CN1871411A - Engine controller and engine operating method - Google Patents

Abstract

[PROBLEMS] To prompt personnel to repair an SCR device if an abnormality occurs in the SCR device so as to appropriately manage the SCR device. [MEANS FOR SOLVING PROBLEMS] If an abnormality having occurred in an SCR device is detected, the output of an engine is limited. In an example, for this limitation, the map used to calculate the injected amount of fuel is changed from the one for the normal operation if an abnormality occurs (S407). Abnormalities to be detected include clogging of an injection nozzle and dilution of the urea water held in a tank.

Description

Engine control device and engine operating method

technical field

The present invention relates to an engine control device and an engine operating method, and more particularly to a technique for purifying nitrogen oxides emitted from an automobile engine by using ammonia as a reducing agent.

Background technique

The _following SCR (Selective Catalytic Reduction , selective catalytic reduction) equipment. This SCR device is installed in the exhaust passage of the engine, and is provided with nozzles injecting an aqueous solution of ammonia or its precursor. Ammonia injected from the nozzle (or ammonia obtained from the precursor) is used as a reducing agent, which reacts with _NOx in the exhaust gas under the action of a catalyst to reduce and purify the _NOx . As an SCR device considering easy storage of ammonia on a vehicle, the following SCR device is known. Such an SCR device is provided with a tank for storing urea as a precursor of ammonia in an aqueous solution state, and in actual operation, urea water supplied from the tank is sprayed into the exhaust passage to use the exhaust gas. Ammonia is generated by hydrolysis of urea as a gas heat (patent document 1).

Patent Document 1: Japanese Patent Laid-Open No. 2000-027627

Contents of the invention

The problem to be solved by the present invention

However, such an SCR device as described above has the following problems. As a setting related to engine operation, there may be a setting that particularly reduces the emission of particulate matter. In this setup, normally _NOx emissions increase. If the SCR device operates normally, the emitted _NOx can be purified by performing a reduction reaction using ammonia. Under such a setting allowing a certain amount of _NOx emission, a case is assumed in which an abnormality occurs in the SCR device such that the injection amount of urea water is changed or the ammonia content (ie, urea concentration) in the urea water is changed. In this case, due to the change in the amount of ammonia added in the exhaust gas, the ratio between _NOx and ammonia deviates from an appropriate value, so that the reduction reaction cannot proceed smoothly, and the removal rate of _NOx cannot meet the requirements . Especially in the case of reduced ammonia addition, NO _x is emitted into the atmosphere without purification. Furthermore, in the case where water other than urea water or a different type of aqueous solution is stored in the storage tank, or in the case where the storage tank is empty, the same result as above results. When such an abnormality occurs in the SCR device, timely repair of the SCR device is required in order to limit the _NOx emission. However, an abnormality that occurs in the SCR device does not appear in the behavior of the vehicle, and therefore, the driver does not notice the abnormality. In addition, even if measures such as operating a warning light or a siren are taken, it may be considered that the driver cannot perform repairs in a timely manner.

The purpose of the present invention is to prompt the driver to repair the SCR device at an early stage so that proper maintenance of the SCR device can be obtained.

The solution to this problem

Therefore, according to the present invention, in an engine provided with an addition device for adding a _NOx reducing agent to exhaust gas, at the abnormality occurrence time when an abnormality occurs in the addition device is detected, the output of the engine is limited . Preferably, when an abnormality occurs, the output characteristics of the engine with respect to the driver's accelerator operation are different from those at normal times other than when the abnormality occurs, or restarting the engine operation after the engine operation is stopped is prohibited.

Effect of the present invention

According to the present invention, when an abnormality occurs in the adding device so that an accurate amount of _NOx reducing agent cannot be added to the exhaust gas of the engine, the output of the engine is limited, for example, the output characteristic of the engine relative to the driver's accelerator operation changes, And at the same accelerator operation amount, the fuel injection amount is reduced compared with that of the normal time. Therefore, it is possible to restrict the movement of the car in a state where _NOx is not effectively purified, and it is also possible to prompt the driver to repair the add-on device. Furthermore, movement may be restricted in addition to or instead of restrictions due to changes in output characteristics, and repair of added equipment may also be facilitated by prohibiting restarts after engine stops.

Other objects, features, and advantages of the present invention will be apparent from the following description of the embodiments with reference to the accompanying drawings.

The entire contents of Japanese Patent Laid-Open Nos. 2003-362411 and 2004-026056 , which are the basis of the priority claims, are hereby incorporated by reference.

Description of drawings

Fig. 1 shows the overall structure of the engine according to the first embodiment of the present invention;

Fig. 2 shows the structure of urea sensor;

Fig. 3 shows the principle of carrying out concentration detection by the urea sensor of Fig. 2;

Figure 4 shows a flow chart of the anomaly detection program;

Fig. 5 shows the flow chart of concentration detection procedure;

Fig. 6 shows the flow chart of urea water injection control program;

Fig. 7 shows a flow chart of the fuel injection amount setting program;

Figure 8 shows a flow chart of the fuel cutoff routine;

FIG. 9 shows a flowchart of a fuel injection amount setting routine according to a second embodiment of the present invention;

Fig. 10 shows the flow chart of the startup control procedure according to the third embodiment of the present invention;

11 shows a flowchart of a fuel injection amount setting routine according to a fourth embodiment of the present invention;

FIG. 12 shows a table for setting the rate of change according to the fourth embodiment;

Fig. 13 shows the concept of output limitation according to the fourth embodiment.

Explanation of reference signs

1: engine; 11: intake channel; 12: turbocharger; 13: buffer tank; 21: injector; 22: common rail; 31: exhaust channel; 32: oxidation catalyst; 33: NO _X purification catalyst; 34: ammonia purification catalyst; 35: EGR pipe; 36: EGR valve; 41: storage tank; 42: urea water supply pipe; 43: nozzle; 44: feed pump; 45: filter; 46: urea water return pipe; 47: Pressure control valve; 48: Air supply pipe; 51: Engine C/U; 61: SCR-C/U; 71, 72: Exhaust temperature sensor; 73: NO _X sensor; 74: Urea sensor; 75: Air Pressure sensor; 76: urea water pressure sensor; 77: component part voltage sensor.

