JPH0486342A - Alcohol mixed fuel injection control unit - Google Patents

Abstract

PURPOSE:To improve the idling stability of an engine and prevent fluctuation of output and air-fuel ratio by providing such a constitution as fixing a correction constant determined according to alcohol concentration to a determined value when the temperature of alcohol mixed fuel reaches a determined temperature corresponding to the alcohol concentration or more. CONSTITUTION:During the operation of an engine 1 using alcohol mixed fuel, a control unit 30 calculates a basic injection quantity Tp on the basis of intake air quantity Q from an airflow meter 5 and engine rotating speed N from a crank angle sensor 34, also calculates a fuel injection quantity Ti' on the basis of alcohol concentration M from an alcohol sensor 15, and outputs an injection pulse having a pulse duty corresponding to the injection quantity Ti' to an injection valve 2. In this case, the temperature of the alcohol mixed fuel is detected by a temperature sensor 28, and when this temperature is a determined temperature or more based on the detected concentration detected by the alcohol sensor 15, a correction constant determined according to the alcohol concentration is fixed to a determined value to calculate the fuel injection quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an alcohol-mixed fuel injection control device adapted to an engine using alcohol-mixed fuel.

[Conventional technology]

Recently, alcohol-mixed gasoline containing methanol has come to be used as fuel for automobile engines instead of pure gasoline.

Naturally, the stoichiometric air-fuel ratio differs between genuine gasoline and alcohol-mixed gasoline, so the fuel injection amount, ignition timing, etc. of the engine also differ.

Here, looking at the fuel injection amount T1 when using genuine gasoline with an alcohol concentration of 0%, T+=Tpxα
X C0EF + T s...(1) However, TP
: Basic injection amount α : Air-fuel ratio feedback correction coefficient C0EF : Various correction coefficients Tg : 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 stoichiometric air-fuel ratio A/F is controlled to be 14.7.

In this way, the air-fuel ratio A/F of genuine gasoline is 14.7, but when using methanol with an alcohol concentration of 100%, it is necessary to control the air-fuel ratio A/F to 65. In the range of alcohol concentration from 0 to 100%, the stoichiometric air-fuel ratio A/F differs by about twice.

Therefore, when using alcohol-mixed gasoline,
) From the formula, the fuel injection amount T,
p X C1xcOEF) +Ts'' (2) However, it is necessary to calculate KX as a correction constant (number of alcohol correction chambers) determined according to the alcohol concentration.

For this reason, engines that use alcohol-mixed gasoline are equipped with an alcohol concentration measuring device called an alcohol sensor, which generates an output voltage corresponding to the alcohol concentration, and calculates equation (2) based on the output voltage value. It is now possible to do this. This type of alcohol concentration measurement device includes a resistance alcohol concentration measurement device that detects alcohol concentration from the electrical conductivity of gasoline and alcohol, and a capacitance alcohol concentration measurement device that uses changes in the dielectric constant of alcohol-mixed gasoline. An optical alcohol concentration measuring device that utilizes a change in refractive index is known.

Regarding the alcohol mixed fuel injection fuel control device, as shown in previously filed Japanese Patent Laid-Open No. 56-98540 (hereinafter referred to as prior art), the correction constant Kx of the fuel injection amount T,' to the engine is It is known that the fuel injection amount T1' is determined based on the output signal of the sensor and is constantly subjected to correction calculation or regulation correction calculation to control the fuel injection amount T1'.

[Problems to be Solved by the Invention] By the way, the alcohol mixed fuel injection fuel control device of the prior art described above constantly corrects the fuel injection amount T1' or uniformly calculates the fuel injection amount T1' using the correction constant Kx determined based on the output signal of the alcohol sensor. Since it performs correction calculations and outputs them for control, if the evaporation characteristics of the fuel changes depending on the alcohol concentration and bubbles are generated in the fuel when the fuel is at high temperature, this will cause the alcohol concentration to be detected. The error becomes large (and the engine air-fuel ratio fluctuates significantly,
There is a problem in that engine idling, acceleration/deceleration, etc. cause breathing problems and rotational fluctuations, resulting in a decrease in drivability.

