The disclosure of Japanese Patent Application No. 2014-127210 filed on Jun. 20, 2014 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a control apparatus for a vehicle. This control apparatus is applied to a vehicle whose engine operating point can be continuously changed, such as a hybrid vehicle that is equipped with a differential mechanism to which an engine and a motor-generator are coupled, or the like.
2. Description of Related Art
As a control apparatus for a hybrid vehicle, there is known an apparatus that controls the engine operating point along an optimal fuel economy curve that determines an upper-limit engine torque at the time of acceleration (see Japanese Patent Application Publication No. 2010-47127 (JP 2010-47127 A)). Moreover, the related art documents associated with the invention include Japanese Patent Application Publication No. 2006-217750 (JP 2006-217750 A), Japanese Patent Application Publication No. 2000-87774 (JP 2000-87774 A), and Japanese Patent Application Publication No. 2008-195088 (JP 2008-195088 A).
The control apparatus of Japanese Patent Application Publication No. 2010-47127 (JP 2010-47127 A) raises the engine power by reducing the engine rotational speed along the optimal fuel economy curve with a view to giving priority to fuel economy and then raising the engine rotational speed again when reacceleration operation is performed by returning and then depressing an accelerator pedal. However, with this control apparatus, the engine rotational speed is temporarily reduced in response to reacceleration operation. Therefore, the engine rotational speed may deviate from a range ensuring an inertia supercharging effect in the case of a naturally aspirated engine. In such a case, the acceleration responsiveness to reacceleration operation deteriorates. Besides, in the case of an engine that is provided with a turbocharger, a delay in supercharging results from a decrease in turbine rotational speed caused by a temporary decrease in engine rotational speed, so the acceleration responsiveness to reacceleration operation deteriorates.
The invention provides a control apparatus for a vehicle that can restrain the acceleration responsiveness to reacceleration operation from deteriorating.
A control apparatus for a vehicle according to one aspect of the invention is provided. The vehicle includes an engine and a transmission. The transmission is configured to continuously change an engine operating point that is defined by a rotational speed of the engine and a torque of the engine. The control apparatus includes an ECU. The ECU is configured to, when a target engine required power increases in response to a reacceleration operation, set the rotational speed and the torque so as to reach a power of the engine to the target engine required power while holding the rotational speed equal to or higher than the rotational speed at a time of the reacceleration operation. The ECU is configured to control the engine operating point based on the set rotational speed and the set torque.
According to this aspect of the invention, the engine operating point is controlled without reducing the rotational speed in response to reacceleration operation. Therefore, the rotational speed is unlikely to deviate from a range ensuring an inertia supercharging effect in the case of a naturally aspirated engine, and a delay in supercharging is suppressed without causing a decrease in turbine rotational speed in the case of an engine equipped with a turbocharger. Thus, the acceleration responsiveness to reacceleration operation can be restrained from deteriorating.
In the aforementioned aspect of the invention, the ECU may be configured to control the engine operating point to an upper-limit engine torque of the engine along an iso-power line that is equal to the target engine required power, when the power of the engine reaches the target engine required power before the engine operating point reaches the upper-limit engine torque. According to this aspect of the invention, the engine operating point is controlled along the iso-power line upon reaching the target engine required power. Therefore, the engine torque can be increased to the upper-limit engine torque while maintaining the target engine required power.
In the aforementioned aspect of the invention, the ECU may be configured to set a target rotational speed of the engine operating point determined by the upper-limit engine torque and the target engine required power. The ECU may be configured to control the engine operating point so as to increase the rotational speed as the power of the engine increases, when the target rotational speed is higher than the rotational speed at the time of the reacceleration operation. According to this aspect of the invention, the engine operating point is controlled so as to increase the rotational speed as the power of the engine increases. Thus, the acceleration responsiveness is higher than in the case where the rotational speed is held equal to the rotational speed at the time of reacceleration operation until the power of the engine is reached to the target engine required power.
