Engine control device

Abstract

To improve startability of an engine regardless of a state of a lock pin in a variable valve train in an engine control device.SOLUTION: An engine control device 30 includes a setting part 31 and a control part 32. When the engine 1 is stopped, the setting unit 31 sets the flag to ON if the oil temperature of the engine oil that drives the variable valve mechanism 10 is equal to or lower than a predetermined temperature, and sets the flag to OFF if the oil temperature exceeds the predetermined temperature. At the start of the engine 1, the control unit 32 performs the normal control when the flag is off, and performs the scavenging control and the normal control when the flag is on. The normal control is a control for starting the engine 1 by cranking while performing both fuel injection and ignition. The scavenging control is control for scavenging the inside of the combustion chamber by cranking without performing both fuel injection and ignition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an engine control device that controls an engine equipped with a hydraulic variable valve mechanism having a lock pin. [Background technology]

[0002] Some hydraulic variable valve timing systems (VVTs) are provided with a lock pin to fix the relative rotational phase of the vanes relative to the housing. In engines equipped with this type of variable valve timing system, a control method is known to resolve the deterioration of startability resulting from improper fitting of the lock pin. For example, a known technique is to suppress a sudden change in the relative phase by controlling a hydraulic oil supply / discharge mechanism that drives the vanes when the relative phase of the vanes is not in the locked phase during engine start-up (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-124619 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, when the lock pin is not properly engaged, the engine may stall with a large valve overlap between the intake and exhaust valves. In this case, some of the exhaust gas remaining in the exhaust pipe may flow back into the combustion chamber, entering the intake port or even the intake passage further upstream. The backflowing exhaust gas changes the air-fuel ratio in the combustion chamber when the engine is subsequently started, preventing a smooth start.

[0005] One of the objects of the present invention, which was devised in light of the above-mentioned problems, is to provide an engine control device that can improve engine startability regardless of the state of the lock pin in the variable valve mechanism. In addition to this object, another object of the present invention is to achieve effects derived from the configurations shown in the "Mode for Carrying Out the Invention" below, which are effects that cannot be obtained with conventional technologies. [Means for solving the problem]

[0006] The disclosed engine control device can be realized as the following disclosed aspects (application examples), which solve at least part of the above-mentioned problems. Each of the aspects from aspect 2 onwards is an aspect that can be selected additionally as appropriate, and each of the aspects can be omitted. None of the aspects from aspect 2 onwards discloses an aspect or configuration that is essential to the present invention.

[0007] Aspect 1. The disclosed engine control device is an engine control device that controls an engine equipped with a hydraulic variable valve mechanism having a lock pin. The engine control device includes a setting unit that, when the engine is stopped, sets a flag to ON if the temperature of engine oil that drives the variable valve mechanism is equal to or lower than a predetermined temperature, and sets the flag to OFF if the oil temperature exceeds the predetermined temperature, and a control unit that, when the engine is started, performs normal control if the flag is OFF, and performs scavenging control and the normal control if the flag is ON.

[0008] The normal control is a control in which the engine is started by cranking while performing both fuel injection and ignition, and the scavenging control is a control in which the combustion chamber is scavenged by cranking without performing either fuel injection or ignition. The predetermined temperature is preferably a temperature corresponding to the boundary between a low temperature range in which a fitting failure of the lock pin may occur when the engine is stopped and a normal temperature range in which the fitting failure does not occur.

[0009] Aspect 2. With respect to an aspect including the aspect 1 described above, it is preferable that the scavenging control has a first control that generates negative pressure in the combustion chamber by cranking with the throttle fully closed, and a second control that promotes the introduction of fresh air into the combustion chamber by cranking with the throttle fully opened after the first control. Aspect 3. With respect to an aspect including Aspect 2 above, it is preferable that the conditions for starting the second control include the pressure in the combustion chamber falling below a predetermined pressure, or the duration of the first control exceeding a first predetermined time, or the engine rotation speed at the time of cranking exceeding a predetermined speed.

[0010] Aspect 4. In an aspect including the aspect 1 described above (for example, an aspect described in any one of Aspects 1 to 3), it is preferable that the termination condition of the scavenging control includes that the implementation time of the scavenging control exceeds a second predetermined time, and that the second predetermined time is shortened as the outside air temperature becomes lower. Aspect 5. In an aspect including the aspect 1 described above (for example, an aspect described in any one of Aspects 1 to 4), it is preferable that the termination condition of the scavenging control includes an estimated amount of fresh air introduced into the combustion chamber exceeding a predetermined value.

[0011] Aspect 6. With respect to an aspect including the above aspect 1 (for example, an aspect described in any one of aspects 1 to 5), it is preferable that the engine is mounted on a vehicle equipped with a starter and a low-voltage battery for starting the engine, and that in the scavenging control, the starter driven by the power of the low-voltage battery cranks the engine.

