Engine Controls

Abstract

The present invention provides an engine control device. When the engine water temperature is below a first low temperature judgment value and the battery temperature is below a second low temperature judgment value when the engine is started, the advance drive of the variable valve drive mechanism is first started. Then, when the advance amount of the variable valve drive mechanism becomes above a predetermined start start judgment value, the cranking is started.

Description

Technical Field

[0001] The present invention relates to an engine control device, and more particularly to an improvement in a control structure for improving cold-temperature starting performance in an engine including an electric variable valve drive mechanism. Background Art

[0002] In engines mounted on vehicles, there are engines equipped with a variable valve drive mechanism that makes the closing timing of the intake valve variable. In Japanese Patent Laid-Open No. 2006-299812, an engine control device for starting an engine equipped with such a variable valve drive mechanism is described. In the engine control device described in the document, when the engine stops, the variable valve drive mechanism is driven to the most retarded position. The most retarded position here refers to the action position of the variable valve drive mechanism in the variable range of the closing timing of the intake valve, where the closing timing is most retarded. In addition, in the engine control device of the document, when the engine is started in a state where the engine temperature is high, combustion is started while the action position of the variable valve drive mechanism is kept at the most retarded position. In addition, in the engine control device of the document, when the engine is started in a state where the engine temperature is low, after cranking starts, combustion is started after the variable valve drive mechanism is driven from the most retarded position to the advance side. In addition, cranking here refers to rotating the crankshaft of the engine using an electric motor such as a starter motor.

[0003] In addition, Japanese Patent Publication No. 2016-078803 describes an engine control device that is mounted on a hybrid vehicle and performs start control of an engine having a variable valve drive mechanism as described above. The hybrid vehicle in this document has an electric motor as a drive source in addition to the engine. In addition, in this hybrid vehicle, the power generated by the electric motor is used to crank the engine when it is started. In the engine control device of this document, similarly to the device of Japanese Patent Publication No. 2006-299812, when the engine is started in a state where the engine temperature is low, after the cranking starts, combustion starts after the variable valve drive mechanism is driven from the most retarded position to the advance side. Moreover, in the engine control device of this document, the lower the battery temperature, the greater the advance amount of the action position of the variable valve drive mechanism at this time. Summary of the invention

[0004] As a variable valve drive mechanism as described above, there is an electric variable valve drive mechanism that is activated by power from a battery. Here, it is considered to use an electric variable valve drive mechanism to drive the variable valve drive mechanism to the advance side during low-temperature starting as described in the above document. In an extremely low temperature environment, the engine is sometimes started when both the engine and the battery are in a low temperature state. When the battery temperature is low, the power supply capacity of the battery decreases. And, as a result, the operating speed of the variable valve drive mechanism sometimes decreases due to insufficient power supply. Therefore, in an extremely low temperature environment, until combustion starts, there is a situation where the operating position of the electric variable valve drive mechanism cannot be advanced to the position required to ensure startability.

[0005] The engine controlled by the engine control device for solving the above-mentioned problem is an engine equipped with an electric variable valve drive mechanism that operates by power supply from a battery to make the closing timing of the intake valve variable. In addition, the engine is started by cranking the crankshaft using external power. Furthermore, the engine control device performs a start control to drive the variable valve drive mechanism in a direction to advance the closing timing of the intake valve before the cranking starts when the engine is started.

[0006] When the engine is started at low temperature, the startability of the engine deteriorates due to the increase in friction and the decrease in the volatility of the fuel. In such a case, there is a situation in which the startability of the engine can be ensured by advancing the closing timing of the intake valve.

[0007] On the other hand, when the battery temperature is low and the power supply capacity of the battery is reduced, the action of the variable valve drive mechanism is sometimes delayed due to insufficient power. Therefore, when starting the engine when both the engine and the battery are at low temperatures, it will take a long time to advance the closing timing of the intake valve, and it may take time to complete the start of the engine. In this regard, in the above-mentioned engine control device, the driving of the variable valve drive mechanism is started before the start of the cranking. Therefore, even if the action speed of the variable valve drive mechanism decreases, the cranking can be started in a state where the closing timing of the intake valve is advanced to a certain extent. Therefore, the deterioration of the startability of the engine in a low temperature environment can be suppressed.