As described hitherto, according to each of the aforementioned aspects of the invention, the engine operating point is controlled without reducing the rotational speed in response to reacceleration operation. Therefore, the rotational speed is unlikely to deviate from the range ensuring an inertia supercharging effect in the case of a naturally aspirated engine, and a delay in supercharging is suppressed without causing a decrease in turbine rotational speed in the case of an engine equipped with a turbocharger. Thus, the acceleration responsiveness to reacceleration operation can be restrained from deteriorating.
Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
First of all, the first embodiment of the invention will be described. As shown in
An intake passage 11 and an exhaust passage 12 are connected to the respective cylinders 10 of the engine 3. The intake passage 11 includes an intake manifold 11a that distributes intake air to the respective cylinders 10. The exhaust passage 12 includes an exhaust manifold 12a that aggregates exhaust gas in the respective cylinders 10. The intake passage 11 is provided with an air cleaner 13 for filtering air, a throttle valve 14 that can adjust the flow rate of air, a compressor 15a of a turbocharger 15, and an intercooler 16. The exhaust passage 12 is provided with a turbine 15b of the turbocharger 15, a start catalyst 17 that purifies exhaust gas mainly in a cold state, and an NOx catalyst 18 that purifies noxious components in exhaust gas. The NOx catalyst 18 is a well-known occlusion-reduction type NOx catalyst.
The engine 3 is provided with an EGR device 20 that recirculates part of exhaust gas to an intake system. The EGR device 20 is equipped with an EGR passage 21 that joins the exhaust passage 12 and the intake passage 11 to each other, an EGR cooler 22 that cools the exhaust gas introduced to the EGR passage 21, and an EGR valve 23 that adjusts the flow rate of EGR gas. The EGR passage 21 is connected at one end thereof on an exhaust side to the exhaust passage 12 between the start catalyst 17 and the NOx catalyst 18, and is connected at the other end thereof on an intake side to the intake passage 11 between the throttle valve 14 and the compressor 15a of the turbocharger 15.
The engine 3 and the first motor-generator 4 are connected to a power split mechanism 6. An output of the power split mechanism 6 is transmitted to an output gear 30. The output gear 30 and the second motor-generator 5 are coupled to each other, and rotate integrally with each other. The power output from the output gear 30 is transmitted to a driving wheel 33 via a reduction gear 31 and a differential gear 32. The first motor-generator 4 has a stator 4a and a rotor 4b. The first motor-generator 4 functions as a generator that generates electricity upon receiving the power of the engine 3 split by the power split mechanism 6, and also functions as an electric motor that is driven by an AC electric power. By the same token, the second motor-generator 5 has a stator 5a and a rotor 5b, and functions as an electric motor and a generator respectively. The respective motor-generators 4 and 5 are connected to a battery 36 via a motor control device 35. The motor control device 35 converts the electric power generated by the respective motor-generators 4 and 5 into a DC electric power to store this DC electric power into the battery 36, and converts the electric power of the battery 36 into an AC electric power to supply the respective motor-generators 4 and 5 therewith.
The power split mechanism 6 is configured as a single pinion-type planetary gear mechanism, and has a sun gear S, a ring gear R, and a planetary carrier C that holds a pinion P meshing with these gears S and R in such a state that the pinion P can rotate around itself and rotate around the planetary carrier C. The sun gear S is coupled to the rotor 4b of the first motor-generator 4, the ring gear R is coupled to the output gear 30, and the planetary carrier C is coupled to a crankshaft 7 of the engine 3. The engine 3 and the first motor-generator 4 are connected to respective rotary elements of the power split mechanism 6 as a differential mechanism. Therefore, the engine operating point of the engine 3, which is defined by the engine rotational speed and the engine torque, can be continuously changed by controlling the first motor-generator 4. Accordingly, a combination of the power split mechanism 6 and the first motor-generator 4 is equivalent to a speed change mechanism according to the invention. Incidentally, there is a damper 8 between the crankshaft 7 and the planetary carrier C. The damper 8 absorbs torque fluctuations of the engine 3.
