JP4844454B2 - EGR device for engine - Google Patents

Description

  The present invention relates to an EGR device for an engine equipped with an EGR gas cooling system that performs a large amount of EGR (exhaust gas recirculation).

  EGR gas cooling has become an indispensable technology as a technology corresponding to recent strict exhaust gas regulations. In general, the EGR gas is cooled by providing an EGR cooler in an EGR passage that connects the exhaust passage and the intake passage of the engine, and flowing cooling water through the EGR cooler.

  In order to cool a larger amount of EGR gas more efficiently and supply it to the engine, the EGR cooler tends to be larger. The EGR gas cooling system 14 shown in FIG. 1 uses a separate EGR cooling water pump 2 (such as an electric pump) to cool the cooling water at the cooling water outlet 2a of the radiator 2 where the cooling water temperature is lowest. The EGR cooler 13 is an EGR coolant channel that is independent of the engine coolant channel and returns the coolant that has passed through the EGR cooler 13 to the coolant inlet 2b of the radiator 2, and a large amount of coolant having a low water temperature can be passed through the EGR cooler 13. It is the most effective EGR gas cooling system for cooling EGR gas.

  By the way, if the EGR cooler is used for a long time, the inside of the EGR cooler may be contaminated by soot or the like in the EGR gas. When this happens, the efficiency of cooling the EGR gas (cooling capacity of the EGR cooler) due to soot accumulated in the EGR cooler decreases, the temperature of the EGR gas recirculated to the intake passage of the engine with respect to the initial stage rises, and the combustion temperature There is a risk that the engine performance will be reduced due to the deterioration of the engine and the decrease in the amount of fresh air.

  Therefore, in recent years, a method for detecting a decrease in the cooling capacity of the EGR cooler due to the contamination of the EGR cooler has been proposed (see Patent Document 1).

  For example, in Patent Document 1, the gas temperature at the gas outlet of the EGR cooler is measured, and when the measured gas temperature is higher than the normal gas temperature estimated from the engine operating state or the like, the cooling capacity of the EGR cooler decreases. A method for detecting this has been proposed. Patent Document 1 discloses that when a decrease in the cooling capacity of the EGR cooler is detected, the inside of the EGR cooler is temporarily heated to a high temperature, so that the soot accumulated in the EGR cooler is oxidized and removed to restore the cooling capacity. Is disclosed.

JP 2003-336549 A

  By the way, in the EGR gas cooling system 14 shown in FIG. 1, the cause of the malfunction of the EGR gas cooling system 14 in which the temperature of the EGR gas recirculated to the intake passage of the engine rises as compared with the normal temperature is as described above. As described above, there are mainly considered to be due to a decrease in the cooling capacity of the EGR cooler 13 due to the contamination inside the EGR cooler 13 and due to a decrease in the capacity (suction capacity or discharge capacity) of the EGR cooling water pump 12.

  When a malfunction of the EGR gas cooling system 14 detected by the increase in soot has occurred, the cause of the malfunction has already been due to a decrease in the cooling capacity of the EGR cooler 13 due to contamination inside the EGR cooler 13, or the EGR cooling Since it is not possible to determine whether the water pump 12 is caused by a decrease in capacity, it is necessary to replace both the EGR cooler 13 and the EGR cooling water pump 12, which increases repair costs.

  If the cause of the malfunction can be identified at the initial stage when the malfunction occurs, maintenance or replacement of only one of the EGR cooler 13 and the EGR cooling water pump 12 having the malfunction is sufficient, so that unnecessary repair costs can be suppressed.

  However, at present, the malfunction of the EGR gas cooling system 14 is caused by a decrease in the cooling capacity of the EGR cooler 13 due to contamination inside the EGR cooler 13 or a decrease in the capacity of the EGR cooling water pump 12 at the initial stage. There is no device that can determine whether or not.

  Accordingly, an object of the present invention is to specify whether the malfunction of the EGR gas cooling system is due to a decrease in the cooling capacity of the EGR cooler or a decrease in the capacity of the EGR cooling water pump.