[0008] In addition, the start control in the engine control device preferably starts the cranking when it is confirmed that the movement amount of the variable valve drive mechanism in the direction of advancing the closing timing of the intake valve reaches a predetermined amount. In this case, it can be ensured that the closing timing of the intake valve at the start of the cranking is a timing that is earlier than a certain timing.

[0009] In addition, when the above-mentioned start control is performed, the start of the cranking will be delayed due to the drive of the variable valve drive mechanism. On the other hand, when both the engine and the battery are not at a low temperature, the startability of the engine can be ensured even if the drive of the variable valve drive mechanism is not started before the cranking. Therefore, the above-mentioned start control is preferably performed under the condition that the temperature of the engine is below the first temperature and the temperature of the battery is below the second temperature. That is, when at least one of the temperature of the engine exceeds the first temperature and the temperature of the battery exceeds the second temperature, the variable valve drive mechanism can be started to start the engine at the same time as the start of the cranking or after the start of the cranking. In addition, whether the above-mentioned start control is performed in such a situation can be determined, for example, in the following manner. That is, based on the detection result of the water temperature sensor that detects the temperature of the engine cooling water, it is determined whether the temperature of the engine is below the first temperature, and based on the detection result of the battery temperature sensor that detects the temperature of the battery, it is determined whether the temperature of the battery is below the second temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0011] Figure 1 It is a diagram schematically showing the structure of one embodiment of an engine control device.

[0012] Figure 2 This is a flowchart of a start control routine executed by the engine control device.

[0013] exist Figure 3 Among them, (a) is a time diagram showing the change of the state of the ignition switch when the engine is started at low temperature using the engine control device, (b) is a time diagram showing the change of the target advance amount and the actual advance amount of the variable valve drive mechanism when the engine is started at low temperature using the engine control device, (c) is a time diagram showing the change of the shaking state when the engine is started at low temperature using the engine control device, and (d) is a time diagram showing the change of the engine speed when the engine is started at low temperature using the engine control device. DETAILED DESCRIPTION

[0014] Below, refer to Figure 1 to Figure 3 An embodiment of the engine control device will be described in detail. In addition, the engine control device 30 of this embodiment controls the engine 10 mounted on the vehicle.

[0015] <Structure of the Engine Control Device 30>

[0016] First, refer to Figure 1 Next, the structure of the engine control device 30 of the present embodiment will be described. The engine 10 that is controlled by the engine control device 30 of the present embodiment includes a plurality of cylinders 11 . Figure 1 In the figure, only one cylinder 11 of the plurality of cylinders 11 is shown. A piston 12 is provided in each cylinder 11 so as to freely reciprocate in the cylinder 11. The piston 12 of each cylinder 11 is connected to a crankshaft 14 as an engine output shaft via a connecting rod 13. The connecting rod 13 converts the reciprocating motion of the piston 12 into a rotational motion and transmits it to the crankshaft 14.

[0017] In each cylinder 11, a combustion chamber 15 for combustion of a mixture is formed by partitioning with a piston 12. An intake valve 16 and an exhaust valve 17 are provided in the combustion chamber 15 of each cylinder 11. The combustion chamber 15 is connected to an intake passage 18 as an inlet passage for intake air via the intake valve 16. In addition, the combustion chamber 15 is connected to an exhaust passage 19 as an exhaust passage for exhaust air via the exhaust valve 17. Both the intake valve 16 and the exhaust valve 17 are valves that are opened and closed in response to the rotation of the crankshaft 14. In response to the opening of the intake valve 16, the combustion chamber 15 is connected to the intake passage 18. In response to the closing of the intake valve 16, the connection between the combustion chamber 15 and the intake passage 18 is cut off. On the other hand, in response to the opening of the exhaust valve 17, the combustion chamber 15 is connected to the exhaust passage 19. In response to the closing of the exhaust valve 17, the connection between the combustion chamber 15 and the exhaust passage 19 is cut off. Furthermore, an ignition device 20 is provided in each combustion chamber 15 of each cylinder 11. The ignition device 20 ignites the air-fuel mixture introduced into the combustion chamber 15 by spark discharge.

