JP2014109229A - Failure diagnosis device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure diagnosis device capable of determining a failure of a flow passage switching valve even when a cooling water temperature sensor of an engine is in failure.SOLUTION: A failure diagnosis device 100 diagnoses a failure of a flow passage switching valve 7 in a cooling system of an engine 1 including the flow passage switching valve 7 for switching a flow passage so that cooling water flows by bypassing a radiator 6 during warming-up of the engine 1 and flows through the radiator 6 after warming-up, and an intercooler 23 arranged to be adjacent to the radiator 6 and cooling intake air of the engine 1. The failure diagnosis device 100 includes an intake air temperature detector 9 for detecting an intake air temperature on the downstream side of the intercooler 23, and a failure determining part 10 for determining the failure of the flow passage switching valve 7 on the basis of the comparison between the intake air temperature during warming-up of the engine 1 and the intake air temperature after warming-up.

Description

  The present invention relates to a failure diagnosis apparatus for diagnosing a failure of a flow path switching valve in an engine cooling system.

  The engine coolant circuit includes a circulation circuit that circulates coolant in the engine, and a radiator circuit that recirculates the coolant after passing through the engine to the radiator and then circulates it back to the engine. Switching of each circuit is performed by a thermostat provided at a branch portion between the circulation circuit and the radiator circuit. When the cooling water temperature reaches a predetermined temperature (for example, 80 ° C.) set in advance, the thermostat opens and switches the cooling water circuit.

  That is, when the coolant temperature is low, such as during cold start, the thermostat is closed and the coolant circuit becomes a circulation circuit. When the coolant temperature reaches a predetermined temperature, the thermostat is opened and the coolant circuit is a radiator circuit. It becomes.

  Here, when a closed failure occurs in which the thermostat is closed, the thermostat does not open even if the coolant temperature exceeds a predetermined temperature.

  In order to detect such a closed failure, Patent Document 1 describes an apparatus for detecting a thermostat failure. The apparatus includes a cooling water temperature sensor that detects a cooling water temperature, and a cooling water temperature estimation unit that estimates a cooling water temperature from an operating state, and detects the detected cooling water temperature and the estimated cooling water temperature. Based on this, the thermostat failure is determined.

JP 2000-104549 A

  However, since the failure detection device of Patent Document 1 uses the signal of the cooling water temperature sensor, it is impossible to detect a failure of the thermostat when the cooling water temperature sensor fails.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a failure diagnosis device capable of determining a failure of a flow path switching valve even if an engine coolant temperature sensor fails. And

  The present invention includes a flow path switching valve that switches a flow path so that cooling water flows around the radiator during warm-up of the engine, and flows through the radiator after warm-up, and is disposed adjacent to the radiator. An intercooler for cooling the intake air of the engine, and a failure diagnosis device for diagnosing a failure of the flow path switching valve in the engine cooling system, the intake air temperature detector detecting an intake air temperature downstream of the intercooler, A failure determination unit that determines a failure of the flow path switching valve based on a comparison between an intake air temperature during warming up of the engine and an intake air temperature after warming up.

  In the present invention, the failure of the flow path switching valve is determined by comparing the intake air temperature during warm-up of the engine and the intake air temperature after warm-up, so even if the coolant temperature sensor fails, the flow path A failure of the switching valve can be determined.

It is a lineblock diagram of an engine carrying a failure diagnostic device concerning an embodiment of the present invention. It is a flowchart which shows the processing content of a controller. It is a time chart which shows the driving | running state in case the failure of a thermostat is determined.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of an engine 1 equipped with a failure diagnosis apparatus 100 according to the present embodiment. In addition, although the diesel engine is mentioned as an example as the engine 1 of this embodiment, a gasoline engine may be used.

  The engine 1 includes an intake passage 2 through which intake air flows, an exhaust passage 3 through which exhaust after combustion flows, and an EGR passage 4 that recirculates part of the exhaust to the intake passage 2.

  The intake passage 2 includes an air cleaner 21, a turbocharger 22, and an intercooler 23 in order from the upstream side. The intake air sucked through the air cleaner 21 is compressed by the turbocharger 22, cooled by the intercooler 23, and then sucked into the combustion chamber of the engine 1.

