JP2011007114A - Oil temperature estimating device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately calculate estimated oil temperature of working fluid of a variable valve timing device.SOLUTION: An average value of start cooling water temperature THWst detected by a cooling water temperature sensor 26 and start intake air temperature THAst detected by an intake air temperature sensor 27 is corrected according to difference between the start cooling water temperature THWst and the start intake air temperature THAst at engine start, and start estimated oil temperature THOst (initial value of estimated oil temperature THO) is accurately calculated. Engine rotation speed is integrated after engine start (during engine operation), estimated oil temperature rise quantity ΔTHO is accurately calculated according to the integrated value of engine rotation speed, and estimated oil temperature THO is accurately determined by adding the estimated oil temperature rise quantity ΔTHO to the start estimated oil temperature THOst. If the estimated oil temperature THO gets higher than cooling water temperature THW (cooling water temperature detected by the cooling water temperature sensor 26), it is determined that actual oil temperature rises to temperature roughly same as cooling water temperature and the cooling water temperature THW is defined as the estimated oil temperature THO.

Description

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

  Recently, in an internal combustion engine mounted on a vehicle, a hydraulically driven variable valve timing that changes the valve timing (opening / closing timing) of an intake valve and an exhaust valve of the internal combustion engine for the purpose of improving output, reducing fuel consumption, and reducing emissions. The number of devices equipped with equipment is increasing. This hydraulically driven variable valve timing device has a high viscosity of hydraulic oil and a decrease in fluidity when the oil temperature of the hydraulic oil (engine oil) is low immediately after the start of the internal combustion engine. There is a characteristic (see FIG. 2) that the responsiveness (response speed of the variable valve timing device) is lowered.

  Therefore, as described in Patent Document 1 (Japanese Patent Laid-Open No. 10-227235), the oil temperature of the hydraulic oil of the variable valve timing device is estimated, and when the estimated oil temperature is outside the predetermined range, the valve timing is There are some which limit the adjustment range (operation range of the variable valve timing device) or prohibit valve timing control (operation of the variable valve timing device) when the estimated oil temperature is lower than a predetermined temperature. In this system, the coolant temperature detected by the coolant temperature sensor when the internal combustion engine is started is set as the initial value of the estimated oil temperature. After the internal combustion engine is started (during operation), the initial value of the estimated oil temperature and the internal combustion engine The estimated oil temperature is calculated based on the operating state (rotation speed, load, etc.).

  Furthermore, as a technique for calculating the initial value of the estimated oil temperature, as described in Patent Document 2 (Japanese Patent Laid-Open No. 2005-207297), when the internal combustion engine is started, it is estimated as the detected water temperature at the previous engine stop. There is one in which an estimated oil temperature initial value is calculated using a difference from the oil temperature, a correction coefficient corresponding to the engine stop time, and a detected water temperature at the time of the current engine start.

Japanese Patent Laid-Open No. 10-227235 (second page, etc.) JP-A-2005-207297 (second page, etc.)

  By the way, in order to meet demands for fuel economy and emission reductions that are expected to become increasingly severe in the future, various calculations (for example, valve timing control) using the estimated oil temperature by improving the calculation accuracy of the estimated oil temperature are improved. It is necessary to improve the controllability of the control which is easily affected by the oil temperature. However, the conventional oil temperature estimation method cannot sufficiently improve the calculation accuracy of the estimated oil temperature, and cannot sufficiently improve the controllability of various controls using the estimated oil temperature.

  It is also possible to provide an oil temperature sensor that detects the oil temperature and to detect the actual oil temperature with high accuracy using the oil temperature sensor. However, in this case, it is necessary to provide a new oil temperature sensor. The demand for cost reduction, which is a technical issue, cannot be met.

