Control device for internal combustion engine

Abstract

To provide a control device for an internal combustion engine capable of accurately correcting friction torque even when a cooling water temperature and an oil temperature are different from each other.SOLUTION: A control device for an internal combustion engine comprises: the internal combustion engine 1; water temperature acquisition means 2 for acquiring a cooling water temperature of the internal combustion engine 1; oil temperature acquisition means 3 for acquiring an oil temperature of the internal combustion engine 1; torque derivation means 4 for deriving friction torque PfOT-BASE of the internal combustion engine 1 from a torque map stored beforehand, on the basis of the cooling water temperature; and torque correction means 5 for calculating corrected friction torque PfOT obtained by correcting the friction torque PfOT-BASE, on the basis of a difference between the cooling water temperature and the oil temperature.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] In a conventional control device for an internal combustion engine (hereinafter referred to as an engine), a combustion torque P obtained by combustion in the engine is expressed as the following formula (1): i From, warm-up friction torque P fSTD , and the correction friction torque P' fOT By subtracting the oil temperature correction, the actual output torque of the engine P OPT The friction torque during warm-up P fSTD is the torque mainly caused by pump loss torque and mechanical loss, and the correction friction torque P' fOT is a correction term caused by changes in viscosity of the lubricating oil based on the oil temperature and the expansion of metals, etc. P OPT =P i -(P fSTD +P' fOT ) (1)

[0003] This correction friction torque P' fOT is generally derived from a torque map stored in advance based on the engine speed and the coolant temperature. However, the coolant temperature and the oil temperature may have different temperature rise and fall characteristics. In this case, the correction friction torque P' determined based on the coolant temperature may be different from the correction friction torque P' determined based on the engine speed and the coolant temperature. fOT There may be an error between the actual amount of correction required and the actual amount of correction.

[0004] For example, as shown in FIG. 6, when we look at the changes in the coolant temperature and oil temperature from the time the engine is started, the coolant temperature reaches the warm-up temperature T W While the oil temperature rises to the temperature limit and is controlled by the thermostat, the oil temperature may rise more slowly than the water temperature. In this case, the correction friction torque P' is calculated based on the cooling water temperature. fOTIf the engine torque is determined by deriving the above, the actual output torque of the engine may be insufficient because the oil temperature is actually low and the friction torque is large. Problems caused by the difference between the coolant temperature and the oil temperature are prominent when the engine is restarted after running as an electric vehicle in a hybrid vehicle (the coolant temperature is low but the oil temperature is high) or when the engine is started in a cold state (the coolant temperature is high but the oil temperature is low).

[0005] In order to solve the problems caused by differences between the cooling water temperature and the oil temperature, for example, in Patent Document 1 listed below, in a system in which a map for calculating engine friction torque according to the engine cooling water temperature is pre-stored, the rotational speed difference between a pre-stored reference engine speed at start-up and the actual engine speed after start-up is detected, and a correction is made to the friction torque map value according to the rotational speed difference (see, for example, paragraphs 0024-0027 of Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-97347 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the configuration disclosed in Patent Document 1, a correction is made to the friction torque map value based on the difference in rotation speed between the reference engine rotation speed at start-up and the actual engine rotation speed after start-up. However, when the cooling water temperature and the oil temperature differ, it is inevitable that the actual engine rotation speed will temporarily deviate from the reference engine rotation speed, which poses a problem in terms of stable torque control.

[0008] Therefore, an object of the present invention is to accurately correct the friction torque even if there is a temperature difference between the cooling water temperature and the oil temperature. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides: An internal combustion engine; A water temperature acquisition means for acquiring a cooling water temperature of the internal combustion engine; an oil temperature acquisition means for acquiring an oil temperature of the internal combustion engine; a torque deriving means for deriving a friction torque of the internal combustion engine from a pre-stored torque map based on the cooling water temperature; a torque correction means for calculating a corrected friction torque by correcting the friction torque based on a difference between the cooling water temperature and the oil temperature; A control device for an internal combustion engine having the above features was constructed.

[0010] In this configuration, It is preferable that the torque correction means calculates the corrected friction torque by multiplying the friction torque by a correction coefficient, and monotonically increases the correction coefficient as a temperature difference obtained by subtracting the oil temperature from the cooling water temperature increases.

[0011] In this configuration, It is preferable that the correction coefficient is greater than 1 when the temperature difference is positive, is 1 when the temperature difference is 0, and is in the range of 0 or more and less than 1 when the temperature difference is negative.

