JP4894569B2 - Temperature sensor failure diagnosis device - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a temperature sensor failure diagnosis device, and more particularly, to provide a temperature detection means for diagnosis permission determination in addition to a temperature sensor to be diagnosed, thereby measuring engine exhaust temperature in an engine equipped with a diesel particulate filter. The present invention relates to a technique for preventing erroneous diagnosis that a temperature sensor used for a wide measurement range is faulty with a simple configuration.

  A diesel particulate filter (hereinafter referred to as “DPF”) is a device generally known to remove particulate matter (hereinafter referred to as “particulate”) discharged from a diesel engine. The DPF includes a filter carrier made of ceramic or the like, and collects particulates in the exhaust gas by the filter carrier and removes them.

  A DPF having an oxidation catalyst upstream of a filter carrier is known as a continuous regeneration type DPF. In this continuous regeneration type DPF, nitrogen monoxide in the exhaust gas is converted into nitrogen dioxide having high oxidation reactivity by an oxidation catalyst, and the particulates deposited on the filter carrier are oxidized and processed by this nitrogen dioxide. The A continuous regeneration type DPF and a urea reduction type NOx catalyst were used together for the purpose of simultaneously reducing particulates and nitrogen oxides (hereinafter referred to as “NOx”), which are air pollutants discharged from a diesel engine. Development of an exhaust purification system is underway.

  In such an exhaust purification device, it is necessary to detect the temperature of the engine exhaust and control the actual exhaust temperature based on this in order to allow the continuous regeneration of the DPF to function well. Under operating conditions where the temperature in the DPF decreases due to a decrease in the exhaust temperature, such as during low-speed driving, and the particulates do not reach the ignition temperature, the particulates cannot be burned or burnt. Even if it is possible to do so, it becomes slow and the processing does not proceed well.

  Therefore, in order to control the inside of the DPF to a temperature range suitable for particulate processing, a temperature sensor (hereinafter referred to as “exhaust temperature sensor”) for detecting the temperature of the engine exhaust is installed upstream or downstream of the DPF. Based on the detected temperature, the fuel supply to the engine is controlled. However, if this exhaust temperature sensor breaks down, it will not be possible to compensate for the decrease in exhaust temperature by controlling the fuel supply, etc., so that the DPF regeneration function cannot be fully exerted, and excessive particulates will be produced. Due to the excessive accumulation, pressure loss in the DPF increases, fuel consumption is reduced, and excessive heat load is applied to the filter carrier due to sudden combustion of excessively accumulated particulates, which may damage the filter carrier.

Therefore, in an exhaust gas purification apparatus that employs a DPF, it is important that an exhaust temperature sensor can be detected immediately when it fails.
Here, techniques that can be applied to the exhaust temperature sensor as techniques for diagnosing a failure of the temperature sensor include the following.
First, the exhaust gas temperature is detected by the temperature sensor, it is determined whether or not the detected temperature is outside a predetermined area set as a normal area, and if this is outside the predetermined area, Diagnose.

Second, the exhaust temperature is detected by the temperature sensor under the condition that the engine is operating stably, and the exhaust temperature in the vicinity of the temperature sensor is estimated under the same condition, and the detected temperature is estimated. When the difference from the temperature is larger than a predetermined value, a failure is diagnosed (Patent Document 1).
JP 2006-022730 A (paragraph number 0027)

However, the above two techniques have the following problems.
That is, with respect to the first technique, in an engine equipped with a DPF, a temperature sensor used for detecting the exhaust temperature generally requires a wide measurement range. It is difficult to diagnose a failure by determining whether or not the area is outside the predetermined area. If the predetermined area is set narrowly so as to force the diagnosis, the temperature that should be in the normal area belongs to the outside of the predetermined area, and an erroneous diagnosis that a failure has occurred is made. It can be.

  On the other hand, for the second technique, the estimation of the exhaust temperature is influenced by various factors such as the structure of the exhaust passage as well as the engine operating state such as the engine speed, the fuel injection amount, and the EGR gas amount. Therefore, it is not always easy, and if this is to be done strictly, the calculation configuration for that will be very complicated. In order to simplify the calculation, the relationship between the engine operating state and the exhaust temperature can be given as data such as a map in advance, but in this case, a lot of man-hours are required to create the map. Become.

