DIAGNOSTIC SYSTEM AND PROCEDURE FOR OXYGEN SENSORS IN HYBRID VEHICLES

Abstract

Diagnostic method for an oxygen sensor for hybrid vehicles with an HSG for driving an internal combustion engine, comprising: Receiving a diagnostic request signal for initiating the oxygen sensor diagnosis from an EMS (Engine Management System) configured to control the internal combustion engine (S12); in response to receiving the diagnostic request signal, determining whether the passive drive condition of the vehicle exists (S14), and disengaging the engine clutch if the passive drive condition exists; Interrupting the fuel supply to the internal combustion engine in response to receiving the diagnostic request signal (S16), wherein the internal combustion engine is operated at a preset reference speed by controlling the HSG when the engine clutch is disengaged; and Diagnosing the oxygen sensor by the EMS (S18) once the fuel supply to the combustion engine has been interrupted, with the combustion engine being driven at the preset reference speed, wherein the diagnosis request signal is set in advance such that the oxygen sensor diagnosis is completed within a preset time according to an emission regulation for the vehicle, wherein the diagnostic request signal is configured as a long fuel cut-off signal that interrupts the fuel supply to the internal combustion engine once for five seconds per case, and as a short fuel cut-off signal that interrupts the fuel supply to the internal combustion engine three times for three seconds per case, and wherein the previously set reference speed is determined based on the cooling water temperature of the vehicle.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to a diagnostic system and method for oxygen sensors in hybrid vehicles, and more particularly to a diagnostic system and method for oxygen sensors in hybrid vehicles with maximum generation of a harmful gas in the event of abnormal operation in such a manner as to enable monitoring of the normal operation of the oxygen sensor. Description of related technology

[0002] Vehicles are often equipped with an oxygen sensor to comply with the emissions standards of various states and countries. Several years ago, vehicles began to be equipped with a diagnostic function that allows the vehicle to diagnose an oxygen sensor while it is active, in order to also comply with OBD (On Board Diagnostic) regulations. KR 2011 0 062 135 A already discloses a hybrid vehicle, and in particular an oxygen sensor monitoring device and a method for a hybrid vehicle that provides for monitoring the oxygen sensor in a state that does not affect the extent of regenerative braking.Furthermore, DE 10 2010 027 983 A1 describes a method for operating an internal combustion engine, in which at least one parameter of the exhaust gas flowing in an exhaust duct is detected by at least one exhaust gas probe. The internal combustion engine is at least temporarily towed by a starting device, during which time fuel injection and combustion do not occur, and during this time and / or after this time, the exhaust gas probe (30, 32) is calibrated. DE 10 2010 050 055 A1 discloses a method, a method for diagnosing an exhaust gas catalytic converter and / or an exhaust gas sensor arranged downstream and / or upstream of the exhaust gas catalytic converter in an exhaust system of an internal combustion engine.According to the invention, the operation of the internal combustion engine with an air-fuel mixture with a substoichiometric air-fuel ratio, the switching off of the internal combustion engine, the carrying out of an unfired overrun operation with the fuel supply switched off after the internal combustion engine has come to a standstill, wherein air sucked in by the internal combustion engine is conveyed through the exhaust system to the exhaust gas catalytic converter and to the exhaust gas sensor, the starting of a self-running of the internal combustion engine with fired operation and a substoichiometric air-fuel ratio and the evaluation of a signal of the exhaust gas sensor, which is provided at least in a time range after switching off until the subsequent self-running of the internal combustion engine, is provided with reference to a predefinable evaluation criterion.Finally, DE 10 2011 113 555 A1 proposes a method for monitoring an on-board diagnostic system for a plug-in hybrid electric vehicle, which includes incrementing the denominator of an N / D ratio for the on-board diagnostic system only when a total time criterion, a vehicle speed criterion, and an idle criterion are met after an internal combustion engine of the vehicle has been supplied with fuel. The diagnostic system behavior is summarized in a single N / D ratio. If an insufficient ratio is identified, the system controls the engine to provide more engine operation and subsequent diagnostic observability.The denominator of the N / D ratio is compared to a verification denominator to identify vehicles that are typically operated such that an engine-on cycle does not begin or is not identified until the very end of the drive cycle, thereby preventing the denominator and a numerator of the N / D ratio from being incremented and thereby providing an incorrect passing power ratio.

