JPH0480233B2 - - Google Patents

Description

14, the microcomputer outputs the switching signal so that continuous pulses are input from the switching means, and then counts the pulses input from the continuous pulse output means 13 to the input port. ,
This count value is compared with a predetermined value, and if the count value does not satisfy a predetermined relationship with the predetermined value, it is determined that the knock sensor 10 is abnormal and the ignition timing is retarded by a predetermined amount. A knock control device characterized in that it is configured to perform control so that knocking does not occur.

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a knock control device for an engine, and more particularly to a knock control device suitable for detecting an abnormality in a knock sensor.

[Conventional technology]

The conventional knock control device disclosed in JP-A-57-176362 detects knocking occurring in the engine by guiding the output of the knock sensor to a knock detection circuit, and retards the ignition timing when knocking occurs. It is configured.

Further, an analog circuit (diagnosis circuit) is provided to determine whether the knock sensor is abnormal, and one of the outputs of the knock detection circuit and the diagnosis circuit is selected and inputted to the microcomputer.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, the output of the knock sensor is led to an analog circuit, the analog circuit detects whether or not there is an abnormality in the knock sensor, and the result of the abnormality judgment by the analog circuit is output to a microcomputer. However, in this way, diagnosis is performed outside the microcomputer,
If the diagnostic results are sent to a microcomputer, ignition noise may mix into the signal between the analog circuit and the microcomputer, or the reference signal of the diagnostic circuit for abnormality detection may fluctuate due to noise, resulting in errors. There is a risk that the diagnostic results obtained will be input into the microcomputer. Furthermore, since the diagnostic circuit constantly compares the output from the knock sensor with a predetermined value to detect abnormalities, it is more susceptible to noise intrusion.

When a signal indicating that the knock sensor is abnormal is input to the microcomputer, the microcomputer enters a backup mode and, for example, delays the ignition timing sufficiently to control the engine so that knocking does not occur. Therefore, if an incorrect diagnosis result is input to the microcomputer from the analog circuit, the ignition timing will vary greatly, and the torque output from the engine will vary greatly.

It is an object of the present invention to provide a knock control system that requires fewer input ports of a microcomputer required for knock control, that can accurately diagnose abnormalities in a knock sensor without the influence of noise, and that makes it possible to avoid torque fluctuations. The purpose is to provide a control device.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a knock sensor for detecting knocking, a bandpass filter that passes a predetermined frequency among the outputs of the knock sensor, and a knock sensor that detects knocking based on the output of the bandpass filter. In a knock control device comprising a knock detection means for outputting a knock signal and a microcomputer for controlling ignition timing according to the output of the knock detection means, a continuous pulse is outputted based on the output of the bandpass filter. pulse output means; and switching means for selecting one of the output of the knock detection means and the output of the continuous pulse output means in response to a switching signal output from the microcomputer and inputting the selected one to an input port of the microcomputer. , the microcomputer outputs the switching signal so that continuous pulses are input from the switching means, then counts the pulses input from the continuous pulse output means to the input port, and calculates this count value in advance. It is compared with a predetermined value, and when the counted value does not satisfy a predetermined relationship with the predetermined value (for example, when it is less than the predetermined value or larger than the predetermined value), it is determined that the knock sensor is abnormal. The ignition timing is retarded by a predetermined amount to prevent knocking.

[Effect]

With the above configuration, the microcomputer that controls the ignition timing can selectively send one of the output of the knock detection means, which detects engine knocking based on the output of the knock sensor, and the output of the continuous pulse output means to the input port. The microcomputer only needs one input port.

On the other hand, since sensor abnormality determination is performed within the microcomputer, external noise is less likely to have a negative effect on the comparison standard for determination.
Since the signal to be diagnosed that is input to the microcomputer is a continuous pulse train, even if noise is mixed in, it is unlikely to have an adverse effect on the determination.

Furthermore, since the timing of the switching signal that takes in continuous pulses from the input port can be set arbitrarily, it is possible to take in the continuous pulse train as a signal to be diagnosed when operating an engine that is difficult to generate noise, and the taking period can also be set. Since it can be set arbitrarily, it is also possible to adjust the sensitivity of the above determination by adjusting the acquisition period.

〔Example〕

An embodiment of the knock control device according to the present invention will be described below with reference to the drawings.

An embodiment of the present invention is shown in FIGS. 1 and 2. FIG.
In the figure, an engine 1 is composed of a plurality of cylinders, and each cylinder is provided with a spark plug 2, respectively. These spark plugs 2 receive high voltage generated from an ignition coil to ignite each cylinder. Control device 4
is a hand pass filter (hereinafter referred to as BPF) 5,
It has a built-in amplifier 6, a microcomputer (hereinafter referred to as MCU), and engine state detectors such as a rotation angle sensor, an intake air amount sensor, an intake pressure sensor, and a throttle position sensor that detect the operating state of the engine 1. Upon receiving the signal of 8, the engine 1
The engine 1 is operated by applying an ignition timing signal to the ignition coil 3 that guides the engine 1 to an appropriate operating state.

