JP2019173675A - Control device of internal combustion engine - Google Patents

Abstract

To further improve fuel economy.SOLUTION: An ECU 40 switch-controls an EGR function of an engine 12 mounted to a vehicle 10 together with a CVT 32 between an on-state and an off-state. Concretely, the ECU 40 performs processing for estimating the heat efficiency of an internal combustion engine in a specified period for accelerating the vehicle 10 on the basis of outputs of a variety of sensors 38 in response to an EGR-on state and an EGR-off state, respectively. The ECU 40 also performs processing for estimating the transmission efficiency of the CVT 32 in the specified period on the basis of the outputs of a variety of the sensors 38 in response to the EGR-on state and the EGR-off state, respectively. Furthermore, the ECU 40 controls the turn-on/off of the EGR function in the specified period on the basis of the heat efficiency and the transmission efficiency which are estimated as above.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to a control device that controls an internal combustion engine mounted on a vehicle together with an automatic transmission.

  An example of this type of control device is disclosed in Patent Document 1. According to this document, when the vehicle is accelerating, the engine operating state does not enter a high-load / low-rotation region in which fuel consumption performance is degraded or misfire is likely to occur due to residual EGR. The gear ratio of the half toroidal CVT is controlled so that it does not enter the region with poor EGR resistance. Thereby, EGR can be performed effectively without causing problems such as a reduction in fuel consumption performance or the occurrence of misfire.

JP 2002-106405 A

  Since the transmission efficiency of CVT fluctuates when the gear ratio is switched, Patent Document 1 does not disclose how to suppress the reduction in fuel efficiency caused by this fluctuation. Therefore, it can be said that there is still room for improving fuel efficiency when the vehicle is viewed as a whole.

  Therefore, a main object of the present invention is to provide a control device for an internal combustion engine that can further improve fuel efficiency.

  An internal combustion engine control device according to the present invention is a control device that switches and controls an EGR (Exhaust Gas Recirculation) function of an internal combustion engine mounted on a vehicle together with an automatic transmission between an on state and an off state. Detection means for detecting the current drive state, and first estimation means for executing processing for estimating the thermal efficiency of the internal combustion engine at a specific time for accelerating the vehicle based on the output of the detection means corresponding to each of the on state and the off state The second estimating means for executing the process of estimating the transmission efficiency of the automatic transmission at a specific time based on the output of the detecting means corresponding to each of the on state and the off state, and the thermal efficiency estimated by the first estimating means And control means for controlling on / off of the EGR function at a specific time based on the transmission efficiency estimated by the second estimation means.

  With respect to the required driving force determined from the accelerator operation of the driver, the EGR function during acceleration of the vehicle is required to increase the torque even under conditions where the degree of torque reduction by maintaining the EGR function in the on state is small and within an allowable range. When the is turned on, depending on the environmental conditions such as the intake air temperature, there is a region where the fuel consumption deteriorates conversely due to an increase in the amount of depression of the accelerator in order to limit the torque reduction due to the ignition delay. In addition, the fuel consumption is not only influenced by the thermal efficiency of the internal combustion engine, but also by the transmission efficiency of the automatic transmission. Therefore, according to the present invention, the thermal efficiency of the internal combustion engine and the transmission efficiency of the automatic transmission are estimated corresponding to each on / off of the EGR function at a specific time for accelerating the vehicle, and specified based on the estimated thermal efficiency and transmission efficiency. The on / off state of the EGR function at the time is controlled. As a result, the fuel efficiency of the vehicle can be further improved.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

It is a block diagram which shows the principal part structure of the vehicle of this Example. It is a flowchart which shows a part of operation | movement of ECU shown in FIG. It is a flowchart which shows a part of other operation | movement of ECU shown in FIG. (A) is a map showing an example of a torque characteristic curve corresponding to EGR on control, and (B) is a map showing an example of a torque characteristic curve corresponding to EGR off control. It is a map which shows an example of the change of the torque correction amount with respect to intake air temperature. (A) is a map corresponding to EGR on control and showing an example of change in torque correction amount with respect to ignition delay amount, and (B) is a map corresponding to EGR off control and change in torque correction amount with respect to ignition delay amount. It is a map which shows an example. (A) is a map showing an example of a fuel injection amount curve corresponding to EGR on control, and (B) is a map showing an example of a fuel injection amount curve corresponding to EGR off control. (A) is a map showing an example of the relationship between the gear ratio and the transmission efficiency of CVT, (B) is a map showing another example of the relationship between the gear ratio and the transmission efficiency of CVT, (C) It is a map which shows another example of the relationship between a gear ratio and the transmission efficiency of CVT, (D) is a map which shows another example of the relationship between a gear ratio and the transmission efficiency of CVT.

