Engine control system

Abstract

The purpose is to prevent deterioration of engine starting performance due to leak-down caused by hydraulic lash adjusters, while also ensuring sufficient automatic engine shutdown time. [Solution] The engine control system 1 of the present invention comprises an engine 10 as a drive source, a hydraulic lash adjuster that adjusts the valve clearance using hydraulic pressure generated by the operation of the engine 10, and a control unit 70 that automatically stops and restarts the engine 10. The control unit 70 restarts the engine 10 based on the crank angle when the engine 10 is stopped and the pressure in the hydraulic lash adjuster.

Description

Technical Field

[0001] The present invention relates to an engine control system.

Background Art

[0002] Conventionally, vehicles capable of automatically stopping and restarting the engine have been known. In Patent Document 1, in a vehicle having a mechanical oil pump and an accumulator connected to the mechanical oil pump for accumulating pressure, based on the accumulated state of the accumulator, an idling stop control device is disclosed that sets the stoppable time of the engine and stops the rotation of the engine with the stoppable time as the upper limit. This idling stop control device sets the stoppable time of the engine based on a predefined map or arithmetic formula such that it becomes longer when the accumulated state of the accumulator is high than when it is low.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, engines in which the valve clearance of the intake and exhaust valves is adjusted by hydraulic lash adjusters have become widespread. In such engines, when the idle stop function is applied, the pressure in the hydraulic lash adjuster decreases according to the automatic stop time of the idle stop, causing a leak-down of the intake and exhaust valves. Since the leak-down characteristics due to the hydraulic lash adjuster differ depending on the crank angle at the time of idle stop (when the engine is stopped), if the leak-down characteristics due to the hydraulic lash adjuster are not taken into consideration, the starting performance when restarting the engine will deteriorate. On the other hand, if the engine is restarted before a leak-down occurs in order to improve the starting performance, the automatic stop time of the idle stop cannot be secured, and fuel efficiency cannot be improved.

[0005] This invention has been made in view of the above-mentioned problems, and aims to prevent deterioration of engine starting performance due to leak-down by hydraulic lash adjusters while ensuring an automatic engine shutdown time. [Means for solving the problem]

[0006] The present invention relates to an engine control system comprising: an engine as a driving source; a hydraulic lash adjuster that adjusts the valve clearance using hydraulic pressure generated by the operation of the engine; and a control unit that automatically stops and restarts the engine, wherein the control unit restarts the engine based on the crank angle when the engine is stopped and the pressure in the hydraulic lash adjuster. [Effects of the Invention]

[0007] According to the present invention, it is possible to prevent deterioration of engine starting performance due to leak-down caused by hydraulic lash adjusters while ensuring an automatic engine shutdown time. [Brief explanation of the drawing]

[0008] [Figure 1]This is a schematic diagram showing an example of the configuration of an engine control system. [Figure 2] This flowchart shows an example of the control process in the first embodiment. [Figure 3] This figure shows an example of a valve lift amount map for the first embodiment. [Figure 4] This figure shows an example of a leak-down characteristic map using a hydraulic lash adjuster in the first embodiment. [Figure 5] This flowchart shows an example of the control process in the second embodiment. [Figure 6] This figure shows an example of a torque map in the second embodiment. [Figure 7] This figure shows an example of a battery capacity map for the second embodiment. [Modes for carrying out the invention]

[0009] The engine control system 1 according to the present invention comprises an engine 10 as a drive source, a hydraulic lash adjuster that adjusts the valve clearance using hydraulic pressure generated by the operation of the engine 10, and a control unit 70 that automatically stops and restarts the engine 10. The control unit 70 restarts the engine 10 based on the crank angle when the engine 10 is stopped and the pressure in the hydraulic lash adjuster. Since the engine 10 can be restarted taking into account the leak-down characteristics by the hydraulic lash adjuster based on the crank angle, it is possible to prevent deterioration of the starting performance of the engine 10 due to leak-down by the hydraulic lash adjuster while ensuring an idle stop time. [Examples]

[0010] <First Example> The engine control system 1 according to the present invention will be described below with reference to the drawings. Figure 1 is a schematic diagram showing an example of the configuration of the engine control system 1. The engine control system 1 is installed in a vehicle carrying occupants. The vehicle in which the engine control system 1 is installed may be, for example, a four-wheeled automobile, and will be equipped with equipment that is typical of a vehicle; the illustration and description of such equipment will be omitted as appropriate.