  Therefore, the problem to be solved by the present invention is to provide an oil temperature estimation device for an internal combustion engine that can improve the calculation accuracy of the estimated oil temperature and satisfy the demand for cost reduction.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a device for estimating an oil temperature of an internal combustion engine that calculates an estimated oil temperature of oil used in the internal combustion engine or its peripheral device, and detects the rotational speed of the internal combustion engine. The rotational speed detecting means for detecting the oil temperature and the oil temperature estimating means for calculating the estimated oil temperature based on the integrated value of the rotational speeds detected by the rotational speed detecting means.

  According to the research of the present inventor, as shown in FIG. 4, there is a correlation between the integrated value of the rotational speed of the internal combustion engine and the oil temperature increase amount, and the internal combustion engine increases as the integrated value of the rotational speed of the internal combustion engine increases. It has been found that there is a characteristic that the amount of heat transferred from the engine to the oil increases and the oil temperature rise increases. Focusing on this characteristic, the present invention calculates the estimated oil temperature based on the integrated value of the rotational speed of the internal combustion engine. Therefore, the relationship between the integrated value of the rotational speed of the internal combustion engine and the amount of increase in the oil temperature is obtained. By using this, the estimated oil temperature can be accurately calculated from the integrated value of the rotational speed of the internal combustion engine. Thereby, the controllability of various controls using the estimated oil temperature (for example, control that is easily influenced by the oil temperature such as valve timing control) can be improved. Moreover, since it is not necessary to newly provide an oil temperature sensor for detecting the oil temperature, it is possible to satisfy the demand for cost reduction, which is an important technical problem in recent years.

  As shown in FIG. 3, after the internal combustion engine is started, the cooling water temperature and the oil temperature gradually rise, but the cooling water temperature tends to rise earlier than the oil temperature and the cooling water temperature tends to be higher than the oil temperature. Thereafter, the oil temperature finally rises to substantially the same temperature as the cooling water temperature, and after the internal combustion engine is warmed up, the cooling water temperature and the oil temperature become substantially the same temperature. Then, after the internal combustion engine is stopped, the cooling water temperature and the oil temperature gradually decrease, and finally after the soak (after a predetermined time or more has passed since the internal combustion engine stopped), the cooling water temperature, the oil temperature, and the intake air temperature. Become almost the same temperature (almost outside temperature).

  In consideration of the relationship between the cooling water temperature, the oil temperature, and the intake air temperature, the cooling water temperature detecting means for detecting the cooling water temperature of the internal combustion engine and the intake air temperature detection for detecting the intake air temperature of the internal combustion engine as in claim 2. Means for calculating an estimated starting oil temperature (initial value of the estimated oil temperature) based on the cooling water temperature detected by the cooling water temperature detecting means and the intake air temperature detected by the intake air temperature detecting means when the internal combustion engine is started Anyway. In this way, the estimated estimated oil temperature can be accurately calculated from the coolant temperature at the start and the intake air temperature at the start using the relationship between the coolant temperature, the oil temperature, and the intake air temperature.

  Specifically, as described in claim 3, when starting the internal combustion engine, the average value of the cooling water temperature and the intake air temperature is corrected according to the deviation between the cooling water temperature and the intake air temperature to obtain the estimated oil temperature at the time of starting. Good. According to the research of the present inventor, it is possible to accurately calculate the estimated oil temperature at the time of starting by correcting the average value of the cooling water temperature and the intake air temperature according to the deviation between the cooling water temperature and the intake air temperature when starting the internal combustion engine. There was found.

  Further, as in claim 4, after the internal combustion engine is started, an estimated oil temperature increase amount is calculated based on the integrated value of the rotational speed, and the estimated oil temperature increase amount is added to the estimated oil temperature at the start time to estimate the oil temperature. It is better to ask. In this manner, the estimated oil temperature can be obtained with high accuracy by adding the estimated oil temperature increase amount calculated with high accuracy to the estimated oil temperature at start-up with high accuracy.

  As described above, after starting the internal combustion engine, the cooling water temperature and the oil temperature gradually increase, but the cooling water temperature tends to rise earlier than the oil temperature and the cooling water temperature tends to be higher than the oil temperature. Eventually, the oil temperature rises to almost the same temperature as the cooling water temperature.

