Patent Publication Number: US-2015060174-A1

Title: In-wheel system for hybrid electric vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0102102 filed in the Korean Intellectual Property Office on Aug. 28, 2013, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to an in-wheel system, and more particularly, to an in-wheel system in a hybrid electric vehicle provided with in-wheel motors and an engine as a driving means. 
     BACKGROUND OF THE INVENTION 
     An in-wheel system is a system in which motors are respectively disposed in wheels to perform distributed control without using a large single motor in a fuel cell vehicle, a plug-in hybrid vehicle, and an electric vehicle (EV) using an electric energy as a main power. Further, the in-wheel system is a system in which a driving motor, a braking device, a bearing, and a decelerator are integrated within the wheel. The in-wheel system has technical advantages that energy efficiency thereof is higher than that of a system driven by one high-capacity motor, it is easy to provide an electric four-wheel drive system, and it is possible to improve running stability of a vehicle by independently driving left and right wheels. 
     In general, the in-wheel system includes a motor that generates a driving power, a cooling device that cools the motor, a decelerator that transmits the driving power of the motor to wheels, a braking device that generates braking force, a steering apparatus that changes a direction of the vehicle, and a suspension supporting the wheels to the vehicle. Such a plurality of components are organically integrated and disposed within the wheel. The in-wheel system typically converts electric energy into a rotational driving power through a stator and a rotor of the motor. After the rotational driving power is decelerated through the decelerator or torque thereof is increased, the rotational driving power is transmitted to a hub, and, thus, a power is transmitted in order of driving the wheels to be rotated. 
     An in-wheel system in a hybrid electric vehicle according to the related art is provided at rear wheels of the vehicle in a front-wheel drive manner or is provided at front wheels of the vehicle in a rear-wheel drive manner to merely assist the driving power of the engine. That is, since in-wheel motors are provided at towed wheels, the in-wheel system according to the related art merely serves to instantaneously assist the driving (for example, 4WD is instantaneously realized on an icy road) or is partly used in only a regenerative braking mode, and there is a technical limitation that it is difficult to organically combine or operate driving powers of the in-wheel motors and the engine. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide an in-wheel system for a hybrid electric vehicle capable of being effectively operated depending on a situation by organically combining driving powers of an engine and in-wheel motors. 
     An exemplary embodiment of the present invention provides an in-wheel system for a hybrid electric vehicle includes an engine that provides a rotational driving power to front wheels or rear wheels, at least one in-wheel motor that is driven by a battery, and is provided at each of the front wheels or each of the rear wheels so as to correspond to the wheels to which the driving power of the engine is transmitted to provide a rotational driving power to the same wheels as the wheels driven by the engine, and a controller that controls the engine and the in-wheel motor to be driven. 
     According to an exemplary embodiment of the present invention, since the in-wheel motors are disposed at the same wheels as driving wheels driven by the engine in the in-wheel system, it is possible to provide various combinations of driving powers by the engine and the in-wheel motors. 
     Particularly, the in-wheel system according to an exemplary embodiment of the present invention can more conveniently implement various control modes such as the EV running mode, the regenerative braking mode, the LSD control mode and the TCS control mode through cooperation of the engine and the in-wheel motors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an in-wheel system for a hybrid electric vehicle according to an exemplary embodiment of the present invention. 
         FIG. 2  is a schematic diagram illustrating an in-wheel system for a hybrid electric vehicle according to another exemplary embodiment of the present invention. 
         FIGS. 3A and 3B  are operation state diagrams illustrating an EV running mode and a driving assist mode in the in-wheel systems for a hybrid electric vehicle of  FIGS. 1 and 2 . 
         FIGS. 4A and 4B  are operation state diagrams illustrating a regenerative braking mode and a cruise control mode in the in-wheel systems for a hybrid electric vehicle of  FIGS. 1 and 2 . 
         FIGS. 5A and 5B  are operation state diagrams illustrating a LSD control mode and a TCS control mode in the in-wheel systems for a hybrid electric vehicle of  FIGS. 1 and 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, the following exemplary embodiments are provided to help understanding of the present invention, and the scope of the present invention is not restricted by the following exemplary embodiments. Further, the following exemplary embodiments are provided to more completely describe the present invention to those having ordinary skill in the art. When it is determined that detailed descriptions of known configurations related to the present invention would obscure the technical gist of the present invention, the descriptions thereof will not be presented. 
       FIG. 1  is a schematic diagram illustrating an in-wheel system for a hybrid electric vehicle according to an exemplary embodiment of the present invention. 
       FIG. 1  illustrates a case where an in-wheel system for a hybrid electric vehicle (hereinafter, referred to as an in-wheel system  100 ) according to an exemplary embodiment of the present invention is applied to a front-wheel drive vehicle. 
