JPH03160106A - Alcohol engine - Google Patents

Abstract

PURPOSE:To improve wear resistance and corrosion resistance of every part of an engine by separating formic acid from engine oil through heating the engine oil, which is mixed with formic acid produced by combustion of alcohol, beyond the boiling point of formic acid, and by discharging the separated formic acid gas outside an oil pan. CONSTITUTION:In an alcohol engine E, a formic acid removing device 7 is provided for removing the formic acid accumulated in engine oil 5 through entering into a crankcase as blow-by gas during combustion of alcohol in a combustion chamber. This formic acid removing device 7 is composed of a heating device 8 for separating the formic acid from the engine oil 5 through heating the engine oil 5 upto a temperature higher than the boiling point of formic acid (100.8 deg.C), and a discharging device 9 for discharging the formic acid gas, which has been separated from the engine oil by using the heating device 8, outside an oil pan 4. In the heating device 8, the engine oil 5 is heated by blowing exhaust gas from an exhaust pipe 11 into a heater element 15, which is submerged into the engine oil 5, through a guide pipe 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an alcohol engine using alcohol fuel containing at least a portion of alcohol.

(Prior Art) Recently, alcohol fuels such as methanol and ethanol have attracted attention as automobile fuels to replace gasoline in view of the depletion of petroleum resources and air pollution.
Japanese Patent No. 22149 describes an alcohol engine using an alcohol mixed fuel that is a mixture of alcohol and gasoline at a predetermined ratio.

By the way, in the alcohol engine mentioned above, formic acid is produced as an intermediate product during alcohol combustion, and this formic acid enters the crankcase together with blow-by gas, accumulates in the engine oil in the oil pan, and deteriorates the engine oil. There is a problem in that the wear resistance and anti-rust/corrosion properties of various parts deteriorate. 7 to 9 show the results of performance tests on gasoline engines and alcohol engines conducted using ordinary engine oil for gasoline engines. However, the test conditions were that the engine speed was 150 rpm, the oil and water temperatures were 50°C, the intake pipe negative pressure was 160 mmHg, and the operating time was 100 hours continuously.

As shown in FIG. 7, in the methanol engine, the amount of increase in the total acid value in the engine oil is higher than that in the gasoline engine, and the amount of decrease in the total base number is also higher, resulting in a significant deterioration of the engine oil. As a result, as shown in FIG. 8, the amount of wear on the cam nose increases significantly, and as shown in FIG. 9, it can be seen that the degree of rust on the plates of the oil bomb and oil strainer increases.

Conventionally, in order to improve the wear resistance and anti-rust/corrosion properties of each part of the engine, technology has been developed to modify the composition of engine oil itself to make it suitable for alcohol engines and suppress its deterioration (see Japanese Patent Application No. 62-90472). ) have been proposed, and materials with high wear resistance, rust prevention, and corrosion resistance are also being researched, but no technology has yet been proposed to remove formic acid from engine oil and prevent engine oil deterioration.

[Problem to be solved by the invention]

As mentioned above, when using engine oil exclusively for alcohol engines, engine oil for gasoline engines cannot be used and the engine oil becomes expensive, and engine oil for gasoline engines is accidentally filled when changing the oil. If this happens, there is a problem that the durability of various parts of the engine, such as the crankshaft and camshaft bearings, cylinder bores and piston rings, valve train and oil pump, will be extremely reduced. On the other hand, although materials with high wear resistance, rust prevention, and corrosion resistance are being researched, a large amount of development work is required to satisfy the functions required for each part of the engine, and currently there are performance and cost limitations. Practical materials have not yet been developed. An object of the present invention is to provide an alcohol engine that can remove formic acid mixed into engine oil, suppress deterioration of the engine oil itself, and improve the wear resistance and antirust/corrosion properties of various parts of the engine. .

