Method and apparatus for estimating temperature of exhaust system component of internal combustion engine

Abstract

To accurately grasp the exhaust system part temperature of each bank of a V-type internal combustion engine, and to perform accurate protection control at high temperature.SOLUTION: The temperature estimation device includes turbine inlet exhaust gas temperature calculation models 21R and 21L for estimating the inlet exhaust gas temperature of the turbine of each bank, turbine expansion calculation models 22R and 22L for estimating the exhaust gas temperature after expansion in the turbine, turbine outlet pipe heat dissipation calculation models 23R and 23L for estimating the exhaust gas temperature at the inlet of the pre-catalytic device of each bank, and catalytic temperature calculation models 24R and 24L for estimating the temperature of each pre-catalytic device. A turbine protection fuel increase / torque cut operation part 25 executes protection control when the turbine inlet exhaust temperature of one bank becomes a threshold temperature or higher, and a catalyst protection fuel increase / torque cut operation part 26 executes protection control when the catalyst temperature of one bank becomes the threshold temperature or higher.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an improvement in a technique for estimating the temperature of exhaust system components for protecting the exhaust system components of an internal combustion engine. [Background technology]

[0002] BACKGROUND ART In order to protect exhaust system components such as exhaust turbines and exhaust purification catalysts provided in the exhaust system of an internal combustion engine from excessive thermal load, a technique for estimating the temperature of exhaust system components from the operating conditions of the internal combustion engine is known.

[0003] Patent Document 1 discloses that in an internal combustion engine that can switch between intake manifold injection and in-cylinder injection, the temperature at which a certain exhaust system part will ultimately converge is estimated by switching between two characteristic convergence temperature maps depending on whether the injection is intake manifold injection or in-cylinder injection. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-37921 Summary of the Invention [Problem to be solved by the invention]

[0005] Internal combustion engines with a pair of banks, such as V-type internal combustion engines and horizontally opposed internal combustion engines, are known. In such internal combustion engines, if the temperature of exhaust system components in one bank is considered to represent the temperatures of exhaust system components in both banks, it is not always possible to accurately determine the temperature of the exhaust system components in each bank. Therefore, for example, torque limitation to protect exhaust system components such as exhaust purification catalysts must be implemented with an excessively large margin, which is undesirable. Patent Document 1 does not disclose any information regarding temperature estimation of exhaust system components in such an internal combustion engine with a pair of banks. [Means for solving the problem]

[0006] The present invention provides an exhaust system component temperature estimation method for an internal combustion engine having a pair of banks, which estimates the temperatures of exhaust system components of each bank based on the engine speed and load of the internal combustion engine, comprising: Prepare a temperature estimation model for each bank that corresponds to the exhaust system layout of each bank. The temperature of the exhaust system components of each bank is estimated using each temperature estimation model. [Effects of the Invention]

[0007] According to this invention, the temperature of the exhaust system components of each bank is estimated using a temperature estimation model corresponding to the exhaust system layout of each bank, thereby improving the accuracy of the temperature estimation. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an explanatory diagram showing the configuration of an intake and exhaust system of a V-type internal combustion engine according to an embodiment; [Figure 2] FIG. 1 is a functional block diagram of a temperature estimation device according to an embodiment. [Figure 3] 4 is a flowchart showing a processing flow of turbine protection control according to an embodiment. [Figure 4] 4 is a time chart showing the operation of protection control according to an embodiment; [Figure 5] 4 is a time chart showing the operation of the catalyst at low temperature in one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment in which the present invention is applied to a V6 internal combustion engine 1 will be described in detail below with reference to the drawings. FIG. 1 shows the configuration of the intake and exhaust systems of the internal combustion engine 1. The internal combustion engine 1 of this embodiment is a four-stroke spark-ignition internal combustion engine (a so-called gasoline engine) and has a right bank 2R and a left bank 2L, each of which includes three cylinders. In the following description, the symbol "R" indicates a component of the right bank 2R, and the symbol "L" indicates a component of the left bank 2L. Each of the banks 2R, 2L is equipped with a turbocharger 3R, 3L, respectively.

[0010] The intake passage 4 of the internal combustion engine 1 branches into separate intake passages 4R, 4L for each bank 2R, 2L downstream of an air cleaner 5 and an air flow meter (e.g., a hot-wire air flow meter) 6. The separate intake passages 4R, 4L pass through compressors 7R, 7L of turbochargers 3R, 3L and merge into each other at a water-cooled intercooler 8. In the illustrated example, intake air is introduced into both banks 2R, 2L via a single electronically controlled throttle valve 9. Alternatively, a throttle valve may be provided for each bank 2R, 2L.

