JP4639995B2 - Thermostat failure diagnosis method and engine cooling device - Google Patents

Description

  The present invention relates to a thermostat, particularly a thermostat failure diagnosis method provided in an engine cooling system, and an engine cooling apparatus.

  As a conventional thermostat failure diagnosis method, there is a method of making a diagnosis using a heat quantity ratio which is a ratio between a heat release amount from a radiator and a heat reception amount from an engine to cooling water (see Patent Document 1).

Explaining this method, when the predicted temperature of the engine cooling water rises to near the thermostat's set valve opening temperature, if the calculated heat ratio is larger than the judgment threshold, the amount of heat released from the radiator is too large. The thermostat is determined to be a valve opening failure that remains open despite the state in which the thermostat should be closed.
JP 2001-73773 A

  However, in the prior art, since the calculated heat quantity ratio is compared with a threshold value to determine a thermostat failure, the thermostat failure cannot be determined directly.

  Accordingly, an object of the present invention is to provide a thermostat failure determination method and an engine cooling device that solve the above-described problems.

The present invention includes a cooling water jacket through which cooling water flows in a cylinder block of an engine, a circulation channel for cooling water flowing out from the cooling water jacket to flow into the cooling water jacket again, and a midway in the circulation channel. A radiator that dissipates the heat of the cooling water, a bypass passage that bypasses the radiator with the cooling water, and controls the flow of the cooling water between the circulation passage and the radiator according to the temperature of the cooling water Then, a thermostat for flowing cooling water into the bypass flow path, a heater flow path branched from the circulation flow path and provided in parallel with the circulation flow path, provided in the heater flow path, An engine cooling device comprising: a heater for heating; and a temperature detecting means for detecting a cooling water temperature in the cooling water jacket. And the heat radiation amount of the click, the heat radiation amount and heat absorption amount of the heater of the radiator is calculated respectively, and the heat radiation amount of the radiator shall be calculated from the cooling water flow entering the radiator, a thermostat closes These calculation results A controller for estimating the temperature of the cooling water in a heated state, wherein the controller closes the estimated cooling water in a temperature range in which the thermostat is closed and prohibits the flow of cooling water between the circulation passage and the radiator. When the temperature is equal to or higher than a predetermined temperature, the temperature detection means detects the cooling water temperature, and when the detected actual cooling water temperature is lower than the predetermined temperature, it is determined that the thermostat is malfunctioning. Engine cooling system.

  In the present invention, first, the temperature of the cooling water in the engine with the thermostat closed is estimated, and when the estimated cooling water temperature reaches a predetermined temperature, the cooling water temperature in the engine is directly measured to The cooling water temperature is compared with a predetermined temperature, and if the temperature is lower than the predetermined temperature, the thermostat is diagnosed as having a failure. Therefore, the failure diagnosis of the thermostat can be diagnosed directly from the cooling water temperature.

  FIG. 1 is a configuration diagram illustrating a circulation flow path of engine cooling water according to the first embodiment.

  Reference numeral 1 denotes a circulation path for cooling water for cooling the engine 2. The circulation path 1 travels through a cooling water jacket 2a through which cooling water for cooling the cylinder block 2b of the engine 2 flows, and cooling water for cooling the cylinder. A radiator 3 that is cooled by wind and a heater 4 that heats the cabin using the heat of cooling water heated by a cylinder are communicated.

  The circulation flow path 1 is configured in parallel with the cooling water circulation flow path 1a branched from the cooling water circulation flow path 1a and the cooling water circulation flow path 1a that returns to the engine 2 when the cooling water that has cooled the engine 2 is radiated by the radiator 3. Heater channel 1b. The cooling water circulation channel 1 a is further provided with a bypass channel 1 d that bypasses the radiator 3.

  A cooling water circulation passage 1a between the radiator 3 and the cooling water jacket 2a is provided with a thermostat 5 to prohibit the cooling water from flowing into the radiator 3 until the cooling water reaches a predetermined temperature, and the cooling water is bypassed. Flows through the channel 1c.

  A first flow meter 6 for detecting the flow rate of the cooling water flowing into the radiator 3 and a first temperature sensor 7 for detecting the temperature thereof are installed at the radiator inlet. The outputs of these sensors 6 and 7 are output to the controller 8. The cooling water jacket 2 a is provided with a second flow meter 9 that detects the flow rate of the cooling water in the jacket and a second temperature sensor 10 that detects the temperature of the cooling water in the jacket, and transmits an output signal to the controller 8. . Similarly, a third flow meter 11 that detects the flow rate of the cooling water flowing into the heater 4 and a third temperature sensor 12 that detects the temperature of the cooling water are installed at the heater inlet. The outputs of these sensors 11 and 12 are output to the controller 8.

