JP5104786B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that controls a fuel injection amount.

  This type of technique is proposed in Patent Documents 1 and 2, for example. Patent Document 1 proposes estimating the in-cylinder temperature and the in-cylinder pressure from the operation state and the post injection (post injection) timing, and calculating the upper limit value and the lower limit value of the post injection amount from the estimation result. ing. Specifically, in this technique, the upper limit value and the lower limit value are set larger as the in-cylinder temperature or the in-cylinder pressure becomes higher. Further, Patent Document 2 proposes detecting the exhaust pressure of the internal combustion engine and adjusting the fuel injection amount for each cylinder based on the deviation between the pulsation amplitude average value of the exhaust pressure and the pulsation amplitude of each cylinder. Yes.

Japanese Patent Laid-Open No. 10-288031 JP-A-2-283835

  By the way, the temperature and pressure in the cylinder basically tend to be different for each cylinder due to variations in fuel injection amount due to deterioration of the injector, air distribution, and swirl variations. That is, there is a tendency that cylinders with low or high temperature or pressure in the cylinder coexist.

  However, in the technique described in Patent Document 1 described above, the post-injection amount is set without considering such variation in each cylinder. For this reason, oil dilution (a phenomenon in which fuel is diluted by mixing with engine oil) may proceed in a low-temperature cylinder. Patent Document 2 does not describe controlling the fuel injection amount in consideration of variations in temperature or pressure of each cylinder.

  The present invention has been made to solve the above-described problems, and provides a control device for an internal combustion engine capable of appropriately controlling the fuel injection amount in consideration of variations in temperature or pressure of each cylinder. The purpose is to provide.

In one aspect of the present invention, an internal combustion engine control apparatus is applied to an internal combustion engine having a plurality of cylinders, and estimates means for estimating the temperature of each cylinder based on temperature pulsations in an exhaust gas collecting portion; The storage means for obtaining the temperature for each cylinder in advance and storing it as a map value, and the absolute value of the difference between the temperature estimated by the estimation means and the temperature stored as the map value in the storage means is predetermined. in case where the value or more, the performs control Ru increases the post injection quantity for higher cylinder than the estimated temperature of the temperature is stored as the map value, the estimated temperature as the map value and a control means for controlling to stop the control or post injection reduces the post injection amount for the lower cylinder than the storage temperature, the control means, the introduction of the EGR gas The Hajimeji and cut at the start of the EGR gas introduction, control for increasing the post injection amount, the control for reducing the post injection amount, and does not perform control to stop the post injection.

The above control device for an internal combustion engine is applied to an internal combustion engine having a plurality of cylinders. Specifically, the estimating means estimates the temperature for each cylinder based on the temperature pulsation in the exhaust gas collecting portion, and the storage means obtains the temperature for each cylinder in advance and stores it as a map value. Then, when the absolute value of the difference between the estimated temperature and the temperature stored as the map value is greater than or equal to a predetermined value, the control means sets the estimated temperature to a cylinder higher than the temperature stored as the map value. On the other hand, the post-injection amount is increased, and the post-injection amount is decreased or the post-injection is stopped for the cylinder whose estimated temperature is lower than the temperature stored as the map value. Thereby, the post injection amount can be appropriately set according to the variation in temperature of each cylinder. Therefore, it is possible to appropriately suppress the oil dilution from proceeding in the low temperature cylinder.
The control means does not perform control for increasing the post injection amount, control for decreasing the post injection amount, or control for stopping the post injection at the start of EGR gas introduction and at the start of EGR gas introduction cut. As a result, it is possible to suppress a decrease in determination accuracy in post-injection amount increase / decrease control.

