Noise investigation method of engine

Abstract

To provide a noise investigation method of an engine for determining whether or not a generation source of the noise of an engine generated by the transmission of vibration to a fuel injection system component is a specific engine component.SOLUTION: When a frequency of noise generated at an engine by the transmission of the vibration of a first engine component to a second engine component which is different from the first engine component is a natural frequency of the first engine component, and an operation state of the engine is a prescribed operation state that a resonance is generated at the first engine component, a noise investigation method of the engine determines that a generation source of the noise is the first engine component, and when the noise generation source is other than a specified case, a computer performs processing for determining that the generation source of the noise is other than the first engine component.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for investigating abnormal noise in an engine. [Background technology]

[0002] Engine noise can be roughly divided into combustion noise caused by combustion and mechanical noise caused by the movement of mechanical parts. Fuel injection system noise caused by fuel injection accounts for a large proportion of mechanical noise. Fuel injection system noise is noise from parts that make up the fuel injection system. Parts that make up the fuel injection system include, for example, injectors, common rails, high-pressure fuel pipes, and nozzle supports. Note that technology for detecting fuel injection system noise is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-180888 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this way, by detecting fuel injection system noise, it is possible to identify that the cause of engine noise is a component that constitutes the fuel injection system (hereinafter referred to as a fuel injection system component). However, it is not possible to identify whether the fuel injection system noise is caused by the vibration of a specific engine component, such as a PCV (Positive Crankcase Ventilation) valve, being transmitted to the fuel injection system component.

[0005] Therefore, an object of the present invention is to provide a method for investigating abnormal engine noise that determines whether the source of abnormal engine noise caused by vibrations transmitted to fuel injection system components is a specific engine component. [Means for solving the problem]

[0006] The engine abnormal noise investigation method of the present invention is a method in which a computer executes processing to determine that the source of the abnormal noise is the first engine component when the frequency of the abnormal noise generated in the engine due to vibration of a first engine component being transmitted to a second engine component different from the first engine component is the natural frequency of the first engine component and the operating state of the engine is a predetermined operating state in which resonance occurs in the first engine component, and to determine that the source of the abnormal noise is other than the first engine component when the specific case is not the specific case. Effect of the Invention

[0007] According to the present invention, it is possible to determine whether or not a predetermined engine part is the source of abnormal engine noise caused by vibrations transmitted to a fuel injection system part. [Brief description of the drawings]

[0008] [Figure 1] This is an example of an engine noise investigation system. [Diagram 2] 1 is an example of a cross-sectional view of a PCV valve. [Diagram 3] 4 is a flowchart showing an example of the operation of the engine abnormal noise investigation system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] As shown in FIG. 1, the engine abnormal noise investigation system ST includes a mobile terminal 100 and a server device 200 as computers. The mobile terminal 100 may be a smart device such as a smartphone or a tablet terminal, or may be a PC (Personal Computer). The mobile terminal 100 and the server device 200 each include a processor and a memory. The processor includes, for example, a CPU (Central Processing Unit). The memory includes, for example, a RAM (Random Access Memory) and a ROM (Read Only Memory). The processor executes a program stored in the memory, whereby the engine abnormal noise investigation system ST executes the engine abnormal noise investigation method. The engine abnormal noise investigation method may correspond to a flowchart described below.

[0011] The mobile terminal 100 and the server device 200 are connected via a communication network NW and a mobile base station BS. The communication network NW includes either the Internet or a LAN (Local Area Network), or both. The mobile terminal 100 and the server device 200 transmit and receive various data to and from each other through wireless and wired communication.

[0012] The vehicle 300 is equipped with an engine 1. The engine 1 is equipped with a cylinder block 12 in which four cylinders 11 are formed and aligned in series in one direction, and a cylinder head 13 attached to the upper part of the cylinder block 12. One of the four cylinders 11 is shown in FIG. 1. A piston 14 is inserted in each cylinder 11 in a reciprocating manner. Each piston 14 is connected to a crankshaft 16 via a connecting rod 15.

