JP2004156505A - Hybrid vehicle that detects torque fluctuations and performs air-fuel ratio control - Google Patents

Abstract

An engine mounted on a hybrid vehicle is operated at a lean limit without increasing torque fluctuation to improve fuel efficiency.
Kind Code: A1 In a hybrid vehicle that is operated while distributing the output of an engine to a generator and an axle at a predetermined ratio, a change in generated power when the engine is operated in a quasi-stationary state is detected. If the engine is operating in a quasi-steady state, the torque fluctuation of the engine appears in the fluctuation of the generated power. Therefore, if the operating air-fuel ratio of the engine is controlled based on the fluctuation of the generated power, the engine can be operated at the lean limit without increasing the torque fluctuation, and the fuel efficiency can be improved.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for appropriately operating an internal combustion engine in a hybrid vehicle including an internal combustion engine and an electric motor as power sources.
[0002]
[Prior art]
A hybrid vehicle can improve fuel consumption efficiency by using a combination of an engine, a generator, and a motor as a power source. In order to further improve the fuel consumption efficiency of the hybrid vehicle, it is effective to set the operating air-fuel ratio of the engine as lean as possible within a range in which torque fluctuation is allowed. In view of these points, in a series hybrid vehicle, there has been proposed a technology for detecting a fluctuation in engine torque by detecting a fluctuation in electric power generated by a generator to make the operating air-fuel ratio of the engine lean (Patent Document 1). 1). Here, the series hybrid vehicle is a hybrid vehicle that drives the axle by supplying the entire output of the engine to a generator, temporarily converting the output into electric energy, and driving the motor using the electric energy. . In such a series hybrid vehicle, since the output of the engine is directly supplied to the generator, when the output of the engine fluctuates, the power generated by the generator fluctuates accordingly. Utilizing such a feature of the series hybrid vehicle, the technology disclosed in Patent Document 1 described above detects fluctuations in engine torque by detecting fluctuations in generated power.
[0003]
Also, the output of the engine is divided into two, one output is transmitted to the axle as it is as a driving force, the other output is once converted to electric energy by a generator, and then returned to mechanical work by the motor again to the axle. A hybrid vehicle of the transmission type has also been proposed (for example, Patent Document 2). Electric energy can be converted into a desired form of driving force by a motor and output. Therefore, if a part of the engine output is converted into electric energy at an appropriate ratio according to the running state of the vehicle, the engine can be efficiently driven without being bound by the running state of the vehicle. It is possible to improve the efficiency of the entire vehicle.
[0004]
In such a hybrid vehicle in which the engine output is divided into two, unlike the case of the series hybrid vehicle, the output of the engine is not directly supplied to the generator. For this reason, the fluctuation of the generated power does not correspond to the fluctuation of the torque of the engine. However, when the vehicle is stopped, all the output of the engine is supplied to the generator. Therefore, similarly to the series hybrid vehicle, it is possible to detect a change in the engine torque from a change in the generated power and to make the operating air-fuel ratio of the engine lean.
[0005]
[Patent Document 1]
JP-A-6-245318
[Patent Document 2]
JP-A-9-308012
[0006]
[Problems to be solved by the invention]
However, in a hybrid vehicle in which the engine output is divided into two, the operating range in which the torque fluctuation can be detected is limited to the narrow operating range of the engine for the following reasons. There is a problem that it is difficult to lean.
[0007]
First, the hybrid vehicle proposed in Patent Document 2 will be described. In this type of hybrid vehicle, an engine and a generator are connected by a planetary gear, and when the engine is operated while the vehicle is stopped, the generator Rotates at a speed increased by a predetermined gear ratio with respect to the rotation speed of the engine. For this reason, if it is attempted to reduce the rotation speed of the generator to the allowable rotation speed, the engine operation region in which torque fluctuation can be detected is limited to the low rotation region.
[0008]
Further, also regarding the load range of the engine, the engine operation range where the torque fluctuation can be detected is limited to the low load range for the following reason. In a hybrid vehicle in which the engine output is divided into two, only a part of the engine output is converted into electric energy, so that the generated power is not so large. Therefore, a secondary battery having a small capacity is generally mounted. It is a target. However, such small-capacity secondary batteries are limited in the amount of power that can be charged per hour from the viewpoint of battery life, and when the vehicle is stopped, the entire output of the engine is supplied to the generator. For this reason, when trying to suppress the generated power of the generator to an allowable range, the conditions under which the torque fluctuation can be detected are limited to conditions where the engine output is small, that is, low load and low rotational speed operating conditions. It will be lost.
[0009]
However, the hybrid vehicle proposed in Patent Document 3 has a structure in which the engine and the axle are electromagnetically coupled to each other, so that there is no limitation due to the gear ratio unlike Patent Document 2. However, even in the hybrid vehicle proposed in Patent Literature 3, the conditions under which the torque fluctuation of the engine can be detected are limited to the operating conditions with a small engine output due to the above-described restriction caused by the capacity of the secondary battery.
[0010]
Of course, if a method that directly detects the pressure in the combustion chamber of the engine is used, torque fluctuations can be detected under a wide range of engine operating conditions without such restrictions, but a dedicated device such as a combustion pressure sensor is required. As a result, the entire configuration becomes complicated.
[0011]
The present invention has been made in order to solve the above-described problems in the conventional technology, and in a hybrid vehicle of a type in which the engine output is divided into two, in a wide engine operation range without complicating the device configuration. It is an object of the present invention to provide a technology capable of detecting an engine torque fluctuation and making the operating air-fuel ratio lean over a wide range.
[0012]
[Means for Solving the Problems and Their Functions and Effects]
In order to solve at least a part of the problems described above, a hybrid vehicle according to the present invention employs the following configuration. That is,
A hybrid vehicle including an electric motor that outputs power to an axle, an internal combustion engine, and a generator that is driven by the internal combustion engine and supplies electric power to the electric motor,
An output distribution mechanism that distributes an output of the internal combustion engine to the generator and the axle at a predetermined ratio;
A quasi-stationary operating state detecting means for detecting that a change in operating conditions of the internal combustion engine is in a quasi-stationary operating state that is equal to or less than a predetermined amount,
Generated power fluctuation detecting means for detecting the amount of fluctuation in the generated power of the generator in the quasi-stationary operation state,
Air-fuel ratio control means for controlling an operating air-fuel ratio of the internal combustion engine based on the detected fluctuation amount of the generated power;
The gist is to provide
[0013]
Further, the control method of the present invention corresponding to the above hybrid vehicle,
A method for controlling an operating air-fuel ratio of an internal combustion engine in a hybrid vehicle including an electric motor that outputs power to an axle, an internal combustion engine, and a generator that is driven by the internal combustion engine and supplies power to the electric motor. ,
Distributing the output of the internal combustion engine to the generator and the axle at a predetermined ratio;
A step of detecting that the fluctuation of the operating condition of the internal combustion engine is in a quasi-stationary operating state that is equal to or less than a predetermined amount,
Detecting a fluctuation amount of the generated power of the generator in the quasi-stationary operation state,
A step of controlling an operating air-fuel ratio of the internal combustion engine based on the detected fluctuation amount of the generated power;
The gist is to provide
[0014]
In such a hybrid vehicle and the control method, when the internal combustion engine is operating in a quasi-steady state of operation, the amount of change in the power generated by the generator is detected, and based on the detected amount of change, the operating idle of the internal combustion engine is determined. Control the fuel ratio. Since the output of the internal combustion engine is distributed to the generator and the axle at a predetermined ratio, the amount of change in the generated power is a value representing the amount of change in the output torque of the internal combustion engine. In addition, since the internal combustion engine can be set to a quasi-steady operating condition under various operating conditions, according to such a method, it is possible to detect a fluctuation amount of the output torque of the internal combustion engine under a wide range of operating conditions. Therefore, if the operating air-fuel ratio of the internal combustion engine is controlled based on the fluctuation amount of the generated power thus obtained, it is possible to control the air-fuel ratio to an appropriate value without increasing the torque fluctuation.
[0015]
In such a hybrid vehicle and control method, a planetary gear is adopted as a mechanism for distributing the output of the internal combustion engine, and a planetary carrier of the planetary gear is connected to the output shaft of the internal combustion engine, a sun gear is connected to the generator, and a ring gear is connected to the axle. It is good to do. According to such a configuration, the output of the internal combustion engine can be reliably distributed to the generator and the axle at a ratio determined by the gear ratio of the planetary gears.
[0016]
Further, in the hybrid vehicle and the control method, when the operation amount of the accelerator pedal provided in the hybrid vehicle is equal to or less than a predetermined value, it may be determined that the vehicle is in the quasi-stationary operation state.
[0017]
Since the operating state of the hybrid vehicle is controlled based on the operation of the accelerator pedal, if the accelerator pedal is not operated, the operating state of the entire vehicle is constant, and thus the operating state of the internal combustion engine is also constant. Can be considered. Therefore, it is preferable that the quasi-steady running state can be easily detected based on the operation amount of the accelerator pedal.
[0018]
In the above-described hybrid vehicle and control method, the fluctuation amount of the generated power may be detected as follows. First, it is also possible to detect that the generator is in a power generation state, confirm that the generator is in a power generation state, and detect a fluctuation amount of a torque command value to the generator.
[0019]
If the generator is in a power generation state, the torque command value to the generator corresponds to the generated power. Therefore, it is preferable to detect the amount of change in the torque command value in this way, since the amount of change in the power generated by the generator can be easily detected.
[0020]
In the above-described hybrid vehicle and control method, the operating air-fuel ratio of the internal combustion engine may be controlled as follows. That is, the amount of change in the power generated by the generator is detected, and when the detected amount of change is larger than the first threshold, the operating air-fuel ratio of the internal combustion engine is enriched. If the detected amount of change is less than the second predetermined threshold value smaller than the first threshold value, the operating air-fuel ratio of the internal combustion engine is made lean.
[0021]
If the fluctuation amount of the generated power is larger than the first threshold value, it is considered that the operating air-fuel ratio of the internal combustion engine becomes too lean and the combustion becomes unstable. In such a case, the air-fuel ratio is increased in the rich direction. I will correct it. Conversely, if the amount of change in the generated power is less than the second threshold smaller than the first threshold, the combustion state of the internal combustion engine is stable, and there is room for further reducing the operating air-fuel ratio. Conceivable. Therefore, in such a case, the operating air-fuel ratio is corrected in the lean direction. This is preferable because the internal combustion engine can be operated at a more appropriate air-fuel ratio.
[0022]
In the above-described hybrid vehicle and control method, the opening of the throttle valve may be controlled as follows in accordance with the control of the operating air-fuel ratio of the internal combustion engine. That is, when the operating air-fuel ratio of the internal combustion engine is made rich, the opening of the throttle valve is corrected to the closed side, and when the operating air-fuel ratio is made lean, the opening of the throttle valve is corrected to the open side. Control may be performed.
[0023]
Generally, when the operating air-fuel ratio is made rich, the output of the internal combustion engine increases, and when the operating air-fuel ratio is made lean, the output tends to decrease. Therefore, it is preferable to correct the opening of the throttle valve in accordance with the control of the air-fuel ratio in this manner, because it is possible to correct the output fluctuation due to the air-fuel ratio fluctuation.
[0024]
Alternatively, in the above-described hybrid vehicle and control method, the operating air-fuel ratio may be learned and controlled as follows. That is, the target air-fuel ratio for controlling the internal combustion engine is stored in association with the operating conditions of the internal combustion engine, and the operating air-fuel ratio of the internal combustion engine is controlled, and the stored target air-fuel ratio is updated. Thus, the target air-fuel ratio may be learned.
[0025]
It is preferable to learn the target air-fuel ratio of the internal combustion engine in this way, since the next time the internal combustion engine is operated under the same operating conditions, it is possible to operate with the optimum air-fuel ratio from the beginning.
[0026]
Further, in the above-described hybrid vehicle and the control method for learning control of the operating air-fuel ratio, the opening degree of the throttle valve may be learned and controlled as follows. That is, by storing the target opening of the throttle valve in association with the operating condition of the internal combustion engine, controlling the opening of the throttle valve, and updating the stored value of the throttle opening. The target opening may be learned.
[0027]
If the target opening of the throttle valve is learned in addition to the operating air-fuel ratio in this way, the next time the internal combustion engine is operated under the same operating conditions, the engine will operate at the optimum air-fuel ratio from the beginning, and the fluctuation of the air-fuel ratio will be reduced. It is preferable because the output fluctuation can be corrected and a stable output can always be generated from the internal combustion engine.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to more clearly explain the operation and effect of the present invention, embodiments of the present invention will be described in the following order.