[0011] The engine control system 1 according to this embodiment includes an engine 10, an engine sensor unit 20, a hydraulic lash adjuster (HLA), an integrated starter generator (ISG) 30 with motor function, a battery 40, a battery sensor unit 50, an electrical load 60, a control unit 70, and the like.

[0012] Engine 10 functions as a power source to drive the vehicle. Engine 10 performs a series of four strokes: an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. Engine 10 has a combustion chamber in which a piston is reciprocally housed, a crank chamber in which a crankshaft is rotatably housed, an intake port which is the inlet for combustion air, and an exhaust port which is the outlet for exhaust gas. Engine 10 also has a spark plug positioned so that its tip is located inside the combustion chamber, an intake valve located between the combustion chamber and the intake port, and an exhaust valve located between the combustion chamber and the exhaust port. The intake valve opens when an intake cam, which rotates in conjunction with the rotation of the crankshaft, presses against the intake side rocker arm, and closes when the pressure is released. Similarly, the exhaust valve opens when an exhaust cam, which rotates in conjunction with the rotation of the crankshaft, presses against the exhaust side rocker arm, and closes when the pressure is released.

[0013] The engine 10 also has a starter motor 11. The starter motor 11 starts the engine 10 by cranking in response to an operation by the occupant to start the engine. The engine 10 also has an oil pan for storing oil and an oil pump for supplying the oil to the lubrication parts of the engine 10. The oil pump is driven as the crankshaft of the engine 10 rotates, sucking up the oil stored in the oil pan and pumping it to the lubrication parts under pressure. The oil pump also supplies oil to the hydraulic lash adjusters. Note that the engine 10 of the present embodiment uses a multi-cylinder gasoline engine, but is not particularly limited. For example, various known engines such as a single-cylinder gasoline engine can be applied.

[0014] The engine sensor unit 20 detects the state of the engine 10. The information detected by the engine sensor unit 20 is transmitted to the control unit 70. Specifically, the engine sensor unit 20 includes a crank angle sensor 21 for detecting the crank angle, a cam angle sensor 22 for detecting the angle of the intake cam or the exhaust cam, an oil temperature sensor 23 for detecting the temperature of the oil, a hydraulic pressure sensor 24 for detecting the hydraulic pressure of the oil supplied by the oil pump, and the like.

[0015] The hydraulic lash adjusters are arranged respectively in the vicinity of the intake port and the exhaust port, and adjust the valve clearance using the hydraulic pressure of the oil supplied by the oil pump. While oil is being supplied, the hydraulic lash adjusters press the intake-side rocker arm and the exhaust-side rocker arm against the intake cam side and the exhaust cam side respectively, making the valve clearances on the intake valve side and the exhaust valve side zero. When the engine 10 stops and the oil supplied to the hydraulic lash adjusters leaks, the pressure (hydraulic pressure) inside the hydraulic lash adjusters decreases. Here, when the pressure inside the hydraulic lash adjusters decreases, a letdown occurs in which the valve lift amount of the intake and exhaust valves decreases according to the characteristics of the hydraulic lash adjusters.

[0016] The ISG30 is connected to the engine 10 via a power transmission member 31 such as an accessory belt. The ISG30 supplies the electric power generated by generating electricity as the engine 10 is driven to the battery 40 or to the electrical load 60. On the other hand, when the vehicle accelerates, the ISG30 assists the driving of the engine 10 using the electric power supplied from the battery 40. Further, the ISG30 starts the engine 10 when the engine 10 automatically stops due to the idling stop function of the control unit 70 and then automatically restarts, regardless of the operation of starting the engine by the occupant.

