JP2001152953A - Misfire diagnostic device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a clue to specify the misfire cause of an engine and to improve service performance. SOLUTION: The control unit 7 of a misfire diagnosing device performs detection of the misfire of an engine 1 based on an output from a magnetic pickup 5 and detects a misfire frequency when a given device, for example, an EGR device and an air-conditioner, is operated and a misfire frequency when it is not operated. When a large difference in a misfire frequency between a device operation time and a device non-operation time is produced, it is diagnosed that the possibility for the device to be a misfire cause is high, and the decision is stored at a memory. This constitution detects the device, having the high possibility for the device to be a misfire cause, by reading a memory content when it is garaged in a dealer due to a misfire NG and improves service performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for diagnosing misfire of an engine.

[0002]

2. Description of the Related Art Various methods for detecting a misfire of an engine have already been proposed.
The apparatus disclosed in Japanese Patent No. 397 performs misfire detection by focusing on fluctuations in the rotation cycle of the engine that occur at the time of misfire.

[0003] Such misfire detection is performed because the emission (HC, HC, etc.) released into the atmosphere when a misfire occurs.
This is because the temperature of the catalyst rises as the amount of components in the exhaust gas such as CO increases, and it is necessary to notify a driver or the like if misfire occurs frequently.

Therefore, conventionally, when a misfire occurs more than a predetermined frequency, the misfire frequency exceeds an allowable limit (hereinafter, misfire N).
G), and the MIL (warning lamp) was turned on or blinked.

[0005]

When a vehicle enters a dealer due to a misfire NG, it is necessary to specify the cause of the misfire. The misfire may be caused by smoldering of a spark plug or other devices such as an air conditioner and an EGR device. It is not easy to identify the cause of the misfire from the state of the vehicle at the time of parking since it occurs even if it is caused by a malfunction.

In many cases, therefore, the cause of the misfire is to be checked in order from the spark plug according to the procedure described in the service manual. In this method, even if there is no abnormality in the spark plug, the spark plug can be used. Until the inspection is performed, and the normal device is also inspected until the cause of the misfire can be identified, there is a problem that it takes time and effort and the service performance is poor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to provide a clue for specifying the cause of a misfire when a vehicle enters a warehouse due to a misfire NG, thereby improving service performance.

[0008]

According to a first aspect of the present invention, there is provided an engine misfire diagnosing apparatus, comprising: means for detecting engine misfire; means for judging an operation state of a predetermined device;
Means for detecting a misfire frequency when the device is operating and a misfire frequency when the device is not operating, based on the detection result, and a predetermined misfire frequency between the misfire frequency when the device is operating and the misfire frequency when the device is not operating. When there is such a gap, there is provided a means for diagnosing that the device is highly likely to be the cause of misfire, and a means for storing the diagnosis result.

In a second aspect based on the first aspect, the means for determining the operation state of the predetermined device is an EGR device,
The operation state of at least one of the variable valve timing mechanism, the swirl control valve, the air conditioner, and the power steering is determined.

[0010]

According to the present invention, the misfire frequency when a certain device (eg, EGR device, variable valve timing mechanism, etc.) is operating and the misfire frequency when it is not operating are detected. Alternatively, a misfire frequency when a certain device is operating in a certain state and a misfire frequency when the certain device is operating in a state different from the certain state are detected. If there is a large difference in the misfire frequency between when the device is operating and when the device is not operating, or when operating in a certain state and when operating in another state, the device may have caused a misfire. Is high, and the diagnosis result is stored in the memory.

Conventionally, when a misfired NG vehicle enters a dealership, it takes time to identify the cause of the misfire. However, according to the present invention, the misfire may be caused by reading the diagnosis result stored in the memory. Since it is possible to know a device that is highly likely to be operating, the operator can start inspection from that device, and service performance is improved.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of a misfire diagnosis device according to the present invention. The misfire diagnosis device of the engine 1 is provided opposite to a ring gear 4 provided on an outer periphery of a flywheel 3. It includes a magnetic pickup 5, a control unit 7 to which an output of the magnetic pickup 5 is input, and an MIL 6 (warning light).

The flywheel 3 is connected to the crankshaft 2 of the engine 1. When the crankshaft 2 rotates, the teeth of the ring gear 4 block the magnetic field generated in the iron core of the magnetic pickup 5. A change in magnetic force occurs and an alternating current is induced. This alternating current is converted into a pulse signal in the control unit 7.

