Abstract:
A method and a system for controlling idle stop of a vehicle that can reduce braking noise and prevent startup delay may be included, wherein the method for controlling may include estimating a disk temperature, determining whether the estimated disk temperature may be lower than or equal to a first predetermined temperature, and prohibiting engine stop according to the idle stop when the estimated disk temperature may be higher than the first predetermined temperature.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Korean Patent Application No. 10-2012-0086379 filed in the Korean Intellectual Property Office on Aug. 7, 2012, the entire contents of which is incorporated herein for all purposes by this reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method and a system for controlling idle stop of a vehicle, and more particularly to a method and a system for controlling idle stop of a vehicle that can reduce braking noise and prevent startup delay. 
         [0004]    2. Description of Related Art 
         [0005]    Recently, researches for improving fuel economy and reducing exhaust gas have been vividly developed due to energy depletion and environmental pollution. An idle stop and go (ISG) system is developed so as to enhance fuel economy and reduce exhaust gas. 
         [0006]    According to the ISG system, an engine is stopped when a vehicle stops and the engine is restarted when the vehicle begins to run. When the engine is restarted, however, an engine speed is raised in a moment and is lowered. After that, the engine speed is stably maintained. At this time, torque is changed quickly and stumble may occur. Recently, an electric stability control system is used so as to prevent occurrence of stumble. The electric stability control system delays start of the vehicle for a predetermined time when the engine is restarted. 
         [0007]    If the start of the vehicle is delayed by using the electric stability control system, however, braking noise may occur. In further detail, the electric stability control system brakes the vehicle when the engine speed increases on restarting of the engine. If the engine speed decreases at this state, momentary vibration may occur at a wheel due to change in driving torque. Particularly, since the electric stability control system releases braking force of the vehicle if the engine speed decreases, braking noise may occur at a point when the braking force is equal to the driving torque. If braking time of the vehicle by the electric stability control system is extended, occurrence of such noise can be prevented. However, the start of the vehicle may be excessively delayed. 
         [0008]    Meanwhile, the braking noise further increases if a disk temperature is raised by sequential braking before the vehicle stops or by quick braking. 
         [0009]    The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
       BRIEF SUMMARY 
       [0010]    Various aspects of the present invention are directed to providing a method and a system for controlling idle stop of a vehicle having advantages of prohibiting engine stop according to the idle stop if a disk temperature is higher than a predetermined temperature. 
         [0011]    In an aspect of the present invention, a method for controlling idle stop of a vehicle may include estimating a disk temperature, determining whether the estimated disk temperature is lower than or equal to a first predetermined temperature, and prohibiting engine stop according to the idle stop when the estimated disk temperature is higher than the first predetermined temperature. 
         [0012]    The estimation of the disk temperature is determined based on work done by braking force. 
         [0013]    The estimation of the disk temperature may include determining the work done by the braking force for a unit time, determining work distributed to one disk among the work done by the braking force, converting the work distributed to the one disk into heat, determining a temperature rise of the one disk, and determining the disk temperature based on the temperature rise of the one disk. 
         [0014]    The determining the disk temperature based on the temperature rise of the one disk is performed by adding temperature rises of the disk for n unit times, and the n is integer larger than or equal to 1. 
