Vehicle control device

Abstract

To provide a control device for a vehicle, by which variations in stop position of an internal combustion engine are suppressed.SOLUTION: A control device for a vehicle having an internal combustion engine as a travel power source, comprises: a stop position control unit that executes stop position control of the internal combustion engine, by temporarily increasing and then decreasing the throttle opening of the internal combustion engine during inertial rotation in which combustion of the internal combustion engine is stopped; a calculation unit that, during execution of the stop position control, calculates a target intake manifold pressure capable of stopping the inertial rotation of the internal combustion engine, as a target value of the intake manifold pressure that is the pressure in an intake passage on a downstream side of a throttle valve of the internal combustion engine; a setting unit that sets an upper limit value lower than the atmospheric pressure; and a throttle control unit that increases the throttle opening so that the intake manifold pressure rises to the target intake manifold pressure when the target intake manifold pressure becomes equal to or less than the upper limit value during execution of the stop position control.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] There is known a technique for performing stop position control of an internal combustion engine by temporarily increasing and then decreasing the throttle opening of the internal combustion engine during inertial rotation when combustion in the internal combustion engine has stopped (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-147276 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above stop position control, if there is variation in the timing at which the throttle opening is increased, there is a risk that variation will also occur in the stop position of the internal combustion engine.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a vehicle control device that suppresses variation in the stop position of an internal combustion engine. [Means for solving the problem]

[0006] The above object is to provide a control device for a vehicle equipped with an internal combustion engine as a driving power source, comprising: a stop position control unit which executes a stop position control of the internal combustion engine by temporarily increasing and then decreasing a throttle opening of the internal combustion engine during inertial rotation with combustion in the internal combustion engine stopped; a calculation unit which calculates a target intake manifold pressure capable of stopping the inertial rotation of the internal combustion engine as a target value of an intake manifold pressure which is the pressure in an intake passage downstream of a throttle valve of the internal combustion engine during execution of the stop position control; a setting unit which sets an upper limit value lower than atmospheric pressure; and a throttle control unit which increases the throttle opening so that the intake manifold pressure rises to the target intake manifold pressure when the target intake manifold pressure becomes equal to or lower than the upper limit value during execution of the stop position control. a prediction unit that predicts a required increase time required for the intake manifold pressure to increase to the upper limit value after the throttle opening is increased; and Equipped with the calculation unit calculates the target intake manifold pressure at a closing timing of an intake valve of the internal combustion engine immediately after the required rise time has elapsed from a current time point. This can be achieved by the vehicle's control device.

[0008] The prediction unit may predict that the required rise time is longer as the current rotation speed of the internal combustion engine is higher.

[0009] The prediction unit may predict that the required rise time is longer as the pressure difference between the current intake manifold pressure and the upper limit value increases.

[0010] The prediction unit may predict that the required rise time is longer as the upper limit value increases.

[0011] The calculation unit may calculate the target intake manifold pressure based on a rate of decrease in a rotation speed of the internal combustion engine and the rotation speed of the internal combustion engine predicted at the valve closing timing.

[0012] The calculation unit may calculate the target intake manifold pressure to be a lower value as the rotation speed of the internal combustion engine predicted at the valve closing timing is lower.

[0013] The calculation unit may calculate the target intake manifold pressure to be a lower value as the decrease rate increases.

[0014] The setting unit may set the upper limit value to a higher value as the vehicle speed of the vehicle increases. Effect of the Invention