The present invention has been made in view of the problems in the prior art described in 1.
When the temperature of the alcohol-mixed fuel reaches a predetermined temperature or higher corresponding to the alcohol concentration, by fixing the correction constant to a predetermined value, the engine air-fuel ratio can be stabilized and controlled, improving engine breathability. An object of the present invention is to provide an alcohol-mixed fuel injection control device that can prevent rotational fluctuations and the like.

[Means to solve the problem]

” - In order to solve the above problems, the features of the configuration adopted by the present invention include a temperature sensor that detects the temperature of the alcohol mixed fuel, and a temperature sensor that measures the temperature of the alcohol mixed fuel at a predetermined temperature corresponding to the alcohol concentration. If the above value is reached, when the fuel injection amount to the engine is calculated by the injection amount calculation means, a constant is fixed to fix the constant to a predetermined value, regardless of the correction constant based on the concentration detected by the alcohol concentration detection means. It consists of means and means.

In this case, the alcohol concentration detecting means is a capacitive alcohol sensor consisting of an L-tubular outer electrode communicating with the fuel pipe and an inner electrode disposed approximately coaxially with the outer electrode. In the tubular outer electrode, it is preferable that the expansion angle O between the inflow pipe section and the outflow pipe section is set to 90° < θ > 180°.

[Function] According to the above configuration, the temperature of the alcohol mixed fuel is detected by the temperature sensor, and the temperature is determined based on the detected concentration detected by the alcohol concentration detection means (if the temperature is higher than a predetermined temperature, the temperature is determined according to the alcohol concentration). The fuel injection amount can be calculated by fixing the correction constant determined at a predetermined value, and the detection error can be prevented from increasing.

Further, the expansion angle O between the inflow pipe portion and the outflow pipe portion of the L-shaped outer electrode of the alcohol concentration detection means is set to 90° and θ<
By setting it to 180'', it is possible to reduce the generation of bubbles in the alcohol-mixed fuel and the passage resistance.

[Example] Hereinafter, an example of the present invention will be described based on FIGS. 1 to 8.

In the figure, reference numeral 1 denotes an engine that constitutes the engine body of an automobile, and an injection valve 2 that injects alcohol-mixed gasoline 9 (described later) into a combustion chamber is provided on the intake side of the engine 1, and an intake valve 2 that injects outside air. A manifold 3 is provided, and an air flow meter 5 for measuring an intake air amount Q is provided between the manifold 3 and the air cleaner 4. Further, an exhaust manifold 6 is provided on the exhaust side of the engine 1, and an oxygen sensor 7 is provided on the exhaust manifold 6. The oxygen sensor 7 detects the oxygen concentration in the exhaust gas, and its detection signal will be described later. The output is output to the control unit 30 that controls the output.

A fuel tank 8 stores alcohol-mixed gasoline 9 as alcohol-mixed fuel, and a fuel pump 10 for discharging the alcohol-mixed gasoline 9 is provided within the fuel tank 8 .

11 is a fuel pipe, one end of the fuel pipe 11 is connected to the discharge side of the fuel pump 10, and a fuel filter 12 is provided in the middle thereof. The other end of the fuel pipe 11 is connected to the inlet side of the injection valve 2 and the pressure regulator 13, and the outflow side of the pressure regulator 13 is connected to the fuel tank 8 via the return pipe 14.

Reference numeral 15 indicates an alcohol sensor as a capacitive alcohol concentration detection means provided in the middle of the fuel supply system such as the fuel pipe 10, and the alcohol sensor 15 is located between the fuel filter 12 and the pressure regulator 13. It is connected in the middle of the fuel pipe 11 to detect the alcohol concentration in the alcohol mixed gasoline 9 flowing inside the fuel pipe 11.

Here, the alcohol sensor 15 is as shown in FIG.
Consisting of a casing 16, a concentration detector 20, a temperature sensor 28, etc., which will be described later, the casing 16 has cylindrical pipe members 17 and 18, which will become an inflow pipe section and an outflow pipe section, joined in an abbreviated or approximately T-shape. The pipe member 1 is formed by
7.18 is formed so that the expansion angle θ satisfies the relationship of 90°<θ×180°. Further, an enlarged diameter portion 17A is formed at one end of the pipe member 17, and the enlarged diameter portion 17A is closed by an insulating stopper 19. The pipe members 17 and 18 of the casing 16 are
For example, it is formed of a conductive iron pipe plated with nickel or the like. The other end of the pipe member 17 becomes an inlet 17B for the alcohol-mixed gasoline 9, and the tip end of the pipe member 18 becomes an outlet 1], 8A, and the inflow 1]], 7B and the outlet 1.8A serve as fuel. It is connected in the middle of the pipe 11 so that the alcohol-mixed gasoline 9 flows in the direction of the arrow A within the casing 16.

