JP3601508B2 - Hybrid vehicle with stepped transmission - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a hybrid vehicle provided with a stepped automatic transmission.
[0002]
[Prior art]
As shown in Japanese Patent Application Laid-Open No. 2000-110603, some parallel hybrid vehicles that drive the vehicle with an engine and an electric motor include a stepped automatic transmission as a transmission.
[0003]
[Problems to be solved by the invention]
However, in the above hybrid vehicle, when only a motor is used as a power source (hereinafter referred to as an acceleration power source) to cover an increase in required driving force during acceleration, the obtained acceleration torque changes depending on the state of charge of the battery at that time. Therefore, there is a problem that a constant driving force cannot be obtained for the accelerator operation. On the other hand, when relying solely on the engine as the accelerating power source, an acceleration torque can be obtained by downshifting, but since the engine is operated at an inefficient operating point, the advantage of fuel economy, which is a merit of a hybrid vehicle, is impaired. .
[0004]
The present invention has been made in view of such technical problems, and has as its object to achieve both stable acceleration performance and reduced fuel consumption by effectively using an engine and a motor as acceleration power sources.
[0005]
[Means for solving the problem]
According to a first aspect of the present invention, in a hybrid vehicle, an engine, an automatic transmission having a plurality of gears and changing a gear ratio discontinuously, and connected to the engine to assist a driving force of the engine as needed. A motor that performs power, a battery that supplies power to the motor, a unit that calculates a maximum torque that can be assisted by the motor from an amount of power stored in the battery, a unit that calculates a required driving force according to an operating state, At the time of increasing the force, when the motor is fully assisted, a determination unit that determines whether the required driving force can be realized even when a higher gear position of the transmission is selected as compared to a case where the assist is not performed. If it is determined that the required driving force can be achieved even when a high gear is selected, this gear is selected and the motor assists the engine. If it is determined that the required driving force is realized and the required driving force cannot be realized at a higher gear, the motor is not assisted and the transmission is shifted down to a lower gear to reduce the required driving force. And control means for realizing it.
[0006]
According to a second aspect of the present invention, when the determination means in the first aspect of the present invention can achieve the required driving force without downshifting the transmission when the motor assists the maximum, the determination means is compared with a case where the assist is not performed. Thus, it is determined that the required driving force can be achieved even when a higher gear position of the transmission is selected.
[0007]
According to a third invention, when the control means in the first or second invention assists the engine with the motor, the assist torque of the motor is set to a torque smaller than the maximum torque that can be assisted.
[0008]
According to a fourth aspect of the present invention, when the control means in the first or second aspect of the invention assists the engine with the motor, the control means controls the engine to a torque on an optimal fuel economy line and reduces a torque corresponding to a required driving force. The motor reduces the torque on the optimal fuel consumption line to assist the motor.
[0009]
[Action and effect]
Therefore, in the hybrid vehicle according to the present invention, at the time of high-load operation, when the maximum assist is provided by the motor, the required driving force is realized even when a higher gear position of the transmission is selected as compared with the case where the assist is not performed. If the required driving force cannot be realized at a higher gear position, for example, if the required driving force cannot be realized unless shifting down after all, even if the assist is performed, no assist is performed, and the required driving force is reduced by downshifting. Power is realized. As a result, the power consumption of the motor can be reduced, and the engine can be operated at a more efficient high-load operating point, and the fuel efficiency can be increased (see FIG. 9). On the other hand, when a higher gear position can be selected by performing the assist, the assist is performed by the motor, so that the vehicle runs in a high-speed gear and fuel efficiency is improved (see FIG. 8).
[0010]
Also, when performing torque assist with a motor, if the assist is performed at the maximum assistable torque, the engine torque will be smaller than the torque on the optimal fuel efficiency line, and the engine efficiency will be reduced, but the torque that is smaller than the maximum assistable torque Assisting the engine makes it possible to operate the engine near the optimal fuel efficiency line. At this time, by shifting the operating point of the engine to a point on the optimal fuel efficiency line and then assisting the motor with the amount obtained by subtracting the torque on the optimal fuel efficiency line from the torque corresponding to the required driving force, the engine can be further improved. The operation can be performed at an efficient operation point, and the fuel efficiency can be further improved.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0012]
FIG. 1 shows a schematic configuration of a hybrid vehicle according to the present invention. An assist motor 2 is mechanically connected to the engine 1. Further, the engine 1 and the motor 2 are connected to drive wheels 7 via a transmission 3, a propeller shaft 4, a differential device 5, and a drive shaft 6. Have been.
