JP5131261B2 - Vehicle control device - Google Patents

Description

  The present invention relates to a vehicle control apparatus including a variable compression ratio engine.

  As this type of technology, the following Patent Document 1 discloses a technology for setting a compression ratio according to an engine speed, a load (engine torque), and a gear ratio of a vehicle transmission in a vehicle including a variable compression ratio engine. Is described.

JP-A-2005-147104

  However, in the technique described in Patent Document 1, when the engine operating ratio is shifted from the low load area to the high load area when the engine compression ratio is low, the engine compression ratio is reduced. Since the compression ratio is changed from the low compression ratio to the high compression ratio and then changed again to the low compression ratio, the compression ratio is frequently changed. In such a variable compression ratio engine that changes the compression ratio using an actuator that is supplied with electric power from the battery, in such a case, the amount of electric power consumed by the battery may increase and fuel consumption may deteriorate.

  The present invention has been made in view of the above points, and an object of the present invention is to suppress deterioration of fuel consumption in a vehicle including a variable compression ratio engine.

  In one aspect of the present invention, there is provided a vehicle control device including an engine capable of changing a compression ratio indicating a degree of compression of an air-fuel mixture using an actuator supplied with electric power from a battery, Compression ratio changing means for setting the compression ratio to be larger as the torque is lower, and when the required driving force changes, the engine operating point before the change is predetermined from the target operating point corresponding to the engine operating point corresponding to the required driving force after the change. Control means for shifting the actual engine operating point along the path of the engine, the compression ratio at the engine operating point before the change of the required driving force is set lower than the compression ratio at the target operating point When the predetermined route passes through an engine operating point where the engine torque is larger than the engine torque at the target operating point, the compression ratio is changed. Stage, until the engine torque in the actual engine operating point is greater than the engine torque at the target operating point, without increasing the actual compression ratio.

  The above-described vehicle control device is a vehicle control device capable of changing the compression ratio indicating the degree of compression of the air-fuel mixture using an actuator supplied with electric power from a battery. The vehicle control device is, for example, an ECU (Electronic Controlled Unit), and includes a compression ratio changing unit and a control unit. The compression ratio changing means sets the compression ratio to be larger as the engine torque is lower. When the required driving force changes, the control means shifts the actual engine operating point along a predetermined path from the engine operating point before the change to the target operating point that is the engine operating point corresponding to the changed required driving force. Let Here, the compression ratio at the engine operating point before the change of the required driving force is set lower than the compression ratio at the target operating point, and the predetermined path is an engine torque larger than the engine torque at the target operating point. In the case of passing through the engine operating point, the compression ratio changing means does not increase the actual compression ratio until the engine torque at the actual engine operating point becomes larger than the engine torque at the target operating point. By doing in this way, since the frequency which changes a compression ratio can be decreased, the electric energy consumed with a battery can be reduced and the deterioration of a fuel consumption can be prevented.

  In another aspect of the vehicle control device, when the predetermined route does not pass through an engine operating point that is an engine torque larger than the engine torque at the target operating point, the compression ratio changing unit includes: Even if the engine torque at the actual engine operating point is smaller than the engine torque at the target operating point, the actual compression ratio is set to the compression ratio at the target operating point. In this way, even during slow acceleration, the amount of power consumed by the battery can be reduced, and deterioration of fuel consumption can be suppressed.

  A control device for a vehicle having an engine capable of changing a compression ratio indicating the degree of compression of an air-fuel mixture using an actuator supplied with electric power from a battery, wherein the compression ratio increases as the engine torque decreases. When the compression ratio changing means to be set and the required driving force change, the actual engine along the predetermined path from the engine operating point before the change to the target operating point corresponding to the engine driving point corresponding to the changed required driving force Control means for shifting the operating point, the compression ratio at the engine operating point before the change of the required driving force is set lower than the compression ratio at the target operating point, the predetermined path, When passing through an engine operating point where the engine torque is larger than the engine torque at the target operating point, the compression ratio changing means Until the engine torque becomes larger than the engine torque at the target operating point at the point, without increasing the actual compression ratio. By doing in this way, the frequency which changes a compression ratio can be decreased and a fuel consumption deterioration can be prevented.