[0015] According to the present invention, it is possible to provide a vehicle control device in which the variation in the stop position of an internal combustion engine is suppressed. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle. [Diagram 2] FIG. 2 is a schematic diagram of the engine. [Diagram 3] FIG. 3 is a timing chart showing an example of the stop position control. [Figure 4] FIG. 4 is a flowchart showing an example of the throttle control executed by the ECU. [Diagram 5] FIG. 5 is a timing chart showing an example of the case where the throttle opening is maintained at the opening A1. [Figure 6] FIG. 6 is a timing chart showing an example of a case where the throttle opening is switched to the opening A2. [Figure 7] FIG. 7 is an example of a map that defines the relationship between the vehicle speed and the upper limit value. [Figure 8] FIG. 8A is an example of a map that defines the relationship between the engine speed and the required rise time, and FIG. 8B is an example of a map that defines the relationship between the upper limit value and the required rise time. [Figure 9] FIG. 9 is an example of a map that defines the relationship between the engine speed and the target intake manifold pressure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] [General configuration of hybrid vehicle] FIG. 1 is a schematic diagram of a hybrid vehicle 1. In the hybrid vehicle 1, a K0 clutch 14, a motor 15, a torque converter 18, and a transmission 19 are provided in this order in a power transmission path from an engine 10 to drive wheels 13. The engine 10 and the motor 15 are mounted as a driving power source for the hybrid vehicle 1. The engine 10 is, for example, a V6 gasoline engine, but the number of cylinders is not limited thereto, and may be an in-line gasoline engine or a diesel engine. The K0 clutch 14, the motor 15, the torque converter 18, and the transmission 19 are provided in a transmission unit 11. The transmission unit 11 and the left and right drive wheels 13 are drivingly connected via a differential 12.

[0018] The K0 clutch 14 is provided between the engine 10 and the motor 15 on the power transmission path. The K0 clutch 14 is switched from a released state to an engaged state when hydraulic pressure is supplied, connecting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 is switched to a released state when the hydraulic pressure supply is stopped, cutting off the power transmission between the engine 10 and the motor 15. The engaged state is a state in which both engagement elements of the K0 clutch 14 are connected and the engine 10 and the motor 15 have the same rotation speed. The released state is a state in which both engagement elements of the K0 clutch 14 are separated.

[0019] The motor 15 is connected to the battery 16 via an inverter 17. The motor 15 functions as a motor that generates driving force for the vehicle in response to power supplied from the battery 16, and also functions as a generator that generates electric power to charge the battery 16 in response to power transmission from the engine 10 and the drive wheels 13. The electric power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

[0020] The inverter 17 is controlled by the ECU 100 described later, and converts the DC voltage from the battery 16 into an AC voltage, or converts the AC voltage from the motor 15 into a DC voltage. In the case of powering operation in which the motor 15 outputs torque, the inverter 17 converts the DC voltage of the battery 16 into an AC voltage and adjusts the power supplied to the motor 15. In the case of regenerative operation in which the motor 15 generates power, the inverter 17 converts the AC voltage from the motor 15 into a DC voltage and adjusts the power supplied to the battery 16.

[0021] The torque converter 18 is a fluid coupling having a torque amplifying function. The transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple stages by switching the gear stage, but is not limited thereto and may be a continuously variable automatic transmission. The transmission 19 is provided between the motor 15 and the driving wheels 13 on the power transmission path. The motor 15 and the transmission 19 are connected via the torque converter 18. The torque converter 18 is provided with a lock-up clutch 20 that is supplied with hydraulic pressure and is engaged to directly connect the motor 15 and the transmission 19.

[0022] The transmission unit 11 is further provided with an oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the oil pump 21 is supplied to the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with hydraulic circuits for the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20, and various hydraulic control valves for controlling the operating hydraulic pressures thereof. It should be noted that a wet clutch may be provided instead of the torque converter 18.

[0023] The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 100 as a control device for the vehicle. The ECU 100 is an electronic control unit including a calculation processing circuit that performs various calculation processes related to vehicle driving control, and a memory that stores control programs and data. The ECU 100 is an example of a vehicle control device, and functionally realizes a stop position control unit, a calculation unit, a setting unit, a throttle control unit, and a prediction unit, which will be described in detail later.

[0024] The ECU 100 controls the operation of the engine 10 and the motor 15. Specifically, the ECU 100 controls the torque and rotation speed of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. The ECU 100 controls the rotation speed and torque of the motor 15 by controlling the inverter 17 to adjust the amount of power exchanged between the motor 15 and the battery 16. The ECU 100 also controls the operation of the K0 clutch 14, the lock-up clutch 20, and the transmission 19 through the control of the hydraulic control mechanism 22.