  In consideration of such behavior of the cooling water temperature and the oil temperature, the cooling water temperature may be set to the estimated oil temperature when the estimated oil temperature becomes higher than the cooling water temperature as in the fifth aspect. In this way, when the estimated oil temperature becomes higher than the cooling water temperature, it is determined that the actual oil temperature has risen to substantially the same temperature as the cooling water temperature, and the cooling water temperature can be made the estimated oil temperature. Thereby, it is possible to prevent an erroneous estimation that the estimated oil temperature is higher than the cooling water temperature.

  By the way, at the time of fuel cut of the internal combustion engine, the amount of heat generated by the internal combustion engine is reduced compared to that at the time of normal operation (fuel injection), so the relationship between the integrated value of the rotational speed of the internal combustion engine and the oil temperature increase amount changes. .

  Therefore, as in claim 6, when the estimated oil temperature is calculated at the time of fuel cut of the internal combustion engine, the integrated value of the rotational speed may be corrected. In this way, when the fuel of the internal combustion engine is cut, the cumulative value of the rotational speed can be corrected in response to the change in the relationship between the cumulative value of the rotational speed of the internal combustion engine and the oil temperature increase amount. Even if the relationship between the rotational speed integrated value and the oil temperature increase changes, the estimated oil temperature increase can be obtained accurately from the corrected integrated value of the rotational speed, and the estimated oil temperature at the time of fuel cut is calculated. Accuracy can be improved.

  Or you may make it correct | amend the estimated oil temperature rise amount calculated | required from the integrated value of rotational speed when calculating an estimated oil temperature at the time of the fuel cut of an internal combustion engine like Claim 7. In this way, when the fuel of the internal combustion engine is cut, the oil temperature increase amount obtained from the rotational speed integrated value is calculated in response to the change in the relationship between the integrated value of the rotational speed of the internal combustion engine and the oil temperature increase amount. Even if the relationship between the accumulated value of the rotation speed and the oil temperature increase amount can be changed, the oil temperature increase amount can be obtained accurately, and the calculation accuracy of the estimated oil temperature at the time of fuel cut is improved. be able to.

FIG. 1 is a diagram showing a schematic configuration of a variable valve timing control system in Embodiment 1 of the present invention. FIG. 2 is a diagram showing response speed characteristics of the variable valve timing device. FIG. 3 is a time chart showing the behavior of the cooling water temperature, the oil temperature, and the intake air temperature. FIG. 4 is a graph showing the relationship between the integrated value of the engine rotation speed and the oil temperature increase amount. FIG. 5 is a diagram conceptually illustrating an example of a correction coefficient map. FIG. 6 is a flowchart for explaining the processing flow of the oil temperature estimation routine according to the first embodiment. FIG. 7 is a flowchart for explaining the flow of processing of the oil temperature estimation routine of the second embodiment.

  Hereinafter, some embodiments will be described which are embodied by applying the mode for carrying out the present invention to the calculation of the estimated oil temperature of the hydraulic oil of the variable valve timing device.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the variable valve timing control system will be described with reference to FIG.
In the engine 11 which is an internal combustion engine, the power from the crankshaft 12 is transmitted to the intake side camshaft 16 and the exhaust side camshaft 17 via the sprockets 14 and 15 by the timing chain 13. The intake side camshaft 16 is provided with a hydraulically driven variable valve timing device 18 (VCT), and the hydraulically driven variable valve timing device 18 rotates the intake side camshaft 16 relative to the crankshaft 12 (VCT phase). ) Is changed to change the valve timing of an intake valve (not shown) driven to open and close by the intake camshaft 16.

  Also, hydraulic oil (oil) in the oil pan 20 is pumped up and supplied to the hydraulic control valve 21 by the oil pump 19 driven by the power of the engine 11, and the variable valve timing device 18 is advanced by the hydraulic control valve 21. The oil pressure (oil amount) supplied to the angle port and the retard port is controlled. A check valve 22 is provided on the inlet port side of the hydraulic control valve 21 to prevent backflow of oil.

