JP4304468B2 - Oil temperature estimation device for internal combustion engine - Google Patents

Description

  The present invention relates to an oil temperature estimation device for an internal combustion engine that estimates the oil temperature of hydraulic oil, lubricating oil, or the like used in the internal combustion engine or its peripheral devices.

  In recent years, internal-combustion engines installed in vehicles have been equipped with hydraulically driven variable valve timing devices that vary the valve timing of intake valves and exhaust valves with hydraulic pressure for the purpose of improving output, reducing fuel consumption, and reducing exhaust emissions. There is something. In this hydraulically driven variable valve timing device, when the oil temperature of the working oil (engine oil) is low immediately after the start of the internal combustion engine or the like, the viscosity of the working oil increases, the fluidity decreases, and the valve timing control There is a characteristic that responsiveness decreases.

Therefore, for example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 10-227235), the oil temperature of the hydraulic oil of the variable valve timing device is estimated, and the estimated oil temperature is a region where the estimated oil temperature is equal to or lower than a predetermined determination temperature. Then, there is one in which valve timing control (operation of the variable valve timing device) is prohibited. In this system, in order to estimate the oil temperature during operation of the internal combustion engine, the cooling water temperature detected by the cooling water temperature sensor at the start of the internal combustion engine is set as an initial value of the estimated oil temperature. The estimated oil temperature is calculated based on the initial value of the estimated oil temperature and the operating state (rotational speed, load, etc.) of the internal combustion engine.
Japanese Patent Laid-Open No. 10-227235 (pages 2 to 4 etc.)

  Incidentally, as shown in the time chart of FIG. 9, generally, during the warm-up operation of the internal combustion engine, the actual water temperature rises faster than the actual oil temperature, and the actual water temperature tends to be higher than the actual oil temperature. When the internal combustion engine is stopped during the warm-up operation and restarted immediately, there is a high possibility that the difference between the actual water temperature and the actual oil temperature at the time of starting is large. However, in the oil temperature estimation method of Patent Document 1 described above, since the detected water temperature at the start is set as the initial value of the estimated oil temperature as it is, the estimation is performed under a condition where the difference between the detected water temperature at the start and the actual oil temperature is large. The difference between the oil temperature initial value and the actual oil temperature (the error of the estimated oil temperature initial value) becomes large, and the estimation accuracy of the oil temperature estimated based on the estimated oil temperature initial value during operation of the internal combustion engine decreases. End up.

If the oil temperature estimation accuracy decreases, for example, the following problems may occur.
As described above, in a system in which valve timing control is prohibited in an area where the estimated oil temperature is equal to or lower than the predetermined determination temperature, if the estimated oil temperature error is large, the estimated oil temperature is reduced before the actual oil temperature sufficiently rises. There is a possibility that the valve timing control is started when the predetermined judgment temperature is exceeded. As a countermeasure, in the conventional system, the estimated temperature is set to a high value in anticipation of an error in the estimated oil temperature, so in practice, the actual oil temperature is already in a temperature range where sufficient valve timing control response can be secured. In spite of the rise, there is an operating region in which the valve timing control is prohibited without the estimated oil temperature exceeding the determination temperature. For this reason, there is a disadvantage that the start timing of the valve timing control is delayed and the output, fuel consumption, and exhaust emission are deteriorated accordingly.

  In the torque control system for an internal combustion engine, when calculating the required indicated torque by calculating the friction loss (mechanical friction loss) based on the estimated oil temperature, if the oil temperature estimation accuracy decreases, the calculation accuracy of the friction loss, The calculation accuracy of the requested indicated torque is lowered, and the torque control accuracy is lowered.

  The present invention has been made in consideration of these circumstances. Therefore, the object of the present invention is to accurately calculate the initial value of the estimated oil temperature and to improve the oil temperature estimation accuracy. An object of the present invention is to provide an oil temperature estimating device for an internal combustion engine.

