JPH01262358A - Fuel supply device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the temperature of liquefied gas fuel in a fuel storage bomb by feeding the fuel from the bomb into a metering solenoid valve after the fuel is pressurized, and by providing a pressure regulator for returning excessive fuel while holding the pressure thereof to a regulated pressure. CONSTITUTION:A liquefied kerosene gas or the like (hereinbelow denoted as fuel) reserved in a fuel bomb 10 is press-fed into a fuel injection nozzle 25 through a metering solenoid valve 16 and a fuel passage 22 under operation of the fuel pump 15 disposed in an outlet passage 13, and is then injected into an intake-air passage 23. Excessive fuel having passed through the metering solenoid valve 16 is returned into the bomb 10 through a passage 17 and a pressure regulator 18 for holding the pressure of fuel at a regulated pressure. In this arrangement, the pressure regulator 18 is disposed in the vicinity of the fuel 10, that is, for example, it may be directly connected to the bomb 10. Thereby, a relative high pressure of the fuel is held until it being discharged into the bomb 10, thereby it is possible to prevent evaporation of the fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel supply device for an internal combustion engine that uses liquefied gas, such as liquefied petroleum gas, as fuel.

(Prior art) For example, in an internal combustion engine that uses liquefied petroleum gas as fuel, which is a liquid under pressure at room temperature but becomes a gas under atmospheric pressure, the fuel is stored in a liquefied state. After being vaporized, it is supplied to the intake passage, and for this purpose, the fuel supply VC system is generally configured as shown in Fig. PTS3 (July 1980, published by Sankaido Co., Ltd., 1゛Automotive Engineering Complete Book Volume 4 1f So 17 Nzn E/n JPIS
205-f:l52011).

The fuel stored in the fuel cylinder (tank) 1 in a liquefied state is i! When the 5IFr valves 2A and 2B are opened, the water flows to the preheater 3, where it is preheated, and then the vaporizer 4 reduces the pressure to approximately atmospheric pressure, and at the same time, it is heated by hot water and vaporized.

A portion of hot water for cooling the engine 5 is guided to the preheater 3 and vaporizer 4 through a circulation passage 6A6B.

The vaporized gaseous fuel is guided to the mixer 8 provided in the intake pipe 7, is sucked into the negative pressure generated according to the amount of engine intake air, and is supplied to the engine 5 while being mixed with air at a predetermined ratio. Ru.

Note that 9 in the figure is a fuel pipe, through which fuel flows as indicated by dotted arrows, and the flow of hot water is indicated by solid arrows.

(Problem to be Solved by the Invention) However, in such a fuel supply device, since the liquid fuel is vaporized in advance and then introduced into the intake passage, it is difficult to use a gasoline engine that injects the liquid fuel directly into the intake passage. As a result, the injected fuel does not remove the heat of vaporization from the intake air, and therefore the intake air temperature decreases due to vaporization, so it is impossible to expect a substantial increase in the amount of intake air (mass flow ff1). There was a limit to the high output of Ennon in the load range.

As a countermeasure to this problem, it is possible to inject and supply liquid fuel directly into the intake passage in the same way as in a gasoline engine (Japanese Patent Application No. 159301 of 1983), but compared to gasoline, liquefied petroleum gas is far more effective. Because it evaporates easily, when restarting the engine while the inside of the engine compartment remains hot, the bubbles generated by evaporation inside the fuel piping cannot escape, blocking the fuel passage and preventing smooth fuel injection. The occurrence of bubbles in the fuel piping can occur when low-temperature fuel is not transferred from the fuel cylinder to the fuel injection nozzle, as is often the case with fuel injection systems for gasoline engines. This can be prevented by circulating a large amount of fuel through a pressure regulator, but since the pressure of the recirculated fuel from the pressure regulator is low, it is easily vaporized by the high heat in the engine room before returning to the fuel cylinder. In this way, a large amount of fuel, including some vaporized fuel, is stored in the fuel cylinder.
If it were to flow, there was a risk that the fuel temperature would rise and the internal pressure of the cylinder would rise beyond the allowable value.

In other words, vaporized fuel has much more heat than liquefied fuel at the same temperature, and if a large amount of such fuel is circulated through a cylinder, the liquid fuel absorbs this heat and the temperature inside the cylinder increases. As the pressure continues to rise, the internal pressure in the cylinder becomes even higher.

This invention aims to solve such problems.

(Means for Solving the Problems) In order to achieve this object, the present invention provides a pump that pressurizes and sends out liquefied gas fuel from a fuel storage cylinder, and a pump that measures the pressurized fuel according to the amount of engine intake air. It consists of a metering means, a valve means for injecting the metered amount of fuel into the intake passage, and a pressure regulator installed near the fuel storage cylinder to maintain the specified pressure and recirculate surplus fuel from the metering means.

(Operation) Since the liquefied fuel from the fuel rudder blade cylinder is pressurized by the pump, it is injected from the valve means into the intake passage in a liquid state. The pressure in the intake passage is low, and the injected fuel instantly vaporizes while taking vaporization heat from the air flowing through the surrounding intake passage, while the intake air temperature decreases and the actual intake air supply amount increases, increasing the engine speed. Increase maximum output.