In another aspect of the present invention, an internal combustion engine control device is applied to an internal combustion engine having a plurality of cylinders, and estimates means for estimating a pressure for each cylinder based on pressure pulsation in an exhaust gas collecting portion. The pressure for each cylinder is obtained in advance and stored as a map value, and the absolute value of the difference between the pressure estimated by the estimation means and the pressure stored as the map value in the storage means is predetermined. in case where the value or more, the performs control Ru increases the post injection quantity for higher cylinder than the estimated pressure pressure stored as the map value, the estimated pressure as the map value and a control means for controlling to stop the control or post injection reduces the post injection amount for the lower cylinder than the stored pressure, said control means opens the introduction of EGR gas During the time and cut start of the EGR gas introduction, control for increasing the post injection amount, the control for reducing the post injection amount, and does not perform control to stop the post injection.

Also by the control device for the internal combustion engine, the post injection amount can be appropriately set according to the variation in the pressure of each cylinder, so that it is possible to appropriately suppress the oil dilution from proceeding. . In addition, since the post injection amount increase / decrease control is not performed at the start of EGR gas introduction and at the start of EGR gas introduction cut, it is possible to suppress a decrease in determination accuracy in the post injection amount increase / decrease control.

1 is a schematic configuration diagram illustrating an example of a vehicle to which an internal combustion engine control device according to the present invention is applied. It is a figure for demonstrating concretely the setting method of the post injection quantity in 1st Example. It is a flowchart which shows the control processing in 1st Example.

Preferred embodiments of the present invention will be described below with reference to the drawings.
[Device configuration]
FIG. 1 is a schematic configuration diagram showing an example of a vehicle 100 to which a control device for an internal combustion engine according to the present invention is applied. In FIG. 1, solid arrows indicate an example of intake and exhaust flows.

  As shown in FIG. 1, a vehicle 100 mainly includes an engine (internal combustion engine) 1, fuel injection valves 15a to 15d, a temperature sensor 16, an air cleaner 19, an intake passage 20, an air flow meter 21, and a throttle. Valves 22a and 22b, a turbocharger 23, an intercooler (IC) 24, an exhaust passage 25, a catalyst 40, an EGR (Exhaust Gas Recirculation) device 50, and an ECU (Electronic Control Unit) 7 are provided.

  The engine 1 is configured as, for example, an in-line four-cylinder diesel engine, and outputs a driving power source in the vehicle 100. Each cylinder of the engine 1 is connected to an intake manifold 11 and an exhaust manifold 12. Hereinafter, the intake manifold is simply referred to as “intake manifold”, and the exhaust manifold is simply referred to as “exhaust manifold”.

  The engine 1 includes fuel injection valves 15a to 15d provided in each cylinder, and a common rail 14 that supplies high-pressure fuel to the fuel injection valves 15a to 15d. Fuel is supplied at high pressure by the pump. The fuel injection valves 15a to 15d have their fuel injection amount and fuel injection timing controlled by control signals S15a to S15d supplied from the ECU 7, respectively. Hereinafter, when the fuel injection valves 15a to 15d are used without being distinguished from each other, they are simply referred to as “fuel injection valve 15”.

  On the intake passage 20 connected to the intake manifold 11, an air cleaner 19 for purifying intake air, an air flow meter 21 for detecting the amount of intake air to the engine 1, throttle valves 22a and 22b for adjusting the amount of air, and intake air A compressor 23a of the turbocharger 23 for supercharging and an intercooler 24 for cooling the intake air are provided.

  On the exhaust passage 25 connected to the exhaust manifold 12, a turbine 23b of the turbocharger 23 rotated by the energy of the exhaust gas and a catalyst 40 configured to be able to purify the exhaust gas are provided. Further, a temperature sensor 16 configured to be able to detect the temperature of the exhaust gas is provided at a location (hereinafter referred to as “exhaust gas collection portion”) where the exhaust gas from each cylinder indicated by an arrow 26 gathers. Yes. The temperature sensor 16 supplies the ECU 7 with a detection signal S16 corresponding to the detected exhaust gas temperature. In addition, the sensor provided in the general vehicle can be used for the detection of the exhaust gas temperature in such an exhaust gas gathering part. Therefore, cost can be suppressed.

