JP2012017723A - Engine oil temperature estimating device of internal combustion engine, and valve timing variable device of internal combustion engine having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine oil temperature estimating device of an internal combustion engine, which can easily and appropriately estimate an engine oil temperature at an engine start.SOLUTION: The engine oil temperature estimating device of the internal combustion engine selects an alternative value of the engine oil temperature θe from a cooling water temperature θw, oil temperature θat for a transmission, and an air temperature θout, and estimates the engine oil temperature θe at the engine start based on the alternative value. The engine oil temperature estimating device includes a determination means for determining whether the distribution of cooling water temperature θw, oil temperature θat for a transmission, and air temperature θout settles in a prescribed range at the engine start, and a setting means for setting a selection mode to a different mode based on the determination result of the determination means when the alternative value of engine oil temperature θe is selected.

Description

  The present invention relates to an engine oil temperature estimation device for an internal combustion engine that estimates an engine oil temperature at the time of starting the engine, and a valve timing variable device for an internal combustion engine that includes this and changes the valve timing of an intake valve or an exhaust valve.

  When the internal combustion engine is in a cold state, the temperature of the engine oil is low and its viscosity is high, so that the sliding resistance of the part to which the engine oil is supplied becomes larger than after the warm-up is completed, and the engine oil is circulated. Therefore, the amount of engine oil supplied to each part of the internal combustion engine, such as a hydraulic device, a lubrication part, a cooling part, etc., tends to be smaller than that after completion of warming up. For this reason, in various controls of the internal combustion engine, there are many controls that take into account the temperature of the engine oil when the engine is cold. For example, in valve timing control in which the valve timing of intake valves and exhaust valves is changed using engine oil as a working medium, engine cooling water temperature is employed as an alternative value for engine oil temperature at engine start. When the engine coolant temperature is low, the engine oil temperature is low and the viscosity is high. Therefore, it is assumed that the change speed of the valve timing is low compared to the state in which the engine oil temperature has risen as after the warm-up is completed. Like to do.

  For example, the valve timing control device described in Patent Document 1 measures the elapsed time from engine stop at the time of engine start, and when the elapsed time is equal to or longer than a predetermined time, the engine cooling water temperature converges to the engine ambient temperature. Therefore, the engine atmosphere temperature or the engine cooling water temperature is estimated as the engine oil temperature.

  However, even if a predetermined time has elapsed from when the engine was stopped to when the engine was started, depending on the temperature conditions at the time of engine stop, the engine oil temperature or the engine cooling water temperature has not yet sufficiently converged to the engine ambient temperature. Can be in Under these circumstances, if the engine coolant temperature is selected as an alternative value for the engine oil temperature, there may be a non-negligible discrepancy between the actual engine oil temperature and the engine oil temperature estimated based on the engine coolant temperature. It cannot be denied that there is.

  On the other hand, in the oil temperature estimation device described in Patent Document 2, the engine oil temperature is estimated based on the engine coolant temperature at the time of the previous engine stop and stored, and this stored value is stored after the engine stop. The engine oil temperature is sequentially calculated with correction based on the elapsed time. Thus, the engine oil temperature is estimated based on the determination result even in a transient state where the engine coolant temperature has not converged to the engine atmosphere temperature.

JP 2003-254098 A JP-A-2005-207297

  In such an oil temperature estimation device, it is necessary to estimate the engine oil temperature in consideration of all these various situations even when the temperature conditions of the internal combustion engine at the time of engine stop are different. It is necessary to continue this process until the engine is started. For this reason, the calculation load accompanying this becomes very large, and there is no guarantee that the engine oil temperature can be estimated with extremely high reliability by such a large load calculation.

  The present invention has been made in view of such conventional circumstances, and an object thereof is to provide an engine oil temperature estimation device for an internal combustion engine that can easily and appropriately estimate the engine oil temperature at the time of engine start. is there.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 selects an alternative value of the engine oil temperature from a plurality of correlation temperatures having a correlation with the engine atmosphere temperature and the engine oil temperature, and the engine oil temperature at the time of engine start based on the alternative value. In the engine oil temperature estimating apparatus for an internal combustion engine that estimates the engine temperature, the plurality of sensors that individually detect the engine ambient temperature and the plurality of correlation temperatures, and the distribution of the temperatures detected by the sensors when the engine is started are within a predetermined range. And a setting unit that sets a selection mode to a different mode based on a determination result of the determination unit when selecting an alternative value of the engine oil temperature. It is said.

  According to the present invention, it is possible to easily and accurately determine a transient state in which the engine oil temperature or the correlation temperature does not converge to the engine ambient temperature such as the outside air temperature after the engine is stopped, and conforms to the determination result. In this way, it is possible to set a selection mode for selecting an alternative value of the engine oil temperature when starting the engine. Therefore, the engine oil temperature at the time of starting the engine can be estimated easily and appropriately.

  According to a second aspect of the present invention, in the engine oil temperature estimating apparatus for an internal combustion engine according to the first aspect, the setting means is such that the distribution of each temperature detected by the determination means is within a predetermined temperature range. When determined, the gist is to select the lowest temperature among the engine ambient temperature and the plurality of correlation temperatures as an alternative value of the engine oil temperature.

  As described above, when it is determined that the distribution of each detected temperature is within the predetermined temperature range, the difference between each temperature including the engine oil temperature and the engine ambient temperature is considered to be small. Can do. However, even in such a case, there may still be a difference between the actual engine oil temperature and the temperature selected as an alternative value. For this reason, for example, when the engine oil temperature estimated based on the substitute value is higher than the actual temperature, the viscosity of the engine oil is lower than the actual temperature, and the pressure loss that occurs when this oil flows is small. There is a concern that it is estimated. When the estimation is made in this way, for example, it is determined that the sliding resistance at the engine oil supply site is smaller than the actual one, or is supplied to the hydraulic equipment, the lubrication site, the cooling site, etc. of the internal combustion engine. It is judged that the amount of engine oil is larger than the actual amount. However, in general, when it is judged that the sliding resistance is larger than the actual one and the amount of engine oil supplied to the hydraulic equipment or the like is smaller than the actual one, in addition to these sliding resistances, the hydraulic equipment, the lubrication It is desirable to guarantee the stability and reliability of each engine control in consideration of the amount of engine oil supplied to the parts, cooling parts, etc. In this regard, according to the above configuration, since the smallest value among the detected temperatures is selected as an alternative value of the engine oil temperature, the engine oil temperature is estimated to be higher than the actual temperature. Therefore, it is possible to prevent the stability and reliability of the control related to the engine oil temperature from deteriorating greatly.

  According to a third aspect of the present invention, in the engine oil temperature estimation device for an internal combustion engine according to the first or second aspect, the setting means includes the engine oil temperature after the engine is stopped among the plurality of correlation temperatures. When the maximum temperature of the deviation degree is the smallest relative temperature regardless of the temperature state at the time of engine stop, and the determination means determines that the distribution of each detected temperature is not within the predetermined temperature range. The gist is to select the relative temperature obtained in advance as an alternative value of the engine oil temperature.