[0013] An intake passage 2 of the engine 1 is provided with an air cleaner 21 that filters the intake air, and an air flow meter 93 that outputs a signal according to the amount of intake air. The intake passage 2 is also provided with an intake air temperature sensor 94 that outputs a signal according to the intake air temperature, and a throttle valve 23 that adjusts the amount of intake air. The throttle valve 23 is driven by a throttle motor 23a. The intake passage 2 includes an intake manifold 24 that distributes the intake air to each cylinder 11, and an intake port 25 provided for each cylinder 11 and connected to the intake manifold 24.

[0014] On the other hand, an O2 sensor 96 that outputs a signal corresponding to the oxygen concentration in the exhaust gas, and a catalytic converter 32 for exhaust purification are provided in the exhaust passage 3. The exhaust passage 3 includes exhaust ports 33 provided for each cylinder 11, and an exhaust manifold 34 that collects the exhaust ports 33.

[0015] The cylinder head 13 is provided with an intake valve 26 that opens and closes the intake port 25, and an exhaust valve 36 that opens and closes the exhaust port 33. The intake valve 26 and the exhaust valve 36 are driven to open and close in synchronization with the crankshaft 16 by a valve mechanism 17 that includes a cam and the like.

[0016] An injector 4 and a spark plug 5 are attached to a cylinder head 13 of each cylinder 11 so as to face the inside of the cylinder 11. When the injector 4 injects fuel from a fuel tank TK into each cylinder 11, an air-fuel mixture is formed in the cylinder 11, and the mixture is ignited by a spark from the spark plug 5 and burns. Combustion pressure generated by the combustion is transmitted to a piston 14, causing the piston 14 to reciprocate. The reciprocating motion of the piston 14 is transmitted to a crankshaft 16 via a connecting rod 15, converted into rotational motion, and output as the output of the engine 1.

[0017] Exhaust gas after combustion is guided to an exhaust passage 3, purified by a catalytic converter 32, and then released into the atmosphere via a muffler (not shown). Fuel used in the engine 1 includes, for example, alcohol fuel such as ethanol, and a mixed fuel of alcohol and gasoline.

[0018] An oil pan 18 that stores lubricating oil OL is attached to the lower portion 12a of the cylinder block 12. The lower portion 12a of the cylinder block 12 and the oil pan 18 are combined to form a crankcase 19 that accommodates the crankshaft 16.

[0019] Here, the engine 1 is provided with a PCV device 7. The PCV device 7 guides blow-by gas, which has blown into the crankcase 19 through the gap between the inner circumferential surface of the cylinder 11 and the outer circumferential surface of the piston 14, to the intake passage 2. The blow-by gas is a gas that contains unburned fuel. The PCV device 7 sends the blow-by gas into the cylinder 11 via the intake passage 2. By mixing the blow-by gas with fresh air and burning it, the release of unburned fuel into the atmosphere is suppressed.

[0020] More specifically, the cylinder block 12 and the cylinder head 13 are provided with a blow-by gas communication passage 71 for guiding the blow-by gas present in the crankcase 19 into the cam chamber 13a. The cam chamber 13a and the intake passage 2 (more specifically, the surge tank 27 or the upstream side of the surge tank 27) are connected to each other by a blow-by gas return passage 72 for guiding the blow-by gas to the intake passage 2.

[0021] A PCV valve 73 for preventing backflow of blow-by gas and adjusting the flow rate is provided at the upstream end of the blow-by gas recirculation passage 72. The PCV valve 73 is an example of a first engine part. When the PCV valve 73 is opened, the blow-by gas present in the crankcase 19 is guided to the intake passage 2.

[0022] The above-mentioned cam chamber 13a is constructed by attaching the oil separator 13b to the cylinder head 13. The oil separator 13b is an example of a second engine part different from the PCV valve 73. Although not shown, inner walls of various shapes are provided in a labyrinth shape inside the oil separator 13b. That is, the cam chamber 13a includes inner walls of various shapes provided in the oil separator 13b.

[0023] The oil mist contained in the blow-by gas collides with the inner wall of the oil separator 13b, whereby the oil mist is liquefied and separated and removed from the blow-by gas. The blow-by gas from which the oil mist has been separated and removed is introduced into the PCV valve 73 in a state in which it contains unburned fuel.