Since the excess fuel from the metering means is maintained at a specified pressure by the pressure regulator, it will not vaporize even if it receives heat from the engine while returning through the fuel pipe. Since the pressure regierator is installed near the fuel storage cylinder, when fuel is released from the pressure regierator into the cylinder, even if some of the fuel is vaporized as pressure is released, the heat required for vaporization is taken away from the cylinder. This prevents an increase in internal fuel temperature and avoids an abnormal increase in internal pressure.

(Example) In FIG. 1, a fuel cylinder (or tank) 10 is arranged in a position sufficiently away from an engine 12, such as in a trunk room 11 of an automobile, and a fuel take-out passage 13 is provided with an electromagnetic cutoff valve that closes when the engine is stopped. A fuel pump 15 is provided downstream of the fuel pump 14 to pressurize fuel and send it to the +1L solenoid valve 16. Fuel pump 15 is driven by an electric motor.

A passage 17 for circulating surplus fuel back to the fuel cylinder 10 is connected from the metering solenoid valve 16, and a passage 17 is connected to the vicinity of the fuel cylinder 10, in this example, directly connected to the fuel cylinder 10.
Pressure regulator 18 that maintains fuel pressure at a specified pressure
will be installed.

The pressure regulator 18 is divided into a fuel chamber 18b connected to the recirculation passage 17 by a diaphragm 18a, and a reference pressure chamber 18c communicating with the inside of the fuel cylinder 10. a predetermined value (e.g. 3, 5 K g/c
m''), a valve 18d connected to the diaphragm 18a opens to recirculate the excess fuel to the fuel cylinder 10, thereby constantly maintaining the pressure in the recirculation passage at a specified value.

Note that an electromagnetic cutoff valve 19 is interposed in the middle of the recirculation passage 17, and is closed when the engine is stopped.

The metering solenoid valve 16 is driven by a pulse signal from a control circuit 20, which will be described later, and is turned on and off.
When the metering solenoid valve 16 is opened, the upstream pressurized fuel (maintained at a specified pressure by the pressure regulator 18) passes through a fuel reservoir 21 and branches into a fuel passage 2 corresponding to each cylinder.
Sent to 2.

The metering solenoid valve 16 includes a solenoid 16a that is energized by a pulse signal, a valve 16b that lifts against a return spring when the solenoid 16a is energized, and a pulp 16.
The metering solenoid valve 16 is preferably installed in a relatively low-temperature position in the engine room.

A fuel injection nozzle 25 is provided in the intake passage 23 of the engine 12 as close as possible to the intake valve 24. When the pressure in the fuel passage 22 fed from the metering solenoid valve 16 exceeds a certain value, the fuel injection nozzle 25 opens one nozzle to inject air into the intake passage 23. Liquid fuel is injected into the boat 26.

As shown in detail in Fig. Pt52, the fuel injection/throttle 25 has a needle valve 25b directly connected to the diaphragm 25a.
) and valve seat) 25c, the fuel chamber 25
The fuel d is ejected from the orifice 25e toward the intake boat 26, and the pressure of the fuel chamber 25d communicating with the fuel passage 22 is built up on one side of the diaphragm 25a, while the pressure on the other side is built up. Passage 2 in the reference pressure chamber 25f
the internal pressure of the fuel cylinder 10 led through 7;
When the load of the return spring 25g is applied and the fuel pressure is higher than the cylinder internal pressure by a certain value (for example, 2.5 Kg/em"), the diaphragm 25a moves and moves the needle valve 25b in the opening direction. .

A hot wire flow rate sensor 31 is provided downstream of the air cleaner 30 in the intake passage 23 and measures the amount of intake air (mass flow ff1) that flows in according to the opening degree of the intake throttle valve 32 that is linked to the accelerator pedal. The output of this flow rate sensor 31 is input to the control circuit 20 together with the output from an engine rotation speed (crank angle) sensor (not shown). A control circuit 20 composed of a microcomputer or the like calculates the amount of fuel to be injected so as to obtain a predetermined air-fuel ratio based on these signals that detect the operating state, and outputs a fuel injection pulse signal in synchronization with the engine rotation. It outputs to the metering solenoid valve 16. Note that when an exhaust gas concentration sensor or the like is installed in the exhaust system, the fuel injection amount is corrected based on the sensor so that the air-fuel ratio is feedback-controlled.

The system is constructed as described above, and its operation will be explained next.

When the engine 12 starts, the electromagnetic cutoff valve 14.19 opens and the fuel pump 15 is driven, so the fuel cylinder 1
0 fuel is sent from the take-out passage 13 to the metering solenoid valve 16 while being pressurized.

The intake air amount is determined according to the opening degree of the throttle valve 32 operated by the driver, and based on this intake air amount signal and rotation speed signal, the control circuit 20 determines the ratio of the injected fuel mixed with this intake air. solenoid valve 1 so as to achieve a predetermined air-fuel ratio.
6. Calculate the valve opening pulse time. When the metering solenoid valve 16 is opened by this pulse signal, pressurized fuel on the upstream side thereof is sent from the fuel reservoir 21 to the fuel passage 22.

