Diagnosis of valve clearance or throttle valve failure on lawn mowers

Abstract

The present invention relates to a method for establishing engine maintenance diagnostics. An engine (1) comprises a throttle valve (2) regulating the air inlet into the engine's intake system, a position sensor (TPS) measuring the position of the throttle valve, a manifold in fluid communication with the throttle valve, a pressure sensor (4) measuring the pressure in the manifold, at least one intake valve (5), a concentration probe (7) measuring the oxygen level, and a concentration controller for varying the ratio of air to fuel in an air-fuel mixture. The method utilizes two air flow measurements to identify problems in the throttle valve or in the clearance at the valve.

Description

Technical Field

[0001] The present invention relates to performing maintenance diagnostics on an engine and, in particular, to a method for revealing the need for maintenance on an engine due to blockage and / or blowby at a throttle or valve. Such an engine is intended to power a lawn mower. Background Art

[0002] In the field of lawn mowers, maintenance is conventionally performed after a certain number of operating hours. This means that maintenance diagnostics are performed by a computer based on an operating hour counter, even if the lawn mower does not necessarily need to be repaired.

[0003] In particular, there is currently no monitoring function available to identify malfunctions, such as blockage, at the throttle valve of a lawn mower. Therefore, maintenance diagnostics for this problem are impossible. Maintenance diagnostics for clearance issues at the intake valves are also impossible. However, it is well known that when these components wear out over time, they can have a significant impact on the proper functioning of the engine, not just with regard to lawn mowers. Both are used in the air intake to control the flow of air and / or air-fuel mixture supplied to the engine. In this regard, it would be advantageous to be able to reveal when one of these two components is no longer functioning properly and requires maintenance. Even more advantageous would be to determine which of the two components is faulty.

[0004] Although the solution proposed in this application is implemented in a lawn mower engine, this is merely an illustrative and non-restrictive example. In fact, the elements involved are not specific to lawn mowers, and the solution can easily be implemented in engines for different applications, in particular motor vehicle engines. Summary of the Invention

[0005] One object of the present application is to propose a method that reveals when an engine requires maintenance due to a fault in its air intake system.

[0006] More precisely, one object of the present application is to identify the intake point where the fault is located, and in particular to identify whether the fault is at the throttle valve or at the intake valve, in order to facilitate maintenance of the engine.

[0007] Another object of the present invention is to exploit hardware components already present on the engine to reveal such faults, thereby avoiding increasing the complexity of the system and incurring additional integration costs.

[0008] To this end, the present application proposes a method for establishing maintenance diagnostics on an engine, the engine comprising: a throttle valve regulating the inlet of air into an intake system of the engine; a position sensor measuring the position of the throttle valve; a manifold in fluid communication with the throttle valve; a pressure sensor measuring the pressure in the manifold; at least one intake valve; a concentration probe measuring the oxygen level; and a concentration controller for varying the ratio of air to fuel in an air / fuel mixture.

[0009] The method is characterized in that it comprises a first set of steps carried out at the end of an engine production line or after maintenance of said engine, the first set of steps comprising the following steps:

[0010] - The engine is ignited and when the engine is in a predetermined condition,

[0011] - Based on the position V of the throttle valve measured by the position sensor TPS mesure Determine the first air flow db in the intake system TPS ,

[0012] - Based on the pressure P in the manifold measured by the pressure sensor mesure Determine the second air flow db in the intake system p ,

[0013] - Determine the reference measurement correction factor F ref , the reference measurement correction factor is selected so that when the reference measurement correction factor is based on the two air flow rates db p or db TPS The same calculation is performed to determine the corrected third air flow rate db cor The reference measurement correction factor is added to the two air flow rates db in the process p or db TPS When the measured value of one of the above is , the corrected third air flow rate db cor is essentially equal to the other of the two air flows,

[0014] - by adding the reference injection correction factor LCL ref To correct the two air flow db TPS or db p The theoretical injection command C of the concentration controller is determined by one of inj , so as to obtain a substantially stoichiometric air-fuel mixture based on measurements from the concentration probe, and

