JPH01229917A - Ignition time sensor - Google Patents

Abstract

PURPOSE:To avoid adhesion of deposit to an end part of a light guiding member thereby to prevent reduction of the transmitted light amount, by providing a light transmitting member between an end face of said light guiding member and an opening at an end part of a casing so that the position of said light transmitting member is spaced from said opening a distance 1mm-1.5 times the inner diameter of said opening. CONSTITUTION:A light transmitting member 15 is provided between an end face 21 of a light guiding member 2 and an opening 13 at an end part of a casing 1. The position of the light transmitting member 5 is so set that a distance from the opening 13 of the casing 1 to the light transmitting member 5 is 1mm-1.5 times of the inner diameter of the opening. Since the gap between the light transmitting member 5 and the casing 1 is tightly sealed, the combustion chamber is completely isolated from within the casing 1, and the burning gas does not invade into the casing 1. Therefore, the reduction of the transmitted light amount due to adhesion of the deposit can be prevented, whereby the ignition time can be correctly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition timing sensor that is installed in an internal combustion engine and that detects ignition timing by guiding combustion light within a combustion chamber into the sensor through a light guiding member.

[Prior Art] In recent years, improvements in output, fuel efficiency, or exhaust gas purification performance have become important issues, particularly in automotive diesel engines and gasoline engines.

One way to achieve this is to install an ignition timing sensor that detects combustion light in the engine combustion chamber, detect the ignition timing from the ignition timing sensor output, and adjust the timing control valve, for example, according to the detection result. It has been proposed to use feedback control to control the fuel injection timing.

An example of such an ignition timing sensor is shown in FIG. In the figure, a light guide member 2 made of a quartz glass rod or an optical fiber is inserted into a cylindrical case 1, and its rear end is fixed to the inner wall of the case 1 with an adhesive 3. A threaded portion 11 is provided on the outer periphery of the cylindrical case 1, so that the cylindrical case 1 can be housed in a recessed engine cylinder head or the like while keeping the inside of the combustion chamber isolated from the outside air.

The tip surface 21 of the light guiding member 2 is semispherical,
The tube 16 is welded to the inner periphery of the tip of the cylindrical case 1 and is exposed into the combustion chamber through the opening at the tip.

The open end of the tube 16 is slightly reduced in diameter along the spherical surface of the distal end surface 21 to prevent the light guiding member 2 from being pulled out in the distal direction.

At the rear end of the light guide member 2, a light receiving element 4 made of a silicon phototransistor or the like is disposed to face the light receiving element 4.
receives the combustion light in the engine combustion chamber extracted through the light guide member 2 and converts it into an electrical signal. The output of the light receiving cable 4 is connected to a lead wire 41 extending from the rear end of the light receiving cable 4.
through the terminal 42 connected to this,
It is input to an electronic control unit (concave) that controls fuel injection timing.

[Problems to be Solved by the Invention] Incidentally, in the ignition timing sensor having the above configuration, the tip surface 2 of the light guide member 2 that guides combustion light in the combustion chamber to the light receiving element 4
1 is exposed in the combustion chamber, deposits such as calcium-based compounds and soot produced by the combustion of oil adhere to the exposed surface of the light guide member 2, which reduces the amount of light passing through the light guide member 2. There was a problem in that the ignition timing was not accurately detected because of the decrease in the amount of ignition.

The object of the present invention is to remove these deposits at the tip of the light guide member.
It is an object of the present invention to provide a highly reliable ignition timing sensor that prevents the adhesion of particles and decreases in the amount of transmitted light.

1. Means for Solving the Problems] The configuration of the present invention will be explained with reference to FIG.
In an ignition timing sensor that guides combustion light entering from the distal end surface 21 of the bipedal light guide member 2 facing into the combustion chamber through the case tip opening 13 to a light receiving section provided outside the combustion chamber, the light guide member 2 and the above-mentioned tip surface 21 of case 1.
- Translucent member 5 made of sapphire between the tip opening 13
is provided to airtightly seal between the outer periphery of the light-transmitting member 5 and the inner periphery of the case 1 to prevent the intrusion of combustion residue, and the installation position of the light-transmitting member 5 is 1 mm from the tip opening 13 of the case 1.
~Length 1.5 times the inner diameter of the opening, e.g. 3.6mm inner diameter
It is set 1 to 5 mm inward.

The light guiding member 2 has a flat plate shape, and includes a light transmitting member 5 and a case 1.
is hermetically sealed with a metal bonding layer 6 containing titanium, preferably titanium and molybdenum. The above-mentioned cylindrical case 1 is 1.2 x 1 at 800°C.
It is composed of a metal material having a coefficient of thermal expansion of 0-5/°C or less. Alternatively, a heater 7 (FIG. 6) may be provided on the back surface of the light-transmitting member 5 at a position that does not significantly block the combustion light.

[Operation] Deposits can be broadly divided into calcium-based deposits whose main component is calcium and soot. Among these, soot burns and peels off at high temperatures of 500 to 600 degrees Celsius or higher, so it can be removed to some extent during operation, but calcium deposits do not decompose even at extremely high temperatures and remain firmly attached, resulting in the amount of light transmitted. This is the main factor contributing to the decrease.

The degree of adhesion of this calcium deposit is determined by the transparent member 5.
This is largely related to the installation position of the case 1, and if it is flush with the tip of the case 1, the amount of deposit will be the largest, and the further inside the case 1, the less calcium-based deposits and the more soot will be.

Then, set the installation position 1 to 5M from the case 1 tip opening 13.
If it is placed inward, the adhesion of soot increases and calcium-based deposits are formed on the soot, and are removed when the soot burns or falls off. In addition, the installation position is 5mm
If it is further inward, too much soot will adhere, and the removal effect by combustion will be reduced. The inner diameter of the opening of this sensor is 3.6 mm, and if the inner diameter changes, the allowable range of the sapphire plate installation position changes. The acceptable range is tip 1.
The allowable length is from 1.5 mm to 1.5 times the inner diameter, and within this range, neither calcium-based tebosite nor its soot partner adhere to the sapphire plate.

Furthermore, in the present invention, sapphire constituting the light transmitting member 5 has superior corrosion resistance compared to, for example, quartz constituting the light guide member 2, so that the surface smoothness is maintained and deposits do not adhere to the sapphire. It becomes easy to peel and prevents adhesion.

Furthermore, if the light-transmitting member 5 is made into a flat plate, the combustion gas collides with the light-transmitting member 5 straight, and the gas flow does not stagnate near the light-transmitting member 5, which prevents deposits from adhering. big. If a heater 7 is provided on the back surface of the transparent member 5, combustion of soot will be promoted.

[Effects of the Invention] The ignition timing sensor of the present invention includes a light-transmitting member made of sapphire between the case tip opening and the light guide member, and the installation position is one cylinder to the inner diameter of the opening from the case tip opening. 1.
Since the length is 5 times longer, deposit adhesion is significantly reduced.

Further, since the space between the light-transmitting member and the case is hermetically sealed, the inside of the case and the combustion chamber are completely shut off, and combustion gas does not enter. Therefore, it is possible to prevent a decrease in the amount of light transmitted due to the attachment of deposits, and it is possible to accurately detect the ignition timing.

[Example] FIG. 1 shows an example of the present invention. In the figure, a light guiding member 2 made of a quartz glass bar is inserted into a cylindrical case 1, and its rear end portion is adhesively fixed to the inner wall of the cylindrical case 1. A threaded portion 11 is provided on the outer periphery of the cylindrical case 1, and the threaded portion 11 is used to fix the inside of the combustion chamber to the cylinder head of the engine (equivalent) while shielding the inside of the combustion chamber from the outside air. is similar to the conventional one (FIG. 2) described above.