[0011] Meanwhile, bank-specific exhaust passages 11R, 11L connected to the exhaust manifolds (not shown) of the banks 2R, 2L are equipped with turbines 12R, 12L of turbochargers 3R, 3L, respectively, and pre-catalytic devices 13R, 13L each consisting of a three-way catalyst are provided at the outlets of these turbines 12R, 12L. The bank-specific exhaust passages 11R, 11L of the banks 2R, 2L merge with each other at a junction 14 downstream of the pre-catalytic devices 13R, 13L. The exhaust passage 11 downstream of the junction 14 is open to the outside via a silencer 15.

[0012] In the bank-specific exhaust passages 11R, 11L, upstream air-fuel ratio sensors 16R, 16L are disposed upstream of the respective turbines 12R, 12L, and downstream O2 sensors 17R, 17L are disposed downstream of the respective pre-catalyst devices 13R, 13L. In the internal combustion engine 1 of one embodiment, air-fuel ratio control is performed for each bank based on the detection signals of these upstream air-fuel ratio sensors 16R, 16L and downstream O2 sensors 17R, 17L. Each turbine 12R, 12L is also provided with a wastegate valve 18R, 18L that bypasses a portion of the exhaust gas without passing through the turbine rotor for boost pressure control.

[0013] The internal combustion engine 1 is controlled by an engine controller 19. The engine controller 19 receives detection signals from the air flow meter 6 that detects the intake air amount, the upstream air-fuel ratio sensors 16R, 16L and downstream O2 sensors 17R, 17L that detect the exhaust air-fuel ratio, as well as sensors (not shown) such as a crank angle sensor that detects the engine rotation speed, a water temperature sensor that detects the coolant temperature, a boost pressure sensor that detects the boost pressure, and an atmospheric pressure sensor that detects the atmospheric pressure. Based on these detection signals and various signals (e.g., an accelerator position signal that indicates the amount of depression of the accelerator pedal, vehicle speed, etc.) input via other controllers, the engine controller 19 optimally controls the fuel injection amount and injection timing, ignition timing, the opening of the throttle valve 9, the boost pressure, the EGR rate of an exhaust gas recirculation device (not shown), etc.

[0014] The engine controller 19 also estimates the temperatures of exhaust system components (for example, the turbines 12R, 12L and the pre-catalyst devices 13R, 13L) based on the rotation speed and load of the internal combustion engine 1, and performs protective control (exhaust temperature reduction control) to prevent these exhaust system components from becoming excessively hot. One example of protective control is suppressing or reducing the exhaust temperature by increasing the fuel injection amount, i.e., enriching the air-fuel ratio, and another example is limiting the torque of the internal combustion engine 1 (for example, reducing the opening of the throttle valve 9 or reducing the boost pressure via the wastegate valves 18R, 18L).

[0015] In the V-type internal combustion engine 1 having the two banks 2R and 2L, the exhaust system layout of each bank 2R and 2L, including the turbochargers 3R and 3L and the pre-catalytic devices 13R and 13L, is generally configured to be approximately symmetrical. However, due to the offset of the cylinder rows of each bank 2R and 2L and the arrangement of the mufflers 15, the exhaust system layouts of the two banks 2R and 2L are different in strict terms. For example, the exhaust pipe lengths from the exhaust ports of each cylinder to the turbines 12R and 12L and the exhaust pipe lengths from the pre-catalytic devices 13R and 13L to the junction 14 tend to be different between the two banks 2R and 2L. Therefore, in one embodiment, a temperature estimation model corresponding to the exhaust system layout of each bank 2R and 2L is prepared, and the temperature of the exhaust system components of each bank 2R and 2L is estimated using each temperature estimation model.

[0016] Fig. 2 shows a functional block diagram of a temperature estimation device according to an embodiment. As shown in Fig. 2, the temperature estimation device according to an embodiment includes, for each of two banks 2R and 2L, turbine inlet exhaust gas temperature calculation models 21R and 21L that estimate the exhaust gas temperature at the inlets of the turbines 12R and 12L, turbine expansion calculation models 22R and 22L that estimate the exhaust gas temperature after expansion in the turbines 12R and 12L based on the exhaust gas temperatures at the inlets of the turbines 12R and 12L, turbine outlet piping heat release calculation models 23R and 23L that estimate the exhaust gas temperature at the inlets of the pre-catalytic devices 13R and 13L of the exhaust gas flowing from the turbines 12R and 12L to the pre-catalytic devices 13R and 13L based on the exhaust gas temperatures after expansion, and catalyst temperature calculation models 24R and 24L that estimate the temperature of the pre-catalytic devices 13R and 13L based on the exhaust gas temperatures at the inlets of the pre-catalytic devices 13R and 13L. In order to execute the above-mentioned protection control, the system is provided with a turbine protection fuel increase / torque cut calculation unit 25 and a catalyst protection fuel increase / torque cut calculation unit 26. In a second embodiment applied to a power generating internal combustion engine of a series hybrid vehicle (to be described later), the system is further provided with a catalyst low temperature engine start request control unit 27.