     Referring to  FIG. 1 , the in-wheel system  100  according to the present exemplary embodiment may include in-wheel motors  130  and an engine  110  as a driving means. 
     The engine  110  may be connected to an axle  112  through a transmission  111  to provide a rotational driving power of the axle  112 . The axle  112  may provide the rotational driving power to wheels W through constant velocity joints  113 . The axle  112  may be connected to input shafts of the constant velocity joints  113 , and output shafts of the constant velocity joints  113  may be connected to hub bearings  132  for driving the wheels W to be rotated. 
     The in-wheel motors  130  may be respectively disposed in the wheels W. At this time, in the in-wheel system  100  according to the present exemplary embodiment, the wheels W driven to be rotated by the engine  110  may be the same as the wheels W in which the in-wheel motors  130  are disposed. In other words, in the front-wheel drive vehicle illustrated in  FIG. 1 , the in-wheel motors  130  may be provided at the front wheels W of the vehicle. 
     The arrangement of the in-wheel motors  130  is different from that in a general in-wheel system according to the related art in which wheels (for example, front wheels) driven by the engine and wheels (for example, rear wheels) provided with the in-wheel motors are different. Accordingly, in the in-wheel system according to the present exemplary embodiment, since the wheels W can be driven through the engine  110  or the in-wheel motors  130  when necessary, it is possible to easily implement TCS (Traction Control System) control and LSD (Limited Slip Differential) control. The detailed description thereof will be described in the description of the operation of the present exemplary embodiment with reference to  FIGS. 3 to 5 . 
     Meanwhile, the in-wheel motor  130  may provide a rotational driving power to the wheel W by a power provided from a battery  133 . The driving power of the in-wheel motor  130  may be transmitted to the wheel W through a decelerator  131  and the hub bearing  132 . This is a known configuration described in the in-wheel system according to the related art, and thus, the detailed description thereof will not be presented. 
     The in-wheel system  100  according to the present exemplary embodiment may include a controller  150  for controlling the engine  110  and the in-wheel motors  130 . The controller  150  selectively controls the engine  110  or the in-wheel motor  130 , or controls both the engine  110  and the in-wheel motor  130  to be used depending on a running condition or a control state. The detailed description thereof will be described in the description of the operation of the present exemplary embodiment with reference to  FIGS. 3 to 5 . 
       FIG. 2  is a schematic diagram illustrating an in-wheel system for a hybrid electric vehicle according to another exemplary embodiment of the present invention. 
       FIG. 2  illustrates a case where an in-wheel system  200  is applied to a rear-wheel drive vehicle. However, it should be noted that the in-wheel system  200  according to the present exemplary embodiment has the same technical gist as that of the aforementioned exemplary embodiment described with reference to  FIG. 1  and has a configuration similar to the in-wheel system  110  according to the aforementioned exemplary embodiment. 
     More specifically, the in-wheel system  200  according to the present exemplary embodiment may include in-wheel motors  230  and an engine  210  as a driving means. At this time, all of the engine  210  and the in-wheel motors  230  may transmit the driving power to the same wheels (that, rear wheels). In other words, in the rear-wheel drive vehicle of the present exemplary embodiment, the in-wheel motors  230  may be attached to the rear wheels W of the vehicle. 
     The engine  210  may be connected to an axle  212  through a transmission  211 , a propeller shaft  214  and a differential gear  215  to provide the rotational driving power. The rear-wheel driving vehicle in the present exemplary embodiment is different from the front-wheel driving vehicle in that the propeller shaft  214  and the differential gear  215  are provided. The axle  212  may be connected to input shafts of constant velocity joints  213 , and output shafts of the constant velocity joints  213  may be respectively connected to hub bearings  232 . Accordingly, the driving power of the engine  210  is transmitted to the constant velocity joints  213  through the axle  212  and is transmitted to the wheels W through the hub bearings  232 , so that the wheels W can be driven to be rotated. Such a configuration is similar to that of the front-wheel drive vehicle of  FIG. 1 . 
     Meanwhile, the in-wheel motors  230  are respectively disposed in the wheels W to provide the rotational driving power to the wheels W by a power provided from a battery  233 . A driving axis of the in-wheel motor  230  is connected to the hub bearing  232  through a decelerator  231 , so that the wheel W can be driven to be rotated. Such a configuration is similar to that of the front-wheel drive vehicle of  FIG. 1 . 
       FIG. 3  is an operation state diagram illustrating an EV running mode and a driving assist mode in the in-wheel systems for a hybrid electric vehicle of  FIGS. 1 and 2 . 
     (a) of  FIG. 3  is an operation state diagram illustrating an operation of the in-wheel system  100  in the EV (Electric Vehicle) running mode for driving the wheels W to be rotated by only the driving power of the in-wheel motor  130  and the battery  133 , and (b) of  FIG. 3  is an operation state diagram illustrating an operation of the in-wheel system  100  in the driving assist mode for assisting the driving power of the engine  110  through the in-wheel motors  130 . 
