JP2006275051A - Engine control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improved engine control method in which a thermostat right or wrong distinction device or the like does not make wrong judgment even if engine automatic stop, start function is added. <P>SOLUTION: In an engine provided with a function performing thermostat right or wrong discrimination process based on first data relating air temperature and water temperature and second data relating engine load accumulation, a function initializing the first and the second data, and the automatic stop/start function, a process discrimination whether the engine is under automatic stop control or not and a process discrimination whether the engine is under initial start or not are provided. If it is determined that the engine is not under automatic stop control and under idling with an ignition key operated, the engine proceeds to the process initializing the first data and the second data. If it is determined that the engine is under automatic stop control, the engine proceeds to thermostat right or wrong distinction process without through distinction process whether the engine is under initial start or not (B6). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an engine control method, and more particularly to a control method for an engine having an automatic stop / start function.

  For the purpose of further reducing the amount of exhaust gas and promoting energy saving, the engine is automatically stopped when a predetermined stop condition is met, and the engine is automatically turned on when a predetermined restart condition is met. A vehicle having a function of starting is known (see Patent Document 1).

  On the other hand, the water-cooled engine is provided with a thermostat that works to keep the water temperature in the water jacket within a predetermined range. However, the abnormal operation of the thermostat causes a decrease in combustion efficiency due to inappropriate engine temperature, Exhaust gas properties and fuel consumption are a factor. Therefore, early detection of thermostat abnormality is one of the important issues in the field of engine control recently.

As a means of early detection of thermostat abnormality, the intake air amount that is uniquely related to the total heat generation amount of the engine is integrated from the start of the engine, and the integration is performed when the integrated value of the intake air amount reaches a predetermined value. The estimated cooling water temperature when the thermostat calculated based on the total calorific value of the engine estimated from the value is assumed to be normal and the actual cooling water temperature measured by the water temperature sensor are compared, and the estimated cooling water temperature and the actual cooling water temperature are compared. When the deviation exceeds a predetermined value, a system for determining that the thermostat is abnormal has been proposed (see Patent Document 2).
JP-A-4-246252 JP-A-11-141337

  However, the combustion control of the engine related to the ignition timing and the fuel injection amount is generally electronically controlled today, but the CPU mounted on the electronic control unit (ECU) needs to perform data initialization and self-diagnosis processing in a timely manner. Conventionally, this processing is generally performed at the time of engine cranking.

  However, when the engine automatic stop / start function is applied to a vehicle equipped with the thermostat correctness determination device as described above, the CPU is initialized at the time of restart after the engine automatic stop. There is a possibility that the thermostat correctness judgment based on the integrated value may be hindered.

  The present invention has been devised to solve such problems of the prior art. The main purpose of the present invention is to make an erroneous determination by a thermostat correctness determination device or the like even if an automatic engine stop / start function is added. It is an object of the present invention to provide an engine control method improved so as not to cause a failure.

  In order to achieve such an object, the present invention has a function of performing a thermostat correctness determination process based on the first data related to the air temperature and water temperature and the second data related to the engine load integration as the basis for calculating the engine cooling loss, In a control method for an engine having a function of initializing the first data and the second data and an automatic stop / start function, a process of determining whether or not an engine automatic stop control is being performed ( Step A1, Step B1, or Step C1) and a process (Step A5, Step B2, or C2) for determining whether or not idling is performed by operating the ignition key. If it is determined that the engine is idling after the ignition key is operated, the first data is displayed. Then, the process proceeds to the process of initializing the second data (A6 or C5), and when it is determined that the engine automatic stop control is being performed, a process of determining whether or not the engine is idling by operating the ignition key is performed. Without proceeding to the process (step B6) of performing the thermostat correctness determination process.