In order to achieve the above object, an oil temperature estimating device for an internal combustion engine according to claim 1 of the present invention provides an estimated oil temperature of an oil used for an internal combustion engine or its peripheral device as an estimated oil temperature ( (Hereinafter referred to as “estimated oil temperature initial value”) in a system provided with an oil temperature estimating means, the cooling water temperature detecting means for detecting the coolant temperature of the internal combustion engine, and the cooling water temperature detecting means when the engine is stopped. The detected water temperature and the estimated oil temperature calculated by the oil temperature estimating means are respectively stored as the detected water temperature at the previous engine stop and the estimated oil temperature at the previous engine stop, or between the detected water temperature and the estimated oil temperature. and a rewritable nonvolatile memory for storing the temperature difference, at the time of engine startup, the are stored in non-volatile memory, the previous engine stop when the detected coolant temperature and the time of the previous engine stop estimated oil temperature or the detection Water temperature and said And the temperature difference between the TeiaburaAtsushi, in which to calculate the engine stop time, the estimated oil temperature initial value calculating means estimates oil temperature initial value based on the detected water temperature at the engine starting.

  In general, the actual water temperature and the actual oil temperature after the engine is stopped gradually decrease with time and finally converge to the same temperature (almost outside temperature). And the actual oil temperature (for example, the difference or ratio between the actual water temperature and the actual oil temperature) changes according to the elapsed time after the engine is stopped. Therefore, the relationship between the actual water temperature and the actual oil temperature when the engine is started uses the relationship between the actual water temperature when the engine is stopped (detected water temperature) and the estimated oil temperature (substitute information of the actual oil temperature) and the engine stop time. Further, if the detected water temperature at the time of starting the engine is used, an estimated oil temperature initial value that is an estimated value of the oil temperature at the time of starting the engine can be calculated.

  In this way, the estimated oil temperature initial value can be calculated in consideration of the relationship between the actual water temperature and the actual oil temperature when the engine is stopped and thereafter, so the internal combustion engine is stopped during the warm-up operation. Even when restarted immediately, the estimated oil temperature initial value can be calculated with high accuracy, and the oil temperature estimation accuracy can be improved. As a result, it is possible to improve the control accuracy of various types of control using the estimated oil temperature (for example, valve timing control, torque control, etc.), or to expand the control execution range, and adverse effects caused by errors in the estimated oil temperature. Can be reduced.

In this case, as in claim 2, the estimated initial oil temperature value may be calculated by the following equation.
THOstart = THWstart− (THWstop−THOstop) × K
THOstart: Estimated initial oil temperature
THWstart: agencies detected water temperature at the time of start-up
THWstop: Detected water temperature at the last engine stop
THOstop: Estimated oil temperature at the last engine stop
K: Correction value obtained from engine stop time In this way, the estimated oil temperature initial value can be calculated by a very simple calculation.

  In the above equation, (THWstop−THOstop) × K may be read from this map using a three-dimensional map having THWstop, THOstop, and engine stop time as parameters. The correction value K may be read from a map having the engine stop time as a parameter, or may be calculated by a mathematical expression having the engine stop time as a variable.

  Further, the behavior of the actual water temperature and the actual oil temperature after the engine is stopped is considered based on the engine stop time and the outside air temperature or the intake air temperature as in claim 3 in consideration that it changes depending on the outside air temperature. May be calculated. In this way, it is possible to calculate the estimated oil temperature initial value in consideration of the outside air temperature (or the intake air temperature that is the substitute information), and to accurately calculate the estimated oil temperature initial value without being affected by the outside air temperature. Can be calculated.

Further, the engine stop time used when calculating the estimated oil temperature initial value may be measured by a timer that operates while the engine is stopped, but is stored in a non-volatile memory as in claim 4 . The engine stop time may be calculated based on the detected water temperature at the previous engine stop and the detected water temperature at the engine start. Generally, the actual water temperature decreases according to the elapsed time after the engine is stopped. Therefore, if the detected water temperature when the engine is stopped and the detected water temperature when the engine is started, the temperature difference between them (the amount of decrease in water temperature when the engine is stopped) From this, the engine stop time can be calculated. In this way, the present invention can be applied to a vehicle that does not include a timer that operates while the engine is stopped.

