Idle stop and go system and method for controlling thereof

An ISG system prevents fuel consumption due to unnecessary idling, by controlling the start of an engine, in accordance with engine stop conditions and restart conditions of a vehicle equipped with an automatic transmission. A method includes determining whether prior conditions for engine stop in an engine controller when an engine is in operation is satisfied, determining whether the engine can be stopped, when the prior conditions for engine stop are satisfied, determining whether engine stop conditions is satisfied, when the engine can be stopped, stopping the engine that is in operation, when the engine stop conditions are satisfied, determining whether key start conditions are satisfied, when the engine is stopped, determining whether restart is possible, when the key start conditions are not satisfied, determining whether conditions for restart are satisfied, when restart is possible, and restarting the engine, when the restart conditions are satisfied.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Korean Patent Application Number 10-2010-0123862 filed Dec. 6, 2010, the entire contents of which application is incorporated herein for all purposes by this reference.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to an ISG system and a method of controlling the ISG system, and more particularly, to an ISG system that can prevent fuel consumption due to unnecessary idling by controlling start of an engine in accordance with engine stop conditions and restart conditions of a vehicle equipped with an automatic transmission, and a method of controlling the ISG system.

2. Description of Related Art

Recently, various efforts are made to reduce greenhouse gases from vehicles, and as a part of that, various methods are considered to improve fuel efficiency. ISG (Idle Stop and Go) systems are increasingly applied all over the world to improve fuel efficiency. The ISG system prevents fuel consumption by stopping an engine in idling, on the basis of information on vehicle speed, the revolution speed of an engine, and the temperature of cooling water etc.

In other words, the ISG system automatically stops the engine idling, when a vehicle stops due to waiting for the traffic light etc., and after a predetermined time, it restarts the engine in accordance with the requirements of a driver controlling the acceleration and brake pedals. The ISG system can achieve fuel effect of about 5˜15% in the actual fuel efficiency mode.

SUMMARY OF INVENTION

Various aspects of the present invention provide for an ISG system and a method of controlling the ISG system, which can prevent fuel consumption due to unnecessary idling, by controlling the start of an engine, in accordance with engine stop conditions and restart conditions of a vehicle equipped with an automatic transmission.

Further, various aspects of the present invention have been made in an effort to provide an ISG system and a method of controlling the ISG system that can improve the operability even right after the engine is restarted, by keeping the hydraulic pressure of the automatic transmission with a sub-pump when the engine is stopped by ISG system such that sense of difference in restarting the engine is not generated, in accordance with the engine restart conditions

Furthermore, various aspects of the present invention have been made in an effort to provide an ISG system and a method of controlling the ISG system that can implement power steering by keeping a motor-driven steering controller operable, when the engine is stopped by the ISG system.

Various aspects of the present invention provide for an ISG system including an engine controller that stops an engine and transmits ISG stop signals to controllers when engine stop conditions for ISG are satisfied, and restart the engine and transmits ISG restart signals to the controllers when engine restart conditions are satisfied, a motor-driven steering controller that allows for power steering even with the engine stopped, by keeping operation of a steering motor, when receiving the ISG stop signal from the engine controller, an automatic transmission controller that controls operation of an oil sub-pump of an automatic transmission to keep hydraulic pressure of the automatic transmission and transmits a shift range of the automatic transmission to the engine controller, when receiving the ISG stop signal from the engine controller, a brake controller that transmits operation of a brake pedal, brake boosting pressure, and vehicle traveling inclination angle to the engine controller, a cluster that shows the ISG operational status transmitted from the engine controller, and transmits signals for whether a hood is open, whether doors of the vehicle are open, and whether seat belts are not fastened to the engine controller, and a battery management system that transmits the charged status of a battery to the engine controller, in which the engine controller controls the operation of the engine in accordance with whether the engine stop conditions and the engine restart conditions are satisfied, in response to the signals from the automatic transmission controller, the brake controller, the cluster, the battery management system, and sensors in the vehicle.

Another exemplary embodiment of the present invention provides a method of controlling an ISG system, the method including determining whether prior conditions for engine stop in an engine controller when an engine is in operation are satisfied, determining whether the engine can be stopped, when the prior conditions for engine stop are satisfied, determining whether engine stop conditions are satisfied, when the engine can be stopped, stopping the engine that is in operation, when the engine stop conditions are satisfied, determining whether key start conditions are satisfied, when the engine is stopped, determining whether restart is possible, when the key start conditions are not satisfied, determining whether conditions for restart are satisfied, when restart is possible, and restarting the engine, when the restart conditions are satisfied.

According to various aspects of the present invention, it is possible to prevent fuel consumption due to unnecessary idling, by controlling the start of an engine, in accordance with engine stop conditions and restart conditions of a vehicle equipped with an automatic transmission.

Further, according to various aspects of the present invention, it is possible to improve the operability even right after the engine is restarted, by keeping the hydraulic pressure of the automatic transmission with a sub-pump when the engine is stopped by ISG system such that sense of difference in restarting the engine is not generated, in accordance with the engine restart conditions.

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, an ISG system includes an engine controller10that controls an ISG of an engine in response to a signal for the operational status of a vehicle, an sensor unit20that transmits signals for the operational status of the vehicle measured by sensors to engine controller10, and controllers30that transmit signals for the operational status of the parts in the vehicle to engine controller10and receive signals for the operational status of the engine transmitted from engine controller10. Further, engine controller10can transmit/receive signals from driving parts40.

Further, a motor-driven steering controller34is controlled to be able to implement power steering even if the engine stops, by keep a steering motor operating, even if it receives an ISG stop signal transmitted from engine controller10. Further, automatic transmission controller33can improve operability in engine restart by keeping the hydraulic pressure of an automatic transmission even while the engine stops by ISG, by operating an oil sub-pump of the automatic transmission, even if it receives an ISG stop signal transmitted from engine controller10. Further, a cluster35can inform a driver that the engine is started or stopped by ISG. Further, cluster35can show whether the engine can be started, engine stop conditions, restart conditions, and whether the engine can be restarted.

Engine controller10checks whether ISG activation conditions are satisfied, on the basis of the signal received by an ISG switch21(S1). Engine controller10determines that the ISG activation condition when the engine operates is satisfied, when ISG switch21is kept on and the ISG system normally operates, with the engine in operation. Further, engine controller10determines that the ISG activation condition when the engine stops is satisfied, when ISG switch21is kept on with the engine stopped.

Further, when the ISG activation conditions are satisfied, engine controller10checks whether prior conditions for engine stop are satisfied, on the basis of the signals transmitted from sensor unit20and controllers30, when engine is in operation (S2). The prior conditions for engine stop and factors for receiving signals for the conditions are those in Table 1.

TABLE 1Prior conditions for Engine Stop1.Key switch 22, Cooling water temperature sensor 25: Temperatureof cooling water above a predetermined level, after engine isstarted by key-on2.Automatic transmission controller 33; Transmission oil temperaturewithin a predetermined range3.Engine RPM sensor 24; Engine RPM under a predetermined RPM4.Vehicle speed sensor 23: Maximum traveling vehicle speed abovea predetermined vehicle speed after engine restarted5.Acceleration pedal sensor 26; acceleration pedal off6.Vehicle speed sensor 23; Vehicle speed 0 Kph7.Engine controller 10; Predetermined time passed after vehicleis restarted

Engine controller10determines that the prior conditions for engine stop are satisfied, when the prior conditions for engine stop are all satisfied, within a predetermined time. Although the predetermined time may be set to about 1 to 5 seconds, it is not limited in the present invention.

The predetermined temperature for the cooling water temperature may be set to 65 degrees C. The predetermined temperature for the temperature range of the transmission oil may be set to 35 to 120 degrees C. The predetermined RPM for the engine RPM may be set to 1200 rpm. The predetermined vehicle speed for the maximum traveling speed may be set to 8 km/h. The predetermined time when a predetermined time passed after restart may be set to 5 seconds. The reference values may be changed in accordance with the status of a vehicle.

