JP5126165B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  The exhaust gas from an internal combustion engine contains particulate matter (hereinafter, “PM”: Particulate Matter) containing carbon as a main component. A technique for providing a particulate filter (hereinafter referred to as “filter”) for collecting PM in an exhaust system of an internal combustion engine is known in order to prevent the emission of PM into the atmosphere.

  In addition, exhaust gas recirculation (hereinafter referred to as “EGR”) for the purpose of reducing the amount of nitrogen oxides (hereinafter referred to as “NOx”) discharged from the internal combustion engine into the atmosphere, improving engine performance, and improving fuel efficiency. Engines that do this are known.

  In Patent Document 1, the amount of PM generated by the engine per unit time is calculated based on the engine load and the engine speed. In Patent Document 2, the PM component ratio is actively controlled to reduce the total amount of PM discharged to the outside. A technique related to the EGR device is disclosed in Patent Document 3.

JP 2000-170521 A JP 2007-231846 A JP 2000-45881 A

  In order to reduce the amount of PM discharged to the outside, a filter can be provided as described above, but it is effective to execute control for reducing the amount of PM in response to an increase in the amount of PM.

  Therefore, an object of the present invention is to provide a control device for an internal combustion engine that can reduce the PM amount in response to an increase in the PM amount.

In order to solve the above problems, the present invention provides an EGR passage that recirculates exhaust gas, an EGR catalyst that purifies exhaust gas that is recirculated in the EGR passage, and an in-cylinder engine that directly injects fuel into the cylinder of the internal combustion engine. An internal combustion engine control device comprising: an injection valve , wherein the estimation means for estimating whether or not the amount of particulate matter in the exhaust gas is increasing based on the temperature of the EGR catalyst; and the operating conditions can be estimated increase in the amount of the particulate matter on the basis of the temperature of the EGR catalyst, determining means for determining whether or not the meet the operating condition of the internal combustion engine, estimation result and the by the estimating means Control means for executing control for reducing the number of injections by which the in-cylinder injection valve injects fuel based on a determination result by the determination means.
According to the present invention, the occurrence of the PM amount can be reduced by executing the control for reducing the number of times the in-cylinder injection valve injects the fuel in response to the increase in the PM amount.

In the present invention, the control means may further execute control for retarding the timing at which the in-cylinder injection valve injects fuel based on the estimation result by the estimation means and the determination result by the determination means. .

The present invention also includes an EGR passage that recirculates exhaust gas, an EGR catalyst that purifies exhaust gas that is recirculated in the EGR passage, and an in-cylinder injection valve that directly injects fuel into the cylinder of the internal combustion engine. A control device for an internal combustion engine, comprising control means for executing control for reducing the number of injections by which the in-cylinder injection valve injects fuel when the temperature of the EGR catalyst is higher than a predetermined threshold value.

In the present invention, the control means may further execute control for retarding a timing at which the in-cylinder injection valve injects fuel when the temperature of the EGR catalyst is higher than the threshold value.

  According to the present invention, it is possible to reduce the PM amount corresponding to the increase in the PM amount.

1 is a schematic configuration diagram of an engine to which the present invention is applied. It is a figure which shows the relationship between the amount of EGR and the temperature of an EGR catalyst. It is a flowchart which shows an example of the process which engine ECU performs. It is a flowchart which shows an example of the process performed when engine ECU estimates the increase in PM amount. It is a figure which shows an example of the map which calculates | requires the predetermined value of intake pipe temperature from an engine speed and intake pipe pressure. It is a timing chart which shows an example of the relationship between the engine operating state and PM density | concentration.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 shows a schematic configuration diagram of an engine as an example of an internal combustion engine controlled by an engine ECU (Electronic Control Unit) corresponding to the control device for the internal combustion engine according to the embodiment of the present invention. Although FIG. 1 shows an in-line four-cylinder gasoline engine as the engine, the engine controlled by the engine ECU is not limited to such an engine.