A concentration detector 20 is provided in the casing 16 and detects the alcohol concentration of the alcohol mixed gasoline 9 flowing inside the casing 16. The concentration detector 20 includes a pipe member 17 serving as an outer electrode, and a pipe member 17. An elongated rod-shaped center electrode 21 protrudes axially from one end side into the pipe member 17 through the plug body 19 and constitutes a coaxial cylindrical counter electrode together with the pipe member 17; An insulating fitting member 23 is fitted to the enlarged diameter portion 17A of the pipe member 17 via the conductive cylinder 22 to be supported together with the plug 19, and a radial direction from the outer end surface of the fitting member 23 is provided. A nut 24 protrudes outward and is attached to one end of the center electrode 21.
By screwing the fitting member 2 through the washer 25,
A terminal 26 on the center electrode 21 side, which is fastened to 2
7 is connected to the pipe member 17 via a conductive cylindrical body 22.

Here, the center electrode 2J of the concentration detector 20 extends in the axial direction inside the pipe member 17, and together with the pipe member 17 constitutes a coaxial cylindrical counter electrode. The center electrode 21 and the pipe member 17 via
By applying a voltage from the outside between the center electrode 21 and the pipe member 17, the alcohol concentration of the alcohol mixed gasoline 9 flowing in the direction of arrow A is determined as follows (3
) It can be detected as a capacitance Cs as shown in the equation.

However, ε: Dielectric constant of alcohol-mixed gasoline °C:
Length R1 of the center electrode: Radius R2 of the center electrode: Radius of the pipe member The concentration detector 20 includes an oscillation circuit and a frequency-voltage conversion circuit (both not shown) connected from the outside between the terminals 26 and 27. ) etc., the capacitance C6 is output voltage ■. and convert it into a control unit 30 (described later).
It is designed to output to .

28 is the inlet 17B of the pipe member 17 and the pipe member 18
Adhesive 29 is placed on the outer peripheral side of the pipe member 17 between the
The temperature sensor 28 is composed of a temperature-sensitive resistance element such as a thermistor or a posistor, and measures the fuel temperature (hereinafter referred to as fuel temperature Tt) of the alcohol-mixed gasoline 9 flowing inside the casing 16 through a pipe. Detection is performed via member 17. That is, the temperature sensor 28 detects the fuel temperature t of the alcohol-mixed gasoline 9 as the temperature transmitted to the pipe member 17, and outputs this detection signal to the control unit 30.

Further, the enlarged diameter portion 17A of the pipe member 17 and the center electrode 2
1, and the distance between the pipe member 17 and the center electrode is r, the relationship R>r holds. This makes it possible to reduce the capacitance due to the dielectric constant of the stopper 19 etc. fixed in the enlarged diameter part 17A, and when the alcohol-mixed gasoline 9 becomes hot and bubbles are generated, most of the diameter enlarges. Since the alcohol concentration occurs near the portion 17A, the detection error of the alcohol concentration M can be reduced, and the center electrode 21 can be firmly held.Furthermore, the pipe member 17.
By setting the expansion angle θ of 18 as described above, it is possible to reduce the generation of bubbles in the alcohol-mixed gasoline 9 and the flow path resistance.

