FR2802241A1 - Malfunction detector for an internal exhaust gas system compares actual setting on valve connecting exhaust system to admission system with target setting obtained with new exhaust gas system - Google Patents

Abstract

A diesel engine discharges exhaust from a collector (9) through a turbine (4b), catalyser (10) and particle collector (12). The turbine (4b) drives a compressor (4a) which pumps admitted air (7) to a reservoir (2). A computer driven valve (18) controls the passage of exhaust gas from collector (9) to reservoir (2) and the actual valve position compared to a target obtained with new exhaust system indicates any particle collector fault

Description

The present invention relates to a device for detecting a malfunction of an exhaust system of an engine. More particularly, the present invention relates to a device for detecting a malfunction in a particulate filter or an EGR passage.

A diesel engine with a diesel particulate filter (DPF) disposed in an exhaust system thereof is known for trapping particulate matter (PM), including soot or burnt fuel, for example this.

However, the DPF undergoes engine operation vibration and receives a large amount of heat from the exhaust gases, as well as cyclic thermal stress from the engine being alternately and repeatedly turned on and off. As a result, malfunction, including rupture, cracking, tearing, the like can occur in the DPF. Specifically, in the case where the DPF comprises a filter element or wire mesh sheet wound into a cylindrical body, a central portion of the filter element may protrude longitudinally from its ends, and thereby be broken. In the case where the DPF comprises a ceramic filter element, cracks may be formed in the filter. When the malfunction occurs in DPF, particulates flow to the atmosphere without being trapped.

DPF malfunction does not provide any significant deterioration in engine performance, such as engine power output and acceleration. So the vehicle driver may not be aware of the malfunction in the DPF. As a result, the DPF continues to malfunction, and as a result the flow of particulate matter into the atmosphere continues.

In order to solve the problem, Japanese Unexamined Patent Publication No. 8-121150 discloses a device for detecting DPF malfunction, in which a sound level sensor is disposed in the exhaust system downstream of the DPF, and the DPF is deteriorated when the detected sound level is above a threshold.

However, the above-mentioned device requires the sound level sensor and signal processing circuitry from the sound level sensor only for detection of a malfunction in the DPF. This complicates the structure of the device and increases the cost of the device. In addition, various kinds of sounds or noises are generated during operation of the engine, and thus such noises can prevent correct detection of a malfunction.

Furthermore, there is a diesel engine provided with an EGR passage (exhaust gas recirculation) connecting the exhaust and intake systems of the engine to one another, and an EGR valve arranged in the passage EGR for controlling a quantity of EGR gas flowing through the EGR passage, in which the EGR ratio is detected, and an opening of the EGR valve is feedback controlled to make the EGR ratio equal a target EGR ratio based on the EGR ratio detected, the target EGR ratio being predetermined based on an engine operating condition.

An object of the invention is to propose a device for detecting a malfunction in an exhaust system of an engine, which is capable of correctly and easily detecting the malfunction and without any particular equipment such as a sensor. sound level.

In accordance with one aspect of the present invention, there is provided a device for detecting a malfunction of the exhaust system of an engine, wherein the engine is provided with an EGR passage connecting the exhaust system and an exhaust system. admitting the engine to each other, an EGR valve disposed in the EGR passage for controlling a quantity of EGR gas flowing through the EGR passage, and wherein the device comprises means for detecting an EGR report , and control means for feedbackly controlling an opening of the EGR valve to make the EGR ratio equal to a target EGR ratio, based on the detected EGR ratio, the target EGR ratio being predetermined based on a condition engine operating system, characterized in that the device further comprises a detection means for detecting an actual opening of the EGR valve when the feedback control the opening of the EGR valve is in progress, an obtaining means for obtaining a reference opening, the reference opening being an opening of the EGR valve required to make the EGR ratio equal to the target EGR ratio, the exhaust system being in a reference condition, the reference condition including at least one condition in which the exhaust system is normal, and a judgment means for judging whether a malfunction has occurred in the engine system; exhaust by comparing the actual opening of the EGR valve to the reference opening.

According to another aspect of the present invention there is provided a device for detecting a malfunction of a particulate filter disposed in an exhaust system of an engine, wherein the engine is equipped with a turbocharger driven by the exhaust gases comprising a turbine disposed in the exhaust system and a compressor disposed in an engine intake system, characterized in that the device comprises means for detecting an actual temperature of the intake gases when the turbocharger is operating, a means for obtaining a reference temperature, the reference temperature being an inlet gas temperature obtained with the filter in a reference position, the reference condition including at least one condition in which the filter is normal, and average judgment intended to judge if a malfunction is t occurred in the filter by comparing the actual temperature of the intake gases with the reference temperature.

The present invention may be better understood from the description of the preferred embodiments of the invention as set forth below in connection with the accompanying drawings.

On the drawings.

Figure 1 shows a general view of a diesel engine; Fig. 2 shows a flowchart for executing feedback control of an EGR valve; Fig. 3 shows a flowchart for performing detection of a DPF malfunction based on the comparison of an opening of an EGR valve; Fig. 4 shows a flowchart for performing detection of a malfunction of an EGR conduit based on the comparison of an opening of an EGR valve; Fig. 5 shows a flowchart for performing the correction of a reference aperture; Fig. 6 shows a flowchart for performing the detection of a malfunction of an EGR cooler based on the comparison of a cooling efficiency of the EGR cooler; Figure 7 shows a simplified view of a diesel engine to explain the parameters; and Fig. 8 shows a flowchart for performing the detection of a malfunction in DPF based on the comparison of a temperature of the inlet gases.

Figure 1 shows the present invention applied to a diesel engine for a vehicle, although the present invention can also be applied to a spark ignition type engine or to a motor for other use.

Referring to Figure 1, reference numeral 1 designates a diesel engine body having four cylinders la. Each cylinder is connected to an equilibrium tank 2 via a corresponding branch 3. The equilibrium tank 2 is connected to an outlet of a compressor 4a of a turbocharger driven by the exhaust gases (or turbocharger) 4 via an intake duct 5 and a charge air cooler 6. The charge air cooler 6 is intended to cool the fresh air discharged from the compressor 4a and is, for example, of the cooling type. by air or water. An inlet of the compressor 4a is connected to an air filter (not shown) via an intake suction duct 7.

intake gas butterfly 8 is disposed in the intake duct 5 in order to reduce the amount of fresh air flowing through the intake duct 5, and is driven by an actuator 8a of the type, for example, electromagnetic or when empty, in response to signals from an engine control unit (ECU) 30. The opening of the throttle valve 8 is controlled to be equal to a target aperture depending on the engine operating condition. In the present first embodiment, the throttle valve 8 is adapted to increase a quantity of EGR gas when the engine speed is low, for example.

