JP2016138505A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine control device that can improve startability of an engine.SOLUTION: An engine control device includes a detection section for detecting a crank angle of an engine and a control section for controlling the engine. The control section executes predetermined start for starting the revolution of the engine by using combustion energy generated by burning fuel in a cylinder to start the engine. When the engine is stopped by stopping injection of fuel by using an injection device (Step S10-Y), if it is predicted that a piston of any cylinder is stopped near a compression top dead center on the basis of a change of the crank angle (Step S30-Y), the control section makes the injection device inject fuel in a cylinder in an expansion stroke until the revolution of the engine is stopped and burn the fuel (Step S40), so as to cause the engine to generate torque.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an engine control device.

  Conventionally, techniques for controlling the stop position of the piston have been proposed. For example, in Patent Document 1, in response to a stop command for an internal combustion engine, means for sending a signal to an actuator to open a throttle valve for controlling a stop position of a piston, and a throttle valve for controlling a stop position of the piston are opened. A device for controlling the stop of the internal combustion engine, comprising: means for stopping ignition of the ignition plug when the engine is stopped. In the control device of Patent Document 1, after turning off the ignition of the engine, when the throttle valve is opened and air is introduced to prevent the piston from stopping near the top dead center, the stop position of the piston is not changed. And a control device that stops the engine without deteriorating the emission.

JP 2010-138722 A

  If the piston stops near the top dead center, the starting performance of the engine will be reduced. Even if the control of the throttle valve or the timing of stopping the ignition is performed, it is difficult to completely control the position where the piston actually stops because variations occur. There is still room for improvement in suppressing the piston from stopping near the top dead center and improving the engine starting performance.

  The objective of this invention is providing the engine control apparatus which can improve the starting performance of an engine.

  An engine control device according to the present invention includes a detection unit that detects a crank angle of an engine and a control unit that controls the engine, and the engine injects fuel into a plurality of cylinders and the cylinders. The control unit executes a predetermined start to start the engine by starting rotation of the engine by combustion energy generated by burning fuel in the cylinder, and the control unit performs the injection When stopping the fuel injection by the device and stopping the engine, if it is predicted that the piston of any of the cylinders will stop near the compression top dead center based on the change in the crank angle, Injecting fuel into the injector in the cylinder in the expansion stroke until rotation stops, and generating torque in the engine by burning the fuel And butterflies.

  When it is predicted that the piston of any cylinder stops near the compression top dead center, the engine control device causes the engine to inject fuel into the cylinder in the expansion stroke and burn the fuel to the engine. Generate torque. Thereby, there exists an effect that it can suppress that a piston stops in the vicinity of a compression top dead center.

  An engine control device of the present invention includes a clutch disposed between an engine and driving wheels, a detection unit that detects a crank angle of the engine, and a control unit that controls the engine and the clutch, The engine has a plurality of cylinders and an injection device that injects fuel into the cylinders, and the control unit starts rotation of the engine by combustion energy generated by burning fuel in the cylinders. A predetermined start for starting the engine is performed, and the control unit changes the crank angle when stopping the engine by stopping fuel injection by the injection device while the clutch is released during traveling. If it is predicted that the piston of any of the cylinders will stop near the compression top dead center based on the Torque is transmitted from the wheel to the engine, and if the vehicle speed is less than the threshold, the fuel is injected into the injector and burned by the cylinder in the expansion stroke until the rotation of the engine stops. Thus, torque is generated in the engine.

  When the engine control device predicts that the piston of any cylinder stops near the compression top dead center, if the vehicle speed is equal to or higher than the threshold, the clutch is engaged to transmit torque from the drive wheels to the engine, If the vehicle speed is less than the threshold value, the fuel is injected into the injection device by the cylinder in the expansion stroke until the rotation of the engine is stopped, and the engine is caused to generate torque by burning the fuel. Thereby, the stop position of the engine is changed by the torque generated from the outside or the torque generated by the engine, and the piston can be prevented from stopping near the compression top dead center.

  The engine control device according to the present invention causes the injection device to inject fuel into the cylinder in the expansion stroke and burn the fuel when the piston of any cylinder is predicted to stop near the compression top dead center. To generate torque in the engine. According to the engine control device of the present invention, it is possible to improve the starting performance of the engine by suppressing the piston from stopping near the compression top dead center.

