JP5664483B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device that controls the amount of fuel injected into a cylinder of an internal combustion engine.

  2. Description of the Related Art Exhaust gas purification systems that purify various components in exhaust gas with an exhaust catalyst provided in an exhaust system of an internal combustion engine have been widely used. In such an exhaust purification system, the purification performance of the exhaust catalyst is controlled by changing the exhaust temperature. For example, in an automobile exhaust purification system equipped with a diesel engine or lean burn gasoline engine, a DPF (diesel particulate filter) for removing PM (particulate matter) in the exhaust gas is installed on the exhaust passage, and the exhaust temperature The control which burns and removes PM on the DPF is performed by raising. In addition, a technique related to catalyst regeneration control that temporarily raises the exhaust gas temperature in order to remove poisoning components such as sulfur compounds that can adhere to the catalyst surface is also known.

  As a typical method for raising the exhaust temperature in a direct injection engine, there are a method for raising the temperature of the exhaust gas in the cylinder and a method for raising the temperature of the exhaust gas discharged from the cylinder on the exhaust passage. In the former, fuel is injected at a timing slightly delayed from the main fuel injection that contributes to engine output (for example, during the expansion stroke). This type of fuel injection is called “combustion post injection” because it is post injection for generating combustion heat.

  On the other hand, the latter injects fuel for combustion on the catalyst at a timing later than the combustion post injection (for example, near the bottom dead center of the crank). This type of fuel injection is called “unburned post injection” because it is a post injection for supplying fuel to the exhaust system without burning it in the cylinder. These multi-stage injections are suitable for controlling the exhaust temperature flexibly while securing the engine output.

  By the way, unburned post-injected fuel tends to collide with the cylinder wall because it is injected when the piston is positioned below the cylinder. Even in the case of an engine in which a combustion chamber cavity is formed on the top surface of the piston, it is difficult to completely prevent fuel from flowing out of the cavity, and a part of the unburned post-injected fuel adheres to the wall surface. If the fuel adhesion amount increases, the fuel outflow amount to the crankcase side via the wall surface also increases. For this reason, in an engine that performs multi-stage injection of fuel as described above, oil dilution (dilution) is likely to proceed, and there is a concern that the lubrication performance of the engine may be reduced due to the diluted oil.

For such a problem, a technique for controlling the execution timing of multistage injection based on the temperature in the cylinder and the exhaust gas temperature has been proposed.
For example, Patent Document 1 describes a fuel injection control device that performs fuel post-injection in an expansion stroke, in which the injection timing is determined based on the temperature in the cylinder. In this technique, the temperature at which the post-injected fuel spray does not reach the cylinder wall surface is set as the target temperature, and the post-injection is performed when the estimated value of the in-cylinder temperature reaches the target temperature. Such control is supposed to prevent dilution of engine oil due to post injection.

  Note that Patent Document 2 relates to fuel injection control in which post injection is performed from the expansion stroke to the exhaust stroke, and the post injection timing based on the in-cylinder temperature at the exhaust valve opening timing and the exhaust temperature in the exhaust passage correlated therewith. Is set. According to this technique, post injection control excellent in raising the temperature of the catalyst can be performed by changing the injection timing according to the in-cylinder temperature or the exhaust gas temperature.

Japanese Patent No. 3358552 JP 2010-121505 A

  However, since the in-cylinder temperature of the engine fluctuates abruptly even during the period of one combustion cycle, there is a problem that oil dilution cannot be effectively prevented by conventional control. That is, the in-cylinder temperature is the gas temperature (gas temperature) in the cylinder, and increases rapidly during the compression stroke and decreases rapidly during the expansion stroke. In general, the in-cylinder temperature of an engine fluctuates periodically with a combustion cycle as a unit. Therefore, as described in Patent Documents 1 and 2, for example, even if the post injection timing is controlled based on the in-cylinder temperature, the in-cylinder temperature is greatly reduced immediately after the post injection is performed. Therefore, fuel adhesion to the cylinder wall surface cannot be properly controlled, and fuel outflow may not be suppressed.

  In addition, oil dilution accompanying post injection occurs through a process in which fuel is attached to the cylinder wall surface and then dragged toward the crankcase as the piston slides. That is, even if fuel adheres to the cylinder wall surface, oil dilution is less likely to occur if the amount of fuel dragged toward the crankcase can be reduced thereafter. Therefore, in order to suppress the oil dilution more efficiently, it is desired to control not only the amount of fuel adhering to the cylinder wall surface but also the amount of evaporation from the cylinder wall surface.

One of the objects of the present case was invented in view of the above problems, and is to suppress oil dilution accompanying multistage injection of an internal combustion engine.
The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

(1) A fuel injection control device for an internal combustion engine disclosed herein includes post injection means for performing post injection after main injection into a cylinder of the internal combustion engine, and estimation means for estimating a wall surface temperature of the cylinder. . Moreover, the control part which controls the fuel amount of the said post injection which the said post injection means implements based on the said wall surface temperature estimated by the said estimation means is provided.
The post-injection means performs combustion post-injection means for performing combustion post-injection for raising the temperature of the exhaust gas, and performs unburned post-injection for supplying unburned components to the exhaust system after the combustion post-injection. Unburned post injection means. The control means reduces the amount of fuel of the unburned post injection performed by the unburned post injection means according to the wall surface temperature.

  For example, when the wall surface temperature is lower than a predetermined temperature, the control means preferably reduces the fuel amount of the post injection. Or it is preferable to reduce the fuel amount of the post injection as the wall surface temperature is lower.

  (2) Further, it is preferable to limit the implementation of the post injection by the post injection means in a predetermined period in a combustion cycle in which the wall surface temperature is lower than a predetermined temperature. In other words, in this case, post-injection is restricted until the combustion cycle at which the wall surface temperature is equal to or higher than a predetermined temperature.

