JP2010071157A - Estimating device of engine oil temperature - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce arithmetic load when estimating an oil temperature of an engine, and to enhance estimation accuracy of the oil temperature without inviting increase in the number of parts. <P>SOLUTION: If a cooling water valve 17 is in a closed state, and fuel injection is performed by a fuel injecting means 13, an oil temperature estimating means 31 estimates an oil temperature OT of an engine 12 by effecting a primary delay processing in which a first weighting has been applied to a cooling water temperature WT. If a cooling water valve 16 is in an open state and fuel injection is performed by the fuel injecting means 13, the oil temperature estimating means 31 estimates the oil temperature OT by effecting the primary delay processing in which a second weighting has been applied to a converged oil temperature OTmap, when driving determined by the number of engine revolutions NE and a load θth. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine oil temperature estimating apparatus suitable for estimating the oil temperature of an engine mounted on a vehicle.

2. Description of the Related Art Conventionally, a technique for estimating the oil temperature of an engine using the temperature of engine coolant rather than directly using an oil temperature sensor is known. As a document disclosing such a technique, for example, the following Patent Document 1 can be cited.
More specifically, in the technique of Patent Document 1, an elapsed time counter (35) that is a timer for counting an elapsed time during which the engine body (10) is being driven is provided. And in the technique of this patent document 1, the engine oil temperature of an engine main body (10) is estimated according to the elapsed time counted by this elapsed time counter (35).
Japanese Patent No. 3447877

In the technique of Patent Document 1, a part of the problem described in the paragraph [0006] of the same document, that is, the point of estimating the oil temperature without using the oil temperature sensor, has been solved. It is thought that there is.
However, in the technique of Patent Document 1, it is necessary to provide an elapsed time counter (35), and the other problem described in the paragraph [0006] of the same document, that is, to reduce the number of parts. It is hard to say that the problem is solved.

However, there may be a view that the elapsed time counter (35) is software and the reduction of hardware parts has been achieved.
However, by providing this elapsed time counter (35) and executing control using this elapsed time counter (35), the control load of the ECU (30) is increased, and the estimated oil temperature ( (TOILP) may be delayed.

Although a method of speeding up the calculation of the estimated oil temperature value (TOILP) by improving the processing capacity of the ECU (30) is conceivable, such a method increases the cost of the ECU (30) itself. End up.
Furthermore, in recent years, a vehicle equipped with a mixed fuel engine that uses a mixed fuel containing gasoline and alcohol, so-called FFV (Flexible Fuel Vehicle), has attracted attention from the viewpoint of protecting the global environment. In the FFV, it is necessary to finely correct the content of the engine feedback control based on the air-fuel ratio in accordance with the oil temperature. This is due to azeotropy between gasoline or ethanol and oil in the oil pan in a predetermined oil temperature range (for example, 25 to 80 ° C.).

In other words, if the estimation of the oil temperature is delayed or the estimation accuracy is lowered, the exhaust gas performance is deteriorated particularly in the FFV, or the drivability is significantly decreased due to the decrease in the output performance of the engine. Such a problem arises.
Of course, even a general gasoline engine, not a mixed fuel engine, can improve exhaust gas performance and drivability by correcting the air-fuel ratio feedback control according to the estimated oil temperature. Is possible.

In other words, timely and highly accurate estimation of the oil temperature is strongly demanded regardless of the type of engine.
The present invention has been devised in view of such problems, and reduces the calculation load when estimating the oil temperature of the engine, and increases the estimation accuracy of the oil temperature without increasing the number of parts. An object of the present invention is to provide an engine oil temperature estimation device capable of

  In order to achieve the above object, an engine oil temperature estimating apparatus according to the present invention (Claim 1) includes an engine mounted on a vehicle, a radiator that radiates cooling water for cooling the engine, and a temperature of the cooling water. A cooling water temperature detecting means for detecting the cooling water and between the engine and the radiator, the cooling water is not passed between the engine and the radiator in the closed state, and the engine and the A cooling water valve for circulating the cooling water to and from the radiator, and an oil temperature estimating means for estimating the oil temperature of the engine according to the open / closed state of the cooling water valve, the oil temperature estimating means comprising: When the cooling water valve is closed, the oil temperature of the engine is estimated by applying a first-order lag process in which the first weighting is applied to the cooling water temperature, and when the cooling water valve is open, the second Is characterized by estimating the oil temperature of the engine by only with applying the applied primary delay processing to the drive during convergence oil temperature is an oil temperature determined in accordance with the operating condition of the engine.

  According to a second aspect of the present invention, there is provided an engine oil temperature estimating apparatus according to the first aspect of the present invention, wherein the fuel injection means for injecting fuel in the engine and the fuel by the fuel injection means when the fuel cut condition is satisfied. Fuel cut control means for executing fuel cut control for prohibiting injection, and the oil temperature estimation means is configured such that when the coolant valve is closed and the fuel cut control means is executing the fuel cut control means, It is characterized in that the oil temperature of the engine is estimated by performing a first-order lag process in which the third weighting is applied to the driven convergence oil temperature that is an oil temperature determined by the engine speed.