[0003] Specifically, in hybrid vehicles, the above-mentioned diagnostic function is performed under the control of an HCU (Hybrid Control Unit), which is configured to control essentially every function in the vehicle, and an EMS (Engine Management System), which is configured to control the internal combustion engine. The decision to turn the internal combustion engine and fuel injection system on and off rests solely with the HCU. Thus, the EMS, which communicates with the HCU, turns the vehicle's internal combustion engine on and off based on control signals from the HCU.

[0004] Specifically, in hybrid vehicles, an oxygen sensor diagnostic function is initiated under the following conditions. When a diagnostic start request is received from the EMS (Engine Management System), the HCU (Hybrid Control Unit) begins controlling the engine operation without shutting down within a specified speed range for a specified period of time with the fuel supply cut off, thus fulfilling a condition for starting the diagnostic function. The diagnostic request signal can be, for example, a long fuel cut signal (5 seconds per case, once in total) and a short fuel cut signal (3 seconds per case, three times in total) to comply with OBD (On Board Diagnostic) regulations.

[0005] The conventional hybrid vehicle is generally configured so that the internal combustion engine is driven in a state where the engine clutch is actively engaged, and the internal combustion engine is operated in a passive state to satisfy the required condition for oxygen sensor diagnostic functions. When an oxygen sensor diagnostic request is received from the EMS, the HCU determines whether the internal combustion engine is currently operating in a passive state. If the above condition is met, the engine clutch is engaged, the fuel injection is shut off, and the fuel supply is cut off. If the condition for oxygen sensor diagnostics is met, the EMS starts oxygen sensor diagnostics.

[0006] However, the conventional diagnostic method for a hybrid vehicle's oxygen sensor suffers from the following problems. First, the driver may experience some uncertainty while applying the engine brake without depressing the clutch pedal because the engine clutch remains engaged. This results in a different perception of the vehicle's operation due to a slight error in the model-based amount of engine friction torque. Second, braking may also cause a feeling of uncertainty, which is also due to the release of the engine clutch during regenerative braking when the driver applies the brake. Therefore, this feeling of uncertainty on the part of the driver is often due to an error that occurs during regenerative braking due to a torque transmission error in the engine clutch.Third, there is a delay in the oxygen sensor diagnostic function due to a start / release condition that occurs while the internal combustion engine is operating passively. Thus, the diagnosis is completed after the vehicle has been running for approximately 20 to 30 minutes. SUMMARY OF THE INVENTION

[0007] It is therefore an object of the present invention to provide a diagnostic method for an oxygen sensor in a hybrid vehicle, by which it is possible to increase regenerative energy, improve fuel efficiency, expand the starting condition for diagnosis of the oxygen sensor and improve driving comfort of the vehicle by eliminating the need for the engine clutch to be engaged in order to satisfy the required conditions for initiating oxygen sensor diagnosis, the above condition being satisfied even when the engine clutch is disengaged.

[0008] The present invention provides a diagnostic method for an oxygen sensor for hybrid vehicles having an HSG for driving an internal combustion engine, having the features of claim 1, and a non-transitory computer-readable medium containing program instructions executed by a processor of a controller, having the features of claim 6.

[0009] More specifically, the passive propulsion condition can only be determined to exist when an internal combustion engine or an electric motor is operating at a first or second speed, respectively. The deceleration range can be determined in response to the SOC (state of charge) values ​​of a battery installed in the vehicle.

[0010] The passive propulsion condition may also require that the vehicle is currently operating in EV (Electric Vehicle) mode. Furthermore, the reference speed when the fuel supply to the combustion engine is interrupted may be determined based on a change in vehicle speed.

[0011] Since the embodiment advantageously uses engine speed control, which requires clutch engagement for oxygen sensor diagnosis, regenerative energy and fuel efficiency can be improved, and since oxygen sensor diagnosis can be initiated without clutch engagement, the vehicle also operates more smoothly. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above and other features of the present invention will now be described in detail with reference to specific embodiments thereof which are shown by way of example only in the accompanying drawings and thus do not limit the present invention; in which: Fig. 1 is a flowchart of the control of a diagnostic method for an oxygen sensor for hybrid vehicles according to an embodiment of the present invention. Fig. 2 is a block diagram of the HCU (Hybrid Control Unit) that executes a diagnostic method for an oxygen sensor for hybrid vehicles according to an embodiment of the present invention.

