KR20100011038A - Method for diagnosing leakage of fuel system on hybrid electric vehicle - Google Patents

Abstract

According to the present invention, in the fuel system in a hybrid vehicle, an engine stop according to idle stop and high control for fuel efficiency improvement of the hybrid vehicle is required, and a negative pressure method for diagnosing the leakage of the fuel system through the existing intake negative pressure. In order to satisfy all the points required for the operation of the engine, the vehicle driving information is determined in detail, and thus, a fuel system capable of diagnosing the leak of the fuel system using the conventional negative pressure method without adding any additional hardware. The aim is to implement a leak diagnosis method.

Accordingly, in the present invention, according to the leak diagnosis condition of the hybrid vehicle, vehicle driving information including whether the accelerator pedal is operated, whether the brake pedal is operated, the current vehicle speed, and the slope of the vehicle speed is read, and the accelerator pedal is released. It is determined whether the brake pedal satisfies the vehicle deceleration condition that is set as the operating condition, and the engine clutch is opened to maintain the engine idle state to maintain the predetermined engine revolutions per minute and the engine negative pressure. A fuel system leak diagnosis method in a hybrid vehicle performing leak diagnosis is provided.

Description

Method for diagnosing leakage of fuel system on Hybrid Electric vehicle

The present invention relates to a method for diagnosing the leakage of a fuel system in a hybrid vehicle, and more particularly, to a conventional gasoline vehicle during vehicle driving in a fuel system of a hybrid vehicle having an engine clutch capable of controlling on / off power of an engine between a transmission and an engine. The present invention relates to a fuel system leak diagnosis method of a hybrid vehicle capable of diagnosing the leak of a fuel system using a negative pressure method similar to the leak diagnosis method of the present invention.

Recently, as environmental pollution accelerates, society's interest in environmentally friendly products is increasing. In the United States and Europe, environmental regulations are being strengthened in proportion to this interest.

Especially in the automobile sector, automobile exhaust gas, which accounts for a large portion of such environmental pollution, is a serious problem, and countries are pressing automakers with various tightening regulations. As a result, the OBD-II regulations restricting the occurrence of pollution problems caused by automobile emissions, which are the main causes of air pollution, are being tightened. In addition to driving performance and safety of vehicles, performance to satisfy environmental regulations is required.

In addition to the combustion gas discharged through the muffler, the exhaust gas of the automobile includes unburned gas emitted from the crankcase and the evaporated gas generated from the fuel system from the fuel tank to the engine as the fuel in the fuel tank evaporates as the external temperature increases. do.

The boil-off gas in the fuel tank is composed of hydrocarbons, which acts as a substance that causes air pollution, such as destroying the ozone layer discharged to the atmosphere.In automobiles, the boil-off gas is collected and stored in the canister. When the engine is started and the coolant temperature and the engine speed reach a certain level, the evaporated gas stored in the canister is introduced into the surge tank to be combusted.

1 and 2 specifically describe a leak diagnosis method of a fuel system of a conventional gasoline vehicle.

As shown in FIG. 1, a leak diagnosis apparatus applied to a conventional general vehicle includes a canister (Canister) 2 which collects and stores evaporated gas evaporated from the fuel tank 1, and is collected by the canister 2. CPSV (Canister Purge Solenoid Valve: 4), which opens and closes the passage so that the boil-off gas flows into the engine side, CSV (Canister Shut-off Valve: 5), which opens and closes the air passage so that external air flows into the canister (2); In addition, the pressure sensor 6 for detecting the pressure in the fuel tank 1 and the boil-off gas collected in the canister 2 are controlled to enter the engine according to the condition of the vehicle, and the fuel tank 1 And an ECU 3 for performing a leak diagnosis of the fuel system from the pressure gradient of the power supply.

In the conventional general vehicle having the above-described configuration, the leak diagnosis for the fuel system is performed as shown in FIG. 2. When the condition of the engine satisfies the leak diagnosis condition, the ECU 3 generates the CPSV 4 and the CSV 5. To stabilize the fuel system and then close the CPSV (4) and CSV (5) for a set T2 time to collect the boil-off gas in the canister (2).