Detailed ways

The present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the overall structure of an automobile engine (hereinafter simply referred to as an engine) according to a first embodiment of the present invention. In this embodiment, a direct injection diesel engine is used as the engine 1 .

An air filter (not shown in the figure) is installed at the inlet portion of the air intake passage 11, and dust entering the air is removed through the air filter. In the intake passage 11, a compressor 12a of a variable nozzle type turbocharger 12 is provided so that intake air is compressed by the compressor 12a and sent out. The compressed intake air flows into a surge tank 13 and distributes it to the cylinders through a manifold section.

In the engine block, an injector 21 is provided on a cylinder head of each cylinder. The injector 21 operates according to a signal from an engine control unit (hereinafter simply referred to as engine C/U) 51 . Fuel delivered by a fuel pump (not shown in the figure) is supplied to the injector 21 through a common rail (common rail) 22, and is directly injected into the combustion chamber by the injector 21.

In the exhaust passage 31, the turbine 12b of the turbocharger 12 is disposed downstream of the manifold portion. The turbine 12b is driven by the exhaust, causing the compressor 12a to be rotated. The angle of the movable blades 121 of the turbine 12b is controlled by an actuator 122 . The rotational speeds of the turbine 12b and the compressor 12a vary according to the angle of the movable vane 121 .

Downstream of the turbine 12b, an oxidation catalyst 32, a _NOx purification catalyst 33, and an ammonia purification catalyst 34 are disposed in this order from the upstream side. The oxidation catalyst 32 oxidizes hydrocarbons and carbon monoxide in the exhaust gas, and also converts nitrogen monoxide (hereinafter abbreviated as NO) in the exhaust gas into _NOx mainly containing nitrogen dioxide (hereinafter abbreviated as NO ₂ ). , thereby performing an operation of adjusting the ratio of NO and NO ₂ contained in the exhaust gas to an optimal ratio for the NO _x reduction reaction (to be described later). The NO _x purification catalyst 33 reduces and purifies NO _x . In this embodiment, in order to promote the reducing action of the _NOx purification catalyst 33, ammonia, which functions as a _NOx reducing agent, is added to the exhaust gas upstream of the _NOx purification catalyst 33.

In this embodiment, urea, which is a precursor of ammonia, is stored in an aqueous solution state in consideration of the ease of storing ammonia on the vehicle. Safety can be ensured by storing ammonia as urea.

The urea water supply pipe 42 is connected to a storage tank 41 for storing urea water, and a urea water nozzle 43 is installed at the front end of the urea water supply pipe 42 . A feed pump 44 and a filter 45 are disposed on the urea water supply pipe 42 in order from the upstream side. The feed pump 44 is driven by an electric motor 441 . The electric motor 441 adjusts the discharge amount from the feed pump 44 , wherein the rotation speed of the electric motor 441 is controlled based on a signal from an SCR control unit (hereinafter, simply referred to as SCR-C/U) 61 . Further, downstream of the filter 45 , a urea water return pipe 46 is connected to the urea water supply pipe 42 . In the urea water return pipe 46 , a pressure control valve 47 is installed to return the remaining urea water in an amount exceeding a specified pressure to the storage tank 41 .

The nozzle 43 is an air-assist type nozzle, and includes a main body 431 and a nozzle part 432 . A urea water supply pipe 42 is connected to the main body 431 , and an air supply pipe 48 that supplies air for boosting (hereinafter simply referred to as boosting air) is also connected to the main body 431 . The air supply pipe 48 is connected to an air tank (not shown in the figure), and supplies the boost air from the air tank. The nozzle portion 432 is provided upstream of the _NOx purification catalyst 33 so as to pass through the housing of the _NOx purification catalyst 33 and the ammonia purification catalyst 34 from the side. The injection direction of the nozzle portion 432 is set toward the end surface of the NO _x purification catalyst 33 in a direction parallel to the flow of exhaust gas.

When urea water is injected, urea in the injected urea water is hydrolyzed by exhaust heat to generate ammonia. The generated ammonia acts as a _NOx reducing agent on the _NOx purification catalyst 33, thereby accelerating _NOx reduction. The ammonia purification catalyst 34 is a catalyst for purifying slip-ammonia passing through the NO _x purification catalyst 33 without contributing to NO _x reduction. Since ammonia has a pungent odor, it is preferable not to purify and preferably not emit ammonia. The oxidation reaction of NO on the oxidation catalyst 32, the hydrolysis reaction of urea, the reduction reaction of NO on _{the NO} purification catalyst 33, and the oxidation reaction of the slipped _ammonia on the ammonia purification catalyst 34 are respectively passed through the following formula (1) to (4) to represent. In the present embodiment, the _NOx purification catalyst 33 and the ammonia purification catalyst 34 are assembled in a single can. However, each of the catalysts 33 and 34 may be packaged separately in individual tanks.

(1)

(2)

(3)

(4)

Furthermore, the exhaust passage 31 is connected to the intake passage 11 via an EGR pipe 35 . Exhaust gas is recirculated to the intake passage 11 via the EGR pipe 35 . In the EGR pipe 35 , an EGR valve 36 is installed, and the flow rate of recirculated exhaust gas is controlled by the EGR valve 36 . Opening of EGR valve 36 is controlled by actuator 361 .