  As shown in FIG. 1, the engine 10 burns an air-fuel mixture obtained by mixing air supplied from an intake system 30 and fuel supplied from a fuel supply system at an appropriate air-fuel ratio in a combustion chamber in a cylinder 201. Then, exhaust gas in the combustion chamber is exhausted from the exhaust system 40. The engine 10 includes an EGR device 50 for performing exhaust gas recirculation, a turbocharger 70, and an intercooler 80.

The engine 10 includes four cylinders 201. Each cylinder 201 is provided with an in-cylinder injector 102 for injecting fuel into the cylinder and an intake port injector 101 for injecting fuel into the intake port. These injectors 101 and 102 are controlled based on the output signal of engine ECU 60, respectively. Each in-cylinder injector 102 is connected to a common fuel distribution pipe 11, and fuel is supplied to each in-cylinder injector 102 via this fuel distribution pipe 11. On the other hand, each intake port injector 101 is connected to a common fuel distribution pipe 12, and fuel is supplied to each intake port injection injector 101 via the fuel distribution pipe 12.
In the present embodiment, an internal combustion engine in which two types of injectors are separately provided will be described. However, the application of the present invention is not limited to such an internal combustion engine. For example, the internal combustion engine may have only one of the in-cylinder injector and the intake port injector.

The intake system 30 of the engine 10 is formed by connecting an intake pipe to an intake manifold connected to a plurality of intake ports of a cylinder head, and for adjusting the amount of air flowing into the intake pipe on the upstream side in the intake direction. A throttle valve 301 is provided. The opening / closing of the throttle valve 301 is controlled based on the output signal of the engine ECU 60.
The intake pipe is provided with an intake pipe temperature / intake pipe pressure measurement sensor group 302 for measuring the intake pipe temperature and the intake pipe pressure. Then, an electric signal corresponding to the intake pipe temperature and the intake pipe pressure is output to the engine ECU 60. In addition, the place where the sensor for measuring the intake pipe temperature and the intake pipe pressure is installed is not limited to this embodiment.

The exhaust system 40 of the engine 10 includes an exhaust passage configured by connecting an exhaust pipe to an exhaust manifold connected to a plurality of exhaust ports of the cylinder head.
The exhaust pipe is provided with an exhaust temperature measurement sensor 401 for measuring the exhaust temperature, and the exhaust temperature measurement sensor 401 outputs an electrical signal corresponding to the exhaust temperature to the engine ECU 60. The place where the sensor for measuring the exhaust temperature is installed is not limited to this embodiment.

  The EGR device 50 reduces NOx by returning a part of the exhaust gas (EGR gas) to the intake system 30 and supplying it again to the combustion chamber, and enters the EGR passage 50a from the upstream side to the EGR catalytic converter 50b, EGR. The cooler 50c and the EGR valve 50d are arranged.

The EGR passage 50 a is a bypass passage that bypasses the combustion chamber from the exhaust system 40 to the intake system 30. The EGR catalytic converter 50b removes unburned gas contained in the exhaust gas flowing into the EGR passage 50a to prevent clogging of the EGR cooler 50c.
The EGR cooler 50c includes a heat exchanger that lowers the temperature of the EGR gas by exchanging heat between the EGR gas and the cooling water of the engine 10, for example. In the present embodiment, a cooling water temperature measuring sensor 202 for measuring the temperature of the cooling water is provided at an outlet on the engine 10 side that discharges the cooling water from the engine 10 to the EGR cooler 50c.
The EGR valve 50d controls the amount of exhaust gas flowing from the exhaust system side to the intake system side in the EGR passage 50a. The EGR valve 50d is provided with a sensor for measuring the opening degree of the EGR valve (EGR valve opening degree), and the sensor outputs an electric signal corresponding to the EGR valve opening degree to the engine ECU 60.

  The turbocharger 70 boosts intake air using exhaust gas, and includes a compressor 70a and a turbine 70b.

