JPH0544773Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an alcohol sensor that detects the alcohol mixing ratio in fuel supplied to an internal combustion engine.

[Conventional technology]

Conventionally, a sensor that detects the alcohol mixture ratio by measuring the inductivity of fuel by taking advantage of the fact that the inductivity of alcohol is much larger than that of gasoline and diesel oil has been known from Japanese Utility Model Application Publication No. 183435/1983. It is. FIG. 4 is a block diagram of a fuel injection system using this type of conventional sensor. In the figure, 1 is a fuel tank, 2 is a fuel pump that sucks up the fuel in tank 1, 3 is a fuel filter,
4 is a fuel distribution pipe. Reference numeral 5 designates an injection valve, 6 a fuel pressure regulator, 7 an alcohol sensor disposed in the tank 1, and 8 a control unit.

Next, the operation will be explained. The fuel in the tank 1 is pressurized by the pump 2 and enters the fuel distribution pipe 4 through the filter 3. At this time, part of the fuel flows to the injection valve 5 and is injected, and the rest passes through the fuel pressure regulator 6 and returns to the tank 1 again. At this time, the fuel pressure is maintained at a predetermined value by the fuel pressure regulator 6.
Since the alcohol sensor 7 is installed inside the tank 1, it transfers information regarding the properties of the fuel inside the tank 1 to the control unit 8, and this control unit 8 calculates the time to open the injection valve 5 based on that information. The engine is actually operated to control the engine's air-fuel ratio to a predetermined value.

[The problem that the idea aims to solve]

Since the conventional fuel injection device is configured as described above, if fuel with a different alcohol mixture ratio than that remaining in the tank 1 is put into the tank 1, the fuel will be injected from the pump 2 at the time of starting immediately after that. Since the pipe leading to the distribution pipe 4 is long, what is actually injected is the fuel remaining in the pipe, which has different properties from the fuel in the tank detected by the alcohol sensor 7. For this reason, the control unit 8
Since the air-fuel ratio is controlled based on erroneous information, the air-fuel ratio at the time of starting cannot take an appropriate value, which causes problems in starting. Also, when installing the alcohol sensor 7 to the tank 1, when the fuel in the tank becomes low,
Since the liquid level drops and dielectric constant detection becomes impossible, the sensor installation position is limited to the lower part of the tank. However, if installed at the bottom of the tank, the sensor 7 will be affected by the moisture that accumulates at the bottom, and the sensor 7 will detect the fuel as having different properties from the fuel actually in the tank, so as mentioned earlier, the control unit 8 is not optimal. There was a problem in that the air-fuel ratio could not be controlled properly, causing engine trouble.

This idea was created to solve the above problems, and detects the alcohol mixture ratio of fuel as part of the fuel injection system that can perform optimal air-fuel ratio control according to the fuel at startup and during normal operation. The purpose is to obtain an alcohol sensor that can

[Means to solve the problem]

The alcohol sensor according to this invention includes a pair of electrodes provided in a fuel flow path, and detects the alcohol mixing ratio in the fuel based on the capacitance between the pair of electrodes. At least one of the fuel filters is constructed of an electrically conductive filter element, and the pair of electrodes is mounted inside the fuel filter to serve also as a filter for the fuel.

[Effect]

In this invention, a pair of electrodes are installed inside the fuel filter to detect the alcohol mixing ratio in the fuel, so when the fuel passes through the electrodes in the filter, the capacitance of the electrodes is detected and the properties of the fuel are determined. Fuel injection control can be performed accordingly. Furthermore, at least one of the pair of electrodes also has a filter function.

〔Example〕

An embodiment of this invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a fuel injection device equipped with an alcohol sensor according to this invention, and is designated by the symbol 1.
8 are the same as the conventional apparatus shown in FIG. 2 and 3 are configuration diagrams of the fuel filter, and in the figures, 9 is a filter element, 9a is a filter element electrode plate, 1
0 is a support that supports the element 9, 11a is a positive electrode plate, 11b is a negative electrode plate, 12 is an electrode plate support, 13a is a positive electrode layer connected to the positive electrode plate 11a, and 13b is a negative electrode plate. This is a negative electrode layer connected to the electrode plate 11b.