  The controller 8 to which the outputs of the first to third flow meters 6, 9, 11 and the first to third temperature sensors 7, 10, 12 are input is further injected with the rotational speed of the engine 2 and fuel injection valve The fuel injection pulse width for controlling the amount of fuel to be supplied, the ignition timing of a spark plug (not shown), and the intake air temperature are input.

  With this configuration, when the cooling water temperature is equal to or lower than the predetermined temperature at which the thermostat 5 is closed, the cooling water flows through the bypass channel 1c and the heating of the cooling water by the heat generation amount of the engine 2 is promoted, and the engine Warm-up time is shortened. When the temperature exceeds the predetermined temperature, the thermostat 5 is opened, the cooling water is supplied to the radiator 3, and the temperature of the cooling water is maintained within a predetermined temperature range.

  On the other hand, the cooling water branched from the cooling water flow channel 1 and flowing through the heater flow channel 1 b is supplied to the heater 4. Heat of the cooling water heated by the engine 2 is absorbed by the heater 4 to heat the air, and the heated air is sent into the vehicle interior and used for heating the vehicle interior.

  FIG. 2 is a flowchart for explaining a failure diagnosis method for the thermostat 5 of the present embodiment. This failure diagnosis is performed at a predetermined interval by the controller 8 and diagnoses an open fixing failure that is not closed when the thermostat 5 is open. The failure diagnosis is cooling that is in a closed state if the thermostat 5 is normal. It is carried out in the water temperature range.

  First, the heat generation amount Q of the engine 2, the heat release amount Q1 from the cylinder block 2b, the heat absorption amount Q2 by the heater 4 and the heat release amount Q3 by the radiator 3 are calculated.

  In step S1, the rotational speed of the engine 2 and the fuel injection pulse width are read, and in step S2, a calorific value map value q of the engine 2 is calculated from a previously stored map as shown in FIG. The calorific value map value q is calculated and stored in advance through experiments or the like.

  In step S3, the ignition timing is read, an ignition timing correction coefficient Ka is set from the read ignition timing, and in step S4, the engine heat generation amount Q is calculated from the following equation.

  On the other hand, in step S5, the cooling water temperature T1, the cooling water flow rate W1, and the intake air temperature TAN in the cooling water jacket 2a are read. In the subsequent step S6, the cylinder block heat dissipation amount Q1 is calculated. The cylinder block heat dissipation amount Q1 can be calculated from the following equation.

  Here, W1: cooling water flow rate, C1: specific heat of the cylinder block 2b, T1: cooling water temperature, TAN: intake air temperature.

  In step S7, the cooling water flow rate W2 and temperature T2 flowing into the heater 4 are read from the outputs of the third flow meter 11 and the third temperature sensor 12, and in step S8, the cooling water flow rate W2 and temperature T2, and further the heater 4 is read. The heat absorption amount Q2 of the heater 4 is calculated from the heat transmissivity K2 between the surface and the atmosphere and the cooling water flow path length L2 in the heater 4 by the following equation.

  On the other hand, the cooling water flow rate W3 and the temperature T3 flowing into the radiator 5 in step S9 are read from the outputs of the first flow meter 6 and the first temperature sensor 7. In step S10, the read cooling water flow rate W3 and temperature T3, From the heat transmissivity K3 of the material constituting the outer surface of the radiator 5 and the cooling water flow path length L3 in the radiator 5, the heat radiation amount Q3 of the radiator 5 is calculated from the following equation.

  In this way, the heat generation amount Q of the engine 2, the cylinder block heat dissipation amount Q1, the heater heat absorption amount Q2, and the radiator heat dissipation amount Q3 are calculated, and the process proceeds to step S11.

  In step S11, the rising temperature ΔT of the cooling water of the engine 2 is calculated from the following equation based on the calculated values Q and Q1 to Q3.

  In subsequent step S12, the rising temperature ΔT calculated in step S11 is added to the previous value Tz of the cooling water temperature to obtain an estimated value T of the cooling water temperature.

  In step S13, the calculated estimated value T of the cooling water temperature is compared with a predetermined temperature Tc. Here, the predetermined temperature Tc is set below the temperature at which the thermostat 5 opens so that the cooling water flows into the radiator 4. If the estimated value T is equal to or higher than the predetermined temperature Tc, the process proceeds to step S14. If the estimated value T has not reached the predetermined temperature Tc, the determination is repeated.

