JPH0610654B2 - Alcohol content detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for determining the properties of fuel supplied to a combustor or the like in a non-contact manner, and particularly in an alcohol-mixed fuel used for an engine of an automobile or the like. For measuring the alcohol content of

[Conventional technology]

Recently, in countries such as the United States and Europe, fuels in which gasoline is mixed with alcohol are becoming popular for automobiles in order to reduce the consumption of petroleum. If such an alcohol-mixed fuel is used as it is in an engine that matches the air-fuel ratio of gasoline fuel, the air-fuel ratio becomes lean due to the fact that alcohol has a smaller stoichiometric air-fuel ratio than gasoline. The fuel injection valve actuator is controlled by detecting the alcohol content of the fuel injection valve, and the air-fuel ratio, ignition timing, etc. are adjusted according to the alcohol content. Conventionally, as the alcohol content rate detecting device as described above, for example, one described in JP-A-57-51920 is known. Such a conventional device will be described below with reference to FIGS. 8 and 9.

FIG. 8 is a block diagram showing a fuel control system provided with a conventional alcohol content rate detecting device, where A is an alcohol content rate detecting device, 20 is an engine of an automobile or the like, and 21 is a fuel provided in an intake pipe. An injection valve, 22 is a fuel tank, 23 is a fuel pump for sucking the fuel in the tank 22, and 25 is a pump 2
3, a high-pressure filter connected via a fuel supply pipe 24 connected to 3, a fuel distribution pipe 26, a thermal pressure regulator 27, a fuel return pipe 28 connected to the regulator 27, the tip of which is in the tank 22. Has reached 29 is an air-fuel ratio sensor, 30 is a spark plug, 31 is a sensor for detecting engine rotation, 32 is an intake pressure sensor,
33 is a sluttle valve, 34 is an air cleaner, and 35
Is a control device, to which signals from the alcohol content detection device A, signals from the air-fuel ratio sensor 29, signals from the engine rotation sensor 31 and the intake pressure sensor 32, which are the state quantities of the engine, are input, and control is performed according to the inputs. Fuel injection valve 21,
The spark plug 30 and the like are driven. When the alcohol mixed fuel is supplied to the fuel tank 22, the alcohol mixed fuel is pressurized by the fuel pump 23 and guided to the alcohol content rate detecting device A through the fuel supply pipe 24 and the high pressure filter 25 when the engine is started. The content is measured. The fuel then flows into the fuel distribution pipe 26, part of which is supplied to the engine from the fuel injection valve 21, and the other is returned to the fuel tank 22 through the fuel pressure regulator 27 and the fuel return pipe 28. The fuel pressure regulator 27 controls the fuel distribution pipe 26 regardless of the amount of fuel injected by the fuel injection valve 21.
The pressure up to is always kept constant. The alcohol content rate measured by the alcohol content rate detection device A is the control device 3
5, the control device 35 determines the engine state based on signals from the engine rotation sensor 31, the intake pressure sensor 32, etc., and controls the valve opening time of the fuel injection valve 21 to change the amount of fuel supplied to the engine. Then, the air-fuel ratio sensor 29 detects the air-fuel ratio, feedback-controls the air-fuel ratio so that it becomes a target value according to the engine state, and controls the ignition timing of the spark plug 30 according to the engine state.

FIG. 9 is a block diagram of a conventional alcohol content rate detecting device A, in which 37 is a cylindrical light-transmitting body formed of optical glass or the like, 9 is a case, 11 is a cylindrical light-transmitting body 37 and a case 9. Between the fuel seals, 3 is a light emitting element made of an LED, 36 is a light receiving element made of a photodiode, 8 is a fuel flow path, 8a
Is a fuel flow, 38a is totally reflected light, 38b is refracted light, 10 is a detection circuit for driving the light emitting element 3 and measuring the amount of light received by the light receiving element 36, and the outer peripheral surface of the cylindrical light transmitting body 37 is a fuel flow path. 8
And evenly contacts the fuel. The light emitted from the light emitting element 3 is incident on the outer peripheral surface of the cylindrical light-transmitting body 37, that is, the boundary surface with the fuel. At this time, the difference between the refractive index Nf of the fuel and the refractive index Nd of the cylindrical light-transmitting body 37. Makes the incident angle to the boundary surface the total reflection angle Ψ =
The light 38a of arc SIN (Nf / Nd) or more is totally reflected and reaches the light receiving element 36, and the light 38b having an incident angle smaller than the total reflection angle ψ is refracted and transmitted into the fuel. Only the light having an incident angle equal to or larger than the total reflection angle Ψ is received. When the alcohol content in the fuel changes, the refractive index Nf of the fuel changes and the total reflection angle ψ also changes, so the amount of light received by the light receiving element 36 changes. By measuring the change in the amount of received light with the detection circuit 10, the alcohol content in the fuel can be obtained.

