The disclosure of Japanese Patent Application No. 2016-075102 filed on Apr. 4, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Technical Field
The present disclosure relates to a vehicle control apparatus and a vehicle control method that can stop a crankshaft at a desired position when an engine stops.
2. Description of Related Art
Japanese Patent Application Publication No. 2011-219019 (JP 2011-219019 A) discloses a vehicle control apparatus that can stop a crankshaft with a crank angle equal to a target angle when an engine stops. The vehicle control apparatus described in Japanese Patent Application Publication No. 2011-219019 (JP 2011-219019 A) controls a motor such that a torque capable of stopping the crankshaft with the crank angle equal to the target angle is output from the motor to the crankshaft.
A vehicle control apparatus performs feedback control of a motor based on a difference between a current crank angle and a target angle, with a view to stopping a crankshaft with a crank angle equal to a target angle. In concrete terms, the vehicle control apparatus performs feedback control of the motor in such a manner as to output a torque that counterbalances an inertial force in a positive rotational direction of the crankshaft (i.e., a torque that acts in a negative rotational direction), based on the difference between the current crank angle and the target angle. As a result, the vehicle control apparatus stops the crankshaft that rotates in the positive rotational direction, with the crank angle equal to the target angle. It should be noted herein that when the response speed of feedback control is an ideal response speed (e.g., the response delay is equal to zero), the vehicle control apparatus can stop the crankshaft with the crank angle remaining equal to the target angle instead of exceeding the target angle. In reality, however, it is difficult to make the response speed of feedback control equal to the ideal response speed. Therefore, there may arise a situation where the crank angle becomes larger than the target angle because the inertial force in the positive rotational direction of the crankshaft cannot be counterbalanced even at a time point when the crank angle becomes equal to the target angle, as a result of the responsiveness of feedback control. That is, a so-called overshoot of the crank angle in the positive rotational direction with respect to the target angle may occur.
This overshoot of the crank angle can be a cause of the following state when an attempt is made to stop the crankshaft under the circumstances where valves that control the flow of air out of/into an engine (i.e., an intake valve and an exhaust valve) are in a closed-valve state.
In concrete terms, when the crank angle becomes larger than the target angle, the vehicle control apparatus controls the motor in such a manner as to output a torque capable of returning the crank angle, which has become larger than the target angle, toward the target angle by rotating the crankshaft in the negative rotational direction. It should be noted, however, that the valves of the engine are in the closed-valve state. Therefore, the pressure of the air in a cylinder has risen by a value corresponding to the overshoot amount of the crank angle. In this case, the pressure of the air in the cylinder acts on a piston as soon as the inertial force in the positive rotational direction of the crankshaft is counterbalanced. As a result, the crankshaft can rotate in the negative rotational direction as a matter of course. Accordingly, the vehicle control apparatus controls the motor in such a manner as to output a torque capable of rotating the crankshaft in the positive rotational direction, with a view to returning the crank angle toward the target angle by controlling the amount of rotation of the crankshaft in the negative rotational direction resulting from the pressure of the air in the cylinder.
Even under the circumstances where the crank angle that has become larger than the target angle is returned toward the target angle, there may arise a situation where the crank angle becomes smaller than the target angle because the crankshaft is not stopped from rotating in the negative rotational direction at a timing when the crank angle becomes equal to the target angle, as a result of the responsiveness of feedback control. That is, an overshoot of the crank angle in the negative rotational direction with respect to the target angle occurs. In this case, the vehicle control apparatus controls the motor in such a manner as to output a torque capable of returning the crank angle, which has become smaller than the target angle, toward the target angle by rotating the crankshaft in the positive rotational direction. As a result, the crankshaft stops with the crank angle equal to the target angle.
It should be noted that the possibility of the occurrence of a situation where the crank angle becomes smaller than the target angle increases as the rotation amount of the crankshaft in the negative rotational direction for returning the crank angle, which has become larger than the target angle, toward the target angle increases. In particular, the possibility of the overshoot amount of the crank angle in the negative rotational direction with respect to the target angle becoming large increases as the rotation amount of the crankshaft in the negative rotational direction increases. The rotation amount of the crankshaft in the positive rotational direction for returning the crank angle, which has become smaller than the target angle, toward the target angle also increases as the overshoot amount of the crank angle in the negative rotational direction with respect to the target angle increases. As a result, the force that is exerted on the piston by the air in the cylinder when the crankshaft is stopped (substantially the pressure of the air in the cylinder) also increases as the rotation amount of the crankshaft in the positive rotational direction immediately before the stop of the crankshaft increases. For example, in the case where the crankshaft rotates in such a manner as to compress the air in the cylinder immediately before stopping, the force with which the air in the cylinder pushes out the piston (substantially the positive pressure of the air in the cylinder) becomes large. For example, in the case where the crankshaft rotates in such a manner as to expand the air in the cylinder immediately before stopping, the force with which the air in the cylinder pulls the piston (substantially the negative pressure of the air in the cylinder) becomes large.
In the case where the crankshaft has stopped under the circumstances where the force that is exerted on the piston by this air in the cylinder is relatively large, the piston may move (i.e., the crankshaft may move) as a result of the pressure of the air in the cylinder after a torque is stopped from being output from the motor due to the stop of the crankshaft. As a result, it may be difficult to stop the crankshaft with the crank angle equal to the target angle.
The disclosure provides a vehicle control apparatus and a vehicle control method that can stop a crankshaft with a crank angle equal to a target angle even in the case where an overshoot of the crank angle with respect to the target angle occurs as a result of the responsiveness of feedback control before stopping the crankshaft.