  In consideration of the above problems, the present invention can prevent erroneous diagnosis that a temperature sensor used for a wide measurement range such as temperature measurement of an engine exhaust has a failure with a simple configuration. An object of the present invention is to provide a temperature sensor failure diagnosis apparatus.

The temperature sensor failure diagnosis apparatus according to the present invention is different from this temperature sensor that detects a temperature correlated with an output from a temperature sensor arranged upstream of a DPF provided in an exhaust passage of an engine to be diagnosed. The temperature detection means arranged downstream of the DPF and whether or not the temperature sensor is malfunctioning, the output of the temperature sensor is set as a normal region with respect to the temperature obtained as the output from the temperature sensor. A first failure determination means for determining based on whether or not the area is in the first region, and permitting or prohibiting determination by the first failure determination means based on the temperature detected by the temperature detection means When the temperature is higher than the lower limit temperature of the first region and the temperature in the first region is within the second region set as the lower limit temperature, the first reason Determination control means for permitting determination by the determination means, wherein the first failure determination means determines whether or not the temperature sensor has failed in response to permission of determination by the determination control means. judge.

  In the present invention, a temperature detection means for diagnosis permission determination is provided in addition to the temperature sensor to be diagnosed, and based on the temperature detected thereby, the determination as to whether or not the temperature sensor has failed is permitted or prohibited. It was. Here, since the temperature detected by the temperature detecting means correlates with the output from the temperature sensor, based on this detected temperature, the range in which the temperature obtained as the output from the normal temperature sensor should be It is possible to grasp. Then, only when this desired range is included in the actually settable area, the predetermined area as the normal area is forcibly narrowed by determining whether or not there is a failure. Therefore, the failure can be diagnosed with a simple configuration.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a configuration of an exhaust purification device of the engine 1. In the present embodiment, the control unit 101 of the engine 1 has a function as a control unit for controlling the exhaust purification device, and this engine control unit (hereinafter referred to as “ECU”) 101 is the first of the present invention. It has a function as a temperature sensor failure diagnosis apparatus according to the embodiment. In the present embodiment, the engine 1 is a direct injection type diesel engine and constitutes a drive source for a vehicle such as a truck.

  An air cleaner (not shown) is attached to the introduction portion of the intake passage 11, and dust in the intake air is removed by the air cleaner. A compressor 12a of a variable nozzle type turbocharger 12 is installed in the intake passage 11, and the intake air is compressed and sent out by the compressor 12a. The compressed intake air is cooled by an intercooler (not shown), then flows into the surge tank 13, and is distributed to each cylinder at the manifold portion.

In the engine body, a fuel supply injector 21 is installed in the cylinder head for each cylinder. The injector 21 is actuated by a signal from the ECU 101. Fuel delivered by a fuel pump (not shown) is supplied to each injector 21 via a fuel supply pipe 22 and a common rail 23, and is injected into the combustion chamber of each cylinder.
A turbine 12b of the turbocharger 12 is installed in the exhaust passage 31 downstream of the manifold portion, and the compressor 12a rotates when the turbine 12b is driven by the exhaust. A DPF (diesel particulate filter) 32 is interposed downstream of the turbine 12b. The DPF 32 includes a honeycomb filter carrier (hereinafter simply referred to as “filter carrier”) 321 made of ceramic, and the particulate matter in the exhaust gas is collected by the filter carrier 321. As the accumulation of particulates in the filter carrier 321 progresses, the effective passage area of the exhaust gas decreases and the pressure loss increases. Therefore, it is necessary to regenerate the DPF 32 by burning the accumulated particulates. . In the present embodiment, an oxidation catalyst 322 is installed upstream of the filter carrier 321, the nitric oxide in the exhaust gas is converted into nitrogen dioxide by the oxidation catalyst 322, and nitrogen dioxide is supplied to the filter carrier 321. Nitrogen dioxide is known to have high oxidation reactivity, and can burn particulates even under relatively low temperature conditions. In this embodiment, the filter carrier 321 and the oxidation catalyst 322 are built in one housing, and a so-called continuous regeneration type DPF 32 is configured. The DPF is not limited to the continuous regeneration type, but may be an intermittent regeneration type. This intermittent regeneration type DPF estimates the amount of particulate accumulation, and performs control for burning the particulate when the amount of accumulation reaches a certain amount. For example, it is possible to burn the accumulated particulates while suppressing the heat load by reducing the excess air ratio compared to during normal operation and performing exhaust gas temperature raising control such as post injection.