A tip opening 1 is provided at the tip of the cylindrical case 1 facing into the combustion chamber.
3 and the distal end surface 21 of the light guide member 2, a flat light transmitting member 5 is disposed and supported by a stopper portion 12 provided on the inner wall. The space between the outer periphery of the transparent member 5 and the inner periphery of the opening 13 is hermetically sealed by a metal bonding layer 6 containing titanium and molybdenum. At this time, the distance '4fJ from the tip opening 13 of the case 1 to the tip of the transparent member 5 is 1 to 5.
It should be within the range of ITlff+.

The transparent members are made of sapphire, which has excellent corrosion resistance and heat resistance. Quartz is a material having a similar rod quality, but quartz has slightly lower corrosion resistance than sapphire and also has an extremely small coefficient of thermal expansion, so it does not bond well with the case 1.

The case 1 is preferably made of a metal material with a small coefficient of thermal expansion, specifically, a coefficient of thermal expansion of 1.0 at 800°C.
2X10'/℃ or less, such as 54Fe-29Ni
-17Co alloy can be suitably used. Thermal expansion coefficient is 1
, 2 x 10"5/'C or more, the difference in coefficient of thermal expansion with the transparent member 5 will be large, and there is a risk that the transparent member 5 will be damaged during the heating and cooling process during bonding. There is.

The case 1 and the transparent member 5 are bonded together as follows. First, a titanium metal thin film is formed on the outer peripheral surface of the light-transmitting member 5 by sputtering, and a molybdenum metal thin film is formed on the outer surface thereof by sputtering.

Next, the surface is plated with nickel, placed in the opening 11 of the case 1, and brazed. The thickness of the titanium metal thin film is 5000, and the thickness of the molybdenum metal thin film is 100.
00 to 15000A.

By doing so, it is possible to create an airtight seal between the case 1 and the light-transmitting member 5, and prevent combustion gas from entering the case 1 and adhering to the light guide member 2 to the deposit 1. . Note that tungsten may be used instead of molybdenum.

In the figure, 22 is an O-ring that seals between the case 1 and the light guide member 2, and a ring made of resin or the like is provided between the O-ring 22 and the contact part 14 provided on the inner wall of the case 1. 1
The arrangement includes a first copper ring 23 tightly fitted to the inner periphery of the case 1 and a second copper ring 24 tightly fitted to the outer periphery of the light guide member 2 via a backup ring 25 . At the rear end of the O-ring 22 is a second hack-a-ra printer 2.
There are 6 printers, and at the rear end there is a hackara printer 26.
A stopper 15 is provided to prevent it from coming off.

Next, the ignition timing sensor of the present invention was installed in a tea cell engine (
Installed in the combustion chamber (auxiliary chamber) of 2400cc>, rotation speed 40
A continuous durability test of 00 r p rr+ and 300 hours was conducted. The distance f4g from the tip opening 13 of the case 1 to the tip of the transparent member 5 was set to 2 mm.

As is clear from the results shown in Figure 3, the amount of transmitted light after 300 hours of durability is 72% of the initial value of 100%, and with the conventional ignition timing sensor shown in Figure 2, the amount of transmitted light after 200 hours of durability is 72% of the initial value of 100%. compared to a decline of up to 2%.
It can be seen that the case for translucency was significantly defeated. here,
The amount of transmitted light was measured by returning the engine operating under durability conditions to an idle state and running the engine idle for 10 minutes, then stopping the engine, removing the sensor, and lightly blowing the surface of the light-transmitting member 5 with tissue paper containing alcohol. This is the value measured afterwards. This work thins out the soot that burns and falls off when the engine is under high load, and reduces adhesion to calcium-based deposits that adhere firmly to translucent materials.
ll! I did 2.

Next, for a sensor with a similar structure, the distance ρ from the tip opening 13 of the case 1 to the tip of the transparent member 5 was set to 0.5 mm.
, 2 mm, 5ITITI+, and 7 mm, and the evaluation was performed. The results are shown in Figure 4. The durability conditions were the same as those in the durability test described above, and changes in sensor output over time were examined with the sensor still installed in the engine. For evaluation, the output voltage of a light-receiving element made of a transistor provided at the rear end of the light guiding member 2 was used. FIG. 5 is a circuit diagram of the light receiving element. In the figure, 5■ is applied to Vcc, and RL is 1.2.
A resistor of Ω was used.