  According to a third aspect of the present invention, there is provided an engine oil temperature estimating apparatus according to the first or second aspect of the present invention, which executes fuel cut control for prohibiting fuel injection by the fuel injection means when a fuel cut condition is satisfied. A fuel cut control means, wherein the oil temperature estimation means assigns a fourth weighting according to the engine speed when the fuel cut control means is executing the fuel cut control means with the cooling water valve open. It is characterized in that the oil temperature of the engine is estimated by performing a first-order lag process applied to a determined driven convergence temperature.

  According to a fourth aspect of the present invention, there is provided an engine oil temperature estimating device according to the present invention, wherein the engine is a mixed fuel using a mixture of gasoline and alcohol as fuel. It is an engine for use.

According to the engine oil temperature estimating apparatus of the present invention, it is possible to reduce the calculation load when estimating the oil temperature of the engine and to increase the accuracy of estimating the oil temperature without increasing the number of parts. (Claim 1)
Further, even in an exceptional operating situation where the engine is performing fuel cut control, the oil temperature reflecting the temperature change of the engine itself can be accurately estimated. (Claims 2 and 3)
Further, it is possible to prevent the exhaust gas performance and drivability from being lowered in a vehicle equipped with a mixed fuel engine, so-called FFV (Flexible Fuel Vehicle). (Claim 4)

Hereinafter, an engine oil temperature estimation device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing the overall configuration, and FIGS. 2 to 5 are schematic diagrams showing the operation thereof. The flowcharts, FIGS. 6 and 7 are schematic time charts showing the operation.
As shown in FIG. 1, a vehicle 10 is equipped with a mixed fuel engine (engine) 12 that uses a fuel (ie, a mixed fuel) 11 in which a gasoline component and an alcohol component are mixed as fuel. Further, the vehicle 10 is equipped with a fuel tank 18 for storing the mixed fuel 11.

  Therefore, this vehicle 10 is a so-called FFV type vehicle. The engine 12 mounted on the vehicle 10 can use a fuel containing only a gasoline component (ie, gasoline fuel) or a fuel containing only an alcohol component (ie, alcohol fuel). In addition, the mixture which can be refueled in the market is a gasoline 15% -alcohol 85% mixed fuel (E85) and a normal gasoline 100% fuel (E0).

The engine 12 has four cylinders (not shown), and each of these cylinders is provided with an injector (fuel injection means) 13.
These injectors 13 are fixed to a delivery pipe 14 and inject the mixed fuel 11 into an intake port (not shown) of the engine 12. The delivery pipe 14 is connected to a fuel line 15 communicating with the inside of the fuel tank 13 so that the mixed fuel 11 delivered from a fuel pump (not shown) can be distributed to each injector 13.

The engine 12 is a water-cooled engine, and a radiator 16 is connected via a cooling water pipe 15.
Further, a thermostat (cooling water valve) 17 is provided between the cooling water pipe 15 and the engine 12.
When the temperature WT of the cooling water becomes equal to or higher than a predetermined water temperature threshold value WT_th, the thermostat 17 is opened due to expansion of wax (not shown) therein, and the cooling water is circulated between the engine 12 and the radiator 16. It can be done. In addition, when the cooling water temperature WT becomes lower than the water temperature threshold value WT_th, the thermostat 17 is closed due to contraction of the wax therein, so that the cooling water does not flow between the engine 12 and the radiator 16. .

The water temperature threshold WT_th is set to about 75 to 90 ° C.
The engine is also provided with a water temperature sensor (cooling water temperature detection means) 21, a rotation speed sensor (rotation speed detection means) 22, and a throttle valve position sensor (engine load detection means) 23.
Among these, the water temperature sensor 21 is a sensor provided in the vicinity of the cooling water inlet of the thermostat 17 and detects the cooling water temperature (cooling water temperature) WT of the engine 12. The coolant temperature WT detected by the water temperature sensor 21 is read by an ECU (Electronic Control Unit) 30 described later.

The rotational speed sensor 22 is a sensor that detects the rotational speed NE of the engine 12, and the detection result NE is read by the ECU 30.
The throttle valve position sensor 23 is a sensor for detecting an opening degree θth of a throttle valve (not shown) of the engine 12, and the detection result θth is read by the ECU 30.

  The vehicle 10 is provided with an accelerator pedal position sensor (not shown). This accelerator pedal position sensor is a sensor that detects the position of an accelerator pedal (not shown), that is, a depression amount Acc of the accelerator pedal by the driver. The detection result Acc by the accelerator pedal position sensor is also read by the ECU 30.

The vehicle 10 is provided with an ECU 30.
The ECU 30 is an electronic control unit including a memory and a CPU (Central Processing Unit), not shown.
Further, the ECU 30 includes, as software, an oil temperature estimation unit (oil temperature estimation unit) 31, an initial oil temperature estimation unit (initial oil temperature estimation unit) 32, a fuel injection control unit (fuel injection control unit) 33, and a fuel. A cut control unit (fuel cut control means) 34 is provided.

The memory of the ECU 30 is provided with an A coefficient map 35, a B coefficient map 36, a C coefficient map 37, a D coefficient map 38, an E coefficient map 39, a normal oil temperature map 41, and a fuel cut oil temperature map 42. ing.
Among these, the oil temperature estimation unit 31 estimates the temperature OT of the engine oil used in the engine 12 according to the open / close state of the thermostat 17 and the fuel injection state by the injector 13.