A first aspect of the disclosure is a vehicle control apparatus for a vehicle. The vehicle includes an engine and a motor. The engine includes at least one cylinder, a valve and a crankshaft. The valve is configured to control flow of air out of and into the at least one cylinder. The motor is configured to adjust a crank angle of the crankshaft by outputting a torque to the crankshaft. The vehicle control apparatus includes an electronic control unit. The electronic control unit is configured to perform feedback control of the motor, during stop control of the engine, based on the crank angle such that the torque is output for stopping the crankshaft at a target angle corresponding to the crank angle at which the valve is in a closed-valve state. The electronic control unit is configured to detect a rotational direction of the crankshaft. The electronic control unit is configured to use a first angle as the target angle during a first period. The first period is a period from start of the feedback control to a timing of first detection of rotation of the crankshaft in a negative rotational direction for returning the crank angle, which has become larger than the target angle, toward the target angle. The first angle corresponding to the crank angle at which the valve is in the closed-valve state. The electronic control unit is configured to use a second angle as the target angle during a second period. The second period is a period from lapse of the first period to a timing of detection of a changeover in a rotational direction of the crankshaft from the negative rotational direction to a positive rotational direction. The second angle is larger than the first angle. The electronic control unit is configured to return the target angle from the second angle to the first angle at a first timing. The first timing is a timing when the crank angle, that has become smaller than the first angle during the second period, becomes equal to or larger than the first angle after lapse of the second period.
In the vehicle control apparatus, the electronic control unit may be configured to use the second angle as the target angle during a third period. The third period may be a period from a timing of second detection of rotation of the crankshaft in the negative rotational direction for returning the crank angle, which has become larger than the target angle for the second time after returning the target angle to the first angle, toward the target angle to a timing of detection of a changeover in the rotational direction of the crankshaft from the negative rotational direction to the positive rotational direction. The electronic control unit may be configured to return the target angle from the second angle to the first angle at a second timing. The second timing may be a timing when the crank angle, which has become smaller than the first angle during the third period, becomes equal to or larger than the first angle after lapse of the third period.
In the vehicle control apparatus, the electronic control unit may be configured to use the second angle as the target angle during the second period. The second angle may gradually increase from the first angle and then gradually decrease toward the first angle.
In the vehicle control apparatus, the first angle may be the crank angle in a latter half of a compression stroke.
A second aspect of the disclosure is a vehicle control apparatus for a vehicle. The vehicle includes an engine and a motor. The engine includes at least one cylinder, a valve and a crankshaft. The valve is configured to control flow of air out of and into the at least one cylinder. The motor is configured to adjust a crank angle of the crankshaft by outputting a torque to the crankshaft. The vehicle control apparatus includes an electronic control unit. The electronic control unit is configured to perform feedback control of the motor, during stop control of the engine, based on the crank angle such that the torque is output for stopping the crankshaft at a target angle corresponding to the crank angle at which the valve is in a closed-valve state. The electronic control unit is configured to detect a rotational direction of the engine. The electronic control unit is configured to use a first gain, during a first period, as a motor gain that prescribes a magnitude of the torque. The first period is a period from start of the feedback control to a timing of first detection of rotation of the crankshaft in a negative rotational direction for returning the crank angle, which has become larger than the target angle, toward the target angle. The electronic control unit is configured to use a second gain as the motor gain during a second period. The second period is a period from lapse of the first period to a timing of detection of a changeover in a rotational direction of the crankshaft from the negative rotational direction to a positive rotational direction. The second gain is a gain that prescribes a larger torque in the positive rotational direction than the first gain. The electronic control unit is configured to return the motor gain from the second gain to the first gain at a first timing. The first timing is a timing when the crank angle, which has become smaller than the target angle during the second period, becomes equal to or larger than the target angle after lapse of the second period.
In the vehicle control apparatus, the electronic control unit may be configured to use the second gain as the motor gain during a third period. The third period may be a period from a timing of second detection of rotation of the crankshaft in the negative rotational direction for returning the crank angle, which has become larger than the target angle for the second time after returning the motor gain to the first gain, toward the target angle to a timing of detection of a changeover in the rotational direction of the crankshaft from the negative rotational direction to the positive rotational direction. The electronic control unit may be configured to return the motor gain from the second gain to the first gain at a second timing. The second timing may be a timing when the crank angle, which has become smaller than the target angle during the third period, becomes equal to or larger than the target angle after lapse of the third period.
In the vehicle control apparatus, the electronic control unit may be configured to use the second gain as the motor gain during the second period. The second gain may be a gain that gradually increases from the first gain and then gradually decreases toward the first gain. The second gain may be a gain that gradually decreases from the first gain and then gradually increases toward the first gain.
In the vehicle control apparatus, the target angle may be the crank angle in a latter half of a compression stroke.
A third aspect of the disclosure is a vehicle control method for a vehicle. The vehicle includes an engine and a motor. The engine includes at least one cylinder, a valve and a crankshaft. The valve is configured to control flow of air out of and into the at least one cylinder. The motor is configured to adjust a crank angle of the crankshaft by outputting a torque to the crankshaft. The vehicle control method includes: performing feedback control of the motor, during stop control of the engine, based on the crank angle such that the torque is output for stopping the crankshaft with the crank angle equal to a target angle corresponding to the crank angle at which the valve is in a closed-valve state; using a first angle as the target angle during a first period; using a second angle as the target angle during a second period; and returning the target angle from the second angle to the first angle at a first timing. The first period is a period from start of the feedback control to a timing of first detection of rotation of the crankshaft in a negative rotational direction for returning the crank angle, which has become larger than the target angle, toward the target angle. The first angle is corresponding to the crank angle at which the valve is in the closed-valve state. The second period is a period from lapse of the first period to a timing detection of a changeover in a rotational direction of the crankshaft from the negative rotational direction to a positive rotational direction. The second angle is larger than the first angle. The first timing is a timing when the crank angle, which has become smaller than the first angle during the second period, becomes equal to or larger than the first angle after lapse of the second period.