Each cylinder 1a, on the other hand, is also connected to an inlet of an exhaust turbine 4b of the turbocharger 4 to drive the compressor 4a, via an exhaust manifold 9. An outlet orifice of the turbine 4b is connected, via an exhaust duct 11, to an exhaust purification catalyst 10 of the type, for example, a three-way catalyst. The catalyst 10 is in turn connected to a diesel particulate filter (DPF) 12 comprising a filter element composed for example of a wire mesh (metal fabric) or a porous material such as a ceramic for trapping the materials. particulates (PM) contained in the exhaust. Additional catalyst may be provided downstream of DPF 12.

An exhaust throttle valve 13 is arranged in the exhaust duct 11 to reduce the amount of exhaust gas flowing through the exhaust duct 11, and is driven by an actuator 13a of the type, for example, electromagnetic or empty, in response to signals from the ECU 30. In the first embodiment, the exhaust throttle valve 13 is adapted to increase an exhaust gas temperature when the DPF 12 is to be cooled or when the engine is in a warming operation.

Each cylinder is provided with a fuel injector 14 for injecting the fuel directly into the cylinder. The fuel injectors 14 are connected to a fuel pump 15 of variable flow type, via a common rail 16 to store the fuel under pressure. Referring again to FIG. 1, the equilibrium tank 2 and the exhaust manifold 9 are connected to each other via an EGR (exhaust gas recirculation) duct 17. An EGR valve 1 is disposed in the EGR conduit 17 for controlling a quantity of gas flowing through the EGR conduit 17, and is driven by an actuator of the electromagnetic type, for example, including a stepper motor, in response to the signals from the ECU 30.

The EGR conduit 17 includes an EGR cooler 19 for cooling the EGR gas. The EGR cooler 19 and water-cooled type, whose cooling water is common to the engine cooling system. Alternatively, the cooler 19 may be of the air-cooled type, or the cooling water may be for its own use. The EGR cooler 19 comprises an EGR pipe connected to the EGR duct 17 through which the gases circulate and around which the cooling water circulates. The EGR cooler 19 eliminates the deterioration of the efficiency per unit volume of the engine due to the EGR gases being at a high temperature, and allows a large amount of EGR to be delivered to the engine. Operation of the EGR cooler 19 is controlled in response to signals from the ECU 30.

When the turbocharger 4 is in operation, fresh air sucked into the intake suction pipe 7 is compressed by the compressor 4a, and is cooled by the charge air cooler 6. When the EGR gas imentation is in operation, the fresh air is then mixed with the EGR gas at the equilibrium tank 2, and is then delivered to the engine together with the EGR gas. Subsequently, the gas mixture including fresh air and EGR gas will be called intake gas. The ECU 30 is composed of a digital computer including a ROM (ROM) 32, a RAM (RAM) 33, a CPU (CPU) 34 and a B-RAM (emergency RAM) 35, an access 36 and an output port 37 interconnected to each other via a bidirectional bus 31. The air quantity sensor or flowmeter 38, generating voltages representing the mass flow rate of fresh air, is disposed in intake suction pipe 7, and may be of the hot wire type. A temperature sensor 39, generating voltages representing a fresh air temperature before entering the compressor 4a, is also disposed in the intake suction pipe 7. A pressure sensor 40, generating voltages representing the pressure in the equilibrium tank 2, is disposed in the equilibrium tank 2, and a temperature sensor 41, generating voltages representing a temperature of the inlet gases in the equilibrium tank 2, is also disposed in the equilibrium tank 2. A temperature sensor 42 generating voltages representing a temperature of the exhaust gas discharged from the turbine 4b, is disposed in an exhaust pipe 20. The EGR valve 18 is provided with a sensor opening 43 generating voltages representing an opening thereof. A depression sensor 44 generating tensions representing depression of the accelerator pedal (not shown), is attached to the accelerator pedal. The body of the engine 1 is provided with a temperature sensor 45 generating voltages representing a temperature of the cooling water of the engine or the EGR cooler 19. The output voltages of the sensors 38 to 45 are delivered at the input to the input port 36 via A / D converters 46.

A motor speed sensor 47 generating pulses representing a motor speed, and a vehicle speed sensor 48 generating pulses representing a vehicle speed are also connected to the input port 36.

The outlet port 37 is connected, via a corresponding drive circuit 50, to the throttle valve actuators 8, the throttle valve 13, and the EGR valve 18, to the fuel injectors 14, at the fuel pump 15 and the EGR cooler 9. The output port 37 is also connected to an alarm 49 via a corresponding driver 50. The alarm 49 may be an electric lamp or a buzzer, and is intended to inform the driver of the vehicle of the occurrence of a malfunction in the exhaust system when it is detected.

It should be noted that the actual opening of the EGR valve 18 can be achieved by using a number of steps in the case where the EGR valve 1 comprises a stepper motor as an actuator, or a duty cycle in the case where the EGR valve 18 is formed by a service control valve, or the power required to drive the EGR valve 18. Accordingly, the opening sensor 43 could be omitted from these variants.

In the engine shown in Fig. 1, the motor is feedback controlled to make idle speed equal to a predetermined speed a target speed, based on the detected idle speed.

In addition, the EGR valve 18 is feedback controlled to make the EGR ratio equal to a target EGR ratio that depends on the engine operating condition, when an EGR condition is set, where the EGR ratio is a ratio of one. amount of EGR gas to that of the intake.

The EGR gas supply suppresses the generation of nitrogen oxides (NOx), and generally, an amount of NOx generated decreases as the amount of EGR gas delivered to the engine increases. However, if the amount of gas becomes excessive, a quantity of oxygen in the cylinder decreases and the combustion can be deteriorated. This can increase the amount of particulate matter and / or generate smoke in a diesel engine.

