JP2005307757A - Controller for hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To change and control valve timing of an engine by taking a condition of a battery into account and improve fuel economy of the engine to achieve high efficiency of the whole hybrid system. <P>SOLUTION: Advance amount is set based on SOC (S1), target torque Tt for realizing the optimum fuel economy by this advance amount is set (S2), a demand torque Td is calculated based on the number of revolutions of the engine and opening of an accelerator (S3), and both of them are compared (S4). In the case of Td<Tt, valve timing is delayed (S5), and throttle opening adjustment and motor regeneration amount adjustment are selectively performed in accordance with SOC (S9, S10) when valve timing reaches delay limit. In the case of Td>Tt, assist of the motor, advancing of valve timing, and throttle opening adjustment are selectively performed in accordance with SOC (S13, S14) to improve fuel economy of the engine and achieve high efficiency of the whole hybrid system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for a hybrid vehicle using both an engine and a motor.

  In recent years, in vehicles such as automobiles, an engine that uses gasoline or other fuel as a power source is used with a motor that generates driving force by electric power from a battery for the purpose of promoting low pollution and resource saving. In addition, hybrid vehicles are being developed that use both an engine and a motor. In such a hybrid vehicle, it is necessary to consider the driving efficiency of both the engine and the motor.

  For this reason, various proposals have been made conventionally. For example, Patent Document 1 discloses a hybrid vehicle that outputs power output from an engine from a drive shaft as a required torque and rotation speed using a planetary gear and a motor. A technique for improving the overall driving efficiency of a vehicle by switching between control for driving an engine with priority on efficiency and control for driving with priority on power is disclosed.

Patent Document 2 discloses that in a hybrid vehicle in which an electric motor is driven as a generator by an engine as a driving power source and the battery is charged, power generation performed during driving by the engine can be performed at an efficient timing. Thus, a technique for suppressing the fuel consumption rate related to power generation and reducing the fuel consumption of the entire vehicle is disclosed.
Japanese Patent Laid-Open No. 11-117782 JP 2001-268709 A

  As disclosed in Patent Document 1 and Patent Document 2, some engines mounted on hybrid vehicles include a variable valve timing mechanism that varies the valve timing of at least one of an intake valve and an exhaust valve. By varying the valve timing via the variable valve timing mechanism, the engine output can be adjusted and the fuel consumption can be reduced. However, when the valve timing is variably controlled, the motor drive that depends on the state of the battery is driven. It is necessary to consider power.

  However, in Patent Document 1 described above, the valve timing is changed to increase engine torque during power-priority control, and in Patent Document 2, a valve is used to avoid large power generation in an output-oriented operation state. Only the valve overlap amount as a result of the variable timing control is monitored, and neither technology actively controls the valve timing in consideration of the state of the battery. The fuel consumption reduction effect by is not effectively utilized.

  The present invention has been made in view of the above circumstances, and by variably controlling the valve timing of the engine in consideration of the state of the battery, it is possible to improve the fuel efficiency of the engine and increase the efficiency of the entire hybrid system. An object of the present invention is to provide a control device for a hybrid vehicle that can be used.

  In order to achieve the above object, a control apparatus for a hybrid vehicle according to the present invention has an engine provided with a variable valve timing mechanism that varies the valve timing of at least one of an intake valve and an exhaust valve, and a driving force by electric power from a battery. In a hybrid vehicle control device that uses a generated motor together, a valve timing setting means for setting a valve timing by the variable valve timing mechanism according to a remaining capacity of the battery, and a valve timing set by the valve timing setting means. A target torque setting means for setting an engine torque that provides the best fuel efficiency as a target torque, a required torque calculation means for calculating a required torque of the engine based on an operating state, the target torque and the required torque are compared, The target torque is the required torque When they do not match, the variable and the valve timing via the variable valve timing mechanism, the target torque is characterized in that a torque adjustment means for controlling so as to coincide with the required torque.

  At this time, the torque adjusting means executes retarding control of the valve timing when the target torque exceeds the required torque, and when the target torque does not reach the required torque, assist control by the motor. It is desirable that the valve timing advance control is selectively executed according to the remaining capacity of the battery, and the valve timing retard control is executed to set a retard limit by the variable valve timing mechanism. It is desirable that the regeneration control by the motor and the throttle opening control of the engine are selectively executed according to the remaining capacity of the battery.

