JPS6254138A - Misfire discriminating device for engine - Google Patents

Abstract

PURPOSE:To discriminate the misfire state with an easy discriminating operation without changing a misfire discrimination level by using a power transducer, an intake air pressure sensor, etc. CONSTITUTION:The intake air pressure detection value of an intake air pressure sensor 3 and the load detection value of a power transducer 4 are read through an A/D converter 14 and are stored temporarily in a RAM 12. The value of intake air pressure corresponding to the load detection value is retrieved from a numerical table stored in a ROM 11. A deviation (e) between the intake air pressure detection value and the retrieved value is calculated and is compared with a certain reference value e0, If it is judged that the deviation (e) exceeds the reference value e0, an accidental fire state variable (j) indicating the duration of the misfire state is counted up. It is discriminated whether the misfire state variable (j) reaches a certain value or not, and a misfire signal is issued from an input/output port 13 if the variable (j) reaches the certain value. Thus, the misfire is discriminated surely by the easy discriminating operation.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention mainly relates to a misfire determination device that determines the occurrence of a misfire in a cylinder in a multi-cylinder internal combustion engine such as a gas engine or a diesel engine.

<Prior Art> Conventionally, the misfire state of an engine has been determined based on the exhaust temperature.

Specifically, a predetermined reference value for the misfire exhaust temperature.

This method determines that a misfire has occurred when the exhaust temperature falls below this reference value, and the system determines whether a misfire has occurred by comparing the exhaust temperature of each cylinder with the average value of the exhaust temperature of all cylinders. There was a method to do this.

However, in the curved method, since the exhaust gas temperature fluctuates significantly up and down depending on the amount of load, it is necessary to set a plurality of reference values at different levels depending on the amount of load. Setting the misfire reference value corresponding to the load amount for each engine in this way is a tedious task and requires a great deal of time and effort.

Furthermore, in the latter method, a temperature sensor must be attached to the exhaust pipe of each cylinder, and the same number of temperature sensors as the number of cylinders is required, which has the disadvantage of increasing costs.

<Purpose of the Invention> The present invention has been made in view of the above-mentioned conventional problems, and is capable of determining a misfire state by a simple determination operation using a small number of sensors and without changing the misfire determination level. The purpose is to do so.

<Structure of the Invention> The inventor of the present invention has investigated the fact that when a misfire occurs in any cylinder of the engine, the intake pressure of the engine increases compared to during normal operation.

In other words, if a misfire occurs in any cylinder, the output of the entire engine will drop momentarily, but the engine is equipped with a governor, and the governor will return the engine speed to a predetermined set speed. Therefore, cylinders that have not experienced a misfire will have to do more work than before the misfire in order to cope with the load at that time, and the governor will open the throttle due to the speed control operation, which will cause the cylinder to The intake pressure of the engine increases.

The present invention is an attempt to achieve the above object based on the above knowledge, and as shown in the functional block diagram of FIG. a storage means for storing the correspondence between the load and the intake pressure during normal operation; and a search means for searching the storage means for an intake pressure value corresponding to the load detection value by the load detection means C. E, a determining means F for determining a misfire state by comparing the searched value of the intake pressure from the searching means E and the value detected by the intake pressure detecting means B; A measuring means G for measuring the duration of the misfire state, and an output means H for outputting a misfire signal indicating the occurrence of a misfire in response to a time-up output of the measuring means G indicating that the misfire state has continued for a certain period of time. A misfire detection device for the engine was constructed.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 2 is a block diagram of a misfire determination device for a gas engine which is an embodiment of the present invention, and the misfire determination device includes:
The engine includes a multi-cylinder gas engine 1, a control section 2, an intake pressure sensor 3 serving as an intake pressure detection means, and an electric quadrature transducer 4 serving as a load detection means.

The intake pressure sensor 3 is attached to an intake manifold 5 of the engine l. A generator 6 is directly connected to the main shaft of the engine 1, and the electric quadrature transducer 4 is attached to the generator 6. In FIG. 2, numeral 7 is a throttle, 8 is a governor, and 9 is a mixer.

