JPH0251068B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an improvement in a fuel supply device that supplies fuel to an intake system of an LPG engine.

(Prior art) Conventionally, a two-stage decompression type vaporizer for a fuel supply system for an LPG engine guides the negative pressure in the vent lily section located upstream of the throttle valve of the mixer to the secondary chamber of the vaporizer. The movement of the valve opening/closing lever applied to the diaphragm opens the fuel passage from the primary chamber to the secondary chamber of the vaporizer, vaporizes and depressurizes the fuel from the fuel tank, and supplies the fuel to the mixer.

Therefore, when negative pressure is not generated in the bench lily, the lever closes the valve with the biasing force of the spring.
The fuel flow control section, which closes the fuel passage from the next chamber to the secondary chamber and controls the amount of fuel supplied to the mixer, has the optimum specifications determined by a fixed jet or screw. The opening area of the fuel supply passage that communicates with Since the negative pressure generated in the engine becomes small, a sufficient amount of fuel cannot be supplied when the amount of intake air is low or in the entire region.

Therefore, in order to compensate for this lack of fuel supply, the diameter of the diaphragm of the secondary decompression chamber or the fuel supply passage must be made extremely large, but in reality this is not possible, and this is disclosed in Japanese Patent Application Publication No. Showa 52-100012
The same thing happens even if the fuel is controlled by an electric actuator as shown in No. 57-122151, and JP-A-57-122151 supplies positive pressure fuel from the primary chamber of the vaporizer to the mixer when the intake air amount is high. , this problem has been solved, but in this case, there are problems such as air-fuel ratio fluctuations caused by supplying fuel directly from the primary chamber to the mixer. In other words, the vaporizer is used as a first-stage decompression chamber and fuel is taken out from the primary chamber. Compared to the characteristics of the secondary chamber shown by the solid line in Fig. 1, the temperature change in the primary chamber is large as shown by the dotted line in Fig. 1 due to the effect of latent heat of vaporization due to fuel vaporization, so the specific gravity of the fuel is This has the disadvantage that when controlling the fuel flow rate using the area of the passage or the opening/closing time, the weight of the supplied fuel increases and the air-fuel ratio changes widely.

(Objective of the Invention) The present invention provides a two-stage decompression type vaporizer with a secondary decompression chamber having almost the same mechanism as the primary decompression chamber.
The next chamber pressure is set to a positive pressure value lower than the primary chamber pressure, and the opening area of the fuel amount control section is controlled by the actuator.
By providing a fuel supply system for LPG engines, we can ensure a sufficient amount of fuel while keeping the air-fuel ratio stable, increase the engine's volumetric efficiency and increase its output, and improve the final deceleration by increasing the output. The purpose is to reduce the ratio and lower the engine speed, thereby improving fuel efficiency.

(Structure of the Invention) FIG. 2 is an overall configuration diagram clearly showing the structure of the present invention. A primary side pressure reducing valve 6 is provided which closes when the pressure in the primary side diaphragm chamber 2 becomes higher than the primary side set pressure determined by the pressure regulating spring 5 pressing the diaphragm 4 of the primary side diaphragm chamber 2, The secondary diaphragm chamber 9 of the vaporizer 1 is connected to the valve hole of the bench lily part of the mixer formed in the intake system 8 of the LPG engine 7.
and the primary side diaphragm chamber 2, the primary side setting is such that the pressure in the secondary side diaphragm chamber 9 is determined by the biasing force of a pressure regulating spring 11 that presses at least the diaphragm 10 of the secondary side diaphragm chamber 9. A secondary side pressure reducing valve 12 is provided which closes when the positive pressure becomes higher than the secondary side set pressure which is lower than the pressure. An on-off valve 15 driven by an actuator 14 is connected to the fuel supply passage 13 between the next side diaphragm chamber 9 and the fuel supply passage 13.
This fuel supply system for an LPG engine is provided with a fuel amount control valve 17 driven by an actuator 16 that changes the passage area of the engine.

(Configuration of an embodiment) Next, the configuration of an embodiment of the present invention is shown in FIGS. 3 to 6.
This will be explained using figures.

