JP2009074524A - Controller of internal-combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an internal-combustion engine capable of setting an optimum fuel consumption line with the efficiency of a continuously variable transmission taken into consideration and changing over the optimum fuel consumption line properly on the basis of the gear ratio. <P>SOLUTION: The controller performs control for internal-combustion engine configured so that its output is transmitted to a continuously variable transmission capable of making stepless speed change continuously. Specifically, an optimum fuel consumption line selecting means selects an optimum fuel consumption line corresponding to the gear ratio calculated on the basis of a request power from the driver among the plurality of lines set for each gear ratio of the transmission. An optimum fuel consumption line changeover means changes over to the selected line. This allows changing over into the optimum fuel consumption line in accordance with the gear ratio of the transmission, to achieve enhancement of the fuel consumption effectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technical field of a control device for an internal combustion engine that controls an internal combustion engine configured to transmit an output to a continuously variable transmission.

  2. Description of the Related Art Conventionally, a technique related to a continuously variable transmission (CVT (Continuously Variable Transmission)) capable of continuously shifting continuously is known. For example, in Patent Document 1, an output torque for a driver's accelerator operation can be arbitrarily changed, and an engine capable of switching a plurality of combustion modes having different optimum fuel consumption lines, and a gear ratio can be continuously changed. A control device combined with a continuously variable transmission is described. In addition, Patent Document 2 describes a technique related to the present invention.

Japanese Patent Laid-Open No. 10-329587 JP 2005-67591 A

  However, the techniques described in Patent Documents 1 and 2 described above take into consideration both the engine efficiency and the efficiency of the continuously variable transmission (hereinafter also referred to as “the continuously variable transmission efficiency”), and the optimum fuel consumption line. The engine is not properly controlled based on this.

  The present invention has been made to solve the above-described problems, and sets an optimal fuel consumption line in consideration of continuously variable transmission efficiency and appropriately switches the optimal fuel consumption line based on a gear ratio. An object of the present invention is to provide a control device for a possible internal combustion engine.

  In one aspect of the present invention, a control device for an internal combustion engine configured to control an internal combustion engine configured to transmit an output to a continuously variable transmission capable of continuously shifting continuously and continuously. An optimum fuel consumption line selecting means for selecting an optimum fuel consumption line corresponding to a speed ratio calculated from a required power from a driver from among a plurality of optimum fuel consumption lines set for each gear ratio in the vehicle; And an optimum fuel consumption line switching means for switching to the optimum fuel consumption line selected by the selection means.

  The control device for an internal combustion engine is preferably used to control an internal combustion engine configured to transmit an output to a continuously variable transmission capable of continuously shifting continuously. Specifically, the optimum fuel consumption line selecting means is configured to select the optimum fuel consumption line corresponding to the speed ratio calculated from the required power from the driver from among a plurality of optimum fuel consumption lines set for each speed ratio in the continuously variable transmission. Select a line. The multiple optimal fuel efficiency lines are set in this way because the optimal fuel efficiency line that optimizes the overall efficiency of the engine and the continuously variable transmission due to the efficiency of the continuously variable transmission (the continuously variable transmission efficiency) This is because it tends to change depending on the gear ratio of the continuously variable transmission. Then, the optimum fuel consumption line switching means switches to the optimum fuel consumption line selected by the optimum fuel consumption line selection means. Thereby, it is possible to switch to an appropriate optimum fuel consumption line according to the gear ratio of the transmission without permission, and it is possible to effectively improve the fuel consumption.

  In one aspect of the control apparatus for an internal combustion engine, the plurality of optimum fuel consumption lines includes a first optimum fuel consumption line and a second optimum fuel consumption line, and the optimum fuel consumption line selecting means is configured to change the gear ratio. Is less than “1”, the first optimum fuel consumption line is selected, and when the speed ratio is “1” or more, the second optimum fuel consumption line is selected.