In this case, the engine stop time is calculated based on the detected water temperature when the engine is stopped and the detected water temperature when the engine is started, and a correction value is calculated based on the engine stop time and the outside air temperature (or intake air temperature) Although the estimated oil temperature initial value may be calculated using this correction value, the process of calculating the engine stop time is omitted as in claim 5 and the previous value stored in the nonvolatile memory is omitted. Based on the detected water temperature when the engine is stopped, the detected water temperature when the engine is started, and the outside air temperature (or intake air temperature), a correction value is calculated to take into account the engine stop time, and the estimated oil temperature initial value is calculated using this correction value. May be calculated. In this way, it is possible to simplify the process of calculating the correction value in consideration of the engine stop time and the outside air temperature.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the following three embodiments.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. On the downstream side of the air flow meter 14, a throttle valve 15 whose opening is adjusted by a DC motor or the like and a throttle opening sensor 16 for detecting the throttle opening are provided.

  Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. A spark plug 21 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each spark plug 21.

  Further, the intake valve 28 of the engine 11 is provided with a hydraulically driven variable intake valve timing device 29 that varies the valve timing of the intake valve 28 with hydraulic pressure. The hydraulic circuit of the variable intake valve timing device 29 is supplied with hydraulic oil (engine oil) in an oil pan (not shown), and the hydraulic pressure is controlled by the hydraulic control valve 30 (OCV), whereby the intake valve is controlled. Timing (valve timing of the intake valve 28) is controlled.

  On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst that purifies CO, HC, NOx, etc. in the exhaust gas. / An exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting lean or the like is provided.

  The cylinder block of the engine 11 includes a cooling water temperature sensor 25 (cooling water temperature detecting means) that detects the cooling water temperature, and a crank angle sensor 26 that outputs a pulse signal each time the crankshaft of the engine 11 rotates a predetermined crank angle. It is attached. Based on the output signal of the crank angle sensor 26, the crank angle and the engine speed are detected.

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 27. The ECU 27 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 20 according to the engine operating state. The ignition timing of the spark plug 21 is controlled.

  Further, the ECU 27 calculates the estimated oil temperature THO of the hydraulic oil as follows by executing each program for calculating the estimated oil temperature shown in FIGS. 2 to 4 described later. First, when the engine is stopped, the difference between the actual water temperature (detected water temperature) THWstop detected by the cooling water temperature sensor 25 and the estimated oil temperature THOstop estimated by this oil temperature estimation method is calculated, and the backup RAM or the like of the ECU 27 can be rewritten. Store in a non-volatile memory.

  Then, at the next engine start, a correction value K1 corresponding to the engine stop time is calculated, and the difference between this correction value K1 and the detected water temperature THWstop and the estimated oil temperature THOstop stored at the previous engine stop, An estimated oil temperature initial value THOstart is calculated using the detected water temperature THWstart detected at the time of engine start.

  In general, the actual water temperature and the actual oil temperature after the engine is stopped gradually decrease with the passage of time and finally converge to the same temperature (almost outside temperature). The difference between the actual oil temperature and the actual oil temperature changes according to the elapsed time after the engine stops. Therefore, the difference between the detected water temperature THWstart when starting the engine and the actual oil temperature THOstart depends on the difference between the detected water temperature THWstop when the engine is stopped and the estimated oil temperature THOstop (actual oil temperature substitute information) and the engine stop time. Using the correction value K1, it can be estimated by the following equation (1).

THWstart−THOstart = (THWstop−THOstop) × K1 (1)
The following equation (2) is derived by solving the above equation (1) for the actual oil temperature THOstart when the engine is started.
THOstart = THWstart− (THWstop−THOstop) × K1 (2)

  From the equation (2) thus obtained, the detected water temperature THWstart at the time of engine start, the difference between the detected water temperature THWstop at the time of engine stop and the estimated oil temperature THOstop, and the correction value K1 according to the engine stop time are obtained. By using this, it is possible to calculate the estimated oil temperature initial value THOstart, which is an estimated value of the actual oil temperature when the engine is started.

After the engine is started, the estimated oil temperature THO is calculated at a predetermined cycle by the following equation using the detected water temperature THW detected by the cooling water temperature sensor 25 and the annealing rate L. At this time, the estimated oil temperature initial value THOstart is used as the first value of the estimated oil temperature THO.
THO (i) = THO (i-1) + {THW-THO (i-1)} * L
Here, THO (i-1) is the previous estimated oil temperature, and THO (i) is the current estimated oil temperature.