Fuel tank 21 in the intake system of LPG engine 20
The pressure in the primary diaphragm chamber 23 is between the primary diaphragm chamber 23 of the vaporizer 22 and the fuel inlet of the vaporizer 22 connected to the fuel tank 21. 1 determined by the biasing force of the pressure regulating spring 25 that presses the diaphragm 24 of the next diaphragm chamber 23
A primary side pressure reducing valve 26 that closes when the pressure becomes higher than the next side setting pressure, in this case a lever 28 whose one end engages with a hook 27 integrated with the diaphragm 24
The rotation of the lever 28 presses the valve element 29 attached to the other end of the lever 28 against the valve seat of the valve hole 31 formed in the main body case 30, thereby closing the valve hole 31. The diaphragm 24 is urged toward the primary diaphragm chamber 23 when the valve is open by a pressure regulating spring 25 whose load can be adjusted by a set screw 33 attached to the main body case 30 with a double nut 32.

Between this primary side diaphragm chamber 23 and the secondary side diaphragm chamber 34 of the vaporizer 22 connected to the intake system of the LPG engine 20, there is a
The pressure within the next diaphragm chamber 34 is at least 2
a secondary side pressure reducing valve 37 that closes when the pressure becomes higher than the secondary side set pressure which is lower than the primary side set pressure determined by the biasing force of the pressure regulating spring 36 that presses the diaphragm 35 of the next side diaphragm chamber 34;
In this case, a valve hole 41 formed in the main body case 30 has a valve body 40 attached to the other end of the lever 39 by rotating the lever 39 with one end engaged with a hook 38 integrated with the diaphragm 35. A secondary side pressure reducing valve 37 is attached that presses against the seat and closes the valve hole 41, and the diaphragm 35 is equipped with a pressure regulating spring 36 whose load can be adjusted by a set screw 43 attached to the main body case 30 with a double nut 42.
The lever 39 is urged in the direction of the secondary diaphragm chamber 34 to open the valve, and the lever 39 is urged in the valve closing direction by a spring 44.

The fuel supply passage 45 between the secondary diaphragm chamber 34 and the intake system of the LPG engine 20 includes:
An on-off valve 46 driven by an actuator, in this case, an on-off valve 46 that opens a valve hole 50 formed in the main body case 30 by movement of a valve body 49 against the urging force of a spring 48 due to excitation of an electromagnetic solenoid 47.
and a fuel amount control valve 51 driven by an actuator that changes the passage area of the fuel supply passage 45, in this case, by forward/reverse rotation of a step motor 52 (not shown), for example, through a rotation-linear conversion mechanism of a nut/screw. The valve hole 5 formed in the bench lily portion 55 of the mixer 54 by the reciprocating movement of the needle 53
A fuel amount control valve 51 that changes the flow path area of the fuel supply passage 45, that is, the effective cross-sectional area of the fuel supply passage 45, is installed.
3, there is an electromagnetic switch which opens and closes when a starter switch 59 is turned on via an ignition switch 58 or when a contact 61 of a relay 60 is turned on during alternator power generation and when an LPG switch 62 on the driver's seat is turned on. A valve 63 and a filter 64 are attached.

The electromagnetic on-off valve 63 of the fuel supply device 65 formed in this way and the electromagnetic solenoid 47 of the on-off valve 46
The step motor 52 of the fuel amount control valve 51 is a fuel temperature sensor 66 that is attached to the fuel supply passage 45 and generates an output corresponding to the fuel temperature.
and an intake air amount sensor 68 that is attached to the intake pipe 67 and generates an output corresponding to the intake air amount.
an intake air temperature sensor 69 that is attached to the intake pipe 67 and generates an output corresponding to the intake air temperature;
A negative pressure switch 72 is installed in the exhaust pipe 73 to detect a change in negative pressure caused by depressing the throttle valve 70 in a negative pressure passage 71 formed downstream of the fully closed throttle valve 70 in the intake pipe 67. Exhaust sensor 74 that changes output near the air-fuel ratio
and a rotational speed sensor 76 that is attached to the distributor 75 and generates an output corresponding to the rotational speed of the engine 20. controlled by the output from

Next, FIG. 4 is an electric circuit diagram of the electric control device 77, and the CPU 79, which is controlled according to the program in the storage section 78, receives signals from the starter switch 59, the negative pressure switch 72, and the rotation speed sensor 76. is input via the input interface 81, and signals from the air amount sensor 68, intake air temperature sensor 69, fuel temperature sensor 66, and exhaust sensor 74 are input via the input interface 81 and the A/D converter 82. The output from the CPU 79 is supplied to the electromagnetic solenoid 47 of the on-off valve 46 and the step motor 52 of the fuel amount control valve 51 via an output interface 83 and respective drive circuits 84 and 85.