[0015] For at least a certain duration T calibrage After that, during the duration T calibrage During this period, the first air flow dbTPS Determination of the second air flow db p Determination of reference measurement value correction factor F ref The steps of determination and correction are performed several times,

[0016] -Store reference measurement correction factor F ref and the reference injection correction factor LCL ref ,

[0017] and wherein the method comprises a second set of steps performed during normal operation of the engine and when the engine is in said predetermined condition,

[0018] The second set of steps includes the following:

[0019] - Based on the position V′ of the throttle valve measured by the position sensor TPS mesure Determine the first air flow rate db′ in the intake system TPS ,

[0020] - Based on the pressure P' in the manifold measured by the pressure sensor mesure Determine the second air flow rate db′ in the intake system p ,

[0021] - Determine the correction factor F for the current measurement value courant The current measurement correction factor is selected so that when the two air flow rates db′ TPS or db′ p The same calculation as in one of the above is used to determine the corrected third air flow rate db′ cor The current measurement correction factor is added to the two air flow rates db′ in the process TpS or db′ p When the measured value of the corresponding one of the above is , the corrected third air flow rate db′ cor Basically equal to two air flow db' TPS or db′ p The other one,

[0022] - by adding the current injection correction factor LCL courant To correct the injection command C' of the concentration controller determined by the corresponding air flow inj , so as to obtain a substantially stoichiometric air-fuel mixture based on measurements from the concentration probe, and

[0023] When the reference measurement value correction factor F ref and the current measurement correction factor F courant When the absolute value of the difference between

[0024] - Establish maintenance diagnostics,

[0025] - Calculate the reference injection correction factor LCL ref and the current injection correction factor LCL courant The absolute value of the difference between V com ,as well as:

[0026] 1) When the absolute value V com When it is less than a certain threshold,

[0027] - If the injection command C′ inj The first air flow db′ obtained from the throttle valve position TPS determining, then establishing a diagnosis of clearance at at least one intake valve, and

[0028] - If the injection command C′ inj The second air flow db′ obtained from the manifold pressure p If it is confirmed, a diagnosis of blockage at the throttle valve is established, or

[0029] 2) On-duty V com When it is greater than the determined threshold,

[0030] If the injection command is determined by the first air flow db′ obtained from the throttle position TPS If it is determined that the throttle valve is blocked, the diagnosis is established, and

[0031] - If the injection command is determined by a second air flow db′ obtained from the manifold pressure p If determined, a diagnosis of the clearance at the at least one intake valve is established.

[0032] The present invention also provides a computer configured to control the ignition and concentration controller of the engine and to receive measurement values ​​from a throttle valve position sensor, a manifold pressure sensor, and a concentration detector. The computer is also suitable for implementing the steps of the above method.

[0033] The present invention also provides a computer program product comprising code instructions recorded on a carrier readable by a computer ECU comprising a memory, so as to implement the steps of the above method when the program is executed on the computer ECU comprising the memory.

[0034] Finally, the present invention provides an engine, characterized in that the engine includes: a throttle valve that regulates the inlet of air into an intake system of the engine; a position sensor that measures the position of the throttle valve; a manifold in fluid communication with the throttle valve; a pressure sensor that measures the pressure in the manifold; at least one intake valve; a concentration sensor that measures the oxygen level; and a concentration controller for varying the ratio of air to fuel in an air / fuel mixture.

[0035] Also included is a computer for implementing the above method.

[0036] The features disclosed in the following paragraphs may be optionally implemented. They may be implemented independently of each other or in combination with each other:

[0037] In one embodiment, the determination conditions of the engine may include an engine temperature between two first predetermined thresholds, an air temperature between two second predetermined thresholds, an air flow in the intake system between two third predetermined thresholds, an engine speed between two fourth predetermined thresholds for a duration at least equal to a fifth determination threshold, and an engine load between two sixth predetermined thresholds.