Accordingly, the target EGR ratio is predetermined to maximize NOX generation suppression, while avoiding combustion deterioration and particulate matter increase, and the EGR ratio is controlled to be equal to the target EGR ratio.

Specifically, an intake gas volume, i.e., a sum of the fresh air and EGR volumes delivered to the engine, is maintained at a substantially constant value which depends on the operating condition of the engine. As a result, in a constant engine operating condition, increasing the amount of EGR gas by increasing the opening of the EGR valve 18 reduces the amount of fresh air and thus increases the EGR ratio, while the reduction in the amount of EGR gas reducing the opening of the EGR valve increases the amount of fresh air and thus reduces the EGR ratio. Thus, the amount of fresh air represents the EGR ratio.

Accordingly, in the first embodiment, a target amount of fresh air, which is a quantity of fresh air necessary to make the EGR ratio equal to the target EGR ratio, is obtained beforehand, by experience, on the basis of the condition engine operation. Then, the operation of the EGR valve 18 is feedback-controlled to make the amount of fresh air 'mass bit' detected by the mass flow meter 38 equal to the target amount of fresh air. As a result, the EGR report is made equal to the target EGR report. The target amount of fresh air is stored in the ROM 32 as a function of the amount of fuel to be injected by the fuel injector 14 or the depression of the accelerator pedal which represents a load of the engine and speed of the engine. engine.

Fig. 2 shows a routine for feedback control of the EGR valve. The subprogram executed by interrupt at each predetermined time interval.

Referring to FIG. 2, in the step it is judged whether the EGR condition is established. In one example, EGR condition is judged to be established when the temperature of the engine cooling water is above a threshold, and when a period of time during which the engine is continuously in operation is greater than a threshold, and when accelerator pedal depression increased. If the EGR condition is not established, the EGR valve 18 is closed and EGR gas supply to the engine is stopped. When the EGR condition is not judged to be established, the subroutine ends. In contrast, when the EGR condition is judged to be established, the routine proceeds to step 61, where the engine speed N, fresh air quantity Gn, and the fuel quantity Qf are read. The amount of fuel Qf was calculated by another routine to obtain the fuel quantity (not shown).

In the next step 62, the target amount of fresh air TGn is calculated on the basis of the engine speed N and the fuel quantity Qf. In the next step 63, it is judged whether a difference in the amount of fresh air detected with respect to the target amount (Gn-TGn) is greater than a positive constant a. When the deviation (Gn TGn) is judged to be greater than the constant a, the routine proceeds to step 64, where a target opening TVEG of the EGR valve 18 is increased to a value dV. Then the subroutine goes to step 67.

In contrast, when the difference (Gn-TGn) is not greater than the constant a, the routine goes to step 65, where 'is judged if the difference (Gn-TGn) is less than a negative constant -a. When the difference (Gn-TGn) is not less than the constant -a, the routine goes to step 67, maintaining the target opening TVEG. When the difference (Gn-TGn) is less than the constant -a, the routine goes to step 66, where the target opening TVEG of the EGR valve 18 is reduced by the value dV. Then the subroutine goes to step 67. It should be noted that the value a is a relatively small value intended to avoid fluctuation of the opening of the EGR valve 18, and may be any value for this purpose. The value dV can be constant or variable depending on the difference (Gn-TGn).

In step 67, the EGR valve 18 is driven to make its opening equal to the target opening TVEG.

The first embodiment will be explained in more detail. Briefly, the first embodiment relates to the detection of a DPF malfunction 12, with the feedback control of the EGR valve 18.

The feedback control of the EGR valve 18 maintains the amount of fresh air at its target amount, and thus the EGR ratio to the target EGR ratio. At this time, the opening of the EGR valve 18 is maintained at a certain opening depending on the operating condition of the engine.

However, if a malfunction occurs in the DPF 12, such as a break or a crack, the opening of the EGR valve 18 deflects relative to the certain opening. Specifically, the DPF 12 malfunction significantly reduces DPF 12 pressure drop and thus lowers the engine back pressure. This will reduce the pressure difference between the inlet port and the outlet port of the EGR conduit 17, which in turn will reduce the amount of EGR gas flowing through the EGR conduit 17 and increase the amount of fresh air. Finally, this will reduce the EGR report. In this condition, the feedback control increases the opening of the EGR valve 18 to maintain the EGR ratio equal to the target EGR ratio. Accordingly, when a malfunction occurs in the DPF 12, the opening of the EGR valve 18 necessarily becomes greater than an opening when the DPF 12 is normal.

In other words, if a reference opening refers to an opening of the EGR valve 18 necessary to make the EGR ratio equal to the target EGR ratio with the DPF 12 being in a reference condition, the reference condition including a condition in which the DPF 12 is normal, the actual opening of the EGR valve 18 is maintained at the reference opening when the DPF 12 is normal, and becomes greater than the reference opening when a malfunction occurs in the DPF 12.

In the first embodiment, the reference opening is first obtained on the basis of the operating condition of the engine, such as the operating speed of the engine N and the fuel quantity Qf, by experience, and is stored in ROM 32 in advance as a function of N and Qf. Then, the actual opening of the EGR valve 18 is detected and is compared with the reference opening whose operating condition of the engine is the same as an engine operating condition, at the actual detected opening. When the actual opening of the EGR valve 18 is greater than the corresponding reference opening, it is judged that a malfunction has occurred in the DPF 12. Otherwise, the DPF 12 is judged to be normal.

Although an opening of the EGR valve 18 necessary to make the EGR ratio equal to the target EGR ratio with the DPF 12 being normal may vary depending on an amount of particulate matter trapped on the DPF 12, the reference aperture can be any opening as long as it renders the EGR ratio equal to the target EGR ratio and is obtained with the normal DPF 12. However, in the first embodiment, the reference aperture is an aperture with a new 12, i.e., the DPF 12 is normal and the amount of trapped particulate matter is substantially zero. In other words, the condition of reference a condition in which the DPF 12 is new. The reference opening with the DPF 12 being new is maximum among those with the normal DPF 12, and thus "drunken a correct judgment of a malfunction.

Fig. 3 shows a routine for detecting a malfunction of the DPF 12. The routine is executed by interrupting each predetermined time interval.