Then, when the time T2 has elapsed, the CPSV 4 is opened for a set T3 time while maintaining the closing of the CSV 5, and the evaporated gas collected in the canister 2 is introduced into the engine using negative pressure to supply the fuel system. All the lines of are formed under atmospheric pressure.

As described above, when the set T3 for flowing the boil-off gas collected in the canister 2 into the engine to form a line of the fuel system below atmospheric pressure has elapsed, the set T4 time after closing the CPSV 4 which is kept open. The leakage of the fuel system is diagnosed by analyzing the inclination of the pressure which enters below atmospheric pressure from the pressure sensor 6 provided in the fuel tank 1.

In the above diagnosis, when the pressure of the fuel tank 1 is detected below the reference pressure as shown in "A" of FIG. 2 at the time of collecting the boil-off gas, it is diagnosed as a failure by the opening error of the CSV (5).

On the contrary, the diagnosis is stopped when the pressure in the fuel tank 1 exceeds the reference pressure, such as "B".

In addition, when the pressure of the fuel tank 1 analyzed for the time T4 is maintained at an atmospheric pressure state such as "C" from the time when the CSV 5 is opened, it is diagnosed that the fuel injection cap is not closed.

In addition, if the state is much higher than the normal pressure, such as "D" of the pressure of the fuel tank 1 analyzed during the T4 time, it is diagnosed that a large leak in the fuel system.

As described above, in order to diagnose a fuel system leak in an existing gasoline vehicle, the engine is always operated so that a negative pressure of the intake system exists.In the engine operating state, a leak diagnosis condition of the fuel system (leak diagnosis activation condition of the fuel system) Leakage, coolant temperature, outside air temperature, vehicle speed condition, post-start time, etc.).

However, in a hybrid vehicle having a power source consisting of an engine and a motor, the idle stop and go control of the engine is performed according to the state of charge (SOC) state of the battery, which causes frequent stops of the engine. Therefore, no negative pressure is generated in the engine intake system. Therefore, when the engine is stopped in the process of performing the leak diagnosis of the fuel system during the operation of the hybrid vehicle, there is a problem that the leak diagnosis of the fuel system is not performed because the intake negative pressure does not occur.

As a result, Toyota's RX400H model is forced to use a separate negative-pressure pump with Overnight Socking for overnight parking in Toyota's RX400H model. After generating a negative pressure, the leak of the fuel system is diagnosed in the same way as in a conventional gasoline vehicle.

In the case of Toyota's PRIUS model, the capacity of the fuel tank itself is varied according to the amount of fuel injected using a specially manufactured bladder type fuel tank, which greatly reduces the amount of evaporated gas in the fuel tank. In the driving condition, the leak of the fuel system is diagnosed in the same way as in the conventional gasoline vehicle.

Alternatively, natural vacuum leak detection (NVLD) is used to diagnose leaks in the fuel system using natural vacuum in the fuel tank when the engine is sufficiently cooled by overnight parking of the vehicle.

As described above, in order to diagnose the leakage of the fuel system in a hybrid electric vehicle, a separate equipment must be installed, and a separate controller and power are required to monitor the leakage of the fuel system. As compared with the above, a problem occurs that adversely affects the performance of the secondary battery of the vehicle.

In addition, when the fuel tank is specially manufactured, the resin type fuel tank configuration and the fuel system line configuration are more complicated than the conventional methods, and thus there is a cost increase, and the leak diagnosis logic is performed when the vehicle runs at a certain speed. In addition, logic for maintaining a constant negative pressure is added, which causes a problem of degrading the power performance of the vehicle.

In the present invention, in the fuel system of the hybrid vehicle, the engine stop according to the idle stop and go control for the fuel efficiency improvement of the hybrid vehicle is required, the negative pressure for diagnosing the leak of the fuel system through the existing intake negative pressure For the method, the vehicle driving information is specified in detail so that the operation of the engine can be satisfied, and when it is determined that the vehicle is decelerated according to the vehicle driving conditions, the engine is operated and the engine is in the idle state. Accordingly, an object of the present invention is to implement a leak diagnosis method of a fuel system in a hybrid vehicle capable of diagnosing the leak of a fuel system using an existing negative pressure method without adding additional hardware.