FIG. 1 is a diagram illustrating a main part of a vehicle according to the first embodiment. FIG. 2 is a schematic configuration diagram of the engine according to the first embodiment. FIG. 3 is a view showing a state where the piston stops at the compression top dead center. FIG. 4 is a diagram for explaining the operation of the engine control apparatus according to the first embodiment. FIG. 5 is a diagram illustrating an example of an engine stop position. FIG. 6 is a diagram illustrating a method for predicting the stop position of the engine. FIG. 7 is a diagram showing a transition until the piston stops at the compression top dead center. FIG. 8 is a diagram showing a transition until the piston stops before the compression top dead center. FIG. 9 is a flowchart showing the operation of the engine control apparatus according to the first embodiment. FIG. 10 is a diagram illustrating a main part of the vehicle according to the second embodiment. FIG. 11 is a flowchart showing the operation of the engine control apparatus according to the second embodiment. FIG. 12 is a time chart according to the stop position control of the second embodiment. FIG. 13 is a diagram illustrating a threshold value of the vehicle speed according to the control of the second embodiment. FIG. 14 is a flowchart showing an operation according to the first modification of the second embodiment.

  Hereinafter, an engine control apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

[First Embodiment]
The first embodiment will be described with reference to FIGS. 1 to 9. The present embodiment relates to an engine control device. FIG. 1 is a diagram showing a main part of a vehicle according to a first embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of an engine according to the first embodiment.

  As shown in FIG. 1, a vehicle 100 according to this embodiment includes an engine control device 1 and an engine 2. The engine 2 converts the combustion energy of fuel into rotational motion. The engine control device 1 of the first embodiment includes a crank angle sensor 30 and an ECU 50. The crank angle sensor 30 is a detection unit that detects the crank angle of the engine 2. A signal indicating the detection result of the crank angle sensor 30 is output to the ECU 50. The ECU 50 is a control unit that controls the engine 2.

  As shown in FIG. 2, the engine 2 of the present embodiment is a so-called direct injection internal combustion engine. The engine 2 includes a plurality of cylinders 20, injection devices 28, and ignition devices 29. The ECU 50 executes injection control for controlling the fuel injection amount and injection timing by the injection device 28 and ignition control for controlling the ignition timing by the ignition device 29. The engine 2 of the present embodiment is a so-called V-type 6-cylinder engine that has six cylinders 20 and the cylinders 20 are arranged in a V shape. In the present embodiment, the six cylinders 20 are classified into the first cylinder 20a, the second cylinder 20b, the third cylinder 20c, the fourth cylinder 20d, the fifth cylinder 20e, and the sixth cylinder 20 according to the order in which the combustion strokes are executed in each cylinder 20. This is referred to as a number cylinder 20f.

  For each cylinder 20, a piston 22, an intake valve 25, an exhaust valve 27, an injection device 28, and an ignition device 29 are arranged. The piston 22 is disposed in the cylinder bore 21 so as to be able to reciprocate. The engine 2 is a so-called four-cycle engine that performs four strokes of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while the piston 22 reciprocates in the cylinder bore 21 twice. In the intake stroke, air is sucked into the combustion chamber 23 from the intake port 24 by moving the piston 22 from the top dead center toward the bottom dead center with the intake valve 25 opened. In the compression stroke, the piston 22 moves toward the top dead center while the intake valve 25 and the exhaust valve 27 are closed, whereby the gas in the combustion chamber 23 is compressed.

  The injection device 28 injects a fuel spray 28 a into the combustion chamber 23 in the cylinder 20. The fuel injected by the injection device 28 and the air in the combustion chamber 23 are mixed to form an air-fuel mixture. The ignition device 29 ignites the air-fuel mixture in the combustion chamber 23. When the air-fuel mixture is ignited and combusted, the piston 22 is pushed down toward the bottom dead center by the combustion pressure (expansion stroke). In the exhaust stroke, the exhaust valve 27 is opened, and the exhaust gas in the combustion chamber 23 is discharged to the exhaust port 26. In the present embodiment, the stroke between the compression stroke and the exhaust stroke is referred to as an expansion stroke regardless of whether or not fuel combustion is performed in the combustion chamber 23. That is, the expansion stroke is a stroke in which the piston 22 moves toward the bottom dead center after exceeding the compression top dead center TDC described later, and the stroke until the exhaust valve 27 is opened.

  The ECU 50 automatically starts and stops the engine 2 when a predetermined engine stop condition is satisfied while traveling or stopped, and restarts the stopped engine 2 when a predetermined restart condition is satisfied. Control (hereinafter simply referred to as “S & S control”) is executed. The predetermined engine stop condition is a condition including, for example, an accelerator-off state. When a predetermined engine stop condition is satisfied, the ECU 50 stops the fuel injection by the injection device 28 in the engine 2 and stops the rotation of the engine 2. The ECU 50 of the present embodiment interrupts power transmission between the engine 2 and the drive wheels when the engine 2 is automatically stopped. The power transmission is interrupted by, for example, releasing a clutch disposed between the engine 2 and the drive wheels.