  Further, the ECU 27 executes a valve timing control program (not shown) to prohibit valve timing control (operation of the variable intake valve timing device 29) when the estimated oil temperature THO is lower than a predetermined determination temperature. Thereafter, when the estimated oil temperature THO exceeds the determination temperature, the valve timing control is permitted, and the hydraulic control valve 30 is controlled so that the actual intake valve timing matches the target intake valve timing.

  Further, the ECU 27 executes a torque control program (not shown) to calculate a required indicated torque by adding an internal loss torque, a friction loss (mechanical friction loss), a pumping loss, and the like to the required shaft torque. The fuel injection amount, ignition timing, throttle opening, etc. are controlled so as to realize the required indicated torque. At this time, since the friction loss changes according to the oil temperature, the ECU 27 calculates the friction loss based on the estimated oil temperature THO or the like.

  Hereinafter, the processing contents of each program for calculating the estimated oil temperature shown in FIGS. 2 to 4 executed by the ECU 27 will be described.

[Processing when the engine is stopped]
The engine stop processing program shown in FIG. 2 is executed at a predetermined cycle while the ECU 27 is powered on. Even after the IG switch (ignition switch) (not shown) is turned off, the ECU 27 is continuously energized for a while in order to execute this program.

  When this program is started, first, in step 101, it is determined whether or not the engine is stopped (immediately after the IG switch is switched from on to off). If it is determined that the engine is stopped, In step 103, the detected water temperature THWstop detected by the cooling water temperature sensor 25 when the engine is stopped and the estimated oil temperature THOstop calculated by the estimated oil temperature calculation program shown in FIG. After storing in the volatile memory, the process proceeds to step 104, where the engine stop time is stored in a non-volatile memory such as a backup RAM. At this time, the engine stop time is read from a clock (not shown) mounted on the vehicle.

  In this program, the detected water temperature THWstop and the estimated oil temperature THOstop are stored in the nonvolatile memory when the engine is stopped, and the temperature difference (THWstop-THOstop) is calculated at the next engine start. The temperature difference (THWstop-THOstop) between the detected water temperature THWstop and the estimated oil temperature THOstop at the time may be stored in advance in a nonvolatile memory when the engine is stopped.

[Calculation of estimated oil temperature initial value]
The estimated oil temperature initial value calculation program shown in FIG. 3 is executed at a predetermined cycle while the ECU 27 is turned on, and serves as an estimated oil temperature initial value calculation means in the claims. When this program is started, first, at step 201, it is determined whether or not the engine is starting (immediately after the IG switch is switched from OFF to ON), and if it is determined that the engine is starting, Proceeding to step 202, the engine stop time is calculated from the engine start time (IG switch-on time) read from a clock or the like and the engine stop time stored when the engine is stopped.

  Thereafter, the process proceeds to step 203, and a correction value K1 corresponding to the engine stop time is calculated by a table or a mathematical expression. In general, the longer the engine stop time, the smaller the difference between the actual water temperature and the actual oil temperature, and the actual oil temperature at the start of the engine approaches the actual water temperature. Therefore, the correction value K1 table shows that the longer the engine stop time, Thus, the correction value K1 becomes smaller, and the estimated oil temperature initial value THOstart is set to approach the detected water temperature THWstart at the time of engine start.

Thereafter, the routine proceeds to step 204, where the detected water temperature THWstart detected at the time of the current engine start, the difference between the detected water temperature THWstop stored at the previous engine stop and the estimated oil temperature THOstop, and the correction value K1 according to the engine stop time Is used to calculate the estimated oil temperature initial value THOstart by the following equation.
THOstart = THWstart− (THWstop−THOstop) × K1

[Estimated oil temperature calculation]
The estimated oil temperature calculation program shown in FIG. 4 is executed at a predetermined cycle while the ECU 27 is turned on, and serves as oil temperature estimating means in the claims. When this program is started, it is first determined in step 301 whether or not the engine has been started. If it is determined that the engine has been started, the process proceeds to step 302 and the intake air amount detected by the air flow meter 14 is determined. Is read.

  Thereafter, the process proceeds to step 303, and the annealing rate L corresponding to the current intake air amount is calculated by a table or a mathematical expression. The table of the annealing rate L is set so that the annealing rate L increases as the intake air amount increases.