[Problems to be Solved by the Invention]

However, in such a conventional alcohol content detection device, since the light emission amount of the light emitting element 3, the light receiving sensitivity of the light receiving element 36, and the peak sensitivity frequency change depending on the temperature, the heat generation of the engine, the rise in the fuel temperature due to the detection, and the like are detected. When the temperature of the apparatus changes, the amount of light received by the light receiving element 36 also changes, and there is a drawback that the alcohol content in the fuel cannot be accurately obtained. Further, in general, the refractive index Nd of the cylindrical light-transmitting body 37 is
Since the total reflection angle Ψ cannot be made too small due to the above restriction, there is a problem that the cylindrical light-transmitting body 37 cannot be shortened so much and the device cannot be downsized. For these reasons, the conventional alcohol content rate detection device has to be installed separately from the engine, and therefore the alcohol content rate of the fuel actually injected from the fuel injection valve 21 is delayed when the engine is started. It is impossible to detect the amount of fuel in the fuel flow path 8 and the fuel distribution pipe 26 of the alcohol content rate detecting device A, especially at the time of starting the engine after refueling fuels having different alcohol content rates. It is expected that there will be a start mode in which there is a difference in alcohol content, and in such a case, a problem that the engine cannot be started will appear in the worst case.

The present invention has been made in order to solve such a conventional problem, and can constantly and accurately detect the alcohol content rate of fuel even if the device temperature changes, and the fuel distribution pipe 26 It is an object of the present invention to obtain a small-sized alcohol content rate detecting device which can be attached also to etc.

[Means for Solving the Problems]

The alcohol content detection device according to the present invention forms a fuel refractive index detection surface in the middle of each of a plurality of elongated optical conductors whose refractive index changes from the surroundings toward the center, and projects it on one end face of the elongated optical conductor. An optical body is provided and a light receiving body is provided on the other end surface.

[Action]

The alcohol content rate detection device of the present invention makes light incident on the fuel refractive index detection surfaces of a plurality of elongated light guides from a light projecting body at one end of the plurality of elongated light guides, and causes total reflection on the fuel refractive index detection surfaces. Light can be received by the light receiving body at the other end of each elongated light guide, the refractive index of the fuel can be detected from the light amount distribution on the light receiving body, and the alcohol content in the fuel can be detected.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a block diagram of an alcohol content detection device according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is an explanatory view of a fuel refractive index detection surface. Is an elongated optical conductor whose refractive index increases monotonically from the periphery to the center, and here, an example using a graded index optical fiber (hereinafter referred to as an optical fiber) is shown.
Is a core of the optical fiber 1, 1b is a grid, 2 is a fuel refractive index detecting surface provided in a part of the elongated optical conductor, 3 is a light emitting element made of, for example, an LED, 4 is a light diffuser, and 5 is light receiving. Here, an example of using a light center of gravity position detecting element made of PSD is shown in the body, 6 is a joint portion of the optical fiber 1, 7 is a supporting member, 8 is a fuel flow path, 8a is a fuel flow, 9 is a case, 10 is A detection circuit, 11 is a fuel seal, and 12 is a filling member.
The fuel refractive index detection surface 2 has a plurality of optical fibers 1 closely supported in parallel with each other on the supporting member 7 and fixed by the filling member 12, and the distance from the center is different as shown in FIG. The surface of the core 1a that has been polished and has a different average refractive index Nd is exposed to form a liquid contact surface with the fuel.
Further, the fuel refractive index detection surface 2 is provided with a fuel flow 8 as shown in FIG.
It is arranged parallel to the fuel flow path 8 so that the pressure loss of a is minimized. One end sides of the plurality of optical fibers 1 are joined to each other to form a joint portion 6, and an equal amount of light is incident on each optical fiber 1 from the light emitting element 3 through the light diffuser 4. On the other end side of the optical fiber 1, the optical center of gravity position detecting element 5 is arranged so that the end of the entire optical fiber 1 is within the effective light receiving width.
And is arranged in a shape along the line to receive the total reflection light from the fuel refractive index detection surface 2. The photocurrent corresponding to the amount of light received from the optical center of gravity position detection element 5 is detected from the electrodes IL and IR, respectively.
Sent to 0. Here, it is preferable that the light emitting element 3, the light diffuser 4, and the light center-of-gravity position detecting element 5 are integrally supported by the supporting member 7. The detection unit as described above is the support member 7
Is attached to the case 9 through a fuel seal 11 around the periphery of the case, and the case 9 is sandwiched between the inlet pipe line of the fuel distribution pipe 26 and the fuel distribution pipe 26, for example.