[0038] According to one embodiment, at each ignition of the engine, the current measurement value correction factor F courant and the current injection correction factor LCL courant may be initialized to the current reference correction factor F calculated in one of the iterations before shutting down the engine. courant and the current injection correction factor LCL courant .

[0039] According to one embodiment, the storing step may be performed after the engine has been switched off.

[0040] According to one embodiment, the engine may be mounted in a lawn mower.

[0041] The method according to the present invention thus allows for engine maintenance diagnostics to be performed when necessary. It also allows for better engine maintenance, as it can detect which components should be the subject of maintenance. In this regard, the method allows for an increase in the service life of engines, particularly lawn mower engines. Furthermore, since the method does not require components that are not already present on the engine, it does not introduce any additional integration complexity and, therefore, does not incur any additional costs for the manufacturer or the user.

[0042] For lawn mowers specifically, it also allows users to reduce costs associated with maintenance of their lawn mowers, as maintenance alarms no longer have to be triggered solely based on a timer, but can also be triggered when a real problem is detected in the air intake system of the lawn mower's engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other features, details, and advantages will become apparent upon reading the following detailed description and analyzing the accompanying drawings, in which:

[0044] Figure 1

[0045] [ Figure 1 ] shows an embodiment of the intake and exhaust system of an engine.

[0046] Figure 2

[0047] [ Figure 2 ] shows an embodiment of a method for establishing maintenance diagnostics for an engine intake system.

[0048] Figure 3

[0049] [ Figure 3 ] shows embodiments of different connections between a computer and other elements of an engine, allowing the implementation of a method for establishing maintenance diagnostics for an engine intake system. DETAILED DESCRIPTION

[0050] Now refer to [ Figure 1 ], which shows an engine 1 in a non-exhaustive manner. Although the method has been carried out in a lawn mower engine, it is applicable to all types of engines and in this respect the lawn mower example is here purely illustrative and not limiting.

[0051] Engine 1 includes an intake system 3, shown on the right side of the figure. This system includes a throttle valve 2, which is mounted in a housing and controls the inlet of air into the system. The position of throttle valve 2 is measured by a position sensor (TPS). Intake system 3 also includes a manifold in fluid communication with throttle valve housing 2. A pressure sensor 4 measures the pressure within the manifold. Furthermore, at least one intake valve 5 is in fluid communication with the manifold.

[0052] Figure 1The left side of the figure shows the exhaust system of the lawn mower engine 1, which comprises as many exhaust valves 6 as the intake system 3 comprises intake valves 5. The exhaust system also comprises a concentration probe 7 that allows the oxygen level in the exhaust gas to be measured. This oxygen level is used to determine the concentration of the air-fuel mixture introduced into the engine 1. In this respect, the air-fuel mixture is described as lean when there is too little fuel relative to the amount of air, and as rich when there is more fuel than required. In this case, the concentration probe is based on a threshold value that separates a lean mixture from a rich mixture, which threshold value symbolizes an ideal air-fuel mixture called stoichiometric. More precisely, a stoichiometric mixture corresponds to an air-fuel ratio that allows a correctly balanced reaction (combustion) between air and fuel.

[0053] Reference Figure 3 The functioning of the lawn mower engine 1 is ensured by the computer ECU which controls, among other things, the ignition. The computer ECU also receives information from the position sensor TPS, the manifold pressure sensor 4 and the concentration probe 7. In particular, it controls the controller for transmitting the fuel injection command C inj The concentration controller 8. The computer ECU also includes a memory for implementing a method for establishing a maintenance diagnosis for the engine 1, which will be referred to below. Figure 2 Provide a description.

[0054] The method consists of two separate phases, each with a set of steps. Figure 2 The phrase "off the production line" here means that the engine 1 is new, in other words, has never been used. The second stage (at Figure 2 The phrase "normal operation of the engine 1" here refers to any operation of the engine 1 except when it is in the first stage. In this case, the engine 1 is no longer new and has not just undergone a maintenance operation, i.e. it has been operating under predetermined conditions for at least a duration T. calibrage Duration T calibrage The limitations of the predetermined conditions will be described below.

