Patent Application
20080120019
The present invention relates to a drive system and a control method of the drive system. More specifically the invention pertains to a drive system including an internal combustion engine equipped with an exhaust treatment catalyst in an exhaust system, as well as to a control method of such a drive system.
One proposed drive system has an adsorbent that is arranged in a branch pipe to absorb uncombusted hydrocarbon (HC) gas (see, for example, Japanese Patent Laying-Open Gazette No. H10-153112). The branch pipe is branched off from an exhaust pipe of an engine and is again joined to the exhaust pipe. This prior art drive system utilizes a negative pressure in an air intake system to open a valve disposed in the branch pipe on a start of the engine. In the open position of the valve, the exhaust gas of the engine is led to the branch pipe and goes through the adsorbent, which absorbs the uncombusted HC gas included in the exhaust gas. The HC gas absorbed to the adsorbent is released with an increase in temperature of the adsorbent and is led to the air intake system via an EGR pipe to be burned out.
This prior art drive system may, however, cause unstable operation of the engine and poor emission on a start of the engine. In a stop condition of the engine, the fuel vapor may be accumulated in the air intake system due to oil-tight leakage of a fuel injection valve with elapse of time. The amount of the fuel vapor accumulated in the air intake system is not fixed but is varied depending upon the time elapsed since a stop of the engine. This undesirably causes a variation in air-fuel ratio on or immediately after a restart of the engine with engine cranking and fuel injection under such conditions. The variation in air-fuel ratio may lead to unstable operation of the engine and cause some trouble, for example, a misfire. One possible measure against this problem increases the amount of fuel injection on the start of the engine by taking into account the potential variation in amount of the fuel vapor accumulated in the air intake system. This, however, undesirably worsens the emission. As mentioned above, the proposed drive system utilizes the negative pressure in the air intake system to open the valve and lead the exhaust gas of the engine to the branch pipe for absorption of the uncombusted HC gas in the exhaust gas to the adsorbent. On a start of the engine with engine cranking, the valve-open timing may be too late to lead the exhaust gas to the branch pipe. In this case, the fuel vapor accumulated in the air intake system does not go through the branch pipe with the adsorbent but is directly discharged to the outside air.
The drive system and the drive system control method of the invention thus aim to prevent a variation in air-fuel ratio on or immediately after a start of an internal combustion engine. The drive system and the drive system control method of the invention also aim to improve emission on a start of the internal combustion engine. The drive system and the drive system control method of the invention further aim to ensure satisfaction of a power demand even during start control of the internal combustion engine.
In order to attain at least part of the above and the other related objects, the drive system and the drive system control method of the invention have the configurations discussed below.
The present invention is directed to a first drive system including an internal combustion engine equipped with an exhaust treatment catalyst in an exhaust system. The first drive system includes: a fuel exhaust adsorption unit that is arranged in the exhaust system to absorb a component of a fuel exhaust; a cranking structure that cranks the internal combustion engine; and a start control module that, in response to a start instruction of the internal combustion engine, controls the cranking structure to crank the internal combustion engine and controls the internal combustion engine to start fuel injection from a fuel injection valve and eventually start the internal combustion engine after cranking of the internal combustion engine progresses to a specific extent that is required for substantial elimination of a fuel vapor accumulated in an air intake system and in a combustion chamber.
In response to a start instruction of the internal combustion engine that is equipped with the exhaust treatment catalyst and the fuel exhaust adsorption unit in the exhaust system, the first drive system of the invention controls the cranking structure to crank the internal combustion engine and controls the internal combustion engine to start fuel injection from the fuel injection valve and eventually start the internal combustion engine after cranking of the internal combustion engine progresses to the specific extent that is required for substantial elimination of the fuel vapor accumulated in the air intake system and in the combustion chamber. The fuel injection is performed to start the internal combustion engine after substantial elimination of the fuel vapor accumulated in the air intake system and in the combustion chamber. This arrangement effectively prevents a variation in air-fuel ratio on or immediately after a start of the internal combustion engine. The fuel exhaust adsorption unit absorbs the component of the fuel exhaust flowed into the exhaust system in the course of cranking the internal combustion engine. This arrangement improves emission on a start of the internal combustion engine. The first drive system of the invention may be mounted a motor vehicle as its driving system. One typical application of the invention is thus a motor vehicle equipped with this first drive system.
