JP2018034671A - Hybrid vehicle and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hybrid vehicle and a control method therefor, which are capable of obtaining necessary brake force as much as possible using a regenerative brake.SOLUTION: A control device 10 compares, in a state where a drive shaft of a motor/generator 12 is disconnected from a drive shaft of an engine 11 by a clutch 15, required brake torque (T) with maximum regenerative brake torque (T), where the former torque is brake torque required for a hybrid vehicle 1 and is estimated on the basis of a present vehicle speed and the latter torque is a maximum value of brake torque that is obtained by regenerative power generation of the motor/generator 12 and is calculated on the basis of a rotation speed of the present motor/generator 12, and controls a transmission 16 so as to step up at least one stage of a gear shift stage of the transmission 16 in a case where the required brake torque is greater than the maximum regenerative brake torque.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a hybrid vehicle having two powers, for example, an engine and a motor, and capable of performing regenerative power generation by the motor, and a control method thereof.

  A vehicle that rotates a generator by kinetic energy at the time of deceleration of the vehicle and collects it in the form of electric energy has become widespread. A constant resistance is generated during power recovery, and this resistance functions as a braking force for the vehicle. Such braking by resistance generated during the recovery of electric energy during deceleration is generally called regenerative braking.

  Particularly, in a hybrid vehicle (HEV: Hybrid Electric Vehicle) having two powers of an internal combustion engine (engine) and a motor generator (motor / generator), it is possible to suitably obtain a braking force by regeneration using the motor / generator. it can. Such a technique is disclosed in Patent Document 1, for example.

JP 2008-290536 A

  In a hybrid vehicle, for example, in a region where the motor is more efficient than the engine, such as in a low rotation region, the engine may be stopped and the vehicle may run only with the motor. In such a case, when the engine does not rotate and fuel is not supplied to the engine (accelerator off, etc.), the braking force (so-called engine brake) generated by the rotational resistance force (loss) of the engine does not occur. Only regenerative braking by the motor / generator will occur.

  When the braking force required by the driver of the vehicle is large and the braking force is insufficient only with regenerative braking, the insufficient braking force is compensated by engine braking, for example, by starting the engine. However, in order to improve fuel efficiency, it is required that the engine brake is not used as much as possible.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a hybrid vehicle and a control method thereof that can obtain as much braking force as possible by regenerative braking.

  The hybrid vehicle of the present invention has an engine mounted on the hybrid vehicle and a drive shaft connected to the drive shaft of the engine, and is rotated by electric power to generate the drive force of the hybrid vehicle together with the engine. A generator that performs regenerative power generation using rotation of a wheel, a transmission that is disposed between the generator and the driving wheel, and that changes a rotation ratio of an input shaft and an output shaft to a plurality of shift stages; A braking torque obtained by regenerative power generation of the generator, calculated based on a required braking torque, which is a braking torque required for the hybrid vehicle, estimated based on a current vehicle speed, and a current rotational speed of the generator. Is compared with the maximum regenerative braking torque, and if the required braking torque is greater than the maximum regenerative braking torque, the transmission changes. And a control unit for controlling the transmission such that at least one raising the stage.

  The control method of the present invention includes an engine mounted on a hybrid vehicle and a drive shaft connected to the drive shaft of the engine, and rotates by electric power to generate a drive force of the hybrid vehicle together with the engine. A generator that performs regenerative power generation using rotation of a wheel, a transmission that is disposed between the generator and the driving wheel, and that changes a rotation ratio of an input shaft and an output shaft to a plurality of shift stages; A control method for a hybrid vehicle having a calculation based on a required braking torque, which is a braking torque required for the hybrid vehicle, estimated based on a current vehicle speed, and a current rotational speed of the generator, The maximum regenerative braking torque that is the maximum value of the braking torque obtained by regenerative power generation of the generator is compared, and the required braking torque is greater than the maximum regenerative braking torque. If no, control the transmission such that at least one raising the gear position of the transmission.

  According to the present invention, the necessary braking force can be obtained by regenerative braking.