Thereafter, the process proceeds to step 304, and the estimated oil temperature THO (i) of this time is calculated by the following equation using the detected water temperature THW detected by the cooling water temperature sensor 25 and the previous estimated oil temperature THO (i-1) and the smoothing rate L. ) Is calculated. At this time, the estimated oil temperature initial value THOstart is used as the first value of the estimated oil temperature THO.
THO (i) = THO (i-1) + {THW-THO (i-1)} * L

  In the first embodiment described above, paying attention to the fact that the difference between the actual water temperature and the actual oil temperature after the engine stops changes according to the elapsed time after the engine stops, The estimated oil temperature initial value THOstart is calculated using the difference between the detected water temperature THWstop and the estimated oil temperature THOstop, the correction value K1 corresponding to the engine stop time, and the detected water temperature THWstart at the time of the current engine start. Therefore, the estimated oil temperature initial value THOstart can be calculated in consideration of the relationship between the actual water temperature and the actual oil temperature when the engine is stopped and thereafter. Therefore, even when the engine 11 is stopped during the warm-up operation and restarted immediately, the estimated oil temperature initial value THOstart can be calculated with high accuracy, and the oil temperature estimation accuracy can be improved. . As a result, the control accuracy of various controls (valve timing control, torque control, etc.) using the estimated oil temperature can be improved, and the control execution range can be expanded, thereby reducing the adverse effects caused by errors in the estimated oil temperature. can do.

Next, Embodiment 2 of the present invention will be described with reference to FIGS.
In the second embodiment, by executing the program shown in FIGS. 5 and 6, the engine stop time and the outside air temperature are taken into consideration that the behavior of the actual water temperature and the actual oil temperature after the engine is stopped changes depending on the outside air temperature. The estimated oil temperature initial value THOstart is calculated using the correction value K2 corresponding to the above.

  In the engine stop time processing program shown in FIG. 5, when it is determined in step 401 that the engine is stopped, the detected water temperature THWstop, the estimated oil temperature THOstop, and the engine stop time when the engine is stopped are stored in a non-volatile manner such as a backup RAM. Store in the memory (steps 403, 404). Thereafter, the process proceeds to step 405, and the outside air temperature detected by the outside air temperature sensor 31 (see FIG. 1) is stored in a non-volatile memory such as a backup RAM.

  In the estimated oil temperature initial value calculation program shown in FIG. 6, when it is determined in step 501 that the engine is starting, the process proceeds to step 502 to calculate the engine stop time.

  Thereafter, the process proceeds to step 503, and an average value (outside temperature average value when the engine is stopped) of the outside temperature detected when the engine is started (when the IG switch is turned on) and the outside temperature stored when the engine is stopped is calculated. Thereafter, the process proceeds to step 504, and a correction value K2 corresponding to the engine stop time and the outside air temperature average value is calculated by a map or a mathematical expression. The map of the correction value K2 is set so that the correction value K2 becomes smaller as the engine stop time becomes longer and the outside air temperature average value becomes lower.

Thereafter, the process proceeds to step 505, where the detected water temperature THWstart detected at the time of the current engine start, the difference between the detected water temperature THWstop stored at the previous engine stop and the estimated oil temperature THOstop, the engine stop time and the outside air temperature average value are determined. The estimated oil temperature initial value THOstart is calculated by the following equation using the corresponding correction value K2.
THOstart = THWstart− (THWstop−THOstop) × K2

  In the second embodiment described above, since the estimated oil temperature initial value THOstart is calculated using the correction value K2 corresponding to the engine stop time and the average outside air temperature, the estimated oil temperature is also considered in consideration of the outside air temperature. The initial value THOstart can be calculated, and the estimated oil temperature initial value THOstart can be accurately calculated without being affected by the outside air temperature. The intake air temperature may be used as substitute information for the outside air temperature.

  In the third embodiment of the present invention, by executing the program shown in FIGS. 7 and 8, the engine stop time is calculated according to the detected water temperature THWstop when the engine is stopped and the detected water temperature THWstart when the engine is started. The correction value K3 is calculated according to the engine stop time and the outside air temperature, and the estimated oil temperature initial value THOstart is calculated using the correction value K3.