( 3 ) Moreover, it is preferable that the said control means increases the fuel quantity of the said combustion post injection which the said combustion post injection means implements according to the said wall surface temperature.
( 4 ) Moreover, it is preferable that the said post injection means maintains the timing at which the said post injection is implemented in each combustion cycle at a predetermined timing irrespective of the said wall surface temperature. That is, it is preferable that the crank angle at which the post injection is performed is controlled to be a constant value without being changed regardless of the wall surface temperature.

( 5 ) Further, it is preferable that the estimating means estimates the wall surface temperature based on an equilibrium temperature of the wall of the cylinder calculated from a gas temperature in the cylinder and a cooling water temperature of the internal combustion engine.
( 6 ) Moreover, it is preferable that the said estimation means estimates the said wall surface temperature by performing a delay process to the time-dependent fluctuation | variation of the said equilibrium temperature.
( 7 ) Moreover, it is preferable that the said estimation means calculates the average value of the gas temperature in the said cylinder for every combustion cycle as said gas temperature.

According to the disclosed fuel injection control device for an internal combustion engine, the amount of post-injected fuel adhering to the wall surface can be adjusted by controlling the fuel amount during post-injection performed after main injection according to the wall surface temperature. Thereby, irrespective of the fluctuation | variation of in-cylinder temperature, the outflow of a fuel into a crankcase can be suppressed and a state with low oil dilution can be maintained. Further, by decreasing the amount of fuel unburnt post injection according to the wall surface temperature, it is possible to reduce the adhesion amount to the cylinder wall surface of the fuel, suppresses effectively the oil diluted with increasing wall temperature be able to.

It is a figure showing the whole combustion injection control device of an internal-combustion engine concerning one embodiment. FIG. 2 is a graph for explaining multi-stage injection controlled by the fuel injection control device of FIG. 1, (a) exemplifies time-dependent fluctuations in cylinder pressure, and (b) shows a fuel control pulse signal and its name. This is just an example. It is a figure for demonstrating the wall surface temperature estimated with the fuel-injection control apparatus of FIG. 1, (a) is a graph which illustrates the equilibrium temperature distribution of gas temperature, wall surface temperature, and cooling water temperature, (b) is each temperature. (C) is a graph for demonstrating the long-term fluctuation | variation of each temperature. 2 is a flowchart illustrating a control procedure performed by the fuel injection control device of FIG. 1. (A)-(c) is a graph for demonstrating the control content by the fuel-injection control apparatus of FIG. 1, respectively.

  A fuel injection control device for an internal combustion engine will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment. In addition, each configuration of the following embodiment can be selected as necessary, or may be appropriately combined, and various modifications can be made without departing from the spirit of the embodiment.

[1. Device configuration]
The fuel injection control device of this embodiment is applied to a diesel engine 10 mounted on a vehicle. FIG. 1 shows one of a plurality of cylinders 11 (cylinders) provided in the engine 10. A piston 12 that reciprocates in the cylinder 11 is connected to a crankshaft 13 via a connecting rod.

  An injector 14 for fuel injection is provided on the upper portion of the cylinder 11. The tip of the injector 14 is provided so as to protrude into the in-cylinder space 11 a of the cylinder 11, and fuel is directly injected into each cylinder 11. A cavity 12a serving as a combustion chamber is formed on the top surface of the piston 12, and the injection direction of fuel supplied from the injector 14 is set in a direction toward the cavity 12a. A fuel pipe 14 a (delivery pipe) is connected to the base end side of the injector 14, and fuel pressurized by a feed pump (not shown) is supplied to each injector 14.

  An intake port and an exhaust port are provided on the ceiling surface of the cylinder 11, and an intake valve and an exhaust valve for opening and closing each of these ports are provided. An intake passage 16 and an exhaust passage 17 are connected to each of the intake port and the exhaust port, and a catalyst device 18 is interposed on the exhaust passage 17. The catalyst device 18 is a catalyst device for purifying exhaust gas, and includes, for example, a three-way catalyst, an oxidation catalyst, DPF, and the like.

  The fuel injection amount from the injector 14 and the injection timing thereof are controlled by the engine control device 1 described later. For example, a control pulse signal (injection signal) is transmitted from the engine control device 1 to each injector 14 and the injection port of each injector 14 is opened only during a period corresponding to the magnitude of the control pulse signal (drive pulse width). . Thus, the fuel injection amount becomes an amount corresponding to the magnitude of the control pulse signal, and the injection timing corresponds to the time when the control pulse signal is transmitted.

  Around the cylinder 11, a water jacket 15 serving as a cooling water flow path is provided. The cooling water here is a refrigerant for cooling the engine 10. The water jacket 15 is connected to a cooling water passage for guiding the cooling water to a heat exchanger such as a radiator (not shown). The cooling water circulates inside the water jacket 15, the radiator, and the cooling water passage.

  A partition wall that partitions the in-cylinder space 11a of the cylinder 11 and the water jacket 15 is hereinafter referred to as a cylinder wall 11b. The cylinder wall 11b is a wall body made of, for example, cast iron or aluminum alloy and formed integrally with the engine block. When a cylinder liner is mounted on the sliding surface with the piston 12, the wall body including the cylinder liner is defined as a cylinder wall 11b.

A temperature sensor 21 for detecting the temperature T _air (gas temperature) of the gas sucked into the cylinder 11 is provided in the intake passage 16. The type of gas to be detected here may be, for example, only fresh air (air), or in the case of the engine 10 equipped with an EGR (Exhaust Gas Recirculation) system, a mixed gas of fresh air and EGR gas. It may be. Further, a cooling water temperature sensor 22 for detecting a cooling water temperature T _wat (cooling water temperature) is provided in the water jacket 15. Information on the gas temperature T _air and the cooling water temperature T _wat detected by these sensors 21 and 22 is transmitted to the engine control device 1.

