JP2010120449A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately suppress generation of a torque shock in the case of switching an operation line for achieving engine torque. <P>SOLUTION: A controller for an internal combustion engine is applied to a hybrid vehicle having an internal combustion engine, a motor generator, and a battery performing the transfer of power with the motor generator. Switching control means performs switching control of the operation line by setting switching time so as not to generate the torque shock by output limit of the battery in the case of switching the operation line for achieving torque in the internal combustion engine. Thus, reduction of electricity generation power for decrease of torque of the internal combustion engine can be appropriately reduced, and the generation of the torque shock can be suppressed even at the time of the output limit of the battery. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine having a variable valve timing mechanism.

  This type of technique is proposed in Patent Document 1, for example. In Patent Document 1, after the acceleration state of the engine is detected, the amount of exhaust gas remaining in the combustion chamber flowing out to the intake passage is reduced during the period from when the exhaust valve closing timing is shifted to the target timing. Therefore, it has been proposed to perform the exhaust valve closing timing shift control during acceleration.

WO2005-056795

  By the way, in the hybrid vehicle, when the valve timing is switched from the advance angle to the non-advance angle when the output of the battery is limited (that is, when the advance timing of the valve timing is canceled), a torque shock may occur. This is because when the battery output is limited, engine power shortage may occur during switching. That is, when there is a margin in battery output, the engine power shortage that occurs at the time of switching can be compensated, but when the battery is output limited, the power shortage cannot be compensated appropriately. Note that Patent Document 1 does not consider such a problem.

  The present invention has been made to solve the above-described problems, and is a control device for an internal combustion engine that can appropriately suppress the occurrence of torque shock when the operation line for realizing the engine torque is switched. The purpose is to provide.

  In one aspect of the present invention, an internal combustion engine control device applied to a hybrid vehicle including an internal combustion engine, a motor generator, and a battery that exchanges power with the motor generator realizes torque in the internal combustion engine. And a switching control unit configured to set a switching time so that a torque shock does not occur due to output limitation of the battery when switching the operating line to perform switching control of the operating line.

  The above control device for an internal combustion engine is suitably applied to a hybrid vehicle including an internal combustion engine, a motor generator, and a battery that exchanges electric power with the motor generator. The switching control means performs control for switching the operation line by setting a switching time so that a torque shock does not occur due to the output limit of the battery when switching the operation line for realizing the torque in the internal combustion engine. Specifically, the switching control means performs switching at the switching time delayed from the switching time set when the output of the battery is limited and when the output of the battery is not limited. As a result, it is possible to appropriately reduce the power generation power decrease corresponding to the torque decrease of the internal combustion engine, and it is possible to suppress the occurrence of torque shock even when the output of the battery is limited. Therefore, for example, smooth acceleration characteristics can be realized.

  In one aspect of the control apparatus for an internal combustion engine, the switching control unit sets the switching time according to the output limit of the battery.

  According to this aspect, the target number of rotations can be quickly shifted to the number of rotations on the operation line after switching (for example, the number of rotations on the optimum fuel consumption line), resulting in an unnecessarily long switching time. It becomes possible to prevent deterioration in fuel consumption.

  In another aspect of the control device for an internal combustion engine, when the operation line is switched, the rotational speed that lowers the upper limit value of the rotational speed increase rate in the internal combustion engine compared to when the switching is not performed. Further comprising an increase rate upper limit setting means.

  According to this aspect, by reducing the inertia due to the increase in the rotational speed of the internal combustion engine, it is possible to appropriately suppress the decrease in the generated power of the motor generator, and smooth acceleration characteristics and the like even when the output of the battery is limited. It can be realized effectively.

  In another aspect of the control device for an internal combustion engine, the rotation speed increase rate upper limit value setting means is provided only in a vehicle speed region in which the torque change of the motor generator is large due to a change in the rotation speed increase rate in the internal combustion engine. The upper limit of the rate of increase in the rotational speed of the internal combustion engine is reduced.

  According to this aspect, it is possible to appropriately suppress deterioration in system efficiency (deterioration in fuel consumption) due to an increase in the amount of battery power taken out.

  In a preferred embodiment, the operating line includes a maximum torque line and an optimum fuel consumption line.

  In a preferred embodiment, the switching control means switches the operation line by switching the valve timing in the variable valve timing mechanism from an advance angle to a non-advance angle.

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

[Device configuration]
FIG. 1 is a schematic configuration diagram of a hybrid vehicle to which the control device for an internal combustion engine according to the present embodiment is applied. Note that broken line arrows in the figure indicate signal input / output.

  Hybrid vehicle 100 mainly includes engine (internal combustion engine) 1, axle 2, drive wheels 3, first motor generator MG 1, second motor generator MG 2, power split mechanism 4, inverter 5, and the like. The battery 6 and an ECU (Electronic Control Unit) 50 are provided.

  The axle 2 is a part of a power transmission system that transmits the power of the engine 1 and the second motor generator MG2 to the wheels 3. The wheels 3 are wheels of the hybrid vehicle 100, and only the left and right front wheels are particularly shown in FIG. The engine 1 is constituted by a gasoline engine or the like, and functions as a power source that outputs the main driving force of the hybrid vehicle 100. The engine 1 is controlled variously by the ECU 50.

  The first motor generator MG1 is configured to function mainly as a generator for charging the battery 6 or a generator for supplying electric power to the second motor generator MG2. Generate electricity. The first motor generator MG1 functions as a regenerative brake at the time of braking (deceleration), for example, and generates electric power by performing a regenerative motion. The second motor generator MG2 is mainly configured to function as an electric motor that assists (assists) the output of the engine 1. These motor generators MG1 and MG2 are configured as, for example, synchronous motor generators, and include a rotor having a plurality of permanent magnets on the outer peripheral surface and a stator wound with a three-phase coil that forms a rotating magnetic field. Power split device 4 corresponds to a planetary gear (planetary gear mechanism) configured with a sun gear, a ring gear, and the like, and is configured to be able to distribute the output of engine 1 to first motor generator MG1 and axle 2. ing.

  Inverter 5 is a DC / AC converter that controls input / output of electric power between battery 6 and first motor generator MG1 and second motor generator MG2. For example, the inverter 5 converts the DC power extracted from the battery 6 into AC power, or supplies AC power generated by the first motor generator MG1 to the second motor generator MG2, respectively. The AC power generated by the motor generator MG1 is converted into DC power and supplied to the battery 6.

  The battery 6 is configured to be capable of functioning as a power source for driving the first motor generator MG1 and / or the second motor generator MG2, and the first motor generator MG1 and / or the second motor. It is a storage battery configured to be able to charge power generated by the generator MG2.

  The ECU 50 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown), and performs various controls on each component in the hybrid vehicle 100. Although details will be described later, the ECU 50 corresponds to a control device for an internal combustion engine in the present invention, and functions as a switching control means and a rotation speed increase rate upper limit setting means.

  FIG. 2 is a schematic configuration diagram of the engine 1 shown in FIG. A solid line arrow in the figure shows an example of a gas flow.

  The engine 1 mainly includes an intake passage 11, a throttle valve 12, a fuel injection valve 14a, an intake valve 14b, an ignition plug 14c, an exhaust valve 14d, a variable valve timing mechanism 14e, a cylinder 15a, and a piston. 15c, a connecting rod 15d, and an exhaust passage 16. In FIG. 2, only one cylinder 15a is shown for convenience of explanation, but the engine 1 actually has a plurality of cylinders 15a.

  Intake air (air) introduced from outside passes through the intake passage 11, and the throttle valve 12 adjusts the flow rate of intake air passing through the intake passage 11. The opening degree of the throttle valve 12 is controlled by a control signal supplied from the ECU 50. The intake air that has passed through the intake passage 11 is supplied to the combustion chamber 15b. The fuel injected by the fuel injection valve (injector) 14a is supplied to the combustion chamber 15b.

  Further, the combustion chamber 15b is provided with an intake valve 14b and an exhaust valve 14d. The intake valve 14b opens / closes to control conduction / interruption between the intake passage 11 and the combustion chamber 15b. The intake valve 14b is controlled by a variable valve timing mechanism 14e for valve timing (valve opening timing or valve closing timing). For example, the intake valve 14b is switched between an advance angle and a non-advance angle of the valve timing. The variable valve timing mechanism 14e is controlled by a control signal supplied from the ECU 50. On the other hand, the exhaust valve 14d opens and closes to control conduction / interruption between the exhaust passage 16 and the combustion chamber 15b.

  In the combustion chamber 15b, the air-fuel mixture of intake air and fuel supplied as described above is burned by being ignited by the spark plug 14c. In this case, the piston 15c reciprocates by combustion, the reciprocating motion is transmitted to the crankshaft (not shown) via the connecting rod 15d, and the crankshaft rotates. Exhaust gas generated by combustion in the combustion chamber 15 b is exhausted from the exhaust passage 16.

  Hereinafter, the variable valve timing mechanism is also referred to as “VVT (Variable Valve Timing)”. Further, the advance angle at the valve timing is referred to as “VVT advance angle”, and the non-advance angle at the valve timing is referred to as “VVT non-advance angle”. The VVT advance angle is a valve timing advanced by a predetermined amount from the reference valve timing, and the predetermined amount to advance is set for each vehicle type in consideration of emission and the like. The VVT advance angle is set when a request to advance the valve timing (hereinafter referred to as “VVT advance angle request”) is on. On the other hand, the VVT non-advance angle corresponds to the reference valve timing described above, and is set when the VVT advance angle request is OFF.

[Control method]
Next, a control method performed by the ECU 50 in the present embodiment will be described. In the following, an example in which the operation line for realizing the engine torque is switched by switching the valve timing from the advance angle to the non-advance angle will be described.

(First embodiment)
In the first embodiment, when the ECU 50 switches from the VVT advance angle to the VVT non-advance angle, the ECU 50 sets the switching time so that a torque shock does not occur due to the output restriction of the battery 6, and from the VVT advance angle to the VVT non-advance angle. Control to switch to. In other words, in the case where the output of the battery 6 is limited, the ECU 50 delays the switching time that is delayed from the switching time that is set when the output of the battery 6 is not limited when the VVT advance angle request is changed from on to off. To shift from the VVT advance angle to the VVT non-advance angle. In other words, when the output of the battery 6 is limited, even if the VVT advance angle request OFF condition is satisfied, the VVT advance angle is not shifted to the VVT non-advance angle during the switching time (that is, the throttle valve 12 is closed). Do not set the valve timing to the non-advanced state).