In the exhaust passage 31 , a temperature sensor 71 for detecting the temperature of the exhaust gas before the addition of urea water is provided between the oxidation catalyst 32 and the NO _x purification catalyst 33 . Downstream of the ammonia purification catalyst 34, a temperature sensor 72 for detecting the temperature of the reduced exhaust gas and a _NOx sensor 73 for detecting the concentration of the reduced _NOx contained in the exhaust gas are provided. Further, in the storage tank 41, a urea sensor 74 for detecting the concentration (hereinafter when only the word "concentration" is used means "urea concentration") Dn of urea contained in the stored urea water is provided. In this embodiment, the urea sensor 74 also has a function of judging the amount of urea water remaining in the storage tank 41 .

Detection signals from temperature sensors 71 and 72, _NOx sensor 73 and urea sensor 74 are output to SCR-C/U61. The SCR-C/U 61 calculates and sets an optimal urea water injection amount based on the input signal to output a command signal according to the set urea water injection amount to the nozzle 43 . In addition, the SCR-C/U61 is connected to the engine C/U51 to enable two-way communication. In addition to the detection signals from the aforementioned sensors 71-74, the SCR-C/U61 also receives booster air pressure Pa, urea water pressure Pu and urea sensor voltage Vs. The boost air pressure Pa is the pressure inside the air supply pipe 48 and is detected by the pressure sensor 75 provided in the air supply pipe 48 . The urea water pressure Pu is the pressure inside the urea water supply pipe 42 and is detected by the pressure sensor 76 provided in the urea water supply pipe 42 downstream of the feed pump 44 . The urea sensor voltage Vs is a voltage output according to the concentration detected by the urea sensor 74 , and is detected by the voltage sensor 77 . SCR-C/U61 detects abnormalities occurring in the urea water injection system as described later based on the judgment results of booster air pressure Pa, urea water pressure Pu, urea sensor voltage Vs and concentration Dn, and the remaining amount of urea water , and outputs a signal indicating the occurrence of an abnormality to the engine C/U51.

In the engine 1, an ignition switch, a starter switch, a crank angle sensor, a vehicle speed sensor, an accelerator sensor, etc. are installed, and detection signals thereof are input to the engine C/U51. The engine C/U51 calculates the engine rotation speed Ne based on the signal input from the crank angle sensor. Engine C/U51 calculates fuel injection amount Qf based on operating conditions such as engine rotation speed Ne, and also outputs information necessary for injection control of urea water such as calculated Qf to SCR-C/U61.

In this embodiment, engine C/U51 corresponds to the first control unit, and SCR-C/U61 corresponds to the second control unit.

FIG. 2 shows the structure of the urea sensor 74 .

The urea sensor 74 has the same structure as that of a flow meter disclosed in Japanese Patent Laid-Open No. 2001-228004, and detects urea concentration based on electrical characteristic values of two temperature sensing elements.

The flowmeter disclosed in the above publication includes a first sensor element having a heater function and a second sensor element not having a heater function. The former first sensor element includes a heater layer, and a resistive temperature sensing layer serving as a temperature sensing element formed on the heater layer in an insulated state (referred to simply as a first resistive temperature sensing layer). The latter second sensor element includes a resistive temperature sensing layer (referred to simply as a second resistive temperature sensing layer) as a temperature sensing element, but does not include a heater layer. Each sensor element is integrated into a resin tank and connected to one end of a fin plate serving as a heat transfer body.

In the urea sensor 74 according to the present embodiment, the sensor element portion 741 is configured to include first and second sensor elements. When detecting the concentration, the sensor element part 741 is immersed in the urea water used, and it is set near the bottom of the storage tank 41 . In addition, each fin plate 7414 and 7415 passes through the tank body 7413 to be exposed inside the storage tank 41 .

The circuit part 742 is connected to the heating layer and the resistive temperature sensing layer of the first sensor element 7411 , and is also connected to the resistive temperature sensing layer of the second sensor element 7412 . The circuit part 742 energizes the heating layer to heat the first resistance temperature sensing layer, and detects the resistance values Rn1 and Rn2 of the heated first resistance temperature sensing layer and the second resistance temperature sensing layer without direct heating . The resistive temperature sensing layer has a characteristic that its resistance value changes in proportion to temperature. The circuit portion 742 calculates the concentration Dn as follows based on the detected resistance values Rn1 and Rn2, and also judges the remaining amount of urea water.

Fig. 3 shows the principle of concentration detection and remaining amount judgment.

Heating of the heater layer is performed by supplying the heater layer with a heater drive current ih for a predetermined period of time Δt01. The circuit portion 742 detects the resistance values Rn1 and Rn2 of the respective resistance temperature sensing layers and also calculates the temperature difference ΔTmp12 (=Tn1−Tn2) between the resistance temperature sensing layers when the current supply to the heater layer is stopped. The temperature difference between the resistive temperature sensing layers depends on the heat transfer characteristics mediated by urea water, and the heat transfer characteristics depend on the urea concentration. Therefore, the calculated temperature difference ΔTmp12 can be converted into the concentration Dn. Furthermore, whether the storage tank 41 is empty can be judged based on the calculated temperature difference ΔTmp12.

In this embodiment, the sensor element part 741 is configured such that in the first sensor element 7411 , the first resistive temperature sensing layer is in contact with the urea water through the fin plate 7414 . However, the sensor element part 741 may be configured to have a measurement chamber for introducing the urea water in the storage tank 41 in the sensor element part 741, so that the urea water passing through the measurement chamber is heated by the heater for the first time. A resistive temperature sensing layer. In this case, the first resistive temperature sensing layer and the urea water are in direct contact with each other.

Next, the operation of the engine C/U51 and the SCR-C/U61 will be described with reference to the flowchart.

First, the operation of SCR-C/U61 will be described.

Fig. 4 shows a flowchart of the anomaly detection program. This routine is started when the ignition switch is turned on, and thereafter, it is repeatedly executed every predetermined time. According to this program, an abnormality occurring in the urea water injection system is detected.

In S101, the boost air pressure Pa, the urea water pressure Pu and the urea sensor voltage Vs are read.

