KR20180070341A - Hybrid vehicle and method of controlling mode transition - Google Patents

Abstract

The present invention relates to a hybrid vehicle and a method of controlling a mode transition therefor and, more specifically, relates to a method of controlling a mode transition to reduce a loss of fuel of an engine that is not operated and a hybrid vehicle to perform the same. According to an embodiment of the present invention, the method of controlling a mode transition of the hybrid vehicle comprises the following steps of: determining whether a first mode is changed to a second mode in accordance with current demand torque; determining engine starting time with an increased speed of an electric motor during expected coupling time of an engine clutch, a target bonding speed, and a current motor speed when the transition to the second mode is required as a result of the determination; and turning on an engine and starting the control of the engine clutch at the determined time.

Description

≪ Desc / Clms Page number 1 > HYBRID VEHICLE AND METHOD OF CONTROLLING MODE TRANSITION FOR HYBRID VEHICLE &

The present invention relates to a hybrid vehicle and a mode switching control method therefor, and more particularly, to a mode switching control method capable of reducing non-driving fuel loss of an engine and a hybrid vehicle for performing the same.

The demand for environmentally friendly vehicles is increasing due to the demand for constant fuel efficiency improvement for vehicles and the strengthening of exhaust gas regulations of each country. Hybrid vehicles (Hybrid Electric Vehicle / Plug-in Hybrid Electric Vehicle, HEV / PHEV) is being provided.

Such a hybrid vehicle can provide optimal output and torque according to how the engine and motor are operated in harmony in the course of traveling with two power sources composed of an engine and a motor. Particularly, in a hybrid vehicle employing a parallel type (TMED: Transmission Mounted Electric Device) hybrid system in which an electric motor and an engine clutch (EC: Clutch) are mounted between the engine and the transmission, Can be simultaneously transmitted to the drive shaft.

In a typical situation of a hybrid vehicle, electric energy is used during initial acceleration (i.e., EV mode). However, since electric energy alone has a limitation in meeting the driver's required power, a moment is required to eventually use the engine as the main power source (i.e., the HEV mode). In this case, in the hybrid vehicle, when the difference between the number of revolutions of the motor and the number of revolutions of the engine is within a predetermined range, the engine clutch is engaged so that the motor and the engine rotate together. At this time, since the engine stall may occur when the engine clutch is engaged when the number of revolutions is too low, the hybrid vehicle is operated at a specific revolution number (hereinafter referred to as "target joining speed" And controls the number of revolutions of the engine and the motor so as to start bonding. The target joining speed may be set differently depending on the engine characteristics of the vehicle, the gear stage of the joining point, and the like.

However, when the engine is started as soon as it is needed as a main power source, there is a case where the actual engine clutch is engaged and waiting for a predetermined time until the engine power is transmitted to the axle of the drive wheel. As a result, fuel loss occurs while the power of the engine does not contribute to driving, which is called "non-driven fuel loss ". The manner in which the non-driven fuel loss occurs will be described with reference to FIG.

1 is a view for explaining an example of a form in which a non-driving fuel loss occurs in a general hybrid vehicle.

Referring to FIG. 1, when the driver operates the accelerator pedal (i.e., APS on), the required torque becomes large, and when it is determined by the vehicle that the driving force of the engine is required to be satisfied due to the power of the motor, The start of the engine is turned on.

When the engine is turned on, the engine speed is rapidly increased (EngSpeed: Engine Speed) because the engine is in a no-load state. However, the motor speed (MotSpeed: Motor Speed) may not reach the target joining speed. In this case, the engine maintains the idle state at the target joining speed up to the joining time, which causes a problem of non-driving fuel loss.

The present invention provides a method for performing mode control more efficiently in a hybrid vehicle and a vehicle for performing the same.

Particularly, the present invention is to provide a mode control method capable of improving non-drive fuel loss in a parallel hybrid vehicle and a vehicle performing the same.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, unless further departing from the spirit and scope of the invention as defined by the appended claims. It will be possible.

