JPH0355776B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention mainly relates to a misfire determination device for determining 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, there is a method in which a constant reference value for the misfire exhaust temperature is set in advance, and when the exhaust temperature falls below this reference value, it is determined that a misfire has occurred. There is a method that determines whether a misfire has occurred by comparing the cylinder exhaust temperature with the average value.

However, in the former method, since the exhaust temperature fluctuates significantly up and down depending on the load amount, it is necessary to set a plurality of reference values at different levels depending on the load amount. Setting the misfire reference value corresponding to the load amount for each engine in this way is
It was a tedious task that required a lot 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, resulting in an increase in cost.

<Object 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. As a result, 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 throttle will open due to the governor's speed control operation, thereby This increases the intake pressure into the cylinder.

The present invention aims to achieve the above object based on the above knowledge, and as shown in the functional block diagram of FIG. storage means D for storing the correspondence between load and intake pressure during normal operation; and search means for searching the storage means D 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 a multi-cylinder gas engine 1,
It includes a control section 2, an intake pressure sensor 3 which is an intake pressure detection means, and a power transducer 4 which is a load detection means.

The intake pressure sensor 3 is attached to an intake manifold 5 of the engine 1. A generator 6 is directly connected to the main shaft of the engine 1, and the power 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 section 2 determines a misfire based on both detection signals from the intake pressure sensor 3 and the power transducer 4, and the control section 2 is configured to determine a misfire based on both detection signals from the intake pressure sensor 3 and the power 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 a CPU 10, a ROM 11,
It includes a RAM 12, an input/output port 13, and an A/D converter 14. The detection signal of the intake pressure sensor 3 and the detection signal of the power transducer 4 are inputted to the A/D converter 14 through amplifiers 15 and 16, respectively, and the detection signal generated by the CPU 10 is inputted from the input/output port 13. A misfire signal is now output.

Next, the operation of the above configuration will be explained based on the flowchart of FIG. First, in step S1, the intake pressure detected by the intake pressure sensor 3 and the load detected by the power transducer 4 are converted into an A/D converter.
Read through converter 14, and once read RAM1
Store in 2. In step S2, the value of the intake pressure corresponding to the detected load value is searched from the numerical table stored in the ROM 11. The ROM 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, the deviation e between the detected value of the intake pressure and the searched value is calculated, and in step S4, this deviation e is compared with a constant reference value _e0 . 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 . For example, the actual intake pressure is significantly different from the intake pressure during normal operation, and in this case, there is a possibility that a misfire has occurred in one of the cylinders.

At this point, it may be determined immediately that a misfire has occurred, but it is conceivable that a deviation e exceeding the reference value e ₀ has appeared due to a cause such as electrical noise. Therefore, when it is determined in step S4 that the deviation e exceeds the reference value _e0 , the process proceeds to step S5, where a misfire state variable j indicating the duration of the misfire state is counted up. Step S4
If it is determined that the deviation e has not reached the reference value _e0 , the process proceeds to step S6, where the misfire status variable j counted up to that point is returned to "0".

In step S7, which follows step S5, it is determined whether the misfire status variable j has reached a certain value, for example "10", and if the misfire status variable j has reached a certain value,
Because the actual intake pressure will continue to deviate significantly from the intake pressure during normal operation for a certain period of time,
Assuming that a misfire has definitely occurred, the process proceeds to step S8, where a misfire signal is output. 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 in the figure. Not limited to examples.

<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, since there is no need to change the misfire determination level (reference value) depending on the load condition, it is not only possible to reliably determine a misfire with a simple determination operation, but also to make multiple misfire determinations depending on the load amount. There is no need for the troublesome work of setting levels in advance, and no great effort or time is required for the setting work.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a flowchart showing the misfire determination operation. 1... Engine, 2... Control unit, 3... Intake pressure sensor (intake pressure detection means), 4... Power transducer (load detection means).

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; a search means for searching for a corresponding intake pressure value; a determination means for determining a misfire state by comparing the search value of the intake pressure from the search means with a value detected by the intake pressure detection means; and a misfire determination by the determination means. A measuring means for measuring the duration of the misfire condition in response to the output; and an output means 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 condition has continued for a certain period of time. An engine misfire determination device characterized by comprising: