Patent Description:
In some vehicles such as construction machineries equipped with multi-cylinder internal combustion engines, the controller of the internal combustion engine has a failure diagnostic function that enables detection of failures, such as disconnection and short circuit, by monitoring the energization of the injectors that inject fuel into the cylinders. Although this failure diagnostic function detects electrical failures of the injectors, it is difficult for the function to detect a mechanical failure of the injectors due to a fuel leak or stiffness. For this reason, failures are often not noticed until a performance deterioration due to the mechanical failure occurs or an obvious abnormal state such as white smoke or black smoke occurs. This means that a malfunction suddenly happens. Such a sudden malfunction may cause downtime of the construction machinery and hinder the stable operation of the construction machinery.

A method then has been proposed, in which fuel injection is intentionally stopped for each cylinder, and a mechanical failure is diagnosed by the operator based on changes in the operating sound of the internal combustion engine based on the hearing of the operator. This method, however, is based on the sensory perception of human hearing, and it not only depends on the rich experiences and advanced knowledge of the operator, but also causes a problem that the results are likely to vary.

<CIT> discloses a fuel injector malfunction monitoring apparatus in which spectral data of the ultrasound component of the operating noise of the combustion engine are monitored.

<CIT> discloses a combustion engine monitoring method in which an actual spectrum is compared with a reference spectrum.

<CIT> discloses a method for conditioned based monitoring of an assembly using a frequency over time evaluation.

Patent Literature <NUM> discloses a method of identifying a faulty injector using the undulation in the rotation fluctuation during one cycle of the cylinders of the multi-cylinder internal combustion engine.

Patent Literature <NUM> discloses a method for identifying a faulty injector based on the indicated fuel injection amount. Specifically, this method stops two of the injectors at the same time to measure a change in the indicated fuel injection amount, and then identifies a faulty injector based on the fact that the faulty injector does not inject fuel.

The method described in Patent Literature <NUM> requires the setting of a threshold for the rotational fluctuation to identify a faulty injector based on the undulation of the fluctuation. In order to improve the diagnostic accuracy, it is also necessary to develop a model tailored to the housing and the environment in which the internal combustion engine operates.

The method described in Patent Literature <NUM> has less effect of the combination of cylinders that stop at the same time when the number of cylinders is large. When the number of cylinders is small such as four cylinders, however, the change in the indicated fuel injection amount may differ depending on the combination of two cylinders that stop at the same time, and this may degrade the diagnostic accuracy.

It is the object of the invention to provide an injector failure diagnostic device and method capable of diagnosing mechanical failures of injectors simply and with high accuracy.

The above object is accomplished by the features of the independent claims.

An injector failure diagnostic device is for a multi-cylinder internal combustion engine having a plurality of injectors, each injector injects fuel to a corresponding cylinder. The injector failure diagnostic device comprises the features of claim <NUM>. It includes an operating sound obtainment unit configured to obtain a current operating sound that is the operating sound when all of the injectors are operated, and obtain a pseudo-failure operating sound sequentially for each of the injectors, the pseudo-failure sound being the operating sound generated by stopping the fuel injection from one injector while maintaining the operation of the remaining injectors; and a faulty injector identification unit configured to determine whether or not the pseudo-failure operating sound of each injector obtained by the operating sound obtainment unit is similar to the current operating sound to identify a faulty injector. Claim <NUM> recites further features.

The injector failure diagnostic device according to the present invention is configured so that the operating sound obtainment unit obtains the current operating sound and the pseudo-failure operating sound for each injector, and the faulty injector identification unit determines whether the pseudo-failure operating sound of each injector is similar or not to the current operating sound to identify a faulty injector. The injector failure diagnostic device therefore easily diagnoses the mechanical failure of the injectors and easily identifies the faulty injector. The accuracy of diagnosis improves as compared with the diagnosis with human hearing.

A method for diagnosing an injector failure diagnosis failures in a multi-cylinder internal combustion engine having a plurality of injectors, each injector injects fuel to a corresponding cylinder. The method has the features of claim <NUM> and includes a current operating sound obtainment step of obtaining a current operating sound that is the operating sound when all of the injectors are operated; a pseudo-failure operating sound obtainment step of obtaining a pseudo-failure operating sound sequentially for each of the injectors, the pseudo-failure sound being the operating sound generated by stopping the fuel injection from one injector while maintaining the operation of the remaining injectors; and a diagnosis step of determining whether or not the pseudo-failure operating sound of each injector obtained by the pseudo-failure operating sound obtainment step is similar to the current operating sound obtained at the current operating sound obtainment step to identify a faulty injector. Claim <NUM> recites further features.