30 is a control unit constituted by, for example, a microcomputer, and the control unit 3
0 is an input/output control circuit 31 and an arithmetic circuit 3 as shown in FIG.
2 and a memory circuit 33, and on the input side of the human output control circuit 31 are an oxygen sensor 7 for detecting the oxygen concentration in exhaust gas, an air flow meter 5 for detecting the intake air amount Q, an engine speed N, and a memory circuit 33. A crank angle sensor 34 that detects the crank angle, an alcohol sensor 15 that detects the alcohol concentration M, a temperature sensor 28 that detects the fuel temperature Tt of alcohol-mixed gasoline, a water temperature sensor 35 that detects the engine cooling water temperature Tw, etc. are connected, Injection valve 2 on the output side
is connected. Moreover, in the memory circuit 33, the above (2
) program for calculating the fuel injection amount T1' shown in FIG. 4, a program for calculating the alcohol concentration correction coefficient KX shown in FIG. 5, and a fuel injection control process shown in FIG. 6. The storage area 33A contains a setting map for the alcohol concentration correction coefficient Kx shown in FIG. 7, a determination map shown in FIG. 8, a predetermined value K Counter CN etc. are stored. Note that the counter CN is a start-reset type counter that is reset to zero when the engine 1 is started.

The present embodiment is configured as described above, but the control unit 30 calculates the basic injection amount TP based on the intake air amount Q from the air flow meter 5, the engine speed N from the crank angle sensor 34, etc. Injection is performed by calculating the fuel injection amount T+' according to equation (2) above based on the alcohol concentration range etc. from the sensor 15, and outputting an injection pulse with a pulse duty corresponding to this injection amount Tl' to the injection valve 2. A quantity T,' of alcohol-mixed gasoline 9 is injected into the engine 1 from the injection valve 2.

Next, its operation will be explained based on FIGS. 4 to 8.

First, based on FIG. 4, is the fuel injection amount T+'? The jf calculation process will be explained.

In step 1, the intake air amount Q, engine speed N, engine water temperature Tw, etc. are read from various sensors, and in step 2, the basic injection amount T is determined.

T, , = KXQ/N - (4) However, K: Calculated as a constant. In step 3, various correction coefficients according to the operating conditions of the engine, such as mixture ratio correction coefficient K, nP, warm-up correction coefficient Ktw, post-start increase correction coefficient K alB acceleration increase correction coefficient K acc, etc. are shown in a diagram based on the engine parameters. The total value C0EF of each correction coefficient is read from a two-dimensional map (memo) that does not correspond to C0EF=Klnp+Kt
Calculate as w + , 10 , , (5).

Next, in step 4, the air-fuel ratio feedback correction coefficient α,
Read out battery voltage correction coefficient T3 and alcohol concentration correction constant Kx. Here, this correction coefficient α is used to determine whether the air-fuel ratio is richer or thinner than the stoichiometric air-fuel ratio based on the signal of the oxygen sensor 7, and to perform feedback control so that the air-fuel ratio of the engine 1 becomes approximately the stoichiometric air-fuel ratio. and when the engine water temperature Tw or fuel temperature T is higher than a predetermined high temperature value, α=1(
fixed value). Further, the battery voltage correction coefficient Ts is for correcting the injection amount change due to the voltage fluctuation of the injection valve 2, and these coefficients α and Ts are calculated according to a flowchart (not shown) and are sequentially updated in the storage area 33A of the storage circuit 33. It is remembered as it is done. Then, the correction constant determined by the alcohol concentration M in the fuel (KX≧
1.0) is set by the alcohol concentration correction constant Kx calculation process shown in FIG.

Next, in step 5, the fuel injection i1T,' is changed to the above (2).
The fuel injection amount T,' is calculated according to the formula, and in step 6, the fuel injection amount T,' is stored in the storage area 33A of the storage circuit 33 while being updated sequentially, and the process is returned in step 7.

Next, the alcohol concentration correction constant Kx calculation process will be explained based on FIG.

At step 11, the alcohol concentration M from the alcohol sensor 20 and the fuel temperature Tf from the temperature sensor 28 are read, and at step 12, a predetermined temperature T for the alcohol concentration M at that time is determined based on the determination map shown in FIG. Read out. Here, the determination map shown in FIG. 8 is a map of the evaporation characteristics of the alcohol concentration mixed fuel that changes depending on the alcohol concentration M, and the fuel temperature T at that time is a predetermined temperature T for the alcohol concentration M. In the following cases, no bubbles are generated in the alcohol-mixed fuel (M in Figure 8).