  A cam angle sensor 23 that outputs a cam angle signal pulse at a specific cam angle for cylinder discrimination is installed on the outer peripheral side of the intake side cam shaft 16, while a predetermined crank angle is provided on the outer peripheral side of the crank shaft 12. A crank angle sensor 24 (rotation speed detecting means) is provided for outputting a crank angle signal pulse every time. Output signals of the cam angle sensor 23 and the crank angle sensor 24 are input to an engine control circuit (hereinafter referred to as “ECU”) 25, and the ECU 25 calculates the actual valve timing (actual VCT phase) of the intake valve. At the same time, the engine speed is calculated based on the frequency (pulse interval) of the output pulses of the crank angle sensor 24.

  Further, various sensors for detecting the engine operating state, such as a cooling water temperature sensor 26 (cooling water temperature detecting means) for detecting the cooling water temperature of the engine 11, an intake air temperature sensor 27 (intake air temperature detecting means) for detecting the intake air temperature of the engine 11, etc. An output signal is input to the ECU 25. The ECU 25 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), thereby performing fuel injection control and ignition control according to the engine operating state.

  Further, the ECU 25 executes a valve timing control routine (not shown) to calculate a target valve timing (target VCT phase) according to the engine operating state, and to calculate the actual valve timing (actual VCT phase) as the target valve timing (target VCT phase). The control duty of the hydraulic control valve 21 is feedback-controlled by, for example, PD control so as to coincide with the (VCT phase), and the hydraulic pressure supplied to the advance port and the retard port of the variable valve timing device 18 is feedback-controlled.

  When the oil temperature of the hydraulic oil (oil) is low, such as immediately after the engine is started, the hydraulically driven variable valve timing device 18 increases the viscosity of the hydraulic oil and lowers the fluidity, and the responsiveness of the valve timing control ( There is a characteristic (see FIG. 2) that the VCT response speed is reduced.

Thus, in the first embodiment, the ECU 25 calculates the estimated oil temperature of the hydraulic oil as follows by executing an oil temperature estimation routine of FIG.
As shown in FIG. 3, after the engine is started, the cooling water temperature and the oil temperature gradually rise, but the cooling water temperature tends to rise earlier than the oil temperature and the cooling water temperature becomes higher than the oil temperature. Finally, the oil temperature rises to substantially the same temperature as the cooling water temperature, and after the engine is warmed up, the cooling water temperature and the oil temperature become substantially the same temperature. After the engine stops, the cooling water temperature and the oil temperature gradually decrease, and finally after soaking (after a predetermined time has elapsed since the engine stopped), the cooling water temperature, the oil temperature, and the intake air temperature are substantially the same temperature. (Almost outside temperature).

  In consideration of the relationship between the cooling water temperature, the oil temperature, and the intake air temperature, first, when starting the engine, the starting cooling water temperature THWst detected by the cooling water temperature sensor 26 and the starting intake air temperature THAst detected by the intake air temperature sensor 27 Based on the equation, the estimated starting oil temperature THOst (initial value of the estimated oil temperature THO) is calculated. According to the study by the present inventor, the average value of the starting coolant temperature THWst and the starting intake air temperature THAst is corrected according to the deviation between the starting coolant temperature THWst and the starting intake air temperature THAst, thereby estimating the starting time. It was found that the oil temperature THOst can be calculated with high accuracy.

  Specifically, the correction coefficient K corresponding to the starting coolant temperature THWst is calculated with reference to the correction coefficient K map shown in FIG. The map of the correction coefficient K is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 25.