[0017] The turbine inlet exhaust gas temperature calculation models 21R, 21L receive the rotation speed and load of the internal combustion engine 1 as inputs, and output the exhaust gas temperature at the inlet of the turbine 12R, 12L of each bank 2R, 2L. In one embodiment, the charging efficiency is used as a parameter indicating the load of the internal combustion engine 1. The charging efficiency is basically determined by the relationship between the intake air mass detected by the air flow meter 6 and the cylinder volume, and corrections are made for the exhaust gas recirculation rate, transient response delays, etc. If the valve timing of the intake and exhaust valves is adjustable, corrections based on this valve timing can also be made.

[0018] The right-bank turbine inlet exhaust temperature calculation model 21R for the right bank 2R is designed based on the exhaust system layout in the right bank 2R, and the left-bank turbine inlet exhaust temperature calculation model 21L for the left bank 2L is designed based on the exhaust system layout in the left bank 2L. This is also true for the subsequent turbine expansion calculation models 22R, 22L, turbine outlet piping heat release calculation models 23R, 23L, and catalyst temperature calculation models 24R, 24L.

[0019] The turbine expansion calculation models 22R, 22L take as input the exhaust gas temperatures at the inlets of the turbines 12R, 12L input from the turbine inlet exhaust gas temperature calculation models 21R, 21L, as well as the rotation speeds of the turbochargers 3R, 3L, the turbine pressure ratio, the amount of gas passing through the turbine, and the turbine efficiency, and output the exhaust gas temperatures after expansion in the turbines 12R, 12L.

[0020] The turbine outlet pipe heat dissipation calculation models 23R, 23L take as input the exhaust gas temperature after expansion input from the turbine expansion calculation models 22R, 22L, as well as the temperature inside the engine room, the air flow velocity flowing inside the engine room, the mass flow rate of gas passing through the turbine outlet pipe, and the thermal conductivity of the turbine outlet pipe, and output the turbine outlet exhaust gas temperature that takes into account the heat dissipation due to heat transfer to the turbine outlet pipe, i.e., the exhaust gas temperature at the inlet of the pre-catalyst device 13R, 13L. The temperature inside the engine room is estimated, for example, from the intake air temperature and coolant temperature of the internal combustion engine 1 and the vehicle speed. The air flow velocity flowing inside the engine room is indicated by the vehicle speed.

[0021] The catalyst temperature calculation models 24R, 24L take as input the exhaust gas temperature at the inlet of the pre-catalyst devices 13R, 13L input from the turbine outlet piping heat dissipation calculation models 23R, 23L, as well as the gas mass flow rate passing through the pre-catalyst devices 13R, 13L, the gas pressure at the inlet of the pre-catalyst devices 13R, 13L, the rotational speed of the internal combustion engine 1, the charging efficiency, and the air-fuel ratio, and output the temperature of the pre-catalyst devices 13R, 13L.

[0022] In this manner, in the above embodiment, the inlet exhaust gas temperatures of the turbines 12R, 12L and the temperatures of the pre-catalyst devices 13R, 13L of each bank 2R, 2L are determined for each bank using a temperature estimation model designed based on the exhaust system layout of each bank 2R, 2L, thereby improving the estimation accuracy.

[0023] The turbine protection fuel increase / torque cut calculation unit 25 executes the aforementioned protective control to protect the turbines 12R, 12L when the inlet exhaust gas temperature of the turbines 12R, 12L in either bank 2R, 2L becomes excessively high. This protective control may be executed simultaneously for both banks 2R, 2L, or may be executed only for the corresponding bank 2R, 2L. Similarly, the catalyst protection fuel increase / torque cut calculation unit 26 executes the aforementioned protective control to protect the pre-catalyst devices 13R, 13L when the temperature of the pre-catalyst devices 13R, 13L in either bank 2R, 2L becomes excessively high. This protective control may be executed simultaneously for both banks 2R, 2L, or may be executed only for the corresponding bank 2R, 2L. For example, the fuel injection amount can be increased and corrected only for one bank.

