JPH0440343A - Alcohol content detecting device - Google Patents

Abstract

PURPOSE:To measure content without any delay even if the temperature of the device varies by making the light emitted by a light emitting element incident on a light-transmissive fuel partition wall and a transparent body, transmitting, refracting, and reflecting the light, and then making the light incident on a linear optical position detecting element. CONSTITUTION:The light emitting element 4 emits the light, which becomes parallel luminous flux 11 and is made incident directly on the light-transmissive fuel partition wall 10 vertically, transmitted in the fuel in a fuel chamber 6, and then made incident on a point P0 on the refracting surface of the transparent body 13 at an angle phi of incidence. The luminous flux 11 is refracted at an angle x of refraction and transmitted in the transparent body 13 and the transmitted light is reflected at a point P1 on a reflecting surface 14 formed at the other end, made incident on a point P2 on the refracting surface again, and refracted into the fuel again. This refracted light is made incident on the point P3 on the partition wall 10 and refracted, and then transmitted in the partition wall 10, and the transmitted light is made incident on the linear optical position detecting element 16 through a condenser lens 15. Photocurrents i1 and i2 corresponding to the incidence position are inputted to a detecting circuit 100, whose output voltage corresponds to the alcohol content in the fuel. Thus, the alcohol content is given in the form of the ratio of the photocurrents, so accurate and continu ous detection becomes possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a device for non-contact determining the properties of fuel supplied to a combustor, etc., and particularly for determining the properties of alcohol-mixed fuel used in automobile engines. This invention relates to a device for measuring alcohol content.

[Conventional technology]

In recent years, in order to reduce oil consumption in the United States and European countries, fuel made by mixing alcohol with gasoline has become popular for use in automobiles. If such an alcohol blended fuel is directly used in an engine that has been matched to the air-fuel ratio of gasoline fuel, the air-fuel ratio will become lean due to the fact that the stoichiometric air-fuel ratio of alcohol is smaller than that of gasoline.
The alcohol content rate in the alcohol mixed fuel is detected to control actuators such as fuel injection valves, and the air-fuel ratio, ignition timing, etc. are adjusted according to the alcohol content rate.

Conventionally, as an alcohol content detection device as described above, the one described in, for example, Japanese Patent Laid-Open No. 57-51920 is known. Such a conventional device will be explained below with reference to FIGS. 5 and 6.

FIG. 5 is a block diagram showing a fuel control system equipped with a conventional alcohol content detection device, in which A is the alcohol content detection device, 37 is an automobile engine, and 36 is an engine 37.
22 is a fuel tank, 23 is a fuel injection valve that injects fuel into
25 is a fuel pump, 25 is a high-pressure filter provided in the middle of the fuel supply pipe 24 connecting this pump 23 and the alcohol content detection device A, 26 is a fuel distribution pipe, 27 is a fuel regierator, 28 is a fuel return pipe, 29 is an air-fuel ratio sensor, 30 is a spark plug, 31 is an engine rotation sensor that detects engine rotation, 32 is an intake pressure sensor,
33 is a throttle valve, 34 is an air cleaner, and 35 is a control device, which includes a signal from the alcohol content detection device A, a signal from the air-fuel ratio sensor 29, an engine rotation sensor 31 and an intake pressure sensor which are the state quantities of the engine 37. A signal such as 32 is input manually, and the fuel injection valve 36 is controlled by a control amount according to the human input.
In FIG. 0, when the fuel tank 22 is filled with alcohol mixed fuel, the engine 3
7 starts, alcohol mixed fuel is pumped to fuel pump 2.
3, and is led to the alcohol content detection device A through the fuel supply pipe 24 and the high pressure filter 25, where the alcohol content is measured. The fuel is then transferred to fuel distribution pipe 2.
6, a portion is supplied to the engine 37 from the fuel injection valve 36, and the rest is returned to the fuel tank 22 through the fuel pressure regulator 27 and fuel return pipe 28.