  In the vicinity of the crankshaft 13, a crank angle sensor 23 (crank angular speed detecting means) for detecting the rotational speed of the crankshaft 13 is provided. For example, a disc-shaped crank plate 13a having irregularities 13b formed on the outer edge portion is fixed to the crankshaft 13. On the other hand, the crank angle sensor 23 is fixed in the vicinity of the outer edge of the crank plate, detects the shape of the unevenness 13b of the crank plate 13a, and outputs a crank pulse signal. The crank pulse signal output here is transmitted to the engine control device 1.

  The cycle of the crank pulse signal output from the crank angle sensor 23 becomes shorter as the crankshaft 13 rotates faster, and the time density of the crank pulse signal depends on the actual engine speed Ne (engine speed) and the crankshaft 13. It corresponds to the angular velocity ω. Therefore, the crank angle sensor 23 can be said to be a means for detecting the engine speed Ne, the crank angle, and the angular velocity ω.

[2. Control configuration]
[2-1. Overview]
This vehicle is provided with an engine control device 1 (Engine Electronic Control Unit) as an electronic control device. The engine control device 1 is configured as, for example, an LSI device or a built-in electronic device in which a microprocessor, ROM, RAM, etc. are integrated, and other electronic control devices, temperature sensors 21, cooling water temperature sensors 22, It is connected to various sensors such as a crank angle sensor 23.

  The engine control device 1 is an electronic control device that controls a wide range of systems related to the engine 10 such as an ignition system, a fuel system, an intake / exhaust system, and a valve operating system. Specific control objects of the engine control device 1 include the fuel injection amount and injection timing from the injector 14, the valve lift and valve timings of the intake and exhaust valves, the intake amount (throttle valve opening), and the EGR amount ( EGR valve opening). In the present embodiment, the function of the engine control device 1 will be described by focusing on the fuel multi-stage injection control.

  As shown in FIG. 1, the engine control apparatus 1 includes a main injection unit 2, a post injection unit 3, a wall surface temperature estimation unit 4, and a control unit 5. Each of these functions may be realized by an electronic circuit (hardware), may be programmed as software, or some of these functions may be provided as hardware, and the other part may be software. It may be a thing.

[2-2. Main injection part]
The main injection unit 2 performs main injection that contributes to the engine output of the engine 10. Here, for example, as shown in FIGS. 2 (a) and 2 (b), fuel pre-injection, main injection, and after-injection, with the crank top dead center from the compression stroke to the expansion stroke (combustion stroke) of the combustion cycle sandwiched between them. The three main injections are controlled. The main injection unit 2 converts the fuel injection amount to be injected in these three types of main injections into control pulse signals of the injectors 14 and transmits the control pulse signals to the injectors 14 according to the timing of each main injection.

  The timing of the main injection with respect to the crank angle is fixed without being changed in each combustion cycle. The crank angle of the engine 10 is grasped based on the crank pulse signal detected by the crank angle sensor 23.

  The pre-injection is to inject fuel into the cylinder 11 prior to the main injection. For example, the injection in the compression stroke before the time when the piston 12 passes the crank top dead center corresponds to this. The fuel injected during pre-injection acts to shorten the ignition delay time.

  The main injection is an injection for obtaining an output required for the engine 10, and is injected into the cylinder 11 around the time when the piston 12 passes the crank top dead center. The magnitude of the output required for the engine 10 is set according to, for example, a driver's request, a request due to an external load, a driving state of the vehicle, and the like.

  The after injection is to inject fuel into the cylinder 11 after the main injection. For example, the injection in the expansion stroke after the time when the piston 12 passes the crank top dead center corresponds to this. The fuel injected at the time of after injection acts so that unburned components, PM, etc. in the fuel injected at the time of main injection are recombusted in the cylinder 11.

  Information on the main injection controlled by the main injection unit 2 is transmitted to the wall surface temperature estimation unit 4. In the present embodiment, information on the fuel injection amount, the injection timing, and the number of injection stages at the time of main injection is transmitted to the wall surface temperature estimation unit 4.

[2-3. Post injection part]
The post injection unit 3 (post injection means) performs post injection after the main injection controlled by the main injection unit 2 to raise the exhaust temperature or the exhaust system (that is, implements temperature rise control) ). Here, as shown in FIGS. 2A and 2B, two types of post-injection, combustion post-injection and unburned post-injection, are controlled after the after-injection in the expansion stroke of the combustion cycle.

  The post-injection unit 3 converts the fuel injection amount to be injected in these two types of post-injection into a control pulse signal for the injector 14 and transmits the control pulse signal to the injector 14 in accordance with the timing of each post-injection. Similarly to the main injection, the post-injection is also made constant without changing the timing with respect to the crank angle in each combustion cycle.

In FIG. 2 (b), the unburned post injection is performed within the expansion stroke, but the exhaust stroke (the time when the piston 12 passes the crank bottom dead center at a later timing) is shown. It may be implemented later).
The post injection unit 3 is provided with a combustion post injection unit 3a and an unburned post injection unit 3b so as to correspond to the above two types of post injection.

  The combustion post-injection unit 3a (combustion post-injection means) performs post-injection for raising the exhaust gas temperature. The fuel injected at the time of combustion post injection is burned in the cylinder 11 and acts to release thermal energy into the exhaust. In addition, since combustion post-injection may have a slight influence on engine output, adjustment of main injection by the main injection unit 2 may be required to obtain a desired output.

Here, the exhaust temperature is controlled in accordance with the state of the exhaust gas flowing through the exhaust passage 17 and the state of the catalyst device 18. For example, when the exhaust temperature estimated from the gas temperature T _air detected by the temperature sensor 21 immediately after the start of the engine 10 has not reached a predetermined temperature, or when the catalyst temperature of the catalyst device 18 has not reached the activation temperature, When the poisoning regeneration of the catalyst device 18 is requested, the combustion post injection unit 3a performs the combustion post injection to raise the exhaust gas temperature.

  The unburned post injection unit 3b (unburned post injection means) performs post injection for supplying unburned components to the exhaust passage 17 side. The fuel injected at the time of unburned post injection remains in the exhaust gas with little combustion in the cylinder 11. Therefore, unburned post injection has little effect on the exhaust temperature immediately after being discharged from the cylinder 11. Note that the effect of unburned post-injection on engine output is negligible.

