JP2002188533A - Gas fuel supplier for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas fuel supplier for an internal combustion engine which can stably perform air/fuel ratio control by attaining promotion of vaporization of fuel without generating a problem of decreasing of an engine output and deteriorating of knocking resisting performance. SOLUTION: In this gas fuel supplier for an internal combustion engine, liquid fuel in a fuel tank 2 is vaporized to gas fuel so as to supply it to a fuel injection valve 4, a vaporizer 11 vaporizing the liquid fuel is provided in a fuel supply passage 6, a heating part 12 for heating the liquid fuel by introducing an engine cooling liquid A into this vaporizer 11 is provided, and a thermostat (cooling liquid temperature control means) 23 controlling a temperature of the engine cooling liquid A to 30 to 40 deg.C is provided in an outlet of this heating part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, propane,
Alternatively, the present invention relates to a gas fuel supply device configured to supply a mixed fuel (LPG) with butane to an internal combustion engine.

[0002]

2. Description of the Related Art It is well known that, for example, in a gasoline engine for an automobile, electronically controlled fuel supply is often functionally superior to fuel supply by a carburetor. That is, the controllability, reliability, learning function, the degree of freedom of the intake system layout, and the like are high, which is advantageous in exhaust gas measures, fuel consumption performance, output performance and the like.

On the other hand, LPG fuel is easily vaporized at normal temperature and normal pressure, and by supplying this gaseous fuel to the engine,
Very good low-pollution characteristics are obtained from the cold start of the engine to the transient state of acceleration / deceleration. In addition, LPG fuel has a higher octane number and a lower carbon ratio than gasoline, so that it can be operated at a high compression ratio.
₂ has the advantage of being able to control emissions.

By using the LPG fuel having such advantages in an electronically controlled fuel supply system having a fuel injection valve, it is possible to reduce the pollution of exhaust gas and reduce the amount of CO ₂ emission. When supplying this type of LPG fuel to the engine, the LPG fuel is vaporized from the fuel tank by the vaporizer, and supplied from the vaporizer to the fuel injection valve via the pressure regulator.

[0005]

By the way, the above LPG
When the fuel is vaporized and supplied to the fuel injection valve, the fuel is not sufficiently vaporized at the time of starting at a very low temperature, the controllability of the air-fuel ratio becomes unstable, and the starting failure is caused. There is.

Here, in order to promote the vaporization of fuel at extremely low temperatures, it is conceivable to introduce an engine coolant into a vaporizer to heat the liquid fuel. However, when the temperature of the engine coolant increases, the temperature of the vaporized gaseous fuel also increases. Therefore, in some cases, there is a concern that the fuel supply amount may decrease and the output of the engine may decrease, or the anti-knock performance may decrease.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and promotes fuel vaporization without stabilizing the air-fuel ratio without causing a problem of a decrease in engine output and a decrease in knocking resistance. It is an object of the present invention to provide a gas fuel supply device for an internal combustion engine that can perform the operation.

[0008]

According to a first aspect of the present invention, there is provided a gas fuel supply apparatus for an internal combustion engine in which liquid fuel in a fuel tank is vaporized into gaseous fuel and supplied to a fuel injection valve. A vaporizer for evaporating the liquid fuel is interposed, and a heating unit for introducing the coolant of the internal combustion engine and heating the liquid fuel is provided in the vaporizer,
The heating unit is provided with coolant temperature control means for controlling the engine coolant to a predetermined temperature.

A second aspect of the present invention is characterized in that, in the first aspect, the coolant temperature control means is configured to maintain an outlet temperature of the heating portion of the engine coolant at 30 to 40 ° C. I have.

A third aspect of the present invention is characterized in that, in the first or second aspect, the coolant temperature control means is a thermostat provided at an engine coolant outlet of the heating section.

[0011]

According to the gas fuel supply device of the first aspect of the present invention, since the liquid fuel is heated by introducing the engine cooling liquid into the vaporizer, the vaporization of the liquid fuel at extremely low temperatures is promoted. The air-fuel ratio control at the time of starting can be stably performed, and poor starting can be prevented.

