JPH0547778B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an alcohol concentration measuring device for measuring the alcohol concentration in a liquid containing alcohol.

[Conventional technology]

Recently, in various countries, alcohol-mixed gasoline, which is a mixture of alcohol and gasoline, has been used as so-called "gasohol." Since genuine gasoline and gasohol naturally have different octane ratings, the air-fuel ratio (weight ratio of air and fuel) A/F of genuine gasoline is 15:1, whereas the air-fuel ratio of gasohol has the characteristics shown in Figure 6. Therefore, if the alcohol concentration is 100%, the air-fuel ratio will be 6:1. Therefore,
When using gasohol, it is necessary to detect the alcohol concentration and control the fuel injection amount, ignition timing, etc.

For this reason, as an alcohol sensor for detecting the alcohol concentration in gasoline, a resistance-type alcohol sensor that detects the alcohol concentration from the difference between the gasoline resistance value and the alcohol resistance value has been studied.

This type of resistive alcohol sensor is shown in FIGS. 7 to 10.

In the figure, 1 is a fuel pipe, and 2 is an alcohol sensor. , 4, and the detection circuit 5 includes a DC power supply 6 connected to the electrode 3 on one side, and a detection resistor 7 provided between the DC power supply 6 and the electrode 4 on the other side. (See Figures 7 and 8).

The alcohol sensor 2 is based on the fact that as the alcohol concentration C in the gasoline interposed between the pair of electrodes 3 and 4 increases, the resistance value decreases (see FIG. 9). The alcohol concentration C is detected using the voltage E.

[Problem to be solved by the invention]

By the way, the voltage characteristics of the resistive alcohol sensor are in the region where the alcohol concentration C is low, for example.
Below 10%, the alcohol concentration C is dominated by the resistance of gasoline, as shown in Figure 10.
In the region below C ₁ , the output voltage E hardly changes, and in the region of low concentration, the alcohol concentration C
There is a problem in that it cannot be detected accurately.

On the other hand, it is generally known that electrolyzers exhibit a polarization effect in which ions accumulate on the electrodes and a relaxation effect in which resistance is exerted to the movement of ions. , 4 is immersed and energized to detect the alcohol concentration C in the alcohol-mixed gasoline.When the alcohol concentration increases, the electricity of the electrodes 3 and 4 decreases due to the polarization effect and relaxation effect. A phenomenon occurs in which conductivity is lost and reduced.

Therefore, when the alcohol concentration C increases, the output voltage E across the detection resistor 7 should increase, but due to the polarization effect and relaxation effect, the output voltage E decreases in the region where the alcohol concentration C is high.

Thus, the output voltage E across the detection resistor 7 becomes the 10th
As shown in the figure, a phenomenon occurs where the alcohol decreases rapidly on the high concentration side, and the voltage characteristics as a whole have two values (C ₂ , C ₃ ) for the same alcohol concentration C above a certain concentration (E _A ). Therefore, there is a problem that the alcohol concentration C cannot be detected accurately.

As mentioned above, in the resistive alcohol sensor 2 according to the prior art, the region in which the detection voltage E proportional to the alcohol concentration C can be obtained is only between the alcohol concentrations _C1 and _C2 . The drawbacks are that the range of use is narrow and the accuracy of the overall voltage characteristics is also poor.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and provides an alcohol solution that enables the alcohol concentration in an alcohol mixed liquid to be measured with high accuracy over a wide range without being influenced by polarization effects or relaxation effects. The present invention provides a concentration measuring device.