  Here, the reason why such switching control is performed will be described with reference to FIGS.

  FIG. 3 is a diagram showing an operation image at the time of transition from the VVT advance angle to the VVT non-advance angle. The horizontal axis represents the engine speed, and the vertical axis represents the engine torque. When shifting from the VVT advance angle to the VVT non-advance angle, for example, the operating point of the engine 1 changes from a point indicated by reference sign A1 in FIG. 3 to a point indicated by reference sign A2. Note that the operation line (shown by a thick solid line) at the time of VVT advance corresponds to the maximum torque line at which the maximum torque can be obtained, and the operation line at the time of non-advance VVT (shown by a broken line) Corresponds to fuel consumption line. That is, the operation line to be used is switched from the maximum torque line to the optimum fuel consumption line by switching from the VVT advance angle to the VVT non-advance angle.

  If such switching is performed at the same time as the condition for turning off the VVT advance angle request when the output of the battery 6 is limited, a torque shock may occur. This is because when the output of the battery 6 is limited, the engine 1 may be insufficient in power at the time of switching. That is, when there is a margin in the battery output, the power shortage of the engine 1 that occurs at the time of switching can be appropriately compensated. However, when the output of the battery 6 is limited, the power shortage of the engine 1 cannot be properly compensated. Because there is a possibility. It should be noted that the engine power is insufficient in this way because the engine 1 side closes the throttle valve 12 and promptly shifts to the VVT non-advanced state, but the target engine speed in the control is limited by the switching time and the rising rate. Because there is.

  FIG. 4 shows an example of a time chart at the time of switching from the VVT advance angle to the VVT non-advance angle at the normal time (when the output of the battery 6 is not limited). FIG. 4 is an example of a time chart when the control according to the present embodiment is not performed, that is, when the control for shifting to the VVT non-advance is performed at the same time when the VVT advance request OFF condition is satisfied. Show.

  FIG. 4 shows, in order from the top, VVT advance request ON / OFF, engine power (shows engine request power, the same applies hereinafter), engine speed, engine torque, and power generated by first motor generator MG1 (hereinafter, “MG1 power generation power”), battery power, output torque of the second motor generator MG2 (hereinafter referred to as “MG2 torque”), and driving force. In FIG. 4, graph B2 corresponds to the target engine speed at the time of VVT advance, graph B3 corresponds to the target engine speed at the time of non-VVT advance, and graph B4 corresponds to the actual target engine speed. To do. Graph B5 corresponds to the upper limit engine torque at the time of VVT advance, graph B6 corresponds to the upper limit engine torque at the time of VVT non-advance, and graph B7 corresponds to the actual engine torque. Further, the graph B8 shows the MG1 generated power when the VVT advance angle is continued, and the graph B9 shows the MG1 generated power at the time of switching from the VVT advance angle to the VVT non-advance angle.

  In this case, at time t11, the condition for turning off the VVT advance angle is established, and at the same time as the condition is established, the VVT advance angle is shifted to the VVT non-advance angle. That is, the throttle valve 12 is closed and the valve timing is set to the non-advanced state. In the switching time T1 from time t11 to time t12 (corresponding to the time until the engine speed shifts to the target engine speed when the VVT is not advanced), the engine speed and the engine torque are shown in graphs B4 and B7, respectively. It changes as shown in. Specifically, the throttle valve 12 is closed at the same time as the VVT advance request OFF condition is satisfied, and the valve timing is set to the non-advance state, so that the engine torque decreases as shown in the graph B7. To do. Therefore, as shown in the graph B9, the MG1 generated power also decreases. Specifically, as indicated by the hatched region B10, the MG1 generated power is greatly reduced as compared with the case where the VVT advance angle is continued (see graph B8). This is due to the decrease in engine torque and the increase in engine rotation inertia as described above.

  Further, at the switching time T1, the battery power changes as shown by the graph B11. In this case, the battery power is not limited by the battery power upper limit B12. This is because the battery power upper limit B12 is at a certain high position because the output of the battery 6 is not limited. Furthermore, as described above, as the MG1 power generation power decreases, as shown in the graph B13, from the supply power (specifically, it corresponds to the power combining the MG1 power generation power and the battery power upper limit; the same applies hereinafter). The fixed upper limit value decreases. In this case, due to the fact that the battery power is not limited to the battery power upper limit B12, as shown in the graph B14, the MG2 torque is not limited by the upper limit value determined from the supply power. Therefore, as shown in the graph B15, the driving force does not decrease (no step is generated). Therefore, it can be said that no shock occurs.

  FIG. 5 shows an example of a time chart when switching from the VVT advance angle to the VVT non-advance angle when the output of the battery 6 is limited. FIG. 5 is an example of a time chart when the control according to the present embodiment is not performed, that is, when the control for shifting to the VVT non-advance is performed at the same time when the VVT advance request OFF condition is satisfied. Show.

  FIG. 5 shows, in order from the top, VVT advance request ON / OFF, engine power, engine speed, engine torque, MG1 generated power, battery power, MG2 torque, and driving force. In FIG. 5, graph C2 corresponds to the target engine speed at the time of VVT advance, graph C3 corresponds to the target engine speed at the time of non-VVT advance, and graph C4 corresponds to the actual target engine speed. To do. Graph C5 corresponds to the upper limit engine torque at the time of VVT advance, graph C6 corresponds to the upper limit engine torque at the time of VVT non-advance, and graph C7 corresponds to the actual engine torque. Further, the graph C8 shows the MG1 generated power when the VVT advance angle is continued, and the graph C9 shows the MG1 generated power at the time of switching from the VVT advance angle to the VVT non-advance angle.