  The engine 2 of the present embodiment is configured to be able to start by a predetermined start. In the present embodiment, the predetermined start is a start method for starting the engine 2 by starting the rotation of the engine 2 by combustion energy (expansion pressure) generated by burning fuel in the cylinder 20. The ECU 50 injects fuel into the combustion chamber 23 of the cylinder 20 in the expansion stroke to start the rotation of the engine 2 that has been stopped at a predetermined start. When the engine 2 starts rotating, the ECU 50 sequentially executes four strokes in each cylinder 20 to increase the engine rotational speed Ne. When the engine speed Ne increases to a predetermined speed, the ECU 50 switches the operation mode of the engine 2 from a start mode by a predetermined start to a normal mode.

  Here, depending on the crank angle of the engine 2 when starting the predetermined start, the start by the predetermined start becomes impossible or difficult. FIG. 3 shows an example of a stop position of the engine 2 at which the predetermined start is impossible or difficult. In FIG. 3, the rotation angle around the origin indicates the crank angle of the engine 2. A thick line from the origin in the radial direction indicates the piston position of each cylinder 20a, 20b, 20c. FIG. 3 shows a state in which the piston 22 of the second cylinder 20b stops at a top dead center TDC (Top Dead Center) where the compression stroke shifts to the expansion stroke. In the following description, the top dead center TDC that shifts from the compression stroke to the expansion stroke is simply referred to as “compression top dead center TDC”. If the engine 2 loses rotational energy when the piston 22 is in the vicinity of the compression top dead center TDC, the in-cylinder pressure of each cylinder 20 is balanced, and the piston 22 is positioned in the vicinity of the compression top dead center TDC. The engine 2 may stop in the state. Even if fuel is injected into the injection device 28 of the second cylinder 20b from this state and combustion is performed, there is a high possibility that the predetermined start will not succeed due to insufficient combustion energy.

  When it is predicted that any one of the pistons 22 of the plurality of cylinders 20 will stop near the compression top dead center TDC, the ECU 50 of the present embodiment stops the rotation of the engine 2 as described below. In the cylinder 20 in the expansion stroke, fuel is injected by the injection device 28 to cause combustion, and torque is generated in the engine 2. Thereby, it can suppress that piston 22 stops in the vicinity of compression top dead center TDC, and the starting performance of engine 2 can be improved.

  FIG. 4 shows the operation when the second cylinder 20b is predicted to stop at the compression top dead center TDC. The piston 22 of the second cylinder 20b is moving toward the compression top dead center TDC. Based on the change in the crank angle, the piston 22 of the second cylinder 20b is predicted to stop at the compression top dead center TDC. The piston 22 of the first cylinder 20a is already in a position corresponding to the expansion stroke beyond the compression top dead center TDC. The ECU 50 causes the injection device 28 of the first cylinder 20a to inject fuel into the combustion chamber 23 and causes the ignition device 29 to perform ignition. The torque indicated by the arrow Y1 is generated by the combustion energy generated in the first cylinder 20a. Due to this torque Y1, the piston 22 of the second cylinder 20b does not stop at the compression top dead center TDC, and the engine 2 rotates beyond the crank angle of the compression top dead center TDC. If the crank angle of the engine 2 exceeds the crank angle of the compression top dead center TDC, the balance of force due to the in-cylinder pressure of each cylinder 20 is lost. As a result, it can be expected that the piston 22 moves to a position where a predetermined start can be performed.

  FIG. 5 shows an example of the stop position of the engine 2 as a result of injecting fuel into the cylinder 20 in the expansion stroke and burning it to generate torque. As shown in FIG. 3, if the piston 22 is positioned in the vicinity of the compression top dead center TDC, the force due to the in-cylinder pressure is balanced and the piston 22 may stop as it is. Will shift to the more advanced side than the vicinity of the compression top dead center TDC, the balance of force will be lost. Thereby, the engine 2 stops at the crank angle at which the second cylinder 20b becomes the cylinder in the expansion stroke, for example, as shown in FIG. The engine 2 is highly likely to stop so that the force due to the in-cylinder pressure of the cylinder 20 in the expansion stroke and the force due to the in-cylinder pressure of the cylinder 20 in the compression stroke are balanced. As described above, the engine control device 1 according to the present embodiment causes the engine 2 to temporarily burn and generate the torque Y1 when the piston 22 is likely to stop at the compression top dead center TDC. The starting position of the engine 2 is improved by changing the stop position of the engine 2.