[0025] The ECU 100 receives signals from an ignition switch 71, a crank angle sensor 72, a motor revolution speed sensor 73, a vehicle speed sensor 74, an air flow meter 75, a pressure sensor 76, and an atmospheric pressure sensor 77. The crank angle sensor 72 detects the revolution speed of the crankshaft of the engine 10, i.e., the engine revolution speed. The motor revolution speed sensor 73 detects the rotation speed of the output shaft of the motor 15. The vehicle speed sensor 74 detects the traveling speed of the hybrid vehicle 1. The air flow meter 75 detects the amount of intake air of the engine 10. The pressure sensor 76 detects the pressure in the intake passage 37 downstream of a throttle valve 40 (hereinafter referred to as intake manifold pressure) which will be described later. The atmospheric pressure sensor 77 detects the atmospheric pressure.

[0026] The ECU 100 runs the hybrid vehicle in either a motor mode or a hybrid mode. In the motor mode, the ECU 100 releases the K0 clutch 14 and runs the vehicle using the power of the motor 15. In the hybrid mode, the ECU 100 switches the K0 clutch 14 to an engaged state and runs the vehicle using at least the power of the engine 10. The hybrid mode includes a mode in which the vehicle runs using only the power of the engine 10, and a mode in which the motor 15 is powered and the vehicle runs using both the engine 10 and the motor 15 as power sources.

[0027] The driving mode is switched based on the vehicle's required driving force calculated from the vehicle speed and accelerator opening, and the state of charge of the battery 16. For example, when the required driving force is relatively small and the SOC (State Of Charge) indicating the amount of charge in the battery 16 is relatively high, the motor mode in which the engine 10 is stopped is selected to improve fuel efficiency. When the required driving force is relatively large or the SOC of the battery 16 is relatively low, the hybrid mode in which the engine 10 is driven is selected.

[0028] The ECU 100 executes intermittent operation control to automatically stop the engine 10 when a predetermined stop condition is satisfied, and to restart the automatically stopped engine 10 when a predetermined restart condition is satisfied. For example, when the accelerator opening becomes zero in the hybrid mode, the ECU 100 automatically stops the engine 10, assuming that the automatic stop condition is satisfied. Also, when the accelerator opening becomes greater than zero, for example, the ECU 100 automatically restarts the engine 10, assuming that the restart condition is satisfied. In the case of automatic stop, the ECU 100 releases the K0 clutch 14 to stop combustion. In the case of automatic restart, the ECU 100 cranks the engine 10 by the motor 15 via the K0 clutch 14 to start combustion, and then engages the K0 clutch 14. Also, when the engine 10 is automatically stopped and the engine 10 is coasting, if the accelerator opening increases again and the restart condition is satisfied, combustion starts and the K0 clutch 14 is engaged.

[0029] [Engine outline] FIG. 2 is a schematic diagram of the engine 10. The engine 10 has cylinders 30, pistons 31, connecting rods 32, a crankshaft 33, an intake passage 35, an intake valve 36, an exhaust passage 37, and an exhaust valve 38. FIG. 2 shows only one of the multiple cylinders 30 of the engine 10. An air-fuel mixture is burned in the cylinder 30. A piston 31 is accommodated in each cylinder 30 so as to be capable of reciprocating, and is connected to a crankshaft 33, which is an output shaft of the engine 10, via a connecting rod 32. The connecting rod 32 converts the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

[0030] The intake passage 35 is connected to the intake port of each cylinder 30 via an intake valve 36. The exhaust passage 37 is connected to the exhaust port of each cylinder 30 via an exhaust valve 38. An air flow meter 75, a pressure sensor 76, and a throttle valve 40 that adjusts the amount of intake air are provided in the intake passage 35. A catalyst 43 for purifying exhaust gas is provided in the exhaust passage 37.