The present invention is also directed to a second drive system including an internal combustion engine equipped with an exhaust treatment catalyst in an exhaust system. The second drive system includes: a fuel exhaust adsorption unit that is arranged in the exhaust system to absorb a component of a fuel exhaust; a changeover mechanism that is driven by an actuator to change over a flow path of the fuel exhaust between a first gas pathway that causes a main portion of the fuel exhaust introduced into the exhaust system to be discharged without transmission through the fuel exhaust adsorption unit and a second gas pathway that causes all the fuel exhaust introduced into the exhaust system to be discharged after transmission through the fuel exhaust adsorption unit; a cranking structure that cranks the internal combustion engine; and a start control module that, in response to a start instruction of the internal combustion engine, drives the actuator and controls the changeover mechanism to change over the flow path of the fuel exhaust to the second gas pathway and controls the internal combustion engine to start cranking the internal combustion engine and eventually start the internal combustion engine after the changeover of the flow path of the fuel exhaust to the second gas pathway by the changeover mechanism.
In the second drive system of the invention, the changeover mechanism is driven by the actuator to change over the flow path of the fuel exhaust between the first gas pathway that causes the main portion of the fuel exhaust introduced into the exhaust system to be discharged without transmission through the fuel exhaust adsorption unit and the second gas pathway that causes all the fuel exhaust introduced into the exhaust system to be discharged after transmission through the fuel exhaust adsorption unit. In response to a start instruction of the internal combustion engine that is equipped with the exhaust treatment catalyst and the fuel exhaust adsorption unit in the exhaust system, the second drive system of the invention drives the actuator and controls the changeover mechanism to change over the flow path of the fuel exhaust to the second gas pathway and controls the internal combustion engine to start cranking the internal combustion engine and eventually start the internal combustion engine after the changeover of the flow path of the fuel exhaust to the second gas pathway by the changeover mechanism. This arrangement desirably prevents direct discharge of the fuel vapor, which is accumulated in the air intake system and is flowed into the exhaust system in the course of cranking the internal combustion engine, without transmission through the fuel exhaust adsorption unit and thus improves the emission on a start of the internal combustion engine. The second drive system of the invention may be mounted a motor vehicle as its driving system. One typical application of the invention is thus a motor vehicle equipped with this second drive system.
In one preferable embodiment of the invention, the second drive system further includes a changeover detection unit that detects the changeover of the flow path of the fuel exhaust to the second gas pathway by the changeover mechanism. The start control module controls the cranking structure to start cranking the internal combustion engine, in response to detection of the changeover of the flow path of the fuel exhaust to the second gas pathway by the changeover detection unit. This arrangement more effectively prevents direct discharge of the fuel vapor, which is accumulated in the air intake system and is flowed into the exhaust system in the course of cranking the internal combustion engine, without transmission through the fuel exhaust adsorption unit.
In one preferable structure of the second drive system of the invention, the start control module controls the internal combustion engine to start fuel injection from a fuel injection valve and eventually start the internal combustion engine after cranking of the internal combustion engine progresses to a specific extent that is required for substantial elimination of a fuel vapor accumulated in an air intake system and in a combustion chamber. The fuel injection is performed to start the internal combustion engine after substantial elimination of the fuel vapor accumulated in the air intake system and in the combustion chamber. This arrangement effectively prevents a variation in air-fuel ratio on or immediately after a start of the internal combustion engine.