[0013]
The engine 1 is provided with an electronically controlled throttle valve in addition to a fuel injection device and an ignition device. The opening of the throttle valve is controlled to adjust the intake air amount of the engine 1 to control the torque of the engine 1. can do. Further, a sensor (crank angle sensor) 11 for detecting the rotation speed of the engine 1 is attached to the engine 1.
[0014]
The motor 2 is used when cranking the engine 1 at the time of starting the engine, assisting the engine output during acceleration, traveling uphill, and the like, and also used to regenerate braking energy during deceleration. In addition, when the remaining battery level is low or the like, power is generated using the surplus torque of the engine 1 and the battery 16 is charged.
[0015]
The motor 2 is connected to a battery 9 via an inverter 8, and supplies necessary power from the battery 9 during power running, and charges the battery 9 with the regenerated power during regenerative operation. A sensor 12 for detecting a voltage between terminals of the battery 9 is attached to the battery 9, and the remaining capacity (charge state) of the battery 9 can be obtained from the detected voltage between terminals.
[0016]
The transmission 3 is a stepped automatic transmission with a lock-up mechanism composed of a planetary gear mechanism, a clutch, a hydraulic circuit, and the like, and shifts using a shift map shown in FIG. Here, the transmission 3 is a stepped transmission having five shift speeds in which the speed ratio from the first gear to the fifth gear changes discontinuously. A sensor 13 for detecting a vehicle speed is attached to an output shaft of the transmission 3.
[0017]
Further, in addition to the sensors 11 to 13 described above, various sensors for detecting a driving state of the vehicle, such as a sensor 14 for detecting an amount of depression of an accelerator pedal by a driver, are attached to the vehicle. The input signal is input to the control device 20.
[0018]
The control of the engine 1, the motor 2, the transmission 3, and the like is performed by a control device 20 including a CPU, a ROM, a RAM, an input / output interface, and the like. The controller 20 determines the driving force required by the driver from the accelerator operation amount and the vehicle speed during normal running, and controls the torque and speed of the engine 1 and the motor 2 and the speed of the transmission 3 so as to obtain the required driving force. Each of the gears is controlled.
[0019]
Since the required driving force increases during acceleration, it is necessary to increase the torque transmitted from the engine 1 or the motor 2 to the driving wheels 7 in accordance with the required driving force. ) Is always borne only by the motor torque, the assistable torque of the motor 2 changes in accordance with the remaining capacity of the battery 16, so that stable acceleration performance cannot be realized. In addition, if the engine 1 is always borne only by the engine torque, the engine 1 is often operated at an inefficient operating point, and the fuel efficiency is deteriorated.
[0020]
Therefore, the control device 20 obtains a torque at which the motor 2 can assist from the remaining battery capacity, and when the motor assist torque can be sufficiently secured, the required driving force is realized by the motor assist, and when the motor assist torque cannot be sufficiently secured. Realizes the required driving force by downshifting the transmission 3 without performing motor assist.
[0021]
FIG. 2 is a flowchart showing the contents of the driving force control during acceleration performed by the control device 20.
[0022]
First, in step S1, a vehicle speed VSP, an engine rotation speed Ne, a battery state of charge SOC, and an accelerator operation amount APO are read as operating parameters. In step S2, the target total driving force tFd is calculated based on the vehicle speed VSP and the accelerator operation amount APO with reference to the map shown in FIG.
[0023]
In step S3, the maximum value Fmmax of the driving force that can be assisted by the motor 2 is calculated based on the rating of the motor 2 and the battery state of charge SOC. The assistable driving force Fmmax is calculated to be larger as the rating of the motor 2 is higher and the state of charge SOC of the battery 9 is higher.
[0024]
In step S4, a value obtained by subtracting the motor assist driving force Fmmax from the target total driving force tFd is converted into an accelerator operation amount equivalent value using a map as shown in FIG. 4, and the accelerator operation amount equivalent value and the vehicle speed VSP are further converted. Referring to a shift map as shown in FIG. 5, a gear position GP1 of the transmission 3 expected when the motor 2 provides the maximum assist is calculated.