[0013] It should be understood that the accompanying drawings are not necessarily to scale, presenting a somewhat simplified representation of the various preferred features illustrative of the principles of the invention. The specific design features of the present invention disclosed herein, including, for example, particular dimensions, orientations, locations, and shapes, will be determined in part by the particular intended application and the environmental conditions at the site of use.

[0014] In the figures, identical reference numerals designate the same or equivalent parts of the present invention in the different figures of the drawing. DESCRIPTION OF CERTAIN EMBODIMENTS

[0015] Various embodiments of the present invention will now be explained in detail, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it should be understood that the present description is not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents, and other embodiments included within the spirit and scope of the invention as defined by the appended claims.

[0016] It is understood that the term "vehicle" or "vehicular" or other similar terms used herein generally refer to motor vehicles, such as passenger cars, including sports utility vehicles (SUVs), buses, trucks, various commercial vehicles, personal watercraft including various boats and ships, aircraft, and the like, and also includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles (chargeable from a wall outlet), hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As used herein, a hybrid vehicle is a vehicle with two or more power sources, e.g., vehicles with both gasoline and electric power.

[0017] Unless expressly stated or obvious from the context, the term "about, approximately," as used herein, should be understood to refer to values ​​within the normal range of engineering tolerances, such as two standard deviations from the mean. "About or approximately" may be understood to mean within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless the context otherwise clearly indicates, all numerical values ​​contained herein are modified by the term "about, approximately."

[0018] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, it is to be understood that the term “comprise,” and forms thereof such as “comprises” or “having,” indicates the presence of stated features, integer quantities, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integer quantities, steps, operations, elements, and / or components, and / or groups thereof. As used herein, the phrase “and / or” includes all combinations of one or more of the listed items.

[0019] Although the description of the embodiment contemplates a plurality of units for executing the example processes, it should be understood that the example processes may also be executed by one or more modules. Furthermore, it should be understood that the term "controller" refers to a hardware device having a memory and a processor. The memory is configured to store the modules, and the processor is specifically configured to execute the modules to perform one or more processes described later.

[0020] Furthermore, the control logic of the present invention may be embodied as a non-transitory computer-readable medium on a computer-readable medium having executable program instructions executed by a processor, controller, and the like. Examples of computer-readable media include ROMs, RAMs, compact disc (CD)-ROMs, magnetic tapes, floppy disks, USB flash drives, smart cards, and optical data storage devices. The computer-readable recording medium may also be distributed in network-coupled computer systems such that the computer-readable medium is stored and executed in a distributed manner, e.g., by a telematics server or a controller area network (CAN).

[0021] The diagnostic method for an oxygen sensor in hybrid vehicles according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0022] The hybrid vehicle in which a diagnostic method for an oxygen sensor in a hybrid vehicle according to the embodiment of the present invention is carried out includes a transmission (T / M) configured to adjust the speed ratio between a drive shaft and a wheel shaft, a drive motor configured to transmit driving force to the drive shaft using electric power from a battery, an engine, a motor clutch configured to transmit the driving force of the engine to a motor shaft, and an HSG (Hybrid Starter Generator) configured to control the state of the engine, for example, when the engine is turned on and off.

[0023] Fig. 1 is a flowchart of the control of the oxygen sensor diagnostic method in hybrid vehicles according to the embodiment of the present invention. The above control procedures can be executed under the control of an HCU 200 (Hybrid Control Unit) (in Fig. 2) which is configured to detect a driver request (i.e., acceleration, braking, etc.) and status information regarding the vehicle, and to control the overall vehicle operation, including an internal combustion engine and a drive motor.

[0024] As from Fig. As shown in Figure 1, the HCU 200 receives a diagnosis request signal for initiating oxygen sensor diagnosis from an EMS (Engine Management System) that controls the engine to execute the oxygen sensor diagnosis method in hybrid vehicles according to the embodiment of the present invention (S12). The diagnosis request signal is set in advance, taking into account the vehicle's OBD (On Board Diagnostic) standards and emission regulations, so that oxygen sensor diagnosis can be completed within a set period of time. The diagnosis request signal may be, for example, a long fuel cut signal configured to cut off fuel supply to the engine once for five seconds per case and a short fuel cut signal that cuts off fuel supply to the engine three times for three seconds each.