  In this aspect, for example, the two optimum fuel consumption lines, that is, the first optimum fuel consumption line determined based only on the engine efficiency and the second optimum fuel consumption line determined based on both the engine efficiency and the continuously variable transmission efficiency. The optimal fuel consumption line can be switched between the two using a line. Also by this, since the optimum fuel consumption line is switched in consideration of the gear ratio of the continuously variable transmission, the fuel consumption can be improved.

  In another aspect of the control apparatus for an internal combustion engine, the optimum fuel consumption line switching unit uses, as a threshold, a power corresponding to the current rotational speed on the optimum fuel consumption line selected by the optimum fuel consumption line selection unit, When the required power is greater than the threshold, the selected optimal fuel consumption line is switched. When the required power is less than or equal to the threshold, the selected optimal fuel consumption line is switched. Absent.

  In this aspect, the optimum fuel consumption line switching means does not perform switching to the selected optimum fuel consumption line, that is, prohibits switching of the optimum fuel consumption line when the required power is equal to or less than the threshold value. Thereby, it is possible to appropriately execute the switching of the optimum fuel consumption line while preventing the deterioration of the drivability due to the switching of the optimum fuel consumption line.

  In another aspect of the control apparatus for an internal combustion engine, the optimum fuel consumption line switching unit uses, as a threshold, a power corresponding to the current rotational speed on the optimum fuel consumption line selected by the optimum fuel consumption line selection unit, When the required power is greater than the threshold value, switching to the selected optimum fuel consumption line is performed at the first shift speed, and when the required power is less than or equal to the threshold value, the first shift speed is changed. Switching to the selected optimum fuel consumption line is performed at a second shift speed slower than the speed.

  In this aspect, the optimum fuel consumption line switching means performs switching of the optimum fuel consumption line at a slow shift speed (second shift speed) that cannot be detected by the driver when the required power is equal to or less than the threshold value. As a result, the optimal fuel consumption line can be appropriately switched while suppressing the uncomfortable feeling given to the driver, and the fuel efficiency can be effectively switched to the optimal fuel consumption line that optimizes the overall efficiency of the engine and the continuously variable transmission. Can be improved.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[overall structure]
FIG. 1 is a block diagram showing a schematic configuration of a vehicle 20 to which the control device for an internal combustion engine according to the present embodiment is applied.

  The vehicle 20 mainly includes an engine (internal combustion engine) 1, a continuously variable transmission (CVT) 2, a differential 3, axles 4a and 4b, wheels 5a and 5b, an ECU (Engine Control Unit) 10, An accelerator opening sensor 11 and a vehicle speed sensor 12 are provided.

  The engine 1 is a device that generates driving power for the vehicle 20 by burning a mixture of intake air and fuel in a combustion chamber. The continuously variable transmission 2 is a mechanism capable of continuously changing gears continuously and is configured to transmit the output of the engine 1. For example, the continuously variable transmission 2 includes two pulleys, and the gear ratio is continuously changed by changing the groove width of the V groove for winding the endless belt in each pulley. The differential 3 is connected to the output rotation shaft of the continuously variable transmission 2 and is configured to absorb the rotational difference between the wheels 5a and 5b, and decelerates the rotation speed of the output rotation shaft of the continuously variable transmission 2. It is configured to be possible. The axles 4 a and 4 b are rotating shafts connected to the wheels 5 a and 5 b, and are configured to be connected to the differential 3. Therefore, in the vehicle 20, the power generated from the engine 1 is transmitted to the wheels 5a and 5b via the crankshaft, the continuously variable transmission 2, the differential 3 and the axles 4a and 4b (not shown).

  The accelerator opening sensor 11 is a sensor that detects the accelerator opening corresponding to the accelerator operation by the driver. The vehicle speed sensor 12 is a sensor that detects the speed (vehicle speed) of the vehicle 20.