  According to the present invention, even when a difference occurs between the engine oil temperature and a plurality of correlation temperatures due to various temperature conditions after the engine is stopped, the relative temperature with the smallest maximum value of the difference is determined for the engine. Since it is used as a substitute value for the oil temperature, it is possible to avoid a situation in which the actual engine oil temperature and the estimated engine oil temperature are significantly different.

  According to a fourth aspect of the present invention, in the engine oil temperature estimating apparatus for an internal combustion engine according to the third aspect, the setting means selects only a temperature corresponding to a maximum value of the degree of deviation from the engine oil temperature as an alternative value. The gist is to estimate the temperature at which the relative temperature is lowered as the engine oil temperature.

  According to the present invention, since the temperature at which the relative temperature selected as the substitute value is reduced by the temperature corresponding to the maximum value of the deviation degree from the engine oil temperature is estimated as the engine oil temperature, the estimated value The temperature is lower than the engine oil temperature regardless of the temperature condition when the engine is stopped and the elapsed time after the engine is stopped. For this reason, the situation where the estimated engine oil temperature becomes higher than the actual engine oil temperature can be avoided, and the stability and reliability of the control related to the engine oil temperature as described above are greatly deteriorated. Will be able to avoid.

  According to a fifth aspect of the present invention, in the engine oil estimating device for an internal combustion engine according to the third or fourth aspect, the transmission for transmitting the engine driving force to the vehicle drive system is mixed with the engine oil. A transmission oil temperature sensor for detecting the temperature of the transmission oil that is not present is further provided, and the setting means selects the detected transmission oil temperature as an alternative value of the engine oil temperature. .

  The inventor of the present application observes the transition of the actual engine oil temperature and various temperatures thereafter through experiments in the case where the operation of the internal combustion engine is stopped under various different situations, and the engine oil temperature and the transmission oil It was found that the maximum value of the divergence degree is the smallest when compared with various other temperatures even when the divergence degree is the highest. The invention according to claim 5 is based on such knowledge. Since the transmission oil temperature among the plurality of correlation temperatures is used as an alternative value of the engine oil temperature, the actual engine oil temperature is appropriately estimated. be able to.

  According to a sixth aspect of the present invention, a variable valve mechanism that changes the valve timing of at least one of an intake valve and an exhaust valve using engine oil as a working medium, and the valve timing can be locked at a specific time prior to engine stop. The engine oil temperature estimating device for an internal combustion engine according to any one of claims 1 to 5, comprising a lock mechanism, and changing the valve timing from the specific time by the variable valve mechanism when the engine is cold The gist is to limit the amount to be smaller when the engine oil temperature estimated by the engine oil temperature estimation device is low than when it is high.

  When the engine oil temperature is low, such as when the engine is cold, the viscosity of the engine oil, which is the working medium of the variable valve mechanism, is high, so that the operation response, that is, the speed when changing the valve timing is lowered. For this reason, if the engine stop operation is performed when the valve timing of the intake valve or the exhaust valve is changed as described above, the engine operation is stopped before the valve timing returns to a specific time. A situation may occur in which the inertial rotation of the crankshaft stops) and the lock mechanism cannot be locked. As is well known, the lock mechanism causes the valve timing of the engine valve to fluctuate unnecessarily even when a sufficient amount of hydraulic fluid cannot be supplied to the variable valve mechanism, such as when the engine is started. However, if the engine is started in a state where the lock mechanism does not function in this way, such unnecessary fluctuations in valve timing are unavoidable.

  In this regard, according to the present invention, the amount of change in the valve timing from the specific timing by the variable valve mechanism is limited to be smaller when the engine oil temperature estimated by the engine oil temperature estimation device is low than when it is high. . As a result, even when the engine stop operation is performed when the operation responsiveness of the variable valve mechanism is degraded, the valve timing can be changed to a specific time, and the function of the lock mechanism can be improved. Can be secured.

  According to a seventh aspect of the present invention, in the valve timing variable device for the internal combustion engine according to the sixth aspect, the variable valve mechanism includes an exhaust side variable valve mechanism that changes a valve timing of the exhaust valve, and the engine is cold. In some cases, the exhaust side variable valve mechanism performs a retard process for retarding the valve timing of the exhaust valve with a predetermined retard amount from the specific timing, and the retard amount in the retard process is The gist is that the valve timing is changed.

  When the engine is cold, by delaying the valve timing of the exhaust valve, the period from when ignition is performed until the exhaust valve is opened is lengthened to ensure the combustion time of the air-fuel mixture in the combustion chamber. Thus, unburned fuel discharged from the combustion chamber can be reduced. On the other hand, when the engine oil temperature is low, such as when the engine is cold, the viscosity of the engine oil, which is the working medium of the exhaust side variable valve mechanism, is high. As described above, the speed at the time decreases. For this reason, if the engine stop operation is performed when the valve timing of the exhaust valve is retarded as described above, the engine operation is stopped before the valve timing returns to the specific time, and the lock mechanism is locked. It is possible that a situation that cannot be performed. As is well known, the lock mechanism causes the valve timing of the exhaust valve to fluctuate unnecessarily even when a sufficient amount of hydraulic fluid cannot be supplied to the exhaust side variable valve mechanism, such as when the engine is started. However, if the engine is started in such a state that the lock mechanism does not function in this way, such unnecessary fluctuations in valve timing are unavoidable.

  In this respect, according to the present invention, the retard amount when retarding the valve timing of the exhaust valve when the engine is cold is limited to be smaller than when it is high when the engine oil temperature estimated at engine start is low. As a result, the amount of unburned fuel discharged can be reduced while ensuring the function of the lock mechanism.

The schematic diagram which shows schematic structure of the control apparatus concerning one Embodiment of this invention, and the internal combustion engine which is a control object of the control apparatus. The graph which shows the relationship between a crank angle, valve lift amount, and valve timing. The correlation diagram which shows the correlation with engine oil temperature, the oil temperature for transmissions, and cooling water temperature. The flowchart which shows the process sequence about the estimation process of the engine oil temperature of the embodiment. The map for calculating the basic retardation amount set by the engine rotational speed and the engine load when the vehicle is traveling. A map for calculating a basic retardation amount set by an engine rotation speed and an engine load when the vehicle is stopped. The map for calculating the upper limit guard value set by the integrated intake air amount and the engine oil temperature during vehicle travel. The map for calculating the upper limit guard value set by the integrated intake air amount and the engine oil temperature when the vehicle is stopped. Explanatory drawing which shows the relationship between the integrated intake air amount at the time of vehicle travel, and the last target valve timing. Explanatory drawing which shows the relationship between the integrated intake air amount at the time of a vehicle stop, and the last target valve timing. The flowchart which shows the process sequence about the final target valve timing calculation process of the cold side exhaust side valve timing control of the embodiment. The graph which shows transition of the intake air temperature and the outside temperature after engine starting. The flowchart which shows a part of the process sequence about the estimation process of the engine oil temperature of other embodiment of this invention.