In the method for diagnosing an injector failure according to the present invention, the current operating sound obtainment step obtains the current operating sound, the pseudo-failure operating sound obtainment step obtains the pseudo-failure operating sound for each injector, and the diagnosis step determines whether the pseudo-failure operating sound of each injector is similar or not to the current operating sound to identify a faulty injector. The method therefore easily diagnoses the mechanical failure of the injectors and easily identifies the faulty injector. The accuracy of diagnosis improves as compared with the diagnosis with human hearing.

The above aspects of the present invention enable simple and accurate diagnosis of mechanical failures of injectors, and also easy identification of a faulty injector.

The following describes some embodiments of an injector failure diagnostic device and a method for injector failure diagnosis according to the present invention, with reference to the drawings. Like reference numerals designate like parts throughout the drawings of the present specification to omit their redundant explanations.

<FIG> is a schematic view showing the configuration of an injector failure diagnostic device according to a first embodiment. The injector failure diagnostic device <NUM> of the present embodiment is to diagnose a failure of a plurality of injectors installed in a multi-cylinder internal combustion engine <NUM>.

The multi-cylinder internal combustion engine <NUM>, which is mounted on a construction machinery, for example, includes four cylinders (first cylinder <NUM>, second cylinder <NUM>, third cylinder <NUM> and fourth cylinder <NUM>) arranged in series, injectors (first injector <NUM>, second injector <NUM>, third injector <NUM> and fourth injector <NUM>) that inject fuel into the inside of the corresponding cylinders, and an injector controller <NUM> that controls the operation of the injectors.

In one example, the injector controller <NUM> includes a microcomputer made up of the combination of a central processing unit (CPU) that executes calculations, a read only memory (ROM) as a secondary storage device that records programs for the calculations, and a random access memory (RAM) as a temporary storage of the calculation progress or temporary control variables. The injector controller <NUM> controls operations including stopping and resuming of the injectors by executing the stored programs.

The injector failure diagnostic device <NUM> is installed in a mobile terminal such as a smartphone, a tablet terminal, a mobile phone, or a personal digital assistant (PDA). The following describes an example of the injector failure diagnostic device <NUM> that is installed in a smartphone <NUM>, which may be other mobile terminals such as a tablet terminal, a mobile phone, and a PDA.

The injector failure diagnostic device <NUM> installed in the smartphone <NUM> is configured to be communicable with the multi-cylinder internal combustion engine <NUM>. For example, the multi-cylinder internal combustion engine <NUM> is equipped with a serial/WIFI converter (not shown), so that the injector failure diagnostic device <NUM> communicates with the multi-cylinder internal combustion engine <NUM> via the serial/WIFI converter. Bluetooth (registered trademark) or wireless local area network (LAN) may be used instead of the serial/WIFI converter.

As shown in <FIG>, the injector failure diagnostic device <NUM> includes a pseudo failure unit <NUM>, an operating sound obtainment unit <NUM>, a faulty injector identification unit <NUM>, and a diagnosis result output unit <NUM>.

The pseudo failure unit <NUM>, in cooperation with the injector controller <NUM> of the multi-cylinder internal combustion engine <NUM>, is configured to generate a pseudo failure to intentionally stop the fuel injection from each injector and then cancel the pseudo failure after a lapse of a predetermined time. Specifically, the pseudo failure unit <NUM> generates a pseudo failure that stops one of the four injectors (i.e., of the first injector <NUM>, the second injector <NUM>, the third injector <NUM>, and the fourth injector <NUM>) while maintaining the operation of the remaining injectors via the injector controller <NUM>. The pseudo failure unit <NUM> generates this pseudo failure for the four injectors in turn.

In one example, the pseudo failure unit <NUM> firstly generates a first pseudo failure via the injector controller <NUM>, which stops the fuel injection of the first injector <NUM> and maintains the operation of the second to fourth injectors <NUM> to <NUM>. After a predetermined time elapses, the pseudo failure unit <NUM> cancels this first pseudo failure by resuming the stopped first injector <NUM> via the injector controller <NUM>. Cancellation of the first pseudo failure means that all of the four injectors are put into operation.