  In the present embodiment, the vicinity of the compression top dead center TDC is a predetermined crank angle range including the compression top dead center TDC. The predetermined crank angle range is, for example, a range from 10 [deg] before the compression top dead center TDC to 10 [deg] after the compression top dead center TDC. The range of the predetermined crank angle in the present embodiment is set as a range in which the engine 2 cannot be started by a predetermined start, and the specific range varies depending on various sources of the engine 2 and the like. When the piston 22 stops near the compression top dead center TDC, even if an expansion (combustion) stroke is executed in the cylinder 20, the engine 2 does not start rotating, or it is difficult to rotate the engine 2. The situation in which it is difficult to rotate the engine 2 is, for example, a situation in which the engine 2 slightly rotates, but the piston 22 in the next combustion sequence cannot exceed the compression top dead center TDC and cannot enter the expansion stroke. It is.

A method for determining whether or not the piston 22 stops at the compression top dead center TDC will be described with reference to FIGS. The ECU 50 of the present embodiment assumes that the loss from the time when the piston 22 of one cylinder 20 passes the compression top dead center TDC to the time when the piston 22 of the next cylinder 20 passes the compression top dead center TDC is equal. Then, the future engine speed Ne is predicted. In the following description, the predicted value of the engine speed Ne is referred to as “predicted engine speed Nep”. Referring to FIG. 6, based on the current engine speed Ne _i and the engine speed Ne _i-120 at the crank angle 120 [deg] ahead, the engine speed at the crank angle 120 [deg] ahead. Ne _{i + 120} is calculated.

If the energy loss of the engine 2 is equal while the crank angle changes by 120 [deg], the following [Equation 1] holds. Here, J: inertia of engine 2, E _loss : _{loss of} engine 2 while crank angle of engine 2 changes by 120 [deg].

The following [Equation 2] is derived from the above [Equation 1]. The ECU 50 calculates the engine rotational speed Ne _i at the crank angle 120 [deg] ahead from the current engine rotational speed Ne _i and the engine rotational speed Ne _i-120 at the crank angle 120 [deg] before by the following [Equation 2]. Calculate ₊₁₂₀ . The predicted engine speed Nep of the present embodiment is a value of the engine speed Ne _{i + 120} at a crank angle of 120 [deg] ahead calculated based on [Equation 2]. In the following description, the value of the engine rotational speed Ne _{i + 120} calculated when the piston 22 of one cylinder 20 is at the compression top dead center TDC is particularly referred to as “predicted TDC speed Net”. The predicted TDC speed Net is a predicted value of the engine rotational speed Ne when the piston 22 of the next cylinder 20 reaches the compression top dead center TDC.

  The ECU 50 calculates the predicted TDC speed Net when the piston 22 of the next cylinder 20 reaches the compression top dead center TDC when the piston 22 of one cylinder 20 is at the compression top dead center TDC. If the predicted TDC speed Net is a negative value, the engine speed Ne decreases to 0 before the piston 22 of the next cylinder 20 reaches the compression top dead center TDC. In this case, after the engine 2 is temporarily stopped, for example, the engine 2 reversely rotates to a position where torque due to the in-cylinder pressure is balanced. On the other hand, when the predicted TDC speed Net is a positive value and the absolute value is sufficiently large, the engine 2 does not stop when the piston 22 of the next cylinder 20 reaches the compression top dead center TDC. Rotate.

  The ECU 50 of the present embodiment predicts that the piston 22 of the next cylinder 20 stops near the compression top dead center TDC when the predicted TDC speed Net is a speed within a predetermined range. The predetermined range of the present embodiment is a range from the negative threshold value Ne1 to the positive threshold value Ne2. The predetermined range is determined based on, for example, experimental results for matching or simulation results. The predetermined range is determined so that the piston 22 can be determined not to stop at the compression top dead center TDC if the predicted TDC speed Net is a value outside the predetermined range.

  A specific example will be described with reference to FIG. The ECU 50 calculates a predicted value (predicted TDC speed Net) of the engine speed at the crank angle CA2 that is 120 [deg] ahead at the crank angle CA1. The calculated value of the predicted TDC speed Net is a value between the threshold Ne1 and the threshold Ne2. In this case, the ECU 50 determines that the engine 2 is stopped in the vicinity of the crank angle CA2 and the piston 22 is stopped in the vicinity of the compression top dead center TDC. In FIG. 7, the crank angle when the engine 2 is actually stopped thereafter is a crank angle in the vicinity of the crank angle CA2 corresponding to the compression top dead center TDC.

  On the other hand, in FIG. 8, the predicted engine speed Nep is 0 at a crank angle between the crank angle CA1 and the crank angle CA2. In this case, the ECU 50 determines that the piston 22 does not stop near the compression top dead center TDC. The actual engine speed Ne becomes 0 between the crank angle CA1 and the crank angle CA2, and then the engine 2 rotates in the reverse direction and stops.