[0025] Upon receipt of the diagnostic request signal, the HCU is configured to determine whether the passive drive condition, with the accelerator pedal deactivated, exists and the vehicle speed is within the previously set deceleration range so that the engine clutch can be disengaged when the passive drive condition exists (S14).

[0026] To determine whether the passive propulsion condition exists (S14), the HCU should monitor the vehicle speed and the electric motor speed. Only when the engine speed and the electric motor speed correspond to the previously set reference value does the passive propulsion condition exist.

[0027] The deceleration range of the passive propulsion condition can be determined according to the state of charge (SOC) values ​​of the battery installed in the vehicle. The passive propulsion condition could further include a condition requiring the vehicle to operate in EV (Electric Vehicle) mode.

[0028] When the engine clutch is disengaged in S14, the engine is driven at a preset reference speed by controlling the HSG, and simultaneously, the fuel supply is cut off in response to the receipt of the diagnostic request signal (S16). The reference speed is determined based on the vehicle's cooling water temperature, and the engine's fuel cut control can be performed based on a change in vehicle speed in response to the receipt of the diagnostic request signal. Finally, once the fuel supply to the engine is cut off because the engine starts operating at the reference speed in S16, a control signal for controlling oxygen sensor diagnosis is transmitted to the EMS (S18).

[0029] The tax procedures described above are based on Fig. 2 with a plurality of control function modules executed by a processor and stored in a memory of the HCU 200. Fig. 2 is a block diagram showing an HCU (Hybrid Control Unit) that executes a diagnostic method with an oxygen sensor for hybrid vehicles according to an embodiment of the present invention.

[0030] How Fig. As shown in Figure 2, the HCU 20 includes a clutch release module 220, an HSG speed control module 240, and a fuel cutoff module 260, which are classified for the purpose of simplified description. It should be understood that the diagnostic method for an oxygen sensor in hybrid vehicles according to the present invention is not limited thereto.

[0031] The clutch enable module 220 includes a passive operation enable determination submodule 222, a passive drive condition determination submodule 224, and an engine clutch enable submodule 226. The passive operation enable determination submodule 222 is configured to determine whether the vehicle is in the passive drive condition by monitoring the vehicle speed and engine speed.

[0032] The passive propulsion condition determination submodule 224 is configured to determine whether the vehicle is currently within a set deceleration range while disabling the accelerator pedal in response to receiving the diagnostic request signal when the passive operation capability determination submodule 222 determines that the passive propulsion condition exists.

[0033] The motor clutch enable submodule 226 is configured to control the motor clutch and specifically to disengage the motor clutch when it is determined that the passive drive condition exists.

[0034] The HSG speed control module 240 operates the engine at a preset reference speed by executing engine speed control functions in the HSG (Hybrid Control Unit). The reference speed is determined based on the vehicle's coolant temperature.

[0035] The fuel shutoff module 260 is configured to interrupt the fuel supply to the engine by shutting off the fuel injection system in response to receiving the diagnostic request signal when the engine is driven at the previously set reference speed by the HSG speed control module 240. The fuel shutoff control of the engine may be performed taking into account a change in vehicle speed in response to receiving the diagnostic request signal.

[0036] The oxygen sensor diagnostic method for hybrid vehicles according to the embodiment of the present invention is directed to transmitting a control signal to the EMS to control the oxygen sensor diagnosis once the fuel supply to the internal combustion engine is interrupted via the HSG. In other words, the oxygen sensor diagnosis can be performed under the control of the HCU.

[0037] As described above, a control signal for controlling and executing oxygen sensor diagnostics is transmitted to the EMS when the fuel supply to the engine is cut off via the HSG. The EMS facilitates oxygen sensor diagnostics according to the engine's control via the HCU without the clutch being engaged.

[0038] Unlike the prior art in which the engine clutch remains engaged, the embodiment of the present invention can perform the oxygen sensor diagnosis functions based on constant speed control of the HSG without the clutch being engaged, so that the regenerative energy and fuel efficiency are improved thanks to the elimination of unnecessary maintenance of the engine clutch being engaged, and since the start conditions for the oxygen sensor diagnosis are changed, the vehicle can be operated more smoothly.