  In order to achieve the above object, the present invention provides an EGR cooling water passage for flowing cooling water from a cooling water outlet side of a radiator to a cooling water inlet side of the radiator, and an EGR cooling water pump disposed in the EGR cooling water passage. In an EGR device for an engine equipped with an EGR gas cooling system having an EGR cooler disposed in the EGR cooling water passage on the cooling water inlet side of the radiator from the EGR cooling water pump, a gas outlet of the EGR cooler Abnormality detection for detecting abnormality of the EGR gas cooling system based on gas temperature detection means for detecting gas temperature, engine rotation speed detection means for detecting engine rotation speed, and gas temperature detected by the gas temperature detection means And the EGR gas detected by the abnormality detecting means based on the engine speed when the abnormality detecting means determines that the abnormality is detected. Abnormalities 却系 is, in which a cause identifying unit configured to identify whether by reduced cooling capability ones or the EGR cooler due to reduced capacity of the EGR coolant pump.

  Here, a cooling water temperature detecting means for detecting the water temperature of the cooling water flowing through the EGR cooler is provided, and the abnormality detecting means is configured such that the gas temperature detected by the gas temperature detecting means is predetermined from the water temperature detected by the cooling water temperature detecting means. When the temperature is higher than the temperature, it may be determined to be abnormal.

  Further, the cause identifying means integrates the number of abnormality detections determined to be abnormal by the abnormality detection means, and the number of abnormality detections accumulated when the engine speed is within a predetermined low rotation range is a predetermined first specified value. If the abnormality detection count accumulated when the engine speed is within the predetermined high rotation range is equal to or greater than the predetermined second specified count, the abnormality of the EGR gas cooling system detected by the abnormality detection means is It is specified that the EGR cooling water pump has a reduced capacity, and the accumulated number of times of abnormality detection when the engine rotation speed is within the predetermined low rotation range is greater than or equal to the predetermined first specified number and the engine rotation speed is the predetermined When the number of abnormality detections accumulated when in the high rotation region is equal to or greater than the predetermined second specified number, the abnormality of the EGR gas cooling system detected by the abnormality detection means is Been made to identify those due to reduced cooling capability of the cooler may be.

  According to the present invention, there is an excellent effect that it is possible to specify whether the malfunction of the EGR gas cooling system is due to a decrease in the cooling capacity of the EGR cooler or a decrease in the capacity of the EGR cooling water pump.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic view of an engine to which an EGR device according to an embodiment of the present invention is applied.

  The engine according to this embodiment is a diesel engine mounted on a vehicle.

  As shown in FIG. 1, the engine includes an engine body 1, and an exhaust passage and an intake passage (not shown) are connected to the engine body 1. The engine main body 1 and the cooling water outlet 2 a of the radiator 2 are connected by an engine cooling water supply pipe 3 that forms an engine cooling water supply water passage. The cooling water cooled by the radiator 2 is in the middle of the engine cooling water supply pipe 3. And is supplied to the engine main body 1 through the engine cooling water supply pipe 3. The engine main body 1 and the cooling water inlet 2b of the radiator 2 are connected by an engine cooling water return pipe 5 that forms an engine cooling water return water passage, and the cooling water discharged from the engine main body 1 is sent to the engine cooling water return pipe. 5 is returned to the radiator 2. In this embodiment, the engine coolant pump 4 is connected to the crankshaft of the engine body 1 and is driven by the rotation of the crankshaft.

  The engine cooling water return pipe 5 and the engine cooling water supply pipe 3 are connected by a bypass pipe 6 that forms a bypass water channel. The bypass pipe 6 is discharged from the engine body 1 at the inlet of the engine cooling water return pipe 5 side. When the temperature of the cooling water flowing through the engine cooling water return pipe 5 is lower than a predetermined temperature (for example, 70 ° C.), the cooling water is not returned to the radiator 2 but from the engine cooling water return pipe 5 through the bypass pipe 6. A thermostat 7 for flowing through the engine coolant supply pipe 3 is provided. Therefore, in the engine according to the present embodiment, when the temperature of the cooling water flowing through the engine cooling water return pipe 5 is lower than the predetermined temperature, the thermostat 7 is automatically closed, and the engine main body 1 is not returned to the radiator 2 without returning the cooling water. Just to circulate.