  With reference to FIG. 9, operation | movement of the engine control apparatus 1 of 1st Embodiment is demonstrated. The flowchart in FIG. 9 is repeatedly executed at predetermined intervals, for example. In step S10, the ECU 50 determines whether or not the engine is being stopped by S & S. The ECU 50 performs step S10 when a predetermined engine stop condition is satisfied and fuel injection by the injection device 28 is stopped, and when the engine rotational speed Ne has not decreased to a predetermined rotational speed (for example, 0). Make an affirmative decision. When an affirmative determination is made in step S10 (step S10-Y), the process proceeds to step S20, and when a negative determination is made (step S10-N), the current control process ends.

  In step S20, the ECU 50 calculates a predicted engine speed Nep. The ECU 50 calculates the predicted engine speed Nep based on the current value of the engine speed Ne acquired from the crank angle sensor 30 and the stored value of the engine speed Ne at the crank angle 120 [deg] before. calculate. When step S20 is executed, the process proceeds to step S30.

  In step S30, the ECU 50 determines whether any of the pistons 22 stops at the compression top dead center TDC. If the value of the predicted TDC speed Net calculated at the timing when the piston 22 passes the compression top dead center TDC is a value within a predetermined range, the ECU 50 makes an affirmative determination in step S30. On the other hand, if the value of the predicted TDC speed Net is not within the predetermined range, the ECU 50 makes a negative determination in step S30. When an affirmative determination is made in step S30 (step S30-Y), the process proceeds to step S40, and when a negative determination is made (step S30-N), the current control process ends.

  In step S40, the ECU 50 causes fuel injection and ignition in the cylinder 20 in the expansion stroke. The ECU 50 commands fuel injection to the injection device 28 of the cylinder 20 that is currently in the expansion stroke, and commands ignition to the ignition device 29 of the cylinder 20. The ECU 50 determines the fuel injection amount based on the estimated amount of air in the cylinder 20 in the expansion stroke. When the fuel injection amount is determined so as to make the air-fuel ratio rich, it is possible to more reliably suppress the generated torque from increasing and the piston 22 from stopping at the compression top dead center TDC. Further, when the air-fuel ratio is made rich, the ignitability of the air-fuel mixture becomes high. On the other hand, when the fuel injection amount is determined so that the air-fuel ratio is lean, the generated torque can be reduced to suppress the shock and the fuel consumption can be suppressed. When combustion is temporarily performed in the engine 2, if the generated combustion energy is too large, the driver may feel uncomfortable due to torque fluctuation. The ECU 50 preferably retards the ignition timing so that the torque fluctuation does not become large. When step S40 is executed, the current control process ends.

  As described above, the ECU 50 of the engine control device 1 according to the present embodiment stops any one of the cylinders 20 based on the change in the crank angle when the fuel injection by the injection device 28 is stopped and the engine 2 is stopped. Is predicted to stop near the compression top dead center TDC (step S30-Y), fuel is injected into the injection device 28 by the cylinder 20 in the expansion stroke until the rotation of the engine 2 stops. And causing the engine 2 to generate torque by burning the fuel (step S40). The engine control device 1 can change the stop position of the engine 2 by generating torque in the engine 2 and suppress the piston 22 from stopping at the compression top dead center TDC.

[Second Embodiment]
The second embodiment will be described with reference to FIGS. 10 to 12. In the second embodiment, components having the same functions as those described in the first embodiment are given the same reference numerals, and duplicate descriptions are omitted. FIG. 10 is a diagram illustrating a main part of the vehicle according to the second embodiment. The second embodiment is different from the first embodiment in that the ECU 60 temporarily engages the clutch 3 (see FIG. 10) when the piston 22 is predicted to stop near the compression top dead center TDC. Thus, torque is transmitted from the drive wheel 7 to the engine 2.

  As shown in FIG. 10, the vehicle 100 according to the second embodiment includes an engine 2, a transmission 4, and an engine control device 101. The engine control device 101 includes a clutch 3, a crank angle sensor 30, and an ECU 60. The transmission 4 according to the present embodiment is a stepped automatic transmission that can be switched from a first gear to a fifth gear. The output shaft of the transmission 4 is connected to the left and right drive wheels 7 via a differential gear 5 and a drive shaft 6. The clutch 3 is disposed between the engine 2 and the transmission 4. The engaged clutch 3 transmits power between the engine 2 and the transmission 4. The opened clutch 3 disconnects the engine 2 and the transmission 4 and interrupts the power transmission path between the engine 2 and the transmission 4. The clutch 3 of this embodiment is a friction engagement type clutch device. The clutch 3 is engaged or released according to the hydraulic pressure supplied by the hydraulic control device. The ECU 60 is a control unit that controls the engine 2 and the clutch 3.