[0039] In other words, with the oxygen sensor diagnostic method for hybrid vehicles according to the present embodiment, the shock and jolt conditions that occur when releasing unnecessary engine clutch engagement can be avoided, and the oxygen sensor can be diagnosed during EV mode while the clutch and drive shaft are disengaged, resulting in an improvement in noise, vibration, and harsh vehicle handling and braking performance. Accordingly, the quality of hybrid vehicles can be improved.

[0040] The invention has been described in detail with reference to exemplary embodiments. However, those skilled in the art will recognize that modifications may be made to these embodiments without departing from the invention, the scope of which is defined in the appended claims.

Claims

[1] Diagnostic method for an oxygen sensor for hybrid vehicles with an HSG for driving an internal combustion engine, comprising: Receiving a diagnostic request signal for initiating the oxygen sensor diagnosis from an EMS (Engine Management System) configured to control the internal combustion engine (S12); in response to receiving the diagnostic request signal, determining whether the passive drive condition of the vehicle exists (S14), and disengaging the engine clutch if the passive drive condition exists; Interrupting the fuel supply to the internal combustion engine in response to receiving the diagnostic request signal (S16), wherein the internal combustion engine is operated at a preset reference speed by controlling the HSG when the engine clutch is disengaged; and Diagnosing the oxygen sensor by the EMS (S18) once the fuel supply to the combustion engine has been interrupted, with the combustion engine being driven at the preset reference speed, wherein the diagnosis request signal is set in advance such that the oxygen sensor diagnosis is completed within a preset time according to an emission regulation for the vehicle, wherein the diagnostic request signal is configured as a long fuel cut-off signal that interrupts the fuel supply to the internal combustion engine once for five seconds per case, and as a short fuel cut-off signal that interrupts the fuel supply to the internal combustion engine three times for three seconds per case, and wherein the previously set reference speed is determined based on the cooling water temperature of the vehicle. [2] The method of claim 1, wherein the passive drive condition exists only when both the speed of the vehicle and the speed of an engine are at a previously set first speed and second speed. [3] The method of claim 1, wherein the deceleration range is determined in response to one or more SOC values ​​of a battery installed in the vehicle. [4] The method of claim 1, wherein the passive propulsion condition further requires that the vehicle be operated in EV mode. [5] The method of claim 1, wherein the fuel supply to the internal combustion engine is interrupted based on a change in vehicle speed. [6] A non-transitory computer-readable medium (200) containing program instructions executed by a processor of a controller, the computer-readable medium (200) comprising: Program instructions that receive a diagnostic request signal from an EMS configured to control the internal combustion engine; Program instructions (220) responsive to receiving the diagnostic request signal to determine whether a passive drive condition of the vehicle exists and to disengage the engine clutch if the passive drive condition is determined to exist; Program instructions (240, 260) that interrupt the fuel supply to the internal combustion engine in response to receipt of the diagnostic request signal and the presence of the passive drive condition, the internal combustion engine running at a preset reference speed; and Program instructions that diagnose the oxygen sensor as soon as the fuel supply to the combustion engine is interrupted, with the combustion engine being driven at the previously set reference speed, wherein the diagnosis request signal is set in advance such that the oxygen sensor diagnosis is completed within a preset time according to an emission regulation for the vehicle, wherein the diagnostic request signal is configured as a long fuel cut-off signal that interrupts the fuel supply to the internal combustion engine once for five seconds per case, and as a short fuel cut-off signal that interrupts the fuel supply to the internal combustion engine three times for three seconds per case, and wherein the previously set reference speed is determined based on the cooling water temperature of the vehicle. [7] The non-transitory computer-readable medium of claim 6, wherein the program instructions that determine whether the passive propulsion condition exists are executed only when both the speed of the vehicle and the speed of an engine are at a preset first speed and second speed. [8] The non-transitory computer-readable medium of claim 6, wherein the deceleration range is determined in response to one or more SOC values ​​of a battery installed in the vehicle. [9] The non-transitory computer-readable medium of claim 6, wherein the passive propulsion condition further requires that the vehicle be operated in EV mode. [10] The non-transitory computer-readable medium of claim 6, wherein the fuel supply to the internal combustion engine is interrupted based on a change in speed of the vehicle.

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