JP3251080B2 - Air-fuel ratio control device for hydrogen engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for a hydrogen engine using a gaseous fuel in which hydrogen gas is used as part or all of the fuel.

[0002]

2. Description of the Related Art In recent years, hydrogen engines using hydrogen gas as part or all of fuel have been developed. By the way, when the hydrogen gas is burned in the cylinder, it reacts with oxygen to form steam, so that a large amount of steam is filled in the cylinder.

Therefore, when the hydrogen engine is cold, the water vapor in the cylinder is saturated and turns into water droplets, which adhere to the inner wall of the cylinder and the spark plug, and the water droplets flow from the cylinder into the oil pan. For this reason, water droplets are mixed into oil (lubricating oil), causing deterioration of the oil and obstructing the flow of the oil, thereby causing the oil to run out. This results in rusting of the engine or wear of the cylinder.

[0004] As a countermeasure, in a hydrogen engine,
Japanese Patent Application Laid-Open No. 2-267309 discloses a technique in which water in oil is separated and the water is removed from the oil to ensure lubricating oil performance.

[0005]

However, in the hydrogen engine disclosed in Japanese Patent Application Laid-Open No. 2-267309, a structure for separating water in oil is added, which causes an increase in the size of the engine. , Which increases costs.
Further, it is impossible to prevent the water droplets from adhering to the inner wall of the cylinder or the like and from being mixed into the oil beforehand.

Further, when the engine is started in a cold state, there is a problem that the above-mentioned water droplets adhere to the spark plug and cause a misfire, thereby causing poor starting. However, in the hydrogen engine disclosed in Japanese Patent Application Laid-Open No. 2-267309, misfire due to the attachment of water droplets to the spark plug cannot be prevented.

The present invention has been made in view of the above circumstances, and has as its object to provide an air-fuel ratio control device for a hydrogen engine that does not generate water droplets even when it is cold.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a supply amount adjusting means for adjusting the supply amount of gaseous fuel using hydrogen gas as a part or all of fuel to an engine, Air-fuel ratio setting means for setting an air-fuel ratio in accordance with an operating state; and an air-fuel ratio control device for a hydrogen engine which controls the supply amount adjusting means to achieve the set air-fuel ratio. Temperature detection means for detecting the temperature of the, the determination means for determining whether the detected temperature is a cold state or less than a preset temperature,
Correction means for correcting the air-fuel ratio set by the air-fuel ratio setting means to a higher air-fuel ratio in the cold state.

Further, the invention according to claim 2 is a supply amount adjusting means for adjusting the supply amount of gaseous fuel using hydrogen gas as a part or all of the fuel to the engine, and an air supply for setting the air-fuel ratio when the engine is started. A fuel ratio setting device, wherein in the air-fuel ratio control device of the hydrogen engine that controls the supply amount adjusting device so as to achieve the set air-fuel ratio, a temperature detecting device that detects a temperature of combustion gas at the time of engine start; Determining means for determining whether the detected temperature is lower than a predetermined temperature in a cold state; and correcting the air-fuel ratio set by the air-fuel ratio setting means to a higher air-fuel ratio in the case of the cold state. Correction means.

Further, misfire detection means for detecting misfire of the engine, and re-correction means for correcting the air-fuel ratio corrected by the correction means to a higher air-fuel ratio when the misfire is detected in a cold state. It is preferable to provide

[0011]

According to the above arrangement, the air-fuel ratio is set in accordance with the operating state of the engine, and the amount of gaseous fuel supplied to the engine is adjusted to the set air-fuel ratio. Further, it is determined whether or not the engine is in a cold state in which the temperature of the combustion gas in the cylinder becomes equal to or lower than a preset temperature. In the case of the cold state, the air-fuel ratio set above is higher than the air-fuel ratio. By correcting the fuel ratio, in a cold state, the concentration of hydrogen gas supplied to the engine is reduced, and the amount of water vapor generated by combustion in the cylinder is reduced, thereby suppressing the generation of water droplets.