  The intercooler 80 cools the intake air boosted by the turbocharger 70 and is disposed between the compressor 70 a of the turbocharger 70 and the throttle valve 301.

  Various controls of the engine 10 are performed by an engine ECU 60 for engine control. The engine ECU 60 is a central processing unit (CPU) that performs various arithmetic processes related to engine control, a ROM (read-only memory) that stores engine control programs and data, and a RAM that temporarily stores arithmetic results of the CPU, etc. (Random Access Memory) and an I / O (input / output port) for exchanging signals with the outside.

The above-described intake air temperature, intake pipe pressure, exhaust gas temperature, EGR valve opening degree, and cooling water temperature are input to the engine ECU 60. Further, the engine ECU 60 includes an engine speed from the rotational speed sensor 90, an engine load factor from the load sensor 91, an in-cylinder pressure from the in-cylinder pressure sensor 92 provided in the cylinder 201, and a variable valve timing mechanism (VVT) position sensor 93. The position of VVT at the time of intake and exhaust is input.
The engine ECU 60 determines whether the amount of PM is increasing and the operating state of the engine 10 based on the input signal from the sensor described above. If the engine ECU 60 determines that the PM amount is increasing, the engine ECU 60 controls the in-cylinder injector 102 and / or the intake port injector 101 in order to reduce the generation of the PM amount (details). Will be described later).
The engine ECU 60 corresponds to the estimation means, determination means, and control means of the present invention.

  Here, the relationship between the amount of EGR gas recirculated to the intake system 30 of the engine 10 and the temperature of the EGR catalyst will be described with reference to FIG. FIG. 2 is a diagram showing the relationship between the amount of EGR gas and the temperature of the EGR catalyst when the engine satisfies predetermined operating conditions (details will be described later). In FIG. 2, the vertical axis represents the temperature of the EGR catalyst (catalyst temperature), and the horizontal axis represents the amount of EGR gas (EGR amount). In FIG. 2, the solid line indicates the state when the amount of PM in the displacement (hereinafter referred to as PM concentration) is as designed (normal time), and the broken line indicates the PM concentration is higher than normal. It shows the state when it rises. If the amount of PM increases, the PM concentration increases, and if the amount of PM decreases, the PM concentration decreases.

  FIG. 2 shows that the temperature of the EGR catalyst when the EGR amount is the same is higher when the PM concentration is increased as indicated by the broken line than when the PM concentration is normal as indicated by the solid line. Therefore, when the temperature of the EGR catalyst is increased, it can be considered that the PM concentration is increased. That is, since it can be determined whether or not the PM concentration is increased based on the temperature of the EGR catalyst, it can be understood that control for reducing the PM amount can be performed based on the determination result.

Next, a process for reducing the PM amount corresponding to the increase in the PM amount, which is executed by the engine ECU 60, will be described with reference to FIGS. FIG. 3 is a flowchart showing a control process executed by engine ECU 60.
First, the engine ECU 60 calls a routine for determining whether or not the PM amount has increased (step S10). The processing in step S10 will be described in detail with reference to FIG.

Next, the engine ECU 60 determines whether or not a determination flag obtained as a result of the process at step S10 is ON (step S20). This determination flag indicates that the PM concentration increases with an increase in the PM amount when the flag is ON, and indicates that the PM concentration is normal when the flag is OFF.
When the determination flag is ON (step S20 / YES), engine ECU 60 executes control for reducing the PM amount (step S30). On the other hand, when the determination flag is OFF (step S20 / NO), the engine ECU 60 ends this process because the PM amount has not increased.