  The EGR apparatus 10 according to the present embodiment includes an EGR cooling water channel 11 that flows cooling water from the cooling water outlet 2a side of the radiator 2 to the cooling water inlet 2b side of the radiator 2, and an EGR disposed in the middle of the EGR cooling water channel 11. An EGR gas cooling system 14 having a cooling water pump 12 and an EGR cooler 13 disposed in the EGR cooling water passage 11 closer to the cooling water inlet 2b of the radiator 2 than the EGR cooling water pump 12 is provided.

  The EGR cooling water channel 11 is closer to the cooling water outlet 2a side of the radiator 2 than the connection part with the bypass pipe 6 and closer to the cooling water inlet 2b side of the radiator 2 than the connection part with the bypass pipe 6. An EGR cooling water pipe 15 connected to the engine cooling water return pipe 5 is provided, and an EGR cooling water pump 12 and an EGR cooler 13 are provided in the middle of the EGR cooling water pipe 15. In the present embodiment, an electric pump with a high discharge pressure specification is used as the EGR cooling water pump 12.

  As the EGR cooler 13, a known configuration can be used. In the present embodiment, as the EGR cooler 13, a counter flow type is used in which the cooling water flows in the opposite direction to the cooling water path in the EGR cooler 13 with respect to the EGR gas flowing in the gas path in the EGR cooler 13. . An EGR passage 16 that connects the exhaust passage and the intake passage of the engine body 1 is connected to the gas inlet / outlet of the EGR cooler 13.

  In the EGR device 10 according to the present embodiment, when the temperature of the cooling water flowing through the engine cooling water return pipe 5 becomes equal to or higher than a predetermined temperature, the thermostat 7 is opened, and a pipe portion (engine cooling water near the cooling water outlet 2a of the radiator 2) is opened. The supply pipe 3) is shared by the engine body 1 side (engine coolant pump 4) and the EGR cooler 13 side (EGR coolant pump 12). As a result, as the engine speed increases, the amount of cooling water supplied to the engine body 1 increases, so that the suction negative pressure of the EGR cooling water pump 12 increases. Therefore, the EGR device 10 according to the present embodiment has a characteristic that the amount of cooling water flowing through the EGR cooler 13 decreases as the engine speed increases.

  By the way, when the capacity of the EGR cooling water pump 12 is reduced, the amount of cooling water supplied to the EGR cooler 13 by the EGR cooling water pump 12 is reduced. In particular, the EGR device 10 according to the present embodiment has a maximum torque point (for example, Since the amount of cooling water flowing through the EGR cooler 13 is reduced in a high rotation range of 2000 rpm or more, the influence of the reduction in the capacity of the EGR cooling water pump 12 becomes significant in the high rotation range of the engine. Therefore, as shown in FIG. 3, the gas temperature at the gas outlet of the EGR cooler 13 rises only in the high rotation region above the maximum torque point Nt of the engine during the early period when the capacity of the EGR cooling water pump 12 is lowered.

  If the EGR cooling water pump 12 having a reduced capacity is continuously used, soot is generated in the high rotation region of the engine and the inside of the EGR cooler 13 is contaminated. Therefore, the gas outlet of the EGR cooler 13 The gas temperature starts to rise even in a low rotation region below the maximum torque point Nt of the engine.

  On the other hand, when the cooling capacity of the EGR cooler 13 is reduced due to contamination inside the EGR cooler 13, the gas temperature at the gas outlet of the EGR cooler 13 does not depend on the engine rotation speed, and the entire engine rotation range (low rotation range). And high rotation range).

  Therefore, by detecting the gas temperature at the gas outlet of the EGR cooler 13 in the low rotation region and high rotation region of the engine, respectively, and comparing the detected gas temperature with the normal gas temperature estimated from the engine operating state and the like. It has been found that the abnormality of the EGR gas cooling system 14 due to the decrease in the capacity of the EGR cooling water pump 12 and the abnormality of the EGR gas cooling system 14 due to the decrease in the cooling capacity of the EGR cooler 13 can be detected separately.