In S102, it is determined whether the assist air pressure Pa is within a predetermined range with a predetermined value Pa2 as an upper limit and a predetermined value Pa1 (<Pa2) as a lower limit. When the boost air pressure Pa is within the range, the routine goes to S103, and when the boost air pressure Pa is not within the range, the routine goes to S108. When a boost air pressure smaller than the value Pa1 is detected, it can be judged that a leak of boost air has occurred in the air supply pipe 42 . When the boost air pressure greater than the value Pa2 is detected, it can be judged that clogging has occurred in the nozzle 43 . In a case where the passage is clogged by urea or the like condensed in the nozzle portion 432, the nozzle 43 is clogged.

In S103, it is judged whether the urea water pressure Pu is equal to or greater than a predetermined value Pu1. When the urea water pressure Pu is equal to or greater than the value Pu1, the routine goes to S104, and when the urea water pressure Pu is smaller than the value Pu1, the routine goes to S108. When the urea water pressure smaller than the value Pu1 is detected, it can be judged that the feed pump 44 fails and cannot provide sufficient pressure to the urea water.

At S104, it is judged whether the urea sensor voltage Vs is equal to or smaller than a predetermined value Vs1. When the urea sensor voltage Vs is equal to or less than the value Vs1, the process proceeds to S105, and when the urea sensor voltage Vs is greater than the value Vs1, the process proceeds to S108. When the urea sensor voltage greater than the value Vs1 is detected, it can be judged that disconnection has occurred in the sensor element portion 741 .

In S105, the remaining amount judgment flag Femp is read, and it is judged whether the read flag Femp is 0 or not. When the flag Femp is 0, the program goes to S106, and when the flag Femp is not 0, the program goes to S108. The remaining amount judgment flag Femp is normally set to 0, and is switched to 1 when it is judged that the storage tank 41 is empty as described below.

In S106, the dilution judgment flag Fdil is read, and it is judged whether the read flag Fdil is 0 or not. When the flag Fdil is 0, the program proceeds to S107, and when the flag Fdil is not 0, the program proceeds to S108. The dilution judgment flag Fdil is normally set to 0, and is switched to 1 when it is judged that the urea water in the storage tank 41 is excessively diluted as described below.

In S107, it is judged that the assumed abnormality has not occurred in the urea water injection system, and the abnormality judgment flag Fscr is set to 0. Here, leakage of booster air, clogging of nozzle 43, malfunction of feed pump 44, disconnection of sensor element portion 741, lack of remaining amount of urea water, and dilution of urea water as detected in the above-described manner are all related to This example relates to the detected exception.

In S108, it is judged that any abnormality has occurred in the urea water injection system, an abnormality judgment flag Fscr is set to 1, and a warning light is also activated to notify the driver of the occurrence of abnormality.

Fig. 5 shows a flow chart of the concentration detection program. This routine is started when the ignition switch is turned on, and thereafter, it is repeatedly executed every predetermined time. According to this program, the concentration Dn is detected, and the remaining amount of urea water is also judged.

In S201, the start switch signal SWstr is read in, and it is judged whether the read signal SWstr indicates 1 or not. When the signal SWstr indicates 1, it is judged that the start switch is turned on, and the routine proceeds to S204 where the concentration Dn is calculated as described below.

In S202, the detection interval counter INT is incremented by 1 (INT=INT+1).

In S203, it is judged whether the value of the counter INT after counting up has reached a predetermined value INT1. When the value of the counter INT reaches the value INT1, it is judged that the detection interval required for the detection concentration Dn is ensured, and the program proceeds to S204, while when the value of the counter INT does not reach the value INT1, it is judged that the detection interval is not ensured, and returns program.

At S204, the detection interval counter INT is set to zero.

In S205 , the heater layer of the urea sensor 74 is energized to directly heat the first resistive temperature sensing layer, and indirectly heat the second resistive temperature sensing layer using urea water as a medium.

In S206, the concentration Dn is calculated. The calculation of the concentration Dn is performed by calculating the temperature difference ΔTmp12 between the resistance temperature sensing layers from the difference between the resistance values Rn1 and Rn2 of the respective resistance temperature sensing layers, and converting the calculated temperature difference ΔTmp12 into the concentration Dn.

At S207, it is judged whether the calculated temperature difference ΔTmp12 is equal to or greater than a predetermined value SL1. When the temperature difference ΔTmp12 is equal to or greater than the value SL1, the process proceeds to S208, and when the temperature difference ΔTmp12 is smaller than the value SL1, the process proceeds to S210. The value SL1 is set as an intermediate value between the temperature difference ΔTmp12 obtained in a state where the urea sensor 74 is in urea water and the temperature difference ΔTmp12 obtained in a state in which the urea sensor 74 is in air.

In S208, it is judged whether the concentration Dn is equal to or greater than a predetermined value D1. When the concentration Dn is equal to or greater than the value D1, the procedure proceeds to S209, and when the concentration Dn is smaller than the value D1, the procedure proceeds to S211. As a concentration that can be detected when urea water is in a water state or a diluted state close to the water state, or when a different type of aqueous solution other than water or urea water is stored in the storage tank 41, the value D1 is set to 0 or a small value close to 0.

In S209, the density Dn is stored as the density storage value D.

At S210, it is judged that the storage tank 41 is empty, and the remaining amount judgment flag Femp is set to 1.

In S211, it is judged that the urea water stored in the storage tank 41 is too dilute to achieve the required _NOx purification efficiency, and the dilution judgment flag Fdil is set to 1.

Fig. 6 shows a flow chart of the urea water injection control program. This routine is started when the ignition switch is turned on, and thereafter, it is repeatedly executed every predetermined time. According to this program, set the urea water injection volume Qu.

In S301, the abnormality judgment flag Fscr is read, and it is judged whether the read flag Fscr is 0 or not. When the flag Fscr is 0, the routine goes to S302, and when the flag Fscr is not 0, it is judged that an abnormality has occurred in the urea water injection system, and the routine goes to S305.