Further, the air-fuel ratio at the time of starting the engine is set, and the amount of gaseous fuel supplied to the engine is adjusted so as to achieve the set air-fuel ratio. Further, it is determined whether or not the temperature of the combustion gas in the cylinder at the time of starting the engine is a cold state in which the temperature is equal to or lower than a preset temperature. By correcting the air-fuel ratio to be higher than the fuel ratio, when the engine is started in a cold state, the concentration of hydrogen gas supplied to the engine decreases, and the water vapor generated by combustion in the cylinder decreases, and the water droplets drop. Is generated and is prevented from adhering to the spark plug.

Further, when the misfire of the engine is detected in the cold state, the corrected air-fuel ratio is corrected to a higher air-fuel ratio, so that the generated water droplets adhere to the spark plug more reliably. Is prevented.

[0014]

An embodiment of the present invention will be described with reference to the drawings.
1 and 2 show the entire structure of a hydrogen engine provided with an air-fuel ratio control device according to one embodiment of the present invention. The hydrogen engine of this embodiment is a rotary piston engine.
In this embodiment, only hydrogen gas is used as the gaseous fuel.

This rotary piston engine has a cylinder constituted by a rotor housing 1 and side housings located on both sides thereof, and a substantially triangular rotor 3 separating three working chambers 2 therein. When the rotor 3 is eccentrically rotated while being supported by the eccentric shaft 4, the volume of each working chamber 2 changes, and an Otto cycle is performed. In a two-rotor rotary piston engine, cylinders are formed before and after a side housing (intermediate housing) at an intermediate position, and a rotor 3 is disposed inside each cylinder. In FIG. 1, two cylinders are shown in an exploded manner for convenience of drawing.

In the side housing, an intake port 6 for supplying air is provided at a position facing the working chamber 2 in the intake stroke. Air is led to the intake port 6 through an intake passage 7. The intake passage 7 is provided with a throttle valve 8 operated by a step motor 9, and detects an air cleaner (not shown) and an intake air amount. An air flow meter 10 and the like are provided. An ignition plug 13 is attached to the rotor housing 1 at a position facing the working chamber in the explosion stroke.

An exhaust port 11 is formed in the rotor housing 1 at a position facing the working chamber 2 in the exhaust stroke, and the exhaust port 11 is connected to an exhaust passage 12.

In order to supply the pressurized hydrogen gas into the cylinder, a hydrogen port (port for supplying gaseous fuel) 15 opened in the working chamber 2 separately from the intake port 6.
The hydrogen port 15 is provided at a position that opens into the working chamber 2 from the middle of the intake stroke to the middle of the compression stroke. A fuel supply passage 17 for introducing hydrogen gas from a metal hydride tank (hereinafter referred to as an MH tank) 16 is provided for the hydrogen port 15. The MH tank 16 is provided with a hydrogen storage alloy capable of storing and releasing hydrogen therein. The MH tank 16 is provided with a hydrogen filling passage, a cooling water passage, and a heating water passage (not shown). The hydrogen storage alloy of the MH tank 16 is heated by the cooling water supplied from the engine water jacket, so that hydrogen is released to the fuel supply passage 17.

A pressure regulator 18 is provided upstream of the fuel supply passage 17. The pressure regulator 18 regulates the hydrogen gas supplied from the MH tank 16 to an appropriate pressure.
For example, the pressure is adjusted to approximately 5 atm (3 to 7 atm). The downstream end of the fuel supply passage 17 is connected to the hydrogen port 15 via a timing valve 20.
The timing valve 20 supplies fuel at a predetermined timing in synchronization with the operation of the engine, and includes, for example, a poppet valve 21 that opens and closes a communication portion between the hydrogen port 15 and the fuel supply passage 17. The poppet valve 21 is opened and closed by a cam provided on a timing valve driving camshaft 22. The camshaft 22 is rotatably supported by the housing, and a pulley 23 provided at one end thereof is connected to the eccentric shaft 4 via a timing belt 24 so that the camshaft 22 rotates synchronously with the eccentric shaft 4. It has become.

The timing of opening / closing the intake port with the rotation of the rotor 3 is set so that the intake port 6 is opened near the top dead center and closed near the bottom dead center, while the timing valve 20 is operated by the intake valve 6. The opening / closing timing is set so that the port 6 is opened during a predetermined period in the first half of the compression stroke after the port 6 is closed. The reason why the timing valve 20 is opened and the supply of the hydrogen gas is started from the time when the intake port 6 is closed and the intake of the air is completed is that the hydrogen having a large volume ratio during the air intake process is used. This is because when the gas is inhaled, the inflow of air is likely to be hindered, and there is a concern that backfire may occur due to outflow of hydrogen gas to the intake passage side.