It can be determined that the correction constant KX is a region, and can be set using the calculation map of the correction constant KX shown in FIG. 7, as in steps 14 and 15 described later. On the other hand, if it is greater than the predetermined value T0, it can be determined that the MK' region in FIG. 8 is where bubbles are generated in the alcohol-mixed fuel.
is set to an arbitrary value KX (fixed value).

Next, in step 13, the read fuel temperature Tf is set to the predetermined temperature T of the determination map. Determine whether it is less than or equal to r Y E S
In the case of "J", the process moves to step 14, and in the case of "NO", the process moves to step 16.

Then, in step 14, the fuel temperature T corresponding to the alcohol concentration M in the determination map of FIG. 8 is the predetermined temperature T. Since the following is true, read out the calculation map of the correction constant Kx shown in FIG.
Store 8 in the correction constant at o and return.

On the other hand, if it is determined in step 13 that it is rNOJ, the fuel temperature T1 is the predetermined temperature T for the alcohol concentration M in the determination map of FIG. Since this is the above, the process moves to step 16. In step 16, as described above, the counter CN, which was reset as CN=O when the engine 1 was started, is changed to
Set N=CN+1 and increment by "1". Then, in step 17, it is determined whether or not the count value of this counter CN is, for example, 3 or more, and in the case of rYESJ, step 18
In the case of rNOJ, the process moves to step 2°.

That is, in steps 16 and 17, after the determination of "NO" in step 13, a delay time is provided until the count value of the counter CN reaches a predetermined number, and when the count value of the counter CN reaches a predetermined number or more, for example, 3 or more, the eighth Since it can be reliably determined that the fuel temperature Tt is in the Mx' region (the predetermined temperature T or higher) of the determination map shown in the figure, the high temperature alcohol mixed gasoline 9 has flowed into the alcohol sensor 15 and bubbles have been generated. It is determined that a detection error has occurred in the alcohol concentration M.

Then, in step 18, the memory area 33 of the memory circuit 33
A preset predetermined value KX' stored in A is read out, and in step 19 the correction constant Kx is set to the predetermined value KX'. Then, in step 20, the correction constant Kx set in step 19 is stored in the storage area 33A of the storage circuit 33, and the process returns in step 21.

Note that the alcohol concentration correction constant Kx calculation process shown in FIG. 5 is repeatedly executed at predetermined time intervals.

Furthermore, the fuel injection control process will be explained based on FIG. 6.

In step 31, the fuel injection amount Tl' set in steps 5-6 shown in FIG. is detected, and in step 33, the fuel injection amount Tl' is determined for each cylinder of the engine 1.
In step 34, the process returns to step 31. Note that this routine is repeatedly executed in accordance with the engine speed N.

Therefore, in the alcohol mixed fuel injection control device according to this embodiment, the fuel temperature T is a predetermined temperature T that is predetermined for the alcohol concentration M. When the concentration above is reached, the correction constant Kx is set as a predetermined value Kx' connected to the correction constant, regardless of the correction constant KX based on the detected concentration of the alcohol sensor 15. It is possible to reliably prevent thick fluctuations due to the negative effect of air bubbles generated in Rotational output can be stabilized.

In addition, a correction constant K set depending on the alcohol concentration M
Since x (Kx≧1) is made larger than the air-fuel ratio feedback constant α, it is possible to perform air-fuel ratio feedback control using the alcohol mixed gasoline 9 having a wide range of alcohol concentrations M.

Furthermore, the expansion angle θ between the vibrator members 17 and 18 that becomes the casing 16 of the alcohol sensor 15 is set to <90' as described above.
By setting <θ<180°, the generation of bubbles in the alcohol-mixed gasoline 9 and the flow path resistance can be reduced, and the detection performance of the alcohol concentration M can be improved.

Thus, in this example, when the fuel is at a high temperature where bubbles are likely to occur in the alcohol-mixed gasoline, the alcohol concentration M
By fixing the correction constant KX based on the predetermined value KX', the error in alcohol concentration detection by capacitance detection is reduced for fuels with a wide range of alcohol concentrations M.
Various effects can be obtained, such as reliably improving the engine output and preventing large fluctuations in the engine air-fuel ratio.

Note that among the programs shown in FIG.
Step 19 is a specific example of constant fixing means which is a component of the present invention.