  The ECU 10 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown). The ECU 10 mainly controls the engine 1 and the continuously variable transmission 2 based on the accelerator opening detected by the accelerator opening sensor 11 and the vehicle speed detected by the vehicle speed sensor 12. In the present embodiment, the ECU 10 executes a process for selecting an optimum fuel consumption line based on the gear ratio of the continuously variable transmission 2 and the like, and a process for switching to the selected optimum fuel consumption line. Thus, ECU10 is corresponded to the control apparatus of the internal combustion engine in this invention. Specifically, the ECU 10 operates as optimum fuel consumption line selection means and optimum fuel consumption line switching means.

[First Embodiment]
Next, a control method according to the first embodiment performed by the ECU 10 will be described.

  In the first embodiment, the ECU 10 presets a plurality of optimum fuel consumption lines for each speed ratio in the continuously variable transmission 2, and switches to the optimum fuel consumption line corresponding to the speed ratio calculated from the power required by the driver. Do. This is because the optimum fuel consumption line that optimizes the overall efficiency of the engine 1 and the continuously variable transmission 2 is determined by the efficiency of the continuously variable transmission 2 (the continuously variable transmission efficiency). This is because they tend to change depending on the situation. That is, when the continuously variable transmission efficiency is added to the engine efficiency, the optimum fuel consumption line at which the overall efficiency is optimum tends to change depending on the gear ratio. Therefore, in the first embodiment, a plurality of optimum fuel consumption lines are preset for each gear ratio. In the present specification, the optimal fuel consumption line means a map (engine map) showing the relationship between the engine speed and the engine torque at which the fuel consumption is optimal.

  FIG. 2 is a diagram showing a specific example of a plurality of optimum fuel consumption lines for each gear ratio. FIG. 2 shows the engine speed on the horizontal axis and the engine torque on the vertical axis. Considering the overall efficiency of the engine 1 and the continuously variable transmission 2 as described above, as shown in FIG. 2, a plurality of optimum fuel consumption lines that optimize the overall efficiency are set for each speed ratio γ.

  FIG. 3 is a diagram illustrating a flow of a fuel consumption calculation method according to the first embodiment. Note that the fuel consumption is calculated by the ECU 10.

First, the ECU 10 acquires the accelerator opening Pap from the accelerator opening sensor 11 and acquires the vehicle speed V from the vehicle speed sensor 12. Then, the ECU 10 calculates the required driving force F in the vehicle 20 from the accelerator opening Pap and the vehicle speed V, and calculates the output rotational speed N ₀ (corresponding to the rotation of the wheels 5a and 5b) from the vehicle speed V. To do. Next, the ECU 10 calculates the output torque T ₀ of the vehicle 20 from the required driving force F, and calculates the output power P ₀ of the vehicle 20 from the output torque T ₀ and the output rotation speed N ₀ .

Next, the ECU 10 obtains the power P _e , the engine speed N _e , the engine torque T _e and the like of the engine 1 as indicated by a broken line area A1 in FIG. Specifically, ECU 10, along with the like gear ratio of the output rotational speed _{N 0} and the continuously variable transmission 2 gamma obtaining an engine speed _{N e,} the engine torque _{T e} from the power _{P e} and the engine speed _{N e} Ask. In this case, ECU 10, the engine torque _{T e,} the engine speed _{N e,} and with obtaining the torque loss _{T loss} of mission from the gear ratio gamma, obtains the power _{P e} from the loss torque _{T loss} of the output power _{P 0} and Mission . That, ECU 10 based on the torque loss _{T loss} of mission varies depending on the gear ratio gamma, to feedback computation and power _{P e} and the engine torque _{T e.} Then, ECU 10 on the basis of the engine speed _{N e} and the engine torque _{T e,} determine the fuel consumption. As a result, it is possible to obtain the fuel consumption that optimizes the overall efficiency of the engine 1 and the continuously variable transmission 2. That is, it is possible to obtain the fuel consumption amount based on the optimum fuel consumption line that optimizes the overall efficiency of the engine efficiency and the continuously variable transmission efficiency.