[0031] Each cylinder 30 is provided with an in-cylinder injection valve 41. The in-cylinder injection valve 41 injects fuel directly into the cylinder 30. Note that instead of or in addition to the in-cylinder injection valve 41, a port injection valve that injects fuel toward an intake port may be provided. Each cylinder 30 is provided with an ignition device 42 that ignites a mixture of intake air introduced through the intake passage 35 and fuel injected by the in-cylinder injection valve 41 by spark discharge.

[0032] [Engine stop position control] During coasting rotation in which combustion in the engine 10 has stopped, a stop position control is executed to control the stop position of the engine 10 by temporarily increasing and then decreasing the throttle opening. In detail, the stop position control is a control for increasing the compression torque to set the stop position of the engine 10 to a desired stop position by ensuring the amount of intake air filled in a predetermined cylinder 30 during coasting rotation of the engine 10. By setting the stop position of the engine 10 to a desired stop position, the cranking torque of the engine 10 required of the motor 15 when restarting the engine 10 can be reduced. For this reason, when restarting the engine 10 while traveling in the motor mode, for example, the portion of the output torque of the motor 15 consumed by the cranking torque is suppressed. As a result, the torque consumed for traveling of the hybrid vehicle 1 out of the output torque of the motor 15 can be secured, and the operating range in which the hybrid vehicle 1 can travel in the motor mode can be secured, thereby improving fuel efficiency.

[0033] FIG. 3 is a timing chart showing an example of the stop position control of the engine 10. FIG. 3 shows the transition of the engine speed [rpm], the throttle opening [deg], and the intake manifold pressure [kPa]. The combustion of the engine 10 is stopped, and the throttle opening is controlled to the opening A1, and the engine speed decreases (time t1). The opening A1 is a value close to 0 and may be 0. Next, the throttle opening increases from the opening A1 to the opening A2 at a predetermined timing (time t2), and the throttle opening is maintained at the opening A2 for a predetermined time. The opening A2 is a value closer to the maximum opening than 0. Next, the throttle opening decreases from the opening A2 to the opening A3 (time t3). The opening A3 is a value close to 0 and may be 0. Due to such a temporary increase in the throttle opening, intake air is introduced into the intake passage 35 downstream of the throttle valve 40, and the intake manifold pressure increases to a value close to the target intake manifold pressure (time t4). The target intake manifold pressure is a target value of the intake manifold pressure suitable for stopping the engine 10. The target intake manifold pressure will be described in detail later.

[0034] Next, the intake valve 36 of the cylinder 30 in the intake stroke closes, and a part of the intake air introduced downstream of the throttle valve 40 is filled into the cylinder 30 (time t5). Next, the intake valve 36 of the cylinder 30 in the intake stroke closes, and a part of the intake air is filled into the cylinder 30 (time t6). The higher the intake manifold pressure when the intake valve 36 closes, the greater the amount of intake air filled into the cylinder 30. After that, the piston 31 of the cylinder 30 filled with intake air first is in the expansion stroke, and the piston 31 of the cylinder 30 filled with intake air next is in the compression stroke, and the rotation of the engine 10 stops (time t7). Here, the cylinder 30 in which the piston 31 stops in the expansion stroke is called an expansion stroke stopped cylinder, and the cylinder 30 in which the piston 31 stops in the compression stroke is called a compression stroke stopped cylinder. After that, the intake manifold pressure returns to atmospheric pressure (time t8).

[0035] As a result, the engine 10 stops at a position where the compression reaction forces of the intake air charged in the expansion stroke stopped cylinder and the compression stroke stopped cylinder are balanced. As a result, when the engine 10 is restarted, cranking of the engine 10 is started by the motor 15 via the K0 clutch 14, and combustion can be started from the compression stroke stopped cylinder, ensuring restartability. The stop position control is an example of a process executed by the stop position control unit.

[0036] [Throttle Control] Next, the throttle control executed in the stop position control will be described. Fig. 4 is a flow chart showing an example of the throttle control executed by the ECU 100. This control is executed repeatedly at predetermined intervals with the ignition on. The ECU 100 judges whether or not the stop position control of the engine 10 is being executed (step S1). If the answer is No in step S1, this control ends.

