JP2593744B2 - Alcohol concentration detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alcohol concentration detecting device for detecting an alcohol concentration in an alcohol mixed liquid, and more particularly to a device for detecting an alcohol concentration by a capacitance type sensor.

[0002]

2. Description of the Related Art In recent years, an alcohol-mixed fuel obtained by mixing alcohol such as methanol and ethanol with gasoline has been proposed as an alternative fuel for an internal combustion engine for an automobile. When such an alcohol-mixed fuel is used, since the stoichiometric air-fuel ratio changes according to the alcohol concentration, the alcohol concentration of the supplied alcohol-mixed fuel is detected, and the fuel supply amount control and the ignition timing control are performed based on the alcohol concentration. (See, for example, JP-A-56-958540).

Therefore, there is known an alcohol concentration detecting device in which a capacitance type alcohol concentration sensor for outputting a voltage corresponding to the alcohol concentration in the mixed fuel is provided in a fuel supply passage of an 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 a fuel supply passage of an engine has a cylindrical portion 2 serving as an outer electrode and an opening 2 a formed in the middle of the cylindrical portion 2. And a cylindrical portion 3 connected in a direction orthogonal to the central axis of the cylinder. A fuel inlet 4 to which a fuel pipe (not shown) is connected is opened at one end of the cylinder 2, and a fuel outlet 5 to which a fuel pipe (not shown) is connected to the opposite end of the cylinder 3.
Is opened. A solid central electrode 6 extending along the central axis of the cylindrical portion 2 is inserted into the cylindrical portion 2. The front end of the central electrode 6 is located a predetermined distance downstream from the fuel inlet 4, and the rear end is The bush 9 and the O-ring 10 fitted to the inner peripheral surface of the rear end of the cylindrical portion 2 penetrate and are supported through an insulator 7 fitted to the inner peripheral surface of the rear end of the cylindrical portion 2 and a pipe 8 made of a conductive member. You. The end of the center electrode 6 protruding from the bush 9 is fixed by a fastener 13 composed of a washer 11 and a nut 12.

[0005] One end of a terminal 14 is clamped and fixed to the joint between the pipe 8 and the bush 9.
Reference numeral 14 is connected to the cylindrical portion 2, that is, the outer electrode 2 via a pipe 8. Further, one end of a terminal 15 is clamped and fixed to a joint between the fastener 13 and the bush 9, and the terminal 15 is connected to the center electrode 6. In the alcohol concentration detecting device, the terminals 14, 15 and an AC power supply and a resistor (both not shown) are connected in series, and the static electricity between the electrodes 2, 6 is determined according to the alcohol concentration in the fuel. The alcohol concentration in the fuel is detected by measuring the output voltage at the resistance using the change in the capacitance C.
The capacitance C is determined as in the following equation.

C = K × s × ε / d where s is the electrode area d is the electrode gap between the center electrode 6 and the outer electrode 2 ε is the relative permittivity of the fuel to be detected K is a proportional constant .

By the way, in such a conventional alcohol concentration sensor, as shown in FIG. 5, when the fuel temperature increases, the capacitance between the electrodes increases, and the sensor output (oscillation frequency) accordingly changes as shown in FIG. Thus, it changes depending on the fuel temperature. Therefore, in the alcohol concentration detecting device, temperature correction is generally performed. And adhesive 18
A temperature sensor 17 is provided on the outer peripheral surface of the cylindrical portion 2 serving as the outer electrode by, for example,
And outputs a detection signal from the temperature sensor 17 to a control unit (not shown) as a temperature of the fuel passing through a sensor for performing the temperature correction, the temperature detected through the cylinder portion 2. The output of the alcohol concentration sensor, which is output based on the change in the capacitance C between 2 and 6, is corrected in the control unit by a temperature correction value.

[0008]

However, since the alcohol concentration sensor according to the conventional alcohol concentration detection device is arranged in the fuel passage between the fuel pump and the fuel injection valve, the alcohol is newly supplied. If the temperature of the fuel differs from the temperature of the fuel flowing in the fuel passage up to that time, the temperature correction may be affected. That is,
When fuel on the side having a high temperature dependency, that is, fuel on the side having a high alcohol concentration is newly supplied, the temperature sensor 17 attached to the outer peripheral surface of the cylindrical portion 2 of the alcohol concentration sensor supplies the newly supplied fuel. Temperature cannot be detected quickly, and there is an error between the detection value detected by the alcohol concentration sensor when performing the above-described temperature correction and the temperature of the fuel actually passing through the alcohol concentration sensor. This may cause insufficiently accurate temperature correction. In particular, when refueling is performed in a state where the engine is sufficiently warmed up, when the engine is restarted, fuel whose temperature is lower than the fuel that has been supplied to the engine until then is supplied, and the sensor has Due to the detection delay, the startability may be deteriorated.

That is, the alcohol concentration sensor is usually provided in the engine room of the vehicle, and the temperature in the engine room may rise to around 100 ° C., so that the cylinder 2 also rises to the same temperature. This is because it takes time for the cylinder 2 to reach the same temperature as the temperature of the new fuel. In order to accurately control the fuel supply amount and the 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.