  The exhaust passage 31 is connected to the intake passage 11 by an EGR pipe 33. A part of the exhaust gas is recirculated to the intake passage 11 through the EGR pipe 33. In the present embodiment, the EGR pipe 33 connects the exhaust passage 31 upstream of the turbine 12 b of the turbocharger 12 and the surge tank 13 interposed in the intake passage 11. An EGR control valve 34 is interposed in the EGR pipe 33, and the flow rate of exhaust gas recirculated by the EGR control valve 34 is controlled. The EGR control valve 34 is actuated by a signal from the ECU 101.

  In the exhaust passage 31, upstream and downstream of the DPF 32, temperature sensors 41 and 42 for detecting the temperature of the engine exhaust are respectively installed. The upstream exhaust temperature sensor 41 (corresponding to a “first exhaust temperature sensor”) is for detecting the temperature Texh1 of the engine exhaust before flowing into the DPF 32. On the other hand, the downstream exhaust temperature sensor 42 (corresponding to a “second exhaust temperature sensor”) is for detecting the temperature Texh2 of the engine exhaust after the particulates have been processed. Detection signals from these exhaust temperature sensors 41 and 42 are output to the ECU 101. ECU 101 receives a signal from a crank angle sensor 151 that generates a signal for each unit crank angle and reference crank angle, and a signal from an accelerator sensor 152 that detects a depression amount of an accelerator pedal by a driver, and an ignition switch (not shown). Signals from the start switch and the coolant temperature sensor are input. As described above, the ECU 101 also functions as a temperature sensor failure diagnosis device. Based on the input signal, the ECU 101 monitors the regeneration status of the DPF 32, and the temperature in the DPF 32 is low, such as during low-speed driving. When it is determined that the exhaust gas temperature is excessively decreased, the exhaust gas temperature is raised by control such as post injection to maintain the regeneration function of the DPF 32, and whether or not the upstream exhaust gas temperature sensor 41 has failed. Determine. The diagnosis of the failure according to the present embodiment is based on permitting diagnosis of the failure of the upstream exhaust temperature sensor 41 when the temperature Texh2 detected by the downstream exhaust temperature sensor 42 is in a predetermined region. is there. In this embodiment, based on the output from the exhaust gas temperature sensor 41 on the upstream side, a disconnection or short circuit failure in the exhaust gas temperature sensor 41 is diagnosed. Hereinafter, the operation of the ECU 101 according to the present embodiment including the diagnosis of the failure of the exhaust temperature sensor 41 will be described with reference to a flowchart.

  FIG. 2 is a flowchart of a basic routine related to fuel supply control of the engine 1. This routine is executed every predetermined time while the ignition switch is on. By this routine, the fuel injection amount Qf for the engine 1 is calculated and set, and exhaust gas temperature raising control for maintaining the regeneration function of the DPF 32 is performed. In the present embodiment, the exhaust gas temperature raising control is performed by post-injection that is delayed from the main injection for injecting fuel of the amount Qf.

In S101, various operating state parameters required for fuel supply control such as the engine speed (which can be calculated based on the signal generation period for each reference crank angle) and the accelerator pedal depression amount are read.
In S102, a fuel supply amount Qf by main injection to the engine 1 is calculated based on the read operation state parameter.

  In S103, it is determined whether or not the failure determination flag Fdgn is zero. When it is 0, it progresses to S104, and when it is not 0, it does not perform exhaust gas temperature raising control by the process of S104-S107, but progresses to S108. The failure determination flag Fdgn is for indicating that the upstream exhaust temperature sensor 41 has failed, and is normally set to 0. In the failure diagnosis routine described later, the exhaust temperature sensor 41 has failed. When it is determined that, it is switched to 1. In the present embodiment, as will be described later, the exhaust gas temperature raising control is performed based on the temperature Texh1 detected by the upstream exhaust gas temperature sensor 41. Therefore, when the exhaust gas temperature sensor 41 is out of order, the exhaust gas temperature rise control is performed. The exhaust gas temperature Texh, which is basic information for temperature control, cannot be accurately obtained, and the exhaust gas temperature raising control cannot be accurately performed, so that a series of processes for that purpose is prohibited by the process of S103. .

