Engine control device and engine control method

Abstract

This engine control device comprises a control unit that receives a detection signal from a cam angle sensor that detects rotation of an intake value or an exhaust valve. When the engine is stopped or restarted, the control unit causes the phase of the intake valve or the exhaust valve to be changed by a valve-timing-variable mechanism. For a prescribed time following the detection timing of detection by the cam angle sensor, the control unit reduces the amount by which the phase is changed by the valve-timing-variable mechanism so as to be less than the amount of change that preceded the detection timing.

Description

Technical Field

[0001] The present invention relates to an engine control device and an engine control method for controlling an engine equipped with a valve timing variable mechanism mounted on a hybrid vehicle.

Background Art

[0002] In recent years, the installation of a hybrid mechanism using an engine and a motor as drive sources has become mainstream as an automotive power train. In hybrid vehicles, the engine stops and restarts frequently compared to conventional vehicles mainly equipped with internal combustion engines. Usually, when the engine is running, burned gas (exhaust gas) flows out of the exhaust pipe. In gasoline vehicles, a three-way catalyst is installed in the exhaust pipe, and the three-way catalyst has the characteristic of having the highest purification efficiency for burned gas during stoichiometric combustion.

[0003] In addition, hybrid vehicles are equipped with an EV mode in which they run only on the motor for fuel efficiency improvement, and the engine is stopped during the EV mode driving period. However, there are scenarios where the engine needs to be restarted due to a decrease in the remaining battery level during EV driving or high-load / high-speed driving requirements of the vehicle due to changes in road conditions. And there is a motoring period during which fuel is not injected and the engine rotates from the fuel cut when entering the EV mode until the engine stops, and from the end of the EV mode until the fuel is injected and the engine fires for the first time by cranking with the motor generator.

[0004] However, when the engine stops and restarts, since fresh air flows out of the exhaust pipe during the fuel cut period, the oxygen storage capacity inside the three-way catalyst becomes oxygen-rich, and the purification efficiency of nitrogen oxides deteriorates. As a result, in order to properly restore the purification efficiency when the engine restarts after stopping, enrich injection is required. That is, in order to prevent enrich injection during engine restart, it is necessary to suppress the outflow of fresh air during the fuel cut of the engine.

[0005] Conventionally, a valve timing variable mechanism that changes the phase of a camshaft that drives an intake valve or an exhaust valve is known. For example, in the valve timing variable mechanism, two intake valves are provided in one cylinder of an engine, and an inner camshaft having an inner cam that drives one intake valve integrally provided on the outer periphery, and an outer camshaft that is disposed on the outer periphery of the inner camshaft so as to be relatively rotatable and has an outer cam that drives the other intake valve integrally provided on the outer periphery. By relatively rotating the inner camshaft and the outer camshaft, the operating angle of the intake valve or the exhaust valve of each cylinder is changed, and the timing of opening and closing of the intake valve or the exhaust valve is controlled.

[0006] During the period from after fuel cut-off until the first explosion, the valve closing times of the intake valve and the exhaust valve are changed by this valve timing variable mechanism, and the increase in the oxygen storage amount is suppressed by causing exhaust gas to flow back from the exhaust pipe to the intake pipe.

[0007] As such a technique, for example, there is one described in Patent Document 1. Patent Document 1 describes a technique of delaying the valve closing time of the intake valve and advancing the valve closing time of the exhaust valve after fuel cut-off, making the combustion chamber volume at the time of exhaust valve closing larger than the combustion chamber volume at the time of intake valve closing, causing exhaust gas to flow back from the exhaust pipe to the intake pipe, reducing the air discharge amount during the motoring period, and suppressing the increase in the oxygen over-increase amount of the three-way catalyst.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in the technology described in Patent Document 1, when the exhaust gas is reversed, if there is exhaust gas in the cycle in which fuel injection is started after motoring starts during restart, the fuel cannot burn and is discharged in an unburned state, resulting in deterioration of exhaust gas and fuel consumption. Conversely, if the start of fuel injection is delayed, when air is discharged after exhaust gas purge, the oxygen storage amount increases and the reverse flow of exhaust gas becomes wasteful. Therefore, in order to start fuel injection immediately after the exhaust gas is discharged, it is necessary to estimate the amount of forward and reverse gas during the period from fuel cut to the first explosion.

[0010] Regarding the flow rate during the period from this fuel cut to the first explosion, assuming that the forward flow is positive and the reverse flow is negative, it is determined by (combustion chamber volume at intake valve closing - combustion chamber volume at exhaust valve closing) × intake pipe pressure constant. The closing timing is determined by the phase (VTC angle) of the valve timing variable mechanism. Therefore, by detecting the closing timing of the intake and exhaust valves for each cycle from fuel cut to the first explosion and integrating the flow rate for each cycle calculated from the closing timing, the flow rate can be estimated. By starting fuel injection in the cycle when the integrated gas amount approaches near zero, fuel can be injected immediately after the exhaust gas is discharged.

