JPH0565818B2 - - 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." Naturally, the octane number of genuine gasoline and gasohol mixed with alcohol will change, so the fuel injection amount, ignition timing, etc. of the engine will also differ, so engines that use alcohol mixed fuel are installed.

Here, when looking at the basic injection amount T _P when using genuine gasoline, if the intake air amount Q, the engine speed is N, and the constant is K, the basic injection amount T _P
is calculated as T _P =K×Q/N (1). Then, the basic injection amount T _P is
Correction is made based on signals from various sensors such as the water temperature sensor and oxygen sensor, and various switches such as the engine switch and throttle valve switch, and finally the fuel injection amount T _i by the injector is calculated as T _i = T _P × α ×α′×C _OEF +T _S ……(2) where α: Air-fuel ratio feedback correction coefficient α′: Basic air-fuel ratio learning correction coefficient C _OEF : Various correction coefficients T _S : Calculated as battery voltage correction coefficient. At this time, the air-fuel ratio feedback correction coefficient α is corrected based on the oxygen concentration signal from the oxygen sensor, and the basic air-fuel ratio learning correction coefficient α' is corrected by learning from the basic injection amount T _P and engine speed N. The air-fuel ratio (weight ratio of air and fuel) A/F is controlled to be 15:1.

In this way, the air-fuel ratio A/F of genuine gasoline is
However, it is known that the air-fuel ratio of alcohol-mixed gasoline has characteristics as shown in FIG. 6, and that when the alcohol concentration is 100%, the air-fuel ratio is 6:1.

Therefore, when using alcohol-mixed gasoline, the fuel injection amount T _i can be calculated from equation (2) as T _i ′=C _K ×T _P ×α×α′×C _OEF +T _S ……(3) However, , C _K : It is necessary to calculate it as a constant determined by the alcohol concentration.

Here, as an alcohol sensor for detecting the alcohol concentration in alcohol-mixed gasoline, a resistance-type alcohol sensor that detects the alcohol concentration from the specific resistance value of gasoline and alcohol is being considered. As shown in Fig. 7, this resistance type alcohol sensor has a pair of electrodes b and c disposed facing each other with a predetermined distance apart in the middle of a pipe a serving as a flow path, and a pair of electrodes b and c are interposed between the electrodes b and c. Based on the fact that the resistance value decreases as the alcohol concentration of the alcohol-mixed gasoline d increases (see Figure 8), the electrodes b and c and the voltage detection resistor e are connected in series to the DC power supply f, and the voltage detection resistor e Output voltage derived from
Alcohol concentration is now detected from changes in V _S.

That is, when the alcohol concentration C increases, the electrodes b,
Since the resistance value of c decreases, the output voltage V _S from the voltage detection resistor e can be derived as a detection voltage directly proportional to the alcohol concentration C. However, when the alcohol concentration C is below the low concentration region, the output voltage
Since V _S is dominated by the resistance of gasoline, the detection voltage hardly changes, and in the region where the alcohol concentration C is high, the output voltage V _S decreases rapidly for reasons explained later. The output voltage V _S of the alcohol sensor has voltage characteristics shown in FIG. 9 with respect to the alcohol concentration C.

[Problem to be solved by the invention]

By the way, it is generally known that in electrolyzers, there is a polarization effect in which ions accumulate on the electrodes, and a relaxation effect in which resistance is exerted to the movement of ions. Even in a resistive alcohol sensor in which electrodes b and c are immersed and energized, as the alcohol concentration increases, the electrical conductivity of electrodes b and c is lost and reduced due to polarization and relaxation effects.

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

Thus, as shown in FIG. 9, the output voltage V _S across the voltage detection resistor e reaches its maximum value on the high alcohol concentration side, for example when the alcohol concentration C = 90%.
Since the output voltage V _S when the alcohol concentration C = 100% is the reference voltage value, since it becomes V _Snax and rapidly decreases.
V _SO , the output voltage V _S1 is greater than the reference voltage value V _SO for the same alcohol concentration C.
has two values, and there is a problem that the alcohol concentration C cannot be measured accurately.

Thus, in the resistance type alcohol sensor according to the prior art, the reference voltage value of the output voltage V _S
The disadvantage is that only the output voltage V _S2 that is less than V _SO can be used as a measurement result, and the range of use of the measurement results is narrow.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and uses a resistive alcohol sensor in combination with an indirect sampling type alcohol sensor that measures alcohol concentration from the potential difference between a pair of electrodes. The present invention provides an alcohol concentration measuring device whose results can be widely used.