  Here, the amount of unburned fuel in the exhaust (or the exhaust air / fuel ratio) is controlled in accordance with the state of the exhaust gas flowing through the exhaust passage 17 and the state of the catalyst device 18. For example, when it is necessary to supply unburned fuel to the catalyst device 18 or when poisoning regeneration of the catalyst device 18 is required, the unburned post injection unit 3b performs unburned post injection and exhausts. Increase unburned components in it.

  As described above, in the post-injection unit 3, combustion post injection and unburned post injection are controlled according to the operating state of the engine 10 and the state of the exhaust system. On the other hand, the wall surface temperature estimation unit 4 and the control unit 5 that will be described in detail below also perform control to limit post injection in the post injection unit 3 in accordance with the wall surface temperature of the cylinder 11. The post injection restriction according to the wall surface temperature is performed with priority over each control in the post injection unit 3. That is, when the determination by the wall surface temperature estimation unit 4 and the control unit 5 and the determination by the post injection unit 3 collide, the post injection is performed based on the determination by the wall surface temperature estimation unit 4 and the control unit 5.

  Information related to post injection controlled by the post injection unit 3 is also transmitted to the wall surface temperature estimation unit 4 in the same manner as information on main injection. In the present embodiment, information on the fuel injection amount, the injection timing, the number of injection stages, etc. at the time of post injection is transmitted to the wall surface temperature estimation unit 4.

[2-4. Wall temperature estimation unit]
The wall surface temperature estimation unit 4 (estimating means) estimates the wall surface temperature T _wal of the cylinder 11. Here, not the in-cylinder temperature (actual gas temperature) in the cylinder 11 but the temperature of the wall surface constituting the inner peripheral surface of the cylinder 11 is estimated. The in-cylinder temperature periodically fluctuates in units of combustion cycles, as indicated by broken lines in FIG. On the other hand, the actual wall surface temperature of the cylinder 11 varies slowly in time while being affected by variations in the in-cylinder temperature (actual gas temperature) and the cooling water temperature _Twat .

Therefore, the wall surface temperature estimation unit 4 calculates the wall surface temperature T _wal in consideration of the response delay of the system to the wall surface temperature estimated according to the heat transfer characteristics from the gas temperature T _gas and the cooling water temperature T _wat. . As a result of such calculation, the calculated value of the wall surface temperature T _wal exhibits a relatively stable behavior regardless of fluctuations in the in-cylinder temperature for each combustion cycle, as indicated by a thick solid line in FIG. The actual temperature state of the wall surface is reflected.

As means for accurately estimating the wall surface temperature T _wal , the wall surface temperature estimating unit 4 is provided with a gas temperature estimating unit 4a, an equilibrium temperature estimating unit 4b, and a delay filter processing unit 4c.
The gas temperature estimation unit 4a calculates the gas temperature T _gas in the cylinder 11. Here, the average value of the temperature of the in-cylinder space 11a for each combustion cycle (so-called in-cylinder temperature) is calculated as the gas temperature T _gas . That is, the gas temperature estimation unit 4a does not calculate the in-cylinder temperature that varies periodically, but calculates the gas temperature T _gas corresponding to the average of the in-cylinder temperature for each combustion cycle.

The gas temperature T _gas is calculated based on the amount of gas in the cylinder 11 (fresh air amount and EGR gas amount), gas specific heat, fuel injection amount, injection timing, number of injection stages, and the like. For example, assuming that the temperature of the gas introduced into the cylinder 11 in the intake stroke is the gas temperature T _air detected by the temperature sensor 21, the temperature when the gas is adiabatically compressed in the compression stroke is calculated. Is calculated by adding the temperature rise due to the amount of heat generated during combustion of the fuel to the gas temperature T _gas . Information of the gas temperature T _gas calculated here is transmitted to the equilibrium temperature estimation unit 4b.

The amount of heat generated during combustion is calculated based on the conversion ratio of combustion energy to heat. Further, the ratio of the thermal energy to the entire combustion energy of the fuel is calculated based on information on the fuel injection amount, the injection timing, and the number of injection stages transmitted from the main injection unit 2 and the post injection unit 3. For example, the gas temperature T _gas may be described as a function of the gas temperature T _air , the gas amount, the gas specific heat, the fuel injection amount, the injection timing, the number of injection stages, etc., and the gas temperature T _gas may be calculated using the function. Good. Alternatively, these relationships may be mapped in advance and stored in the gas temperature estimation unit 4a. Regarding the calculation of the gas temperature T _gas , the range of the in-cylinder temperature referred to when calculating the average value is not limited to one combustion cycle, for example, the average value of the in-cylinder temperature in two combustion cycles. The gas temperature T _gas may be used.

The equilibrium temperature estimation unit 4b estimates the representative equilibrium temperature T _eq2 of the cylinder wall 11b based on the gas temperature T _gas calculated by the gas temperature estimation unit 4a and the cooling water temperature T _wat detected by the cooling water temperature sensor 22. Is. Here, one side of the cylinder wall 11b is in contact with the gas in the gas temperature T _gas, and the temperature T _eq1 (equilibration at equilibrium when the other surface is in contact with the cooling water of the cooling water temperature T _wat Temperature) is estimated, and the representative value is calculated as the representative equilibrium temperature T _eq2 .

The distribution of the equilibrium temperature T _eq1 of the cylinder wall 11b includes, for example, the gas temperature T _gas , the heat transfer coefficient from the _gas , the heat conductivity inside the cylinder wall 11b, the cooling water temperature T _wat , the heat transfer coefficient for the cooling water, etc. Calculated based on _Further , the distribution of the equilibrium temperature T _eq1 may be calculated in consideration of information such as the engine speed of the engine 10, the gas flow rate in the in-cylinder space 11a, and the cooling water flow rate. As a simpler method, the relationship between the various parameters described above may be previously mapped and stored in the equilibrium temperature estimation unit 4b.