  The EGR device 10 is based on a gas temperature detecting means for detecting the gas temperature at the gas outlet of the EGR cooler 13, an engine speed detecting means for detecting the engine speed, and a gas temperature detected by the gas temperature detecting means. , An abnormality detecting means for determining an abnormality of the EGR gas cooling system 14, and an EGR detected by the abnormality detecting means based on the engine rotational speed detected by the engine rotational speed detecting means when the abnormality detecting means is determined to be abnormal A cause identifying means for identifying whether the abnormality of the gas cooling system is due to a decrease in the capacity of the EGR cooling water pump 12 or a decrease in the cooling capacity of the EGR cooler 13 due to contamination inside the EGR cooler 13; ing.

  Further, the EGR device 10 includes a cooling water temperature detecting means for detecting the temperature of the cooling water flowing through the EGR cooler 13.

  In the present embodiment, the gas temperature detection means includes a gas temperature sensor 17 provided in the EGR passage 16 near the gas outlet of the EGR cooler 13. The gas temperature sensor 17 is electrically connected to the computer 18, and a detection signal (gas temperature signal Tegr) from the gas temperature sensor 17 is input to the computer 18.

  In the present embodiment, the engine rotation speed detection means includes an engine rotation speed sensor 19 provided in the engine body 1. The engine rotation speed sensor 19 is electrically connected to the computer 18, and a detection signal (engine rotation speed signal Nrpm) from the engine rotation speed sensor 19 is input to the computer 18.

  In the present embodiment, the cooling water temperature detecting means detects the water temperature at the cooling water inlet of the EGR cooler 13, and the cooling water temperature sensor 20 provided in the EGR cooling water pipe 15 near the cooling water inlet of the EGR cooler 13. Consists of. The cooling water temperature sensor 20 is electrically connected to the computer 18, and a detection signal (water temperature signal Tw) from the cooling water temperature sensor 20 is input to the computer 18.

  As shown in FIGS. 2 and 3, in the present embodiment, the computer 18 serves as the abnormality detection means described above, and the computer 18 has an engine rotational speed Nrpm detected by the engine rotational speed sensor 19 equal to or lower than the engine maximum torque point Nt. Is within the low rotation range (N1 <Nrpm <N2), the gas temperature Tegr at the gas outlet of the EGR cooler 13 detected by the gas temperature sensor 17 is a predetermined first temperature from the water temperature Tw detected by the cooling water temperature sensor 20. When it is higher than ΔTw1 (for example, 5 ° C.) (Tegr> Tw + ΔTw1), it is determined that the EGR gas cooling system 14 is abnormal.

  Further, the computer 18 detects the gas temperature sensor 17 when the engine rotation speed Nrpm detected by the engine rotation speed sensor 19 is in a high rotation region (N3 <Nrpm <N4) equal to or higher than the maximum torque point Nt of the engine. When the gas temperature Tegr at the gas outlet of the EGR cooler 13 is higher than the water temperature Tw detected by the cooling water temperature sensor 20 by a predetermined second temperature ΔTw2 (for example, 10 ° C.) (ΔTw2> ΔTw1) or more (Tegr> Tw + ΔTw2). It is determined that the cooling system 14 is abnormal.

  Since the first temperature ΔTw1 and the second temperature ΔTw2 are different depending on the target engine system, they are obtained by experiments or the like.

  In the present embodiment, when the computer 18 serves as the cause identifying means described above, and the computer 18 determines that there is an abnormality in the EGR gas cooling system 14 (Tegr> Tw + ΔTw1 or Tegr> Tw + ΔTw2), the engine rotational speed sensor 19 When the detected engine speed Nrpm is within the low engine speed range (N1 <Nrpm <N2), the low rotation abnormality detection count WL is integrated, and the engine speed Nrpm detected by the engine speed sensor 19 is When it is in the high rotation region (N3 <Nrpm <N4), the high rotation abnormality detection count WH is integrated.

  In the present embodiment, the abnormality determination of the EGR gas cooling system 14 in the low engine speed range is not performed in the entire region below the maximum torque point Nt, but within a predetermined range N1 (for example, 1600 rpm) -N2 (for example, 1800 rpm). ing. In addition, the abnormality determination of the EGR gas cooling system 14 in the high engine speed range is not performed over the entire region above the maximum torque point Nt, but within a predetermined range N3 (for example, 2200 rpm) -N4 (for example, 2400 rpm).