[0017] The battery 40 is charged by the supply of the electric power generated by the ISG30, and supplies the electric power for driving the electrical load 60 to the electrical load 60. Note that the battery 40 in the present embodiment uses a lead battery, but is not particularly limited, and various batteries can be applied.

[0018] The battery sensor unit 50 detects the state of the battery 40. The battery sensor unit 50 includes a voltage sensor 51 that detects the voltage of the battery 40, a current sensor 52 that detects the current of the battery 40, and a temperature sensor 53 that detects the temperature of the battery 40. The information detected by the battery sensor unit 50 is transmitted to the control unit 70. The control unit 70 can detect the remaining battery capacity of the battery 40 based on each information detected by the battery sensor unit 50.

[0019] The electrical load 60 is various electronic devices provided in the vehicle. The electrical load 60 is driven by the electric power supplied from the battery 40 or the electric power supplied from the ISG30. The electrical load 60 is, for example, an audio device such as a car audio, a headlight device, a power window device, or the like.

[0020] The control unit 70 controls the entire engine control system 1. The control unit 70 is, for example, an ECU (Electronic Control Unit). The control unit 70 has a hardware configuration that includes a CPU, ROM, RAM, etc. The ROM stores programs for controlling each component of the vehicle or engine control system 1, various maps described later, and predetermined information in advance. The RAM is a work memory that temporarily stores programs and data. The CPU controls the entire engine control system 1 by reading the programs stored in the ROM, loading them into the RAM, and executing them.

[0021] Furthermore, the control unit 70 has an idle stop function. Specifically, the control unit 70 automatically stops the engine 10 by cutting off fuel injection when the idle stop transition conditions (for example, when the brake pedal is pressed and the remaining battery capacity of the battery 40 is above a predetermined level) are met (idle stop). On the other hand, the control unit 70 restarts the engine 10 by injecting fuel and starting the engine 10 with the ISG 30 when the idle stop release conditions (for example, when the brake pedal is released or when the set idle stop time has elapsed) are met (idle stop release). Furthermore, the control unit 70 may be shared with the ECU that controls the vehicle, or it may be different from the ECU that controls the vehicle. Also, the control unit 70 is not limited to being composed of a single ECU, but may be composed of multiple ECUs working together.

[0022] In the engine control system 1 configured as described above, when the control unit 70 initiates idle stop, the pressure in the hydraulic lash adjuster decreases according to the automatic stop time (idle stop time), causing leak-down of the intake and exhaust valves. Here, if the valve lift amount of the intake valve decreases due to the leak-down, the compression ratio increases, which worsens the starting performance of the engine 10. On the other hand, if the engine 10 is restarted before the leak-down occurs in order to improve the starting performance of the engine 10, the idle stop time cannot be secured.

[0023] Therefore, in this embodiment, focusing on the leak-down characteristics of the hydraulic lash adjuster, the control unit 70 controls the engine 10 to restart based on the crank angle when the engine 10 is stopped and the pressure inside the hydraulic lash adjuster. The control process by the control unit 70 according to the first embodiment will be described below with reference to the flowchart in Figure 2. The flowchart in Figure 2 starts with the operation of starting the engine and driving the vehicle by the occupants.

[0024] In S1, the control unit 70 starts the engine 10 with the starter motor 11 and drives the vehicle while supplying power to the battery 40 and electrical load 60 by generating electricity with the ISG 30. In S2, the control unit 70 determines whether the conditions for transitioning to idle stop have been met. If the conditions for transitioning to idle stop have been met, the process proceeds to S3; otherwise, it returns to S1.

[0025] In S3, the control unit 70 stops power generation by the ISG 30 and starts idling stop. Specifically, the control unit 70 automatically stops the engine 10 without any operation by the occupants by cutting off fuel injection. In S4, the control unit 70 starts measuring the idle stop time since the idle stop was initiated.

[0026] In S5, the control unit 70 acquires information about the stopping position of the engine 10. As information about the stopping position of the engine 10, the control unit 70 acquires the crank angle information of the crankshaft, which has stopped rotating, from the crank angle sensor 21.