[0025]
In step S5, the target total driving force tFd is converted into an accelerator operation amount equivalent value using a map as shown in FIG. 4, and further based on the accelerator operation amount equivalent value and the vehicle speed VSP, a shift map as shown in FIG. With reference to the above, the gear position GP2 of the transmission 3 expected when the vehicle is accelerated by the engine 1 alone without assisting by the motor 2 is calculated.
[0026]
In step S6, it is determined whether the gear position GP1 calculated in step S4 is larger than the gear position GP2 calculated in step S5, that is, whether it is not necessary to perform downshifting by motor assist and traveling in a high-speed gear becomes possible. Is determined.
[0027]
When the gear position GP1 is larger than the gear position GP2, that is, when the vehicle can run at a higher gear position than when the assist is not performed by performing the assist (when the vehicle can travel at a higher gear position without downshifting, etc.). Then, the process proceeds to step S7 and thereafter in order to select the high gear position GP1 and perform the assist by the motor 2. On the other hand, when the gear position GP1 is equal to the gear position GP2, that is, when the vehicle cannot travel at a higher gear position than when the assist is not performed, the motor assist is not performed, and the lower gear position GP2 is not performed. The process proceeds to step S10 and subsequent steps in order to cope with an increase in the required driving force by shifting down to.
[0028]
In step S7, in which the motor assist is performed, the engine torque on the optimal fuel efficiency line is calculated based on the engine speed Ne with reference to the map shown in FIG. 6, and is set as the target torque of the engine 1. In step S8, a torque (target total torque) required to realize the target total driving force tFd at the gear position GP1 is calculated based on the gear position GP1 and the target total driving force tFd, and the target engine torque is calculated from the target total torque. Is reduced to calculate the target assist torque of the motor 2.
[0029]
In step S9, after selecting the gear position GP1, the throttle opening of the engine 1 is controlled so that the torque of the engine 1 achieves the target engine torque, and the torque of the motor 2 becomes the target assist torque. Thus, the power supplied to the motor 2 is controlled.
[0030]
If the transmission gear position up to this point is GP1, the command in step S9 is to maintain the gear position GP1, and if the transmission gear position up to this point is higher than GP1, The command in S9 is to shift down to the gear position GP1.
[0031]
On the other hand, in step S10 where it is determined that the motor assist is not performed, the target engine torque is calculated with reference to the map shown in FIG. 6 based on the engine rotation speed Ne and the gear position GP2. In step S11, the gear position of the transmission 3 is changed to the gear position. The position is changed to the position GP2 (shift down), and the throttle opening of the engine 1 is controlled so that the target engine torque is realized.
[0032]
Therefore, according to the above-described driving force control, at the time of a high load such as acceleration, it is first determined whether or not the target total driving force can be achieved with the high-speed gear without downshifting by motor assist. The motor assist is performed only when the target total driving force can be realized by the gear, and otherwise, the downshift is performed without performing the motor assist.
[0033]
FIG. 7 shows how the operating point of the engine 1 changes during acceleration. When the accelerator pedal is depressed during operation at the operation point {circle around (1)} and the required driving force increases, the torque required of the engine 1 also increases as indicated by the arrow in the figure. If the required torque of the engine 1 exceeds the maximum torque of the engine 1 as in this case, in order to achieve the required driving force, the speed of the transmission 3 is shifted down from the fifth gear to the fourth gear. Then, it is necessary to shift the operating point to the operating point (3) which is on the same output line as (2) or to run the motor 2 to assist and reduce the torque borne by the engine 1.
[0034]
At this time, when the remaining amount of the battery 9 is large and the assistable torque of the motor 2 is large, and the required driving force can be realized only by the motor assist without downshifting, the motor assist is performed as shown in FIG. The torque required for the engine 1 is reduced below the maximum torque so that the vehicle can continue to run in the current higher gear, thereby suppressing the engine rotation speed and the fuel consumption.
[0035]
Further, at this time, when assisting by the motor 2 is performed with the maximum torque that can be assisted, the operating point of the engine 1 moves from (2) to (5) as shown by a broken arrow in the figure and moves away from the optimal fuel efficiency line, and Since the operating efficiency of the engine 1 decreases, the operating point of the engine 1 is set to {circle around (4)} on the optimal fuel economy line, and the difference between the required torque and the torque on the optimal fuel economy line is assisted by the motor 2.