  In step S14, it is compared whether or not the elapsed time D since the condition of step S13 has been satisfied has exceeded a predetermined time Dc. The passage of a predetermined time after the condition in step S13 is satisfied, thereby promoting an increase in the coolant temperature. When the predetermined time Dc has elapsed, the process proceeds to step S15, and when it has not elapsed, the determination is repeated. The predetermined time Dc is 1 minute or less.

  In step S15, the actual cooling water temperature Tr in the cooling water jacket 2a is read from the second temperature sensor 10 and compared with a predetermined temperature Tc. If the cooling water temperature Tr is equal to or higher than the predetermined temperature Tc, the thermostat 5 is closed and is in a normal cooling water temperature rising state. In step S16, it is determined that the thermostat 5 is normal and the control is finished.

  On the other hand, if the cooling water temperature Tr is lower than the predetermined temperature Tc in step S15, the thermostat 5 should be closed, there is a valve open fixing failure state that is fixed in the open state, and the cooling water flows into the radiator 3, The cooling water is not sufficiently heated. In this case, the process proceeds to step S17, where it is determined that the thermostat 5 is, and in step S18, a failure of the thermostat 5 is notified to the driver or the like using the alarm device 13.

  FIG. 4 is a timing chart showing the failure diagnosis of the thermostat 5 of this embodiment in time series.

  Heat generation occurs as the engine 2 is started, and the cooling water temperature starts to increase from the temperature at which the thermostat 5 should be closed to both the estimated temperature T and the actual temperature Tr. When the estimated temperature T reaches the predetermined temperature Tc at time t1, a failure diagnosis condition for the thermostat 5 is established (step S13), and the cooling water is heated until the predetermined time Dc elapses after the diagnosis condition is established (step S14). .

  Then, the actual temperature Tr of the cooling water is detected using the second temperature sensor 10 at time t2 when the predetermined time Dc has elapsed. If the actual cooling water temperature Tr at time t2 is equal to or higher than the predetermined temperature Tc as indicated by a broken line, the thermostat 5 is closed and determined to be normal. On the other hand, when the predetermined temperature Tc has not been reached as indicated by the alternate long and short dash line, the thermostat 5 is broken and opened, so that the cooling water flows into the radiator 3 and the heat of the cooling water is dissipated sufficiently. It is diagnosed that the cooling water is not heated.

  Therefore, in this embodiment, first, the temperature T of the cooling water in the engine 2 with the thermostat 5 normally closed is estimated, and when the estimated cooling water temperature T reaches the predetermined temperature Tc, By directly measuring the actual cooling water temperature Tr and comparing the actual cooling water temperature Tr with the predetermined temperature Tc, the thermostat 5 is fixed in an open state and cannot be closed. Can be diagnosed.

  Moreover, since the cooling water temperature is estimated as a trigger for starting the failure diagnosis and the diagnosis is started when the estimated cooling water temperature T becomes equal to or higher than the predetermined temperature Tc, erroneous diagnosis of the thermostat 5 can be prevented.

  FIG. 5 is a block diagram showing the configuration of the second embodiment. This embodiment is different from the first embodiment in that the detection of the flow rate of each part is calculated using a map and the cooling water temperature is represented by the detection temperature of the cooling water jacket 2a. Different. Note that configurations not particularly described are the same as those in the first embodiment.

In FIG. 5, only the 2nd temperature sensor 10 which detects the cooling water temperature T1 in the cooling water jacket 2b is provided with respect to the structure of 1st Embodiment, and other temperature sensors and flowmeters are not used. For the temperature of each part, the coolant temperature T1 detected by the second temperature sensor 10 is used as the coolant temperature flowing into the radiator 3 and the heater 4. Further, the coolant flow rate of each part is calculated based on the relationship with the engine speed from a map as shown in FIG. As shown in this map, the cooling water flow rate is
Cooling water flow rate W1 in the cooling water jacket 2a> Cooling water flow rate W3 of the radiator 3> Cooling water flow rate W2 of the heater 4
The relationship is set.

  FIG. 7 is a flowchart illustrating the failure diagnosis method for the thermostat 5 according to the present embodiment. This failure diagnosis is performed at predetermined intervals by the controller 8 to diagnose an open fixing failure of the thermostat 5, and the failure diagnosis is performed in an operating state in which the thermostat 5 is in a closed state if the thermostat 5 is normal.

  In comparison with the flowchart of the first embodiment, only different steps will be described below, and steps not particularly described are the same as those of the flowchart of the first embodiment.

  The feature of this embodiment is the method for setting the coolant flow rate and coolant temperature as described above, and steps S5, S7, and S9 in the flowchart of the first embodiment are changed to steps S21 to S23, respectively.