  According to the first embodiment described above, it is possible to switch to an appropriate optimum fuel consumption line according to the gear ratio of the continuously variable transmission 2, and it is possible to effectively improve fuel consumption (fuel consumption).

[Second Embodiment]
Next, a control method according to the second embodiment performed by the ECU 10 will be described.

  In the second embodiment, as in the first embodiment described above, the optimum fuel consumption line is switched according to the gear ratio using a plurality of preset optimum fuel consumption lines. However, the second embodiment is different from the first embodiment in that two optimum fuel consumption lines are used as the plurality of optimum fuel consumption lines and the two optimum fuel consumption lines are switched depending on the gear ratio. Specifically, in the second embodiment, the ECU 10 determines the first optimum fuel consumption line determined based only on the engine efficiency, and the second determined based on both the engine efficiency and the continuously variable transmission efficiency. Two optimal fuel consumption lines of the optimal fuel consumption line are used, and the optimal fuel consumption line is switched between the two. More specifically, the ECU 10 selects the second optimum fuel consumption line when the gear ratio is 1 or more, and selects the first optimum fuel consumption line when the gear ratio is less than 1.

  FIG. 4 is a diagram for explaining a method of switching the optimum fuel consumption line according to the second embodiment. 4A shows the relationship between engine torque (horizontal axis) and continuously variable transmission efficiency (vertical axis), and FIG. 4B shows the transmission ratio (horizontal axis) and continuously variable transmission efficiency. The relationship with (vertical axis) is shown. FIG. 4A shows that the continuously variable transmission efficiency increases (the continuously variable transmission efficiency improves) as the engine torque increases. Further, as shown in FIG. 4B, the continuously variable transmission efficiency is the highest when the gear ratio is approximately 1 (the continuously variable transmission efficiency is improved), and as the gear ratio is further away from 1, the continuously variable transmission. It can be seen that the efficiency decreases (the continuously variable transmission efficiency decreases).

  According to FIG. 4, when the gear ratio is 1 or more, when the output power of the engine 1 is constant, the continuously variable transmission efficiency increases as the gear ratio decreases, and when the engine torque increases, the continuously variable transmission. It turns out that efficiency becomes large. Therefore, when the gear ratio is 1 or more, it can be said that the cost for improving the continuously variable transmission efficiency of the continuously variable transmission 2 is large due to a synergistic effect. In other words, it can be said that the overall efficiency tends to improve. Therefore, when the gear ratio is 1 or more, it is considered that there is a point where the fuel consumption is minimum at a position away from the optimum fuel consumption line determined based only on the engine efficiency. As described above, in the second embodiment, when the gear ratio is 1 or more, both the engine efficiency and the continuously variable transmission efficiency are used without using the first optimum fuel consumption line determined based only on the engine efficiency. The second optimum fuel consumption line determined based on the above is used.

  On the other hand, when the gear ratio is less than 1, when the output power of the engine 1 is constant, the continuously variable transmission efficiency increases as the gear ratio increases, but when the engine torque decreases, the continuously variable transmission. Efficiency is reduced. When the speed ratio is less than 1, when the output power of the engine 1 is constant, the continuously variable transmission efficiency decreases as the speed ratio decreases. However, when the engine torque increases, the continuously variable transmission efficiency increases. Become. Therefore, when the gear ratio is less than 1, the improvement efficiency of the continuously variable transmission 2 of the continuously variable transmission 2 is small because the effects of improving the overall efficiency cancel each other. Therefore, in this case, it is considered that the point at which the fuel consumption is minimized is generally located on the optimum fuel consumption line determined based only on the engine efficiency. As described above, in the second embodiment, when the gear ratio is less than 1, only the engine efficiency is used without using the second optimum fuel consumption line determined based on both the engine efficiency and the continuously variable transmission efficiency. The first optimum fuel consumption line determined based on the above is used.