In order to achieve the above object, the present invention provides the following configuration.

The present invention provides a method of determining whether information detected while driving a hybrid vehicle satisfies a leak diagnosis condition, and when the leak diagnosis condition is satisfied, determining whether the vehicle deceleration condition is satisfied by reading vehicle driving information. And, if the vehicle deceleration condition is satisfied, opening an engine clutch and maintaining an idle state of the engine; and if a predetermined engine revolutions per minute and a predetermined engine negative pressure are generated as the idle state of the engine is maintained, A method of diagnosing a leak of a fuel system in a hybrid vehicle, the method comprising performing a leak diagnosis of a fuel system in a negative pressure manner while maintaining the predetermined engine revolutions per minute and an engine underpressure.

In addition, the vehicle driving information to be read provides a fuel system leak diagnosis method for a hybrid vehicle, characterized in that it includes whether the accelerator pedal is operated, whether the brake pedal is operated, the current vehicle speed, and the slope of the vehicle speed.

The vehicle deceleration condition is a fuel system leak diagnosis method for a hybrid vehicle, characterized in that the accelerator pedal is released, the brake pedal is set to the operating condition.

Here, when the leak diagnosis of the fuel system is completed through the above-described process, the method further includes returning to the normal driving state of the hybrid vehicle and driving the engine according to the normal driving condition. Provides a system leak diagnosis method.

As described above, the fuel system leak diagnosis method in the hybrid vehicle according to the present invention enables the fuel system leak diagnosis logic used in the existing gasoline vehicle to be used, and thus the fuel system leak diagnosis method of the fuel system leak in the existing hybrid vehicle fuel system. In this case, the performance of the secondary battery may be degraded due to the change of the engine operating condition or the performance of the secondary battery caused by the large power consumption to perform the leak diagnosis when the engine is sufficiently cooled due to the overnight parking of the vehicle. It can be improved.

In addition, by providing a fuel system leak diagnosis method that ensures the reliability of the diagnosis without adding additional hardware, there is an effect of reducing the manufacturing cost.

In the present invention for achieving the above object, in a fuel system of a hybrid vehicle including an engine clutch capable of controlling the power of the engine on and off between the transmission and the engine, it is determined according to the detailed vehicle driving information while driving the vehicle By maintaining the engine in the idle state (idle) to maintain the negative pressure of the engine, it provides a fuel system leak diagnostic method in a hybrid vehicle applying the negative pressure fuel system leak diagnosis method used in the conventional gasoline vehicle.

Hereinafter, a detailed configuration of the present invention will be described in detail with reference to the accompanying drawings.

3 is a system configuration diagram of a hybrid vehicle having an engine clutch.

As shown in FIG. 3, the hybrid vehicle applied to the present invention has an engine clutch between the motor and the engine, and operates in an electric vehicle (EV) mode driven by the motor when the engine clutch is open. In the closed state, the engine is operated in a hybrid electric vehicle (HEV) mode in which driving by both a motor and an engine is possible, and the starting of the engine is controlled by an integrated starter generator (ISG).

As described above, the hybrid vehicle determines a battery state of charge (SOC) state in order to improve fuel economy, and performs idle stop and go control of an engine according to the battery SOC state. Frequent shutdowns of the engine occur.

However, the leak diagnosis method of the fuel system of a gasoline vehicle using the conventional negative pressure method satisfies the leak diagnosis conditions such as highland temperature, coolant temperature, outside temperature, vehicle speed condition, and post-starting time, regardless of the vehicle driving conditions. A leak diagnosis method for enabling a leak diagnosis according to a negative pressure generation, in which an engine operation is required to generate a negative pressure.