The vehicle 1 is controlled by an electronic control unit (an ECU) 40. The ECU 40 executes various kinds of control for the engine 3 and the respective motor-generators 4 and 5. The main control executed by the ECU 40 in association with the invention will be described hereinafter. Signals of a multitude of sensors are input to the ECU 40. However, as those associated with the invention, respective signals of an accelerator opening degree sensor 41 that outputs a signal corresponding to a depression amount of an accelerator pedal (not shown) (an accelerator opening degree), a vehicle speed sensor 42 that outputs a signal corresponding to a speed of the vehicle 1 (a vehicle speed), an SOC sensor 43 that outputs a signal corresponding to a storage ratio of the battery 36, a first resolver 44 that outputs a signal corresponding to a motor rotational speed of the first motor-generator 4, a second resolver 45 that outputs a signal corresponding to a motor rotational speed of the second motor-generator 5, and a crank angle sensor 46 that outputs a signal corresponding to an engine rotational speed of the engine 3 are input to the ECU 40.
The ECU 40 calculates a required power required by a driver with reference to the output signal of the accelerator opening degree sensor 41 and the output signal of the vehicle speed sensor 42, and controls the vehicle 1 while making changeovers among various modes in such a manner as to optimize the system efficiency for the required power. For example, in a low-load range in which the thermal efficiency of the engine 3 decreases, an EV mode in which the combustion of the engine 3 is stopped and the second motor-generator 5 is driven is selected. Besides, when the storage ratio of the battery 36 turns out to be insufficient with reference to the signal of the SOC sensor 43, an engine running mode is selected to execute control for restraining the battery 36 from consuming electric power. Furthermore, the engine 3 alone cannot secure a sufficient torque, a hybrid mode in which the engine 3 and the second motor-generator 5 serve as driving sources for running is selected. When the hybrid mode is selected, the required power is output through summation of an engine power of the engine 3 and a motor power of the second motor-generator 5. As is well known, in a scene in which importance is attached to fuel economy, the engine 3 is controlled such that the engine operating point moves in principle along an optimal fuel economy curve that is set in advance so as to optimize the thermal efficiency. Incidentally, the engine operating point is defined by the engine rotational speed and the engine torque.
The control according to the first embodiment of the invention is characterized by the control contents at the time of reacceleration operation, namely, at the time when the accelerator pedal of the vehicle 1 is depressed again after being released. Before describing a concrete processing executed by the ECU 40, the outline of the control according to the first embodiment of the invention will be described in conjunction with a comparative example, with reference to an example of a control result shown in
As shown in
Then, as indicated by a solid line of
On the other hand, in the case of the comparative example indicated by the broken curves in
Next, a concrete processing that is executed by the ECU 40 to realize the aforementioned control will be described. As shown in
In step S2, the ECU 40 refers to the signal of the crank angle sensor 46, acquires an engine rotational speed Ne, and determines whether or not the engine rotational speed Ne is equal to or higher than a predetermined minimum rotational speed Nemin. The minimum rotational speed Nemin is appropriately set as an execution condition of the aforementioned present control, and is set to, for example, 1000 rpm. If the engine rotational speed Ne is equal to or higher than the minimum rotational speed Nemin, the ECU 40 proceeds to step S3. Otherwise, the ECU 40 proceeds to step S5 to execute normal engine control.