As is clear from FIG. 4, the rate of decrease in sensor output is the smallest when Ω"" 2 mm, and the effect decreases even if ρ is longer or shorter than this. In particular, when it exceeds 9 or 5M, the rate of decrease in sensor output becomes large, and there is no significant difference from conventional products.

In addition, when the sensor was removed from the engine and the state of deposits was examined, it was found that the conventional product had a lot of calcium deposits and not much soot. On the other hand, the product of the present invention showed a lot of soot adhesion and less calcium-based deposits.

And 1. When Q = 2mm, there is little adhesion of both soot and calcium deposits, and when D = 0.5M, some calcium deposits are observed. That is, the shorter the number 1, the less soot and the more calcium-based deposits are attached. On the other hand, as ρ increases, soot increases, and when N=7 mm, soot that cannot be contained remains even at high rotations of 4000 rpm, resulting in a large rate of decrease in sensor output. From the above results, it is considered desirable that ρ be in the range of 1 to 5 ITIm, preferably 1 to 3M.

FIG. 6 shows another embodiment of the present invention, in which a transparent member 5 is disposed 7 in the opening at the tip of the cylindrical case 1 and supported by a stopper 17 provided at the tip of the case 1. -F The space between the transparent member 5 and the collar 17 is airtightly sealed by the metal bonding layer 6.

As shown in FIG. 7, on the back surface of the light-transmitting member 5, a shield 7 made of a platinum film is formed in an annular shape along the periphery. A lead wire 71 extends from the heater 7 and connects the light guide member 2
It is connected to an electrode rod 72 arranged around the outer periphery. Electrode rod 72
is embedded and fixed in fluororubber 73.

In the above configuration, the heater 7 heats the transparent member 5 by 500°
If heated to a temperature of .degree. C. or higher, the combustion of soot is promoted even during low-speed, low-load operation, which further improves the effect of preventing deposits and improves reliability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an ignition timing sensor showing an embodiment of the present invention, FIG. 2 is a sectional view of a conventional ignition timing sensor, and FIG. 3 is a sectional view of a conventional ignition timing sensor.
The figure shows the temporal change in the amount of transmitted light during the durability test.
Fig. 4 is a diagram showing the time course of the sensor output in the durability test, Fig. 5 is a circuit diagram of the light receiving element used in the durability test, and Fig. 6 is a diagram showing the main components of an ignition timing sensor showing another embodiment of the present invention. FIG. 7 is a view of the transparent member viewed from the back side. 1... Cylindrical case 13... Opening 2... Light guiding member 5... Light transmitting member 6... Metal bonding layer 7. ...Heater 1 Figure 13/' Figure 2 Figure 6

Claims (1)

[Scope of Claims] (1) A light guide member is inserted into a cylindrical case provided through a wall of a combustion chamber of an internal combustion engine, and light enters from the front end surface of the light guide member facing into the combustion chamber through the opening at the front end of the case. In the ignition timing sensor, a light-transmitting member made of sapphire is provided between the tip surface of the light guiding member and the tip opening of the case, and a light-transmitting member made of sapphire is provided between the tip surface of the light guide member and the tip opening of the case. The outer periphery of the transparent member and the inner periphery of the case are sealed airtight to prevent combustion gas from entering, and the installation position of the transparent member is set at a distance of 1 mm to 1.5 times the inner diameter of the opening from the opening at the tip of the case. The ignition timing sensor is characterized by being set to (2) The ignition timing sensor according to claim 1, wherein the light-transmitting member has a flat plate shape and is airtightly sealed with a metal bonding layer containing titanium. (3) The ignition timing sensor according to claim 2, wherein the metal bonding layer contains titanium and molybdenum. (4) The ignition timing sensor according to claim 1, wherein the cylindrical case is made of a metal material having a coefficient of thermal expansion of 1.2 x 10^-^5/C or less at 800C. (5) The ignition timing sensor according to claim 1, further comprising a heater provided on the back surface of the transparent member at a position that does not significantly block combustion light.