Vehicle control method for energy recovery

A hybrid vehicle control method is provided, in which a drive motor and an engine generate power and a hybrid starter generator connected to the engine generates electric power. The vehicle control method includes determining whether the vehicle is in a regenerative control mode and selecting a regenerative torque for the hybrid starter generator connected to the engine. The selected regenerative torque is applied to the hybrid starter generator and electric power is generated with the regenerative torque selected by the hybrid starter generator. In the regenerative torque selection, the regenerative torque with which maximum regenerative energy is produced is selected based on regenerative torque selection factors including a hybrid starter generator rotation speed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0099198 filed in the Korean Intellectual Property Office on Jul. 13, 2015, the entire contents of which are incorporated herein by reference.

BACKGROUND

(a) Field of the Invention

The present invention relates to a vehicle control method and system, and more particularly, to a vehicle control method and system for energy recovery.

(b) Description of the Related Art

An electric-powered vehicle refers to a vehicle that uses a drive motor to receive power from a battery and to produce the vehicle driving force using the supplied power. The electric-powered vehicle includes an electric vehicle that uses a drive motor to produce any driving force for the vehicle or a hybrid vehicle that uses a drive motor to produce part of the driving force for the vehicle. The hybrid vehicle includes a drive motor driven by electricity and an engine that produces a driving force by fuel combustion, and the engine transmits the driving force to a drive shaft by being selectively connected to the drive shaft. When the engine and the drive shaft are disconnected, the engine may stop.

SUMMARY

The present invention provides a vehicle control method and system that are capable of producing electricity using inertia of an engine separated from a drive shaft and reducing vibration generated when the engine stops.

An exemplary embodiment of the present invention provides a hybrid vehicle control method in which a drive motor and an engine generate power and a hybrid starter generator connected to the engine generates electric power, the method may include: determining whether the vehicle is in a regenerative control mode; selecting a regenerative torque for the hybrid starter generator connected to the engine; applying the selected regenerative torque to the hybrid starter generator; and generating electric power with the regenerative torque by the hybrid starter generator. In the regenerative torque selection, the regenerative torque with which maximum regenerative energy is produced may be selected based on regenerative torque selection factors including a hybrid starter generator rotation speed.

The regenerative torque selection factors may further include vehicle speed, and the regenerative torque may be selected based on the hybrid starter generator rotation speed and the vehicle speed. Additionally, the regenerative torque may increase as the vehicle speed increases. The hybrid starter generator rotation speed may be proportional to the rotation speed of the engine. The regenerative torque selection may be performed based on at least one regenerative energy map with the regenerative torque selected based on the regenerative torque selection factors.

The vehicle control method may further include identifying the driving mode of the vehicle, and the regenerative torque selection may be performed based on a plurality of regenerative energy maps that correspond to a plurality of driving modes. Additionally, the vehicle control method may include comparing the revolutions per minute (RPM) of the engine or hybrid starter generator with a reference RPM, and when the RPM of the engine or hybrid starter generator is greater than the reference RPM, the regenerative torque selection and the regenerative torque application may be repeated.

The application of the regenerative torque to the hybrid starter generator may include: applying a newly selected second regenerative torque, which is different from a first regenerative torque, to the hybrid starter generator that generates electric power with the first regenerative torque; and changing the torque applied to the hybrid starter generator from the first regenerative torque to the second regenerative torque. In the changing of the regenerative torque from the first regenerative torque to the second regenerative torque, the torque applied to the hybrid starter generator may change linearly. Further, the determination of whether the vehicle is in the regenerative control mode may include determining whether the engine is separated from a drive shaft.

The vehicle control method according to the exemplary embodiment of the present invention offers the advantage of optimizing energy efficiency by generating electric power using the inertia of the engine, selecting the regenerative torque that enables the hybrid starter generator to produce maximum energy, and applying the regenerative torque to the hybrid starter generator.

DETAILED DESCRIPTION

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. In the present invention, the term “on” implies being positioned above or below a target element, and does not imply being necessarily positioned on the top on the basis of a gravity direction.

In the following detailed description, exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described exemplary embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. Because the size and thickness of each element shown in the drawings are arbitrarily shown for better understanding and ease of description, the present invention is not limited thereto.