[0011] The phase of this variable valve timing variable mechanism can be detected by the signals of the cam angle sensor and the crank angle sensor. However, during engine stop and restart, the phase of the variable valve timing variable mechanism continues to change. As a result, there is a problem that a deviation occurs between the phase (VTC angle) of the variable valve timing variable mechanism detected at the timing when the cam angle sensor outputs and the phase (VTC angle) of the variable valve timing variable mechanism at the actual closing timing.

[0012] In particular, from engine stop to restart, since the engine speed decreases and the phase change amount per cycle increases, this deviation becomes significant, and there is a concern that the deviation in the timing of exhaust gas discharge will increase.

[0013] An object of the present invention is to provide an engine control device and an engine control method that can reduce the deviation between the phase (VTC angle) of a variable valve timing mechanism calculated at the timing detected by a cam angle sensor and the phase (VTC angle) of the variable valve timing mechanism at the actual valve closing timing, taking into account the above problems.

Means for Solving the Problems

[0014] In order to solve the above problems and achieve the object, an engine control device is an engine control device for controlling an engine mounted on a hybrid vehicle that is driven by cooperation between the output of an engine including a valve timing variable mechanism that changes the phase of at least one of an intake valve and an exhaust valve and the output of an electric motor. The engine control device includes a control unit that receives a detection signal from a cam angle sensor that detects the rotation of the intake valve or the exhaust valve. When the engine is stopped or restarted, the control unit changes the phase of the intake valve or the exhaust valve by the valve timing variable mechanism, and makes the change amount of the phase of the valve timing variable mechanism smaller than the change amount before the detection timing from the detection timing detected by the cam angle sensor.

[0015] An engine control method is an engine control method for controlling an engine mounted on a hybrid vehicle that is driven by cooperation between the output of an engine including a valve timing variable mechanism that changes the phase of at least one of an intake valve and an exhaust valve and the output of an electric motor. And it includes the processes shown in (1) to (3) below. (1) A process of changing the phase of the intake valve or the exhaust valve by the valve timing variable mechanism when the engine is stopped or restarted. (2) A process of receiving a detection signal from a cam angle sensor that detects the rotation of the intake valve or the exhaust valve. (3) A process of making the change amount of the phase of the valve timing variable mechanism smaller than the change amount before the detection timing from the detection timing detected by the cam angle sensor for a predetermined time.

Advantages of the Invention

[0016] According to the engine control device and the engine control method having the above configuration, during the period from the engine stop process to the engine restart in a hybrid vehicle, the deviation between the phase (VTC angle) of the variable valve timing mechanism calculated at the timing detected by the cam angle sensor and the phase (VTC angle) of the variable valve timing mechanism at the timing when the valve is actually closed can be reduced.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

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Figure 7

Figure 8

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Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0018] Hereinafter, example embodiments of the engine control device and the engine control method will be described with reference to FIGS. 1 to 13. In each figure, common members are denoted by the same reference numerals.

[0019] 1. Example embodiment First, the engine control device and the engine control method according to the example embodiment (hereinafter referred to as "this example") will be described with reference to FIGS. 1 to 10.

[0020] First, the configuration of an engine equipped with an electric valve timing variable mechanism will be described with reference to FIG. 1. In the present embodiment, an internal combustion engine is used as an example of the engine. Hereinafter, the present invention will be described assuming a case where it is applied to a hybrid vehicle having two power sources, a traction motor and an engine. Further, this embodiment is a series hybrid vehicle equipped with a traction motor for running, and the engine is used for power generation to charge the battery. When the battery charge capacity becomes low, the engine is operated to charge the battery, and when the battery charge capacity becomes high, the engine is stopped. At high vehicle speeds or high loads, the engine is operated and the vehicle runs on electricity generated without passing through the battery.

[0021] [Engine configuration] FIG. 1 shows a configuration example of an engine 50 equipped with an electric valve timing variable mechanism. The engine 50 shown in FIG. 1 is configured as an in-line four-cylinder naturally aspirated engine. In the engine 50, a combustion chamber is formed by a cylinder head 1, a cylinder block 2, and a piston 3 inserted into the cylinder block 2. The piston 3 is connected to a crankshaft 5 via a connecting rod 4. A crank angle sensor 6 provided near the crankshaft 5 detects the rotational speed of the crankshaft 5 (engine rotational speed).

[0022] The intake pipe 7 and the exhaust pipe 8 are each branched into two and connected toward the combustion chamber of one cylinder. Two intake valves 9 and two exhaust valves 10 are provided to open and close the openings of the respective connection portions between the combustion chamber, the intake pipe 7, and the exhaust pipe 8. An intake cam 11 is provided above the intake valve 9, and an exhaust cam 12 is provided above the exhaust valve 10. The rotation of the intake cam 11 opens and closes the intake valve 9, and the rotation of the exhaust cam 12 opens and closes the exhaust valve 10.

[0023] On the side of the engine 50, an intake cam pulley 28 connected to the intake cam 11, an exhaust cam pulley 29 connected to the exhaust cam 12, and a crank pulley 30 connected to the crankshaft 5 are provided (see FIG. 2). The intake cam pulley 28, the exhaust cam pulley 29, and the crank pulley 30 are connected via a timing belt 24. Thus, when the engine 50 operates, the rotation of the crankshaft 5 rotates the intake cam 11 and the exhaust cam 12. The intake cam pulley 28 and the exhaust cam pulley 29 are set so that the intake cam 11 and the exhaust cam 12 rotate once while the crankshaft 5 rotates twice.