As shown in FIG. _3A , the equilibrium temperature T _eq1 has a distribution that changes with a constant gradient in the thickness direction of the cylinder wall 11b. Therefore, the representative equilibrium temperature T _eq2 may be set between the temperature on the cylinder space 11a side and the temperature on the cooling water side. For example, the average value of the equilibrium temperature T _eq1 in the cylinder wall 11b may be the representative equilibrium temperature T _eq2 , or the maximum value of the equilibrium temperature T _eq1 (equilibrium temperature T _eq1 at the end on the cylinder space 11a side) is representative. The equilibrium temperature T _eq2 may be used. The representative equilibrium temperature T _eq2 estimated here is transmitted to the delay filter processing unit 4c.

The delay filter processing unit 4c estimates the wall surface temperature T _wal by performing a delay process on the temporal variation of the representative equilibrium temperature T _eq2 . Here, the wall surface temperature T _wal is estimated based on a model that responds with a delay to the change in the representative equilibrium temperature T _eq2 . For example, as shown in FIG. 3B, when the representative equilibrium temperature T _eq2 increases, a model is used in which the wall temperature T _wal fluctuates with delays such as primary delay, _dead time, and secondary delay. Is done. As a simpler method, the wall surface temperature T _wal may be _obtained by filtering the representative equilibrium temperature T _eq2 using a delay filter for signal processing. The wall surface temperature T _wal acquired here is transmitted to the control unit 5.

[2-5. Control unit]
The control unit 5 (control means) limits post injection at the post injection unit 3 based on the wall surface temperature T _wal estimated by the wall surface temperature estimation unit 4. Here, when the wall surface temperature T _wal is lower than the predetermined temperature T _A , a control signal for reducing the amount of unburned post injection fuel is transmitted to the unburned post injection section 3b. Alternatively, a control signal for reducing the fuel amount to 0 is transmitted to the unburned post injection unit 3b. On the other hand, when the wall temperature T _wal is equal to or higher than the predetermined temperature T _A, the above-described limitations is tought, control of the fuel injection amount by the unburnt post injection portion 3b is performed.

The control unit 5 functions to change only the fuel injection amount without changing the injection timing of the unburned post injection set by the unburned post injection unit 3b. That is, as shown in FIG. 2B, the crank angle corresponding to the time at which post injection is performed is constant regardless of the wall surface temperature T _wal .

For example, when the wall temperature T _wal rises from the state lower than the predetermined temperature T _A to a state equal to or higher than the predetermined temperature T _A, if the injection timing of the already unburned post injection in the combustion cycle of that time has passed, the Normal unburned post injection is performed from the next combustion cycle. As a result, the amount of fuel adhering to the cylinder wall 11b is appropriately controlled as compared with the in-cylinder temperature that repeatedly increases and decreases in units of combustion cycles.

[3. flowchart]
FIG. 4 illustrates a flowchart of the temperature increase control performed by the engine control device 1. The series of controls shown in this flowchart is repeatedly performed at a predetermined period set in advance in the engine control apparatus 1.
In step A10, it is determined whether or not the event execution flag is on. The event here means various controls for raising the exhaust temperature (or the exhaust system). For example, when the poisoning regeneration of the catalyst device 18 is requested, the event execution flag is set to ON. . When the exhaust temperature does not need to be raised, the event execution flag is set to off. The condition for setting the event execution flag to ON is set according to, for example, the operating state of the engine 10, the traveling environment, the operating states of various devices in the exhaust system, and the like.

  If the event execution flag is on, the process proceeds to step A20. On the other hand, when it is off, there is no need to raise the exhaust gas temperature, so this flow is terminated as it is. In this case, the main injection unit 2 controls the fuel injection amount and injection timing of the main injection according to the output required for the engine 10.

  In step A20, temperature increase control for increasing the exhaust gas temperature is performed. For example, as the control related to the intake air amount, various throttles (throttle valve and EGR valve) of the intake system are controlled so that the intake air amount to the cylinder 11 such as the fresh air amount and the EGR amount decreases. In the case of the engine 10 provided with a supercharger, control for increasing the supercharging pressure may be performed in step A20, or the load on the engine 10 is increased by driving an air conditioner or a power generator. Control may be implemented.

  In the subsequent step A30, it is determined whether or not a preset condition for starting combustion post injection is satisfied. Here, the start condition of the combustion post-injection is determined according to the elapsed time after detecting that the event execution flag is ON, the operating states of various throttles executed in step A20, and the like. If the start condition is satisfied here, the control proceeds to step A40. If the start condition is not satisfied, the flow is terminated as it is.

  In step A40, the combustion post injection unit 3a performs the combustion post injection. That is, a control pulse signal corresponding to the combustion post-injection is output from the post-injection unit 3 to the injector 14, and fuel for raising the temperature is injected after the main injection. At this time, the control pulse signal of the main injection output from the main injection unit 2 to the injector 14 is also changed. For example, the main injection amount is corrected in the decreasing direction, and the after injection amount is corrected in the increasing direction.

  In step A40, the exhaust gas temperature further rises due to the combustion post injection. However, since the combustion post injection may affect the engine output, it is desirable to appropriately adjust the main injection and the after injection amounts in order to keep the output constant.

In the subsequent step A50, the wall surface temperature estimation unit 4 estimates the wall surface temperature T _wal of the cylinder 11. Here, first, the in-cylinder temperature in the cylinder 11 is calculated in the gas temperature estimation unit 4a, and the gas temperature T _gas obtained by averaging the fluctuation of the in-cylinder temperature over the time taken for one combustion cycle is calculated. Subsequently, in the equilibrium temperature estimation unit 4b, the distribution of the equilibrium temperature T _eq1 the cylinder wall 11b on the basis of the gas temperature T _gas and cooling water temperature T _wat is calculated, the representative equilibrium temperature T _eq2 is estimated. Furthermore, time delay variation over time of the delay filtering unit 4c in a representative equilibrium temperature T _eq2 is added, the final wall surface temperature T _wal is estimated. As shown in FIG. 3A, the wall surface temperature T _wal acquired here accurately simulates the actual temperature of the cylinder wall 11b that is in a temperature equilibrium state between the gas temperature T _gas and the cooling water temperature T _wat. Will be.