[0018] An air flow meter 21, a throttle valve 22, and an injector 23 are provided in the intake passage 18. The air flow meter 21 is a sensor for detecting the intake air flow rate GA in the intake passage 18. The throttle valve 22 is a valve for adjusting the intake air flow rate GA by changing the flow passage area of ​​the intake air. The injector 23 is a fuel injection device for injecting fuel into the intake air.

[0019] Furthermore, the engine 10 is provided with a variable valve drive mechanism 24 that makes the valve timing of the intake valve 16, that is, the opening and closing valve timing of the intake valve 16 variable. The variable valve drive mechanism 24 is configured as an electric mechanism that operates using the power supplied from the vehicle-mounted battery 25. In addition, the crankshaft 14 of the engine 10 is connected to an electric motor 26. The electric motor 26 operates using the power supplied from the battery 25. And, the electric motor 26 applies a rotational force to the crankshaft 14 using the power generated in accordance with its operation. In the following description, applying a rotational force to the crankshaft 14 using the power of the electric motor 26 is described as shaking. In addition, in the present embodiment, the power of the electric motor 26 becomes an external power that rotates the crankshaft 14 when the engine 10 is started.

[0020] Furthermore, in the following description, the action position of the intake valve 16 where the valve timing is most retarded within the action range of the variable valve drive mechanism 24 is recorded as the most retarded position. The closing timing of the intake valve 16 at the most retarded position becomes a timing that is retarded from the intake bottom dead center. Furthermore, in the following description, the action direction of the variable valve drive mechanism 24 toward the valve timing advance side of the intake valve 16 is recorded as the advance direction. Furthermore, the action direction of the variable valve drive mechanism 24 toward the valve timing retarded side of the intake valve 16 is recorded as the retarded direction. Furthermore, the action position of the variable valve drive mechanism 24 is represented by the action amount from the most retarded position to the advance direction, i.e., the advance amount VT.

[0021] The engine control device 30 of the present embodiment is an electronic control unit that controls the engine 10 constructed as described above. The engine control device 30 includes a processing unit 31, a dedicated read memory 32, and a read-write memory 33. In addition, detection signals of various sensors provided in various parts of the vehicle are input to the engine control device 30. Among the sensors that input detection signals to the engine control device 30, in addition to the above-mentioned air flow meter 21, a water temperature sensor 34, a battery temperature sensor 35, and a crank angle sensor 36 are also included. The water temperature sensor 34 is a sensor that detects the temperature of the engine cooling water, that is, the engine water temperature THW. The battery temperature sensor 35 is a sensor that detects the temperature of the battery 25. In the following description, the temperature of the battery 25 is recorded as the battery temperature THB. The crank angle sensor 36 is a sensor that detects the rotation angle of the crankshaft 14, that is, the crank angle. In addition, the engine control device 30 obtains the rotation speed of the crankshaft 14, that is, the engine speed NE, based on the detection result of the crank angle sensor 36. The engine control device 30 receives a signal indicating the operation state of the ignition switch 37, which is a switch for starting and stopping the engine 10. The engine control device 30 receives a signal from the variable valve drive mechanism 24 indicating the current value of the advance amount VT.

[0022] Programs and data for engine control are stored in advance in the read-only memory 32 of the engine control device 30. The arithmetic processing unit 31 executes various processes related to engine control by executing the programs read from the read-only memory 32. The arithmetic processing unit 31 temporarily stores the calculation results and the detection results of each sensor in the read-write memory 33.

