JP5738576B2 - Water temperature sensor failure judgment device - Google Patents

Description

  The present invention relates to a water temperature sensor failure determination device.

  In general, various exhaust gas countermeasure systems for automobiles are designed to work normally when the engine is sufficiently warmed up. For example, a part of the exhaust gas is extracted from the exhaust side and used in an EGR cooler. So-called exhaust gas, which is cooled and then returned to the intake side, and the exhaust gas returned to the intake side suppresses the combustion of fuel in the engine and lowers the combustion temperature to reduce the generation of NOx. Exhaust gas recirculation (abbreviated EGR) is also controlled so that exhaust gas recirculation is stopped and engine warm-up is prioritized when the engine is cold (cold state) during cold start. Whether or not the engine is sufficiently warmed up is determined by measuring the temperature of the cooling water passing through the engine with a water temperature sensor.

  On the other hand, there is a thermostat in the cooling water circulation path of the engine, and when the temperature of the cooling water at the cold start is low, the water path for circulating the cooling water between the engine and the radiator is closed by the operation of the thermostat and from the engine. By opening a water channel that returns the cooling water to the engine without passing through the radiator, the cooling water is circulated without passing through the radiator to give priority to warming up the engine.

  As is well known in the art, this type of thermostat melts the wax enclosed in the casing when the temperature of the cooling water rises, and opens the valve via a needle, a spring or the like by expansion when the wax melts. The operation is performed on the mechanical principle.

  As prior art document information relating to this type of engine cooling system, there is the following Patent Document 1 and the like.

JP 2003-278544 A

  However, in recent years, the vehicle exhaust system that monitors the occurrence of failures in vehicle exhaust gas countermeasure systems, lights up warning lights, etc. when a failure occurs, notifies the driver of the occurrence of the failure, and records the failure details The provision of a failure diagnosis device (onboard diagnosis: abbreviation OBD) is mandatory in each country, and it is required to be able to perform failure diagnosis of the water temperature sensor.

  That is, if a failure occurs in the water temperature sensor and the temperature of the cooling water of the engine has risen sufficiently, but the detected value does not fluctuate at a low temperature, the engine continues to operate in a cold state. This is because the operation in which the exhaust gas countermeasure system cannot be operated normally is continued.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a water temperature sensor failure determination device capable of monitoring the warm-up performance of an engine during a cold start and detecting whether or not a water temperature sensor has failed. And

  The present invention relates to a failure determination device for a water temperature sensor that detects the temperature of cooling water that has passed through an engine, and monitors the temperature increase of the cooling water during cold start by inputting a detection signal from the water temperature sensor and starts the operation. Control for determining failure of the water temperature sensor when the fuel injection amount of the engine from the start is integrated and the measured value of the temperature rise of the cooling water when the fuel injection amount reaches a predetermined integrated value does not exceed the threshold value The apparatus is characterized in that the temperature rise width when the fuel injection amount of the engine from the start of the engine reaches a predetermined integrated value under the condition that the thermostat is fully opened is set as a threshold value.

  Thus, according to this configuration, the temperature rise of the cooling water at the cold start is monitored by the control device based on the detection signal from the water temperature sensor, and the fuel injection amount of the engine from the start of the start by the control device. Even if the fuel injection amount reaches a predetermined integrated value, if the measured value of the temperature rise of the cooling water does not exceed the threshold value, the controller determines that the water temperature sensor has failed. .

  That is, even if the thermostat breaks down and the cooling water circulation to the radiator continues with the fully open state, if the water temperature sensor is normal, the measured value of the temperature rise of the cooling water falls below the threshold value. The measured value of the temperature rise of the water temperature sensor is lower than the threshold value corresponding to the lowest temperature rise assumed due to the failure of the thermostat. It is considered that no detected value is output.

According to the water temperature sensor failure determination device of the present invention described above, by monitoring the engine warm-up performance at the time of cold start, it is possible to detect the presence or absence of the failure of the water temperature sensor as distinguished from the failure of the thermostat. Therefore, measures such as repairs can be taken immediately when a failure of the water temperature sensor occurs, and the situation where the exhaust gas countermeasure system cannot be operated normally due to continued operation of the engine in the cold state due to the failure of the water temperature sensor. It is possible to achieve an excellent effect of being able to solve the problem.

It is the schematic which shows an example of the form which implements this invention. It is a graph which shows the relationship between the temperature of a cooling water, and the integrated value of fuel injection quantity.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 and 2 show an example of an embodiment of the present invention. Reference numeral 1 in FIG. 1 denotes an engine that is a diesel engine, and the engine 1 includes a turbocharger 2. The intake air 4 introduced from the air cleaner 3 is sent to the compressor 2a of the turbocharger 2 through the intake pipe 5, and the intake air 4 pressurized by the compressor 2a is sent to the intercooler 6 to be cooled. Further, the intake air 4 is guided to the intake manifold 7 and distributed to each cylinder of the engine 1, and the exhaust gas 8 discharged from each cylinder of the engine 1 is passed through the exhaust manifold 9 to the turbine of the turbocharger 2. The exhaust gas 8 that is sent to 2b and drives the turbine 2b is discharged to the outside of the vehicle through the exhaust pipe 10.