         [0015]    The method mat may further include determining whether an engine stop condition according to the idle stop is satisfied, wherein an engine is stopped according to the idle stop when the engine stop condition is satisfied and the estimated disk temperature is lower than or equal to the first predetermined temperature. 
         [0016]    When the estimated disk temperature is higher than the first predetermined temperature, the engine stop according to the idle stop is prohibited. 
         [0017]    When the estimated disk temperature is lower than or equal to a second predetermined temperature, the estimating the disk temperature is repeated. 
         [0018]    When the estimated disk temperature is higher than the second predetermined temperature, the engine stop accordion to the idle stop is continuously prohibited. 
         [0019]    The method may further include determining whether an engine restart condition is satisfied after the engine is stopped, and restarting the engine when the engine restart condition is satisfied. 
         [0020]    The method may further include determining whether an operation of an electric brake system is needed when the engine is restarted, and operating the electric brake system when the operation of the electric brake system is needed. 
         [0021]    The operated electric brake system is released when a predetermined condition is satisfied. 
         [0022]    In another aspect of the present invention, a system for controlling idle stop of a vehicle may include a speed sensor for detecting a vehicle speed, a brake pedal position sensor for detecting operation of a brake, and a controller for controlling the idle stop and restart of the vehicle based on detected values by the speed sensor and the brake pedal position sensor, wherein the controller estimates a disk temperature based on the detected values by the speed sensor and the brake pedal position sensor, and prohibits engine stop according to the idle stop when the estimated disk temperature is higher than or equal to a first predetermined temperature. 
         [0023]    The controller determines work distributed to one disk from work done by braking force for a unit time, determines a temperature rise of the one disk by converting the work distributed to the one disk into heat, and determines the disk temperature based on the temperature rise of the one disk. 
         [0024]    The controller determines the disk temperature by adding temperature rises of the disk for n unit times, and the n is integer larger than or equal to 1. 
         [0025]    The controller determines whether an engine stop condition according to the idle stop is satisfied, and stops an engine when the engine stop condition is satisfied and the estimated disk temperature is lower than or equal to the first predetermined temperature. 
         [0026]    When the estimated disk temperature is higher than the first predetermined temperature, the engine stop according to the idle stop is prohibited. 
         [0027]    When the estimated disk temperature is lower than or equal to a second predetermined temperature, the controller repeats estimating the disk temperature. 
         [0028]    The controller restarts the engine when an engine restart condition is satisfied after the engine is stopped. 
         [0029]    The system may further include an electric brake system for braking the vehicle, wherein the controller operates an electric brake system until a predetermined condition is satisfied when the engine is restarted. 
         [0030]    The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  is a schematic diagram of a vehicle at which a system for controlling idle stop according to an exemplary embodiment of the present invention is mounted. 
           [0032]      FIG. 2  is a block diagram of a system for controlling idle stop according to an exemplary embodiment of the present invention. 
           [0033]      FIG. 3  is a flowchart of a method for controlling idle stop according to an exemplary embodiment of the present invention. 
           [0034]      FIG. 4  is a flowchart of a method for estimating a disk temperature according to an exemplary embodiment of the present invention. 
           [0035]      FIG. 5  is a schematic diagram for explaining a method for estimating a disk temperature according to an exemplary embodiment of the present invention. 
       