[0023] <Start Control>

[0024] Next, the start control performed by the engine control device 30 when the start of the engine 10 is requested by the on operation of the ignition switch 37 will be described. In addition, the engine control device 30 performs the stop control of the engine 10 when the stop of the engine 10 is requested by the off operation of the ignition switch 37. And, the engine control device 30 drives the variable valve drive mechanism 24 to the most retarded position during the stop control. Therefore, the advance amount VT of the variable valve drive mechanism 24 when the start of the engine 10 is requested becomes "0".

[0025] Figure 2 This is a flowchart of a start-up control routine executed by the engine control device 30 when starting the engine 10. The engine control device 30 executes the processing of this routine when the ignition switch 37 is turned on and the start of the engine 10 is requested. In addition, when pre-processing such as sensor operation confirmation is required before starting the engine 10, the processing of this routine can be started after such pre-processing is completed.

[0026] When this routine is started in response to the on operation of the ignition switch 37, the engine control device 30 first obtains the current values ​​of the engine water temperature THW and the battery temperature THB in step S100. Then, the engine control device 30 determines in step S110 whether the engine water temperature THW is below a predetermined first low temperature judgment value T1 and the battery temperature THB is below a predetermined second low temperature judgment value T2. In addition, if the engine control device 30 makes an affirmative determination in step S110 (Yes), the processing proceeds to step S120, and if the engine control device 30 makes a negative determination (No), the processing proceeds to step S140.

[0027] When the processing enters step S120, the engine control device 30 starts driving the variable valve drive mechanism 24 in the advance direction in step S120. Specifically, the target value of the advance amount VT is changed from "0" to the predetermined advance amount V2 during low temperature start. In addition, in the following description, the target value of the advance amount VT of the variable valve drive mechanism 24 is recorded as the target advance amount, and the actual value of the advance amount VT of the variable valve drive mechanism 24 is recorded as the actual advance amount. In addition, in the following description, the drive of the variable valve drive mechanism 24 in the advance direction is recorded as the advance drive of the variable valve drive mechanism 24. Then, the engine control device 30 waits for the actual advance amount to become greater than the predetermined start start determination value V1 (S130: Yes), and the processing enters step S140. As the start start determination value V1, a value greater than "0" and less than the advance amount V2 during low temperature start is pre-set.

[0028] When the process enters step S140, the engine control device 30 starts cranking, that is, starts the rotation drive of the crankshaft 14 by the electric motor 26 in step S140. After starting the rotation of the crankshaft 14, the engine control device 30 then starts fuel injection and ignition in step S150. Furthermore, when the engine speed NE becomes equal to or higher than the predetermined start completion determination value N1 (S160: Yes), the engine control device 30 ends the cranking in step S170 and ends the process of the start control routine.

[0029] Furthermore, in this embodiment, Figure 2 The processing of steps S120 to S170 is a processing corresponding to the low temperature start control. In addition, in the present embodiment, the first low temperature judgment value T1 corresponds to the first temperature, and the second low temperature judgment value T2 corresponds to the second temperature.

[0030] <Functions and Effects of Implementation Methods>

[0031] The operation and effects of the engine control device 30 according to the present embodiment will be described.

[0032] As described above, the engine 10 that is controlled by the engine control device 30 of the present embodiment includes the electric variable valve drive mechanism 24. When the operation position of the variable valve drive mechanism 24 is the most retarded position, the closing timing of the intake valve 16 becomes a timing that is retarded from the timing when the piston 12 is located at the intake bottom dead center. If the intake valve 16 is opened until the timing is retarded from the timing when the piston 12 reaches the intake bottom dead center, a part of the intake air sucked into the combustion chamber 15 until the piston 12 reaches the intake bottom dead center will be blown back to the intake passage 18. Therefore, if the closing timing of the intake valve 16 is retarded from the timing when the piston 12 reaches the intake bottom dead center, the intake filling rate of the cylinder 11 will decrease.

[0033] In the following description, the start of the engine 10 when both the engine 10 and the battery 25 are in a low temperature state is described as a low temperature start, and the start of the engine 10 when this is not the case is described as a normal start. The engine control device 30 at the time of the normal start starts cranking without advancing the variable valve drive mechanism 24. As described above, the advance amount VT of the variable valve drive mechanism 24 at the time of the start request of the engine 10 becomes "0". Therefore, at the time of the normal start, the engine 10 is started in a state where the action position of the variable valve drive mechanism 24 is the most retarded position.