  FIG. 5 is a diagram showing specific examples of the first optimum fuel consumption line and the second optimum fuel consumption line. FIG. 5 shows the engine speed on the horizontal axis and the engine torque on the vertical axis. In this case, the first optimum fuel consumption line is indicated by a symbol C1, and the second optimum fuel consumption line is indicated by a symbol C2.

  Also according to the second embodiment described above, since the optimum fuel consumption line is switched in consideration of the gear ratio of the continuously variable transmission 2, the fuel consumption can be improved.

  In addition, although embodiment which uses only two optimal fuel consumption lines was shown above, it is not limited to this. In another example, the first optimal fuel consumption line determined based only on the engine efficiency is used, and both the engine efficiency and the continuously variable transmission efficiency are taken into consideration, and a plurality of ( (2 or more) optimum fuel consumption lines can be used. In this case, the ECU 10 selects the first optimum fuel consumption line when the transmission ratio is less than 1, and when the transmission ratio is 1 or more, the ECU 10 selects the transmission ratio from the plurality of optimum fuel consumption lines. The optimum fuel consumption line can be selected.

[Third Embodiment]
Next, a control method according to the third embodiment performed by the ECU 10 will be described.

  The third embodiment is different from the first and second embodiments described above in that it relates to a method for switching the optimum fuel consumption line. Specifically, in the third embodiment, the ECU 10 executes a predetermined process when switching to the optimum fuel consumption line selected by any one of the methods of the first and second embodiments described above. Specifically, the ECU 10 determines whether or not to switch the optimum fuel consumption line based on the required power from the driver.

  More specifically, the ECU 10 uses power corresponding to the current engine speed on the optimum fuel consumption line to be switched as a threshold (hereinafter referred to as “power threshold”), and the required power is larger than the power threshold. Is switched to the optimal fuel consumption line, and when the required power is less than or equal to the power threshold, the optimal fuel consumption line is not switched. That is, when the required power is less than or equal to the power threshold, switching of the optimum fuel consumption line is prohibited. This is because, in the vicinity of the speed ratio threshold value for switching between the two optimal fuel consumption lines, the driver may frequently cross the threshold value with a slight accelerator operation, but this causes frequent switching of the optimal fuel efficiency line. This is to prevent the occurrence of rotation speed fluctuation and deterioration of drivability.

  FIG. 6 is a diagram for explaining a method of switching the optimum fuel consumption line according to the third embodiment. In FIG. 6, the engine speed is shown in the horizontal direction and the engine torque is shown in the vertical direction. FIG. 6 shows a situation during downshift (that is, when there is a downshift request).

  FIG. 6A is a diagram for explaining a case where the optimum fuel consumption line is switched. In the present situation, it is assumed that the traveling power is power 71 and the optimal fuel consumption line 61 is used. That is, the operating point of the engine 1 is located at the point indicated by the symbol C <b> 1 on the optimal fuel consumption line 61. At this time, it is assumed that there is a request corresponding to the required power 72 from the driver. Here, from the intersection D1 between the current engine speed and the optimum fuel consumption line 62 to be switched (the optimum fuel consumption line selected by the method of any one of the first and second embodiments described above), the power threshold 73 is set. Is obtained. In this case, it can be said that the required power 72 is larger than the power threshold 73. Therefore, the ECU 10 promptly switches the optimum fuel consumption line as indicated by the white arrow in FIG. As a result, the operating point of the engine 1 moves to the point indicated by the symbol C2 on the optimum fuel consumption line 62. Specifically, the ECU 10 switches from the optimum fuel consumption line 61 to the optimum fuel consumption line 62 at a predetermined shift speed. In the following, such switching is referred to as “first optimum fuel consumption line switching control”, and the shift speed when the first optimum fuel consumption line switching control is executed is referred to as “first shift speed”.