[0012] Aspect 7. In an aspect including the aspect 1 described above (for example, an aspect described in any one of Aspects 1 to 6), it is preferable that the engine is mounted on a vehicle having a generator and a high-voltage battery connected to the engine, and that in the scavenging control, the generator driven by the power of the high-voltage battery cranks the engine. [Effects of the Invention]

[0013] According to the disclosed engine control device, even if backflow of exhaust gas caused by improper fitting of the lock pin occurred when the engine was stopped the previous time, the exhaust gas can be discharged into the exhaust passage before the next engine start, thereby improving engine startability regardless of the state of the lock pin in the variable valve mechanism. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an engine and an engine control device. [Figure 2] 4 is a table showing control details of the engine control device. [Figure 3] 10 is a flowchart relating to flag setting when stopping the engine. [Figure 4] 4 is a flowchart relating to control when starting the engine. [Figure 5] This is a graph showing the time-dependent fluctuations in scavenging control and normal control, where (A) is the engine speed, (B) is the throttle opening, (C) is the intake manifold pressure, and (D) is the estimated amount of fresh air introduced into the combustion chamber. DETAILED DESCRIPTION OF THE INVENTION

[0015] The disclosed engine control device is applied to an engine (internal combustion engine) equipped with a hydraulic variable valve mechanism having a lock pin. The variable valve mechanism is a mechanism for changing the opening and closing timing of the engine's intake and exhaust valves. The opening and closing timing of the intake and exhaust valves can be changed, for example, by changing the relationship (relative phase) between the rotation angle of the camshaft and the rotation angle of the housing that supports the camshaft.

[0016] A vane shaped like a blade is fixed to the end of the camshaft. The vane is housed in a hollow cylindrical housing. The housing is set up to rotate at half the angular speed of the crankshaft. Two chambers are formed inside the housing, each defined by the vane. These two chambers are called the advance chamber and the retard chamber. The relative phase of the vane with respect to the housing (i.e., the relative phase of the camshaft) is changed by generating an oil pressure difference between the advance chamber and the retard chamber, causing the vane to rotate. The oil pressure difference can be generated by adjusting the flow rate of engine oil (hydraulic fluid) filled in each of the advance chamber and the retard chamber.

[0017] The lock pin is a shaft-shaped member used to fix the relative phase of the camshafts. The lock pin is housed, for example, together with a spring, inside an axial hole drilled in the vane and is provided so as to be slidable in the axial direction. A recess into which the end of the lock pin can be fitted is provided in a position of the housing facing the axial hole of the vane. The relative phase of the camshafts is mechanically fixed by sliding the lock pin along the axial hole and fitting it into the recess.

[0018] The state in which the lock pin and the recess are engaged is called the "locked state," and the state in which they are disengaged is called the "unlocked state." The spring force of the lock pin is set so that it is in the locked state when the engine is stopped (when the oil pressure in the advance and retard chambers is low) and is in the unlocked state when the oil pressure in the advance and retard chambers rises. Note that the relative phase of the camshafts in the locked state corresponds to a state in which the valve overlap of the intake and exhaust valves is relatively small.

[0019] The inventors of this invention discovered that when the engine oil temperature is relatively low when the engine is stopped, the lock pin may fail to fit due to an imbalance in the oil pressure in each chamber and the spring force. When this failure occurs, the relative phase of the camshafts may fluctuate randomly, resulting in a large valve overlap between the intake and exhaust valves. This may cause some of the exhaust gas remaining in the exhaust pipe to gradually flow back into the combustion chamber while the engine is stopped, and then into the intake port or intake passage.

[0020] The backflowing exhaust gas can change the air-fuel ratio and oxygen concentration in the combustion chamber when the engine is subsequently started, potentially impairing engine startability. Therefore, the inventors of the present invention have devised a method for improving engine startability by scavenging the combustion chamber in advance, taking into account the possibility of exhaust gas backflow. On the other hand, if the engine oil temperature is sufficiently high when the engine is stopped, there is a high possibility that lock pin misfit will not occur. Therefore, the need for scavenging is determined based on the engine oil temperature. An example of implementing this control is described in detail below. [Example]

[0021] [1. Vehicle] 1 is a diagram showing the configuration of an engine control device 30 according to an embodiment and the configuration of an engine 1 that is the object of its control. The engine control device 30 and the engine 1 can be mounted on, for example, a vehicle, a ship, a power generation device, a machine tool, etc. In this embodiment, the engine control device 30 and the engine 1 are mounted on a vehicle. Vehicles that can mount the engine control device 30 and the engine 1 include ICE (Internal Combustion Engine) vehicles, HEVs (Hybrid Electric Vehicles), and PHEVs (Plug-in Hybrid Electric Vehicles).