More specifically, the oil temperature estimation unit 31 calculates and estimates the oil temperature OT using the following equation (1) when the thermostat 17 is in the closed state and the fuel injection is performed by the injector 13. It is supposed to be.
OT (n) = Kot_cls * OT (n-1) + (1-Kot_cls) / (1-Kwt_cls) * (WT (n) -Kwt_cls * WT (n-1)) (1)
OT (n): Current calculation value of oil temperature OT (n-1): Previous calculation value of oil temperature WT (n): Current detection value of cooling water temperature WT (n-1): Previous detection value of cooling water temperature Kot_cls: Oil temperature smoothing coefficient (A coefficient)
Kwt_cls: Cooling water temperature annealing coefficient (B coefficient)
Here, the current calculated value OT (n) of the oil temperature is recorded in the memory of the ECU 30 by the oil temperature estimation unit 31. That is, the current calculated value OT (n) of the oil temperature recorded in the memory of the ECU 30 is used as the previous calculated value OT (n−1) of the oil temperature in the next calculation using the above equation (1). It is like that.

The current detection value WT (n) of the cooling water temperature is obtained by the oil temperature estimation unit 31 reading the detection result of the water temperature sensor 21.
The A coefficient Kot_cls is a coefficient for the previous calculated value OT (n−1) of the oil temperature when the thermostat 17 is in the closed state, and is read from the A coefficient map 35 by the oil temperature estimation unit 31. .

Further, the oil temperature estimating unit 31 applies the engine speed NE read by the speed sensor 22 and the throttle valve opening θth read from the throttle valve position sensor 23 to the A coefficient map 35, so that The A coefficient Kot_cls adapted to the operating state of the engine 12 at the time is read out.
In other words, the A coefficient map 35 is configured to define the A coefficient Kot_cls based on the engine speed NE and the throttle valve opening θth (that is, the load of the engine 12).

In the above equation (1), the term “(1-Kot_cls) / (1-Kwt_cls)” is referred to as first weighting.
That is, the oil temperature estimation unit 31 estimates the oil temperature OT of the engine 12 by performing a first-order lag process in which the first weighting is applied to the coolant temperature WT.

On the other hand, when the thermostat 17 is in the open state and the fuel injection is performed by the injector 13, the oil temperature estimation unit 31 estimates the oil temperature OT using the following equation (2). .
OT (n) = Kot_opn × OT (n−1) + (1−Kot_opn) × OTmap (2)
OT (n): Current calculated value of oil temperature OT (n-1): Previously calculated value of oil temperature OTmap: Map value of oil temperature (converged oil temperature during driving)
Kot_opn: Oil temperature annealing coefficient (C coefficient)
The oil temperature map value OTmap indicates the oil temperature OT that converges when the fuel injection is performed by the injector 13, and is read from the normal time oil temperature map 41 by the oil temperature estimation unit 31. ing.

  More specifically, the oil temperature estimation unit 31 sets the engine speed NE read by the speed sensor 22 and the throttle valve opening θth read from the throttle valve position sensor 23 in the normal oil temperature map 41. By applying this, it is possible to read out the oil temperature map value OTmap during execution of the fuel injection control that is suitable for the operating state of the engine 12 at that time.

In other words, the normal oil temperature map 41 is configured to define the oil temperature map value OTmap based on the engine speed NE and the throttle valve opening θth (that is, the engine load).
That is, when the thermostat 17 is in the open state, the cooling water passes through the radiator 16, and therefore, the cooling water temperature WT is a converged cooling water temperature determined by the rotational speed NE of the engine 12 and the load (that is, the throttle valve opening θth). It converges to WTcon.

Of course, even if the thermostat 17 is in the open state, the oil itself does not flow through the radiator 16.
However, as long as the cooling water temperature WT converges to the convergence cooling water temperature WTcon, the oil temperature OT is also an oil temperature (that is, an oil temperature map value) determined by the rotational speed NE of the engine 12 and the load (that is, the throttle valve opening θth). OTmap).

The C coefficient Kot_opn is a coefficient for the previous calculated value OT (n−1) of the oil temperature when the thermostat 17 is in the open state, and as a coefficient for the oil temperature map value OTmap when the thermostat 17 is in the open state. Are also used.
Further, the C coefficient Kot_opn is calculated from the C coefficient map 37 by the engine temperature NE read from the rotation speed sensor 22 and the throttle valve opening θth read from the throttle valve position sensor 23 by the oil temperature estimation unit 31. As a result, the C coefficient Kot_opn suitable for the operating state of the engine 12 at that time is read out.

In other words, the C coefficient map 37 is configured to define the C coefficient Kot_opn based on the engine speed NE and the throttle valve opening θth (that is, the load of the engine 12).
In the above equation (2), the term “(1-Kot_opn)” is referred to as second weighting.
That is, the oil temperature estimation unit 31 estimates the oil temperature OT of the engine 12 by performing a first-order lag process in which the second weighting is applied to the driving convergence oil temperature OTmap_m.

Here, both formulas will be described again while comparing the above formulas (1) and (2).
In the equation (1), the current detection value WT (n) of the cooling water temperature and the A coefficient Kwt_cls, which are parameters regarding the cooling water temperature WT, are used.
And the case where Formula (1) is used is a case where the thermostat 17 is a closed state. In this case, since the cooling water does not pass through the radiator 16, the cooling water temperature WT is changing every moment. Therefore, in this equation (1), the oil temperature OT is estimated in consideration of parameters related to the cooling water temperature WT such as the current detection value WT (n) of the cooling water temperature and the A coefficient Kwt_cls. It is.