[0027] In S6, the control unit 70 identifies which cylinder will be compressed first when the idle stop is released (when the engine 10 is restarted) (hereinafter referred to as the compression cylinder). The control unit 70 can identify the compression cylinder based on the information received from the cam angle sensor 22. Note that if the engine 10 is a single-cylinder engine, S6 is omitted.

[0028] In S7, the control unit 70 determines whether the intake valve corresponding to the identified compression cylinder is open, that is, whether the intake valve has not yet closed. The control unit 70 determines whether the intake valve is open based on the crank angle information of the crankshaft. If the intake valve corresponding to the compression cylinder is open, the process proceeds to S8. The reason for determining whether the intake valve corresponding to the compression cylinder is open is that if the intake valve is open, the pressure in the hydraulic lash adjuster that adjusts the valve clearance of the intake valve will decrease as time passes after the idle stop is initiated. In other words, if the intake valve corresponding to the compression cylinder is open, the pressure in the hydraulic lash adjuster decreases, which reduces the valve lift amount of the intake valve, making it necessary to perform idle stop limiting processing to prevent deterioration of the starting performance of the engine 10.

[0029] In S8, the control unit 70 determines the stopping position of the open intake valve. Specifically, the control unit 70 obtains valve lift amount information based on the crank angle information obtained from the crank angle sensor 21 as the stopping position of the intake valve.

[0030] Figure 3 shows a valve lift amount map that associates the crank angle with the valve lift amount of the intake valve, with the horizontal axis representing the crank angle and the vertical axis representing the valve lift amount. As shown in Figure 3, in this embodiment, the intake valve remains open even when the engine 10 transitions from the intake stroke to the compression stroke, and as the compression stroke progresses, the valve lift amount of the intake valve decreases until it becomes 0. Based on the valve lift amount map shown in Figure 3, the control unit 70 can obtain information that, for example, if the crank angle when the engine 10 stops is θ1, the valve lift amount as the stopping position of the intake valve is L1. The valve lift amount map shown in Figure 3 is stored in the control unit 70 in advance.

[0031] In S9, the control unit 70 performs idle stop limiting processing based on the leak-down characteristics of the hydraulic lash adjuster. Here, the idle stop time is set so that the engine 10 is restarted before the intake valve closes, based on the leak-down characteristics of the hydraulic lash adjuster. Figure 4 shows a map illustrating the leak-down characteristics due to the hydraulic lash adjuster. The horizontal axis represents the pressure inside the hydraulic lash adjuster (HLA), and the vertical axis represents the lift reduction of the intake valve. The pressure inside the hydraulic lash adjuster corresponds to the hydraulic pressure inside the engine 10. The map shown in Figure 4 shows the pressure inside the hydraulic lash adjuster when the intake valve is closed due to leak-down by the hydraulic lash adjuster. The map shown in Figure 4 is calculated experimentally, empirically, or theoretically and is stored in the control unit 70 in advance.

[0032] Based on the map shown in Figure 4, the control unit 70 can obtain information that, for example, if the intake valve's stopping position is at valve lift amount L1, the pressure inside the hydraulic lash adjuster when the intake valve closes due to leak-down is P1. Therefore, if the idle stop is released before (immediately before) the pressure inside the hydraulic lash adjuster drops to P1, the starting performance of the engine 10 will not deteriorate because the intake valve is still open, and the idle stop time can be made as long as possible.