In the middle of the fuel supply passage 17, a flow control valve 25 is provided. The flow control valve 25 is operated by an electric actuator, for example, a step motor 26, which operates according to a control signal from a control unit (ECU) 27. This E
The CU 27 includes a flow control unit 271 and a correction unit 272, and the air flow meter 10, an accelerator opening sensor 2 that detects an accelerator opening (an operation amount of an accelerator pedal).
8, a speed sensor 29 for detecting the engine speed, a pressure sensor 30 for detecting the pressure in the fuel supply passage 17 downstream of the pressure regulator 18, and an O for detecting the oxygen concentration in the exhaust gas.
_The throttle valve 8 is opened by receiving detection signals from a _second sensor 31, a water temperature sensor 32 for detecting the temperature of the cooling water in the engine water jacket, an exhaust temperature sensor 33 for detecting the temperature of the exhaust gas in the exhaust passage 12, and the like. Degree, flow control valve 25
And the like to control the degree of opening.

The flow rate control means 271 determines the excess air ratio λ according to the operating state of the engine, such as the intake air amount, accelerator opening and engine speed, from a map stored in advance.
Is calculated, and the opening of the flow control valve 25 (or a step motor driving amount corresponding to the opening) is calculated from the value of the excess air ratio λ, and the flow control valve 25 is adjusted to correspond to the opening.
Is output to the step motor 26 in order to control.

For example, the value of the excess air ratio λ is set by a map as shown in FIG. That is, the region A where the engine load is high (for example, the accelerator opening is 90% or more).
In, the value of the excess air ratio λ is set to approximately “1.0”, and is set so that a high engine torque is obtained. Also, in the region B where the engine load is low (for example, when the accelerator opening is 90
%), The value of excess air ratio λ is
For example, a value that is approximately equal to or greater than “1.3” and that corresponds to the intake air amount, the engine speed, and the like is extracted from the map. Since the flammable range of the air-fuel ratio of the air-fuel mixture of the hydrogen gas is extremely wide, a relatively high value can be set as the value of the excess air ratio λ. The flow control means 27
1 indicates that when the engine is started (starting region C), the value of the excess air ratio λ is set to approximately “1.0” in order to start the engine in a short time.

The correcting means 272 determines the temperature of the combustion gas in the cylinder from the temperature of the cooling water, the temperature of the exhaust gas, etc., and determines whether the temperature of the determined combustion gas is lower than a predetermined temperature. In the case of the state, in order to make the air-fuel mixture lean, the value of the excess air ratio λ is changed to a value of, for example, “1.5” or more based on, for example, a pre-stored map for a cold state (correction). I do. That is, in the cold state, as shown in the map of FIG. 5, the mixture is set to be lean not only in the low load region but also in the high load region, and the mixture is set to be lean at the time of starting. In this case, the value of the excess air ratio λ becomes high only in the operation region where the value of the excess air ratio λ is relatively low (the mixture is rich) at least in the warm state, for example, only in the high load region and the starting region ( The direction may be changed so that the mixture becomes lean. Further, the value of the excess air ratio λ may be increased even in a low load region.

The correcting means 272 detects a fluctuation (wander) of the engine speed in a cold state, and when the fluctuation of the engine speed exceeds an allowable range, the ignition plug 1
It is determined that a misfire has occurred due to the attachment of water droplets to the sample No. 3, and the corrected value of the excess air ratio λ is corrected to a higher value. As a result, the concentration of water vapor in the combustion gas is further reduced, and the attachment of water droplets to the ignition plug 13 is more reliably prevented.

Next, the control operation of the flow control valve 25 performed by the ECU 27 will be described with reference to the flowchart of FIG.

First, an intake air amount, an accelerator opening, an engine speed, and the like are read as input information (step S).
1) Then, it is determined whether or not the current engine operation state is the engine start state based on whether or not the starter switch is on or whether or not the engine speed is equal to or lower than a predetermined speed (step S2).