The figure which shows the structure of the hybrid vehicle in this Embodiment Flowchart for explaining the operation of the control device during deceleration of the hybrid vehicle The figure which shows an example of the map which shows the relationship (characteristic) of the vehicle speed and braking torque for every braking element The figure which illustrated the map which shows the relationship between the rotation speed of a motor / generator, and the maximum regenerative braking torque _{Treg_MAX} . Diagram illustrating a relationship between the rotational speed and the braking torque of the motor / generator maximum regenerative braking torque T _{Reg_MAX} becomes the required braking torque T _req above

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a hybrid vehicle 1 in the present embodiment. In the present embodiment, the hybrid vehicle 1 is, for example, a commercial vehicle or a passenger vehicle equipped with a gasoline engine or a diesel engine as an internal combustion engine.

  As shown in FIG. 1, the hybrid vehicle 1 includes a control device 10, an engine 11, a motor / generator 12, a battery 13, an inverter 14, a clutch 15, a transmission 16, a propeller shaft 17, a differential gear 18, and drive wheels 19.

  The output of the engine 11 and / or the motor / generator 12 is transmitted to the drive wheels 19 via the propeller shaft 17 and the differential gear 18. With such a configuration, the hybrid vehicle 1 travels at a reduced speed by the engine 11 (engine brake travel mode), travel by regeneration by the motor / generator 12 (motor / generator regeneration travel mode), and the engine 11 and the motor / motor. It is possible to travel by selecting one of a plurality of travel modes, such as travel in which the generator 12 performs regeneration in cooperation (cooperative regeneration travel mode).

  The hybrid vehicle 1 travels by a motor / generator 12 during deceleration or traveling on a downhill road (motor / generator regenerative travel mode), or travel in which the engine 11 and the motor / generator 12 cooperate (cooperative regenerative travel mode). Can operate the motor / generator 12 as a generator by the rotational force of the drive wheels 19 and charge (regenerate) the generated power (regenerative power) to the battery 13.

  The control device 10 controls operations of the engine 11, the motor / generator 12, the battery 13, the inverter 14, the clutch 15, and the transmission 16. The engine 11, the motor / generator 12, the battery 13, the inverter 14, the clutch 15, and the transmission 16 are controlled by, for example, separately provided ECUs (Electric Control Units) for mutual CAN (Control Area Network) communication. However, in the present embodiment, description will be made assuming that each component is controlled by one control device 10.

  The control device 10 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) storing a control program, a working memory such as a RAM (Random Access Memory), and the like. The CPU reads out a control program from the ROM and develops it in the RAM, and performs centralized control of operations of the engine 11, the motor / generator 12, the battery 13, the inverter 14, the clutch 15, and the transmission 16 in cooperation with the developed control program.

  The motor / generator 12 generates driving force for traveling the hybrid vehicle 1 using electric power supplied from the battery 13. The motor / generator 12 also operates as a generator that charges the battery 13 by being driven by power from other sources. Here, as power for operating the motor / generator 12 as a generator, for example, there is power of the engine 11. In addition, the motor / generator 12 generates power as a generator by the rotation of the drive wheels 19 transmitted through the differential gear 18 and the propeller shaft 17 when the hybrid vehicle 1 is decelerated or traveling on a downhill road. .

  The battery 13 supplies electric power to the motor / generator 12 when driving of the motor / generator 12 is requested, and is charged by the electric power generated by the motor / generator 12 when the motor / generator 12 operates as a generator. Is done.

  When the drive of the motor / generator 12 is requested, the inverter 14 converts the DC power of the battery 13 into three-phase AC power and supplies it to the motor / generator 12 when the motor / generator 12 operates as a generator. The three-phase AC power generated by the motor / generator 12 is converted into DC power and supplied to the battery 13.

  The clutch 15 connects or disconnects the drive shaft of the engine 11 and the drive shaft of the motor / generator 12. When the clutch 15 is connected, the hybrid vehicle 1 can transmit power to the engine 11 by the motor / generator 12. When clutch 15 is connected, hybrid vehicle 1 selects either an engine brake travel mode using only engine 11 or a cooperative regenerative travel mode in which engine 11 and motor / generator 12 cooperate. be able to.

  On the other hand, when the clutch 15 is disengaged, the hybrid vehicle 1 can efficiently regenerate without receiving friction of the engine 11 in the motor / generator regeneration mode using only the motor / generator 12.