[0024] The operating state of the engine 1 is controlled by an engine ECU (Electronic Control Unit) 8. The engine ECU 8 is equipped with a CPU, RAM, ROM, a communication interface, etc. The ROM of the engine ECU 8 stores various control programs related to engine control, maps to be referenced when executing the various control programs, etc. The CPU of the engine ECU 8 executes arithmetic processing based on the various control programs and maps stored in the ROM. The RAM of the engine ECU 8 temporarily stores the results of the arithmetic processing by the CPU, data input from each sensor, etc.

[0025] The engine ECU 8 is connected to various sensors, such as a crank position sensor 91, a water temperature sensor 92, an air flow meter 93, an intake air temperature sensor 94, a throttle opening sensor 95, and an O2 sensor 96. Although not shown, an intake pressure sensor provided in the surge tank 27 is also connected to the engine ECU 8. The intake pressure sensor detects a surge tank internal pressure that indicates the internal pressure inside the surge tank 27. The engine ECU 8 can estimate the engine speed based on the crank position detected by the crank position sensor 91 and a known method. The engine ECU 8 can also estimate an intake manifold pressure that indicates the pressure of the intake manifold 24 based on the surge tank internal pressure and a known method. The engine ECU 8 may specify the surge tank internal pressure as the intake manifold pressure.

[0026] On the other hand, the engine ECU 8 is connected to a throttle motor 23a that drives the throttle valve 23, the injector 4, an igniter 51, and the like. The engine ECU 8 controls various parts provided in the engine 1 based on detection signals from various sensors. For example, the engine ECU 8 controls the ignition timing of the spark plug 5. The engine ECU 8 may also control the drive of the throttle motor 23a.

[0027] The mobile terminal 100 accesses the engine ECU 8 of the vehicle 300 through wireless or wired communication based on an operation by an operator of a vehicle manufacturer, an engine parts manufacturer, a vehicle dealer, a vehicle repair shop, or the like. When the mobile terminal 100 accesses the engine ECU 8, the mobile terminal 100 acquires vehicle specifications and a time-series operating state from the engine ECU 8. The vehicle specifications include, for example, the dimensions of the vehicle 300, the type and specifications of the engine 1, and installed parts. The operating state includes, for example, the engine speed of the engine 1 and the above-mentioned intake manifold pressure. In FIG. 1, the mobile terminal 100 acquires the vehicle specifications and the operating state from outside the vehicle 300, but it may also acquire them from inside the vehicle 300.

[0028] Furthermore, the mobile terminal 100 records abnormal sounds generated in the engine 1 based on the operation of the operator. The mobile terminal 100 is equipped with a microphone. When the engine 1 is operating, the mobile terminal 100 records abnormal sounds generated in the engine 1 via the microphone. The mobile terminal 100 acquires the vehicle specifications and the driving state, and upon recording an abnormal sound, cooperates with the server device 200 to determine whether the source of the abnormal sound is the PCV valve 73 or not, based on the vehicle specifications, the driving state, the abnormal sound, etc.

[0029] Next, the configuration of the PCV valve 73 and the principle of generation of abnormal noise will be described with reference to FIG.

[0030] The PCV valve 73 has an inlet hole 73a that introduces the blow-by gas GS into the PCV valve 73. The PCV valve 73 has a locking portion 73b on the side where the inlet hole 73a opens. The inlet hole 73a opens at the center of the locking portion 73b. The PCV valve 73 also has a discharge hole 73c that discharges the blow-by gas GS. The PCV valve 73 has a cylindrical hose connection portion 73d. The discharge hole 73c opens into the hose connection portion 73d.

[0031] The PCV valve 73 includes a body 73e. An O-ring 73f is attached to the body 73e. A male thread portion 73g having a male thread for fastening the PCV valve 73 to the oil separator 13b is provided on a portion of the body 73e closer to the hose connection portion 73d than the O-ring 73f. The body 73e includes a combination of a first unit UT1 and a second unit UT2. The locking portion 73b is provided on the first unit UT1. The male thread portion 73g is provided on the outer circumferential surface of the first unit UT1. The hose connection portion 73d is provided on the second unit UT2.

[0032] The first unit UT1 accommodates a valve body 73h that is displaceable in the direction of extension of an axis C1, which is the central axis of the body 73e. The valve body 73h is formed in a cylindrical shape that is tall in the direction of extension of the axis C1. The diameter of the valve body 73h is made smaller toward the discharge hole 73c. ​​The first unit UT1 includes a valve seat 73i on which the valve body 73h can be seated. The inlet hole 73a is closed by the valve body 73h being seated on the valve seat 73i.