[0055] In a first stage, the method aims to determine two reference correction factors. The first factor corresponds to the reference correction factor F of the measurement value made by the position sensor TPS of the throttle valve 2 or the measurement value made by the manifold pressure sensor 4 ref The second factor corresponds to the injection command C provided by the concentration controller 8. inj Reference injection correction factor LCL refThese reference correction factors have a value of zero when the lawn mower is new and are also reinitialized to this value after maintenance operations on the vehicle.

[0056] In the second phase, the method monitors the first current measurement value correction factor F courant , and when it deviates from the reference measurement value determined during the first phase the correction factor F ref When it is too far, maintenance diagnosis is performed. In addition, the injection command C′ provided by the concentration controller 8 is monitored. inj The second current correction factor LCL courant Relative to the reference correction factor LCL ref The deviation will allow determining whether the fault is caused by the clearance at the at least one intake valve 5 or by the throttle valve 2 .

[0057] Thus, the first step of the method, corresponding to the first step of the first set of steps of the first phase, consists in igniting 100 the lawn mower engine 1. In this case, the purpose is to place the engine 1 under predetermined conditions in order to be able to determine the reference factor F ref and LCL ref .

[0058] The method performs the second step only when the engine is in a predetermined condition.

[0059] The predetermined conditions of engine 1 include an engine temperature between two first predetermined thresholds. They also include an air temperature between two second predetermined thresholds. They also include an air flow in the intake system between two third predetermined thresholds. They also include an engine speed between two fourth predetermined thresholds for a duration at least equal to a fifth predetermined threshold. Finally, they include an engine load between two sixth predetermined thresholds.

[0060] Once these conditions are met simultaneously, the method executes the following steps. However, once one of these conditions is no longer valid, the method is temporarily stopped.

[0061] In order to determine the two reference correction factors F ref and LCL ref , advantageously, for a determined duration T corresponding to the accumulated duration calibrage , all these conditions must exist. The cumulative duration here means the duration T calibrage can be identified as a time counter, and once all the above determined conditions are met, the time counter is incremented to the duration T calibrageIt is not reset to zero when the engine 1 is stopped, but only when the vehicle undergoes a maintenance operation. It is of course zero when the engine 1 leaves the production line.

[0062] Therefore, when a predetermined condition is met, the method executes a method based on the position V of the throttle valve 2 measured by the position sensor TPS. TPS_mesure Determine the first air flow db in the intake system 3 TPS The second step 110. Specifically, the position sensor TPS sends the position measurement value V to the computer ECU of the engine 1. TPS_mesure , the computer ECU is based on the measured value V TPS_mesure Determine the air flow rate in the intake system db TPS .

[0063] The third step of the method comprises determining the manifold pressure P measured by the pressure sensor 4 based on the manifold pressure P mesure Determine 120 a second air flow rate db in the intake system 3 p As for the position sensor TPS, the pressure sensor 4 will be used for the pressure measurement value P of the pressure in the manifold mesure The measured value P is sent to the computer ECU. mesure Determine the second air flow db in the intake system p .

[0064] Now there are two air flows db in the intake system of engine 1 TPS and db p Under ideal conditions, the two flow values ​​should be identical. However, even if the vehicle is new or has just undergone maintenance operations, this is often not the case, and db TPS ≠db p As is known, the difference between the two air flow rates corresponds to a defect in the tightness of clearance of at least one intake valve 5 or a blockage at the throttle valve 2. When the engine 1 is in the first stage, since the engine is considered new or has just been repaired, the defect is considered to be minimal.

[0065] The fourth step of the method comprises determining 130 a reference throttle correction factor F ref . Reference throttle correction factor F ref is chosen so that when it is added to the measured value V TPS_mesure When the two elements V TPS_mesure +F ref The sum should give a second air flow rate essentially equal to db p The corrected third air flow db cor (db cor =db p ). This corrected third air flow dbcor The calculation should be based on the determination of the first air flow db TPS The same calculation is performed, using the sum V TPS_mesure +F ref Instead of the measured value V TPS_mesure .