Further, in the above embodiment, the predetermined value of the correction constant Kx is preset as an arbitrary value, but the present invention is not limited to this.
The fuel temperature T is the predetermined temperature T. The correction constant KX before reaching the above value may be set to a predetermined value KX' and stored in the storage area 33A of the storage circuit 33.

[Effects of the Invention] As detailed above, according to the present invention, in a fuel injection device for injecting and supplying alcohol mixed fuel to an engine, an alcohol concentration detection means for detecting alcohol concentration and an alcohol concentration detection means for detecting the alcohol concentration in the middle of the fuel supply system are provided. A temperature sensor is provided to detect the temperature, and a correction constant determined according to the alcohol concentration detected by the alcohol concentration detection means is set such that the temperature of the alcohol mixed fuel detected by the temperature sensor reaches a predetermined temperature or higher corresponding to the alcohol concentration. In this case, the setting of the correction constant based on the alcohol concentration is fixed at a predetermined value without using the alcohol concentration detection means, so the engine's idle stability can be improved, and output fluctuations, air-fuel ratio fluctuations, etc. can be improved. can be effectively prevented.

Further, the alcohol concentration detection means is a capacitive alcohol sensor, and the outer electrode has an L-shaped tubular shape communicating with the fuel pipe, and the expansion angle O between the inlet pipe part and the outlet pipe part is set to 90.
By setting °〈θ to 180°, it is possible to reduce bubble generation and flow path resistance, and the alcohol concentration M
The detection performance of the engine can be improved, the accuracy of the engine output can be improved, and large fluctuations in the engine air-fuel ratio can be prevented.

[Brief explanation of the drawing]

Fig. 1 is an overall view of an alcohol mixed fuel injection control device showing an embodiment of the present invention, Fig. 2 is a vertical sectional view of an alcohol sensor, Fig. 3 is a control block diagram, and Fig. 4 is a fuel injection amount TI.
A flowchart showing the calculation process, FIG. 5 is a flowchart showing the calculation process of the alcohol concentration correction constant Kx, FIG. 6 is a flowchart showing the fuel injection control process, and FIG. 7 is a flowchart showing the calculation process of the alcohol concentration correction constant Kx. FIG. 8 is an explanatory diagram of the calculation map, and FIG. 8 is an explanatory diagram of the determination map stored in the storage area of the control unit. 1... Engine, 2... Injection valve, 8... Fuel tank,
9... Alcohol mixed gasoline 1.11... Fuel pipe, 15... Alcohol sensor (alcohol concentration detection means), 28... Temperature sensor, 16... Casing (outer electrode), 17... Pipe member (inflow pipe part), 1
8... Pipe member (outflow pipe part), 21... Center electrode (inner electrode). Patent applicant: Japan Electronics Co., Ltd. Agent: Kazuhiko Hirose, patent attorney

Claims (2)

[Claims] (1) A fuel tank that stores alcohol mixed fuel, a fuel pump that discharges the fuel in the fuel tank, an injection valve that injects fuel supplied from the fuel pump to the engine via a fuel pipe, and the fuel tank , alcohol concentration detection means that is provided at a desired position in the fuel supply system including the fuel pump and fuel piping and detects the alcohol concentration in the fuel, and a correction constant that is determined according to the concentration detected by the alcohol concentration detection means. In the alcohol mixed fuel injection control device, the alcohol mixed fuel injection control device includes an injection amount calculation means for calculating the amount of fuel injected from the injection valve, and a temperature sensor for detecting the temperature of the alcohol mixed fuel; When the temperature reaches a predetermined temperature or higher corresponding to the alcohol concentration, when the injection amount calculation means calculates the fuel injection amount to the engine, the correction constant based on the concentration detected by the alcohol concentration detection means is not used; An alcohol mixed fuel injection control device comprising constant fixing means for fixing the constant to a predetermined value. (2) The alcohol concentration detection means is a capacitive alcohol sensor consisting of an L-shaped tubular outer electrode communicating with the fuel pipe and an inner electrode disposed approximately coaxially with the outer electrode, and the L-shaped 2. The alcohol mixed fuel injection control device according to claim 1, wherein the tubular outer electrode has a widening angle θ between the inflow pipe portion and the outflow pipe portion set to 90°<θ<180°.