  In this case, at time t21, the condition for turning off the VVT advance angle is established, and at the same time as the condition is established, the VVT advance angle is switched to the VVT non-advance angle. That is, the throttle valve 12 is closed and the valve timing is set to the non-advanced state. In the switching time T2 from time t21 to time t22 (corresponding to the time until the engine speed shifts to the target engine speed when the VVT is not advanced), the engine speed and the engine torque are shown in graphs C4 and C7, respectively. It changes as shown in. Specifically, since the throttle valve 12 is closed and the valve timing is set to the non-advanced state at the same time when the VVT advance request OFF condition is satisfied, the engine torque decreases as shown in the graph C7. To do. Therefore, as shown in the graph C9, the MG1 generated power also decreases. Specifically, as indicated by the hatched area C10, the MG1 generated power is greatly reduced as compared with the case where the VVT advance angle is continued (see graph C8). This is due to the decrease in engine torque and the increase in engine rotation inertia as described above.

  Further, at the switching time T2, the battery power changes as indicated by the graph C11. In this case, the battery power is limited by the battery power upper limit C12. This is because the battery power upper limit C12 is at a certain low position because the output of the battery 6 is limited. Therefore, as shown in the graph C13, the upper limit value determined from the supply power is greatly reduced, and as shown in the graph C14, the MG2 torque is limited by the upper limit value determined from the supply power. Thereby, as shown in the graph C15, the driving force is reduced (a step is generated). Thus, a shock can occur.

  From the above, in the first embodiment, when switching from the VVT advance angle to the VVT non-advance angle, the ECU 50 sets the switching time so as not to generate a torque shock due to the output restriction of the battery 6, and sets the VVT advance angle. To switch from VVT to non-advanced VVT. Specifically, when the output of the battery 6 is limited, the ECU 50 delays the switching time set when the VVT advance request is turned from on to off when the output of the battery 6 is not limited. At the switching time, the VVT advance angle is shifted to the VVT non-advance angle. More specifically, the ECU 50 sets the valve timing to the non-advanced state after the engine speed reaches the target engine speed when the VVT is not advanced. As a result, even when the output of the battery 6 is limited, the MG1 power generation decrease corresponding to the engine torque decrease can be appropriately reduced, and the occurrence of torque shock can be suppressed. Therefore, smooth acceleration characteristics can be realized.

  Next, the control method in the first embodiment will be specifically described with reference to FIGS. 6 and 7.

  FIG. 6 shows an example of a time chart when the control method according to the first embodiment is performed when the output of the battery 6 is limited. FIG. 6 shows, in order from the top, VVT advance request ON / OFF, engine power, engine speed, engine torque, MG1 generated power, battery power, MG2 torque, and driving force. In FIG. 6, graph D2 corresponds to the target engine speed at the time of VVT advance, graph D3 corresponds to the target engine speed at the time of non-VVT advance, and graph D4 corresponds to the actual target engine speed. To do. Graph D5 corresponds to the upper limit engine torque at the time of VVT advance, graph D6 corresponds to the upper limit engine torque at the time of VVT non-advance, and graph D7 corresponds to the actual engine torque. Further, the graph D8 shows the MG1 generated power when the VVT advance angle is continued, and the graph D9 shows the MG1 generated power at the time of switching from the VVT advance angle to the VVT non-advance angle.

  In this case, the condition for turning off the VVT advance request is satisfied at time t31. In the first embodiment, the ECU 50 does not immediately switch from the VVT advance to the VVT non-advance when the VVT advance request OFF condition is satisfied. Specifically, ECU 50 switches from VVT advance to VVT non-advance at time t32 after time t31. More specifically, the ECU 50 closes the throttle valve 12 and sets the valve timing to the non-advanced state when the engine speed reaches the target engine speed when the VVT is not advanced (time t32). .

  At the switching time T3, the engine speed and the engine torque change as indicated by graphs D4 and D7, respectively. Specifically, since the VVT advance request OFF condition is satisfied and the VVT non-advance is not made at the same time (in other words, VVT non-advance until the engine speed reaches the target engine speed at the non-VVT advance). Therefore, the engine torque gradually decreases as shown in the graph D7. Further, at the switching time T3, the MG1 generated power changes as shown by the graph D9. In this case, as indicated by the hatched region D10, the MG1 generated power is slightly reduced as compared with the case where the VVT advance angle is continued (see graph D8). It can be seen that the amount of decrease in the MG1 generated power indicated by the hatched area D10 is smaller than the amount of decrease in the MG1 generated power shown in FIGS. This is because the sudden drop in engine torque has decreased as shown by graph D7.

  Further, at the switching time T3, the battery power changes as indicated by the graph D11. In this case, since the output of the battery 6 is limited, the battery power upper limit D12 is in a position that is somewhat low, but the battery power is not limited to the battery power upper limit D12. Furthermore, at the switching time T3, the MG2 torque changes as shown in the graph D14, but the MG2 torque is not limited by the upper limit value determined from the supply power shown in the graph D13. This is because the drop in the upper limit value determined from the supply power is reduced by the reduction in the MG1 power generation reduction as described above. Therefore, as shown in the graph D15, the driving force does not decrease (no step is generated). Therefore, it can be said that no shock occurs.

