _{_1} , the cooling effect of the urea addition valve 42 can be maintained.

Therefore, according to the injection control device of the present embodiment, it is possible to reliably prevent the urea addition valve 42 from being damaged due to heat damage. In addition, the NOx purification action of the SCR 41 can be effectively continued by executing urea injection even with a small amount as compared with the conventional device that completely stops urea injection at the time of excessive injection. Also, forced regeneration or the like of the DPF 32, when the high exhaust gas temperature conditions under the valve open sticking occurs also, by executing the second intermittent injection mode Q _{_2,} NOx purification action of the cooling and SCR41 urea addition valve 42 In addition to this effect, the urea addition valve 42 can be returned from the valve-open fixed state.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

For example, the application of the first intermittent injection mode _{Q_1} and the second intermittent injection mode _{Q_2} is not limited to the urea addition valve 42, and can be applied to the fuel injection of the fuel addition valve 33. In this case, failure due to heat damage of the fuel addition valve 33 can be effectively prevented. Further, the post-stage post-treatment device 40 is not limited to the SCR 41, and may be a NOx storage reduction catalyst (LNT). Further, the engine 10 is not limited to a diesel engine, and can be widely applied to other internal combustion engines such as a gasoline engine.

DESCRIPTION OF SYMBOLS 10 Engine 11 Exhaust passage 20 Exhaust flow sensor 21 Exhaust temperature sensor 22 Engine rotation sensor 23 Accelerator opening sensor 24 Vehicle speed sensor 25 Outside air temperature sensor 26 Cooling water temperature sensor 27 NOx sensor 30 Pre-stage post-processing apparatus 31 DOC
32 DPF
33 Fuel addition valve 40 Post-stage post-treatment device 41 SCR
42 Urea addition valve 50 ECU
51 Normal-time Injection Control Unit 52 Urea Excess Injection Determination Unit 53 Valve Open Adherence Determination Unit 54 Intermittent Injection Control Unit 55 Failure Determination Unit

Claims (4)

An injection control device for an injection valve that injects an additive upstream of an exhaust purification catalyst arranged in an exhaust passage of an internal combustion engine,
Excessive injection determination means for determining whether or not the additive injection of the injection valve is excessive injection;
An open adhering determination means for determining whether or not the injection valve is in an open valve adhering state;
When the over-injection determining means determines that the injection valve is over-injected, and the open adhesion determining means determines that the injection valve is not in the valve-open fixed state, the injection valve has a predetermined injection interval. 1 injection is instructed, the injection valve determines that the excessive injection determination means determines that the injection valve is over-injected, and the open sticking determination means determines that the injection valve is in the valve open sticking state. And an injection instruction means for instructing a second intermittent injection having an injection interval longer than that of the first intermittent injection . The injection instruction means includes
After causing the injection valve to execute the first intermittent injection, when the excessive injection determination means determines that the injection valve does not become excessive injection, or after causing the injection valve to execute the second intermittent injection, When the open adhering determination means determines that the injection valve is not in the valve open adhering state, and the over injection determining means determines that the injection valve does not become excessive injection, the operation of the internal combustion engine is performed on the injection valve. The injection control device according to claim 1 , wherein an injection amount corresponding to a state is instructed. Injection amount of the first intermittent injection, the internal combustion engine is set much higher becomes the high load, the injection quantity of the second intermittent injection, according to claim 1 or less is set than injection amount of the first intermittent injection 2. The injection control device according to 2. The injection valve injects urea water as an additive,
The injection control device according to any one of claims 1 to 3 , wherein the exhaust purification catalyst is a selective reduction catalyst that purifies nitrogen compounds in exhaust using ammonia generated by hydrolysis from urea water as a reducing agent. .

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