A knock sensor 10 for detecting knocking is disposed on a part of the wall surface 9 of the engine 1. A signal from the knock sensor 10 is input to the control device 4, and when knocking occurs, the knock sensor 10 is inputted to the control device 4. The ignition timing signal is modified to prevent knocking.

The control device 4 constitutes a knock detection circuit as shown in FIG. 2, and its operation will be explained below using the signal time chart shown in FIG. The signal from the knock sensor 10 is input to the BPF 5 via the input terminal 11, and only vibration waves in a desired frequency band are passed through, resulting in a waveform as shown in A. This signal A is sent to the knock pulse shaping section 12, which is a knock detection means. and an abnormal signal detection section 13 which is continuous pulse output means. The signal A distributed to the knock pulse shaping section 12 and the abnormal signal detection section 13 is outputted as a signal B (hereinafter referred to as a knock signal) and a signal C consisting of continuous pulses (hereinafter referred to as a fail signal), respectively, and is outputted as a signal B (hereinafter referred to as a knock signal) and a signal C (hereinafter referred to as a fail signal) consisting of continuous pulses. 14. This switching means 14 includes the MCU 7
A switching signal E controlled by an interrupt signal D of a desired period sent from the CS port 7a of the switch is applied, and when this signal E is applied, either the knock signal B or the fail signal C selected by this signal E is applied. is input to the input port 7b of the MCU 7. Knock signal B or fail signal C determined by the switching signal E
Knock detection or fail detection is performed in the MCU 7 using knock signal B or fail signal C, respectively, and work corresponding to each input element is performed. In other words, if a knock signal called signal B is input during work in the knock detection zone,
When the internal counter of the MCU 7 reaches a desired value, the ignition timing is retarded by a predetermined amount at the position of arrow F relative to the predetermined ignition timing to prevent knocking.
Additionally, if an abnormality undesirable for knock control occurs at point Z during work in the fail detection zone, the normal pulse train is interrupted as shown in fail signal C, or becomes less than the desired value, and this fail signal C is When inputted, the ignition timing is controlled to be retarded by a predetermined amount at the position of arrow G so that knocking does not occur.

As mentioned above, one input port 7b of MCU7
Since the engine is controlled by sequentially inputting multiple input signals to the engine 1, even if the number of input elements for controlling engine 1 increases and the use of input ports is restricted, the limited input ports can be used efficiently. In addition, the number of input signal processing circuits can be reduced. Furthermore, according to this embodiment, since the input signal is input and processed in the form of a pulse train, it is possible to perform highly accurate control by eliminating the variations and changes over time of the conventional A/D conversion processing section. It is also less prone to noise.

In this embodiment, an example has been described in which the number of pulses of the fail signal C during abnormal conditions is reduced compared to normal times, but the control function is the same even when the number of pulses during fail increases from the number of pulses during normal conditions. , it goes without saying that effects completely equivalent to those of this embodiment can be obtained.

〔Effect of the invention〕

As explained above, in the present invention, the number of microcomputer input ports required for knock control can be reduced. Additionally, since abnormalities in the knock sensor are detected within the microcomputer, compared to abnormality detection using analog circuits, there are fewer false diagnoses due to noise, the accuracy of abnormality detection is improved, and torque fluctuations can be avoided. becomes. Furthermore, an analog circuit for detecting an abnormality in the knock sensor is not required, and the device can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing one embodiment of the knock control device according to the present invention, FIG. 2 is a partial circuit configuration diagram of the control section of FIG. 1, and FIG. 3 is an operation time chart of FIG. 2. . 1...Engine, 4...Control device, 5...Band pass filter, 7...Microcomputer,
10... Knock sensor, 12... Knock pulse shaping section, 13... Abnormal signal detection section, 14... Switching means.

Claims (1)

[Claims] 1 Knock sensor 1 for detecting knocking
0, a bandpass filter 5 that passes a predetermined frequency of the output of the knock sensor, a knock detection means 12 that outputs a knock signal based on the output of the bandpass filter, and an output of the knock detection means. and a microcomputer 7 that controls the ignition timing accordingly, the continuous pulse output means 13 outputting continuous pulses based on the output of the bandpass filter.
and a switching means for selecting either the output of the knock detection means or the output of the continuous pulse output means according to the switching signal E outputted from the microcomputer and inputting the selected one to the input port of the microcomputer.