  In the engine stop time processing program shown in FIG. 7, when it is determined in step 601 that the engine is stopped, the detected water temperature THWstop and the estimated oil temperature THOstop when the engine is stopped are stored in a non-volatile memory such as a backup RAM. (Step 603). Thereafter, the detected water temperature THWstop and the outside air temperature detected when the engine is stopped are stored in a non-volatile memory such as a backup RAM (steps 604 and 605).

  In the estimated oil temperature initial value calculation program shown in FIG. 8, when it is determined in step 701 that the engine is being started, the routine proceeds to step 702, where the detected water temperature THWstop when the engine is stopped and when the engine is started (when the IG switch is on). The engine stop time corresponding to the detected water temperature THWstart is calculated using a map or a mathematical expression.

  The engine stop time map shows that in a region where the detected water temperature THWstart at the time of engine start is equal to or higher than the detected water temperature THWstop at the time of engine stop, the engine stop time becomes 0, and the detected water temperature THWstart at engine start becomes the detected water temperature THWstop at engine stop. In the lower region, the engine stop time is set longer as the detected water temperature THWstop at the time of engine stop becomes higher and as the detected water temperature THWstart at the time of engine start becomes lower.

  After calculating the engine stop time, the process proceeds to step 703, and the average value of the outside air temperature detected when the engine is started (when the IG switch is on) and the outside air temperature stored when the engine is stopped (the outside air temperature average value when the engine is stopped). After the calculation, the process proceeds to step 704, where a correction value K3 corresponding to the engine stop time and the outside air temperature average value is calculated using a map or a mathematical expression.

Thereafter, the process proceeds to step 705, in accordance with the detected water temperature THWstart at the time of the current engine start, the difference between the detected water temperature THWstop stored at the previous engine stop and the estimated oil temperature THOstop, the engine stop time and the average outside air temperature. The estimated oil temperature initial value THOstart is calculated by the following equation using the corrected value K3.
THOstart = THWstart− (THWstop−THOstop) × K3
The intake air temperature may be used as substitute information for the outside air temperature.

  In the third embodiment described above, the engine stop time is calculated based on the detected water temperature THWstop when the engine is stopped and the detected water temperature THWstart when the engine is started. Therefore, the timer that operates while the engine is stopped is not provided. It can also be applied to vehicles.

  In the third embodiment, the engine stop time is calculated based on the detected water temperature THWstop when the engine is stopped and the detected water temperature THWstart when the engine is started, and based on the engine stop time and the outside air temperature (or intake air temperature). The correction value K3 is calculated, and the estimated oil temperature initial value THOstart is calculated using the correction value K3. However, the processing for calculating the engine stop time is omitted, and the detected water temperature THWstop when the engine is stopped and the engine Based on the detected water temperature THWstart at the start and the outside air temperature (or intake air temperature), a correction value for taking into account the engine stop time is directly calculated by a map or a mathematical formula, and the estimated oil temperature initial value is calculated using this correction value. THOstart may be calculated. In this way, it is possible to simplify the process of calculating the correction value in consideration of the engine stop time and the outside air temperature.

  In the first to third embodiments, the estimated oil temperature initial value THOstart is calculated using the difference between the detected water temperature THWstop when the engine is stopped and the estimated oil temperature THOstop, but the detected water temperature THWstop and the estimated oil when the engine is stopped is calculated. The method for calculating the estimated initial oil temperature value THOstart may be changed as appropriate, such as calculating the estimated initial oil temperature value THOstart using a ratio with the temperature THOstop. Furthermore, it goes without saying that the calculation method of the estimated oil temperature THO based on the estimated oil temperature initial value THOstart may be appropriately changed.

  Further, the present invention is not limited to the calculation of the estimated initial oil temperature value of the hydraulic oil of the variable intake valve timing device, but the calculation of the estimated initial oil temperature value of the lubricating oil or hydraulic oil used in the engine or its peripheral devices. Can be applied widely.