[0024] An electric intake valve timing variable mechanism (VTC) 41 capable of changing the phase of the intake cam 11 (intake valve 9) is provided on the intake cam 11. Similarly, an electric exhaust valve timing variable mechanism (VTC) 42 capable of changing the phase of the exhaust cam 12 (exhaust valve 10) is provided on the exhaust cam 12. Further, a motor generator that acts as a generator during power generation and acts as a motor when the engine 50 starts and stops is provided on the crankshaft 5. The change in the angle of the intake cam 11, that is, the rotation speed of the intake cam 11, is detected by an intake cam angle sensor 31 installed on the intake cam 11 (see FIG. 2).

[0025] An injector 13 is provided on the intake side of the combustion chamber, and a spark plug 14 and a spark coil 15 are provided above the combustion chamber. The fuel is stored in a fuel tank and sent to a high-pressure fuel pump through a fuel pipe by a feed pump.

[0026] Upstream of the intake pipe 7, a collector 22 is provided, which has a larger diameter of the air flow path than other parts. The intake pipes 7 are connected to each cylinder from this collector 22. Also, a throttle 23 capable of changing the amount of air inhaled into the cylinder is provided upstream of the collector 22.

[0027] A three-way catalyst 17 is provided downstream of the exhaust pipe 8. An air-fuel ratio sensor 18 is provided upstream of the three-way catalyst 17, and an oxygen sensor 19 is provided downstream of the three-way catalyst 17. Also, a temperature sensor 20 is provided in the three-way catalyst 17, and the temperature sensor 20 detects the temperature of the three-way catalyst 17. A water temperature sensor 21 for measuring the temperature of the water flowing around the cylinder block 2 is provided in the cylinder block 2.

[0028] Signals such as the water temperature and engine speed output by each sensor are input to an engine control unit (ECU: Engine Control Unit) 100 (see FIG. 4). The ECU 100 controls the on / off of fuel injection and the VTC angle (phase) of the electric valve timing variable mechanisms 41 and 42 based on the information obtained from these signals. Hereinafter, the valve timing variable mechanisms 41 and 42 may be referred to as VTC (Valve Timing Control).

[0029] FIG. 2 is a perspective view showing the configuration around the crankshaft 5. As shown in FIG. 2, a crank angle plate 25 that rotates in synchronization with the crankshaft 5 is provided on the crankshaft 5. And a crank angle sensor 6 is provided in proximity to the crank angle plate 25. Also, the crank angle plate 25 is provided on a crank pulley 30 connected to the crankshaft 5. A timing belt 24 is wound around the crank pulley.

[0030] The timing belt 24 is wound around an intake cam pulley 28 connected to the camshaft of the intake cam 11 and an exhaust cam pulley 29 connected to the camshaft of the exhaust cam 12. Further, an intake cam angle plate 26 that rotates in synchronization with the camshaft is provided on the camshaft of the intake cam 11, and similarly, an exhaust cam angle plate 27 that rotates in synchronization with the camshaft is provided on the camshaft of the exhaust cam. An intake cam angle sensor 31 is provided near the intake cam angle plate 26, and an exhaust cam angle sensor 32 is provided near the exhaust cam angle plate 27.

[0031] FIG. 3 is a diagram showing the configurations of the intake cam angle plate 26, the exhaust cam angle plate 27, and the crank angle plate 25. As shown in FIG. 3, a convex portion 26a and a concave portion 26b are provided on the peripheral edge of the intake cam angle plate 26. Similarly, a convex portion 27a and a concave portion 27b are provided on the peripheral edge of the exhaust cam angle plate 27. The intake cam angle sensor 31 and the exhaust cam angle sensor 32 detect the change from the concave portions 26b and 27b to the convex portions 26a and 27a during the rotation of the intake cam 11 and the exhaust cam 12. Then, the CPU 102 of the ECU 100, which will be described later, calculates the cam angle from the detection signals of the intake cam angle sensor 31 and the exhaust cam angle sensor 32.

[0032] Further, the intake cam angle plate 26 and the exhaust cam angle plate 27 are provided with convex portions 26a and 27a every 90°. The widths of the plurality of convex portions 26a of the intake cam angle plate 26 are different. The state of the four-cylinder cycle is discriminated by the difference in the widths of the convex portions 26a. Although the widths of the plurality of convex portions 27a of the exhaust cam angle plate 27 are constant, the exhaust cam angle plate 27 may also detect the cam angle by changing the length of the convex portion 27a.

[0033] Further, a plurality of convex portions 25a are provided on the peripheral edge of the crank angle plate 25. The crank angle sensor 6 detects the convex portion 25a during the rotation of the crank angle plate 25. Then, the CPU 102 of the ECU 100, which will be described later, calculates the crank angle from the detection signal of the crank angle sensor 6.