Thereafter, the estimated starting oil temperature THOst is obtained by the following equation using the starting coolant temperature THWst, the starting intake air temperature THAst, and the correction coefficient K.
THOst = (THWst + THAst) / 2 + (THWst−THAst) × K / 2

  Thus, the average value of the starting coolant temperature THWst and the starting intake air temperature THAst is corrected according to the deviation between the starting coolant temperature THWst and the starting intake air temperature THAst, and the estimated starting oil temperature THOst is accurately obtained. calculate.

  Then, after the engine is started (during engine operation), the engine rotational speed is integrated, and an estimated oil temperature increase amount ΔTHO is calculated based on the integrated value of the engine rotational speed. According to the research of the present inventor, as shown in FIG. 4, there is a correlation between the integrated value of the engine rotational speed and the oil temperature increase amount, and the hydraulic oil from the engine 11 increases as the integrated value of the engine rotational speed increases. It has been found that there is a characteristic that the amount of heat transferred to the oil increases and the oil temperature rise increases. Focusing on this characteristic, referring to a map of the estimated oil temperature increase ΔTHO (a map of the relationship between the integrated value of the engine rotation speed and the oil temperature increase shown in FIG. 4), the integration of the engine rotation speed The estimated oil temperature rise amount ΔTHO corresponding to the value is accurately calculated. The map of the estimated oil temperature increase ΔTHO is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 25.

Thereafter, the estimated oil temperature THO is obtained by adding the estimated oil temperature increase ΔTHO to the estimated estimated oil temperature THOst.
THO = THOst + ΔTHO
Thus, the estimated oil temperature increase THOst calculated accurately is added to the estimated oil temperature increase THOst calculated accurately to obtain the estimated oil temperature THO accurately.

  As described above, after starting the engine, the cooling water temperature and the oil temperature gradually rise, but the cooling water temperature tends to rise earlier than the oil temperature and the cooling water temperature tends to be higher than the oil temperature. The oil temperature rises to almost the same temperature as the cooling water temperature. Considering the behavior of the cooling water temperature and the oil temperature, when the estimated oil temperature THO is higher than the cooling water temperature THW (the cooling water temperature detected by the cooling water temperature sensor 26), the actual oil temperature is almost the same as the cooling water temperature. It is determined that the temperature has risen, and the coolant temperature THW is set to the estimated oil temperature THO.

The ECU 25 uses the estimated oil temperature THO obtained as described above for various controls.
For example, in the valve timing control, when the control duty of the hydraulic control valve 21 is feedback-controlled so that the actual valve timing matches the target valve timing and the hydraulic pressure supplied to the variable valve timing device 18 is feedback-controlled, the estimated oil temperature The control duty of the hydraulic control valve 21 is corrected according to THO. Alternatively, when the estimated oil temperature THO is outside the predetermined range, the valve timing adjustment range (operation range of the variable valve timing device 18) is limited, or when the estimated oil temperature THO is equal to or lower than the predetermined temperature, the valve timing control (variable). The operation of the valve timing device 18 may be prohibited.

  In the torque control, the required indicated torque is calculated by adding the internal loss torque, friction loss (mechanical friction loss), pumping loss, etc. to the required shaft torque, and the fuel injection amount to realize the required indicated torque, When controlling the ignition timing, the throttle opening, etc., the friction loss changes according to the oil temperature, so the friction loss is calculated based on the estimated oil temperature THO.

Hereinafter, the processing content of the oil temperature estimation routine of FIG. 6 executed by the ECU 25 will be described.
The oil temperature estimation routine shown in FIG. 6 is repeatedly executed at a predetermined cycle while the ECU 25 is turned on, and serves as oil temperature estimation means in the claims. When this routine is started, first, at step 101, it is determined whether or not the engine is being started based on whether or not the IG switch (ignition switch) has just been switched from OFF to ON.

  If it is determined in step 101 that the engine is being started (immediately after the IG switch is switched from OFF to ON), the process proceeds to step 102, and the starting coolant temperature THWst detected by the coolant temperature sensor 26 is read. Thereafter, the routine proceeds to step 103, where the start-time intake air temperature THAst detected by the intake air temperature sensor 27 is read.