Hereinafter, an embodiment in which the present invention is embodied as a control device for a variable valve timing device that changes the valve timing of an exhaust valve will be described.
As shown in FIG. 1, the combustion chamber 11 of the internal combustion engine 10 has an intake passage 21 for taking intake air into the combustion chamber 11 from the outside and an exhaust passage 31 for discharging the exhaust of the combustion chamber 11 to the outside. It is connected. The intake passage 21 is provided with a throttle valve 22 that adjusts the intake air amount Ga according to its opening (throttle opening TA). The exhaust passage 31 is provided with an exhaust purification device 32 carrying a three-way catalyst for purifying hydrocarbons, carbon monoxide, and nitrogen oxides contained in the exhaust.

  In addition, the internal combustion engine 10 is provided with a variable valve timing device in order to stabilize engine combustion, improve exhaust properties and fuel consumption, increase engine output, and the like. This variable valve timing device includes different variable valve mechanisms such as an intake side variable valve mechanism 40 that changes the valve timing of the intake valve 41 and an exhaust side variable valve mechanism 50 that changes the valve timing of the exhaust valve 51. I have.

  The intake side variable valve mechanism 40 changes the relative rotation phase of the intake camshaft (not shown) with respect to the crankshaft (not shown) based on the hydraulic pressure of the hydraulic oil supplied from the oil pump 12, so that the intake valve 41 valve timing is changed. On the other hand, the exhaust-side variable valve mechanism 50 changes the relative rotation phase of the exhaust camshaft (not shown) with respect to the crankshaft based on the hydraulic pressure of the hydraulic oil supplied from the oil pump 12, thereby Change the valve timing. The oil pump 12 is an engine-driven pump that is driven based on the rotation of the crankshaft.

  Various devices of the internal combustion engine 10 including the variable valve timing device are controlled by the control device 60. The control device 60 includes a memory, an A / D conversion circuit, a drive circuit, and the like in addition to the CPU. In addition, various sensors are connected to the control device 60, and the detection signals thereof are appropriately captured. For example, the water temperature sensor 71 detects the temperature of engine cooling water circulating in a water jacket (not shown) (hereinafter referred to as “cooling water temperature θw”). The intake air temperature sensor 72 detects the temperature of intake air taken in by the internal combustion engine 10. The throttle position sensor 73 detects the throttle opening degree TA. An air flow meter 74 provided in the intake passage 21 detects an intake air amount Ga. The outside air temperature sensor 75 detects the temperature of outside air (hereinafter referred to as “outside air temperature θout”). The crank position sensor 76 detects the rotation angle of the crankshaft, and the control device 60 calculates the rotation speed of the crankshaft per unit time, that is, the engine rotation speed NE based on this rotation angle. The exhaust side cam position sensor 77 outputs a signal corresponding to the rotational phase of the exhaust camshaft. A transmission oil temperature sensor 78 provided in an automatic transmission (not shown) is a temperature of transmission oil used for hydraulic operation and lubrication of various gear mechanisms in the automatic transmission (hereinafter referred to as “transmission oil”). Temperature θat "). The vehicle speed sensor 79 detects the vehicle speed. And the control apparatus 60 performs various arithmetic processing by taking in the detection signal of the said various sensors 71-79 suitably, and controls the internal combustion engine 10 and its auxiliary machine based on the result.

  For example, the control device 60 sets target values for the valve timings of the intake valve 41 and the exhaust valve 51 based on the engine rotational speed NE and the engine load KL, and the actual valve timings of the intake valve 41 and the exhaust valve 51. , The intake side variable valve mechanism 40 and the exhaust side variable valve mechanism 50 are driven so as to coincide with the target value.

  The variable valve mechanisms 40 and 50 of these variable valve timing devices are respectively provided with lock mechanisms 45 and 55 for locking the valve timings of the intake valve 41 and the exhaust valve 51 at specific times, respectively. That is, the lock mechanism 45 provided in the intake side variable valve mechanism 40 locks the valve timing of the intake valve 41 to the most retarded timing, while the lock mechanism 55 provided in the exhaust side variable valve mechanism 50 includes: The valve timing of the exhaust valve 51 is locked at the most advanced timing. As described above, each of the lock mechanisms 45 and 55 reduces the valve overlap between the intake valve 41 and the exhaust valve 51, thereby suppressing the blow-back of the exhaust during normal start and ensuring good engine startability. ing.

  However, although it is possible to ensure good engine startability by suppressing the exhaust gas blowback during normal startup, the air-fuel mixture is fogged in the combustion chamber 11 at the cold start and immediately after the start. Therefore, incomplete combustion of the air-fuel mixture occurs, and the unburned components of the fuel contained in the exhaust gas are likely to increase. Further, even in the exhaust purification device 32, the catalyst bed temperature does not rise to the activation temperature, so even if the unburned component of the fuel contained in the exhaust increases in this way, it is sufficiently purified. Can not do it.

  Therefore, the control device 60 according to the present embodiment delays the valve timing of the exhaust valve 51 and delays the valve opening timing of the exhaust valve 51 in order to reduce the discharge amount of unburned fuel during cold weather (hereinafter referred to as “the control valve 60”). , “Cold exhaust side valve timing control”).

  As shown in FIG. 2, when the exhaust valve 51 is retarded from the valve timing suitable for its normal start to delay the valve opening timing, in other words, by the lock mechanism 55 of the exhaust side variable valve mechanism 50. When the valve timing of the exhaust valve 51 is retarded than when the valve timing is locked at the most advanced timing, the period from when ignition is performed until the exhaust valve 51 is opened corresponds to the amount of retardation. It becomes longer by the period. That is, a long combustion period of the air-fuel mixture can be ensured. In this way, the unburned fuel is reduced by increasing the period during which the air-fuel mixture can be combusted by delaying the opening timing of the exhaust valve 51.

  As described above, when the engine is cold, it is required to retard the valve timing of the exhaust valve 51 in order to reduce the discharge amount of unburned fuel, but when the valve timing of the exhaust valve 51 is retarded in this way. It is desirable to consider the operation responsiveness of the exhaust side variable valve mechanism 50 as follows.

  That is, when the temperature of the engine oil (hereinafter referred to as “engine oil temperature θe”) is low, such as when the engine is cold, the viscosity of the engine oil is high. Therefore, the operation response of the exhaust side variable valve mechanism 50 using this as a working medium. That is, the speed when changing the valve timing is lowered. For this reason, if the engine stop operation is performed while the valve timing of the exhaust valve 51 is retarded as described above, the valve timing may become the most advanced timing depending on the magnitude of the retard amount at that time. Situations may occur where engine operation stops before returning. That is, even when the engine stop operation is performed, the oil pump 12 can be driven to return the valve timing to the most advanced timing while the crankshaft is inertially rotated. Because the inertial rotation of the crankshaft stops before the valve timing returns to the most advanced angle timing, the lock mechanism 55 cannot be locked.