Further, in the present invention, since the temperature of the engine coolant is controlled to be a predetermined temperature, an abnormal temperature rise of the gaseous fuel can be prevented, and a decrease in the engine output due to a decrease in the fuel supply amount can be prevented. A decrease in knocking resistance can be prevented.

According to the second aspect of the present invention, since the outlet temperature of the heating portion of the engine coolant is maintained at 30 to 40 ° C., when the gaseous fuel pressure of the commercially available LPG fuel is set to 0.4 Mpa, the temperature becomes 40 ° C. It can be easily vaporized below.

According to the third aspect of the present invention, since the temperature control of the engine coolant is performed by the thermostat, the temperature control can be performed accurately with a simple structure, and the cost increase can be suppressed.

[0015]

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

FIGS. 1 to 6 are views for explaining a gas fuel supply device for an internal combustion engine according to one embodiment (first embodiment) of the present invention, and FIG. 1 is an overall configuration diagram of the gas fuel supply device. , Fig. 2 is a sectional view of the thermostat, and Fig. 3 is EC
FIG. 4 is a characteristic diagram showing the relationship between the vapor pressure of LPG fuel and the temperature, FIG. 5 is a characteristic diagram showing the relationship between the gas fuel pressure and the maximum opening of the throttle valve, and FIG. It is a flowchart figure which shows a driving operation.

In FIG. 1, reference numeral 1 denotes a gas fuel supply device, which vaporizes liquid fuel filled in a fuel tank 2 into gaseous fuel and supplies it to each fuel injection valve 4 of an engine 3. . The engine 3 is a water-cooled four-cycle in-line four-cylinder engine, in which the fuel injection valves 4 are mounted for each cylinder, and a common delivery pipe 5 is connected to each fuel injection valve 4.

An upstream end 6a of a fuel supply pipe 6 is inserted into the fuel tank 2, and a downstream end 6b of the fuel supply pipe 6 is connected to a fuel supply port 5a of the delivery pipe 5. ing. A fuel filling port 2b for injecting liquid fuel is formed in the upper wall of the fuel tank 2.

A fuel pump 7 is arranged in the fuel tank 2. The discharge port 7a of the fuel pump 7 is connected to the upstream end 6a of the fuel supply pipe 6, and the suction port 7b opens into a concave portion 2a formed at the bottom of the fuel tank 2.

A manual valve 8 is connected to a downstream portion of the fuel supply pipe 6 outside the fuel tank 2, and a solenoid valve 9 is connected to a downstream side of the manual valve 8. On the downstream side, a fuel filter 1 for filtering liquid fuel
0 are integrally connected. The solenoid valve 9 is for shutting off fuel supply in an emergency, for example.

A vaporizer 11 for vaporizing liquid fuel is provided downstream of the fuel filter 10 in the fuel supply pipe 6. The vaporizer 11 is formed by integrally connecting a heating unit 12, a surge tank unit 13, and a pressure setting unit 14 in this order from the upstream side.
1 is supplied to the delivery pipe 5.

A relief pipe 18 having a relief valve 19 interposed is connected to the upstream end 6a of the fuel supply pipe 6, and the relief pressure of the relief valve 19 is controlled by the gas pressure at the outlet of the pressure setter 14. It is set equal to or slightly smaller than the fuel pressure set value. The relief fuel opening 19a of the relief valve 19 is formed at a position higher than the suction port 7b of the fuel pump 7 and is directed in a direction opposite to the suction port 7b.

A check valve 20 is interposed between the discharge port 7a of the fuel pump 7 and the relief pipe 18, and the check valve 20 allows discharge of liquid fuel from the fuel pump 7,
It has a function of preventing backflow to the fuel pump 7 side.

The heating unit 12 is a hermetically sealed unit formed separately from the surge tank unit 13.
A part 6 c of the fuel supply pipe 6 is inserted into the inside 2. The heating section 12 is formed with a coolant inlet 12a and an outlet 12b connected thereto. A coolant supply hose (not shown) for introducing the engine coolant A from the engine 3 is connected to the coolant inlet 12a, and a coolant recovery hose (not shown) is connected to the outlet 12b. Have been.