Next, the pseudo failure unit <NUM> generates a second pseudo failure via the injector controller <NUM>, which stops the fuel injection of the second injector <NUM> and maintains the operation of the first injector <NUM>, the third injector <NUM>, and the fourth injector <NUM>. After a predetermined time elapses, the pseudo failure unit <NUM> cancels this second pseudo failure by resuming the stopped second injector <NUM> via the injector controller <NUM>.

Subsequently, the pseudo failure unit <NUM> similarly generates and cancels the third pseudo failure, and the fourth pseudo failure in this order.

In one example, the operating sound obtainment unit <NUM> is a microphone built in the smartphone <NUM>, and obtains the current operating sound that is the operating sound when the four injectors are operated, and obtains the pseudo-failure operating sound that is the operating sound when the above-mentioned first to fourth pseudo failure happens. This operating sound obtainment unit <NUM> is electrically connected to the faulty injector identification unit <NUM>, and outputs the obtained current operating sound and pseudo-failure operating sound to the faulty injector identification unit <NUM>.

The faulty injector identification unit <NUM> obtains the current operating sound and the pseudo-failure operating sound (i.e., the first pseudo-failure operating sound, the second pseudo-failure operating sound, the third pseudo-failure operating sound, and the fourth pseudo-failure operating sound) from the operating sound obtainment unit <NUM>. The faulty injector identification unit <NUM> then determines whether each pseudo-failure operating sound is similar or not to the current operating sound to identify a faulty injector.

Specifically, the faulty injector identification unit <NUM> compares the first pseudo-failure operating sound, the second pseudo-failure operating sound, the third pseudo-failure operating sound, and the fourth pseudo-failure operating sound one by one with the current operating sound, and thus determines whether each of the sounds is similar or not to the current operating sound. For this similarity determination, the similarity is calculated between the current operating sound and the pseudo-failure operating sound of each injector based on the peaks of the frequency appearing in the frequency domain (e.g., the peaks observed at the integer multiple components of the ratio of the primary combustion frequency of the engine (i.e., multi-cylinder internal combustion engine) to the number of cylinders) as shown in <FIG>, for example. This enables a determination with a high degree of accuracy about whether or not each pseudo-failure operating sound is similar to the current operating sound. In <FIG>, the horizontal axis represents the frequency and the vertical axis represents the sound pressure level.

Instead of calculating a similarity based on the frequency peaks observed in the frequency domain as stated above, the similarity determination may be made by deleting the dimension of the data for visualization about the feature vector of each operational sound using the principal component analysis (PCA). Or it may be performed by calculating the cross-correlation function (similarity of the time axis) of each operating sound, or by performing a fast Fourier transform on the audio data of each operating sound and pattern-matching the frequency characteristics.

If it is determined that there is no similarity, the faulty injector identification unit <NUM> determines that there is no faulty injector. If it is determined that any pseudo-failure operating sound is similar, the faulty injector identification unit <NUM> identifies the injector corresponding to that pseudo-failure operating sound as the faulty injector.

The diagnosis result output unit <NUM> is electrically connected to the faulty injector identification unit <NUM>, and receives a diagnostic result from the faulty injector identification unit <NUM> and informs the operator or the like of the result. For example, the diagnosis result output unit <NUM> informs the operator by displaying the presence or not of a faulty injector and information on the identified faulty injector, if any, such as the number of the injector, on the display screen of the smartphone <NUM>. The information on the identified faulty injector may be displayed on the display screen of the smartphone <NUM> and also may be transmitted to a server described later.

In the injector failure diagnostic device <NUM> according to the present embodiment, the operating sound obtainment unit <NUM> obtains the current operating sound and the pseudo-failure operating sound for each injector, and the faulty injector identification unit <NUM> determines whether the pseudo-failure operating sound of each injector is similar or not to the current operating sound to identify a faulty injector. The injector failure diagnostic device <NUM> therefore easily diagnoses the mechanical failure of the injectors and easily identifies the faulty injector. The accuracy of diagnosis improves as compared with the diagnosis with human hearing.

The operating sound obtainment unit <NUM> and the faulty injector identification unit <NUM> are installed in a smartphone that is easy to carry, which enables handy and easy diagnosis for a mechanical failure of the injectors at the site.