A fourth aspect of the disclosure is a vehicle control method for a vehicle. The vehicle includes an engine and a motor. The engine includes at least one cylinder, a valve and a crankshaft. The valve is configured to control flow of air out of and into the at least one cylinder. The motor is configured to adjust a crank angle of the crankshaft by outputting a torque to the crankshaft. The vehicle control method includes: performing feedback control of the motor, during stop control of the engine, based on the crank angle such that the torque is output for stopping the crankshaft at a target angle corresponding to the crank angle at which the valve is in a closed-valve state; using a first gain, during a first period, as a motor gain that prescribes a magnitude of the torque; using a second gain as the motor gain during a second period; and returning the motor gain from the second gain to the first gain at a first timing. The first period is a period from start of the feedback control to a timing of first detection of rotation of the crankshaft in a negative rotational direction for returning the crank angle, which has become larger than the target angle, toward the target angle. The second period is a period from lapse of the first period to a timing of detection of a changeover in a rotational direction of the crankshaft from the negative rotational direction to a positive rotational direction. The second gain is a gain that prescribes a larger torque in the positive rotational direction than the first gain. The first timing is a timing when the crank angle, which has become smaller than the target angle during the second period, becomes equal to or larger than the target angle after lapse of the second period.
Features, advantages, and technical and industrial significance of an exemplary embodiment will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
A vehicle control apparatus according to the embodiment of the disclosure will be described hereinafter with reference to the drawings.
First of all, the configuration of a vehicle 1 according to the present embodiment will be described with reference to the block diagram of
The engine 11 is driven through the combustion of fuel such as gasoline, light oil or the like. The engine 11 functions as a main motive power source of the vehicle 1. A crank angle sensor 111 is attached to the engine 11. The crank angle sensor 111 detects a crank angle θc of a crankshaft of the engine 11. The crank angle sensor 111 outputs the detected crank angle θc to the ECU 19.
The motor-generator 12 functions as a generator for charging the battery 14. In the case where the motor-generator 12 functions as a generator, a rotary shaft of the motor-generator 12 rotates through the motive power of the engine 11. In addition, the motor-generator 12 can rotate the crankshaft by being driven through the use of the electric power that is supplied from the battery 14 via the inverter 15. The motor-generator 12 mainly outputs a torque Tm to the crankshaft such that the crankshaft stops (i.e., the engine 11 stops) with the crank angle θc equal to a target stop angle θtgt, in stopping the engine 11.
A rotational speed sensor 121 is attached to the motor-generator 12. The rotational speed sensor 121 detects a rotational speed of the motor-generator 12 (hereinafter referred to as “a motor rotational speed”) Nm. The rotational speed sensor 121 outputs the detected motor rotational speed Nm to the ECU 19.
The motor-generator 13 functions as an electric motor that supplies a motive power of the vehicle 1, by being driven through the use of the electric power that is supplied from the battery 14 via the inverter 15.
The battery 14 is an electric power supply source that supplies each of the motor-generators 12, 13 with an electric power for driving each of the motor-generators 12, 13. The battery 14 is a rechargeable storage battery.
The inverter 15 converts a DC electric power taken out from the battery 14 into an AC electric power, and supplies this AC electric power to each of the motor-generators 12, 13. Furthermore, the inverter 15 converts an AC electric power generated by the motor-generator 12 into a DC electric power, and supplies this DC electric power to the battery 14.
The motive power split mechanism 16 is a planetary gear mechanism that is equipped with a sun gear (not shown), a planetary carrier (not shown), a pinion gear (not shown) and a ring gear (not shown). A rotary shaft of the sun gear is coupled to the rotary shaft of the motor-generator 12. A rotary shaft of the ring gear is coupled to the axle 17 that transmits a driving force to the wheels 18. Furthermore, the axle 17 is coupled to a rotary shaft of the motor-generator 13 via a reduction gear (not shown). A rotary shaft of the planetary carrier, which is located between the sun gear and the ring gear, is coupled to the crankshaft. Rotation of the engine 11 is transmitted to the sun gear and the ring gear by the planetary carrier and the pinion gear. That is, the motive power of the engine 11 is distributed to two systems.
The ECU 19 is configured to be able to control the entire operation of the vehicle 1. In the present embodiment, the ECU 19 carries out a crank stop operation in particular. The crank stop operation is an operation of controlling the motor-generator 12 in such a manner as to output, to the crankshaft, the torque Tm capable of stopping the crankshaft with the crank angle θc equal to the target stop angle θtgt, in stopping the engine 11.
In order to carry out the crank stop operation, the ECU 19 is equipped with a rotation detection unit 191 and a motor control unit 192, as logical or physical processing blocks that are realized therein. The rotation detection unit 191 detects a rotational direction of the crankshaft, based on the crank angle θc that is output by the crank angle sensor 111. The motor control unit 192 generates a torque command value Ttgt indicating a target value of the torque Tm based on a detection result of the rotation detection unit 191, the crank angle θc, the motor rotational speed Nm and the target stop angle θtgt. The torque command value Ttgt indicates the torque Tm capable of stopping the crankshaft with the crank angle θc equal to the target stop angle θtgt. The ECU 19 outputs a switching control signal S corresponding to the torque command value Ttgt to the inverter 15. The switching state of a switching element with which the inverter 15 is equipped is changed over in accordance with the switching control signal S. As a result, the motor-generator 12 outputs the torque Tm corresponding to the torque command value Ttgt.
Subsequently, the crank stop operation will be described. In the present embodiment, the ECU 19 can carry out at least one of first to third examples of the crank stop operation. Accordingly, the first to third examples of the crank stop operation will be described hereinafter sequentially.