Here, the control for reducing the amount of PM specifically means that the in-cylinder injector 102 injects fuel by delaying the timing at which the in-cylinder injector 102 injects fuel into the cylinder 201. Any one of decreasing the number of injections performed and increasing the number of times the intake port injector 101 injects fuel out of the number of times the intake port injector 101 and in-cylinder injector 102 inject fuel. The above control.
When the injection timing is on the advance side, the PM amount may increase due to deterioration of fuel atomization due to piston wet. Accordingly, the engine ECU 60 can reduce the generation of piston wet by retarding the fuel injection timing of the in-cylinder injector 102 and reduce the amount of PM generated. In addition, when the in-cylinder injector 102 performs a plurality of injections, the second injection may interfere with the intake valve, thereby degrading the homogeneity of the fuel and increasing the PM amount. Therefore, the engine ECU 60 can reduce the amount of PM generated by reducing the number of injections of the in-cylinder injector 102.

Next, a process for determining an increase in the PM amount executed by the engine ECU 60 will be described with reference to FIG. FIG. 4 is a flowchart showing the process executed in step S10 of FIG.
First, whether the engine ECU 60 satisfies a condition that allows the engine ECU 60 to start a process for determining an increase in PM amount (hereinafter abbreviated as a PM amount increase determination process) by the processes from step S101 to step S103 described later. It is determined whether or not the engine 10 is in steady operation.

  The engine ECU 60 determines whether or not the cooling water temperature is within a predetermined range (step S101). By step S101, the engine ECU 60 can determine whether or not the engine 10 is in warm-up operation and whether or not the EGR cooler 50c is in steady operation and its performance is constant.

  If the coolant temperature is within the predetermined range (step S101 / YES), engine ECU 60 determines whether control of EGR device 50 is being executed (step S102). On the other hand, when the coolant temperature is not within the predetermined range (step S101 / NO), the engine ECU 60 does not satisfy the condition for allowing the engine ECU 60 to start the PM amount increase determination process, and thus turns off the determination flag described above. (Step S109). Then, the engine ECU 60 ends this process.

  When the engine ECU 60 is executing the control of the EGR device 50 (step S102 / YES), the engine 10 is in a steady operation within a predetermined time after the end of the transient operation in which the engine speed and the engine load factor increase. It is determined whether or not there is (step S103). On the other hand, if the engine ECU 60 is not executing the control of the EGR device 50 (step S102 / NO), the condition that allows the engine ECU 60 to start the PM amount increase determination process is not satisfied, so the determination flag described above is turned OFF. (Step S109). Then, the engine ECU 60 ends this process. In step S <b> 103, engine ECU 60 can make a determination based on the engine speed from engine speed sensor 90 and the engine load from engine load sensor 91.

  The engine ECU 60 acquires the intake pipe temperature from the intake pipe temperature / intake pipe pressure measurement sensor group 302 (step S104) when it is in a predetermined range and is in steady operation from the end of the transient operation (step S103 / YES). On the other hand, if the engine ECU 60 does not satisfy the condition for starting the control within the predetermined range from the end of the transient operation (NO in step S103), the aforementioned determination flag is turned OFF (step S109). Then, the engine ECU 60 ends this process.

  When the engine ECU 60 acquires the intake pipe temperature Tm in step S104, the engine ECU 60 determines whether or not the intake pipe temperature Tm exceeds a predetermined value A (step S105). Here, since the predetermined value A used for comparison with the intake pipe temperature Tm in step S105 is determined using the map shown in FIG. 5, the map will be described.

FIG. 5 is a map for obtaining the predetermined value A used for comparison with the intake pipe temperature Tm in step S105. The predetermined value A is determined based on the engine speed and the intake pipe pressure. The engine ECU 60 can acquire the engine speed from the speed sensor 90 and the intake pipe pressure from the intake pipe temperature / intake pipe pressure measurement sensor group 302.
In the map of FIG. 5, what is indicated by A1 to A42 is a predetermined value temperature of the intake pipe determined from the engine speed and the intake pipe pressure. The theoretical intake pipe temperature increases as the engine speed increases, and increases as the intake pipe pressure increases.
If the PM concentration is normal, the intake pipe temperature Tm takes a value equal to or less than a predetermined value A. Therefore, when the intake pipe temperature Tm exceeds the predetermined value A, it is considered that the PM concentration has increased.