  Referring to FIG. 1, a vehicle 10 of this embodiment includes a 4-stroke engine (internal combustion engine) 12 having three cylinders 141 to 143 formed as a power source. Further, the engine 12 has an EGR (Exhaust Gas Recirculation) function, and the exhaust gas is recirculated when the EGR function is on.

  When an IG on operation is performed by an ignition key (not shown), the ECU 40 turns on the relay 22 to start the engine 12. The electric power of the battery 24 is supplied to the starter 26 via the relay 22 in the on state. The starter 26 rotates the drive plate 28 attached to the end of the crankshaft 16 to perform cranking.

  The engine 12 is started by cranking, and a piston (not shown) provided in each of the cylinders 141 to 143 moves up and down at a speed at which the crankshaft 16 can rotate at an idle speed. The rotational force of the crankshaft 16 is transmitted to the rotating shaft 20 s of the alternator 20 via the belt 18, and the battery 24 is charged by the power generated by the alternator 20.

  Note that the rotation speed of the crankshaft 16 changes according to the depression amount of an accelerator pedal (not shown). Further, the vehicle 10 includes engine speed, vehicle speed, accelerator opening (accelerator pedal depression amount), accelerator opening speed (accelerator pedal depression velocity), intake pipe pressure, intake air temperature, ignition retardation amount for suppressing knocking, and the like. The current driving state is detected by various sensors 38.

  A torque converter 30 is provided between the drive plate 28 and the CVT 32, and the torque of the engine 12 is transmitted to the CVT 32 via the torque converter 30. CVT 32 drives drive shaft 36 coupled to differential mechanism 34 according to the torque transmitted from torque converter 30 and the current gear ratio.

  The ECU 40 executes the acceleration EGR control process shown in FIGS. 2 and 3. A control program corresponding to this flowchart is stored in the memory 40m. When executing the acceleration EGR control process, the ECU 40 functions as an EGR on / off control device together with various sensors 38.

  Further, the memory 40m stores the maps shown in FIGS. 4A, 4B, 5, 6A, 6B, 7A, and 7B. Further, a plurality of maps including the maps shown in FIGS. 8A to 8D are stored.

  Among these, the map in FIG. 4A is a torque characteristic curve map showing torque characteristic curves Ct1a to Ct4a corresponding to EGR on control and drawn for each different intake pipe pressure, and in FIG. 4B. The map is a torque characteristic curve graph showing torque characteristic curves Ct1b to Ct4b drawn for each different intake pipe pressure corresponding to EGR off control. In both maps of FIG. 4A and FIG. 4B, the engine speed is assigned to the horizontal axis and the torque is assigned to the vertical axis.

  The map in FIG. 5 is a torque correction amount map showing an example of a change in torque correction amount with respect to the intake air temperature. The map in FIG. 6A is a torque correction amount map corresponding to EGR on control and showing an example of a change in torque correction amount with respect to the ignition delay amount. The map in FIG. 6B is a torque correction amount map corresponding to EGR off control and showing an example of a change in torque correction amount with respect to the ignition delay amount.

  The map in FIG. 7A is a fuel injection amount curve map showing fuel injection amount curves Cg1a to Cg4a corresponding to EGR on control and drawn for different intake pipe pressures. The map in FIG. 7B is a fuel injection amount curve map showing fuel injection amount curves Cg1b to Cg4b corresponding to EGR off control and drawn for different intake pipe pressures. In these maps, the engine speed is assigned to the horizontal axis, and the fuel injection amount is assigned to the vertical axis.

  The map of FIG. 8A is a CVT efficiency map corresponding to a torque of 10 Nm and an engine speed of 1000 rpm, and showing the relationship between the gear ratio and the transmission efficiency of CVT 32, and the graph of FIG. Is a CVT efficiency map corresponding to the torque of the engine and the engine speed of 1000 rpm and showing the relationship between the gear ratio and the transmission efficiency of CVT32.