Engine controller10checks whether the engine can be stopped, on the basis of the signals transmitted from sensor unit20, controllers30, and driving parts40, when the prior conditions for engine step are satisfied (S3). Engine controller10determines that the engine cannot be stopped, when the current status is not included in engine stop prohibition conditions described in Table 2, and prohibits engine stop, when at least one of the engine stop prohibition conditions is satisfied.

TABLE 2Engine Stop Prohibition Condition1.Cluster 35: At least on of hood, driver's door, and seat belt open2.Battery management system 36: Vehicle battery unsatisfactorilycharged3.Air conditioning system 32: Prohibition of engine stop asked4.OBD2 diagnosis system 42: Prohibition of engine stop asked5.Motor-driven steering controller 34: Steering angle above apredetermined angle6.Fully automatic parking system 43: Fully automatic parking systemactivated7.Brake controller 31: Within predetermined time after brake system(ABS, TCS, ESC, DBC) activated8.Transmission controller 33: Within predetermined time after gear isshifted to R-stage9.Brake controller 31: Malfunction of hill-start assist control (HAC)10.Shift controller 33: Shift controller conditions not satisfied11.Brake controller 31: Brake boosting pressure under reference level12.Vehicle speed sensor 23; Vehicle speed rapidly decreased (rate ofchange of vehicle speed or rate of change of brake hydraulic pressureabove predetermined level)13.Inclination angle sensor 28; Uphill/downhill inclination angle abovepredetermined level in traveling14.Atmospheric pressure sensor 27; Atmospheric pressure less than pre-determined level15.Starter motor 41; Number of operational times of starter motor abovepredetermined level16.Engine controller 10; Problem in ISG-relating parts

Engine controller10prohibits the engine from stopping, even if the engine can be stopped by ISG until the engine stop prohibition conditions are solved if the engine stop prohibition conditions are satisfied.

The battery charged state for determining that the battery is unsatisfactorily charged may be set to 79%. Further, the predetermined angle that is the reference for determining whether the steering angle is excessive may be set to +/−180. The predetermined time after the brake system is activated may be set to 10 seconds. The predetermined time after the gear is shifted to the R-stage may be set to 1 second. The shift controller determines that the conditions are unsatisfactory, when any one of CAN communication error of the shift controller, malfunction of shift controller33, and a problem in a transmission sub-pump controller. The reference level of the brake boosting pressure may be set to −35 kPa. It is determined that the vehicle speed rapidly decreases, when it is −10 m/s2. The predetermined level of the uphill and downhill inclination angle in traveling may be set to −/+12%, respectively. The predetermined level of the atmospheric pressure may be set to 800 kPa. The predetermined level of the number or operational times of the start motor may be set to 350,000 times. The reference values may be changed in accordance with the status of a vehicle.

Engine controller10determines that the engine can be stopped and checks whether the engine stop conditions are satisfied, on the basis of the signals from controllers30, when all the engine stop prohibition conditions are not satisfied (S4). Examples of engine stop conditions and factors for transmitting signals for the conditions are those in Table 3.

TABLE 3Engine Stop Condition1.Automatic transmission controller 33, brake controller 31; Shift gearat D-state, brake pedal on, and brake hydraulic pressure above a pre-determined level2.Automatic transmission controller 33, brake controller 31; shift gearswitched from D-range to N-range and brake pedal on

Engine controller10determines that the engine stop conditions are satisfied, when at least one of the engine stop conditions is satisfied and a predetermined time has passed. Further, the predetermined lever for determining whether the brake hydraulic pressure is above a predetermined level may be set to 8 bar, but it can be changed in accordance with the status of a vehicle.

Engine controller10stops the engine, when the engine stop conditions are satisfied (S5). Further, when engine controller10checks whether the engine cannot be restarted by ISG and a key start condition where restart is possible in key-on is satisfied, before determining whether the engine can be restarted by ISG, when the engine stops (S6). That is, engine controller10checks whether the key start condition is satisfied, on the basis of the signals from controllers30(S6). Examples of key start conditions and factors for transmitting signals for the conditions are those in Table 4.