The flow of the first example of the crank stop operation will be described with reference to the flowchart of
When it is determined as a result of the determination in step S1 that the stop of the engine 11 is not requested (No in step S1), the ECU 19 ends the crank stop operation. In this case, the ECU 19 may restart the crank stop operation shown in
On the other hand, when it is determined as a result of the determination in step S1 that the stop of the engine 11 is requested (Yes in step S1), the ECU 19 starts a stop control operation for stopping the engine 11. In concrete terms, the ECU 19 controls a fuel injection device in such a manner as to stop the supply of fuel to the engine 11. In parallel with the stop control operation, the motor control unit 192 sets a first angle θ1 as a target stop angle θtgt (step S2). The first angle θ1is a parameter that is stored in advance by the ECU 19 as the default target stop angle θtgt.
The first angle θ1 may be an angle at which a desired technical effect can be obtained through the stop of the crankshaft with the crank angle θc equal to the first angle θ1. For example, the first angle θ1 may be an angle that can be assumed by the crank angle θc in the latter half of a compression stroke (e.g., the crank angle θc corresponds to an angle that is larger than BTDC 0° and smaller than BTDC 90°). For example, the first angle θ1 may be an angle that can be assumed by the crank angle θc in the vicinity of an end of a compression stroke (e.g., the crank angle θc corresponds to an angle that is larger than BTDC 0° and smaller than BTDC 10°). In this case, a technical effect of reducing vibrations and noise in restarting the stopped engine 11 is obtained.
In addition, the first angle θ1 corresponds to the crank angle θc in the case where valves (i.e., an intake valve and an exhaust valve) that are installed in at least one of cylinders of the engine 11 to control the flow of air out of/into the at least one of the cylinders are in a closed-valve state. It should be noted herein that “the closed-valve state” in the present embodiment includes not only a state where the valves are completely closed (i.e., the outflow/inflow of air is completely blocked) but also a state where the change in the pressure of the air in the cylinder resulting from rotation of the crankshaft increases by a predetermined amount or more since the outflow/inflow of air is mostly blocked although the outflow/inflow of air via the valves is not completely blocked. In concrete terms, the state where the change in the pressure of the air in the cylinder increases by the predetermined amount or more means a state where the pressure of the air in the cylinder that has changed as a result of rotation of the crankshaft becomes so high as to push down or pull up a piston. The angle that can be assumed by the crank angle θc in the latter half of the above-mentioned compression stroke corresponds to the crank angle θc in the case where the intake valve and the exhaust valve are in the closed-valve state.
For the sake of convenience of explanation, it will be assumed hereinafter that the first angle θ1 is an angle that can be assumed by the crank angle θc in the vicinity of the end of a compression stroke.
After that, the motor control unit 192 changes the target stop angle θtgt as necessary (step S3). The operation of changing the target stop angle θtgt in step S3 of
As shown in
When it is determined as a result of the determination in step S31 that the crankshaft rotates in the negative rotational direction (Yes in step S31), the motor control unit 192 sets a second angle θ2 as the target stop angle θtgt (step S32). The second angle θ2 is larger than the first angle θ1. That is, the second angle θ2 corresponds to an angle that is obtained by adding an offset amount in the positive rotational direction to the first angle θ1. The second angle θ2 may be a parameter that is stored in advance by the ECU 19, or a parameter that is calculated by the ECU 19 as appropriate. As is the case with the first angle θ1, the second angle θ2 preferably corresponds to the crank angle θc in the case where the intake valve and the exhaust valve that are installed in at least one of the cylinders are in the closed-valve state. It should be noted, however, that the second angle θ2 may be different from the crank angle θc in the case where the intake valve and the exhaust valve that are installed in at least one of the cylinders are in the closed-valve state.
On the other hand, when it is determined as a result of the determination in step S31 that the crankshaft does not rotate in the negative rotational direction (No in step S31), the engine 11 is assumed to rotate in the positive rotational direction. This is because when the engine 11 is stopped, the crank stop operation ends as a result of a determination in step S9 of
When it is determined as a result of the determination in step S33 that the current crank angle θc is equal to or larger than the first angle θ1 (Yes in step S33), the motor control unit 192 sets the first angle θ1 as the target stop angle θtgt (step S34). On the other hand, when it is determined as a result of the determination in step S33 that the current crank angle θc is smaller than the first angle θ1 (No in step S33), the motor control unit 192 does not change the target stop angle θtgt. Therefore, in the case where the first angle θ1 is set as the target stop angle θtgt, the target stop angle θtgt is held equal to the first angle θ1. In the case where the second angle θ2 is set as the target stop angle θtgt, the target stop angle θtgt is held equal to the second angle θ2.
Referring to
After that, the motor control unit 192 calculates a target value of the motor rotational speed Nm (a target rotational speed Nmtgt) based on the target moving amount Rtgt calculated in step S4 (step S5). The motor control unit 192 calculates the target rotational speed Nmtgt based on a map that prescribes a relationship between the target moving amount Rtgt and the target rotational speed Nmtgt. In particular, when the target moving amount Rtgt is equal to or larger than 360° (i.e., the crankshaft rotates by 360° or more before stopping), the motor control unit 192 calculates the target rotational speed Nmtgt based on a first map shown in
After that, the motor control unit 192 calculates a difference ΔNm between the current motor rotational speed Nm and the target rotational speed Nmtgt (step S6). After that, the motor control unit 192 calculates the torque command value Ttgt based on the difference ΔNm (step S7). That is, the motor control unit 192 calculates the torque command value Ttgt by performing feedback control (e.g., PI control) for making the difference ΔNm equal to zero. After that, the motor control unit 192 generates the switching control signal S corresponding to the torque command value Ttgt, and outputs the generated switching control signal S to the inverter 15 (step S8). As a result, the motor-generator 12 outputs the torque Tm corresponding to the torque command value Ttgt.