[Means to solve the problem]

The alcohol engine according to the present invention is an alcohol engine that uses alcohol fuel containing at least a portion of alcohol, and is attached to an oil pan and heats engine oil mixed with formic acid that has grown due to the combustion of alcohol to a temperature higher than the boiling point of formic acid. and a discharging means for guiding the formic acid vapor separated by the heating means to the outside of the oil pan. [Function] In the alcohol engine according to the present invention, formic acid produced by combustion of alcohol is mixed into the engine oil, but the heating means attached to the oil pan heats the engine oil to a temperature higher than the boiling point of formic acid. The engine oil is heated to separate formic acid from the engine oil, and the separated formic acid vapor is led out of the oil pan by the exhaust means.
It is possible to prevent formic acid from accumulating in engine oil, and it is possible to prevent engine oil from deteriorating due to formic acid.

〔Effect of the invention〕

According to the alcohol engine according to the present invention, as detailed in the [Operation] section above, by providing the heating means and the discharge means, formic acid is prevented from accumulating in the engine oil and deterioration of the engine oil is prevented. Therefore, even when engine oil for gasoline engines is used, sufficient wear resistance and rust/corrosion prevention properties can be ensured for each part of the engine.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

This embodiment is a case where the present invention is applied to an in-line four-cylinder alcohol engine.

As shown in FIG. 1, an exhaust manifold 2 is provided at the upstream portion of an exhaust passage 1 of an engine E, a catalytic converter 3 for purifying exhaust gas is interposed in the middle, and a muffler is provided at the downstream end. (not shown) is open to the atmosphere. Engine oil 5 for lubricating various parts of the engine E is stored in the oil pan 4 of the engine E, and a strainer 6 for filtering the engine oil 5 is installed in the front part of the oil pan 4 so that its lower end is inside the engine oil 5. It is provided in a state where it is immersed in the water.

The engine E is equipped with a formic acid removal device 7 having the following structure in order to remove formic acid that enters the crankcase from the combustion chamber as blow-by gas during alcohol combustion and accumulates in the engine oil 5. .

The formic acid removal device 7 heats the engine oil 5 to a temperature higher than the boiling point of formic acid (100.8°C) to remove the engine oil 5.
The oil pan 4 is provided with a horizontal heating device 8 for separating formic acid from the oil pan 4, and a discharge mechanism 9 for discharging the formic acid vapor G separated by the heating mechanism 8 to the outside of the oil pan 4.

To explain the heating mechanism 8, as shown in FIGS. 1 and 2, an inlet pipe 12 and an exhaust pipe l3 are provided in the middle of an exhaust pipe 11 that connects the intake manifold 2 and the catalytic converter 3. A first solenoid valve 14 is provided at intervals, and a first solenoid valve 14 is interposed in the middle of the discharge pipe 13.
The exhaust pipe 13 penetrates the wall of the oil van in an oil-tight manner and is introduced into the engine oil 5, and the end thereof is connected to a heater element 1 consisting of a hollow vibrator shaped like a coil.
The heater element 15 is immersed in the engine oil 5, and when the first solenoid valve l4 is opened, the exhaust gas flowing through the exhaust pipe 1l passes through the inlet pipe l2 to the heater element 15. After heating the heater element 15, the engine oil 5 is returned to the exhaust pipe 11 via the exhaust pipe 13, and the engine oil 5 is heated to a temperature higher than the boiling point of formic acid by exhaust gas heat through the heater element 15.
Formic acid is separated from the engine oil 5. Incidentally, the inlet pipe 12 and the discharge pipe 13 are covered with a heat insulating tube 16 inside the engine oil 5.

To explain the above-mentioned discharge mechanism 9, as shown in FIGS. The lower end thereof is opened into the engine oil 5, and a formic acid discharge pipe l8 is fixed to the upper end surface of the housing case l7.
penetrates the wall of the oil pan 4 in an oil-tight manner and is connected to the exhaust pipe 11 just in front of the catalytic converter 3. A second solenoid valve 19 is interposed in the middle of the formic acid discharge pipe l8, and the heater element 15 The heated and vaporized formic acid vapor G is stored in the upper part of the storage case 17 and is discharged into the exhaust pipe 11 through the formic acid discharge pipe 18 when the second solenoid valve 19 is opened. The heater element 15 and the storage case 17 are preferably arranged as far away from the strainer 6 as possible in order to prevent the vaporized formic acid vapor G from being sucked into the strainer 6.