It is a figure showing roughly the whole composition of vehicles concerning this embodiment. It is a schematic diagram which shows the cross-sectional structure of an engine. It is a figure which shows the mode of the transition of the engine operating point by the general vehicle control method. It is a figure which shows the mode of the transition of the engine operating point by the control method of the vehicle which concerns on 1st Embodiment. It is a flowchart which shows an example of the control processing of the vehicle which concerns on 1st Embodiment. It is a figure which shows the mode of the transition of the engine operating point by the control method of the vehicle which concerns on 2nd Embodiment. It is a figure which shows the fuel-consumption best range in the case of compression ratio variable and fixed. It is a figure which shows the fuel consumption optimal line by the control method of the vehicle which concerns on 3rd Embodiment. It is a flowchart which shows an example of the control processing of the vehicle which concerns on 3rd Embodiment.

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

[Device configuration]
FIG. 1 schematically shows an overall configuration of a vehicle 100 to which a vehicle control device of the present invention is applied. FIG. 2 is a schematic diagram showing a cross-sectional configuration of the engine 10. In FIGS. 1 and 2, broken-line arrows indicate signal flows.

  First, the overall configuration of the vehicle 100 will be described with reference to FIG. The vehicle 100 includes an engine 10, a transmission 110, and an ECU (Electronic Controlled Unit) 60. As will be described in detail later, the engine 10 is a variable compression ratio engine capable of changing the compression ratio indicating the degree of compression of the air-fuel mixture. The engine 10 has a plurality of cylinders 34. For example, in the example shown in FIG. 1, the engine 10 is an inline 4-cylinder engine. The engine 10 has an intake passage 50 for supplying intake air into the combustion chamber of each cylinder 34 and an exhaust passage 58 for discharging exhaust gas from the combustion chamber of each cylinder 34. The intake passage 50 is provided with a throttle valve 52 for adjusting the intake air amount supplied into the combustion chamber of each cylinder 34 and an air flow sensor 57 for detecting the intake air amount. The opening degree of the throttle valve 52 is adjusted by the electric actuator 53. The engine 10 is controlled by a control signal from an ECU (Electronic Controlled Unit) 60.

  The output from the engine 10 is transmitted to the continuously variable transmission 110 via the crankshaft 43. In the example illustrated in FIG. 1, the continuously variable transmission 110 is a belt-type continuously variable transmission. The transmission 110 includes a primary pulley 110a, a secondary pulley 110b, and a belt 111 made of metal or the like wound around both pulleys. The belt effective diameter is changed by moving the movable sheaves 110aa and 110ba of both pulleys in the axial direction (the direction indicated by the double-ended arrows), and the output from the engine 10 is shifted when being transmitted from the primary pulley 110a to the secondary pulley 110b. Is done. The secondary pulley 110 b is connected to the drive shaft 143, and the output from the secondary pulley 110 b is transmitted to the drive shaft 143. The output transmitted to the drive shaft 143 is transmitted to the drive wheels. The continuously variable transmission 110 is controlled by a control signal from the ECU 60. Needless to say, the continuously variable transmission 110 is not limited to a belt-type continuously variable transmission, and various other continuously variable transmissions can be used instead.

The ECU 60 includes a CPU, a ROM, a RAM, an A / D converter, and the like (not shown). The ECU 60 performs control in the vehicle based on detection signals supplied from various sensors in the vehicle. For example, the ECU 60 obtains the required driving force based on a detection signal received from a sensor such as an accelerator opening sensor 61 that detects the opening of the accelerator, and based on the obtained required driving force, The step transmission 110 is controlled.

  Next, the configuration of the engine 10 will be described with reference to FIG. The engine 10 mainly includes a cylinder head 20, a cylinder block unit 30, and a main moving unit 40.

  The cylinder block unit 30 includes an upper block 31 to which the cylinder head 20 is attached and a lower block 32 in which the main moving unit 40 is accommodated. Further, an actuator 33 is provided between the upper block 31 and the lower block 32, and by driving the actuator 33, the upper block 31 can be moved in the vertical direction with respect to the lower block 32. ing. The actuator 33 is, for example, an electric, hydraulic or pneumatic driving device, and electric power for driving is supplied from a battery. The actuator 33 is controlled by a control signal S33 from the ECU 60. A cylindrical cylinder 34 is formed inside the upper block 31, and the outer surface of the cylinder 34 is cooled by cooling water.

  The main moving 40 includes a piston 41 provided inside the cylinder 34, a crankshaft 43 that rotates inside the lower block 32, a connecting rod 42 that connects the piston 41 to the crankshaft 43, and the like. These constitute a so-called crank mechanism, and as the crankshaft 43 rotates, the piston 41 moves up and down in the cylinder 34 as the crankshaft 43 rotates. Conversely, if the piston 41 moves up and down, the crankshaft 43 moves into the lower block 32. It is designed to rotate at. A crank angle sensor 44 that detects the crank angle is provided in the vicinity of the crankshaft 43. The crank angle sensor 44 transmits a detection signal S44 corresponding to the detected crank angle to the ECU 60.