[0034] The convex portions 25a of the crank angle plate 25 are provided every 10 degrees along the peripheral edge of the crank angle plate 25. Further, there are two toothless portions 25c where the convex portions 25a are not provided on the peripheral edge of the crank angle plate 25. Then, when the crank angle sensor 6 detects this toothless portion 25c, the CPU 102 determines the top dead center and the bottom dead center.

[0035] [Control system including ECU] Next, a control system including the ECU 100 will be described with reference to FIG. 4. FIG. 4 shows a block diagram of a control system including the ECU 100.

[0036] As shown in FIG. 4, the ECU 100, which shows an example of an engine control device, has a CPU (Central Processing Unit) 102 showing a control unit, a RAM (Random Access Memory) 103, and a ROM (Read Only Memory) 104. The CPU 102 is connected to an intake cam angle sensor 31, an exhaust cam angle sensor 32, and a crank angle sensor 6. Further, the CPU 102 is connected to an intake VTC controller 106 that controls an intake valve timing variable mechanism 41 and an exhaust VTC controller 107 that controls an exhaust valve timing variable mechanism 42.

[0037] The CPU 102 calculates the cam angles of the intake cam 11 and the exhaust cam 12 from the signals detected by the intake cam angle sensor 31 and the exhaust cam angle sensor 32. The CPU 102 calculates target values for the intake VTC controller 106 and the exhaust VTC controller 107 from the calculated cam angles. Then, the CPU 102 outputs the calculated target values to the intake VTC controller 106 and the exhaust VTC controller 107. The intake VTC controller 106 and the exhaust VTC controller 107 control the driving of the valve timing variable mechanisms 41 and 42 based on the target values received from the CPU 102 and control the VTC angle (phase).

[0038] The CPU 102 calculates the cam angle during the period from the rising timing of the signals detected by the cam angle sensors 31 and 32 (the timing of detecting the convex portions 26a and 27a) after the crank angle sensor 6 detects the toothless portion 25c of the crank angle plate 25. And, the longer the timing at which the crank angle sensor 6 detects the toothless portion 25c and the detection timing of the cam angle sensors 31 and 32, the more the cams 11 and 12 are in a state of being changed to the retard side. Also, the uneven positions of the cam angle plates 26 and 27 are set to the maximum lift positions of the camshafts. Therefore, the CPU 102 detects and calculates the VTC angles (phases) of the valve timing variable mechanisms 41 and 42 at the timing when the lift amounts of the intake and exhaust valves of each cylinder reach the maximum.

[0039] The RAM 103 temporarily stores the current positions of the cams 11 and 12 and the numerical values during calculation. Also, the ROM 104 stores the target cam angles of the cams 11 and 12 based on the rotational speed and the air flow rate. When the operating state of the engine, for example, the rotational speed changes, the CPU 102 calculates the cam angle to be changed from the current cam angles of the cams 11 and 12 stored in the RAM 103 and the cam angle MAP for the rotational speed stored in the ROM 104. Then, the CPU 102 calculates the change speed of the VTCs 41 and 42 from the cam angle that needs to be changed, and in the case of an electric VTC, the motor rotational speed. The CPU 102 controls the cam angle by outputting the calculated results to the respective VTC controllers 106 and 107.

[0040] 2. Operation Example Next, an operation example of the engine control device having the above-described configuration will be described with reference to FIGS. 5 to 11. Note that the operation example described below is an operation example in which the engine is operated while the vehicle is running to charge the battery, and the engine is stopped because the remaining battery level has reached the target value. FIG. 5 shows the cam profile in one combustion cycle according to the operation example, and FIG. 6 shows the cam profile after fuel cut. FIG. 7 is a graph showing the fuel cut flag and the engine rotational speed.

[0041] During operation under power generation operating conditions, combustion occurs at a rotational speed, load, and valve timing that result in good combustion efficiency of the engine with respect to the target power generation amount. When the ECU100 determines that the remaining battery level is sufficient, the connection between the crankshaft 5 and the motor generator is disengaged to place the engine in an unloaded state in order to stop the engine. Further, the valve timing is changed to the no-load firing shown in FIG. 5, the fuel injection amount is decreased, and the engine speed is decreased to, for example, 1600 r / min shown in FIG. 7.

[0042] When the CPU102 confirms the decrease in the engine speed, the engine stop mode is turned ON and the fuel cut flag is turned ON. When the fuel cut flag is turned ON, fuel injection is cut off. Then, the CPU102 starts changing the valve timing from the valve timing shown in FIG. 5 to the valve timing shown in FIG. 6. In the example shown in FIGS. 5 and 6, the change angle of the VTC angle (phase) on the intake side is such that the valve closing timing is set to be retarded by 100 deg. On the exhaust side, the valve closing timing is set to be advanced by 60 deg.

[0043] Note that the maximum speed (referred to as the "phase change speed") at which the phases of the intake valve 9 and the exhaust valve 10 in the VTCs 41 and 42 in this example are changed is set to, for example, 250 deg.CA / s.

[0044] When the fuel cut flag is ON, fuel injection is prohibited and the engine rotates by inertia. Therefore, as shown in FIG. 7, the engine speed decreases from 1600 r / min to 0 r / min over 0.5 seconds.