[0012] In this configuration, The apparatus further includes a rotation speed acquisition means for acquiring a rotation speed of the internal combustion engine, It is preferable to change the magnitude of the correction coefficient for the temperature difference in accordance with the acquired rotation speed.

[0013] In this configuration, When it is determined that the warm-up of the internal combustion engine is complete, use of the torque correction means is stopped and the friction torque derived by the torque derivation means is applied to the control of the internal combustion engine, while when the internal combustion engine is stopped based on vehicle control after the warm-up is completed and then restarted, use of the torque correction means is resumed and the corrected friction torque is calculated and applied to the control of the internal combustion engine. Effect of the Invention

[0014] In this invention, the friction torque of an internal combustion engine derived based on the coolant temperature is corrected based on the difference between the coolant temperature and the oil temperature. Therefore, the friction torque can be accurately corrected even when there is a temperature difference between the coolant temperature and the oil temperature, for example, when the engine of a hybrid vehicle is restarted after being driven as an electric vehicle, or when the engine is cold started. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a block diagram showing an embodiment of a control device for an internal combustion engine according to the present invention; [Diagram 2] A diagram showing the relationship between water temperature and friction torque [Diagram 3] A diagram showing the relationship between temperature difference and correction coefficient [Figure 4] A diagram showing the change in coolant temperature and oil temperature when switching from motor driving to engine driving. [Diagram 5] A diagram showing the changes in coolant temperature and oil temperature during cold start [Figure 6] A diagram showing changes in coolant temperature and oil temperature when the engine is started DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] An embodiment of a control device for an internal combustion engine (hereinafter, abbreviated as the control device) according to the present invention is shown in schematic form in Fig. 1. This control device has as its main components an internal combustion engine 1 (hereinafter, referred to as the engine, and given the same reference numeral as the internal combustion engine 1), a water temperature acquisition means 2, an oil temperature acquisition means 3, a torque derivation means 4, and a torque correction means 5.

[0017] This control device controls the combustion torque P obtained by the combustion in the engine 1 as shown in the following formula (2). i From, warm-up friction torque P fSTD , and the compensation friction torque P fOT By dividing the above, the actual output torque P of engine 1 is OPT The friction torque during warm-up P fSTD is the torque mainly caused by pump loss torque and mechanical loss, and the compensation friction torque P fOT is a correction term caused by changes in viscosity of the lubricating oil based on the oil temperature and the expansion of metals, etc. P OPT =P i -(P fSTD +P fOT ) (2)

[0018] The engine 1 is provided with a rotation speed acquisition means 6 for acquiring the rotation speed of the engine. The following description is based on the assumption that the vehicle is a hybrid vehicle equipped with a gasoline engine, and in particular a plug-in hybrid vehicle (PHEV) that allows external charging or external power supply. Note that this control device is not limited to hybrid vehicles, and can be widely applied to vehicles equipped with an internal combustion engine, such as general gasoline engine vehicles and diesel engine vehicles.

[0019] The water temperature acquisition means 2 is a means for acquiring the temperature of the cooling water that cools the engine 1, and in this embodiment, a water thermometer is used.

[0020] The oil temperature acquisition means 3 is a means for acquiring the temperature of the lubricating oil that lubricates the engine 1, and in this embodiment, an oil temperature gauge is employed.

[0021] The torque calculation means 4 calculates the friction torque P of the engine 1 from a torque map stored in advance in a control unit (not shown) of the vehicle based on the coolant temperature. fOT-BASE This torque map is calculated based on the relationship between the cooling water temperature, engine speed, and friction torque P fOT-BASE This is a map of the relationship between the friction torque P fOT-BASE As shown in Fig. 2, the lower the coolant temperature (i.e., oil temperature), the larger the torque, and the higher the coolant temperature, the smaller (approaching 0). This torque map is based on the premise that the coolant temperature and the oil temperature are almost the same.

[0022] The torque correction means 5 calculates the friction torque P based on the difference between the cooling water temperature and the oil temperature. fOT-BASE Corrected friction torque P fOT This correction friction torque P fOT is the friction torque P fOT-BASE Correction factor K OT That is, it is calculated by the following formula (3). P fOT =K OT ×P fOT-BASE (3)

[0023] From the above equations (2) and (3), the effective output torque P of engine 1 is OPT can be expressed as the following equation (4). P OPT =P i -(P fSTD +K OT ×P fOT-BASE ) (4)

[0024] Correction factor K OT As shown in Fig. 3, is determined so as to monotonically increase as the temperature difference ΔT obtained by subtracting the oil temperature from the cooling water temperature increases. This is because the larger the temperature difference ΔT, the greater the degree of decrease in the oil temperature compared to the cooling water temperature. fOT-BASE Since the actual friction torque is larger than the friction torque P derived based on the coolant temperature,fOT-BASE This is because a large correction corresponding to the difference between the friction torque and the actual friction torque is required.