  Further, the vehicle 100 includes an EGR device 50 that recirculates exhaust gas from the upstream side of the turbine 23b to the downstream side of the compressor 23a. The EGR device 50 includes an EGR passage 31 and an EGR valve 33. The EGR passage 31 is a passage connecting the upstream position of the turbine 23b in the exhaust passage 25 and the downstream position from the intercooler 24 in the intake passage 20, and an EGR for controlling the amount of exhaust gas to be recirculated is provided on the passage. A valve 33 is provided.

The ECU 7 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown), and performs various controls on each component in the vehicle 100. In the present embodiment, the ECU 7 mainly supplies the control signals S15a to S15d to the fuel injection valves 15a to 15d based on the detection signal S16 supplied from the temperature sensor 16, so that the fuel injection valves 15a to 15a. Control for 15d is performed. Specifically, the ECU 7 controls the fuel injection amounts of the fuel injection valves 15 a to 15 d based on the exhaust gas temperature in the exhaust gas collecting portion 26 detected by the temperature sensor 16. Although details will be described later, the ECU 7 corresponds to a control device for an internal combustion engine in the present invention, and functions as an estimation means, a storage means, and a control means.
[Control method]
Next, a control method performed by the ECU 7 in this embodiment will be described.

(First embodiment)
In the first embodiment, the ECU 7 takes into account variations in the temperature or pressure of each cylinder, and the fuel injection amount when the fuel injection valves 15a to 15d perform post injection (hereinafter referred to as “post injection amount”). Control over. The reason for this is as follows. In general, the temperature and pressure in a cylinder tend to be different for each cylinder due to variations in fuel injection amount due to deterioration of a fuel injection valve (injector), air distribution, and swirl variations. That is, there is a tendency that cylinders with low or high temperature or pressure in the cylinder coexist. Therefore, when the post injection amount is set uniformly in all the cylinders, the oil dilution may proceed in the low temperature cylinder.

  Therefore, in the first embodiment, the post-injection amounts of the fuel injection valves 15a to 15d are set in consideration of the temperature variation of each cylinder. Specifically, the ECU 7 first estimates the temperature of each cylinder (meaning the in-cylinder temperature of each cylinder; the same applies hereinafter) based on the pulsation of the temperature in the exhaust gas collecting portion, and is obtained by the estimation. The temperature of each cylinder is compared with the temperature of each cylinder that is obtained in advance by experiments or the like and stored as a map value. This map value corresponds to the target in-cylinder temperature in each cylinder.

  Thereafter, when the difference (absolute value) between the estimated cylinder temperature and the map value is equal to or greater than a predetermined value, the ECU 7 increases the post-injection amount for the cylinder whose estimated temperature is higher than the map value. (Increase). On the other hand, when the difference (absolute value) between the estimated cylinder temperature and the map value is equal to or greater than a predetermined value, the ECU 7 performs post-injection for a cylinder whose estimated temperature is lower than the map value. Decrease the amount (decrease) or stop post injection.

  By doing so, it is possible to appropriately suppress the oil dilution from proceeding in the low temperature cylinder.

  FIG. 2 is a diagram for specifically explaining a post injection amount setting method in the first embodiment. In FIG. 2, the horizontal axis indicates time, and the vertical axis indicates the temperature for each cylinder. Here, in the engine 1 of four cylinders (# 1 to # 4), the temperature for each cylinder when fuel is performed in the order of “# 1” → “# 3” → “# 4” → “# 2”. An example of change is shown. Specifically, the solid line indicates an example of the temperature for each actual cylinder (that is, the temperature estimated based on the temperature pulsation in the exhaust gas collecting portion), and the broken line indicates the cylinder stored as a map value. An example of each temperature is shown.