  Therefore, in this embodiment, when the engine is cold, the valve timing of the exhaust valve 51 is retarded, and the valve timing of the exhaust valve 51 is maximized even if the engine is stopped during such retarding operation. Both of the two requirements, such as returning to the advance timing and being able to be locked by the lock mechanism 55, are satisfied. Specifically, the engine oil temperature θe at the time of starting the engine is appropriately estimated, and the retard amount when the valve timing of the exhaust valve 51 is retarded when the engine is cold based on the estimated engine oil temperature θe. I am trying to set it.

  Next, the process for estimating the engine oil temperature at the time of engine start will be described with reference to FIGS. FIG. 3 shows that when the engine operation is stopped in a state where the internal combustion engine 10 is in various operating states, the engine oil temperature θe and the engine oil temperature θe when a predetermined period elapses after the engine operation is stopped. FIG. 5 is a correlation diagram showing a correlation between corresponding transmission oil temperature θat and cooling water temperature θw.

  In FIG. 3, when the engine oil temperature θe is “γ”, the transmission oil temperature θat may be “α1” or “α2” depending on the operating state before the engine is stopped. The cooling water temperature θw may also be “β1” or “β2”. However, even when the operating state before the engine is stopped in this way, the deviation degree of the transmission oil temperature θat with respect to the engine oil temperature θe is the maximum value shown in FIG. 3 (hereinafter referred to as “maximum deviation degree Δα”). ") Is not exceeded. On the other hand, the maximum value (hereinafter referred to as “maximum deviation degree Δβ”) related to the same deviation degree of the coolant temperature θw is larger than the maximum deviation degree Δα of the transmission oil temperature θat. That is, the transmission oil temperature θat has a higher correlation with the engine oil temperature θe than the cooling water temperature θw.

FIG. 4 is a flowchart showing a series of processes when estimating the engine oil temperature θe at the time of starting the engine.
As shown in FIG. 4, in this estimation process, the control device 60 first determines in step S110 whether or not it is a start time. That is, it is determined whether or not the engine is started by the driver. If it is determined in step S110 that the engine is starting (step S110: YES), in step S120, the coolant temperature sensor 71, the outside air temperature sensor 75, and the transmission oil temperature sensor 78 cause the cooling water temperature θw and the outside air temperature, respectively. θout and transmission oil temperature θat are detected. In addition, the time of engine starting here refers to the period until it becomes possible to perform independent operation from cranking.

  Next, in step S130, it is determined whether or not the distribution of the cooling water temperature θw, the transmission oil temperature θat, and the outside air temperature θout detected in step S120 has converged within a predetermined range. Specifically, it is determined whether or not the difference between the highest temperature and the lowest temperature (hereinafter referred to as “temperature difference Δθ”) among these temperatures θw, θat, and θout is within a predetermined value Δθα. Here, when the temperature difference Δθ is within the predetermined value Δθα, the difference between the temperatures θw and θat including the engine oil temperature θe and the outside air temperature θout is small, and it is considered that the temperature has converged to the outside air temperature θout. (Step S130: YES).

  On the other hand, when the temperature difference Δθ is larger than the predetermined value Δθα, the distribution of the respective temperatures θw, θat, θout including the engine oil temperature θe does not converge within the predetermined range, and the transient before the convergence is reached. It is determined that the current state is present (step S130: NO).

  If it is determined in step S130 that the temperature difference Δθ is within the predetermined value Δθα (step S130: YES), in step S140, the cooling water temperature θw, the transmission oil temperature θat, and the outside air temperature θout are the largest. A low temperature is set as the engine oil temperature θe when the engine is started.

Here, the reason why the lowest temperature among the coolant temperature θw, the transmission oil temperature θat, and the outside air temperature θout is selected is as follows.
That is, when the estimated engine oil temperature θe is higher than the actual temperature, there is a concern that the viscosity of the engine oil is lower than the actual temperature, and that the pressure loss generated when the engine oil circulates is also small. is there. When the estimation is made in this way, for example, it is judged that the sliding resistance at the engine oil supply site is smaller than the actual one, or the hydraulic oil, the lubrication site, the cooling site, etc. of the internal combustion engine 10 are supplied. It is judged that the amount of engine oil to be used is larger than the actual amount. However, in general, when it is judged that the sliding resistance is larger than the actual one and the amount of engine oil supplied to the hydraulic equipment or the like is smaller than the actual one, in addition to these sliding resistances, the hydraulic equipment, the lubrication It is desirable to guarantee the stability and reliability of each engine control in consideration of the amount of engine oil supplied to the parts, cooling parts, etc. For this reason, as described above, the lowest temperature among the temperatures θw, θat, and θout is estimated as the engine oil temperature θe at the time of engine start.

  On the other hand, when it is determined in step S130 that the temperature difference Δθ is larger than the predetermined value Δθα (step S130: NO), that is, between the engine oil temperature θe, the coolant temperature θw, and the transmission oil temperature θat. In step S150, based on the correlation between the engine oil temperature θe, the coolant temperature θw, and the transmission oil temperature θat (see FIG. 2), the difference between the engine oil temperature θe and the engine oil temperature θe is determined. The transmission oil temperature θat, which is obtained in advance as the relative temperature at which the maximum value of the deviation degree is the smallest, is selected as the engine oil temperature θe. Further, a temperature obtained by reducing the transmission oil temperature θat by an amount corresponding to the maximum deviation degree Δα is set as the engine oil temperature θe. The engine oil temperature θe set in this way is estimated to be the same or always lower than the actual engine oil temperature θe regardless of the temperature condition at the time of engine stop and the elapsed time after the stop. The situation where the engine oil temperature θe becomes higher than the actual engine oil temperature θe can be avoided, and the stability and reliability of the control related to the engine oil temperature θe as described above can be avoided. Will be able to.

  Subsequently, referring to FIGS. 5 to 11, a target valve timing calculation process of the cold exhaust side valve timing control that is executed based on the engine oil temperature θe at the time of engine start estimated by the engine oil temperature estimation process. Will be described in detail.

  As described above, the retard amount when retarding the valve timing of the exhaust valve 51 in the cold exhaust side valve timing control is the same as the valve timing of the exhaust valve 51 even if the engine stop operation is performed during the retard operation. It is desirable that the amount can be locked by the lock mechanism 55 after returning to the most advanced timing. In addition to this, the amount of retardation varies depending on whether the vehicle is running or the vehicle is stopped.

  That is, when the vehicle travels, the engine operation is stopped by the driver after the accelerator operation is released, so that the engine is stopped. Therefore, there is a time margin until the engine is stopped. For this reason, even if the engine stop operation is performed during the retard operation, it is possible to secure time for returning the valve timing of the exhaust valve 51 to the most advanced timing and locking it by the lock mechanism 55. On the other hand, when the vehicle is stopped, the time until the engine is stopped is shorter than when the vehicle is traveling, so the retarding operation is performed with the same amount of retardation as when the vehicle is traveling. When the engine stop operation is performed, the valve timing of the exhaust valve 51 cannot be returned to the most advanced angle timing, and the valve timing may not be locked by the lock mechanism 55.