  The drive shaft of the motor / generator 12 is connected to the input shaft of the transmission 16. The transmission 16 is, for example, an AMT (Automated Manual Transmission), a torque converter AT (Automatic Transmission), or an MT (Manual Transmission), and includes a clutch mechanism and a transmission mechanism that connect or disconnect the drive shaft of the motor / generator 12 and the propeller shaft 17. Have. In the present embodiment, illustration of the clutch mechanism and the transmission mechanism is omitted. While the hybrid vehicle 1 is traveling, the control device 10 operates the clutch mechanism and the speed change mechanism of the transmission 16 based on the vehicle speed, the required torque, and the like, thereby enabling smooth traveling.

  The hybrid vehicle 1 of the present embodiment having such a configuration achieves improved fuel efficiency by efficiently performing regeneration by the motor / generator 12 during deceleration. Below, in order to perform the regeneration by the motor / generator 12 efficiently, the control which the control apparatus 10 performs is demonstrated in detail.

  FIG. 2 is a flowchart for explaining the operation of the control device 10 when the hybrid vehicle 1 is decelerated. As a precondition in FIG. 2, it is assumed that the engine 11 and the motor / generator 12 are disconnected by the clutch 15 and the hybrid vehicle 1 is traveling in the motor / generator regenerative travel mode using only the motor / generator 12.

In step S1, the control device 10 acquires information such as the vehicle speed, accelerator opening, and brake pressure of the hybrid vehicle 1 from a sensor or the like not shown in FIG. 1, and calculates the requested braking torque based on these information. To do. The braking torque calculated by the control device 10 in step S1 is hereinafter referred to as a required braking torque T _req . The required braking torque T _req is a virtual total value of the braking torque required by the hybrid vehicle 1 estimated by the control device 10 according to the state of the hybrid vehicle 1 at that time. That is, in the state where the clutch 15 is disengaged, the engine brake and the exhaust brake, which are actually the braking force due to the engine 11, are not generated, but the brake torque is estimated in step S1 as the engine brake and the exhaust brake are generated. It is carried out.

The method by which the control device 10 calculates the required braking torque T _req of the hybrid vehicle 1 is not particularly limited in the present embodiment, but may be calculated by the following method, for example. The control device 10 acquires parameters such as the accelerator opening, the brake pressure, and the vehicle speed from various sensors provided at various locations of the hybrid vehicle 1, and based on the parameters, determines the braking torque for each braking element of the hybrid vehicle 1. The required braking torque T _req is calculated by calculating and adding or subtracting them. The braking element means at least one element that generates the braking torque of the hybrid vehicle 1.

FIG. 3 is a diagram showing an example of a map showing the relationship (characteristic) between the vehicle speed and the required braking torque for each braking element. In FIG. 3, four elements of engine brake, exhaust brake, vehicle weight * road gradient, and vehicle running resistance are illustrated as braking elements. With reference to the map shown in FIG. 3, the control device 10 calculates the engine brake, exhaust brake, vehicle weight * road gradient, and braking torque for each running resistance corresponding to the state of the hybrid vehicle 1 at that time. The required braking torque T _req is calculated by adding the braking torque of the brake, exhaust brake, vehicle weight * road slope, and subtracting the braking torque of the running resistance from the result.

Returning to the description of FIG. In step S2, the control device 10 calculates the maximum regenerative braking torque T _{reg_MAX} based on the vehicle speed at that time (the number of rotations of the motor / generator 12). The maximum regenerative braking torque T _{reg_MAX} is the maximum value of the braking force that the motor / generator 12 can generate by regeneration at the vehicle speed of the hybrid vehicle 1 at that time. For example, the control device 10 acquires the rotational speed of the motor / generator 12 from a sensor or the like not shown in FIG. 1, and refers to a map showing the relationship between the rotational speed of the motor / generator 12 and the maximum regenerative braking torque T _{reg_MAX} . The maximum regenerative braking torque T _{reg_MAX} at that time is calculated. FIG. 4 is a diagram illustrating a map showing the relationship between the rotation speed of the motor / generator 12 and the maximum regenerative braking torque T _{reg_MAX} . In addition, the control apparatus 10 may calculate the rotation speed of the motor / generator 12 from, for example, the vehicle speed, the gear ratio, the tire circumference, and the like instead of referring to the map.