  FIG. 7 is a flowchart showing the control processing in the first embodiment. This process is repeatedly executed by the ECU 50 at a predetermined cycle.

  First, in step S101, the ECU 50 determines whether or not a condition for turning off the VVT advance angle request is satisfied. For example, the ECU 50 determines whether or not the state should be switched from the VVT advance angle to the VVT non-advance angle based on the driving state or the like. If the condition for turning off the VVT advance angle request is satisfied (step S101; Yes), the process proceeds to step S102. If the condition for turning off the VVT advance angle request is not satisfied (step S101; No), the process ends. To do.

  In step S102, the ECU 50 determines whether or not the switching time has elapsed. The switching time is set, for example, to the time required for the engine speed to reach the target engine speed when the VVT is not advanced. When the switching time has elapsed (step S102; Yes), the process proceeds to step S103. In this case, the ECU 50 performs control to shift from the VVT advance angle to the VVT non-advance angle. Specifically, the ECU 50 transmits a control signal for turning off the VVT advance angle to the engine 1 side (step S103). For example, the ECU 50 transmits a control signal to the variable valve timing mechanism 14e so as to be set to a valve timing that is not advanced (a reference valve timing). Then, the process ends. On the other hand, when the switching time has not elapsed (step S102; No), the process ends.

  According to the first embodiment described above, it is possible to appropriately suppress the occurrence of torque shock when switching from the VVT advance angle to the VVT non-advance angle when the output of the battery 6 is limited.

(Second Embodiment)
Next, a second embodiment will be described. The second embodiment is different from the first embodiment in that the switching time is changed in accordance with the output limit of the battery 6. Specifically, in the second embodiment, the ECU 50 sets the time for switching the target engine speed from the rotation speed used at the VVT advance angle to the rotation speed used at the VVT non-advance angle according to the output limit of the battery 6. Set. For example, the ECU 50 sets the switching time to a longer time as the output limit of the battery 6 is lower, and sets the switching time to a shorter time as the output limit of the battery 6 is higher.

  With reference to FIG.8 and FIG.9, the control method in 2nd Embodiment is demonstrated concretely.

  FIG. 8 is a diagram illustrating an example of a switching time setting method. Specifically, FIG. 8 shows a table showing the relationship between the battery output limit and the switching time. From this, it can be seen that the switching time increases as the battery output limit decreases, and the switching time decreases as the battery output limit increases. In the second embodiment, the ECU 50 sets the switching time according to the battery output restriction based on the relationship between the battery output restriction and the switching time. For example, the ECU 50 sets the switching time based on a map that predetermines the relationship between the battery output limit and the switching time, an arithmetic expression that defines the relationship between the battery output limitation and the switching time, or the like.

  FIG. 9 shows an example of a time chart when the control method according to the second embodiment is performed when the output of the battery 6 is limited. FIG. 9 shows VVT advance angle request on / off, engine power, engine speed, engine torque, MG1 generated power, battery power, MG2 torque, and driving force in order from the top. In FIG. 9, graph E2 corresponds to the target engine speed at the time of VVT advance, graph E3 corresponds to the target engine speed at the time of non-VVT advance, and graph E4 corresponds to the actual target engine speed. To do. Further, the graph E5 corresponds to the upper limit engine torque at the time of VVT advance, the graph E6 corresponds to the upper limit engine torque at the time of VVT non-advance, and the graph E7 corresponds to the actual engine torque. Further, the graph E8 shows the MG1 generated power when the VVT advance angle is continued, and the graph E9 shows the MG1 generated power at the time of switching from the VVT advance angle to the VVT non-advance angle.

  In this case, the condition for turning off the VVT advance request is satisfied at time t41. Also in the second embodiment, the ECU 50 does not immediately switch from VVT advance to VVT non-advance when the VVT advance request OFF condition is satisfied. Specifically, the ECU 50 shifts from the VVT advance angle to the VVT non-advance angle at time t42 after time t41. More specifically, the ECU 50 closes the throttle valve 12 and sets the valve timing to the non-advanced state when the engine speed reaches the target engine speed when the VVT is not advanced.

  In the second embodiment, the ECU 50 switches the target engine speed from the speed used at the VVT advance time to the speed used at the VVT non-advance time (from time t41) according to the output limit of the battery 6. Time T4) until time t42 is set. For example, the ECU 50 sets the switching time T4 based on a map that predetermines the relationship between the output limit of the battery 6 and the switching time, an arithmetic expression that defines the relationship between the output limit of the battery 6 and the switching time, or the like. .

  In the switching time T4 described above, the engine speed and the engine torque change as shown by graphs E4 and E7, respectively. Specifically, since the VVT advance request OFF condition is satisfied and the VVT non-advance is not made at the same time (in other words, VVT non-advance until the engine speed reaches the target engine speed at the non-VVT advance). Therefore, the engine torque gradually decreases as shown in the graph E7. Further, at the switching time T4, the MG1 generated power changes as shown by the graph E9. In this case, as indicated by the hatched region E10, the MG1 generated power is slightly reduced as compared with the case where the VVT advance angle is continued (see graph E8). It can be seen that the decrease amount of the MG1 generated power shown by the hatched area E10 is smaller than the decrease amount of the MG1 generated power shown in FIG. This is because the switching time is set in consideration of the output limit of the battery 6, and the sudden drop of the engine torque and the inertia due to the increase of the engine speed are appropriately reduced.

