JPS59190638A - Knocking detecting device for engine - Google Patents

Abstract

PURPOSE:To eliminate the effect of vibration noises, by computing the vibration noises generated by a cylinder head based on the amount of deviation in outputs of knock sensors arranged on the cylinder head and a cylinder block. CONSTITUTION:A cylinder head 4 is mounted on and fixed to a cylinder block 2 of an engine body 1 through a gasket 3. Knock sensors 22 and 23 are attached to the cylinder head 4 and the cylinder block 2, respectively, and pick up the synthesized vibration of the knocking and valve noises and the synthesized vibration of the knocking and attenuating valve noises. Based on the difference between the outputs of both knock sensors, i.e., the amount of attenuation in the mechanical noise, the mechanical noise generated in the cylinder head is computed. Then, the mechanical noise is subtracted from the output of the knocking sensor 22, and a true knocking level is obtained. Whether the knocking state is present or not is judged by a judging means (i), and an ignition-time control circuit (j) and the like are controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine knocking detection device.

(Prior art) In recent years, many engines, especially automobile engines, have adjusted their ignition timing to obtain the optimum ignition timing within a range that does not cause knocking, in order to improve output or save fuel. For this purpose, it is first necessary to detect engine knocking (knocking level).

However, as shown in Japanese Patent Laid-Open No. 54-87307, the knock sensor used to detect knocking picks up not only knocking but also mechanical noise generated in the cylinder head. be. Therefore, it is not possible to accurately determine whether or not knocking is occurring, and as a result, the ignition timing cannot be advanced to the limit of the knocking state, which limits the ability to improve output and fuel efficiency.

In particular, the biggest factor in the mechanical noise generated in the cylinder head mentioned above is the noise caused when the intake and exhaust valves take off and land (hereinafter referred to as valve noise), that is, the cam of the camshaft (or rocker arm). When the valve is in contact with the valve (# seated) and when the valve is seated on the intake/exhaust port opening edge (intake/exhaust valve seat) of the cylinder head.

(Object of the Invention) The present invention has been made in consideration of the above-mentioned circumstances, and is intended to eliminate the influence of mechanical noise generated in the cylinder head and to accurately detect whether or not a knocking state is occurring. The object of the present invention is to provide a soaking detection device for an engine.

(Structure of the Invention) In principle, the present invention is based on the principle that vibrations due to knocking occur in the same way in cylinder blocks, while mechanical noise generated in cylinder heads is caused by gaskets between the cylinder head and cylinder block. This is based on the discovery that the noise level is transmitted to the cylinder block at a more attenuated level than that at the cylinder head. If the mechanical noise generated in the cylinder head corresponding to this attenuation noise is calculated from data obtained in advance through experiments, it is possible to know the knocking (true knocking level) with this noise removed. .

Specifically, as shown in Fig. 1, a first knock sensor is installed in the cylinder head to pick up vibrations that are a combination of knocking and mechanical noise generated in the cylinder head, while a second knock sensor is installed in the cylinder block.
A knock sensor is provided to pick up the combined vibration of knocking and damping noise.

Then, the deviation detection means detects the difference between the outputs of the two knock sensors, that is, the amount of attenuation of mechanical noise, and the noise level calculation means calculates the mechanical noise generated in the cylinder head corresponding to this deviation amount, and furthermore, the first knock sensor The true knocking level is obtained by subtracting this mechanical noise from the output using a subtraction means. After this, as in the conventional case, the determining means determines whether or not there is knocking yd;, and the ignition retention period control circuit etc. may be controlled.

(Example) Fig. 2 shows a reciprocating engine with a turbocharger, which is generally equipped with so-called knock control. A cylinder head 4 is mounted and fixed via a gasket 3.

Intake air is supplied into each cylinder (combustion chamber) of the engine main body l via an air cleaner 5, an air flow chamber 6, a throttle chamber 7, a surge tank 8, an intake manifold 9, and an intake port 10. The path from the intake port 10 to the intake port 10 constitutes an intake passage 11. The intake port 1O is opened and closed by an intake valve 13 that moves to and from the intake valve seat 12 of the cylinder head 4.

In addition, exhaust gas is extracted from exhaust bow) 14, exhaust manifold 1
5, is discharged from an exhaust passage 17 consisting of an exhaust pipe 16, etc.;
The exhaust port 14 is opened and closed by an exhaust valve 19 that is moved to and from an exhaust valve seat 18 of the cylinder head.

In the figure, reference numeral 20 denotes a turbocharger, the compressor wheel 20a of which is disposed within the intake passage 11, and the turbine shaft 20 relative to the compressor wheel 20a.
A turbine wheel 20c connected via b is disposed within the exhaust passage 17. Therefore, the turbine wheel 20 is rotationally driven by high-temperature, high-pressure exhaust gas.
c rotates the compressor wheel 20a, and supercharging is performed under predetermined conditions.