In the first and second drive system of the invention that controls the internal combustion engine to start fuel injection from a fuel injection valve and eventually start the internal combustion engine after cranking of the internal combustion engine progresses to a specific extent, the start control module may control the internal combustion engine to start the fuel injection from the fuel injection valve and start the internal combustion engine after cranking of the internal combustion engine continues for a predetermined time period, which expects the progress of cranking to the specific extent.
In the first and second drive system of the invention, the start control module may function in response to a first start instruction of the internal combustion engine after system activation.
In one preferable structure of either of the first drive system and the second drive system of the invention, the exhaust treatment catalyst is arranged downstream the fuel exhaust adsorption unit to convert the component of the fuel exhaust absorbed by the fuel exhaust adsorption unit and later released from the fuel exhaust adsorption unit. The component of the fuel exhaust released from the fuel exhaust adsorption unit is converted by the active exhaust treatment catalyst.
In one preferable embodiment of either of the first drive system and the second drive system of the invention, the drive system is designed to directly or indirectly use output power of the internal combustion engine and enable output of power to a driveshaft and further includes: a driveshaft motor that outputs power to the driveshaft; an accumulator unit that receives and transmits electric power from and to the driveshaft motor; and a power demand setting module that sets a power demand in response to an operator's manipulation. The start control module controls the driveshaft motor to output a power equivalent to the set power demand to the driveshaft. This arrangement ensures satisfaction of the power demand, although a relatively long time is required for a start of the internal combustion engine. In this embodiment, the start control module may control the driveshaft motor to output the power equivalent to the set power demand to the driveshaft within an output limit of the accumulator unit. This arrangement effectively prevents over discharge of the accumulator unit. In one preferable application, the drive system of this embodiment further includes an electric power-mechanical power input output mechanism that is connected with an output shaft of the internal combustion engine and with the driveshaft to function as the cranking structure with input and output of electric power and mechanical power and to output at least part of the output power of the internal combustion engine to the driveshaft after a start of the internal combustion engine. One typical example of the electric power-mechanical power input output mechanism includes: a three shaft-type power input output module that is linked to three shafts, the output shaft of the internal combustion engine, the driveshaft, and a third rotating shaft, and automatically inputs and outputs power from and to a residual one shaft based on powers input from and output to any two shafts among the three shafts; and a rotating shaft motor that is capable of inputting and outputting power from and to the third rotating shaft. Another typical example of the electric power-mechanical power input output mechanism is a pair-rotor motor that has a first rotor connected to the output shaft of the internal combustion engine and a second rotor connected to the driveshaft and is driven to rotate the first rotor relative to the second rotor through electromagnetic operations of the first rotor and the second rotor.
The present invention is directed to a first control method of a drive system including: an internal combustion engine equipped with an exhaust treatment catalyst in an exhaust system; a fuel exhaust adsorption unit that is arranged in the exhaust system to absorb a component of a fuel exhaust; and a cranking structure that cranks the internal combustion engine. In response to a start instruction of the internal combustion engine the first control method of the drive system (a) controls the cranking structure to crank the internal combustion engine; and (b) controls the internal combustion engine to start fuel injection from a fuel injection valve and eventually start the internal combustion engine after cranking of the internal combustion engine progresses to a specific extent that is required for substantial elimination of a fuel vapor accumulated in an air intake system and in a combustion chamber.
In response to a start instruction of the internal combustion engine that is equipped with the exhaust treatment catalyst and the fuel exhaust adsorption unit in the exhaust system, the first control method of the drive system of the invention controls the cranking structure to crank the internal combustion engine and controls the internal combustion engine to start fuel injection from the fuel injection valve and eventually start the internal combustion engine after cranking of the internal combustion engine progresses to the specific extent that is required for substantial elimination of the fuel vapor accumulated in the air intake system and in the combustion chamber. The fuel injection is performed to start the internal combustion engine after substantial elimination of the fuel vapor accumulated in the air intake system and in the combustion chamber. This arrangement effectively prevents a variation in air-fuel ratio on or immediately after a start of the internal combustion engine. The fuel exhaust adsorption unit absorbs the component of the fuel exhaust flowed into the exhaust system in the course of cranking the internal combustion engine. This arrangement improves emission on a start of the internal combustion engine.