It is a schematic block diagram of the whole engine control system in Example 1 of this invention. 6 is a flowchart illustrating a flow of processing of a processing program for engine stop according to the first embodiment. 6 is a flowchart illustrating a flow of processing of an estimated oil temperature initial value calculation program according to the first embodiment. 3 is a flowchart illustrating a flow of processing of an estimated oil temperature calculation program according to the first embodiment. It is a flowchart which shows the flow of a process of the estimated oil temperature initial value calculation program of Example 2. FIG. It is a flowchart which shows the flow of a process of the estimated oil temperature calculation program of Example 2. FIG. 10 is a flowchart illustrating a flow of processing of an estimated oil temperature initial value calculation program according to a third embodiment. 10 is a flowchart illustrating a flow of processing of an estimated oil temperature calculation program according to a third embodiment. It is a time chart which shows the behavior of the actual water temperature and the actual oil temperature during warm-up operation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Internal combustion engine (engine), 12 ... Intake pipe, 14 ... Air flow meter, 15 ... Throttle valve, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 25 ... Cooling water temperature sensor (cooling water temperature detection means) 27 ... ECU (estimated oil temperature initial value calculating means), 29 ... Variable intake valve timing device, 31 ... Outside air temperature sensor

Claims (5)

Oil for an internal combustion engine provided with oil temperature estimating means for calculating an estimated oil temperature of oil used in the internal combustion engine or its peripheral device based on an estimated oil temperature at the time of starting the engine (hereinafter referred to as “estimated oil temperature initial value”) In the temperature estimation device,
Cooling water temperature detecting means for detecting the temperature of the cooling water of the internal combustion engine;
The water temperature detected by the cooling water temperature detecting means when the engine is stopped and the estimated oil temperature calculated by the oil temperature estimating means are stored as the detected water temperature at the previous engine stop and the estimated oil temperature at the previous engine stop, respectively, or A rewritable nonvolatile memory for storing a temperature difference between the detected water temperature and the estimated oil temperature;
When the engine is started, the detected water temperature at the previous engine stop, the estimated oil temperature at the previous engine stop or the temperature difference between the detected water temperature and the estimated oil temperature, and the engine stop time stored in the nonvolatile memory When the oil temperature estimation apparatus for an internal combustion engine, characterized by comprising the estimated oil temperature initial value calculating means for calculating the estimated oil temperature initial value based on the detected water temperature at the engine starting. 2. The oil temperature estimating device for an internal combustion engine according to claim 1, wherein the estimated oil temperature initial value calculating means calculates the estimated oil temperature initial value by the following equation.
THOstart = THWstart− (THWstop−THOstop) × K
THOstart: Estimated initial oil temperature
THWstart: agencies detected water temperature at the time of start-up
THWstop: Detected water temperature at the last engine stop
THOstop: Estimated oil temperature at the last engine stop
K: Correction value obtained from engine stop time   3. The oil temperature estimating device for an internal combustion engine according to claim 2, wherein the estimated oil temperature initial value calculating means calculates the correction value based on an engine stop time and an outside air temperature or an intake air temperature. The estimated oil temperature initial value calculating means calculates the engine stop time based on a detected water temperature at the previous engine stop and a detected water temperature at the engine start stored in the nonvolatile memory. An oil temperature estimating device for an internal combustion engine according to any one of claims 1 to 3. Oil for an internal combustion engine provided with oil temperature estimating means for calculating an estimated oil temperature of oil used in the internal combustion engine or its peripheral device based on an estimated oil temperature at the time of starting the engine (hereinafter referred to as “estimated oil temperature initial value”) In the temperature estimation device,
Cooling water temperature detecting means for detecting the temperature of the cooling water of the internal combustion engine;
Rewritable to store the water temperature detected by the cooling water temperature detecting means when the engine is stopped and the estimated oil temperature calculated by the oil temperature estimating means as the detected water temperature at the previous engine stop and the estimated oil temperature at the previous engine stop, respectively. Non-volatile memory,
During engine starting, a correction value for considering the engine stop time based on the non-volatile memory to the detected coolant temperature at engine stop of the previous stored during the engine start detecting water temperature and the outside air temperature or intake air temperature Prefecture calculated, and the correction value, the stored in the nonvolatile memory, the estimated oil temperature at the time of detection temperature and the previous engine stop at the previous engine stop, based on the detected water temperature at the engine starting the An oil temperature estimation device for an internal combustion engine, comprising: estimated oil temperature initial value calculation means for calculating an estimated oil temperature initial value.

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