  FIG. 6B is a diagram for explaining a case where the optimum fuel consumption line is not switched. In the present situation, it is assumed that the traveling power is power 74 and the optimum fuel consumption line 63 is used. That is, it is located at the point indicated by the symbol C2 on the optimum fuel consumption line 63. At this time, it is assumed that there is a request corresponding to the required power 75 from the driver. Here, from the intersection D2 between the current engine speed and the optimum fuel consumption line 64 to be switched (the optimum fuel consumption line selected by the method of any one of the first and second embodiments described above), the power threshold value 76 is obtained. Is obtained. In this case, it can be said that the required power 75 is equal to or less than the power threshold value 76. Therefore, the ECU 10 does not switch the optimal fuel consumption line. That is, the ECU 10 prohibits switching of the optimal fuel consumption line in order to prevent deterioration of drivability due to switching of the optimal fuel consumption line. As a result, as indicated by the white arrow in FIG. 6B, the operating state of the engine 1 changes on the optimal fuel consumption line 63, and the operating point of the engine 1 is indicated by the symbol C4 on the optimal fuel consumption line 63. Move to a point.

  FIG. 7 is a flowchart showing the switching process of the optimum fuel consumption line according to the third embodiment. This process is repeatedly executed by the ECU 10.

  First, in step S <b> 101, the ECU 10 acquires the accelerator opening from the accelerator opening sensor 11. Then, the process proceeds to step S102. In step S102, the ECU 10 calculates the driver's required power from the accelerator opening acquired in step S101. Then, the process proceeds to step S103.

  In step S103, the ECU 10 obtains a power threshold value corresponding to the current engine speed on the optimum fuel consumption line to be switched. That is, the ECU 10 determines the power threshold value from the intersection of the current engine speed and the optimum fuel consumption line to be switched (the optimum fuel consumption line selected by the method of any one of the first and second embodiments described above). Ask. Then, the process proceeds to step S104.

  In step S104, the ECU 10 determines whether or not there is a downshift request. If there is a downshift request (step S104; Yes), the process proceeds to step S105. If there is no downshift request (step S104; No), the process proceeds to step S107. In this case, the ECU 10 does not switch the optimum fuel consumption line (step S107). Then, the process exits the flow.

  In step S105, the ECU 10 determines whether or not the required power obtained in step S102 is greater than the power threshold obtained in step S103. Here, the ECU 10 determines whether or not the optimum fuel consumption line may be switched. When the required power is larger than the power threshold (step S105; Yes), the process proceeds to step S106. In this case, it can be said that the optimum fuel consumption line may be switched. In other words, it is considered that the deterioration of drivability due to the switching of the optimum fuel consumption line hardly occurs. Therefore, in step S106, the ECU 10 promptly switches the optimal fuel consumption line. Specifically, the ECU 10 executes the first optimum fuel consumption line switching control described above. When the above process ends, the process exits the flow.

  On the other hand, when the required power is equal to or less than the power threshold (step S105; No), the process proceeds to step S107. In this case, it can be said that the optimum fuel consumption line should not be switched. That is, it is considered that there is a high possibility that deterioration of drivability due to switching of the optimum fuel consumption line will occur. Therefore, in step S107, the ECU 10 does not switch the optimum fuel consumption line, in other words, uses the current optimum fuel consumption line. That is, the ECU 10 prohibits switching of the optimum fuel consumption line in order to prevent deterioration of drivability. When the above process ends, the process exits the flow.

  In the above description, the method for switching the optimum fuel consumption line at the time of downshift has been described with reference to FIGS. 6 and 7. However, the optimum fuel consumption line can be switched by the same method at the time of upshift.

  According to the third embodiment described above, it is possible to appropriately execute the switching of the optimum fuel consumption line while preventing the deterioration of the drivability due to the switching of the optimum fuel consumption line.

[Fourth Embodiment]
Next, a control method according to the fourth embodiment performed by the ECU 10 will be described.