The present invention is directed to a second control method of a drive system including: an internal combustion engine equipped with an exhaust treatment catalyst in an exhaust system; a fuel exhaust adsorption unit that is arranged in the exhaust system to absorb a component of a fuel exhaust; a changeover mechanism that is driven by an actuator to change over a flow path of the fuel exhaust between a first gas pathway that causes a main portion of the fuel exhaust introduced into the exhaust system to be discharged without transmission through the fuel exhaust adsorption unit and a second gas pathway that causes all the fuel exhaust introduced into the exhaust system to be discharged after transmission through the fuel exhaust adsorption unit; and a cranking structure that cranks the internal combustion engine. In response to a start instruction of the internal combustion engine, the second control method of the drive system (a) drives the actuator and controlling the changeover mechanism to change over the flow path of the fuel exhaust to the second gas pathway; and (b) controls the internal combustion engine to start cranking the internal combustion engine and eventually start the internal combustion engine after the changeover of the flow path of the fuel exhaust to the second gas pathway by the changeover mechanism.
In the second control method of the drive system of the invention, the changeover mechanism is driven by the actuator to change over the flow path of the fuel exhaust between the first gas pathway that causes the main portion of the fuel exhaust introduced into the exhaust system to be discharged without transmission through the fuel exhaust adsorption unit and the second gas pathway that causes all the fuel exhaust introduced into the exhaust system to be discharged after transmission through the fuel exhaust adsorption unit. In response to a start instruction of the internal combustion engine that is equipped with the exhaust treatment catalyst and the fuel exhaust adsorption unit in the exhaust system, the second control method of the drive system of the invention drives the actuator and controls the changeover mechanism to change over the flow path of the fuel exhaust to the second gas pathway and controls the internal combustion engine to start cranking the internal combustion engine and eventually start the internal combustion engine after the changeover of the flow path of the fuel exhaust to the second gas pathway by the changeover mechanism. This arrangement desirably prevents direct discharge of the fuel vapor, which is accumulated in the air intake system and is flowed into the exhaust system in the course of cranking the internal combustion engine, without transmission through the fuel exhaust adsorption unit and thus improves the emission on a start of the internal combustion engine.
One mode of carrying out the invention is described below as a preferred embodiment with reference to the accompanied drawings.
The engine 22 is an internal combustion engine that consumes a hydrocarbon fuel, such as gasoline or light oil, to output power. As shown in
As illustrated in
The engine 22 is under control of an engine electronic control unit 24 (hereafter referred to as engine ECU 24). The engine ECU 24 receives, via its input port (not shown), signals from various sensors that measure and detect the conditions of the engine 22. The signals input into the engine ECU 24 include a crank position from a crank position sensor 150 measured as the rotational position of the crankshaft 26, a cooling water temperature from a water temperature sensor 152 measured as the temperature of cooling water for the engine 22, a cam position from a cam position sensor 154 measured as the rotational position of a camshaft driven to open and close the intake valve 128 and an exhaust valve for gas intake and exhaust into and from the combustion chamber, a throttle valve position from a throttle valve position sensor 156 detected as the opening of the throttle valve 124, an intake negative pressure or an amount of intake air from a vacuum sensor 158 measured as the load of the engine 22, and a valve-closing switch signal from a valve-closing switch 149 detecting the setting of the exhaust flow changeover valve 147 in the closed position. The engine ECU 24 outputs, via its output port (not shown), diverse control signals and driving signals to drive and control the engine 22, for example, driving signals to the fuel injection valve 126, driving signals to a throttle motor 136 for regulating the position of the throttle valve 124, control signals to an ignition coil 138 integrated with an igniter, control signals to a variable valve timing mechanism 160 to vary the open and close timings of the intake valve 128, and driving signals to the actuator 148 for opening and closing the exhaust flow changeover valve 147. The engine ECU 24 communicates with the hybrid electronic control unit 70. The engine ECU 24 receives control signals from the hybrid electronic control unit 70 to drive and control the engine 22, while outputting data regarding the driving conditions of the engine 22 to the hybrid electronic control unit 70 according to the requirements.