In step A60, estimated in the previous step the wall temperature T _wal whether at least the predetermined temperature T _A is determined. Here, when the wall surface temperature T _wal <the predetermined temperature T _A , this flow is finished as it is. In this case, only the combustion post injection of the two types of post injection is performed. On the other hand, when the wall surface temperature T _wal ≧ predetermined temperature T _A in step A60, the process proceeds to step A70. Note that the determination content in step A60 corresponds to the start condition of unburned post injection. Therefore, it is good also as a structure which determines conditions other than wall surface temperature _Twal at this step.

  In step A70, it is determined whether unburned post injection is incomplete. This is to determine whether or not Step A100, which will be described later, has been performed during the current event, and proceeds to Step A80 when unburned post injection is not being performed or is being performed. If Step A100 has already been completed (if unburned post injection has been completed), the process proceeds to Step A110.

  In step A80, unburned post injection is performed in the unburned post injection section 3b. That is, a control pulse signal corresponding to unburned post injection is output from the post injection unit 3 to the injector 14, and unburned post injection is performed after the combustion post injection.

  In Step A90, it is determined whether or not the elapsed time (control time) from the start time has reached a predetermined time or more. Here, when it is determined that the elapsed time of the unburned post injection is equal to or longer than the predetermined time, the process proceeds to step A100, and the unburned post injection ends. On the other hand, when the elapsed time is less than the predetermined time, this flow is finished as it is. That is, the control between steps A10 to A90 is repeated until the unburned post injection is performed for a sufficient period. Note that the determination content in step A90 corresponds to the unburned post injection termination condition, and other conditions may be determined.

  When unburned post-injection is completed in step A100, only the combustion post-injection is performed out of the two types of post-injection. Further, in the subsequent step A110, it is determined whether or not the elapsed time (control time) of the combustion post injection is equal to or longer than the second predetermined time. If it is determined that the elapsed time of the combustion post injection is equal to or longer than the second predetermined time, the process proceeds to step A120, and the combustion post injection is also ended. Note that the end timings of the unburned post injection and the combustion post injection may be set at the same time without being distinguished as described above.

  Further, the intake air amount, the supercharging pressure, the engine load, and the like controlled in step A20 may be configured to end before and after step A120, or may be configured to end before and after step A100. Thereafter, when the operating state of the engine 10 returns to the state before the event execution flag is turned on, the event execution flag is set to off and the temperature increase control is completed.

[4. Action]
FIG. 5A illustrates the fluctuation of the fuel injection amount and the like when the temperature raising control is performed along the above flowchart. FIG. 5A is a graph showing, in order from the top, the event execution flag, wall surface temperature T _wal , main injection amount, after injection amount, combustion post injection amount, and unburned post injection amount.

The operation state of the engine 10 before the time t ₀ is a normal operation state in which the event execution flag is set to OFF, and the main injection unit 2 performs fuel injection of main injection according to the output required for the engine 10. The amount and injection timing are controlled.
When the event execution flag is set to ON at time t ₀ , the exhaust gas temperature raising control is started, and the intake air amount to the cylinder 11 decreases. Thereafter, when the start condition of the combustion post injection time t ₁ is satisfied, the control pulse signal corresponding to the combustion post injection from the post injection unit 3 is outputted, the combustion post injection is started. At the same time, a control pulse signal is also output from the main injection unit 2, and the main injection amount is corrected in the decreasing direction, and the after injection amount is corrected in the increasing direction.

By these temperature increase controls, the wall surface temperature T _wal gradually increases. Further, the engine output is maintained constant by appropriately adjusting the amount of decrease in the main injection amount and the amount of increase in the after injection amount. On the other hand, the wall temperature T _wal is in a state lower than the predetermined temperature T _A, the amount of fuel unburnt post injection is set to 0 by the control unit 5. Thus, while also for some time after time t ₁ is the non-implementation unburned post-injection.

When the wall surface temperature T _wal becomes equal to or higher than the predetermined temperature T _{A at} time t ₂ , the restriction on unburned post injection by the control unit 5 is released. In response to this, a post-injection unit 3 outputs a control pulse signal corresponding to unburned post injection, and unburned post injection is started. Here at time t ₃ when unburned post injection is started, as shown in FIG. 2 (b), a time corresponding to the crank angle to unburned post injection is performed. Therefore, a time difference smaller than the cycle of the combustion cycle at time t ₂ can occur between time t ₂ and time t ₃ .

That is, unburned post injection is not necessarily the wall temperature T _wal is started at time t ₂ became equal to or higher than the predetermined temperature T _A, merely the injection timing according to the crank angle of each combustion cycle, the time t ₂ beginning on or after the time t _3. Thereby, when compared with control in which the fuel injection timing within one combustion cycle is made variable, the influence of the pulsation of the fuel pipe 14a given to the amount of fuel injected from the injector 14 is reduced.

By starting the unburned post injection, unburned components in the exhaust increase. The unburned components are supplied to the catalyst device 18 on the exhaust passage 17 and consumed for raising the catalyst temperature and for poisoning regeneration. Also, the time t ₃ or later is continued combustion post-injection, the wall temperature T _wal is gradually increased.

When the unburned post-injection termination condition is satisfied at time t ₄ when a predetermined time has elapsed from time t _{3, the} unburned post-injection control pulse signal output from the post-injecting unit 3 is stopped, and unburned post-injection is performed. finish. On the other hand, even after the unburned post injection ends, the combustion post injection is continued for a while for the purpose of adjusting the output of the engine 10, and the correction of the main injection (main injection and after injection) is continued accordingly. Is done.