The fuel pressure regulator 27 always maintains the pressure up to the fuel distribution pipe 26 at a constant value, regardless of the amount of fuel injected by the fuel injection valve 36. When the alcohol content measured by the alcohol content detection device A is input to the control amount r35, the control device 35 detects the engine rotation sensor 31 and the intake pressure sensor 3.
The engine condition is determined based on the 2nd class signal, and the fuel injection valve 2
1 by controlling the valve opening time to change the amount of fuel supplied to the engine 37, detecting the air-fuel ratio with the air-fuel ratio sensor 29, and feedback-controlling the air-fuel ratio so that it becomes a target value corresponding to the engine state, Further, the ignition timing of the spark plug 300 is controlled according to the engine condition.

FIG. 6 shows the configuration of a conventional alcohol content detection device A, in which 1 is a cylindrical transparent body made of optical glass or the like, 2 is a case, and 3 is a cylindrical transparent body 1 and a case 2. 4 is a light emitting element such as an LED, 5 is a light receiving element such as a photodiode, 6 is a fuel chamber, 6a is a fuel inlet, 6b is a fuel outlet, 7a is totally reflected light, 7b is refracted light, 100 is a detection circuit that drives the light-emitting element 4 and measures the amount of light received by the light-receiving element 5. The outer circumferential surface of the cylindrical transparent body l is in uniform contact with the fuel in the fuel chamber 6. The light emitted from the light-emitting element 4 is is incident on the outer peripheral surface of the cylindrical transparent body 1, that is, the interface with the fuel, but at this time, the refractive index Nt of the fuel and the cylindrical transparent body 1
Due to the difference between the refractive index of
is totally reflected and reaches the light receiving element 5, and the incident angle is the total reflection angle ψ
Since the smaller light 7b is refracted and transmitted through the fuel, the light receiving element 5 receives only the light whose incident angle on the boundary surface is greater than or equal to the total reflection angle φ. When the alcohol content in the fuel changes,
Since the refractive index N of the fuel changes and the total reflection angle φ changes, the amount of light received by the light receiving element 5 changes. By measuring this change in the amount of light received by the detection circuit 100, the alcohol content in the fuel can be determined.

[Problem to be solved by the invention]

However, in such a conventional alcohol content detection device, the amount of light emitted by the light emitting element 4, the light receiving sensitivity of the light receiving element 5, and the peak sensitivity frequency change depending on the temperature, so detection is detected based on engine heat generation and the resulting rise in fuel temperature. When the temperature of the device changes, the amount of light received by the light-receiving element 5 also changes, and the alcohol content in the fuel cannot be determined accurately.

Additionally, because the angle of total reflection ψ cannot generally be made too small due to the restriction of the refractive index N4 of the cylindrical transparent body 1, there is a problem that the cylindrical transparent body 1 cannot be made very short and the device cannot be miniaturized. . For these reasons, conventional alcohol content detection devices have to be installed separately from the engine, so they do not actually detect the fuel injection valve 36, especially when starting the engine.
It is impossible to detect the alcohol content of the fuel injected from the fuel chamber 6 of the alcohol content detection device A without delay, especially when starting the engine after refueling with fuel with a different alcohol content. It is also expected that there will be a starting mode in which there will be a difference in the alcohol content in the fuel distribution pipe 26.
In such a case, it is expected that in the worst case, a problem will occur in which the engine cannot be started.

This invention was made to solve these conventional problems, and it is possible to continuously and accurately detect the alcohol content of fuel without any delay even when the device temperature changes. The purpose of the present invention is to obtain a small-sized alcohol content detection device that can be installed near 26 or the like.

[Means to solve the problem]

The alcohol content detection device according to the present invention detects the alcohol content in the fuel by detecting the refractive index of the fuel. a fuel partition, a light-transmitting body provided with a fuel refractive surface on one side and a reflective surface on the other side, and having a refractive index equal to or higher than the refractive index of the light-transmitting fuel partition; a light-absorbing member that covers at least an outer circumferential surface of the body excluding the refracting surface, and the light emitted from the light emitting element is incident on the refracting surface of the light-transmitting body with the fuel on one side through the transparent fuel partition wall. The refracted light is reflected by the reflective surface on the other side of the light-transmitting body, and then made incident on the refracting surface again, and the refracted light at the refracting surface is again transmitted to the one-dimensional light through the light-transmitting fuel partition wall. The light is made incident on the position detection element.

