REAL-TIME DIAGNOSTIC METHOD FOR A BROKEN INTAKE VALVE IN AN INTERNAL COMBUSTION ENGINE

Abstract

The procedure includes the steps of a) calculating an estimated diameter (DSe) of the intake valve from a measurement of the internal combustion engine's (MT) filling (R) and a measurement of the internal combustion engine's crankshaft angle (AV), b) comparing the estimated diameter to a nominal diameter (DSn) of the intake valve, and c) diagnosing intake valve failure when the estimated diameter deviates from the nominal diameter beyond a calibrated threshold (TH1). Fig. 3

Description

Title of the invention: METHOD FOR REAL-TIME DIAGNOSTIC OF A BROKEN INTAKE VALVE IN AN INTERNAL COMBUSTION ENGINE

[0001] The invention relates generally to the diagnosis of faults in an internal combustion engine. More particularly, the invention relates to a method for real-time diagnosis of intake valve failure in an internal combustion engine, such as, for example, an internal combustion engine of a motor vehicle.

[0002] In an internal combustion engine, the intake and exhaust valves mounted on the cylinder head are essential functional components that are subjected to enormous stresses. Thus, two types of failures affecting one or more valves of an internal combustion engine are well known to those skilled in the art and consist of localized combustion of the valve and bending or breakage of the valve stem.

[0003] As illustrated in Figs. 1 and 2, localized combustion CO of a valve SP can occur for various reasons at the level of its seat PO. The function of the valve seat PO, by coming into contact with the valve seat SG mounted on the cylinder head CU, is to ensure a closing junction JO of the cylinder head manifold opening TB which leads into the engine's combustion chamber.

[0004] Valve damage by combustion is initially caused by hot combustion gases escaping between the valve seat PO and the valve face SG when the valve closes imperfectly. This imperfect closure can be due, for example, to insufficient clearance between the end of the valve stem and its rocker arm CL, to carbon residue generated by incomplete combustion that prevents the valve from closing completely, to defective grinding of the seat SG and / or the valve seat PO, or to other reasons. The valve seat PO is burned by the pressurized combustion gases that leak through the imperfect closure.Without repair, valve deterioration caused by combustion worsens over time, resulting in, among other things, excessive fuel consumption, reduced engine power, and potentially further damage to the internal combustion engine, leading to substantial repair costs. Early detection of valve deterioration in an internal combustion engine is therefore of significant importance.

[0005] In the prior art, solutions are known for diagnosing faults in the valve actuation components of an internal combustion engine. By against, to the knowledge of the inventing entity, no solution has been proposed to detect in real time, during the operation of the internal combustion engine, a physical alteration of the body of a valve, in other words a "valve breakage", in particular for an intake valve.

[0006] Thus, patent application EP2236798A1 describes a method for diagnosing the valve actuation in an electro-hydraulic controlled variable distribution system.

[0007] Patent application EP1096113A1 relates to an electromagnetically controlled valve distribution system and describes a method for ensuring valve actuation in the event of a detected failure of the magnetic drive of the valves, so as to compensate for a temporary fault until the restoration of a normal operating cycle.

[0008] Patent application JP2011122504A1 describes a device using an acceleration sensor to monitor a variation in the clearance between the end of the stem of a valve and its associated rocker arm during the operation of the internal combustion engine.

[0009] It is desirable to propose a real-time diagnostic method for the breakage of an intake valve in an internal combustion engine, which is simple, economical and robust for implementation in a motor vehicle, but not exclusively.

[0010] According to a first aspect, the invention relates to a real-time diagnostic method for intake valve breakage in an internal combustion engine, comprising the steps of a) calculating an estimated diameter of the intake valve from a measurement of the internal combustion engine filling and a measurement of the crankshaft angle of the internal combustion engine, b) comparing the estimated diameter to a nominal diameter of the intake valve and c) diagnosing intake valve breakage when the estimated diameter deviates from the nominal diameter beyond a calibrated threshold.

[0011] According to a particular feature of the process, step a) includes a calculation of the estimated diameter using a numerical simulation loop.

[0012] According to another particular feature, step a), for calculating the estimated diameter using the numerical simulation loop, includes obtaining, using mapping, a reference permeability coefficient from the filling measurement.

[0013] According to yet another particular feature, the numerical simulation loop includes a calculation of an error between the reference permeability coefficient and an estimated permeability coefficient, the estimated diameter being obtained by convergence of the error in said numerical simulation loop.

[0014] The invention also relates to a computer comprising a memory in which program instructions are stored for the implementation of the method as briefly described above.

[0015] According to a particular embodiment, the computer is an engine control computer for a vehicle with internal combustion traction.