  When the engine 2 is automatically stopped in the S & S control while the vehicle 100 is traveling, the ECU 60 stops the fuel injection by the injection device 28 with the clutch 3 opened, and decreases the rotational speed of the engine 2. When the ECU 60 stops the engine 2 while the clutch 3 is released while the vehicle 100 is running, when any of the pistons 22 of the plurality of cylinders 20 is predicted to stop near the compression top dead center TDC, The piston 22 is prevented from stopping in the vicinity of the compression top dead center TDC by burning the fuel in the cylinder 20 in the expansion stroke to generate torque and engaging the clutch 3. When the clutch 3 is engaged during traveling, torque is transmitted from the drive wheels 7 to the engine 2 via the clutch 3. The engine 2 is driven by this torque, and the stop position of the engine 2 changes. Thereby, it is suppressed that the piston 22 stops in the vicinity of the compression top dead center TDC.

  In the second embodiment, similarly to the first embodiment, the stop position control of the engine 2 by burning the fuel in the cylinder 20 in the expansion stroke is referred to as “first control” and the engine by engaging the clutch 3. The stop position control 2 is referred to as “second control”. In the second control, unlike the first control, the rotational position of the engine 2 can be changed without consuming fuel. Therefore, fuel consumption can be reduced.

  When the piston 22 is predicted to stop near the compression top dead center TDC, the ECU 60 according to the present embodiment determines whether to execute the first control or the second control based on the vehicle speed. In the present embodiment, a lower limit value of the vehicle speed that permits execution of the second control is defined. This lower limit (threshold value) is determined from the viewpoint of suppressing drivability deterioration due to the occurrence of a shock. When the clutch 3 is engaged during traveling at a low vehicle speed, it is easier for the driver to feel uncomfortable with the torque fluctuation than when the clutch 3 is engaged during traveling at a high vehicle speed. For this reason, when the vehicle speed is lower than the threshold value, the ECU 60 does not execute the second control and changes the stop position of the engine 2 by the first control.

  The operation of the engine control apparatus 101 according to the second embodiment will be described with reference to FIGS. 11 and 12. The flowchart of FIG. 11 is repeatedly executed at predetermined intervals, for example. In the time chart of FIG. 12, (a) crank angle, (b) engine rotation speed, and (c) clutch command torque are shown. The clutch command torque is a command value for the torque capacity (engagement force) of the clutch 3. The hydraulic pressure supplied to the clutch 3 is controlled according to the clutch command torque. (A) In the column of the crank angle, a transition when the stop position control of the engine 2 is not performed is indicated by a broken line. The solid line shows the transition of the crank angle when the stop position control of the present embodiment is performed. Note that (a) the crank angle indicates the crank angle from when the piston 22 of one cylinder 20 passes the compression top dead center TDC to when the piston 22 of the next cylinder 20 passes the compression top dead center TDC. Has been. That is, the value of the crank angle is reset to 0 each time the piston 22 passes through the compression top dead center TDC.

  The operation from step S110 to step S120 is the same as that from step S10 to step S20 in the first embodiment (FIG. 9). If it is determined affirmative in step S130 that the piston 22 stops at the compression top dead center TDC (step S130-Y), the process proceeds to step S140. If a negative determination is made (step S130-N), the current control process is performed. finish. In FIG. 12, an affirmative determination is made in step S130 at time t1, and the process proceeds to step S140.

  In step S140, the ECU 60 determines whether or not the vehicle speed is equal to or higher than a threshold value. As shown in FIG. 13, the threshold value of the present embodiment varies depending on the gear position. The threshold value V4 at the fourth speed stage is greater than the threshold value V5 at the fifth speed stage, and the threshold value V3 at the third speed stage is greater than the threshold value V4 at the fourth speed stage. The threshold value V5 of the fifth speed shift stage, which is the highest speed shift stage, is set to the lowest speed value. Execution of the second control is prohibited at the second gear and the first gear. This is because when the clutch 3 is engaged at a low speed, a shock due to torque fluctuation is likely to occur. The threshold value VX for the first gear and the second gear is a value larger than the maximum speed assumed in the vehicle 100. The ECU 60 makes an affirmative determination in step S140 when the current vehicle speed is greater than or equal to a threshold value corresponding to the current gear position. If an affirmative determination is made in step S140 (step S140-Y), the process proceeds to step S150, and if a negative determination is made (step S140-N), the process proceeds to step S160.

  In step S150, the ECU 60 engages the clutch 3. The ECU 60 outputs clutch instruction torque to the hydraulic control device to engage the clutch 3. The value of the clutch command torque at this time is to make the clutch 3 slip-engage. In FIG. 12, the clutch 3 is instructed to be engaged at time t1. The torque transmitted through the clutch 3 increases the rotational energy of the engine 2. As a result, the engine 2 further rotates beyond the crank angle at which the position of the piston 22 becomes the compression top dead center TDC. When the crank angle of engine 2 passes the crank angle corresponding to compression top dead center TDC at time t2, ECU 60 changes the clutch instruction torque to 0 at time t3. As a result, the clutch 3 is released, the engine 2 is disconnected from the drive wheel 7, and the engine 2 stops at time t4. When step S150 is executed, the current control process ends.