[0066] The purpose here is to make the first air flow db obtained based on the position of the throttle valve 2 TPS and the second air flow rate db obtained based on the manifold pressure p consistent.

[0067] Therefore, the computer ECU can determine the third air flow rate db for calculating the corrected cor Reference throttle correction factor F ref , in order to compensate the first air flow db TPS and the second air flow db p The original difference between .

[0068] Naturally, it is sufficient to correct one of the two measurements to make the two air flows consistent. In this sense, the correction factor F ref Can be applied to pressure measurement value P mesure , and the third air flow db cor Then it will be based on the second air flow db p The third air flow rate db is determined by calculation. cor will be substantially equal to the first air flow db TPS (db cor =db TPS ) without compromising the good functionality of the method.

[0069] The fifth step of the method consists in adding the reference injection correction factor LCL ref To correct 140 the injection command C from the concentration controller 8 inj The purpose of performing this correction is to obtain a stoichiometric air-fuel mixture based on the measurement value of the concentration probe 7. The air-fuel mixture should be ideal and therefore stoichiometric, but it will fluctuate under actual operating conditions. Then, the computer ECU receives the measurement value from the concentration probe 7 and determines the reference injection correction factor LCL ref The latter is sent to the concentration controller 8 so that it provides a modified injection command C inj ×(1+LCL ref ), considering the theoretical injection command C inj and the reference injection correction factor LCL established under actual conditions ref Both.

[0070] In addition, the theoretical injection command Cinj From the initial two air flow db TPS and db p In fact, since the stoichiometric mixture is based on the ideal air-fuel ratio, the injection command C inj is determined as a function of the air flow rate in the intake system.

[0071] Advantageously, the theoretical injection command C inj The air flow rate for which this calculation is not used to determine the corrected third air flow rate is obtained. In other words, if the reference measurement correction factor F ref is added to the measured value V of the throttle valve 2 position TPS_mesure If, however, a correction factor is added to the pressure measurement P mesure On, the injection command will be based on the air flow obtained from the position of throttle valve 2.

[0072] It should be understood that by executing the above steps 110 to 140, two reference correction factors are obtained, a reference correction factor TPS ref For the throttle valve and a reference correction factor LCL ref for injection. However, in order for these reference correction factors to actually represent the corrections to be performed in order to give a substantially constant air flow between two calculated air flows, and a substantially stoichiometric air-fuel mixture, it is necessary to repeat the steps described several times. In practice, the first set of steps is performed several times, insofar as the first correction may be a rough correction, in order to be able to store precise reference correction factors. These then allow the operation of the engine 1 to be optimized by aiming to obtain an air-fuel mixture as close as possible to the stoichiometric mixture, thus guaranteeing the ideal theoretical efficiency of the engine 1. To this end, Figure 2 shows the method returning to determine the first air flow db TPS The loop of step 110.

[0073] Only if the first set of steps has been executed for a certain duration T calibrage When the reference correction factor F for the throttle valve is stored 160 ref and the reference correction factor LCL for injection ref , during the duration T calibrage During this period, the first air flow db TPS Determination step 110, the second air flow db p Determination step 120, reference throttle correction factor F ref The determination step 130 and the correction step 140 have been performed multiple times.

[0074] Advantageously, the storing step 160 is only carried out after the engine 1 has been shut down 150 .

[0075] As mentioned above, the duration T determined calibrage is cumulative and acts as a timer. This means that even if the engine 1 is turned off, once it is turned on again and is under the predetermined conditions, the time counter increases without returning to zero and once it reaches the duration T calibrage , correction factor F for the throttle valve ref and the correction factor LCL for injection ref The measure also includes temporarily storing these values ​​in the memory of the computer ECU in a first phase until the duration T calibrage , so that the calibration (or adaptation) of the correction factor does not start again immediately after the engine is turned off. For this reason, a loop (dashed line) from the calibration step 140 back to the engine ignition step 100 is also shown.

