JPS6255468A - Combustion light detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To detect a combustion light by providing a filter which is coated in a film form over the end surface at the side of a photoelectric transfer element of a light detection member. CONSTITUTION:A combustion light from a combustion chamber enters into an end face 11 of a light detecting member (glass bar made from SiO2), passes through the member, and is deprived of the harmful infrared ray contained by a filter which is provided on the surface of the other end 12 of the member. Then the rest of the light reaches a photoelectric transfer element 4 so as to be transformed into an electric signal. The detected signal is inputted into both an ignition timing detecting circuit 7 and an engine control circuit 8 so that a fuel injection pump 9 may be driven at an optimum condition. In this case, a thin layer of Al2O3 is coated over the filter 6, on which an alternate multi-layer consisting of a thin layer of TiO2 and a thin layer of SiO2, is also coated by means of the spattering method. Consequently, as the infrared ray which is emitted under the high engine speed and high loading conditions, can be removed, only the light produced from real combustion can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a combustion light detection device that obtains electrical signals for controlling fuel injection timing and the like of an internal combustion engine.

[Prior art and its problems]

In internal combustion engines, actual ignition timing within a combustion chamber is detected, and fuel injection timing is controlled based on this detection signal. The ignition timing is detected here by detecting combustion light within the combustion chamber.

(Japanese Unexamined Patent Publication No. 58-70029, etc.) As a combustion light detection device, for example, a light detection member made of a rod-shaped glass material having optical transparency and one end of which is inserted into the combustion chamber is used to detect the light inside the combustion chamber. A photoelectric conversion element provided at the other end of the photodetecting member converts the signal into an electrical signal.

However, with such a detection device, as the operating conditions of the five engines change, that is, the temperatures of the walls of the five combustion chambers differ between idling and high-speed, high-load conditions, so it is difficult to detect the latter condition. In this case, infrared light is emitted when intake air is compressed, and this may activate a photoelectric conversion element.

As a result, 9 engines are idling and rotating at high speed.

It was difficult to detect accurate ignition timing under conditions where both high-load conditions were repeated.

In order to solve this problem, we developed a photodetector element.

Alternatively, it has been found that it is effective to provide an independent infrared shielding filter between the element and the photodetecting member. Another problem is that the high-pressure gas in the combustion chamber enters the detection device through the gap between the light detection member and its housing, and the end surfaces of the filter and light detection member are exposed to carbon fines and tar contained in the gas. may be contaminated by As a result, especially when the engine is idling, the amount of light decreases, making it difficult for combustion light to efficiently reach the photoelectric conversion element. [Problems to be Solved by the Invention] The present invention has been made to solve the problem that combustion light is difficult to efficiently reach a photoelectric conversion element.

[Means for solving problems]

The present invention relates to a light detection member that transmits combustion light within a combustion chamber of an internal combustion engine to the outside of the combustion chamber, and a filter that removes infrared components in the combustion light that has passed through the light detection member.

In a combustion light detection device for an internal combustion engine, which includes a photoelectric conversion element that converts combustion light that has passed through the filter into an electrical signal, the filter includes a coating formed on an end surface of the photodetection member on the side where the photoelectric conversion element is installed. This is a combustion light detection device characterized by being a film.

The present invention will be described below with reference to two drawings.

FIG. 1 is a sectional view showing an example of a combustion light detection device.

In this figure, 1 is a photodetecting member.

Glass, etc., which has excellent heat resistance, impact resistance, and high light transmittance, is preferable. 2 is a photodetector housing made of a hollow heat-resistant material. The housing 2 is configured to be attached to the engine with the end face 11 of the photodetecting member peeking into the combustion chamber (not shown) through a male threaded portion 21 formed therein. 3 is a photoelectric conversion element 4 The housing 2 is a photoelectric conversion unit with a built-in internal thread 31.
It is screwed into the male thread 22 formed in the. Reference numeral 5 denotes a shock absorbing material for absorbing the shock of combustion pressure acting on the photodetecting member 1. 6 is a filter coated with a film on the surface of the end face 12 of the photodetecting member. The structure of the filter is 2, for example, a structure in which thin layers of TiO□ and SiO□ are alternately laminated (referred to as an alternating thin layer multilayer).

In this structure, a thin layer of Al2O3 is added to the end surface side of the photodetecting member, a structure in which a thin layer of Al2O3 is added to an alternating thin layer of MgPz and ZrO□, or a thin layer of CeF3 is added to the end surface side of the photodetecting member.
There is a structure in which a thin layer of MgO is added to a thin layer of alternating layers of Z and ZnS. These multilayer coating films are filters that have characteristics of interfering and reflecting light between multiple layers and sharply blocking unnecessary infrared components, and can be formed by sputtering. Material of each thin layer.

The thickness is arbitrarily determined depending on the desired shielding wavelength. The shielding wavelength is usually 6000 Å or more.

Further, the filter may be one in which the end surface 12 is coated with powders of TiO2 and MgF2.

[Effect]

Combustion light in the combustion chamber passes through the material of the photodetector through the end surface 11 of the photodetector, harmful infrared components are removed by a filter 6 provided on the surface of the other end 12, and the remainder is transferred to the photoelectric conversion element 4. and is converted into an electrical signal.

The detected signal is supplied to the ignition timing detection circuit 79 and the engine control circuit 8, and together with other signals such as the engine speed, this control circuit drives the fuel injection pump 9 under optimal conditions if the engine is a diesel engine. .