[0016] The invention also relates to an assembly consisting of an internal combustion engine and a computer as indicated above, as well as a thermal traction vehicle comprising such an assembly.

[0017] Other advantages and features of the present invention will become more apparent upon reading the detailed description below of a particular embodiment of the invention, with reference to the accompanying drawings, in which:

[0018] [Fig-1] Fig. 1 is a partial cross-sectional view of a valve mounted in a cylinder head of an internal combustion engine.

[0019] [Fig.2] Fig.2 is a front view showing an example of a valve damaged by combustion.

[0020] [Fig.3] The [Fig.3] is a block diagram showing an assembly consisting of an internal combustion engine and a computer in which is housed an embedded software module for the implementation of the process according to the invention.

[0021] [Fig.4] is an explanatory diagram showing exploited mathematical relationships by the method according to the invention.

[0022] With reference to Figs. 3 and 4, a particular embodiment of the method according to the invention for the real-time diagnosis of the breakage of an intake valve in an internal combustion engine is now described below.

[0023] With particular reference to [Fig. 3], in this embodiment, the invention is considered to be applied in a motor vehicle with internal combustion engine traction. The method of the invention is implemented in the assembly consisting of the vehicle's MT internal combustion engine and a CTRL control unit. The CTRL control unit is typically the engine control unit responsible for managing the vehicle's MT internal combustion engine.

[0024] The CTRL engine control unit manages different control and diagnostic strategies for the MT internal combustion engine depending on the operating conditions of the engine and the vehicle. The CTRL engine control unit monitors the operation of the MT internal combustion engine and the vehicle's powertrain by cooperating with other control units managing different functional components, through the exchange of information and commands via a data communication network (not shown), typically of the "CAN" type.

[0025] The implementation of the method according to the invention uses an embedded software module M0D_SW which is hosted in the CTRL engine control computer. As shown in [Fig. 3], the MOD_SW software module is implemented in a MEM memory of the CTRL engine control unit. The MOD_SW software module enables the implementation of the method according to the invention by the execution of program code instructions by a processor (not shown) of the CTRL engine control unit.

[0026] The method according to the invention exploits functions EQ1 and EQ2 shown in [Fig.4] to diagnose the breakage of an intake valve SPA.

[0027] The function EQ1, namely R=f(CfB), provides the filling, denoted R, of a cylinder of the MT internal combustion engine based on the permeability coefficient, denoted CfB, of the engine's air intake system. This function EQ1 is characterized on a reference MT internal combustion engine and is stored in memory in the CTRL engine control unit, typically in the form of a map.

[0028] The EQ2 function is a theoretical function that provides the permeability coefficient CfB from the diameter DS (see [Fig.4]) of the SPA inlet valve, and other variable or constant physical quantities, namely:

[0029] - Cd(AV) which is the pressure loss coefficient as a function of the angle of crankshaft AV;

[0030] - AVmax which is the crankshaft angle corresponding to the maximum lift of the SPA valve;

[0031] - L which is the width of the law L=2.(BA), in the lifting law LOI, shown in [Fig.4], which gives the LV lift of the SPA valve as a function of the camshaft angle AAC;

[0032] - AL which is the bore diameter of the engine cylinder; and

[0033] - NS which is the number of SPA intake valves.

[0034] By using the EQ2 function, it is possible to calculate the diameter DS of the intake valve SPA from the measured or estimated values, namely the permeability coefficient CfB and the crankshaft angle AV, and the nominal engine constants, namely the lift-law width L, the bore diameter AL, and the number NS of intake valves. The permeability coefficient CfB is given by the EQ1 function from the measured filling R.

[0035] With reference to [Fig. 3], the method of the invention detects a break in the intake valve SPA by comparing an estimated diameter, hereinafter referred to as DSe, with a nominal diameter, hereinafter referred to as DSn, of the valve. The nominal diameter DSn is a constant nominal characteristic that is fixed during the design of the reference MT internal combustion engine. The estimated diameter DSe is calculated in real time, dynamically, as described above, from the filling R and the crankshaft angle AV, using the functions EQ1 and EQ2. The method of the invention diagnoses an actual break in the intake valve SPA when the calculated diameter DSe deviates from the nominal diameter DSn beyond a calibrated threshold.

[0036] As schematically represented in [Fig.3], in the MOD_SW software module, the calculation of the estimated diameter DSe uses a numerical simulation loop BS, with convergence obtained by feedback.

[0037] The BS numerical simulation loop essentially comprises five function calculation operators Fl to F5, one subtraction operator SI and three multiplication operators Ml to M3.

