JPH0313558Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a gaseous fuel supply device for a supercharged engine that supplies gaseous fuel to the intake passage of the engine and supercharges the engine.

(Prior art) Engines that use liquid fuels such as LPG (liquefied propane gas) and LNG (liquefied natural gas), especially LPG, are widely used for commercial purposes such as taxis. It is generally stored in a cylinder, reduced in pressure and vaporized by a vaporizer, and then supplied to the intake passage of the engine as gaseous fuel.

This vaporizer generally includes a primary chamber and a secondary chamber, and reduces the pressure of the liquid fuel in the high-pressure cylinder to a pressure slightly higher than atmospheric pressure in the primary chamber and expands (vaporizes) it. The pressure of the gaseous fuel reduced in the secondary chamber is further reduced to approximately atmospheric pressure, and then the fuel is supplied to the intake passage. Then, in order to maintain the pressure in this secondary chamber at a predetermined level,
Atmospheric pressure is introduced into the back surface of the secondary diaphragm defining the secondary chamber, that is, into the secondary diaphragm chamber, and in response to the displacement of the secondary diaphragm due to the pressure difference between the secondary chamber and the secondary diaphragm chamber, Primary room and 2
By adjusting the opening degree of a secondary valve provided at a communication port with the next chamber, the pressure within the secondary chamber is controlled to a predetermined value.

Incidentally, in recent years, it has been desired to increase the output of engines using gaseous fuel as described above, and for this reason, supercharging has been considered. In order to adjust the supply of gaseous fuel accompanying this supercharging, a system has been proposed in which supercharging pressure is supplied to the secondary diaphragm chamber of the vaporizer (Utility Model Application No. 56-173752). (see publication). That is, a supercharger and a throttle valve are disposed downstream of the supercharger in the intake passage of the engine, and gaseous fuel from the vaporizer is supplied to the intake passage between the supercharger and the throttle valve. By supplying supercharging pressure to the secondary diaphragm chamber of the vaporizer, the amount of fuel discharged from the secondary chamber is increased by dealing with the increase in the amount of intake air accompanying supercharging. As the pressure in the chamber becomes higher than the pressure in the secondary chamber, the fuel pressure in the secondary chamber increases).

(Problem to be solved by the invention) As mentioned above, when supercharging pressure is supplied to the secondary diaphragm chamber of the vaporizer, the throttle valve is suddenly fully closed or almost fully closed during supercharging. During deceleration, due to the inertia of the supercharger, etc., the supercharging pressure does not immediately decrease following the closing operation of the throttle valve, but rather tends to increase temporarily. For this reason, even during deceleration, a fairly large boost pressure still acts on the secondary diaphragm chamber, and the fuel pressure in the secondary chamber remains high, allowing a large amount of fuel to flow into the intake passage. You will end up spitting it out. Therefore, when the throttle valve is opened again after deceleration, a large amount of fuel is supplied to the engine at once, resulting in a temporary overload.

In order to solve this problem, it may be possible to install an on-off valve that closes during deceleration in the fuel passage between the secondary chamber of the vaporizer and the intake passage, but even in this case, Because the fuel pressure in the secondary chamber is maintained high due to the influence of the supercharging pressure acting on the secondary diaphragm chamber, when the throttle valve is opened and the on-off valve is opened again, this high fuel pressure 2 A large amount of fuel is temporarily discharged from the next chamber,
I was bound to end up with an overachiever.

Therefore, the purpose of the present invention is to improve the performance of the vaporizer by using gaseous fuel and performing supercharging.
To provide a gaseous fuel supply device for a supercharged engine, which supplies supercharging pressure to a diaphragm chamber and is capable of preventing overcharging immediately after opening a throttle valve again after deceleration. .