  As shown in the figure, in the cylinder of “# 3”, as indicated by the arrow A1, it can be seen that the actual temperature is considerably higher than the map value (the actual temperature is higher than the map value by a predetermined value or more). In the first embodiment, the ECU 7 performs a process of increasing the post injection amount for such a cylinder. On the other hand, in the cylinder of “# 4”, as indicated by the arrow A2, it is understood that the actual temperature is considerably lower than the map value (the actual temperature is lower than the map value by a predetermined value or more). In the first embodiment, the ECU 7 performs a process of reducing the post injection amount or stopping the post injection for such a cylinder.

  FIG. 3 is a flowchart showing the control process in the first embodiment. This process is mainly performed to set and learn the post-injection amount according to the temperature variation of each cylinder. The process is repeatedly executed by the ECU 7. This process is executed when there is a request for post injection.

  First, in step S101, the ECU 7 issues a post injection request. Then, the process proceeds to step S102.

  In step S102, the ECU 7 acquires the exhaust gas temperature in the exhaust gas collecting portion from the temperature sensor 16, and estimates the temperature of each cylinder based on the pulsation at the exhaust gas temperature. Specifically, the ECU 7 obtains the temperature of each cylinder from the pulsation of the exhaust gas temperature based on a predetermined map and a predetermined arithmetic expression. Then, the process proceeds to step S103.

  In step S103, the ECU 7 compares the temperature of each cylinder estimated in step S102 with the temperature of each cylinder (corresponding to the target temperature in each cylinder) obtained in advance by experiments or the like and stored as a map value. To do. Then, the process proceeds to step S104.

  In step S104, the ECU 7 determines whether or not the difference (absolute value) between the estimated temperature of each cylinder and the map value is less than a predetermined value. If the difference is less than the predetermined value (step S104; Yes), the process proceeds to step S106. In this case, the ECU 7 does not correct the post-injection amount as described above, and learns the variation in the actual temperature of each cylinder after the completion of the post-injection (step S106). Then, the process ends.

  On the other hand, if the difference (absolute value) between the estimated temperature of each cylinder and the map value is not less than the predetermined value (step S104; No), that is, if the difference is greater than or equal to the predetermined value, the process proceeds to step S105. Proceed to In step S105, the ECU 7 increases the post-injection amount for cylinders whose estimated temperature is higher than the map value, and decreases the post-injection amount for cylinders whose estimated temperature is lower than the map value. Or stop the post injection. For example, the ECU 7 sets an amount to increase or decrease the post injection amount based on the difference between the estimated cylinder temperature and the map value. In this case, the ECU 7 increases the amount to be increased or decreased as the difference is larger. Then, the process proceeds to step S106, and the ECU 7 learns the variation in actual temperature of each cylinder after the end of post injection. Thereafter, the process ends.

  According to the processing described above, the post injection amount can be appropriately set according to the temperature variation of each cylinder. Therefore, it is possible to appropriately suppress the oil dilution from proceeding in the cylinder having a low temperature.

(Second embodiment)
Next, a second embodiment will be described. In the second embodiment, the EGR gas introduction start time (hereinafter referred to as “EGR start time”) and the EGR gas introduction cut start (hereinafter referred to as “EGR cut start time”) are first. The post injection amount increase / decrease control as shown in the embodiment is stopped. This is because when the EGR is started and when the EGR cut is started, the exhaust gas collecting part and the state (pressure, etc.) of the EGR passage 31 fluctuate rapidly, so that the detection accuracy and estimation accuracy of the temperature and pressure of each cylinder deteriorate. It is because it tends to do. That is, when the post injection amount is increased or decreased in such a state, the intended effect may not be obtained.

Therefore, in the second embodiment, the ECU 7 prohibits post-injection amount increase / decrease control as described above at the start of EGR and at the start of EGR cut (specifically, until a predetermined time elapses after the start of EGR cut). To do. By doing so, it is possible to suppress a decrease in determination accuracy in post-injection amount increase / decrease control.
[Modification]
In the above, the embodiment has been described in which the post-injection amounts of the fuel injection valves 15a to 15d are set in consideration of the temperature variation of each cylinder. In another example, the ECU 7 can set the post-injection amount of each fuel injection valve 15a to 15d based on the pressure variation of each cylinder instead of the temperature of each cylinder.

