JPH0312657B2 - - 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 no load is applied to the bench lily, the lever closes the valve with the biasing force of the spring.
The fuel flow control unit, which closes the fuel passage from the next chamber to the secondary chamber and controls the amount of fuel supplied to the mixer, uses a fixed jet or screw to determine the optimum specifications and mixes the fuel with the secondary chamber. In this case, even if an attempt is made to increase the volumetric efficiency of the engine and improve the engine output by increasing the diameter of the intake air, that is, the diameter of the vent lily, Since the negative pressure generated in the fuel tank 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 electrically controlled by an actuator as in No. 57-122151, and JP-A-57-122151 supplies positive pressure fuel from the secondary chamber of the vaporizer to the mixer when the amount of intake air is high. However, in this case, problems such as air-fuel ratio fluctuations caused by supplying fuel directly from the primary chamber to the mixer, i.e.,
When a vaporizer is used as a first-stage decompression chamber and fuel is taken out from the primary chamber, the characteristics in the primary chamber are as shown in Figure 1 due to the influence of the latent heat of vaporization due to the vaporization of the fuel, compared to the characteristics of the secondary chamber shown by the solid line in Figure 1. As shown by the dotted line, the temperature change is large, so the fuel specific weight change is large,
This has the disadvantage that when the fuel flow rate is controlled by the area of the passage or the opening/closing time, the weight of supplied fuel increases and the air-fuel ratio changes significantly.

(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 opening area of the fuel amount control section is controlled by the actuator while the secondary pressure reducing chamber pressure is set to a positive pressure value lower than the primary pressure reducing chamber pressure, and the secondary pressure reducing chamber pressure is changed in response to changes in engine load. By providing a fuel supply system for an LPG engine that maintains a stable air-fuel ratio, a sufficient amount of fuel can be secured as the engine load increases, increasing the volumetric efficiency of the engine and increasing output. In addition to improving fuel efficiency by reducing the final reduction ratio and lowering engine speed by increasing output, the electric actuator drive improves control resolution in the low fuel flow range to improve air-fuel ratio control accuracy. Furthermore, it is an object of the present invention to improve the followability of fuel supply during transient operation, thereby improving fuel efficiency and drivability.

(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, Between the secondary diaphragm chamber 9 of the vaporizer 1 connected to the intake system 8 of the LPG engine 7 and the primary diaphragm chamber 2,
As the engine load increases, the pressing force of the diaphragm 10 in the secondary diaphragm chamber 9 is increased, and the pressure in the secondary diaphragm chamber 9 is determined by the pressing force of the diaphragm 10 in the secondary diaphragm chamber 9. The intake system 8 of the LPG engine 7 is provided with a secondary side pressure reducing valve 12 that closes when the positive pressure becomes higher than the secondary side set pressure, which is lower than the pressure.
An LPG engine is provided with an on-off valve 15 driven by an actuator 14 and a fuel amount control valve 17 driven by an actuator 16 that changes the passage area of the fuel supply passage 13 in the fuel supply passage 13 between the diaphragm chamber 9 and the secondary diaphragm chamber 9. in the fuel supply system.

(Configuration of Embodiment) Next, the configuration of the first embodiment of the present invention will be described with reference to FIGS. 3 to 6.

Vaporizer 2 that vaporizes and depressurizes the fuel from the fuel tank 21 and supplies it to the intake system of the LPG engine.
2 primary side diaphragm chamber 23 and fuel tank 21
Between the fuel inlet of the vaporizer 22 connected to A primary side pressure reducing valve 26 that closes when the pressure increases, in this case a valve that is attached to the other end of the lever 28 by engaging the hook 27 integral with the diaphragm 24 at one end and rotating the lever 28. Valve seat 3 of valve hole 31 with body 29 formed in main body case 30
2 and closes the valve hole 31.
is attached, and 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.