[0033] The first unit UT1 is provided with a main spring 73j that biases the valve body 73h toward the valve seat 73i. When an external force that exceeds the biasing force of the main spring 73j occurs, the valve body 73h moves away from the valve seat 73i and the inlet hole 73a is opened.

[0034] The first unit UT1 is also provided with a flow rate adjustment section 73k. The flow rate adjustment section 73k has an annular shape on the inside through which the valve body 73h can pass. The flow rate adjustment section 73k restricts the flow path from the inlet hole 73a to the discharge hole 73c. ​​Since the diameter of the valve body 73h is smaller toward the discharge hole 73c, when the valve body 73h is displaced in the extension direction of the axis C1 and passes through the flow rate adjustment section 73k, the flow path cross-sectional area, which is the gap between the flow rate adjustment section 73k and the valve body 73h, is changed. By changing the flow path cross-sectional area, the flow rate of the blow-by gas GS passing through the PCV valve 73 is adjusted.

[0035] The second unit UT2 is attached to the end of the first unit UT1 on the discharge hole 73c side. The second unit UT2 is provided with a cushion spring 73l for restricting the displacement of the valve body 73h in the direction of the discharge hole 73c.

[0036] The PCV valve 73 is attached to the oil separator 13b by fastening a male thread portion 73g of the body 73e to a female thread portion 73n including a female thread provided on the inner peripheral surface of the valve mounting portion 73m of the oil separator 13b. An O-ring 73f attached to the body 73e seals between the outer peripheral surface of the body 73e and the inner peripheral surface of the valve mounting portion 73m.

[0037] With this configuration, the PCV valve 73 adjusts the flow rate of the blow-by gas GS. That is, the valve body 73h is displaced so that the differential pressure between the first atmospheric pressure on the crankcase 19 side and the second atmospheric pressure on the intake manifold 24 side (hereinafter referred to as the front-rear differential pressure) and the reaction force (i.e., the restoring force) with the main spring 73j are balanced. The crankcase 19 side is the upstream side of the blow-by gas GS. The intake manifold 24 side is the downstream side of the blow-by gas GS.

[0038] This adjusts the flow rate of the blow-by gas GS. Due to the configuration of the PCV valve 73, when the forced vibration frequency due to the external pressure (specifically, the first and second atmospheric pressures) matches the natural vibration frequency of the PCV valve 73, a resonance phenomenon occurs in the valve body 73h. When the resonance phenomenon occurs, for example, the valve body 73h vibrates violently.

[0039] More specifically, when the engine 1 is running, the pressure differential across the PCV valve 73 fluctuates periodically due to pressure pulsation in the crankcase 19 caused by intake pulsation and the reciprocating motion of the piston 14. The period of this fluctuation is determined based on the number of cylinders 11 in the engine 1 and the arrangement of the cylinders 11. For example, if the engine 1 is an in-line four-cylinder engine, the period of fluctuation occurs twice per rotation of the engine 1.

[0040] In an operating state in which such a fluctuation period corresponds to the natural frequency of the PCV valve 73, the valve body 73h vibrates violently due to a resonance phenomenon and collides with the body 73e and the flow rate adjustment unit 73k. For example, the valve body 73h vibrates violently three-dimensionally, such as in the vertical direction corresponding to the displacement direction of the piston 14 and in the horizontal direction corresponding to the arrangement direction of the cylinders 11. This causes the valve body 73h to collide with the body 73e and the flow rate adjustment unit 73k. In this way, the collision of the valve body 73h with the body 73e causes the PCV valve 73 to vibrate, and a collision sound between the valve body 73h and the body 73e is generated in the PCV valve 73.

[0041] When the PCV valve 73 vibrates, the vibration of the PCV valve 73 is transmitted to, for example, the oil separator 13b to which the PCV valve 73 is attached. The vibration noise caused by this vibration is amplified at the resonance frequency and radiated as a vibration noise. As a result, the frequency of the abnormal noise generated in the engine 1 can be uniquely identified for each engine 1. Due to this principle, the abnormal noise is generated in the engine 1.