In S104, the temperature Texh1 of the engine exhaust before flowing into the DPF 32, which is detected by the upstream exhaust temperature sensor 41, is read.
In S105, it is determined whether or not the read exhaust temperature Texh1 is equal to or higher than a preset threshold value Trgn for determining whether or not regeneration is possible. When it is equal to or higher than Trgn, the process proceeds to S108, and when it is less than Trgn, the process proceeds to S106 in order to increase the temperature in the DPF 32 by post injection.

In S106, a fuel supply amount Qp by post injection is calculated. The post injection amount Qp is set to a larger value based on the exhaust gas temperature Texh1 as the difference between the threshold value Trgn and the exhaust gas temperature Texh1 (= Trgn−Texh1) is larger.
In S <b> 107, the calculated post injection amount Qp is set in the drive circuit of the injector 21 in order to perform post injection.

In S108, the main injection amount Qf is set in the drive circuit of the injector 21, and the fuel supply control in this routine is terminated.
FIG. 3 is a flowchart of a failure diagnosis routine according to the present embodiment. This routine is executed every predetermined time on condition that a certain time has elapsed after the engine 1 is started. By this routine, it is determined whether or not the upstream exhaust temperature sensor 41 has failed, and a failure determination flag Fdgn is set.

In S201, it is determined whether or not the engine 1 is in steady operation. When the steady operation is being performed, the process proceeds to S202 in order to diagnose the failure through the following steps. When the steady operation is not being performed, this routine is terminated.
In S202, the temperature Texh2 of the engine exhaust after the particulate processing by the DPF 32, which is detected by the exhaust temperature sensor 42 on the downstream side, is read.

  In S203, it is determined whether or not the read exhaust temperature Texh2 is in a diagnosis permission region having predetermined values T21 and T22 as lower and upper limits, respectively. If it is in the diagnosis-permitted area, the process proceeds to S204 to perform failure diagnosis in the subsequent steps. If not, the routine is terminated. The diagnosis permission area defined for the exhaust temperature Texh2 corresponds to the “second area” according to the present embodiment, and is set as an area in a range different from a normal determination area (S205) described later. .

In S204, the output voltage E1 from the exhaust temperature sensor 41 is read in order to diagnose a failure of the exhaust temperature sensor 41 on the upstream side.
In S205, it is determined whether or not the read output voltage E1 is in a normal determination region having predetermined values Esll and Eslh as lower and upper limits, respectively. If it is in the normal determination area, the exhaust temperature sensor 41 is assumed to be normal, and the process proceeds to S206. The normality determination region defined for the output voltage E1 from the upstream exhaust temperature sensor 41 corresponds to the “first region” according to the present embodiment.

In S206, a value CNT of a determination confirmation counter (to be described later) is reset to zero.
In S207, it is assumed that the exhaust temperature sensor 41 is normal, and the failure determination flag Fdgn is set to 0.
In S208, the value CNT of the determination confirmation counter is incremented by one.
In S209, it is determined whether or not the counter value CNT after the increase has reached a predetermined value CNTsl. When it has been reached, the process proceeds to S210, and if it has not been reached, this routine is terminated and the determination relating to diagnosis is suspended.

In S210, the failure determination flag Fdgn is set to 1 to determine the determination that there is a failure.
FIG. 4 is an explanatory diagram of the failure diagnosis control according to the present embodiment. 4A shows the relationship between the exhaust temperature Texh1 and the sensor output value (voltage E1) with respect to the upstream exhaust temperature sensor 41, and FIG. 4B shows the exhaust with respect to the exhaust temperature sensor 42 on the downstream side. The relationship between temperature Texh2 and sensor output value (voltage E2) is shown.

  In the present embodiment, as part of the regeneration control of the DPF 32, a failure of the exhaust temperature sensor 41 for detecting the engine exhaust temperature Texh1 is diagnosed. The exhaust temperature sensor 41 has a very wide measurement range as compared with a temperature sensor used for general temperature measurement. Therefore, there is a fluctuation range of the voltage E1 that the exhaust temperature sensor 41 can output in a normal state. It is not possible to set a range of abnormal output that should not be output widely. If the range of this abnormal output is set forcibly for diagnosis, it may be erroneously determined that a failure has occurred even though it is normal, and its adverse effect is great.