Accordingly, the present invention does not operate the engine while the vehicle is in a stopped state, thereby obtaining fuel efficiency improvement effect due to the engine stop, and at the time of operating the engine during deceleration driving of the vehicle through detailed vehicle driving conditions related to the driver's deceleration intention. In this way, it is possible to provide diagnostic logic for generating negative pressure of the engine and performing leak diagnosis.

The leak diagnosis method of the fuel system in such a hybrid vehicle will be described in detail as follows.

4 is a flowchart showing the control flow of the fuel system leak diagnosis method in the hybrid vehicle of the present invention.

As shown in FIG. 4, first, an engine of an engine management system (EMS) is used to perform a leak diagnosis of a fuel system while driving in accordance with a Federal Test Procedure (FTP) of a hybrid vehicle. The Engine Control Unit (ECU) sends an enable bit to the Hybrid Control Unot (HCU) when leak diagnostic conditions such as high ground, coolant temperature, ambient temperature, vehicle speed conditions and post-start time are activated. do. If the leak diagnosis condition of the fuel system is not activated, the leak diagnosis of the fuel system is terminated. (See step 10)

When the leak diagnosis condition is activated and an activation bit corresponding thereto is transmitted to the hybrid controller, the hybrid controller may monitor vehicle driving information to generate a constant negative pressure in the engine with reference to the activation bit. In this case, the vehicle driving information includes whether the accelerator pedal is operated, whether the brake pedal is operated, the current vehicle speed, and the inclination of the vehicle speed. This is to determine the driver's intention to decelerate by driving. (See step 20)

Next, the vehicle deceleration condition is determined based on the vehicle driving information monitored by the hybrid controller in the above step, and the regenerative braking is determined, and the engine is operated to maintain the idle state of the engine. In this case, the vehicle deceleration condition for which the leak diagnosis is performed may be set as a condition regarding whether the accelerator pedal is released and the brake pedal is operated. The driver releases the accelerator pedal and presses the brake pedal according to the vehicle deceleration condition. Determining that the vehicle is in regenerative braking according to whether the brake is activated (see step 30), performing regenerative braking with the motor by opening the engine clutch, and operating the engine through the integrated starting generator to maintain the engine in the idle state. Proceed. (See step 40)

At this time, when the engine is in operation and the engine RPM is present, the hybrid controller directly controls the engine to maintain the idle state. In this case, the leak diagnosis of the fuel system is terminated when the determined vehicle driving condition does not correspond to the above condition.

If the idle state of the engine is maintained according to the above steps, the engine controller monitors the engine rpm and the engine negative pressure, and when the engine rpm and the engine negative pressure suitable for the leakage diagnosis of the fuel system are generated, the engine system leaks. Since the conditions for diagnosis are satisfied, the leak diagnosis of the fuel system is performed using the same negative pressure method as in the conventional gasoline vehicle. When the leak diagnosis of the fuel system is performed, the engine controller transmits the leak diagnosis bit to the hybrid controller through a predetermined leak diagnosis bit. (See step 50)

According to the above process, the hybrid controller receiving the leak diagnosis bit from the engine controller maintains the engine at the predetermined revolutions per minute and negative pressure required to perform the leak diagnosis through the leak diagnosis bit of the received fuel system. Continue leak diagnosis of the system. (See step 60)

Next, when the leak diagnosis of the fuel system is completed, the engine controller resets the leak diagnosis bit, and drives the engine according to the driving conditions of the normal hybrid vehicle through the hybrid controller to diagnose the fuel system leak of all processes. To exit. (See step 70, step 80)

In FIG. 5, a general leak diagnosis time is shown in a negative pressure leak diagnosis in a gasoline vehicle, and accordingly, comparison with a leak diagnosis time in a fuel system leak diagnosis method in a hybrid vehicle of the present invention is possible.

The most important thing in the diagnosis of the conventional negative pressure fuel system leak is the condition of activation of the leak diagnosis of the fuel system (alert, coolant temperature, ambient temperature, vehicle speed condition, post-start time, etc.) while maintaining the engine revolutions per minute and the negative pressure. The engine idle state must be maintained for more than a predetermined time. Leak diagnosis of the fuel system is possible only when these conditions are satisfied.