  Further, at the switching time T4, the battery power changes as indicated by the graph E11. In this case, since the output of the battery 6 is limited, the battery power upper limit E12 is at a considerably low position, but the battery power is not limited to the battery power upper limit E12. This is because the switching time is set based on the output limit of the battery 6 as described above. Furthermore, at the switching time T4, the MG2 torque changes as shown in the graph E14, but the MG2 torque is not limited by the upper limit value determined from the supply power shown in the graph E13. This is because the drop in the upper limit value determined from the supply power is reduced by the reduction in the MG1 power generation reduction as described above. Therefore, as shown in the graph E15, the driving force does not decrease (no step is generated). Therefore, it can be said that no shock occurs.

  According to the second embodiment described above, since the switching time is set according to the output limit of the battery 6, the target engine speed is quickly shifted to the target engine speed (optimum fuel consumption line) when the VVT is not advanced. This makes it possible to prevent deterioration in fuel consumption while realizing smooth acceleration characteristics.

(Third embodiment)
Next, a third embodiment will be described. In the third embodiment, when switching from the VVT advance angle to the VVT non-advance angle, the upper limit value of the engine speed increase rate in the engine 1 (hereinafter referred to as “engine speed increase rate”) is compared to when the switch is not performed. This is different from the first and second embodiments described above in that the upper limit is called.

  The reason why the engine speed increase rate upper limit value is lowered in this way is as follows. When switching from VVT advance to VVT non-advance, the target engine speed changes, but when the target engine speed changes in this way, the deviation between the target engine speed and the actual engine speed tends to increase. It is in. In that case, in the feedback control for setting the target engine speed, if the deviation between the target engine speed and the actual engine speed increases, the engine speed increase rate increases. As a result, the engine speed increases due to an increase in the engine speed increase rate, and the MG1 generated power decreases due to the inertia due to the engine speed increase, so that smooth driving force characteristics may not be realized. There is. Therefore, in the third embodiment, when switching from the VVT advance angle to the VVT non-advance angle, the engine speed increase rate upper limit value is decreased.

  FIG. 10 shows an example of a time chart at the time of switching from the VVT advance angle to the VVT non-advance angle when the upper limit value of the engine speed increase rate is not changed as described above when the output of the battery 6 is limited. ing. FIG. 10 shows VVT advance angle request on / off, engine power, engine speed, engine speed increase rate, MG1 power generation, battery power, MG2 torque, and driving power in order from the top. In FIG. 10, a graph F2 corresponds to the target engine speed, and a graph F3 corresponds to the actual engine speed. The graph F5 corresponds to the engine speed increase rate upper limit value, and the graph F6 corresponds to the actual engine speed increase rate. Further, the graph F8 shows the MG1 generated power when the VVT advance angle is continued, and the graph F9 shows the MG1 generated power at the time of switching from the VVT advance angle to the VVT non-advance angle.

  In this case, the condition for turning off the VVT advance request is established at time t51, and the transition is made from the VVT advance to the VVT non-advance at time t52 after the switching time T5 has elapsed from time t51. That is, the throttle valve 12 is closed and the valve timing is set to the non-advanced state. At the switching time T5, the actual engine speed changes as shown by the graph F3. In accordance with the deviation between the actual engine speed and the target engine speed, the engine speed increase rate changes as shown by a graph F6. Specifically, in the period T51, the engine speed increase rate increases and decreases. In this case, since the engine speed increase rate upper limit value F5 is set to a position that is somewhat high (specifically, it is not changed from the value before the condition for turning off the VVT advance request is satisfied), such an engine. Changes in the speed increase rate are allowed.

  Due to the increase in the inertia due to the increase in the engine speed, the MG1 generated power decreases in the period T51 as shown by the graph F9. In the period T51, as shown by the graph F11, the battery power is limited by the battery power upper limit F12. Therefore, in the period T51, as shown by the graph F13, the upper limit value determined from the supply power is greatly reduced, and as shown in the graph F14, the MG2 torque is limited by the upper limit value determined from the supply power. Thereby, as shown in the graph F15, the driving force is reduced (a step is generated). Thus, a shock can occur.

  FIG. 11 shows an example of a time chart when the control method according to the third embodiment is performed when the output of the battery 6 is limited. FIG. 11 shows VVT advance angle request on / off, engine power, engine speed, engine speed increase rate, MG1 power generation, battery power, MG2 torque, and driving power in order from the top. In FIG. 11, a graph G2 corresponds to the target engine speed, and a graph G3 corresponds to the actual engine speed. Graph G5 corresponds to the engine speed increase rate upper limit value, and graph G6 corresponds to the actual engine speed increase rate. Further, the graph G8 shows the MG1 generated power when the VVT advance angle is continued, and the graph G9 shows the MG1 generated power at the time of switching from the VVT advance angle to the VVT non-advance angle.