  First, in upstream step S20 of steps S21 to S23, the engine speed, the cooling water temperature T1 of the cooling water jacket, and the intake air temperature TAN are read. In step S21, the cooling water flow rate W1 in the cooling water jacket 2a is calculated from the engine speed using the map of FIG. 6, and in step S22, the cooling water flow rate W2 flowing into the heater 4 is similarly calculated. In step S23, A cooling water flow rate W3 flowing into the radiator 3 is calculated.

  The calculated cooling water flow rates W1 to W3 and the cooling water temperature T1 are respectively used for calculating the heat quantities Q1 to Q3 of each part in steps S6, S8, and S10.

  Therefore, in the second embodiment, only by providing one temperature sensor 10 and a map for calculating the coolant flow rate, the same operation and effect as the first embodiment can be achieved, and the cost of the sensor and the like can be achieved. Can be reduced.

  In the case where an electric pump is provided in the cooling water flow path, the cooling water can be circulated by the electric pump regardless of the operating state of the engine. Therefore, for example, when the flow rate of the cooling water flowing into the heater 4 is calculated by calculation based on the rotational speed of the engine, it cannot be accurately calculated unless the cooling water inflow by the electric control pump is taken into consideration. Therefore, when an electric control pump is provided, the coolant flow rate is calculated according to the engine speed and the driving state of the electric control pump.

  In addition, when two cooling water flow paths, that is, a flow path for cooling the cylinder block of the engine and a flow path for cooling the cylinder head, are configured independently as engine cooling water flow paths, A thermostat and a temperature sensor are installed respectively. In such a configuration, since the temperature of the cylinder block and the temperature of the cylinder head may be significantly different, it is desirable to determine the failure of the thermostat in each cooling water flow path.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea of the present invention.

It is a block diagram explaining the circulation flow path of engine cooling water. 4 is a flowchart for explaining a failure diagnosis method for a thermostat 5. It is a map which calculates the calorific value map value q of a cylinder. It is a timing chart which shows failure diagnosis of a thermostat in time series. It is a block diagram of 2nd Embodiment explaining the circulation flow path of engine cooling water. It is a map which calculates a cooling water flow rate. 6 is a flowchart of a second embodiment for explaining a failure diagnosis method for a thermostat 5.

Explanation of symbols

1a Circulating channel 1b Heater channel 1c Bypass channel 2 Engine 2a Cooling water jacket 2b Cylinder block 3 Radiator 4 Heater 5 Thermostat 6 First flow meter 7 First temperature sensor 8 Controller 9 Second flow meter 10 Second temperature sensor 11 Third flow meter 12 Third temperature sensor

Claims (3)

A cooling water jacket in which cooling water flows through the cylinder block of the engine;
A circulation channel for cooling water flowing out from the cooling water jacket to flow into the cooling water jacket again;
A radiator that is provided in the middle of this circulation flow path and dissipates heat of the cooling water;
A bypass passage through which the cooling water bypasses the radiator;
A thermostat for controlling the flow of the cooling water between the circulation flow path and the radiator according to the temperature of the cooling water to flow the cooling water into the bypass flow path;
A heater channel branched from the circulation channel and provided in parallel with the circulation channel;
A heater provided in the heater flow path for heating the cabin;
Temperature detecting means for detecting a cooling water temperature in the cooling water jacket;
In the engine cooling device with
The heat generation amount of the engine, the heat dissipation amount of the cylinder block, the heat dissipation amount of the radiator, and the heat absorption amount of the heater are calculated, respectively, and the heat dissipation amount of the radiator is calculated from the flow rate of cooling water flowing into the radiator. , Equipped with a controller that estimates the temperature of the cooling water when the thermostat is closed from these calculation results,
When the estimated cooling water temperature is equal to or higher than a predetermined temperature in a temperature range in which the thermostat is closed and prohibiting the flow of cooling water between the circulation flow path and the radiator, the controller detects the cooling water. An engine cooling apparatus, wherein a water temperature is detected, and when the detected actual cooling water temperature is lower than a predetermined temperature, it is determined that the thermostat is malfunctioning. 2. The engine cooling apparatus according to claim 1, wherein the predetermined temperature is lower than a temperature at which the thermostat prohibits cooling water from entering and exiting between the circulation flow path and the radiator. 2. The engine cooling apparatus according to claim 1, wherein the controller detects the cooling water temperature by the temperature detection unit after a predetermined time has elapsed after the cooling water temperature reaches the predetermined temperature.

Images