  In step S160, the ECU 60 causes fuel injection and ignition in the cylinder 20 in the expansion stroke. When step S160 is executed, the current control process ends.

  As described above, the ECU 60 of the engine control apparatus 101 according to the second embodiment determines the crank angle when stopping the engine 2 by stopping the fuel injection by the injection device 28 while the clutch 3 is released during traveling. If it is predicted that the piston 22 of any one of the cylinders 20 will stop near the compression top dead center TDC based on the change (step S130-Y), if the vehicle speed is equal to or higher than the threshold (step S140-Y), the clutch 3 To be transmitted to the engine 2 from the drive wheel 7 (step S150). On the other hand, if the vehicle speed is less than the threshold value (step S140-N), the ECU 60 causes the injection device 28 to inject fuel into the cylinder 20 that is in the expansion stroke until the rotation of the engine 3 stops, and combusts the fuel. Thus, torque is generated in the engine 2 (step S160). According to the second control in which the clutch 3 is engaged, it is possible to change the stop position of the engine 2 while reducing the fuel consumption. The ECU 60 changes the stop position of the engine 2 by the first control in a vehicle speed range where a shock is likely to occur when the clutch 3 is engaged. Therefore, the engine control apparatus 101 of the present embodiment can achieve both improvement in the starting performance of the engine 2 and reduction in fuel consumption.

[First Modification of Second Embodiment]
A first modification of the second embodiment will be described. FIG. 14 is a flowchart showing an operation according to the first modification of the second embodiment. In the first modification of the second embodiment, the difference from the second embodiment is that when an engine stop request is generated by S & S control, an upshift is performed in advance to a gear stage that can execute the second control. It is. In this modification, the ECU 60 has a function as a vehicle control device that controls the engine 2, the clutch 3, and the transmission 4.

  With reference to FIG. 14, the operation of the engine control apparatus 101 in the first modification of the second embodiment will be described. The flowchart shown in FIG. 14 is repeatedly executed at predetermined intervals, for example. Note that the flowchart of FIG. 14 is executed alternately with the flowchart of the second embodiment (FIG. 11), for example.

  In step S210, the ECU 60 determines whether or not there is an engine stop request by S & S control. The ECU 60 makes an affirmative determination in step S210 when a predetermined engine stop condition is satisfied during engine running. When an affirmative determination is made in step S210 (step S210-Y), the process proceeds to step S220, and when a negative determination is made (step S210-N), the current control process ends.

  In step S220, the ECU 60 determines whether or not the vehicle speed is greater than or equal to a threshold value. The ECU 60 makes an affirmative determination in step S220 when the current vehicle speed is greater than or equal to a threshold value corresponding to the current gear position. If an affirmative determination is made in step S220 (step S220-Y), the process proceeds to step S230. If a negative determination is made (step S220-N), the process proceeds to step S240.

  In step S230, the ECU 60 opens the clutch 3. When step S230 is executed, the process proceeds to step S270.

  In step S240, the ECU 60 determines whether or not the threshold value is less than the vehicle speed due to the upshift. In step S240, it is determined whether or not there is a shift stage in which execution of the second control is permitted at the current vehicle speed. For example, it is assumed that the current vehicle speed is a value between the threshold value V4 of the fourth speed gear stage and the threshold value V5 of the fifth speed gear stage shown in FIG. 13, and the current gear stage is the fourth speed gear stage. In this case, if the upshift is made to the fifth speed in advance, the second control can be executed. On the other hand, when the current vehicle speed is lower than the threshold value V5, there is no gear stage whose threshold value is less than the current vehicle speed. In other words, even if the upshift is performed, the second control cannot be executed. The ECU 60 makes an affirmative determination in step S240 when the current vehicle speed is greater than or equal to the fifth speed shift threshold value V5. If an affirmative determination is made in step S240 (step S240-Y), the process proceeds to step S250, and if a negative determination is made (step S240-N), the process proceeds to step S230.

  In step S250, the ECU 60 opens the clutch 3. When step S250 is executed, the process proceeds to step S260.

  In step S260, the ECU 60 performs an upshift. The ECU 60 upshifts the transmission 4 to a gear position where the threshold value is less than the current vehicle speed. When step S260 is executed, the process proceeds to step S270.

  In step S270, the ECU 60 stops fuel injection by the injection device 28. The ECU 60 commands the engine 2 to stop fuel injection by the injection device 28 in each cylinder 20. When step S270 is executed, the current control process ends.