The power distribution and integration mechanism 30 has a sun gear 31 that is an external gear, a ring gear 32 that is an internal gear and is arranged concentrically with the sun gear 31, multiple pinion gears 33 that engage with the sun gear 31 and with the ring gear 32, and a carrier 34 that holds the multiple pinion gears 33 in such a manner as to allow free revolution thereof and free rotation thereof on the respective axes. Namely the power distribution and integration mechanism 30 is constructed as a planetary gear mechanism that allows for differential motions of the sun gear 31, the ring gear 32, and the carrier 34 as rotational elements. The carrier 34, the sun gear 31, and the ring gear 32 in the power distribution and integration mechanism 30 are respectively coupled with the crankshaft 26 of the engine 22, the motor MG1, and the reduction gear 35 via ring gear shaft 32a. While the motor MG1 functions as a generator, the power output from the engine 22 and input through the carrier 34 is distributed into the sun gear 31 and the ring gear 32 according to the gear ratio. While the motor MG1 functions as a motor, on the other hand, the power output from the engine 22 and input through the carrier 34 is combined with the power output from the motor MG1 and input through the sun gear 31 and the composite power is output to the ring gear 32. The power output to the ring gear 32 is thus finally transmitted to the driving wheels 63a and 63b via the gear mechanism 60, and the differential gear 62 from ring gear shaft 32a.
Both the motors MG1 and MG2 are known synchronous motor generators that are driven as a generator and as a motor. The motors MG1 and MG2 transmit electric power to and from a battery 50 via inverters 41 and 42. Power lines 54 that connect the inverters 41 and 42 with the battery 50 are constructed as a positive electrode bus line and a negative electrode bus line shared by the inverters 41 and 42. This arrangement enables the electric power generated by one of the motors MG1 and MG2 to be consumed by the other motor. The battery 50 is charged with a surplus of the electric power generated by the motor MG1 or MG2 and is discharged to supplement an insufficiency of the electric power. When the power balance is attained between the motors MG1 and MG2, the battery 50 is neither charged nor discharged. Operations of both the motors MG1 and MG2 are controlled by a motor electronic control unit (hereafter referred to as motor ECU) 40. The motor ECU 40 receives diverse signals required for controlling the operations of the motors MG1 and MG2, for example, signals from rotational position detection sensors 43 and 44 that detect the rotational positions of rotors in the motors MG1 and MG2 and phase currents applied to the motors MG1 and MG2 and measured by current sensors (not shown). The motor ECU 40 outputs switching control signals to the inverters 41 and 42. The motor ECU 40 communicates with the hybrid electronic control unit 70 to control operations of the motors MG1 and MG2 in response to control signals transmitted from the hybrid electronic control unit 70 while outputting data relating to the operating conditions of the motors MG1 and MG2 to the hybrid electronic control unit 70 according to the requirements.
The battery 50 is under control of a battery electronic control unit (hereafter referred to as battery ECU) 52. The battery ECU 52 receives diverse signals required for control of the battery 50, for example, an inter-terminal voltage measured by a voltage sensor (not shown) disposed between terminals of the battery 50, a charge-discharge current measured by a current sensor (not shown) attached to the power line 54 connected with the output terminal of the battery 50, and a battery temperature Tb measured by a temperature sensor 51 attached to the battery 50. The battery ECU 52 outputs data relating to the state of the battery 50 to the hybrid electronic control unit 70 via communication according to the requirements. The battery ECU 52 calculates a state of charge (SOC) of the battery 50, based on the accumulated charge-discharge current measured by the current sensor, for control of the battery 50.