On the other hand, in the equation (2), these parameters regarding the coolant temperature WT are not used, and the oil temperature map value OTmap is used.
And the case where Formula (2) is used is a case where the thermostat 17 is an open state. In this case, since the coolant passes through the radiator 16, the coolant temperature WT converges to a converged coolant temperature TWcon determined by the rotational speed NE of the engine 12 and the load (that is, the throttle valve opening θth).

Next, a description will be given of points focused on when the fuel cut control is being executed.
When the thermostat 17 is in a closed state and fuel injection is prohibited by the injector 13, that is, when fuel cut control is being executed by the fuel cut control unit 34, the oil temperature estimation unit 31 uses the following equation (3 ) Is used to estimate the oil temperature OT.

OT (n) = Kot_clsm × OT (n−1) + (1−Kot_clsm) × OTmap_m (3)
OT (n): Current calculation value of oil temperature OT (n-1): Previous calculation value of oil temperature OTmap_m: Map value of oil temperature during execution of fuel cut control (converged oil temperature during driving)
Kot_clsm: Oil temperature annealing coefficient (D coefficient)
An oil temperature map value OTmap_m during execution of fuel cut control indicates an oil temperature OT that converges when fuel injection by the injector 13 is prohibited. The oil temperature estimation unit 31 performs an oil temperature map during fuel cut. 42 is read out.

More specifically, the oil temperature estimating unit 31 applies the engine speed NE read by the speed sensor 22 to the oil temperature map 42 at the time of fuel cut, so that the oil temperature estimating unit 31 is adapted to the operating state of the engine 12 at that time. The oil temperature map value OTmap_m during execution of the fuel cut control can be read out.
In other words, the oil temperature map 42 at the time of fuel cut is configured to define the oil temperature map value OTmap based only on the engine speed NE, regardless of the throttle valve opening θth (that is, the engine load). ing.

That is, when the thermostat 17 is in the closed state and the fuel cut control is being executed, the cooling water does not pass through the radiator 16, but the cooling water temperature WT is equal to the convergence cooling water temperature WTcon_m determined only by the rotational speed NE of the engine 12. Converge.
Then, as long as the cooling water temperature WT converges to the convergence cooling water temperature TWcon_m, the oil temperature OT of the engine 12 in the driven state is also determined by the oil temperature determined only by the rotational speed NE of the engine 12 (that is, during fuel cut control execution). The oil temperature map value OTmap_m) converges.

  The D coefficient Kot_clsm is a previously calculated value OT (n−1) of the oil temperature when the fuel cut control is being executed (that is, when the engine 12 is in the driven state) and the thermostat 17 is in the closed state. And is also used as a coefficient for the oil temperature map value OTmap_m when the fuel cut control is executed with the thermostat 17 closed.

The D coefficient Kot_clsm is adapted to the operating state of the engine 12 at that time by applying the engine speed NE read by the speed sensor 22 to the D coefficient map 38 by the oil temperature estimating unit 31. The D coefficient Kot_clsm is read out.
In other words, the D coefficient map 38 is configured to define the D coefficient Kot_clsm based only on the engine speed NE, regardless of the throttle valve opening θth (that is, the engine load).

In the above equation (3), the term “(1-Kot_clsm)” is referred to as third weighting.
That is, the oil temperature estimation unit 31 estimates the oil temperature OT of the engine 12 by performing a first-order lag process in which the third weighting is applied to the driven convergence oil temperature OTmap_m.

On the other hand, when the thermostat 17 is in the open state and the fuel injection is prohibited by the injector 13, that is, when the fuel cut control is being executed by the fuel cut control unit 34, the oil temperature estimation unit 31 uses the following formula: The oil temperature OT is estimated using (4).
OT (n) = Kot_opnm × OT (n−1) + (1−Kot_opnm) × OTmap_m (4)
OT (n): Current calculation value of oil temperature OT (n-1): Previous calculation value of oil temperature OTmap_m: Map value of oil temperature during execution of fuel cut control (converged oil temperature during driving)
Kot_opnm: Oil temperature annealing coefficient (E coefficient)
Here, the map value OTmap_m of the oil temperature during the execution of the fuel cut control is the same as that in the equation (3), and therefore the description thereof is omitted here.

  The E coefficient Kot_opnm is the previous calculated value OT (n−1) of the oil temperature when the fuel cut control is being executed (that is, when the engine 12 is in the driven state) and the thermostat 17 is in the open state. And is also used as a coefficient for the oil temperature map value OTmap_m when the fuel cut control is being executed.

The E coefficient Kot_opnm is adapted to the operating state of the engine 12 at that time by applying the engine speed NE read by the speed sensor 22 by the oil temperature estimation unit 31 to the E coefficient map 39. The E coefficient Kot_opnm is read out.
In other words, the E coefficient map 39 is configured to define the E coefficient Kot_opnm based only on the engine speed NE, regardless of the throttle valve opening θth (that is, the engine load).