(Means and actions for solving the problem) In order to achieve the above-mentioned object, in the present invention, supercharging pressure (supercharging residual pressure) is supplied to the secondary chamber of the vaporizer during deceleration. Due to the supercharging pressure acting on the secondary diaphragm chamber during deceleration, the
The fuel pressure in the secondary chamber is prevented from increasing, that is, the displacement of the secondary diaphragm in the direction of increasing fuel pressure is restricted. Specifically, a turbocharger and a throttle valve are disposed downstream of the supercharger in the intake passage of the engine, and gas from the secondary chamber of the vaporizer is provided in the intake passage between the turbocharger and the throttle valve. In a gaseous fuel supply device for a supercharged engine, which supplies fuel and also supplies supercharging pressure to a secondary diaphragm chamber of the vaporizer, the fuel is supplied between the secondary chamber of the vaporizer and the intake passage. An on-off valve that is closed during deceleration is connected to the passage, and a check valve that allows flow from the intake passage toward the secondary chamber is connected in parallel with the on-off valve. It has a simple structure.

(Example) An example of the present invention will be described below based on the attached drawings.

In the figure, an engine 1 has a combustion chamber 3 defined by a reciprocating piston 2, and an intake port 4 and an exhaust port 5 are open to the combustion chamber 3. The intake port 4 is connected to the intake valve 6, and the exhaust port 5 is connected to the exhaust valve 7.
It is opened and closed at known timing in synchronization with the engine output shaft (not shown).

In the intake passage 8 connected to the intake port 4, from the upstream side, an air cleaner 9, a compressor wheel 10a of a supercharger (turbocharger in the embodiment) 10, a bench lily (mixer) 11, a throttle valve 12, and a surge tank 13 are provided. is installed. Further, the exhaust passage 14 connected to the exhaust port 5 is connected to the turbine wheel 1 of the supercharger 10.
0b is arranged, and this turbine wheel 10b and the compressor wheel 10a are connected to the shaft 1.
Connected by 0c. Thereby, when the turbine wheel 10b is rotated by the exhaust energy, the compressor wheel 10a is also rotated, and supercharging is performed.

In the figure, 21 is a vaporizer, which is a partition wall 22
The main casing 22 has a partition wall 2.
On one side of 2a, a primary chamber 24 is defined by the partition wall 22a and the primary diaphragm 23. This primary chamber 24 contains liquid fuel.
A fuel inlet 25 connected to a high-pressure cylinder (not shown) storing LPG is opened, and the opening degree of this fuel inlet 25 is adjusted by a primary valve 26. That is, the primary valve 26 is held at one end of a primary valve lever 28 that swings about a fulcrum 27, while the other end of the primary valve lever 28 is connected to the primary diaphragm via a hook 29. It is linked to 23. As a result, the opening degree of the fuel inlet 25 by the primary valve 26 is adjusted by the displacement of the primary diaphragm 23 according to the pressure inside the primary chamber 24, and the inside of the primary chamber 24 is always maintained at a predetermined pressure. Retained.

On the other hand, on the other side of the partition wall 22a, a secondary chamber 31 is defined by a secondary diaphragm 30, and this secondary chamber 31 and the primary chamber 24 are communicated with each other through a communication port 32. There is. This communication port 32
The opening degree of is adjusted by the secondary valve 33. That is, the secondary valve 33 is held at one end of a secondary valve lever 35 that swings about a fulcrum 34, while the other end of the secondary valve lever 35 is connected to the secondary diaphragm 30. This results in
When the secondary diaphragm 30 expands and deforms toward the secondary chamber 31, the degree of opening of the communication port 32 by the secondary valve 33 is increased, that is, the fuel pressure within the secondary chamber 31 is increased.

Note that although the vaporizer 21 is shown in a simplified manner in the drawings, the structure of the vaporizer 21 itself is the same as the conventional one, so a detailed explanation will be omitted.