Next, the operation of this embodiment will be described with reference to FIGS. FIG. 4 is an operation explanatory view of one embodiment of the alcohol content rate detecting device of the present invention, FIG. 5 is an explanatory view of the optical center-of-gravity position detecting element 5, and FIGS. 6 (a) and 6 (b) show this. FIG. 4 is an explanatory view of a change in received light amount distribution with respect to an alcohol content rate on the optical center-of-gravity position detecting element 5 in the embodiment.
Reference numeral 5 is a division unit. In FIG. 4, the light emitting element 3 is driven by the light emitting element drive unit 101 to emit light, and the emitted light is incident on the N = m optical fibers 1 through the light diffuser 4 with an approximately equal amount of light. Of these, the N = i-th and j-th optical fibers 1i and 1j in which the average refractive indexes on the refractive index detection surface 2 are Ndi and Ndj, respectively, are shown. The optical fiber 1j is the fiber whose refractive index detection surface 2 is the fiber. Ndi <N because it is close to the center
I'm a dj. As described above in the conventional example, assuming that the refractive index Nf of the fuel changes depending on the alcohol content, the critical incident angle Ψ = arc SIN at which the incident light causes total reflection on the refractive index detection surface 2.
Since (Nf / Nd), if the critical incident angles with respect to the optical fibers 1i and 1j are Ψi and Ψj, respectively, Ndi <Ndj and Ψi> Ψj.
Becomes Light incident on the refractive index detection surface 2 at the incident angle θ = Ψj is totally reflected by the optical fiber 1j and propagates to the other end of the fiber, but is refracted by the optical fiber 1i at the refraction angle x and transmitted into the fuel. The amount of light propagating to the other end of the fiber is the optical fiber
It is significantly smaller than 1j. The difference in the amount of light propagating to the other end of the optical fiber 1 forms a light amount distribution on the optical center-of-gravity position detection element 5, and this light amount distribution is caused by a change in the critical incident angle Ψ due to a change in the refractive index Nf of the fuel. , Alcohol content changes as shown in FIGS. 6 (a) and 6 (b). As shown in FIG. 5, the optical barycentric position detection element 5 has a P-shaped surface on the surface of silicon.
Layer (resistive layer) 41, N layer 42 on the back surface, and I layer 43 in the middle are formed. When a light spot is incident, the distance from the incident light position to the electrodes IL and IR passes through the resistive layer and is reversed. The proportional split photocurrents iR and iL are extracted from the electrodes IL and IR. The extracted photocurrents iR and iL are detected by the detection circuit 1 as shown in FIG.
0 is input to the photocurrent amplifying unit 102 and is subtracted by the subtracting unit 10.
In step 3, iR-iL is added, and after iR + iL is obtained in the adder 104, the division unit 105 outputs the signal proportional to the position signal X = (L / 2) × (iR-iL) / (iR + iL) Vout is required. L is the effective light receiving width of the light center of gravity position detecting element 5. As shown in FIG. 6 (a), the average incident angle θ on the refractive index detecting surface 2 is 1
Critical incident angle Ψ in m optical fibers 1 at the time of 00%
If it is larger, the light is totally reflected on all the other ends of the m optical fibers 1, and the light amount distribution on the optical center-of-gravity position detecting element 5 becomes substantially uniform, and iR and iL are substantially the same. The signal X takes a value close to 0, but when the alcohol content in the fuel decreases, the refractive index Nf increases, and the critical incident angle Ψ in all the optical fibers 1 becomes large. Therefore, in the m optical fibers 1, In order from the smallest average refractive index Nd on the refractive index detection surface 2, total reflection does not occur on the refractive index detection surface 2 and light is not propagated to the other end side of the fiber, and the light amount distribution is toward the electrode IR side. The position signal X becomes large due to the bias IL / IR. Therefore, the output Vout corresponding to the position signal X is inversely proportional to the alcohol content rate. Here, the detection accuracy of the alcohol content rate is as small as several meters of the optical fiber 1, and the user may freely select it according to the purpose of use. In such a configuration,
Since the alcohol content rate in the fuel is detected by the light receiving position on the light center of gravity position detecting element 5, that is, the light amount distribution, the temperature of the detecting portion of the detecting device changes due to heat generation of the engine,
Even if the light emission amount of the light emitting element 3 and the light receiving sensitivity of the light center-of-gravity position detecting element 5 change, it is always accurate regardless of the temperature change of the detecting portion
The alcohol content in the fuel can be detected continuously. Further, since the alcohol content rate is detected by the minute refractive index detecting surface 2 provided in the middle of the optical fiber 1, there is an effect that the detecting section to be inserted into the fuel can be downsized.