In the above equation (4), the term “(1-Kot_opnm)” is referred to as fourth weighting.
That is, the oil temperature estimation unit 31 estimates the oil temperature OT of the engine 12 by performing a first-order lag process in which the fourth weighting is applied to the driven convergence oil temperature OTmap_m.

The initial oil temperature estimation unit 32 estimates an initial oil temperature OT_0 that is an oil temperature of the engine 12 when the engine 12 is started. The oil temperature estimation unit 31 described above estimates the oil temperature OT of the engine 12 using the initial oil temperature OT_0 estimated by the initial oil temperature estimation unit 32.
More specifically, the initial oil temperature estimation unit 32 compares the stop-time cooling water temperature WT_stop (definition will be described later) with the stop-time oil temperature OT_stop (definition will be described later). When the cooling water temperature WT_stop at the time of stop is lower, that is, when the following equation (5) is satisfied, the oil temperature OT_stop at the time of stop is used as the initial oil temperature OT_0.

WT_start> OT_stop (5)
WT_stop: Stop-time coolant temperature OT_stop: Stop-time oil temperature Here, the stop-time coolant temperature WT_stop is the coolant temperature detected by the water temperature sensor 21 when the engine 12 is stopped.

The stop-time oil temperature OT_stop is the oil temperature OT of the engine 12 estimated by the oil temperature estimation unit 31 when the engine 12 was stopped last time.
On the other hand, the initial oil temperature estimation unit 32 initializes the start-time coolant temperature WT_start when the stop-time coolant temperature WT_stop is lower than the stop-time oil temperature OT_stop, that is, when the following expression (6) is satisfied. The oil temperature OT_0 is used.

WT_start <OT_stop (6)
The starting coolant temperature WT_start is the coolant temperature WT detected by the water temperature sensor 21 when the engine 12 is started.
Further, the initial oil temperature estimating unit 32 recognizes that the engine 12 has started when an ignition switch (not shown) provided in the vehicle is turned on.

The fuel injection control unit 33 is configured to inject mixed fuel from each injector 13 by sending a pulse signal to each injector 13 of the engine 12.
When the fuel cut condition (both of the following (i) and (ii)) is satisfied, the fuel cut control unit 34 stops the operation of the fuel injection control unit 33, thereby injecting the mixed fuel by each injector 13. It is forbidden.

(I) The accelerator pedal depression amount Acc is substantially zero. (Ii) The engine rotational speed NE is equal to or greater than the set idle rotational speed. When at least one of i) and (ii) is not satisfied, the operation of the fuel injection control unit 33 is resumed, and the prohibition of the injection of the mixed fuel by each injector 13 is cancelled.

Since the engine oil temperature estimation device according to an embodiment of the present invention is configured as described above, the following operations and effects are achieved.
First, setting control of the initial oil temperature OT_0 will be described using the flowchart of FIG.
The initial oil temperature estimation unit 32 reads the cooling water temperature WT detected by the water temperature sensor 21 when the ignition switch (not shown) is turned on from off (step S11) (step S12). Note that the coolant temperature WT read here is WT_start in Expression (6).

  Thereafter, the initial oil temperature estimation unit 32 determines whether or not the starting coolant temperature WT_start obtained in step S12 is equal to or higher than the stop oil temperature OT_stop (step S13). The stop-time oil temperature OT_stop is the oil temperature OT of the engine 12 estimated by the oil temperature estimation unit 31 when the engine 12 was stopped last time, as described above when describing the equation (5). Further, the stop time oil temperature OT_stop is recorded in a memory (not shown) of the ECU 30.

When the start-time coolant temperature WT_start is equal to or higher than the stop-time oil temperature OT_stop (Yes route in step S13), the initial oil temperature estimation unit 32 sets the stop-time oil temperature OT_stop as the oil temperature initial value read from the memory. Set as OT_0 (step S14).
On the other hand, when the starting cooling water temperature WT_start is lower than the stopping oil temperature OT_stop (No route of Step S13), the initial oil temperature estimating unit 32 sets the starting cooling water temperature WT_start as the oil temperature initial value OT_0 (Step S15). ).

Here, the setting of the oil temperature initial value OT_0 will be described again using the time charts shown in FIGS. 6 and 7, the fuel cut control by the fuel cut control unit 34 is not executed.
In FIGS. 6 and 7, the change in the coolant temperature WT is indicated by a broken characteristic line LWT, and the change in the oil temperature OT is indicated by a solid characteristic line LOT.

  As shown in FIG. 6, when the ignition switch is turned on from off, the engine 12 starts (time point t0), and then both the coolant temperature WT and the oil temperature OT rise. However, as indicated by the characteristic lines LWT and LOT, the rate of change of the coolant temperature WT is considerably larger than the rate of change of the oil temperature OT, and the difference (temperature difference) between the coolant temperature WT and the oil temperature OT gradually increases. It will spread. This is due to the fact that the cooling water and oil have different thermal conductivities, and more specifically, because the cooling water has a characteristic that it is more easily heated and cooler than oil. .

  If the ignition switch is turned off from the on-state before the cooling water temperature WT reaches the water temperature threshold WT_th (time point t1), the oil temperature OT (that is, the oil temperature OT_stop at the time of stop) at this time The cooling water temperature WT_stop at the time of stop becomes smaller. This phenomenon is also due to the fact that the rate of change of the cooling water temperature WT is considerably larger than the rate of change of the oil temperature OT.