[0022] A PHEV is a hybrid electric vehicle that can externally charge a secondary battery (high-voltage battery) that serves as a power source for the traction motor, or externally supply power from the high-voltage battery to various electrical appliances. A PHEV is equipped with at least either a charging port (inlet) for inserting a charging cable that supplies power from an external charging facility, or an outlet for external power supply.

[0023] The engine 1 is an internal combustion engine such as a gasoline engine or a diesel engine. The engine 1 is equipped with a hydraulic variable valve mechanism 10 having at least a lock pin. The engine 1 is provided with an injector 8 for injecting fuel and a spark plug 9 for igniting the fuel. However, if the engine 1 is a diesel engine, the spark plug 9 may be omitted. Although FIG. 1 shows only one cylinder of the engine 1, the engine 1 may have multiple cylinders.

[0024] If the vehicle is an HEV or PHEV, the vehicle is equipped with at least a traction motor 2, a generator 3, a clutch 4, and a high-voltage battery 5. If the vehicle is an ICE vehicle, the vehicle is equipped with at least a starter 6 and a low-voltage battery 7. The starter 6 and low-voltage battery 7 can also be added to HEVs and PHEVs. The generator 3 and high-voltage battery 5 can also be added to ICE vehicles.

[0025] The traction motor 2 is a device that serves as a drive source for the vehicle together with the engine 1. The traction motor 2 has the function of propelling the vehicle using battery power stored in the high-voltage battery 5 and power generated by the generator 3, as well as the function of charging the high-voltage battery 5 with power generated by regeneration. A speed change mechanism (not shown) may be installed on the power transmission path connecting the traction motor 2 and the drive wheels.

[0026] The generator 3 has both the function of starting (cranking) the engine 1 using battery power stored in the high-voltage battery 5 and the function of generating electricity using the driving force of the engine 1. The high-voltage battery 5 is a secondary battery, such as a lithium-ion secondary battery, for supplying high-voltage power (for example, power of several hundred volts or more) to drive the vehicle. The high-voltage battery 5 is connected to the traction motor 2 and the generator 3 via a converter and inverter (not shown).

[0027] The clutch 4 is disposed on the power transmission path connecting the engine 1 and the drive wheels. When the clutch 4 is disengaged (released), the engine 1 and the generator 3 are disconnected from the drive wheels, and the traction motor 2 is connected to the drive wheels. Therefore, for example, by operating only the traction motor 2, EV driving (motor-only driving) is achieved. In addition, by operating the engine 1 and causing the generator 3 to generate electricity, series driving is achieved.

[0028] On the other hand, when the clutch 4 is connected (engaged), the engine 1, the traction motor 2, and the generator 3 are all connected to the drive wheels. Therefore, for example, by operating only the engine 1, so-called ENGine-powered driving (engine-only driving) is achieved. In addition, by driving the traction motor 2 and the generator 3, parallel driving is achieved. Note that some of the driving modes, such as EV driving, ENG driving, series driving, and parallel driving, may be omitted as appropriate.

[0029] The starter 6 is a device for starting (cranking) the engine 1 using battery power stored in a low-voltage battery 7. The starter 6 is also called a cell motor or starter motor, and if it also has a power generation mechanism, it is also called a starter dynamo. The low-voltage battery 7 is a secondary battery, such as a lead-acid battery, for supplying low-voltage power (for example, power of several tens of volts at most) to drive various electrical components.

[0030] The intake system of the engine 1 is provided with an intake passage 11, a throttle valve 12, and an intake manifold 13, while the exhaust system is provided with an exhaust passage 14 and an exhaust manifold 15. An EGR passage 16 is provided between the intake passage 11 and the exhaust passage 14 to recirculate a portion of the exhaust gas. An EGR valve 17 is installed in the EGR passage 16. The connection position of the EGR passage 16 with respect to the intake passage 11 and the exhaust passage 14 can be changed as appropriate.

[0031] The engine 1 is provided with sensors for detecting information related to the operating state of the engine 1. The oil temperature sensor 20 detects the temperature of the engine oil that drives the variable valve mechanism 10. The oil temperature may be detected near the variable valve mechanism 10 or at another location (for example, inside the oil pan). The engine speed sensor 21 detects the engine speed (number of engine revolutions per unit time). The intake manifold pressure sensor 22 detects the intake manifold pressure (pressure inside the intake manifold). The outside air temperature sensor 23 detects the outside air temperature (temperature of the outside air and air passing through the intake passage 11). The airflow sensor 24 detects the intake flow rate (flow rate of air passing through the throttle valve 12). The oxygen concentration sensor 25 detects the oxygen concentration in the exhaust passage 14. Information detected by these sensors is transmitted to the engine control device 30, which will be described later.