[0045] During the period when fuel is not injected and the engine rotates, if the valve timing remains as shown in FIG. 5, the air remaining in the combustion chamber at the timing of valve closing in the compression stroke is discharged to the exhaust pipe 8, so the air is discharged to the three-way catalyst 17. However, by switching to the valve timing shown in FIG. 6, the combustion chamber volume at the valve closing timing becomes only the clearance volume of the cylinder head, and it is possible to suppress the discharge of air to the exhaust pipe 8.

[0046] However, air is discharged during the transitional period when switching the valve timing from FIG. 5 to FIG. 6. Therefore, by advancing the closing timing of the exhaust valve 10 and making the combustion chamber volume when the exhaust valve 10 closes larger than the combustion chamber volume when the intake valve closes, backflow can be generated. As a result, the air discharged transiently after switching to the valve timing shown in FIG. 6 can be made to flow backward.

[0047] Also, the power of the battery is consumed by vehicle running, and when the remaining amount falls below the lower limit, the engine 50 restarts. When the exhaust gas discharged into the exhaust pipe 8 during firing before fuel cut is made to flow backward into the intake pipe 7 when generating this backflow, if fuel is injected in a state where exhaust gas exists at restart, combustion cannot occur and the unburned fuel is discharged into the exhaust pipe 8. As a result, it causes deterioration of fuel consumption and exhaust. Therefore, it is necessary to estimate the flow rates of air and exhaust gas after fuel cut and cancel the fuel cut flag at the timing when the exhaust gas flowing backward into the intake pipe 7 is discharged.

[0048] FIG. 8 is a graph showing the correlation between the volume difference at the closing times of the intake and exhaust valves and the amount of air per cycle. The vertical axis in FIG. 8 indicates the volume flow rate (air amount) per cycle per cylinder, and the horizontal axis indicates the volume difference between the closing time (IVC) of the intake valve 9 and the closing time (EVC) of the exhaust valve 10.

[0049] As shown in FIG. 8, in a cycle without combustion after fuel cut, it can be seen that there is a correlation between the volume obtained by subtracting the combustion chamber volume at the closing time (EVC) of the exhaust valve 10 from the combustion chamber volume at the closing time (IVC) of the intake valve 9 and the gas volume discharged from the combustion chamber. Therefore, when the combustion chamber volume at EVC is larger than the combustion chamber volume at IVC, backflow occurs. Therefore, the CPU 102 calculates the VTC angle from the signals of the cam angle sensors 31 and 32 for the closing times (IVC, EVC) of the intake valve 9 and the exhaust valve 10, and can know the volume at the closing time.

[0050] FIG. 9 is a diagram showing an example of the profile of an intake valve by a conventional VTC. The horizontal axis shows how the stroke in the engine cylinder changes in the order of the expansion stroke, exhaust stroke, intake stroke, and compression stroke, and the vertical axis shows the sequential lift amount [mm] of the intake valve 9.

[0051] As shown in FIG. 9, the intake valve 9 is changed from profile Q1 to profile Q3 in one cycle by the intake VTC 41. Further, the IVC of the intake valve 9 and the VTC angle of the intake VTC 41 are detected by the intake cam angle sensor 31 at the maximum lift amount in profile Q2 during the transition period from profile Q1 to profile Q3. Then, the CPU 102 calculates the valve closing timing (IVC) based on the timing detected at the time of profile Q2. Also, as described above, the CPU 102 detects and calculates the VTC angle (phase) of the valve timing variable mechanisms 41 and 42 at the timing when the lift amounts of the intake valve 9 and the exhaust valve 10 of each cylinder reach the maximum.

[0052] However, the intake valve 9 is continuously changed to the retard side by the intake VTC 41. Therefore, the actual valve closing timing (IVC) is the timing when the lift amount in profile Q3 becomes the minimum. Therefore, a deviation occurs between the valve closing timing calculated when the VTC angle is calculated at the maximum lift position of the intake valve 9 and the actual valve closing timing. As a result, the volume difference between the valve closing timing (IVC) of the intake valve 9 and the valve closing timing (EVC) of the exhaust valve 10, that is, the error between the true value and the estimated value of the forward flow rate and the reverse flow rate has been enlarged.

[0053] FIG. 10 is a graph showing the VTC angles (phases) of the intake VTC 41 and the exhaust VTC 42 according to the engine speed at the time of fuel cut. The vertical axis represents the VTC angle, and the horizontal axis represents time. Also, the vertical lines indicated by the dotted lines in the graph indicate the detection timings of the cam angle sensors 31 and 32.

[0054] As shown in FIG. 10, when the fuel cut flag is ON, the VTC angle of the intake VTC 41 and the VTC angle of the exhaust VTC 42 are changed toward the target values in FIG. 6. Also, the CPU 102 in this example calculates the VTC angle (phase) at the timing when the cam angle sensors 31 and 32 are detected. Then, the volume at the valve closing timing is calculated from the calculated VTC angle (phase). At this time, the CPU 102 outputs a control signal to each of the VTC controllers 106 and 107 so as to hold the VTC angle (phase) at the timing when the cam angle sensors 31 and 32 are detected for a predetermined time. Therefore, the change speed of the VTC angle (phase) becomes almost zero or small. That is, the CPU 102 makes the change amount of the VTC angle (phase) smaller than the change amount before the detection timing detected by the cam angle sensors 31 and 32.

[0055] The time for holding this VTC angle is set based on the cam profile from the lift top to the valve closing timing. That is, each of the VTCs 41 and 42 holds the VTC angle (phase), that is, does not change the VTC angle (phase), for the time from when the cam angle sensors 31 and 32 are detected until the intake valve 9 and the exhaust valve 10 are actually closed. Thereby, the deviation between the phase (VTC angle) of the variable valve timing mechanism calculated at the timing detected by the cam angle sensor and the phase (VTC angle) of the variable valve timing mechanism at the actually closed timing can be reduced.

[0056] Also, when a predetermined time has elapsed, the CPU 102 outputs a control signal to each of the VTC controllers 106 and 107 so as to change the VTC angle (phase) toward the target value.

[0057] FIG. 11 is a graph showing the gas flow rate and the estimated value. The vertical axis represents the integrated value of the gas flow rate, and the horizontal axis represents time. As shown in FIG. 11, the error between the flow rate per cycle (solid line) calculated with the VTC angle calculated at the timing detected by the cam angle sensor and the actual flow rate indicated by the dotted line can be reduced.

[0058] 3. Engine Stop Processing Operation Next, with reference to FIG. 12, the engine stop processing operation in the engine control device having the above-described configuration will be described. FIG. 12 is a flowchart showing the engine stop processing operation.

[0059] As shown in FIG. 12, also, the ECU 100 operates the engine 50 and performs a power generation operation to charge the battery (step S11). Next, the ECU 100 determines whether or not the remaining amount of the battery has reached a predetermined value or less (step S12). If the remaining amount of the battery exceeds the predetermined value in step S12, the ECU 100 reduces the fuel injection amount of the engine 50 and performs an unloaded operation (step S13).

[0060] Next, the ECU 100 determines whether or not the engine speed has reached a predetermined value or less (step S14). If it is determined in step S14 that the engine speed has reached a predetermined value or less, the ECU 100 cuts (stops) the fuel injection (step S15).

[0061] Next, the ECU 100 performs control to change the VTC angle of the intake VTC 41 to a retarded angle so as to reach the target value (step S16). Also, the ECU 100 receives the crank angle signal detected by the crank angle sensor 6 (step S17), and receives the intake cam angle signal detected by the intake cam angle sensor 31 (step S18). That is, in steps S17 and S18, the ECU 100 detects the closing timing of the intake valve 9.

[0062] Next, the ECU 100 calculates (computes) the VTC angle of the intake VTC 41 (step S19). Then, the ECU 100 determines whether or not the calculated VTC angle has reached the target value (step S20). In step S20, if it is determined that the VTC angle has not reached the target value, the ECU 100 calculates the crank angle (target value) until the intake valve 9 closes (step S21). Next, the ECU 100 outputs a control signal to the intake VTC controller 106 so as to hold the VTC angle of the intake VTC 41 at the VTC angle calculated in step S19. Then, the intake VTC controller 106 performs holding control of the VTC angle of the intake VTC 41 (step S22).

[0063] Next, the ECU 100 determines based on the crank angle sensor 6 whether or not the crank angle has reached the target value calculated in step S21 (step S23). In the process of step S23, if it is determined that the crank angle has reached the target value, the ECU 100 returns to the process of step S16. That is, control is performed so that the VTC angle of the intake VTC 41 becomes the target value on the retard side. Also, in the process of step S23, if it is determined that the crank angle has not reached the target value, the ECU 100 returns to the process of step S22. That is, the VTC angle of the intake VTC 41 is held in the state of the VTC angle calculated in step S19.

[0064] Also, in step S20, if it is determined that the VTC angle has reached the target value, the ECU 100 outputs a control signal to the intake VTC controller 106 so as to hold the VTC angle in the state of the target value. Then, the intake VTC controller 106 performs holding control of the VTC angle of the intake VTC 41 (step S24). Then, the ECU 100 determines whether or not the engine has stopped (step S25).

[0065] Similarly, the same process is performed on the exhaust valve 10 side. That is, when the process of step S15 is performed, the ECU 100 controls the VTC angle of the exhaust VTC 42 to change to an advanced angle so as to reach the target value (step S26). Further, the ECU 100 receives the crank angle signal detected by the crank angle sensor 6 (step S27) and receives the exhaust cam angle signal detected by the exhaust cam angle sensor 32 (step 28). That is, the ECU 100 detects the closing timing of the exhaust valve 10 in steps S27 and S28.

[0066] Next, the ECU 100 calculates (computes) the VTC angle of the exhaust VTC 42 (step S29). Then, the ECU 100 determines whether the calculated VTC angle has reached the target value (step S30). In step S30, if it is determined that the VTC angle has not reached the target value, the ECU 100 calculates the crank angle (target value) until the exhaust valve 10 closes (step S31). Next, the ECU 100 outputs a control signal to the exhaust VTC controller 107 so as to hold the VTC angle of the exhaust VTC 42 at the VTC angle calculated in step S29. Then, the exhaust VTC controller 107 performs hold control on the VTC angle of the exhaust VTC 42 (step S32).