  When the cylinder head 20 is attached to the cylinder block unit 30, a combustion chamber is formed in a portion surrounded by the lower surface side (side contacting the upper block 31) of the cylinder head 20, the cylinder 34 and the piston 41. Therefore, if the upper block 31 is moved upward using the actuator 33, the cylinder head 20 is also moved upward along with this, and the volume in the combustion humidity is increased, so that the compression ratio can be lowered. Conversely, if the cylinder head 20 is moved downward together with the upper block 31, the volume in the combustion chamber can be reduced and the compression ratio can be increased. The compression ratio can be detected by using a compression ratio sensor 63 provided in the lower block 32. For example, a stroke sensor is used as the compression ratio sensor 63, and the compression ratio is detected by detecting the relative position of the upper block 31 with respect to the lower block 32. The compression ratio sensor 63 transmits a detection signal S63 corresponding to the detected compression ratio to the ECU 60.

  The cylinder head 20 is formed with an intake port 23 for taking intake air into the combustion chamber and an exhaust port 24 for discharging exhaust gas from the combustion chamber. An intake passage 50 is connected to the intake port 23, and an exhaust passage 58 is connected to the exhaust port 24. Here, an intake valve 21 is provided at a portion where the intake port 23 opens into the combustion chamber, and an exhaust valve 22 is provided at a portion where the exhaust port 24 opens into the combustion chamber. The intake valve 21 and the exhaust valve 22 are driven by electric actuators 73 and 74, respectively. By opening and closing the intake valve 21 and the exhaust valve 22 at an appropriate timing in accordance with the movement of the piston 41, intake air can be drawn into the combustion chamber or exhaust gas can be discharged from the combustion chamber. The electric actuators 73 and 74 that drive the intake valve 21 and the exhaust valve 22 are controlled by control signals S73 and S74 from the ECU 60.

  The air flow sensor 57 provided in the intake passage 50 transmits a detection signal S57 corresponding to the detected intake air amount to the ECU 60. The electric actuator 53 for adjusting the opening of the throttle valve 52 is controlled by a control signal S53 from the ECU 60.

  Further, the cylinder head 20 is provided with a fuel injection valve 26 for injecting fuel into the combustion chamber and an ignition plug 27 for igniting an air-fuel mixture formed in the combustion chamber. The fuel injection valve 26 and the spark plug 27 are controlled by control signals S26 and S27 from the ECU 60. When the fuel injection valve 26 injects fuel into the combustion chamber, a mixture of intake air and fuel sucked from the intake passage 50 via the intake port 23 is formed in the combustion chamber, and the spark plug 27 ignites. The air-fuel mixture is burned. The force pushing the piston 41 generated by the combustion at this time becomes the power of the engine 10. Thereafter, the exhaust in the combustion chamber is discharged to the exhaust passage 58 via the exhaust port 24. The fuel injection valve is not limited to providing the direct injection type fuel injection valve 26 as shown in FIG. 2. Instead of or in addition to this, a fuel injection valve may be provided in the intake passage 50. Needless to say.

[First Embodiment]
Next, a vehicle control method according to the first embodiment of the present invention will be described.

  As can be seen from the above, the engine 10 is a variable compression ratio engine capable of changing the compression ratio. In the variable compression ratio engine, the compression ratio of the air-fuel mixture is changed in accordance with the operating conditions in order to achieve both improvement in conversion efficiency to mechanical work, that is, improvement in thermal efficiency and increase in maximum output. Specifically, the ECU 60 linearly changes the compression ratio according to changes in engine torque. For example, the ECU 60 ensures a sufficient maximum output by setting the low compression ratio side under a high torque condition, and improves the thermal efficiency by setting the high compression ratio side under a low / medium torque condition.

  Here, a general vehicle control method in the vehicle 100 on which the engine 10 as the variable compression ratio engine is mounted will be described with reference to FIG. FIG. 3 is a diagram showing a state of transition of the engine operating point when a general vehicle control method during rapid acceleration is performed.

