JPH04297861A - Alcohol concentration detector - Google Patents

Abstract

PURPOSE:To achieve a higher detection accuracy of the concentration of alcohol by a method wherein the temperature of a fuel passing through a sensor section is predicted based on the temperature of a structural member of the sensor section and the temperature of the fuel in a fuel tank and the concentration of alcohol detected with the sensor section is corrected based on the temperature of the fuel passing through the sensor section subjected to the prediction to enable accurate temperature correction with the elimination of effect on response of a temperature sensor. CONSTITUTION:A temperature sensor 22 is provided in a fuel tank 21 to detector the temperature Tt of a fuel in the fuel tank 21 and a temperature sensor 17 is applied to detect the temperature Ts of a cylinder part 2 of an alcohol concentration sensor 20. A temperature correction is performed for a detection value detected based on a change in electrostatic capacitance C between electrodes 2 and 6 as follows: a map is used to determine what a difference H becomes of between the temperature Th of the fuel passing through the alcohol concentration sensor 20 and the temperature Ts of the cylinder part 2 detected actually with the temperature sensor 17 depending on a temperature difference T between the Ts and Tt. The use of the difference H allows the correction and setting of the temperature Th of the fuel passing through the alcohol concentration sensor 20 to accomplish a temperature correction based on the temperature Th.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alcohol concentration detection device for detecting the alcohol concentration in an alcohol mixed liquid, and more particularly to one for detecting alcohol concentration using a capacitive sensor section.

0002

BACKGROUND OF THE INVENTION In recent years, alcohol mixed fuel, which is a mixture of gasoline and alcohol such as methanol or ethanol, has been proposed as an alternative fuel for automobile internal combustion engines. When such alcohol mixed fuel is used, the stoichiometric air-fuel ratio changes depending on the alcohol concentration, so the alcohol concentration of the supplied alcohol mixed fuel is detected and the fuel supply amount and ignition timing are controlled based on this alcohol concentration. (For example, see Japanese Patent Laid-Open No. 56-958540, etc.).

[0003] Therefore, an alcohol concentration detection device is known which is constructed by interposing a capacitance type alcohol concentration sensor that outputs a voltage corresponding to the alcohol concentration in the mixed fuel in the fuel supply passage of the internal combustion engine. . Here, this capacitance type alcohol concentration sensor is conventionally configured as shown in FIG.

That is, a cylindrical housing 1 constituting a part of the fuel supply passage of the engine has a cylindrical portion 2 serving as an outer electrode, and an opening 2a formed in the middle of the cylindrical portion 2. and a cylindrical portion 3 connected in a direction perpendicular to the central axis of the cylinder. A fuel inlet portion 4 to which a fuel pipe (not shown) is connected is opened at one end of the cylinder portion 2, and a fuel outlet portion 5 to which a fuel pipe (not shown) is connected to the opposite end of the cylinder portion 3.
is opened. A solid center electrode 6 is inserted into the cylindrical portion 2 and extends along its central axis.The tip of the center electrode 6 is located a predetermined distance downstream from the fuel inlet 4, and the rear end is It is penetrated and supported by a bush 9 and an O-ring 10 fitted to the inner circumferential surface of the rear end of the cylindrical portion 2 via an insulator 7 fitted to the inner circumferential surface of the rear end of the cylindrical portion 2 and a pipe 8 made of a conductive member. Ru. The protruding end of the center electrode 6 from the bush 9 is fixed by a fastener 13 consisting of a washer 11 and a nut 12.

One end of a terminal 14 is clamped and fixed at the joint between the pipe 8 and the bush 9, and the terminal 14 is connected to the cylindrical portion 2, that is, the outer electrode 2, via the pipe 8. Further, one end of a terminal 15 is clamped and fixed to the joint between the fastener 13 and the bush 9, and this terminal 15 is connected to the center electrode 6. In the alcohol concentration detection device, the terminals 14 and 15
, an AC power source, and a resistor (both not shown) are connected in series, and the output voltage at the resistor is determined by using the fact that the capacitance C between the electrodes 2 and 6 changes depending on the alcohol concentration in the fuel. The alcohol concentration in the fuel is detected by measuring the alcohol concentration in the fuel. Note that the capacitance C is determined as shown in the following equation.

[0006]C=K×s×ε/d...■
However, s is the electrode area d is the electrode interval ε between the center electrode 6 and the outer electrode 2, and the relative dielectric constant K of the detected fuel is a proportionality constant.