If the engine is in the starting state (YES in step S2), it is determined whether the temperature of the combustion gas in the cylinder is higher than a preset temperature based on the temperature of the cooling water, the temperature of the exhaust gas, and the like. Is determined (step S
3) In the case of a warm state (YES in step S3),
As the value of the excess air ratio λ from the map of FIG. 4, for example, a rich value of approximately “1.0” is set (step S).
4). On the other hand, when the temperature of the combustion gas is in a cold state that is equal to or lower than the set temperature (NO in step S3), FIG.
, The value of the excess air ratio λ is set to a lean value of, for example, “1.5” or more (step S5).

Next, it is determined whether or not the ignition plug 13 has misfired based on whether or not the fluctuation of the engine speed is within an allowable range (step S6). If the engine speed fluctuates beyond the allowable range, it is determined that the ignition plug 13 has misfired (YES in step S11), and the value of the excess air ratio λ set in step S5 is made leaner. (Step S7).
On the other hand, if the engine speed is stable (NO in step S6), it is determined that the ignition plug 13 has not been misfired, and the value of the excess air ratio λ set in step S4, step S5 or step S7 is determined. Flow control valve 2
5 is calculated, and the flow control valve 25 is controlled so as to correspond to the opening (steps S8 and S9).

On the other hand, when the engine is in the normal operating state in step S2 (NO in step S2), it is determined whether the temperature of the combustion gas is in the above-mentioned warm state based on the temperature of the cooling water, the temperature of the exhaust gas, and the like. Is determined (step S10),
In the case of the warm state (YES in step S10), the value of the excess air ratio λ is extracted from the map of FIG. 4 (step S11). On the other hand, in the case of a cold state (step S11
NO), the value of the excess air ratio λ is corrected to a lean value of, for example, “1.5” or more according to the map of FIG. 5 (step S12).

Next, whether or not the ignition plug 13 has misfired is determined from the fluctuation of the engine speed as in step S6 described above (step S13). And
If it is determined in step S13 that the spark plug 13 has misfired (YES in step S13), the value of the excess air ratio λ corrected in step S12 is corrected to a value that makes the airflow leaner (step S14). ). Thereafter, the process proceeds to step S8, in which the flow control valve 25 is controlled based on the value of the excess air ratio λ. On the other hand, if it is determined in step S13 that the ignition plug 13 has not been misfired (NO in step S13), the process proceeds to step S8, and the flow regulating valve 25 is controlled based on the value of the excess air ratio λ. You.

As described above, when the engine is started in the warm state, the air-fuel mixture becomes rich as the value of the excess air ratio λ, for example, approximately “1” in order to start the engine in a short time. .0 "is set, but in the cold state, the mixture becomes lean as the value of the excess air ratio λ.
For example, it is corrected to a value of “1.5” or more. This is because when the excess air ratio λ is low (rich state),
Since the concentration of hydrogen gas in the air-fuel mixture is high, the concentration of water vapor in the combustion gas in the cylinder increases, and in a cold state, the water vapor in the cylinder saturates to form water droplets, and This is because they adhere. Then, due to the adhesion of the water droplets, the ignition plug 13 is misfired, and a starting failure occurs. For this reason, by increasing the excess air ratio λ in the cold state, the concentration of hydrogen gas in the air-fuel mixture is reduced to suppress water vapor generated in the cylinder, prevent the generation of water droplets, and prevent the occurrence of poor starting. Preventing.

During normal operation of the engine in the warm state, for example, when the engine becomes heavily loaded, the value of the excess air ratio λ is set to, for example, about “1.0”. Even in the case of load, the air-fuel mixture is corrected to a lean value, for example, a value of 1.5 or more, as the value of the excess air ratio λ. In this case as well, in the cold state, the air-fuel mixture becomes lean and the steam generated by the combustion of the hydrogen gas in the cylinder is suppressed. In the cold state, the steam in the combustion gas is saturated and becomes water droplets to form water droplets. Is prevented. Therefore, it is possible to prevent water droplets generated in the cylinder from flowing into the oil pan and being mixed into the oil.

In the cold state, it is determined whether the ignition plug 13 has misfired. If the misfire has occurred, the value of the excess air ratio λ is corrected so that the air-fuel mixture becomes leaner. Misfire of the ignition plug 13 is more reliably prevented.

In the above embodiment, only hydrogen gas is used as the gaseous fuel. However, the present invention is not limited to this, and ethane, propane, city gas and the like are mixed with hydrogen gas. Is also good.