Referring to FIG. 3, in step 70, it is judged whether an indicator XF1, which represents the occurrence of a malfunction of the DPF 12 and which has been initialized to be reset (XF1 = 0) , is reset. When the flag XF1 is reset, the routine goes to step 71, where it is judged whether the EGR valve feedback control 18 is in progress. If the feedback command is stopped, the subroutine ends. If the feedback command is in progress, the routine goes to step 72, where the engine speed N, the fuel quantity Qf, and the actual opening of the VEG EGR valve are read. In the next step 73, the reference opening RVEG is calculated on the basis of the engine speed N and the fuel quantity Qf.

In the next step 74, it is judged whether a deviation of the actual opening of the EGR valve 18 from the reference opening (VEG-RVEG) is greater than a positive constant b. When the deviation (VEG-RVEG) judged to be greater than the constant b, the routine goes to step 75, where the flag XF1 is set (XF1 = 1). When the XF1 flag is set, the alarm 49 is activated. It should be noted that the constant b is a relatively small value intended to avoid poor judgment due to equipment tolerances such as sensors or valves, or environmental conditions such as temperature and atmospheric pressure. In contrast, when the deviation (VEG-RVEG) is not greater than the constant b, the routine ends and the flag is kept to be reset.

When the flag XF1 has been set in step 70, the routine ends. The XF1 flag will be returned to manually reset when the DPF 12 is repaired or changed.

It will be noted in the first embodiment that the actual opening of the EGR valve 18 is compared to the reference opening. Alternatively, actual opening of the EGR valve 18 may be compared to an opening different from the reference opening mentioned above, but determined based on 1 reference opening.

Then, the second embodiment according to the present invention will be explained. The second embodiment relates to a detection of malfunction of the EGR conduit 17, in particular of the EGR cooler 19, with the EGR valve feedback control 18.

In the diesel engine shown in Figure 1, the inlet port of the EGR conduit 17 is upstream DPF 12, and thus the EGR gas flowing through the EGR conduit 17 may contain particulate matter. Thus, the EGR conduit 17 may become fouled due to particulate adhering and accumulating webs on the inner surface of the EGR conduit 17. In particular, the EGR cooler 19 EGR pipe usually has a smaller cross section than the EGR conduit. 17. In addition, the gaseous carbon or fuel contained in the EGR gases is cooled and liquefied while flowing through the EGR cooler's EGR pipe 19. As a result, the EGR cooler EGR pipe 19 can become easily fouled. The fouling of the EGR duct 17 including the EGR cooler 19 reduces the amount of EGR gas delivered to the engine and thus deteriorates the suppression of the generation of NOx EGR gas.

Likewise, when the EGR conduit 17 deforms to reduce the cross section thereof, or when the EGR gases leak from the EGR conduit 17, the amount of EGR gas is reduced. As a result, in the second embodiment, malfunction of the EGR conduit 17 as mentioned above is detected. A detailed explanation of this follows.

When a malfunction occurs in the EGR conduit 17, the amount of EGR gas is reduced, which increases the amount of fresh air. At this time, as in the first embodiment, the feedback control of the EGR valve 18 increases the opening of the EGR valve to avoid reducing the EGR ratio. Accordingly, when a malfunction occurs in the EGR conduit 17, the opening of the EGR valve 18 necessarily becomes larger than an opening with a normal EGR conduit 17.

In other words, if a reference opening refers to an opening of the EGR valve 18 requiring to make the EGR ratio equal to the target EGR ratio with the normal EGR conduit 17, the actual opening of the EGR valve is maintained at the reference opening when the EGR conduit 17 and normal, and becomes greater than the reference opening when a malfunction occurs in the EGR conduit 17.

While the reference opening could be obtained beforehand for various engine operating conditions, only the reference opening, with the operating condition of the engine under reference operating conditions, is obtained beforehand in the second embodiment. Then, the actual opening of the EGR valve 18 is detected when the engine operating condition is in the reference operating condition, and is compared to the reference opening. When the actual opening of the EGR valve 18 is greater than the corresponding reference opening, it is judged that a malfunction has occurred in the EGR conduit 17. Otherwise, EGR conduit 17 is judged to be normal.

The reference operating condition can be any operating condition. However, if the motor is a high speed condition or a high load operating condition, the return pressure becomes relatively high and thus a reduction in the amount of EGR gas can be low, even a malfunction has occurred in the conduit EGR 17. This prevents correct detection of malfunction.

Accordingly, the reference operating condition is preferably a low speed operating condition where the motor speed is below threshold, or a low load operating condition where the motor load is less than a threshold. is also preferably a constant operating condition. Accordingly, in a second embodiment, the reference operating condition is a constant idle condition after the warming operation has been completed. in other words, the reference opening RVEGI is an opening of the EGR valve 18 necessary to make the EGR ratio equal to the target EGR ratio, the EGR duct 17 being normal and the engine running idle constant. This is obtained in advance from experience and is stored in advance in ROM 32.

Fig. 4 shows a routine for detecting a malfunction in line 17. This subroutine is executed by interrupting each predetermined time interval.

Referring to FIG. 4, in the step it is judged whether an indicator XF2, which represents the occurrence of a malfunction in the EGR conduit 17 and which has been initiated to be reset (XF2 = 0), has been reset. When the XF2 flag has been set, the subroutine ends. When the flag XF2 is reset, subroutine goes to step 81, where it is judged whether the feedback control of the EGR valve 18 is in progress. If the feedback command is stopped, the subroutine ends. If feedback control is in progress, the routine proceeds to step 82, where it is judged whether the motor is in constant idle operation. If the motor is not in constant idle operation, the routine ends. If the motor is in constant idle operation, the routine proceeds to step 83, where the actual opening of the VEG EGR valve and the RVEGI reference opening are read.