  Therefore, in this embodiment, a retard amount (hereinafter referred to as “basic retard amount VTb”) for retarding the valve timing of the exhaust valve 51 in the cold exhaust side valve timing control is obtained through map calculation. The calculation map used at that time is divided into when the vehicle is running and when the vehicle is stopped, and stored in the memory of the control device 60. Whether the vehicle is traveling or when the vehicle is stopped can be determined that the vehicle is traveling on the condition that the vehicle speed detected by the vehicle speed sensor 79 is equal to or higher than a determination value.

  As shown in FIGS. 5 and 6, the calculation map for obtaining the basic retard amount VTb in the cold exhaust side valve timing control is the engine rotation speed in both cases of vehicle travel and vehicle stop. NE and engine load KL are used as parameters. That is, by referring to these calculation maps, the basic retardation amount VTb can be obtained based on the engine speed NE and the engine load KL.

  As shown in FIG. 5, the basic retardation amount VTbrun when the vehicle travels varies in the range from the maximum value VTb4 to the minimum value VTb0. In FIG. 5, VTb0, VTb1, VTb2, VTb3, and VTb4 represent representative values of the basic retardation amount VTbrun corresponding to the engine speed NE and the engine load KL. On the other hand, as shown in FIG. 6, the basic retardation amount VTbstop when the vehicle is stopped varies in the range from the maximum value VTb3 to the minimum value VTb0. In FIG. 6, VTb0, VTb1, VTb2, and VTb3 represent representative values of the basic retardation amount VTbstop corresponding to the engine speed NE and the engine load KL. For these representative values, the magnitude relationship of (VTb4> VTb3> VTb2> VTb1> VTb0) is established, and if the engine speed NE and the engine load KL are the same, the basic delay set when the vehicle is stopped. The angular amount VTbstop is smaller than the basic retardation amount VTbrun set when the vehicle is traveling. Further, the basic retardation amount VTbrun corresponding to the time when the vehicle is traveling is set more finely than the setting manner of the basic retardation amount VTbstop when the vehicle is stopped. In the present embodiment, since VTb0 is set to “0”, the basic retard amounts VTbrun and VTbstop selected based on the engine speed NE and the engine load KL are “0” and the valve of the exhaust valve 51 is set. The retard control related to the timing is prohibited.

  Furthermore, as described above, when the engine is cold, the operation responsiveness of the exhaust side variable valve mechanism 50, that is, the speed at which the valve timing is changed, decreases, so that the valve timing of the exhaust valve 51 is retarded. Even if the engine stop operation is performed during such a retard operation, the retard amount is set so that both of the two requirements such that the valve timing of the exhaust valve 51 can be returned to the most advanced timing and locked by the lock mechanism 55 are satisfied. It is desirable to set.

  Therefore, in the present embodiment, in order to appropriately set the retardation amount, an upper limit guard value for limiting based on the engine oil temperature θe estimated at the time of engine start and the cumulative intake air amount ΣGa from the time of engine start. VTg is set, and a valve timing that is finally targeted (hereinafter referred to as “final target valve timing VTf”) is determined based on the upper limit guard value VTg and the basic retardation amount VTb described above. .

  In setting the upper limit guard value VTg, it is desirable to set it in consideration of whether the vehicle is stopped or traveling. Therefore, in the present embodiment, the upper limit guard value VTg is obtained through map calculation in the cold exhaust side valve timing control, and the map at that time is divided into when the vehicle is running and when the vehicle is stopped and stored in the memory of the control device 60. I remember it.

  FIGS. 7 and 8 show the upper guard value VTgrun corresponding to when the vehicle is traveling and VTgstop corresponding to when the vehicle is stopped. As shown in these figures, for the upper limit guard values VTgrun and VTgstop corresponding to both cases when the vehicle is running and when the vehicle is stopped, the calculation map for obtaining these is the integrated intake air amount ΣGa, the engine oil temperature θe, and the like. Is the parameter. That is, by referring to these calculation maps, the upper guard value VTg can be obtained based on the cumulative intake air amount ΣGa and the engine oil temperature θe.

  As shown in FIG. 7, upper limit guard value VTgrun during vehicle travel varies in a range from maximum value VTg4 to minimum value VTg0. In FIG. 7, VTg0, VTg3, and VTg4 represent representative values of the upper limit guard value VTgrun corresponding to the cumulative intake air amount ΣGa and the engine oil temperature θe. On the other hand, as shown in FIG. 8, upper limit guard value VTgstop when the vehicle is stopped varies in the range from maximum value VTg3 to minimum value VTg0. In FIG. 8, VTg0, VTg1, VTg2, and VTg3 represent representative values of the upper guard value VTgstop corresponding to the integrated intake air amount ΣGa and the engine oil temperature θe. These representative values are set when the vehicle stops if the magnitude relationship of (VTg4> VTg3> VTg2> VTg1> VTg0) is established and the integrated intake air amount ΣGa and the engine oil temperature θe are the same. Upper limit guard value VTgstop is set to a value smaller than upper limit guard value VTgrun set when the vehicle travels. In this way, when the vehicle is stopped, the time until the engine is stopped is shorter than when the vehicle is running, so the upper guard value VTg when the vehicle is stopped is set small. In this embodiment, since VTg0 is “0”, the upper limit guard values VTgrun and VTgstop selected based on the integrated intake air amount ΣGa and the engine oil temperature θe are “0”, and the valve timing of the exhaust valve 51 is set. Therefore, the retard angle control is prohibited.

  By the way, as described above, the cold exhaust side valve timing control suppresses the stabilization of the combustion state and the discharge of unburned fuel due to this when the engine is cold, that is, when the engine oil temperature θe is low. It is carried out for the purpose. However, if a predetermined time elapses after the engine is started, the temperature of the combustion chamber 11 rises and the combustion of the air-fuel mixture is promoted to reduce the discharge of unburned fuel. The need to execute is low. Further, when the catalyst bed temperature of the exhaust purification device 32 rises to the activation temperature, even if some unburned fuel is discharged from the combustion chamber 11, it can be purified by the exhaust purification device 32, which adversely affects the exhaust properties. Will not be affected. In this case, it is not meaningful to execute the cold exhaust side valve timing control to ensure a long combustion time of the air-fuel mixture.

  Therefore, in the present embodiment, the initial temperature state of the combustion chamber 11 and the exhaust purification device 32 is grasped based on the engine oil temperature θe, and the temperature rise of the combustion chamber 11 and the exhaust purification device 32 is based on the integrated intake air amount ΣGa. I try to keep track of the degree. That is, the upper limit guard values VTgrun and VTgstop shown in FIGS. 7 and 8 are basically set to smaller values as the engine oil temperature θe is lower and as the integrated intake air amount ΣGa is larger.

  As shown in FIGS. 9 and 10, the final target valve timing VTf in the cold exhaust side valve timing control is the basic retard amount VTb calculated in FIGS. 5 and 6, and FIGS. It is calculated based on the upper limit guard value VTg calculated in the above.

