JP2639181B2 - Sensor fail detection method for knock control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a sensor failure of a knock control device used for controlling ignition timing of an internal combustion engine in an automobile or the like.

2. Description of the Related Art A conventional knock detection device has been configured using a microcomputer so that knocking can be detected from an output signal of a vibration sensor for detecting engine vibration and a reference signal.

FIG. 4 schematically shows a conventional knock control device.
In FIG. 4, reference numeral 1 denotes a vibration sensor for detecting engine vibration, and this vibration sensor 1 detects engine vibration, converts it into an electric signal, and outputs it. 2 is a bandpass filter for extracting only necessary frequency components of the electric signal output from the vibration sensor 1, 3 is a comparator, 4 is a digital / analog (D /
A) The converter 5 is a microcomputer. The output signal of the vibration sensor 1 (waveform A in FIG. 5) and the digital signal of a plurality of bits output from the microcomputer 5 are D /
The output signal (waveform B in FIG. 5) converted into an analog signal by the A converter 4 is compared by the comparator 3 and the comparison output is output to the microcomputer 5 as an interrupt signal F. Reference numeral 6 denotes a distributor.
Sends a reference signal (waveform C in FIG. 5). Numeral 7 denotes a waveform shaping circuit, which shapes the waveform of the output signal of the distributor 6 so that the interrupt signal waveform C of the microcomputer 5 is obtained. Reference numeral 8 denotes an igniter. The igniter 8 ignites with an output signal (waveform D in FIG. 5) from the microcomputer 5.

Next, the operation of the above conventional example will be described with reference to FIG. With microcomputer 5 generates a knock gate signal G ₁ to a predetermined period of occurrence of knocking from the reference signal C, and generates a noise gate signal G ₂ to a predetermined time period causing no knocking. At this time, regardless of the presence or absence of knock, it is necessary to set each gate so as to avoid a period in which the output signal of the vibration sensor 1 is affected by, for example, valve seating vibration, in order to prevent erroneous detection. And the vibration sensor 1
An output signal from the (waveform A), the output signal from the D / A converter 4 (waveform B), are compared in a noise gate G _2. Here, when both output signals are A> B, the comparator 3
An interrupt signal F, which is an output signal from the microcomputer 2, is input to the microcomputer 5, and based on the result, the next noise gate G ₂
The output (waveform B) from the D / A converter 4 that is sent out is increased. Conversely, when both output signals are A <B, the interrupt signal F is not output, so that the next output (waveform B) from the D / A converter 4 is reduced. In this way, the level in the noise gate G _2, i.e. after the detection of the noise level, when the noise level is continued following the state sensor failure determination value sensor - determined to fail, the noise level exceeds the judgment value Sometimes this noise level is multiplied by the best factor and this is used for the next knock gate G ₁
The output (waveform B) of the middle D / A converter 4 is transmitted as a knock determination level. In the case of A> B in knock gate G _1, an interrupt signal F from the comparator 3 is input to the microcomputer 5, the result by determining that there knock, timing output of the ignition and start charging (waveform D) Is delayed by a predetermined delay angle and sent to the igniter 8. When A <B, the comparator 3 outputs the interrupt signal F
When this state continues, the retardation of the ignition and charging start timing output (waveform D) is reduced. Here, the reason why the microcomputer is used is to enable fine control. For example, the knock determination level is calculated by the following equation: knock determination level = noise level × coefficient. By precisely dividing the coefficient by the number of revolutions, the knock determination level can be accurately created. A microcomputer can do this without increasing the number of components, and has many other advantages, such as accurate control of the amount of retardation.

However, these fine controls are also limited to the case where the resolution of the noise level is good, or the case where the noise level itself is large even if the resolution is poor.

However, in the above-described conventional knock detection device, depending on the load condition of the engine, the engine vibration becomes extremely small, thereby reducing the noise level. However, there is a problem that the sensor is erroneously detected as a failure even though it is not a sensor failure. For this reason, conditions that reduce engine vibration, such as low rotation,
It has been necessary to take measures such as prohibiting sensor failure under conditions such as low load.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a sensor fail detection method capable of always performing accurate sensor fail detection regardless of operating conditions.

Means for Solving the Problems In order to achieve the above object, the present invention performs a noise level detection based on a vibration sensor output at a noise gate for a predetermined period in which knocking does not occur, and detects the noise level in a knock gate for a predetermined period in which knocking occurs. Knocking is detected based on the output of the vibration sensor and the detected noise level, and it is determined whether or not a condition for reducing the noise level at the noise gate has been satisfied. The gate period is changed, and a sensor failure is detected based on a noise level at the noise gate.

The present invention is configured as described above, and when the condition that the noise level is reduced during the noise level detection period for generating the knock determination level is satisfied, the noise level is set to include the period during which the engine vibration is large. To change the noise gate period for detection, the difference between the vibration level at the time of sensor failure and the level at the normal time can be sufficiently large.
Reliable sensor failure detection can be performed.

Embodiment FIGS. 1 and 2 show a control flowchart according to an embodiment of the present invention for controlling the knock control device shown in FIG. 4, and FIG. 3 shows an operation waveform diagram of the knock control device.