[0036]
On the other hand, when the required driving force cannot be achieved by motor assist without shifting down, the operating point is shifted from (2) to (6) on the equal output line by shifting down as shown in FIG. Change to ▼ to achieve the required driving force. If the motor is further assisted in this downshifted state, the operating point of the engine 1 departs from the best fuel efficiency line as shown by the arrow in the figure, resulting in poor efficiency. Therefore, the motor assist by the motor 2 is not performed (motor assist). Ban).
[0037]
Further, for example, during driving in the fifth gear, the accelerator pedal is greatly depressed, and the required driving force is greatly increased. Without the motor assist, the required driving force cannot be realized without shifting down to the third gear. In the case where it is possible to travel in the fourth gear (higher gear position than the third gear) by motor assist with the maximum torque that can be assisted, it is necessary to shift down to the fourth gear. Under this condition, the operating point of the engine 1 is set on the optimal fuel consumption line, and the difference between the required torque and the torque on the optimal fuel consumption line is assisted by the motor 2.
[0038]
As described above, in the hybrid vehicle according to the present invention, at the time of high load, the shift down is performed only in a situation where the required driving force cannot be realized by the motor assist unless the shift down is performed. As a result, the frequency of traveling in the high-speed gear increases, so that the rotation of the engine 1 can be suppressed low and the fuel consumption can be suppressed low.
[0039]
Although the above embodiment is a hybrid vehicle having a planetary gear type stepped automatic transmission, the present invention is similarly applied to a continuously variable transmission having a mode in which the transmission changes stepwise. be able to.
[0040]
In the above embodiment, the motor 2 is arranged between the engine 1 and the transmission 3. However, the present invention is not limited to this. For example, the motor 2 may be attached to an arbitrary position of the engine 1, The connection may be made by a belt or a chain so as to rotate synchronously with the engine 1 with a predetermined gear ratio.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a hybrid vehicle according to the present invention.
FIG. 2 is a flowchart showing the contents of driving force control during acceleration.
FIG. 3 is a map for calculating a driving force from a vehicle speed and an accelerator operation amount.
FIG. 4 is a map for converting a driving force into an accelerator operation amount equivalent value.
FIG. 5 is a shift map of a transmission.
FIG. 6 is a fuel efficiency performance map of the engine.
FIG. 7 is a diagram showing a state where a torque required for an engine changes during acceleration.
FIG. 8 is a diagram illustrating a state in which motor assist is performed during acceleration.
FIG. 9 is a diagram illustrating a state in which a downshift is performed without performing motor assist during acceleration.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 engine 2 motor 3 transmission 9 battery 11 engine rotation speed sensor 12 battery terminal voltage sensor 13 vehicle speed sensor 14 accelerator operation amount sensor 20 controller

Claims (4)

Engine and
An automatic transmission having a plurality of gears and changing the gear ratio discontinuously;
A motor connected to the engine and assisting the driving force of the engine as needed;
A battery for supplying power to the motor;
Means for calculating the maximum torque that can be assisted by the motor from the amount of charge of the battery;
Means for calculating the required driving force according to the operating state;
A determination unit configured to determine whether the required driving force can be realized even when a higher gear position of the transmission is selected as compared to a case where assist is not performed when the required driving force increases and the motor assists to the maximum. ,
If it is determined that the required driving force can be achieved even when a higher gear is selected, this gear is selected and the motor is used to assist the engine to achieve the required driving force. When it is determined that the required driving force cannot be realized, control means for performing the required driving force by shifting down the transmission to a lower gear without performing assist by the motor,
A hybrid vehicle comprising: In a case where the determination unit can achieve the required driving force without downshifting the transmission when the motor is fully assisted with the motor, a higher gear position of the transmission is set as compared with a case where the assist is not performed. The hybrid vehicle according to claim 1, wherein it is determined that the required driving force can be realized even when the hybrid vehicle is selected. 3. The hybrid vehicle according to claim 1, wherein when the control unit assists the engine with the motor, the control unit sets the assist torque of the motor to a torque smaller than a maximum torque that can be assisted. 4. When the control unit assists the engine with the motor, the control unit controls the engine to a torque on an optimal fuel efficiency line, and subtracts a torque obtained by subtracting the torque on the optimal fuel efficiency line from a torque corresponding to a required driving force. The hybrid vehicle according to claim 1, wherein the vehicle is assisted.

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