[0042] Therefore, the presence or absence of abnormal noise and the magnitude of the abnormal noise are determined by the position of the valve body 73h, as well as the magnitude and fluctuation period of the pressure difference between the front and rear of the engine 1. That is, the conditions for the occurrence of abnormal noise can be expressed by the relationship between the engine speed and the intake manifold pressure of the engine 1 for each combination of the PCV valve 73 and the model of the engine 1. For this reason, if the server device 200 has a DB (database) that defines this relationship for each of the above combinations, the mobile terminal 100 can access this DB and investigate and identify whether the source of the abnormal noise is the PCV valve 73. Note that such a DB may be constructed, for example, as shown in Table 1 below.

[0043] [Table 1]

[0044] In FIG. 2, the inner diameter of the valve mounting portion 73m is indicated as diameter R1. Also, the dimension of the locking portion 73b in the direction perpendicular to the axis C1 is indicated as width D1. Width D1 represents the dimension of the portion where the dimension of the locking portion 73b is maximum in the direction perpendicular to the axis C1. As shown in FIG. 2, the width D1 of the locking portion 73b is larger than the diameter R1. That is, the locking portion 73b is provided at the end of the PCV valve 10 on the inlet hole 72a side in a shape that prevents it from being inserted into the valve mounting portion 73m.

[0045] 2, the dimension of the second unit UT2 in a direction perpendicular to the axis C1 is smaller than the diameter R1. Specifically, when the dimension of the portion of the second unit UT2 where the diameter is maximum in the direction perpendicular to the axis C1 is width D2, the width D2 of the second unit UT2 is smaller than the diameter R1. Since the maximum diameter of the second unit UT2 is width D2, the diameter of the hose connection portion 73d is smaller than width D2.

[0046] Next, the operation of the engine abnormal noise investigation system ST will be described with reference to FIG.

[0047] For example, when an operator starts an abnormal sound diagnosis application program installed in the mobile terminal 100 to investigate an abnormal sound generated in the engine 1, the mobile terminal 100 acquires vehicle specifications (step S1). Specifically, the mobile terminal 100 accesses the engine ECU 8 and acquires the vehicle specifications stored in the engine ECU 8 by wireless communication. By acquiring the vehicle specifications, the mobile terminal 100 can identify the combination of the engine model and the PCV valve part number of the PCV valve 73 contained in the vehicle specifications.

[0048] When the processing of step S1 is completed, the mobile terminal 100 acquires the natural frequency and the abnormal sound generation conditions (step S2). More specifically, the mobile terminal 100 transmits to the server device 200 the combination of the engine model and PCV valve part number that can be identified in the processing of step S1. The server device 200 references the above-mentioned DB (see Table 1), extracts from the DB the natural frequency and the abnormal sound generation conditions of the PCV valve 73 that correspond to this combination, and transmits them to the mobile terminal 100. In this way, the mobile terminal 100 acquires the natural frequency and the abnormal sound generation conditions. The abnormal sound generation conditions include a combination of the engine speed and the intake manifold pressure when abnormal sound caused by the PCV valve 73 occurs.

[0049] When the process of step S2 is completed, the mobile terminal 100 instructs the engine 1 to operate under the conditions under which an abnormal sound of unknown cause occurs (step S3). Here, the abnormal sound generated by the engine 1 may be caused by vibration of the PCV valve 73 or may not be caused by vibration of the PCV valve 73. An example of an abnormal sound not caused by vibration of the PCV valve 73 is an abnormal sound generated by the sudden opening of the throttle valve 23. The mobile terminal 100 specifies one of various abnormal sound generating conditions registered in advance in the mobile terminal 100, and instructs the engine 1 to operate. As a result, the engine 1 operates and transitions to an operating state.

[0050] When the process of step S3 is completed, the mobile terminal 100 records the abnormal sound (step S4). As described above, the mobile terminal 100 operates the engine 1 under the abnormal sound generation condition, and therefore, an abnormal sound is generated from the engine 1. The mobile terminal 100 records the abnormal sound generated from the engine 1 via the microphone of the mobile terminal 100.