[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. an indirect sampling type alcohol sensor, which has a pair of detection electrodes located between the detection electrodes and arranged facing each other with a predetermined distance between them, and which detects alcohol concentration using the potential difference between the detection electrodes; A resistive alcohol sensor that detects alcohol concentration from the resistance value between each energizing electrode of an indirect sampling alcohol sensor, and a detection voltage of the resistive alcohol sensor when the alcohol in the alcohol mixed liquid is at a predetermined high concentration. a first determination means for determining whether or not the detection voltage of the indirect sampling type alcohol sensor is smaller than a first reference voltage value; a second determining means for determining whether or not the detected voltage of the resistive alcohol sensor is greater than a preset second reference voltage value;
When it is determined that the detection voltage of the resistive alcohol sensor is smaller than the reference voltage value, the alcohol concentration is calculated using the detection voltage of the resistive alcohol sensor, and the first determining means determines that the detected voltage of the resistive alcohol sensor is smaller than the first
When it is determined that the voltage is higher than the reference voltage value,
The second determining means determines whether the detected voltage of the indirect sampling type alcohol sensor is larger than the second reference voltage value, and when it is determined that the detected voltage is larger than the second reference voltage value, the detected voltage of the resistive type alcohol sensor is used to determine whether alcohol is detected or not. The alcohol concentration is calculated, and when it is determined that the alcohol concentration is smaller, the alcohol concentration is calculated as a predetermined alcohol concentration regardless of the detected voltage of the resistive alcohol sensor.

[Effect]

By configuring the present invention in this way, the detection voltage of the resistive alcohol sensor is not only smaller than the first reference voltage value, but also in a range larger than the first reference voltage value and smaller than the second reference voltage value. However, it is possible to calculate the alcohol concentration using the detection voltage of the resistance type alcohol sensor, and when the detection voltage of the indirect sampling type alcohol sensor is smaller than the second reference voltage value, the alcohol concentration can be calculated as a predetermined alcohol concentration. Therefore, the output voltage of the resistive alcohol sensor has one value over the entire alcohol concentration range.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 5.

In the figure, reference numeral 1 indicates an indirect sampling type alcohol sensor that assists a resistance type alcohol sensor 10, which will be described later. Reference numerals 2 and 3 constitute the alcohol sensors 1 and 10 of each of these methods, and are energizing electrodes consisting of a pair of electrode plates spaced apart in the fuel pipe a (see Fig. 7). The current-carrying electrode 2 is connected to a DC power source 4, and the other current-carrying electrode 3 is connected to the DC power source 4 via a fixed resistor 5, so that a constant voltage is applied thereto.

Reference numerals 6 and 7 denote detection electrodes consisting of another pair of electrode plates provided between the pair of current-carrying electrodes 2 and 3, in order to indirectly measure the potential difference of the gasoline interposed between them. The detection electrodes 6 and 7 are spaced from the energizing electrodes 2 and 3 by a predetermined distance, and are arranged facing each other with a predetermined distance from each other. Reference numeral 8 denotes a voltage detection device connected between the pair of detection electrodes 6 and 7 in order to detect the potential difference between the pair of detection electrodes 6 and 7. Here, as will be described in detail later, the output voltage V of the indirect sampling type alcohol sensor 1 rises in a region where the alcohol concentration C is low and reaches the maximum value V _nax , and then the alcohol concentration C
It has a voltage characteristic that decreases in inverse proportion to .
An amplifier 9 is connected to the voltage detection device 8 for converting the detected voltage V having the above-mentioned characteristics into a transmittable output voltage (see FIG. 3).

On the other hand, 10 is a resistive alcohol sensor that detects the alcohol concentration C in gasoline in the fuel pipe a together with the indirect sampling type alcohol sensor 1, and the resistive alcohol sensor 10 has a pair of The voltage across the fixed resistor 5 connected in series to the current-carrying electrodes 2 and 3 is detected as the voltage.
The alcohol concentration C is detected by utilizing the fact that the resistance value between _the current-carrying electrodes 2 and 3 changes depending on the alcohol concentration C, and the detected voltage V As shown in _FIG . 4, it has voltage characteristics similar to those of the conventional resistance alcohol sensor.

Thus, in the embodiment, the indirect sampling type alcohol sensor 1 is composed of the current-carrying electrodes 2, 3, the DC power source 4, the detection electrodes 6, 7, the voltage detecting device 8, etc., and the resistance-type alcohol sensor 10 is composed of the current-carrying electrodes 2, 3, 3. It is composed of a DC power supply 4, a fixed resistor 5, etc.

