JPH08246948A - Internal combustion engine - Google Patents

Abstract

PURPOSE: To improve detection precision of knocking by a method wherein, during knocking, the resonance frequency of a constituting part is regulated so that detectable vibration detectable by a knock sensor is encouraged. CONSTITUTION: When a piston 16 used in an internal combustion engine having a knock sensor is cast and moulded, a machining margin 16g attributed to rigidity of a skirt part 16e is arranged on the back of an upper surface part 16f. At the machining process of the piston 16, a machining margin 16g is cut as vibration generated at the skirt part 16e is monitored by using an acceleration pickup 32 and an FFT 34. During knocking of the internal combustion engine, a resonance frequency to encourage vibration detectable by a knock sensor is set to a target frequency. At a point of time when the magnitude of vibration of the target frequency generated at the piston 16 exceeds the target frequency, cutting of the machining margin 16g is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine, and more particularly to a vehicle-mounted internal combustion engine equipped with a knock sensor.

[0002]

2. Description of the Related Art Conventionally, ignition timing control using a knock sensor has been performed in the field of vehicle-mounted internal combustion engines. That is, in the internal combustion engine, the output is improved as the ignition timing is advanced toward the normal side, but if the ignition timing is advanced transiently, unfavorable knocking occurs due to the characteristics of the internal combustion engine. Further, when knocking occurs in the internal combustion engine, vibration having a specific frequency (hereinafter referred to as knock frequency) occurs around the combustion chamber. Therefore, if the presence or absence of vibration is monitored using the knock sensor, the knocking occurrence state can be detected.

On the other hand, in the ignition timing control described above, the ignition timing is gradually advanced until the knock sensor detects the vibration with the knock frequency, and when the vibration with the knock frequency is detected, a predetermined value is set. Feedback control for retarding the ignition timing by the step angle of is executed. In this case, the ignition timing of the internal combustion engine is always controlled to the vicinity of the limit angle at which knocking occurs, so that excellent output characteristics are realized in the internal combustion engine.

[0004]

The vibration generated when the internal combustion engine is knocked is the vibration generated when the air column vibration generated in the combustion chamber when the internal combustion engine is knocked is transmitted to the piston, the cylinder block, the intake and exhaust valves, and the like. Therefore, if the specifications of the piston and the like are different, the knocking frequency will be different.

On the other hand, for example, the actual Kaihei 2-1328.
As disclosed in Japanese Patent Publication No. 34, etc., various configurations have been conventionally disclosed for pistons and the like. However, in general, determination of specifications of the piston and the like and machining thereof should be performed with consideration for influence on knocking frequency and the like. It was usually done without being done.

Therefore, in the conventional internal combustion engine, for example, when the specifications of the piston or the like are changed at the trial production stage, or when the design is changed to improve the piston or the like, the knocking frequency becomes lower than that of the knocking sensor. There is a case where the accuracy of knocking detection is deteriorated by moving out of the detection range. Further, even if such a design change is not made, if the frequency characteristic of the piston or the like changes due to a processing error or the like at the time of production, similarly, the knocking detection accuracy deteriorates.

In this sense, the conventional internal combustion engine whose specifications are set without considering the influence on the knocking frequency and which is constructed by using the processed components uses a knock sensor and is always highly accurate. It was not always appropriate as a configuration for realizing various knocking detections.

The present invention has been made in view of the above points, and an internal combustion engine that solves the above problems by setting the resonance frequencies of the components around the combustion chamber according to the characteristics of the knock sensor. The purpose is to provide.

[0009]

SUMMARY OF THE INVENTION In an internal combustion engine equipped with a knock sensor, the above object is to promote the resonance frequency of the components around the combustion chamber to a vibration that can be detected by the knock sensor when the internal combustion engine is knocked. Is achieved by an internal combustion engine having a predetermined frequency.

[0010]

In the present invention, the components around the combustion chamber are controlled so that their resonance frequencies have specific values.
For this reason, when vibrations due to knocking occur in the combustion chamber, vibrations of the peculiar resonance frequency occur in the components around the combustion chamber. The resonance frequency is set to a frequency that promotes vibration that can be detected by the knock sensor. Therefore, when vibration due to knocking occurs in the combustion chamber, the vibration is reliably detected by the knocking sensor.

[0011]

FIG. 1 shows an internal combustion engine 1 according to an embodiment of the present invention.
An overall configuration diagram of 0 is shown. As shown in FIG.
Includes a combustion chamber 14 inside the cylinder block 12. A piston 16 connected to a connecting rod 15 is slidably fitted in the combustion chamber 14, and an intake valve 18 and an exhaust valve 20 for opening and closing an intake port and an exhaust port (not shown) are provided. .

The cylinder block 12 is provided with a spark plug 22 so that its tip is exposed in the combustion chamber 14, and vibrations in a specific frequency band transmitted to the cylinder block 12 are detected. A knock sensor 24 is provided. Here, the sensor output of the knock sensor 24 is supplied to the ignition timing control unit 28 via the amplifier 26, and the ignition plug 22 is supplied with the drive signal from the ignition timing control unit 28.

The ignition timing control unit 28 determines whether or not knocking has occurred in the internal combustion engine 10 based on the signal supplied from the knock sensor 24, and if knocking is not recognized, the ignition timing control unit 28 gradually increases. Change the ignition timing to the advanced side. Then, when it is recognized that knocking has occurred in the internal combustion engine 10, the ignition timing is retarded by a predetermined step angle, and thereafter the ignition timing is gradually changed to the advance side until knocking is recognized again. (Hereinafter, simply referred to as ignition timing control) is executed.

In this case, if the knocking that occurs when the ignition timing is controlled near the advance limit can be accurately detected, the ignition timing of the internal combustion engine 10 can be kept at a high output without causing harmful knocking. Therefore, it is possible to maintain the ideal ignition timing. In this sense, it is extremely important for the internal combustion engine 10 to accurately detect knocking.

On the other hand, the internal combustion engine 10 of this embodiment is
Is the frequency characteristic of the knock sensor 24 and the internal combustion engine 10
It is characterized in that the resonance frequency of the piston 16 is controlled to a predetermined value in consideration of the influence of other components. More specifically, in this embodiment, since the knock sensor 24 is a sensor having a sensitivity peak at 6 to 9 kHz, the resonance frequency of the piston 16 is 7
The piston 16 is managed so as to be in the vicinity of kHz.

In the internal combustion engine 10, the resonance frequency of the piston 16 has a great influence on the knock frequency, and when the resonance frequency of the piston 16 is controlled to be near 7 kHz, the characteristics of the knock sensor 24 will be described. And internal combustion engine 1
Even if there are variations in the components of 0, the knock frequency of the internal combustion engine 10 can be stably kept within the peak sensitivity of the knock sensor 24.

Therefore, according to the internal combustion engine 10 of the present embodiment, even when the design of the piston 16 is changed, and when various processing errors are superimposed in the manufacturing process of the internal combustion engine 10, Knocking can always be detected accurately, and the effects of the ignition timing control described above can be fully enjoyed.

The direction in which the resonance frequency of the piston 16 is controlled to the target value will be described below with reference to FIGS. Here, FIG. 2 is a machining step diagram showing an example of a machining procedure of the piston 16, and FIG. 3 is a front sectional view (FIG. 3A) and a bottom view (FIG. 3B) of the piston 16 in the machining process. )), And FIG. 4 is a conceptual diagram for explaining a method of executing the resonance adjustment processing which is the characteristic processing of this embodiment.

In FIG. 2, "material" represents the piston 16 immediately after casting. That is, in the processing of the piston 16, first, in the first step, the inner diameter of the piston 16 after casting is processed. Next, in the second step and the third step, the ring oil hole of the piston 16 and the ring 16
a to 16c are processed, and in the fourth step, a pin hole 16c for inserting a pin connecting the piston 16 and the connecting rod 15 (see FIG. 1) is processed.