    
    
       [0036]    It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
         [0037]    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 
       [0038]    Reference will now be made in detail to various 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 various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
         [0039]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0040]      FIG. 1  is a schematic diagram of a vehicle at which a system for controlling idle stop according to an exemplary embodiment of the present invention is mounted. 
         [0041]    As shown in  FIG. 1 , a vehicle  1  includes an engine  70  (please refer to  FIG. 2 ) as a power source, and rotates a wheel  6  using power generated at the engine  70 . A brake apparatus  4  is mounted at the wheel  6  and brakes the vehicle  1  by hindering rotation of a disk  2  fixed to the wheel  6  by frictional force. 
         [0042]    In addition, an idle stop and go (ISG) system  50  and an electric brake system  60  are mounted at the vehicle  1 . 
         [0043]    The ISG system  50  stops the engine  70  if the vehicle stops and restarts the engine  70  if the vehicle starts. The ISG system  50  is well known to a person of an ordinary skill in the art and accordingly detailed description thereof will be omitted. 
         [0044]    The electric brake system  60 , independent of an operation of a brake pedal, brakes the vehicle  1 . That is, the electric brake system  60  generates hydraulic pressure applied to a brake piston and brakes the vehicle  1  without the operation of the brake pedal if a predetermined condition is satisfied. The electric brake system  60  may be included in an electric stability control system mounted at the vehicle  1  or may be mounted at the vehicle  1  independent of the electric stability control system. 
         [0045]    Meanwhile, the vehicle  1  may be any type of vehicles at which the ISG system  50  and the electric brake system  60  are mounted such as a gasoline vehicle, a diesel vehicle, a hybrid vehicle, and so on. 
         [0046]      FIG. 2  is a block diagram of a system for controlling idle stop according to an exemplary embodiment of the present invention. 
         [0047]    As shown in  FIG. 2 , a system for controlling idle stop according to an exemplary embodiment of the present invention includes a speed sensor  10 , an acceleration sensor  20 , a brake pedal position sensor  30 , a controller  40 , the ISG system  50 , and the electric brake system  60 . 
         [0048]    The speed sensor  10  detects a speed of the vehicle  1  and transmits a signal corresponding thereto to the controller  40 . The speed sensor  10  may be an ABS sensor mounted at the wheel  6  of the vehicle  1 . 
         [0049]    The acceleration sensor  20  detects an acceleration of the vehicle  1  and transmits a signal corresponding thereto to the controller  40 . The acceleration sensor  20  and the speed sensor  10  may be mounted respectively. On the contrary, the acceleration of the vehicle  1  may be calculated based on the speed of the vehicle  1  detected by the speed sensor  10 . 
         [0050]    The brake pedal position sensor  30  detects an operation of a brake and transmits a signal corresponding thereto to the controller  40 . The signal of the brake pedal position sensor  30  is 1 if the brake is operated, but the signal of the brake pedal position sensor  30  is 0 if the brake is not operated. 
         [0051]    The controller  40  is electrically connected to the speed sensor  10 , the acceleration sensor  20 , and the brake pedal position sensor  30 , and receives electrical signals corresponding to values detected by the sensors. The controller  40  can be realized by one or more processors activated by a predetermined program, and the predetermined program can be programmed to perform each step of a method for controlling idle stop of a vehicle according to an exemplary embodiment of the present invention. 
         [0052]    The controller  40  controls operations of the ISG system  50  and the electric brake system  60  based on the electrical signals transmitted from the sensors. 
         [0053]    A method for controlling idle stop according to an exemplary embodiment of the present invention will hereinafter be described in detail. 
         [0054]      FIG. 3  is a flowchart of a method for controlling idle stop according to an exemplary embodiment of the present invention. 
         [0055]    If the engine  70  is started at step S 100 , the vehicle  1  runs according to manipulations of a driver at step S 110 . The control portion  40  determines whether an engine stop condition according to the idle stop is satisfied at step S 120 . The engine stop condition according to the idle stop may be satisfied if the vehicle is stopped, the brake pedal is operated, a brake pressure is higher than or equal to a predetermined pressure, charge amount of a battery is higher than or equal to a predetermined charge amount. The engine stop condition is not limited to the above-mentioned condition and may include any suitable condition. 
         [0056]    If the engine stop condition according to the idle stop is not satisfied at the step S 120 , the controller  40  returns to the step S 110 . If the engine stop condition according to the idle stop is satisfied at the step S 120 , the controller  40  estimates a disk temperature at step S 130 . 
         [0057]    Estimation of the disk temperature will be described in further detail with reference to  FIG. 4  and  FIG. 5 . 
         [0058]      FIG. 4  is a flowchart of a method for estimating a disk temperature according to an exemplary embodiment of the present invention, and  FIG. 5  is a schematic diagram for explaining a method for estimating a disk temperature according to an exemplary embodiment of the present invention. 
         [0059]    As shown in  FIG. 5 , a temperature change (sumT) of the disk for a predetermined time (n*Δt) is calculated so as to estimate the disk temperature T, and the predetermined time is divided into n unit times (Δt). According to an exemplary embodiment of the present invention, a temperature rise ΔT of the disk for the unit time is calculated, the temperature change (sumT) of the disk is calculated by adding the temperature rises ΔT of the disk, and the disk temperature T is calculated by adding the temperature change (sumT) of the disk to a previous disk temperature T P . 
         [0060]    In addition, work for unit time (Δt) done by braking force is calculated so as to calculate the disk temperature rise ΔT. 
         [0061]    As shown in  FIG. 4 , the controller  40  substitutes 1 into i and substitutes 0 into the temperature change (sumT) of the disk before performing estimation of the disk temperature at step S 300 . Herein, i means step number. 
         [0062]    After that, the controller  40  calculates work (ΔE i ) done by the braking force from (i−1) step to i step at step S 310 . The work (ΔE i ) done by the braking force from (i−1) step to i step is calculated from the following equation. 
         [0000]    
       