The exhaust passage 3 includes a turbine 31, a DOC (Diesel Oxidation Catalyst) 32, a DPF (Diesel Particulate Filter) 33, and an SCR (Selective Catalytic Reduction) catalyst 34 in order from the upstream side. The turbine 31 is rotated by the exhaust pressure and rotationally drives the turbocharger 22 disposed on the same axis. The DOC 32 oxidizes NO (nitrogen monoxide) in the exhaust gas to NO ₂ (nitrogen dioxide). The DPF 33 is a filter that collects particulate matter in the exhaust gas. The SCR catalyst 34 selectively reduces and purifies NOx (nitrogen oxide) using ammonia as a reducing agent generated from the urea aqueous solution.

  The EGR passage 4 is branched from the upstream side of the turbine 31 of the exhaust passage 3 and connected to the downstream side of the intercooler 23 of the intake passage 2. The EGR passage 4 includes an EGR cooler 41 that cools the exhaust flowing through the EGR passage 4 and an EGR valve 42 that adjusts the amount of exhaust introduced into the intake passage 2.

  The engine 1 further includes, as a cooling system, a cooling water circuit 5 for circulating the cooling water, a radiator 6 provided in the cooling water circuit 5 for cooling the cooling water, and a thermostat 7 capable of switching the cooling water circuit 5. Prepare. The cooling water circuit 5 includes a circulation circuit (not shown) that circulates the cooling water in the engine 1 while bypassing the radiator 6, and a radiator circuit 51 that circulates the cooling water via the radiator 6.

  The intercooler 23 is disposed close to the vehicle front side of the radiator 6, and the cooling air flowing through the intercooler 23 and the cooling water flowing through the radiator 6 are cooled by the operation of the cooling fan 8. Since the intercooler 23 is disposed in the vicinity of the radiator 6, when the cooling fan 8 is not operating or when the traveling wind of the vehicle is not generated, the radiator 6 is inserted into the intake air of the engine 1 that passes through the intercooler 23. The heat of the flowing cooling water is transmitted.

  The thermostat 7 uses a predetermined temperature (for example, 80 ° C.) set in advance as a threshold, and closes when the cooling water temperature is lower than the predetermined temperature, and opens when the cooling water temperature is equal to or higher than the predetermined temperature. The cooling water circuit 5 becomes a circulation circuit in which the cooling water bypasses the radiator 6 when the thermostat 7 is closed, and becomes a radiator circuit 51 in which the cooling water flows through the radiator 6 when the thermostat 7 is opened. Thereby, when the cooling water temperature is low, warming up of the cooling water is promoted, and when the cooling water temperature becomes high, heat is radiated from the radiator 6, so that the cooling water temperature can always be maintained within an appropriate temperature range. .

  Next, a failure diagnosis apparatus 100 for diagnosing a failure of the thermostat 7 in the cooling system of the engine 1 will be described.

  The failure diagnosis apparatus 100 monitors the operating state of the engine 1, an intercooler outlet temperature sensor 9 that is provided downstream of the intercooler 23 in the intake passage 2 and detects the temperature of intake air immediately after passing through the intercooler 23. And a controller 10 that performs failure determination based on a signal transmitted from the intercooler outlet temperature sensor 9.

  FIG. 2 is a flowchart showing the processing contents of the controller 10. This process is executed when the ignition switch of the vehicle is turned on and the engine 1 is started.

  In step S1, the controller 10 sets a flag F to 0. The flag F is 1 when a value is stored in a temperature T1 described later. Here, the flag F is set to 0 for reset.

  In step S2, the controller 10 determines whether or not the engine start is a cold start. If it is determined that the engine is a cold start, the process proceeds to step S3. If it is determined that the engine is not a cold start, the process ends. The cold start means engine start in a state where the cooling water of the engine 1 is sufficiently cooled (for example, cooling water temperature≈outside air temperature). Therefore, in the case of engine restart in a state where the cooling water is not cooled, it is determined that it is not a cold start, and the process ends.