  Further, the computer 18 is configured such that the accumulated low rotation abnormality detection number WL is less than a predetermined first specified number (for example, 50 times) and the accumulated high rotation abnormality detection number WH is a predetermined second specified number (for example, 100 times) or more. In this case (WL <50 and WH ≧ 100), it is specified that the detected abnormality of the EGR gas cooling system 14 is due to a decrease in the capability of the EGR cooling water pump 12.

  On the other hand, when the integrated low rotation abnormality detection number WL is not less than the predetermined first specified number and the integrated high rotation abnormality detection number WH is not less than the predetermined second specified number (WL ≧ 50 and WH ≧ 100). ) Specifies that the detected abnormality of the EGR gas cooling system 14 is due to a decrease in the cooling capacity of the EGR cooler 13 due to contamination inside the EGR cooler 13.

  Further, the computer 18 determines that the integrated low rotation abnormality detection number WL is less than the predetermined first specified number and the integrated high rotation abnormality detection number WH is less than the predetermined second specified number (WL <50 and WH <100). Even in such a case, if the gas temperature Tegr at the gas outlet of the EGR cooler 13 detected by the gas temperature sensor 17 is higher than a predetermined temperature Tth (eg, 120 ° C.), it is determined that the gas path in the EGR cooler 13 is clogged. To do. Since the gas path in the EGR cooler 13 is rapidly fouled or clogged, it is desirable to issue a warning without providing a specified number of times for determining whether fouling or clogging, or to issue a warning with a small specified number of times. In the present embodiment, a warning is issued by a single determination without providing a specified number of times.

  Furthermore, the EGR device 10 includes warning means that can be operated by the computer 18, and the computer 18 operates the warning means when the cause of the abnormality of the EGR gas cooling system 14 is specified.

  In the present embodiment, the warning means includes a warning display device 21 provided in a driver's seat or the like. When the computer 18 specifies that the abnormality of the EGR gas cooling system 14 is due to the decrease in the capacity of the EGR cooling water pump 12, the computer 18 operates the warning display device 21 to give a warning display of “EGR cooling water pump malfunction”, When it is specified that the abnormality of the EGR gas cooling system 14 is due to a decrease in the cooling capacity of the EGR cooler 13 due to the contamination inside the EGR cooler 13, the warning display device 21 is operated to give a warning display of "EGR cooler malfunction" The driver is prompted to perform maintenance / replacement of the EGR cooling water pump 12 and maintenance / replacement of the EGR cooler 13. When the computer 18 determines that the gas path in the EGR cooler 13 is clogged, the computer 18 operates the warning display device 21 to display a warning message “Clogged EGR cooler gas path”. In the present embodiment, the warning display device 21 is used as the warning means. However, other means such as a lamp or a buzzer may be used, or a plurality of means may be used in combination.

  In short, the EGR device 10 according to the present embodiment has a characteristic that when the capacity of the EGR cooling water pump 12 is reduced, the amount of cooling water flowing to the EGR cooler 13 is reduced in the high rotation region of the engine. By detecting the gas temperature at the gas outlet of the EGR cooler 13 in the rotation region and the high rotation region, and comparing the detected gas temperature with the normal gas temperature estimated from the engine operating condition etc. Among them, whether the malfunction of the EGR gas cooling system 14 is due to a decrease in the capacity of the EGR cooling water pump 12 or a decrease in the cooling capacity of the EGR cooler 13 due to contamination inside the EGR cooler 13 is specified. Is possible.

  Since the abnormality detection and cause identification described above are executed by the computer 18, the processing contents executed by the computer 18 will be described using the flowchart of FIG. This processing flow is executed by the computer 18 from engine start (step S1) to engine stop.

  First, in step S2, the low rotation abnormality detection count WL and the high rotation abnormality detection count WH, which are the cause identification criteria, are read from the memory. Here, the low rotation abnormality detection number WL and the high rotation abnormality detection number WH read from the memory indicate the number of times that an abnormality has been determined in the low rotation region and high rotation region of the engine before the previous engine operation, respectively.