Next, in step S3, the control device 10 compares the required braking torque T _req calculated in step S1 with the maximum regenerative braking torque T _{reg_MAX} calculated in step S2. When the required braking torque T _req requested by the hybrid vehicle 1 is larger than the maximum regenerative braking torque T _{reg_MAX that} can be generated by the motor / generator 12 at that time (step S3: YES), the control device 10 performs the process at step S4. Proceed to On the other hand, if this is not the case, that is, if the required braking torque T _req requested by the hybrid vehicle 1 is _{equal to} or less than the maximum regenerative braking torque T _{reg_MAX that} can be generated by the motor / generator 12 at that time (step S3: NO), the control device 10 Terminates the process.

Here, when the required braking torque T _req requested by the hybrid vehicle 1 is _{equal to} or less than the maximum regenerative braking torque T _{reg_MAX that} can be generated by the motor / generator 12 at that time (step S3: NO), that is, This means that all of the braking force required by the hybrid vehicle 1 can be covered in the motor travel mode in which only the motor travels. For this reason, the control apparatus 10 complete | finishes a process, without performing further control.

On the other hand, if the required braking torque T _req requested by the hybrid vehicle 1 is larger than the maximum regenerative braking torque T _{reg_MAX that} can be generated by the motor / generator 12 at that time (step S3: YES), the motor / This means that the regenerative braking force generated by the generator 12 cannot cover all of the braking force required by the hybrid vehicle 1. Therefore, in such a case, the control device 10 performs control for compensating for the insufficient braking torque in steps S4 to S6 described below.

  In step S4, the control device 10 determines whether or not the transmission 16 can be shifted up. The determination may be performed based on, for example, whether or not there is a gear stage to be shifted up from the current gear stage, and / or a gear stage restriction based on the rotation speed of the motor / generator 12. If control device 10 determines that the upshift is possible (step S4: YES), the process proceeds to step S5, and if not (step S4: NO), the process proceeds to step S6.

In step S5, the control device 10 controls the transmission 16 to shift up. Here, the control device 10 may control the transmission 16 so as to shift up by one stage, for example. By shifting up the transmission 16, the control device 10 can reduce the rotational speed of the motor / generator 12. As illustrated in FIG. 4, when the rotational speed of the motor / generator 12 decreases, the maximum regenerative braking torque T _{reg_MAX} that can be generated by the motor / generator 12 increases, so that the required braking torque T _req is insufficient at the time of step S3. It becomes possible to supplement the braking torque corresponding to that amount.

On the other hand, in step S6, the control device 10 connects the clutch 15. Here, when the engine 11 is stopped, the control device 10 starts the engine 11 at the same time as the clutch 15 is connected. As a result, the braking force of the engine 11 (so-called engine brake) is transmitted to the drive wheels 19 via the propeller shaft 17. For this reason, the control device 10 can smoothly compensate the torque that is insufficient for the required braking torque T _req at the time of step S3 by the engine brake. When the braking torque generated by the engine is larger than the braking torque that is less than the required braking torque T _req , the excess braking torque may be reduced from the output torque of the motor / generator 12.

As described above, the hybrid vehicle of the present invention has an engine (engine 11) and a drive shaft connected to the drive shaft of the engine, and rotates with electric power to generate a drive force together with the engine. A generator (motor / generator 12) that performs regenerative power generation using rotation, and a transmission that is disposed between the generator and the drive wheels and that changes the rotation ratio of the input shaft and the output shaft to a plurality of gear stages. (Transmission 16), the required braking torque (T _req ), which is the braking torque required for the hybrid vehicle, estimated based on the current vehicle speed, and the generator speed calculated based on the current rotational speed of the generator The maximum regenerative braking torque (T _{reg_MAX} ), which is the maximum value of the braking torque obtained by regenerative power generation, is compared, and the required braking torque is greater than the maximum regenerative braking torque. And a control device (control device 10) for controlling the transmission so as to raise at least one gear position of the transmission.

With such a configuration, when the required braking torque T _req is larger than the maximum regenerative braking torque T _{reg_MAX} , the transmission 16 is shifted up, so that the maximum regenerative braking torque T _{reg_MAX} becomes large, and the braking for the insufficient amount Torque can be compensated. In other words, by reducing the rotation speed of the motor / generator 12 by shifting up, the control device 10 reduces the rotation speed of the motor / generator 12 so that the maximum regenerative braking torque T _{reg_MAX} is greater than the required braking torque T _req. It will be able to fit inside.