[0076] In this case, the correction factor F for the throttle valve ref and the correction factor LCL for injection ref The correction values ​​represent those when the engine is in good condition, since they are obtained when the engine is new or when the engine has just undergone a maintenance operation.

[0077] The storage 160 of the reference correction factors terminates the first phase of the method and is therefore the last step of the first set of steps.

[0078] Now, during the second phase of the method, ie during normal operation of the engine 1, the current correction factor must be retrieved and compared with the reference correction factor F ref and LCL ref The comparison is made in order to reveal the fault.Now, the first step in the second set of steps is identical to those in the first stage.

[0079] Thus, when the engine 1 is in a predetermined condition, the first step of the second set of steps comprises the following steps: TPS_mesure Determine 210 a first air flow rate db′ in the intake system TPS .

[0080] The second step consists in determining the pressure P′ in the manifold based on the pressure measured by the pressure sensor 4. mesure Determine 220 a second air flow rate db′ in the intake system p .

[0081] The first step involves determining 230 the current throttle correction factor Fcourant , which is selected so that when the first air flow rate db′ TPS The same calculation is used to determine the corrected third air flow rate db′ cor is added to the measured value V′ TPS_mesure When the corrected third air flow db' cor Basically equal to the second air flow db' p .

[0082] In this third determination step 230 of the second set of steps, it is of course assumed that the current measurement value correction factor F courant is a correction factor F based on the reference measurement value in the first set of steps ref The air flow rate used during the determination was the same as the air flow rate determined in order to be able to compare the two results.

[0083] The fourth step consists in adding the current injection correction factor LCL courant To correct 240 the theoretical injection command C′ of the concentration controller 8 determined by the corresponding air flow inj , in order to obtain a substantially stoichiometric air-fuel mixture based on the measurement values ​​from the concentration probe 7. In this case, the corresponding air flow corresponds to the air flow selected in the first stage in order to determine the reference injection correction factor LCL ref For example, if the second air flow rate db is selected in the first stage p To determine the theoretical injection command C inj , then during this phase the selected mesure The second air flow rate db′ obtained p This allows you to compare the current injection correction factor LCL courant and the reference injection correction factor LCL ref .

[0084] It will be understood that the determination of these current correction factors allows the operation of the engine 1 to be optimized throughout its life, by aiming to continuously adapt the air-fuel mixture so as to bring it as close as possible to the stoichiometric mixture. In fact, as in the first stage, this is an adaptation to the actual conditions of use of the engine 1.

[0085] In a preferred embodiment, at each iteration of the method, the current correction factor F for the measured value is courant and the current correction factor LCL for injection courant The current correction factors calculated in iteration i thus replace the current correction factors calculated in iteration i-1 before iteration i in the memory.

[0086] Thus, at each ignition of the engine, the current correction factors may be initialized directly to the respective values ​​stored in the memory, these values ​​corresponding to the last values ​​they had before the engine was shut down.

[0087] It is also contemplated that each current correction factor may be stored in memory to replace the previous correction factor, for example, not at every iteration but every n iterations (which is done), or simply periodically.

[0088] At the end of the fourth step 240 of correction, the computer ECU possesses all the information that can reveal the presence of a fault.

[0089] Therefore, when referring to the throttle correction factor F ref and the current throttle correction factor F courant The absolute value of the difference between the two is greater than the threshold value Δ F In the fifth step 250, fault diagnosis is performed. In fact, the reference throttle correction factor F ref and the current throttle correction factor F courant The significant difference between the two air flow rates db′ TPS and db′ p This difference can be explained by a clearance fault of at least one intake valve 5 or a blockage at the throttle valve.

[0090] The cause of the fault must now be determined by identifying which air flow has deviated.