Next, reference numeral 11 denotes an alcohol concentration calculation device consisting of a CPU, etc., and the input side of the alcohol concentration calculation device 11 is connected to the amplifier 9 and the resistive alcohol sensor 1.
0 are connected to each other, and the output side is connected to an injection amount calculation device 13, which will be described later. Reference numeral 12 denotes a storage device such as ROM or RAM connected to the alcohol concentration calculation device 11;
In addition to the program shown in FIG. 5, a reference voltage value V _SO (hereinafter referred to as a first reference voltage value V _SO ) when the alcohol concentration C = 100% detected by the resistive alcohol sensor 10 is written. The reference voltage value V _O of the indirect sampling type alcohol sensor 1 when the alcohol concentration C = 90%, when the output voltage V _S of the resistance type alcohol sensor 10 reaches the maximum value V _Snax (hereinafter referred to as the second
A data map of output voltage _V vs. alcohol concentration C shown as a characteristic diagram in FIG. 4 is stored. The alcohol concentration calculation device 11 performs concentration calculation processing, which will be described later, based on data stored in the storage device 12, and then outputs an alcohol concentration signal C to the injection amount calculation device 13.

Here, regarding the second reference voltage value _VO , the output voltage of the resistive alcohol sensor 10
V _S has a maximum value in the high concentration area of alcohol concentration C
Take V _Snax . Therefore, based on the alcohol concentration C=90% corresponding to the maximum value V _Snax , the voltage value when the indirect sampling type alcohol sensor 1 detects the alcohol concentration C=90% is the reference voltage value V _O
This is set in advance as . Since the output voltage V of the indirect sampling alcohol sensor 1 decreases inversely to the alcohol concentration C,
On the alcohol concentration side lower than C=90%, the output voltage V becomes V>V _O with respect to the reference voltage value V _O , and on the alcohol concentration side higher than C=90%, V<V _O
becomes.

Next, 13 is a fuel injection amount calculation device, and the injection amount calculation device 13 injects fuel based on the alcohol concentration signal C, the engine rotation speed N from the crank angle sensor 14, the intake air amount Q from the air flow meter 15, etc. The amount is calculated and a fuel injection signal C is output to the injection valve 16. Moreover, 17 in the figure is an alcohol concentration meter.

The present embodiment is constructed as described above.Next, the operation of the indirect sampling type and resistance type alcohol sensors 1 and 10 will be described first, and then the calculation process of alcohol concentration will be described.

A pair of current-carrying electrodes 2, 3 and a pair of detection electrodes 6, 7 provided between them of the indirect sampling type alcohol sensor 1 are immersed in alcohol-mixed gasoline d in a fuel pipe a. In this state, a DC power source 4 is placed between the pair of current-carrying electrodes 2 and 3.
Apply a constant voltage from At this time, when the alcohol concentration C in the alcohol-mixed gasoline interposed between the current-carrying electrodes 2 and 3 is high, the resistance value is small, so the potential difference between the electrodes 2 and 3 becomes small; conversely, when the alcohol concentration C is low, , since the resistance value is large, the potential difference between electrodes 2 and 3 becomes large.

Therefore, a pair of detection electrodes 6 and 7 interposed between the current-carrying electrodes 2 and 3 is used to reduce the potential difference between the current-carrying electrodes 2 and 3 at the portion where the detection electrodes 6 and 7 are provided. Detected by voltage detection device 8.

Next, indirect sampling type alcohol sensor 1
The reason why the output voltage V takes the maximum value _Vnax in the low concentration region of alcohol concentration _C1 as shown in FIG. 4 will be explained in detail.

First, when the alcohol concentration C in Fig. 4 is in a high concentration region of 90% or more, the resistance value between each current-carrying electrode 2 and 3 decreases significantly in inverse proportion to the alcohol concentration C, and the potential difference becomes small. Therefore, each detection electrode 6, 7 disposed between each current-carrying electrode 2, 3
The potential difference between them also becomes smaller, and the output voltage V decreases as shown in FIG.

Next, the alcohol concentration C in Figure 4 is C ₁ ~ 90
% range, the potential difference between each of the energizing electrodes 2 and 3 decreases depending on the alcohol concentration C, as in the case of the high concentration region. The potential difference between them also becomes smaller, and the output voltage V decreases.

That is, in the region where the alcohol concentration is C ₁ or more, the potential difference between the current-carrying electrodes 2 and 3 is inversely proportional to the alcohol concentration, so that the part of the voltage detected by the detection electrodes 6 and 7 between the current-carrying electrodes 2 and 3 is inversely proportional to the alcohol concentration. The potential difference (output voltage V) is also inversely proportional to the alcohol concentration C.