After that, the motor control unit 192 determines whether or not the engine 11 is stopped (step S9). For example, when the time-derivative value of the crank angle θc remains equal to zero over a predetermined time, the motor control unit 192 may determine that the engine 11 is stopped. When it is determined as a result of the determination in step S9 that the engine 11 is not stopped (No in step S9), the ECU 19 carries out the operation from step S3 to step S8 again. On the other hand, when it is determined as a result of the determination in step S9 that the engine 11 is stopped (Yes in step S9), the ECU 19 ends the crank stop operation. In this case, the ECU 19 may start the crank stop operation shown in
Subsequently, a technical effect of the first example of the crank stop operation will be described with reference to timing charts shown in
First of all,
After that, the inertial force in the positive rotational direction of the crankshaft gradually decreases. As a result, the target moving amount Rtgt becomes smaller than 360° at a time point t52. That is, the target moving amount Rtgt at the time point t52 indicates that the crankshaft should stop as soon as the crank angle θc subsequently becomes equal to the target stop angle θtgt. Therefore, the motor control unit 192 controls the motor-generator 12 through the use of the second map. In this case as well, the motor-generator 12 outputs the torque Tm that acts in the negative rotational direction, in such a manner as to counterbalance the inertial force in the positive rotational direction of the crankshaft and stop the crankshaft as soon as the crank angle θc subsequently becomes equal to the target stop angle θtgt.
However, as described above, the torque command value Ttgt that prescribes the torque Tm is calculated through feedback control. Therefore, as a result of the responsiveness (e.g., a response delay or the like) of feedback control, the torque command value Ttgt may not become equal to a value capable of stopping the crankshaft as soon as the crank angle θc becomes equal to the target stop angle θtgt (i.e., the difference Δθ becomes to zero). In this case, as shown in
Even when the crank angle θc becomes larger than the target stop angle θtgt, the motor-generator 12 outputs the torque Tm that acts in the negative rotational direction, in such a manner as to counterbalance the inertial force in the positive rotational direction of the crankshaft. As a result, the inertial force in the positive rotational direction of the crankshaft becomes equal to zero at a time point t54.
It should be noted herein that the first angle θ1 is an angle that can be assumed by the crank angle θc in the vicinity of the end of a compression stroke as described above. Furthermore, the first angle θ1 corresponds to the crank angle θc in the case where the intake valve and the exhaust valve are in the closed-valve state. Accordingly, immediately before the time point t54, the crankshaft rotates such that the piston compresses the air in a combustion chamber. Therefore, at the time point t54, a force that acts in such a manner as to push down the piston (i.e., rotate the crankshaft in the negative rotational direction) is applied from the air in the combustion chamber to the piston. Furthermore, the inertial force in the positive rotational direction of the crankshaft is equal to zero at the time point t54. Therefore, at and after the time point t54, the crankshaft rotates in the negative rotational direction due to the force that is applied to the piston from the air in the combustion chamber.
At and after the time point t54, the crankshaft rotates in the negative rotational direction due to the force (so-called reaction) of the air in the combustion chamber. Therefore, the motor-generator 12 outputs the torque Tm that acts in the positive rotational direction, such that the crankshaft stops as soon as the crank angle θc becomes equal to the target stop angle θtgt through adjustment of the rotation amount of the crankshaft in the negative rotational direction. Therefore, when the crank angle θc is in the vicinity of the target stop angle θtgt (i.e., the absolute value of the difference Δθ is equal to or smaller than a predetermined value), the motor-generator 12 is controlled in consideration of the behavior of the crankshaft corresponding to the force of the air in the combustion chamber as well as the second map (the same holds true for the first example of the crank stop operation as well as the completive example). On the other hand, the torque command value Ttgt that prescribes the torque Tm that acts in the positive rotational direction is also calculated through feedback control. Therefore, as shown in
Even when the crank angle θc becomes smaller than the target stop angle θtgt, the motor-generator 12 outputs the torque Tm that acts in the positive rotational direction, in such a manner as to adjust the rotation amount of the crankshaft in the negative rotational direction. As a result, the rotational direction of the crankshaft changes over from the negative rotational direction to the positive rotational direction at a time point t55. At the time point t55, the crank angle θc is smaller than the target stop angle θtgt. Therefore, the motor-generator 12 continues to output the torque Tm that acts in the positive rotational direction, such that the crankshaft stops with the crank angle θc equal to the target stop angle θtgt. As a result, the crank angle θc becomes equal to the target stop angle θtgt at a time point t56.
However, the force that is applied to the piston from the air in the combustion chamber in such a manner as to push down the crankshaft is larger in the case where the rotation amount of the crankshaft in the positive rotational direction during a period from the time point t55 to the time point t56 (i.e., the rotation amount of the crankshaft immediately before the stop of the crankshaft) is relatively large than in the case where the rotation amount of the crankshaft in the positive rotational direction during the period from the time point t55 to the time point t56 is relatively small. Therefore, at and after the time point t56 as well, the motor-generator 12 needs to continue to output the relatively large torque Tm that acts in the positive rotational direction, such that the crankshaft does not rotate as a result of a force that is received by the piston from the air in the combustion chamber. When the motor-generator 12 stops outputting the torque Tm at a time point t57, the crankshaft rotates in the negative rotational direction as a result of the force that is received by the piston from the air in the combustion chamber. Accordingly, it is difficult for the crankshaft to stop with the crank angle θc equal to the target stop angle θtgt.
In view of this technical problem that arises in the comparative example of the crank stop operation, according to the first example of the crank stop operation, the target stop angle θtgt is changed from the first angle θ1 to the second angle θ2, with a view to making the rotation amount of the crankshaft in the negative rotational direction relatively small and making the amount of subsequent rotation of the crankshaft in the positive rotational direction relatively small.