Hereinafter, a vehicle driving system and a control method thereof according to exemplary embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1is a block diagram showing the configuration of a vehicle driving system according to an exemplary embodiment of the present invention. Referring toFIG. 1, a vehicle1equipped with a vehicle driving system100according to the present exemplary embodiment may include an engine200and a drive motor130as power sources.

A driving force generated from the engine200and/or the drive motor130may be transmitted to a drive shaft500through a transmission700. The drive motor130may be connected to the transmission700to transmit the driving force generated from the drive motor130to the drive shaft500. In addition, a plurality of clutches600may be interposed between the engine200and the drive motor130, and the clutches600may selectively connect the engine200and the drive motor130. Accordingly, the driving force generated from the engine200may be transmitted to the drive shaft500through the transmission700when the clutches600are engaged.

The vehicle driving system100may further include a battery300, an inverter400, and a hybrid starter and generator110. The battery300may be connected to the drive motor130and the hybrid starter generator (HSG)110through the inverter400, and may be configured to supply power to the drive motor130and the HSG110. The inverter400may be configured to convert direct current (DC) power from the battery300to alternating current (AC) power to selectively supply the AC power to the drive motor130and the HSG110.

The HSG110may be electrically connected to the inverter400, and may be mechanically connected to the engine200via a belt unit140. The HSG110may be configured to start the engine200using the power of the battery300, or generate electric power by the inertia of the engine200when the engine slows down or stops, and store the generated electric power in the battery300. The vehicle driving system100according to the present exemplary embodiment may be configured to generate electric power using a torque generated by the inertia of the engine200disconnected from the drive shaft500. Accordingly, the vehicle driving system100may include a controller120configured to operate the HSG110, the inverter400, and the drive motor130.

The controller120may be implemented by one or more microprocessors that operate by a preset program, and the preset program may include a series of commands for performing each step of a method according to an exemplary embodiment of the present invention to be described later. In particular, the controller120may be configured to calculate the regenerative torque T to be applied to the HSG110, and may adjust the current such that a proper amount of current is applied to the HSG110based on the regenerative torque T. Therefore, the engine200connected to the HSG110stops, during which the HSG110generates electric power, i.e., regenerative energy Er, as it rotates with the engine200by the inertia of the engine200.

Hereinafter, a process in which the controller120calculates regenerative torque T will be described in detail.FIG. 2is a view showing a process of generating a hybrid starter generator torque in the vehicle driving system ofFIG. 1. Referring toFIG. 2, the controller120may include a selection unit121configured to calculate regenerative torque T, and the selection unit121may be configured to select the regenerative torque at which maximum regenerative energy is produced, based on regenerative torque selection factors including HSG rotation speed S.

Hereinafter, a regenerative energy map exemplifying HSG rotation speed S, regenerative torque T, and regenerative energy produced with the rotation speed S and the regenerative torque T will be explained.

Referring to Table 1, the horizontal axis indicates the rotation speed of the HSG110, and the vertical axis indicates regenerative torque T. Additionally, Table 1 shows the regenerative energy ER that corresponds to each value of HSG rotation speed and each value of regenerative torque T, and the largest amount of regenerative energy Er produced with a specific value of HSG rotation speed may be referred to as maximum regenerative energy Er_Max. The HSG rotation speed may be proportional to the rotation speed of the engine200connected to the HSG110. For example, when the rotation ratio between the HSG110and the engine200is 1:1, the HSG rotation speed may be about the same as that of the engine200, and when the rotation ratio is 1:2, the HSG rotation speed may be about half that of the engine200.

Meanwhile, a plurality of regenerative energy maps may be provided based on the driving mode selected by the driver. In other words, in the vehicle1equipped with the driving system100according to the present exemplary embodiment, the controller120may be configured to set the driving style to various styles such as fuel efficiency-oriented driving style or acceleration-oriented driving style, and a plurality of regenerative energy maps may be created to correspond to the plurality of driving styles, respectively. Alternatively, the controller120may be configured to provide various driving modes such as fuel efficiency-oriented driving mode or acceleration-oriented driving mode, and a plurality of regenerative energy maps may be created to correspond to the plurality of driving modes, respectively. The controller120may be configured to identify the driving mode or the driving style before selecting a regenerative torque T, and select a regenerative torque T from the regenerative energy map that corresponds to the driving mode or driving style.

In an exemplary embodiment, the selection unit121may be configured to select a regenerative torque T based on the HSG rotation speed S, among all of the regenerative torque selection factors. However, unless specifically mentioned otherwise, it should be understood that a regenerative torque T may be selected either using other factors like vehicle speed, for example, apart from the HSG rotation speed S, among all of the regenerative torque selection factors, or using the HSG rotation speed S and other factors.