A thermostat 23 is provided at the outlet 12b of the heating section 12 as cooling liquid control means. As shown in FIG. 2, the thermostat 23 opens a coolant inlet 25 a of a coolant passage 25 formed in the housing 24 into the heating unit 12.
The cooling liquid outlet 25b is configured to be connected to the outlet 12b. A thermostat valve 26 for opening and closing the coolant passage 25 is provided in the housing 24.
The thermostat valve 26 is connected to a temperature-sensitive operating element 28 such as bimetal or thermowax. This temperature-sensitive operating element 28
Is configured to close the thermostat valve 26 when the temperature of the engine coolant A reaches 30 to 40 ° C., and to open the thermostat valve 26 when the temperature is below this temperature. In addition, 2
5c is a bypass passage.

The vaporization of the liquid fuel in the portion 6c of the fuel supply pipe 6 is promoted by the engine coolant A introduced into the heating section 12, and the gaseous fuel is supplied to the surge tank section 13. When the temperature of the engine coolant A exceeds 30 to 40 ° C., the thermostat valve 26 closes. In this way, the fuel injection pressure is controlled below the vapor pressure, and a stable fuel injection pressure can be obtained without operating the fuel pump 7.

The surge tank 13 has a fuel supply pipe 6c opening through the heating unit 12 therein. A dam plate 30 extending from the top wall to the bottom wall is arranged in the surge tank portion 13. The gaseous fuel that has flowed into the surge tank 13 from the fuel supply pipe 6c flows to the bottom 13b of the surge tank 13 along the weir plate 30 and the bottom 1b.
3b, and flows into the pressure setting device 14 from an outflow portion 13a formed at the upper end of the surge tank portion 13.

The volume of the surge tank 13 is set to 3 to 7.5% of the total stroke volume of the engine 3.
A liquid fuel level sensor 3 is provided in the surge tank 13.
The level sensor 31 detects the presence or absence of liquid fuel accumulated in the bottom 13b of the surge tank 13.

The pressure setting device 14 is connected to the surge tank 13
The pressure is adjusted so that the gaseous fuel flowing in from the pressure reaches the set pressure. Specifically, the set pressure is, for example, 0.2 to 0.2.
The gas fuel is set to a value within the range of 45 Mpa, and the gaseous fuel is supplied to each of the fuel injection valves 4 at the set pressure.

Here, the set pressure is set to a value equivalent to the fuel injection pressure. This set pressure is based on the fuel characteristics of the LPG. That is, as shown in FIG. 4, when the above set pressure is set on the low pressure side, for example, 2 kg / cm ² (0.2 Mpa), about -15% in the case of 100% propane.
In the case of 50 ° C., 50% propane and 50% butane, the evaporation temperature of the liquid fuel is reduced to about 0 ° C., so that the limit temperature at which operation can be performed without using any special device can be extended to a lower temperature side. However, a fuel injection valve capable of injecting a large amount of fuel is required to cope with the actual machine, and there is a problem in that the size of the fuel injection valve is increased and the degree of freedom of the layout is reduced due to the increase in size. In addition, a decrease in responsiveness due to an increase in the mass of the valve movable portion of the fuel injection valve causes a problem such as a decrease in the high-speed rotation limit of the engine.

On the other hand, the pressure value is set to the high pressure side, for example, 4.5.
kg / cm ² (0.45Mpa)
The evaporating temperature of the liquid fuel is increased to about 5 ° C. in the case of propane 100%, and to about 20 ° C. in the case of propane 50% / butane 50%, and the operating conditions requiring devices such as the present embodiment are expanded. . In this case, propane 1 with low lubricity
When the liquid fuel of 00% is used, the load on the fuel pump increases and the power consumption also increases. Further, the structural requirement for gas leakage from the fuel supply pipe or the like increases. In consideration of such points, the set pressure is 0.2 to 0.4.
It is desirable to select within the range of 5 Mpa. This value is sufficiently lower than the fuel injection pressure (5 bar (0.5 MPa) + vapor pressure) of an LPG system that directly injects liquid fuel that is in practical use.

The gas fuel supply device 1 has an ECU 35. The ECU35 is, lambda (0 ₂₎ sensor (not shown) disposed in the engine 3, the intake pressure sensor, intake air temperature sensor, a throttle opening sensor, coolant temperature sensor, a crankshaft angle sensor, a cam shaft angle sensor, etc. Of the fuel injection valve 4, the injection amount, the ignition timing of the ignition coil, and the like are controlled based on the detected values a.