This primary side diaphragm chamber 23 and the vaporizer 22 connected to the intake system of the LPG engine
A pressing spring 38 is installed between the diaphragm 36 of the negative pressure operated diaphragm device 35 and the diaphragm 37 of the secondary diaphragm chamber 34, and The diaphragm 3 is attached so that the pressing force can be adjusted by the set screw 39.
A secondary side pressure reducing valve 41 that closes when the positive 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 40 that presses the pressure regulating spring 40; A lever 43 is freely connected to the diaphragm 37 via a rod 42.
A secondary side pressure reducing valve 41 is attached to which the valve element 44 attached to the other end of the lever 43 is pressed into contact with the valve seat 46 of the valve hole 45 formed in the main body case 30, thereby closing the valve hole 45. There is.

A fuel supply passage 47 between this secondary side diaphragm chamber 34 and the intake system of the LPG engine has an actuator-driven on-off valve 48, in this case an actuator-driven on-off valve 48, which resists the biasing force of a spring 50 due to the excitation of an electromagnetic solenoid 49. An on-off valve 48 that opens a valve hole 52 formed in the main body case 30 by movement of the valve body 51, and an actuator-driven fuel amount control valve 53 that changes the passage area of the fuel supply passage 47, in this case a step motor 54. The mixer 5 is rotated in forward and reverse directions (not shown), for example, by reciprocating movement of the needle 55 via a nut-screw rotation-linear conversion mechanism.
A fuel amount control valve 53 that changes the flow path area of a valve hole 58 formed in the bench lily portion 57 of No. 6, that is, the effective cross-sectional area of the fuel supply passage 47 is attached.

The electromagnetic solenoid 49 of the on-off valve 48 of the fuel supply device 59 formed in this way and the fuel amount control valve 5
The step motor 54 of No. 3 is the fuel supply passage 47.
A fuel temperature sensor 60 is attached to the intake pipe 61 and generates an output corresponding to the fuel temperature; an intake air amount sensor 62 is attached to the intake pipe 61 and generates an output corresponding to the intake air amount; An intake air temperature sensor 63 that generates an output corresponding to the intake air temperature, a throttle sensor 65 that generates an output that corresponds to the opening degree of the throttle valve 64 of the intake pipe 61, and an output that corresponds to the negative pressure of the intake pipe 61. a negative pressure sensor 66 that generates an output, a starter 67 that generates an output when starting the engine, and a rotational speed sensor 6 that is attached to the distributor 68 and generates an output that corresponds to the engine rotational speed.
The negative pressure of the intake pipe 61 is introduced into the diaphragm device 35 of the vaporizer 22 under the control of the output from the electric control device 70, which optimally controls the fuel supply to the engine in response to the input signals from the vaporizer 22 and the vaporizer 22. There is.

Next, FIG. 5 is an electric circuit diagram from the electric control device 70, and the CPU 72, which is controlled according to the program in the storage section 71, has a starter 67, an ignition switch 73, and a rotation speed sensor 69. In addition to inputting signals via the input interface 74, the intake air amount sensor 62 and the negative pressure sensor 6
6, intake air temperature sensor 63, and fuel temperature sensor 6
0 and the signals from the throttle sensor 65 are inputted via the input interface 75 and the A/D converter 76, and the signals from the electromagnetic solenoid 4 of the on-off valve 48 are input.
9 and the step motor 54 of the fuel amount control valve 53 are supplied with output from the CPU 72 via an output interface 76 and respective drive circuits 77 and 78.

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

Ignition switch 73 before starting the engine
In the on state, in step 101, the needle 55 of the fuel amount control valve 53 is set to the initial setting position of the preset opening area, and the on-off valve 48 is held in the closed state. Signals corresponding to the stop and operating states of the engine are input from the switch 73, starter 67, and sensors 60, 63, 65, 66, and 69, and it is determined in step 102 whether the engine is in the starting state. At step 103, the target position of the needle 55 of the fuel quantity control valve 53 for starting the engine is calculated by the CPU, and the engine is controlled to start under optimal conditions.If the engine is not in the starting state at step 102, the engine operating state is changed at step 104. If it is stopped, the process returns to step 101.
If it is in operation, the fuel amount control valve 5 is turned off in step 105.
The target position of the needle 55 of No. 3 is calculated by the CPU 72, and the engine is optimally controlled according to its operating state. In step 106, it is determined whether the engine is decelerating, and if it is, the step
At 107, the target position of the needle 55 of the fuel amount control valve 53 corresponding to the deceleration state is calculated by the CPU 72, and the engine is optimally controlled in accordance with the deceleration state.