In the fifth step, the outer diameter of the piston 16 is finished. Here, in this embodiment, the wall pressure of the skirt portion 16e of the piston 16 is also controlled in this step. The details of this step will be described later. Then, in the sixth to eighth steps, each pin hole 1
Processing for providing a relief groove for supplying oil to the inside of 6d, measurement of the outer diameter of the piston 16, and removal of dowels for removing unnecessary portions are performed.

By the way, the piston 16 shown in FIG. 3 shows the form at the time when the eighth step is finished. As shown in the figure, the piston 16 has a top surface 16f on the back surface thereof. Processing allowance (portion shown by hatching in FIG. 3) 16g for adjusting the rigidity of the skirt portion 16e
Is provided.

In FIG. 2, the ninth step is a step of adjusting the resonance frequency of the piston 16 by cutting the machining allowance 16g. The working process of the piston 16 in the present embodiment is designed so that the piston 16 will be in a substantially final form when the eighth process is completed. Therefore, when the resonance frequency of the piston 16 is adjusted in the ninth step, the resonance frequency does not change due to subsequent processing. Hereinafter, the content of the resonance adjustment processing will be described with reference to FIG.

In FIG. 4, the piston 16 is supported by the chuck 30 of the processing equipment. An acceleration pickup 32 is attached to the skirt portion 16e of the piston 16. Further, the acceleration pickup 32 is connected to an FFT 34 that converts each frequency signal included in the output signal into a spectrum. And FFT34
The frequency spectrum formed by
Is supplied to.

The control device 36 controls the machining allowance 1 of the piston 16.
A device for controlling the drive motor 40 of the end mill 38 that cuts 6 g, in order to continue the cutting by the end mill 38 until the signal strength of the specific frequency band in the frequency spectrum supplied from the FFT 34 reaches the target level, Perform predetermined control.

By the way, when the cutting of the machining allowance 16g by the end mill 38 is started in the situation shown in FIG. 4, the vibration accompanying the cutting is transmitted to the piston 16. And
The vibration is detected by the acceleration pickup 32 and transmitted to the FFT 34. At this time, among the vibrations transmitted to the piston 16, the vibration having a frequency close to the resonance frequency of the piston 16 is amplified, and the other vibrations are attenuated. Therefore, the FFT 34 has a peak near the resonance frequency of the piston 16. A spectrum with is formed.

In the present embodiment, the piston 16 is designed so that the piston 16 as a whole has a resonance frequency of a little over 7 kHz, and the skirt portion 16e as a main component has a resonance frequency near 2 kHz. The original is set. Therefore, the FFT 34 forms a spectrum having peaks near 7 kHz and 2 kHz.

On the other hand, the control device 36 pays attention to the vibration of 7 kHz which is the resonance frequency to be applied to the piston 16, until the acceleration intensity detected at that frequency, that is, the vibration intensity reaches the target level. The cutting of 16 g of machining allowance by the end mill 38 is continued.

In this case, 7 kHz before cutting the machining allowance of 16 g
The resonance frequency, which was strong, gradually decreases as the rigidity of the piston 16 decreases with the cutting of the machining allowance 16g, and when the resonance frequency decreases to the vicinity of the target value of 7 kHz, the cutting by the end mill 38 is performed at that time. It will be terminated.

Therefore, in the present embodiment, when the cutting by the end mill 38 is completed, that is, when the resonance adjustment processing is completed, the resonance frequency of the piston 16 is accurately adjusted to the target value of 7 kHz. After that, if the weight is adjusted in the tenth step in FIG. 2 thereafter, the piston 16 whose resonant frequency is accurately controlled to around 7 kHz can be completed.

By the way, in the piston 16 of this embodiment,
As described above, the vibration near the resonance frequency of 7 kHz, which is the resonance frequency of the entire piston 16, as well as the vibration near 2 kHz, which is the resonance frequency formed mainly by the skirt portion 16e, is amplified. Here, the vibration near 2 kHz is a vibration greatly influenced by the rigidity of the skirt portion 16e, and when the rigidity of the skirt portion 16e is low, that is, the skirt portion 16e.
Is thin, the frequency is lowered and the skirt 16e
If the rigidity is high, that is, if the skirt portion 16e is thick, its frequency increases.