A pH sensor 20 for detecting the Behar value of the engine oil 5 is provided on the lower wall of the oil pan 4, and an oil temperature sensor 2 for detecting the temperature of the engine oil 5.
A catalyst temperature sensor 22 is provided on the side wall of the catalytic converter 3 to detect the temperature of the catalyst material therein.

The control unit 25 for controlling the engine E includes a pe-har sensor 20 for controlling the formic acid removal device 7.
Detection signals from the oil temperature sensor 21 and catalyst temperature sensor 22 are input, and control signals are output from the control unit 25 to the solenoid valves 14 and 19, respectively.

The control unit 25 has a general structure mainly based on Microconbee Utah, and includes an A/D converter that converts detection signals from switches and sensors into A/D, an injector, and solenoid valves 14 and 19. A drive circuit for driving is also provided. In the ROM of the control unit 25, control programs, maps, etc. necessary for controlling the engine E are input and stored in advance, and a control program for formic acid removal control, which will be described later, is input and stored in advance.

By the way, when alcohol is combusted, formic acid is produced as an intermediate product, and this formic acid enters the crankcase from the combustion chamber along with blow-by gas and accumulates in the engine oil 5 in the oil pan 4, and this formic acid causes damage to the engine. Oil 5 deteriorates rapidly.

Therefore, in this formic acid removal control, when the pH value of the engine oil 5 becomes below a predetermined value, the engine oil 5 is heated to the boiling point of formic acid (100.8°C) or higher, and the formic acid is evaporated and separated from the engine oil 5. By discharging the engine oil to the outside of the oil pan 4, deterioration of the engine oil 5 is prevented.

Next, the formic acid removal control routine performed by the control unit 25 will be explained based on the flowchart shown in FIG. In addition, St (i=1, 2, 3,...
) indicates each step. When this control is started with the start of the engine E, necessary initial settings are performed, and then detection signals from the Beher sensor 20 and the catalyst temperature sensor 22 are read (S1).

Next, it is determined whether the pH value has become less than a predetermined value α, that is, whether the engine oil 5 has become acidic due to formic acid (S2), and if NO, the pH value has become less than a predetermined value α. S1 and S2 are repeated until the time is reached. That is, the cumulative amount of blow-by gas increases in proportion to the driving time of the automobile, and the accumulated amount of formic acid in the engine oil 5 gradually increases, making the engine oil 5 acidic. The pH value of the engine oil 5, which gradually decreases in inverse proportion to time, is detected, and S1 and S2 are repeated until the pH value becomes equal to or less than a predetermined value α.

When the pH value falls below the predetermined value α, the timer TM starts counting a predetermined time t (S3), and the first and second solenoid valves 14 and 19 are activated (S4). That is, by opening the first solenoid valve 14, high-temperature exhaust gas is introduced into the heater element 15 through the introduction pipe 12, and the engine oil 5 in the storage case 17 is heated to a temperature higher than the boiling point of formic acid via the heater element 15. The formic acid mixed in the engine oil 5 evaporates and the storage case 1
When the second solenoid valve 19 is opened, the formic acid vapor G accumulated in the upper part of the storage case 17 is discharged into the exhaust pipe 11 immediately before the catalytic converter 3 through the formic acid discharge pipe 18. Thereafter, the formic acid vapor G discharged into the exhaust pipe 11 is once decomposed into hydrogen and carbon dioxide by the heat of the exhaust gas, the carbon dioxide is discharged as it is to the outside of the exhaust passage 1 via the catalyst material, and the hydrogen is decomposed by the catalyst material. After activation, it is discharged to the outside of the exhaust passage II as water vapor.