FIG. 3is a flowchart showing a control method of the vehicle driving system ofFIG. 1. Referring toFIG. 3, the controller120may be configured to determine whether the vehicle1is currently in regenerative control mode (S100). In other words, the controller120may be configured to determine whether the vehicle1is in the regenerative control mode by determining whether the engine200is separated from the drive shaft500, that is, whether the clutches600are disengaged.

When the vehicle1is currently in the regenerative control mode, the controller120may be configured to identify the driving mode selected by the driver or the driving style (S200). Further, the controller120may be configured to select a regenerative torque T from the regenerative energy map that corresponds to the driving mode or driving style (S300). In other words, the selection unit121may be configured to select the regenerative torque T with which maximum regenerative energy Er is produced, from the regenerative energy map, based on the HSG rotation speed.

Furthermore, the controller120may be configured to apply the selected regenerative torque T to the HSG110(S400), and the HSG110connected to the engine200may be configured to generate electric power based on the applied regenerative torque T (S500). In other words, the controller120may be configured to calculate the proper or appropriate amount of current that enables the regenerative torque T to be applied to the HSG110, and apply the calculated amount of current to the HSG110. The controller120may then be configured to compare the RPM (Rd) of the engine200or HSG110with a reference RPM (Rr) (S600), and cease the operation when the RPM (Rd) of the engine200or HSG110is less than the reference RPM (Rr). When the RPM (Rd) of the engine200or HSG110is less than the reference RPM (Rr), the amount of electric power generation may be less compared to the amount of current applied to the HSG110to apply the regenerative torque T. Accordingly, current may no longer be applied to the HSG110.

When the RPM (Rd) of the engine200or HSG110is greater than the reference RPM (Rr), the controller120may be configured to repeat the driving mode identification step S200, the regenerative torque selection step S300, and the regenerative torque application step S400. In particular, the RPMs of the engine200and HSG110may be decreased by the regenerative power generation of the driving system100. Accordingly, when repeating the step S300, the controller120may be configured to select a regenerative torque T that matches or corresponds to the current HSG rotation speed and apply the selected regenerative torque T to the HSG110.

In other words, when the RPM (Rd) of the HSG110that generates electric power with a preset first regenerative torque T1is decreased, a second regenerative torque T2may be selected based on the decreased RPM (Rd) and applied to the HSG110. Accordingly, when the second regenerative torque T2is applied to the HSG110that generates electric power with the first regenerative torque T1, the controller120may be configured to linearly change the regenerative torque T of the HSG110from the first regenerative torque T1to the second regenerative torque T2. As the regenerative torque T of the HSG110changes linearly, slip or damage of the belt unit140connecting the HSG110and the engine200may be avoided.

According to the exemplary embodiment of the present invention, energy efficiency may be optimized by generating electric power using the inertia of the engine200, selecting the regenerative torque that enables the HSG to produce maximum energy, and applying it to the HSG.

FIG. 4is a view showing a process of generating a hybrid starter generator torque in a vehicle driving system according to another exemplary embodiment of the present invention. The present exemplary embodiment is the same as the control method ofFIGS. 1 to 3according to the above-explained exemplary embodiment, except for the selection of a regenerative torque T by the selection unit121. Accordingly, the following description will be focused on distinctive characteristics of the present exemplary embodiment. Referring toFIG. 4, the selection unit121of the controller120according to the present exemplary embodiment may be configured to select a regenerative torque T based on the HSG rotation speed S and the speed V of the vehicle1.

In other words, the regenerative torque T at which maximum regenerative energy Er is produced may be selected based on two factors, i.e., the HSG rotation speed S and the speed V of the vehicle1, among the above regenerative torque selection factors. The maximum amount of regenerative energy Er based on the HSG rotation speed S is substantially the same as in the above-explainedFIGS. 1 to 3. The regenerative energy map may be created in which the regenerative torque T increases as the speed V of the vehicle1increases since as the speed of the vehicle1increases, the passenger becomes less sensitive to noise due to external noise such as wind noise, and a greater amount of regenerative torque T is required to stop the engine200more rapidly.

DESCRIPTION OF SYMBOLS

100: vehicle driving system

130: drive motor

500: drive shaft