The hybrid electronic control unit 70 is constructed as a microprocessor including a CPU 72, a ROM 74 that stores processing programs, a RAM 76 that temporarily stores data, and a non-illustrated input-output port, and a non-illustrated communication port. The hybrid electronic control unit 70 receives various inputs via the input port: an ignition signal from an ignition switch 80, a gearshift position SP from a gearshift position sensor 82 that detects the current position of a gearshift lever 81, an accelerator opening Acc from an accelerator pedal position sensor 84 that measures a step-on amount of an accelerator pedal 83, a brake pedal position BP from a brake pedal position sensor 86 that measures a step-on amount of a brake pedal 85, and a vehicle speed V from a vehicle speed sensor 88. The hybrid electronic control unit 70 communicates with the engine ECU 24, the motor ECU 40, and the battery ECU 52 via the communication port to transmit diverse control signals and data to and from the engine ECU 24, the motor ECU 40, and the battery ECU 52, as mentioned previously.
The hybrid vehicle 20 of the embodiment thus constructed calculates a torque demand to be output to the ring gear shaft 32a functioning as the drive shaft, based on observed values of a vehicle speed v and an accelerator opening Acc, which corresponds to a driver's step-on amount of an accelerator pedal 83. The engine 22 and the motors MG1 and MG2 are subjected to operation control to output a required level of power corresponding to the calculated torque demand to the ring gear shaft 32a. The operation control of the engine 22 and the motors MG1 and MG2 selectively effectuates one of a torque conversion drive mode, a charge-discharge drive mode, and a motor drive mode. The torque conversion drive mode controls the operations of the engine 22 to output a quantity of power equivalent to the required level of power, while driving and controlling the motors MG1 and MG2 to cause all the power output from the engine 22 to be subjected to torque conversion by means of the power distribution integration mechanism 30 and the motors MG1 and MG2 and output to the ring gear shaft 32a. The charge-discharge drive mode controls the operations of the engine 22 to output a quantity of power equivalent to the sum of the required level of power and a quantity of electric power consumed by charging the battery 50 or supplied by discharging the battery 50, while driving and controlling the motors MG1 and MG2 to cause all or part of the power output from the engine 22 equivalent to the required level of power to be subjected to torque conversion by means of the power distribution integration mechanism 30 and the motors MG1 and MG2 and output to the ring gear shaft 32a, simultaneously with charge or discharge of the battery 50. The motor drive mode stops the operations of the engine 22 and drives and controls the motor MG2 to output a quantity of power equivalent to the required level of power to the ring gear shaft 32a. The torque conversion drive mode is equivalent to the charge-discharge drive mode under the condition of the charge-discharge power of the battery 50 equal to 0. Namely the torque conversion drive mode is regarded as one type of the charge-discharge drive mode. The hybrid vehicle 20 of the embodiment is accordingly driven with a switchover of the drive mode between the motor drive mode and the charge-discharge drive mode.
The description regards the operations of the hybrid vehicle 20 of the embodiment having the configuration discussed above, especially a series of start control for a first start of the engine 22 after system activation.
In the start control routine of
The CPU 72 waits until elapse of a preset time period since the start of cranking the engine 22 (step S140) and inputs a rotation speed Ne of the engine 22 (step S150). When the input rotation speed Ne of the engine 22 reaches or exceeds a preset reference rotation speed Nref (step S160), the CPU 72 gives a start instruction to the engine ECU 24 to perform fuel injection control and ignition control (step S170). The fuel injection from the fuel injection valve 126 starts after elapse of the preset time period for cranking the engine 22, because of the following reason. In a stop condition of the engine 22, the fuel vapor may be accumulated in an air intake system due to oil-tight leakage of the fuel injection valve 126 with elapse of time. The accumulated fuel vapor undesirably causes a variation in air-fuel ratio on or immediately after a restart of the engine 22, even when the fuel injection from the fuel injection valve 126 is regulated to attain a target air-fuel ratio. This variation in air-fuel ratio may lead to some trouble, for example, a misfire. The preset time period is accordingly specified as an engine cranking time required for substantial elimination of the fuel vapor accumulated in the air intake system and is set equal to 5 seconds in this embodiment.