  That is, as indicated by solid lines in FIGS. 9 and 10, when the basic retardation amount VTb is larger than the upper limit guard value VTg, the final target valve timing VTf is set to a value equal to the upper limit guard value VTg. . As a result, the retard amount of the valve timing of the exhaust valve 51 controlled through the cold exhaust side valve timing control becomes smaller as the operation responsiveness of the exhaust side variable valve mechanism 50 cannot be ensured when the engine is cold. Become. Further, the more the engine temperature is increased and the combustion state of the air-fuel mixture is improved, and the more the unburned fuel contained in the exhaust gas can be efficiently purified by the activation of the exhaust gas purification device 32, the colder the colder the fuel becomes. The retard amount of the valve timing of the exhaust valve 51 controlled through the hour exhaust side valve timing control is reduced.

  Specifically, as indicated by a one-dot chain line in FIGS. 9 and 10, the cumulative intake air amount ΣGa becomes smaller as it becomes larger than “S1”, and becomes “0” when it reaches “S2”. An upper guard value VTg is set. “S1” indicates that the engine temperature rises, and the operation responsiveness of the exhaust side variable valve mechanism 50 can be secured to some extent, and a stable combustion state of the air-fuel mixture can be obtained to some extent, and the exhaust purification device 32 is activated. This is the integrated intake air amount ΣGa when the gasification starts. In “S2,” the engine temperature further increases, and the operation responsiveness of the exhaust side variable valve mechanism 50 can be secured, and a stable combustion state of the air-fuel mixture is obtained, and the exhaust purification device 32 is completely activated. Is the integrated intake air amount ΣGa.

  As shown in FIG. 9, when the vehicle travels, even if the engine stop operation is performed during the retard operation, the time for returning the valve timing of the exhaust valve 51 to the most advanced timing and locking by the lock mechanism 55 is secured. Therefore, it is not necessary to limit the basic retardation amount VTb with the upper guard value VTg when the engine is cold. Therefore, the basic retardation amount VTb is set as the final target valve timing VTf until the integrated intake air amount ΣGa reaches “S1”. In addition, after “S1”, since it is not necessary to gradually improve the combustion of the air-fuel mixture by the cold exhaust side valve timing control, the upper limit guard value VTg is set as the final target valve timing VTf.

  On the other hand, as shown in FIG. 10, when the vehicle is stopped, there is a possibility that the valve timing cannot be locked by the lock mechanism 55 because the time until the engine is stopped is shorter than when the vehicle is traveling. For this reason, it is necessary to limit the basic retardation amount VTb by the upper limit guard value VTg as the operation responsiveness of the exhaust side variable valve mechanism 50 cannot be ensured when the engine is cold. Thus, when the basic retard amount VTb exceeds the upper limit guard value VTg until the integrated intake air amount ΣGa reaches “S1”, the upper limit guard value VTg is set as the final target valve timing VTf, and When the basic retardation amount VTb is equal to or less than the upper limit guard value VTg, the basic retardation amount VTb is set as the final target valve timing VTf. In addition, after “S1”, since it is not necessary to gradually improve the combustion of the air-fuel mixture by the cold exhaust side valve timing control, the upper limit guard value VTg is set as the final target valve timing VTf.

  As described above, in the present embodiment, the engine oil temperature θe and the integrated intake air amount ΣGa are set to the basic retard amount VTb set based on the engine speed NE and the engine load KL, respectively, when the vehicle is running and when the vehicle is stopped. The final target valve timing VTf in the cold exhaust side valve timing control is set by applying the upper limit guard value VTg set based on the above.

  With reference to FIG. 11, the target valve timing calculation process of the cold side exhaust side valve timing control will be described. This process is repeatedly executed at a predetermined control cycle by the control device 60 when the engine is cold.

  When this process is started, the control device 60 first determines in step S210 whether the vehicle is traveling or when the vehicle is stopped, and then refers to the calculation map of FIG. 5 or FIG. 6 to determine the engine speed NE and the engine. A basic retardation amount VTb is calculated based on the load KL. Next, in step S220, with reference to the calculation map of FIG. 7 or FIG. 8 set for the vehicle state determined in step S210, that is, when the vehicle is running or when the vehicle is stopped, the integrated intake air amount ΣGa And upper limit guard value VTg is calculated based on engine oil temperature θe. In step S230, it is determined whether or not the basic retardation amount VTb calculated in step S210 is smaller than the upper limit guard value VTg calculated in step S220.

  If it is determined in step S230 that the basic retard amount VTb is smaller than the upper limit guard value VTg (step S230: YES), the retard amount limit in the cold exhaust side valve timing control by the upper limit guard value VTg is limited. In step S240, the final target valve timing VTf is set to the basic retardation amount VTb. On the other hand, if it is determined in step S230 that the basic retard amount VTb is equal to or greater than the upper guard value VTg (step S230: NO), the retard amount in the cold exhaust side valve timing control based on the upper guard value VTg. In step S250, the final target valve timing VTf is set to the upper limit guard value VTg.

  When the final target valve timing VTf is thus calculated based on the engine oil temperature θe and the integrated intake air amount ΣGa at the time of starting the engine, the control device 60 drives the exhaust-side variable valve mechanism 50 based on the final target valve timing VTf. . In other words, the exhaust side variable valve mechanism 50 is driven so that the valve timing of the exhaust valve 51 coincides with the final target valve timing VTf, and the retardation amount of the valve timing of the exhaust valve 51 is set.

According to the embodiment described above, the following effects can be obtained.
(1) It is determined whether or not the difference Δθ between the highest temperature and the lowest temperature among the coolant temperature θw, the transmission oil temperature θat, and the outside temperature θout is within a predetermined value Δθα. When the temperature difference Δθ is within the predetermined value Δθα, the difference between the temperatures θw and θat including the engine oil temperature θe and the outside air temperature θout is small, and can be regarded as converging on the outside air temperature θout. . On the other hand, when the temperature difference Δθ is larger than the predetermined value Δθα, the distribution of the temperatures θw, θat, θout including the engine oil temperature θe does not converge within the predetermined range, and is in a transient state. It becomes possible to judge.

  (2) When it is determined that the temperature difference Δθ is within the predetermined value Δθα, the lowest temperature among the cooling water temperature θw, the transmission oil temperature θat, and the outside air temperature θout is set to the engine oil temperature θe at the time of starting the engine. Set as. As a result, it is possible to suppress the estimation of the engine oil temperature θe as a higher temperature than the actual temperature, and the stability and reliability of the control related to the engine oil temperature θe are greatly deteriorated due to this. It will be possible to avoid.

  (3) When it is determined that the temperature difference Δθ is larger than the predetermined value Δθα, that is, it is assumed that there is a divergence between the engine oil temperature θe, the coolant temperature θw, and the transmission oil temperature θat. In this case, the transmission oil temperature θat is selected as the engine oil temperature θe. As a result, it is possible to avoid a situation where the actual engine oil temperature θe and the estimated engine oil temperature θe are significantly different.

  (4) When it is determined that the temperature difference Δθ is larger than the predetermined value Δθα, a temperature obtained by lowering the transmission oil temperature θat by an amount corresponding to the maximum deviation degree Δα is set as the engine oil temperature θe. I made it. As a result, the estimated value is the same as or always lower than the actual engine oil temperature θe regardless of the temperature condition at the time of engine stop and the elapsed time after the stop. For this reason, the situation where the estimated engine oil temperature θe becomes higher than the actual engine oil temperature θe can be avoided, and the stability and reliability of the control related to the engine oil temperature θe are greatly deteriorated. It will be possible to avoid.