  Next, in step S3, the timer T1 is started, and measurement / abnormality detection / cause determination is started for one minute from the timer T1 start (engine start) (because it is unstable immediately after the engine start), and one minute from the timer T1 start. When the time has elapsed (T1> 60 sec), the timer T1 is reset, and measurement / abnormality detection / cause identification is started.

  In this processing flow, after performing measurement / abnormality detection / cause identification for 20 seconds using the timer T2 (steps S6, S7, S8), the process returns to step S3 to stop measurement / abnormality detection / cause identification for one minute. To do.

  In step S9, the coolant temperature sensor 20 measures the water temperature Tw at the coolant inlet of the EGR cooler 13, the gas temperature sensor 17 measures the gas temperature Tegr at the gas outlet of the EGR cooler 13, and the engine speed sensor 19 rotates the engine. Measure the speed Nrpm.

  In step S10, it is determined whether or not the engine rotation speed Nrpm measured by the engine rotation speed sensor 19 is in the low rotation region (N1 <Nrpm <N2). If the decision result in the step S10 is YES, the process proceeds to a step S12, and if NO, the process proceeds to a step S11, and whether or not the engine rotation speed Nrpm measured by the engine rotation speed sensor 19 is in the high rotation region (N3). <Nrpm <N4) is determined. If the determination result in step S11 is YES, the process proceeds to step S13. If NO, the process returns to step S7. If it is within the measurement time (T2 <20 sec in this embodiment), the measurement / abnormality detection / cause is repeated. Perform identification.

  If the decision result in the step S10 is YES, in a step S12, is the gas temperature Tegr at the gas outlet of the EGR cooler 13 measured by the gas temperature sensor 17 higher than the water temperature Tw measured by the cooling water temperature sensor 20 by the first temperature ΔTw1 or more? It is determined whether or not (Tegr> Tw + ΔTw1). If the determination result in step S12 is YES, it is determined that there is an abnormality and the process proceeds to step S14. If NO, it is determined that there is no abnormality and the process returns to step S7.

  If the decision result in the step S11 is YES, in a step S13, is the gas temperature Tegr at the gas outlet of the EGR cooler 13 measured by the gas temperature sensor 17 higher than the water temperature Tw measured by the cooling water temperature sensor 20 by the second temperature ΔTw2 or more? It is determined whether or not (Tegr> Tw + ΔTw2). If the determination result in step S13 is YES, it is determined that there is an abnormality and the process proceeds to step S15. If NO, it is determined that there is no abnormality and the process returns to step S7.

  If the decision result in the step S12 is YES, in the step S14, 1 is added to the low rotation abnormality detection number WL (WL = WL + 1), and in the step S16, the low rotation abnormality detection number WL in the memory is replaced. move on.

  If the decision result in the step S13 is YES, in the step S15, 1 is added to the high rotation abnormality detection number WH (WH = WH + 1), and in the step S17, the high rotation abnormality detection number WH in the memory is replaced. move on.

  In step S18, it is determined whether or not the low rotation abnormality detection number WL is less than the first prescribed number and the high rotation abnormality detection number WH is less than the second prescribed number (WL <50 and WH <100). If the determination result in step S18 is YES, the process proceeds to step S23. If NO, the process proceeds to step S19, where the low rotation abnormality detection number WL is less than the first specified number and the high rotation abnormality detection number WH is the second specified number. It is determined whether or not the number is greater than or equal to the number of times (WL <50 and WH ≧ 100).

  If the decision result in the step S19 is YES, in a step S21, the warning display device 21 is operated to display a warning message “EGR cooling water pump malfunction”, and the process returns to the step S7, whereas if NO, the process goes to a step S20. move on.

  In step S20, it is determined whether or not the low rotation abnormality detection count WL is equal to or greater than the first specified count and the high rotation abnormality detection count WH is equal to or greater than the second specified count (WL ≧ 50 and WH ≧ 100).

  If the decision result in the step S20 is YES, in a step S22, the warning display device 21 is operated to give an “EGR cooler malfunction” warning display, and the process returns to the step S7, whereas if NO, the process returns to the step S7.