  In order to deal with such a problem, in the present embodiment, based on the temperature Texh2 detected by the downstream exhaust temperature sensor 42, it is determined whether or not a failure can be diagnosed based on the output from the upstream exhaust temperature sensor 41. If it is determined that the diagnosis is possible, the diagnosis is permitted and the diagnosis is actually performed. The engine exhaust temperature Texh2 downstream of the DPF 32 is higher than that upstream due to particulate combustion in the DPF 32, but correlates with the output from the upstream exhaust temperature sensor 41. From this, it is possible to grasp the range where the voltage E1 obtained as the output from the exhaust temperature sensor 41 in the normal state should be based on the temperature Texh2 detected by the downstream exhaust temperature sensor 42. . In the present embodiment, when the engine exhaust temperature Texh2 downstream of the DPF 32 is in the range of temperatures T21 to T22, the voltage E1 obtained as the output from the upstream exhaust temperature sensor 41 is in the range of voltages E11 to E12. As a power, a normal determination region (Esll to Eslh) that includes this desired range is set. In order to prevent erroneous diagnosis, the diagnosis permission area (T21 to T22) is set as a narrower area than the normal determination area (more precisely, the temperature areas T11 to T12 corresponding to the normal determination areas Esll to Eslh). is doing.

  In the present embodiment, the exhaust temperature sensor 42 on the downstream side corresponds to “temperature detection means”. Further, the function as “first failure determination means” is shown in FIG. 2 by the processing of S204 to 210 in the flowchart shown in FIG. 3, and the function as “determination control means” is shown in FIG. The functions as “temperature control means” are realized by the processes of S104 to S107 in the flowchart.

According to this embodiment, the following effects can be obtained.
In the present embodiment, an exhaust temperature sensor 42 for diagnosis permission determination is provided in addition to the exhaust temperature sensor 41 to be diagnosed, and whether or not the exhaust temperature sensor 41 has failed based on the temperature Texh2 detected thereby. Judgment is permitted or prohibited. As described above, the temperature Texh2 detected by the exhaust temperature sensor 42 is correlated with the engine exhaust temperature Texh1 upstream of the DPF 32, and the exhaust temperature sensor 41 in a normal state is based on the exhaust temperature Texh2. It is possible to grasp the range in which the voltage E1 obtained as an output from (which is uniquely related to the temperature Texh1) should be. Therefore, according to the present embodiment, the normal determination region is forcibly narrowed by performing the determination regarding the diagnosis only when the range to be included is included in the normal determination regions (Esll to Eslh) that can be actually set. A failure can be diagnosed with a simple configuration without setting. According to the present embodiment, the temperature Texh2 detected by the downstream exhaust temperature sensor 42 is used as information for determining whether or not the failure of the upstream exhaust temperature sensor 41 can be diagnosed. Even when there is a large difference between the temperatures Texh1 and Texh2 detected by these devices, such as a device with a large heat capacity such as DPF 32 interposed between the exhaust temperature sensors 41 and 42, the failure is properly diagnosed. can do.

Hereinafter, other embodiments of the present invention will be described. The difference between each embodiment described below and the first embodiment lies only in the contents of the failure diagnosis control, and the overall configuration of the engine 1 is the same as that shown in FIG. The basic contents of are the same as shown in FIG.
FIG. 5 is a flowchart of a failure diagnosis routine according to the second embodiment of the present invention. Similarly to the first embodiment, this routine is also executed at predetermined time intervals on the condition that a certain time has elapsed after the engine 1 is started. It is determined whether or not the exhaust gas temperature sensor 41 is malfunctioning. In the first embodiment, when the temperature Texh2 of the engine exhaust downstream of the DPF 32 is not in the diagnosis permission region, the determination regarding the diagnosis is prohibited (S203 in FIG. 3). The normal determination area (Esll to Eslh) is made different from the case in the diagnosis permission area. FIG. 6 is an explanatory diagram of the failure diagnosis control according to the present embodiment. The failure diagnosis control according to the present embodiment will be described with reference to FIG. 6 as appropriate.