  In FIG. 3, FLO indicates the fuel efficiency optimum line. LWOT indicates a power line when the accelerator is fully opened. LPrl, LPrm, and LPra indicate isocompression ratio lines. In the following, the compression ratios at the equal compression ratio lines LPrl, LPrm, and LPra are Prl, Prm, and Pra, respectively. In these isocompression ratio lines, the compression ratio Prl at the isocompression ratio line LPrl at which the engine torque is highest is the lowest compression ratio, and the compression ratio Pra at the isocompression line LPra at which the engine torque is the lowest is the compression ratio. Become. Therefore, hereinafter, for convenience of explanation, the compression ratio Prl is sometimes referred to as “low compression ratio”, the compression ratio Prm is sometimes referred to as “medium compression ratio”, and the compression ratio Pra is sometimes referred to as “high compression ratio”. LEPa and LEPb indicate equal driving force lines where the driving force is constant.

  In FIG. 3, broken line arrows connecting engine operating points Ap, Hp, Ip, Bp, Cp, and Dp indicate engine operating point paths when a general vehicle control method is performed during rapid acceleration. . The engine operating point corresponding to the required driving force before the accelerator is depressed is the point Ap. At the point Ap, the engine 10 is in a state where the accelerator opening is set to “0”, that is, in a fuel-cut state where no fuel is supplied into the combustion chamber of the engine 10. A target engine operating point (hereinafter referred to as “target operating point”) corresponding to the required driving force after the accelerator is depressed is the point Dp. Here, the target operating point Dp is set on the fuel efficiency optimum line FLO.

  In a general vehicle control method, when the accelerator is depressed, the ECU 60 obtains the accelerator opening based on the detection signal from the accelerator opening sensor 61 and determines the engine opening based on the detection signal from the crank angle sensor 44. Find the number of revolutions. Then, the ECU 60 determines the required driving force after the accelerator is depressed based on the accelerator opening and the engine speed. Next, the ECU 60 obtains a target operating point Dp on the fuel efficiency optimal line FLO corresponding to the necessary driving force. Then, the ECU 60 increases the engine torque to the torque when the accelerator is fully opened (hereinafter referred to as “WOT torque”) to thereby change the actual engine operating point (hereinafter referred to as the actual engine operating point) from the point Ap. Transfer to point Bp via Hp and Ip. Thereafter, the ECU 60 shifts the actual engine operating point to the point Cp on the same equal driving force line LEPa as the target operating point Dp due to the increase in the engine speed, and then decreases the engine torque so that the The actual engine operating point is shifted to the target operating point Dp along LEPa.

  Here, the ECU 60 changes the compression ratio of the engine 10 as the actual engine operating point shifts. The compression ratio at the point Ap is set to Prl, and is set lower than the compression ratio Prm at the target operating point Dp. As described above, at the point Ap, the engine 10 is in a fuel cut state. In this fuel cut state, it is required to secure the fuel cut time as long as possible. Therefore, in the fuel cut state, in order to prevent the vehicle from decelerating too much, the compression ratio is set to a low compression ratio at which engine friction is reduced.

  When the actual engine operating point shifts from the point Ap to the point Hp, since the compression ratio at the point Hp is set to Pra, which is a high compression ratio, the ECU 60 sets the Pra, which is a low compression ratio, to Pra. Change the compression ratio to When the actual engine operating point shifts from the point Hp to the point Bp via the point Ip, the ECU 60 changes the compression ratio from the high compression ratio to the low compression ratio. Specifically, the ECU 60 changes the compression ratio in order from Pra to Prm and Prl. When the actual engine operating point shifts from the point Bp to the point Cp, the ECU 60 keeps Prl without changing the compression ratio. When the actual engine operating point shifts from the point Cp to the point Dp, the ECU 60 changes the compression ratio from Prl, which is a low compression ratio, to Prm, which is a medium compression ratio. That is, in a general vehicle control method, when the accelerator is depressed from the fuel cut state and the required driving force changes, the ECU 60 temporarily changes the compression ratio from the low compression ratio to the high compression ratio. Then, after changing again to a low compression ratio, it is changed to a medium compression ratio.

  As described above, in a general vehicle control method, the frequency of changing the compression ratio of the engine 10 is increased, so that the power consumption of the battery consumed by the actuator 33 increases, which may lead to deterioration in fuel consumption.

  Therefore, in the vehicle control method according to the first embodiment, when the accelerator is depressed from the fuel cut state, the ECU 60 causes the engine torque at the actual engine operating point to be larger than the engine torque at the target operating point Dp. Until then, the actual compression ratio is not increased. Hereinafter, this will be specifically described with reference to FIG.

  FIG. 4 is a diagram illustrating the transition of the engine operating point when the vehicle control method according to the first embodiment is performed. Here, the code | symbol in FIG. 4 shall show the same meaning as the code | symbol shown in FIG.