Returning to FIG. 4 again, the process executed by the engine ECU 60 will be described. If the intake pipe temperature Tm exceeds the predetermined value A (step S105 / YES), the engine ECU 60 acquires the EGR valve opening, the exhaust temperature, the in-cylinder pressure, and the VVT position (step S106). Next, the engine ECU 60 determines whether or not the EGR valve opening, exhaust temperature, in-cylinder pressure, and VVT position acquired in step S106 are within predetermined ranges (step S107).
The engine ECU 60 can determine whether or not the amount of EGR gas is constant based on the opening degree of the EGR valve, and can determine the ability of the EGR catalyst to purify the exhaust gas based on the exhaust gas temperature. Further, the engine ECU 60 can determine whether or not abnormal combustion has occurred in the combustion chamber based on the in-cylinder pressure, and can determine whether or not the amount of air taken into the cylinder is constant based on the VVT position. Here, abnormal combustion in the combustion chamber and the amount of air taken into the cylinder are factors that directly affect the intake pipe temperature Tm.

Step S105 is a step of estimating whether or not the PM concentration is increasing. Here, as described with reference to FIG. 2, when the operating condition of the engine 10 satisfies the predetermined operating condition, when the PM concentration increases, the temperature of the EGR catalyst also increases, so the intake pipe temperature also increases. That is, when the intake pipe temperature exceeds the predetermined value A, it can be estimated that the PM concentration has increased.
However, the relationship shown in FIG. 2 is established when the operating condition of the engine 10 satisfies a predetermined operating condition. Therefore, in step S107, the engine ECU 60 determines whether or not the acquired value from each sensor is within a predetermined range. That is, the case where the operating condition of the engine 10 described in FIG. 2 satisfies the predetermined operating condition means the case where the operating condition of the engine 10 satisfies the condition of step S107. In other words, step S107 is a step of determining whether or not the engine operating condition satisfies the operating condition that allows the engine ECU 60 to estimate the increase in PM concentration based on the intake pipe temperature.

If the determination result in step S107 is YES, the engine ECU 60 sets the determination flag to ON, assuming that the PM concentration has increased (step S108). On the other hand, if the determination result in step S107 is NO, engine ECU 60 turns off the determination flag because it cannot determine whether the PM concentration has increased based on the intake pipe temperature (step S109). Then, the engine ECU 60 ends this process.
Note that step S106 and step S107 may be executed after step S103, and then step S104 and step S105 may be executed. In this case, the engine ECU 60 determines that the operating conditions under which the engine ECU 60 can estimate the increase in PM concentration based on the intake pipe temperature are satisfied and the PM concentration is increasing. Set the flag to ON.

Next, PM amount reduction control by the engine ECU 60 under the operating conditions shown in FIG. 6 will be described. FIG. 6 is a time chart showing the relationship between the operating conditions of the engine 10 and the PM concentration.
Until time A when the vehicle is traveling at 100 km / h, since the intake pipe temperature Tm does not exceed the predetermined value A, the engine ECU 60 does not execute a control process for reducing the PM amount.

In addition, in the time from time A to time B when the vehicle shifts from traveling at 100 km / h to traveling at 120 km / h, it corresponds to a transient operation state in which the engine speed increases and the engine load factor also increases. The engine ECU 60 does not execute a control process for reducing the PM amount. In FIG. 6, in this transient operation state, the PM concentration increases, and the intake pipe temperature Tm increases as the PM concentration increases.
Since the vehicle starts steady operation at 120 km / h at time B, the engine ECU 60 starts the PM amount increase determination process described with reference to FIG. Since the engine ECU 60 has the intake pipe temperature Tm exceeding the predetermined value temperature A obtained from the map shown in FIG. 5, does the engine operating condition satisfy the condition for determining the increase in PM concentration from the intake pipe temperature? Determine whether or not. In FIG. 6, the engine ECU 60 determines that the engine operating condition satisfies the operating condition that can estimate the increase in PM concentration based on the intake pipe temperature, so that the fuel of the in-cylinder injector 102 at time C is determined. The number of injections is reduced. By this control, the PM amount is reduced, so the PM concentration is reduced. As the PM concentration decreases, the intake pipe temperature Tm also decreases.