In the next step 84, it is judged whether a deviation of the actual opening of the EGR valve 18 from the reference opening (VEG-RVEGI) is greater than a positive constant c. When the deviation (VEG-RVEGI) is judged to be greater than the constant c, the routine goes to step 85 where the flag XF2 is set (XF2 = 1). When the XF2 flag is set, the alarm 49 is activated. It should be noted that the constant c is relatively small as the constant b of the second embodiment. In contrast, when the deviation (VEG-RVEGI) is not greater than the constant c, the subroutine ends and the flag XF2 is kept to be reset. As in step 82 in FIG. 4, it is judged whether the operating condition of the engine is in the reference operating condition. In this case, the utente can be executed on the basis of at least one of the engine speed, the thrust of the throttle valve, the fuel quantity, the temperature of the cooling water of the engine , the opening of the throttle valve 8, the opening of the throttle valve 13, a judgment if the DPF 12 clogs and a judgment if the DPF is not in cooling operation. In addition, it can be performed considering the conditions of the auxiliary devices such as a compressor for an air conditioner and a pump for a power steering.

The third embodiment according to the present invention will be explained as a variant of the second embodiment.

In the second embodiment, the reference opening RVEGI is obtained and stored in the ROM 32 in advance. However, the EGR device including the EGR conduit 17, the EGR valve 18 and the EGR cooler 19 may include irregularities, and thus the initial reference opening previously obtained may not be a correct value for a particular EGR device. Accordingly, in the third embodiment, the initial reference aperture is corrected on the basis of the actual opening of the EGR valve 18 obtained by the feedback control thereof, with the new EGR device.

Specifically, when the EGR device is new, that is, the vehicle itself is new or the EGR device is replaced with a new one, a correction coefficient KC is calculated. The correction coefficient KC is an average value of a difference of 1 actual opening of the EGR valve 18 with respect to the initial reference opening (VEG-RVEGI) over predetermined periods of time. Then, the initial reference opening is corrected using the correction coefficient KC (RVEGI = RVEGI + KC). As a result, correct detection of a malfunction is ensured.

Fig. 5 shows a routine for correction of the reference opening RVEGI. This routine is executed by interrupting each predetermined time interval.

Referring to FIG. 5, in step 90, there is a flag XC, which represents a completion of a reference opening correction RVEGI and which has been initialized to be reset (XC = 0), was reset to 0. When the XC flag has been set, the subroutine terminates.When the XC flag is reset, the routine proceeds to step 91, where it is reset. judged whether the feedback control of the EGR valve 18 is in progress If the feedback control is stopped, the routine is terminated If the feedback command is in progress, the routine proceeds to step 92 where It is judged whether the engine is in constant idle operation.If the engine is not running idle steady, the subroutine ends.If the engine is running idle steady, the subroutine goes to step 93 , where a counter i, which represents the number of executions of the present subroutine, e In the next step 94, the detected actual opening VEG of the EGR valve 18 and the initial reference opening RVEGI are read. In the next step 95, the ith difference D (i) is calculated (D (i) = VEG-RVEGI). In the next step 96, it is judged whether the counter i is equal to a constant n. If the counter i is not equal to the constant n, the subroutine ends. If i = n, the routine goes to step 97 where the correction coefficient KC is calculated (KC = (D (1) + <B> ... </ B> + D (n)) / n ). In the next step 98, the reference opening is corrected by KC (RVEGI = RVEGI + KC). In the next step 99, the corrected reference opening RVEGI is stored in the RAM 33. In the next step 100, the indicator XC is set.

After completion of the correction, a detection of a malfunction in the EGR conduit 17 is performed using the corrected reference opening RVEGI. The XC indicator is reset manually when the EGR device is replaced by a new one.

It should be noted that the RVEGI corrected reference aperture is an average value of the actual aperture of the EGR valve 18, and thus can be obtained even without the initial reference aperture. However, the initial reference opening is stored in advance in the ROM 32 for detection of a malfunction before the correction is completed.

In the embodiments mentioned above, the EGR ratio is controlled by controlling the EGR valve 18 only. In this case, when the EGR valve 18 is fully open, the amount of EGR gas or the EGR ratio can not be increased. This can prevent the actual EGR ratio from being equal to the target EGR ratio.

Accordingly, when the EGR valve 18 is fully open, the throttle valve 8 can be feedback-controlled to make the actual EGR ratio equal to the target EGR ratio. In this case, a second reference opening, which is an opening necessary for the throttle valve 8 to make the actual EGR ratio equal to the target EGR ratio with the DPF 12 or the normal EGR conduit 17, is predetermined. Then, the actual opening of the throttle valve 8 is detected, and is compared to the second reference opening. If the actual opening of the throttle valve 8 is less than the second reference opening, it can be judged that a malfunction has occurred in the DPF 12 or EGR 17. The lower throttle valve opening Gas' intake 8 reduces the amount of fresh air and increases the amount of EGR gas.

Next, the fourth embodiment according to the present invention will be explained. The fourth embodiment relates to the detection of a malfunction of the EGR cooler 19 without the feedback control of the EGR valve 18.

In the embodiments mentioned above, the feedback control of the EGR valve 18 is necessary for the detection of a malfunction. Thus, there may be a case where the detection can not be performed while the feedback control is stopped, such as the high load operation of the motor. Accordingly, in the fourth embodiment, the malfunction detection is performed based on the cooling efficiency of the EGR cooler 19.

Specifically, when the EGR cooler 19 is normal or is not fouled, a cooling efficiency of the EGR cooler 19 is maintained at some efficiency depending on the engine operating condition. However, when particulate matter adheres to the EGR cooler pipe EGR inner surface 19 and thus when the EGR cooler 19 is fouled, the contact surface area between the EGR gas flowing through the EGR pipe and the cooling water is scaled down. This lowers the heat exchange efficiency of the EGR cooler 19 and thereby lowers the cooling efficiency of the EGR cooler 19. In addition, the fouling of the EGR cooler 19 can increase the pressure in the EGR pipe and thus, can increase the temperature of the EGR gas.

In other words, if a reference efficiency refers to an efficiency of the EGR cooler 19 obtained when the EGR cooler 19 is normal, the actual efficiency of the EGR cooler 19 is maintained at the reference efficiency when the EGR cooler 19 is normal, and becomes less than the reference efficiency when a malfunction occurs in the EGR cooler 19. In the fourth embodiment, the reference efficiency with the normal EGR cooler 19 and the engine operating condition in the reference operating condition is obtained beforehand, and is stored in advance in the ROM. Then, the actual cooling efficiency of the EGR cooler 19 detected when the operating condition of the engine is in the operating condition of the engine. reference and is compared to the reference efficiency. When the actual cooling efficiency of the EGR cooler 19 is lower than the reference efficiency, it is judged that a malfunction has occurred in the EGR cooler 19. Otherwise, the cooler 19 is considered normal.