According to an aspect of the present invention, there is provided a method for controlling a mode switching of a hybrid vehicle, the method comprising: determining whether to switch from a first mode to a second mode according to a current demand torque; Determining a starting point of the engine using the increase speed of the electric motor, the target joining speed, and the current motor speed during the expected engagement time of the engine clutch when the switching to the second mode is required as a result of the determination; And initiating joint control of the engine start and the engine clutch at the determined point in time.

Further, a parallel hybrid vehicle according to an embodiment of the present invention includes an engine controller for controlling an engine; A clutch controller for controlling the engine clutch; And determining whether or not to switch from the first mode to the second mode according to the current required torque, and when it is determined that the switching to the second mode is required as a result of the determination, And a hybrid controller for controlling the engine controller and the clutch controller so that the engine start and the engagement control of the engine clutch are started at the determined point in time, using the speed and the current motor speed.

The hybrid vehicle according to at least one embodiment of the present invention configured as described above can perform mode switching control more efficiently.

In particular, the predicted increase time of the motor speed and the increase rate of the motor speed during the predetermined time are predicted, and the optimal engine start time is determined by this, so that the non-driven fuel loss can be reduced.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

1 is a view for explaining an example of a form in which a non-driving fuel loss occurs in a general hybrid vehicle.
2 shows an example of a powertrain structure of a hybrid vehicle to which embodiments of the present invention can be applied.
3 is a block diagram showing an example of a control system of a hybrid vehicle to which embodiments of the present invention can be applied.
4 is a view for explaining a principle of determining an engine start time according to an embodiment of the present invention.
5 is a flowchart illustrating an example of a mode switching control process according to an embodiment of the present invention.
6 is a view for explaining a difference between a mode switching method and a general mode switching method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise. In addition, parts denoted by the same reference numerals throughout the specification denote the same components.

In addition, in the case of a "revolution number" such as a motor or an engine constituting a power train, for example, in the case of RPM, it may be used in the same meaning as the "speed"

First, a hybrid vehicle structure to which embodiments of the present invention can be applied will be described with reference to FIG.

2 shows an example of a powertrain structure of a hybrid vehicle to which embodiments of the present invention can be applied.

2, a parallel type hybrid system in which an electric motor (or a drive motor 140) and an engine clutch 130 are mounted between the internal combustion engine (ICE) 110 and the transmission 150 A powertrain of a hybrid vehicle is shown.

In such a vehicle, in general, when the driver steps on the accelerator, the motor 140 is first driven using the power of the battery in the state where the engine clutch 130 is opened, and the power of the motor is transmitted to the transmission 150 and the decelerator 150. [ (FD) drive (Final Drive, 160). When the vehicle is gradually accelerated and a gradually larger driving force is required, the auxiliary motor (or the startup power generation motor) 120 is operated to drive the engine 110. [

Accordingly, when the rotational speeds of the engine 110 and the motor 140 become equal to each other, the engine clutch 130 is engaged and the engine 110 and the motor 140 together drive the vehicle (i.e., ). The engine clutch 130 is opened and the engine 110 is stopped (i.e., the EV mode transition is performed in the HEV mode) if the predetermined engine off condition such as the vehicle deceleration is satisfied. At this time, 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 starting power generation motor 120 functions as a start motor when the engine is started, and operates as a generator when the rotation energy of the engine is recovered after startup or during startup. Therefore, the hybrid start generator (HSG: Hybrid Start Generator ").

The correlation between the controllers in the vehicle to which the power train described above is applied is shown in Fig.

3 is a block diagram showing an example of a control system of a hybrid vehicle to which embodiments of the present invention can be applied.

3, in the hybrid vehicle to which the embodiments of the present invention can be applied, the internal combustion engine 110 is controlled by the engine controller 210, the starting power generation motor 120 is controlled by a motor control unit (MCU) 220 And the engine clutch 130 can be controlled by the clutch controller 230, respectively. Here, the engine controller 210 may be an engine management system (EMS). Also, the transmission 150 is controlled by the transmission controller 250.

Each controller is connected to a mode switching controller (or hybrid controller) 240 that controls the overall mode switching process as its upper controller, and is controlled by the mode switching controller 240 to change the traveling mode, Information and / or information necessary for engine stop control to the engine 240, or to perform an operation according to the control signal.