Thereafter, the process proceeds to step 104, and the correction coefficient K corresponding to the starting coolant temperature THWst is calculated with reference to the correction coefficient K map shown in FIG. 5, and then the process proceeds to step 105, where the starting coolant temperature THWst and the starting coolant temperature are started. The estimated starting oil temperature THOst (initial value of the estimated oil temperature THO) is obtained by the following equation using the hour intake temperature THAst and the correction coefficient K.
THOst = (THWst + THAst) / 2 + (THWst−THAst) × K / 2

  Thus, the average value of the starting coolant temperature THWst and the starting intake air temperature THAst is corrected according to the deviation between the starting coolant temperature THWst and the starting intake air temperature THAst, and the estimated starting oil temperature THOst is accurately obtained. calculate.

  On the other hand, if it is determined in step 101 that the engine is not started (not immediately after the IG switch is switched from OFF to ON), the process proceeds to step 106 and after the engine is started (after completion of the engine start). If it is determined whether or not the engine has been started (before engine start is completed), the process proceeds to step 107, the integrated value of the engine speed is reset to “0”, and then the process proceeds to step 108. The estimated oil temperature rise amount ΔTHO is reset to “0”.

  Thereafter, if it is determined in step 106 that the engine has been started (after completion of engine start), the process proceeds to step 109, the current engine speed is read, the process proceeds to step 110, and the engine up to the previous time is read. The current engine rotational speed is added to the rotational speed integrated value to update the engine rotational speed integrated value.

  Thereafter, the process proceeds to step 111, and a map of the estimated oil temperature rise amount ΔTHO (a map of the relationship between the integrated value of the engine speed and the oil temperature rise amount shown in FIG. 4) is referred to. An estimated oil temperature increase amount ΔTHO corresponding to the integrated value is calculated.

After this, the routine proceeds to step 112, where the estimated oil temperature THO is obtained by adding the estimated oil temperature increase ΔTHO to the starting estimated oil temperature THOst.
THO = THOst + ΔTHO
Thus, the estimated oil temperature increase THOst calculated accurately is added to the estimated oil temperature increase THOst calculated accurately to obtain the estimated oil temperature THO accurately.

  Thereafter, the routine proceeds to step 113, where it is determined whether or not the estimated oil temperature THO is equal to or lower than the current cooling water temperature THW (cooling water temperature detected by the cooling water temperature sensor 26), and the estimated oil temperature THO is equal to or lower than the cooling water temperature THW. If it is determined, the routine is terminated as it is.

  On the other hand, if it is determined in step 113 that the estimated oil temperature THO is higher than the cooling water temperature THW, it is determined that the actual oil temperature has risen to substantially the same temperature as the cooling water temperature, and the process proceeds to step 114. The cooling water temperature THW is assumed to be the estimated oil temperature THO.

  In the first embodiment described above, when the engine is started, the average value of the starting coolant temperature THWst and the starting intake air temperature THAst is corrected according to the deviation between the starting coolant temperature THWst and the starting intake air temperature THAst. Then, the estimated oil temperature THOst at the start is accurately calculated, and after the engine is started, the estimated oil temperature increase ΔTHO is accurately calculated according to the integrated value of the engine rotation speed, and this estimated oil temperature increase ΔTHO is calculated as the estimated oil temperature at the start Since the estimated oil temperature THO is obtained by adding to the temperature THOst, the estimated oil temperature THO can be calculated with high accuracy. Thereby, the controllability of various controls using the estimated oil temperature THO (for example, control that is easily influenced by the oil temperature such as valve timing control) can be improved. Moreover, since it is not necessary to newly provide an oil temperature sensor for detecting the oil temperature, it is possible to satisfy the demand for cost reduction, which is an important technical problem in recent years.

  In the first embodiment, when the estimated oil temperature THO is higher than the cooling water temperature THW, it is determined that the actual oil temperature has risen to substantially the same temperature as the cooling water temperature, and the cooling water temperature THW is set to the estimated oil temperature THO. Thus, it is possible to prevent an erroneous estimation that the estimated oil temperature THO is higher than the coolant temperature THW.