At S302, the fuel injection amount Qf, the _NOx concentration NOx (or the output from the _NOx sensor 73) and the concentration stored value D are read.

In S303, the urea water injection amount Qu is calculated. Calculation of the urea water injection quantity Qu is performed by calculating the basic injection quantity from the fuel injection quantity Qf and the _NOx concentration NOx, and also correcting the calculated basic injection quantity using the concentration stored value D. When the concentration storage value D is large and the urea content per unit injection amount is high, the basic injection amount is corrected and reduced. On the other hand, when the concentration stored value D is small and the urea content per unit injection amount is low, the basic injection amount is corrected and increased.

In S304 , an operation signal based on the calculated urea water injection amount Qu is output to the nozzle 43 .

In S305, since it is impossible to inject urea water in an accurate amount with respect to the _NOx emission amount in a state where an abnormality occurs in the urea water injection system, the injection of urea water is stopped. When the urea water injection amount is less than an appropriate value, there is a possibility that NO _x is discharged into the atmosphere without being purified. On the contrary, when the injection amount of urea water is larger than the appropriate value, not only the urea water is consumed unnecessarily, but also the excessively produced ammonia may not be completely decomposed by the ammonia purification catalyst 34 and may be discharged into the atmosphere. Furthermore, not only when the storage tank 41 is empty but also when urea water is excessively diluted or when not urea water but water or the like is stored in the storage tank 41 , it is impossible to add ammonia in an amount necessary for _NOx purification.

Next, the operation of engine C/U51 will be described.

Fig. 7 shows a flowchart of a fuel injection amount setting routine. This routine is started when the ignition switch is turned on, and thereafter, it is repeatedly executed every predetermined time. According to this program, the fuel injection quantity Qf is set.

In S401, the operating state of the engine 1 such as the engine rotational speed Ne and the accelerator opening, or the accelerator operation amount and APO in this embodiment are read.

In S402, the abnormality judgment flag Fscr is read, and it is judged whether the read flag Fscr is 0 or not. When the flag Fscr is 0, the routine goes to S403, and when the flag Fscr is not 0, it is judged that an abnormality has occurred in the urea water injection system, and the routine goes to S404.

At S403, a map for normal operation is selected, and the selected map is also retrieved based on the read operation state Ne and APO, thereby setting the fuel injection quantity Qf.

In S404, disconnect the connection between the starter and the starter's power supply unit such as an alternator, a battery, etc., so that the starter does not work at the next starting time after the operation of the engine 1 is stopped, to prohibit restarting of the engine operation. start.

In S405, the vehicle speed VSP is read. The vehicle speed VSP can be directly detected by detecting the rotational speed of the transmission output shaft. However, it is also possible to indirectly detect the vehicle speed VSP by converting the engine rotational speed Ne at the transmitted gear ratio.

At S406, it is judged whether the read vehicle speed VSP is equal to or greater than a predetermined value VSP1. When the vehicle speed VSP is equal to or greater than the value VSP1, the process proceeds to S407, and when the vehicle speed VSP is smaller than the value VSP1, the process proceeds to S403.

At S407, a map for the output-limited operation is selected, and the selected map is also retrieved based on the read operating state Ne and APO, thereby setting the fuel injection quantity Qf. Under the same Ne and APO, the fuel injection quantity Qf set using this map is smaller than the fuel injection quantity Qf set using the map of normal operation, thus, the output (ie, output torque) of the engine 1 is limited. In this embodiment, the torque generated at the time of the output-limited operation is made to be the minimum torque required for stable movement on a flat road at a speed of the predetermined value VSP1, so that the torque exceeding the predetermined value is limited for a period of time until the occurrence of abnormality is eliminated. Velocity movement with value VSP1. When an abnormality occurs in the urea water injection system, since the injection of the urea water is stopped (S305) as described above, thereby avoiding the unstable injection of the urea water, it is as possible as possible by the comprehensive engine control including the setting of the fuel injection amount Qf effectively suppress NO _X generation itself.

In S408, the fuel cut flag Fcut is read, and it is judged whether the read flag Fcut is 0 or not. When the flag Fcut is 0, the program goes to S409, and when the flag Fcut is not 0, the program goes to S410. The fuel cut flag Fcut is normally set to 0, and is switched to 1 when it is judged that fuel supply is to be stopped, as described below.

At S409, the fuel injection quantity Qf set in the above-described manner is set as the output injection quantity Qfset, and an operation signal according to the output injection quantity Qfset is output to the injector 21.

In S410, the fuel injection quantity Qf is set to 0, thereby stopping the fuel injection.

FIG. 8 shows a flowchart of the fuel cut routine. This routine is started when the ignition switch is turned on, and thereafter, it is repeatedly executed every predetermined time. According to this program, the fuel cut flag Fcut is set.

In S501, the accelerator opening APO is read.

At S502, it is judged whether the read accelerator opening APO is equal to or smaller than a predetermined value APO1. When the accelerator opening APO is equal to or smaller than the value APO1, the routine goes to S503, and when the accelerator opening APO is larger than the value APO1, the routine goes to S504.

At S503, the fuel cut flag Fcut is set to 1 to stop fuel injection.

In S504, the abnormality judgment flag Fscr is read, and it is judged whether the read Fscr is 0 or not. When the flag Fscr is 0, the program goes to S505, and when the flag Fscr is not 0, the program goes to S507.

In S505, the counter CNT is incremented by 1 (CNT=CNT+1). This counter CNT corresponds to the elapsed time from the time when an abnormality occurred in the urea water injection system.

In S506, it is judged whether the counted up counter CNT reaches a predetermined value CNT1. When the counter CNT reaches the predetermined value CNT1, the procedure goes to S503, and when the counter CNT does not reach the value CNT1, the procedure goes to S508.