3, A is an output signal of the vibration sensor 1, and B is an output signal of the D / A converter 4 to be compared with the output signal A of the vibration sensor 1. C is a reference signal indicating the operation of the engine, for example, a crank signal, F is the timing of ignition and start of charging, E,
G indicates the timing of the gate. Generally a knock gate
G ₁ is the period duration whose level increases knocking noise gate G ₂ is the normal vibration level regardless of knock occurring.

The gates G ₁ , G of the timings E, G thus set
_2, step whether a condition that the noise level based on the control flowchart shown in FIG. 2 is decreased is established
Check at 18. The check in step 18, for example, at least one of whether the engine speed has become 1500 rpm or less, whether the air pressure in the intake manifold has become 400 mmHg or less, and whether the cooling water temperature has become 80 ° C or less. Do. If the noise level is reduced condition is determined not to be satisfied in step 18, the noise gate G ₂ is set to 150 degrees 130 degrees in the step 19, the noise level is reduced condition is satisfied in Step 18 If it is determined that there is a knock, the output level from the vibration sensor 1 is determined during the period in which the influence of the valve seating vibration or the like appears in the output signal of the vibration sensor 1 regardless of the presence or absence of knocking, that is, between the sensor failure and the normal time. Step to change to a period where the difference is large
At 20, and changes the noise gate G ₂ to 120 degrees 100 degrees. Note the angle change of the noise gate G ₂ is one in which can be easily realized by changing the timer settings for creating the noise gate G _2.

Next, the operation of the above embodiment will be described with reference to FIG. First, calculated during the noise gate G _2, whether there is an output that is noise valve comparator 3 is checked in step 10, thereby the level VSF _n for sensor failure in the microcomputer 5 as shown in the following equation (Steps 11 and 12).

When there is a pulse (Yes), VSF _n = VSF _n-1 (1 + α) ... Step 11 When there is no pulse (No), VSF _n = VSF _n-1 (1-β) ... Step 12 where α and β are A positive constant.

Then comparing the sensor failure determination values of the sensor failure determining levels VSF _n in step 13. If YES is determined in Step 13, the count value is increased by +1 in Step 14, and if NO is determined in Step 13, the count value is set to 0 in Step 15. Steps 14 and 15 are steps for counting the number of times that the level VSF _n for sensor failure is determined to be continued and smaller than the sensor failure determination value. After increasing the count value in step 14, in step 16, the count value m is set to a predetermined determination value, for example, 10
0 It is determined whether or not the number of ignitions is greater than
If it is determined that the number is greater than the number of ignitions, it is determined in step 17 that the sensor has failed.

According to the above embodiment, when the condition that the noise level for calculating the knock determination level becomes smaller, by changing the noise gate G _2, the output level at the time of sensor failure and normal Since the difference can be made large, the sensor failure can be accurately detected.

In the above embodiment, as shown in FIG. 1, the sensor failure is determined by the number of ignitions continuously determined that the sensor failure level VSF _n is smaller than the sensor failure determination value. level VSF _n of use is one that may be detected the sensor failure by the determined and predetermined time duration less than the sensor failure determination values.

Advantageous Effects of the Invention As is clear from the above embodiment, the present invention provides a vibration sensor that changes a noise gate to a large period of engine vibration when a condition that a noise level in a noise gate is reduced is satisfied. Since the output level difference of the vibration sensor between the sensor failure state in which is broken and the normal state can be increased, there is an advantage that the sensor failure state can be reliably detected.

[Brief description of the drawings]

1 and 2 are control flowcharts for implementing a sensor failure detection method of a knock control device according to an embodiment of the present invention, FIG. 3 is a control waveform diagram of the method of the present invention, and FIG.
FIG. 5 is a schematic block diagram of a knock control device for implementing the method of the present invention, and FIG. 5 is a control waveform diagram of a conventional knock control device. 1 ... Vibration sensor, 2 ... Band filter, 3 ... Comparator,
4 ... D / A converter, 5 ... microcomputer, 6 ...
… Distributor, 7… Waveform shaping circuit, 8… igniter.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-97070 (JP, A) JP-A-2-70981 (JP, A) JP-A-59-43973 (JP, A) 151948 (JP, U)

Claims (3)

(57) [Claims] A noise level is detected based on a vibration sensor output from a noise gate during a predetermined period in which knocking does not occur. Based on the vibration sensor output and a detected noise level in a knock gate during a predetermined period in which knocking occurs. Detecting knocking, determining whether a condition for reducing the noise level at the noise gate is satisfied, and changing the noise gate period for performing the noise level detection when the condition is satisfied, changing the noise level at the noise gate to A method for detecting a sensor failure in a knock control device, comprising: detecting a sensor failure based on the detected failure. 2. The noise gate period is changed to a period including a valve sitting vibration generation period when a condition for reducing a noise level in the noise gate is satisfied.
A sensor failure detection method for a knock control device according to claim 1. 3. The sensor failure of the knock control device according to claim 1, wherein the noise gate period is changed when at least one of the number of revolutions at the noise gate, the air pressure in the intake manifold, and the cooling water temperature falls below a predetermined value. Detection method.