[0034] On the other hand, when the temperature of the engine 10 is low, the friction caused by the high viscosity of the engine oil increases. In addition, the volatility of the fuel decreases, and it is difficult to obtain the combustion torque. Therefore, when starting at low temperature, the startability of the engine 10 cannot be ensured while keeping the action position of the variable valve drive mechanism 24 in the most retarded position. In addition, when the battery temperature THB is low, the maximum value of the instantaneous power that the battery 25 can output becomes smaller. And, as a result, the power of the cranking electric motor 26 decreases. Therefore, when the engine 10 is at a low temperature and the battery 25 is also at a low temperature, the startability of the engine 10 is further deteriorated.

[0035] In this regard, in the present embodiment, during low-temperature starting, the engine 10 is started in a different procedure from that during normal starting described above. During low-temperature starting, the variable valve drive mechanism 24 is driven in advance to an action position where the advance amount VT becomes the advance amount V2 during low-temperature starting. As a result, the intake filling rate of the cylinder 11 is increased and the combustion efficiency of the fuel in the cylinder 11 is increased, thereby reducing the deterioration of the startability of the engine 10 during low-temperature starting. In addition, even when the engine water temperature THW is below the first low-temperature judgment value T1, the advance amount VT of the variable valve drive mechanism 24 that can ensure the startability of the engine 10 is set to the value of the advance amount V2 during low-temperature starting.

[0036] Here, consider the case where the variable valve drive mechanism 24 is started to be advanced to the action position where the advance amount VT becomes the advance amount V2 during low-temperature starting at the same time as the start of the cranking. In such a case, as long as the advance drive of the variable valve drive mechanism 24 can be completed in a sufficiently short time, the startability of the engine 10 can be ensured. On the other hand, when the battery 25 is at a low temperature, the power supply capacity of the battery 25 decreases. And, as a result, the operation of the variable valve drive mechanism 24 is delayed due to insufficient power. Therefore, when the temperature of the battery 25 is low, even if the advance drive of the variable valve drive mechanism 24 is started at the same time as the cranking, the startability of the engine 10 may not be ensured. Therefore, in the present embodiment, during low-temperature starting when both the engine 10 and the battery 25 are in a low-temperature state, the advance drive of the variable valve drive mechanism 24 is started before the start of the cranking.

[0037] Figure 3 1 shows an example of the control method of the engine control device 30 of the present embodiment during low temperature startup. In addition, (a) shows the change of the operation state of the ignition switch 37. (b) shows the change of the target advance amount and the actual advance amount of the variable valve drive mechanism 24. (c) shows the change of the cranking state of the engine 10. (d) shows the change of the engine speed NE.

[0038] exist Figure 3In the process, the ignition switch 37 is turned on at time t0. During low-temperature starting, the engine control device 30 does not start cranking at this time t0 and changes the target advance amount of the variable valve drive mechanism 24 from "0" to the advance amount V2 during low-temperature starting. That is, in the present embodiment, during low-temperature starting, the advance drive of the variable valve drive mechanism 24 is started before the start of cranking. At a subsequent time t1, the actual advance amount of the variable valve drive mechanism 24 reaches the start start judgment value V1. The engine control device 30 starts cranking at this time t1. In the engine 10, fuel injection and ignition are started after the start of cranking. At a subsequent time t2, the engine 10 becomes a fully exploded state, and when the engine speed NE rises to the start completion judgment value N1, the engine control device 30 ends the cranking.

[0039] Thus, in the present embodiment, at the time of low temperature starting, first, the advance drive of the variable valve drive mechanism 24 is started. Then, when the actual advance amount of the variable valve drive mechanism 24 reaches the start start determination value V1, the cranking is started. Therefore, even when the operating speed of the variable valve drive mechanism 24 is reduced, the period from the start of the cranking to the completion of the start is not likely to be prolonged.