In concrete terms,
From the time point t61 to the time point t64, the engine 11 continues to rotate in the positive rotational direction, so the target stop angle θtgt is not set to the second angle θ2. Therefore, the target stop angle θtgt is held equal to the first angle θ1, regardless of whether the crank angle θc is equal to or larger than the first angle θ1. On the other hand, at and after the time point t64, the crankshaft rotates in the negative rotational direction. As a result, the target stop angle θtgt is changed from the first angle θ1 to the second angle θ2 at the time point t64.
At and after the time point t64, as is the case with the comparative example, the motor-generator 12 outputs the torque Tm that acts in the positive rotational direction. Furthermore, the rotational direction of the crankshaft changes over from the negative rotational direction to the positive rotational direction at a time point t65. Besides, it is assumed that an overshoot of the crank angle θc in the negative rotational direction with respect to the pre-change target stop angle θtgt (i.e., the first angle θ1) has occurred at the time point t65. On the contrary, in the case where an overshoot of the crank angle θc in the negative rotational direction with respect to the pre-change target stop angle θtgt (i.e., the first angle θ1) does not occur after the crankshaft rotates in the negative rotational direction, an operation different from the crank stop operation shown in
It should be noted herein that the rotation amount of the crankshaft in the negative rotational direction that is needed to make the crank angle θc coincident with the target stop angle θtgt is smaller in the case where the target stop angle θtgt is set to the second angle θ2 than in the case where the target stop angle θtgt is held equal to the first angle θ1. Therefore, the rotation amount of the crankshaft in the negative rotational direction at and after the time point t64 is made smaller in the case where the target stop angle θtgt is set to the second angle θ2 than in the case where the target stop angle θtgt is held equal to the first angle θ1, so the torque Tm that is output at and after the time point t64 and that acts in the positive rotational direction is relatively large. As a result, the rotation amount of the crankshaft in the negative rotational direction at and after the time point t64 is small, so the rotation amount of the crankshaft in the positive rotational direction at and after the time point t65 is also small. Accordingly, at the time point t66, the force that is applied to the piston from the air in the combustion chamber in such a manner as to push down the crankshaft is also small. Therefore, at and after the time point t66, even when the motor-generator 12 does not continue to output the relatively large torque Tm that acts in the positive rotational direction, the crankshaft does not rotate as a result of a force that is received by the piston from the air in the combustion chamber. Therefore, even if the motor-generator 12 stops outputting the torque Tm at a time point t67, the crankshaft does not rotate in the negative rotational direction as a result of a force that is received by the piston from the air in the combustion chamber. Accordingly, the crankshaft can appropriately stop with the crank angle θc equal to the target stop angle θtgt. That is, according to the first example of the crank stop operation, even in the case where the crankshaft rotates in the negative rotational direction as a result of the responsiveness of feedback control before stopping, the crankshaft can stop with the crank angle θc equal to the target stop angle θtgt.
The rotation amount of the crankshaft in the negative rotational direction resulting from the responsiveness of the above-mentioned feedback control tends to increase as the number of cylinders with which the engine 11 is equipped decreases. This is because the possibility of rotation of the crankshaft in the negative rotational direction due to the air compressed in a certain cylinder being counterbalanced by the behavior of the crankshaft in the other cylinder(s) decreases as the number of cylinders decreases. Therefore, the technical effect according to the first example of the crank stop operation is more remarkable in the case where the number of cylinders of the engine 11 is equal to or smaller than a predetermined number than in the case where the number of cylinders of the engine 11 is larger than the predetermined number. For example, the technical effect according to the first example of the crank stop operation is more remarkable in the case where the number of cylinders is equal to or smaller than 4 (or equal to or smaller than 6) than in the case where the number of cylinders is larger than 4 (or larger than 6). Incidentally, in the case where the engine 11 is equipped with a plurality of cylinders, the ECU 19 may carry out the first example of the above-mentioned crank stop operation as to at least one of the plurality of the cylinders. In this case, at least one of the cylinders that is subjected to the first example of the crank stop operation is preferably a cylinder in which the target stop angle θtgt is set to the first angle θ1 corresponds to the crank angle θc in the case where the intake valve and the exhaust valve are in the closed-valve state.
Incidentally, as described above, the second angle θ2 is the target stop angle θtgt that is set for the purpose of making the rotation amount of the crankshaft in the negative rotational direction small. In other words, the second angle θ2 is the target stop angle θtgt that is set for the purpose of making large the torque Tm that is output under the circumstances where the crankshaft rotates in the negative rotational direction and that acts in the positive rotational direction. Accordingly, the second angle θ2 is preferably set to an appropriate value in advance based on the specification of the vehicle 1 or the like, from the standpoint of achieving this purpose.
In the foregoing description, rotation of the crankshaft in the negative rotational direction resulting from the responsiveness of feedback control occurs only once. However, rotation of the crankshaft in the negative rotational direction resulting from the responsiveness of feedback control may occur twice or more. That is, the crankshaft may repeat a cycle of rotation consisting of rotation in the negative rotational direction and rotation in the positive rotational direction a plurality of times, as a result of the responsiveness of feedback control. In this case as well, the crankshaft can be stopped with the crank angle θc equal to the target stop angle θtgt, by carrying out the first example of the above-mentioned crank stop operation. For example,
In the foregoing description, the motor control unit 192 returns the target stop angle θtgt to the first angle θ1 at a timing when the crank angle θc becomes equal to or larger than the pre-change target stop angle θtgt (i.e., the first angle θ1) after the rotational direction of the crankshaft changes over from the negative rotational direction to the positive rotational direction. However, the motor control unit 192 may return the target stop angle θtgt to the first angle θ1 at a timing when a predetermined period elapses after the rotational direction of the crankshaft changes over from the negative rotational direction to the positive rotational direction. In this case, even when an overshoot of the crank angle θc in the negative rotational direction with respect to the pre-change target stop angle θtgt (i.e., the first angle θ1) has not occurred upon a changeover in the rotational direction of the crankshaft from the negative rotational direction to the positive rotational direction, the crankshaft stops with the crank angle θc equal to the first angle θ1 as the original target stop angle θtgt.