A. Device configuration:
A-1. Configuration of hybrid vehicle:
A-2. Overview of hybrid vehicle operation:
B. Air-fuel ratio control of the first embodiment:
C. Air-fuel ratio control of the second embodiment:
D. Modification:
[0029]
A. Device configuration:
A-1. Configuration of hybrid vehicle:
FIG. 1 is an explanatory diagram illustrating a schematic configuration of a hybrid vehicle 100 according to the present embodiment. As shown, the hybrid vehicle 100 has an engine 110, a motor generator (MG1) 120, and a motor generator (MG2) 130, and the engine 110 and the two motor generators MG1 and MG2 are planetary. They are connected to each other by a gear 140. Although described in detail later, engine 110 and MG2 mainly output driving force for driving the vehicle, and MG1 is mainly driven by engine 110 and mainly functions as a generator. Planetary gear 140 serves to transmit the output from MG2 to drive wheels 172 via chain belt 174 and axle 170, and serves as a power split mechanism for distributing the output from engine 110 to MG1 and drive wheels 172. It also has a role as a transmission that reduces or increases the rotation speed of the MG 2 and the engine 110 and transmits the rotation to the drive wheels 172. The function of the planetary gear 140 will be described later.
[0030]
The engine 110 has four combustion chambers, and generates power by burning a mixture of air and fuel in each combustion chamber. An intake passage 190 is connected to each combustion chamber, and an air cleaner 196 is provided upstream of the intake passage 190. After the foreign matter is removed by the air cleaner 196, the air is supplied into the combustion chamber via the intake passage 190. A throttle valve 186 for adjusting the amount of air flowing into the combustion chamber is provided in the intake passage 190, and the throttle valve 186 is driven by an electric actuator 188. The intake passage 190 branches off downstream of the throttle valve 186 and is connected to each combustion chamber. At a portion where the branched intake passage 190 is connected to each combustion chamber, a fuel injection valve 192 for injecting fuel is provided for each combustion chamber. The fuel injected from the fuel injection valve 192 is supplied together with air into the combustion chamber to form an air-fuel mixture. Each combustion chamber is provided with an ignition plug (not shown), and the mixture can be ignited and burned by blowing a spark from the ignition plug. Exhaust gas generated when the air-fuel mixture burns in the combustion chamber is discharged from the exhaust passage 180. A purification catalyst 200 is provided in the exhaust passage 180, and harmful substances contained in exhaust gas can be purified by the purification catalyst 200.
[0031]
The engine 110 has an electronic control unit (hereinafter, engine ECU) 112 for controlling the engine. The engine ECU 112 is a known microcomputer to which a CPU, a RAM, a ROM, an A / D converter, a D / A converter, a timer, and the like are connected so as to be able to exchange data with each other via a bus. A crank angle sensor 118 is provided at the tip of the crankshaft 114, and the engine ECU 112 acquires information on the rotational position (crank angle) of the crankshaft 114 based on the output of the crank angle sensor 118. The engine ECU 112 drives the electric actuator 188, the fuel injection valve 192, the ignition plug, and the like at appropriate timings under the control of the hybrid ECU 160, which will be described later, while synchronizing with the rotation of the crankshaft 114. Control the operating state.
[0032]
The planetary gear 140 is arranged at a central portion thereof, a ring gear 148 provided concentrically outside the sun gear 142, and disposed between the sun gear 142 and the ring gear 148, and rotates around the outer periphery of the sun gear 142. It comprises a plurality of planetary pinion gears 144 that revolve while rotating, and a planetary carrier 146 that is coupled to the end of the crankshaft 114 of the engine and supports the rotation shaft of each planetary pinion gear 144. Sun gear 142 is coupled to rotor 123 of MG 1 via sun gear shaft 141, and ring gear 148 is coupled to rotor 133 of MG 2 via ring gear shaft 147. Planetary carrier 146 is coupled to crankshaft 114 of the engine.
[0033]
In the planetary gear 140 having such a configuration, the three axes of the sun gear shaft 141, the ring gear shaft 147, and the crankshaft 114 serve as power input / output shafts, and the power input / output to any two of the three shafts is provided. Once determined, the power input / output to the remaining one axis is determined. A chain belt 174 is connected to the ring gear 148, and power is transmitted to drive wheels 172 via the chain belt 174 and the axle 170 to drive the hybrid vehicle 100.
[0034]
MG1 is an AC synchronous motor, which includes a rotor 123 having a plurality of permanent magnets 122 on an outer peripheral surface, a stator 125 around which a three-phase coil 124 for forming a rotating magnetic field is wound, and the like. The stator 125 is fixed to the case 138, and the rotor 123 is coupled to the sun gear shaft 141 of the planetary gear 140 as described above. The sun gear shaft 141 is provided with a resolver 126 for detecting the rotation angle of the rotor 123. MG1 is connected to motor ECU 156 via inverter 152. Motor ECU 156 supplies AC current having an appropriate current value at an appropriate frequency from battery 150 to three-phase coil 124 by controlling inverter 152, thereby controlling the operation of MG1.
[0035]
MG2 is also an AC synchronous motor similar to MG1, and includes a rotor 133 having a plurality of permanent magnets 132 on its outer peripheral surface, a stator 135 around which a three-phase coil 134 for forming a rotating magnetic field is wound, and the like. The rotor 133 of the MG 2 is connected to the ring gear shaft 147 of the planetary gear 140, and the stator 135 is fixed to the case 138. The ring gear shaft 147 is provided with a resolver 136 that detects the rotation angle of the rotor 133. MG2 is connected to motor ECU 156 via inverter 154, and motor ECU 156 controls the operation of MG2 by controlling inverter 154.
[0036]
The hybrid vehicle 100 includes a hybrid ECU 160 that controls the entire vehicle in addition to the engine ECU 112 and the motor ECU 156. These ECUs are microcomputers having the same configuration as the engine ECU 112 described above. The hybrid ECU 160 detects various information such as the accelerator position sensor 162, the brake switch 164, and the battery 150 to determine the operating conditions of the vehicle as a whole, and based on the detected information, the engine ECU 112 and the motor ECU 156 And the operations of MG1 and MG2.