(Operation of the embodiment) Next, the operation of the embodiment will be explained according to the flowchart of FIG.

When the ignition switch 58 is in the ON state before the engine 20 is started, the needle 53 of the fuel amount control valve 51 is set to an initial setting position with a preset opening area in step 101, and the on-off valve 46 is set to an initial setting position with a preset opening area.
is held in a closed state, and in this state, the CPU 79 has switches 59, 72 and sensors 68, 76, 6.
Signals corresponding to the state of the engine 20 are inputted from 9, 66, and 74, and in step 102, it is determined whether the engine 20 is in a stopped state based on whether the engine 20 is running at a set rotation speed or higher. If so, turn on the starter switch 59 in step 109.
Determine whether it is on. If the starter switch 59 is off in step 109, the process returns to step 101. If the starter switch 59 is on, the needle 53 of the fuel amount control valve 51 is used to start the engine.
The CPU 79 calculates the target position. Furthermore, when the contact 61 of the relay 60 and the LPG switch 62 are turned on, the electromagnetic on-off valve 63 opens and the fuel tank 2
The liquefied LPG fuel from 1 is vaporized and depressurized into the primary side diaphragm chamber 23 of the vaporizer 22 via the primary pressure reducing valve, and the pressure is reduced again via the secondary pressure reducing valve, and then the on-off valve attached to the vaporizer 22 is removed in step 111. 46 is opened and fuel supply to the mixer 54 is started. Step 110 at step 112
The calculated signal is sent to the step motor 52, the needle 53 is controlled to the target position, and fuel suitable for starting is sent to the engine 20.

When step 112 is completed, the process returns to step 102 and it is again determined whether the engine 20 is in an operating state. If the rotational speed is equal to or higher than the set rotational speed at which the engine is recognized to be in operation, the process moves to step 103. In step 103, when the negative pressure switch 72 is on and the engine is in the idle operating range, it is determined in step 104 whether the engine speed is equal to or higher than the set speed for fuel cut during deceleration, and if it is higher than the set speed, the engine 20 is in the deceleration state. It is determined that there is, and step 1
At 05, the on-off valve 46 of the electromagnetic solenoid 47 is closed. At step 103, the negative pressure switch 72 is turned off.
If it is determined in step 104 that the engine speed is less than or equal to the set rotation speed, the on-off valve 47 of the electromagnetic solenoid 47 is opened in step 108 because the engine 20 is in normal operation or idle operation.

After steps 105 and 108 are completed, in either case, step 106 calculates the position of the needle 53 of the fuel amount control valve 51 that provides the target air-fuel ratio when the engine 20 is operating, and step 107 calculates the position of the needle 53 of the fuel amount control valve 51.
Outputs a signal to.

In the air-fuel ratio control by the fuel amount control valve 51, fuel is supplied from the vaporizer 22 to the mixer 5 under positive pressure.
4, it is possible to sufficiently supply fuel even if the intake diameter of the mixer 54 is increased, and as a result, it is possible to increase the volumetric efficiency of the engine 20 and improve the output. By increasing the output, the speed reduction ratio can be reduced to lower the usable rotation range of the engine 20, thereby improving fuel efficiency.

That is, the effect of controlling the pressure in the secondary diaphragm chamber 34 to a positive pressure lower than the pressure in the primary diaphragm chamber 23 is as follows.

The fuel pressure in the fuel tank 21 inevitably changes depending on the fuel components and temperature, and the pressure in the primary diaphragm chamber 23 also changes due to the pressure regulating mechanism of the vaporizer 22, but the pressure in the secondary diaphragm chamber 34 is reduced by two steps. When the internal pressure of the fuel tank 21 changes while the pressure is set to positive pressure, the rate of change in the pressure in the secondary diaphragm chamber 34 can be made smaller than the rate of change in the pressure in the primary diaphragm chamber 23.

This is 1 when the pressure change in the fuel tank 21 is ΔP, the pressure change in the primary diaphragm chamber 23 is ΔP ₁ , and the pressure in the secondary diaphragm chamber 34 is P ₂ .
The rate of pressure change _in the next diaphragm chamber ₂₃ is as shown _by the dotted line in FIG. There is a relationship of K ₁ <1.

Furthermore _, the rate of pressure change in the _secondary diaphragm chamber ₃₄ is as shown by _the solid line in FIG. The equation is satisfied by the pressure regulating mechanism, and as a result, even if the internal pressure of the fuel tank 21 changes, the fuel supply pressure from the vaporizer 22 to the mixer 54 is stabilized, and the control accuracy of the fuel flow rate can be improved.