  In step S3, the controller 10 determines whether or not the engine 1 is in an idle state. If it is determined that the engine is in the idle state, the process proceeds to step S4. If it is determined that the engine is not in the idle state, the process in this step is executed again. The idle state means a state of the engine 1 when the vehicle is stopped and there is no intention of acceleration from the driver. That is, the determination that the engine 1 is in the idle state is established when both the engine speed is within a predetermined low rotation range and the engine torque is within a predetermined low torque range. Therefore, when it is determined in step S2 that the engine is cold-started and the process proceeds to this step, it is determined that the engine is in the idle state in this step because it is immediately after the engine is started.

  When the engine 1 is in an idle state, the vehicle is stopped and no running wind is generated, so the intake air passing through the intercooler 23 is easily affected by the heat of the cooling water in the radiator 6. Therefore, it is possible to improve the accuracy of failure determination by performing failure determination described later in the idle state.

  In addition to the determination that the engine is in the idle state, the fact that the cooling fan is stopped may be added to the determination condition of this step. Thereby, it can be determined that the intake air passing through the intercooler 23 is more susceptible to the influence of the heat of the cooling water in the radiator 6, and the accuracy of failure determination described later can be improved.

  In step S4, the controller 10 determines whether or not the flag F is zero. If it is determined that the flag F is 0, the process proceeds to step S5, and if it is determined that the flag F is not zero, the process proceeds to step S7.

  In step S5, the controller 10 stores the temperature detected by the intercooler outlet temperature sensor 9 as T1. That is, the temperature T1 is the intercooler outlet temperature in the idle state at the cold start.

  In step S6, the controller 10 sets the flag F to 1. That is, the flag F is 1 when a value is stored in the temperature T1, and is 0 when it is not stored. After this step is executed, the process proceeds to step S4. If it is determined in step S4 that the flag F is not 0, the process proceeds to step S7.

  In step S7, the controller 10 determines whether or not the warm-up end time has elapsed since the engine 1 was started. If it is determined that the warm-up end time has elapsed, the process proceeds to step S8. If it is determined that the warm-up end time has not elapsed, the process proceeds to step S3. Since the process of this flowchart is started when the engine 1 is started, an elapsed time from the start of the engine can be integrated by separately providing a timer that starts counting when the process of step S1 is executed. The warm-up end time is set in advance to such a time that it can be assumed that the temperature of the cooling water is sufficiently increased, the thermostat 7 is opened, and the cooling water circuit 5 is the radiator circuit 51.

  In step S8, the controller 10 stores the temperature detected by the intercooler outlet temperature sensor 9 as T2. That is, the temperature T2 is the intercooler outlet temperature in the idle state after the warm-up is completed.

  In step S9, the controller 10 determines whether or not the difference between the temperature T2 and the temperature T1 is greater than the failure determination value. If it is determined that the difference between the temperature T2 and the temperature T1 is greater than the failure determination value, the process proceeds to step S10, and it is determined that the thermostat 7 has not failed. On the other hand, if it is determined that the difference between the temperature T2 and the temperature T1 is equal to or less than the failure determination value, the process proceeds to step S11, and it is determined that the thermostat 7 is broken.

  Since the cooling water does not flow into the radiator 6 immediately after the cold start, the temperature of the cooling water in the radiator 6 is almost equal to the outside air temperature, and the temperature T1 of the intake air passing through the intercooler 23 is influenced by the heat of the cooling water. I do not receive it. After that, when the warm-up end time has elapsed, it is assumed that the high-temperature cooling water has flowed into the radiator 6, so the temperature of the cooling water in the radiator 6 is high, and the temperature T2 of the intake air passing through the intercooler 23 is the heat of the cooling water. It is considered that the failure judgment value is higher than the temperature T1. Therefore, it can be determined that the thermostat 7 has a closed failure by determining whether the difference between the temperature T2 and the temperature T1 is equal to or less than the failure determination value in step S9.

  FIG. 3 is a time chart showing an operation state when a failure of the thermostat 7 is determined.

  When the engine 1 is cold-started and becomes idle at time t1, the temperature detected by the intercooler outlet temperature sensor 9 is stored as T1. Thereafter, the intercooler outlet temperature rises as the engine speed increases as the vehicle travels. This is because the heat of the turbine 31 provided in the exhaust passage 3 is transmitted to the turbocharger 22 via the rotating shaft, and the intake air temperature rises. Further, the coolant temperature rises as the engine load increases.