More specifically, the mode switching controller 240 determines whether to perform the mode switching according to the driving state of the vehicle. For example, the mode switching controller determines a time point when the engine clutch 130 is released and controls the oil pressure (in case of wet EC) or the torque capacity control (in case of dry EC) at the time of release. Also, the mode switching controller 240 can 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 switching controller can control the torque of the starting power generation motor 120 to control the engine rotation energy recovery for engine stop control. In addition, the mode switching controller 240 can control the lower controller to determine the mode change condition and switch the mode at the time of mode switching control.

Of course, it is apparent to those skilled in the art that the control period connection relationship and the function / division of each controller described above are illustrative and not limited to the names. For example, the mode switching controller 240 may be implemented such that the corresponding function is provided in any one of the other controllers, and the corresponding functions may be distributed in two or more of the other controllers.

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

In one embodiment of the present invention, a method for determining an optimal engine start-up time to minimize the non-driving fuel loss of the engine when the HEV mode is switched in the hybrid vehicle is proposed.

According to the present embodiment, the engine start time can be judged by using the time at which the engine reaches the target joining speed and the rate of increase of the current motor speed. This will be described with reference to FIG.

4 is a view for explaining a principle of determining an engine start time according to an embodiment of the present invention.

In FIG. 4, it is assumed that the APS is maintained at a constant value, and the rate of increase of the motor speed (MotSpeed) is also constant. Under this assumption, if the estimated time required from the engine start to the engagement of the engine clutch (i.e., "Cranking time" or "Predicted engagement time") is known, As a result, if the engine is started at the time when the current motor rotation speed is equal to or higher than the target junction speed when the value of the motor rotation speed increases during the expected engagement time, The engine clutch can be engaged immediately because the target joining speed is reached. Therefore, the engine power can be directly utilized as the driving force, so that the non-driving fuel loss can be minimized.

In other words, the starting point of the engine can be expressed as follows based on the current motor revolution number.

- current motor speed> target junction speed - total motor speed increase during engagement time

Here, the total motor speed increase during the engagement time is a value obtained by multiplying the motor speed increase rate by the anticipated engagement time as described above.

A mode switching method to which the above-described method of determining the engine startup time according to the present embodiment is applied will be described with reference to FIG.

5 is a flowchart illustrating an example of a mode switching control process according to an embodiment of the present invention.

5, it is assumed that the hybrid vehicle is running in the EV mode.

Referring to FIG. 5, the hybrid controller 240 may calculate the current demand torque of the driver through the APS variation amount or the BPS variation amount (S510).

Here, the required torque can be obtained as a function of the pedal position value Pedal (n) sensed by the current pedal sensors APS and BPS. More specifically, the value '(n)' has a positive value when the accelerator pedal APS is operated and may have a negative value when the brake pedal BPS is operated.

At this time, when the APS and the BPS are simultaneously detected by the driver's faulty operation, the hybrid controller can apply the brake override function to ignore the APS change and calculate the required torque only by changing the BPS.

In accordance with the calculated required torque, the hybrid controller 240 may determine whether switching from the EV mode to the HEV mode is required (i.e., whether the driving force of the engine is required) (S520).

If it is determined that the HEV mode needs to be changed, the hybrid controller 240 may determine the increase rate of the motor during the coupling time (S530). Here, the increase rate of the motor during the engagement time is a value obtained by multiplying the motor speed increase rate by the anticipated engagement time as described above. The motor speed increase rate may be calculated by obtaining the RPM information of the motor from the motor controller 220 and the expected engagement time may be a predetermined value according to the configuration and specifications of the engine and engine clutch of the vehicle, It is needless to say that a plurality of values may be set by other variables such as the number of gears.

Hybrid controller 240 determines whether or not the condition of " current motor speed> target joining speed - total motor speed increase during engagement time " is satisfied (S540), and if so, turns on the engine and starts engine clutch engagement control The controller 210 and the clutch controller 230 may be controlled (S550).

Accordingly, when the engagement of the engine clutch is completed (S560), the hybrid controller 240 can control the HEV mode travel to be performed (S570). If it is determined that the HEV switch is unnecessary in S520, or if the condition of S540 is satisfied The EV mode driving can be maintained (S580).