The present invention can be applied not only to a rotary piston engine but also to a reciprocating engine.

[0037]

According to the first aspect of the present invention, in the air-fuel ratio control apparatus for a hydrogen engine, when the engine is in a cold state, the air-fuel ratio set by the air-fuel ratio setting means is set higher than the air-fuel ratio. Therefore, the concentration of the hydrogen gas supplied to the engine in a cold state becomes low, and the steam generated by combustion in the cylinder can be reduced. Therefore, water droplets are generated in the cylinder in the cold state, and it is possible to prevent the water droplets from being mixed into the oil, thereby preventing deterioration of the oil, running out of oil, and the like.

In the air-fuel ratio control apparatus for a hydrogen engine according to the present invention, when the engine is in a cold state when the engine is started, the air-fuel ratio set by the air-fuel ratio setting means is set to be smaller than the air-fuel ratio. Since the air-fuel ratio is corrected to a high value, it is possible to prevent the generation of water droplets in the cylinder by starting the engine in a cold state, and to prevent the water droplets generated in the cylinder from adhering to the spark plug and causing a misfire. It is possible to prevent poor starting in the cold state.

Further, when the misfire of the engine is detected in the cold state, the corrected air-fuel ratio is corrected to a higher air-fuel ratio, so that the generated water droplets are more reliably prevented from adhering to the spark plug. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic view of the overall structure of a hydrogen engine according to one embodiment of the present invention.

FIG. 2 is a schematic diagram showing a control system for a flow control valve and the like.

FIG. 3 is a flowchart showing a control operation of a flow control valve performed by a control unit.

FIG. 4 is a map showing a value of an excess air ratio with respect to an operation state in a warm state.

FIG. 5 is a map showing a value of an excess air ratio with respect to an operation state in a cold state.

[Explanation of symbols]

Reference Signs List 8 throttle valve 10 air flow meter 25 flow control valve 26 step motor 27 control unit (ECU) 28 accelerator opening sensor 29 rotation speed sensor 31 O ₂ sensor 32 water temperature sensor 33 exhaust temperature sensor 271 flow control means 272 correction means

Continuation of front page (56) References JP-A-63-246460 (JP, A) JP-A-3-37367 (JP, A) JP-A-2-267309 (JP, A) JP-A-62-103438 (JP) JP-A-50-24624 (JP, A) JP-A-63-24345 (JP, U) JP-A-2-101052 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB) Name) F02D 19/02-45/00 F02M 21/02

Claims (3)

(57) [Claims] 1. A supply amount adjusting means for adjusting an amount of supply of gaseous fuel using hydrogen gas as a part or all of fuel to an engine, and an air-fuel ratio setting means for setting an air-fuel ratio according to an operation state of the engine. In the air-fuel ratio control device of the hydrogen engine that controls the supply amount adjusting means so as to achieve the set air-fuel ratio, a temperature detecting means for detecting the temperature of the combustion gas in the cylinder; Determining means for determining whether or not a cold state in which the temperature is equal to or lower than a set temperature;
An air-fuel ratio controller that corrects the air-fuel ratio set by the air-fuel ratio setting unit to a higher air-fuel ratio in the cold state. 2. A fuel supply system comprising: a supply amount adjusting unit that adjusts a supply amount of gaseous fuel that uses hydrogen gas as a part or all of fuel to an engine; and an air-fuel ratio setting unit that sets an air-fuel ratio at the time of starting the engine. In the air-fuel ratio control device for a hydrogen engine that controls the supply amount adjusting means so as to achieve the set air-fuel ratio, a temperature detecting means for detecting a temperature of the combustion gas at the time of starting the engine, and the detected temperature is set in advance. Determining means for determining whether or not the engine is in a cold state in which the temperature is equal to or lower than the temperature, and correcting means for correcting the air-fuel ratio set by the air-fuel ratio setting means to a higher air-fuel ratio in the case of the cold state. An air-fuel ratio control device for a hydrogen engine. 3. The air-fuel ratio control device for a hydrogen engine according to claim 1, wherein said misfire detection means detects misfire of said engine, and said correction means corrects said misfire when said engine is in a cold state. An air-fuel ratio control device for a hydrogen engine, comprising: a re-correction unit that corrects the set air-fuel ratio to a higher air-fuel ratio.