  As shown in FIG. 4, the path of the actual engine operating point when the vehicle control method according to the first embodiment is performed is the path of the actual engine operating point when the general vehicle control method is performed. Is the same.

  In the example shown in FIG. 4, the ECU 60 obtains the engine operating point that is the lowest compression ratio in the route after the fuel cut is restored, and the actual compression ratio until the actual engine operating point passes the engine operating point that becomes the lowest compression ratio. Is kept at the low compression ratio at the point Ap.

  Specifically, in FIG. 4, the compression ratio at the point Ap is Prl. Further, in the path after returning from the fuel cut, the engine operating points at which the lowest compression ratio is achieved are points Bp and Cp, and the lowest compression ratio is Prl. Therefore, the ECU 60 maintains the actual compression ratio at Prl while the actual engine operating point shifts from the point Ap to the point Cp. Thereafter, when the actual engine operating point shifts from the point Cp to the point Dp, the ECU 60 changes the compression ratio from Prl to Prm.

  In other words, the ECU 60 determines the actual compression ratio until the engine torque at the actual engine operating point becomes larger than the engine torque at the target operating point Dp, that is, until the actual engine operating point shifts to the point Ip. Is kept at the compression ratio Prl at the point Ap without increasing it. After the engine torque at the actual engine operating point becomes larger than the engine torque at the target operating point Dp, that is, after the actual engine operating point shifts to the point Ip, the ECU 60 determines the general compression ratio with respect to the general compression ratio. Control similar to the vehicle control method is performed. Specifically, when the actual engine operating point shifts from the point Ip to the point Cp via the point Bp, the ECU 60 maintains the actual compression ratio at Prl, and the actual engine operating point changes from the point Cp to the point Cp. When shifting to Dp, the ECU 60 changes the actual compression ratio from Prl, which is a low compression ratio, to Prm, which is a medium compression ratio.

  In the above-described embodiment, the compression ratio at the point Ap in the fuel cut state is set to Prl, which is the lowest compression ratio, but is not limited thereto, and instead is set to be lower than Prl. It may be done.

  As described above, in the vehicle control method according to the first embodiment, the ECU 60 determines that the engine torque at the actual engine operating point is greater than the engine torque at the target operating point Dp when the accelerator is depressed from the fuel cut state. The actual compression ratio is not increased until the value increases. In this way, it is only necessary to change the compression ratio from the low compression ratio to the medium compression ratio. Thereby, compared with a general vehicle control method, the frequency of changing the compression ratio can be reduced, so that the amount of power consumed by the battery can be reduced, and deterioration of fuel consumption can be suppressed. it can.

  Next, the vehicle control process according to the first embodiment will be described with reference to the flowchart of FIG.

  First, in step S <b> 101, the ECU 60 obtains the engine speed based on the detection signal from the crank angle sensor 44 and obtains the accelerator opening based on the detection signal from the accelerator opening sensor 61. In the subsequent step S102, the ECU 60 determines the required driving force based on the engine speed and the accelerator opening determined in step S101. The required driving force may be obtained based only on the accelerator opening instead of being obtained based on the accelerator opening and the engine speed. Thereafter, the ECU 60 proceeds to the process of step S103.

  In step S103, the ECU 60 determines whether or not the fuel cut state has occurred in the previous control process. Specifically, the ECU 60 determines that the fuel cut state has been established when the engine speed is equal to or higher than a predetermined speed and the accelerator is off in the previous control process. If it is determined that the fuel cut state has been reached (step S103: Yes), the ECU 60 proceeds to the process of step S104. On the other hand, when the ECU 60 determines that the fuel cut state has not been established (step S103: No), the ECU 60 returns to the control process. Here, the predetermined number of revolutions is an appropriate value and is stored in the ROM of the ECU 60 or the like.

  In step S104, the ECU 60 determines whether or not the vehicle has returned from the fuel cut state this time. Specifically, the ECU 60 determines that the vehicle has returned from the fuel cut state when the accelerator opening obtained in the process of step S101 is greater than or equal to a predetermined value. When it is determined that the ECU 60 has returned from the fuel cut state (step S104: Yes), the process proceeds to step S105. On the other hand, when it is determined that the ECU 60 has not returned from the fuel cut state (step S104: No), the control process is returned. Here, the predetermined value is a conforming value and is stored in the ROM of the ECU 60 or the like.

  In step S105, the ECU 60 obtains a target operating point (point Dp in FIG. 4) on the fuel efficiency optimum line based on the required driving force obtained in step S102, and obtains a route to the target operating point.