[For production]

The alcohol content detection device of the present invention allows light emitted from a light emitting element to enter a refracting surface with fuel on one side of a light transmitting body through a light transmitting fuel partition, and directing this refracted light to the light transmitting body. After being reflected by the reflecting surface on the other side, the light is made to enter the refracting surface again, and the light refracted by the refracting surface is again made to enter the one-dimensional optical position sensing element via the light-transmitting fuel partition. By measuring the change in the refractive index of the fuel due to the change in the alcohol content in the fuel as a change in the light incident position on the one-dimensional optical position detection element, the alcohol content in the fuel can be detected with high accuracy.

In addition, the light absorbing member prevents a portion of the incident light from being scattered when a foreign object or the like adheres to the refractive surface, repeatedly reflecting on the side surface of the transparent body, and being received as stray light by the one-dimensional optical position detection element. It acts to prevent.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows a configuration diagram of an alcohol content detection device according to the present invention, and in the figure, the same parts as those of the conventional example shown in FIG. 6 are given the same reference numerals. 8 is the aperture, 9 is the collimating lens,
10 is a translucent fuel partition, 11 is a parallel light beam, 12 is a fuel inlet/outlet to the fuel chamber 6, 13 is a translucent body, one side is in contact with the fuel, and the other side is provided with a reflective surface 14, and 15 is a condenser. Lens 16 is a one-dimensional optical position detection element, and here the case is shown in which a semiconductor device detection element (hereinafter referred to as PSD) is used; 18 is a black light absorbing member covering the outer peripheral surface of the transparent body 13; A driving section 101 that drives the light emitting element 4 with a detection circuit, a preamplification section 102 for photocurrent of the PSD 16,
It consists of an addition section 103 and a division section 104. Also, Figure 2 shows P
An explanatory diagram of the SD, FIG. 3 is an output characteristic diagram of the device.

Next, the operation of the embodiment will be explained. In FIG. 1, when the light emitting element 4 is driven by the drive unit 101 of the detection circuit 100 to emit light, the emitted light passes through the aperture 8 and becomes a parallel light beam 11 at the collimating lens 13. The light is perpendicularly incident on the partition wall lO and transmitted therethrough, and after further passing through the fuel in the fuel chamber 6, it is incident on the refractive surface of the transparent body 13 at an incident angle ψ at 80 points. The refracting surface is in contact with the fuel flowing into the fuel chamber 6 from the fuel inlet/outlet 12, and the parallel light beam 14
is the refractive index N of the fuel and the refractive index N of the transparent body 13 at 80 points.

Due to the difference between the two, it is refracted at a refraction angle X x = arcSIN (Nd2/NrXSINψ). The parallel light beam 11 refracted at the refraction angle X at 80 points passes through the transparent body 13 and reaches the reflective surface 14 formed at the other end
It is reflected at point P of , and P! is reflected again on the refracting surface. point, and is refracted into the fuel □ according to the above relational expression between the incident angle ψ and the refraction angle X.

The refracted light at these 22 points is transmitted to the transparent fuel partition wall 10.
It enters at the layer point and is similarly refracted according to the above relational expression between the incident angle ψ and the refraction angle χ, then passes through the translucent fuel partition lO, enters the condenser lens 15, and reaches the PSD 16. . The focal length of the condenser lens 15 is selected so that the parallel light beam 11 is substantially focused on the PSD 16.

It is advantageous that the light-emitting element 4 used emits near-infrared light of about 900 nm to match the light receiving frequency sensitivity range of the PSD 16, and that the drive unit 101 causes the drive unit 101 to emit pulsed light so as to eliminate dark current depending on the temperature of the PSD 16. In addition, the translucent fuel partition l
By making the refractive index N□ of O smaller than the refractive index N, t of the light-transmitting body 13, the change in the refraction angle at the atmospheric interface of the light-transmitting fuel partition wall 10 can be made smaller, and reflection can be prevented, thereby increasing the transmittance of the optical system. This is advantageous in that it is possible to increase the change in the angle of refraction at the refractive surface of the light transmitting body 13 with respect to the fuel, and it is possible to increase the gain of light incident position change on the PSD 16 with a small light transmitting body 13.