Then, when the ignition switch is turned on again from the OFF state and the engine 12 is restarted (time point t2), the initial oil temperature estimation unit 32 detects the oil estimated by the oil temperature estimation unit 31 when the engine 12 was stopped last time. The temperature OT, that is, the stop time oil temperature OT_stop is set as the initial oil temperature OT_0.
This is due to the fact that the relationship shown by the above equation (5) is established between the oil temperature OT and the cooling water temperature WT at time t1, and in this case, the initial oil temperature estimation unit No. 32 sets the stop time oil temperature OT_stop as the initial oil temperature OT_0.

  As shown in FIG. 7, when the ignition switch is turned on from off, the engine 12 starts (time point t0), and then both the coolant temperature WT and the oil temperature OT rise. Thereafter, when the coolant temperature WT reaches the water temperature threshold value WT_th, the coolant temperature WT converges to a predetermined temperature (convergent coolant temperature WTcon). For this reason, when the operation period of the engine 12 becomes relatively long, the oil temperature OT exceeds the coolant temperature WT.

Therefore, after that, when the ignition switch is turned from on to off (time point t3), the coolant temperature WT (that is, the coolant temperature WT_stop at the time of stop) becomes smaller than the oil temperature OT (that is, the oil temperature OT_stop at the time of stop). .
After that, when the ignition switch is turned on again from the OFF state and the engine 12 is restarted (time point t4), the initial oil temperature estimating unit 32 detects the water temperature WT detected by the water temperature sensor 21 at the time point t4, that is, at the time of start-up. Cooling water temperature WT_start is set as initial oil temperature OT_0.

This is because the relationship shown as the above equation (6) is established between the oil temperature OT and the cooling water temperature WT at the time point t3. In this case, the initial oil temperature estimation unit 32 performs the start-up cooling water. This is because the temperature WT_start is set as the initial oil temperature OT_0.
That is, as shown in FIG. 6, when the engine 12 was previously stopped (time point t1), the oil temperature OT (ie, the oil temperature OT_stop at the time of stop) is greater than the coolant temperature WT (ie, the coolant temperature WT_stop at the time of stop). If the engine temperature is too low, then the oil temperature OT does not become higher than the coolant temperature WT unless the engine 12 is operated again.

On the other hand, as shown in FIG. 7, at the previous stop (time point t3) of the engine 12, the coolant temperature WT (ie, the stop-time coolant temperature WT_stop) is greater than the oil temperature OT (ie, the stop-time oil temperature OT_stop). If the temperature is too low, then the cooling water temperature WT does not become higher than the oil temperature OT unless the engine 12 is operated again.
Thus, when the engine 12 is restarted (time point t2 in FIG. 6 and time point t4 in FIG. 7), the ECU 30 can acquire two parameters, the oil temperature at stop OT_stop and the coolant temperature at start WT_start. However, the initial oil temperature estimation unit 32 sets the smallest one of these two parameters as the initial oil temperature OT_0.

  That is, if the initial oil temperature OT_0 is set too high or low, the accuracy of the estimation result of the oil temperature OT itself is naturally lowered. However, according to the present invention, the initial oil temperature OT_0 is approximated to the actual oil temperature OT at the time of restart of the engine 12 as much as possible. The estimation accuracy of the oil temperature OT can be increased.

Further, in the FFV engine 12, it is common to estimate the concentration of the alcohol component in the fuel based on an air-fuel ratio feedback (so-called O ₂ feedback) control amount. However, when the fuel (so-called oil-diluted fuel) contained in the oil evaporates as the oil temperature OT increases and flows into the cylinder, the air-fuel ratio becomes rich. That is, in this case, the O ₂ feedback control amount is disturbed by the evaporated oil-diluted fuel, and the accuracy of estimating the concentration of the alcohol component in the fuel based on the O ₂ feedback control amount is reduced.

However, if the evaporation amount of the oil-diluted fuel corresponding to the oil temperature OT can be estimated, it is possible to prevent the estimation accuracy of the alcohol component amount in the fuel from being lowered. It is assumed to be estimated.
According to the present invention, since the oil temperature OT can be accurately estimated, it is possible to greatly contribute to accurately estimating the alcohol component concentration in the FFV engine 12.

Note that when the oil temperature OT is relatively low, the evaporation rate of the diluted fuel is relatively small. Thereafter, as the oil temperature OT increases, the evaporation rate of the diluted fuel increases. However, when the warm-up of the engine 12 is completed and the oil temperature OT is sufficiently high, most of the diluted fuel has evaporated, so even if the evaporation rate is high, the evaporation amount is not so large.
In other words, there is a strong demand to accurately obtain the oil temperature OT while the engine 12 is warmed up, but the present invention can meet such a demand.

Next, the estimation control of the oil temperature OT will be described using the flowcharts of FIGS.
First, in step S21 of FIG. 3, the oil temperature estimation unit 31 determines that the rotational speed NE of the engine 12 detected by the rotational speed sensor 22 falls below a predetermined idle lower limit rotational speed NE_MIN (for example, about 500 to 600 rpm) It is determined that the engine 12 is stalling or starting (Yes route of step S21).