The ECU 35, together with the detected value a, includes a fuel tank pressure sensor 36 provided in the fuel tank 2, a liquid fuel level sensor 31 provided in the surge tank section 13, and a pressure setting device. 14, each detection value b from the gaseous fuel pressure sensor 37 disposed on the outlet side of
c and d are inputted, and the fuel pump 7, the solenoid valve 9, the throttle valve 3a and the like are driven and controlled based on the detected values a to d.

The ECU 35 functions as throttle opening control means. The throttle opening control means regulates the maximum opening of the throttle valve 3a according to the detection value d from the gas fuel pressure sensor 37 as shown in FIG. For example, when the set pressure is 0.4 Mpa and the gas fuel pressure is 0.25 Mpa, the maximum opening of the throttle valve 3a is restricted to 40%. In this case, when the gas fuel pressure is 0.25 Mpa and the engine rotation speed is higher than the set rotation speed set based on the gas fuel pressure, the maximum opening of the throttle valve is regulated to a smaller opening. Is also possible.

When the gaseous fuel pressure is 0.4 Mpa or less, a rated output operation disable signal is output to the display lamp 39, and the display lamp 39 is turned on. This informs the driver that the rated output operation is not possible.

The ECU 35 functions as fuel pump control means. This fuel pump control means drives the fuel pump 7 when the detected value d from the gaseous fuel pressure sensor 37 is equal to or less than a set value, and when the detected value c from the liquid fuel level sensor 31 exceeds a predetermined value, The operation of the fuel pump 7 is stopped even if the pressure is equal to or lower than the set value.

That is, as shown in FIG. 6, after the engine is started, the gas fuel pressure at the outlet of the pressure setter 14 is 0.4 Mpa while the liquid fuel level sensor in the surge tank 13 is not sensing. If it is less than the temperature, it is determined that the temperature of the liquid fuel is low, and the fuel pump 7 is operated to actively supply the fuel to the vaporizer 11 (steps S1 to S1).
S3).

On the other hand, when the liquid fuel flowing into the surge tank 13 reaches a predetermined level or more while the fuel pump 7 is operating, the fuel pump 7 is stopped (step S).
4). Even if the liquid fuel in the surge tank 13 is below a predetermined level, the gaseous fuel pressure remains at the set value (0.4 Mp).
a) In the above case, the fuel pump 7 is stopped.

According to the gas fuel supply apparatus 1 of the present embodiment, the maximum opening of the throttle valve 3a is regulated in accordance with the gas fuel pressure in the pressure setting device 14, so that the amount of evaporation of the liquid fuel, When the pressure is low, the maximum opening of the throttle valve 3a is regulated to a small opening, so that the fuel injection pressure can be secured and the outflow of the liquid fuel can be prevented, and the fuel injection control can be performed stably. Can be.

In this embodiment, when the liquid fuel flowing into the surge tank 13 reaches a predetermined level, the operation of the fuel pump 7 is stopped, so that an excessive supply of fuel to the vaporizer 11 by the fuel pump 7 can be avoided. In addition, it is possible to secure the fuel injection pressure and prevent the outflow of the liquid fuel, so that the fuel injection control can be stably performed as described above.

Since the surge tank 13 is provided in the vaporizer 11, the gaseous fuel vaporized in the heating part 12 can be stored, and the gaseous fuel in the high load region can be stored without increasing the gaseous fuel set pressure so much. The required amount of fuel can be secured.

Further, since the capacity of the surge tank section 13 is set to 3 to 7.5% of the engine displacement, the operation control of the fuel pump 7 when liquid fuel flows in can be stably performed. Fuel ratio control can be easily performed.

In the present embodiment, the fuel pump 7 is operated when the gaseous fuel pressure in the pressure setting device 14 is 0.4 Mpa or less in a state where no liquid fuel flows into the surge tank portion 13. The fuel can be stably supplied even when the temperature in the fuel tank 2 is lower than the normal temperature, and from this point, stable fuel injection control can be performed.