If metal powder, etc. mixed in the fuel adheres to the refractive surface of the transparent body 13, especially the light incident points Pa and Pm, a part of the incident light will be scattered and the light will be scattered on the outer peripheral surface of the transparent body 13 In order to prevent the light from being repeatedly reflected and received as stray light by the PSD 16, a light absorbing member 18 finished in black is provided.

Next, referring to FIG. 2, the principle of optical position detection of the PSD 16 will be explained. PSD is an optical center of gravity position detection element using a silicon photodiode, and consists of a resistive layer (P layer), an intermediate layer,
It is composed of three N layers, and when a light spot is incident, photocurrents i, , i1 pass through the uniform resistance layer from the incident position, are divided into electrodes 11+12, and flow, resulting in a photocurrent of 11+
+1 is divided and output in inverse proportion to the distance to the electrode.

Now, let the distance from the electrode 11 to the light incidence position be X, and PS
If the distance between the electrodes of D is L, then the position X is X=L X i
It is given by t/(it + L). At this time, since the position X coincides with the center of gravity of the incident light, the light spot does not necessarily have to have a minute diameter.

In FIG. 1, each electrode of the PSD 16! ,, Photocurrent from I□ III I! is input to the detection circuit 100,
Before! After being amplified by the amplifying section 102, 11 and 18 are added together by the adding section 103, and from the addition result i, the dividing section 1
The voltage ■ corresponding to the position signal X is obtained by dividing ti/(++ 1 it) by 04. , is output as . At this time, the output of the adding section 103 is fed back to the driving section 101, and the light emission intensity of the light emitting element 4 is controlled so that the addition result C+ + ++ 1) is constant. When the refractive index N of the fuel changes as the alcohol content in the fuel changes,
Since the refraction angle χ between the light-transmitting body 13 and the fuel of the light-transmitting fuel partition wall 10 changes, the incident position X of the emitted light from the light emitting element 4 onto the PSD 16 changes, and the output voltage of the detection circuit changes. v, l, and L have values according to the alcohol content.

Figure 3 shows the output voltage vs. methyl alcohol content in gasoline fuel. 1. showed a change in

Since the refractive index of methyl alcohol is smaller than that of gasoline, as the methyl alcohol content increases, the PSD1
Since the light incident position on the electrode 6 shifts to the electrode 1 side and the photocurrent i becomes small, the output voltage V 6@t is inversely proportional to the methyl alcohol content. When the temperature of the detection device A changes due to heat generation from the engine, a rise in fuel temperature, etc., the light emitting element 4
Although the amount of light emitted by the PSD16 and the total photocurrent amount of the PSD16 change, the alcohol content rate is given by the ratio of photocurrents, so it is possible to accurately and continuously measure the alcohol content in the fuel regardless of temperature changes to the detection device. Can be detected. Furthermore, since the alcohol content is detected on only a small portion of the liquid-contacting surfaces of the transparent body 13 and the transparent fuel partition wall 10, there is an advantage that the detection section inserted into the fuel passage can be made smaller.

FIG. 4 is a sectional view of the detection section of the alcohol content detection device of the present invention. Reference numeral 17 denotes a holder having the function of holding the aperture 8, the collimating lens 9, and the condenser lens 15. The translucent fuel partition lO is a flat plate made of white glass or inexpensive optical glass, and is insulated from the fuel side with the case 2 by a seal 3a. The light-transmitting body 13 is a rectangular columnar or cylindrical optical glass whose one end is cut at a predetermined angle with respect to the column axis to serve as a contact surface (refraction surface) with the fuel, and the other end is formed by depositing a metal film or the like to reflect light. [14 was formed to serve as a back mirror. Reference numeral 19 denotes a light-absorbing member that covers the outer circumferential surface of the transparent body 13 except for the contact surface, and is made of, for example, black alumite-treated aluminum. Therefore, since the reflective surface 14 does not touch the fuel, there is no adhesion of dirt in the fuel, no influence of g-erosion caused by the fuel, and no deterioration of reflectance.The lower structure of the case 2 is sealed with the fuel seal 3b. A fuel chamber 6 is formed, and its fuel inlet/outlet 12 is provided with a fuel port 6a and a fuel outlet 6b, respectively, and a light emitting element 4 and a PSD 16 are attached to a high pressure side pipe such as a fuel distribution pipe 26 near a fuel injection valve 36. is fixed to the substrate of the detection circuit 100.

In the above embodiment, the one-dimensional optical position sensing element 16 is a PSD.
The case using a photodiode array, C
It is clear to those skilled in the art that similar effects can be expected even if a digit-1 detection element such as a CD is used. Furthermore, the insulation between the translucent fuel partition wall 10 and the fuel side is not based on the fuel seal 3a, but the space between the translucent fuel partition wall 10 and the case 2 is filled with a sealing agent.
This can be done by adhesion or the like, or by welding or brazing to the case 2 after metalizing the circumferential surface of the translucent fuel partition 10. Furthermore, although the above embodiments described detection of alcohol content in fuel, it goes without saying that the present invention can also be applied to measuring the refractive index of other liquids.

〔Effect of the invention〕

As explained above, this invention includes a light emitting element, a one-dimensional optical position sensing element, a translucent fuel partition, a refractive surface for fuel on one side, and a reflective surface on the other side. A light-transmitting body is provided, and the light emitted from the light-emitting element is made to enter a refracting surface with fuel on one side of the light-transmitting body through the light-transmitting fuel partition wall, and the refracted light is transmitted through the light-transmitting body. After being reflected by the reflection surface on the other side, the light is made to enter the refraction surface again, and the light refracted by the refraction surface is made to enter the one-dimensional optical position detection element again through the light-transmitting fuel partition. Since the alcohol content in the fuel is detected by the light incident position on the one-dimensional optical position detection element, the detection device can be made smaller and can be installed in the pipe near the fuel injection valve. The alcohol content in the fuel injected by the fuel injection valve can be detected continuously without delay, and the alcohol content can be detected with high accuracy regardless of temperature changes in the detection device. Furthermore, even if a part of the incident light is scattered due to foreign matter in the fuel adhering to the refracting surface, a light absorbing member is provided to prevent the scattered light from being received by the one-dimensional optical position sensing element, resulting in a stable alcohol content. Detection becomes possible.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an alcohol content detection device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the optical position detection principle of PSD, and Fig. 3 is the output characteristics of the device with respect to methanol content in gasoline fuel. 4 is a sectional view of the detection unit of the alcohol content detection device of the present invention, FIG. 5 is a configuration diagram of a fuel control system equipped with a conventional alcohol content detection device, and FIG. 6 is a conventional alcohol content detection device. FIG. 2 is a configuration diagram of a rate detection device. 4...Light emitting element, 6...Fuel chamber, 8...Aperture, 9
... collimating lens, 10... translucent fuel partition,
13... Translucent body, 14... Reflective surface, 15... Condenser lens, 16... One-dimensional optical position detection element, 18
．． 19... Light absorption member, 100... Detection circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] An alcohol content detection device that detects the alcohol content in the fuel by detecting the refractive index of the fuel includes a light emitting element, a one-dimensional optical position detection element, a translucent fuel partition, and a refraction device with the fuel on one side. a light-transmitting body having a refractive index equal to or higher than the refractive index of the light-transmitting fuel partition wall, and a reflective surface on the other side; The light-absorbing member covers the light-absorbing member, and makes the light emitted from the light-emitting element enter the refracting surface with the fuel on one side of the light-transmitting body through the light-transmitting fuel partition wall, and transmitting the refracted light to the other side of the light-transmitting body. After being reflected by the reflective surface on the side, the light is made to enter the refracting surface again, and the refracted light at the refracting surface is made to enter the one-dimensional optical position detection element again via the transparent fuel partition wall. Characteristic alcohol content detection device.