  The map of FIG. 8C is a CVT efficiency map corresponding to a torque of 30 Nm and an engine speed of 1000 rpm and showing the relationship between the gear ratio and the transmission efficiency of CVT 32. The map of FIG. 8D is 40 Nm. Is a CVT efficiency map corresponding to the torque of the engine and the engine speed of 1000 rpm and showing the relationship between the gear ratio and the transmission efficiency of CVT32. In addition to these CVT efficiency maps, a plurality of CVT efficiency maps corresponding to different combinations of torque and engine speed are stored in the memory 48m.

  The transmission efficiency of the CVT 32 decreases due to an increase in pinching pressure of the steel belt accompanying a shift, and an increase in mechanical loss of the hydraulic pump. Therefore, in the above-described CVT efficiency map, the amount of decrease in transmission efficiency increases as the gear ratio increases (the deceleration width increases).

  Referring to FIG. 2, in step S01, it is repeatedly determined whether or not a precondition consisting of the following conditions (A) to (F) is satisfied.

  As condition (A), “the intake air temperature is above a predetermined value” is imposed, and as condition (B), “when knocking occurs below a predetermined engine load range when the accelerator pedal is depressed last time” is imposed. As the condition (C), “the accelerator opening is equal to or greater than a predetermined value” is imposed.

  In addition, as condition (D), “the accelerator opening speed is a predetermined value or more” is imposed, and as condition (E), “that a predetermined time or more has passed since the previous precondition was satisfied”. As the condition (F), “the amount of depression of the accelerator pedal is reduced after the previous precondition is satisfied” is imposed.

  If the determination result in step S01 is updated from NO to YES, that is, if all of the conditions (A) to (F) are satisfied, the process proceeds to step S02. In step S02, the driving force required for accelerating the vehicle 10 is estimated as the “required driving force” based on the current engine speed, vehicle speed, accelerator opening, and accelerator opening speed.

  In step S03, a torque characteristic curve map for EGR ON control (see FIG. 4A), a torque correction amount map (see FIGS. 5 and 6A), and a fuel injection amount curve map (see FIG. 7A). ) Is selected. In step S04, a torque specific curve corresponding to the current intake pipe pressure is defined with reference to the torque characteristic curve map selected in step S03. In step S05, with reference to the torque characteristic curve defined in step S04, the torque corresponding to the current engine speed is estimated as “base torque”.

  In step S06, a torque correction amount corresponding to the current intake air temperature is calculated with reference to the torque correction amount map shown in FIG. 5, and the current ignition delay amount is referred to with reference to the torque correction amount map selected in step S03. A torque correction amount corresponding to is calculated. In step S07, the estimated torque is determined based on the base torque estimated in step S05 and the torque correction amount calculated in step S06.

  In step S08, the engine output is estimated based on the current engine speed and the estimated torque determined in step S07. In step S09, a fuel injection amount curve corresponding to the current intake pipe pressure is defined with reference to the fuel injection amount curve map selected in step S03. In step S10, the fuel injection amount corresponding to the current engine speed is estimated with reference to the fuel injection amount curve defined in step S09. In step S11, the thermal efficiency of the engine 12 is estimated based on the engine output estimated in step S08 and the fuel injection amount estimated in step S10.

  In step S12, the gear ratio is estimated from the current engine speed and vehicle speed. In step S13, a CVT efficiency map corresponding to the current engine speed and the estimated torque determined in step S07 is selected from a plurality of CVT efficiency maps including the CVT efficiency maps shown in FIGS. 8A to 8D. Select. In step S13, the transmission efficiency of CVT 32 corresponding to the gear ratio estimated in step S12 is estimated with reference to the selected CVT efficiency map.

  In step S14, the total fuel efficiency of the vehicle 10 is estimated as “vehicle efficiency” based on the thermal efficiency of the engine 12 estimated in step S11 and the CVT 32 transmission efficiency estimated in step S13. In step S15, the actual driving force of the vehicle 10 is estimated based on the estimated torque determined in step S07, the current engine speed, the gear ratio selected in step S12, the vehicle efficiency estimated in step S14, and the like.

  In step S16, the actual driving force estimated in step S15 is subtracted from the required driving force estimated in step S02 (that is, the value of the difference between the required driving force and the actual driving force is calculated), and the subtraction value obtained thereby. Is determined to be less than or equal to the threshold value. If the determination result is NO, it is considered that the required driving force is large, the EGR function is turned off in step S21, and the process returns to step S01. (Exit from the control loop.)