In the air-fuel ratio control by the fuel amount control valve 53, fuel is supplied from the vaporizer 22 to the mixer 5 under positive pressure.
6, it is possible to supply sufficient fuel even if the diameter of the intake part of the mixer 56 is increased, and as a result, the volumetric efficiency of the engine can be increased and the output can be improved. By increasing the output, it is possible to reduce the reduction ratio and lower the operating speed range of the engine, 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 ΔP1, and the pressure in the secondary diaphragm chamber 34 is P2.
The rate of pressure change in the next diaphragm chamber 23 is as shown by the dotted line in FIG. In a relationship.

Furthermore, the rate of pressure change in the secondary diaphragm chamber 34 is as shown by the solid line in Figure 7, ΔP2∞K2×ΔP1... (2) where K2<1 Equations (1) and (2) above are the pressure regulating mechanism. 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 56 is stabilized, and the control accuracy of the fuel flow rate can be improved.

The vaporizer 22 has a primary side diaphragm chamber 23
The depressurized and vaporized fuel is transferred to the secondary diaphragm chamber 3.
4, the pressure is further reduced by the force of the fuel in the primary diaphragm chamber 23 pushing the secondary pressure reducing valve 41, and the pressure in the secondary diaphragm chamber 34 applied to the secondary diaphragm chamber 37, resulting in the pressure being reduced by the rod. The pressure spring 38 is activated by a positive pressure determined by the balance between the force acting in the direction of closing the secondary side pressure reducing valve 41 via the pressure spring 42 and the force of the pressure spring 38 pushing the secondary side diaphragm chamber 37. The stronger the biasing force, the higher the pressure in the secondary diaphragm chamber 34.

On the other hand, when the negative intake pressure from the intake pipe 61 introduced into the pressure control diaphragm device 35 of the secondary diaphragm chamber 34 exceeds the biasing force of the pressure regulating spring 40, the diaphragm 36
The pressure spring 38 moves to the right in FIG. 4 against the urging force of 0 to reduce the amount of deflection of the pressing spring 38, and the load becomes smaller, so the pressure in the secondary diaphragm chamber 34 becomes lower.

As a result, the fuel supply pressure of the vaporizer 22 is low when the engine is under a light load, and becomes high when the engine is under a high load, thereby achieving the following effects.

(1) The fuel supply pressure from the vaporizer 22 is determined by the pressure that can supply the maximum required amount of fuel, and the amount of change in air-fuel ratio per unit stroke of the stepping motor 54 is determined by the fuel supply pressure as shown in FIG. The lower the value, the smaller the value.

This is because if the opening area of the valve hole 58 that changes with the needle 55 of the fuel amount control valve 53 is A, and the pressure before and after the needle 55 is ΔP, the fuel flow rate Gf becomes Gf∞A×√, so ΔP is small. This is because the change in fuel flow rate with respect to the area change per unit stroke of the stepping motor 54 becomes smaller. Engine operating performance in a load range can be improved, fuel efficiency characteristics can be improved, and exhaust gas levels can be reduced.

(2) When the load suddenly changes, the pressure difference before and after the fuel quantity control valve 53 is amplified by the vaporizer 22 as shown in Fig. 9, so from the formula Gf∞A×√ shown in (1) above, the required Valve hole 5
The amount of change in the area of the 8 openings, that is, the amount of stroke of the stepping motor 54 can be reduced, which improves the responsiveness of the fuel control system and significantly improves the operating characteristics of the engine in the transient operating range. can be improved.

Next, FIGS. 10 and 11 show a second embodiment of the present invention, in which the biasing force of a pressure regulating spring 83 for pressing a diaphragm 82 in a secondary diaphragm chamber 81 constituting a vaporizer 80 is adjusted. By using an electromagnetic device, for example, an electromagnetic solenoid 84, in place of the diaphragm device 35 of the first embodiment, and by switching the electromagnetic solenoid 84 on and off with a negative pressure switch 85 operated by an intake negative pressure, The configuration, operation, and effects are substantially the same as in the first embodiment, except that the pressure in the secondary diaphragm chamber 81 is changed as shown in FIG. 11 by the intake negative pressure.