  The control apparatus for a hybrid vehicle according to the present invention can variably control the valve timing of the engine in consideration of the state of the battery to improve the fuel efficiency of the engine and increase the efficiency of the entire hybrid system.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 relate to an embodiment of the present invention, FIG. 1 is a schematic configuration diagram showing a power system of a hybrid vehicle, FIG. 2 is an explanatory diagram showing a variable range of intake valve opening / closing timing, and FIG. FIG. 4 is an explanatory diagram showing the characteristics of the advance amount map, FIG. 5 is an explanatory diagram showing the characteristics of the fuel consumption rate map, and FIG. 6 is an explanatory diagram showing the torque characteristics depending on the closing timing of the intake valve.

  FIG. 1 shows a schematic system configuration of a power system and its control system in a hybrid vehicle (HEV) using both an engine and a motor. In FIG. 1, reference numeral 1 denotes an engine, and reference numeral 2 denotes a motor. In the present embodiment, an example in which the vehicle travels mainly by the power of the engine 1 and uses the driving force of the motor 2 as auxiliary power will be described.

  As a control system for controlling the power system of the engine 1 and the motor 2, an engine control unit (ECU) 3 for controlling the engine 1 and a motor control unit 4 for controlling the motor 2 are provided. A battery that sends and receives power and a calculation unit that performs energy management such as calculation of the state of charge (SOC) of the battery, control of cooling and charging, abnormality detection, and protection operation when abnormality is detected The battery unit 5 packaged in the above is provided. Each of the units 3, 4, and 5 is controlled by a microcomputer and connected to each other via a communication line such as a CAN (Controller Area Network).

  The engine 1 is provided with an electronic throttle device 7 controlled by the ECU 3 in the intake passage 6. The intake air adjusted by the electronic throttle device 7 and fuel from a fuel injection valve (not shown) are mixed to produce a piston 8. It is supplied to the upper combustion chamber 9. In the combustion chamber 9, an intake valve 10 that opens and closes inflow of air-fuel mixture from the intake passage 6 and an exhaust valve 12 that opens and closes outflow of exhaust gas to the exhaust passage 11 are exposed.

  In this embodiment, the exhaust valve 12 is driven by the exhaust cam 13 and the opening / closing timing is set according to the cam profile of the exhaust cam 13, while the intake valve 10 is opened / closed by the variable valve timing mechanism 14 controlled by the ECU 3. Variable. The variable valve timing mechanism 14 is, for example, a well-known hydraulically driven variable valve timing mechanism, and continuously varies the rotation phase of the intake camshaft with respect to the crankshaft 15.

  On the other hand, the motor 2 is connected to the crankshaft 15 of the engine 1 via a power transmission mechanism 16 and generates driving force upon receiving power supply from the battery unit 5 under the control of the motor control unit 4. The battery is supplied (charged) by regenerative power generation. The motor control unit 4 is a control unit including a motor drive circuit such as an inverter, and performs drive control and regenerative control of the motor 2 in accordance with a control command from the ECU 3.

  The ECU 3 optimally controls the engine 1 and the motor 2 on the basis of various sensors for detecting the driving state and information from the battery unit 5 to enable highly efficient operation as a hybrid system. Examples of signals from the sensors input to the ECU 3 include a crank angle sensor 17 that detects the rotational position of the crankshaft 15 for calculating the engine speed and control timing, and a cam angle that detects the rotational position of the intake cam. There is a signal from a sensor 18, an accelerator opening sensor 19 that detects a depression amount (accelerator opening) of an accelerator pedal (not shown), and the like. Information input from the battery unit 5 to the ECU 3 includes remaining capacity information (SOC information) in which the remaining capacity of the battery is expressed in a state of charge (SOC).

  Here, in order to achieve high-efficiency operation of the entire hybrid system, it is important to efficiently control the engine 1 that is the main power source to reduce fuel consumption. In general, the factors that greatly affect the fuel consumption of the engine include the valve timing of the intake valve and the exhaust valve. For the intake valve, the fuel consumption improves as the closing timing is made slower than near the bottom dead center. The closer to the bottom dead center, the worse the fuel consumption. As for the exhaust valve, if the opening timing is made earlier than near the bottom dead center, the fuel consumption deteriorates, and the closer to the bottom dead center, the better the fuel consumption.

  Therefore, in the present embodiment, the exhaust cam 13 of the engine 1 has a cam profile in which the exhaust valve 12 is opened before bottom dead center and the exhaust valve 12 is closed slightly past the top dead center. The ECU 3 variably controls the opening / closing timing of the intake valve 10 of the engine 1 based on the SOC information of the battery and controls the assist amount by the motor 2 to improve the fuel efficiency of the engine 1 and increase the efficiency of the entire hybrid vehicle. Plan.