In S301, it is determined whether or not the engine 1 is in steady operation. Only when the operation is in a steady state, the process proceeds to S302, and processing relating to diagnosis determination in the subsequent steps is executed.
In S302, the temperature Texh2 detected by the downstream exhaust temperature sensor 42 is read.
In S303, the output voltage E1 from the upstream exhaust temperature sensor 41 is read.

In S304, it is determined whether or not the read exhaust temperature Texh2 is in a predetermined diagnosis permission region (T21 to T22). When it is in the diagnosis permission area, the process proceeds to S305, and when not, the process proceeds to S306.
In S305, it is determined whether or not the read output voltage E1 is in the first normal determination region RE1 (Esll1 to Eslh1) as the “first region”. If it is in the first normality determination area RE1, the process proceeds to S307, and if not, the process proceeds to S308. The first normality determination area RE1 is set to a relatively narrow range.

  In S306, it is determined whether or not the read output voltage E1 is in the second normal determination region RE2. If it is in the second normal determination area RE2, the process proceeds to S307, and if not, the process proceeds to S308. The second normal determination region RE2 corresponds to the “third region” according to the present embodiment, and is set in a wider range than the first normal determination region RE1 as shown in FIG. . FIG. 6A shows a normal determination region RE1 when the exhaust temperature Texh2 is in the diagnosis permission region, and FIG. 6B shows a normal determination region RE2 when the exhaust temperature Texh2 is not in the diagnosis permission region.

In S307, assuming that the exhaust temperature sensor 41 is normal, the failure determination flag Fdgn is set to 0.
In S308, it is assumed that the exhaust temperature sensor 41 has failed, and the failure determination flag Fdgn is set to 1.
In the present embodiment, the function as “first failure determination means” is performed by the processing of S303, 305, 307, and 308 in the flowchart shown in FIG. The function as “determination means” and the function as “determination control means” are realized by the processing of S302 and S304 in the flowchart.

  According to the present embodiment, since the ranges of the normal determination areas RE1 and RE2 are different depending on whether the temperature Texh2 downstream of the DPF 32 is in the diagnosis permission area (T21 to T22) or not, the diagnosis permission area The failure diagnosis accuracy in the case of (2) can be improved, and even if it is not in this region, the failure can be diagnosed with appropriate accuracy by the second normal determination region RE2 installed in a wide range.

  In the above description, the diagnosis target is the exhaust gas temperature sensor 41 on the upstream side, and determination regarding diagnosis is permitted or prohibited based on the temperature Texh2 detected by the exhaust gas temperature sensor 42 on the downstream side. However, the exhaust temperature sensor to be diagnosed is not limited to the upstream one but may be the downstream one. The content of the failure diagnosis control when the downstream exhaust temperature sensor 42 is a diagnosis target may be the same as that shown in FIG. 3 or 5, and those skilled in the art can use this without any specific illustration. I can understand.

  Further, the case where the exhaust temperature sensor is employed as the “temperature detection means” for diagnosis permission determination has been described above, but what can be employed as the “temperature detection means” is not limited to the exhaust temperature sensor. . For example, as a third embodiment of the present invention, an intake air temperature sensor that detects the temperature of air taken into the engine 1 can be employed. FIG. 7 shows a flowchart of a failure diagnosis routine in this case. In the present embodiment, an intake air temperature sensor is attached to the surge tank 13 in addition to the configuration of the engine 1 shown in FIG. In an engine including an air flow meter, an intake air temperature sensor integrated with the air flow meter may be used. The temperature sensor to be diagnosed may be the exhaust gas temperature sensor 41 installed upstream of the DPF 32 as in the first embodiment. The failure diagnosis control according to the present embodiment will be described with reference to FIG.

In S401, it is determined whether or not the engine 1 is in steady operation. Only when the operation is steady, the process proceeds to S402.
In S402, the temperature Tint detected by the intake air temperature sensor is read.
In S403, it is determined whether or not the read intake air temperature Tint is in a diagnosis permission region having predetermined values T31 and T32 as lower and upper limits. If it is in the diagnosis permission area, the process proceeds to S404. If not, this routine is ended, and the determination regarding the diagnosis in the subsequent steps is prohibited. This diagnosis permission region (T31 to T32) indicates whether or not the range where the voltage E1 obtained as an output from the exhaust temperature sensor 41 in a normal state should be included in the normal determination region that can be actually set. As a region for discrimination, a relatively narrow intake air temperature range is set.