The control unit 7 calculates the fluctuation of the rotation cycle of the engine 1 based on the pulse signal, and detects misfire of the engine 1 based on the fluctuation of the rotation cycle. When a misfire occurs more than a predetermined frequency, the control unit 7 turns on or blinks the MIL 6 (warning lamp) and performs misfire diagnosis as described later to give a clue to the cause of the misfire.

Next, the misfire diagnosis process performed by the control unit 7 will be described with reference to the flowchart shown in FIG. This flowchart is executed by the control unit 7 for each ignition.

First, in step S1, misfire of the engine 1 is detected. In this embodiment, the fluctuation of the rotation cycle of the engine 1 is calculated based on the output from the magnetic pickup 5,
Although misfire detection is performed based on the fluctuation of the rotation cycle, another method may be used for the misfire detection method.

Next, in step S2, it is checked whether the operation of the EGR device (exhaust gas recirculation device) has caused a misfire. The check of the possibility of the EGR device causing a misfire is performed according to the flowchart shown in FIG.

To explain this, first, in step S
At 21, it is determined whether the EGR device is operating. That is, it is determined whether or not the exhaust gas is being recirculated to the intake system of the engine. Here, when it is determined that the EGR device is operating, the process proceeds to step S22, and when it is determined that the EGR device is not operating, the process proceeds to step S27.

In step S22, it is determined whether a misfire has been detected in step S1. If it is determined that a misfire has occurred, the process proceeds to step S23, where the counter A is incremented. Here, the counter A is a counter that is cleared to zero when the engine is started, and is used to measure the number of misfires from when the EGR device operates to when the engine 1 rotates a predetermined number. On the other hand, if it is determined that there is no misfire, the process proceeds to step S24.

In step S24, it is determined whether or not the engine 1 has been rotated at a predetermined speed after the operation of the EGR device and the flag F1 is zero. Here, the flag F1 is a flag that is cleared to zero when the engine is started, and is set to 1 when the measurement of the misfire frequency during the operation of the EGR device is completed. EG
If the engine 1 has rotated a predetermined number after the R device has been activated and the flag F1 is zero, the flow proceeds to step S25, and if not, the flow proceeds to step S32.

In step S25, the value of the counter A is substituted for the parameter B. In step S26, the value of the counter A is cleared, and 1 indicating that the measurement of the misfire frequency during the operation of the EGR device has been completed is substituted for the flag F1. I do.

On the other hand, in step S27, in which it is determined that the EGR device is not operating, the process proceeds to step S1, where it is determined whether or not misfire has been detected in step S1. If it is determined that a misfire has occurred, the process proceeds to step S28, and the counter C is incremented. Here, the counter C is a counter that is cleared to zero when the engine is started, and is used to measure the number of misfires from when the EGR device is deactivated to when the engine 1 rotates at a predetermined speed. On the other hand, if it is determined that there is no misfire, the process proceeds to step S29.

In step S29, it is determined whether or not the engine 1 rotates a predetermined number after the EGR device is deactivated and the flag F2 is zero. Here, the flag F2 is a flag that is cleared to zero when the engine is started, and is substituted with 1 when the measurement of the misfire frequency when the EGR device is not operated is completed. If the engine 1 is rotated at a predetermined speed after the EGR device is deactivated and the flag F1 is zero, step S30 is performed.
If not, the process proceeds to step S32.

In step S30, the value of the counter C is substituted for the parameter D. In step S31, the value of the counter C is cleared, and the flag F2 is set to 1 indicating that the measurement of the misfire frequency when the EGR device is not operated is completed. substitute.

In step S32, it is determined whether the flag F1 is 1 and the flag F2 is 1. When the flag F1 and the flag F2 are 1, that is, when both the misfire frequency when the EGR device is activated and the misfire frequency when the EGR device is not activated are already measured, a misfire occurs due to the operation of the EGR device. The process proceeds to step S33 in order to determine whether or not there is. On the other hand, if the flag F is zero or the flag F2 is zero, the measurement has not yet been completed, and the process ends without diagnosing the EGR device.