[0067] Next, the ECU 100 determines based on the crank angle sensor 6 whether the crank angle has reached the target value calculated in step S31 (step S33). In the process of step S33, if it is determined that the crank angle has reached the target value, the ECU 100 returns to the process of step S36. That is, the VTC angle of the exhaust VTC 42 is controlled to be the target value on the advanced angle side. Also, in the process of step S33, if it is determined that the crank angle has not reached the target value, the ECU 100 returns to the process of step S32. That is, the VTC angle of the exhaust VTC 42 is held in the state of the VTC angle calculated in step S29.

[0068] Also, in step S30, when it is determined that the VTC angle has reached the target value, the ECU 100 outputs a control signal to the exhaust VTC controller 107 so as to hold the VTC angle in the state of the target value. Then, the exhaust VTC controller 107 performs holding control on the VTC angle of the exhaust VTC 42 (step S34). And the ECU 100 determines whether the engine 50 has stopped (step S35).

[0069] Also, in the processes of steps S25 and S35, when it is determined that the engine 50 has stopped (YES determination in steps S25 and S35), the engine stop processing operation by the ECU 100 ends.

[0070] Also, the ECU 100 calculates the closing timings (EVC, IVC) of the intake valve 9 and the exhaust valve 10 based on the VTC angles calculated in steps S19 and S29, and calculates the volume at the closing timing of the combustion chamber.

[0071] 4. Engine starting processing operation Next, the engine starting processing operation in the engine control device having the above-described configuration will be described with reference to FIG. 13. FIG. 13 is a flowchart showing the engine starting processing operation.

[0072] As shown in FIG. 13, first, the ECU 100 drives a motor using the power of the battery and starts motoring (step S51). The ECU 100 receives the crank angle signal detected by the crank angle sensor 6 (step S52), and receives the intake cam angle signal detected by the intake cam angle sensor 31 (step S53). That is, the ECU 100 detects the closing timing of the intake valve 9 in steps S52 and S53. Next, the ECU 100 calculates (computes) the VTC angle of the intake VTC 41 (step S54).

[0073] The ECU 100 controls the VTC angle of the intake VTC 41 to advance so as to reach the target value (step S55). Then, the ECU 100 determines whether the calculated VTC angle has reached the target value (step S56). In step S56, if it is determined that the VTC angle has not reached the target value, the ECU 100 calculates the crank angle (target value) until the intake valve 9 closes (step S57). Next, the ECU 100 outputs a control signal to the intake VTC controller 106 so as to hold the VTC angle of the intake VTC 41 at the VTC angle calculated in step S54. Then, the intake VTC controller 106 performs holding control on the VTC angle of the intake VTC 41 (step S58).

[0074] Next, the ECU 100 determines, based on the crank angle sensor 6, whether the crank angle has reached the target value calculated in step S57 (step S59). In the process of step S59, if it is determined that the crank angle has reached the target value, the ECU 100 returns to the process of step S55. That is, the VTC angle of the intake VTC 41 is controlled to be the target value on the advancing side. Also, in the process of step S59, if it is determined that the crank angle has not reached the target value, the ECU 100 returns to the process of step S58. That is, the VTC angle of the intake VTC 41 is held in the state of the VTC angle calculated in step S54.

[0075] Also, in step S56, if it is determined that the VTC angle has reached the target value, the ECU 100 outputs a control signal to the intake VTC controller 106 so as to hold the VTC angle in the state of the target value. Then, the intake VTC controller 106 performs holding control on the VTC angle of the intake VTC 41 (step S60).

[0076] Similarly, the same process is performed on the exhaust valve 10 side. The ECU 100 receives the crank angle signal detected by the crank angle sensor 6 (step S62) and receives the exhaust cam angle signal detected by the exhaust cam angle sensor 32 (step S63). That is, in steps S62 and S63, the ECU 100 detects the closing timing of the exhaust valve 10. Next, the ECU 100 calculates the VTC angle of the exhaust VTC 42 (step S64).

[0077] The ECU 100 controls the retard change so that the VTC angle of the exhaust VTC 42 reaches the target value (step S65). Then, the ECU 100 determines whether the calculated VTC angle has reached the target value (step S66). In step S56, if it is determined that the VTC angle has not reached the target value, the ECU 100 calculates the crank angle (target value) until the exhaust valve 10 closes (step S67). Next, the ECU 100 outputs a control signal to the exhaust VTC controller 107 so as to hold the VTC angle of the exhaust VTC 42 at the VTC angle calculated in step S64. Then, the exhaust VTC controller 107 performs hold control on the VTC angle of the exhaust VTC 42 (step S68).

[0078] Next, the ECU 100 determines based on the crank angle sensor 6 whether the crank angle has reached the target value calculated in step S67 (step S69). In the process of step S69, if it is determined that the crank angle has reached the target value, the ECU 100 returns to the process of step S65. That is, control is performed so that the VTC angle of the exhaust VTC 42 becomes the target value on the retard side. Also, in the process of step S69, if it is determined that the crank angle has not reached the target value, the ECU 100 returns to the process of step S68. That is, the VTC angle of the exhaust VTC 42 is held in the state of the VTC angle calculated in step S64.