  Next, Embodiment 2 of the present invention will be described with reference to FIG. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.

  When the fuel of the engine 11 is cut, the amount of heat generated by the engine 11 is reduced as compared with that during normal operation (during fuel injection), so the relationship between the integrated value of the engine speed and the oil temperature increase ΔTHO changes.

  Therefore, in the second embodiment, the ECU 25 executes an oil temperature estimation routine shown in FIG. 7 to be described later, thereby correcting the integrated value of the engine speed when calculating the estimated oil temperature THO when the fuel of the engine 11 is cut. I am doing so. As a result, at the time of fuel cut, the integrated value of the engine rotational speed is corrected in response to a change in the relationship between the integrated value of the engine rotational speed and the oil temperature increase amount.

  The routine of FIG. 7 is obtained by changing the processing of step 110 of the routine of FIG. 6 described in the first embodiment to the processing of steps 110a to 110c, and the processing of each other step is the same as that of FIG. is there.

  In the oil temperature estimation routine of FIG. 7, if it is determined in step 106 that the engine has been started (after completion of the engine start), the process proceeds to step 109, the current engine speed is read, and then the process proceeds to step 110a. Then, it is determined whether or not the fuel is being cut.

  If it is determined in step 110a that the fuel cut is not in progress, the process proceeds to step 110b, and the integrated value of the engine speed is calculated by the method during normal operation (the same method as step 110 in FIG. 6). In this case, the current engine rotational speed is added to the previous integrated value of the engine rotational speed to update the integrated value of the engine rotational speed.

  On the other hand, if it is determined in step 110a that the fuel is being cut, the process proceeds to step 110c, and an integrated value of the engine speed is calculated by the method at the time of fuel cut. In this case, for example, by correcting the current engine rotational speed in a decreasing direction, adding the corrected engine rotational speed to the previous accumulated engine rotational speed, and updating the accumulated engine rotational speed, Correct the integrated value of the engine speed in the decreasing direction. Alternatively, after adding the current engine rotational speed to the previous integrated value of the engine rotational speed to obtain the integrated value of the engine rotational speed, the integrated value of the engine rotational speed may be corrected in the decreasing direction. good. Thereby, at the time of fuel cut, compared with the time of normal operation (at the time of fuel injection), the integration rate at the time of integrating the engine speed is reduced.

  Thereafter, the process proceeds to step 111, and a map of the estimated oil temperature rise amount ΔTHO (a map of the relationship between the integrated value of the engine speed and the oil temperature rise amount shown in FIG. 4) is referred to. An estimated oil temperature increase amount ΔTHO corresponding to the integrated value is calculated.

  In the above-described second embodiment, when the estimated oil temperature is calculated when the fuel is cut, the integrated value of the engine speed is corrected. Therefore, the integrated value of the engine speed and the oil temperature increase amount are calculated when the fuel is cut. The integrated value of the engine speed can be corrected in response to the change in the relationship between the engine speed and the corrected engine The estimated oil temperature rise amount ΔTHO can be accurately obtained from the integrated value of the speed, and the calculation accuracy of the estimated oil temperature THO at the time of fuel cut can be improved.

  In the second embodiment, when the estimated oil temperature THO is calculated when the fuel is cut, the integrated value of the engine rotation speed is corrected. However, when the estimated oil temperature THO is calculated when the fuel is cut, the engine rotation is corrected. You may make it correct | amend estimated oil temperature rise amount (DELTA) THO calculated | required from the integrated value of speed. In this way, when the fuel is cut, the estimated oil temperature increase ΔTHO obtained from the engine rotation speed integrated value is corrected in response to a change in the relationship between the engine rotation speed integrated value and the oil temperature increase amount. Even if the relationship between the integrated value of the engine speed and the oil temperature increase amount changes, the estimated oil temperature increase amount ΔTHO can be obtained accurately, and the calculation accuracy of the estimated oil temperature THO at the time of fuel cut can be obtained. Can be improved.