By the way, in such a conventional alcohol concentration sensor, as the fuel temperature increases, as shown in FIG. 5, the capacitance between the electrodes increases, and accordingly, the sensor output (oscillation frequency) changes as shown in FIG. It varies depending on the fuel temperature. Therefore, in alcohol concentration detection devices, temperature correction is generally performed. And adhesive 18
A temperature sensor 1 is installed on the outer peripheral surface of the cylindrical portion 2, which becomes the outer electrode.
7 and outputs a detection signal from the temperature sensor 17 to a control unit (not shown), using the temperature detected through the cylindrical portion 2 as the temperature of the fuel passing through the sensor for implementing the temperature correction, The alcohol concentration sensor output based on the change in capacitance C between the electrodes 2 and 6 is corrected within the control unit using a temperature correction value.

[0008]

[Problems to be Solved by the Invention] However, since the alcohol concentration sensor related to the conventional alcohol concentration detection device is installed in the fuel passage between the fuel pump and the fuel injection valve, it cannot be used when newly refueled. If the temperature of the fuel flowing through the fuel passage is different from the temperature of the fuel flowing in the fuel passage up to that time, there is a risk that the temperature correction will be affected. That is, when a fuel with higher temperature dependence, that is, a fuel with a higher alcohol concentration, is newly refueled, the temperature sensor 17 attached to the outer peripheral surface of the cylindrical portion 2 of the alcohol concentration sensor is refueled. The temperature of the fuel cannot be detected quickly, resulting in a difference between the detected value detected by the alcohol concentration sensor when performing the temperature correction described above and the temperature of the fuel that actually passes through the alcohol concentration sensor. There is a risk that an error will occur and temperature correction will not be sufficiently accurate. In particular, if the engine is refueled after it has been sufficiently warmed up, when the engine is restarted, fuel with a lower temperature than the fuel that was previously supplied to the engine will be supplied, causing the sensor to There is a risk that starting performance will deteriorate due to the detection delay.

That is, since the alcohol concentration sensor is normally installed in the engine room of a vehicle, and the temperature in the engine room can rise to around 100°C, the cylindrical portion 2 also rises to the same temperature. This is because it takes time for the cylinder portion 2 to reach the same temperature as the new fuel. In order to accurately control the fuel supply amount and ignition timing based on the alcohol concentration, it is necessary to accurately measure the amount of methanol, and it is necessary to improve the detection accuracy of the alcohol concentration sensor.

In view of the above-mentioned conventional circumstances, the present invention provides an alcohol sensor that eliminates the influence of the responsiveness of a temperature sensor, enables accurate temperature correction, and thereby improves the detection accuracy of alcohol concentration. The purpose of the present invention is to provide a concentration detection device.

[0011]

[Means for Solving the Problems] Therefore, as shown in FIG. 1, the present invention forms a sensor section by installing electrodes in a fuel passage through which fuel passes, and reduces the capacitance between the electrodes. An alcohol concentration detection device that detects alcohol concentration by detecting a change, comprising: a sensor section temperature detection means that detects the temperature of a component of the sensor section; and a sensor section temperature detection means that detects the temperature of a component of the sensor section; The temperature of the fuel passing through the sensor section is determined from the output of the sensor section temperature detection section based on the temperature of the constituent members of the sensor section and the temperature of the fuel in the fuel tank. The present invention is configured to include a fuel temperature prediction means for predicting, and a correction means for correcting the alcohol concentration detected by the sensor section based on the fuel temperature of the sensor section predicted by the fuel temperature prediction means.

0012

[Operation] In this configuration, the temperature of the constituent members of the sensor section and the temperature of the fuel in the fuel tank are determined based on the heat capacity of the fuel passage from the fuel tank to the sensor section detected by the sensor section temperature detection means. From the output of the sensor part temperature detection means, the temperature of the fuel when passing through the sensor part can be determined in advance by experiment or analysis. Therefore, the temperature of the freshly refueled fuel when it passes through the sensor section is predicted by the fuel temperature prediction means based on both of the detected temperature values.

Then, the alcohol concentration detected by the sensor section is corrected based on the predicted temperature of the fuel passing through the sensor section.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings. In the following description, since the overall configuration of the alcohol concentration sensor 20 is the same as that of the conventional example shown in FIG. 4, the same reference numerals will be given and the description thereof will be omitted. The alcohol concentration detection device shown in FIG. This device detects alcohol concentration by detecting changes in capacitance.