  In this case, the condition for turning off the VVT advance request is established at time t61, and the transition is made from the VVT advance to the VVT non-advance at time t62 after the switching time T6 has elapsed from time t61. That is, the throttle valve 12 is closed and the valve timing is set to the non-advanced state. At the switching time T6, as shown by the graph G3, the actual engine speed changes. Further, at the switching time T6, as shown by the graph G5, the engine speed increase rate upper limit value is set. Specifically, in the third embodiment, the ECU 50 sets the engine speed increase rate upper limit value to a value that is at least lower than the upper limit value before the condition for turning off the VVT advance request is satisfied. As a result, as shown in graphs G2 and G3, although there is a certain degree of deviation between the actual engine speed and the target engine speed, as shown in graph G6, the engine speed increase rate becomes the engine speed. It is limited by the number increase rate upper limit G5, and the engine speed increase rate does not change significantly.

  As a result, at the switching time T6, as shown by the graph G9, the MG1 generated power changes. In this case, as indicated by the hatched region G10, the MG1 generated power is slightly reduced as compared with the case where the VVT advance angle is continued (see graph G8). It can be seen that the amount of decrease in the MG1 generated power indicated by the hatched region G10 is smaller than the amount of decrease in the MG1 generated power shown in FIG. This is because the inertia due to the increase in engine speed has decreased because the engine speed increase rate upper limit value has been decreased.

  Further, at the switching time T6, the battery power changes as indicated by the graph G11. In this case, since the output of the battery 6 is limited, the battery power upper limit G12 is at a position that is somewhat low, but the battery power is not limited to the battery power upper limit G12. Furthermore, at the switching time T6, the MG2 torque changes as shown in the graph G14, but the MG2 torque is not limited by the upper limit value determined from the supply power shown in the graph G13. This is because the drop in the upper limit value determined from the supply power is reduced by the reduction in the MG1 power generation reduction as described above. Therefore, as shown in the graph G15, the driving force does not decrease (no step is generated). Therefore, it can be said that no shock occurs.

  According to the third embodiment described above, by reducing the inertia due to the increase in the engine speed, it is possible to appropriately suppress the decrease in the MG1 generated power, and the occurrence of torque shock even when the output of the battery 6 is limited. Can be suppressed. Therefore, smooth acceleration characteristics can be realized.

(Fourth embodiment)
Next, a fourth embodiment will be described. The fourth embodiment differs from the third embodiment in that the engine speed increase rate upper limit value is reduced only in the vehicle speed range where the MG2 torque change is large due to the engine speed increase rate change. Specifically, the ECU 50 decreases the engine speed increase rate upper limit value only in the low vehicle speed range, and does not decrease the engine speed increase rate upper limit value when the vehicle speed is not in the low vehicle speed range (that is, the upper limit value used in normal times). Set to).

  The reason for this is as follows. If the engine speed increase rate upper limit is reduced as described above, the engine speed increase rate is limited, and it takes more time than necessary to reach the target engine speed. There is. In this case, there is a possibility that the amount of power taken out from the battery 6 increases and the system efficiency deteriorates. Therefore, in the fourth embodiment, in order to suppress such deterioration of system efficiency, the engine speed increase rate upper limit value is set only in the vehicle speed range (low vehicle speed range) in which the MG2 torque change is large due to the change in the engine speed increase rate. In the vehicle speed range where the MG2 torque change due to the change in the engine speed increase rate is relatively small (vehicle speed range other than the low vehicle speed range), the engine speed increase rate upper limit value is not decreased.

  Here, with reference to FIG.12 and FIG.13, the control method in 4th Embodiment is demonstrated concretely.

  FIG. 12 is a diagram showing a map defining the engine speed increase rate upper limit value. Specifically, FIG. 12A shows a map used at the time of switching (hereinafter referred to as “switching engine speed increase rate upper limit map”). FIG. 12B shows a map used during normal time (hereinafter referred to as “normal engine speed increase rate upper limit map”) that does not switch from VVT advance to non-VVT advance. . Each map shows the relationship between the rotational speed deviation (corresponding to the deviation between the target engine rotational speed and the actual engine rotational speed; the same applies hereinafter) and the engine rotational speed increase rate upper limit value.

  As shown in FIG. 12, when the engine speed increase rate upper limit map at the time of switching is used, it is understood that the engine speed increase rate upper limit value having a small value is set regardless of the rotational speed deviation. In contrast, when the normal engine speed increase rate upper limit map is used, it is understood that the engine speed increase rate upper limit value corresponding to the engine speed deviation is set. Specifically, the engine speed increase rate upper limit value having a larger value is set as the rotation speed deviation becomes larger, and the engine speed increase rate upper limit value having a smaller value is set as the rotation speed deviation becomes smaller.

  In the fourth embodiment, the ECU 50 sets the engine speed increase rate upper limit value based on either the switching engine speed increase rate upper limit map or the normal engine speed increase rate upper limit map. Specifically, when switching from VVT advance to VVT non-advance, the ECU 50 uses the upper engine speed increase rate upper limit map when the vehicle speed is low, and when the vehicle speed is not low, A normal engine speed increase rate upper limit map is used. It is not limited to setting the engine speed increase rate upper limit value using the map as described above, but based on an arithmetic expression that defines the relationship between the engine speed deviation and the engine speed increase rate upper limit value. It is also possible to set the engine speed increase rate upper limit value.

  FIG. 13 is a flowchart showing a control process in the fourth embodiment. This process is repeatedly executed by the ECU 50 at a predetermined cycle.