[0033] The control unit 70 calculates the upper limit of the idling stop time based on the pressure inside the hydraulic lash adjuster when the intake valve is closed, which is obtained using the map shown in Figure 4. Here, let Pnow be the pressure in the hydraulic lash adjuster when the engine 10 is stopped, α be the rate of pressure decrease in the hydraulic lash adjuster from the time the engine 10 is stopped (pressure decrease per unit time), t be the upper limit of the idling stop time, and let P1 be the pressure in the hydraulic lash adjuster when the intake valve is closed. Then the following equation (1) holds. Pnow-α×t=P1...Equation (1)

[0034] By rearranging equation (1), we obtain equation (2). t = (Pnow - P1) / α ... Equation (2) Here, pressure Pnow can be obtained from the hydraulic sensor 24, pressure P1 can be obtained based on the map shown in Figure 4, and the pressure reduction rate α is calculated in advance experimentally, empirically, or theoretically. Therefore, the control unit 70 can calculate the upper limit value t of the idling stop time using equation (2). In other words, since pressure P1 can be obtained based on the crank angle θ1 when the engine is stopped, the control unit 70 can calculate the upper limit value t of the idling stop time based on the pressure of the hydraulic lash adjuster when the engine 10 is stopped, and the crank angle when the engine 10 is stopped.

[0035] Furthermore, since the pressure reduction rate α changes depending on the oil temperature, a pressure reduction rate α corresponding to the oil temperature can be used. In other words, the control unit 70 can calculate the upper limit value t of the idling stop time based on the pressure of the hydraulic lash adjuster when the engine 10 is stopped, the crank angle when the engine 10 is stopped, and the oil temperature. Here, the calculated upper limit t is the time the intake valve is closed. Therefore, the control unit 70 sets the idle stop time to the calculated upper limit t minus a predetermined time so that the engine can be restarted before the upper limit t is reached. After S9 is completed, the process proceeds to S11.

[0036] On the other hand, if the intake valve corresponding to the identified compression cylinder is not open in S7, the process proceeds to S10. In S10, the control unit 70 does not perform idle stop limiting processing based on the leak-down characteristics of the hydraulic lash adjuster, but sets the idle stop time to a time determined in a different way than in S9. For example, the control unit 70 can set the idle stop time to a predetermined time that is longer than the idle stop time set in S9. After S10 is completed, the process proceeds to S11.

[0037] In S11, the control unit 70 determines whether the set idling stop time has elapsed. If it has elapsed, proceed to S14; otherwise, proceed to S12. In S12, the control unit 70 determines whether the idle stop release condition has been met outside of the idle stop time. If the idle stop release condition has been met, the process proceeds to S14; otherwise, the process proceeds to S13. In S13, the control unit 70 continues the idle stop function and returns to S11.

[0038] In S14, the control unit 70 cancels the idle stop function by restarting the engine 10 using the ISG 30. In this case, if the process proceeds to S14 via S8 and S9, the engine 10 will be restarted before the pressure in the hydraulic lash adjuster reaches the pressure at which the intake valve closes, calculated based on the crank angle when the engine 10 is stopped. In other words, since the engine 10 is restarted before the intake valve closes, the increase in the compression ratio is suppressed, which prevents deterioration of the engine 10's starting performance. Furthermore, even if leakage down occurs due to the hydraulic lash adjuster, the idling stop time can be continued until just before the intake valve closes, thus ensuring sufficient idling stop time and preventing deterioration of fuel efficiency. On the other hand, if the process proceeds to S14 via S10, the engine 10 is restarted after the intake valve closes, so the control unit 70 controls the ISG 30 to drive the engine 10 with a torque that allows for a good start.

[0039] In S15, the control unit 70 resets the idle stop time to 0. The flowchart in Figure 2 is executed repeatedly until the occupant stops the engine.

[0040] As described above, according to this embodiment, the control unit 70 restarts the engine 10 based on the crank angle when the engine 10 stops and the pressure in the hydraulic lash adjuster. Therefore, compared to the case where the engine 10 is restarted based only on the hydraulic pressure when the engine stops, the engine 10 can be restarted taking into account the leak-down characteristics by the hydraulic lash adjuster based on the crank angle. This prevents deterioration of the starting performance of the engine 10 due to leak-down by the hydraulic lash adjuster while ensuring sufficient idle stop time.