  In step S106, the ECU 60 obtains the minimum compression ratio in the path after the fuel cut return, and in the subsequent step S107, the ECU 60 determines an engine operating point (hereinafter referred to as a "minimum compression ratio point") that becomes the minimum compression ratio. Ask. In FIG. 4, the lowest compression ratio on the path is Prl, and the lowest compression ratio points are points Bp and Cp.

  In step S108, the ECU 60 holds the compression ratio at Prl until the actual engine operating point shifts to the lowest compression ratio point. In FIG. 4, the compression ratio is maintained at Prl until the actual engine operating point shifts to the point Bp.

  In step S109, the ECU 60 determines whether or not the actual engine operating point has shifted to the lowest compression ratio point. In FIG. 4, the ECU 60 determines whether or not the actual engine operating point has shifted to the point Bp. When it is determined that the actual engine operating point has not shifted to the lowest compression ratio point (step S109: No), the ECU 60 returns to the process of step S108. On the other hand, when it is determined that the actual engine operating point has shifted to the lowest compression ratio point (step S109: Yes), the ECU 60 proceeds to the process of step S110 and performs normal compression ratio control. Specifically, referring to FIG. 4, when the actual engine operating point shifts from the point Bp to the point Cp, the ECU 60 maintains the actual compression ratio at Prl, and the actual engine operating point is changed from the point Cp. When shifting to the point Dp, the ECU 60 changes the actual compression ratio from Prl to Prm. Thereafter, the ECU 60 returns this control process.

  As described above, in the vehicle control method according to the first embodiment, when the compression ratio at the engine operating point before the required driving force change is a low compression ratio, the ECU 60 operates at the actual engine operating point. The actual compression ratio is not increased until the engine torque is greater than the engine torque at the target operating point. Thereby, since the frequency which changes a compression ratio can be reduced, the electric energy consumed by a battery can be reduced and the deterioration of a fuel consumption can be suppressed.

[Second Embodiment]
Next, a vehicle control method according to the second embodiment of the present invention will be described. In the vehicle control method according to the first embodiment, the control at the time of rapid acceleration has been described. In the vehicle control method according to the second embodiment, the control at the time of slow acceleration will be described.

  FIG. 6 is a diagram showing how the engine operating point shifts when the vehicle control method during slow acceleration is performed. Here, the code | symbol in FIG. 6 shall show the same meaning as the code | symbol shown in FIG. 3, FIG.

  At the time of slow acceleration, unlike the case of sudden acceleration, the actual engine operating point does not pass through engine operating points (points Bp and Cp in FIG. 4) that are larger than the engine torque at the target operating point Dp. The target operating point Dp is shifted along the fuel efficiency optimum line FLO. In a general vehicle control method during slow acceleration, as shown in FIG. 6, the actual engine operating point shifts from the point Ap to the target operating point Dp along the fuel efficiency optimum line FLO via the points Jp and Kp. To do.

  Here, the ECU 60 changes the compression ratio of the engine 10 as the actual engine operating point shifts. In a general vehicle control method, when the accelerator is depressed and the actual engine operating point shifts from the point Ap to the point Jp, the compression ratio at the point Jp is set to Pra. The ratio is changed from Prl, which is a low compression ratio, to Pra, which is a high compression ratio. When the actual engine operating point shifts from the point Jp to the point Kp, the ECU 60 changes the compression ratio from Pra to Prb. Here, Prm <Prb <Pra. When the actual engine operating point shifts from the point Kp to the point Dp, the ECU 60 changes the compression ratio from Prb to Prm. That is, even during slow acceleration, in general vehicle control, the ECU 60 is consumed by the battery because it changes the compression ratio from the low compression ratio to the high compression ratio and then to the medium compression ratio. There is a possibility that the amount of electric power increases and the fuel consumption deteriorates.

  Therefore, in the vehicle control method according to the second embodiment, during slow acceleration, the ECU 60 sets the actual compression ratio even when the engine torque at the actual engine operating point is smaller than the engine torque at the target operating point. The compression ratio at the target operating point is set.

  Specifically, when the actual engine operating point shifts from the point Ap to the point Jp, the ECU 60 changes the compression ratio from Prl to Prm, which is the compression ratio at the target operating point. Thereafter, when the actual engine operating point shifts to the target operating point Dp via the point Kp, the ECU 60 maintains the compression ratio at Prm. By doing so, the frequency of changing the compression ratio can be reduced even during slow acceleration, so that the amount of power consumed by the battery can be reduced and deterioration of fuel consumption can be suppressed.

  Instead of the above, the ECU 60 maintains the compression ratio at Prl when the actual engine operating point shifts from the point Ap to the point Kp, and the actual engine operating point changes from the point Kp to the point Dp. When shifting, the compression ratio may be changed from Prl to Prm. However, as described above, when the actual engine operating point shifts from the point Ap to the point Jp, that is, at the earliest possible stage of the transition, the compression ratio is changed from the low compression ratio Prl to the medium compression ratio Prm. This is more preferable because the engine efficiency can be further increased.

[Third Embodiment]
Next, a vehicle control method according to the third embodiment of the present invention will be described. In the vehicle control method according to the third embodiment, a vehicle control method when the compression ratio change fails for some reason and the compression ratio is fixed will be described. This will be specifically described below with reference to FIGS.

  FIG. 7A is a diagram showing the best fuel efficiency range when the compression ratio is fixed, and FIG. 7B is a diagram showing the best fuel efficiency range when the compression ratio is variable. is there.

  As shown in FIG. 7 (a), when the compression ratio is fixed, the best fuel efficiency region exists on the high torque side as in the case of a general engine in which the compression ratio is fixed in advance. On the other hand, as shown in FIG. 7B, when the compression ratio is variable, the engine efficiency on the low / medium torque side is improved by increasing the expansion ratio by timing control of the intake valve 21. The best fuel economy range is on the middle torque side. In other words, because the best fuel efficiency is different when the compression ratio is variable and when the compression ratio is fixed, the actual engine operating point is within the best fuel efficiency when the compression ratio is variable, even though the compression ratio change has failed and the compression ratio is fixed. If driving is performed so that the position is located, the fuel consumption may deteriorate.

  Therefore, in the vehicle control method according to the third embodiment, when the compression ratio is fixed, the ECU 60 sets the fuel efficiency optimal line compared to the fuel efficiency optimal line when the compression ratio is variable. It is set to be shifted to the high torque side.

  FIG. 8 is a diagram showing fuel efficiency optimum lines when the compression ratio is variable and when the compression ratio is fixed. In FIG. 8, FLOa is a fuel efficiency optimal line when the compression ratio is variable, and FLOb and FLOc are fuel efficiency optimal lines when the compression ratio is fixed. Here, FLOb is a fuel efficiency optimal line when fixed at a high compression ratio, and FLOc is a fuel efficiency optimal line when fixed at a low compression ratio.

  As described above, when the compression ratio is fixed, the best fuel efficiency region is on the high torque side as compared with the case where the compression ratio is variable. Therefore, as shown in FIG. 8, the fuel efficiency optimal lines FLOb and FLOC when the compression ratio is fixed are set to be shifted to the high torque side as compared to the fuel efficiency optimal line FLOa when the compression ratio is variable. By doing in this way, even if the compression ratio is fixed, it becomes possible to perform an operation that optimizes fuel consumption.

  Here, when the compression ratio is fixed at a high compression ratio, the engine efficiency decreases due to the occurrence of knocking in the vicinity of the operation line LWOT. Therefore, the fuel efficiency optimal line FLOB when the high compression ratio is fixed is set on the low torque side as compared with the fuel efficiency optimal line FLOC when the low compression ratio is fixed. That is, as the compression ratio at the time of fixation increases, the fuel efficiency optimal line is set to a lower torque side. By doing in this way, it becomes possible to perform the driving | operation which becomes fuel-consumption optimal according to the compression ratio at the time of fixation.

  As described above, in the vehicle control method according to the third embodiment, when the compression ratio is fixed, the ECU 60 optimizes fuel consumption compared to the fuel efficiency optimal line when the compression ratio is variable. Set by shifting the line to the high torque side. As a result, even when the compression ratio is fixed, it is possible to perform an operation that optimizes fuel consumption.

  Next, the vehicle control process according to the third embodiment will be described with reference to the flowchart of FIG.

  In step S201, the ECU 60 determines whether or not the battery voltage of the battery that supplies power to the actuator 33 is lowered, specifically, whether or not the voltage is equal to or lower than a predetermined voltage. Here, the predetermined voltage is obtained in advance as an appropriate value by experiment or the like and stored in the ROM of the ECU 60 or the like.

  In step S201, when the ECU 60 determines that the battery voltage is not equal to or lower than the predetermined voltage, it is determined that the battery voltage has not decreased (step S201: No), and the process proceeds to step S202. On the other hand, when it is determined that the battery voltage is equal to or lower than the predetermined voltage (step S201: Yes), the ECU 60 proceeds to the process of step S203, assuming that the battery voltage has decreased.