Furthermore, in this embodiment, the fuel flow rate is controlled by controlling the passage opening area by the step motor 52, thereby eliminating the disadvantages of the conventional method, namely, that with a fixed jet or needle, as the amount of intake air theoretically decreases, This solves the conventional drawback that the air-fuel mixture becomes too rich, making it impossible to run the engine.On the other hand, in gasoline engines, the conventional fuel injection valve
Even when used to control the fuel flow rate of LPG, since LPG supplies fuel in the form of gas, a sufficient supply amount cannot be ensured unless the injection valve is made very large or multiple injection valves are used.

Note that the step motor 52 for the fuel amount control valve 51 in this embodiment can be replaced with any actuator such as a linear solenoid, and the electromagnetic on-off valve 63 can be an on-off valve driven by any actuator. The fuel amount control valve 51 can also have the function of an electromagnetic on-off valve 63, and an intake pressure sensor can be used instead of the intake air amount sensor 68 to detect the amount of intake air. In addition to the sensor used in this embodiment, any other sensor such as a fuel flow rate sensor, throttle opening sensor, or fuel tank pressure sensor may be used to improve the performance of the fuel supply device 65 of this embodiment.
In addition to the LPG-dedicated engine 20, it can also be used in combination with gasoline engines.

(Effects of the Invention) The present invention provides a two-stage decompression type vaporizer in which the mechanism of the secondary decompression chamber is almost the same as that of the primary decompression chamber.
By setting the next chamber pressure to a positive pressure value lower than the primary chamber pressure and controlling the opening area of the fuel amount control section with an actuator, even if the diameter of the intake section of the mixer is increased in an LPG engine, the air-fuel mixture By securing a sufficient amount of fuel while keeping the air-fuel ratio stable, the volumetric efficiency of the engine is increased and output is increased, and by increasing the output, the final reduction ratio is reduced and the engine speed is lowered, thereby reducing fuel consumption. This has the effect of making it possible to improve the situation.

[Brief explanation of the drawing]

FIG. 1 is a comparative characteristic diagram of a conventional embodiment, FIG. 2 is an overall configuration diagram clearly showing the configuration of the present invention, FIG. 3 is an explanatory diagram of an embodiment of the present invention, and FIG. 4 is an electric circuit diagram thereof. FIG. 5 is a flow chart thereof, and FIG. 6 is a characteristic diagram thereof. 1... Vaporizer, 2... Primary side diaphragm chamber, 3... Fuel tank, 4, 10... Diaphragm, 5, 11... Pressure regulating spring, 6... Primary side pressure reducing valve, 7... LPG engine , 8...Intake system,
9...Secondary side diaphragm chamber, 12...Secondary side pressure reducing valve, 13...Fuel supply passage, 14, 16...Actuator, 15...Opening/closing valve, 17...Fuel amount control valve.

Claims (1)

[Scope of Claims] 1. Between the primary diaphragm chamber of the vaporizer that vaporizes and depressurizes LPG and the fuel inlet of the vaporizer, there is a control system in which the pressure in the primary diaphragm chamber presses at least the diaphragm of the primary diaphragm chamber. The vaporizer is provided with a primary side pressure reducing valve that closes when the pressure becomes higher than a primary side set pressure determined by the biasing force of a pressure spring, and is connected to a valve hole in a bench lily part of a mixer formed in an intake system of an LPG engine. The primary side setting is provided between the secondary side diaphragm chamber and the primary side diaphragm chamber, where the pressure in the secondary side diaphragm chamber is determined by the biasing force of a pressure regulating spring that presses at least the diaphragm of the secondary side diaphragm chamber. A secondary side pressure reducing valve is provided that closes when the positive pressure is higher than the secondary side set pressure, which is lower than the pressure, and the valve hole and the secondary side diaphragm are provided in the vent lily part of the mixer formed in the intake system of the LPG engine. 1. A fuel supply device for an LPG engine, characterized in that a fuel supply passage between the fuel supply passage and the chamber is provided with an actuator-driven on-off valve and an actuator-driven fuel amount control valve that changes the passage area of the fuel supply passage. 2. The fuel supply system for an LPG engine according to claim 1, wherein the actuator for driving the on-off valve is an electromagnetic device. 3. The fuel supply system for an LPG engine according to claim 1, wherein the actuator for driving the fuel quantity control valve is a step motor.