  Also in the fourth embodiment, the ECU 10 executes the predetermined process when switching to the optimum fuel consumption line selected by any one of the methods of the first and second embodiments described above, in the third embodiment described above. It is the same. However, in the third embodiment, the optimum fuel consumption line is not switched when the required power is equal to or less than the power threshold, whereas in the fourth embodiment, the required power is equal to or less than the power threshold. The difference is that the optimal fuel consumption line is switched. In the fourth embodiment as well, when the required power is larger than the power threshold, the optimum fuel consumption line is switched similarly to the third embodiment (that is, the first optimum fuel consumption line switching control is executed).

  Specifically, in the fourth embodiment, when the required power is less than or equal to the power threshold, the ECU 10 switches the optimum fuel consumption line at a slow speed change that is not perceptible to the driver. That is, when the required power is equal to or less than the power threshold, the ECU 10 switches the optimum fuel consumption line at the second shift speed that is slower than the first shift speed described above (hereinafter, such switching is referred to as “ This is referred to as “second optimum fuel consumption line switching control”). By doing so, even when the change in the required power from the driver is small and does not exceed the power threshold, it is possible to appropriately switch the optimal fuel consumption line while suppressing the uncomfortable feeling given to the driver.

  FIG. 8 is a diagram for explaining the second optimum fuel consumption line switching control described above. In FIG. 8, the engine speed is shown in the horizontal direction, and the engine torque is shown in the vertical direction. FIG. 8 shows a situation during downshift (that is, when there is a downshift request).

  In the present situation, it is assumed that the traveling power is power 77 and the optimum fuel consumption line 65 is used. That is, the operating point of the engine 1 is located at the point indicated by the symbol C5 on the optimal fuel consumption line 65. At this time, it is assumed that there is a request corresponding to the required power 78 from the driver. Here, from the intersection D3 between the current engine speed and the optimum fuel consumption line 66 to be switched (the optimum fuel consumption line selected by the method of any one of the first and second embodiments described above), the power threshold 79 Is obtained. In this case, it can be said that the required power 78 is equal to or less than the power threshold 79. Therefore, the ECU 10 executes the second optimum fuel consumption line switching control. Specifically, the ECU 10 switches the optimum fuel consumption line at a slow shift speed (second shift speed) that cannot be detected by the driver. As a result, the operating point of the engine 1 moves to the point indicated by the symbol C6 on the optimum fuel consumption line 66 as indicated by the white arrow in FIG. In this case, the engine speed is slightly reduced.

  FIG. 9 is a diagram showing changes in engine speed and the like during the second optimum fuel consumption line switching control. In FIG. 9, time is shown in the horizontal direction. Further, the graph 81 shows the power (traveling power) of the engine 1, the graph 82 shows the engine speed, the graph 83 shows the engine torque, and the graph 84 shows the vehicle speed.

  In this case, it is assumed that there is a downshift request at time t11. Therefore, the ECU 10 starts switching the optimal fuel consumption line at time t11. In this case, since the required power is less than or equal to the power threshold, the ECU 10 executes the second optimum fuel consumption line switching control time. Specifically, the ECU 10 switches the optimum fuel consumption line at a slow shift speed (second shift speed) that cannot be detected by the driver. For example, the ECU 10 performs a shift so that the engine speed changes at about “−200 (rpm / sec)”. By switching the optimum fuel consumption line in this way, as indicated by the white arrow in FIG. 9, the engine speed is slowly decreased and the engine torque is slowly increased. At time t12, the power of the engine 1 reaches the required power. Thereafter, at time t13, the power of the engine 1 reaches the power threshold value.

  FIG. 10 is a flowchart showing the switching process of the optimum fuel consumption line according to the fourth embodiment. This process is repeatedly executed by the ECU 10.

  Since the processing of steps S201 to S207 is the same as the processing of steps S101 to S107 described above (see FIG. 7), the description thereof is omitted. Here, only the process of step S208 will be described.