[0037] If the answer is Yes in step S1, the ECU 100 sets an upper limit value and a lower limit value (step S2). The upper limit value is set to a value lower than the atmospheric pressure detected by the atmospheric pressure sensor 77. The lower limit value is set to a value lower than the upper limit value. The setting of the upper limit value and the lower limit value will be described in detail later. Step S2 is an example of a process executed by the setting unit.

[0038] Next, the ECU 100 predicts the required rise time required for the intake manifold pressure to rise to the upper limit value if the throttle opening is increased from A1 to A2 and maintained at A2 for a predetermined time (step S3). The prediction of the required rise time will be described in detail later. Step S3 is an example of a process executed by the prediction unit.

[0039] Next, the ECU 100 calculates a target intake manifold pressure at the closing timing of the intake valve 36 immediately after the required rise time has elapsed from the current time (step S4). The target intake manifold pressure is a target value of the intake manifold pressure that can stop the inertial rotation of the engine 10, as will be described in detail later. Step S4 is an example of a process executed by the calculation unit.

[0040] Next, the ECU 100 determines whether the target intake manifold pressure is equal to or lower than the upper limit and equal to or higher than the lower limit (step S5). If the answer is No in step S5, the ECU 100 maintains the throttle opening at A1 (step S6). If the answer is Yes in step S5, the ECU 100 maintains the throttle opening at A2 for a predetermined time so that the intake manifold pressure becomes the target intake manifold pressure (step S7). Next, the ECU 100 maintains the throttle opening at A3 (step S8).

[0041] Next, a case where the throttle opening is maintained at the opening A1 in the stop position control will be described. FIG. 5 is a timing chart supporting an example of a case where the throttle opening is maintained at the opening A1. FIG. 5 shows the closing timings C1, C2, and C3 of the intake valves 36 of each of the cylinders 30. The ECU 100 grasps the crank angle corresponding to the closing timing of the intake valves 36 of each cylinder 30, such as the closing timing C1. In the example of FIG. 5, the closing timing C1 immediately before the current time t11 is within the required rise time, so the target intake manifold pressure at the closing timing C1 is not calculated, and the target intake manifold pressure at the closing timing C2 immediately after the time t12 when the required rise time has elapsed is calculated (step S4). In the example of FIG. 5, the target intake manifold pressure is higher than the upper limit, so the result of the determination in step S5 at the current time t11 is No, and the throttle opening is maintained at the opening A1 (step S6).

[0042] Next, a case where the throttle opening is switched from the opening A1 to the opening A2 in the stop position control will be described. FIG. 6 is a timing chart showing an example of a case where the throttle opening is switched to the opening A2. The target intake manifold pressure at the valve closing timing C3 immediately after the time t22 when the required increase time has elapsed from the current time t21 is calculated (step S4). In the example of FIG. 6, since the target intake manifold pressure is between the upper limit and the lower limit, the result of the determination in step S5 is Yes at the current time t21, and the throttle opening is maintained at the opening A2 for a predetermined time so that the intake manifold pressure becomes the target intake manifold pressure (step S7). As a result, the intake manifold pressure rises to a level close to the target intake manifold pressure at the valve closing timing C3, and the intake amount of the cylinder 30 corresponding to each of the valve closing timings C3 and C4 can be secured to a degree that allows the inertial rotation of the engine 10 to be stopped. The valve closing timings C3 and C4 correspond to the expansion stroke stop cylinder and the compression stroke stop cylinder described above.

[0043] As described above, the timing at which the throttle opening increases from A1 to A2 is set to the point at which the target intake manifold pressure is equal to or lower than the upper limit and equal to or higher than the lower limit. This makes it possible to suppress the variation in the intake manifold pressure when the intake valve 36 of the expansion stroke stop cylinder is closed, and thus the variation in the intake air charge amount in the expansion stroke stop cylinder. Similarly, it is possible to suppress the variation in the intake manifold pressure when the intake valve 36 of the compression stroke stop cylinder is closed, and thus the variation in the intake air charge amount in the compression stroke stop cylinder. This also suppresses the variation in the compression torque that stops the inertial rotation of the engine 10, and thus the variation in the stop position of the engine 10.