[0032] The vehicle is provided with sensors for detecting information related to the vehicle's running state and the driver's operation state. An accelerator pedal stroke sensor 26 detects the accelerator pedal depression stroke (accelerator opening). A brake pedal stroke sensor 27 detects the brake pedal depression stroke. A vehicle speed sensor 28 detects the vehicle speed (vehicle running speed). An ignition key switch 29 detects the operating position of the key inserted by the driver. If the vehicle is an HEV or PHEV, a main switch (push button switch) may be used instead of the ignition key switch 29. Information detected by these sensors is transmitted to an engine control device 30, which will be described later.

[0033] [2. Engine control device] The engine control device 30 is a computer (electronic control unit, ECU) that controls the operating state of the engine 1. The engine control device 30 has a built-in processor (arithmetic processing unit) and memory (storage device). The contents of the control (control program) performed by the engine control device 30 are stored in the memory and executed by the processor. The engine control device 30 may be provided as a single device or may be provided as separate devices.

[0034] The engine control device 30 acquires information obtained by various sensors as well as information from the high-voltage battery 5 and the low-voltage battery 7, and controls the operating state of various devices based on this information to control the operating state of the engine 1. Specific examples of the various devices include the generator 3, starter 6, injector 8, spark plug 9, throttle valve 12, and EGR valve 17.

[0035] As shown in Fig. 1, the engine control device 30 includes a setting unit 31 and a control unit 32. These elements are shown by classifying the functions of the engine control device 30 for convenience. These elements can be written as independent programs, or can be written as a composite program that combines multiple elements. These elements can be integrated and implemented in a single engine control device 30, or can be distributed and implemented in multiple engine control devices 30.

[0036] The setting unit 31 has a function of setting a control flag based on the engine oil temperature when the engine 1 that has been operating is stopped. The setting unit 31 sets the flag to on (F=1) when the oil temperature is equal to or lower than a predetermined temperature, and sets the flag to off (F=0) when the oil temperature exceeds the predetermined temperature. The predetermined temperature is preferably a temperature corresponding to the boundary between a low temperature range in which a lock pin may fail to fit when the engine 1 is stopped and a normal temperature range in which a lock pin will not fail to fit. Specifically, the predetermined temperature is, for example, a temperature within a range of 0 to 50°C.

[0037] The control unit 32 has a function of starting the stopped engine 1 when a predetermined engine start condition is met. At this time, the control unit 32 uses different methods based on the flag set by the setting unit 31. When the flag is off (F=0), the control unit 32 simply performs normal control. On the other hand, when the flag is on (F=1), the control unit 32 performs scavenging control and normal control. The scavenging control is performed before the normal control.

[0038] Normal control is a control in which the engine 1 is started by cranking while both fuel injection by the injector 8 and ignition by the spark plug 9 are performed. In contrast, scavenging control is a control in which the combustion chamber is scavenged by cranking without performing either fuel injection by the injector 8 or ignition by the spark plug 9. By performing scavenging control, even if exhaust gas flows back into the combustion chamber or the intake passage 11, the exhaust gas is expelled into the exhaust passage 14. This improves the startability of the engine 1 in normal control, which is performed after scavenging control. The device that cranks the engine 1 in each of normal control and scavenging control is the generator 3 or the starter 6. In a vehicle that has both of these, either one may be used.

[0039] The engine start conditions determined by the control unit 32 can be various known conditions such as those shown below. For example, the control unit 32 can determine that the engine start conditions are met when at least one of the following is met. However, the engine start conditions are not limited to these. The ignition key switch 29 is in the IG (ignition) position. The main switch was turned on. - Idling stop control has been cancelled. (The brake pedal is released or the accelerator pedal is depressed.) The conditions for starting the engine while driving in EV mode have been met. (The high-voltage battery 5 is not charged enough, or the vehicle speed is too high.)

[0040] Various known conditions such as those shown below can be applied as engine stop conditions. However, the engine stop conditions are not limited to these. The engine stop conditions may be determined by the control unit 32, or by another control device (not shown). The control and processing for stopping the engine 1 may be the responsibility of the control unit 32, or may be the responsibility of another control device (not shown). The ignition key switch 29 is in the OFF position. The main switch was turned off. - Idling stop control has been initiated. (The brake pedal was pressed continuously while the vehicle speed was 0.) The engine stop conditions were met while driving in a mode other than EV driving. (The high-voltage battery 5 is not charged enough, or the vehicle speed has slowed down.)

[0041] The scavenging control of this embodiment includes two different controls, namely, a first control and a second control. The first control is a control that generates negative pressure in the combustion chamber by cranking with the throttle fully closed. The second control is a control that promotes the introduction of fresh air into the combustion chamber by cranking with the throttle fully opened after the first control. Even if only the second control is performed without performing the first control, it is possible to scavenge the combustion chamber.