  When the required power is less than or equal to the power threshold (step S205; No), the process proceeds to step S208. In step S208, the ECU 10 executes second optimum fuel consumption line switching control. That is, since the required power is equal to or less than the power threshold value, the ECU 10 executes the second optimum fuel consumption line switching control in order to suppress the uncomfortable feeling given to the driver when the optimum fuel consumption line is switched. Specifically, the ECU 10 switches the optimum fuel consumption line at a slow shift speed (second shift speed) that cannot be detected by the driver. When the above process ends, the process exits the flow.

  In the above description, the method for switching the optimum fuel consumption line at the time of downshift has been described with reference to FIGS. 8 to 10. However, the optimum fuel consumption line can be switched by the same method at the time of upshift.

  According to the fourth embodiment described above, the optimum fuel consumption line can be appropriately switched while suppressing the uncomfortable feeling given to the driver, and the optimum fuel consumption line at which the overall efficiency of the engine 1 and the continuously variable transmission 2 is optimized. The fuel efficiency can be improved by effectively switching to.

1 is a block diagram showing a schematic configuration of a vehicle to which a control device for an internal combustion engine according to an embodiment is applied. It is the figure which showed the specific example of the some optimal fuel consumption line for every gear ratio. It is a figure which shows the flow of the calculation method of the fuel consumption in 1st Embodiment. It is a figure for demonstrating the switching method of the optimal fuel consumption line which concerns on 2nd Embodiment. It is a figure which shows the specific example of a 1st optimal fuel consumption line and a 2nd optimal fuel consumption line. It is a figure for demonstrating the switching method of the optimal fuel consumption line which concerns on 3rd Embodiment. It is a flowchart which shows the switching process of the optimal fuel consumption line which concerns on 3rd Embodiment. It is a figure for demonstrating 2nd optimal fuel consumption line switching control. It is a figure which shows changes, such as an engine speed at the time of 2nd optimal fuel consumption line switching control. It is a flowchart which shows the switching process of the optimal fuel consumption line which concerns on 4th Embodiment.

Explanation of symbols

1 engine (internal combustion engine)
2 Continuously variable transmission (CVT)
3 Differential 5a, 5b Wheel 10 ECU
11 Accelerator opening sensor 12 Vehicle speed sensor 20 Vehicle

Claims (4)

A control device for an internal combustion engine that controls an internal combustion engine configured to transmit an output to a continuously variable transmission capable of continuously shifting continuously and continuously,
An optimum fuel consumption line selecting means for selecting an optimum fuel consumption line corresponding to a speed ratio calculated from a required power from a driver from a plurality of optimum fuel consumption lines set for each speed ratio in the continuously variable transmission;
An internal combustion engine control device comprising: an optimum fuel consumption line switching means for switching to the optimum fuel consumption line selected by the optimum fuel consumption line selection means. The plurality of optimum fuel consumption lines is composed of two lines, a first optimum fuel consumption line and a second optimum fuel consumption line,
The optimum fuel consumption line selection means selects the first optimum fuel consumption line when the gear ratio is less than “1”, and the second optimum fuel consumption line when the gear ratio is “1” or more. The control device for an internal combustion engine according to claim 1, wherein: The optimum fuel consumption line switching means uses, as a threshold value, the power corresponding to the current rotational speed on the optimum fuel consumption line selected by the optimum fuel consumption line selection means,
When the required power is greater than the threshold, switch to the selected optimal fuel consumption line,
3. The control device for an internal combustion engine according to claim 1, wherein when the required power is equal to or less than the threshold value, switching to the selected optimum fuel consumption line is not performed. The optimum fuel consumption line switching means uses, as a threshold value, the power corresponding to the current rotational speed on the optimum fuel consumption line selected by the optimum fuel consumption line selection means,
When the required power is greater than the threshold, switching to the selected optimal fuel consumption line at the first shift speed,
The switch to the selected optimum fuel consumption line is performed at a second shift speed that is slower than the first shift speed when the required power is less than or equal to the threshold value. 3. The control device for an internal combustion engine according to 2.

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