FIG. 5 is a diagram illustrating the relationship between the rotational speed of the motor / generator 12 and the braking torque at which the maximum regenerative braking torque T _{reg_MAX} is _equal to or greater than the required braking torque T _req . In FIG. 5, the solid line indicates the maximum regenerative braking torque T _{reg_MAX} , and the alternate long and _short dash line indicates the required braking torque T _req . In FIG. 5, a region where the maximum regenerative braking torque T _{reg_MAX} is larger than the required braking torque T _req by the control device 10 reducing the rotation speed of the motor / generator 12 by shifting up, that is, shifting to the left in FIG. 5. It will be able to fit inside.

  In the embodiment described above, the drive shaft of the engine 11 and the drive shaft of the motor / generator 12 are disconnected by the clutch 15. However, the drive shaft of the engine 11 and the motor / generator 12 are driven by the clutch 15. In a state where the shaft is disconnected, the engine 11 may be operating (rotating) or may be stopped.

Further, in the above-described embodiment, as a method of calculating the required braking torque T _req by the control device 10, the braking torque of the braking elements such as engine brake, exhaust brake, vehicle weight * road gradient is added, and based on the result. Although the required braking torque T _req is calculated by subtracting the braking torque of the running resistance, the present invention is not limited to this. For example, any of the braking torques may be omitted, or the required braking torque T _req may be calculated by adding or subtracting braking torques by braking elements other than those illustrated in FIG.

  The present invention is useful for a hybrid vehicle capable of performing regenerative power generation using rotation of drive wheels.

DESCRIPTION OF SYMBOLS 1 Hybrid vehicle 10 Control apparatus 11 Engine 12 Motor / generator 13 Battery 14 Inverter 15 Clutch 16 Transmission 17 Propeller shaft 18 Differential gear 19 Drive wheel

Claims (5)

The engine mounted on the hybrid vehicle,
A generator that has a drive shaft connected to the drive shaft of the engine, rotates by electric power to generate the driving force of the hybrid vehicle together with the engine, and performs regenerative power generation using rotation of drive wheels;
A transmission that is disposed between the generator and the drive wheel and that shifts the rotation ratio between the input shaft and the output shaft to a plurality of shift stages;
A braking torque obtained by regenerative power generation of the generator, calculated based on a required braking torque, which is a braking torque required for the hybrid vehicle, estimated based on a current vehicle speed, and a current rotational speed of the generator. And a maximum regenerative braking torque that is a maximum value of the control unit, and if the required braking torque is greater than the maximum regenerative braking torque, the control device that controls the transmission to increase at least one gear position of the transmission When,
Hybrid vehicle having A clutch that is disposed between the engine and the generator and that connects or disconnects the drive shaft of the engine and the drive shaft of the generator;
The control device compares the required braking torque and the maximum regenerative braking torque when the engine drive shaft and the generator drive shaft are disconnected by the clutch, and determines the required braking torque. Is greater than the maximum regenerative braking torque, the transmission is controlled to increase at least one shift stage of the transmission.
The hybrid vehicle according to claim 1. When the required braking torque is greater than the maximum regenerative braking torque and the transmission speed cannot be increased due to restrictions on the transmission, the control device may connect the engine drive shaft and the generator drive shaft. Control the clutch to connect,
The hybrid vehicle according to claim 2. The control device virtually calculates the required braking torque for each braking element that is at least one element that generates the braking torque of the hybrid vehicle, and adds the braking torques of all the braking elements or Estimate by subtraction,
The hybrid vehicle according to claim 1. It has an engine mounted on a hybrid vehicle and a drive shaft connected to the drive shaft of the engine. The drive shaft is rotated by electric power to generate the driving force of the hybrid vehicle together with the engine. A control method for a hybrid vehicle, comprising: a generator that performs regenerative power generation; and a transmission that is disposed between the generator and the drive wheel and that shifts a rotation ratio of an input shaft and an output shaft to a plurality of shift stages. Because
A braking torque obtained by regenerative power generation of the generator, calculated based on a required braking torque, which is a braking torque required for the hybrid vehicle, estimated based on a current vehicle speed, and a current rotational speed of the generator. A maximum regenerative braking torque that is a maximum value of the transmission torque, and when the required braking torque is greater than the maximum regenerative braking torque, the transmission is controlled to increase at least one shift stage of the transmission.
Control method of hybrid vehicle.

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