  In step S23, it is determined whether or not the gas temperature Tegr at the gas outlet of the EGR cooler 13 measured by the gas temperature sensor 17 is higher than a predetermined temperature Tth (Tegr> 120 ° C.).

  If the decision result in the step S23 is YES, in a step S24, the warning display device 21 is operated to give a warning display of “clogged EGR cooler gas path”, and the process returns to the step S7. Return.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various other embodiments can be adopted.

  For example, in the above-described embodiment, as the EGR cooler 13, the counterflow type in which the cooling water flows in the opposite direction to the cooling water path in the EGR cooler 13 with respect to the flow direction of the EGR gas flowing in the gas path in the EGR cooler 13. However, the EGR cooler 13 is not limited to this, and as the EGR cooler 13, the cooling water path in the EGR cooler 13 with respect to the flow direction of the EGR gas in which the cooling water flows through the gas path in the EGR cooler 13. A forward flow type that flows in the same direction may be used. In that case, the cooling water temperature detecting means (cooling water temperature sensor 20) detects the water temperature at the cooling water outlet of the EGR cooler 13, and the first temperature ΔTw1 and the second temperature ΔTw2 (ΔTw2> ΔTw1) are: Since it differs depending on the target engine system, it is obtained by experiments.

1 is a schematic view of an engine to which an EGR device according to an embodiment of the present invention is applied. It is a process flowchart which a computer performs. It is a graph which shows the change of the gas temperature of the gas exit of an EGR cooler when the capability of an EGR cooling water pump falls.

Explanation of symbols

2 Radiator 2a Cooling water outlet 2b Cooling water inlet 10 EGR device 11 EGR cooling water channel 12 EGR cooling water pump 13 EGR cooler 14 EGR gas cooling system 17 Gas temperature sensor (gas temperature detecting means)
18 Computer (Abnormality detection means, cause identification means)
19 Engine rotation speed sensor (Engine rotation speed detection means)
20 Cooling water temperature sensor (cooling water temperature detection means)

Claims (3)

An EGR cooling water passage for flowing cooling water from the cooling water outlet side of the radiator to the cooling water inlet side of the radiator, an EGR cooling water pump disposed in the EGR cooling water passage, and cooling of the radiator more than the EGR cooling water pump In an engine EGR device equipped with an EGR gas cooling system having an EGR cooler disposed in the EGR cooling water channel on the water inlet side,
Gas temperature detection means for detecting the gas temperature at the gas outlet of the EGR cooler, engine rotation speed detection means for detecting the engine rotation speed,
An abnormality detecting means for performing abnormality determination of the EGR gas cooling system based on the gas temperature detected by the gas temperature detecting means;
Based on the engine speed when the abnormality detecting means determines that an abnormality has occurred, the abnormality of the EGR gas cooling system detected by the abnormality detecting means is due to a decrease in the performance of the EGR cooling water pump or the EGR cooler. An engine EGR device comprising a cause identifying means for identifying whether the cooling capacity is reduced. Cooling water temperature detecting means for detecting the temperature of the cooling water flowing through the EGR cooler,
2. The engine EGR device according to claim 1, wherein the abnormality detection unit determines that an abnormality occurs when a gas temperature detected by the gas temperature detection unit is higher than a water temperature detected by the cooling water temperature detection unit by a predetermined temperature or more. The cause identifying means is
Accumulating the number of abnormality detections determined as abnormal by the abnormality detection means, and
When the engine rotation speed is within a predetermined low rotation range, the number of abnormality detections integrated is less than a predetermined first specified number and when the engine rotation speed is within a predetermined high rotation range, If more than two specified times, specify that the abnormality of the EGR gas cooling system detected by the abnormality detection means is due to a decrease in capacity of the EGR cooling water pump,
The number of abnormality detections accumulated when the number of abnormality detections accumulated when the engine rotation speed is within the predetermined low rotation range is equal to or greater than the first predetermined number of times and the engine rotation speed is within the predetermined high rotation range. The engine EGR according to claim 1 or 2, wherein an abnormality of the EGR gas cooling system detected by the abnormality detection means is determined to be caused by a decrease in cooling capacity of the EGR cooler. apparatus.

Images