  In addition, a circulation path 13 is provided between the engine 1 and the radiator 11 so that the cooling water 12 can be circulated between the two. 12 is extracted to the outlet portion 14 and returned from the outlet portion 14 to the inlet portion 15 via the radiator 11.

  The inlet 15 to the engine 1 in the circulation path 13 is provided with a thermostat 16 that closes the channel of the cooling water 12 returned from the radiator 11 to the inlet 15, and when the temperature of the cooling water 12 is low, the thermostat 16, the water passage for returning the cooling water 12 from the radiator 11 to the engine 1 is closed and the bypass port 17 that connects the inlet portion 15 and the outlet portion 14 is opened, so that the cooling water 12 does not pass through the radiator 11. Circulation is prioritized to warm up the engine 1.

  Here, in the illustrated example, an example of an inlet control type in which the thermostat 16 is provided in the inlet portion 15 to the engine 1 is shown, but an outlet control type in which the thermostat 16 is provided in the outlet portion 14 from the engine 1 may be used. Of course.

  Further, a water temperature sensor 18 for detecting the temperature of the cooling water 12 that has passed through the engine 1 is provided at the inlet 15, and a detection signal 18 a of the water temperature sensor 18 is input to the control device 19. The control device 19 monitors the temperature rise of the cooling water 12 at the cold start based on the detection signal 18a from the water temperature sensor 18, integrates the fuel injection amount of the engine 1 from the start of the start, and The failure of the water temperature sensor 18 is determined when the temperature rise of the cooling water 12 when the amount reaches a predetermined integrated value does not exceed the threshold value.

That is, as shown in the graph of FIG. 2, when the temperature of the cooling water 12 at the start of the start is T ₀ , the temperature of the cooling water 12 rises and saturates as shown by a chain line A in FIG. When the variation due to environmental conditions is stabilized at an earlier stage than the saturating rate, for example, the fuel injection amount of the engine 1 is determined by using the integrated value Q ₁ of the fuel injection amount that will increase the water temperature of about 10 ° C. When the temperature rise of the cooling water 12 does not exceed the threshold value ΔT ₂ when the integrated value Q ₁ is reached, it is determined that the water temperature sensor 18 has failed.

Here setting, in the control device 19, the temperature rise when the fuel injection amount of the engine 1 from the beginning of startup under conditions thermostat 16 is fully opened reaches a predetermined integrated value Q ₁ as the threshold [Delta] T ₂ Thus, the failure of the water temperature sensor 18 can be determined in distinction from the failure of the thermostat 16.

That is, the solid line B in FIG. 2 shows the transition of the temperature rise of the cooling water 12 under the condition that the thermostat 16 is fully opened. However, if the thermostat 16 fails and the radiator 11 is fully opened, the cooling to the radiator 11 is performed. Even if the circulation of the water 12 has been continued, if the water temperature sensor 18 is normal, the temperature rise of the cooling water 12 below the solid line B should not occur, and the integrated value Q ₁ If the measured value of the temperature rise of the water temperature sensor 18 is lower than the threshold value ΔT ₂ corresponding to the lowest temperature rise assumed due to the failure of the thermostat 16, the water temperature sensor 18 itself fails and is normal. It is considered that no detected value is output.

Thus, in this way, the control device 19 monitors the temperature rise of the cooling water 12 at the time of cold start based on the detection signal 18a from the water temperature sensor 18, and the control device 19 from the start of the start. When the fuel injection amount of the engine 1 is integrated, and the fuel injection amount reaches the predetermined integrated value Q ₁ , the measured value of the temperature rise width of the cooling water 12 does not exceed the threshold value ΔT _2. Thus, the failure of the water temperature sensor 18 is determined.

Therefore, according to the above embodiment, by monitoring the warm-up performance of the engine 1 at the time of cold start, it is possible to detect the occurrence of the failure of the water temperature sensor 18 as distinguished from the failure of the thermostat 16 . When the failure of the water temperature sensor 18 occurs, it is possible to immediately take measures such as repair, and due to the failure of the water temperature sensor 18, the engine 1 continues to operate in the cold state and the exhaust gas countermeasure system cannot be operated normally. It can be resolved early.

  The water temperature sensor failure determination device of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Engine 12 Cooling water 16 Thermostat 18 Water temperature sensor 18a Detection signal 19 Control apparatus

Claims (1)

  An apparatus for determining a failure of a water temperature sensor for detecting a temperature of cooling water that has passed through an engine, wherein a detection signal from the water temperature sensor is input to monitor a rise in temperature of the cooling water during a cold start and the engine from the start of the start A controller for determining failure of the water temperature sensor when the measured value of the temperature rise of the cooling water when the fuel injection amount reaches a predetermined integrated value does not exceed the threshold value, A water temperature sensor failure determination device, characterized in that a temperature rise width when the fuel injection amount of the engine from the start of the engine reaches a predetermined integrated value under a condition where the thermostat is fully opened is set as a threshold value.

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