Therefore, even when the alcohol concentration C is in a low concentration region below _C1 , theoretically and ideally, the output voltage V between the detection electrodes 6 and 7 is inversely proportional to the alcohol concentration C, and the voltage detection device 8 It should increase until it becomes undetectable.

However, in reality, the output voltage V between each of the detection electrodes 6 and 7 peaks when the alcohol concentration C is C ₁ and then decreases, and is proportional to the alcohol concentration C in a low concentration region smaller than C ₁ .

That is, when the alcohol concentration C becomes less than _C1 ,
Since the presence of gasoline increases and this gasoline can be considered as a substantial insulator, the resistance value between each current-carrying electrode 2 and 3 increases significantly, and each current-carrying electrode 2 and 3 receives a direct current. Most of the power supply voltage of power supply 4 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 2, 3 increases, the voltage between each current-carrying electrode 2, 3 does not change linearly, and the electrical conductivity near the electrode surface of each current-carrying electrode 2, 3 increases. decreases, so it changes rapidly, and as a result, the change near the center between the current-carrying electrodes 2 and 3 becomes small.

Since no voltage is applied to each of the detection electrodes 6 and 7 disposed between the current-carrying electrodes 2 and 3, and no polarization effect occurs, the detection electrodes 6 and 7 are the current-carrying electrodes. A gradual voltage change near the center between 2 and 3 is detected, and the output voltage V becomes small.

Thus, as shown in Figure 4, the alcohol concentration
It is possible to obtain a voltage characteristic in which the maximum value V _nax is reached in the low concentration region of _C1 , and as the alcohol concentration C increases, the output voltage V decreases linearly.With this voltage characteristic, the alcohol concentration C in gasoline can be can be measured. Further, when detecting the alcohol concentration C, since no current is applied to the detection electrodes 6 and 7, the electrodes 6 and 7 are not affected by polarization effects or relaxation effects. Therefore, even if the current-carrying electrodes 2, 3 exhibit polarization effects or relaxation effects, the detection electrodes 6, 7 can accurately detect the potential difference between the current-carrying electrodes 2, 3.

Incidentally, as described above, the output voltage V from the indirect sampling type alcohol sensor 1 has a voltage characteristic that once rises in the low concentration region and reaches the maximum value V _nax , and then decreases in inverse proportion to the alcohol concentration C. On the other hand, the output voltage V _S of the resistive alcohol sensor 10 has two values when the voltage value is larger than the first reference voltage value V _SO , but when it is a voltage value smaller than the first reference voltage value V SO , the output voltage V _S has two values. In this case, the voltage characteristic has only one value for alcohol concentration C.

Therefore, in the embodiment, by utilizing the characteristics of the output voltages V and V _S of the indirect sampling type alcohol sensor 1 and the resistive alcohol sensor 10 described above, the output voltage V _S of the resistive alcohol sensor 10 is adjusted to the alcohol concentration C. The alcohol concentration is calculated from the output voltages V and V _S of both alcohol sensors 1 and 10 so that the alcohol concentration becomes one value over the entire range.

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 11 reads out the first reference voltage value V _SO from the storage device 12 (step 1). On the other hand, the alcohol calculation device 11 is a resistive alcohol sensor 10.
The alcohol concentration detection signal is read as the detection voltage value V _S (step 2).

Next, the alcohol concentration calculating device 11 calculates the detection voltage value V _S of the resistance type alcohol sensor 1 and the reference voltage value.
Compare with V _OS to see if V _S > V _SO (step 3). When the determination is "NO", the detection voltage V _S of the resistive alcohol sensor 10 is a detection voltage V _S2 that is smaller than the first reference voltage value V _SO , and the detection voltage V _S2 has a value of 1 for the alcohol concentration C. This detection voltage V _S2 is used to determine a constant C _K that depends on the alcohol concentration C (step 4).

On the other hand, when the determination in step 3 is "YES", the process proceeds to step 5, where the alcohol concentration calculation device 11 calculates the second reference voltage value V _O from the storage device 12.
At the same time, the alcohol concentration detection signal is read from the indirect sampling type alcohol sensor 1 as the detected voltage value V (step 6), and it is determined from the detected voltage value V and the second reference voltage value V _O whether V<V _O. (Step 7). When the determination is "NO", the detection voltage of the resistance alcohol sensor 10
V _S is the detection voltage V _S1 in the area before reaching the maximum value V _Snax
Therefore, return to step 4 and calculate the detected voltage V _S1
Determine the constant C _K that depends on the alcohol concentration using (Step 4).

On the other hand, if the determination is ``YES'' in step 7, the detection voltage of the resistive alcohol sensor
Since V _S is rapidly decreasing from the maximum value V _Snax ,
Proceed to step 8, hold the detection voltage V _S , and set a constant to make the alcohol concentration C = 90%, for example.
Determine C _K.

In this way, a constant C _K that depends on the alcohol concentration C when the detected voltage V _S is less than a certain voltage reference value V _SO and a constant that makes the alcohol concentration C = 90% when the detected voltage V S exceeds the voltage reference value V _SO are determined. Once determined, the process moves to step 9, where the fuel injection amount T _i is calculated using the C _K.

As described above, according to the embodiment, the output voltage V _S of the resistive alcohol sensor 10 is a constant reference voltage value V _SO
Since it always has a value of 1 even when it is larger, the output voltage V _S has good linearity, and therefore can be used with high accuracy and a wide range of use.

In addition, in the example, the resistance type alcohol sensor 10
The output voltage V _S has been described as having the maximum value V _Snax at a position where the alcohol concentration C is about 90%, but the maximum value V _Snax with respect to the alcohol concentration C varies depending on the performance of the resistive alcohol sensor 10. Of course.

Further, in the alcohol concentration calculation process, step 3 is a specific example of the first determining means of the present invention, and step 7 is a specific example of the second determining means of the present invention, but the present invention does not apply to these specific examples. It is not limited.

Furthermore, although alcohol-mixed gasoline was exemplified as the alcohol-mixed liquid in the examples, the present invention can also be applied to other alcohol-mixed liquids.

〔Effect of the invention〕

As described in detail above, the present invention is such that when the detection voltage of the resistive alcohol sensor becomes larger than a predetermined reference voltage value, and the detection voltage of the indirect sampling alcohol sensor becomes smaller than the predetermined reference voltage value, By outputting a predetermined alcohol concentration signal regardless of the detection voltage of the resistive alcohol sensor, the resistive alcohol sensor is configured to take one value over the entire alcohol concentration range, so the output voltage has good linearity. It is possible to obtain an alcohol concentration measuring device with high accuracy and a wide range of use of detection results.

[Brief explanation of drawings]

1 to 5 relate to embodiments of the present invention,
Figure 1 is a circuit diagram that integrates an indirect sampling type alcohol sensor and a resistance type alcohol sensor, Figure 2 is an explanatory diagram of the configuration of an indirect sampling type alcohol sensor, and Figure 3 shows an alcohol concentration measuring device integrated into a fuel injection control device. A system configuration diagram when applied, Fig. 4 is a characteristic diagram showing the relationship between alcohol concentration and output voltage, Fig. 5 is a flow chart showing the process of calculating the fuel injection amount from alcohol concentration, Fig. 6
9 to 9 relate to the prior art, FIG. 6 is a diagram showing the relationship between alcohol concentration and air-fuel ratio, FIG. 7 is a diagram illustrating the configuration of a resistance-type alcohol sensor, and FIG. 8 is a diagram showing the relationship between alcohol concentration and detection resistance. A diagram showing the relationship, FIG. 9 is a characteristic diagram showing the relationship between alcohol concentration and output voltage. 1...Indirect sampling type alcohol sensor,
10...Resistive alcohol sensor, 11...Alcohol concentration calculation device, 12...Storage device, 13...
...Injection amount calculation 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. An indirect sampling type alcohol sensor that has a pair of detection electrodes and detects alcohol concentration using the potential difference between the respective detection electrodes, and a resistance value between each energizing electrode of the indirect sampling type alcohol sensor. a resistive alcohol sensor for detecting alcohol concentration; and a resistive alcohol sensor for determining whether a detection voltage of the resistive alcohol sensor is smaller than a first reference voltage value when alcohol in the alcohol mixed liquid is at a predetermined high concentration. and determining whether the detected voltage of the indirect sampling type alcohol sensor is larger than a second reference voltage value preset with reference to the alcohol concentration corresponding to the maximum value of the detected voltage of the resistive type alcohol sensor. and second determination means for determining, when the first determination means determines that the detected voltage of the resistive alcohol sensor is smaller than the first reference voltage value, the resistive alcohol sensor detects the detected voltage of the resistive alcohol sensor. When the alcohol concentration is calculated by voltage and the first determining means determines that the detected voltage of the resistive alcohol sensor is greater than the first reference voltage value, the second determining means performs the indirect sampling. It is determined whether the detected voltage of the resistive alcohol sensor is larger than the second reference voltage value, and when it is determined that it is larger, the alcohol concentration is calculated based on the detected voltage of the resistive alcohol sensor, and if it is further smaller. An alcohol concentration measuring device configured to calculate a predetermined alcohol concentration when a determination is made, regardless of the detected voltage of the resistive alcohol sensor.