At S507, the counter CNT is set to 0.

At S508, the fuel cut flag Fcut is set to 0, thereby performing fuel injection.

In this embodiment, the storage tank 41 , the urea water supply pipe 42 , the nozzle 43 , the feed pump 44 and the air supply pipe 48 constitute the reducing agent addition equipment. The urea sensor 74 has two functions: as a first sensor for detecting the concentration of urea and as a second sensor for judging the remaining amount of urea water. In addition, in addition to the functions of SCR-C/U61, the function of the entire flow chart shown in Figure 4 corresponds to the abnormality detection part in this embodiment, and the entire flow chart shown in Figure 7 and the flow chart shown in Figure 8 The functions of S504-S507 in the figure correspond to the control components in this embodiment.

According to this embodiment, the following effects can be achieved.

First, when an abnormality occurs in the urea water injection system, the map for setting the fuel injection quantity is switched such that the fuel injection quantity Qf is lower than that at normal time under the same accelerator opening APO, and The output of engine 1 is limited. Therefore, when an abnormality occurs, the movement of the car can be restricted, and the driver is urged to repair the urea water injection system, so that proper maintenance of the urea water injection system can be realized.

Second, the output of the engine 1 is limited only when the vehicle speed VSP exceeds a predetermined value VSP1, so that the minimum function as an automobile can be ensured. Therefore, it is possible to effectively prompt the repair while avoiding traffic disturbance or the like due to excessive limitation of the engine output.

Third, when an abnormality occurs in the urea water injection system, restarting of the engine operation is prohibited, and in addition, after a predetermined time elapses, fuel injection is stopped, thereby stopping the engine operation. Therefore, the driver can be prompted to go to the service station for repair in time. In the present embodiment, since the warning light is activated when the occurrence of abnormality is detected, the driver can be aware of the occurrence of abnormality in time to go to the service station. Incidentally, in the present embodiment, when a predetermined time elapses after the occurrence of an abnormality is detected, fuel supply is immediately stopped (S410). However, the structure may also be such that the fuel injection quantity Qf is gradually decreased to gradually stop the fuel supply.

Fourth, as an abnormality occurring in the urea water injection system, a lack of remaining amount of urea water or dilution of urea water is detected, thereby facilitating appropriate management of urea water. In particular, the latter dilution is detected, and thus, inappropriate or wrong use of over-diluted urea water, different types of aqueous solutions other than urea water, etc. can be prevented.

Next, other embodiments of the present invention will be described.

FIG. 9 shows a flowchart of a fuel injection amount setting routine according to the second embodiment. This routine is also started when the ignition switch is turned on, and thereafter, it is repeatedly executed every predetermined time. Each step in which processing is the same as that in the flowchart shown in FIG. 7 is denoted by the same reference numeral.

In this routine, after various operating states such as accelerator opening APO are read (S401), at S601, the fuel injection amount Qf is set based on the read operating states. When it is judged that the abnormality judgment flag Fscr is 1 and accordingly an abnormality occurs in the urea water injection system (S402), the connection between the starter and the power supply unit is disconnected (S404). After reading in the vehicle speed VSP (S405), it is judged that the read vehicle speed VSP is equal to or greater than the predetermined value VSP1, and the program proceeds to S602. In S602, the preset Qf is multiplied by the coefficient x1, and the obtained value (=Qf ×x1) instead of the fuel injection quantity Qf. This coefficient x1 is a coefficient for limiting the output of the engine 1 and is set to a value greater than 0 and less than 1. When it is judged that the fuel cut flag Fcut is not 0 (S408), the fuel injection amount Qf is set to 0 (S410), thereby stopping the fuel injection. The fuel injection quantity Qf set in the above-described manner is set as the output injection quantity Qfset (S409), thereby operating the injector 21.

In this embodiment, the function of the entire flowchart shown in FIG. 9 (and S504 to S507 in the flowchart shown in FIG. 8 ) corresponds to the control means.

According to the present embodiment, in addition to the first to fourth effects described above, since there is no need to prepare separate fuel injection amount setting maps for normal time and abnormality occurrence time, the storage capacity of engine C/U51 can be reduced.

Fig. 10 shows a flow chart of a startup control program according to the third embodiment. This program is started when the start switch is turned on. With respect to the first embodiment, the present embodiment provides a modified example of the control for prohibiting restarting of the engine operation when an abnormality occurs. The fuel injection amount setting routine is given as a routine in which the processing of S404 in the routine ( FIG. 7 ) of the first embodiment is omitted.

In S701, the start switch signal SWstr is read, and it is judged whether the read signal SWstr is 1 or not. When the signal SWstr is 1, the program proceeds to S702, and at S702, start control as described below is performed.

In S702, the abnormality judgment flag Fscr is read, and it is judged whether the read flag Fscr is 0 or not. When the flag Fscr is 0, the routine goes to S703, and when the flag Fscr is not 0, it is judged that an abnormality has occurred in the urea water injection system and the routine goes to S704.

At S703, a normal fuel injection amount Qfstr for start control (hereinafter simply referred to as a start time injection amount) is set. The start-time injection amount Qfstr is set to a value larger than the fuel injection amount corresponding to the stoichiometric air-fuel ratio in accordance with the cooling water temperature Tw and the like.

At S704, the start-time injection quantity Qfstr is set to 0 in order to prohibit the start-up engine operation.

At S705, it is judged whether the combustion is completed, and when it is judged that the start of engine operation is completed, the routine is terminated to shift to the fuel injection amount setting routine. Here, the combustion completion judgment is performed based on the engine rotation speed Ne, and when the rate of change of the engine rotation speed Ne per unit time reaches a predetermined value, it is judged that the engine operation is started.

In this embodiment, the functions of S702 and S704 in the flowchart shown in FIG. 10 (and the entire flowchart shown in FIG. 7 (excluding S404) and S504 to S507 in the flowchart shown in FIG. 8 ) correspond to to control parts.

According to the present embodiment, when an abnormality occurs, the restart of the engine operation is prohibited by stopping the fuel supply, and self-starting of the starter can be performed. Thus, in an emergency, for example, when the engine stops at a railway crossing or the like, evacuation from the place can be performed.

FIG. 11 shows a flowchart of a fuel injection amount setting routine according to the fourth embodiment. This routine is started when the ignition switch is turned on, and thereafter, it is repeatedly executed every predetermined time.

In this routine, various operating states such as accelerator opening APO and vehicle speed VSP are read (S401), and based on the read operating states, the fuel injection amount (corresponding to the second fuel supply amount) Qf is set (S601) . When it is judged that the abnormality judgment flag Fscr is 1 and accordingly an abnormality occurs in the urea water injection system (S402), the connection between the starter and the power supply unit is disconnected (S404), and in addition, at S801, a limit injection amount ( corresponds to the first fuel supply amount) Qflmt. The limited injection quantity Qflmt is set as the injection quantity for limiting the output of the engine 1 when an abnormality occurs, and in this embodiment, based on the actual vehicle speed VSP, the limited injection quantity Qflmt is calculated according to the following formula. In the following formula, Qfvsp is set as the fuel injection amount required for stable movement on a flat road at vehicle speed VSP when abnormality occurrence is detected, and by retrieving the table to calculate Qfvsp. Also, Qfdlt is a correction amount based on the difference DLT (=VSP-VSP1) between the vehicle speed VSP and the predetermined value VSP1, and is calculated by accumulating the rate of change DQ assuming the rate of change DQ per execution cycle of the program. The larger the speed difference DLT, the larger the rate of change DQ is calculated ( FIG. 12 ), and when the vehicle speed VSP is smaller than the predetermined value VSP1 , DQ is calculated as a negative value.

Qflmt=Qfvsp-Qfdlt (5a)

Qfdlt=Qfdlt+DQ (5b)

In S802, it is judged whether the fuel injection amount Qf is larger than the limited injection amount Qflmt. When the fuel injection amount Qf is large, the fuel injection amount is limited by replacing the fuel injection amount Qflmt with the limited injection amount Qflmt, after which the routine proceeds to S408. At times other than the above, the program goes directly to S408. Subsequent processing is the same as the above-mentioned processing. When it is judged that the fuel cut flag Fcut is not 0 (S408), the fuel injection amount Qf is set to 0 (S410), thereby stopping the fuel injection. The fuel injection quantity Qf set in the above-described manner is set as the output injection quantity Qfset (S409), thereby operating the injector 21.

In this embodiment, the function of the entire flowchart shown in FIG. 11 (and S504 to S507 in the flowchart shown in FIG. 8 ) corresponds to the control means.

In the present embodiment, in the setting of the limited injection amount Qflmt, the vehicle speed VSP is fed back, so that the adjustment of the limited injection amount Qflmt is performed based on the vehicle speed VSP. Therefore, when an abnormality occurs, the vehicle speed VSP can be accurately controlled at the predetermined value VSP1 to suppress _NOx emission until the urea water injection system is repaired. Furthermore, the larger the speed difference DLT, the larger the rate of change DQ of the correction amount Qfdlt (ie, the limited injection amount Qflmt) is calculated to be a larger value. Therefore, it is possible to quickly and smoothly converge vehicle speed VSP to predetermined value VSP1.

FIG. 13 shows a time chart of the accelerator opening APO, the vehicle speed VSP, and the fuel injection amount (ie, the output injection amount Qfset) Qf before and after the occurrence of the abnormality. At time t1, when the accelerator pedal is depressed, the fuel injection amount Qf according to the accelerator opening APO and the like is set, and the vehicle speed VSP increases. At time 2, when an abnormality occurs in the urea water injection system, the output injection amount Qfset is decreased at a speed according to the speed difference DLT (ie, rate of change DQ), and the vehicle speed VSP is limited to a predetermined value VSP1. At time 3, when the accelerator pedal is returned, and the fuel injection quantity Qf is lower than the limit injection quantity Qflmt, the fuel injection quantity Qf is set as the output injection quantity Qfset, thereby achieving deceleration. Thereafter, at time 4, when the accelerator pedal is depressed again, if the abnormality occurring in the urea water injection system has not been eliminated, the limited injection quantity Qflmt is set as the output injection quantity Qfset, and the output of the engine 1 is limited.

In this embodiment, the vehicle speed VSP is fed back to calculate the limited injection amount Qflmt so that the vehicle speed VSP coincides with the predetermined value VSP1. However, it is also possible to prohibit movement at a speed exceeding the predetermined value VSP1 by setting the limited injection amount Qflmt as follows. That is, the fuel injection amount required for moving on a flat road with the predetermined value VSP1 is stored in engine C/U51 in advance as a limited injection amount Qflmt. When an abnormality occurs, the smaller one of the fuel injection amount Qf calculated based on the accelerator opening APO and the like and the stored limit injection amount Qflmt is set as the output injection amount Qfset. Preferably there is no sudden reduction in engine torque during high speed driving. Therefore, by unconditionally selecting the fuel injection quantity Qf until a predetermined period of time elapses after the occurrence of the abnormality, switching from the fuel injection quantity Qf to the limited injection quantity Qflmt can be delayed for the predetermined period of time, or by using the stored limited injection As the target value, the limited injection quantity Qflmt can be set with a predetermined delay in the change toward the target value.

In the above description, ammonia is produced by hydrolysis of urea, but the catalyst for this hydrolysis is not specified. In order to increase hydrolysis efficiency, a hydrolysis catalyst may be provided upstream of the NO _x purification catalyst 33 .

Furthermore, in the above description, an example has been described for the case where ammonia is employed as the _NOx reducing agent. However, hydrocarbons can also be used instead of ammonia.

As the engine, a diesel generator or a gasoline generator other than the direct injection type may be used.

Although the present invention has been described according to several preferred embodiments, the scope of the present invention is not limited to the description, but can be judged based on the disclosure within the scope of the claims according to the applicable clause.

Claims (20)

1. An engine control device configured to cooperate with an engine comprising dosing means for adding _NOx reducing agent to the exhaust of the engine, the engine control device comprising: control unit for controlling the engine, wherein The control unit detects an abnormality that has occurred in the adding device to limit the output of the engine at the abnormality occurrence time when the abnormality occurrence is detected. 2. The engine control device according to claim 1, wherein when the abnormality occurs, the control unit makes the output characteristic of the engine relative to the driver's accelerator operation different from that of the normal time except for the abnormality occurrence time. different. 3. The engine control device according to claim 2, wherein the control unit makes the amount of fuel supplied to the engine at the same accelerator operation amount different from the amount of fuel supplied to the engine at the normal time when the abnormality occurs , so that the output characteristics of the engine are different. 4. The engine control apparatus according to claim 3, wherein the control unit reduces the fuel supply amount when the abnormality occurs compared with the fuel supply amount at the normal time based on the same accelerator operation amount. 5. The engine control device according to claim 3, wherein: the engine is installed on the vehicle, and Wherein, when the abnormality occurs, the control unit calculates the first fuel supply amount for controlling the vehicle speed at a predetermined value, also calculates the second fuel supply amount according to the accelerator operation amount, and supplies the first and second fuel supply The smaller of the amounts is set as the final fuel supply amount. 6. The engine control device according to claim 3, wherein: the engine is installed on the vehicle, and Wherein, the control unit stores a first fuel supply amount set in advance as a fuel supply amount for maintaining a vehicle speed at a predetermined value, and when an abnormality occurs, calculates a second fuel supply amount from an accelerator operation amount, and The smaller one of the first and second fuel supply amounts is set as the final fuel supply amount. 7. The engine control device according to claim 3, wherein: the engine is installed on the vehicle, and Wherein, the control unit detects the vehicle speed, and changes the fuel supply amount only when the detected vehicle speed is greater than a predetermined value. 8. The engine control device according to claim 1, wherein the control unit prohibits restarting the engine operation after the engine operation is stopped to limit the output of the engine. 9. The engine control apparatus according to claim 8, wherein the control unit disconnects a connection between a starter for starting the engine and a power supply unit of the starter, thereby prohibiting restarting the engine operation. 10. The engine control apparatus according to claim 8, wherein the control unit prohibits supply of fuel to the engine, thereby prohibiting restarting of the engine operation. 11. The engine control apparatus according to claim 1, wherein the control unit stops the engine after a predetermined period of time has elapsed since the occurrence of the abnormality was detected. 12. The engine control device according to claim 1, wherein: the engine includes a storage tank for storing an aqueous solution of _NOx reducing agent or precursor thereof added to the exhaust by the addition device, and Wherein, the control unit includes a first sensor for detecting the concentration of the _NOx reducing agent or the precursor contained in the aqueous solution stored in the storage tank, and when detected by the first sensor When the concentration value of is outside the predetermined range, an abnormality that occurs in the adding equipment is detected. 13. The engine control device according to claim 12, wherein the first sensor includes a sensor element portion provided in the storage tank, and a circuit portion connected to the sensor element portion, wherein The sensor element part includes a heater and a temperature sensing element, the temperature sensing element is set to be in direct or indirect contact with the aqueous solution in the storage tank, and the temperature sensing element is heated by the heater, the temperature The sensing element has the property that its electrical characteristic value changes according to its temperature, and The circuit part drives the heater and also detects an electric characteristic value of the heated temperature sensing element, and detects the concentration of the _NOx reducing agent or the precursor based on the detected electric characteristic value. 14. The engine control device according to claim 1, wherein: the engine includes a storage tank for storing an aqueous solution of _NOx reducing agent or precursor thereof added to the exhaust by the addition device, and Wherein, the control unit includes a second sensor, the second sensor is used to detect the remaining amount of the aqueous solution stored in the storage tank, and when the value of the remaining amount detected by the second sensor is less than a predetermined value, the Add exceptions that occurred in the device. 15. The engine control device according to claim 1, wherein the _NOx reducing agent is ammonia. 16. The engine control device according to claim 15, wherein the adding device adds urea as a precursor of ammonia to the exhaust gas, thereby adding a _NOx reducing agent. 17. The engine control apparatus according to claim 1, wherein, when an abnormality occurs, the control unit operates a warning device for notifying a driver of the occurrence of the abnormality. 18. The engine control device according to claim 1, characterized in that it comprises: a first control unit for controlling the engine; and a second control unit for controlling the adding device, wherein the second control unit controls the adding device both when an abnormality occurs and at normal times other than the abnormality occurs, and The second control unit operates the adding device to add the _NOx reducing agent in an amount according to the engine operating state at normal time, and stops adding the _NOx reducing agent by the adding device when an abnormality occurs. 19. An engine control device configured to cooperate with an engine comprising addition means for adding _NOx reducing agent to the exhaust of the engine, the engine control device comprising: detection means for detecting anomalies that have occurred in the added device; and A control means for limiting the output of the engine at the abnormality occurrence time when the abnormality occurrence is detected by the detection means. 20. A method for operating an engine at an abnormality occurrence time when an abnormality occurs in an additive device provided in the engine to reduce _NOx A reducing agent is added to the exhaust of the engine, the method comprising the steps of: At normal times, the engine is operated with a first characteristic in which an output of the engine corresponding to the driver's accelerator operation amount is obtained, wherein the operating state of the engine is detected and added by the adding device an amount of _NOx reducing agent corresponding to the detected operating state; and At the time of abnormality occurrence, the engine is prohibited from operating, or the engine is operated with a second characteristic in which the output relative to the The output of the accelerator operation volume.

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