In Figure 1, the fuel in tank 1 is pumped to pump 2.
After being pressurized, the fuel passes through a fuel filter 3 and flows into a distribution pipe 4. At this time, part of the fuel is transferred to the injector 5.
The remaining fuel passes through the fuel pressure regulator 6 and returns to the tank 1. Inside the filter 3, in FIG. 2, cylindrical electrode plates 11a and 11b are installed coaxially downstream of a cylindrical filter element 9, and in FIG. A cylindrical filter element electrode plate 9a made of a material similar to the above is disposed at the center. The filter element electrode plate 9a functions as a positive electrode plate, and the negative filter element electrode plate 9b on the inner side constitutes a first capacitance detection section, and further, the negative filter element electrode plate 9b and The positive filter element electrode plate 9a located inside the negative filter element electrode plate 9b constitutes a second capacitance section. Therefore, compared to what is shown in FIG. 2, there are two capacitance detection sections, the detection area is expanded, and the detection accuracy is improved accordingly. Further, in the above embodiment, each of the filter element electrode plates 9a and 9b also serves as a filter, but for example, only the filter element electrode plate 9a may serve as a filter.

Next, the detection principle of the alcohol sensor will be explained. Now, when a pair of electrode plates is placed in alcohol mixed fuel, the capacitance between the electrodes is expressed by equation (1).

C=ε・s/d...(1) Here, C is capacitance, s is area facing the electrodes, and d
is the distance between the electrodes, and ε is the dielectric constant.

Therefore, since the electrode facing area s and the inter-electrode distance d in equation (1) are constant, it is understood that if a change in capacitance C is detected, a change in dielectric constant ε can be detected. On the other hand, the dielectric constant of alcohol mixed fuel is (2)
It is expressed by the formula.

ε=(1-k)・ε1+k・ε2 (2) Here, ε1 is the dielectric constant of gasoline, ε2 is the dielectric constant of alcohol, and k is the mixing ratio of alcohol in gasoline. Thus, if the dielectric constant ε1 of gasoline and the dielectric constant ε2 of alcohol are known, it is possible to derive the alcohol mixing ratio k by detecting the capacitance C, as is clear from equations (1) and (2). can.

Next, the operation will be explained. In Figure 1,
When the fuel entering from the pump 2 passes through an alcohol sensor 7 installed in the filter 3, its capacitance is detected and information is transferred to the control unit 8. Based on this information, fuel injection control can be performed depending on the fuel properties. In FIG. 2, fuel entering from the pump 2 passes through the filter element 9, passes through the holes in the electrode plates 11a and 11b, collects in the center, and flows to the fuel distribution pipe 4.
At this time, the capacitance corresponding to the relative dielectric constant of the fuel passing through the electrode plates 11a and 11b is
Detected from 3b. In Figure 3, pump 2
After passing through the electrode plate 9a, the fuel that enters from the electrode plate 9a gathers in the center and flows to the distribution pipe 4. At this time, the fuel passing through the electrode plate 9a is detected as a capacitance corresponding to its relative dielectric constant, as in the case of FIG. Since the dielectric constant of the injected fuel can be measured in this way, changes in the alcohol mixing ratio in the fuel can be detected with good responsiveness. Furthermore, compared to the conventional example, reliability is improved because the average alcohol mixing ratio of the fuel flowing to the distribution pipe 4 can be detected without being affected by the amount of fuel remaining in the tank 1 or the moisture accumulated at the bottom. Further, since the sensor 7 is incorporated into the fuel filter 3, the conventional device can be used as is by replacing only the filter 3 without changing the arrangement or configuration of the fuel injection device.

In the embodiment, there were two types: the filter element 9 and the capacitance detection section were provided separately upstream and downstream, or the detection section itself had a filter function, but the filter element 9 and the capacitance detection section The detection parts may be arranged alternately, or a part of the detection parts may be an electrode plate having a filter function. Furthermore, a combination of an electrode plate having a filter function and a filter element 9 may be used.

[Purpose of invention]

As described above, according to this invention, since a capacitance detection section is installed in the fuel filter,
The alcohol mixing ratio of fuel can be detected as part of a fuel injection device that can perform optimal air-fuel ratio control depending on the fuel. It also provides responsiveness and reliability that can be used even during startup. Furthermore, since at least one of the capacitance detection electrodes is also used as a filter, the number of parts is reduced and assembly and workability are improved.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a fuel injection system equipped with the alcohol sensor of this invention, Figures 2 and 3 are configuration diagrams of a fuel filter, and Figure 4 is a block diagram of a fuel injection system equipped with a conventional sensor. be. 1...Fuel tank, 2...Fuel pump, 3...
Fuel filter, 7...Alcohol sensor, 9...
...Filter element, 9a...Filter element electrode plate, 11a...Positive electrode plate, 11b...
...Negative electrode plate. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of utility model claims] Equipped with a pair of electrodes provided in the fuel flow path,
In the alcohol sensor that detects the alcohol mixing ratio in fuel based on the capacitance between the pair of electrodes, at least one of the pair of electrodes is configured with a conductive filter element, and the pair of electrodes is installed inside the fuel filter. The alcohol sensor also serves as a filter for the above fuel.