  As is clear from the above description, according to this embodiment, the engine ECU 60 can estimate whether the PM concentration is increasing based on the intake pipe temperature. And since engine ECU60 performs the control process which reduces PM amount corresponding to the increase in PM amount, PM generation amount can be reduced.

  In the embodiment, the intake pipe temperature is used to estimate whether the PM concentration is rising. However, the temperature of the EGR catalyst is acquired to determine whether the PM concentration is rising. Also good. In this case, a sensor for acquiring the temperature of the EGR catalyst may be attached to the EGR catalytic converter 50b, and a signal from the sensor may be input to the engine ECU 60.

The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.
For example, it is reasonable to implement the determination process for determining whether the PM amount is increasing or the control process for reducing the PM amount by the engine ECU 60, but for example, other electronic control devices or dedicated electronic devices It may be realized by hardware such as a circuit or a combination thereof. In this regard, the engine control device of the present invention may be realized by, for example, a plurality of electronic control devices or a combination of electronic control devices and hardware such as electronic circuits.

DESCRIPTION OF SYMBOLS 10 ... Engine 11, 12 ... Fuel supply pipe 30 ... Intake system 40 ... Exhaust system 50 ... EGR apparatus 50a ... EGR passage 50b ... EGR catalytic converter 50c ... EGR cooler 50d ... EGR valve 60 ... Engine ECU
70 ... Turbocharger 70a ... Compressor 70b ... Turbine 80 ... Intercooler 90 ... Rotational speed sensor 91 ... Load sensor 92 ... In-cylinder pressure sensor 93 ... VVT position sensor 101 ... Injector injector 102 ... In-cylinder injector 201 ... Cylinder 202 ... Cooling water temperature measurement sensor 301 ... Throttle valve 302 ... Intake pipe temperature / intake pipe pressure measurement sensor group 401 ... Exhaust temperature measurement sensor

Claims (4)

A control device for an internal combustion engine, comprising: an EGR passage that recirculates exhaust gas; an EGR catalyst that purifies exhaust gas recirculated in the EGR passage; and an in-cylinder injection valve that injects fuel directly into a cylinder of the internal combustion engine Because
Estimating means for estimating whether the amount of particulate matter in the exhaust gas is increasing based on the temperature of the EGR catalyst;
The operating conditions of the estimating means can estimate the increase in the amount of the particulate matter on the basis of the temperature of the EGR catalyst, determining means for determining whether or not the operating condition of the internal combustion engine meets,
Control means for executing control for reducing the number of times the in-cylinder injection valve injects fuel based on the estimation result by the estimation means and the determination result by the determination means;
A control device for an internal combustion engine, comprising: The control means further executes control for retarding a timing at which the in-cylinder injection valve injects fuel based on an estimation result by the estimation means and a determination result by the determination means. The control apparatus of the internal combustion engine described in 1. A control device for an internal combustion engine, comprising: an EGR passage that recirculates exhaust gas; an EGR catalyst that purifies exhaust gas recirculated in the EGR passage; and an in-cylinder injection valve that injects fuel directly into a cylinder of the internal combustion engine Because
A control device for an internal combustion engine, comprising: control means for executing control for reducing the number of injections of fuel by the in-cylinder injection valve when the temperature of the EGR catalyst is higher than a predetermined threshold value. . Wherein when the temperature of the EGR catalyst is higher than said threshold value, according to claim 3, wherein the cylinder injection valve is characterized in that it further executes control for retarding the timing for injecting fuel Control device for internal combustion engine.

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