[0044] [How to set the upper limit] Next, a method for setting the upper limit value will be described. Fig. 7 is an example of a map that specifies the relationship between the vehicle speed and the upper limit value. The horizontal axis indicates the vehicle speed [km / h], and the vertical axis indicates the upper limit value [kPa]. This map is created in advance based on experimental results, etc., and is stored in the memory of the ECU 100. The ECU 100 refers to this map and sets the upper limit value based on the vehicle speed detected by the vehicle speed sensor 74. As shown in Fig. 7, the upper limit value is set to a higher value as the vehicle speed increases.

[0045] Here, the higher the upper limit value, the higher the target intake manifold pressure is calculated as. However, the higher the intake manifold pressure, the greater the amount of air charged in each of the expansion stroke stop cylinders and the compression stroke stop cylinders, and the greater the compression torque of the engine 10 during coasting. This may increase the vibration of the engine 10, causing discomfort to the occupants. However, when the vehicle speed is high, the occupants are less likely to feel such vibration of the engine 10. For this reason, by setting the upper limit value to a higher value as the vehicle speed increases, the coasting rotation of the engine 10 can be stopped early within a range that does not cause discomfort to the occupants. The upper limit value is set to a value at least lower than the atmospheric pressure regardless of the vehicle speed. This is because the intake manifold pressure cannot be made higher than the atmospheric pressure.

[0046] In addition, the upper limit value specified in the map of Fig. 7 is set not to be too high, taking restartability into consideration. If the upper limit value is too high, even if it is below atmospheric pressure, the amount of intake air charged into the expansion stroke stopped cylinder or the compression stroke stopped cylinder will be too large. This is because, when restarting the engine 10 immediately after it is stopped or while it is rotating by inertia, the compression torque will be too high, which may impair restartability.

[0047] 7, the upper limit value changes linearly with respect to the vehicle speed, but the present invention is not limited to this and may change in a curved manner. Also, the upper limit value may be calculated by an arithmetic expression that uses the vehicle speed as an argument.

[0048] [How to set the lower limit] The lower limit is set to a value lower than the atmospheric pressure by a predetermined value. The lower limit is set not to be too low, taking into consideration variations in the stop position and the restartability of the engine 10. If the lower limit is too low, the target intake manifold pressure is also calculated as a low value, which may reduce the compression torque and cause variations in the stop position of the engine 10. In addition, when the engine 10 is restarted, combustion starts from a cylinder that is stopped during the compression stroke. If the lower limit is too low, the amount of intake air charged in the cylinder that is stopped during the compression stroke cannot be secured, which may cause a decrease in restartability.

[0049] [How to predict the time required for ascent] A method for predicting the required rise time will be described. FIG. 8A is an example of a map that specifies the relationship between the engine speed and the required rise time. The horizontal axis indicates the engine speed [rpm], and the vertical axis indicates the required rise time [ms]. This map is created in advance based on experimental results, etc., and is stored in the memory of the ECU 100. The ECU 100 refers to this map and predicts the required rise time based on the engine speed detected by the crank angle sensor 72. As shown in FIG. 8A, the required rise time becomes longer as the engine speed increases. This is because the intake manifold pressure in a state in which the throttle opening is maintained at opening A1 is lower when the engine speed is high than when it is low.

[0050] 8A also shows cases where the differential pressure between the intake manifold pressure detected by pressure sensor 76 and the upper limit value is large and small. The required rise time is longer when this differential pressure is large than when it is small. Note that the intake manifold pressure detected by pressure sensor 76 refers to the intake manifold pressure detected by pressure sensor 76 at the current time when the required rise time is predicted. In other words, it is the intake manifold pressure when the throttle opening is maintained at opening A1.