In step S3, the ECU 40 determines whether or not there is established an operating condition under which priority is given to the driving force and a target engine required power Tag_Pa is larger than a current engine required power Pe. The operating condition under which priority is given to the driving force is, for example, a condition that the accelerator opening degree be equal to or larger than 90%, or a condition that a sport mode be selected by turning ON a sport mode switch (not shown) in the case where the vehicle 1 is configured to allow the driver to select a sport mode in which the kinetic performance is higher than in a normal mode, as a running mode of the vehicle 1, by operating the sport mode switch. The target engine required power Tag_Pa and the engine required power Pe are calculated based on operating parameters such as an accelerator opening degree, a vehicle speed and the like, through the execution of a control routine (not shown). However, since the control routine is known, detailed description thereof will be omitted. If a positive determination is made in step S3, the ECU 40 proceeds to step S4 to execute driving force priority control shown in
As shown in
In step S413, the ECU 40 determines whether or not the engine operating point has reached the target engine required power Tag_Pe by comparing the engine required power Pe_n determined in step S412 with the target engine required power Tag_Pe. If the engine operating point has not reached the target engine required power Tag_Pe, the ECU 40 proceeds to step S414 to hold the engine rotational speed constant as described with reference to
On the other hand, if the engine operating point has reached the target engine required power Tag_Pe, the ECU 40 proceeds to step S415 to fix the subsequent engine required power Pe_n as the target engine required power Tag_Pe. In step S416, the ECU 40 determines a subsequent engine rotational speed Ne_n from the current engine rotational speed Tmp_Ne. In the case of
In step S417, the ECU 40 determines whether or not the engine operating point has reached a minimum engine rotational speed Min Ne [Tag_Pe] that can be realized by the target engine required power Tag_Pe on the optimal fuel economy curve L that determines the upper-limit engine torque. In this case, the ECU 40 determines whether or not the engine operating point has reached the minimum engine rotational speed Min Ne [Tag_Pe] by confirming whether or not the engine rotational speed Ne_n determined in step 5416 has become equal to or lower than the minimum engine rotational speed Min Ne [Tag_Pe]. If the engine operating point has reached the minimum engine rotational speed Min Ne [Tag_Pe], the engine operating point is located at an intersection point of an iso-power line of the target engine required power Tag_Pe and an optimal fuel economy curve. If the engine operating point has reached the minimum engine rotational speed Min_Ne [Tag_Pe], the ECU 40 proceeds to step S418 to determine the engine operating point. Otherwise, the ECU 40 proceeds to step S419.
In step S419, the ECU 40 determines the engine operating point by setting a subsequent engine torque Te_n based on the engine required power Pe_n and the engine rotational speed Ne_n that have been determined in the aforementioned process. Then, the ECU 40 operates the first motor-generator 4 such that the engine 3 is operated at the engine operating point determined in step S419. Incidentally, a function F(a, b) that is used to set the engine torque Te_n is defined by an expression 1 shown below.
F(a,b)=*60*1000/(2π*b) 1
The engine rotational speed is held equal to the engine rotational speed at the time of reacceleration operation before the engine operating point reaches the target engine required power as described with reference to
Next, the second embodiment of the invention will be described with reference to
As indicated by a broken curve in
Driving force priority control according to the present embodiment of the invention is executed based on control routines shown in
If it is determined in step S423 of
In step S4242, the ECU 40 determines the subsequent engine rotational speed Ne_n from the current engine rotational speed Tmp_Ne. In this case, the ECU 40 determines a value obtained by adding a constant Kn_up to the current engine rotational speed Tmp_Ne as the subsequent engine rotational speed Ne_n such that the engine rotational speed increases at a certain rate as the engine power increases, and then ends the processing. Incidentally, the increasing of the engine rotational speed at a certain rate as the engine power increases is nothing more than an example. For instance, the rate may be changed in accordance with the deviation between the target engine rotational speed Tag_N and the current engine rotational speed Tmp_Ne.
In step S4243, the ECU 40 holds the engine rotational speed constant. That is, the ECU 40 sets the subsequent engine rotational speed Ne_n equal to the current engine rotational speed Tmp_Ne stored in step S411, and then ends the processing.
According to the control routines of
The invention is not limited to the aforementioned first and second embodiments thereof, but can be carried out in various modes within the range of the gist of thereof In each of the aforementioned embodiments of the invention, the invention is applied to the engine equipped with the turbocharger. However, the invention is also applicable to a naturally aspirated engine. Besides, the configuration of the hybrid vehicle is not limited to that of
Number | Date | Country | Kind |
---|---|---|---|
2014-127210 | Jun 2014 | JP | national |