In step S33, it is determined whether the deviation between the parameter B indicating the misfire frequency when the EGR device is operating and the parameter D indicating the misfire frequency when the EGR device is not operating is within a predetermined value. That is, parameters B and D
Is determined whether the following expression is satisfied: DX−B <D + X (X: predetermined value, for example, 5). When the parameters B and D satisfy the above equations, the misfire frequency hardly changes regardless of whether the EGR device is operating or not, so that the process proceeds to step S34, and the EGR device may have caused a misfire. Diagnose that sex is low. On the other hand, parameter B,
If D does not satisfy the above expression, the misfire frequency greatly changes depending on the operation or non-operation of the EGR device.
Proceeding to 35, it is diagnosed that there is a high possibility that the EGR device has caused a misfire. Then, these diagnostic results are stored in the memory in the control unit 7.

It is determined whether or not B / D <X is satisfied instead of the above equation.
The process may proceed to step S34, and if not satisfied, proceed to step S35. In this case, X is set to, for example, 1.5.

In step S36, the flags F1 and F2 are reset to zero to prepare for the next diagnosis.

After checking the possibility of the EGR device causing a misfire as described above, the flow returns to the flowchart of FIG. 2 and, in step S3, a VTC (variable valve timing mechanism, for example, a crank having an intake valve opened) is selected. Check that there is a possibility that the angular period is controlled according to the operating conditions). Although a flowchart for checking the possibility that the VTC is the cause of the misfire is not shown, FIG.
This is almost the same as the flow of the EGR device failure check shown in FIG. The misfire number is compared with the number of misfires. If the difference between the two is smaller than a predetermined value, it is diagnosed that the possibility of VTC causing a misfire is low.
Diagnose that TC is highly likely to be the cause of misfire.

Similarly, in steps S4, S5 and S6, the SCV
(Swirl control valve), air conditioner and power steering pump are checked for possible misfires.

Therefore, in the present embodiment, the number of misfires until the engine 1 rotates a predetermined number is measured for each of the predetermined devices (EGR device, VTC, SCV, etc.) during operation and non-operation. When there is a device that has a difference in misfire frequency between operation and non-operation that is equal to or more than a predetermined value, the device has some trouble (increased friction, malfunction of valve, etc.),
It is determined that there is a high possibility that a misfire has occurred by operating the device. For example, when there is a large difference between the misfire frequency when the EGR device is activated and the misfire frequency when the EGR device is not activated, it is determined that there is some malfunction in the EGR device, and that misfire has occurred due to the malfunction. .

Since the result of the judgment is stored in the memory in the control unit 7, when a vehicle is brought into the dealer, an external reading device is connected to the control unit 7 to read out the contents of the memory, thereby causing a misfire. Device that is likely to cause the problem. For example, when it is stored in the memory that the possibility that the EGR device has caused the misfire is high, the worker refers to the information to check the operation state of the EGR valve and perform the operation from the inspection of the EGR device. You can start.

As described above, according to the present invention, the worker can start the work from the inspection of the device which is highly likely to have caused the misfire, so that the time required for identifying the cause of the misfire is reduced, and the service is reduced. Performance can be improved.

Although the embodiment of the present invention has been described above, the device for determining the possibility of causing a misfire is not limited to the above-mentioned EGR device, VTC, SCV, etc. A device that may cause a misfire may be used.

The method of using the judgment result stored in the memory is not limited to the above method.
The blinking pattern of IL6 may be changed for each device so that it is possible to know from the blinking pattern which device has a high possibility of causing a misfire. Alternatively, if the vehicle has an in-vehicle monitor, a device that is likely to cause a misfire may be displayed on the in-vehicle monitor.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a misfire diagnosis device according to the present invention.

FIG. 2 is a flowchart showing a process of misfire diagnosis performed by a control unit.

FIG. 3 is a flowchart for checking a possibility that the EGR device has caused a misfire.

[Explanation of symbols]

 Reference Signs List 1 engine 4 ring gear 5 magnetic pickup 6 MIL 7 control unit

Claims (2)

[Claims] 1. A means for detecting a misfire of an engine, a means for determining an operation state of a predetermined device, and a misfire frequency when a device is activated and a misfire frequency when a device is not activated for a predetermined device based on the detection result. Means for detecting, when there is a predetermined gap or more between the misfire frequency when the device is operating and the misfire frequency when the device is not operating, means for diagnosing that the device is highly likely to be the cause of the misfire, Means for storing the diagnosis result. An engine misfire diagnosis device, comprising: 2. The system according to claim 1, wherein said means for determining the operating state of said predetermined device determines at least one of an EGR device, a variable valve timing mechanism, a swirl control valve, an air conditioner, and a power steering. 2. The engine misfire diagnostic device according to claim 1.