[0024] In the above embodiment, the inlet exhaust gas temperatures of the turbines 12R, 12L and the temperatures of the pre-catalyst devices 13R, 13L, which are prerequisites for initiating protective control, are estimated for each bank with high accuracy, eliminating the need to set the threshold temperature for initiating protective control with an excessive margin of error. In other words, unnecessary initiation of protective control can be avoided.

[0025] 3 is a flowchart showing the processing flow of turbine protection control in one embodiment. In step 1, as described above, the inlet exhaust gas temperature of the turbines 12R, 12L is calculated for each bank 2R, 2L based on the rotational speed and charging efficiency of the internal combustion engine 1. In step 2, the inlet exhaust gas temperature of each turbine 12R, 12L is compared with a predetermined threshold temperature for protecting the turbines 12R, 12L to determine whether it is equal to or higher than the threshold temperature. If the temperatures of both banks 2R, 2L are below the threshold temperature, the process proceeds to step 3, and normal operation continues.

[0026] If the temperature of either of the two banks 2R, 2L is above the threshold temperature, the process proceeds to step 4, where the amount of fuel is increased. This fuel increase is performed little by little so that the air-fuel ratio gradually becomes richer while the temperature is above the threshold temperature. In step 5, the limit of the increase rate under the operating conditions at that time is determined, and in step 6, it is determined whether the increase rate has reached its limit. If the increase rate has not reached its limit, the process proceeds to step 7, where operation with the fuel increase continues. If the increase rate has reached its limit, the process proceeds to step 8, where torque is cut to protect the turbines 12R, 12L and operation continues. Note that, as mentioned above, the amount of fuel can also be increased for each individual bank 2R, 2L.

[0027] 3 shows only the turbine protection control, the same applies to the catalyst protection of the pre-catalyst devices 13R, 13L. Note that the threshold temperature for protecting the pre-catalyst devices 13R, 13L may be different from the threshold temperature for protecting the turbines 12R, 12L.

[0028] FIG. 4 is a time chart showing the operation of the protection control according to one embodiment. From top to bottom, the chart shows (a) the rotational speed of the internal combustion engine 1, (b) the torque of the internal combustion engine 1, (c) the estimated turbine inlet exhaust gas temperature, and (d) the estimated catalyst temperature. Column (c) shows the estimated inlet exhaust gas temperatures of the turbines 12R and 12L of the banks 2R and 2L, respectively, output by the turbine inlet exhaust gas temperature calculation models 21R and 21L. These estimated inlet exhaust gas temperatures are compared with a predetermined turbine threshold temperature #1. Similarly, column (d) shows the estimated catalyst temperatures of the pre-catalyst devices 13R and 13L, respectively, output by the catalyst temperature calculation models 24R and 24L. These estimated catalyst temperatures are compared with a predetermined catalyst threshold temperature #2.

[0029] In the example of FIG. 4, at time t1, the estimated inlet exhaust gas temperature of the turbine 12R of the right bank 2R reaches the turbine threshold temperature #1, so that protective control (exhaust gas temperature reduction control) is initiated and torque is suppressed.

[0030] Next, a catalyst warm-up operation in a second embodiment will be described in which the above-described internal combustion engine 1 is used as a power-generating internal combustion engine of a series hybrid vehicle. A series hybrid vehicle is configured to include a power-generating motor generator that operates mainly as a generator, an internal combustion engine that drives the power-generating motor generator in response to a power demand, a traction motor generator that operates mainly as a motor to drive the drive wheels, and a battery that stores the generated power. In such a series hybrid vehicle, the internal combustion engine is operated in response to a power demand, so the internal combustion engine is stopped while the battery's SOC is high and the required driving force can be met by the battery output.

[0031] If the internal combustion engine is stopped for a long time and the temperature of the pre-catalyst devices 13R, 13L drops, the next time the internal combustion engine is started, the catalyst may not be able to purify the exhaust gas sufficiently. Therefore, the internal combustion engine is started when the temperature of the pre-catalyst devices 13R, 13L falls below a certain threshold temperature (start-request threshold temperature #3).

[0032] 2, the engine controller 19 further includes a low-temperature catalyst engine start request control unit 27 to which the estimated catalyst temperatures of the pre-catalyst devices 13R, 13L output by the catalyst temperature calculation models 24R, 24L, respectively, are input. The low-temperature catalyst engine start request control unit 27 commands the internal combustion engine 1 to start when the temperature of the pre-catalyst devices 13R, 13L in either bank 2R, 2L falls below a start request threshold temperature #3 while the internal combustion engine 1 is stopped.

