Hybrid vehicle and method of changing operation mode for the same

Abstract

A method of changing an operation mode of a hybrid vehicle may include determining a current operation mode, determining a predicted travel distance in a first mode when the current operation mode is the first mode or a current driving load satisfies a criterion for switching to the first mode as a result of the determination, determining whether an engine is warmed up, and determining whether to drive in the first mode or a second mode according to the determined predicted travel distance and whether the engine is warmed up.

Claims

1. A method of changing an operation mode of a vehicle, the method comprising: determining, by a controller, a current operation mode; determining, by the controller, a predicted travel distance in a first mode when the current operation mode is the first mode or a current driving load satisfies a criterion for switching to the first mode as a result of the determination; determining, by the controller, whether an engine is warmed up; and determining, by the controller, whether to drive in the first mode or a second mode according to the determined predicted travel distance and whether the engine is warmed up; and controlling, by the controller, the vehicle to drive in the first mode or the second mode based on the determined predicted travel distance and on determination of whether the engine is warmed up.

2. The method according to claim 1, wherein the current driving load is determined through at least one of a speed of the vehicle, a required torque, and a load level.

3. The method according to claim 1, wherein the predicted travel distance is determined through at least one of a type of a front road, a length of the front road, a gradient of the front road, and congestion information.

4. The method according to claim 1, wherein whether the engine is warmed up is determined using a catalyst temperature of an exhaust gas catalytic converter.

5. The method according to claim 4, wherein the catalyst temperature is determined using at least one of a temperature of a coolant, a speed of the vehicle, and an elapsed time since the engine stops.

6. The method according to claim 1, wherein the determining of whether to drive in the first mode or the second mode includes: determining to drive in the second mode when the predicted travel distance is less than a predetermined value and the engine is not warmed up.

7. The method according to claim 1, Wherein the determining of whether to drive in the first mode or the second mode includes: determining to drive in the first mode when the predicted travel distance is greater than a predetermined value and the engine is not warmed up; and performing warmup control of the engine.

8. The method according to claim 1, wherein the determining of whether to drive in the first mode or the second mode includes: determining to drive in the first mode without warmup control of the engine when the engine is warmed up.

9. The method according to claim 1, wherein the first mode includes a charge depleting (CD) mode, and the second mode includes a charge sustaining (CS) mode.

10. A computer-readable recording medium recording a program for executing the method of changing the operation mode according to claim 1.

11. A vehicle comprising: an engine; and a controller configured to determine a predicted travel distance in a first mode and whether the engine is warmed up when a current operation mode is the first mode or a current driving load satisfies a criterion for switching to the first mode, to determine whether to drive in the first mode or a second mode according to the determined predicted travel distance and whether the engine is warmed up, and to control the vehicle to drive in the first mode or the second mode based on the determined predicted travel distance and on determination of whether the engine is warmed up.

12. The vehicle according to claim 11, wherein the current driving load is determined through at least one of a speed of the vehicle, a required torque, and a load level.

13. The vehicle according to claim 11, wherein the predicted travel distance is determined through at least one of a type of a front road, a length of the front road, a gradient of the front road, and congestion information.

14. The vehicle according to claim 11, wherein whether the engine is warmed up is determined using a catalyst temperature of an exhaust gas catalytic converter.

15. The vehicle according to claim 14, wherein the catalyst temperature is determined using at least one of a temperature of a coolant, a speed of the vehicle, and an elapsed time since the engine stops.

16. The vehicle according to claim 11, wherein the controller is configured to determine to drive in the second mode when the predicted travel distance is less than a predetermined value and the engine is not warmed up.

17. The vehicle according to claim 11, wherein the controller is configured to determine to drive in the first mode and is configured to perform warmup control of the engine when the predicted travel distance is greater than a predetermined value and the engine is not warmed up.

18. The vehicle according to claim 11, wherein the controller is configured to determine to drive in the first mode without warmup control of the engine when the engine is warmed up.

19. The vehicle according to claim 11, wherein the first mode includes a charge depleting (CD) mode, and the second mode includes a charge sustaining (CS) mode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates an example of mode switch performed in a typical PHEV;

(2) FIG. 2 illustrates an example of mode switch performed in a typical PHEV when an adaptive mode switching method is applied;

(3) FIG. 3 illustrates an example of engine warmup performed when mode switch is performed in a typical PHEV;

(4) FIG. 4 illustrates a powertrain structure of a hybrid vehicle to which embodiments of the present invention may be applied;

(5) FIG. 5 is a block diagram illustrating an exemplary control system of a hybrid vehicle to which embodiments of the present invention may be applied;

(6) FIG. 6 is a flowchart illustrating an exemplary procedure of adaptive mode switch control according to an exemplary embodiment of the present invention; and

(7) FIG. 7 illustrates mode switch for each driving load that occurs when adaptive mode switch is controlled according to an exemplary embodiment of the present invention.