[0040] Incidentally, the deterioration of the startability caused by the increase of friction during low-temperature start-up and the decrease of the volatility of the fuel is also suppressed by increasing the amount of fuel injection compared to the normal start-up. However, if the startability during low-temperature start-up is to be ensured only by increasing the amount of fuel injection without driving the variable valve drive mechanism 24 in advance, a large increase in the amount of fuel injection is required, and the fuel economy and exhaust performance of the engine 10 are deteriorated. In contrast, if the variable valve drive mechanism 24 is not driven in advance during low-temperature start-up, the startability can be ensured even if the amount of fuel injection is not increased too much. Therefore, the deterioration of the fuel economy and exhaust performance of the engine 10 during low-temperature start-up can be suppressed.

[0041] In addition, in the present embodiment, the above-mentioned low temperature start control is performed when the engine 10 is started in a state where the engine water temperature THW is less than the first low temperature judgment value T1 and the battery temperature THB is less than the second low temperature judgment value T2. As the value of the first low temperature judgment value T1, the lower limit value of the engine water temperature THW that can ensure the startability of the engine 10 in a state where the operating position of the variable valve drive mechanism 24 is the most delayed position is set. In addition, as the value of the second low temperature judgment value T2, the lower limit value of the battery temperature THB that obtains the operating speed of the variable valve drive mechanism 24 above a certain speed is set.

[0042] According to the engine control device 30 of the present embodiment described above, the following effects can be achieved.

[0043] (1) When the intake air filling rate of the cylinder 11 is high, the compression reaction force of the intake air in the compression stroke becomes larger, and therefore, the rotational variation of the crankshaft 14 becomes larger. Therefore, when the engine 10 is started in the state of the intake air filling rate being high, the rotational variation of the crankshaft 14 is likely to cause the gear rattle of the drive system and the vibration of the vehicle body. In contrast, in the engine control device 30 of the present embodiment, during normal start-up, the engine 10 is started in the state where the action position of the variable valve drive mechanism 24 is the most retarded position. Therefore, during normal start-up, the engine 10 is started in the state where the intake air filling rate of the cylinder 11 is reduced, and the gear rattle of the drive system and the vibration of the vehicle body can be suppressed.

[0044] (2) The engine control device 30 of the present embodiment starts the engine 10 in a state where the variable valve drive mechanism 24 is driven in advance at the time of low-temperature start. When the variable valve drive mechanism 24 is driven in advance from the most retarded position, the intake air filling rate of the cylinder 11 becomes higher, and the fuel combustion efficiency is improved. Therefore, it is possible to suppress the deterioration of the startability of the engine 10 at the time of low-temperature start.

[0045] (3) When the battery temperature THB is low, the battery 25 may not be able to supply sufficient power and the operating speed of the variable valve drive mechanism 24 may decrease. In the present embodiment, the variable valve drive mechanism 24 is started to be driven in advance before the start of cranking at low temperature. Therefore, even when the battery temperature THB is low and the operating speed of the variable valve drive mechanism 24 decreases, the period from the start of cranking to the completion of cranking is unlikely to become long.

[0046] (4) The variable valve drive mechanism 24 is driven to the most retarded position when the engine 10 is stopped. Therefore, it is not necessary to drive the variable valve drive mechanism 24 during normal startup.

[0047] This embodiment can be implemented by being modified as follows. This embodiment and the following modified examples can be implemented in combination with each other within the range that there is no technical contradiction.

[0048] In the above embodiment, during low temperature starting, the oscillation is started when the advance amount VT becomes greater than the start start advance amount V1. Alternatively, the oscillation may be started when the advance amount VT reaches the low temperature starting advance amount V2. In this case, the oscillation is started after the variable valve drive mechanism 24 advances to the low temperature starting advance amount V2.