  (5) The outside air temperature θout is adopted as the engine atmosphere temperature. Thereby, compared with the case where the intake air temperature θal is employed as the engine atmosphere temperature, the engine atmosphere temperature that is not affected by the engine heat after the engine is stopped can be set.

  (6) When the upper limit guard value VTg is applied to the basic retardation amount VTb, that is, in consideration of the engine oil temperature θe estimated at the time of engine start and the temperature rise after the engine start, The final target valve timing was set. Thereby, even when the operation responsiveness of the exhaust side variable valve mechanism 50 is lowered, the valve timing of the exhaust valve 51 can be returned to the most advanced angle timing and locked by the lock mechanism 55.

  Here, since the estimated engine oil temperature θe is the appropriate engine oil temperature θe as described above, the reliability in the cold exhaust side valve timing control and the certainty of locking by the lock mechanism 55 are ensured. Can do.

  (7) The final target valve timing VTf at the cold exhaust side valve timing is set by categorizing whether the vehicle is operating or when the vehicle is stopped. As a result, when the time to stop the engine is short when the vehicle is stopped, the retard operation is performed, and even if the engine stop operation is performed during this retard operation, the valve timing of the exhaust valve 51 is advanced most. The lock mechanism 55 can be locked after returning to the angular timing.

  (8) The more the engine temperature rises and the combustion state of the air-fuel mixture improves, the colder the colder the more the exhaust purification device 32 is activated and the unburned fuel contained in the exhaust can be efficiently purified. The retard amount of the valve timing of the exhaust valve 51 controlled through the hour exhaust side valve timing control is set small. Thereby, it is possible to prevent the valve timing of the exhaust valve 51 from being delayed unnecessarily.

(Other embodiments)
The embodiment of the present invention is not limited to the above-described embodiment, and can be carried out, for example, in the following manner. The following modifications are not applied only to the above-described embodiment, and different modifications can be combined with each other.

  In the above embodiment, when it is determined that the temperature difference Δθ is larger than the predetermined value Δθα, a value obtained by subtracting the temperature corresponding to the maximum deviation degree Δα from the transmission oil temperature θat is set as the engine oil temperature θe. However, this subtraction correction can be omitted and the transmission oil temperature θat can be set as the engine oil temperature θe. Even if it is such a structure, there can exist the effect of (1)-(3) and (5)-(8) mentioned above.

  In the above embodiment, when it is determined that the temperature difference Δθ is larger than the predetermined value Δθα, a value obtained by subtracting the temperature corresponding to the maximum deviation degree Δα from the transmission oil temperature θat is estimated as the engine oil temperature θe. However, a correlation temperature that is always lower than the engine oil temperature θe regardless of the engine operating state can be obtained in advance, and this can be estimated as the engine oil temperature θe. Even if it is such a structure, there can exist the effect of (1)-(3) and (5)-(8) mentioned above.

  In the above embodiment, when it is determined that the temperature difference Δθ is larger than the predetermined value Δθα, the engine ambient temperature for estimating the engine oil temperature θe at the time of starting is the outside air temperature θout. Instead of this, the intake air temperature θal may be used. Even if it is such a structure, there can exist the effect of (1)-(4) and (6)-(8) mentioned above.

  In general, there is a possibility that intake air whose temperature has increased in the intake passage 21 due to engine heat immediately after start-up, and therefore, it is not preferable to detect the intake air temperature θal having such increased temperature as the engine ambient temperature.

  Therefore, in this embodiment, after a predetermined time has elapsed after the engine is started, in other words, the intake air whose temperature has risen in the intake passage 21 is scavenged to the combustion chamber 11 side, and the outside air that is hardly affected by the engine heat is taken into the intake passage. After being introduced into the engine 21, the intake air temperature θal is detected and adopted as the engine atmosphere temperature.

  As shown in FIG. 12, when the engine is started at timing t1, the intake air temperature θal deviates from the outside temperature θout between timings t1 and t2 due to the influence of the temperature condition when the engine is stopped. Often in a state. Then, after the timing t2, the intake air temperature θal tends to converge to the outside air temperature θout as the outside air is introduced. At timing t3, the intake air temperature θal when the intake air temperature θal converges to the outside air temperature θout is detected, and this is adopted as the engine ambient temperature.

  With reference to FIG. 13, the process of estimating the engine oil temperature when the intake air temperature θal is employed as the engine atmosphere temperature will be described. Note that this engine oil temperature estimation process is a process for estimating the engine oil temperature θe at the time of engine start, and is executed when the condition for engine start is satisfied in the control device 60. The

  In this process, when it is determined in step S110 in FIG. 4 that the engine is starting (step S110: YES), it is determined in step S310 whether a predetermined time has elapsed after the engine is started. If it is determined in step S310 that a predetermined time has elapsed after the engine is started (step S310: YES), it is determined that the intake air temperature θal has converged to the outside air temperature θout. The intake air temperature θal is detected. In the subsequent processing, the processing after step S130 in FIG. 4 is adopted, and the intake air temperature θal detected in step S320 is adopted in place of the outside air temperature θout in the estimation processing of the engine oil temperature θe shown in FIG. . If it is determined in step S310 that the predetermined time has not elapsed since the engine was started (step S310: NO), the process waits until the predetermined time has elapsed.

  As described above, when the intake air temperature θal is used instead of the external air temperature θout, even in an internal combustion engine that does not have the external air temperature sensor 75, the engine oil temperature θe is reduced after the intake air temperature θal converges to the external air temperature θout. The estimation process can be appropriately executed. On the other hand, when the intake air temperature θal is in a transitional state until it converges to the outside air temperature θout, the engine oil temperature θe cannot be appropriately estimated by this processing. For this reason, it takes a long time to estimate the oil temperature θe, the engine oil temperature θe is estimated immediately after the engine is started, and the estimated engine oil temperature θe is used for various controls executed by the internal combustion engine 10. It will not be possible.

  In the above embodiment, when it is determined that the temperature difference Δθ is within the predetermined value Δθα, the lowest temperature among the cooling water temperature θw, the transmission oil temperature θat, and the outside air temperature θout is set to the engine at the time of starting the engine. The oil temperature θe was set. On the other hand, when the temperature difference Δθ is within the predetermined value Δθα, it is determined that the temperatures θe, θw, θat have converged to the outside air temperature θout, and the outside air temperature θout is estimated as the engine oil temperature θe. You may make it do. Even if it is such a structure, there can exist the effect of (1) and (3)-(8) mentioned above.

  In the above embodiment, when the vehicle is traveling and when the vehicle is stopped, the upper limit guard value VTg is set for each basic retardation amount VTb and the final target valve timing VTf is calculated. The final target valve timing VTf can also be calculated without setting the upper limit guard value VTg when the engine is cold. That is, when the vehicle is traveling, it is possible to secure a certain amount of time until the engine is stopped, and the valve timing of the exhaust valve 51 can be locked at the most advanced timing prior to stopping the engine. It is also possible to omit the restriction process for the basic retardation amount VTb.