  The opening / closing timing of the intake valve 10 is varied within the range shown in FIG. 2 via the variable valve timing mechanism 14, and at the most retarded angle, at a position slightly past the top dead center (for example, 10 ° CA after the top dead center). It is controlled to close at a predetermined position (for example, 100 ° CA after bottom dead center) after opening the bottom dead center, and at the most advanced angle, the position of the top dead center (for example, top dead center). It is controlled to open at 30 ° CA) and close at the bottom dead center.

  In the following, a process for improving the efficiency mainly including the valve timing control of the engine 1 based on the SOC information will be described with reference to the flowchart of the control routine shown in FIG.

  The control routine of FIG. 3 is performed by the ECU 3 under operating conditions except for a state where the SOC of the battery is low (for example, about 30 to 40%) and the battery needs to be charged quickly or when the accelerator is fully open. A valve timing setting means that is executed and sets the valve timing by the variable valve timing mechanism according to the remaining capacity of the battery; a target torque setting means that sets the engine torque that provides the best fuel consumption at the set valve timing as the target torque; A request torque calculating means for calculating the required torque of the engine based on the state, the target torque is compared with the required torque, and when the target torque does not match the required torque, the valve timing is varied via the variable valve timing mechanism 14; Torque adjustment means for controlling the target torque to match the required torque There is realized.

  Note that the processing by the control routine of FIG. 3 is canceled at the time of rapid charging and full-running, and the valve overlap timing with the exhaust valve 12 is increased by advancing the opening / closing timing of the intake valve 10 (for example, the most advanced angle). As a result, the charging efficiency and the scavenging efficiency are increased and the stroke volume is increased, so that the engine is operated at a high output.

  When the control routine of FIG. 3 starts, first, in step S1, the SOC information from the battery unit 5 is read, the advance amount map is referred to based on the current SOC, and the intake valve via the variable valve timing mechanism 14 is read. 10 valve timing (advance amount) is set. As shown in FIG. 4, the advance amount map defines basic characteristics of the opening / closing timing of the intake valve 10 based on the SOC of the battery. The advance amount map is set such that the advance amount becomes smaller as the SOC decreases. Yes.

  That is, the operation state in which the SOC of the battery is low is a state in which the operation amount of the engine 1 must be increased by reducing the operation amount of the motor 2, and in such a state, the opening / closing timing of the intake valve 10 is set. By setting it as late as possible, the valve overlap between the intake valve 10 and the exhaust valve 12 is reduced, and the fuel consumption is reduced by reducing the pumping loss caused by the delayed closing effect of the intake valve. Therefore, experiments or simulations are performed in advance in consideration of the displacement and output characteristics of the engine 1, power transmission characteristics (power distribution characteristics) between the engine 1 and the motor 2, and the fuel consumption of the engine 1 using the battery SOC as a parameter. An optimal advance amount is obtained to improve the above, and a map using this as the basic advance amount is created and stored in the ECU 3, and the advance amount corresponding to the SOC is determined with reference to this map.

  Next, the process proceeds to step S2, and a fuel efficiency rate map corresponding to the advance amount set in step S1 is referred to based on the engine speed, and a target torque Tt of the engine is set. As shown in FIG. 5, the fuel consumption rate map is a map of characteristics represented by an equal fuel consumption rate curve with respect to the engine speed and engine torque. Is determined as the target torque Tt. The fuel consumption rate map is prepared in advance in the ECU 3 for each advance amount.

  In the subsequent step S3, the engine speed and the accelerator opening are read, and the required torque Td is calculated by referring to a map or the like. This required torque Td determines the engine torque corresponding to the driving force requested by the driver from the accelerator opening reflecting the amount of operation of the driver and the engine speed reflecting the engine output state. In terms of numbers, the required torque Td increases as the accelerator opening increases.

  In step S4, the target torque Tt determined from the fuel consumption rate map is compared with the required torque Td corresponding to the driver's required driving force. If the target torque Tt matches the required torque Td, the engine can be operated with the best fuel efficiency. If the target torque Tt exceeds the required torque Td (Td <Tt), that is, If the torque at which the fuel efficiency is optimal at the valve timing determined from the SOC of the battery exceeds the actually required torque, the process proceeds from step S4 to step S5 onward to retard the valve timing and reduce the torque. Processing to suppress and improve fuel efficiency is performed.