[Means to solve the problem]

In order to solve the above-mentioned problems, the configuration adopted by the present invention includes a pair of current-carrying electrodes that are spaced apart and facing each other in an alcohol mixed liquid and to which a constant voltage is applied, and the pair of current-carrying electrodes. A potentiometric alcohol sensor has a pair of detection electrodes that are located between the detection electrodes and are arranged to face each other with a predetermined distance between them, and detects alcohol concentration using the potential difference between the respective detection voltages, and the potential difference A resistive alcohol sensor detects alcohol concentration from a resistance value between each energizing electrode of the resistive alcohol sensor, and the detection voltage of the resistive alcohol sensor corresponds to the maximum value of the detection voltage to be detected by the potentiometric alcohol sensor. determination means for determining whether the voltage is higher or lower than a reference voltage value, and when the determination means determines that the detected voltage of the resistive alcohol sensor is lower than the reference voltage value, the potential difference type The alcohol concentration is calculated as a predetermined alcohol concentration regardless of the detection voltage of the alcohol sensor, and when it is determined that the alcohol concentration is equal to or higher than the reference voltage value, the alcohol concentration is calculated using the detection voltage of the potentiometric alcohol sensor.

[Effect]

A reference voltage value based on the alcohol concentration corresponding to the maximum value of the detection voltage detected by the potentiometric alcohol sensor is set in advance. When the detection voltage of the resistive alcohol sensor is below the reference voltage value,
By calculating the alcohol concentration as a predetermined alcohol concentration, the output voltage of the potentiometric alcohol sensor is 1 over the entire alcohol concentration range.
Therefore, it is possible to measure alcohol concentration with good linearity, high accuracy, and a wide measurement range.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, as an example of the present invention, a case where an alcohol concentration measuring device is applied to a fuel injection control device will be described in detail with reference to FIGS. 1 to 5.
Note that the same reference numerals are given to the same components as those of the prior art described above, and the explanation thereof will be omitted.

In the figure, 11 is a potentiometric alcohol sensor, and 12 and 13 constitute the alcohol sensor 11, and are current-carrying electrodes consisting of a pair of electrode plates spaced apart in the fuel pipe 1. The electrode 12 is connected to a DC power supply 14, and the other current-carrying electrode 13 is connected to the DC power supply 14 via a fixed resistor 15, so that a constant voltage is applied thereto.

16 and 17 are the pair of electrodes 12 and 1 in order to measure the potential difference of the gasoline interposed between them.
A detection electrode consisting of another pair of small electrode plates provided between the electrodes 16 and 17, each of which is separated from the current-carrying electrodes 12 and 13 by a predetermined distance, and
They are arranged facing each other with a predetermined distance from each other. Reference numeral 18 indicates the detection electrodes 16 and 1 in order to detect the potential difference between the pair of detection electrodes 16 and 17.
This is a voltage detection device connected between 7 and 7. here,
The output voltage V of the potentiometric alcohol sensor 11 is
As will be described in detail later, the voltage has a voltage characteristic that rises in a region where the alcohol concentration C is low, reaches the maximum value V _nax , and then decreases in inverse proportion to the alcohol concentration C. An amplifier 19 is connected to the voltage detection device 18 for converting the detected voltage V having the above-described characteristics into a transmittable output voltage (see FIG. 3).

On the other hand, 20 is the potentiometric alcohol sensor 1
1, a resistive alcohol sensor 20 detects the alcohol concentration C in gasoline in the fuel pipe 1, and the resistive alcohol sensor 20 has a pair of current-carrying electrodes 12, substantially similar to the alcohol sensor 2 described in the prior art. , 13 is derived as the detection voltage E, and the alcohol concentration can be determined by utilizing the fact that the resistance value between the current-carrying electrodes 12 and 13 changes depending on the alcohol concentration. It detects and outputs a detection voltage E to an alcohol concentration calculation device 21, which will be described later.

Next, reference numeral 21 denotes an alcohol concentration calculation device consisting of a CPU, etc. The input side of the alcohol concentration calculation device 21 is connected to the amplifier 19 and the resistive alcohol sensor 20, and the output side is connected to an injection amount calculation device 23, which will be described later. It is connected. Reference numeral 22 denotes a storage device such as ROM or RAM connected to the alcohol concentration calculating device 21;
2 contains, in addition to the program shown in FIG. 5, a reference voltage value V ₁ detected by the resistive alcohol sensor 20 and a data map of the output voltage V-alcohol concentration C shown as a characteristic diagram in FIG. 4. Stored. And alcohol concentration calculation device 2
1 performs a concentration calculation device (described later) based on data stored in a storage device 22, and then outputs an alcohol concentration signal C to an injection amount calculation device 23.

Here, regarding the reference voltage value _V1 ,
The output voltage V of the potentiometric alcohol sensor 11 takes a maximum value V _nax in the low alcohol concentration region. Therefore, using the alcohol concentration C ₄ corresponding to the maximum value V _nax as a reference, the voltage value when the resistance type alcohol sensor 20 detects the alcohol concentration C ₄ is set as the output voltage V of the potentiometric alcohol sensor 11.
It is assumed that the voltage reaches the maximum value _Vnax , and that voltage value is preset as the reference voltage value _V1 .

Next, 23 is a fuel injection amount calculation device, and the injection amount calculation device 23 injects fuel based on the alcohol concentration signal C, the engine rotation speed N from the crank angle sensor 24, the intake air amount Q from the air flow meter 25, etc. The amount is calculated and a fuel injection signal C is output to the injection valve 26. Further, 27 in the figure is an alcohol concentration meter.

The present embodiment is configured as described above, but first, the potentiometric and resistance alcohol sensors 11 and 20 are
We will discuss the effect of , and then explain the calculation process for alcohol concentration.

A pair of current-carrying electrodes 12 and 13 and a pair of detection electrodes 16 and 17 provided between them of the potentiometric alcohol sensor 11 are immersed in alcohol-mixed gasoline in the fuel pipe 1. In this state, a constant voltage is applied from the DC power supply 14 between the pair of current-carrying electrodes 12 and 13. At this time, when the alcohol concentration C in the alcohol-mixed gasoline interposed between the current-carrying electrodes 12 and 13 is high, the resistance value is small, so the potential difference between the electrodes 12 and 13 becomes small; conversely, when the alcohol concentration C is low, Since the resistance value is large, the potential difference between the electrodes 12 and 13 becomes large.

Therefore, by a pair of detection electrodes 16 and 17 interposed between the current-carrying electrodes 12 and 13, the detection electrode 1 out of the potential difference between the current-carrying electrodes 12 and 13
A voltage detection device 18 detects the potential difference between the portions 6 and 17 provided.

Next, the reason why the output voltage V of the potentiometric alcohol sensor 11 takes the maximum value V _nax in the low alcohol concentration region as shown in FIG. 4 will be explained in detail.

First, if the alcohol concentration C in _FIG .
The resistance value between the electrodes 3 significantly decreases in inverse proportion to the alcohol concentration C, and the potential difference therebetween decreases, so the potential difference between the detection electrodes 16 and 17 disposed between the energizing electrodes 12 and 13 also decreases. As a result, the output voltage V decreases as shown in FIG.

Next, the alcohol concentration C in Figure 4 is C ₄ ~ _{C 2}
Even when the concentration is in the middle concentration range, the potential difference between the current-carrying electrodes 12 and 13 becomes smaller depending on the alcohol concentration C, as in the high-concentration range. The potential difference between them also becomes smaller, and the output voltage V decreases.

That is, in the region where the alcohol concentration is _C4 or higher, the potential difference between the current-carrying electrodes 12 and 13 is inversely proportional to the alcohol concentration, so the detection electrodes 16 and 17
A part of the potential difference (output voltage V) detected between the current-carrying electrodes 12 and 13 is also inversely proportional to the alcohol concentration C.

Therefore, even when the alcohol concentration C is in a low concentration region below _C4 , theoretically and ideally, the output voltage V between the detection electrodes 16 and 17 is inversely proportional to the alcohol concentration C, and the voltage detection device 18 It should increase until it becomes impossible to turn.

However, in reality, the output voltage V between the detection electrodes 16 and 17 peaks when the alcohol concentration C is _C4 , and then decreases, and is proportional to the alcohol concentration C in a low concentration region smaller than _C4 .

That is, when the alcohol concentration C becomes less than _C4 ,
Since the abundance ratio of gasoline increases and this gasoline can be considered as a substantial insulator, the resistance value between each current-carrying electrode 12 and 13 increases significantly, and each current-carrying electrode 12 and 13 receives a direct current. Most of the power supply voltage of power supply 14 is applied.

Here, the polarization effect and relaxation effect described above become apparent when the alcohol concentration is high, and also appear when the voltage applied to the electrodes is large even when the alcohol concentration is low. Therefore, when the voltage applied to each current-carrying electrode 12, 13 increases, the voltage between each current-carrying electrode 12, 13 does not change linearly, and electrical conduction occurs near the electrode surface of each current-carrying electrode 12, 13. Since the degree decreases, it changes rapidly, and as a result, the change near the center between the current-carrying electrodes 12 and 13 becomes small.

Since no voltage is applied to each of the detection electrodes 16 and 17 disposed between the current-carrying electrodes 12 and 13 and no polarization effect occurs, the detection electrodes 16 and 17 are the current-carrying electrodes. A gradual voltage change near the center between 12 and 13 is detected, and the output voltage V becomes small.

In this way, as shown in FIG. 4, it is possible to obtain a voltage characteristic in which the maximum value V _nax is reached in the low concentration region of alcohol concentration C, and as the alcohol concentration C increases, the output voltage V decreases linearly. The alcohol concentration C in gasoline can be measured using the characteristic. Therefore, the linearity of the output voltage V is better than that of the conventional resistance alcohol sensor.
Measurement results can be used in a wide range of applications, and concentration can be measured with high precision. Furthermore, when detecting the alcohol concentration C, no current is applied to the detection electrodes 16 and 17.
The electrodes 16, 17 are not affected by polarization effects or relaxation effects. Therefore, the current-carrying electrodes 12,1
Even if a polarization effect or a relaxation effect appears in 3, the detection electrodes 16 and 17 can accurately detect the potential difference between the current-carrying electrodes 12 and 13.

By the way, as mentioned above, since the output voltage V from the potentiometric alcohol sensor 11 rises once in the low concentration region and takes the maximum value _Vnax , the alcohol concentration C
There is a problem that the alcohol concentration C cannot be detected accurately. On the other hand, the output voltage E of the resistive alcohol sensor according to the prior art has two values (C ₂ , C ₃ ) in the high concentration region of alcohol concentration C;
In the region of concentration lower than C ₂ , the voltage characteristic has only one value for alcohol concentration C.

Therefore, in the embodiment, by utilizing the characteristics of the output voltage E of the resistive alcohol sensor described above, the output voltage V of the potentiometric alcohol sensor 11 is
A resistive alcohol sensor 20 is used in combination with the potentiometric alcohol sensor 11 so that the alcohol concentration C becomes one value over the entire alcohol concentration C, and the alcohol concentration described below is determined from the detection voltages V and E of both alcohol sensors 11 and 20. It is configured to perform arithmetic processing.

Therefore, this arithmetic processing will be described with reference to the program shown in FIG. First, when the engine is started and processing is started, the alcohol concentration calculation device 21 reads alcohol concentration detection signals from the potentiometric alcohol sensor 11 and the resistance alcohol sensor 20 as detection voltage values V and E, respectively (step 1). , step 2). On the other hand, the alcohol concentration calculation device 21 reads the reference voltage value V ₁ from the storage device 22 in the next step 3.

Next, the alcohol concentration calculating device 21 calculates the detection voltage value E of the resistance type alcohol sensor 20 and the reference voltage value.
It is compared with _V1 and its size is determined (step 4). When it is determined in step 4 that E≧V ₁ , the process moves to the next step 5, where the detected voltage V-alcohol concentration C map shown in FIG. 4 stored in the storage device 22 is accessed, and the detected voltage V The alcohol concentration C corresponding to the alcohol concentration C is determined, and the alcohol concentration signal C is output to the injection amount calculation device 23. On the other hand, when it is determined in step 4 that E<V ₁ , the detected voltage V of the potentiometric alcohol sensor 11 is less than the maximum value V _nax , so the process moves to step 6 and holds the detected voltage V, for example, Injection amount calculation device 2 as concentration signal C= _C1
Output to 3.

In this way, the output voltage V of the potentiometric alcohol sensor 11, which has two values over the entire range of the alcohol concentration C, always has only one value, so the output voltage V has good linearity and therefore high accuracy. The potentiometric alcohol sensor 11, whose detection results can be used over a wide range of applications, can be used for calculation of fuel injection amount, engine control, etc.

In addition, in the example, the potentiometric alcohol sensor 1
Although it has been described that the output voltage V of No. 1 reaches the maximum value V _nax at a position where the alcohol concentration C is about 10%, it goes without saying that it varies depending on the performance of the potentiometric alcohol sensor 11.

Furthermore, step 4 is a specific example of the determination means of the present invention, and steps 5 and 6 are specific examples of the calculation means of the present invention, but the present invention is not limited to these step processes, and may be performed using a hardware circuit. It may be configured as follows. Furthermore, although alcohol-mixed gasoline was exemplified as the alcohol-mixed liquid in the examples, the present invention can be applied to other alcohol-mixed liquids.

〔Effect of the invention〕

As described in detail above, the present invention outputs a predetermined alcohol concentration when the detected voltage value of the resistive alcohol sensor falls below a predetermined reference voltage value, regardless of the detected voltage by the potentiometric alcohol sensor. By doing this, the potentiometric alcohol sensor is configured to take a single value over the entire alcohol concentration range, making it possible to create an alcohol concentration measuring device with good output voltage linearity, high accuracy, and a wide range of use for detection results. can.

[Brief explanation of the drawing]

1 to 5 relate to embodiments of the present invention,
Figure 1 is a circuit diagram of a potentiometric alcohol sensor, Figure 2 is an explanatory diagram of the configuration of a potentiometric alcohol sensor,
Fig. 3 is a system configuration diagram when the alcohol concentration measuring device is applied to a fuel injection control device, Fig. 4 is a characteristic diagram showing the relationship between alcohol concentration and output voltage, and Fig. 5 is a flowchart showing concentration calculation processing. , Fig. 6 to Fig. 10 relate to the prior art, Fig. 6 is a diagram showing the relationship between the air-fuel ratio and the alcohol concentration, Fig. 7 is an explanatory diagram of the configuration of the resistance type alcohol sensor, and Fig. 8 is the resistance type alcohol sensor. The circuit diagram of the sensor, Figure 9 is a diagram showing the relationship between alcohol concentration and detection resistance,
FIG. 10 is a characteristic diagram showing the relationship between alcohol concentration and output voltage. DESCRIPTION OF SYMBOLS 11... Potential difference type alcohol sensor, 20... Resistance type alcohol sensor, 21... Alcohol concentration calculating device, 22... Memory device, 23... Injection amount calculating device.

Claims (1)

[Claims] 1. A pair of current-carrying electrodes that are spaced apart and facing each other in an alcohol mixed liquid and to which a constant voltage is applied; and a pair of current-carrying electrodes that are spaced apart and facing each other by a predetermined distance between the pair of current-carrying electrodes. A potentiometric alcohol sensor has a pair of detection electrodes, and detects alcohol concentration using the potential difference between the detection electrodes, and the alcohol concentration is determined from the resistance value between each energizing electrode of the potentiometric alcohol sensor. a resistive alcohol sensor that detects the resistive alcohol sensor, and determines whether the detected voltage of the resistive alcohol sensor is larger or smaller than a reference voltage value corresponding to the maximum value of the detected voltage to be detected by the potentiometric alcohol sensor. and a determining means for determining that the detected voltage of the resistive alcohol sensor is smaller than a reference voltage value, the alcohol concentration is calculated as a predetermined alcohol concentration regardless of the detected voltage of the potentiometric alcohol sensor. . An alcohol concentration measuring device configured to calculate alcohol concentration using the detected voltage of the potentiometric alcohol sensor when it is determined that the voltage is equal to or higher than a reference voltage value.