[0042] On the other hand, by performing the first control before the second control, the negative pressure in the combustion chamber increases, and fresh air can be forcefully flowed into the combustion chamber during the second control. This improves the efficiency of scavenging, and exhaust gas scavenging can be completed in a short time. Note that the first control is not a required control and can be omitted. If the first control is omitted, the second control is immediately performed when a predetermined engine start condition is met.

[0043] The main flow of scavenging control and normal control is as follows. First, when the conditions for implementing scavenging control are met, the first control is started (implemented). The first control is continued unless a predetermined transition condition is met. After that, when the transition condition is met, the first control ends, and the second control is started (implemented). The second control is continued unless a predetermined scavenging completion condition is met. After that, when the scavenging completion condition is met, the second control ends, and normal control is started (implemented). The normal control is continued unless a predetermined engine start completion condition is met. After that, when the engine start completion condition is met, the normal control ends.

[0044] Specific examples of the transition condition are as follows: The control unit 32 can determine that the transition condition is met when, for example, at least one of the following is met. - The intake manifold pressure (pressure inside the combustion chamber) has fallen below a specified pressure. The duration of the first control exceeded the first predetermined time. - The engine speed due to cranking exceeds the specified speed.

[0045] Specific examples of the scavenging completion condition are given below: The control unit 32 can determine that the scavenging completion condition is met when, for example, at least one of the following is met. The duration of scavenging control has exceeded the second predetermined time. (The execution time of the second control has exceeded the second predetermined time.) The estimated amount of fresh air introduced into the combustion chamber exceeded a specified value. The exhaust gas in the exhaust passage 14 can be considered to have been purged. (The oxygen concentration in the exhaust passage 14 has reached a concentration equivalent to that of the outside air.)

[0046] The estimated value of the fresh air volume can be calculated based on the intake air flow rate (instantaneous value, integrated value) detected by the air flow sensor 24 and the engine rotation speed (instantaneous value, integrated value) due to cranking. The estimated value of the fresh air volume increases as the air density increases, and therefore may be corrected to be increased as the outside air temperature detected by the outside air temperature sensor 23 decreases. Similarly, the first predetermined time period and the second predetermined time period may be corrected to be shortened as the outside air temperature decreases. Furthermore, when the engine 1 is cold, frictional resistance increases, making it difficult to increase the engine rotation speed due to cranking. Therefore, the first predetermined time period and the second predetermined time period may be corrected to be extended as the outside air temperature, oil temperature, engine coolant temperature, etc. decrease.

[0047] The engine start completion conditions determined by the control unit 32 can be various known conditions such as those shown below. For example, the control unit 32 can determine that the engine start completion conditions are met when at least one of the following is met. However, the engine start completion conditions are not limited to these. The engine speed exceeds the specified self-sustaining speed. - The engine torque exceeds the specified self-sustaining torque. The normal control execution time has exceeded the third specified time.

[0048] FIG. 2 is a table showing an example of the control contents of the engine control device 30. In each of the scavenging control and normal control performed when starting the engine 1, the engine 1 is cranked with the EGR valve 17 closed. The purpose of cranking in scavenging control is to scavenge exhaust gas that is likely to have flowed back. Therefore, in scavenging control, neither fuel injection by the injector 8 nor ignition by the spark plug 9 is performed. On the other hand, the purpose of cranking in normal control is to provide an impetus to start the engine 1 to rotate independently. Therefore, in normal control, both fuel injection by the injector 8 and ignition by the spark plug 9 are performed.

[0049] The scavenging control includes a first control performed first and a second control performed thereafter. The purpose of cranking during the first control is to increase the negative pressure in the combustion chamber. Therefore, in the first control, the throttle valve 12 is fully closed. On the other hand, the purpose of cranking during the second control is to promote the introduction of fresh air into the combustion chamber by utilizing the intake inertia effect. Therefore, in the second control, the throttle valve 12 is fully open. In the subsequent normal control, in order to suppress excessive surging of the engine 1 (a sharp increase in the engine rotation speed immediately after startup), the throttle valve 12 is fully closed again.

[0050] In this embodiment, "fully closed" means a state where the throttle opening is sufficiently reduced, and does not necessarily mean that the throttle opening is 0 [%]. Similarly, "fully open" means a state where the throttle opening is sufficiently opened, and does not necessarily mean that the throttle opening is 100 [%]. The full closure during the first control may be read as the first opening V1, the full opening during the second control may be read as the second opening V2, and the full closure during the normal control may be read as the third opening V3. The magnitude relationship among these is 0 ≦ V1 < V2 ≦ 100 [%], 0 ≦ V3 < V2 ≦ 100 [%]. V1 may be the same as V3, may be different, or either may be larger.

[0051] [3. Flowchart] Figure 3 is a flowchart related to flag setting when stopping the engine 1. The control shown in this flowchart is repeatedly executed at a predetermined cycle in the engine control device 30 during the operation of the engine 1. In step A1, in the control unit 32, it is determined whether the engine stop condition is satisfied. If this condition is satisfied, the process proceeds to step A2, and if it is not satisfied, the control for this cycle ends.