[0037]
B-2. Overview of hybrid vehicle operation:
The operation principle of the hybrid vehicle 100 having the above configuration, particularly, the function of the planetary gear 140 will be described. When the power (ie, rotation speed and torque) input / output to any two of the three shafts of the sun gear shaft 141, the ring gear shaft 147, and the crankshaft 114 is determined, the remaining one The power (rotational speed and torque) input to and output from the shaft is determined. The relationship between the rotational speed and the torque input / output between these three axes can be easily obtained by using the alignment chart.
[0038]
FIG. 2 is an alignment chart showing the relationship between the rotation speed and the rotation direction of each gear connected to the three axes of the planetary gear 140. Here, the vertical axis represents the rotation speed of each gear (the sun gear 142, the ring gear 148, the planetary carrier 146), that is, the rotation speed of the engine 110, MG2, and MG1. On the other hand, the horizontal axis represents the gear ratio of each gear. Assuming that the number of teeth of the sun gear 142 with respect to the number of teeth of the ring gear 148 is ρ, the vertical axis corresponding to the planetary carrier 146 is located at a coordinate position that internally divides the distance between the sun gear 142 and the ring gear 148 into 1: ρ.
[0039]
Now, it is assumed that the rotational speed of the planetary carrier 146, ie, the engine 110, is Ne, and the rotational speed of the ring gear 148, ie, the MG2, is Nr. On the alignment chart shown in FIG. 2, the rotation speed Ne is plotted on the coordinate axis C representing the planetary carrier, the rotation speed Nr is plotted on the coordinate axis R representing the ring gear, and both plot points are connected by a straight line. Considering such a straight line, the rotation speed Ns of the sun gear 142, that is, the MG1 can be obtained as the coordinates of the intersection of the obtained straight line and the coordinate axis S representing the sun gear. Such a straight line is called an operating collinear line. If any two rotation speeds among the planetary carrier 146, the ring gear 148, and the sun gear 142 are determined in this manner, two coordinate points are plotted on a collinear chart, and an operation collinear line connecting both plot points is performed. By considering the above, another rotation speed can be obtained.
[0040]
Next, the relationship between torques input and output between the three axes of the planetary gear 140 will be described. In order to obtain the relationship between the torques on the alignment chart, the operating collinear is treated as if it were a rigid body, and the torque is treated as a force acting on the rigid body. For example, consider a case where the engine 110 generates a torque Te and outputs a torque Tr from the drive wheels 172. The torque output from the drive wheel 172 appears as a reaction torque Tr applied on the coordinate axis R on the operating collinear line.
[0041]
Now, at the position of the coordinate axis C, a torque Te is applied to the operation collinear line from below. Then, as shown in FIG. 3, it is considered that this torque Te is distributed and acts on the coordinate axis S and the coordinate axis R. Here, assuming that a torque applied on the coordinate axis S is a torque Tes, the torque Tes is
Tes = Te · ρ / (1 + ρ) (1)
And the torque acting on the coordinate axis R is the torque Ter, the torque Ter is:
Ter = Te / (1 + ρ) (2)
It is expressed as
[0042]
When the torque Tr is to be output from the drive wheels 172, the torque Ter is distributed from the engine 110, so that the insufficient torque Tr-Ter may be output from the MG2. This can be obtained as follows by considering the balance of the torque on the operating collinear line. First, when the torque Tr 1 is output from the drive wheel 172, the reaction torque Tr 1 is applied to the position of the coordinate axis R on the operating collinear line. Therefore, on the coordinate axis R, in order to balance the torque Ter distributed from the engine 110, the reaction torque Tr, and the output torque of the MG2, the torque Tm2 to be output by the MG2 is calculated as Tm2 = Tr−Ter. be able to.
[0043]
Further, considering the balance on the coordinate axis S, the torque Tm1 to be output by the MG1 can be obtained. That is, since only the torque Tes distributed from the engine 110 is applied to the coordinate axis S, a torque having the same value may be output from the MG1 in the reverse direction.
[0044]
Here, as indicated by the coordinate axis S in the alignment chart of FIG. 2, the rotation direction of the MG1 is opposite to the direction of the torque Tm1. This indicates that MG1 is operating as a generator. Further, as shown on the coordinate axis R, the rotation direction of the MG2 and the direction of the torque Tm2 are the same. This indicates that MG2 is operating as a motor. In other words, the power is being consumed by MG2 while the power is being generated by MG1.
[0045]
FIG. 3 is a collinear chart when the engine 110 is operated with the hybrid vehicle 100 stopped. First, considering the rotation speed, the rotation speed of the ring gear 148 becomes Nr = 0 in response to the stop of the vehicle, so that the operating collinear line passes through the origin of the coordinate axis R. At this time, if the rotational speed Ne of the engine 110 is set on the coordinate axis C, as shown in FIG. 3, the operating collinear is determined to be one, and the rotational speed Ns of the sun gear is determined by passing the operating collinear on the coordinate axis S. Can be obtained as coordinates. As illustrated, the rotation speed Ns of the sun gear (that is, the rotation speed of MG1) is a rotation speed that is increased by 1+ (1 / ρ) times the rotation speed Ne of the engine 110.
[0046]
Next, the torque to be output from MG1 and MG2 will be considered. The torque Te output from the engine 110 is distributed to Tes on the coordinate axis S and Ter on the coordinate axis R according to the above-described equations (1) and (2). Each of MG1 and MG2 may output torques Tm1 and Tm2 in opposite directions so as to balance the torque thus distributed. At this time, while the rotation direction of MG1 is the (+) direction, the generated torque Tm1 is in the (-) direction, which is opposite to the rotation direction, so that MG1 generates electric power as a generator. I understand.
[0047]
As described above, the torque output from drive wheels 172 and transmitted to axle 170 of hybrid vehicle 100 or the rotational speed of axle 170 is determined by a combination of the rotational speeds of engine 110, MG1, MG2 and the output torque. Generally, the engine has operating conditions under which the energy efficiency is the highest, so that the rotational speeds and output torques of the MG1 and MG2 can be controlled so that the engine 110 operates under the operating conditions that are as efficient as possible. . In this way, the energy efficiency of the engine can be greatly improved, and thus the energy efficiency of the entire hybrid vehicle can be greatly improved.