  In step S202, the ECU 60 determines whether or not the change in the compression ratio has failed based on the detection signal from the compression ratio sensor 63. Specifically, the ECU 60 determines that the change in the compression ratio has failed when the compression ratio does not change with respect to the change in the engine torque. When the ECU 60 determines that the change in the compression ratio has failed (step S202: Yes), the ECU 60 proceeds to the process of step S203. On the other hand, when the ECU 60 determines that the change in the compression ratio has not failed (step S202: No), the ECU 60 returns this control process.

  In step S <b> 203, the ECU 60 obtains the current compression ratio based on the detection signal from the compression ratio sensor 63. In subsequent step S204, the ECU 60 uses the relationship between the compression ratio at the fixed time and the fuel efficiency optimum line shown in FIG. 8 as a map to obtain and set the fuel efficiency optimum line according to the current compression ratio. Thereafter, the ECU 60 proceeds to the process of step S205.

  In step S205, the ECU 60 sets a target operating point on the fuel efficiency optimal line corresponding to the current compression ratio. Thereafter, the ECU 60 returns this control process.

  As can be seen from the above, in this control process, steps S203 and S204 are performed not only when the compression ratio fails but also when the battery voltage of the battery that supplies power to the actuator 33 decreases. ing. This is because when the battery voltage decreases, there is a possibility that a delay occurs in the change of the compression ratio with respect to the movement of the actual engine operating point, resulting in deterioration of fuel consumption. However, it goes without saying that only one of the determinations may be made instead of making the determination for both when the battery voltage decreases and when the change in the compression ratio fails.

  As described above, in the vehicle control method according to the third embodiment, the ECU 60 performs the fuel consumption when the compression ratio is fixed as compared to the fuel efficiency optimum line when the compression ratio is variable. Set the optimal line by shifting it to the high torque side. As a result, even when the compression ratio is fixed, it is possible to perform an operation that optimizes fuel consumption.

[Modification]
In addition, this invention is not limited to the above-mentioned embodiment, It can implement with a various form within the range of the summary of this invention.

  In each of the above-described embodiments, the ECU 60 linearly changes the compression ratio in accordance with changes in engine torque, but the method of changing the compression ratio is not limited to this. Instead of doing this, the ECU 60 may give a range to the magnitude of the engine torque set to a predetermined compression ratio. In this case, an equal compression ratio band having a certain width is set in FIGS. 3 and 4 instead of the equal compression ratio line.

  In each of the above-described embodiments, the compression ratio of the engine 10 is changed by moving the upper block 31 in the vertical direction with respect to the lower block 32. However, as a variable compression ratio engine to which the present invention can be applied, The present invention is not limited, and can be applied to an engine having another variable compression ratio mechanism. For example, by connecting the piston and crankshaft with a plurality of links, rotating the control shaft and changing the position of the eccentric shaft formed on the control shaft, the posture of the link is controlled, so that the piston top dead center position The present invention can also be applied to a variable compression ratio engine that changes the compression ratio to change the compression ratio. In short, the present invention can be applied to any engine that changes the compression ratio using an actuator supplied with electric power from a battery.

10 Engine 60 ECU
61 Accelerator opening sensor 110 continuously variable transmission

Claims (2)

A control device for a vehicle including an engine capable of changing a compression ratio indicating a degree of compression of an air-fuel mixture using an actuator supplied with electric power from a battery,
Compression ratio changing means for setting the compression ratio to be larger as the engine torque is lower;
Control means for shifting an actual engine operating point along a predetermined path from an engine operating point before the change to a target operating point that is an engine operating point corresponding to the changed required driving force when the required driving force changes; Have
The compression ratio at the engine operating point before the change of the required driving force is set lower than the compression ratio at the target operating point,
When the predetermined route passes through an engine operating point at which the engine torque is larger than the engine torque at the target operating point, the compression ratio changing means is configured such that the engine torque at the actual engine operating point is the target operating point. An actual compression ratio is not increased until the engine torque becomes larger than the engine torque in the vehicle.   When the predetermined path does not pass through an engine operating point that is an engine torque larger than the engine torque at the target operating point, the compression ratio changing means is configured so that the engine torque at the actual engine operating point is 2. The vehicle control device according to claim 1, wherein an actual compression ratio is set to a compression ratio at the target operating point even when the engine torque is smaller than that at the point.

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