[0041] Furthermore, according to this embodiment, the engine 10 is restarted before the pressure in the hydraulic lash adjuster reaches the pressure at which the intake valve closes, calculated based on the crank angle when the engine 10 is stopped. Therefore, even if a leak-down occurs due to the hydraulic lash adjuster, restarting the engine before the intake valve closes prevents the engine 10's starting performance from deteriorating due to the leak-down caused by the hydraulic lash adjuster, while still ensuring sufficient idle stop time.

[0042] <Second Example> Next, the control process by the control unit 70 according to the second embodiment will be explained with reference to the flowchart in Figure 5. In the second embodiment, even if the intake valve is closed by leak-down by the hydraulic lash adjuster from an open state and the engine 10 is restarted, the system will continue idling stop if the starting performance of the engine 10 does not deteriorate. In the flowchart in Figure 5, processes S21 to S23 are added to the flowchart in Figure 2, and processes similar to those in the flowchart in Figure 2 are given the same step numbers as in the flowchart in Figure 2, and explanations will be omitted as appropriate.

[0043] In S7, if the intake valve corresponding to the compression cylinder is open, proceed to S8. In S8, the control unit 70 identifies the stop position of the open intake valve. In S21, the control unit 70 obtains information on the additional torque required to restart the engine if the intake valve were to close due to leak-down by the hydraulic lash adjuster, based on the stopping position of the open intake valve.

[0044] Figure 6 is a torque map showing the relationship between the crank angle when the engine is stopped and the additional torque (restart torque) required to restart the engine if the intake valve were to close due to leak-down by the hydraulic lash adjuster from the intake valve's stopped position. In Figure 6, the horizontal axis is the crank angle and the vertical axis is the amount of additional torque. In Figure 6, the required additional torque is largest at the beginning of the compression stroke, and gradually decreases to zero as the compression stroke progresses. If the intake valve stops at the beginning of the compression stroke, the valve lift amount of the intake valve is large, so the torque required to restart the engine is small. If the intake valve closes due to leak-down by the hydraulic lash adjuster from such a state of large valve lift, the additional torque required to restart the engine will increase. Based on the torque map shown in Figure 6, the control unit 70 can obtain information on the required additional torque T1, for example, if the crank angle when the engine 10 is stopped is θ1. The torque map shown in Figure 6 is stored in the control unit 70 in advance.

[0045] In S22, the control unit 70 obtains information on the battery capacity required to restart the engine after closing the intake valve, based on the additional torque information acquired in S21. Figure 7 shows a battery capacity map that correlates additional torque with the battery capacity required for restarting, with the horizontal axis representing additional torque and the vertical axis representing the required battery capacity. As shown in the battery capacity map in Figure 7, when the additional torque is 0, the normal battery capacity is required, whereas as the additional torque increases, the required battery capacity increases. Based on the battery capacity map shown in Figure 7, the control unit 70 can obtain information that, for example, if the additional torque required to restart the engine 10 is T1, then the battery capacity required to restart the engine is SOC1. The battery capacity map shown in Figure 7 is calculated experimentally, empirically, or theoretically and is stored in the control unit 70 in advance for each oil temperature.

[0046] In S23, the control unit 70 determines whether the current battery capacity is equal to or greater than the required battery capacity, which is obtained using the battery capacity map shown in Figure 7. Information on the current battery capacity can be obtained from the battery sensor unit 50. For example, suppose the control unit 70 obtains information on the battery capacity SOC1 required to restart the engine based on the battery capacity map shown in Figure 7, and obtains the current battery capacity SOCnow from the battery sensor unit 50. In this case, the control unit 70 determines whether the current battery capacity SOCnow is equal to or greater than the required battery capacity SOC1.

[0047] If the current battery capacity is not equal to or less than the required battery capacity (i.e., less than the required battery capacity), the process proceeds to S9 as described in the first embodiment, and idle stop limiting processing is performed based on the leak-down characteristics of the hydraulic lash adjuster. Therefore, the engine 10 can be restarted without requiring the additional torque calculated in S21 to restart the engine 10 before the intake valve closes. Furthermore, if the current battery capacity is not equal to or greater than the required battery capacity, the control unit 70 may perform a different process than that in S9, not limited to proceeding to S9. For example, the control unit 70 may control the engine 10 to restart if the pressure in the hydraulic lash adjuster when the engine 10 stops falls below a predetermined amount.