     For the sake of convenience in description, although the reference numerals of the components used in the exemplary embodiment of  FIG. 1  have been represented in  FIG. 3 , the components of the exemplary embodiment of  FIG. 2  may be similarly operated as in the description of  FIG. 3 . 
     Referring to (a) of  FIG. 3 , the in-wheel system  100  according to the present exemplary embodiment may be controlled to be driven in the EV running mode for running the vehicle by only the power of the battery  133 . In such a case, the controller  150  stops the driving of the engine  110 , and selectively drives only the in-wheel motors  130 . The driving wheels W can be driven to be rotated through the in-wheel motors  130 . 
     Meanwhile, referring to (b) of  FIG. 3 , the in-wheel system  100  according to the present exemplary embodiment may be controlled to be driven or used in the driving assist mode. In such a case, the controller  150  drives all of the engine  110  and the in-wheel motors  130 , and the driving power by the engine  110  and the driving power by the in-wheel motor  130  are transmitted to the wheel W. The wheel W can be driven to be rotated. 
       FIG. 4  is an operation state diagram illustrating a regenerative braking mode and a cruise control mode in the in-wheel systems for a hybrid electric vehicle of  FIGS. 1 and 2 . 
     (a) of  FIG. 4  illustrates an operation of the in-wheel system in the regenerative braking mode, and (b) of  FIG. 4  illustrates an operation of the in-wheel system in the cruise control mode. For the sake of convenience in description, the reference numerals of the components used in the exemplary embodiment of  FIG. 1  have been represented in the drawing. 
     Referring to (a) of  FIG. 4 , when the in-wheel system is in the regenerative braking mode, the controller  150  may selectively stop the driving of the in-wheel motors  130 . In this case, the driving axes of the in-wheel motors  130  may be passively rotated by the wheels W and the hub bearings  132 , and the in-wheel motors  130  generate a power through rotating of the driving axes, and the power is used to charge the battery  133 . 
     Referring to (b) of  FIG. 4 , even when the in-wheel system is in the cruise control mode in which the vehicle runs at a constant speed, the driving control may be performed similarly to the aforementioned description. That is, the controller  150  selectively drives only the engine  110  to provide the rotational driving power to the wheels W. Meanwhile, the driving of the in-wheel motors  130  is stopped, and the battery  133  may be charged by the rotation of the wheels W. 
       FIG. 5  is an operation state diagram illustrating a LSD control mode and a TCS control mode in the in-wheel systems for a hybrid electric vehicle of  FIGS. 1 and 2 . 
     Referring to (a) of  FIG. 5 , when the vehicle starts after stopping, if there is a difference in frictional force between left and right road surfaces, the in-wheel system  200  according to the present exemplary embodiment can implement the LSD (Limited Slip Differential) control function for preventing one wheel W 1  from slipping or idling. 
     For example, when the vehicle starts after stopping, if one wheel W 1  idles on an icy road I, the controller  250  can forcibly apply a load L through the in-wheel motor  130  provided at the one wheel W 1 . Accordingly, since the driving power is further concentrated on the other wheel W 2 , the vehicle can normally start. 
     Meanwhile, referring to (b) of  FIG. 5 , when there is a difference in frictional force between left and right road surfaces, the in-wheel system  100  according to the present exemplary embodiment can easily implement the TCS (Traction Control System) control function for preventing a posture of the vehicle from being destabilized. 
     For example, when one wheel W 1  slips on the icy road during the running or turning of the vehicle, posture stability and running stability of the vehicle are degraded. In such a case, the controller  150  selectively generates the load L through the in-wheel motor  130  of the slipping wheel W 1 , and the driving power is equally distributed to the left and right wheels W 1  and W 2 . Accordingly, it is possible to improve the posture stability and running stability of the vehicle. 
     As described above, in the in-wheel systems according to the exemplary embodiments of the present invention, since the in-wheel motors are disposed at the same wheels as the driving wheels driven by the engine, it is possible to provide various combinations of driving powers by the engine and the in-wheel motors. Particularly, the in-wheel systems according to the exemplary embodiments of the present invention can more conveniently implement various control modes such as the EV running mode, the regenerative braking mode, the LSD control mode and the TCS control mode through cooperation of the engine and the in-wheel motors. In addition, since existing LSD equipment and a TCS sensor can be removed, it is possible to reduce a weight of the vehicle and manufacturing cost. 
     Although an exemplary embodiment of the present invention has been described, those skilled in the art will variously modify and change the present invention through supplement, change, deletion, addition of the constituent element, and the like, without departing from the spirit of the present invention defined in the claims, and the modification and the change will belong to the scope of the right of the present invention.