In this case, the oil temperature estimation unit 31 determines that the current oil temperature, that is, the current estimated value OT (n) of the oil temperature is the initial oil temperature obtained by the initial oil temperature estimation unit 32 in step S14 or S15 of FIG. It is estimated that the value is OT_0.
On the other hand, when the rotational speed NE of the engine 12 becomes equal to or higher than the predetermined idle lower limit rotational speed NE_MIN, the oil temperature estimating unit 31 determines that the engine 12 is not stalling or starting and that the engine 12 is operating (step S21). No route).

Here, when the cooling water temperature WT is lower than the water temperature threshold value WT_th (Yes route of step S23), the thermostat 17 is in a closed state, and the cooling water heated by the engine 12 does not circulate in the radiator 16, and the engine 12 Circulate inside.
At this time, the pulse width INJ_PW of the pulse signal output from the fuel injection control unit 33 to the injector 13 is not zero. In other words, the fuel cut control unit 34 is not operating, and the injector 13 injects mixed fuel. Is performed (Yes route in step S24), the oil temperature estimation unit 31 calculates the current estimated value OT (n) of the oil temperature using the above-described equation (1) (step S25).

On the other hand, when the cooling water temperature WT is equal to or higher than the water temperature threshold value WT_th (No route in step S23; to FIG. 3 (P1)), the thermostat 17 is opened and the cooling water heated by the engine 12 circulates in the radiator 16. To do.
At this time, if the pulse width INJ_PW of the pulse signal output from the fuel injection control unit 33 to the injector 13 is larger than zero and the mixed fuel is being injected by the injector 13 (Yes route in step S26), the oil temperature is estimated. The unit 31 calculates the current estimated value OT (n) of the oil temperature using the above equation (2) (step S27).

  On the other hand, the thermostat 17 is in the open state (No route of step S23; to FIG. 3 (P1), the pulse width INJ_PW of the pulse signal output from the fuel injection control unit 33 to the injector 13 is zero, that is, the fuel cut When the fuel cut control is executed by the control unit 34 and the fuel mixture is not injected by the injector 13 (No route of step S26; to FIG. 5 (P4)), the oil temperature estimation unit 31 The current estimated value OT (n) of the oil temperature is calculated using Expression (4) (Step S29).

  Further, when the thermostat 17 is in the closed state (No route in step S23 in FIG. 3), the fuel cut control is being executed by the fuel cut control unit 34, and the fuel mixture is not being injected by the injector 13. (No route of step S24; to FIG. 4 (P2)), the oil temperature estimation unit 31 calculates the current estimated value OT (n) of the oil temperature using the above-described equation (3) (step S28).

As described above, according to the engine oil temperature estimation device according to the embodiment of the present invention, when estimating the oil temperature OT of the engine 12, the calculation load of the ECU 30 is avoided and the number of components is increased. The accuracy of estimation of the oil temperature OT can be increased without incurring the problem.
In addition, by accurately calculating the initial oil temperature OT_0 that is the oil temperature of the engine 12 at the time of starting the engine 12, the accuracy of estimating the oil temperature OT can be increased.

Even if the engine 12 is in an exceptional operating condition in which fuel cut control is being executed, the oil temperature OT reflecting the temperature change of the engine 12 itself can be accurately estimated.
Further, in the vehicle 10 equipped with the engine 12 for mixed fuel, so-called FFV, when the estimation accuracy of the oil temperature OT is lowered, the exhaust gas performance is lowered and the drivability is lowered due to the lowered output performance of the engine 12. However, according to the present invention, by accurately estimating the oil temperature OT, it is possible to effectively prevent the exhaust gas performance and drivability from being lowered even in the FFV.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various modifications can be made without departing from the spirit of the present invention. An example is shown below.
In the above-described embodiment, the case where the rotational speed NE of the engine 12 is detected by the rotational speed sensor 22 has been described, but the ECU 30 may calculate the engine rotational speed NE by using the output signal of the crank angle sensor. Good.

  In the above-described embodiment, the case where the thermostat 17 is a wax type and only one water temperature threshold value WT_th is set has been described as an example. However, the present invention is not limited to such an embodiment. For example, an electric thermostat may be used instead of the wax thermostat 17, and the first threshold WT_th1 and the second threshold WT_th2 indicating a temperature lower than the first threshold may be set as the water temperature threshold WT_th.

Then, by opening and closing the thermostat so that the cooling water temperature WT exceeds the first threshold value WT_th1, the electric thermostat is opened, and when the cooling water temperature WT falls below the second threshold value WT_th2, the thermostat is opened and closed. You may make it prevent.
In the above-described embodiment, the case where the engine 12 is a mixed fuel engine has been described as an example. However, the present invention is not limited to such a case. For example, a gasoline engine or a diesel engine may be used.

  In the above-described embodiment, the A coefficient map 35 is configured to define the A coefficient Kot_cls based on the engine speed NE and the throttle valve opening θth (that is, the load of the engine 12). Further, the oil temperature estimation unit 31 applies the engine speed NE read by the speed sensor 22 and the throttle valve opening θth read from the throttle valve position sensor 23 to the A coefficient map 35, so that The case where the A coefficient Kot_cls adapted to the operation state of the engine 12 at the time point is read has been described. However, the present invention is not limited to such a case. For example, the A coefficient map 35 may not be provided, and the A coefficient Kot_cls may be corrected according to the engine speed NE.