  The ECU 60 of the present modification can increase the rate of executing the second control when the piston 22 is predicted to stop near the compression top dead center TDC by upshifting the transmission 4 in advance. it can. Therefore, it is possible to reduce the fuel consumption.

  Note that the ECU 60 may upshift the transmission 4 even when the vehicle speed is equal to or higher than the threshold (step S220-Y) when there is an engine stop request by S & S control. By setting the gear stage of the transmission 4 to the high speed gear stage in advance, torque fluctuation when the clutch 3 is engaged can be reduced. For example, when an engine stop request is generated by S & S control, the ECU 60 shifts the transmission 4 to a shift stage on a higher speed side than a shift stage based on a predetermined shift line. The shift timing is preferably after the clutch 3 is released (steps S230 and S250).

[Second Modification of Second Embodiment]
A second modification of the second embodiment will be described. The clutch 3 may be any clutch as long as it disconnects the power transmission path between the engine 2 and the drive wheels 7 by being in an open state and connects the engine 2 and the drive wheels 7 by being in an engaged state. The clutch 3 only needs to be disposed between the engine 2 and the drive wheel 7, and may be provided on the drive wheel 7 side of the transmission 4, for example. Alternatively, the clutch 3 may be a clutch inside the transmission 4. In this case, the clutch 3 is, for example, any clutch for forming a shift stage of the transmission 4.

[First Modification of Each Embodiment]
A first modification of the first embodiment and the second embodiment will be described. The method for determining whether or not the piston 22 stops near the compression top dead center TDC is not limited to the method of each of the above embodiments. As an example, it is possible to determine that the piston 22 stops in the vicinity of the compression top dead center TDC when the engine speed Ne when each piston 22 passes through the top dead center is a value within a predetermined range. . In other words, instead of transition of the engine rotational speed Ne, it may be determined that the piston 22 stops near the compression top dead center TDC based on the instantaneous value of the engine rotational speed Ne.

[Second Modification of Each Embodiment]
The ECUs 50 and 60 are not limited to automatically stopping the engine 2 by S & S control or the like, but may control the stop position of the engine 2. For example, when the engine 2 is stopped in response to an engine stop operation by the driver, the ECUs 50 and 60 execute the stop position control of each of the above embodiments and modifications. Thereby, when the engine 2 is started next time, a predetermined start can be performed, and the start performance of the engine 2 is improved.

[Third Modification of Each Embodiment]
The number of cylinders and the arrangement of the engine 2 are not limited to those exemplified in the embodiment. For example, the number of cylinders may be 4 cylinders or 8 cylinders, and the arrangement of the cylinders 20 may be in-line. The engine 2 may be capable of a starting method other than the predetermined starting. For example, the engine 2 may be capable of being started by cranking a starter motor or a motor generator.

  The contents disclosed in each of the above embodiments and modifications can be executed in appropriate combination.

1,101 Engine control device 2 Engine 3 Clutch 4 Transmission 7 Drive wheel 20 Cylinder 22 Piston 28 Injection device 29 Ignition device 30 Crank angle sensor (detection unit)
50, 60 ECU (control unit)
100 vehicles

Claims (2)

A detector for detecting the crank angle of the engine;
A control unit for controlling the engine;
With
The engine includes a plurality of cylinders and an injection device that injects fuel into the cylinders.
The control unit executes a predetermined start to start the engine by starting rotation of the engine by combustion energy generated by burning fuel in the cylinder,
When the control unit stops the fuel injection by the injection device and stops the engine, it is predicted that the piston of any one of the cylinders stops near the compression top dead center based on the change in the crank angle. In this case, the engine is caused to generate torque by injecting fuel into the injection device in the cylinder in the expansion stroke until the rotation of the engine stops, and burning the fuel. Engine control device. A clutch disposed between the engine and the drive wheel;
A detector for detecting a crank angle of the engine;
A control unit for controlling the engine and the clutch;
With
The engine includes a plurality of cylinders and an injection device that injects fuel into the cylinders.
The control unit executes a predetermined start to start the engine by starting rotation of the engine by combustion energy generated by burning fuel in the cylinder,
When the control unit stops the engine by stopping the fuel injection by the injection device while the clutch is released during traveling, the piston of any of the cylinders is changed based on the change in the crank angle. When it is predicted to stop near the compression top dead center, if the vehicle speed is equal to or higher than a threshold value, the clutch is engaged to transmit torque from the drive wheels to the engine, and if the vehicle speed is lower than the threshold value, the engine An engine control device characterized by causing the engine to generate torque by injecting fuel into the injection device in the cylinder in the expansion stroke until the rotation of the engine stops and burning the fuel.

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