[0051] When the process of step S4 is completed, the mobile terminal 100 acquires the operating state (step S5). For example, the mobile terminal 100 accesses the engine ECU 8 and acquires the operating state of the engine 1 from the engine ECU 8. Since the operating state includes the engine speed and the intake manifold pressure during operation under the abnormal noise generation condition, the mobile terminal 100 can acquire the engine speed and the intake manifold pressure as the operating state. Note that the order of the process of step S4 and the process of step S5 may be reversed. The mobile terminal 100 may execute the process of step S4 and the process of step S5 in parallel.

[0052] When the process of step S5 is completed, the mobile terminal 100 identifies the frequency of the abnormal sound (step S6). More specifically, the mobile terminal 100 identifies the frequency of the abnormal sound recorded in the process of step S4 by using a frequency analysis function incorporated in the abnormal sound diagnosis application program. Note that the mobile terminal 100 may transmit the abnormal sound recorded in the process of step S4 as data to the server device 200, and the server device 200 may identify the frequency of the abnormal sound.

[0053] When the process of step S6 ends, the mobile terminal 100 determines whether or not a predetermined condition is satisfied (step S7). More specifically, the mobile terminal 100 determines whether or not the frequency of the abnormal sound identified in the process of step S6 as the predetermined condition is the natural frequency acquired in the process of step S2. The mobile terminal 100 also determines whether or not the combination of engine speed and intake manifold pressure acquired as the operating state in the process of step S5 as the predetermined condition is the combination of engine speed and intake manifold pressure acquired as the abnormal sound generation condition in the process of step S2.

[0054] In a specific case where the frequency of the abnormal sound is the natural frequency and the combination of the engine speed and the intake manifold pressure acquired as the operating state is the combination of the engine speed and the intake manifold pressure acquired as the abnormal sound occurrence condition, the mobile terminal 100 determines that the predetermined condition is satisfied (step S7: YES).On the other hand, in cases other than this specific case, the mobile terminal 100 determines that the predetermined condition is not satisfied (step S7: NO).

[0055] If the predetermined condition is satisfied, the mobile terminal 100 determines that the source of the abnormal sound is the PCV valve 73 (step S8) and ends the process. On the other hand, if the predetermined condition is not satisfied, the mobile terminal 100 determines that the source of the abnormal sound is an engine part other than the PCV valve 73 (step S9) and ends the process.

[0056] In this way, according to the engine abnormal noise investigating method of this embodiment, the mobile terminal 100 can determine, either alone or in cooperation with the server device 200, whether or not the source of the abnormal noise of the engine 1 is the PCV valve 73. Since unburned fuel remains in the blow-by gas GS, the oil separator 13b, which is different from the PCV valve 73, corresponds to an engine part that injects fuel.

[0057] When the valve body 73h of the PCV valve 73 vibrates violently due to the resonance phenomenon and hits the body 73e or the like, the vibration of the PCV valve 73 is transmitted to the oil separator 13b. In this way, abnormal noise is generated in the engine 1 due to the vibration of the PCV valve 73. According to the method for investigating abnormal engine noise, it can be determined whether the source of such abnormal engine noise is the PCV valve 73.

[0058] Although a preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims.

[0059] For example, in the above-described embodiment, the mobile terminal 100 and the server device 200 are used in combination, but all of the processes executed by the server device 200 may be executed by the mobile terminal 100 alone. Also, in the above-described embodiment, the PCV valve 73 is described as an example of the first engine part, but the first engine part does not have to be limited to the PCV valve 73. For example, the first engine part may be an engine part that has a valve and a spring and in which a resonance phenomenon may occur, such as a VSV (Vacuum Switching Valve) or a VRV (Vacuum Regulating Valve). [Explanation of symbols]

[0060] 1 Engine 13b Oil separator 19 Crankcase 24 Intake manifold 73 PCV valve 73e Body 73h Valve body 73j main spring 73k flow adjustment section 73l Cushion spring 100 Mobile Devices 200 Server device 300 vehicles GS Blow-by gas

Claims

[Claim 1] determining that the source of the abnormal noise is the first engine component in a specific case where a frequency of the abnormal noise generated in the engine due to vibration of a first engine component being transmitted to a second engine component different from the first engine component is the natural frequency of the first engine component and the operating state of the engine is a predetermined operating state in which resonance occurs in the first engine component; determining that the source is other than the first engine part when the particular case is not present; A method for investigating abnormal engine noise in which processing is performed by a computer.

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