Then, at time t ₅ from the time t ₁ the second predetermined time has elapsed the termination condition of the combustion post injection is satisfied, the control pulse signal of the combustion post injection from the post injection unit 3 is stopped. Further, the main injection unit 2 cancels the correction of the main injection amount and the after injection amount, and outputs the same control pulse signal as before the time t ₁ . As a result, the wall surface temperature T _wal is lowered and stabilized at a predetermined steady temperature. Further, the event execution flag is reset from on to off, and the exhaust gas temperature raising control is completed.

[5. effect]
According to said embodiment, the following effects can be acquired.
(1) In said engine control apparatus 1, the fuel quantity at the time of the post injection implemented after main injection is controlled according to wall surface temperature _Twal . For example, when the wall surface temperature T _wal is lower than the predetermined temperature T _A , the amount of unburned post injection fuel is reduced or set to zero. In this way, by controlling the post fuel injection amount with reference to the wall surface temperature T _wal , the amount of post-injected fuel adhering to the wall surface compared to the case of referring to the in-cylinder temperature that varies greatly from combustion cycle to combustion cycle. Can be adjusted with high accuracy.

Further, since the wall surface temperature T _wal fuel quantity of unburned post injection when less than the predetermined temperature T _A is limited, it is possible to reduce the adhesion amount of the fuel in the cylinder wall 11b. On the other hand, this limit for the wall temperature T _wal is eliminated when the above predetermined temperature T _A, the fuel can be increased amount of evaporation from the wall surface even when adhering to the cylinder walls 11b. Therefore, oil dilution can be suppressed.

Furthermore, since the above-described post-injection control is control using the wall surface temperature T _wal , it is possible to suppress the outflow of fuel into the crankcase regardless of fluctuations in the cylinder temperature. Can be kept low.

(2) For example, as shown in FIG. 4 and FIG. 5 (a), in the control unit 5, the amount of fuel unburnt post injection in the combustion cycle wall surface temperature T _wal is less than a predetermined temperature T _A to 0 when control the wall temperature T _wal unburned post injection only the combustion cycle becomes equal to or higher than the predetermined temperature T _a is performed. That is, even if unburned post-injected fuel adheres to the wall surface of the cylinder wall 11b, the unburned fuel is likely to evaporate, so that the oil dilution is unlikely to increase.

  In this way, rather than simply performing post injection based on the demand from the exhaust system, the amount of fuel adhering to the wall surface is suppressed after estimating the combustion cycle in which the attached fuel is unlikely to evaporate. By restricting the post-injection to prohibit unburned post-injection and permitting unburned post-injection only in the combustion cycle that easily evaporates, it is possible to effectively suppress an increase in the oil dilution.

(3) Further, in the engine control apparatus 1 described above, as shown in FIG. 5A, when the post injection amount is limited, the fuel injection amount is reduced only to unburned post injection that most easily affects oil dilution. The combustion post injection is maintained even when the unburned post injection is not performed (between times t _{1 and} t ₃ ). By such control, it is possible to effectively suppress an increase in the oil dilution while increasing the wall surface temperature _Twal .

(4) Moreover, in said engine control apparatus 1, the injection timing of unburned post injection is not changed irrespective of wall surface temperature _Twal . That is, as shown in FIG. 2B, the crank angle corresponding to the time at which the post injection is performed is constant regardless of the wall surface temperature T _wal .
Thereby, the fluctuation | variation of the fuel injection quantity by the pulsation inside the fuel piping 14a connected to the injector 14 can be prevented, and the injection quantity of the post injection fuel can be adjusted appropriately. Therefore, it is possible to prevent a problem that a large amount of fuel is unintentionally injected from the injector 14, and to reduce the amount of fuel adhering to the wall surface of the cylinder wall 11b and the amount of oil dilution.

(5) In the engine control apparatus 1 described above, the equilibrium temperature T _eq1 is calculated from the gas temperature T _gas and the cooling water temperature T _wat, and the representative equilibrium temperature T _eq2 is calculated from the distribution. Thus, by calculating the temperature of the cylinder wall 11b under the thermal equilibrium condition, it is possible to improve the estimation accuracy of the wall surface temperature _Twal of the cylinder wall 11b. In addition, by improving the estimation accuracy of the wall surface temperature T _wal , it becomes possible to accurately evaluate the easiness of fuel evaporation from the wall surface, and the amount of post-injected fuel adhering to the wall surface can be controlled appropriately. it can.

(6) Further, in the engine control apparatus 1 described above, the wall surface temperature T _wal is estimated by _performing a delay process on the temporal variation of the representative equilibrium temperature T _eq2 . Accordingly, it is possible to estimate an accurate wall surface temperature T _wal in consideration of a delay in heat transfer from the combustion gas in the cylinder 11 to the cylinder wall 11b and a delay in heat transfer from the cylinder wall 11b to the cooling water. Therefore, the estimation accuracy of the wall surface temperature T _wal can be further improved.

(7) In the engine control apparatus 1 described above, the average value of the temperature in the cylinder 11 (so-called in-cylinder temperature) for each combustion cycle is calculated as the gas temperature T _gas . That is, the gas temperature T _gas corresponding to the averaged in-cylinder temperature for each combustion cycle is calculated. In this way, by performing the process of averaging the cylinder temperature that fluctuates greatly and abruptly in each stroke of the combustion cycle, the calculation amount of the calorie can be calculated while maintaining the characteristics of the thermal environment with the cylinder wall 11b as the main component. Can be reduced. Therefore, the engine control apparatus 1 can provide a highly reliable temperature estimation model that achieves both high calculation speed and reliable calculation accuracy.