Thus, as shown in FIG. 5, in the section between the 12th hill and the 13th hill where the idle state of the vehicle engine is the longest during driving according to the Federal Test Procedure (FTP) of the gasoline vehicle, that is, the engine Leak diagnosis of the fuel system is possible in the "E" section, in which the idle state is maintained for 30 seconds or more.

However, in a hybrid vehicle with an engine clutch, when performing the leak diagnosis method of the fuel system according to the present invention, the engine clutch can be opened from the deceleration (brake operation) of the driver, and the engine can be idled, thereby regeneratively The idle state of the engine for leak diagnosis can be maintained for more than 30 seconds, calculated from the "F" point of the second hill, which is the braking point, and therefore freer than the gasoline vehicle while driving according to the Federal Test Procedure (FTP). Leak diagnosis of the fuel system can be performed in the region.

In FIG. 6, a fuel system leak diagnosis method of a hybrid vehicle illustrates a change graph of major factors in performing a leak diagnosis as the engine clutch is switched from a closed state to an open state through the steps illustrated in FIG. 4. .

As shown in FIG. 6, when the engine is under load, the driver releases the accelerator pedal to release acceleration, and the brake is activated to enter the regenerative braking state. Since the clutch opens and the engine maintains the idling state, the vehicle speed decreases, and the engine revolutions per minute indicate a state of maintaining a predetermined value. Therefore, by maintaining the idle state of the engine, the inside of the fuel system is maintained at a predetermined negative pressure, and the engine revolutions per minute are maintained at a predetermined rotational speed, so that the diagnosis of the fuel system by the negative pressure method without additional hardware is required. Leak can be performed.

While the invention has been described with reference to the preferred embodiments, those skilled in the art will appreciate that modifications and variations of the elements of the invention may be made without departing from the scope of the invention. In addition, many modifications may be made to particular circumstances or materials without departing from the essential scope of the invention. Therefore, the invention is not limited to the details of the preferred embodiments of the invention, but will include all embodiments within the scope of the appended claims.

1 is a schematic configuration diagram of a fuel system leak diagnosis apparatus for a gasoline vehicle according to the prior art.

Figure 2 is a pressure change curve with time according to the opening and closing of each valve when the fuel system leak diagnosis of a gasoline vehicle according to the prior art

3 is a schematic configuration diagram of a hybrid vehicle according to the present invention;

Figure 4 is a flow chart showing the control flow of the fuel system leak diagnosis method in a hybrid vehicle according to the present invention.

5 is a general leak diagnosis time in the leakage diagnosis of the negative pressure method in the gasoline vehicle.

Figure 6 is a graph showing the change in the main factors in the leakage diagnosis in the engine clutch open state.

Claims (4)

Determining whether information detected while driving the hybrid vehicle satisfies the leak diagnosis condition; Determining whether the vehicle deceleration condition is satisfied by reading vehicle driving information when the leak diagnosis condition is satisfied; If the vehicle deceleration condition is satisfied, opening an engine clutch and maintaining an idle state of the engine; When a predetermined engine revolutions per minute and a predetermined engine negative pressure are generated as the idle state of the engine is maintained, the leak diagnosis of the fuel system is performed in a negative pressure manner while maintaining the predetermined engine revolutions per minute and the engine negative pressure. Step by step; A fuel system leak diagnosis method in a hybrid vehicle. The method of claim 1, wherein the vehicle driving information to be read includes whether the accelerator pedal is operated, whether the brake pedal is operated, the current vehicle speed, and the slope of the vehicle speed. The fuel system leak diagnosis method of claim 1, wherein the vehicle deceleration condition is set to a condition in which the accelerator pedal is released and the brake pedal is in operation. The method according to any one of claims 1 to 3, further comprising the step of returning to the normal driving state of the hybrid vehicle and driving the engine according to the normal driving condition when the leak diagnosis of the fuel system is completed through the above process. A fuel system leak diagnosis method for a hybrid vehicle.

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