In the present embodiment, since the relief pressure of the relief valve 19 is equal to or less than the gaseous fuel pressure in the pressure setting unit 14, the liquid fuel is pumped to the surge tank 13 when the fuel pump 7 is operated. Can be prevented.

Further, since the check valve 20 is disposed on the discharge port 7a side of the fuel pump 7, it is possible to prevent the gas generated in the fuel supply pipe 6 from flowing back into the fuel pump 7 when the engine is stopped. Further, the fuel opening 1 of the relief valve 19
Since the nozzle 9a is directed in a direction opposite to the suction port 7b of the fuel pump 7, the backflow gas discharged from the fuel opening 19a of the relief valve 19 can be prevented from being sucked into the fuel pump 7.

According to the present embodiment, since the heating section 12 for introducing the engine coolant A into the vaporizer 11 and heating the liquid fuel is provided, the vaporization of the liquid fuel at a low temperature can be promoted, and the starting can be performed. The air-fuel ratio control at the time can be stably performed, and poor starting can be prevented.

In this embodiment, since the temperature of the engine coolant A is controlled at 30 to 40 ° C., it is possible to prevent an abnormal temperature rise of the gaseous fuel and to prevent a decrease in the engine output due to a decrease in the fuel supply amount. A decrease in thermal efficiency due to a decrease in knocking resistance can be prevented.

Since the outlet temperature of the heating section 12 of the engine coolant A is maintained at 30 to 40 ° C., when the gaseous fuel pressure of the commercially available LPG fuel is set at 0.4 Mpa, the temperature is easily reduced to 40 ° C. or lower. Can be vaporized.

Further, since the temperature control of the engine coolant A is performed by the thermostat 23, the temperature control can be performed accurately with a simple structure, and the increase in cost can be suppressed.

FIG. 7 is a view for explaining a gas fuel supply system according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. Is omitted.

In the gas fuel supply device 40 of the present embodiment,
The pressure setting device 41 is provided independently of the vaporizer 11. A heating unit 12 and a surge tank unit 13 are provided integrally with the vaporizer 11, and the pressure setting unit 41 is disposed downstream of the vaporizer 11 and close to the fuel injection valve 4.

In the present embodiment, since the pressure setting device 41 is provided independently of the vaporizer 11, it is possible to increase the degree of freedom of the arrangement position of the pressure setting device 41. In this case, the fuel injection pressure can be stably maintained, and the re-liquefaction of the gaseous fuel due to the temperature drop can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a gas fuel supply device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a thermostat of the gas fuel supply device.

FIG. 3 is a control diagram of an ECU of the gas fuel supply device.

FIG. 4 is a characteristic diagram showing a relationship between vapor pressure and temperature of the LPG fuel of the embodiment.

FIG. 5 is a characteristic diagram showing a relationship between a gas fuel pressure and a maximum opening degree of a throttle valve in the embodiment.

FIG. 6 is a flowchart illustrating an operation of a fuel pump of the gas fuel supply device.

FIG. 7 is an overall configuration diagram of a gas fuel supply device according to a second embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1,40 Gas fuel supply device 2 Fuel tank 3 Water-cooled 4-cycle engine (internal combustion engine) 4 Fuel injection valve 6 Fuel supply pipe 11 Vaporizer 12 Heating unit 23 Thermostat (Coolant temperature control means) A Engine coolant

Claims (3)

[Claims] In a gas fuel supply apparatus for an internal combustion engine, wherein a liquid fuel in a fuel tank is vaporized into a gaseous fuel and supplied to a fuel injection valve, a vaporizer for vaporizing the liquid fuel is provided in a fuel supply passage. A heating unit for introducing the coolant of the internal combustion engine into the vaporizer to heat the liquid fuel; and a coolant temperature control unit for controlling the engine coolant to a predetermined temperature in the heating unit. A gas fuel supply device for an internal combustion engine, characterized by: 2. The cooling liquid temperature control means according to claim 1, wherein the temperature of the outlet of the heating section of the engine cooling liquid is 30 to 40.
A gas fuel supply device for an internal combustion engine, wherein the gas fuel supply device is configured to be maintained at a temperature of ° C. 3. The gas fuel supply device for an internal combustion engine according to claim 1, wherein the coolant temperature control means is a thermostat provided at an engine coolant outlet of the heating unit.