[0091] The injection command from the concentration controller 8 includes two items, the first of which corresponds to the theoretical command G′ inj , the theoretical order G′ inj is determined based on one of the two air flows, to which is added the injection correction factor, C′ inj ×(1+LCL courant ). Under the predetermined conditions of the engine 1, if the current injection correction factor LCL courant Almost equal to the reference injection correction factor (LCL courant ≈LCL ref ), then the theoretical command C inj and C′ inj Almost equal (C inj ≈C′ inj ), and therefore the flow (theoretical command C inj and C′ inj is estimated based on these flows) (e.g., from pressure measurements P mesure Determined air flow db p and db′ p ) is also almost equal (dbp ≈db′ p ). In this case, it is not the air flow rate db′ of the second stage p Relative to the air flow of the first stage db p There is a deviation. It is another air flow db' TPS In the second stage, a deviation occurs, and the air flow db' TPS Indicates where the fault is located.

[0092] Therefore, the method includes calculating the reference injection correction factor LCL ref and the current injection correction factor LCL courant The absolute value of the difference between V com The sixth step 260, (V com =|LCL ref -LCL courant |)

[0093] Four different situations can be distinguished, which are described as follows:

[0094] 1) On duty (V com ) is less than the determined threshold Δ LcL When (V com <Δ LcL ):

[0095] - If the theoretical injection command C′ inj The air flow db obtained from the throttle position TPS If it is determined, a diagnosis of a gap existing at at least one intake valve 5 is established at 261, and

[0096] - If the theoretical injection command C′ inj The air flow rate db obtained from the manifold pressure p If yes, a diagnosis of a fault at the throttle valve 2 is established 262 .

[0097] 2) On duty (V com ) is greater than the determined threshold Δ LcL When (V com >Δ LcL ):

[0098] - If the theoretical injection command C′ inj The air flow db obtained from the throttle position TPS If it is determined, the diagnosis of the fault at throttle valve 2 is established at 262, and

[0099] - If the theoretical injection command C′ inj The air flow rate db obtained from the manifold pressure p If it is determined, a diagnosis is established 261 that clearance exists at at least one intake valve 5 .

[0100] This method can be used in Figure 1 In particular, the method can be implemented in conventional lawn mowers for which engine maintenance is based solely on an operating hour counter and not on actual fault diagnosis.

Claims

1. A method for establishing maintenance diagnostics on an engine, the engine (1) comprising: a throttle valve (2) regulating the inlet of air into the intake system of the engine; a position sensor (TPS) that measures the position of the throttle valve (2); a manifold in fluid communication with the throttle valve (2); a pressure sensor (4) that measures the pressure in the manifold; at least one intake valve (5); a concentration probe (7) that measures the oxygen level; and a concentration controller (8) for varying the ratio of air to fuel in an air-fuel mixture, The method is characterized in that it comprises a first set of steps carried out at the end of a production line of the engine (1) or after maintenance of the engine (1), said first set of steps comprising the following steps: - ignition (100) of the engine (1), and when the engine (1) is in a predetermined condition, - Based on the position V of the throttle valve (2) measured by the position sensor (TPS) TPS_mesure Determine (110) a first air flow rate db in the intake system TPS , - based on the pressure P in the manifold measured by the pressure sensor (4) mesure Determine (120) a second air flow rate db in the intake system p , - Determine (130) the reference measurement correction factor (F ref ), the reference measurement correction factor is selected so that ... p or db TPS The same calculation is performed to determine the corrected third air flow rate db cor The reference measurement correction factor is added to the two air flow rates db p or db TPS When the measured value of one of the above is cor is essentially equal to the other of the two air flows, - By adding the reference injection correction factor (LCL ref ) to correct (140) by two air flow db TPS or db p The theoretical injection command C of the concentration controller (8) is determined by one of inj , in order to obtain a substantially stoichiometric air-fuel mixture based on the measurements from said concentration probe (7), and After at least one determined time duration, during which the first air flow rate db TPS Determination (110), the second air flow db p Determination (120), the reference measurement value correction factor (F ref ) are performed several times, - storing (160) said reference measurement correction factor (F ref ) and the reference injection correction factor (LCL ref ), and wherein the method comprises a second set of steps performed during normal operation of the engine (1) and when the engine (1) is in the predetermined condition, The second set of steps comprises the following steps: - Based on the position V' of the throttle valve (2) measured by the position sensor (TPS) TPS_mesure Determine (210) a first air flow rate db' in the intake system TPS , - Based on the pressure P' in the manifold measured by the pressure sensor (4) mesure Determine (220) a second air flow rate db' in the intake system p , - Determine (230) the current measurement value correction factor (F courant ), the current measurement correction factor is selected so that when the current measurement correction factor is based on the two air flow rates db' TPS or db' p The same calculation is performed to determine the corrected third air flow rate db' cor The current measurement correction factor is added to the two air flow rates db' TPS or db' p When the measured value of the corresponding one of the above is , the corrected third air flow rate db' cor Basically equal to two air flow db' TPS or db' p The other one, - By adding the current injection correction factor (LCL courant ) to correct (240) the injection command C' of the concentration controller (8) determined by the corresponding air flow inj , in order to obtain a substantially stoichiometric air-fuel mixture based on the measurements from said concentration probe (7), and When the reference measurement correction factor (F ref ) and the current measurement correction factor (F courant The absolute value of the difference between F hour, - Establish (250) maintenance diagnostics, - Calculate (260) the reference injection correction factor (LCL) ref ) and the current injection correction factor (LCL courant ) is the absolute value of the difference between com ),as well as: 1) When the absolute value (V com ) is less than the determined threshold Δ LcL hour, - If the injection command C' inj The first air flow rate db' obtained from the position of the throttle valve (2) TPS is determined, then a diagnosis of the clearance at the at least one intake valve (5) is established (261), and - If the injection command C' inj The second air flow rate db' obtained from the manifold pressure p If it is determined, a diagnosis of a blockage at the throttle valve (2) is established (262), or 2) On duty (V com ) is greater than the determined threshold Δ LcL hour, - If the injection command C' inj The first air flow rate db' obtained from the position of the throttle valve (2) TPS If determined, a diagnosis of a blockage at the throttle valve (2) is established (262), and - If the injection command C' inj The second air flow rate db' obtained from the manifold pressure p If determined, a diagnosis of the clearance at the at least one intake valve (5) is established (261).