FIG. 6 shows a subroutine for detecting fouling of the EGR cooler 19. This routine is executed by interrupting each predetermined time interval.

Referring to FIG. 6, in the step, it is judged whether an indicator XF3, which represents the appearance of a fouling of the EGR cooler 19 and has been initialized to be reset (XF3 = 0), has reset. When the XF3 flag has been set the subroutine ends. When the flag XF3 is reset, the routine goes to step 111, where it is judged whether the EGR cooler 19 is operating. The EGR cooler 19 is in operation when the temperature of the engine cooling water is above a threshold, the engine speed is above a threshold the accelerator pedal depression is above a threshold and the temperature exhaust gas detected by the temperature sensor 42 is greater than a threshold, for example. When the EGR cooler 19 is not in operation, the subroutine terminates. When the EGR cooler 19 is in operation, the routine proceeds to step 112, where it is judged whether the engine is in the predetermined reference operating condition. If the motor is not in the reference operating condition, the routine ends. If the engine is in the reference operating condition, the routine goes to step 113, where the actual cooling efficiency of the cooler EFFCL is calculated. In the next step 114, the reference efficiency REFF is read.

In the next step 115, it is judged whether a deviation of the actual cooling efficiency of the EGR cooler 19 from the reference efficiency (REFF-EFFCL) is greater than a positive constant d. When the deviation (REFF-EFFCL) is judged to be greater than the constant d, the routine proceeds to step 116, where the flag XF3 is set (XF3 = 1). When the XF3 flag is set, the alarm 49 is activated. In contrast, when the deviation (REFF-EFFCL) does not exceed the constant d, the subroutine ends and the flag XF3 is kept to be reset.

Next, the calculation of the actual cooling efficiency EFFCL of the EGR cooler 19 is explained with reference to Fig. 7. The cooling efficiency EFFCL is calculated using the following equation EFFCL = (TEGI-TEGO) / (TEGI -THW) ... (1) Here, TEGI represents a temperature of the EGR gases flowing in the EGR cooler 19 or before being cooled by the EGR cooler 19, or exhaust gases flowing in the exhaust turbine 4b or before being expanded by the exhaust turbine 4b. TEGO represents a temperature of the EGR gases evacuated from the EGR cooler 19 or after having been cooled by the EGR cooler 19. THW represents a temperature of the cooling water circulating in the EGR cooler and is detected by the sensor 45.

The temperature of the incoming TEGI EGR gas is calculated or estimated on the basis of the temperature of the exhaust gases discharged from the exhaust turbine 4b and the thermal energy consumed in the exhaust turbine 4b. Specifically, TEGI is calculated using the following theoretical equation for exhaust turbine 4b.

 ETB = (TEGI-TEXA) / (TEGI (1-1 / (PEXB / PIG) 248) <B> ... </ B> (2) Here, ETB represents an efficiency of the exhaust turbine 4b TEXA represents a temperature of the exhaust gas flowing through the exhaust pipe 20 or having been expanded by the exhaust turbine 4b.PEXB represents a pressure of the exhaust gas at the exhaust manifold 9 or before The exhaust turbine 4b PIG represents a pressure of the inlet gas or the mixture of fresh air gases and EGR gases at the level of the equilibrium tank 2.

The efficiency of the ETB turbine which is a specific value for the exhaust turbine 4b is obtained beforehand, by experiment, and is stored in the ROM 32. The pressure PIG and the temperature TEXA are detected by the corresponding sensors 40, 42. The PEXB pressure is calculated on the basis of the PIG pressure and the amount of fresh air Gn. As a result, the temperature of the incoming TEGI EGR gases is calculated using Equation 2).

In addition, the temperature of the evacuated EGR gas TEGO is calculated or estimated on the basis of the ratio of the temperature of the fresh air discharged from the charge air cooler 6 and the temperature of the inlet gases. Specifically, TEGO is calculated using the following equation. = TEGO + RATIO (1-RATIO) TFAO ... (3) Here, TIG represents an inlet gas temperature at the equilibrium tank level 2. REPORT represents an EGR report. TFAO represents a fresh air temperature evacuated charge air cooler 6 or after being cooled by the charge air cooler 6, or before being mixed with the EGR gas.

The temperature of the TIG intake gases is detected by the sensor 41. The ratio EGR ratio is calculated on the basis of GALL representing a total quantity of the intake gases delivered to the engine, and the amount of fresh air Gn (ratio = (GALL-Gn) / GALL). The total quantity GALL is calculated on the basis of the PIG inlet gas pressure and the engine filling efficiency, which is calculated on the basis of the engine speed N. The amount of fresh air Gn is detected by the sensor 38. The filling efficiency can be obtained beforehand and stored in ROM 32.

The TFAO temperature of the fresh air after being cooled by the charge air cooler 6 is calculated on the basis of the cooling efficiency EIC of the charge air cooler 6, and the TFAI temperature of the charge air cooler 6. fresh air before being cooled by the charge air cooler 6 or after having been compressed by the compressor 4a. The efficiency of the charge air cooling EIC is calculated on the basis of the speed of the vehicle V detected by the sensor 48, and the amount of fresh air Gn.

The TFAI temperature of the fresh air before cooling is calculated using the following theoretical equation for the compressor 4a.

 ECMP TF ((PFAI / PIG) 0, 286_1) / (TFAI-TF) <B> ... </ B> (4) Here, ECMP represents an efficiency of the compressor 4a. TF represents a temperature of the fresh air circulating in the compressor 4a or before being compressed by the compressor 4a. PFAI represents a pressure of the fresh air circulating in the charge air cooler 6 or before being cooled by the charge air cooler 6 or after having been compressed by the compressor 4a.

The efficiency of the ECMP compressor which is a specific value for the compressor 4a is calculated on the basis of the amount of fresh air Gn and the fresh air pressure PFAI. The fresh air temperature TF and the inlet gas pressure PIG are detected by the corresponding sensors 39, 40. The fresh air pressure PFAI is calculated by subtracting a pressure loss of the charge air cooler 6 from the pressure of the PIG inlet gases. As a result, the TFAI temperature of fresh air before cooling is calculated using equation (4).