(8) It may be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of features illustrative of the basic principles of the invention. The predetermined design features of the present invention as disclosed wherein, including, for example, predetermined dimensions, orientations, locations, and shapes will be determined in part by the particularly intended application and use environment.

(9) In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

(10) Reference will now be made in detail to embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

(11) Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. As used herein, the suffixes module and unit are added or used interchangeably to simply facilitate preparation of the present specification and are not intended to suggest meanings or functions distinguished therebetween.

(12) Hereinafter, a hybrid vehicle structure to which embodiments of the present invention may be applied will be described with respect to FIG. 4.

(13) FIG. 4 illustrates a powertrain structure of a hybrid vehicle to which embodiments of the present invention may be applied.

(14) FIG. 4 shows the powertrain of a hybrid vehicle employing a parallel type hybrid system having an electric motor (or drive motor) 140 and an engine clutch 130 which are mounted between an internal combustion engine (ICE) 110 and a transmission 150.

(15) Generally, in such a vehicle, when the driver steps on the accelerator after startup, the motor 140 is first driven using the power of the battery with the engine clutch 130 open, and the power of the motor moves the wheels via the transmission 150 and a final drive (FD) 160 (i.e., in the EV mode). When a larger driving force is required as the vehicle gradually speeds up, a secondary motor (or starter/generator motor) 120 may be operated to drive the engine 110.

(16) Accordingly, when the rotation speeds of the engine 110 and the motor 140 become equal to each other, the engine clutch 130 is engaged, and wherein the engine 110 and the motor 140 together drive the vehicle (i.e., transition from the EV mode to the HEV mode). When a predetermined engine off condition including deceleration of the vehicle, is satisfied, the engine clutch 130 is open and the engine 110 is stopped (i.e., transition from the HEV mode to the EV mode). As such, the vehicle uses the driving force of the wheel to charge the battery through the motor, which is called braking energy regeneration or regenerative braking. Therefore, the starter/generator motor 120 functions as a starter motor when the engine is started, and operates as a generator when the rotational energy of the engine is collected after the engine is started or turned off. Therefore, the starter/generator motor 120 may be referred to as a hybrid starter generator (HSG).

(17) A correlation between controllers in the vehicle to which the powertrain described above is applied is shown in FIG. 5.

(18) FIG. 5 is a block diagram illustrating an exemplary control system of a hybrid vehicle to which embodiments of the present invention may be applied.

(19) Referring to FIG. 5, in a hybrid vehicle to which embodiments of the present invention may be applied, the internal combustion engine 110 may be controlled by an engine management system (EMS) 210, and the torque of the starter/generator motor 120 and/or motor 140 may be controlled by a motor control unit (MCU) 220. The engine clutch 130 may be controlled by a clutch controller 230. Here, the engine management system (EMS) 210 is also called an engine controller. In addition, the transmission 150 is controlled by a transmission controller 250.

(20) Each controller is connected to a mode switch controller (or hybrid control unit) 240, which is a upper-level controller that is configured to control the entire mode switch processes, and may be controlled by the mode switch controller 240 to provide information necessary for change of the operation mode and control of the engine clutch for gearshift and/or information necessary for engine stop control to the mode switch controller 240 or may perform an operation according to a control signal.

(21) The mode switch controller 240 determines whether to perform the mode switch operation based on the operation state of the vehicle. For example, the mode switch controller is configured to determine the time to open the engine clutch 130. When the engine clutch (EC) 130 is open, the mode switch controller 240 is configured to perform hydraulic control (in a case of the wet EC) or torque capacity control (in a case of the dry EC). Further, the mode switch controller 240 may determine the state of the EC (Lock-up, Slip, Open, etc.) and control the fuel injection stop time of the engine 110. In addition, the mode switch controller may control the torque of the starter/generator motor 120 to control recovery of the rotational energy of the engine to control engine stop. In addition, in adaptive mode switch control, the mode switch controller 240 may determine the mode change condition and control a lower controller to perform the mode switch operation.

(22) Of course, it is apparent to those skilled in the art that the connection relation between the controllers and the functions/division of the controllers described above are illustrative and not limited to the names thereof. For example, the mode switch controller 240 may be implemented, and wherein the corresponding function is provided in any one of the other controllers or that the corresponding function is distributed to and provided by two or more of the other controllers.

(23) Hereinafter, a more efficient mode switch control method according to an exemplary embodiment of the present invention will be described based on the vehicle structure described above.