Next, FIG. 13 shows a third embodiment of the present invention, in which
In this case, the first diaphragm chamber 91 of the vaporizer 90 is used for adjusting the biasing force of the pressure regulating spring 93 for pressing the diaphragm 92 of the secondary diaphragm chamber 91.
A stepping motor 94 is used in place of the diaphragm device 35 of the embodiment, and the stepping motor 94 is operated based on the output from a negative pressure sensor (not shown) that generates an output proportional to the intake negative pressure. The configuration, operation, and effects are almost the same as those of the first embodiment.

(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.
The fuel control part By controlling the opening area of the engine with an actuator, it is possible to secure a sufficient amount of fuel as the engine load increases while keeping the air-fuel ratio stable, increasing the volumetric efficiency of the engine and increasing output. This improvement not only reduces the final reduction ratio and lowers the engine speed used to improve fuel efficiency, but also improves the control resolution in the low fuel flow range by driving the electric actuator to improve the control accuracy of the air-fuel ratio. This has the effect of improving the followability of fuel supply during transient operation, thereby improving fuel efficiency and driving characteristics.

That is, in the present invention, the pressure in the secondary chamber of the vaporizer is made positive, and LPG at this positive pressure is supplied to the valve hole formed in the bench lily part of the mixer.
The engine output can be greatly increased by increasing the intake port of the mixer, and it is equipped with a diaphragm mechanism that controls the positive vaporizer secondary chamber pressure in accordance with the engine negative pressure in the entire operating range. Since the fuel passage area is changed by the fuel amount control valve driven by the actuator, the engine negative pressure changes the positive pressure in the vaporizer secondary chamber, and the actuator is driven while the fuel amount is automatically controlled. As a result, the width of movement of the actuator can be reduced, and as a result, the accuracy and responsiveness of controlling the amount of fuel by driving the actuator can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is a comparative characteristic diagram of a conventional embodiment, Fig. 2 is an overall configuration diagram clearly showing the structure of the present invention, Fig. 3 is an explanatory diagram of the first embodiment of the present invention, and Fig. 4 is a detailed diagram of its main parts. 5 is its electrical circuit diagram, FIG. 6 is its flowchart, FIGS. 7 to 9 are its characteristic diagrams, FIG. 10 is a detailed view of the main part of the second embodiment of the present invention, and FIG. 1
FIG. 1 is a characteristic diagram thereof, and FIG. 12 is a detailed diagram of a main part of a third embodiment of the present invention. 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. A primary side pressure reducing valve is provided which closes when the primary side set pressure determined by the biasing force of a pressure spring is exceeded, and the secondary side diaphragm chamber and the primary side diaphragm of the vaporizer are connected to the intake system of the LPG engine. The diaphragm pressing force in the secondary diaphragm chamber is increased as the engine load increases, and the pressure in the secondary diaphragm chamber is determined by the diaphragm pressing force in the secondary diaphragm chamber. A secondary side pressure reducing valve is provided that closes when the positive pressure becomes higher than the secondary side set pressure, which is lower than the set pressure, and an actuator is installed in the fuel supply passage between the intake system of the LPG engine and the secondary side diaphragm chamber. It is characterized by providing a driven on-off valve and an actuator-driven fuel control valve that changes the passage area of the fuel supply passage.
Fuel supply system for LPG engine. 2. As a means for increasing the diaphragm pressing force in the secondary diaphragm chamber as the engine load increases, a diaphragm device is used that changes the amount of deflection of a pressure regulating spring that presses the diaphragm. As stated in paragraph 1
Fuel supply system for LPG engine. 3. As a means for increasing the diaphragm pressing force in the secondary diaphragm chamber as the engine load increases, an electromagnetic device is used that changes the amount of deflection of a pressure regulating spring that presses the diaphragm. The fuel supply device for the LPG engine according to item 1. 4. A stepping motor that changes the amount of deflection of a pressure regulating spring that presses the diaphragm is used as means for increasing the pressing force of the diaphragm in the secondary diaphragm chamber as the engine load increases. A fuel supply system for an LPG engine according to scope 1.