As a result, the cool air TFAO temperature after cooling is calculated based on the efficiency of the charge air cooler EIC and the TFAI temperature of the fresh air before cooling. As a result, the TEGO evacuated EGR gas temperature is calculated using equation (2). As a result, the actual efficiency EFFCL of the EGR cooler is calculated using equation (1). Alternatively, one or more sensors may be provided to detect the aforementioned pressures and temperatures PFAI, PEXB, TFAI, TFAO, TEGI and TEGO. In addition, the incoming TEGI EGR gas temperature can be estimated based on the amount of fresh air, the temperature of the cooling water, the amount of fuel and the cyclic efficiency of the engine. The temperature of TEGO evacuated gas EGR can be estimated as follows. First, the TIG temperature is assumed. Then, an assumed TEGO is calculated using the TIG pressure, the fill efficiency, the TFAO temperature and the assumed TIG, and the TIG temperature is calculated using the assumed TEGO. The calculation is repeated until the calculated TIG using the assumed TEGO is equal to the assumed TIG.

Next, the fifth embodiment according to the present invention will be explained. The fifth embodiment relates to the detection of a DPF malfunction without the feedback control of the EGR valve 18.

As previously indicated, if the DPF 12 is broken, the pressure at the exit port of the exhaust turbine 4b drops. This increases the exhaust energy given to the turbine 4b, and thus increases the pressure at the outlet of the compressor 4. This, in turn, increases the temperature of the fresh air at the level of the compressor. compressor outlet port 4a, and the temperature of the TIG inlet gas. Accordingly, when a malfunction occurs in the DPF 12, the temperature of the TIG inlet gas necessarily becomes greater than a temperature with the normal DPF 12. At this time, the temperature of the TIG intake gases will become higher, even considering the cooling of the charge air cooler 6 and / or the mixing with the EGR gases at elevated temperature.

In other words, if a reference temperature refers to an inlet gas temperature obtained with the DPF 12 in a reference condition, the reference condition including at least one condition in which the filter is normal, the actual temperature intake gas is maintained at the reference temperature when the DPF 12 is normal, and becomes higher than the reference temperature when a malfunction occurs in the DPF 12.

It should be noted that in the case where the DPF 12 is disposed upstream of the exhaust turbine 4b, the temperature of the inlet gas also increases when the DPF 12 is broken, since the pressure at the orifice of Turbine 4b input increases at this time.

In the fifth embodiment, the reference temperature is previously obtained based on the engine operating condition, such as the engine speed N, the fuel quantity Qf, and the amount of fresh air Gn, by experience , and is stored in advance in the ROM 32 as a function of N, Qf and Gn. Then, the actual temperature of the intake gases is detected, and is compared to the reference temperature of which an engine operating condition is the same as a motor operating condition at the actual detected temperature. When the actual temperature of the inlet gases is higher than the corresponding reference temperature, it is judged that a malfunction has occurred in the DPF 12. Otherwise, the DPF 12 is judged to be normal. The change of the amount of fresh air Gn due, for example, to the change of the intake throttle opening 8 will change the work of the compressor 4a, thus change the temperature of the intake gases. Accordingly, the reference temperature in the fifth embodiment is predetermined as a function of fresh air quantity Gn. However, it will be appreciated that during the feedback control of the valve 18, the amount of fresh air Gn depends on the engine speed N and the fuel quantity Qf, as previously mentioned.

Fig. 8 shows a routine for detecting a malfunction in DPF 12. This routine is executed by interrupting each predetermined time interval.

Referring to Fig. 8, in step 120, if a flag XF1 is reset, if the flag XF1 is set, the routine ends when the flag XF1 is reset. the subroutine goes to step 121 where it is judged whether the engine operating condition is constant When any of the engine speed N, the fuel quantity Qf and the amount of fresh air Gn change of a predetermined value compared to that of the last cycle of treatment, the condition of operation of the engine is not considered to be constant and the subroutine ends.If otherwise, the operating condition of the engine is considered to be constant and the routine proceeds to step 122, where the engine speed N, the fuel quantity Qf, the fresh air quantity Gn and the actual temperature of the TIG intake gases are read. , the reference temperature RTIG is calculated on the basis of the speed of the engine N, the quantity of fuel Qf and the quantity of fresh air Gn.

In the next step 124, it is judged whether a difference in the actual temperature of the intake gases with respect to the reference temperature (TIG-RTIG) is greater than a constant e. When the deviation (TIG-RTIG) is less than the reference temperature, the routine ends. When the deviation (TIG-RTIG) is greater than the reference temperature, the routine goes to step 125 the indicator XF1 is set. It should be noted that the constant e is a relatively small value as the constant b in the second embodiment.

Inlet gas temperature .TIG and reference temperature may vary depending on atmospheric temperature. Therefore, they should be corrected on the basis of atmospheric temperature.

When the DPF 12 is broken, the turbine speed of the exhaust turbine 4b and / or the pressure of the inlet gases will also increase. Thus, a detection of a malfunction in the DPF 12 can be performed by comparing the turbine speed or inlet pressure with the corresponding reference value with the normal DPF 12. In addition, the turbocharger 4 is typically provided with a relief valve which is usually closed and opens to communicate the upstream and downstream of the exhaust turbine 4b mutually when the air pressure Compressed charge by compressor 4a increases to a threshold. The relief valve should open when the DPF 12 is broken and thus, the detection of a malfunction in the DPF 12 can be executed depending on whether the relief valve opens.

Alternatively, when the DPF 12 becomes dirty, the amount of exhaust gas flowing to the exhaust turbine 4b is reduced. This reduces the speed of the exhaust turbine and lowers the temperature of the intake gases. Thus, it can be judged that the DPF 12 is fouled when the temperature of the inlet gas is below a reference temperature. In this case, the reference temperature may be an inlet gas temperature obtained with the normal DPF 12 and the amount of trapped particulate matter being the maximum possible amount. The maximum possible amount may be a threshold to initiate the DPF 12 recovery operation.

According to the present invention, it is possible to provide a device for detecting a malfunction in an exhaust system. an engine that is able to correctly and easily detect the malfunction.