[0048]
In general, the engine tends to have a lower energy efficiency if the rotational speed is too low or the generated torque is too small and the output value of the power is too small. Therefore, when the power value to be output to the axle is too small, the operation of engine 110 is stopped, MG2 is driven by the electric power stored in battery 150, and the vehicle may be driven as a so-called electric vehicle.
[0049]
When the vehicle decelerates, the axle 170 rotates the ring gear 148 via the chain belt 174, so that the rotation is used to generate power in the MG 2 and store the power in the battery 150. By performing such a so-called regenerative operation, kinetic energy of the vehicle at the time of deceleration can be recovered as electric energy. When the vehicle starts or runs at a low speed, by using the electric power thus stored, the fuel consumption efficiency of the entire vehicle can be improved.
[0050]
As described above, the hybrid ECU 160 performs control for appropriately operating the engine 110, MG1, and MG2 according to the driving state of the vehicle. Hereinafter, the operation control performed by the hybrid ECU 160 will be briefly described.
[0051]
FIG. 4 is a flowchart showing the flow of the operation control routine. When the driving control routine is started, the hybrid ECU 160 first performs a process of determining the driving power Pd to be output from the axle 170 (step S100). The drive power Pd can be determined based on the accelerator position sensor 162 and the rotational speed of the axle. That is, since the accelerator pedal is depressed when the driver of the vehicle feels that the output torque is insufficient, the depression amount of the accelerator pedal (output of the accelerator position sensor 162) is set to the torque desired by the driver. Yes, it is. If the torque is multiplied by the rotation speed, the driving power desired by the driver can be obtained. Therefore, the drive power Pd to be output from the axle 170 can be determined to be an appropriate value when the output of the accelerator position sensor 162 and the rotation speed of the axle are determined. In the present embodiment, an appropriate value of the drive power Pd for the accelerator position sensor 162 and the rotational speed of the axle is experimentally obtained in advance, and is stored in the hybrid ECU 160 in the form of a map in advance.
[0052]
Next, charge / discharge power Pb and accessory drive power Ph are calculated (step S102). The charging / discharging power Pb is power required for charging / discharging the battery 150, and takes a positive value when the battery 150 needs to be charged and a negative value when it needs to be discharged. The accessory drive power Ph is a power required to drive an accessory such as an air conditioner. The auxiliary equipment driving power Ph is calculated by detecting the driven auxiliary equipment and adding the power required for driving these auxiliary equipment. After calculating the driving power Pd, the charging / discharging power Pb, and the accessory driving power Ph, the required power is calculated by adding them (step S104). Here, the required engine power Pe is the power that the engine 110 should output.
[0053]
Next, hybrid ECU 160 sets the operating conditions of engine 110 based on the calculated required engine power Pe (step S106). The operating condition of the engine is set by a combination of the target rotation speed Ne and the target torque Te of the engine. In the RAM incorporated in the hybrid ECU 160, operating conditions such that the fuel consumption efficiency of the engine is as high as possible with respect to the required engine power Pe are stored in advance, and by referring to this RAM, the rotational speed of the engine is determined. , Set the generated torque.
[0054]
After setting the operating conditions of engine 110, hybrid ECU 160 sets a torque command value and a rotation speed command value for each of MG1 and MG2 (step S108). When the driving power Pd is calculated in step S100, the rotation speed of the ring gear shaft 147 can be calculated based on this value because the rotation speed of the axle has already been detected. Further, the torque Tr applied to the ring gear shaft 147 can be obtained from the driving power Pd and the rotation speed Nr. Therefore, if the rotation speed Ne of the engine 110 and the generated torque Te are determined in step S106, the rotation speeds and the output torques of the MG1 and MG2 can be determined based on the operation collinear shown in FIG. In step S108, a rotation speed command value and a torque command value for MG1 and MG2 are calculated based on the rotation speed and the output torque thus determined.
[0055]
After the operating conditions of engine 110 and the torque command value and the rotation speed command value for MG1 and MG2 are determined as described above, control of engine 110 is performed according to the determined operating conditions (step S110). The control of MG2 is performed (step S112).
[0056]
The control of the engine 110 is performed as follows. In the RAM in the engine ECU 112, an appropriate throttle opening and an operating air-fuel ratio for a combination of the target rotation speed Ne and the target torque Te of the engine are stored in advance in the form of a map. FIG. 5 conceptually shows how the throttle opening is stored in the form of a map, and FIG. 6 conceptually shows how the operating air-fuel ratio of the engine is stored in the form of a map. I have. The engine ECU 112 controls the electric actuator 188 to set the opening of the throttle valve 186 to an appropriate opening by referring to the map shown in FIG. Further, the fuel injection valve 192 is driven so as to reach the set air-fuel ratio with reference to the map shown in FIG. By driving the throttle valve 186 and the fuel injection valve 192 in this manner, the engine 110 can be operated at the target rotation speed Ne and the target torque Te. In other words, in the maps shown in FIGS. 5 and 6, appropriate values for operating the engine 110 at the target rotation speed Ne and the target torque Te are set in advance.
[0057]
On the other hand, a known method for controlling a synchronous motor can be applied to control the motor generator. In the present embodiment, control by so-called proportional integration control is performed. That is, the current torque of each motor is detected, and the voltage command value to be applied to each phase is set based on the deviation from the target torque and the target rotation speed. The applied voltage value is set by a proportional term, an integral term, and a cumulative term of the deviation. The proportional coefficient according to each term is set to an appropriate value by experiment or the like. The voltage thus set is input to inverters 152 and 154, and is applied to MG1 and MG2 by so-called PWM control.
[0058]
By periodically executing the above-described operation control routine, the hybrid ECU 160 can appropriately operate the hybrid vehicle according to the operation of the driver.
[0059]
B. Air-fuel ratio control of the first embodiment:
Hybrid vehicle 100 described above can operate engine 110 efficiently using MG1 and MG2, but in order to further improve the fuel consumption efficiency, the operating air-fuel ratio of engine 110 is made leaner. Is effective. However, if the engine is too lean, poor combustion occurs, the output torque fluctuates, and if the combustion deteriorates further, the fuel consumption efficiency is reduced. In the first embodiment, the following control is performed in order to further improve the fuel consumption efficiency while avoiding the occurrence of such a situation.