In the foregoing description, the first angle θ1 is an angle that can be assumed by the crank angle θc in the vicinity of the end of a compression stroke. Therefore, immediately before starting to rotate in the negative rotational direction, the crankshaft rotates such that the piston compresses the air in the combustion chamber. However, immediately before starting to rotate in the negative rotational direction, the crankshaft may rotate such that the piston expands the air in the combustion chamber. In this case as well, the force that acts in such a manner as to pull up the piston (i.e., rotate the crankshaft in the negative rotational direction) (i.e., the force that is substantially corresponds to a negative pressure) is applied without fail to the piston from the air in the combustion chamber. Accordingly, the first example of the above-mentioned crank stop operation may be carried out not only in the case where immediately before starting to rotate in the negative rotational direction, the crankshaft rotates such that the piston compresses the air in the combustion chamber, but also in the case where immediately before starting to rotate in the negative rotational direction, the crankshaft rotates such that the piston expands the air in the combustion chamber. In this case as well, the above-mentioned effect is appropriately received.
The second example of the crank stop operation is different from the first example of the above-mentioned crank stop operation in that the gradually changing (i.e., gradually increasing/decreasing) second angle θ2 is used. In the first example of the crank stop operation, the fixed (i.e., unchanging) second angle θ2 is used. The second example of the crank stop operation is identical in other operational details to the first example of the crank stop operation. The gradually changing second angle θ2 is set by the operation of changing the target stop angle θtgt in step S3 of
As shown in
On the other hand, if it is determined as a result of the determination in step S31 that the crankshaft does not rotate in the negative rotational direction (No in step S31), the motor control unit 192 determines whether or not the current crank angle θc is equal to or larger than the first angle θ1 (step S33). If it is determined as a result of the determination in step S33 that the current crank angle θc is equal to or larger than the first angle θ1 (Yes in step S33), the motor control unit 192 sets the first angle θ1 as the target stop angle θtgt (step S34).
On the other hand, if it is determined as a result of the determination in step S33 that the current crank angle θc is smaller than the first angle θ1 (No in step S33), the motor control unit 192 determines whether or not the second angle θ2 is set as the target stop angle θtgt (step S42). If it is determined as a result of the determination in step S42 that the second angle θ2 is not set as the target stop angle θtgt (No in step S42), the target stop angle θtgt is held equal to the first angle θ1. If it is determined as a result of the determination in step S42 that the second angle θ2 is set as the target stop angle θtgt (Yes in step S42), the motor control unit 192 sets the gradually changing second angle θ2 as the target stop angle θtgt (step S43).
In order to set the gradually changing second angle θ2 in steps S41 and S43, the motor control unit 192 sets the second angle θ2 whose difference from the previous target stop angle θtgt is equal to or smaller than a predetermined amount. The operation shown in
As shown in
As shown in
Incidentally, the amount of each change in the second angle θ2 decreases as the cycle on which the operation shown in
As shown in the flowchart of
As shown in
If it is determined as a result of the determination in step S31 that the crankshaft rotates in the negative rotational direction (Yes in step S31), the motor control unit 192 sets a second gain k2 as the control gain k (step S102). In the present embodiment, the control gain k includes at least one of a proportional gain kp and an integral gain ki that are used in feedback control (PI control) performed by the above-mentioned motor control unit 192. Therefore, the motor control unit 192 sets a second gain kp2 as the proportional gain kp and/or sets a second gain ki2 as the integral gain ki.The second gain kp2 is the proportional gain kp capable of prescribing the torque Tm that is larger than the torque (especially the torque that acts in the positive rotational direction, the same will hold true) Tm prescribed by a first gain kp1 that will be described later. The second gain ki2 is the integral gain ki capable of prescribing the torque Tm that is larger than the torque Tm prescribed by a first gain ki1 that will be described later. The second gains kp2 and ki2 may be parameters that are stored in advance by the ECU 19, or may be parameters that are calculated by the ECU 19 as appropriate. It should be noted, however, that the control gain k may be an arbitrary gain capable of adjusting the magnitude of the torque Tm.
On the other hand, if it is determined as a result of the determination in step S31 that the crankshaft does not rotate in the negative rotational direction (No in step S31), the motor control unit 192 determines whether or not the current crank angle θc is equal to or larger than the target stop angle θtgt (step S103).
If it is determined as a result of the determination in step S103 that the current crank angle θc is equal to or larger than the target stop angle θtgt (Yes in step S103), the motor control unit 192 sets the first gain k1 as the control gain k (step S104). That is, the motor control unit 192 sets the first gain kp1 as the proportional gain kp and/or sets the first gain ki1 as the integral gain The first gain ki. The first gain k1 (i.e., the first gain kp1 and the first gain ki1) is a parameter that is stored in advance by the ECU 19 as the default control gain k. On the other hand, if it is determined as a result of the determination in step S103 that the current crank angle θc is smaller than the target stop angle θtgt (No in step S103), the motor control unit 192 does not change the control gain k. Therefore, when the first gain k1 is set as the control gain k, the control gain k is held equal to the first gain k1. When the second gain k2 is set as the control gain k, the control gain k is held equal to the second gain k2.