The secondary chamber 31 of the vaporizer 21 and the bench lily 11 of the intake passage 8 are connected through a fuel passage (so-called low-pressure fuel passage) 41, and the fuel passage 41 has an electromagnetic opening/closing valve that is closed during deceleration. valve 4
2 are connected. This fuel passage 41 includes a bypass passage 43 that bypasses the on-off valve 42, and this bypass passage 43 includes a vent lily 11.
A check valve 44 is connected that allows flow only toward the secondary chamber 31 from the side. In addition, the back side of the secondary diaphragm 30 in the vaporizer 21,
That is, the secondary diaphragm chamber 36 is connected to the intake passage 8 between the compressor wheel 10a and the bench lily 11 via a pipe 45. Note that the on-off valve 42 is the throttle valve 12.
It is linked with an idle switch (not shown) that operates when the engine is fully closed, and when the idle switch operates and the engine speed reaches a predetermined value (a rotation speed slightly higher than the idle speed). It is starting to be considered closed.

Next, the operation of the above configuration will be explained. now,
When the throttle valve 12 is open and supercharging is being performed, supercharging pressure is acting on the secondary diaphragm chamber 36, so the fuel pressure in the secondary chamber 31 is high according to this supercharging pressure. becomes. Therefore,
During supercharging operation, a sufficient amount of fuel corresponding to the supercharging pressure is supplied from the secondary chamber 31 to the intake passage 8 from the fuel passage 41 through the open/close valve 42, which is open, and from the bench lily 11.

During sudden deceleration when the throttle valve 12 is fully closed from the supercharging state, the on-off valve 42 is quickly closed. This prevents a large amount of fuel in the secondary chamber 31 from being discharged into the intake passage 8 immediately after deceleration. Even during this deceleration, due to the inertia of the supercharger 10, the compressor wheel 1
Since supercharging pressure is acting in the intake passage 8 downstream of Oa, the secondary diaphragm chamber 36 remains under this supercharging pressure. However, the supercharging pressure in the intake passage 8 is also simultaneously supplied to the secondary chamber 31 through the check valve 44.
secondary diaphragm 30 toward the direction of increase in fuel pressure.
displacement is regulated. As a result, even immediately after the throttle valve 12 is opened again, the increase in fuel pressure in the secondary chamber 31 is suppressed, so overload is prevented.

In the above embodiments, an exhaust turbocharger is used as the supercharger 10, but the supercharger 10 can be similarly applied to a so-called supercharger type that is mechanically driven by an engine output shaft.

(Effects of the invention) As is clear from the above, the invention has the following effects:
Overburden when the throttle valve is opened again after deceleration can be prevented.

In particular, the above-mentioned prevention of overburden can be achieved by simply providing an on-off valve and a check valve in parallel with each other in the fuel passage from the vaporizer to the intake passage, so the structure is extremely simple and can be implemented at low cost and easily. It is.

[Brief explanation of the drawing]

The figure is an overall system diagram showing one embodiment of the present invention. 1... Engine, 8... Intake passage, 10... Supercharger, 11... Bench lily, 12... Throttle valve, 14... Exhaust passage, 21... Vaporizer,
24...Primary chamber, 25...Fuel inlet, 30...2
Secondary diaphragm, 31... Secondary chamber, 32... Communication port, 33... Secondary valve, 36... Secondary diaphragm chamber, 41... Fuel passage, 42... Open/close valve, 4
3... Bypass passage, 44... Check valve, 45...
Piping (for boost pressure supply).

Claims (1)

[Claims for Utility Model Registration] A supercharger and a throttle valve are disposed downstream of the supercharger in the intake passage of an engine, and a secondary chamber of a vaporizer is disposed in the intake passage between the supercharger and the throttle valve. In a gaseous fuel supply device for a supercharged engine, which supplies gaseous fuel from the vaporizer and supercharging pressure to a secondary diaphragm chamber of the vaporizer, the secondary chamber of the vaporizer and the intake passage An on-off valve that is closed during deceleration is connected to the fuel passage between the two, and a check valve that allows flow from the intake passage side toward the secondary chamber is connected in parallel with the on-off valve. A gaseous fuel supply device for a supercharged engine, characterized by: