Engine and method for diagnosing engine

Abstract

To provide an engine and a method for diagnosing the engine with which NOx sensor failure can be diagnosed with greater accuracy.SOLUTION: The engine is configured such that, under the control of an electronic control device, a NOx sensor failure diagnosis operation S103 accompanied by a DPF regeneration process, EGR stoppage, and urea water injection stoppage is performed, and detection data for a pair of NOx concentrations J and K detected by a pair of NOx sensors during this NOx sensor failure diagnosis operation are transmitted S105 to an engine diagnosis tool, located outside the engine, which performs failure diagnosis S108 for the pair of NOx sensors on the basis of the detection data. In this method for diagnosing the engine, the NOx sensor failure diagnosis S108 is carried out by the engine diagnosis tool on the basis of detection data transmitted from the engine.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an engine and a method for diagnosing an engine, and more particularly to an engine and a method for diagnosing an engine that can improve the failure diagnosis accuracy of a NOx sensor.

Background Art

[0002] Conventionally, there has been an engine that performs failure diagnosis of a NOx sensor based on detection of the NOx concentration in engine exhaust (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] 《Problem》 There is a risk that the failure diagnosis accuracy of the NOx sensor may be reduced. In the engine of Patent Document 1, when the exhaust temperature is low, the exhaust flow rate is unstable, urea crystals remain in the exhaust passage, and moreover, if EGR is continued, the NOx concentration becomes low, so that the accuracy of the detection data of the NOx concentration detected by the NOx sensor is reduced. Further, if the aqueous urea is being injected, the detection data of the NOx concentration changes greatly due to the NOx purification function of SCR. For this reason, there is a risk that the failure diagnosis accuracy of the NOx sensor may be reduced.

[0005] An object of the present invention is to provide an engine and a method for diagnosing an engine that can improve the failure diagnosis accuracy of a NOx sensor.

Means for Solving the Problems

[0006] The main configuration of the present invention is as follows. (The invention according to claim 1) Under the control of an electronic control unit, a NOx sensor failure diagnosis operation involving DPF regeneration processing, EGR stop, and urea water injection stop is performed, and detection data of a pair of NOx concentrations detected by the pair of NOx sensors in this NOx sensor failure diagnosis operation is transmitted to an engine diagnosis tool outside the engine that performs a failure diagnosis of the pair of NOx sensors based on this detection data. The engine is characterized by this configuration.

[0007] (The invention according to claim 3) Under the control of an electronic control unit, the engine is made to perform a NOx sensor failure diagnosis operation involving DPF regeneration processing, EGR stop, and urea water injection stop. In this NOx sensor failure diagnosis operation, detection data of a pair of NOx concentrations detected by a pair of NOx sensors on the upstream and downstream sides of the exhaust of the SCR is transmitted to an engine diagnosis tool, and based on the above detection data, the engine diagnosis tool is made to perform a failure diagnosis of the NOx sensors. A method for diagnosing an engine is characterized by this configuration. [Advantages of the Invention]

[0008] The invention according to claim 1 or claim 3 has the following advantages. [Effect 1] The accuracy of the failure diagnosis of a pair of NOx sensors can be improved. During the NOx sensor failure diagnosis operation, the exhaust gas is heated up by the DPF regeneration processing, the exhaust gas flow rate is stabilized, the urea crystals adhering in the exhaust passage are burned off, and further, the EGR stop raises the NOx concentration. Therefore, the accuracy of the detection data of the NOx concentration by the pair of NOx sensors is improved. Moreover, this detection data is not affected by the NOx purification function of the SCR due to the stop of urea water injection and is difficult to change. In this way, by transmitting a pair of detection data of NOx concentrations that are highly accurate and difficult to change to the engine diagnosis tool, the engine diagnosis tool can perform a failure diagnosis of the pair of NOx sensors based on the detection data of the pair of NOx concentrations, and the accuracy of the failure diagnosis of the pair of NOx sensors can be improved.

[0009] [Effect 2] The failure diagnosis of a pair of NOx sensors can be performed while the exhaust device is mounted on the engine. In the NOx sensor failure diagnosis operation, the detection data of the pair of NOx concentrations detected by the pair of NOx sensors is transmitted to an engine diagnosis tool outside the engine for performing a failure diagnosis of the pair of NOx sensors based on this detection data. Therefore, the failure diagnosis of the NOx sensors can be performed while the exhaust device is mounted on the engine.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0011] Figs. 1 to 6 are diagrams for explaining an engine and a method for diagnosing the engine according to an embodiment of the present invention. In this embodiment, a vertical in-line multi-cylinder diesel engine and a method for diagnosing this engine will be described.

[0012] As shown in Fig. 1, this engine (1) includes an electronic control unit (8), an intake device (10), a fuel supply device (11), and an exhaust device (12). An engine cooling fan (1c) is arranged on the front side of the engine (1), and a flywheel (1d) is arranged on the rear side of the engine (1). The electronic control unit (8) is an engine ECU. ECU is an abbreviation for electronic control unit. The intake device (10) includes, in order from the upstream side of the intake passage, an air cleaner (10a), an intake throttle valve (10b), an intake sensor (10c), and an intake manifold (10d). The opening / closing timing and opening degree of the intake throttle valve (10b) are controlled by the electronic control unit (8). The intake sensor (10c) detects the intake air flow rate and intake air temperature. Further, EGR is performed from the exhaust device (12) to the intake device (10) via the EGR device (5). EGR is an abbreviation for exhaust gas recirculation. The EGR device (5) includes, in order from the EGR upstream side, an EGR cooler (5a) and an EGR valve (5b), and the opening / closing of the EGR valve (5b) is controlled by the electronic control unit (8).

[0013] As shown in Fig. 1, the fuel supply device (11) is of a common rail type and includes a common rail (11a) and fuel injectors (11b) that inject fuel into each cylinder (1a). The fuel injector (11b) is controlled by the electronic control unit (8), opens the valve for a predetermined time at a predetermined timing, and injects a predetermined amount of fuel. The fuel injection amount is adjusted by the governor function of the electronic control unit (8) based on the accelerator position detected by the accelerator sensor (13) and the actual engine rotation speed detected by the engine rotation speed sensor (14). Further, under the control of the electronic control unit (8), in the DPF regeneration process, in addition to the main injection, post-injection is performed from the fuel injector (11b). Further, after-injection may be performed between the main injection and the post-injection.

[0014] As shown in FIG. 1, the exhaust device (12) includes, in order from the upstream side of the exhaust, an exhaust manifold (12a), a DOC (6a), a DPF (6), an aqueous urea injector (9), an SCR (7), and an ASC (7a). The DOC (6) and the DPF (7) are housed in a DPF case (6b), the SCR (7) and the ASC (7a) are housed in an SCR case (7b), a mixing passage (12b) is provided between the DPF case (6b) and the SCR case (7b), the aqueous urea injector (9) is disposed upstream of this mixing passage (12b), and the aqueous urea (9a) injected from the aqueous urea injector (9) into the mixing passage (12b) is mixed with the exhaust gas (15) and supplied to the SCR (7).

[0015] DOC is an abbreviation for diesel oxidation catalyst, which oxidizes CO (carbon monoxide) and NO (nitric oxide) in the exhaust gas (15), and during the DPF regeneration process, catalytically combusts the after-injection fuel and post-injection fuel injected from the fuel injector (11b) to raise the temperature of the exhaust gas (15), and incinerates and removes the PM deposited on the DPF (7). PM is an abbreviation for particulate matter. DPF is an abbreviation for diesel particulate filter, which captures PM in the exhaust gas. SCR is an abbreviation for a selective catalytic reduction type catalyst, which adsorbs ammonia to the SCR (7) with the aqueous urea (9a) injected into the exhaust gas (15) from the aqueous urea injector (9), and uses this as a reducing agent to reduce NOx (nitrogen oxides) in the exhaust gas to obtain N2 (nitrogen gas) and H2O (water vapor). ASC is an abbreviation for an ammonia purification oxidation catalyst, which is for preventing the slip of NH3 (ammonia).

[0016] As shown in FIG. 1, the exhaust device (12) includes, from the upstream side of the exhaust, a DOC inlet side exhaust temperature sensor (6c), a DPF inlet side exhaust temperature sensor (6d), an exhaust differential pressure sensor (6e), a DPF outlet side exhaust temperature sensor (6f), a NOx sensor (3) on the upstream side of the exhaust of the SCR (7), an SCR inlet side exhaust temperature sensor (7c), and a NOx sensor (4) on the downstream side of the exhaust of the SCR (7). During normal operation of the engine, NOx reduction operation is performed by EGR and the SCR (7) accompanied by urea water injection. When the differential pressure between the inlet and outlet of the DPF (6) detected by the exhaust differential pressure sensor (6e) indicates that the PM deposition amount has reached the necessary amount for starting regeneration, and when the DOC (6) has reached its activation temperature due to the temperature increase by the exhaust (15), the DPF regeneration process is started.

[0017] As shown in FIG. 1, the urea water (9a) in the urea water tank (9b) is pumped by the urea water pump (9c) to the urea water injector (9). The urea water injector (9) is controlled by the electronic control unit (8) and is opened at a predetermined timing for a predetermined time, and a predetermined amount of urea water (9a) is injected into the mixing passage (12b). The injection amount of the urea water (9a) is calculated by the calculation unit of the electronic control unit (8) of the engine (1) based on the pair of NOx concentrations (J)(K) detected by the pair of NOx sensors (3)(4) and the intake air flow rate detected by the intake air sensor (10c). A urea water level sensor (9d) and a urea water temperature sensor (9e) are arranged in the urea water tank (9b), and the electronic control unit (8) of the engine (1) causes the display device (1b) of the engine (1) to display advice on replenishment of the urea water (9a) and prevention of freezing of the urea water (9a).

[0018] As shown in FIG. 1, the display device (1b) of the engine (1) is connected to the electronic control unit (8) of the engine (1). This display device (1b) of the engine (1) is arranged on an operation panel such as a dashboard of the engine-mounted machine, and displays the engine failure determination display (S6) of FIG. 3 described later, etc. The engine-mounted machine refers to a traveling or stationary agricultural machine, construction machine, etc. equipped with the engine (1). Examples of traveling machines include tractors and backhoes, and examples of stationary machines include engine generators. For the display device (1b) of the engine (1), a liquid crystal display, an organic EL display, etc. can be used. EL is an abbreviation for electroluminescence.

[0019] The outline of the diagnostic procedure of the engine (1) by the electronic control unit (8) of this engine (1) is as follows. As shown in FIG. 3, the electronic control unit (8) of this engine (1) performs a failure diagnosis (S4) of the engine (1) during normal engine operation. When a failure determination (S5) of the engine (1) is made, a failure display of the engine is displayed (S6) on the display device (1b) of the engine (1), and at the same time, a recommendation for a failure diagnosis of the NOx sensor is displayed. The user of the engine-mounted machine who has confirmed this display (S6) requests a service technician to perform a failure diagnosis of the NOx sensor. The service technician uses the engine diagnostic tool (2) to cause the electronic control unit (8) of the engine (1) to perform a NOx sensor failure diagnosis operation (S103)(S203). Based on the confirmation of the NOx sensor failure determination (S110)(S210) by the NOx sensor failure diagnosis (S108)(S208), after replacing the NOx sensor, an engine function recovery confirmation diagnosis (S309) for the NOx purification function after the NOx sensor replacement shown in FIG. 6(A) is performed. When a failure determination (S5) of the engine (1) is made, the output of the engine (1) is restricted by the electronic control unit (8) of this engine (1), and the engine-mounted machine becomes inoperable, guiding the user to request a service technician to perform a failure diagnosis of the NOx sensor.

[0020] As shown in FIG. 1, this engine (1) includes a DPF (6), an SCR (7), a pair of NOx sensors (3)(4) on the upstream and downstream sides of the exhaust of the SCR (7), an electronic control unit (8), an EGR device (5), and a urea water injector (9).

[0021] As shown in FIG. 3, in this engine (1), during normal operation, the failure diagnosis (S4) of the engine (1) is performed by the electronic control unit (8) of the engine (1) based on the NOx purification rate of the SCR (7) during engine operation. When a failure determination (S5) of the engine (1) is made, this determination result is displayed (S6) on the display device (1b) of the engine (1). Normal operation refers to operations other than the NOx sensor failure diagnosis operations (S103) (S203) shown in FIGS. 4(B) and 5(B) and the engine function recovery confirmation operation (S303) after NOx sensor replacement shown in FIG. 6(B). During normal operation, NOx reduction processing is performed by EGR and urea water injection.

[0022] As shown in FIGS. 4(B) and 5(B), this engine (1) performs NOx sensor failure diagnosis operations (S103) (S203) involving DPF regeneration processing, EGR stop, and urea water injection stop under the control of the electronic control unit (8). Detection data of a pair of NOx concentrations (J) (K) detected by the pair of NOx sensors (3) (4) in this NOx sensor failure diagnosis operation (S103) (S203) is transmitted (S105) (S205) to an engine diagnosis tool (2) outside the engine (1) that performs failure diagnosis (S108) (S208) of the pair of NOx sensors (3) (4) based on this detection data.

[0023] The following effects can be obtained with this engine. That is, during the NOx sensor fault diagnosis operation (S103) shown in FIGS. 4(B) and 5(B), the exhaust gas is heated up during the DPF regeneration process to stabilize the exhaust gas flow rate, and the urea crystals adhering in the exhaust passage (12c) are burned out. Further, in order to increase the NOx concentration by stopping EGR, the accuracy of the detection data of the NOx concentrations (J) and (K) by the pair of NOx sensors (3) and (4) is improved. Moreover, this detection data is not affected by the NOx purification function of the SCR (7) due to the stop of urea water injection and is difficult to change. In this way, by transmitting the detection data of the pair of NOx concentrations (J) and (K), which is highly accurate and difficult to change, to the engine diagnostic tool (2) (S105)(S205), as shown in FIGS. 4(A) and 5(A), the engine diagnostic tool (2) can perform the fault diagnosis (S108)(S208) of the pair of NOx sensors (3) and (4) based on the detection data of the pair of NOx concentrations (J) and (K), and the accuracy of the fault diagnosis (S108)(S208) of the pair of NOx sensors (3) and (4) can be improved.

[0024] Also, the following effect can be obtained with this engine. As shown in FIGS. 4(A) and 5(A), in order to transmit the detection data of the pair of NOx concentrations (J) and (K) detected by the pair of NOx sensors (3) and (4) in the NOx sensor fault diagnosis operation (S103)(S203) to the engine diagnostic tool (2) outside the engine (1) that performs the fault diagnosis (S108)(S208) of the pair of NOx sensors (3) and (4) based on this detection data (S105)(S205), it is possible to perform the fault diagnosis of the NOx sensors (3) and (4) while the exhaust device (12) illustrated in FIG. 1 is mounted on the engine (1).

[0025] The DPF regeneration process associated with the NOx sensor failure diagnosis operations (S103) (S203) shown in FIGS. 4(A) and 5(A) is carried out even when the PM accumulation amount has not reached the necessary amount for starting regeneration, which is different from the DPF regeneration process during normal operation. This DPF regeneration process, similar to that during normal operation, is carried out by causing post-injection from the fuel injector (1b) after the exhaust gas temperature at the inlet side of the DOC (6a) shown in FIG. 1 has reached the activatable temperature of the DOC (6a). When the exhaust gas temperature at the inlet side of the DOC (6a) is low, the opening degree of the intake throttle valve (10b) is reduced, the main injection fuel is increased, after-injection is carried out, etc., to raise the exhaust gas temperature at the inlet side of the DOC (6a) to the activatable temperature of the DOC (6a). In addition, when the exhaust pipe fuel injection valve is provided, the DPF regeneration process can also be carried out by exhaust pipe injection of the exhaust pipe fuel injection valve instead of the post-injection of the fuel injector (11b).

[0026] As shown in FIG. 6(B), this engine is configured to perform an engine function recovery confirmation operation (S303) for the NOx purification function after NOx sensor replacement involving DPF regeneration process, EGR stop, and urea water injection under the control of the electronic control unit (8), and transmit (S305) the detection data of the pair of NOx concentrations (J) (K) detected by the pair of NOx sensors (3) (4) in this function recovery confirmation operation (S303) to the engine diagnosis tool (2) that performs an engine function recovery confirmation diagnosis (S309) for the NOx purification function after NOx sensor replacement based on this detection data.

[0027] The following effects can be obtained with this engine. That is, during the engine function recovery confirmation operation (S303) for the NOx purification function after NOx sensor replacement shown in FIG. 6(B), the exhaust gas is heated up by the DPF regeneration process to stabilize the exhaust gas flow rate, and the urea crystals adhering in the exhaust passage (12c) shown in FIG. 1 are burned off. To increase the NOx concentration by stopping EGR, the accuracy of the detection data of the NOx concentrations (J) and (K) by the pair of NOx sensors (3) and (4) shown in FIG. 6(B) is improved. In this way, by transmitting the pair of highly accurate NOx concentrations (J) and (K) as detection data to the engine diagnostic tool (2), as shown in FIG. 6(A), the engine diagnostic tool (2) can perform a function recovery confirmation diagnosis (S309) of the engine after NOx sensor replacement based on the detection data of the pair of NOx concentrations (J) and (K), and the accuracy of the function recovery confirmation diagnosis (S309) of the engine for the NOx purification function after NOx sensor replacement by the engine diagnostic tool (2) is improved.

[0028] Next, the diagnostic method of the above engine (1) will be described. The diagnosis of this engine (1) is performed in the order of the failure diagnosis (S4) of the engine (1) during normal operation shown in FIG. 3, the failure diagnosis (S108)(S208) of the NOx sensor, the replacement of the NOx sensor based on the confirmation of the NOx sensor failure determination display (S110)(S210) shown in FIGS. 4(A) and 5(A), and the function recovery confirmation diagnosis (S309) of the engine for the NOx purification function after NOx sensor replacement shown in FIG. 6(A).

[0029] First, as shown in FIG. 3, the electronic control unit (8) of the engine (1) causes a failure diagnosis (S4) to be performed on the engine (1) during normal operation based on the NOx purification rate of the SCR (7) during engine operation. When a failure determination (S5) of the engine (1) is made, the failure determination of the engine is displayed (S6) on the display device (1b) of the engine (1), and at the same time, a recommendation for NOx sensor failure diagnosis is displayed.

[0030] Next, when a user who has confirmed the above display (S6) of the display device (1b) of the engine (1) requests a service technician to perform a failure diagnosis of the NOx sensor, the service technician, as shown in FIG. 4(B), causes the engine (1) to perform a NOx sensor failure diagnosis operation (S103) involving DPF regeneration processing, EGR stop, and urea water injection stop under the control of the electronic control unit (8). In this NOx sensor failure diagnosis operation (S103), detection data of a pair of NOx concentrations (J) and (K) detected by a pair of NOx sensors (3) and (4) on the upstream side and the downstream side of the exhaust of the SCR (6) is transmitted (S105) to the engine diagnosis tool (2). As shown in FIG. 4(A), based on the above detection data, the engine diagnosis tool (2) performs a failure diagnosis (S108) of the NOx sensor.

[0031] The following effects can be obtained with this engine diagnosis method. That is, during the NOx sensor failure diagnosis operation (S103) shown in FIG. 4(B), the exhaust gas is heated up by the DPF regeneration process to stabilize the exhaust gas flow rate, and the urea crystals adhering in the exhaust passage (12c) are burned off. Further, since the NOx concentration is increased by stopping the EGR, the accuracy of the detection data of the NOx concentrations (J) and (K) by the pair of NOx sensors (3) and (4) is improved. Moreover, this detection data is not affected by the NOx purification function of the SCR (7) due to the stop of the urea water injection and is difficult to change. By transmitting (S105)(S205) the detection data of the pair of NOx concentrations (J) and (K) that is highly accurate and difficult to change to the engine diagnosis tool (2), as shown in FIG. 4(A), the engine diagnosis tool (2) can perform a failure diagnosis (S108) of the pair of NOx sensors (3) and (4) based on the detection data of the pair of NOx concentrations (J) and (K), and the accuracy of the failure diagnosis (S108) of the pair of NOx sensors (3) and (4) can be improved.

[0032] The following effect can also be obtained with this engine diagnosis method As shown in FIG. 4(A), in order to transmit the detection data of the pair of NOx concentrations (J) and (K) detected by the pair of NOx sensors (3) and (4) in the NOx sensor failure diagnosis operation (S103)(S203) to the engine diagnosis tool (2) outside the engine (1) that performs the failure diagnosis (S108)(S208) of the pair of NOx sensors (3) and (4) based on this detection data, the exhaust device (12) shown in FIG. 1 can be mounted on the engine (1) and the failure diagnosis (S108)(S208) of the NOx sensors (3) and (4) can be performed.

[0033] As shown in FIG. 4(A), in the engine diagnosis tool (2), when the absolute value of the difference between the pair of NOx concentrations (J) and (K) exceeds a predetermined determination threshold value (L), a failure determination (S109) of the NOx sensor is performed, and when the absolute value of the difference is less than or equal to the predetermined determination threshold value (L), a normal determination (S111) of the pair of NOx sensors (3) and (4) is performed.

[0034] As shown in FIG. 4(A), in the engine diagnosis tool (2), corresponding to the failure determination (S109) of the NOx sensor or the normal determination (S111) of the pair of NOx sensors (3) and (4), a failure determination display (S110) of the NOx sensor shown in FIG. 4(A) or a normal determination display (S112) of the pair of NOx sensors (3) and (4) is performed on the tool display unit (2a) of the engine diagnosis tool (2) shown in FIG. 1.

[0035] As shown in FIG. 4(A), when the failure determination display (S110) of the NOx sensor is made, a replacement advice display for one of the NOx sensors and a failure diagnosis advice display for the NOx sensor after replacement of one of the NOx sensors are also made. The service technician who has confirmed this display replaces either one of the pair of NOx sensors (3) and (4) with a NOx sensor that has been confirmed to be normal in advance, and performs the failure diagnosis (S208) of the NOx sensor after replacement of one of the NOx sensors shown in FIG. 5(A). Also, as shown in FIG. 4(A), when the normal determination display (S112) of a pair of NOx sensors (3) and (4) is made, at the same time, an inspection advisory display for components other than the pair of NOx sensors (3) and (4) is also made. The service technician who has confirmed this display inspects sensors such as the SCR inlet side exhaust temperature sensor (7c) and actuators such as the urea water injector (9).

[0036] In response to the failure determination (S119) of the NOx sensors shown in FIG. 4(A), after the NOx sensors are replaced, as shown in FIG. 5(B), under the control of the electronic control unit (8), a NOx sensor failure diagnosis operation (S203) after NOx sensor replacement is performed, which involves DPF regeneration processing, EGR stop, and urea water injection stop. In this NOx sensor failure diagnosis operation (S203), detection data of a pair of NOx concentrations (J) and (K) detected by the pair of NOx sensors (3) and (4) including the replaced NOx sensor (3) is transmitted (S205) to the engine diagnosis tool (2). As shown in FIG. 5(A), based on the above detection data, the engine diagnosis tool (2) performs a failure diagnosis (S208) of the NOx sensors after NOx sensor replacement.

[0037] As shown in FIG. 5(A), in the engine diagnosis tool (2), when the absolute value of the difference between the pair of NOx concentrations (J) and (K) exceeds a predetermined determination threshold value (L), a failure determination (S209) of the non-replaced NOx sensor (4) is performed. When the absolute value of the difference is less than or equal to the predetermined determination threshold value (L), a normal determination (S211) of the pair of replaced and non-replaced NOx sensors (3) and (4) is performed.

[0038] As shown in FIG. 5(A), in the engine diagnosis tool (2), corresponding to the failure determination (S209) of the non-replaced NOx sensor (4) or the normal determination (S311) of the pair of replaced and non-replaced NOx sensors (3) and (4), a failure determination display (S210) of the non-replaced NOx sensor (4) or a normal determination display (S212) of the pair of replaced and non-replaced NOx sensors (3) and (4) is made on the tool display section (2a) of the engine diagnosis tool (2).

[0039] As shown in Fig. 5(A), when a failure determination display (S210) of the NOx sensor is made, a replacement advice display for the other (unreplaced) NOx sensor and a function recovery confirmation diagnosis advice display for the engine after NOx sensor replacement are also made. The service technician who confirmed this display replaces the other (unreplaced) NOx sensor with a NOx sensor that has been previously confirmed to be normal, and performs a function recovery confirmation diagnosis of the engine for the NOx purification function after NOx sensor replacement shown in Fig. 6. Also, as shown in Fig. 5(A), when a normal determination display (S212) of a pair of NOx sensors (3)(4) is made, a function recovery confirmation diagnosis advice display for the engine for the NOx purification function after NOx sensor replacement is also made, and the service technician who confirmed this display performs a function recovery confirmation diagnosis of the engine for the NOx purification function after NOx sensor replacement shown in Fig. 6.

[0040] In response to the failure determination (S109) of the NOx sensor shown in Fig. 4(A) or Fig. 5(A) or the failure determination (S109)(S209) of the unreplaced NOx sensor (4), after the NOx sensor is replaced, as shown in Fig. 6(B), under the control of the electronic control unit (8), the engine (1) is made to perform a function recovery confirmation operation (S303) of the engine after NOx sensor replacement involving DPF regeneration processing, EGR stop, and urea water injection. The detection data of a pair of NOx concentrations (J)(K) detected by a pair of NOx sensors (3)(4) including the replaced NOx sensor in this function recovery confirmation operation (S303) of the engine is transmitted (S305) to the engine diagnostic tool (2). As shown in Fig. 6(A), based on the transmitted data, the engine diagnostic tool (2) is made to perform a function recovery confirmation diagnosis (S309) of the engine for the NOx purification function after NOx sensor replacement.

[0041] As shown in Fig. 6(A), in the engine diagnostic tool (2), when the absolute value of the difference between the theoretical NOx purification rate (E) and the actual NOx purification rate (F) of the SCR (7) calculated based on the detection data of the pair of NOx concentrations (J) (K) is equal to or less than a predetermined determination threshold value (G), an engine function recovery confirmation determination (S310) for the NOx purification function is made. When the absolute value of the difference exceeds the determination threshold value (G), an engine function recovery unconfirmed determination (S312) for the NOx purification function is made.

[0042] As shown in Fig. 6(A), in the engine diagnostic tool (2), corresponding to the engine function recovery confirmation determination (S311) or the engine function recovery unconfirmed determination (S313), a NOx sensor replacement engine function recovery confirmation determination display (S311) or an engine function recovery unconfirmed determination display (S313) is made on the tool display unit (2a) of the engine diagnostic tool (2).

[0043] As shown in Fig. 6(A), when an engine function recovery unconfirmed determination display (S313) for the NOx purification function is made, an inspection advice display for parts other than the pair of NOx sensors (3) (4) is also made. The service technician who has confirmed this display inspects sensors such as the SCR inlet side exhaust temperature sensor (7c) and parts such as the urea water injector (9).

[0044] As shown in Fig. 1, the engine diagnostic tool (2) is a portable information terminal device equipped with an electronic control function such as a notebook personal computer or a tablet, and includes a tool display unit (2a), a failure diagnosis instruction switch (2b), a function recovery confirmation diagnosis instruction switch (2c), and a transmission / reception unit (2d) that transmits and receives data and signals wired or wirelessly between the transmission / reception unit (8a) of the electronic control unit (8) of the engine (1). The tool display unit (2a) can use a liquid crystal display, an organic EL display, etc., similar to the display device (1b) of the engine (1). In this case, on the tool display unit (2a), the failure determination display (S110) (S210) of the NOx sensor and the normal determination display (S112) (S212) of a pair of NOx sensors shown in FIGS. 4(A) and 5(A) can be displayed as character information. Also, a display lamp or an LED can be used for the tool display unit (2a). LED is an abbreviation for light emitting diode. In this case, on the tool display unit (2a), the above display can be discriminatively displayed by lighting, flashing, extinguishing, etc.

[0045] This engine diagnosis method will be described based on the flowcharts shown in FIGS. 3 to 6. FIG. 3 is a flowchart of engine failure diagnosis during normal operation. This failure diagnosis is performed under the control of the electronic control unit (8). In step (S1), the SCR upstream NOx concentration (J), the SCR downstream NOx concentration (K), and other data are input to the input unit of the electronic control unit (8). Other data refers to data necessary for the calculation of the theoretical NOx purification rate (E), the calculation of the actual NOx purification rate (F), and the setting of the determination threshold value (G) described later. Specifically, it refers to the exhaust temperature at the SCR inlet side for estimating the catalyst temperature of the SCR (7), the intake air flow rate for estimating the flow rate of the exhaust gas (15), the injection amount of the urea water (9a) of the urea water injector (9) for estimating the ammonia adsorption amount of the SCR (7), etc.

[0046] In step (S2), the electronic control unit (8) calculates the theoretical NOx purification rate E and the actual NOx purification rate (F) in the calculation unit, and in step (S3), the determination threshold value (G) is set. The determination threshold value (G) is a positive number. In step (S4), when the failure determination condition of the engine (1) is satisfied, the diagnosis unit of the electronic control unit (8) determines the failure of the engine (1) in step (S5). The determination condition for the failure of the engine (1) in step (S4) is that the absolute value of the difference between the theoretical NOx purification rate (E) and the actual NOx purification rate (F) exceeds the determination threshold value (G). In step (S6), the display instruction unit of the electronic control device (8) causes the display device (1b) of the engine (1) to perform a failure determination display (S6) of the engine (1), and also causes a recommendation display for NOx sensor diagnosis to be performed.

[0047] Figure 4 is a flowchart of NOx sensor failure diagnosis (the first time). This NOx sensor failure diagnosis (the first time) is performed by a service technician using an engine diagnosis tool (2) at the request of a user who has confirmed the recommendation display for NOx sensor diagnosis in step (S6) shown in Figure 3 on the display device (1b) of the engine (1).

[0048] In step (S101) shown in Figure 4(A), based on the command operation of the failure diagnosis instruction switch (2b) of the engine diagnosis tool (2) shown in Figure 1 by the service technician, a signal for an NOx sensor failure diagnosis command is transmitted from the diagnosis command unit of the engine diagnosis tool (2). In step (S102) shown in Figure 4(B), when the reception determination unit of the electronic control device (8) of the engine (1) affirms the reception of the signal for the NOx sensor failure diagnosis command, in step (S103), an NOx sensor failure diagnosis operation is performed under the control of the operation control unit of the electronic control device (8). The NOx sensor failure diagnosis operation involves DPF regeneration processing, EGR stop, and urea water injection stop. This DPF regeneration processing, EGR stop, and urea water injection stop are automatically performed by the electronic control device (8) of the engine (1) based on the signal for the NOx sensor failure diagnosis command. In step (S104), the data acquisition unit of the electronic control device (8) of the engine (1) acquires detection data of a pair of SCR upstream NOx concentrations (J) and SCR downstream NOx concentrations (K), and in step (S105), the above pair of detection data is transmitted from the transmission / reception unit (8a) of the electronic control device (8) shown in Figure 1 to the transmission / reception unit (2d) of the engine diagnosis tool (2).

[0049] In step (S106) shown in FIG. 4(A), when it is affirmed by the reception determination unit of the engine diagnostic tool (2) that the pair of detection data has been received, the determination threshold value setting unit of the engine diagnostic tool (2) sets a determination threshold value (L) in step (S107). The determination threshold value (L) is a positive number. In step (S108), the diagnostic unit of the engine diagnostic tool (2) performs a NOx sensor failure diagnosis. The determination condition for NOx sensor failure in the NOx sensor failure diagnosis in step (S108) is that the absolute value of the difference between the detection data of the pair of SCR upstream NOx concentration (J) and SCR downstream NOx concentration (K) exceeds the determination threshold value (L). When this determination condition is satisfied, in step (S109), the failure determination unit of the engine diagnostic tool (2) makes a NOx sensor failure determination. In step (S110), the display instruction unit of the engine diagnostic tool (2) causes the tool display unit (2a) to display a failure determination of the NOx sensor, and also displays an exchange advice for one of the NOx sensors and an advice for diagnosing the failure of the NOx sensor after the replacement of one of the NOx sensors.

[0050] In the NOx sensor failure diagnosis in step (S108) shown in FIG. 4(A), since it is impossible to determine which one of the pair of NOx sensors (3) and (4) is faulty, the exchange advice display for one of the NOx sensors in step (S110) does not specify either of the pair of NOx sensors (3) and (4). In this case, the service technician will arbitrarily select one of the pair of NOx sensors (3) and (4) and replace this one NOx sensor with a NOx sensor that has already been confirmed to be normal. In addition, when it can be predicted that the probability of one of a pair of NOx sensors (3) and (4) failing is high due to the difference in the heat loads received by the pair of NOx sensors, the replacement advice display of one of the NOx sensors in step (S110) may specify the NOx sensor with a high probability of failure among the pair of NOx sensors (3) and (4). In this case, the service technician can replace the specified NOx sensor among the pair of NOx sensors (3) and (4) with a NOx sensor that has already been confirmed to be normal according to the specified advice. The NOx sensor specified in the replacement advice display of one of the NOx sensors in step (S110) may be either of the pair of NOx sensors (3) and (4).

[0051] As shown in FIG. 4(A), when the determination condition for NOx sensor failure is not satisfied in the NOx sensor failure diagnosis in step (S108), that is, when the absolute value of the difference between the detection data of the pair of SCR upstream NOx concentrations (J) and the SCR downstream NOx concentration (K) is equal to or less than the determination threshold value (L), in step (S111), the failure determination unit of the engine diagnostic tool (2) makes a normal determination of the pair of NOx sensors (3) and (4). In step (S112), the display instruction unit of the engine diagnostic tool (2) causes the tool display unit (2a) to display a normal determination of the pair of NOx sensors (3) and (4), and at the same time, display an inspection advice for parts other than the pair of NOx sensors (3) and (4), and advise the service technician to inspect sensors such as the SCR inlet side exhaust temperature sensor (7c) and actuators such as the urea water injector (9).

[0052] FIGS. 5(A) and 5(B) show the flow of NOx sensor failure diagnosis (second time). This NOx sensor failure diagnosis (second time) is performed using the engine diagnostic tool (2) after a service technician who has confirmed the replacement advice display of one of the NOx sensors in step (S110) shown in FIG. 4(A) on the tool display unit (2a) of the engine diagnostic tool (2) replaces one of the NOx sensors with a NOx sensor that has already been confirmed to be normal.

[0053] The NOx sensor fault diagnosis (second time) shown in Fig. 5 is performed in the same procedure as the NOx sensor fault diagnosis (first time) shown in Fig. 4 after replacing one of the pair of NOx sensors in the NOx sensor fault diagnosis (first time) shown in Fig. 4. The processing of steps (S201) to (S212) excluding the advisory display of steps (S210) and (S212) shown in Fig. 5 is the same as the processing of steps (S101) to (S112) with the last two digits of the NOx sensor fault diagnosis (first time) shown in Fig. 4. The displays of steps (S210) and (S212) shown in Fig. 5 differ from the displays of steps (S110) and (S112) shown in Fig. 4(A) in the following points. That is, the display of step (S110) is a fault determination display of the NOx sensor, an advisory display for replacing one NOx sensor, and an advisory display for fault diagnosis of the NOx sensor after replacing one NOx sensor. In contrast, the display of step (S210) is a fault determination display of the NOx sensor and an advisory display for confirmation diagnosis of engine function recovery after NOx sensor replacement. Also, the display of step (S112) is a normal determination display of a pair of NOx sensors and an advisory display for inspecting parts other than the pair of NOx sensors. In contrast, the display of step (S212) is a normal determination display of a pair of NOx sensors and an advisory display for confirmation diagnosis of engine function recovery after NOx sensor replacement.

[0054] The reason for giving an advisory display for replacing the other (unreplaced) NOx sensor in step (S210) is that since one NOx sensor has been replaced with a sensor that has been confirmed to be normal in advance, it is presumed that the NOx sensor fault determination in step (S209) is due to the fault of the other (unreplaced) NOx sensor. Also, the reason for giving an advisory display for confirmation diagnosis of engine function recovery after NOx replacement in step (S210) is that the other (unreplaced) NOx sensor has also been replaced with a NOx sensor that has been confirmed to be normal in advance, and both of the pair of NOx sensors (3) and (4) become normal, and engine function recovery for the NOx purification function after NOx sensor replacement is expected. In addition, the reason for performing the engine recovery confirmation diagnosis advice display after NOx exchange in step (S212) is that it is confirmed by the normal determination of the pair of NOx sensors in step (S211) that both of the pair of NOx sensors (3) and (4) are normal, and engine function recovery for the NOx purification function after NOx sensor exchange is expected.

[0055] Figure 6 is a flow chart of the engine function recovery confirmation diagnosis for the NOx purification function after NOx sensor exchange. This engine function recovery confirmation diagnosis after NOx sensor exchange is usually performed by a service technician using the engine diagnostic tool (2) after confirming the engine function recovery confirmation diagnosis advice display for the NOx purification function after NOx sensor exchange in step (S110) shown in Fig. 4(A) or step (S210)(S212) shown in Fig. 5(A) on the display device (1b) of the engine (1).

[0056] In step (S301) shown in Fig. 6(A), based on the command operation of the engine diagnostic tool (2) by the service technician, a signal of the engine function recovery confirmation diagnosis command is transmitted from the diagnosis command unit of the engine diagnostic tool (2). In step (S302) shown in Fig. 6(B), when the reception determination unit of the electronic control unit (8) of the engine (1) affirms the reception of the signal of the function recovery confirmation diagnosis command, in step (S103), the engine function recovery confirmation operation is performed under the control of the operation control unit of the electronic control unit (8). The NOx sensor failure diagnosis operation involves DPF regeneration processing, EGR stop, and urea water injection. This DPF regeneration processing, EGR stop, and urea water injection stop are automatically performed by the electronic control unit (8) of the engine (1) based on the signal of the engine function recovery confirmation diagnosis command. In step (S304), the data acquisition unit of the electronic control unit (8) of the engine (1) acquires a pair of SCR upstream NOx concentrations (J), SCR downstream NOx concentrations (K), and other detection data, and in step (S305), the above detection data is transmitted from the transmission / reception unit (8a) of the electronic control unit (8) to the transmission / reception unit (2d) of the engine diagnostic tool (2).

[0057] In step (S306) shown in FIG. 6(A), when the reception of the detection data is affirmed by the reception determination unit of the engine diagnostic tool (2), in step (S307), the theoretical NOx purification rate (E) and the actual NOx purification rate (F) are calculated by the calculation unit of the engine diagnostic tool (2), and in step (S308), the determination threshold value (G) is set by the threshold value setting unit of the engine diagnostic tool (2). The determination threshold value (G) is a positive number. In step (S309), the engine diagnostic tool (2) performs a function confirmation diagnosis of the engine in the diagnosis unit. The determination condition for the unconfirmed function recovery of the engine in the function confirmation diagnosis of the engine in step (S309) is that the absolute value of the difference between the theoretical NOx purification rate (E) and the actual NOx purification rate (F) is less than or equal to the determination threshold value (G). When this determination condition is satisfied, in step (S310), the function confirmation determination unit of the engine diagnostic tool (2) makes a function recovery confirmation determination of the engine, and in step (S311), the display instruction unit of the engine diagnostic tool (2) causes the tool display unit (2a) to display the function recovery confirmation determination of the engine. When the function confirmation determination unit of the engine diagnostic tool (2) makes a function recovery confirmation determination in step (S310), the output limit of the engine (1) is released by the electronic control unit (8) of the engine (1).

[0058] As shown in FIG. 6(A), in the function recovery confirmation diagnosis of the engine in step (S309), when the determination condition for the function recovery confirmation of the engine is not satisfied, that is, when the absolute value of the difference between the theoretical NOx purification rate (E) and the actual NOx purification rate (F) exceeds the determination threshold value (G), in step (S312), the failure determination unit of the engine diagnostic tool (2) makes an unconfirmed function recovery determination of the engine, and in step (S313), the display instruction unit of the engine diagnostic tool (2) causes the tool display unit (2a) to display the unconfirmed function recovery determination of the engine and also displays an inspection advice for components other than the pair of NOx sensors (3)(4).

[0059] When diagnosing the failure of a pair of NOx sensors (3) and (4) or confirming the function recovery of the engine's NOx purification function after replacing the NOx sensors, if the user can use the engine diagnostic tool (2), the user can also perform the diagnosis by themselves.

Description of symbols

[0060] (1)…Engine, (2)…Engine diagnostic tool, (2a)…Tool display section, (3)…NOx sensor on the upstream side of the exhaust, (4)…NOx sensor on the downstream side of the exhaust, (5)…EGR device, (6)…DPF, (7)…SCR, (8)…Electronic control device, (9)…Urea water injector, (E)…Theoretical purification rate, (F)…Actual purification rate, (G)…Judgment threshold, (J)…NOx concentration on the upstream side of SCR, (K)…NOx concentration on the downstream side of SCR, (L)…Judgment threshold, (S103)…NOx sensor failure diagnosis operation, (S105)…Transmit detection data to the engine diagnostic tool, (S108)…Failure diagnosis of the NOx sensor, (S109)…Failure judgment of the NOx sensor, (S110)…Failure judgment display of the NOx sensor, (S111)…Normal judgment of a pair of NOx sensors, (S112)…Normal judgment display of a pair of NOx sensors, (S203)…NOx sensor failure diagnosis operation after replacing the NOx sensor, (S205)…Transmit detection data to the engine diagnostic tool, (S208)…Failure diagnosis of the NOx sensor after replacing the NOx sensor, (S209)…Failure judgment of the non-replaced NOx sensor, (S210)…Failure judgment display of the non-replaced NOx sensor, (S211)…Normal judgment of a pair of replaced and non-replaced NOx sensors, (S212)…Normal judgment display of a pair of replaced and non-replaced NOx sensors, (S303)…Function recovery confirmation operation of the engine after replacing the NOx sensor, (S305)…Transmission, (S309)…Function recovery confirmation diagnosis of the engine, (S310)…Function recovery confirmation judgment of the engine, (S311)…Function recovery unconfirmed judgment display of the engine, (S312)…Function recovery unconfirmed judgment of the engine, (S313)…Function recovery unconfirmed judgment display of the engine.

Claims

1. An engine comprising a DPF, an SCR, a pair of NOx sensors on the upstream and downstream sides of the exhaust of the SCR, an electronic control unit, an EGR device, and a urea water injector, configured to perform a NOx sensor failure diagnosis operation involving DPF regeneration processing, EGR stop, and urea water injection stop under the control of the electronic control unit, and transmit detection data of a pair of NOx concentrations detected by the pair of NOx sensors in this NOx sensor failure diagnosis operation to an engine diagnosis tool outside the engine for performing a failure diagnosis of the pair of NOx sensors based on this detection data.

2. In the engine according to Claim 1, configured to perform an engine function recovery confirmation operation for the NOx purification function after NOx sensor replacement involving DPF regeneration processing, EGR stop, and urea water injection under the control of the electronic control unit, and transmit detection data of a pair of NOx concentrations detected by the pair of NOx sensors in this function recovery confirmation operation to the engine diagnosis tool for performing a function recovery confirmation diagnosis of the engine for the NOx purification function after NOx sensor replacement based on this detection data.

3. Under the control of the electronic control unit, cause the engine to perform a NOx sensor failure diagnosis operation involving DPF regeneration processing, EGR stop, and urea water injection stop, and transmit detection data of a pair of NOx concentrations detected by a pair of NOx sensors on the upstream and downstream sides of the exhaust of the SCR in this NOx sensor failure diagnosis operation to the engine diagnosis tool, and cause the engine diagnosis tool to perform a failure diagnosis of the NOx sensor based on the above detection data.

4. In the engine diagnosis method according to Claim 3, in the engine diagnosis tool, when the absolute value of the difference between the pair of NOx concentrations exceeds a predetermined determination threshold, perform a failure determination of the NOx sensor, and when the absolute value of the difference is equal to or less than the predetermined determination threshold, perform a normal determination of the pair of NOx sensors.

5. In the engine diagnosis method according to Claim 4, in the engine diagnosis tool, corresponding to the failure determination of the NOx sensor or the normal determination of the pair of NOx sensors, cause a failure determination display of the NOx sensor or a normal determination display of the pair of NOx sensors to be performed on the tool display unit of the engine diagnosis tool.

6. In the engine diagnostic method according to claim 4, in response to the failure determination of the NOx sensor, after the NOx sensor is replaced, under the control of the electronic control unit, a NOx sensor failure diagnosis operation after NOx sensor replacement involving DPF regeneration processing, EGR stop, and urea water injection stop is performed. In this NOx sensor failure diagnosis operation, detection data of a pair of NOx concentrations detected by the pair of NOx sensors including the replaced NOx sensor is transmitted to the engine diagnostic tool, and based on the above detection data, the engine diagnostic tool performs a failure diagnosis of the NOx sensor after NOx sensor replacement. This is the engine diagnostic method characterized by this.

7. In the engine diagnostic method according to claim 6, in the engine diagnostic tool, when the absolute value of the difference between the pair of NOx concentrations exceeds a predetermined determination threshold value, a failure determination of the non-replaced NOx sensor is performed. When the absolute value of the difference is less than or equal to the predetermined determination threshold value, a normal determination of the pair of replaced and non-replaced NOx sensors is performed. This is the engine diagnostic method characterized by this.

8. In the engine diagnostic method according to claim 7, in the engine diagnostic tool, corresponding to the failure determination of the non-replaced NOx sensor or the normal determination of the pair of replaced and non-replaced NOx sensors, a failure determination display of the non-replaced NOx sensor or a normal determination display of the pair of replaced and non-replaced NOx sensors is performed on the tool display unit of the engine diagnostic tool. This is the engine diagnostic method characterized by this.

9. In the engine diagnostic method according to claim 4 or claim 7, in response to the failure determination of the NOx sensor or the failure determination of the non-replaced NOx sensor, after the NOx sensor is replaced, under the control of the electronic control unit, a function recovery confirmation operation of the engine for the NOx purification function after NOx sensor replacement involving DPF regeneration processing, EGR stop, and urea water injection into the engine is performed. In this function recovery confirmation operation of the engine, detection data of a pair of NOx concentrations detected by the pair of NOx sensors including the replaced NOx sensor is transmitted to the engine diagnostic tool, and based on the transmitted data, the engine diagnostic tool performs a function recovery confirmation diagnosis of the engine for the NOx purification function after NOx sensor replacement. This is the engine diagnostic method characterized by this.

10. In the engine diagnostic method according to claim 9, In the engine diagnostic tool, when the absolute value of the difference between the theoretical NOx purification rate and the actual NOx purification rate of the SCR calculated based on the detection data of the pair of NOx concentrations is equal to or less than a predetermined determination threshold value, a determination is made as to whether the function of the engine has been restored with respect to the NOx purification function. When the absolute value of the difference exceeds the determination threshold value, a determination is made that the function of the engine has not been restored with respect to the NOx purification function. A method for diagnosing an engine, characterized by this.

11. In the method for diagnosing an engine according to Claim 10, In the engine diagnostic tool, corresponding to the determination of whether the function of the engine has been restored or the determination that the function of the engine has not been restored, a display indicating that the function of the engine has been restored or a display indicating that the function of the engine has not been restored after the NOx sensor is replaced is performed on the tool display unit of the engine diagnostic tool. A method for diagnosing an engine, characterized by this.

Images