  In this case, in the cold exhaust side valve timing control of the above embodiment, after calculating the basic retardation amount VTb in step S210, it is determined whether the vehicle is running or the vehicle is stopped. If it is determined that the vehicle is traveling, the processes of steps S220 and S230 are omitted, and the final target valve timing VTf is set to the basic retardation amount VTb in step S240. Even if it is such a structure, there can exist the effect of (1)-(5) and (7) and (8) which were mentioned above.

  In the above embodiment, the upper limit guard value VTg is calculated based on the estimated engine oil temperature θe and the integrated intake air amount ΣGa. However, the upper limit guard value VTg is calculated based only on the estimated engine oil temperature θe. Can also be set. Even if it is such a structure, there can exist the effect of (1)-(8) mentioned above.

  In the above embodiment, the engine start time is the period from cranking to the time when self-sustained operation becomes possible, but immediately after self-sustained operation becomes possible, that is, after self-sustained operation becomes possible, The period during which the temperature in 11 does not change can also be the time of engine start. Even if it is such a structure, there can exist the effect of (1)-(8) mentioned above.

  In the above embodiment, the configuration is shown in which the valve timing of the exhaust valve 51 is retarded to suppress the discharge of unburned fuel when the engine is cold, but instead of this, or in addition to this, the valve of the intake valve 41 A configuration in which the timing is advanced can also be adopted. When this configuration is adopted, the combustion timing is increased by advancing the valve timing of the intake valve 41, blowing back part of the exhaust gas from the exhaust passage 31 to the combustion chamber 11, that is, increasing the internal EGR amount. The temperature inside the chamber 11 can be raised. And by raising the temperature inside the combustion chamber 11 in this way, the combustion of the air-fuel mixture can be promoted, and the discharge of unburned fuel can be suppressed. Even if it is such a structure, there can exist an effect according to (1)-(8) mentioned above.

  In the previous modification, the configuration in which the valve timing of the exhaust valve 51 is retarded and the valve timing of the intake valve 41 is advanced is exemplified. However, for example, since the fuel injection amount is small at a low engine load, When the valve timing of the exhaust valve 51 is retarded and the valve timing of the intake valve 41 is advanced, when the valve overlap increases, the internal EGR amount increases and the temperature inside the combustion chamber 11 rises. However, although atomization of the air-fuel mixture is promoted, combustion tends to become unstable due to a decrease in the amount of air-fuel mixture introduced into the combustion chamber 11. On the other hand, since the fuel injection amount can be secured at a high engine load, combustion does not become unstable even if the valve overlap is increased and the internal EGR is increased. Therefore, the internal EGR is advanced by advancing the intake valve 41. By increasing the mist to promote atomization, it is possible to suppress the discharge of unburned fuel.

  Thus, while the engine timing is high, the valve timing of the exhaust valve 51 is retarded and the valve timing of the intake valve 41 is advanced, while at the time of low engine load, the valve timing of the intake valve 41 is not advanced. A configuration in which the valve timing of the exhaust valve 51 is retarded is also conceivable.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Combustion chamber, 12 ... Oil pump, 21 ... Intake passage, 22 ... Throttle valve, 31 ... Exhaust passage, 32 ... Exhaust purification catalyst, 40 ... Intake side variable valve mechanism, 41 ... Intake valve, 45 ... Lock mechanism, 50 ... Exhaust side variable valve mechanism, 51 ... Exhaust valve, 55 ... Lock mechanism, 60 ... Control device, 71 ... Water temperature sensor, 72 ... Intake temperature sensor, 73 ... Throttle position sensor, 74 ... Air flow meter 75 ... Outside air temperature sensor, 76 ... Crank position sensor, 77 ... Exhaust side cam position sensor, 78 ... Transmission oil temperature sensor, 79 ... Vehicle speed sensor.

Claims (7)

An engine oil temperature of an internal combustion engine that selects an alternative value of the engine oil temperature from a plurality of correlation temperatures correlated with the engine ambient temperature and the engine oil temperature, and estimates the engine oil temperature at the time of engine start based on the alternative value In the estimation device,
A plurality of sensors for separately detecting the engine ambient temperature and the plurality of correlation temperatures;
Determining means for determining whether or not the distribution of each temperature detected by each sensor at the time of engine startup converges within a predetermined range;
An engine oil temperature estimation device for an internal combustion engine, comprising: a setting unit that sets a selection mode to a different mode based on a determination result of the determination unit when selecting the alternative value of the engine oil temperature. When the determination unit determines that the distribution of each detected temperature is within a predetermined temperature range, the setting unit determines the lowest temperature among the engine ambient temperature and the plurality of correlation temperatures as the engine oil temperature. The engine oil temperature estimation device for an internal combustion engine according to claim 1, wherein the engine oil temperature estimation device is selected as an alternative value of The setting means obtains in advance a relative temperature at which the maximum value of the degree of deviation from the engine oil temperature after engine stop is the smallest among the plurality of correlation temperatures regardless of the temperature state at the time of engine stop, and the determination means 2. The method according to claim 1, wherein when it is determined that the distribution of each detected temperature is not within a predetermined temperature range, the previously obtained relative temperature is selected as an alternative value for the engine oil temperature. 3. An engine oil temperature estimating apparatus for an internal combustion engine according to 2. The said setting means estimates the temperature which reduced the relative temperature selected as an alternative value only by the temperature corresponding to the maximum value of the deviation | shift degree with the said engine oil temperature as said engine oil temperature. An engine oil temperature estimating device for an internal combustion engine according to claim 1. In the engine oil estimating apparatus for an internal combustion engine according to claim 3 or 4,
The transmission that transmits the engine driving force to the vehicle drive system is further provided with a transmission oil temperature sensor that detects the temperature of the transmission oil that is not mixed with the engine oil,
The setting means selects the detected transmission oil temperature as an alternative value of the engine oil temperature. An engine oil temperature estimation device for an internal combustion engine, comprising: 6. A variable valve mechanism that changes the valve timing of at least one of an intake valve and an exhaust valve using engine oil as a working medium; a lock mechanism that can lock the valve timing at a specific time prior to engine stop; and An engine oil temperature estimating device for an internal combustion engine according to any one of
When the engine is cold, the amount of change in the valve timing from the specific timing by the variable valve mechanism is limited to be smaller when the engine oil temperature estimated by the engine oil temperature estimation device is low than when it is high. A variable valve timing apparatus for an internal combustion engine. The variable valve timing apparatus for an internal combustion engine according to claim 6,
The variable valve mechanism includes an exhaust-side variable valve mechanism that changes the valve timing of the exhaust valve. When the engine is cold, the exhaust-side variable valve mechanism causes the valve timing of the exhaust valve to be delayed by a predetermined time from the specific time. A variable valve timing apparatus for an internal combustion engine, which executes a retard processing for retarding with an angular amount, and uses the retard amount in the retard processing as a change amount of the valve timing.

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