TABLE 4Key Start Condition1.Engine controller 10; Number of times of abnormal engine startabove predetermined number of times2.Cluster 35; Hood open with engine stopped3.Brake controller 31; Brake off and safety condition removed, withengine stopped4.Engine controller 10; Problem in ISG-relating parts, with enginestopped

Although the predetermined number of times may be set to one time when the engine fails to be started within two seconds, it is not limited in the present invention.

Engine controller10determines that engine restart is impossible by ISG and restart in key-on is possible, when at least one of the key start conditions is satisfied, and restarts the engine when the key is at ON (S9).

Further, engine controller10checks whether engine can be restarted by ISG, when all of the key start conditions are not satisfied (S7). Engine controller10determines that the engine cannot be restarted for safety, when a predetermined time has passed and the acceleration pedal is ON after the engine stopped. Engine controller10determines that the engine can be restarted, if the engine restarts is not impossible.

Engine controller10checks whether the condition for restart is satisfied, when determining that the engine can be restarted (S8). Engine controller10determines that the conditions for engine restart are satisfied, when at least one of an automatic restart condition, a forcible restart condition, and an ISG inactivation condition is satisfied.

First, examples of automatic restart conditions where restart is implemented by operating the shift gear and the brake pedal by the driver are as those in Table 5. A signal for the shift gear is transmitted from automatic transmission controller33to engine controller10and a signal for brake pedal and hydraulic pressure is transmitted from brake controller31to engine controller10.

TABLE 5Automatic Restart Condition1.Brake hydraulic pressure under predetermined level at D-range2.Predetermined time passed after switching gear to R-stage3.Brake off right after switching gear to R-stage4.Brake on when vehicle stops, from N-stage to P-stage5.Gear shifted to manual range

The predetermined level of the brake hydraulic pressure may be set to a value that is 20% less than the maximum hydraulic pressure. Further, the predetermined time after shifting may be set to 1 second. The reference values may be changed in accordance with the status of a vehicle.

Engine controller10restart the engine when determining that at least one of the automatic restart conditions is satisfied (S9). Examples of forcible restart conditions for forcibly restarting the engine are as those in Table 6.

TABLE 6Forcible Restart Condition1.Brake controller 31; Brake boosting pressure decreased in stoppingengine2.Vehicle speed sensor 23; Vehicle speed generated in stopping engine3.Battery management system 36; Batter requiring to be charged4.Air-conditioning controller 32; Order for operating air-conditioningsystem generated5.Inclination angle sensor 28; Inclination angle above predeterminedrange in stopping engine6.Brake controller 31; Safety condition removed in stopping engine,with brake on

The brake boosting pressure reduced in stopping the engine may be set to 35 kPa. The predetermined range of inclination angle may be set to −16% to +16%. The reference values may be changed in accordance with the status of a vehicle.

Engine controller10restart the engine when determining that at least one of the forcible restart conditions is satisfied (S9).

Further, engine controller10determines that the ISG inactivation conditions are satisfied, when at least one of that the ISG switch is turned off when the engine is in operation, that the ISG system breaks when the engine is in operation, and that the ISG switch is turned off when the engine is stopped is satisfied. Further, engine controller10inactivates the ISG of the engine and restarts the engine, when determining that the ISG inactivation conditions are satisfied (S9).

According to the ISG system and a method of controlling the ISG system, it is possible to prevent fuel consumption due to unnecessary idling, by stopping the engine under predetermined situations, such as stopping the vehicle and waiting the traffic lights, in accordance with the engine stop conditions of the vehicle equipped with an automatic transmission. Further, according to the ISG system and the method of controlling the ISG system, it is possible to keep the operability even right after the engine is restarted, by keeping the hydraulic pressure of the automatic transmission and keeping the steering system operable when the engine is stopped by ISG such that sense of difference in restarting the engine is not generated, in accordance with the engine restart conditions.