[0038] The Fl operator is the inverse function, denoted f()1 in [Fig.3], of the aforementioned function EQ1. The Fl operator, for the measured filling R supplied at the input, delivers at the output a reference value CfBr of the permeability coefficient which is that which must be obtained with a SPA supply valve in perfect working order.

[0039] The F2 operator is a "PID" type corrector (for "Proportional-Integral-Derivative") performing the correction of a loop error E.

[0040] The loop error E is provided by the subtraction operator SI, which calculates the difference, CfBr-CfBe, between the reference permeability coefficient CfBr and an estimated permeability coefficient CfBe. Advantageously, to improve the convergence and stability of the BS loop, the subtraction operator SI may include a threshold (not shown) to set the loop error, E=0, to zero when it is less than a calibrated percentage (5%, for example) of CfBr.

[0041] When the BS loop converges, the operator F2 delivers at output the estimated diameter DSe of the SPA supply valve.

[0042] Operators F3 to F5 and operators M1 to M3 are responsible for calculating the aforementioned estimated permeability coefficient CfBe, using the function EQ2.

[0043] The operator F3 outputs the pressure loss coefficient Cd(AV) corresponding to the measured crankshaft angle AV. The product of the coefficient Cd(AV) and (L / 2)1, where L is the aforementioned law width, is calculated by the multiplication operator ML

[0044] The operator F4 calculates the integral between AV=0 and AV=AVmax of the product Cd(AV). (L / 2)1 supplied as input by the operator ML

[0045] The multiplication operator M2 calculates the product of the integral provided by the operator F4 with the number of valves NS and the expression (DSe / AL)2 and provides as output the estimated permeability coefficient CfBe.

[0046] The expression (DSe / AL)2 is obtained with the operators M3 and F5. The multiplication operator M3 calculates the fraction DSe / AL between the estimated diameter DSe, available at the output of the corrector F2, and the bore diameter AL of the engine cylinder. The squaring of the fraction DSe / AL is done by the operator F5, denoted (.. .)2 in [Fig.3],

[0047] As shown in [Fig. 3], the comparison between the estimated diameter DSe and the nominal diameter DSn of the intake valve SPA for valve failure diagnosis is performed using a subtraction operator S2 and a calibrated threshold TH1. When the difference between the diameters DSe and DSn exceeds the value of the calibrated threshold, a valve failure alert AL is issued. In the vehicle, the AL alert will typically generate an "OBD" type fault code usable by the on-board diagnostic system and / or an "APV" type fault code for after-sales vehicle maintenance and root cause identification of malfunctions.

[0048] The invention is not limited to the particular embodiment described herein by way of example. A person skilled in the art may, depending on the applications of the invention, make various modifications and variations falling within the scope of the invention's protection.

Claims

Demands

1. A method for real-time diagnosis of intake valve (IV) failure in an internal combustion engine (ICE), comprising the steps of a) calculating an estimated diameter (ED) of said intake valve (ED) from a measurement of the filling (R) of said internal combustion engine (ICE) and a measurement of the crankshaft angle (CA) of said internal combustion engine (ICE), b) comparing said estimated diameter (ED) to a nominal diameter (ND) of said intake valve (ED), and c) diagnosing failure of said intake valve (ED) when said estimated diameter (ED) deviates from said nominal diameter (ND) beyond a calibrated threshold (TH1), said step a) comprising the calculation of said estimated diameter (ED) using a numerical simulation loop (BS) comprising,- Obtaining, using mapping, a reference permeability coefficient (CfBr) from said filling measurement (R); - Calculating an error (E) between said reference permeability coefficient (CfBr) and an estimated permeability coefficient (CfBe); - A PID control system determining, as a function of the error (E), an estimated diameter (DSe), the estimated permeability coefficient (CfBe) being calculated by the following general relationship: CfB - dAv(AV) = Σvs. With CfB, the permeability coefficient, Cd(AV) the pressure loss coefficient as a function of the crankshaft angle AV, AVmax the crankshaft angle corresponding to the maximum lift of the intake valve, L the lift width, AL the bore diameter of the engine cylinder, NS the number of intake valves; - said estimated diameter being obtained by convergence of said error (E) in said numerical simulation loop.

2. Calculator (CTRL) characterized in that it includes a memory (MEM) storing program instructions (MOD_SW) for the implementation of the method according to claim 1.

3.

4.

5. Calculator according to claim 2, characterized in that it is formed by an engine control computer (CTRL) of a thermal traction vehicle. Assembly consisting of an internal combustion engine (MT) and a computer (CTRL), characterized in that said computer is a computer according to claim 2 or 3. Thermal traction vehicle characterized in that it comprises an assembly (MT, CTRL) according to claim 4.

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