[0060]
FIG. 7 is a flowchart illustrating a flow of the air-fuel ratio control performed in the hybrid vehicle of the first embodiment. This control is executed in the main routine for controlling the operating state of the hybrid vehicle shown in FIG. Hereinafter, description will be made according to the flowchart.
[0061]
When the air-fuel ratio control is started, it is first determined whether or not the engine is ON (step S200). Since the hybrid vehicle sometimes runs by the motor (MG2) with the engine stopped, first, it is confirmed that the engine is in the operating state.
[0062]
Next, a process of detecting a change amount dθ of the throttle opening of the engine 110 is performed (step S202). The engine ECU 112 controls the electric actuator 188 that drives the throttle valve 186, and the change amount dθ of the throttle opening can be easily detected.
[0063]
When the change amount dθ of the throttle opening is detected in this way, a magnitude relationship with a predetermined threshold value α is determined (step S204). If the change amount dθ is smaller than the threshold α (step S204: yes), it is determined that the engine 110 is operating in a substantially steady state (quasi-steady running state), and that it is possible to detect torque fluctuation. Conversely, if the change amount dθ is larger than the threshold α (step S204: no), it is determined that the engine 110 is not operating in the quasi-steady operation state and is not suitable for detecting torque fluctuation.
[0064]
If it is determined that engine 110 is operating in the quasi-steady operating state, subsequently, it is determined whether MG1 is in the power generation state (step S206). Whether or not MG1 is in the power generation state can be determined based on the direction of the torque applied to MG1 and the rotation direction. That is, when the direction of the torque and the rotation direction are opposite, MG1 is in the power generation state. Conversely, when the direction of the torque and the rotation direction match, MG1 consumes power and Can be determined to be in a state in which is generated.
[0065]
When it is confirmed that the engine 110 is operating in the quasi-steady operation state (step S204: yes) and the MG1 is in the power generation state (step S206: yes), in order to detect a torque fluctuation of the engine 110, The following processing is performed. First, the counter N is incremented by 1 (step S208), and a process of detecting a torque command value to the MG1 and accumulating it as a variation VI of the torque command value is performed (step S210). The torque command value to MG1 is determined in the operation control routine described above with reference to FIG.
[0066]
Then, it is determined whether or not the counter N has reached a predetermined value Nth (step S212). If the counter N has not reached the predetermined value Nth (step S212: no), the process exits the air-fuel ratio control of FIG. 7 and returns to FIG. Return to the indicated main routine. Then, when the main routine is executed next, if the engine 110 is in the quasi-steady operation state (step S204: yes) and the MG1 is in the power generation state (step S206: yes), the counter N is incremented by one. Then (step S208), the variation VI of the torque command value to MG1 is accumulated (step S210). When the engine 110 is not in the quasi-stationary operation state (step S204: no) or when the MG1 is not in the power generation state (step S206: no), the counter N is reset (step S214).
[0067]
In this way, the counter N reaches the predetermined value Nth during several rounds of the main routine (step S212: yes), so that the accumulated fluctuation amount VI of the torque command value is compared with the predetermined first threshold value β1. The processing is performed (step S216). When the variation VI is smaller than the first threshold value β1, a process for making the air-fuel ratio of the engine 110 lean is performed (step S218). Conversely, when the variation VI is larger than the first threshold β1 (step S216: no), the variation VI is compared with a predetermined second threshold β2 this time (step S220). Here, the second threshold value β2 is set to a value larger than the first threshold value β1. If the variation VI is larger than the second threshold value β (step S220: yes), a process for enriching the air-fuel ratio of the engine 110 is performed (step S222). If the fluctuation amount VI is smaller than the second threshold value β2, the process returns to the main routine without performing the air-fuel ratio correction and exiting the air-fuel ratio control process shown in FIG.
[0068]
In the first embodiment, by correcting the air-fuel ratio of the engine 110 in this way, it is possible to further improve the fuel consumption efficiency without causing a change in the output torque of the engine. This is for the following reason.
[0069]
It is known that the amount of engine torque fluctuation is closely related to the operating air-fuel ratio of the engine. The operating air-fuel ratio is also closely related to the fuel consumption efficiency of the engine. FIG. 8 is an explanatory diagram conceptually showing the relationship between the operating air-fuel ratio of the engine, torque fluctuation, and fuel consumption efficiency. As shown in the figure, the fuel consumption efficiency is improved as the operating air-fuel ratio becomes leaner from the stoichiometric ratio (stoichiometric air-fuel ratio) by decreasing the fuel ratio. However, if the air-fuel ratio becomes too lean, the combustion state deteriorates, so that the engine output torque fluctuates and the fuel consumption efficiency also deteriorates. From this, it can be seen that the fuel consumption efficiency of the engine is best when the operating air-fuel ratio is as lean as possible within a range where the amount of variation in the output torque does not increase.
[0070]
On the other hand, as described with reference to FIG. 2, the output of engine 110 is distributed to MG1 and the axle according to equations (1) and (2). Therefore, when the output torque of engine 110 fluctuates, the output distributed to MG1 also fluctuates. From this, the torque fluctuation amount of the engine 110 has a substantially one-to-one correspondence with the fluctuation amount of the generated power in the MG1 in the quasi-stationary operation state. FIG. 9 conceptually shows such a correspondence. As described above, since the torque fluctuation of the engine 110 and the fluctuation amount of the generated power of the MG1 have the relationship shown in FIG. 9, the operating air-fuel ratio of the engine should be made lean within a range where the fluctuation amount of the generated power does not increase. Thus, the engine 110 can be operated under the condition of the best fuel consumption efficiency.
[0071]
In the air-fuel ratio control of the first embodiment shown in FIG. 7, when the variation VI of the torque command value MG1 is smaller than the first threshold value β1, it is determined that there is still room for leaning the air-fuel ratio. To perform lean correction. If the variation VI is larger than the second threshold value β2, it is determined that the vehicle is too lean, and the enrichment correction is performed. For this reason, it becomes possible to operate the engine 110 under the operating conditions with the best fuel consumption efficiency.
[0072]
C. Air-fuel ratio control of the second embodiment:
In the above-described first embodiment, the operating air-fuel ratio of the engine 110 is controlled based on the amount of change in the generated power. However, since the output of the engine varies depending on the operating air-fuel ratio, the throttle is corrected to correct this output change. The opening of the valve 186 may also be controlled. Hereinafter, such a second embodiment will be described.