[0048] On the other hand, if the current battery capacity is greater than or equal to the required battery capacity, the process proceeds to S10 as described in the first embodiment, and the idling stop limiting process is not performed. Instead, the idling stop time is set to a time determined by a different method than in S9. That is, for example, the control unit 70 sets the idling stop time to a predetermined time that is longer than the idling stop time set in S9.

[0049] In the subsequent S14, the control unit 70 cancels the idle stop by restarting the engine 10 with the ISG 30. Note that if the process proceeds to S14 via S8, S21-S23 and S10, the engine 10 is restarted after the intake valve has closed, so the control unit 70 controls the ISG 30 to drive the engine 10 with the additional torque calculated in S21 to ensure a smooth start.

[0050] Furthermore, if, in S12, the conditions for canceling the idle stop are not met outside of the idle stop time, and the system proceeds to S13, the control unit 70 continues the idle stop and returns to S23. Upon returning to S23, the control unit 70 again determines whether the current remaining battery capacity is equal to or greater than the required battery capacity, obtained using the battery capacity map shown in Figure 7. Therefore, it is possible to compare the remaining battery capacity, which has decreased due to the continuation of the idle stop, with the required battery capacity.

[0051] As described above, according to this embodiment, the control unit 70 calculates the restart torque based on the crank angle when the engine stops, using the torque map, and also calculates the battery capacity required to output the calculated restart torque. If the current remaining battery capacity is less than the battery capacity required to output the restart torque, the engine is restarted based on the pressure in the hydraulic lash adjuster. In this way, if there is insufficient battery capacity to restart when the intake valve closes due to a leak-down, the engine can be restarted before the intake valve closes based on the pressure in the hydraulic lash adjuster to prevent deterioration of starting performance.

[0052] On the other hand, if the current battery capacity is greater than or equal to the battery capacity required to output the restart torque, the idle stop limiting process is not executed, and instead, for example, the idle stop time is set to a predetermined time longer than the idle stop time set in S9. In this way, even if the restart torque required to restart after a leak-down occurs and the intake valve closes becomes large, if the battery capacity is sufficient, the idle stop time can be extended by not executing the idle stop limiting process based on the leak-down characteristics of the hydraulic lash adjuster.

[0053] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and modifications can be made within the scope of the present invention, and each embodiment may be combined as appropriate. [Explanation of symbols]

[0054] 1: Engine control system 10: Engine 20: Engine sensor unit 21: Crank angle sensor 22: Cam angle sensor 23: Oil temperature sensor 24: Oil pressure sensor 24 30: ISG 40: Battery 50: Battery sensor unit 51: Voltage sensor 52: Current sensor 53: Temperature sensor 60: Electrical load 70: Control unit

Claims

1. The engine as the power source, A hydraulic lash adjuster that adjusts the valve clearance using the hydraulic pressure generated by the operation of the aforementioned engine, An engine control system comprising a control unit that automatically stops and restarts the engine, The control unit, An engine control system characterized by restarting the engine based on the crank angle when the engine stops and the pressure in the hydraulic lash adjuster.

2. The control unit, The engine control system according to claim 1, characterized in that the engine is restarted before the pressure in the hydraulic lash adjuster reaches the pressure at which the intake valve closes, calculated based on the crank angle when the engine is stopped.

3. A torque map is stored that associates the restart torque required to restart the engine when the intake valve closes due to a decrease in pressure within the hydraulic lash adjuster from an open state with the crank angle when the engine stops. The control unit, The restart torque is calculated from the torque map based on the crank angle when the engine stops, and the battery capacity required to output the calculated restart torque is then calculated. The engine control system according to claim 1 or 2, characterized in that if the remaining battery capacity is less than the battery capacity required to output the calculated restart torque, the engine is restarted based on the pressure in the hydraulic lash adjuster.

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