In this third example of the crank stop operation as well as the first example of the crank stop operation, the torque Tm that is output under the circumstances where the crankshaft rotates in the negative rotational direction is larger than in the case where the control gain k is held equal to the first gain k1 (see
Incidentally, in the third example of the crank stop operation as well as the second example of the crank stop operation, the gradually changing second gain k2 may be set as the control gain k. For example, the gradually increasing second gain k2 may be set as the control gain k. For example, the gradually decreasing second gain k2 may be set as the control gain k. For example, the second gain k2 that gradually decreases and then gradually increases may be set as the control gain k. For example, the second gain k2 that gradually increases and then gradually decreases may be set as the control gain k. Besides, in the third example of the crank stop operation as well as the first example of the crank stop operation, the target stop angle θtgt may be changed between the first angle θ1 and the second angle θ2.
According to the aforementioned configuration, during the second period in which the crankshaft rotates in the negative rotational direction with a view to returning the crank angle, which has exceeded the target angle, toward the target angle, the relatively large second angle is used as the target angle. Therefore, the rotation amount of the crankshaft in the negative rotational direction is smaller than in the case where the relatively small first angle is used as the target angle during the second period. As a result, the overshoot amount of the crank angle in the negative rotational direction with respect to the target angle is also small. Therefore, the rotation amount of the crankshaft in the positive rotational direction after a changeover in the rotational direction of the crankshaft from the negative rotational direction to the positive rotational direction is also small. Therefore, the moving amount of a piston resulting from this rotation in the positive rotational direction is also small, and the degree of compression (or expansion) of the air in the cylinder by the piston decreases. As a result, the force that is exerted on the piston by the air in the cylinder when the crankshaft is stopped is also small. Accordingly, the possibility of the piston moving (i.e., the crankshaft moving) as a result of a pressure of the air in the cylinder is low after the torque is stopped from being output due to the stop of the crankshaft. Therefore, the vehicle control apparatus according to the aforementioned configuration can stop the crankshaft with the crank angle equal to the target angle (i.e., the first angle), even in the case where an overshoot of the crank angle with respect to the target angle occurs as a result of the responsiveness of feedback control before stopping the crankshaft.
In addition, the target angle is returned from the second angle to the first angle at the first timing when the crank angle, which has become smaller than the first angle as a result of the responsiveness of feedback control, becomes equal to or larger than the first angle. Accordingly, the second angle that is larger than the first angle as the original target angle is not used as the target angle for a longer time than necessary. Therefore, the vehicle control apparatus according to the aforementioned configuration can stop the crankshaft with the crank angle equal to the target angle (i.e., the first angle).
According to the aforementioned configuration, the vehicle control apparatus can stop the crankshaft with the crank angle equal to the target angle (i.e., the first angle), even in the case where a state of rotation of the crankshaft in the negative rotational direction as a result of the responsiveness of feedback control occurs a plurality of times. In addition, the second angle that is larger than the first angle as the original target angle is not used as the target angle for a longer time than necessary, even in the case where a state of rotation of the crankshaft in the negative rotational direction as a result of the responsiveness of feedback control occurs a plurality of times. Therefore, the vehicle control apparatus according to the aforementioned configuration can stop the crankshaft with the crank angle equal to the target angle (i.e., the first angle).
According to the aforementioned configuration, the torque is prevented from rapidly changing when the target angle changes over from the first angle to the second angle or from the second angle to the first angle.
In the case where the angle that can be assumed by the crank angle in the latter half of the compression stroke is equal to the first angle, the force that is exerted on the piston by the air in the cylinder when the crankshaft is stopped is likely to be relatively large. Therefore, according to the aforementioned configuration, the effect of making it possible to lower the possibility of the piston moving as a result of the pressure of the air in the cylinder is more remarkable.
According to the aforementioned configuration, during the second period in which the crankshaft rotates in the negative rotational direction with a view to returning the crank angle, which has exceeded the target angle, toward the target angle, the relatively large torque in the positive rotational direction is output. Therefore, the rotation amount of the crankshaft in the negative rotational direction is smaller than in the case where the relatively small torque in the positive rotational direction is output during the second period. In consequence, the vehicle control apparatus according to the aforementioned configuration can receive an effect similar to the effect that can be received by the above-mentioned vehicle control apparatus according to the first aspect of the disclosure.
In addition, the motor gain is returned from the second gain to the first gain at the first timing when the crank angle, which has become smaller than the target angle as a result of the responsiveness of feedback control, becomes equal to or larger than the target angle. Accordingly, the second gain that is different from the first gain as the original motor gain is not used as the motor gain for a longer time than necessary. Therefore, the vehicle control apparatus according to the second aspect of the disclosure can stop the crankshaft with the crank angle equal to the target angle.
According to the aforementioned configuration, the vehicle control apparatus according to the second aspect of the disclosure can stop the crankshaft with the crank angle equal to the target angle, even in the case where a state of rotation of the crankshaft in the negative rotational direction as a result of the responsiveness of feedback control occurs a plurality of times. In addition, the second gain that is different from the first gain as the original motor gain is not used as the motor gain for a longer time than necessary, even in the case where a state of rotation of the crankshaft in the negative rotational direction as a result of the responsiveness of feedback control occurs a plurality of times. As a result, the vehicle control apparatus according to the aforementioned configuration can stop the crankshaft with the crank angle equal to the target angle.
According to the aforementioned configuration, the torque is prevented from rapidly changing when the motor gain changes over from the first gain to the second gain or from the second gain to the first gain.
According to the aforementioned configuration, the effect of the vehicle control apparatus, namely, the effect of making it possible to lower the possibility of the piston moving as a result of the pressure of the air in the cylinder is more remarkable.
Incidentally, the disclosure can be changed as appropriate within such a range as not to contradict the gist or concept of the disclosure that can be read from the claims and the entire specification. A vehicle control apparatus subjected to such a change is also included in the technical concept of the disclosure.
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2016-075102 | Apr 2016 | JP | national |
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20170282890 A1 | Oct 2017 | US |