  Similarly, in the above-described embodiment, the C coefficient map 37 is configured to define the C coefficient Kot_opn based on the engine speed NE and the throttle valve opening θth (that is, the load of the engine 12). In addition, the oil temperature estimation unit 31 applies the engine speed NE read by the speed sensor 22 and the throttle valve opening θth read from the throttle valve position sensor 23 to the C coefficient map 37, so that The case where the C coefficient Kot_opn suitable for the operating state of the engine 12 at the time is read has been described. However, the present invention is not limited to such a case. For example, the C coefficient map 37 may not be provided, and the C coefficient Kot_opn may be corrected according to the engine speed NE.

  In the above-described embodiment, the case where the throttle valve opening θth is handled as indicating the load of the engine 12 has been described, but the present invention is not limited to such a case. For example, the charging efficiency obtained from the detection result of the air flow sensor (not shown) of the engine 12 may be handled as indicating the load of the engine 12.

It is a typical block diagram which shows the whole structure of the estimation apparatus of the engine oil temperature which concerns on one Embodiment of this invention. It is a flowchart which shows operation | movement of the estimation apparatus of the engine oil temperature which concerns on one Embodiment of this invention, Comprising: The case where the oil temperature initial value is calculated | required is shown. It is a flowchart which shows operation | movement of the estimation apparatus of the engine oil temperature which concerns on one Embodiment of this invention, Comprising: The case where oil temperature is calculated | required is shown. It is a flowchart which shows operation | movement of the estimation apparatus of the engine oil temperature which concerns on one Embodiment of this invention, Comprising: The case where oil temperature is calculated | required is shown. It is a flowchart which shows operation | movement of the estimation apparatus of the engine oil temperature which concerns on one Embodiment of this invention, Comprising: The case where oil temperature is calculated | required is shown. It is a time chart which shows operation | movement of the estimation apparatus of the engine oil temperature which concerns on one Embodiment of this invention, Comprising: The case where an engine operating period is comparatively short is shown. It is a time chart which shows operation | movement of the estimation apparatus of the engine oil temperature which concerns on one Embodiment of this invention, Comprising: The case where the driving | running period of an engine is comparatively long is shown.

Explanation of symbols

10 Vehicle 12 Engine for mixed fuel (engine)
13 Injector (fuel injection means)
16 Radiator 17 Thermostat (cooling water valve)
21 Water temperature sensor (cooling water temperature detection means)
31 Oil temperature estimation part (oil temperature estimation means)
32 Initial oil temperature estimation unit (initial oil temperature estimation means)
34 Fuel cut control unit (fuel cut control means)
WT Cooling water temperature OT Oil temperature NE Engine speed θth Engine load OTmap_m Converging oil temperature during driving OTmap_m Converging oil temperature during driving Kot_cls Smoothing coefficient for oil temperature during fuel injection with thermostat closed (A coefficient)
Kwt_cls Cooling water temperature smoothing coefficient during fuel injection with thermostat closed (B coefficient)
Kot_opn Smoothing coefficient for oil temperature (C coefficient) during fuel injection with thermostat open
Kot_clsm Smoothing coefficient for oil temperature (D coefficient) during fuel cut with thermostat closed
Kot_opnm Smoothing coefficient for oil temperature (E coefficient) during fuel cut with thermostat open

Claims (4)

An engine mounted on the vehicle,
A radiator that dissipates cooling water for cooling the engine;
Cooling water temperature detection means for detecting the temperature of the cooling water;
The cooling water is interposed between the engine and the radiator. The cooling water does not flow between the engine and the radiator in the closed state, and the cooling water flows between the engine and the radiator in the open state. A cooling water valve,
Oil temperature estimating means for estimating the oil temperature of the engine according to the open / close state of the cooling water valve,
The oil temperature estimating means includes
When the cooling water valve is in a closed state, an oil temperature of the engine is estimated by applying a first-order lag process in which a first weight is applied to the cooling water temperature,
When the cooling water valve is in the open state, the engine oil temperature is reduced by applying a first-order lag process in which the second weighting is applied to the driving convergence oil temperature that is an oil temperature determined according to the operating state of the engine. An estimation device for engine oil temperature, characterized by estimating. Fuel injection means for injecting fuel in the engine;
Fuel cut control means for executing fuel cut control for prohibiting fuel injection by the fuel injection means when the fuel cut condition is satisfied,
The oil temperature estimating means includes
When the fuel cut control means is executing the fuel cut control with the cooling water valve closed, the third weighting is applied to the driven convergent oil temperature, which is the oil temperature determined by the engine speed. 2. The engine oil temperature estimating apparatus according to claim 1, wherein the engine oil temperature is estimated by performing the first-order lag processing. Fuel cut control means for executing fuel cut control for prohibiting fuel injection by the fuel injection means when the fuel cut condition is satisfied,
The oil temperature estimating means includes
When the fuel cut control is executed by the fuel cut control means with the cooling water valve open, a first-order lag process is applied in which the fourth weighting is applied to the driven convergence temperature determined by the engine speed. The engine oil temperature estimation device according to claim 1 or 2, wherein the engine oil temperature is estimated by this. The engine oil temperature estimating device according to any one of claims 1 to 3, wherein the engine is a mixed fuel engine using a mixture of gasoline and alcohol as fuel.

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