  Specifically, the ECU 7 first estimates the pressure of each cylinder (meaning the in-cylinder pressure of each cylinder; the same applies hereinafter) based on the pressure pulsation in the exhaust gas collecting portion, and obtains each of the estimations obtained by the estimation. The pressure of each cylinder is compared with the pressure of each cylinder that is obtained in advance by experiments or the like and stored as a map value. This map value corresponds to the target in-cylinder pressure in each cylinder. The pressure in the exhaust gas collecting part can be obtained by installing a pressure sensor at the position where the temperature sensor 16 is provided.

  Thereafter, when the difference (absolute value) between the estimated cylinder pressure and the map value is equal to or greater than a predetermined value, the ECU 7 increases the post-injection amount for a cylinder whose estimated pressure is higher than the map value. (Increase). In contrast, when the difference (absolute value) between the estimated cylinder pressure and the map value is equal to or greater than a predetermined value, the ECU 7 performs post-injection for a cylinder whose estimated pressure is lower than the map value. Decrease the amount (decrease) or stop post injection. In this case, the ECU 7 can execute a process as shown in FIG. 3, for example.

  Also according to the above modification, the post-injection amount can be appropriately set according to the variation in pressure of each cylinder, so that it is possible to appropriately suppress the oil dilution from proceeding. In such a modification, as described in the second embodiment, as described above, at the start of EGR and at the start of EGR cut (specifically, from the start of EGR cut until a predetermined time elapses). It is possible to prohibit the increase / decrease control of the post injection amount.

  In addition, it is not limited to acquiring the temperature or pressure of exhaust gas from the sensor (temperature sensor 16 etc.) provided in the exhaust gas collection part. In another example, the temperature or pressure of the exhaust gas can be acquired from a sensor (temperature sensor or pressure sensor) installed in each cylinder.

1 engine (internal combustion engine)
7 ECU
15a to 15d Fuel injection valve 16 Temperature sensor 20 Intake passage 23 Turbocharger 25 Exhaust passage 40 Catalyst 50 EGR device 100 Vehicle

Claims (2)

Applied to internal combustion engines with multiple cylinders,
Estimating means for estimating the temperature of each cylinder based on the pulsation of the temperature in the exhaust gas collecting portion;
Storage means for obtaining the temperature for each cylinder in advance and storing it as a map value;
When the absolute value of the difference between the temperature estimated by the estimation means and the temperature stored as the map value in the storage means is equal to or greater than a predetermined value, the estimated temperature is stored as the map value performs control Ru increases the post injection quantity for higher cylinder than the control or post the estimated temperature reduces the post injection amount for the lower cylinder than the storage temperature as the map value Control means for performing control to stop the injection ,
The control means does not perform control to increase the post injection amount, control to decrease the post injection amount, and control to stop the post injection at the start of EGR gas introduction and at the start of EGR gas introduction cut. A control device for an internal combustion engine. Applied to internal combustion engines with multiple cylinders,
Estimating means for estimating the pressure of each cylinder based on the pressure pulsation in the exhaust gas collecting portion;
Storage means for obtaining a pressure for each cylinder in advance and storing it as a map value;
When the absolute value of the difference between the pressure estimated by the estimating means and the pressure stored as the map value in the storage means is a predetermined value or more, the estimated pressure is stored as the map value performs control Ru increases the post injection quantity for higher cylinder than the control or post the estimated pressure reduces the post injection amount for the lower cylinder than the stored pressure as the map value Control means for performing control to stop the injection ,
The control means does not perform control to increase the post injection amount, control to decrease the post injection amount, and control to stop the post injection at the start of EGR gas introduction and at the start of EGR gas introduction cut. A control device for an internal combustion engine.

Images