[0025] In addition, the monotonically increasing here means that the correction coefficient K increases as the temperature difference ΔT increases. OT This is a broad concept that means that the correction coefficient K OT Not only does the correction coefficient K always increase, but also the correction coefficient K increases when the temperature difference ΔT increases. OT This also includes the case where the temperature difference is constant within a certain range.

[0026] In this embodiment, the correction coefficient K OT is an exponential value that is greater than 1 when the temperature difference ΔT is positive (the cooling water temperature is higher than the oil temperature), is 1 when the temperature difference ΔT is 0 (the cooling water temperature and the oil temperature are equal), and is in the range of 0 to less than 1 when the temperature difference ΔT is negative (the cooling water temperature is lower than the oil temperature). OT The relationship is an example, and the correction coefficient K is proportional to the magnitude of the temperature difference ΔT in the positive range. OT In addition, when the temperature difference ΔT is in the negative range, the correction coefficient K OT Alternatively, it may be set to a constant value in the range of 0 or more and less than 1.

[0027] An application example of this control device will be described. In a hybrid vehicle equipped with an engine 1 and a motor (not shown), engine running driven by the engine 1 and motor running driven by the motor are switched appropriately based on the vehicle's running conditions (accelerator depression amount, load, vehicle speed, etc.). During engine running, both the coolant temperature and oil temperature are high. Here, when switching from engine running to motor running, as shown in FIG. 4 for example, the coolant temperature drops significantly, while the lubricating oil temperature is more difficult to drop than the coolant temperature, and the warm-up temperature T W It remains close to.

[0028] Here, when the vehicle is switched from motor running to engine running, the torque deriving means 4 derives the friction torque P of the engine 1 from a torque map stored in advance based on the cooling water temperature acquired by the water temperature acquisition means 2. fOT-BASE (P shown by the dashed line in Figure 4) fOT However, the friction torque P fOT-BASE is based on the assumption that the cooling water temperature and the oil temperature are almost the same. When the cooling water temperature is lower than the oil temperature, such as after switching from motor driving to engine driving, excessive friction torque P fOT-BASE This excessive friction torque P fOT-BASE If no correction is made to the output torque P OPT In order to obtain this excessive friction torque P fOT-BASE The corresponding combustion torque P i will be output.

[0029] In this control device, the torque correction means 5 corrects the friction torque P fOT-BASE Corrected friction torque P based on the temperature difference ΔT fOT By calculating the above formula (3), the excessive friction torque P derived due to the cooling water temperature being lower than the oil temperature acquired by the oil temperature acquisition means 3 can be calculated. fOT-BASE Specifically, when the cooling water temperature is lower than the oil temperature, the temperature difference ΔT is a negative value, and the temperature difference ΔT and the correction coefficient K OT Based on the relationship, the correction factor K OT is a value between 0 and 1. The derived friction torque P fOT-BASE This correction coefficient K OT Multiplying by this gives the original friction torque P fOT-BASE (See the graph shown by the dashed line in Fig. 4.) fOT is calculated (P shown by the solid line in Figure 4). fOT The corrected friction torque P fOTBy applying this to the control of engine 1, the output torque P OPT can be generated.

[0030] In addition, when the engine 1 is started in a cold state (especially when the engine is started in a sub-freezing environment), the cooling water temperature is increased to the warm-up temperature T W The oil temperature tends to rise relatively quickly, whereas the oil temperature tends to rise slower than the cooling water temperature. Here, based on the cooling water temperature acquired by the water temperature acquisition means 2, the torque derivation means 4 calculates the friction torque P fOT-BASE When the friction torque P fOT-BASE is the friction torque P that is too small for the actual oil temperature (low oil temperature) fOT-BASE This excessively small friction torque P fOT-BASE If no correction is made to the above, the engine 1 may experience problems such as misfire.

[0031] When the coolant temperature is higher than the oil temperature, the temperature difference ΔT is a positive value. OT Based on the relationship, the correction factor K OT is greater than 1. The derived friction torque P fOT-BASE This correction coefficient K OT Multiplying by this gives the original friction torque P fOT-BASE Correction friction torque P fOT The corrected friction torque P fOT By applying this to the control of the engine 1, malfunctions such as misfires in the engine 1 can be prevented.