[0052] In step A2, the temperature of the engine oil that drives the variable valve mechanism 10 is detected. In the following step A3, it is determined whether the oil temperature is equal to or lower than a predetermined temperature. If the oil temperature is equal to or lower than the predetermined temperature, the process proceeds to step A4, where the value of flag F is set to F=1 in the setting unit 31 (i.e., the flag is on). F=1 means that if the engine 1 is stopped in this state, there is a high possibility that the lock pin will not fit properly and that exhaust gas will flow backward.

[0053] On the other hand, if the oil temperature exceeds the predetermined temperature, the process proceeds to step A5, where the setting unit 31 sets the value of flag F to F=0 (i.e., the flag is off). F=0 means that even if the engine 1 is stopped as it is, there is a high possibility that the lock pin will not malfunction and exhaust gas will not flow back. The value of flag F (flag state) set in steps A4 and A5 is stored in, for example, a non-volatile memory or a data storage device. In the following step A6, the control unit 32 performs a known engine stop process (for example, stopping fuel injection and ignition) and stops the engine 1. The value of flag F (flag state) is retained until the next time the engine 1 is started. After the engine 1 is stopped, the control shown in FIG. 4 is executed.

[0054] 4 is a flowchart relating to the control when starting the engine 1. The control shown in this flowchart is repeatedly executed in the engine control device 30 (mainly the control unit 32) at predetermined intervals while the engine 1 is stopped. In step B1, it is determined whether or not the engine start condition is met. If this condition is met, the process proceeds to step B2, and if not, the control for this cycle ends. In step B2, it is determined whether or not the value of flag F is 1. If this condition is met, the process proceeds to step B3, and if not, the process proceeds to step B8.

[0055] In step B3, the first control of the scavenging control is performed. In the first control, the throttle valve 12 is controlled to be fully closed, and the EGR valve 17 is controlled to be fully closed. Neither fuel injection by the injector 8 nor ignition by the spark plug 9 is performed, and cranking by the generator 3 or the starter 6 is performed. This increases the negative pressure in the combustion chamber. In the following step B4, it is determined whether a transition condition from the first control to the second control is satisfied. If the transition condition is not satisfied, the control returns to step B3, and the first control continues. If the transition condition is satisfied, the control proceeds to step B5.

[0056] In step B5, the second control of the scavenging control is performed. In the second control, the states of the EGR valve 17, the injector 8, and the spark plug 9 are the same as those in the first control. Meanwhile, the throttle valve 12 is controlled to be fully open, and cranking is performed by the generator 3 or the starter 6. This promotes the introduction of fresh air into the combustion chamber. In the following step B6, it is determined whether or not the scavenging completion condition is satisfied. If the scavenging completion condition is not satisfied, the control returns to step B5, and the second control is continued. If the scavenging completion condition is satisfied, the value of flag F is set to F=0 in step B7, and then the process proceeds to step B8.

[0057] In step B8, normal control is performed. If F=1 in step B2, normal control is performed after scavenging control. If F=0 in step B2, scavenging control is not performed and only normal control is performed. In normal control, the throttle valve 12 is controlled to be fully closed, and the EGR valve 17 is controlled to be fully closed. Furthermore, fuel injection by the injector 8 and ignition by the spark plug 9 are both performed, and cranking by the generator 3 or the starter 6 is performed. This causes the engine 1 to start.

[0058] In the following step B9, it is determined whether or not the engine start completion condition is satisfied. If the engine start completion condition is not satisfied, the control returns to step B8, and normal control continues. If the engine start completion condition is satisfied, the control of this flowchart ends. After the engine 1 is started, the control shown in FIG. 3 is executed.

[0059] [4. Time Chart] FIG. 5 is a graph showing the time-dependent fluctuations in scavenging control and normal control, where (A) represents the engine speed, (B) represents the throttle opening, (C) represents the intake manifold pressure, and (D) represents the estimated amount of fresh air introduced into the combustion chamber.

[0060] When the engine 1 is stopped and the flag is on (F=1), scavenging control is initiated when the engine start condition is met at time t0. In the first control of scavenging control, cranking is performed without fuel injection or ignition, with the throttle valve fully closed (see Figures 5(A) and 5(B)). As a result, the estimated amount of fresh air gradually increases, and the intake manifold pressure gradually decreases (see Figures 5(C) and 5(D)).

[0061] When a transition condition is met at time t1, the first control ends and the second control starts. The transition condition may be, for example, that the intake manifold pressure falls below a predetermined pressure (see FIG. 5C), or that the duration of the first control exceeds a first predetermined time (the time corresponding to t1-t0) (see FIG. 5A). In the second control, the throttle is fully opened, and cranking without fuel injection or ignition is performed (see FIGS. 5A and 5B). This promotes the introduction of fresh air into the combustion chamber, and the estimated fresh air amount increases rapidly (see FIG. 5D).