[0051] FIG. 8B is an example of a map that specifies the relationship between the upper limit value and the required rise time. The horizontal axis indicates the upper limit value [kPa], and the vertical axis indicates the required rise time [ms]. ECU 100 also refers to this map to predict the required rise time based on the upper limit value. As shown in FIG. 8B, the required rise time becomes longer as the upper limit value becomes closer to atmospheric pressure. This is because the closer the intake manifold pressure rises to atmospheric pressure, the slower the rise rate of the intake manifold pressure becomes, and the longer the time required for the intake manifold pressure to rise to the upper limit value becomes.

[0052] 8A and 8B, the required rise time varies linearly with respect to the engine speed and the upper limit, but is not limited thereto and may vary curvedly. Also, the required rise time may be calculated by an arithmetic expression using the engine speed, the differential pressure, and the upper limit as arguments.

[0053] [How to calculate target intake manifold pressure] Next, a method for calculating the target intake manifold pressure will be described. As described above, the target intake manifold pressure is a target value of the intake manifold pressure that can stop the inertial rotation of the engine 10. During the inertial rotation of the engine 10, the inertial torque IT, friction torque FT, and compression torque CT of the engine 10 satisfy the following relationships. IT>FT+CT…(1)

[0054] The inertia torque IT indicates the torque in the forward rotation direction of the engine 10. The friction torque FT and the compression torque CT indicate the torque in the reverse rotation direction of the engine 10. The inertia torque IT is proportional to the engine speed, and the lower the engine speed, the lower the inertia torque IT. The friction torque FT is proportional to the rate of decrease in the engine speed, and the greater the rate of decrease in the engine speed, the greater the friction torque FT. The compression torque CT increases as the intake air filling amount of each of the expansion stroke stop cylinder and the compression stroke stop cylinder increases. Here, the intake air filling amount of each of the expansion stroke stop cylinder and the compression stroke stop cylinder increases as the intake manifold pressure at the closing timing of the intake valve 36 increases. In other words, the higher the intake manifold pressure at the closing timing of the intake valve 36, the greater the compression torque CT.

[0055] The freewheeling of the engine 10 will stop when the following equation is true: IT-FT=CT…(2) Therefore, the ECU 100 calculates the intake manifold pressure when the formula (2) is satisfied as the target intake manifold pressure. Specifically, the ECU 100 calculates the target intake manifold pressure by referring to the following map. FIG. 9 is an example of a map that specifies the relationship between the engine speed and the target intake manifold pressure. The horizontal axis indicates the engine speed [rpm], and the vertical axis indicates the target intake manifold pressure [kPa]. FIG. 9 also shows a case where the engine speed reduction rate is small and a case where the engine speed reduction rate is large. The target intake manifold pressure shown in FIG. 9 satisfies the relationship of the above formula (2). As shown in FIG. 9, the lower the engine speed, the lower the target intake manifold pressure is calculated. This is because, as described above, the lower the engine speed, the lower the inertia torque IT is, and the smaller the compression torque CT is when the above formula (2) is satisfied. As shown in FIG. 9, the higher the engine speed reduction rate, the lower the target intake manifold pressure is calculated. As described above, the greater the rate of decrease in engine speed, the greater the friction torque FT, and therefore the smaller the compression torque CT when the above formula (2) is satisfied.

[0056] For example, in the example shown in Fig. 5, the engine speed R2 at the valve closing timing C2 is predicted based on the engine speed R1 at the current time t11 and the rate of decrease in the engine speed. The rate of decrease in the engine speed is calculated based on the amount of change in the engine speed per unit time, and the engine speed R2 at the valve closing timing C2 is predicted assuming that the rate of decrease in the engine speed is constant. The ECU 100 calculates the target intake manifold pressure based on the engine speed R2 and the rate of decrease by referring to the map in Fig. 9. In the example shown in Fig. 5, the target intake manifold pressure is calculated to be a value higher than the upper limit.