         
           
             
               Δ 
                
               
                   
               
                
               
                 E 
                 i 
               
             
             = 
             
               
                 
                   - 
                   
                     B 
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                 · 
                 
                   W 
                   
                     2 
                      
                     g 
                   
                 
               
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                   ( 
                   
                     
                       a 
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                     + 
                     
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                     ( 
                     
                       
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         [0063]    Herein, B i  represents the signal of the brake pedal position sensor  30 , W represents a load of the vehicle, g represents acceleration of gravity, a i  represents acceleration at i step, and V i  represents the vehicle speed at i step. As described above, B, may be 0 or 1. 
         [0064]    After the work (ΔE i ) done by the braking force from (i−1) step to i step is calculated, the controller  40  calculates work (ΔE i,Front/2 ) distributed to one disk  2  of front wheels at step S 320 . The work (ΔE i,Front/2 ) distributed to the one disk  2  of the front wheels is calculated from the following equation. 
         [0000]    
       
         
           
             
               
                 
                   
                     Δ 
                      
                     
                         
                     
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                       E 
                       
                         i 
                         , 
                         
                           Front 
                           / 
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                   = 
                   
                     
                       ( 
                       
                         R 
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                             H 
                             L 
                           
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         [0065]    Herein, L represents a wheel base (please see  FIG. 1 ), H represents a height of mass center of the vehicle (please see  FIG. 1 ), and R represents static load distribution ratio. 
         [0066]    The work distributed to the one disk  2  of the front wheels is calculated in an exemplary embodiment of the present invention, but the present invention is not limited to this. That is, work distributed to one disk of rear wheels or the work distributed to the one disk  2  of the front wheels and the work distributed to the one disk of the rear wheels can be calculated. 
         [0067]    The controller  40  converts the work (ΔE i,Front/2 ) distributed to the one disk  2  of the front wheels into heat (Q i,Front/2 ) at step S 330 . The work (ΔE i,Front/2 ) distributed to the one disk  2  of the front wheels is converted into the heat through the following equation. 
         [0000]    
       
      
       Q 
       i,Front/2 
       =A·ΔE 
       i,Front/2  
      
     
         [0068]    Herein, A represents thermal equivalent of work. 
         [0069]    After that, the controller  40  calculates a temperature rise (ΔTi) of the one disk  2  of the front wheels at step S 340 . The temperature rise (ΔTi) of the one disk  2  of the front wheels is calculated from the following equation. 
         [0000]    
       
         
           
             
               Δ 
                
               
                   
               
                
               
                 T 
                 i 
               
             
             = 
             
               
                 Q 
                 
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                   , 
                   
                     Front 
                     / 
                     2 
                   
                 
               
               
                 ρ 
                  
                 
                     
                 
                  
                 cv 
               
             
           
         
       