[0079] Also, in step S66, when it is determined that the VTC angle has reached the target value, the ECU 100 outputs a control signal to the exhaust VTC controller 107 so as to hold the VTC angle in the state of the target value. Then, the exhaust VTC controller 107 performs holding control on the VTC angle of the exhaust VTC 42 (step S70).

[0080] When the processes of step S60 and step S70 are completed, the ECU 100 performs motoring operation (step S71). Next, the ECU 100 determines whether or not the engine speed has reached a predetermined value or more (step S72). If it is determined in step S72 that the engine speed has reached a predetermined value or more, fuel injection is started (step S73), and no-load operation is performed (step S74). Thereby, the engine start process by the ECU 100 is completed.

[0081] Also, in the above-described embodiment example, an example in which the phases of both the intake valve 9 and the exhaust valve 10 are changed by the intake VTC 41 and the exhaust VTC 42 has been described, but the present invention is not limited thereto. For example, at least only one of the intake VTC 41 and the exhaust VTC 42 may be provided, and the phase of at least only one of the intake valve 9 and the exhaust valve 10 may be changed.

[0082] Note that the present invention is not limited to the embodiments described above and shown in the drawings, and various modifications can be made without departing from the gist of the invention described in the claims.

[0083] Also, each of the above-described configurations, functions, processing units, etc. may be realized by hardware by designing a part or all of them by, for example, an integrated circuit. As the hardware, a processor device in a broad sense such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) may be used.

[0084] Also, in the flowcharts describing the time-series processing shown in FIGS. 12 and 13, a plurality of processes may be executed in parallel or the order of the processes may be changed, as long as the processing results are not affected.

[0085] Also, in each of the above-described embodiments, the control lines and information lines show those considered necessary for explanation, and not all control lines and information lines are necessarily shown on the product. In practice, it may be considered that almost all components are interconnected.

Explanation of Reference Numerals

[0086] 1…Cylinder head, 2…Cylinder block, 3…Piston, 4…Connecting rod, 5…Crankshaft, 6…Crank angle sensor, 7…Intake pipe, 8…Exhaust pipe, 9…Intake valve, 10…Exhaust valve, 11…Intake cam, 12…Exhaust cam, 17…Three-way catalyst, 25…Crank angle plate, 25a…Protrusion, 25c…Tooth missing part, 26…Intake cam angle plate, 26a…Protrusion, 26b…Recess, 27…Exhaust cam angle plate, 27a…Protrusion, 27b…Recess, 28…Intake cam pulley, 29…Exhaust cam pulley, 30…Crank pulley, 31…Intake cam angle sensor, 32…Exhaust cam angle sensor, 41…Intake valve timing variable mechanism (Intake VTC), 42…Exhaust valve timing variable mechanism (Exhaust), 50…Engine, 100…Engine control unit (engine control device), 102…CPU (control unit), 103…RAM, 104…ROM, 106…Intake VTC controller, 107…Exhaust VTC controller

Claims

1. An engine control device for controlling an engine mounted on a hybrid vehicle driven by cooperation of the output of an engine provided with a valve timing variable mechanism for changing the phase of at least one of an intake valve and an exhaust valve and the output of an electric motor, comprising a control unit that receives a detection signal from a cam angle sensor that detects rotation of an intake cam that opens and closes the intake valve or an exhaust cam that opens and closes the exhaust valve, wherein the control unit when the engine is stopped or restarted, changes the phase of the intake valve or the exhaust valve by the valve timing variable mechanism, and for a predetermined time from the detection timing which is the rising timing of a signal for detecting a convex portion provided on the intake cam or the exhaust cam detected by the cam angle sensor, makes the amount of change in the phase of the valve timing variable mechanism smaller than the amount of change before the detection timing Engine control device.

2. The control unit calculates the predetermined time for holding the phase of the valve timing variable mechanism based on the crank angle of the crankshaft of the engine. The engine control device according to claim 1.

3. When the predetermined time has elapsed, the control unit increases the amount of change in the phase of the valve timing variable mechanism. The engine control device according to claim 1.

4. The control unit holds the phase of the valve timing variable mechanism at the phase at the detection timing for the predetermined time. The engine control device according to claim 3.

5. An engine control method for controlling an engine mounted on a hybrid vehicle driven by cooperation of the output of an engine provided with a valve timing variable mechanism for changing the phase of at least one of an intake valve and an exhaust valve and the output of an electric motor, comprising a process of changing the phase of the intake valve or the exhaust valve by the valve timing variable mechanism when the engine is stopped or restarted, a process of receiving a detection signal from a cam angle sensor that detects rotation of an intake cam that opens and closes the intake valve or an exhaust cam that opens and closes the exhaust valve, and a process of making the amount of change in the phase of the valve timing variable mechanism smaller than the amount of change before the detection timing for a predetermined time from the detection timing which is the rising timing of a signal for detecting a convex portion provided on the intake cam or the exhaust cam detected by the cam angle sensor Engine control method including.

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