The CPU 72 subsequently specifies whether the start of the engine 22 is complete or incomplete (step S180). In the case of the complete start of the engine 22, the CPU 72 waits until complete warm-up of the first catalytic conversion unit 134 (filled with the three-way catalyst) and the three-way catalyst 141 included in the second catalytic conversion unit 140 (step S190) and gives a valve-opening instruction to the engine ECU 24 to open the exhaust flow changeover valve 147 (step S200). The start control routine is then terminated. The HC included in the exhaust is converted by the catalytic functions of the three-way catalyst in the first catalytic conversion unit 134 and the three-way catalyst 141 in the second catalytic conversion unit 140. The HC absorbed by the HC adsorbent 146 is released at high temperatures and is introduced into the three-way catalyst 141 for catalytic conversion.
The description regards drive control of the engine 22 and the motors MG1 and MG2 at a start of the engine 22.
In the drive control routine of
After the data input, the CPU 72 sets a torque demand Tr* to be output to the ring gear shaft 32a or the driveshaft linked with the drive wheels 63a and 63b as a required torque for the hybrid vehicle 20, based on the input accelerator opening Acc and the input vehicle speed V (step S220). A concrete procedure of setting the torque demand Tr* in this embodiment stores in advance variations in torque demand Tr* against the accelerator opening Acc and the vehicle speed V as a torque demand setting map in the ROM 74 and reads the torque demand Tr* corresponding to the given accelerator opening Acc and the given vehicle speed V from this torque demand setting map. One example of the torque demand setting map is shown in
The CPU 72 subsequently identifies the value of the flag F representing a start of cranking the engine 22 (step S230). When the flag F is equal to 0, a value ‘0’ is set to a torque command Tm1* as a torque to be output from the motor MG1 (step S240). When the flag F is equal to 1, on the other hand, a cranking torque Tcr required for cranking the engine 22 is set to the torque command Tm1* of the motor MG1 (step S250).
After setting the torque command Tm1* of the motor MG1, the CPU 72 calculates an upper torque restriction Tmax as a maximum possible torque output from the motor MG2 according to Equation (1) given below (step S260). The calculation subtracts the product of the torque command Tm1* and the current rotation speed Nm1 of the motor MG1, which represents the power consumption (power generation) of the motor MG1, from the output limit Wout of the battery 50 and divides the difference by the current rotation speed Nm2 of the motor MG2:
Tmax=(Wout−Tm1*·Nm1)/Nm2 (1)
The CPU 72 then calculates a tentative motor torque Tm2tmp as a torque to be output from the motor MG2 from the torque demand Tr*, the torque command Tm1* of the motor MG1, a gear ratio ρ of the power distribution integration mechanism 30, and the gear ratio Gr of the reduction gear 35 according to Equation (2) given below (step S270):
Tm2tmp=(Tr*+Tm1*/ρ)/Gr (2)
The CPU 72 compares the calculated upper torque restriction Tmax with the calculated tentative motor torque Tm2tmp and sets the smaller to a torque command Tm2* of the motor MG2 (step S280). Such setting of the torque command Tm2* of the motor MG2 restricts the torque demand Tr* to be output to the ring gear shaft 32a or the driveshaft within the range of the output limit Wout of the battery 50. Equation (2) is readily led from the alignment chart of
After setting the torque commands Tm1* and Tm2* of the motors MG1 and MG2 in the above manner, the CPU 72 sends the torque commands Tm1* and Tm2* to the motor ECU 40 (step S290). The motor ECU 40 receives the torque commands Tm1* and Tm2* and performs switching control of the switching elements included in the respective inverters 41 and 42 to drive the motor MG1 with the torque command Tm1* and the motor MG2 with the torque command Tm2*.
The processing of steps S210 to S290 is repeated until completion of the start of the engine 22 (step S300) by execution of the start control routine of
As described above, at the time of a first start of the engine 22 after system activation, the hybrid vehicle 20 of the embodiment starts fuel injection from the fuel injection valve 126 to start the engine 22 after cranking the engine 22 for the preset time period. Such control ensures start of fuel injection from the fuel injection valve 126 after substantial elimination of the fuel vapor accumulated in the air intake system. This effectively prevents a variation of the air-fuel ratio and stabilizes the drive of the hybrid vehicle 20 on or immediately after a start of the engine 22. The motor MG2 is driven and controlled to output the torque demand Tr* to the ring gear shaft 32a or the driveshaft. The drive control of this embodiment satisfies output of the torque demand Tr* to the ring gear shaft 32a, although requiring a relatively long time for a complete start of the engine 22.
The hybrid vehicle 20 of the embodiment starts cranking the engine 22 after closing the exhaust flow changeover valve 147. Such control enables the fuel vapor accumulated in the air intake system to be effectively absorbed by the HC adsorbent 146. This improves the emission on the start of the engine 22. The closed position of the exhaust flow changeover valve 147 is confirmed by the valve-closing switch signal output from the valve-closing switch 149. This further ensures effective absorption of the fuel vapor accumulated in the air intake system to the HC adsorbent 146.
The hybrid vehicle 20 of the embodiment starts cranking the engine 22 after confirming the closed position of the exhaust flow changeover valve 147 based on the valve-closing switch signal output from the valve-closing switch 149. This method is, however, not restrictive but any other suitable technique may be applied to confirm the closed position of the exhaust flow changeover valve 147. One applicable technique measures the electric current applied to the electric actuator 148 for confirmation of the closed position of the exhaust flow changeover valve 147. A modified flow of the start control may not directly confirm the closed position of the exhaust flow changeover valve 147 but may start cranking the engine 22 after elapse of a preset time period since output of a valve-closing instruction. When a distance between the air intake system and the HC adsorbent 146 is in a specified range, the start control may immediately start cranking the engine 22 without confirming the closed position of the exhaust flow changeover valve 147.
In the hybrid vehicle 20 of the embodiment, the second catalytic conversion unit 140 is designed to introduce the HC, which is absorbed by the HC adsorbent 146 and is later released from the HC adsorbent 146, into the three-way catalyst 141 for catalytic conversion. The HC absorbed by the HC adsorbent 146 and later released from the HC adsorbent 146 may directly be led to the air intake system via an EGR pipe to be burned out.
The hybrid vehicle 20 of the embodiment includes two catalytic conversion units, that is, the first catalytic conversion unit 134 and the second catalytic conversion unit 140. The hybrid vehicle may, however, have only one catalytic conversion unit, that is, the second catalytic conversion unit 140, or may have three or more catalytic conversion units.
In the hybrid vehicle 20 of the embodiment, the power of the engine 22 is output via the power distribution integration mechanism 30 to the ring gear shaft 32a or the driveshaft connected to the drive wheels 63a and 63b. The technique of the invention is, however, not restricted to this configuration but may also be applicable to a hybrid vehicle 220 of a modified configuration shown in
The technique of the invention is applicable to the hybrid vehicle of any other structure including: an engine equipped with an HC adsorbent and an exhaust treatment catalyst for catalytic conversion in an exhaust system; and a cranking device for cranking the engine. The technique of the invention is not restricted to the hybrid vehicles but is also applicable to conventional motor vehicles without a drive motor, as well as drive systems that are not mounted on the motor vehicles.
The embodiment discussed above is to be considered in all aspects as illustrative and not restrictive. There may be many modifications, changes, and alterations without departing from the scope or spirit of the main characteristics of the present invention.
The technique of the present invention is preferably applicable to the manufacturing industries of drive systems and automobiles.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-116541 | Apr 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/308362 | 4/14/2006 | WO | 00 | 7/9/2007 |