〔Effect of the invention〕

When the combustion light detection device of the present invention is used for a long period of time, high-pressure combustion gas seems to enter the device, albeit in a small amount, probably from the outer periphery of the light detection member 1. Then,
The fine carbon powder and tar contained in the invading gas are exposed to the end surface of the optical detection member.

It may adhere to the surfaces of filters and photoelectric conversion elements and contaminate them. As a result, the amount of light reaching the photoelectric conversion element decreases, and accurate ignition timing detection may not be possible.

However, in the device of the present invention, since the filter 6 is coated on the end surface 12 of the photodetecting member 1 in the form of a film, the surface that is contaminated by combustion gas is reduced.

As a result, it is possible to obtain the effect that the amount of light reaching the photoelectric conversion element 4 does not decrease for a long period of time.

Furthermore, since the end face of the light detection member is coated with a filter, the combustion light that has entered the light detection member is less likely to be reflected in the necessary wavelength component light. As a result, it is possible to obtain the effect that component light of a desired wavelength effectively reaches the photoelectric conversion element.

〔Example〕

Example 1 A combustion light detection device having the structure shown in FIG. 1 was manufactured using a 5 iOz glass rod (length 70 mm, diameter 6 mm) as a light detection member. On the end surface 12 of the photodetecting member 1, there is a frame 4 J'v
Tar 6 Tor L Te AhOz Chisel 1 layer 61 (*Sa 1+
)and.

Thickness of the alternating multilayer CTi0□ layer consisting of a thin layer 62 of Tie and a thin layer 63 of Sing on top of it: h+t4.
F+ks+tl. .

Thickness of SiO□ layer: Lit L%+ jff+ L+
++ tl t) was coated by sputtering. The structure of the coating film is schematically shown in FIG. Table 1 also shows the thickness of each thin layer. Four sets of device numbers 101 to 104 were used to combine the thicknesses of each layer.

Table 1 On the other hand, a phototransistor having the photosensitivity characteristics shown in FIG. 3 was used as the photoelectric conversion element.

Example 2゜A11as of the filter of Example 1 was replaced with CeFs, T
A combustion light detection device was manufactured in the same manner as in Example 1 except that i01 was replaced with ZrO□ and Sin was replaced with MgF 2 as the filter 6. Two types of combinations of the thickness of each thin layer were carried out with device numbers 105 and 106, and the thickness of each layer is shown in Table 2.

Table 2 Example 3 747L/ter (7) A120 of Example 1. A combustion light detection device was manufactured in the same manner as in Example 1 except that a filter was used in which MgO was replaced with MgO, TiOz was replaced with ZnS, and Sing was replaced with CaF2. The thickness combination of each thin layer is device number xo7. The thickness of each layer is shown in Table 3.

After examining the light detection characteristics of the combustion light detection devices listed in Table 3, they were installed in a diesel internal combustion engine to detect combustion light. The cutoff wavelengths (wavelengths at which transmittance attenuates to 50%) of each device are shown in Tables 1 to 3. Also.

The photodetection characteristics are shown in FIG. The curve number in the figure indicates the device number.

As a result of combustion light detection, infrared light is thought to be generated due to the high temperature of the gas in the combustion chamber due to the compression process (this infrared light is not seen during idling (low speed)).
Since the light can be cut out, only the light from actual combustion can be detected.

As a comparative example, a separately prepared glass plate was fabricated with the alternating thin layers of Example 1, and the plate was placed between the photodetection member and the photoelectric conversion element to detect light for a long time (500 minutes).
time) went. As a result, the photodetection signal level was reduced to only 95% in the case of the 9th invention, but it was reduced to 80% in the case of the comparative example.

After the test, we disassembled the device and investigated, and found that the decrease in signal level was due to the filter surface or the photoelectric conversion element.

It was found that this was due to contaminants adhering to the end face of the photodetecting member.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view for explaining the present invention in detail, Fig. 2 is a schematic diagram showing a cross section of a filter in an example, and Fig. 3 is a cross-sectional view of a photoelectric conversion element used in an example. FIG. 4 is a diagram showing the sensitivity characteristics of the combustion light detection device of the example. 1... Light detection member, 2... Housing 3...
Photoelectric conversion section, 4... Photoelectric conversion element 6... Filter

Claims (4)

[Claims] (1) A light detection member that transmits combustion light in the combustion chamber of an internal combustion engine to the outside of the combustion chamber, a filter that removes the infrared component of the combustion light that has passed through the light detection member, and an electrical signal that converts the combustion light that has passed through the filter. In the combustion light detection device for an internal combustion engine, the filter includes a photoelectric conversion element that converts
A combustion light detection device characterized by a coating film formed on an end face of a photodetection member on the side where a photoelectric conversion element is installed. (2) The above coating film consists of TiO_2 and SiO_
The combustion light detection device according to claim (1), characterized in that the combustion light detection device is comprised of an alternating thin layer of Al_2O_3 and a thin layer of Al_2O_3 provided on the light detection member side of the alternating thin layer. . (3) The above coating film is composed of MgF_2 and ZrO_
The combustion light detection device according to claim (1), characterized in that the combustion light detection device is comprised of an alternating thin layer of Al_2O_3 and a thin layer of Al_2O_3 provided on the light detection member side of the alternating thin layer. . (4) The above-mentioned coating film is composed of thin alternating multilayers of CaF_2 and ZnS, and a thin layer of MgO provided on the photodetecting member side of the thin alternating multilayers. The combustion light detection device described in (1).