[0049] In the above embodiment, the action position of the variable valve drive mechanism 24 is driven toward the most retarded position when the engine 10 is stopped. Also, the engine 10 is started while the action position of the variable valve drive mechanism 24 is maintained at the most retarded position during normal start-up, and on the other hand, the variable valve drive mechanism 24 is driven from the most retarded position toward the advance direction to start the engine 10 during low-temperature start-up. When the engine 10 is stopped, the variable valve drive mechanism 24 may be driven toward an action position other than the most retarded position. In this case, during low-temperature start-up, the variable valve drive mechanism 24 is driven from the action position driven when the engine 10 is stopped toward the advance direction.

[0050] In the above embodiment, whether the temperature of the engine 10 is equal to or lower than the first temperature is determined based on the engine water temperature THW, but the determination may be made based on other parameters indicating the temperature state of the engine 10 such as the temperature of the engine oil.

[0051] It is also possible to determine whether the temperature of the engine 10 is below the first temperature and the temperature of the battery 25 is below the second temperature based on the soaking time and the outside air temperature. The soaking time is the time from when the engine 10 stops to when it is restarted. If the soaking time becomes longer, the temperature of the engine 10 and the battery 25 will converge to a temperature close to the outside air temperature. Therefore, based on the soaking time being more than a certain time and the outside air temperature being less than a certain temperature, it can be determined that the engine 10 and the battery 25 are both in a low temperature state. In addition, in this case, the above-mentioned certain temperature becomes a temperature corresponding to the first temperature and the second temperature.

[0052] When the engine 10 is in a low temperature state, the battery 25 is also considered to be in a low temperature state. Figure 2 The determination in step S110 is made without using the battery temperature THB. That is, in the above-mentioned case, it may be determined that both the engine 10 and the battery 25 are in a low temperature state based on the engine water temperature THW or the engine oil temperature being equal to or lower than a certain temperature.

[0053] The maximum value of the instantaneous power that the battery 25 can output also changes according to the storage amount of the battery 25. That is, the less the storage amount of the battery 25 is, the smaller the maximum value of the instantaneous power that the battery 25 can output under the condition that the battery temperature THB is constant. Therefore, the second low temperature judgment value T2 can also be variably set according to the storage amount of the battery 25. Specifically, when the storage amount of the battery 25 is small, a larger value can be set as the value of the second low temperature judgment value T2 than when the storage amount is large.

[0054] There is an engine such as an engine mounted on a hybrid vehicle, in which different batteries are used to supply power to the variable valve drive mechanism 24 and to the electric motor 26 for turning. In an engine having such a structure, the temperature of the battery supplying power to the variable valve drive mechanism 24 is used to determine whether or not the cold start control is necessary.

[0055] Even if the engine 10 is cold, the operating speed of the variable valve drive mechanism 24 will not decrease unless the battery 25 is cold. Therefore, in such a case, the variable valve drive mechanism 24 may be started to be driven at the same time as the start of the swing or after the start of the swing.

[0056] The low-temperature start control in the above embodiment may also be performed during normal start. In this case, when the engine 10 and the battery 25 are at low temperatures, the variable valve drive mechanism 24 is started to be driven before the cranking starts. Therefore, in this case, the deterioration of the startability of the engine 10 at low temperatures can be suppressed.

Claims

1. An engine control device, which controls an engine having an electric variable valve drive mechanism that is operated by power from a battery to make the closing timing of an intake valve variable, and is started by cranking a crankshaft using external power, The engine control device is characterized in that: When the engine is started, a start control is performed to drive the variable valve drive mechanism in a direction to advance the closing timing of the intake valve before the cranking starts. In the startup control, when it is confirmed that the operation amount of the variable valve drive mechanism in the direction of advancing the closing timing of the intake valve reaches a predetermined amount, the cranking is started. The start control is executed on the condition that, when the start of the engine is requested, the temperature of the engine is equal to or lower than a first temperature and the temperature of the battery is equal to or lower than a second temperature.

2. The engine control device according to claim 1, characterized in that: Based on the detection result of the water temperature sensor detecting the temperature of the engine cooling water, it is determined whether the temperature of the engine is below the first temperature, and based on the detection result of the battery temperature sensor detecting the temperature of the battery, it is determined whether the temperature of the battery is below the second temperature.

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