[0032] In this way, regardless of whether the temperature difference ΔT is positive or negative, the corrected friction torque P fOT Therefore, for example, in a hybrid vehicle, it is not necessary to switch the torque map when switching from motor driving to engine driving and when starting the engine in a cold state.fOT This can reduce the complexity of the control involved in the calculation of

[0033] This correction factor K OT The magnitude of the correction coefficient K for the temperature difference ΔT can be changed according to the rotation speed of the engine 1 acquired by the rotation speed acquisition means 6. Specifically, as shown by the arrow in FIG. 3, when the engine 1 is rotating at high speed, OT (see arrow HR), and when engine 1 is running at low speed, the correction coefficient K OT The size of can be increased (see arrows LR).

[0034] When engine 1 is running at low speed, the oil temperature does not rise easily, and the compensation friction torque P fOT Since we want to set the correction coefficient K for the temperature difference ΔT to a large value, OT However, when the engine 1 is rotating at high speed, the oil temperature is relatively likely to rise (for example, exceed 100°C), and the correction coefficient K OT When is large, the compensation friction torque P fOT In this way, the correction coefficient K for the temperature difference ΔT depending on the rotation speed OT By changing the magnitude of the compensation friction torque P, it is possible to obtain an appropriate magnitude over the entire range from low to high revolutions. fOT can be calculated.

[0035] In addition, in this control device, when it is determined that the warm-up of the engine 1 is completed (for example, when the oil temperature exceeds the cooling water temperature), the use of the torque correction means 5 is stopped, and the friction torque P derived by the torque derivation means 4 is fOT-BASE is applied to the control of the engine 1, and when the engine 1 is stopped based on the control of the vehicle after the warm-up is completed (for example, when the engine runs are switched to the motor runs, or when the engine is stopped during the engine runs), and then restarted, the use of the torque correction means 5 is resumed, and the friction torque P derived by the torque derivation means 4 is fOT-BASE Corrected friction torque P fOTcan be calculated and applied to the control of the engine 1.

[0036] When engine 1 has finished warming up, the oil temperature is higher than the cooling water temperature, so the compensation friction torque P fOT There is little need to calculate the corrected friction torque P. Therefore, by stopping the use of the torque correction means 5 at this timing, the load on the control device can be reduced. Furthermore, when the engine 1 is stopped and then restarted based on the control of the vehicle after the warm-up is completed, the cooling water temperature often drops while the oil temperature is high, as shown in FIG. 4. Therefore, by restarting the use of the torque correction means 5 at this timing, it is possible to calculate an appropriate corrected friction torque P corresponding to the high oil temperature. fOT can be calculated.

[0037] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. Therefore, the scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. For example, although the present embodiment has been described taking an internal combustion engine mounted on a vehicle as an example, the present invention may be applied to internal combustion engines of ships, aircraft, etc. [Explanation of symbols]

[0038] 1. Internal combustion engine 2 Water temperature acquisition means 3 Oil temperature acquisition means 4 Torque derivation method 5. Torque correction means 6. Method of acquiring rotation speed P fOT-BASE Friction Torque P fOT Compensation Friction Torque K OT Correction factor ΔT temperature difference

Claims

1. An internal combustion engine; A water temperature acquisition means for acquiring a cooling water temperature of the internal combustion engine; an oil temperature acquisition means for acquiring an oil temperature of the internal combustion engine; a torque deriving means for deriving a friction torque of the internal combustion engine from a pre-stored torque map based on the cooling water temperature; a torque correction means for calculating a corrected friction torque by correcting the friction torque based on a difference between the cooling water temperature and the oil temperature; having the torque correction means calculates the corrected friction torque by multiplying the friction torque by a correction coefficient, and monotonically increases the correction coefficient as a temperature difference obtained by subtracting the oil temperature from the cooling water temperature increases; A control device for an internal combustion engine that reduces an increase amount of the correction coefficient when the temperature difference becomes large, when the operating state of the internal combustion engine is a state in which an oil temperature is likely to rise.

2. The correction coefficient is greater than 1 when the temperature difference is positive, is 1 when the temperature difference is 0, and is in the range of 0 to less than 1 when the temperature difference is negative. The control device for an internal combustion engine according to claim 1.

3. When it is determined that the warm-up of the internal combustion engine is completed, the use of the torque correction means is stopped and the friction torque derived by the torque derivation means is applied to the control of the internal combustion engine, while when the internal combustion engine is stopped based on the control of the vehicle after the warm-up is completed and then restarted, the use of the torque correction means is resumed and the corrected friction torque is calculated and applied to the control of the internal combustion engine. The control device for an internal combustion engine according to claim 1 or 2.

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