Here, as a configuration according to the present invention, a temperature sensor is provided in the fuel tank 21 on the upstream side of the alcohol concentration sensor 20 as a tank internal temperature detection means for detecting the temperature Tt of the fuel in the fuel tank 21. A sensor 22 is provided, and a temperature sensor 17 is attached to the outer peripheral surface of the cylindrical portion 2 to detect the temperature Ts of the cylindrical portion 2 of the alcohol concentration sensor 20 as a sensor portion temperature detection means. These fuel temperatures Tt and Ts are output to the control unit 23. Then, the alcohol concentration is detected by subjecting the detection value detected based on the change in capacitance C between the electrodes 2 and 6 to temperature correction.

Next, according to the flowchart shown in FIG.
The operation related to detection and correction of alcohol concentration performed by the control unit 23 will be explained. Step 1 (
In the figure, it is written as S1. (Similarly below), the voltage S corresponding to the change in capacitance between the outer electrode 2 and the center electrode 6 of the alcohol concentration sensor 20 is read. In step 2, the temperature Ts of the cylinder portion 2 of the alcohol concentration sensor 20 and the temperature Tt of the fuel are read.

In step 3, the temperature difference T between the temperatures Ts and Tt read in step 2 is calculated. Step 4
Now, based on the temperature difference T calculated in step 3, the temperature Th of the fuel passing through the alcohol concentration sensor 20 and the temperature T of the cylinder portion 2 actually detected by the temperature sensor 17 are determined.
The difference H from s is determined using a map. Incidentally, the difference H with respect to the temperature difference T is stored in advance in the map through experiments or the like.

In step 5, the alcohol concentration sensor 2
The temperature Th of the fuel passing through 0 is predicted and corrected based on the temperature Ts of the cylinder portion 2 and the difference H. That is, this step functions as a fuel temperature prediction means. In step 6, the voltage S read in step 1 is corrected according to the temperature Th of the fuel passing through the alcohol concentration sensor 20. That is, this step functions as a correction means.

Therefore, even when the fuel tank 21 is filled with fuel at different temperatures, the temperature Th of the fuel passing through the alcohol concentration sensor 20 is equal to the temperature Ts of the cylinder portion 2 and the difference H.
Since the correction setting is immediately made based on the alcohol concentration sensor 20, the alcohol concentration detected by the alcohol concentration sensor 20 is corrected without being affected by the delay in response, thereby making it possible to perform accurate temperature correction. That is, when the engine is refueled and started again after the engine has been sufficiently warmed up, the temperature is corrected in accordance with the newly supplied low temperature fuel, resulting in good startability.

[0020] After the sensor section approaches the temperature of the new fuel sufficiently after the engine starts, the reliability of the detected value of the sensor section increases. Therefore, for example, after a predetermined period of time has elapsed after startup, the temperature correction may be switched to using the detected value of the sensor unit as is.

[0021]

[Effects of the Invention] As explained above, according to the present invention,
The temperature of the fuel passing through the sensor section is predicted based on the temperature of the constituent members of the sensor section and the temperature of the fuel in the fuel tank, and the temperature of the fuel passing through the sensor section is predicted based on the predicted temperature of the fuel passing through the sensor section. Since the alcohol concentration detected by the sensor section is corrected, the influence of the responsiveness of the temperature sensor is eliminated, allowing accurate temperature correction, thereby improving the detection accuracy of alcohol concentration.

[Brief explanation of drawings]

[Fig. 1] Functional block diagram showing the configuration of the present invention

[Fig. 2] A configuration diagram showing an embodiment of the present invention.

[Fig. 3] Flowchart showing the control contents of the embodiment same as above.

[Figure 4] Cross-sectional view of an example of a conventional alcohol concentration detection device

[Figure 5] Temperature characteristic diagram of capacitance between electrodes

[Figure 6] Diagram showing the relationship between sensor output frequency and alcohol concentration

[Explanation of symbols]

2 Cylindrical part (outer electrode) 4 Fuel inlet section 6 Center electrode 17 Temperature sensor 20 Alcohol concentration sensor 21 Fuel tank 22 Temperature sensor 23 Control unit

Claims (1)

[Claims] 1. An alcohol concentration detection device that detects alcohol concentration by installing an electrode in a fuel passage through which fuel passes to form a sensor section and detecting a change in capacitance between the electrodes. sensor section temperature detection means for detecting the temperature of the constituent members of the sensor section; in-tank fuel temperature detection means for detecting the temperature of fuel in the fuel tank upstream of the sensor section; and temperature of the constituent members of the sensor section. and a fuel temperature prediction means for predicting the temperature of the fuel passing through the sensor section from the output of the sensor section temperature detection means based on the temperature of the fuel in the fuel tank, and the sensor section predicted by the fuel temperature prediction means. An alcohol concentration detection device comprising: a correction means for correcting the alcohol concentration detected by the sensor unit based on the temperature of the fuel.