     
         [0070]    Herein, ρ represents a density of the disk, c represents a specific heat of the disk, and v represents a volume of a friction surface of the disk. 
         [0071]    After that, the controller  40  calculates the temperature change (sumT) of the disk to i step by adding the temperature rise (ΔTi) of the one disk  2  of the front wheels to the temperature change (sumT) of the disk to (i−1) step at step S 350 . 
         [0072]    After that, the controller  40  determines whether i equals to n at step S 360 . Herein, n is number of unit times and is integer larger than or equal to 1. 
         [0073]    If i is smaller than n, the controller  40  adds 1 to I and returns to the step S 310 . 
         [0074]    If i equals to n, the controller  40  calculates the disk temperature T by adding the temperature change (sumT) of the disk to the previous disk temperature T P  at step S 370 . Herein, the previous disk temperature T P  may be the disk temperature calculated previously or a room temperature. If the brake is not operated for a long time, the previous disk temperature is the room temperature. If the brake, on the contrary, is operated frequently, the disk temperature may be calculated when the brake operates and may be used as the disk temperature calculated previously. In this case, cooling effect of the disk for a time when the brake is not operated may be taken into consideration. 
         [0075]    If the disk temperature is estimated at the step S 130 , the controller  40  determines whether the estimated disk temperature is lower than or equal to a first predetermined temperature at step S 140 . Herein, the first predetermined temperature may be a temperature within a range of 50° C.-300° C. 
         [0076]    If the disk temperature is higher than the first predetermined temperature, the controller  40  prohibits engine stop according to idle stop at step S 200 . That is, because it is possible that braking noise can occur due to high disk temperature, the controller  40  prevents the ISG system  50  from entering an engine stop mode. 
         [0077]    In addition, the controller  40  determines whether the estimated disk temperature is lower than or equal to a second predetermined temperature at step S 210 . Herein, the second predetermined temperature may be equal to the first predetermined temperature or not. The second predetermined temperature is used for preventing that the ISG system  50  cannot enter the engine stop mode due to a wrongly estimated disk temperature. 
         [0078]    If the estimated disk temperature is lower than or equal to the second predetermined temperature at the step S 210 , the controller  40  returns to the step S 110 . 
         [0079]    If the estimated disk temperature is higher than the second predetermined temperature at the step S 210 , the controller  40  continuously prohibits the engine stop according to the idle stop at the step S 200 . 
         [0080]    Meanwhile, if the estimated disk temperature is lower than or equal to the first predetermined temperature at the step S 140 , the controller  40  executes the engine stop according to the idle stop at step S 150 . That is, the controller  40  controls the ISG system  50  to enter an engine stop mode. 
         [0081]    In a state that the engine is stopped, the controller  40  determines whether an engine restart condition is satisfied at step S 160 . The engine restart condition may be satisfied if the brake pedal does not operate or shift range is changed. The engine restart condition is not limited to the above-described conditions and can include any suitable conditions. 
         [0082]    If the engine restart condition is not satisfied, the controller  40  returns to the step S 150 . 
         [0083]    If the engine restart condition is satisfied, the controller  40  restarts the engine  70 . That is, the controller  40  controls the ISG system  50  to restart the engine  70 . 
         [0084]    When the engine  70  is restarted, the controller  40  determines whether an operation of the electric brake system  60  is needed. The operation of the electric brake system  60  is determined to be needed if a predetermined time has not passed since the engine  70  was restarted. The predetermined time may be, but is not limited to, 1 second. 
         [0085]    If it is determined at the step S 180  that the operation of the electric brake system  60  is needed, the controller  40  operates the electric brake system  60 . That is, the electric brake system  60  is controlled to generate hydraulic pressure for braking. 
         [0086]    If it is determined at the step S 180  that the operation of the electric brake system  60  is not needed (i.e., it is determined that the predetermined time has passed since the engine  70  was restarted), the controller  40  stops the electric brake system  60 . That is, the hydraulic pressure generated by the electric brake system  60  is released. 
         [0087]    As described above, because the engine stop according to the idle stop is prohibited if the disk temperature is higher than or equal to a predetermined temperature according to an exemplary embodiment of the present invention, occurrence of braking noise may be prevented. 
         [0088]    For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
         [0089]    The foregoing descriptions of specific 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 in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.