The following describes a method for injector failure diagnosis using the injector failure diagnostic device <NUM> with reference to <FIG>. <FIG> is a flowchart that explains the method for injector failure diagnosis, <FIG> is a diagram for explaining the operating sound obtainment and the pseudo-failures, and <FIG> and <FIG> are schematic diagrams for explaining the operation with a smartphone.

The method for injector failure diagnosis of the present embodiment includes: a current operating sound obtainment step of obtaining, as the current operating sound, the operating sound during the operation of four injectors; a pseudo-failure operating sound obtainment step of stopping fuel injection from one of the four injectors and maintaining the operation of the remaining three injectors to obtain a pseudo-failure operating sound, and sequentially obtaining the pseudo-failure operating sound of the four injectors; and a diagnosis step of determining whether or not the pseudo-failure operating sound of each injector obtained at the pseudo-failure operating sound obtainment step is similar to the current operating sound obtained at the current operating sound obtainment step to identify a faulty injector. In one example, this method for injector failure diagnosis is conducted when the multi-cylinder internal combustion engine <NUM> is idling (at the minimum rotation speed of the internal combustion engine).

Specifically, the operator first prepares the injector failure diagnostic device <NUM> by selecting the application software for the injector failure diagnosis device <NUM> installed on the smartphone <NUM> (see <FIG>). Next, the operator selects the model of the multi-cylinder internal combustion engine <NUM> to be diagnosed (see <FIG>).

Subsequently, in step S101 shown in <FIG>, the method obtains the current operating sound that is the operating sound during the operation of the four injectors via the operating sound obtainment unit <NUM>. At this time, the operator follows the procedure displayed on the screen of the smartphone <NUM> to bring the smartphone <NUM> close to the multi-cylinder internal combustion engine <NUM> of the construction machinery toward the designated recording position (see <FIG> and <FIG>), and record the current operating sound with the microphone built into the smartphone <NUM> for a certain period of time (e.g., about <NUM> seconds) (see <FIG>). After the recording ends, the operating sound obtainment unit <NUM> transmits the recorded sound as the current operating sound to the faulty injector identification unit <NUM>.

Step S101 corresponds to the "current operating sound obtainment step" recited in the claims.

In step S102 following step S101, the method generates pseudo failures. At this time, as shown in <FIG>, the operator presses a pseudo-failure start button displayed on the screen of the smartphone <NUM> to select the pseudo failure unit <NUM> of the injector failure diagnostic device <NUM>. This results in transmission of an instruction to generate a pseudo failure to the injector controller <NUM> of the multi-cylinder internal combustion engine <NUM>, which controls to generate a first pseudo failure that stops the fuel injection from the first injector <NUM> and maintains the operation of the second to fourth injectors <NUM> to <NUM>.

Specifically, as shown in <FIG>, in response to transmission of an instruction to stop the first injector <NUM> from the injector failure diagnostic device <NUM> to the multi-cylinder internal combustion engine <NUM>, the injector controller <NUM> receives the instruction and transmits a control signal for stopping to the first injector <NUM>. This stops the fuel injection of the first injector <NUM>. The second to fourth injectors <NUM> to <NUM> keep operating without stopping.

In step S103 following step S102, the method obtains the operating sound during pseudo failures. At this time, the operator follows the procedure displayed on the screen shown in <FIG> to bring the operating sound obtainment unit <NUM> (the smartphone <NUM> having the built-in microphone in this case) close to the multi-cylinder internal combustion engine <NUM> toward the designated recording position, and record the operating sound of the multi-cylinder internal combustion engine <NUM> for a certain period of time (a time similar to the recording time in step S101) (see <FIG>). After the recording ends, the operating sound obtainment unit <NUM> transmits the recorded sound data as the first pseudo-failure operating sound to the faulty injector identification unit <NUM>.

In step S104 following step S103, the method cancels the pseudo failure. Specifically, after a predetermined time (e.g., <NUM> sec. ) elapses, the pseudo failure unit <NUM> transmits a cancellation instruction to the injector controller <NUM> of the multi-cylinder internal combustion engine <NUM> to resume the stopped first injector <NUM> via the injector controller <NUM>. As shown in <FIG>, in response to reception of an instruction to resume the first injector <NUM>, the injector controller <NUM> transmits a control signal to resume the first injector <NUM>. This resumes the first injector <NUM> to return to the state in which all of the four injectors are in operation.