[0062] When the scavenging completion condition is met at time t2, the second control (scavenging control) ends and normal control begins. The scavenging completion condition may be, for example, that the estimated amount of fresh air exceeds a predetermined value (see FIG. 5(D)), or that the duration of scavenging control exceeds a second predetermined time (a time corresponding to t2-t0) (see FIG. 5(A)). In normal control, the throttle opening is fully closed, and cranking accompanied by fuel injection and ignition is performed (see FIGS. 5(A) and 5(B)). This causes the engine 1 to start self-sustaining rotation. When the engine start completion condition is met at time t3, the normal control ends.

[0063] [5. Effects] (1) The engine control device 30 of this embodiment controls the engine 1 equipped with a hydraulic variable valve mechanism 10 having a lock pin, and includes a setting unit 31 and a control unit 32. When the engine 1 is stopped, the setting unit 31 sets a flag to on (F=1) if the temperature of the engine oil that drives the variable valve mechanism 10 is equal to or lower than a predetermined temperature, and sets the flag to off (F=0) if the oil temperature exceeds the predetermined temperature.

[0064] When starting the engine 1, the control unit 32 performs normal control if the flag is off, and performs scavenging control and normal control if the flag is on. Normal control is control for starting the engine 1 by cranking while performing both fuel injection and ignition. Scavenging control is control for scavenging the combustion chamber by cranking without performing fuel injection or ignition.

[0065] With this configuration, even if backflow of exhaust gas occurs due to improper fitting of the lock pin in the variable valve mechanism 10, the exhaust gas can be scavenged from the intake passage 11 and the combustion chamber into the exhaust passage 14, and the engine 1 can be started after scavenging. Therefore, regardless of the state of the lock pin in the variable valve mechanism 10, the startability of the engine 1 can be improved.

[0066] Furthermore, in HEVs and PHEVs, the engine 1 may be started to assist acceleration while the vehicle is traveling using the traction motor 2. The engine control device 30 described above can improve acceleration performance in such situations. Furthermore, even in a cold state (a state in which the engine oil temperature is in a low temperature range) in which lock pin engagement failure is likely to occur, the subsequent startability of the engine 1 is improved, making it possible to appropriately perform idling stop control and control to return from the idling stop state, thereby improving the convenience of the electric vehicle.

[0067] (2) The scavenging control of this embodiment includes a first control and a second control. The first control generates negative pressure in the combustion chamber by cranking with the throttle fully closed. The second control promotes the introduction of fresh air into the combustion chamber by cranking with the throttle fully opened after the first control. This makes it possible to progress and complete scavenging in a short time by utilizing the intake inertia effect. Therefore, the startability of the engine 1 can be further improved.

[0068] (3) The start conditions for the second control may include the pressure in the combustion chamber falling below a predetermined pressure, the duration of the first control exceeding a first predetermined time, or the engine speed due to cranking exceeding a predetermined speed. By using these start conditions, it is possible to accurately determine whether a negative pressure suitable for achieving the intake inertia effect has been generated. This further improves the startability of the engine 1.

[0069] (4) The termination condition of the scavenging control may include the execution time of the scavenging control exceeding a second predetermined time, and the second predetermined time may be shortened as the outside air temperature decreases. This allows the progress and completion of scavenging to be determined accurately, taking into account the air density. Therefore, the startability of the engine 1 can be further improved.

[0070] (5) The termination condition for scavenging control may include an estimated amount of fresh air introduced into the combustion chamber exceeding a predetermined value. This allows the progress and completion of scavenging to be determined with high accuracy, taking into account the air introduction speed. This further improves the startability of the engine 1. The estimated amount of fresh air can be calculated based on the detected values ​​of the engine speed sensor 21 and the air flow sensor 24. The estimated amount of fresh air may be increased as the outside air temperature decreases.

[0071] (6) The engine 1 described above can be mounted on a vehicle equipped with a starter 6 and a low-voltage battery 7 for starting the engine 1. Furthermore, in scavenging control, the starter 6 driven by the power of the low-voltage battery 7 can crank the engine 1. This can improve the startability of the engine 1, for example, in an ICE vehicle that does not have a generator 3 or a high-voltage battery 5. Furthermore, in an HEV or PHEV that has a generator 3 or a high-voltage battery 5, the startability of the engine 1 can be improved while conserving the power of the high-voltage battery 5. Furthermore, the startability of the engine 1 can be improved regardless of the charging rate or operating temperature conditions of the high-voltage battery 5.