Note that 21 in the figure is a catalyst for purifying exhaust gas.

A first knock sensor 22 is attached to the cylinder head 4, while a 27th knock sensor 23 is attached to the cylinder block 2, and outputs from both knock sensors 22, 23 are input to a control unit 24. The control unit 24 controls the destroyer 25, that is, the ignition timing, in accordance with the outputs from both sensors 22 and 23.

Here, the knock sensor 22 includes a cylinder and a rad 4.
vibrations, namely knocking and valve noise (actually, mechanical noise other than pulp noise is also picked up, but since this other mechanical noise is sufficiently small compared to valve noise, this mechanical noise can be treated as valve noise. (The following is a representative explanation) and pick-amplify the composite vibration. The second knock sensor 23 detects vibrations of the cylinder block 2, that is, knocking and damped valve noise (due to the presence of the gasket 3, the valve noise is attenuated and transmitted to the cylinder block 2).
Pick up the combined vibration. Of course, the control unit 24 has the functions of the above-mentioned deviation detection means, noise level calculation means, subtraction means, and discrimination means.

Next, the control by the control unit 24 will be explained for each step P1 to P9 based on the control circuit of FIG. 3 and with reference to FIGS. 5(1) to 5(5). That's it.

Steps PI, P2 Band pass filters BPF+ and BPF2 are applied to the outputs (Ao, Ba) from both knock sensors 22 and 23 to cut vibrations in frequency bands unrelated to knocking, such as vibrations of the vehicle body while driving. (A, →A1.BO+B,
).

Ste.mp.P.

A filter is applied by the IG (ignition) mask circuit 11425 to cut electrical noise at the time of ignition (AI→A2.BI→B2) Step P4 Here, the differential amplification circuit 26 as a deviation detection means The output B2 of the second knock sensor is subtracted from the output A2 of the first knock sensor 2, and as a result, the cylinder head 4
The damped valve noise C1 that is damped and transmitted to the cylinder block 2 is obtained.

Step P5 Here, the arithmetic circuit 27 as a noise level calculation means
According to the damping valve noise CI, for example, the fourth
The true valve noise C2 is calculated from the function shown in the figure. Of course, the function shown in Figure 4 was created based on data obtained in advance through experiments, and it can be created by taking into account factors such as engine speed, engine cooling water temperature, oil temperature, and boost pressure. good.

Step P.

Here, the valve noise C2 is subtracted from the output A2 of the first knock sensor by a subtraction circuit 28 as a subtraction means.
Then, calculate the true knocking level D1.

Step Pf, pg Here, the comparison circuit 29 serving as a determining means compares the knocking level D1 with the pack ground level BGL to determine whether or not there is a knocking state.

Note that the comparison itself is performed in the same manner as before.

Step P9: The ignition timing control circuit 30 controls the ignition timing based on the comparison and determination made in step P7, as in the conventional case.

That is, if it is determined that the engine is in a non-knocking state, the ignition timing is delayed, and if it is determined that the engine is not in a knocking state, the ignition timing is advanced, thereby obtaining the optimum ignition timing within a range where knocking does not occur.

Although the embodiments have been described above, the present invention also includes cases in which control is performed by a digital computer. Further, the knocking detection according to the present invention can be used not only for ignition timing adjustment but also for other purposes such as controlling supercharging pressure.

(Effects of the Invention) As is clear from the above, in the present invention, it is possible to accurately detect the knocking level by eliminating the influence of mechanical noise generated by the cylinder head. As a result, for example, the ignition timing can be made more suitable than before, which is extremely effective in terms of engine control, such as improving fuel efficiency and output.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of the present invention, FIG. 2 is a system diagram showing an embodiment of the present invention, and FIG. 3 is a system diagram showing an embodiment of the present invention.
The control circuit in the embodiment shown in FIG. 2, FIG. 4 is a diagram showing the relationship between pulp noise attenuation amount and valve noise, and FIGS. FIG. 3 is a diagram showing signal waveforms. 2φΦ・-・Cylinder block 4・・・・Cylinder head 22・・・17th sensor 23・・・・・・・・Control unit 26・・・・Differential increase l] circuit 27・・Arithmetic circuit 28 ...Reference subtraction circuit 29"...Comparison circuit Fig. 5 Fig. 3 Fig. 4 Noyce M Mechanism vC1

Claims (1)

[Claims] (1) A first knock sensor disposed on the cylinder head, a second knock sensor disposed on the cylinder block, and a deviation detection means for receiving the outputs of both the knock sensors and detecting the amount of deviation between the outputs of the two knock sensors. , noise level calculation means for calculating a noise level corresponding to vibration noise generated by the cylinder head corresponding to the deviation amount; subtraction means for subtracting the noise level from the first knock sensor output; and the subtraction value and setting. 1. A knocking detection device for an engine, comprising: a determining means for determining the presence or absence of knocking by comparing the values with the values.