  At time t2, when the cooling water temperature reaches a predetermined temperature of the thermostat 7, if the temperature is normal, the thermostat 7 is opened and the cooling water flows to the radiator 6, and the cooling water temperature decreases. If 7 is closed, the valve does not open and the cooling water does not flow to the radiator 6, so the cooling water temperature further increases.

  When the idle state is reached at time t3, since the warm-up end time has already elapsed, the temperature detected by the intercooler outlet temperature sensor 9 is stored as T2. Here, if the thermostat 7 is closed, the high-temperature cooling water does not flow to the radiator 6 even once the engine is started, so the temperature of the cooling water in the radiator 6 is kept low. As a result, the intake air passing through the intercooler 23 disposed close to the radiator 6 does not receive heat transfer from the cooling water in the radiator 6, so that the temperature T2 hardly changes from the temperature T1. Therefore, the difference between the temperature T1 and the temperature T2 is equal to or less than the failure determination value, and it is determined that the thermostat 7 has failed.

  According to the above embodiment, there exist the effects shown below.

  The intake air temperature at the cold start when the engine 1 is warming up is compared with the intake air temperature after the end of the warm-up time, and it is determined that the thermostat 7 has failed, so the coolant temperature is detected. Even if the sensor fails, the failure of the thermostat 7 can be detected.

  Furthermore, the amount of heat transferred from the turbocharger 22 to the intake air according to the engine speed and the engine torque is taken into account by setting the intake air temperature used for determining the failure of the thermostat 7 to the intake air temperature when the engine 1 is in an idle state. Therefore, the failure of the thermostat 7 can be determined with high accuracy.

  Further, when the difference between the warm-up intake air temperature and the warm-up intake air temperature is equal to or less than the failure determination value, it is determined that the thermostat 7 has failed. Therefore, the temperature of the cooling water in the radiator 6 after the engine is started Can be determined with higher accuracy, and the failure determination accuracy of the thermostat 7 can be further improved.

  Furthermore, since the temperature of the intake air used for determining the failure of the thermostat 7 is the outlet temperature of the intercooler 23, a change in the intake air temperature affected by the heat of the cooling water in the radiator 6 can be detected more accurately. The failure determination accuracy of the thermostat 7 can be further improved.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  For example, in the above embodiment, the failure determination is performed using the intake air temperature at the outlet of the intercooler 23 detected by the intercooler outlet temperature sensor 9, but instead, the downstream intake temperature (for example, the intake temperature) The intake air temperature in the manifold) may be used.

  Furthermore, in the said embodiment, although the cooling water circuit 5 was switched to the circulation circuit and the radiator circuit 51 with the thermostat 7, you may switch the cooling water circuit 5 using another flow-path switching mechanism. In this case, a failure of the flow path switching mechanism can be determined instead of the thermostat.

1 Engine 6 Radiator 7 Thermostat (flow path switching valve)
9 Intercooler outlet temperature sensor (intake air temperature detector)
10 Controller (Failure judgment unit)
23 Intercooler 100 Failure diagnosis device

Claims (4)

The cooling water flows around the radiator while the engine is warming up, and the flow path switching valve that switches the flow path so that the cooling water flows through the radiator after the warming up is disposed close to the radiator. A failure diagnosis device for diagnosing a failure of the flow path switching valve in an engine cooling system comprising an intercooler that cools intake air of the engine,
An intake air temperature detector for detecting the intake air temperature downstream of the intercooler;
A failure determination unit that determines a failure of the flow path switching valve based on a comparison between an intake air temperature during warm-up of the engine and an intake air temperature after warm-up;
A failure diagnosis apparatus comprising: The failure diagnosis device according to claim 1,
The failure determination unit determines a failure of the flow path switching valve based on a comparison between an intake air temperature in an idle state during warm-up of the engine and an intake air temperature in an idle state after warm-up;
A fault diagnosis apparatus characterized by that. The failure diagnosis device according to claim 1 or 2,
The failure determination unit determines that the flow path switching valve has failed when the difference between the intake air temperature during warm-up and the intake air temperature after warm-up is equal to or less than a failure determination value.
A fault diagnosis apparatus characterized by that. The fault diagnosis apparatus according to any one of claims 1 to 3, wherein
The intake air temperature detector detects an outlet temperature of the intercooler as an intake air temperature;
A fault diagnosis apparatus characterized by that.

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