  If the decision result in the step S16 is YES, it is judged in a step S17 whether or not a map for EGR off control is being selected. If the determination result is NO, the process proceeds to step S18, the torque characteristic curve map for EGR off control (see FIG. 4B), the torque correction amount map (see FIGS. 5 and 6B), and the fuel injection amount curve. A map (see FIG. 7B) is selected. When the process of step S18 is completed, the process returns to step S04.

  On the other hand, if the determination result of step S17 is YES, it will progress to step S19. In step S19, the vehicle efficiency estimated corresponding to the EGR on control is compared with the vehicle efficiency estimated corresponding to the EGR off control and the vehicle efficiency estimated corresponding to the EGR off control. It is determined whether the vehicle efficiency is estimated corresponding to the off control. If the determination result is YES, it is selected in step S20 to maintain the ON control of the EGR function, and the process returns to step S02. On the other hand, if the determination result is NO, the EGR function is turned off in step S21, and then the process returns to step S01. (Exit from the control loop.)

  As can be seen from the above description, the ECU 40 controls the EGR function of the engine 12 mounted on the vehicle 10 together with the CVT 32 between the on state and the off state. Specifically, the ECU 40 executes processing for estimating the thermal efficiency of the internal combustion engine at a specific time for accelerating the vehicle 10 based on the outputs of the various sensors 38 corresponding to each of the EGR on state and the EGR off state ( S02 ~ S11, S16). The ECU 40 also executes processing for estimating the transmission efficiency of the CVT 32 at the specific time based on the outputs of the various sensors 38 corresponding to each of the EGR on state and the EGR off state (S03, S12, S13, S16). . The ECU 40 further controls on / off of the EGR function at the specific time based on the thermal efficiency and the transmission efficiency thus estimated (S14, S19 to S21).

  With respect to the required driving force determined from the accelerator operation of the driver, the EGR function during acceleration of the vehicle is required to increase the torque even under conditions where the degree of torque reduction by maintaining the EGR function in the on state is small and within an allowable range. When the is turned on, depending on the environmental conditions such as the intake air temperature, there is a region where the fuel consumption deteriorates conversely due to an increase in the amount of depression of the accelerator in order to limit the torque reduction due to the ignition delay. Further, the fuel consumption is not only influenced by the thermal efficiency of the engine 12, but also depends on the transmission efficiency of the CVT 32. Therefore, in this embodiment, the thermal efficiency of the engine 12 and the transmission efficiency of the CVT 32 at a specific time for accelerating the vehicle 10 are estimated corresponding to each on / off of the EGR function, and specified based on the estimated thermal efficiency and the transmission efficiency. The on / off state of the EGR function at the time is controlled. Thereby, fuel consumption can be further improved.

  In this embodiment, if the required driving force estimated based on the accelerator opening and the accelerator opening speed and the actual driving force estimated based on the estimated torque or the selected gear ratio are large (from the driver's accelerator operation). The ECU 40 determines that the degree of torque reduction by maintaining the EGR function in the on state is large with respect to the determined required driving force), and the ECU 40 turns off the EGR function (S16, S21) and returns to step S01. (Exit from control loop). As a result, it is possible to achieve a driving that matches the driver's acceleration image (avoidance of an increase in the accelerator pedal to compensate for the lack of driving force due to EGR on).

  In this embodiment, the CVT 32 is mounted on the vehicle 10, but another automatic transmission such as an AT may be mounted instead of the CVT 32.

DESCRIPTION OF SYMBOLS 10 ... Vehicle 12 ... Engine 30 ... Torque converter 32 ... CVT
36 ... Drive shaft 40 ... ECU

Claims (1)

A control device for switching and controlling an EGR function of an internal combustion engine mounted on a vehicle together with an automatic transmission between an on state and an off state,
Detecting means for detecting a current driving state of the vehicle;
First estimating means for executing processing for estimating thermal efficiency of the internal combustion engine at a specific time for accelerating the vehicle based on an output of the detecting means, corresponding to each of the on state and the off state;
Second estimating means for executing processing for estimating the transmission efficiency of the automatic transmission at the specific time based on the output of the detecting means corresponding to each of the on-state and the off-state; and the first estimating means A control device for an internal combustion engine, comprising: control means for controlling on / off of the EGR function at the specific time based on the thermal efficiency estimated by the second estimation means and the transmission efficiency estimated by the second estimation means.

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