[6. Modified example]
In FIG. 5A of the above-described embodiment, the control for setting the fuel amount of the unburned post injection to 0 when the wall surface temperature T _wal is lower than the predetermined temperature T _A is exemplified, but the unburned post injection is completely performed. It is not necessary to stop. For example, when the wall temperature T _wal is less than a predetermined temperature T _A, the wall temperature T _wal is considered to be a control for reducing the amount of fuel than in the above predetermined temperature T _A. By reducing the amount of unburned post-injection when the amount of fuel evaporation from the wall surface is small, the outflow of fuel into the crankcase can be suppressed and oil dilution can be prevented.

The relationship between the wall surface temperature T _wal and the unburned post injection amount can be _variously assumed. For example, as shown in FIG. 5B, the unburned post injection amount may be determined according to the wall surface temperature T _wal . In this case, it is conceivable that the unburned post injection amount is decreased (the limit amount is increased) as the wall surface temperature T _wal is lower, and the unburned post injection amount is increased as the wall surface temperature T _wal is higher. With such control, the amount of post-injected fuel adhering to the wall surface can be accurately adjusted, and the outflow of fuel into the crankcase can be effectively suppressed.

  Moreover, as shown in FIG.5 (c), while making unburned post injection quantity reduce, it is also considered to set it as control which increases combustion post injection quantity. For example, when it is necessary to make the fuel injection amount in the post injection constant, the combustion post injection amount may be increased so as to correspond to the decrease amount in the unburned post injection. That is, the increase amount of the combustion post injection and the decrease amount of the unburned post injection are matched. As described above, by distributing the fuel injection amount in the category of post injection, it is possible to prevent the oil from being diluted while reducing the influence on the operation state of the engine 10 and other fuel injection control.

Further, by increasing the fuel post injection amount, it is possible to raise the wall surface temperature T _wal positively, it can be wall surface temperature T _wal to shorten the time taken until the predetermined temperature or higher T _A. Thereby, exhaust performance can be improved in a short time.

In the above-described embodiment, the control for limiting the unburned post injection amount when the wall surface temperature T _wal is low is exemplified, but this increases the unburned post injection amount when the wall surface temperature T _wal is high. It can also be regarded as control. When the wall surface temperature T _wal sufficient for evaporation from the fuel wall surface is secured, the unburned post injection amount can be increased to increase the unburned components in the exhaust. The temperature raising rate can be increased, and the exhaust performance can be further improved.

In the above-described embodiment, the wall surface temperature T _wal is calculated in consideration of the response delay of the system to the wall surface temperature estimated according to the heat transfer characteristics from the gas temperature T _gas and the cooling water temperature T _wat. However, there are various concrete methods for calculating the wall surface temperature T _wal . For example, the equilibrium temperature T _eq1 of the cylinder wall 11b may be calculated based on the cooling water temperature T _wat and its change tendency, and the wall surface temperature T _wal may be calculated based on the equilibrium temperature T _eq1 . Alternatively, when the equilibrium temperature T _eq1 of the cylinder wall 11b is not calculated, a sensor for detecting the temperature inside the wall body is embedded in the cylinder wall 11b, and the wall surface temperature T _wal is calculated based on the detected temperature. It is good also as a structure to estimate.

  Moreover, although what controlled the fuel injection of the diesel engine 10 was shown in the above-mentioned embodiment, the application object of this invention is not limited to this. The present invention can be applied to any direct-injection engine that injects fuel into at least the cylinder 11 and is capable of multi-stage fuel injection.

DESCRIPTION OF SYMBOLS 1 Engine control apparatus 2 Main injection part 3 Post injection part (post injection means)
3a Combustion post injection part (combustion post injection means)
3b Unburned post injection part (unburned post injection means)
4 Wall temperature estimator (estimator)
4a Gas temperature estimation unit 4b Equilibrium temperature calculation unit 4c Delay filter processing unit 5 Control unit (control means)
10 Engine 11 Cylinder 14 Injector 15 Water jacket
T _gas temperature, T _wat cooling water temperature, T _eq1 equilibrium temperature, T _eq2 representative equilibrium temperature
T _wal wall temperature, T _A predetermined temperature (wall temperature judgment threshold)

Claims (7)

Post-injection means for performing post-injection after main injection into the cylinder of the internal combustion engine;
Estimating means for estimating the wall surface temperature of the cylinder;
Control means for controlling the fuel amount of the post injection performed by the post injection means based on the wall surface temperature estimated by the estimation means ;
The post injection means,
Combustion post injection means for performing combustion post injection related to temperature rise of the exhaust temperature;
Unburned post injection means for performing unburned post injection related to the supply of unburned components to the exhaust system after the combustion post injection,
The fuel injection control device for an internal combustion engine, wherein the control means reduces the amount of fuel of the unburned post injection performed by the unburned post injection means in accordance with the wall surface temperature . 2. The fuel for an internal combustion engine according to claim 1, wherein the control unit limits the implementation of the post injection by the post injection unit during a predetermined period in a combustion cycle in which the wall surface temperature is lower than a predetermined temperature. Injection control device. The fuel injection control device for an internal combustion engine according to claim 1 or 2 , wherein the control means increases the fuel amount of the combustion post injection performed by the combustion post injection means in accordance with the wall surface temperature. . The said post-injection means maintains the timing at which the said post-injection is implemented in each combustion cycle at a predetermined timing irrespective of the said wall surface temperature, The any one of Claims 1-3 characterized by the above-mentioned. A fuel injection control device for an internal combustion engine. The said estimation means estimates the said wall surface temperature based on the equilibrium temperature of the wall body of the said cylinder calculated from the gas temperature in the said cylinder, and the cooling water temperature of the said internal combustion engine, The said wall surface temperature is estimated. 5. The fuel injection control device for an internal combustion engine according to claim 4 . 6. The fuel injection control apparatus for an internal combustion engine according to claim 5 , wherein the estimating means estimates the wall surface temperature by performing a delay process on the temporal variation of the equilibrium temperature. The fuel injection control device for an internal combustion engine according to claim 5 or 6 , wherein the estimation means calculates an average value of gas temperatures in the cylinder for each combustion cycle as the gas temperature.

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