FIG. 7 is a sectional view showing another embodiment of the present invention,
A plurality of optical fibers 1 are closely supported on the surface of a hollow plate-shaped supporting member 7 having a curved tip, and then fixed by a filling member 12, and the optical fiber 1 is refracted in the middle of the optical fiber 1 to come into contact with the fuel. The refractive index detection surface 2 is formed. In this embodiment, the refractive index detection surface 2 is provided at two front and back sides of the support member 7. In such a configuration, the end portion of the optical fiber 1 can be arranged on the same side, and the light emitting element 3, the light receiving body 5, etc. can be arranged and supported on the same side.
The fuel seal 11 is provided with a detector that integrally holds the light receiver 5 and the like.
There is an advantage that the degree of freedom in mounting is increased and the mounting is simple, such as being inserted and mounted in the fuel flow path 8 such as the fuel distribution pipe 26 via the. Further, by providing the refractive index detection surface 2 at a plurality of positions, the alcohol content rate of the fuel in the fuel flow path 8 can be detected more uniformly, and the amount of light contributing to the total reflection in the incident light can be increased. An effect that the detection accuracy of the light amount distribution in the body 5 can be improved can also be expected.

Although the graded index type optical fiber is used as the elongated optical conductor 1 in the above embodiment, the refractive index is not limited to the above optical fiber, but the refractive index at least near the refractive index detection surface changes monotonically from the periphery toward the center. Any elongated optical conductor can be used. Further, in the above embodiment, the structure in which the ends of a plurality of elongated light guides are bundled and light is emitted from one light emitting element to the elongated light guides is shown, but a light emitting element is associated with each elongated light guide. Alternatively, a plurality of elongated optical conductors may be divided into a number of sets, and light emitting elements may be associated with the respective sets. Further, in the light receiver, each elongated optical conductor may be associated with a light receiving element such as a photodiode. It is obvious to those skilled in the art that the light amount distribution may be calculated from the output of each light receiving element, or other light position detecting elements such as CCD may be used. Furthermore, in the above embodiment, the detection of the alcohol content in the fuel is shown, but it goes without saying that it can be applied to the measurement of the refractive index of other liquids.

〔The invention's effect〕

As described above, according to the present invention, the fuel refractive index detection surface is formed on a plurality of elongated optical conductors whose refractive index changes from the periphery toward the center, and the light projecting body is provided on one end surface of the optical conductor.
Since a light receiver is provided on the other end surface to detect the alcohol content in the fuel, the detector can be downsized, and the detector is installed in the pipe line near the fuel injection valve, so the powder valve The alcohol content in the injected fuel can be continuously detected without delay. Further, the alcohol content rate can be accurately detected regardless of the temperature change of the detection device.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an alcohol content rate detecting device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, FIG. 3 is an explanatory view of a fuel refractive index detecting surface, and FIG. FIG. 6 is an explanatory view of the operation of the alcohol content rate detection device, FIG. 5 is an explanatory view of the optical center-of-gravity position detection element, and FIGS. 6 (a) and 6 (b) are explanatory views of changes in the received light amount distribution with respect to the alcohol content rate FIG. 7 is a sectional view of an alcohol content rate detecting device according to another embodiment of the present invention, FIG. 8 is a configuration diagram of a fuel control system including a conventional alcohol content rate detecting device, and FIG. 9 is a conventional alcohol content rate. It is sectional drawing of a detection apparatus. 1 ... Optical fiber, 1a ... Core, 2 ... Refractive index detecting surface, 3 ... Light emitting element, 5 ... Optical centroid position detecting element, 10 ...
… Detection circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An alcohol content rate detecting device for detecting an alcohol content rate in a fuel based on a difference in refractive index between a light guide and a fuel, wherein a fuel refractive index is provided in a part of each of a plurality of elongated light guides. A detection surface is formed, a light emitter is provided on one end surface of this elongated light guide to make it enter the fuel refractive index detection surface, and a light receiver is provided on the other end surface to receive light reflected by the fuel refractive index detection surface. In this configuration, the alcohol content rate is detected by the change in the light amount distribution on the photoreceptor, and the plurality of elongated light guides are elongated light guides whose refractive index changes from the periphery to the center. A device for detecting an alcohol content, characterized in that a part of each of the light guides is formed by removing a part of each of the light guides with a different thickness so that the average refractive index of the elongated light guides on the detection surface is different.