2. The method according to the preceding claim, characterized in that The predetermined conditions of the engine (1) include an engine temperature between two first predetermined thresholds, an air temperature between two second predetermined thresholds, an air flow in the intake system between two third predetermined thresholds, an engine speed between two fourth predetermined thresholds for a duration at least equal to a fifth predetermined threshold, and an engine load between two sixth predetermined thresholds.

3. The method according to any one of claims 1 or 2, characterized in that At each ignition of the engine, the current measurement value correction factor (F courant ) and the current injection correction factor (LCL courant ) are respectively initialized to the current measurement correction factor (F courant ) and the current injection correction factor (LCL courant ).

4. The method according to claim 1 or 2, characterized in that The storing step (160) is only performed after the engine (1) has been shut down (150).

5. A computer program product comprising code instructions recorded on a carrier readable by a computer (ECU) comprising a memory, so as to implement the steps of the method according to any one of the preceding claims when the program is executed on a computer (ECU) comprising a memory.

6. A computer (ECU), characterized in that: The computer (ECU) is adapted to control the ignition and concentration controller (8) of the engine (1), and is adapted to receive measurement values ​​from the position sensor (TPS) of the throttle valve (2), the pressure sensor (4) of the manifold and the concentration probe (7), And wherein the computer (ECU) is further adapted to implement the steps of the method according to any one of claims 1 to 4.

7. An engine (1), characterized in that The engine comprises: a throttle valve (2) regulating the inlet of air into an intake system of the engine; a position sensor (TPS) measuring the position of the throttle valve (2); a manifold in fluid communication with the throttle valve (2); a pressure sensor (4) measuring the pressure in the manifold; at least one intake valve (5); a concentration probe (7) measuring the oxygen level; and a concentration controller (8) for varying the ratio of air to fuel in an air-fuel mixture. And the engine further comprises a computer (ECU) implementing the steps of the method according to any one of claims 1 to 4.

8. A lawn mower, characterized in that: It comprises an engine (1) as claimed in claim 7.

Images