[0033] FIG. 5 is a time chart showing the operation of an engine start request in one embodiment. As with FIG. 4, from top to bottom, the chart shows (a) the rotational speed of the internal combustion engine 1, (b) the torque of the internal combustion engine 1, (c) the estimated turbine inlet exhaust gas temperature, and (d) the estimated catalyst temperature. Column (c) shows the estimated inlet exhaust gas temperatures of the turbines 12R and 12L of the banks 2R and 2L output by the turbine inlet exhaust gas temperature calculation models 21R and 21R, respectively. Column (d) shows the estimated catalyst temperatures of the pre-catalyst devices 13R and 13L output by the catalyst temperature calculation models 24R and 24L, respectively. These estimated catalyst temperatures are compared with a predetermined start request threshold temperature #3 while the internal combustion engine 1 is stopped.

[0034] In the example of FIG. 5, the temperature of the pre-catalyst device 13L of the left bank 2L falls below the start-up request threshold temperature #3 at time t11, and the internal combustion engine 1 is started.

[0035] In the second embodiment, both pre-catalyst devices 13R, 13L can be reliably maintained at the start-request threshold temperature #3 or higher, so that deterioration of exhaust purification performance when the internal combustion engine 1 is restarted can be avoided.

[0036] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible. For example, the present invention is not limited to turbocharged internal combustion engines, but may also be applied to non-supercharged internal combustion engines that do not have a turbocharger. Furthermore, the exhaust system components that are the subject of temperature estimation are not limited to the turbine and pre-catalyst device described above, and may be any component. [Explanation of symbols]

[0037] 1...Internal combustion engine 2R...Right bank 2L...Left bank 3R, 3L...Turbocharger 11R, 11L...separate bank exhaust passages 12R, 12L...Turbines 13R, 13L...Pre-catalyst device 19...Engine controller 21R, 21L...Turbine inlet exhaust temperature calculation model 22R, 22L...Turbine expansion calculation model 23R, 23L...Turbine outlet piping heat dissipation calculation model 24R, 24L... Catalyst temperature calculation model 25...Fuel increase and torque cut calculation unit for turbine protection 26...Fuel increase and torque cut calculation unit for catalyst protection 27... Engine start request control unit when catalyst is cold

Claims

1. 1. A method for estimating exhaust system component temperatures for an internal combustion engine having a pair of banks, the method estimating temperatures of exhaust system components for each bank based on engine speed and load of the internal combustion engine, Prepare a temperature estimation model for each bank that corresponds to the exhaust system layout of each bank. The temperature of each bank's exhaust system components is estimated using each temperature estimation model. A method for estimating the temperature of exhaust system components in an internal combustion engine.

2. Each bank is equipped with an exhaust purification catalyst, and the temperature of each exhaust purification catalyst is estimated. When the estimated temperature of either one of the exhaust purification catalysts reaches a catalyst protection temperature threshold, the exhaust temperature reduction control is started.

2. The method for estimating the temperature of an exhaust system component of an internal combustion engine according to claim 1.

3. Each bank is equipped with a turbocharger, and the exhaust temperature at each turbine inlet is estimated. when the estimated exhaust gas temperature at either turbine inlet reaches a turbine protection temperature threshold, the exhaust gas temperature reduction control is started; 2. The method for estimating the temperature of an exhaust system component of an internal combustion engine according to claim 1.

4. The internal combustion engine is an internal combustion engine for generating electricity in a series hybrid vehicle, Each bank is equipped with an exhaust purification catalyst, and the temperature of each exhaust purification catalyst is estimated. starting the internal combustion engine when the estimated temperature of either one of the exhaust purification catalysts falls below a start request threshold while the internal combustion engine is stopped; 2. The method for estimating the temperature of an exhaust system component of an internal combustion engine according to claim 1.

5. Each bank is equipped with an exhaust purification catalyst as an exhaust system component. The exhaust pipe length from the exhaust port to the exhaust purification catalyst is different on both banks.

2. The method for estimating the temperature of an exhaust system component of an internal combustion engine according to claim 1.

6. Each bank is provided with an exhaust purification catalyst as an exhaust system component, and the exhaust passages of both banks merge with each other downstream of the exhaust purification catalyst, The exhaust pipe lengths from the exhaust purification catalyst to the junction point are different on both banks.

2. The method for estimating the temperature of an exhaust system component of an internal combustion engine according to claim 1.

7. an internal combustion engine having a pair of banks; a controller for estimating the temperature of exhaust system components based on the rotational speed and load of the internal combustion engine; An exhaust system component temperature estimation device for an internal combustion engine, The above controller is Each bank has a temperature estimation model that corresponds to the exhaust system layout of that bank. The temperature of each bank's exhaust system components is estimated using each temperature estimation model. An exhaust system component temperature estimation device for internal combustion engines.

Images