In step S105 following step S104, the injector failure diagnostic device <NUM> determines whether or not a pseudo failure has occurred for all the injectors. If it is determined that a pseudo failure has not yet occurred for all of these injectors, the process returns to step S102 to generate pseudo failures again. Since this embodiment includes the four injectors, pseudo failures corresponding to the second injector <NUM>, the third injector <NUM> and the fourth injector <NUM> occur in order, and the operating sound during the second to fourth pseudo failures is obtained accordingly.

Steps S102 to S105 correspond to the "pseudo-failure operating sound obtainment step" recited in the claims.

If it is determined in step S105 that pseudo failures have already occurred for all injectors, the process proceeds to step S106 to determine whether or not each pseudo-failure operating sound is similar to the current operating sound. To this end, the faulty injector identification unit <NUM> compares the first pseudo-failure operating sound, the second pseudo-failure operating sound, the third pseudo-failure operating sound, and the fourth pseudo-failure operating sound one by one with the current operating sound by the similarity determination method as stated above, and thus determines whether each of the sounds is similar or not to the current operating sound.

If it is determined that none of the first pseudo-failure operating sound, the second pseudo-failure operating sound, the third pseudo-failure operating sound and the fourth pseudo-failure operating sound are similar to the current operating sound, the faulty injector identification unit <NUM> determines that there is no faulty injector (see step S <NUM>). That is, if there is no pseudo-failure operating sound similar to the current operating sound, this means that the current operating sound is normal operating sound. This indicates that all injectors are operating normally.

If it is determined in step S106 that there is a similarity between the sounds, the faulty injector identification unit <NUM> identifies the faulty injector that is the injector corresponding to the pseudo-failure operating sound similar to the current operating sound (see step S <NUM>). For example, the determination may indicate that the first pseudo-failure operating sound and the second pseudo-failure operating sound are similar to the current operating sound. In this case, intentionally stopping of the first injector <NUM> corresponding to the first pseudo-failure operating sound and the second injector <NUM> corresponding to the second pseudo-failure operating sound will lead to the resulting operating sound that is similar to the first pseudo-failure operating sound or the second pseudo-failure operating sound. This indicates that the first injector <NUM> and the second injector <NUM> do not inject fuel and thus are faulty injectors. This allows the first injector <NUM> and the second injector <NUM> to be identified as faulty injectors.

Steps S106 to S108 correspond to the "diagnosis step" recited in the claims.

The method for injector failure diagnosis according to the present embodiment obtains the current operating sound and the pseudo-failure operating sound for each injector, and determines whether the obtained pseudo-failure operating sound of each injector is similar or not to the current operating sound to identify a faulty injector. The method therefore easily diagnoses the mechanical failure of the injectors and easily identifies the faulty injector. The accuracy of diagnosis improves as compared with the diagnosis with human hearing.

The method for injector failure diagnosis of the present embodiment is carried out when the multi-cylinder internal combustion engine <NUM> is idling. In this way, the method starts diagnosing after setting the multi-cylinder internal combustion engine <NUM> at the lowest rotational speed, which leads to the detection of an initial failure of the injectors caused by a fuel leak or stiffness, and thus enables a timely proposal for repair to the customer.

Note that, in this embodiment, the order of step S101 of obtaining the current operating sound and steps S102 to S105 of obtaining the pseudo-failure operating sounds may be reversed.

<FIG> is a schematic view showing the configuration of an injector failure diagnostic device according to a second embodiment. The injector failure diagnostic device 1A of this embodiment differs from the first embodiment described above in that the faulty injector identification unit <NUM> is provided in a server <NUM>, but the other configuration is the same as that of the first embodiment.

As shown in <FIG>, the injector failure diagnostic device 1A of this embodiment is configured so that a pseudo failure unit <NUM>, an operating sound obtainment unit <NUM> and a diagnosis result output unit <NUM> are provided in the smartphone <NUM>, while the faulty injector identification unit <NUM> is provided in the server <NUM>. The server <NUM> is located in the control center, for example, and is configured to be communicable with the smartphone <NUM>.