(24) As described above, in the typical adaptive mode switching method, ineffective control that causes engine warmup every time the CS mode in which the engine is used is entered may occur in a situation where switch between the modes (from the CD to the CS mode and vice versa) may frequently occur according to the operation condition. To prevent ineffective control, it is provided in the present exemplary embodiment that the predicted CS mode travel distance be determined at the time of determination of switching from the CD mode to the CS mode in the vehicle, and the engine warmup control be performed in consideration of the fuel efficiency and the system efficiency based on the determination.

(25) That is, in the exemplary embodiment of the present invention, the future CS mode travel distance may be predicted using the current state (i.e., temperature) of the engine and the frond road information acquired through the navigation device in the vehicle. As such, the CD mode may be maintained to prevent unnecessary engine warmup when the predicted distance is short. When the predicted distance is long, the vehicle may be driven in the CS mode after warmup of the engine. In addition, to determine the state of the engine, the temperature of the catalytic converter is estimated by applying the temperature modeling of the engine. When the catalyst is sufficiently heated at the estimated temperature, switching to the CS mode may be immediately performed even when the predicted CS mode travel distance is short. Accordingly, system efficiency may be improved.

(26) Hereinafter, a method of determining the predicted CS mode travel distance according to the present exemplary embodiment will be described.

(27) The hybrid controller is configured to determine the predicted CS mode travel distance based on the type, length, gradient, and congestion information related to the front road from the navigation device during the adaptive mode switch (adaptive CD/CS) control.

(28) The predicted CS mode travel distance (hereinafter referred to as CS.sub.pred for simplicity) may be determined through a function considering at least one of the type, length, gradient, and congestion information related to the front road. For example, the method of obtaining CS.sub.pred may be expressed as follows.
CS.sub.pred=f(front road type, length, gradient, congestion information)

(29) Next, the engine temperature modeling for determining whether or not to warm up the engine according to the present exemplary embodiment will be described.

(30) The reason for introducing the modeling in the present exemplary embodiment is that a typical vehicle engine is not provided with a detector for directly measuring the catalyst temperature in the catalytic converter. Of course, when a temperature detector is provided in the catalytic converter, a detected value may be directly used instead of the temperature modeling.

(31) The temperature of the catalytic converter (hereinafter, referred to as Cat.sub.temp for simplicity) may be estimated by estimating the temperature of the catalytic converter based on the engine coolant temperature and the vehicle speed and taking into account decrease in catalyst temperature after the engine is stopped. For example, the method of obtaining Cat.sub.temp may be expressed as follows.
Cat.sub.temp=f(coolant temperature, vehicle speed, time after engine stop)

(32) In the adaptive mode switch control using CS.sub.pred and Cat.sub.temp, the engine warmup control method according to the present exemplary embodiment is implemented as follows.

(33) Using the values of CS.sub.pred and Cat.sub.temp in addition to the mode switch criterion according to the existing typical driving load conditions as mode switch criteria, whether to switch to the CS mode may be determined by three control types according to four cases as follows. Case 1: CS.sub.pred<predetermined value, Cat.sub.temp<predetermined value Control type 1: Switching to the CS mode is prohibited, and the CD mode is maintained. This means that the predicted CS mode travel distance is shorter than a predetermined distance and the engine is not warmed up. Therefore, there is a high possibility of switching to the CD mode immediately after warmup of the engine, and thus unnecessary warmup is prevented. Case2: CS.sub.pred>predetermined value, Cat.sub.temp<predetermined value Control type 2: In the instant case, the predicted CS mode travel distance is long enough, while the engine warmup is required. Accordingly, the fuel is consumed for warmup control, but efficiency degradation is not significant. Therefore, the CS mode may be entered through warmup control. Case3: CS.sub.pred<predetermined value, Cat.sub.temp>predetermined value, Case4: CS.sub.pred>predetermined value, Cat.sub.temp>predetermined value Control type 3: In both cases, the engine is already warmed up, and thus switching to the CS mode does not require the warmup operation. Therefore, the mode is immediately switched to the CS mode according to the driving load without the engine warmup control.

(34) Hereinafter, the mode switch control and the corresponding engine warmup control method will be described with respect to the flowchart of FIG. 6.

(35) FIG. 6 is a flowchart illustrating an exemplary process of adaptive mode switch control according to an exemplary embodiment of the present invention.

(36) FIG. 6 is a flowchart illustrating an exemplary process of determining an auxiliary motor torque according to an exemplary embodiment of the present invention.

(37) Referring to FIG. 6, adaptive mode switch (adaptive CDCS) control may be initiated first (S610). Initiation of the present control may be performed according to conditions including the driver's mode setting, adoption of the mode of the hybrid controller according to satisfaction of a predetermined condition, default setting of the hybrid controller, and destination input to the navigation device, but embodiments of the present invention are not limited thereto.