In S404, the output voltage E1 from the exhaust temperature sensor 41 which is the diagnosis target is read.
In S405, it is determined whether or not the read output voltage E1 is in the normal determination region (Esll3 to Eslh3). If it is in the normal determination area, the process proceeds to S406, and if not, the process proceeds to S407.
In S406, the exhaust temperature sensor 41 is assumed to be normal, and the failure determination flag Fdgn is set to 0.

In S407, it is assumed that the exhaust temperature sensor 41 has failed, and the failure determination flag Fdgn is set to 1.
In the present embodiment, the function as “first failure determination means” is realized by the processing of S404 to 407 in the flowchart shown in FIG. 7, and the function as “determination control means” is realized by the processing of S402 and 403 in the flowchart. Is done.

In the present embodiment, the basic content of the fuel supply control may be the same as that shown in FIG.
The present invention can be applied not only to a diesel engine but also to a gasoline engine.

Configuration of diesel engine according to first embodiment of the present invention Flow chart of basic routine of fuel supply control according to the embodiment Flow chart of failure diagnosis routine according to the embodiment Explanatory drawing about failure diagnosis control which concerns on embodiment same as the above Flowchart of a failure diagnosis routine according to the second embodiment of the present invention Explanatory drawing about failure diagnosis control which concerns on embodiment same as the above Flowchart of a failure diagnosis routine according to the third embodiment of the present invention that employs an intake air temperature sensor as the temperature detection means.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 11 ... Intake passage, 12 ... Turbocharger, 12a ... Turbocharger compressor, 12b ... Turbocharger turbine, 13 ... Surge tank, 21 ... Injector, 23 ... Common rail, 31 ... Exhaust passage, 32 ... Diesel Particulate filter, 321 ... Filter carrier, 322 ... Oxidation catalyst, 33 ... EGR pipe, 34 ... EGR control valve, 41 ... First exhaust temperature sensor as "diagnostic object", 42 ... Second exhaust temperature sensor, 101 ... engine control unit, 151 ... crank angle sensor, 152 ... accelerator sensor.

Claims (5)

A temperature detecting means for detecting a temperature correlated with an output from a temperature sensor arranged upstream of the DPF provided in the exhaust passage of the engine to be diagnosed, different from the temperature sensor and arranged downstream of the DPF ; ,
It is determined whether or not the temperature sensor is out of order based on whether or not the output of the temperature sensor is in a first region set as a normal region with respect to the temperature obtained as the output from the temperature sensor. First failure determination means;
The determination by the first failure determination unit is permitted or prohibited based on the temperature detected by the temperature detection unit, and the detected temperature is higher than the lower limit temperature of the first region And a determination control unit that permits determination by the first failure determination unit when the temperature is within the second region set as the lower limit temperature in the first region .
The first failure determination unit is a temperature sensor failure diagnosis apparatus that determines whether or not the temperature sensor is in failure in response to the determination permission by the determination control unit. The temperature sensor failure diagnosis apparatus according to claim 1 , wherein the second region is a region including a continuous temperature having an upper limit and a lower limit. When the determination by the first failure determination means is prohibited by the determination control means, this is set as a wider area than the first area based on the temperature obtained as the output from the temperature sensor. and, the third as a normal region is determined whether the outside area, according fault further to claim 1 or 2 Ru is configured to include a second failure determining means for determining said temperature sensor Temperature sensor failure diagnosis device. The temperature detecting means uses the exhaust temperature sensor to be diagnosed as a first exhaust temperature sensor, and the second exhaust gas installed in a passage portion different from the first exhaust temperature sensor in the exhaust passage of the engine. The temperature sensor failure diagnosis apparatus according to any one of claims 1 to 3, which is a temperature sensor. The failure diagnosis device according to any one of claims 1 to 4 ,
A particulate filter installed in the exhaust passage of the engine for collecting particulates in the exhaust;
An engine exhaust gas purification apparatus comprising temperature control means for controlling the actual engine exhaust temperature based on the exhaust gas temperature detected by the exhaust gas temperature sensor as the temperature sensor.

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