In the injector failure diagnostic device 1A having this structure, the operating sound obtainment unit <NUM> transmits each obtained operating sound to the faulty injector identification unit <NUM> in the server <NUM>, and the faulty injector identification unit <NUM> transmits the similarity determination results of the operating sounds and the identification results of the failure injector to the diagnosis result output unit <NUM>.

The injector failure diagnostic device 1A of this embodiment has the same actions and advantageous effects as those of the first embodiment described above, and the faulty injector identification unit <NUM> provided in the server <NUM> increases the speed of processing the similarity determination of the operating sounds and the identification of the faulty injector compared with the injector failure diagnostic device <NUM> of the first embodiment.

The method for injector failure diagnosis using the injector failure diagnostic device 1A is the same as that described in the first embodiment above, and the redundant explanations are omitted.

<FIG> is a schematic view showing the configuration of an injector failure diagnostic device according to a third embodiment. The injector failure diagnostic device 1B of this embodiment differs from the first embodiment described above in that the faulty injector identification unit <NUM> and the diagnosis result output unit <NUM> are provided in an internal combustion engine controller <NUM> of the multi-cylinder internal combustion engine <NUM>, but the other configuration is the same as that of the first embodiment.

As shown in <FIG>, the injector failure diagnostic device 1B of this embodiment is configured so that a pseudo failure unit <NUM> and an operating sound obtainment unit <NUM> are provided in the smartphone <NUM>, while the faulty injector identification unit <NUM> and the diagnosis result output unit <NUM> are provided in the internal combustion engine controller <NUM>.

In one example, the internal combustion engine controller <NUM> includes a microcomputer made up of the combination of a central processing unit (CPU) that executes calculations, a read only memory (ROM) as a secondary storage device that records programs for the calculations, and a random access memory (RAM) as a temporary storage of the calculation progress or temporary control variables. The internal combustion engine controller <NUM> controls the overall operation of the multi-cylinder internal combustion engine <NUM> by executing the stored programs.

The internal combustion engine controller <NUM> includes an injector controller <NUM> as well as the faulty injector identification unit <NUM> and the diagnosis result output unit <NUM>. This internal combustion engine controller <NUM> is configured to be communicable with the smartphone <NUM>.

In the injector failure diagnostic device 1B having this structure, the operating sound obtainment unit <NUM> transmits each obtained operating sound to the faulty injector identification unit <NUM> in the internal combustion engine controller <NUM>, and the faulty injector identification unit <NUM> transmits the similarity determination results of the operating sounds and the identification results of a failure injector to the diagnosis result output unit <NUM> to inform the operator or the like of the results via the diagnosis result output unit <NUM>.

In one example, the diagnosis result output unit <NUM> includes a display for displaying the diagnosis result and a flashing lamp for alerting the operator. If necessary, the diagnosis result output unit <NUM> may be provided in both the internal combustion engine controller <NUM> and the smartphone <NUM>. In this case, the operator is allowed to confirm the diagnosis results with both of the internal combustion engine controller <NUM> (that is, with the construction machinery) and with the smartphone <NUM>.

The injector failure diagnostic device 1B of this embodiment has the same actions and advantageous effects as those of the first embodiment described above, and the faulty injector identification unit <NUM> and the diagnosis result output unit <NUM> provided in the internal combustion engine controller <NUM> increase the speed of processing the similarity determination of the operating sound and the identification of the faulty injector compared with the injector failure diagnostic device <NUM> of the first embodiment.

The method for injector failure diagnosis using the injector failure diagnostic device 1B is the same as that described in the first embodiment above, and the redundant explanations are omitted.

<FIG> is a schematic view showing the configuration of an injector failure diagnostic device according to a fourth embodiment. The injector failure diagnostic device 1C of this embodiment differs from the first embodiment described above in that it does not include a smartphone, the pseudo failure unit <NUM>, the operating sound obtainment unit <NUM> and the diagnosis result output unit <NUM> are provided in the internal combustion engine controller <NUM> of the multi-cylinder internal combustion engine <NUM>, and the faulty injector identification unit <NUM> is provided in the server <NUM>, but the other configuration is the same as that of the first embodiment.

As shown in <FIG>, the injector failure diagnostic device 1C of the present embodiment is configured so that the pseudo failure unit <NUM>, the operating sound obtainment unit <NUM>, and the diagnosis result output unit <NUM> are provided in the internal combustion engine controller <NUM>. The internal combustion engine controller <NUM> controls the overall operation of the multi-cylinder internal combustion engine <NUM> as described above, and is configured to be communicable with the server <NUM>.