  Alternatively, a map of the estimated oil temperature increase ΔTHO for fuel cut (a map that defines the relationship between the integrated value of the engine speed during fuel cut and the estimated oil temperature increase ΔTHO) is prepared in advance. In some cases, the estimated oil temperature increase ΔTHO corresponding to the integrated value of the engine speed may be calculated with reference to a map of the estimated oil temperature increase ΔTHO for fuel cut.

  Further, the present invention is not limited to the calculation of the estimated oil temperature of the hydraulic fluid of the variable valve timing device on the intake side, but the engine or its peripheral devices (for example, the variable valve timing device on the exhaust side, the variable on the intake side or the exhaust side). The present invention can be widely applied to the calculation of the estimated oil temperature of lubricating oil and hydraulic oil used in valve lift devices, power steering devices, and the like.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Crankshaft, 16 ... Intake side camshaft, 17 ... Exhaust side camshaft, 18 ... Variable valve timing device, 19 ... Oil pump, 21 ... Hydraulic control valve, 23 ... Cam angle sensor 24 ... Crank angle sensor (rotational speed detection means) 25 ... ECU (oil temperature estimation means) 26 ... Cooling water temperature sensor (cooling water temperature detection means) 27 ... Intake air temperature sensor (intake air temperature detection means)

Claims (7)

In an oil temperature estimation device for an internal combustion engine that calculates an estimated oil temperature of oil used in the internal combustion engine or its peripheral device,
Rotation speed detection means for detecting the rotation speed of the internal combustion engine;
An oil temperature estimation device for an internal combustion engine, comprising: an oil temperature estimation unit that calculates the estimated oil temperature based on an integrated value of the rotation speed detected by the rotation speed detection unit. Cooling water temperature detecting means for detecting the cooling water temperature of the internal combustion engine;
An intake air temperature detecting means for detecting the intake air temperature of the internal combustion engine,
The oil temperature estimating means includes means for calculating an estimated starting oil temperature based on the cooling water temperature detected by the cooling water temperature detecting means and the intake air temperature detected by the intake air temperature detecting means when the internal combustion engine is started. 2. The oil temperature estimating device for an internal combustion engine according to claim 1, wherein the oil temperature estimating device is an internal combustion engine.   The oil temperature estimating means corrects an average value of the cooling water temperature and the intake air temperature according to a deviation between the cooling water temperature and the intake air temperature when starting the internal combustion engine, and obtains the estimated oil temperature at the start time. The oil temperature estimating device for an internal combustion engine according to claim 2, comprising:   The oil temperature estimating means calculates an estimated oil temperature increase amount based on an integrated value of the rotational speed after starting the internal combustion engine, and adds the estimated oil temperature increase amount to the estimated oil temperature at the time of starting to estimate the estimated oil temperature. 4. The oil temperature estimating apparatus for an internal combustion engine according to claim 2, further comprising means for obtaining a temperature.   The said oil temperature estimation means has a means to make the said cooling water temperature into the said estimated oil temperature when the said estimated oil temperature becomes higher than the said cooling water temperature, The any one of Claim 1 thru | or 4 characterized by the above-mentioned. Oil temperature estimation device for internal combustion engine of   The said oil temperature estimation means has a means to correct | amend the integrated value of the said rotational speed, when calculating the said estimated oil temperature at the time of the fuel cut of an internal combustion engine, The Claim 1 thru | or 5 characterized by the above-mentioned. An oil temperature estimating device for an internal combustion engine.   The said oil temperature estimation means has a means to correct | amend the estimated oil temperature rise amount calculated | required from the integrated value of the said rotational speed when calculating the said estimated oil temperature at the time of the fuel cut of an internal combustion engine. The oil temperature estimation device for an internal combustion engine according to any one of claims 5 to 6.

Images