[0010] In view of the above, the present invention eliminates the influence of the responsiveness of the temperature sensor and enables accurate temperature correction, thereby improving the alcohol concentration detection accuracy. It is an object to provide a concentration detection device.

[0011]

Therefore, according to the present invention, as shown in FIG. 1, an electrode is provided in a fuel passage through which fuel passes to form a sensor section, and a capacitance between the electrodes is reduced. In an alcohol concentration detecting device for detecting an alcohol concentration by detecting a change, a sensor unit temperature detecting means for detecting a temperature of a constituent member of the sensor unit, and a fuel temperature in a fuel tank on an upstream side of the sensor unit. Detecting the temperature of the fuel passing through the sensor section from the output of the sensor section temperature detecting section based on the temperature of the fuel in the fuel tank and the temperature of the constituent members of the sensor section; A configuration comprising: fuel temperature prediction means for predicting; and 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. It was.

[0012]

In such a configuration, the temperature of the component 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 detecting means. From the output of the sensor section temperature detecting means, the temperature of the fuel passing through the sensor section can be obtained in advance by experiment or analysis. Therefore, the temperature of the newly refueled fuel at the time of passing through the sensor section is predicted by the fuel temperature predicting means based on the two detected temperatures.

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

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. In the following description, the overall configuration of the alcohol concentration sensor 20 is the same as that of the conventional example shown in FIG. FIG.
The alcohol concentration detection device shown in FIG. 1 has an alcohol concentration sensor 20 formed by installing an outer electrode 2 and a center electrode 6 in a part of a fuel passage 24 communicating with a fuel tank 21.
This is a device for detecting the alcohol concentration by detecting a change in the capacitance between the first and sixth alcohols.

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

Next, according to the flowchart shown in FIG.
The operation related to the detection and correction of the alcohol concentration performed by the control unit 23 will be described. In step 1 (referred to as S1 in the figure, the same applies hereinafter), a voltage S corresponding to a 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, a temperature difference T between the temperatures Ts and Tt read in step 2 is calculated. Step 4
Then, how the difference H between the temperature Th of the fuel passing through the alcohol concentration sensor 20 and the temperature Ts of the cylinder portion 2 actually detected by the temperature sensor 17 is calculated based on the temperature difference T calculated in step 3. Is determined using a map.
In this map, the difference H with respect to the temperature difference T is stored in advance by an experiment or the like.

In step 5, the alcohol concentration sensor 20
Is predicted and corrected based on the temperature Ts of the cylinder portion 2 and the difference H. That is, this step has the function of the fuel temperature estimating 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, the step performs the function of the correction unit.

Therefore, even when fuel of a different temperature is supplied to the fuel tank 21, the temperature Th of the fuel passing through the alcohol concentration sensor 20 is immediately corrected and set based on the temperature Ts of the cylinder 2 and the difference H. Therefore, the alcohol concentration detected by the alcohol concentration sensor 20 is corrected without being affected by the delay of the response, so that accurate temperature correction can be performed. That is, when refueling is performed and the engine is restarted in a state where the engine is sufficiently warmed up, temperature correction is performed according to the newly refueled fuel having a low temperature, and the startability is also improved.

After the start, the sensor portion sufficiently approaches the fuel temperature due to the passage of new refueling fuel, so that the reliability of the detection value of the sensor portion increases. Therefore, for example, after a lapse of a predetermined time from the start, the detection value of the sensor unit may be switched to temperature correction using the detected value as it is.

[0021]

As described above, according to the present invention,
Predict the temperature of the fuel passing through the sensor unit based on the temperature of the constituent members of the sensor unit and the temperature of the fuel in the fuel tank, and based on the predicted temperature of the fuel passing through the sensor unit. Since the alcohol concentration detected by the sensor unit is corrected, the influence of the responsiveness of the temperature sensor is eliminated, so that accurate temperature correction can be performed, thereby improving the detection accuracy of the alcohol concentration.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a configuration diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart showing control contents of the embodiment.

FIG. 4 is a cross-sectional view of an example of a conventional alcohol concentration detection device.

FIG. 5 is a temperature characteristic diagram of capacitance between electrodes.

FIG. 6 is a diagram showing a relationship between a sensor output frequency and an alcohol concentration.

[Explanation of symbols]

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

Claims (1)

(57) [Claims] An alcohol concentration detecting device for detecting an alcohol concentration by arranging an electrode in a fuel passage through which a fuel passes to form a sensor portion and detecting a change in capacitance between the electrodes. Sensor part temperature detecting means for detecting the temperature of the constituent members of the sensor part, fuel temperature detecting means for detecting the temperature of the fuel in the fuel tank on the upstream side of the sensor part, and temperature of the constituent parts of the sensor part Fuel temperature estimating means for estimating the temperature of fuel passing through the sensor part from the output of the sensor part temperature detecting means based on the temperature of the fuel in the fuel tank and the sensor part estimated by the fuel temperature estimating means A correction unit for correcting the alcohol concentration detected by the sensor unit based on the temperature of the fuel.