Further, the control unit 2 determines whether a misfire has occurred based on a rain detection signal from the intake pressure sensor 3 and the electric quadrangle transducer 4. It functionally includes a state determining means F, a measuring means G, and a misfire signal output means H. The control unit 2 includes cputo,
ROMII, RAM 12, input/output board 13, and A
/D converter 14. The A/D converter 14 receives the detection signal of the intake pressure sensor 3 and the detection signal of the electric quadrature transducer 4 through an amplifier 15.
16 and from the input/output port 13.
A misfire signal generated by the PU 10 is output.

Next, the operation of the above configuration will be explained based on the flowchart of FIG. First, in step Sl, the intake pressure detected by the intake pressure sensor 3 and the load detected by the electric quadrature transducer 4 are converted into an A/D converter! 4 and temporarily stores it in RAM 12. In step S2, the value of the intake pressure corresponding to the detected load value is searched from the numerical table stored in the ROMII. The rZOM 11 stores in advance the load amount and the corresponding intake pressure during normal operation in the form of a numerical table.

In the next step S3, a deviation e between the detected value and the search value of the intake pressure is calculated, and in step S4, this deviation e is set to a constant reference value e. Compare with. These two steps are for determining whether the actual intake pressure (detected value) deviates significantly from the intake pressure during normal operation (search value), and if the deviation e exceeds the reference value e0, This means that the actual intake pressure deviates significantly from the intake pressure during normal operation, and in that case, there is a possibility that a misfire has occurred in one of the cylinders.

At this point, it may be determined that a misfire has occurred immediately, but the reference value e may be determined due to electrical noise or other causes. It is conceivable that a deviation e exceeding . Therefore, in step S4, the deviation e is set to the reference value e. If it is determined that the misfire condition has exceeded the period of time, the process moves to step S5, and a misfire condition variable j indicating the duration of the misfire condition is counted up.

In step S4, the deviation e is set to the reference value e. If it is determined that the misfire status variable j has not been reached, the process advances to step S6, and the misfire status variable j counted up to that point is returned to "0".

In step S7 following step S5, the misfire state change j
determines whether it has reached a certain value, for example "10",
If the misfire status variable j reaches a certain value, the actual intake pressure will continue to deviate significantly from the intake pressure during normal operation for a certain period of time, so it is assumed that a misfire has definitely occurred, and the process proceeds to step S8. , outputs a misfire signal. This misfire signal causes a display to indicate that a misfire has occurred or an alarm to sound.

In the above embodiment, the power transducer 4 was used as the load detection means, but in an engine used to drive a heat pump, the discharge pressure sensor of the compressor can be used as the load detection means, and the load detection means is not shown. The example is not limited to.

<Effects of the Invention> As described above, according to the present invention, a misfire can be determined using the load detection means and the intake pressure detection means, and the number of detection means is only two. Can be manufactured at low cost.

Moreover, the misfire judgment level (standard value) depends on the load condition.
Since there is no need to change the misfire detection level, it is not only possible to reliably judge a misfire with a simple judgment operation, but also eliminates the troublesome work of setting multiple misfire judgment levels in advance according to the amount of load. No great effort or time is required for the setting work.

[Brief explanation of drawings]

Figure 1 is a functional block diagram that clearly shows the configuration of the present invention, Figure 2 is a functional block diagram clearly showing the configuration of the present invention.
The figure is a block diagram of an embodiment of the present invention, and FIG. 3 is a flowchart showing the misfire determination operation. DESCRIPTION OF SYMBOLS 1... Engine, 2... Control part, 3... Intake pressure sensor (intake pressure detection means), 4... Electric quadrature transducer (load detection means). Applicant Yanmar Diesel Co., Ltd. Attorney Patent Attorney Oka 1) Hide Kazu Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) Means for detecting the intake pressure of the engine, means for detecting the load, storage means for storing the correspondence between the load and the intake pressure during normal operation, and load detection by the load detection means from the storage means. a search means for searching for an intake pressure value corresponding to the intake pressure value; a determining means for determining a misfire state by comparing the retrieved value of the intake pressure from the searching means with a value detected by the intake pressure detecting means; A measuring means for measuring the duration of a misfire state in response to a misfire determination output, and an output for outputting a misfire signal indicating the occurrence of a misfire in response to a time-up output of the measuring means indicating that the misfire state has continued for a certain period of time. A misfire determination device for an engine, comprising: means.