[0072] (7) The engine 1 described above can be mounted on a vehicle equipped with a generator 3 and a high-voltage battery 5 connected to the engine 1. Furthermore, in scavenging control, the generator 3 driven by the power of the high-voltage battery 5 can crank the engine 1. This can improve the startability of the engine 1, for example, in an HEV or PHEV that does not have a starter 6. Furthermore, the startability of the engine 1 can be improved while conserving the power of the low-voltage battery 7. Furthermore, the startability of the engine 1 can be improved regardless of the charge rate or operating temperature conditions of the low-voltage battery 7.

[0073] [6. Other] The above-described embodiment is merely illustrative, and is not intended to exclude various modifications and applications of techniques not explicitly stated in the present embodiment. Each configuration of the present embodiment can be modified in various ways without departing from the spirit of the present embodiment. Furthermore, each configuration of the present embodiment can be selected or combined as needed.

[0074] In the above embodiment, the first control and the second control are performed as scavenging controls, but the first control can be omitted. At least, by cranking without performing fuel injection or ignition (in other words, by performing only the second control without performing the first control), the combustion chamber can be scavenged, and the startability of the engine 1 can be improved regardless of the state of the lock pin in the variable valve mechanism 10.

[0075] The generator 3 or the starter 6 may be used to crank the engine 1 depending on the vehicle's running environment, temperature conditions, charging rate, etc. For example, the engine 1 may be cranked using the power of one battery with a higher battery temperature, or the engine 1 may be cranked using the power of one battery with a higher charging rate. The generator 3 and the starter 6 may also be used together to crank the engine 1. [Industrial Applicability]

[0076] The present invention is applicable to the engine control device manufacturing industry, and to the manufacturing industries of vehicles, ships, power generation equipment, machine tools, etc., equipped with engines and engine control devices. The engine control device of the present invention is applicable to engines equipped with variable valve mechanisms having lock pins. The engine control device of the present invention is also applicable to vehicles equipped with engines equipped with variable valve mechanisms having lock pins, and is applicable to ICE vehicles, HEVs, and PHEVs. [Explanation of symbols]

[0077] 1 engine 2. Drive motor 3. Generator 4. Clutch 5 High-voltage battery 6 Starter 7 Low voltage battery 8 injectors 9 Spark plugs 10 Variable valve mechanism 11 Intake passage 12 Throttle valve 13 Intake manifold 14 Exhaust passage 15 Exhaust manifold 16 EGR passage 17 EGR valve 20 Oil temperature sensor 21 Engine speed sensor 22 Intake manifold pressure sensor 23 Outside air temperature sensor 24 Airflow sensor 25 Oxygen concentration sensor 26 Accelerator pedal stroke sensor 27 Brake pedal stroke sensor 28 Vehicle speed sensor 29 Ignition key switch 30 Engine control device 31 Setting section 32 Control section

Claims

1. An engine control device for controlling an engine equipped with a hydraulic variable valve mechanism having a lock pin, a setting unit that sets a flag to ON when an oil temperature of engine oil that drives the variable valve mechanism is equal to or lower than a predetermined temperature when the engine is stopped, and sets the flag to OFF when the oil temperature exceeds the predetermined temperature; a control unit that, when starting the engine, performs normal control if the flag is off, and performs scavenging control and the normal control if the flag is on, The normal control is a control for starting the engine by cranking while performing both fuel injection and ignition, The scavenging control is a control for scavenging the combustion chamber by cranking without performing either the fuel injection or the ignition. An engine control device characterized by:

2. The scavenging control includes a first control for generating a negative pressure in the combustion chamber by cranking with the throttle fully closed, and a second control for promoting the introduction of fresh air into the combustion chamber by cranking with the throttle fully opened after the first control.

2. The engine control device according to claim 1.

3. The start condition of the second control is The pressure in the combustion chamber falls below a predetermined pressure, or The implementation time of the first control exceeds a first predetermined time, or This includes engine speed exceeding a specified speed when cranking.

3. The engine control device according to claim 2.

4. the termination condition of the scavenging control includes that an implementation time of the scavenging control exceeds a second predetermined time, The lower the outside air temperature, the shorter the second predetermined time.

4. The engine control device according to claim 1, wherein the engine control device comprises:

5. The condition for terminating the scavenging control includes that an estimated amount of fresh air introduced into the combustion chamber exceeds a predetermined value.

4. The engine control device according to claim 1, wherein the engine control device comprises:

6. the engine is mounted on a vehicle equipped with a starter for starting the engine and a low-voltage battery; In the scavenging control, the starter driven by the power of the low-voltage battery cranks the engine.

4. The engine control device according to claim 1, wherein the engine control device comprises:

7. The engine is mounted on a vehicle having a generator and a high-voltage battery connected to the engine, In the scavenging control, the generator driven by the power of the high-voltage battery cranks the engine.

4. The engine control device according to claim 1, wherein the engine control device comprises:

Images