[0073]
FIG. 10 is a flowchart illustrating the flow of the air-fuel ratio control performed in the hybrid vehicle of the second embodiment. This control is executed in the main routine for controlling the operating state of the hybrid vehicle shown in FIG. The air-fuel ratio control of the second embodiment is significantly different from the air-fuel ratio control of the first embodiment described above with reference to FIG. 7 in that the throttle valve opening is controlled. Hereinafter, the description will be made in accordance with the flowchart, focusing on the differences from the first embodiment.
[0074]
Also in the second embodiment, when control is started, first, it is determined whether or not the engine is ON (step S300). Next, a process of detecting a change amount dθ of the throttle opening of the engine 110 is performed (step S302). Then, a magnitude relationship between the detected change amount dθ of the throttle opening and the predetermined threshold α is determined (step S304). If the change dθ is smaller than the threshold α (step S304: yes), the engine 110 Is determined to be in a quasi-stationary operation state. On the other hand, when the change amount dθ is larger than the threshold α (step S304: no), it is determined that the engine 110 is not operating in the quasi-stationary operation state and is not suitable for detecting a torque fluctuation.
[0075]
If it is determined that engine 110 is operating in the quasi-steady operating state, subsequently, it is determined whether MG1 is in the power generation state (step S306). As described above, whether or not MG1 is in the power generation state can be determined based on the direction of the torque applied to MG1 and the rotation direction.
[0076]
When it is confirmed that the engine 110 is operating in the quasi-steady operation state (step S304: yes) and the MG1 is in the power generation state (step S306: yes), it is determined that the torque fluctuation of the engine 110 can be detected. Then, the following processing is performed. First, the counter N is incremented by 1 (step S308), and a process of detecting a torque command value to the MG1 and accumulating it as a variation VI of the torque command value is performed (step S310). Next, it is determined whether or not the counter N has reached a predetermined value Nth (step S312). If the counter N has not reached the predetermined value Nth (step S312: no), the process exits the air-fuel ratio control of FIG. 7 and returns to FIG. Return to the indicated main routine. Thus, each time the main routine is turned, the operating state of the engine 110 and the MG1 is determined. If the engine is in the quasi-steady operating state and the MG1 is in the power generating state, the counter N is incremented by 1 (step S308). ), The variation VI of the torque command value to MG1 is accumulated (step S310). When the engine 110 is not in the quasi-stationary operation state (step S304: no) or when the MG1 is not in the power generation state (step S306: no), the counter N is reset (step S314).
[0077]
Since the counter N reaches the predetermined value Nth during several rounds of the main routine (step S312: yes), the accumulated fluctuation amount VI of the torque command value is compared with the predetermined first threshold value β1. The processing is performed (step S316). Then, when the fluctuation amount VI is smaller than the first threshold value β1, a process of making the air-fuel ratio of the engine 110 lean is performed (step S318). If the air-fuel ratio is made lean in this manner, the output of the engine 110 decreases. To compensate for this, in the air-fuel ratio control of the second embodiment, a process of correcting the opening of the throttle valve by a predetermined amount to the open side is performed ( Step S320). The correction amount of the throttle opening can be set in advance according to the correction amount of the air-fuel ratio.
[0078]
On the other hand, when the variation VI is greater than the first threshold value β1 (step S316: no), the variation amount VI is compared with a predetermined second threshold value β2 (step S322). Also in the air-fuel ratio control of the second embodiment, the second threshold value β2 is set to a value larger than the first threshold value β1. If the fluctuation amount VI is larger than the second threshold value β (step S322: yes), a process for enriching the air-fuel ratio of the engine 110 is performed (step S324). Since the output of the engine 110 increases when the air-fuel ratio is enriched in this manner, in the air-fuel ratio control of the second embodiment, a process of correcting the throttle opening by a predetermined amount to the close side to compensate for this is performed (step S326). On the other hand, when the fluctuation amount VI is smaller than the second threshold value β2, the process returns to the main routine without performing the air-fuel ratio correction and exiting the air-fuel ratio control process shown in FIG.
[0079]
In the air-fuel ratio control of the second embodiment described above, similarly to the air-fuel ratio control of the first embodiment, the air-fuel ratio of the engine 110 is corrected to improve the fuel consumption efficiency, and the engine associated with the correction of the air-fuel ratio is improved. It is possible to suppress a change in output. For this reason, it is possible to maintain a favorable driving state without giving the driver of the hybrid vehicle an uncomfortable feeling.
[0080]
D. Modification:
There are various modifications of the various embodiments described above. Hereinafter, these modifications will be briefly described.
[0081]
(1) First modification:
In the various embodiments described above, the fact that the engine 110 is operating in the quasi-steady state of operation is detected based on the opening of the throttle valve 186 provided in the engine 110. However, simply, the accelerator position sensor 162 detects the depression amount of the accelerator pedal, and if the change in the depression amount is equal to or less than a predetermined value, it may be determined that the engine 110 is operating in a quasi-steady operation state. good. As described above, since the operating states of the engines 110, MG1, and MG2 are controlled based on the amount of depression of the accelerator pedal, it is considered that if the amount of depression is constant, the operation states of the engine and MG1, MG2 are also constant. be able to. Thus, by making a determination based on the amount of depression of the accelerator pedal, it is possible to easily detect that the engine 110 is operating in a quasi-steady state of operation.
[0082]
(2) Second modification:
In the above-described embodiment, the operating air-fuel ratio or the operating air-fuel ratio and the throttle opening are corrected in accordance with the torque fluctuation amount of the engine. However, the operating air-fuel ratio and the throttle opening may be learned. That is, the target values of the target air-fuel ratio and the throttle opening of the engine are stored in the maps shown in FIGS. Therefore, learning is performed by updating the set value of the map with the corrected operating air-fuel ratio or throttle opening. In this way, when the engine 110 is operated next under the same operating conditions, the engine 110 is controlled using the learned operating air-fuel ratio and the throttle opening. Therefore, the driving efficiency of the hybrid vehicle can be further improved.
[0083]
Although various embodiments have been described above, the present invention is not limited to all the above embodiments, and can be implemented in various modes without departing from the gist thereof. For example, in the above-described embodiment, the hybrid vehicle is a so-called mechanical distribution type hybrid vehicle using planetary gears. However, the present invention can be similarly applied to an electric distribution type hybrid vehicle.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a configuration of a hybrid vehicle according to an embodiment.