In the present embodiment, the operating sound obtainment unit <NUM> is configured to record the operating sound using a microphone placed in the engine room, for example, in accordance with an instruction from the internal combustion engine controller <NUM>.

In the injector failure diagnostic device 1C having this structure, the operating sound obtainment unit <NUM> transmits each obtained operating sound to the faulty injector identification unit <NUM> in the server <NUM>, and the faulty injector identification unit <NUM> transmits the similarity determination results of the operating sounds and the identification results of a failure injector to the diagnosis result output unit <NUM>.

The injector failure diagnostic device 1C of this embodiment has the same actions and advantageous effects as those of the first embodiment described above, and the configuration including the pseudo failure unit <NUM>, the operating sound obtainment unit <NUM> and the diagnosis result output unit <NUM> in the internal combustion engine controller <NUM> of the multi-cylinder internal combustion engine <NUM> and the faulty injector identification unit <NUM> in the server <NUM> allows the operator to easily diagnose the injector failure without going to the site.

The method for injector failure diagnosis using the injector failure diagnostic device 1C automatically starts under preset conditions (for example, once/<NUM> hours or when the engine revolution speed reaches the minimum speed). For example, when the multi-cylinder internal combustion engine has been in operation for <NUM> hours, the internal combustion engine controller <NUM> activates the injector failure diagnostic device 1C to carry out failure diagnosis of each injector. The specific process in the method for injector failure diagnosis is the same as that described in the first embodiment above except that no smartphone is used, and the redundant explanations are omitted.

<FIG> is a schematic view showing the configuration of an injector failure diagnostic device according to a fifth embodiment. The injector failure diagnostic device 1D of this embodiment differs from the first embodiment described above in that it does not include a smartphone, and all of the pseudo failure unit <NUM>, the operating sound obtainment unit <NUM>, the faulty injector identification unit <NUM> and the diagnosis result output unit <NUM> are provided in the internal combustion engine controller <NUM> of the multi-cylinder internal combustion engine <NUM>, but the other configuration is the same as that of the first embodiment.

The injector failure diagnostic device 1D of this embodiment has the same actions and advantageous effects as those of the first embodiment described above, and the configuration including the pseudo failure unit <NUM>, the operating sound obtainment unit <NUM>, the faulty injector identification unit <NUM> and the diagnosis result output unit <NUM> in the internal combustion engine controller <NUM> of the multi-cylinder internal combustion engine <NUM> allows the operator to easily diagnose the injector failure without going to the site.

The method for injector failure diagnosis using the injector failure diagnostic device 1D automatically starts under preset conditions (for example, once/<NUM> hours or when the engine revolution speed reaches the minimum speed). For example, when the multi-cylinder internal combustion engine has been in operation for <NUM> hours, the internal combustion engine controller <NUM> activates the injector failure diagnostic device 1D to carry out failure diagnosis of each injector. The specific process in the method for injector failure diagnosis is the same as that described in the first embodiment above except that no smartphone is used, and the redundant explanations are omitted.

Claim 1:
An injector failure diagnostic device (<NUM>) for a multi-cylinder internal combustion engine having a plurality of injectors (<NUM> - <NUM>), wherein each injector (<NUM> - <NUM>) injects fuel to a corresponding cylinder (<NUM> - <NUM>), said injector failure diagnostic device comprising:
an operating sound obtainment unit (<NUM>) configured to obtain a current operating sound that is the operating sound when all of the injectors (<NUM> - <NUM>) are operated, and obtain a pseudo-failure operating sound sequentially for each of the injectors, the pseudo-failure sound being the operating sound generated by stopping the fuel injection from one injector while maintaining the operation of the remaining injectors; and
a faulty injector identification unit (<NUM>) configured to determine whether or not the pseudo-failure operating sound of each injector obtained by the operating sound obtainment unit is similar to the current operating sound to identify a faulty injector,
wherein the faulty injector identification unit (<NUM>) is configured to calculate said similarity based on the operating sound pressures observed at peaks of frequency at the integer multiple components of the ratio of the primary combustion frequency of the engine to the number of cylinders (<NUM> - <NUM>) in a frequency domain of the pseudo-failure operating sound of each injector and the current operating sound.