Claims (18)

<U> CLAIMS </ U> 1. Device for detecting a malfunction in an engine exhaust system, in which the engine is provided with an EGR passage connecting the exhaust system and an engine intake system one to the other. another, and an EGR valve disposed in the EGR passage for controlling a quantity of EGR gas flowing through the EGR passage, and wherein the device comprises means for detecting an EGR ratio and control means for controlling by feedback an opening of the EGR valve to make the EGR ratio equal to a target EGR ratio, based on the detected EGR ratio, the target EGR ratio being predefined on the basis of an engine operating condition, characterized in that the device further comprises a detecting means for detecting an actual opening of the EGR valve when the feedback control of the opening of the EGR valve in progress, a means of obtaining it is intended to obtain a reference opening, the reference opening being an opening of the EGR valve necessary to make the EGR ratio equal to the target EGR ratio, the EGR system being in a reference condition, the reference condition including at least a condition in which the exhaust system is normal, and judgment means for judging whether a malfunction has occurred in the exhaust system by comparing the actual opening of the EGR valve to the reference opening. 2. Device according to claim 1, characterized in that the judging means judges that a malfunction has occurred in the exhaust system when the actual opening of the EGR valve is greater than the reference opening. 3. Device according to claim 2, wherein a particulate filter is disposed in the exhaust system downstream of an inlet port of the EGR passage, characterized in that the judging means judges that a malfunction is occurring in the filter when the actual opening of the valve is greater than the reference opening, the reference opening being an opening of the EGR valve necessary to make the EGR ratio equal to the target EGR ratio, the filter being in the reference condition, the reference condition including at least one condition in which the filter is normal. 4. Device according to claim 3, characterized in that the condition of reference a condition in which the filter is new. 5. Device according to claim 2, characterized in that the judging means judges that a malfunction has occurred in the EGR passage when the actual opening of the EGR valve is greater than the reference opening, the opening of reference being an opening of the EGR valve necessary to make the EGR ratio equal to the target EGR ratio, the EGR passage being in the reference condition, the reference condition including at least one condition in which the EGR passage is normal. 6. Device according to claim 5, wherein an EGR cooler is disposed in the EGR passage for cooling the EGR gas flowing therethrough, characterized in that the judging means judges that a malfunction has occurred in the cooler. EGR when the actual opening of the EGR valve is greater than the reference opening, the reference opening being an opening of the EGR valve necessary to make the EGR ratio equal to the target EGR ratio, the EGR cooler being in the condition reference, the reference condition including at least one condition in which the EGR cooler is normal. Device according to claim 1, characterized in that the reference opening is predetermined on the basis of the operating condition of the engine, and in that the actual opening of the EGR valve is compared with the reference opening. whose engine operating condition is the same as that of the actual opening of the detected EGR valve. 8. Device according to the claim, characterized in that obtaining means obtains the actual opening of the EGR valve when the operating condition of the engine in a reference operating condition and in that the judgment means judges whether a bad operation occurred in the exhaust system by comparing the actual opening of the EGR valve to the reference opening, the reference opening being an opening of the EGR valve necessary to make the EGR ratio equal to the target EGR ratio, the exhaust system being in the reference condition and the operating condition of the engine being in the reference operating condition. 9. Device according to claim, characterized in that reference operating condition is a condition in which the engine in a condition operating at low speed or low load. 10. Device according to claim 1, characterized in that the reference opening is established on the basis of the actual opening of the EGR valve, the exhaust system being in the reference condition and feedback control of the opening of the valve being in process. Apparatus according to claim 1, wherein a throttle valve is disposed in the engine intake system, and wherein the control means controls feedback of the throttle valve and throttle valve openings. to make the EGR ratio equal to the target EGR ratio, based on the detected ratio, characterized in that the detecting means detects actual opening of the throttle valve when the feedback control of the throttle valve opening admission is in progress, in that the obtaining means obtains a second reference opening which is an opening of the throttle valve admission required to make the EGR ratio equal to the target EGR ratio, the exhaust system being in the condition reference, and a judging means judges whether a malfunction has occurred in the exhaust system by comparing the actual opening of the intake throttle valve to the uxth reference opening. 12. Device for detecting a malfunction in a particulate filter disposed in an exhaust system of an engine, wherein the engine is provided with an exhaust-driven turbocharger having a turbine disposed in the system exhaust system and a compressor arranged in an engine intake system, characterized in that the device comprises means for detecting an actual temperature of the exhaust gas when the turbocharger is in operation, a means of obtaining for to obtain a reference temperature, the reference temperature being a temperature of the inlet gases obtained with the filter in a reference condition, the reference condition including at least one condition in which the filter is normal, a judgment means for judge if a malfunction has occurred in the filter by comparing the actual temperature e intake gas at the reference temperature. 13. Device according to claim 12, characterized in that the judging means judges that a malfunction has occurred in the filter when the actual temperature of the inlet gas is higher or lower than the reference temperature. 14. Device according to claim 12, characterized in that the reference condition is a condition in which filter is new. 15. Device according to claim 12, characterized in that the reference temperature is predetermined on the basis of the operating condition of the engine, and in that the actual temperature of the intake gas is compared with the reference temperature whose condition engine operation is the same as the actual inlet gas temperature detected. 16. Device according to claim 12, characterized in that the obtaining means obtains the actual temperature of the intake gas when the operating condition of the engine is in a reference operating condition, and in that the means of judgment judges whether a malfunction has occurred in the filter by comparing the actual temperature of the intake to the reference temperature, the reference temperature being an inlet gas temperature obtained with the filter in the reference condition and operating condition of the engine in the reference operating condition. Device according to claim 16, characterized in that the reference operating condition is a condition in which the engine is in a low speed or low load operating condition. 18. Device according to claim 1 or 12, wherein an EGR cooler is disposed in the EGR passage for cooling the EGR gas flowing therethrough, characterized in that the device further comprises a means for obtaining an efficiency of actual cooling of the EGR cooler, means for obtaining a reference efficiency, which is a cooling efficiency of the EGR cooler obtained with the EGR cooler in the reference condition, the reference condition including at least one condition in which the EGR cooler is normal, and means for judging whether a malfunction has occurred in the EGR cooler by comparing the actual cooling efficiency with the reference efficiency.