  First, in step S201, the ECU 50 determines whether or not a condition for turning off the VVT advance angle request is satisfied. For example, the ECU 50 determines whether or not the state should be switched from the VVT advance angle to the VVT non-advance angle based on the driving state or the like. When the condition for turning off the VVT advance angle request is satisfied (step S201; Yes), the process proceeds to step S202. When the condition for turning off the VVT advance angle request is not satisfied (step S201; No), the process ends. To do.

  In step S202, the ECU 50 determines whether the switching time has elapsed. The switching time is set to a time required for the engine speed to reach the target engine speed when the VVT is not advanced, for example, and is set in consideration of the output limit of the battery 6. If the switching time has elapsed (step S202; Yes), the process proceeds to step S203. In this case, the ECU 50 performs control to shift from the VVT advance angle to the VVT non-advance angle. Specifically, the ECU 50 transmits a control signal for turning off the VVT advance angle to the engine 1 side (step S203). For example, the ECU 50 transmits a control signal to the variable valve timing mechanism 14e so as to be set to a valve timing that is not advanced (a reference valve timing). Then, the process ends. On the other hand, when the switching time has not elapsed (step S202; No), the process proceeds to step S204.

  In step S204, the ECU 50 determines whether or not the vehicle speed is a low vehicle speed. If the vehicle speed is low (step S204; Yes), the process proceeds to step S205. In this case, the ECU 50 sets the engine speed increase rate upper limit value using the engine speed increase rate upper limit map at the time of switching (step S205). That is, the engine speed increase rate upper limit value is decreased in order to appropriately suppress the MG1 power generation decrease by reducing the inertia due to the engine speed increase. Then, the process ends.

  On the other hand, if the vehicle speed is not low (step S204; No), that is, if the vehicle speed is medium or high, the process proceeds to step S206. In this case, the ECU 50 sets the engine speed increase rate upper limit value using the normal engine speed increase rate upper limit map (step S206). That is, the upper limit value of the engine speed increase rate is not changed from the upper limit value at the normal time in order to suppress the deterioration of the system efficiency due to the increase in the amount of battery power taken out. Then, the process ends.

  According to the fourth embodiment described above, it is possible to appropriately suppress deterioration of system efficiency (deterioration of fuel consumption) while realizing smooth acceleration characteristics even when the output of the battery 6 is limited.

[Modification]
The present invention is not limited to the case of switching the advance / non-advance angle of the valve timing in the intake valve 14b, but is also applied to the case of switching the advance / non-advance angle of the valve timing in the exhaust valve 14d. Can do.

  Further, the present invention is not limited to being applied when the advance / non-advance angle of the valve timing is switched. The present invention can be applied to a case where the operation line for realizing the engine torque is switched, in addition to the case where the advance / non-advance angle of the valve timing is switched.

The schematic block diagram of the hybrid vehicle which concerns on this embodiment is shown. The schematic block diagram of an engine is shown. It is a figure which shows the operation | movement image at the time of the transition from VVT advance angle to VVT non-advance angle. The time chart at the time of switching from the VVT advance angle to the VVT non-advance angle at the normal time is shown. The time chart at the time of switching from VVT advance angle to VVT non-advance angle when the output of the battery is limited is shown. The time chart at the time of performing the control method in 1st Embodiment is shown. It is a flowchart which shows the control processing in 1st Embodiment. It is a figure for demonstrating the setting method of switching time. The time chart at the time of performing the control method in 2nd Embodiment is shown. The time chart at the time of switching from VVT advance to VVT non-advance when the engine speed increase rate upper limit is not changed is shown. The time chart at the time of performing the control method in 3rd Embodiment is shown. It is the figure which showed the map which prescribes | regulates an engine speed increase rate upper limit. It is a flowchart which shows the control processing in 4th Embodiment.

Explanation of symbols

1 engine (internal combustion engine)
3 Drive Wheel 4 Power Dividing Mechanism 5 Inverter 6 Battery 12 Throttle Valve 14b Intake Valve 14d Exhaust Valve 14e Variable Valve Timing Mechanism 50 ECU
MG1 first motor generator MG2 second motor generator 100 hybrid vehicle

Claims (6)

A control device for an internal combustion engine applied to a hybrid vehicle including an internal combustion engine, a motor generator, and a battery that exchanges power with the motor generator,
When switching an operation line for realizing torque in the internal combustion engine, a switching control unit is provided for setting a switching time so as not to generate a torque shock due to output limitation of the battery and performing control for switching the operation line. A control device for an internal combustion engine characterized by the above.   The control device for an internal combustion engine according to claim 1, wherein the switching control means sets the switching time in accordance with an output limit of the battery.   The rotation speed increase rate upper limit setting means for lowering the upper limit value of the rotation speed increase rate in the internal combustion engine when switching the operation line as compared to when not performing the switching. The control apparatus of the internal combustion engine described in 1.   The rotational speed increase rate upper limit setting means lowers the upper limit value of the rotational speed increase rate in the internal combustion engine only in a vehicle speed range where the torque change of the motor generator is large due to a change in the rotational speed increase rate in the internal combustion engine. The control device for an internal combustion engine according to claim 3.   The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the operation line includes a maximum torque line and an optimum fuel consumption line.   The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the switching control means switches the operation line by switching the valve timing in the variable valve timing mechanism from an advance angle to a non-advance angle.

Images