  According to the present invention as described above, when restarting after the engine automatic stop control, the processing steps executed at the initial start jump, so that the accumulated data for use in determining whether the thermostat operation is correct is not initialized. That's it. Therefore, a great effect can be achieved in preventing erroneous determination of the thermostat correct / incorrect determination device or the like when the engine automatic stop control function is added.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram of an engine cooling system to which the present invention is applied. In FIG. 1, a water jacket 2 formed in a cylinder block of an engine 1 has a cooling water supply passage 3 and a water pump 4 on one side. The other side is connected to the top side of the radiator 5 via the cooling water discharge passage 6 and the thermostat 7. The cooling water discharge passage 6 communicates with the upstream side of the water pump 4 via a bypass passage 8 branched in front of the thermostat 7.

  The cooling water discharged from the water pump 4 returns to the water pump 4 from the water jacket 2 via the bypass passage 8 when the thermostat 7 is closed, and passes through the cooling water discharge passage 6 from the water jacket 2 when the thermostat 7 is opened. It flows into the radiator 5 via the above.

  On the other hand, a fan 10 driven by an electric motor 9 is attached to the radiator 5. The fan 10 is intermittently driven by applying the voltage of the battery B through a water temperature switch 11 provided on the bottom side of the radiator 5. Therefore, by opening and closing the thermostat 7 and dissipating heat from the radiator 5, the water temperature in the water jacket 2, that is, the engine temperature is maintained within a predetermined range.

  Note that a heater 12 for heating the passenger compartment is connected between the water jacket 2 and the cooling water supply passage 3, and a part of the cooling water heated by the engine 1 is used as a heating heat source. It is like that.

  The electric motor 9 that drives the fan 10 includes a cooling water temperature sensor 13 for detecting the water temperature downstream of the radiator 5, a rotation sensor 14 for detecting the rotation speed of the engine 1, and a load for the engine 1. An electronic control unit 18 for controlling the engine 1 based on detected values such as an intake negative pressure sensor 15, a vehicle speed sensor 16 for detecting the traveling speed of the vehicle, and an air temperature sensor 17 for detecting an atmospheric temperature. Is also connected.

  The engine 1 automatically stops when a predetermined condition that can be confirmed or estimated that the vehicle has stopped is satisfied. When this automatic stop control is executed, an automatic stop execution flag is set in the control program.

  By the way, the abnormal operation of the thermostat 7 causes a decrease in combustion efficiency due to an inappropriate engine temperature, which causes deterioration of exhaust gas properties and fuel consumption. Therefore, the electronic control unit 18 of the engine 1 incorporates a monitoring system for the operating state of the thermostat 7.

  Next, the thermostat monitor execution permission routine will be described with reference to FIG. First, it is determined whether or not the current state is under automatic stop control (step A1). Here, when it is determined that the automatic stop control is being performed (step A1: affirmative), the initial values of the air temperature and the water temperature are both within a predetermined range (for example, −6.7 to 45 degrees Celsius), and at the time of initial start. It is determined whether or not the value obtained by subtracting the air temperature from the water temperature is within a predetermined value (for example, 6 degrees Celsius) (step A2). If it is determined that these conditions are satisfied (step A2: affirmative), the monitor execution permission flag is set to 1 (step A3). Otherwise (step A2: negative), the monitor execution permission flag is set. Is set to 0 (step A4).

  If it is determined in step A1 that the automatic stop control is not currently being performed, it is determined whether or not the engine is in the start mode, that is, whether or not the engine is idling after the ignition key is operated (step A5). When it is determined that the engine is not in the start mode (step A5: negative), the process proceeds to step A2, and when it is determined that the engine is in the start mode (step A5: affirmative), the temperature and water temperature that are the basis for calculating the cooling loss. The data related to is initialized (step A6).

  Next, the thermostat monitor routine will be described with reference to FIG. First, it is determined whether or not the automatic stop control is being performed (step B1). If it is determined that the automatic stop control is being performed (step B1: affirmative), the start mode determination step B2 is jumped to the thermostat monitor permission flag. Is checked to determine whether or not the execution of the thermostat monitor is permitted (step B3). Here, if it is determined that the monitor execution is permitted (flag is 1, step B3: affirmative), thereafter, the cooling loss integration is calculated from the amount of heat released by using the heater, the amount of heat released by the traveling wind, and the atmospheric temperature. A value is calculated (step B4), and an estimated water temperature when the thermostat is assumed to be normal is calculated from the engine load integrated value obtained separately from this value (step B5). The estimated water temperature is compared with the actually measured water temperature to determine whether the thermostat operation is correct (step B6).