(38) During the adaptive mode switch control, the hybrid controller is configured to determine the current mode based on an driving load reference. As a result of the determination, when the current mode is the CS mode or it is necessary to switch to the CS mode (S620), the hybrid controller may acquire the value of CS.sub.pred and the value of Cat.sub.temp and compare the same with predetermined reference values (S630, S640A, S640B).

(39) Here, the driving load reference may mean that the driving load estimated by the combination of the vehicle speed, the required torque, and the load level is set as a primary criterion for switch to the CS mode, while in the case of DUCDTE, a control operation causing the SOC to be exhausted within the DUC through the CD mode driving may be additionally performed. The DUC may be estimated by utilizing past information on the vehicle or the navigation destination.

(40) The predetermined values may be set differently depending on the powertrain configuration including the motor output power, the battery capacity, and the engine characteristics for each of the values of CS.sub.pred and Cat.sub.temp.

(41) As a result of the determination, when CS.sub.pred<predetermined value and Cat.sub.temp<predetermined value, the hybrid controller may determine to drive in the CD mode (S650A).

(42) Alternatively, when CS.sub.pred<predetermined value and Cat.sub.temp>predetermined value, or when CS.sub.pred>predetermined value and Cat.sub.temp>predetermined value, the hybrid controller may determine to drive in the CS mode without engine warmup control (S650B).

(43) Alternatively, when CS.sub.pred>predetermined value and Cat.sub.temp<predetermined value as a result of the determination, the hybrid controller may determine to drive in the CS mode along with the engine warmup control (S650C).

(44) Hereinafter, a predetermined embodiment of performing the mode switch control and the corresponding engine warmup control method will be described with respect to FIG. 7.

(45) FIG. 7 illustrates mode switch for each driving load that occurs when adaptive mode switch is controlled according to an exemplary embodiment of the present invention.

(46) Referring to FIG. 7, the adaptive mode switch control is applied to the hybrid vehicle according to the exemplary embodiment of the present invention, and the vehicle is driven in the CD mode in the city section (section CD 1) since the driving load is less than the CS mode switch reference at the start of driving in the city.

(47) Thereafter, the vehicle enters a national highway on which the driving load exceeds the CS mode switch reference, and the hybrid controller compares the value of CS.sub.pred value and the value of Cat.sub.temp with the predetermined values. Since the national highway section is relatively short and is immediately followed by a city section where the driving load is low (i.e., CS.sub.pred<predetermined value), and the vehicle travels in the CD mode from the beginning without the engine warmed up (i.e., Cat.sub.temp<predetermined value), the hybrid controller may determine to travel on the national highway section in the CD mode (section CD 2), although CS travel is favorable in terms of driving load.

(48) In a next city section (section CD 3), the CD mode is maintained because the driving load is low.

(49) Thereafter, since the driving load reference is high on the highway, the hybrid controller is configured to determine whether or not to switch modes. As such, the hybrid controller switches to the CS mode along with engine warmup control because the highway section is sufficiently long (i.e., CS.sub.pred>predetermined value) even though the engine has not been warmed up (Cat.sub.temp<predetermined value) (section CS 1).

(50) After the highway section ends, a city section in which the driving load is low appears to be, and the hybrid controller is configured to determine to switch to the CD mode (section CD 4).

(51) Thereafter, when a national highway section that cause a high driving load but is relatively short (i.e., CS.sub.pred>predetermined value), the hybrid controller switches to the CS mode without engine warmup control when the catalyst has not cooled yet (i.e., Cat.sub.temp>predetermined value) (section CS 2).

(52) The present invention described above may be implemented as a computer-readable code on a medium on which a program is recorded. The computer-readable medium includes all kinds of recording devices in which data that may be read by a computer system is stored. Examples of the computer-readable medium include a hard disk drive (HDD), a solid state drive (SSD), a silicon disk drive (SDD), a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device.

(53) As apparent from the above description, the present invention has effects as follows.

(54) A hybrid vehicle related to at least one exemplary embodiment of the present invention configured as described above may more efficiently control mode switch.

(55) Particularly, in controlling adaptive mode switch, unnecessary engine warmup may be prevented, and fuel efficiency on the actual road may be improved.

(56) It will be appreciated by those skilled in the art that the effects that can be achieved with the present invention are not limited to what has been described above and other effects of the present invention will be clearly understood from

(57) For convenience in explanation and accurate definition in the appended claims, the terms upper, lower, internal, outer, up, down, upper, lower, upwards, downwards, front, rear, back, inside, outside, inwardly, outwardly, internal, external, internal, outer, forwards, and backwards are used to describe features of the exemplary embodiments with respect to the positions of such features as displayed in the figures.

(58) The foregoing descriptions of predetermined exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described to explain predetermined principles of the invention and their practical application, to be configured for others skilled in the art to make and utilize exemplary embodiments of the present invention, as well as alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.