Next, the oil temperature signal from the oil temperature sensor 21 is read (S5
), the oil temperature T0 is a temperature at which the engine oil 5 thermally deteriorates or a sufficient film thickness cannot be ensured on sliding parts (for example, 13
It is determined whether the temperature is higher than 0°C (S6
), in the case of No, it is determined whether or not the timer TM becomes TM=O (S7), and the heating mechanism 8 is turned on until the oil temperature T0 becomes 130°C or higher or the timer TM becomes TM=O. The engine oil 5 is heated and formic acid is separated, and the separated formic acid vapor G is sent to the exhaust pipe 11 by the exhaust mechanism 9.
As shown in FIG.
quickly returns to near neutrality. The engine oil 5 in the oil van 4 is stirred by an oil pump, a balancing weight, etc. for supplying the engine oil 5 to each part of the engine E, and also flows into the storage case 17, so that the formic acid in the entire engine oil 5 is It will be removed.

When the oil temperature T0 becomes 130"C or more or the timer TM becomes TM=O, both solenoid valves 14 and 19 are closed (S8) and the process returns to S1, and the Beher value of the engine oil 5 becomes less than the predetermined value α. S3 to S8 are executed each time.

As described above, by providing the formic acid removal device 7 with a simple structure consisting of the heating mechanism 8 and the discharge mechanism 9, the engine oil 5 is heated to a temperature higher than the boiling point of formic acid.
The formic acid can be separated from the oil pan 4 and discharged to the outside of the oil pan 4.
It is possible to suppress the deterioration of the engine oil 5 due to formic acid and improve the wear resistance, rust prevention, and corrosion resistance of each part of the engine E. Moreover, the heating temperature by the heater element 15 is 100°C.
As described above, water in the engine oil 5 can also be removed, and deterioration of the engine oil 5 due to water can also be prevented.

In place of the second solenoid valve 19, as shown in FIG. 5, a formic acid tank 26 is provided in the middle of the formic acid discharge pipe 18 to store formic acid vapor G as a gas or dissolved in water. A solenoid 27 is installed on the side of the formic acid tank 26.
A pump driven by
≦150°C), the formic acid stored in the formic acid tank 26 is pumped into the exhaust pipe immediately before the catalytic converter 3 by the pump 28.
You can also make it squirt inward. In this case, the ejected formic acid is heated to 160''C or more by the heat of the exhaust gas and decomposed into carbon dioxide and hydrogen, and the decomposed hydrogen can be used to activate the catalyst material at a low temperature.

In the formic acid removal control described above, formic acid is removed from the engine oil 5 when the pH value of the engine oil 5 becomes less than a predetermined value α, but as shown in FIG. Alternatively, formic acid may be removed every time the cumulative operating time exceeds a predetermined time.

The heating time by the heater element 15 is a predetermined time t.
Although it is set to 1, the heating may be interrupted when the pH value of the engine oil 5 reaches a predetermined approximately neutral value or higher. Instead of the heater element 15, an electric heater or the like may be used to heat the engine oil 5.

In this embodiment, the engine oil is heated intermittently, but the formic acid may be removed by constant heating. Further, although the formic acid separated from the engine oil 5 is discharged to the exhaust passage 1, it may be discharged to the intake passage and re-burned.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an engine and a formic acid removal device, FIG. 2 is a vertical cross-sectional view of main parts of the formic acid removal device, and FIG. 3 is a flowchart of formic acid removal control. Figure 4 is a diagram showing the relationship between operating time and engine oil Beher value, Figure 5 is a side view of the formic acid removal device in the vicinity of the formic acid tank according to the modified example, and Figure 6 is a diagram showing the relationship between mileage and formic acid concentration. Diagrams showing the relationships, Figures 7 to 9, show the results of performance tests between gasoline engines and conventional alcohol engines. Figure 7 shows the increase in total acid value and total base number of engine oil. FIG. 8 is a graph showing the amount of wear on the cam nose, and FIG. 9 is a graph showing the ratings of the oil pump plate and oil strainer. E - Engine, G - Formic acid vapor, 7 - Formic acid removal device, 8 - Heating mechanism, 9 - Discharge standby.

Claims (1)

[Claims] (1) In an alcohol engine using alcohol fuel containing at least a portion of alcohol, a heating means attached to the oil pan that heats engine oil mixed with formic acid produced by combustion of alcohol to a temperature higher than the boiling point of formic acid to separate the engine oil. and a discharge means for guiding the formic acid vapor separated by the heating means to the outside of the oil pan.