Therefore, the resonance frequency for an appropriate skirt thickness is measured in advance, and in the fifth step, the piston 16
When performing the outer diameter finishing process of the piston 16, in order to ensure proper vibration strength at its resonance frequency, the piston 16
If the outer diameter processing is performed, it is possible to accurately control the wall thickness of the skirt portion 16e.

FIG. 5 is a conceptual diagram for explaining the method of executing the outer diameter finishing process (fifth step) adopted in this embodiment, focusing on this point. In the figure, the same components as those shown in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted.

That is, the outer diameter finishing process shown in FIG.
This is processing for processing the outer peripheral surface of the skirt portion 16e of the piston 16 using the skirt processing blade 50. Also,
In the figure, the control device 50 pays attention to the vibration near the resonance frequency of 2 kHz which is formed mainly by the skirt portion 16e, and the machining of the skirt portion 16e is continued until the vibration intensity falls within a preset range. Therefore, predetermined control is performed.

In this case, the outer diameter finishing process is finished when the skirt portion 16e is processed to have a predetermined wall thickness, so that highly accurate wall thickness management of the skirt portion 16e is realized. By the way, in order to manage the wall thickness of the skirt portion 16e without using the above method, it is necessary to measure the wall thickness with a caliper or the like, but since the shape of the skirt portion 16e is generally complicated, It is difficult to make the measurement nondestructively. Therefore, in that case,
Management of the wall thickness of the skirt portion 16e involves complicated work,
You have to do it randomly.

On the other hand, as described above, if the wall thickness is controlled during the outer diameter finishing process, it is possible to easily control the total number. Adopted in this embodiment,
The thickness management method described above also has an excellent effect in this respect. By the way, in the present embodiment, the target value of the resonance frequency of the piston 16 is set in the vicinity of 7 kHz which is approximately the center value of the peak sensitivity band of the knock sensor 24, but the target value of the resonance frequency is limited to this value. However, the value may be set to a value that promotes vibration that can be detected by the knock sensor during knocking of the internal combustion engine.

Further, in this embodiment, the internal combustion engine 10
Among the components around the combustion chamber of FIG. 1, the resonance frequency of the piston 16 is managed, but the components for which the resonance frequency should be managed are not limited to this.
For example, when the resonance frequency of other components such as the intake valve 18 or the exhaust valve 20 has a great influence on the knock frequency, the resonance of those other components in addition to the piston 16 or instead of the piston 16 is performed. The frequency may be managed.

[0037]

As described above, according to the present invention, since the resonance frequency of the components around the combustion chamber is controlled to a specific frequency, vibration in the frequency band that can be detected by the knock sensor at the time of knocking occurs. It occurs reliably and with relatively high strength. Therefore, according to the internal combustion engine of the present invention, knocking detection can be performed accurately in any case.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing the overall configuration of an internal combustion engine that is an embodiment of the present invention.

FIG. 2 is a process drawing of a piston used in the internal combustion engine of this embodiment.

FIG. 3 (A) is a front sectional view of a piston used in the internal combustion engine of the present embodiment before resonance adjustment processing. FIG.
FIG. 6B is a bottom view of the piston used in the internal combustion engine of the present embodiment before resonance adjustment processing.

FIG. 4 is a conceptual diagram for explaining the content of resonance adjustment processing of a piston used in the internal combustion engine of the present embodiment.

FIG. 5 is a conceptual diagram for explaining the details of the outer diameter finishing process of the piston used in the internal combustion engine of the present embodiment.

[Explanation of symbols]

 10 Internal Combustion Engine 12 Cylinder Block 14 Combustion Chamber 16 Piston 16e Skirt 16f Top Surface 16g Machining Allowance 24 Knock Sensor 32 Accelerometer 34 FFT 36 Controller 38 End Mill 40 Drive Motor

Claims (1)

[Claims] 1. An internal combustion engine equipped with a knock sensor, wherein a resonance frequency of components around a combustion chamber is set to a predetermined frequency that promotes vibration that can be detected by the knock sensor when the internal combustion engine is knocked. Internal combustion engine.