FIG. 2 is an alignment chart showing a relationship between power output from an engine and power generated by two motor generators.
FIG. 3 is an alignment chart showing a relationship between an output of an engine and a power generated by two motor generators when the vehicle stops.
FIG. 4 is a flowchart showing a flow of an operation control routine of the hybrid vehicle.
FIG. 5 is an explanatory diagram conceptually showing a state in which the throttle opening of the engine is stored in the form of a map.
FIG. 6 is an explanatory diagram conceptually showing how the operating air-fuel ratio of the engine is stored in the form of a map.
FIG. 7 is a flowchart illustrating a flow of an air-fuel ratio control process according to the first embodiment.
FIG. 8 is an explanatory diagram conceptually showing a relationship between an operating air-fuel ratio of an engine, torque fluctuation, and fuel consumption efficiency.
FIG. 9 is an explanatory diagram conceptually showing a correspondence relationship established between an engine torque fluctuation amount and a generated power fluctuation amount.
FIG. 10 is a flowchart illustrating a flow of an air-fuel ratio control process according to a second embodiment.
[Explanation of symbols]
100 ... Hybrid vehicle
110 ... Engine
112 ... Engine ECU
114 ... Crankshaft
118 ... Crank angle sensor
122: permanent magnet
123 ... rotor
124 three-phase coil
125 ... stator
126 ... Resolver
132 ... permanent magnet
133 ... rotor
134 ... three-phase coil
135 ... stator
136 ... Resolver
138 ... Case
140 ... Planetary gear
141: sun gear shaft
142 ... Sun Gear
144: Planetary pinion gear
146: Planetary carrier
147 ... Ring gear shaft
148 ... Ring gear
150 ... battery
152,154 ... Inverter
156 ... motor ECU
160 ... Hybrid ECU
162: accelerator position sensor
164: brake switch
170 ... axle
172 ... Drive wheel
174 ... chain belt
180 ... exhaust passage
186 ... Throttle valve
188 ... Electric actuator
190 ... intake passage
192 ... Fuel injection valve
196… Air cleaner
200 ... Purification catalyst

Claims (9)

A hybrid vehicle including an electric motor that outputs power to an axle, an internal combustion engine, and a generator that is driven by the internal combustion engine and supplies electric power to the electric motor,
An output distribution mechanism that distributes an output of the internal combustion engine to the generator and the axle at a predetermined ratio;
A quasi-stationary operating state detecting means for detecting that a change in operating conditions of the internal combustion engine is in a quasi-stationary operating state that is equal to or less than a predetermined amount,
Generated power fluctuation detecting means for detecting the amount of fluctuation in the generated power of the generator in the quasi-stationary operation state,
A hybrid vehicle comprising: air-fuel ratio control means for controlling an operating air-fuel ratio of the internal combustion engine based on the detected amount of generated power fluctuation. The hybrid vehicle according to claim 1,
A hybrid vehicle, wherein the output distribution mechanism is a planetary gear mechanism including a planetary carrier connected to the internal combustion engine, a sun gear connected to the generator, and a ring gear connected to the axle. The hybrid vehicle according to claim 1,
An accelerator pedal operated by a driver of the hybrid vehicle,
The hybrid vehicle, wherein the quasi-steady state detecting means is means for determining the quasi-steady state when the operation amount of the accelerator pedal is equal to or less than a predetermined value. The hybrid vehicle according to claim 1,
The generated power fluctuation detection means,
Power generation state detection means for detecting that the generator is in a power generation state,
With a command torque fluctuation detecting means for detecting a fluctuation amount of a torque command value to be absorbed by the generator,
A hybrid vehicle which is means for detecting a variation in the generated power based on a variation in the torque command value in the power generation state. The hybrid vehicle according to claim 1,
The air-fuel ratio control means,
Air-fuel ratio enrichment means for enriching the operating air-fuel ratio of the internal combustion engine when the detected amount of variation in the generated power is greater than a predetermined first threshold;
Air-fuel ratio leaning means for leaning the operating air-fuel ratio of the internal combustion engine when the detected fluctuation amount of the generated power is less than a predetermined second threshold smaller than the first threshold. Hybrid vehicle. The hybrid vehicle according to claim 1,
Throttle valve driving means for driving a throttle valve provided in the internal combustion engine;
A throttle that corrects the opening of the throttle valve to the closed side when the operating air-fuel ratio is enriched, and corrects the opening of the throttle valve to the open side when the operating air-fuel ratio is leaned. A hybrid vehicle comprising an opening correction means. The hybrid vehicle according to claim 1,
Operating condition detecting means for detecting operating conditions of the internal combustion engine,
A target air-fuel ratio for controlling the internal combustion engine, and target air-fuel ratio storage means for storing the target air-fuel ratio in association with operating conditions of the internal combustion engine,
The hybrid vehicle is a means for controlling the operating air-fuel ratio of the internal combustion engine and learning the target air-fuel ratio by updating the stored target air-fuel ratio. The hybrid vehicle according to claim 7, wherein
Throttle valve driving means for driving a throttle valve provided in the internal combustion engine;
A throttle that corrects the opening of the throttle valve to the closed side when the operating air-fuel ratio is enriched, and corrects the opening of the throttle valve to the open side when the operating air-fuel ratio is leaned. Opening correction means,
Operating condition detecting means for detecting operating conditions of the internal combustion engine,
Target opening degree storage means for storing the target opening degree of the throttle valve in association with the operating condition of the internal combustion engine,
The hybrid vehicle, wherein the throttle opening correction means is means for correcting the opening of the throttle valve and learning the target opening by updating the stored target opening. A method for controlling an operating air-fuel ratio of an internal combustion engine in a hybrid vehicle including an electric motor that outputs power to an axle, an internal combustion engine, and a generator that is driven by the internal combustion engine and supplies power to the electric motor. ,
Distributing the output of the internal combustion engine to the generator and the axle at a predetermined ratio;
A step of detecting that the fluctuation of the operating condition of the internal combustion engine is in a quasi-stationary operating state that is equal to or less than a predetermined amount,
Detecting a fluctuation amount of the generated power of the generator in the quasi-stationary operation state,
Controlling the operating air-fuel ratio of the internal combustion engine based on the detected fluctuation amount of the generated power.

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