  Specifically, in step S5, the valve timing is retarded by a set amount, and a new target torque Tt corresponding to the retarded valve timing is set. As shown in FIG. 6, the amount by which the valve timing is retarded is determined by referring to the engine torque characteristic with respect to the engine speed at each closing timing of the intake valve 10 to minimize the influence on the operating state. And

  Next, the process proceeds to step S6 to check whether the target torque Tt matches the required torque Td. If Td = Tt, the routine is exited. If Td ≠ Tt, the valve timing is delayed in step S7. Check whether keratinization has reached the retard limit (the most retarded position of the variable range). If the retard limit has not been reached, the process returns to step S5 to repeat the valve timing, and if the valve timing has reached the retard limit before Td = Tt. Then, the process proceeds from step S7 to step S8 to check the SOC state of the battery.

  As a result, when the SOC is large and the battery has a margin in step S8, the process proceeds from step S8 to step S9, and the process of suppressing the torque is performed by adjusting the throttle opening through the electronic throttle device 7, and the routine is performed. Exit. The throttle opening is adjusted in increments of the set opening in proportion to the required torque Td, and finally adjusted in the throttle closing direction so that the target torque Tt is lowered to the required torque Td. In step S8, if the SOC is low, the process proceeds from step S8 to step S10, and the target torque Tt is changed to the required torque Td by adjusting the engine torque by adjusting the regeneration amount of the motor 2 to suppress the engine torque. Control to match.

  On the other hand, if the target torque Tt does not exceed the required torque Td in step S4 (Td ≧ Tt), the process proceeds from step S4 to step S11 to check whether the target torque Tt matches the required torque Td. . As a result, when Td = Tt, the best fuel efficiency can be obtained by operating the engine 1 at the previously determined target torque Tt. In the case of Td> Tt, that is, when the required driving force cannot be ensured with the torque that provides the best fuel efficiency at the valve timing determined from the SOC of the battery, the process proceeds from step S11 to step S12 and the subsequent steps. Control according to the SOC is performed.

  In step S12, the SOC of the current battery is checked. If the SOC is large and the battery has a margin, the process proceeds to step S13, where a control command is output from the ECU 3 to the motor control unit 4 to drive the motor 2, and the engine 1 is targeted. The driving torque that is insufficient with respect to the required torque Td when operating at the torque Tt is compensated by the assist of the motor 2. In step S12, if the battery SOC is low and assist by driving the motor 2 cannot be expected, the process proceeds from step S12 to step S14, the valve timing is advanced in proportion to the required torque Td, and the throttle opening is increased. The engine output is increased so as to satisfy the required torque Td by adjusting in the opening direction.

  As described above, in the present embodiment, the engine torque that provides the best fuel consumption at the valve timing set according to the remaining capacity of the battery is set as the target torque, and the target torque matches the required torque based on the operating state. Thus, the valve timing is variably controlled, thereby reducing the fuel consumption of the engine and realizing high-efficiency operation as the whole hybrid vehicle.

Schematic configuration diagram showing the power system of a hybrid vehicle Explanatory diagram showing the variable range of intake valve opening and closing timing Flow chart of control routine Explanatory drawing showing the characteristics of the advance amount map Explanatory diagram showing characteristics of fuel efficiency map Explanatory drawing showing the torque characteristics depending on the closing timing of the intake valve

Explanation of symbols

1 Engine 2 Motor 3 Engine control unit 4 Motor control unit 5 Battery unit 10 Intake valve 12 Exhaust valve 14 Variable valve timing mechanism Td Required torque Tt Target torque
Agent Patent Attorney Susumu Ito

Claims (3)

In a hybrid vehicle control device that uses an engine having a variable valve timing mechanism that varies the valve timing of at least one of an intake valve and an exhaust valve, and a motor that generates driving force by electric power from a battery,
Valve timing setting means for setting valve timing by the variable valve timing mechanism according to the remaining capacity of the battery;
Target torque setting means for setting, as a target torque, engine torque that provides the best fuel efficiency at the valve timing set by the valve timing setting means;
Requested torque calculating means for calculating the required torque of the engine based on the operating state;
The target torque is compared with the required torque, and when the target torque does not match the required torque, the valve timing is varied via the variable valve timing mechanism, and control is performed so that the target torque matches the required torque. And a torque adjusting means for controlling the hybrid vehicle. The torque adjusting means includes
When the target torque exceeds the required torque, the valve timing retarding control is executed. When the target torque does not reach the required torque, the assist control by the motor and the valve timing advance control are performed. The hybrid vehicle control device according to claim 1, wherein the control is selectively executed according to a remaining capacity of the battery. The torque adjusting means includes
When the retarding control of the valve timing is executed and the retarding limit by the variable valve timing mechanism is reached, the regeneration control by the motor and the throttle opening control of the engine are selectively performed according to the remaining capacity of the battery. The hybrid vehicle control device according to claim 2, wherein the control device is executed as follows.

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