Here, in the case where the process proceeds from step S540 to step S580, the hybrid controller 240 may return to step S520 or step S540 to repeatedly determine the engine start time while the EV mode travel is performed.

Hereinafter, the effect of the comparison between the above-described embodiment and the comparative example will be described with reference to FIG.

6 is a view for explaining a difference between a mode switching method and a general mode switching method according to an embodiment of the present invention.

In FIG. 6, the motor speed (MotSpeed), the engine speed (EngSpeed) at the time of the normal HEV mode control, and the engine speed at the HEV mode control according to the embodiment of the present invention Are shown on the graph.

Referring to FIG. 6, in the normal HEV mode switching control, the engine start and the engine clutch engagement control are started immediately when it is determined that the driving force of the engine is required (that is, the HEV switching need is determined) The non-driven fuel loss occurs. However, according to the embodiment of the present invention, engine startup and engine clutch engagement control are started at a time when the formula of "current motor RPM> target junction speed-motor speed increase during engagement time" is satisfied, .

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

Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all conversions within the scope of equivalents of the present invention are included in the scope of the present invention.

Claims (19)

A mode switching control method for a hybrid vehicle,
Determining whether to switch from the first mode to the second mode according to the current required torque;
Determining a starting point of the engine using the increase speed of the electric motor, the target joining speed, and the current motor speed during the expected engagement time of the engine clutch when the switching to the second mode is required as a result of the determination; And
And starting the engine starting and the engagement control of the engine clutch at the determined point in time. The method according to claim 1,
The increase rate of the electric motor during the expected engagement time is determined by:
And the speed increase rate of the electric motor is multiplied by the expected engagement time. 3. The method of claim 2,
Wherein the determining comprises:
Wherein the current motor speed is determined to be the engine start time point when the current motor speed is greater than a value obtained by subtracting the increase speed of the electric motor during the engagement time from the target junction speed. The method according to claim 1,
Wherein the predicted joining time and the target joining speed are set so that,
Wherein the predetermined value is a predetermined value. The method according to claim 1,
Wherein the engine clutch comprises:
Wherein the engine is disposed between the engine and the electric motor. The method according to claim 1,
The current required torque is determined by the following equation:
Wherein the determination is based on the position of the accelerator pedal and the brake pedal. The method according to claim 1,
Wherein the first mode includes an EV mode, and the second mode includes an HEV mode. The method according to claim 1,
Further comprising: maintaining the first mode until the determined engine start time. The method according to claim 1,
And traveling in the second mode when engine clutch engagement is completed according to the engagement control of the engine clutch. A computer-readable recording medium on which a program for executing the mode switching control method according to any one of claims 1 to 9 is recorded. In a hybrid vehicle,
An engine controller for controlling the engine;
A clutch controller for controlling the engine clutch; And
When the switching to the second mode is required as a result of the determination, it is determined that the increase speed of the electric motor during the anticipated engagement time of the engine clutch, the target joint speed And a hybrid controller for controlling the engine controller and the clutch controller so as to determine an engine starting point using the current motor speed and to start the engine starting and the engagement control of the engine clutch at the determined point in time. 12. The method of claim 11,
The increase rate of the electric motor during the expected engagement time is determined by:
And multiplying the speed increase rate of the electric motor by the expected engagement time. 13. The method of claim 12,
The hybrid controller includes:
And determines a time point at which the current motor speed is greater than a value obtained by subtracting the increase speed of the electric motor during the engagement time from the target junction speed. 12. The method of claim 11,
Wherein the predicted joining time and the target joining speed are set so that,
The hybrid vehicle is a predetermined value. 12. The method of claim 11,
Wherein the engine clutch comprises:
And the engine is disposed between the engine and the electric motor. 12. The method of claim 11,
The current required torque is determined by the following equation:
Based on the position of the accelerator pedal and brake pedal, the hybrid car is judged. 12. The method of claim 11,
Wherein the first mode comprises an EV mode and the second mode comprises an HEV mode. 12. The method of claim 11,
The hybrid controller includes:
And maintains the first mode until the determined engine start time. 12. The method of claim 11,
The hybrid controller includes:
And controls to travel in the second mode when engagement of the engine clutch is completed according to the engagement control of the engine clutch.

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