[0057] Similarly, in the example shown in Fig. 6, the engine speed R3 at the valve closing timing C3 is predicted based on the engine speed R1a at the current time t21 and the rate of decrease in the engine speed. The ECU 100 calculates the target intake manifold pressure based on the engine speed R3 and the rate of decrease by referring to the map in Fig. 9. In the example shown in Fig. 6, the target intake manifold pressure is calculated as a value between an upper limit value and a lower limit value.

[0058] 9, the target intake manifold pressure changes linearly with respect to the engine speed, but the present invention is not limited to this and may change in a curved manner. The target intake manifold pressure may be calculated by an arithmetic expression that uses the engine speed and the rate of decrease in the engine speed as arguments.

[0059] Although a lower limit value is set in step S2, it is not necessarily limited to this and it is not necessary to set a lower limit value. If the throttle opening can be increased immediately when the target intake manifold pressure becomes equal to or lower than the upper limit value, it is possible to suppress the variation in the intake air charge amount in the expansion stroke stopped cylinder and the compression stroke stopped cylinder, and thus the variation in the stop position.

[0060] In the above embodiment, a hybrid vehicle is controlled by a single ECU 100, but this is not limited to the above. The above-mentioned control may be performed by multiple ECUs, such as an engine ECU that controls the engine 10, a motor ECU that controls the motor 15, and a clutch ECU that controls the K0 clutch 14.

[0061] In the above embodiment, the hybrid vehicle 1 has been described as an example, but the invention is not limited to this. For example, the stop position control of the present embodiment can be applied to an engine vehicle that is provided with only an engine as a driving power source and in which the engine is automatically stopped and automatically restarted by an idling stop function.

[0062] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0063] 1 Hybrid vehicle (vehicle) 10 Engine (internal combustion engine) 40 Throttle valve 100 ECU (vehicle control device, stop position control unit, calculation unit, setting unit, throttle control unit, prediction unit)

Claims

1. In a control device for a vehicle equipped with an internal combustion engine as a driving power source, a stop position control unit that executes a stop position control of the internal combustion engine by temporarily increasing and then decreasing a throttle opening of the internal combustion engine during inertial rotation in which combustion of the internal combustion engine has stopped; a calculation unit that calculates a target intake manifold pressure, which is a pressure in an intake passage downstream of a throttle valve of the internal combustion engine, during execution of the stop position control, at which inertial rotation of the internal combustion engine can be stopped; A setting unit that sets an upper limit value that is lower than atmospheric pressure; a throttle control unit that increases the throttle opening degree so that the intake manifold pressure rises to the target intake manifold pressure when the target intake manifold pressure becomes equal to or lower than the upper limit value during execution of the stop position control; a prediction unit that predicts a required rise time required for the intake manifold pressure to rise to the upper limit value after the throttle opening degree is increased, The control device for a vehicle, wherein the calculation unit calculates the target intake manifold pressure at a closing timing of an intake valve of the internal combustion engine immediately after the required rise time has elapsed from a current time point.

2. The vehicle control device according to claim 1 , wherein the prediction unit predicts the required rise time to be longer as the current rotation speed of the internal combustion engine is higher.

3. 3. The control device for a vehicle according to claim 1, wherein the prediction unit predicts the required rise time to be longer as a difference in pressure between the current intake manifold pressure and the upper limit value increases.

4. The vehicle control device according to claim 1 , wherein the prediction unit predicts the required rise time to be longer as the upper limit value increases.

5. 5. The control device for a vehicle according to claim 1, wherein the calculation unit calculates the target intake manifold pressure based on a rate of decrease in a rotation speed of the internal combustion engine and a rotation speed of the internal combustion engine predicted at the valve closing timing.

6. The control device for a vehicle according to claim 5 , wherein the calculation unit calculates the target intake manifold pressure to be a lower value as the rotation speed of the internal combustion engine predicted at the valve closing timing decreases.

7. The control device for a vehicle according to claim 5 or 6, wherein the calculation unit calculates the target intake manifold pressure to be a lower value as the decrease rate increases.

8. The vehicle control device according to claim 1 , wherein the setting unit sets the upper limit value to a higher value as the vehicle speed of the vehicle increases.

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