  Here, an outline of the thermostat correctness determination will be described. As shown in FIG. 4, when the estimated water temperature indicated by the solid line reaches the failure judgment value (for example, 75 degrees Celsius) before the actually measured water temperature indicated by the thin dotted line reaches the normal judgment value (for example, 70 degrees Celsius), the temperature rises. Since the temperature rate is too high, it is determined as a failure. Further, when the measured water temperature indicated by the thick dotted line does not reach the normal judgment value, and the estimated water temperature indicated by the solid line does not reach the failure judgment value, the measured water temperature is lower than the estimated water temperature and the temperature difference is a predetermined value (for example, If it is 15 degrees Celsius) or higher, the rate of temperature rise is too low and it is determined that there is a failure.

  If the average vehicle speed is equal to or higher than a predetermined value (for example, 30 km / h), that is, the vehicle is running, it is determined that the measured water temperature (thin two-dot chain line) reaches the normal determination value earlier than the estimated water temperature (solid line). In addition, when the measured vehicle temperature (thick two-dot chain line) reaches the normal judgment value, the average vehicle speed is equal to or lower than a predetermined value, that is, when the vehicle is traveling at low speed or stopped, the estimated water temperature (solid line) is a predetermined value (for example, 60 degrees Celsius). If it is below, it is determined as normal.

  If it is determined in step B1 that the automatic stop control is not in progress (step B1: negative), it is determined in step B2 whether or not the engine is in the start mode. If it is determined that the engine is in the start mode (step B2: “Yes” unconditionally jumps to the subsequent steps, that is, the processing steps related to the thermostat correctness determination processing. If it is determined that the engine is not in the start mode (No at Step B2), the thermostat monitor permission flag is checked at Step B3 to determine whether or not the monitor is permitted. If the monitor permission flag is 0 (No in Step B3), the subsequent steps (B4) are performed. Jump to B6).

  In addition, as shown in FIG. 5, the engine load integration is not in the automatic stop control (step C1: negative), is not in the start mode (step C2: negative), and monitoring is permitted (step C3). : Affirmative) is performed in step C4. When the automatic stop control is being performed (step C1: affirmative), the subsequent steps (C2 to C5) are jumped to, and when the engine is in the start mode (step C2: affirmative) and when the monitor permission has not been issued (step C2: affirmative) Step C3: No) initializes data related to engine load integration (step C5).

  The integration of the engine load is obtained by correcting the fuel injection time with a function of the engine speed and the intake negative pressure.

It is a schematic diagram of an engine cooling system to which the present invention is applied. It is a schematic flowchart of the execution permission routine of a thermostat monitor. It is a schematic flowchart of a thermostat monitor routine. It is a cooling-water temperature rising characteristic diagram in connection with failure determination of a thermostat. It is a schematic flowchart of an engine load integration routine.

Explanation of symbols

1 Engine 18 controller

Claims (1)

A function for performing a thermostat correct / incorrect determination process based on the first data relating to the air temperature and water temperature which are the basis for calculating the engine cooling loss and the second data relating to the engine load integration, and the initialization of the first data and the second data. A control method for an engine having a function to perform and an automatic stop / start function,
A process for determining whether or not the engine automatic stop control is in progress;
A process for determining whether or not the ignition key is idling when operated,
When it is determined that the engine automatic stop control is not being performed and it is determined that the idling is performed by operating the ignition key, the process proceeds to a process of initializing the first data and the second data,
When it is determined that the engine automatic stop control is being performed, the engine control proceeds to a process of performing a thermostat correct / incorrect determination process without going through the process of determining whether the ignition key is operated or not. Method.

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