The pressure on the upstream side of the metering solenoid valve 16 is such that the fuel sent from the fuel pump 15 is controlled by the pressure regulator 18 to maintain the pressure in the fuel cylinder 10 at a certain constant value (approximately 3.5 bi/cm2).
), and the pressure on the downstream side is set by the fuel injection nozzle 25 to exceed the pressure of the fuel cylinder 10 by a certain value (approximately 2.5 kg/c+++2).

Therefore, the differential pressure between the upstream and downstream sides of the metering solenoid valve 16 is always a constant value (approximately I K g/0m2), and the flow rate of fuel flowing through the metering solenoid valve 16 is determined depending only on its opening time. Ru.

Particularly in this case, the metering solenoid valve 16 is placed in a relatively low-temperature part of the engine room, and the fuel pressures upstream and downstream of the above-mentioned path are kept high, so there is no vaporization of fuel in the metering section, and the liquid fuel The metrological properties of are very stable.

And the total! i While the pressure of the fuel sent into the fuel passage 22 with the opening of the solenoid valve 16 exceeds the set pressure of the gouya 7 ram 25a of the fuel injection nozzle 25, the needle valve 25b opens and liquid fuel flows into the intake passage. It is injected on 23. Intake passage 2
Since the pressure in step 3 is low, below atmospheric pressure, the injected fuel absorbs heat from the intake air and instantly vaporizes.
It is inhaled by the body.

Since the injected liquid fuel is vaporized inside the intake passage 23 in this way, it is possible to lower the temperature of the intake air that has been deprived of the heat of vaporization, and to increase the substantial intake air filling efficiency. High output can be achieved.

By the way, surplus fuel that is not sent to the fuel reservoir 21 side after the metering solenoid valve 16 is closed is returned to the fuel cylinder 10 from the recirculation passage 17, but the pressure regulator 18 controls the excess fuel until just before it is released into the fuel cylinder 10. Since the pressure is maintained at a constant value (approximately 3.5 kg/c162) higher than the internal pressure of the cylinder, even if the fuel temperature in the recirculation passage 17 becomes higher than the fuel in the cylinder, it hardly vaporizes.

Therefore, the circulating fuel does not carry a large amount of heat taken from the surroundings (engine room) by vaporization into the fuel cylinder 10, and the temperature of the fuel in the cylinder does not rise much.

Further, the fuel released from the pressure radiator 18 into the fuel cylinder 10 is approximately 3.5Kir/cI11' at this moment.
However, since the pressure generator 18 is directly connected to the fuel cylinder 10 and the heat necessary for vaporization is taken from the fuel cylinder 10, the exchange of heat is canceled out and the temperature of the stored fuel inside increases. It doesn't lead to an increase.

On the other hand, in the vicinity of the engine 12, the fuel in the fuel injection nozzle 25 and the fuel passage 22 may reach a high temperature due to the influence of the heat released from the engine, and the fuel pressure may be approximately 2.5K higher than the cylinder internal pressure.
Even though the "g/am" is kept at a very high value, some fuel may vaporize. However, as the pressure increases due to fuel vaporization, the fuel injection nozzle 25
Since the ram 25a is displaced and the side valve 25b is lifted to release the vaporized fuel, the increase in volume due to vaporization does not impede fuel supply. In other words, vapor lock due to generated bubbles is avoided, and the engine speed is particularly low. Stable rotation characteristics are maintained even in the range.

(Effects of the Invention) As described above, according to the present invention, a pressure regulator is provided which pressurizes liquefied gas fuel from a fuel storage cylinder and sends it to a metering solenoid valve, while refluxing excess fuel while maintaining a specified pressure. Because it is installed near the fuel storage cylinder, excess fuel, which is maintained at a specified pressure by the pressure regulator, will not vaporize even if it receives heat from the Ennon on the way back through the fuel pipe, and will not be transferred from the pressure regulator to the cylinder. When the fuel is released, even if some of it vaporizes as the pressure is released, the heat required for vaporization is taken away from the cylinder.
Therefore, it is possible to prevent an increase in internal fuel temperature and avoid an abnormal increase in internal pressure.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, FIG. 2 is a sectional view of a fuel injection nozzle, and FIG. 3 is a configuration diagram of a conventional example. 10... Fuel cylinder (tank), 12... Engine, 13... Take-out passage, 15... Fuel pump, 16...
... Metering solenoid valve, 17... Return passage, 18... Pressure regulator, 20... Control circuit, 22... Fuel passage, 23... Intake passage, 25... Fuel injection nozzle.

Claims (1)

[Claims] A pump that pressurizes and sends out liquefied gas fuel from a fuel storage cylinder, a metering device that measures the pressurized fuel according to the amount of engine intake air, a valve device that injects the metered amount of fuel into the intake passage, and 1. A fuel supply system for an internal combustion engine, comprising a pressure regulator installed near a fuel storage cylinder to maintain surplus fuel at a specified pressure and recirculate it.