JPH04171257A - Fuel supplier for gas engine - Google Patents

Abstract

PURPOSE:To suitably control a flow rate both at the time of acceleration and at the time of deceleration by making variable a capacity of a surge tank interposed between a regulator of a fuel passage and a main jet thereof in such a manner as to have a large capacity in a low load region of an engine while to have a small capacity in a high load region. CONSTITUTION:In a region of a small opening degree of a throttle valve 24, i.e., at a no-load or low load of an engine 4, a diaphragm 8 is displaced in such a position as to make a surge tank 7 have a large capacity. When the opening degree of the throttle valve 24 becomes large at the time of acceleration, the diaphragm 8 is displaced in such a position as to make the surge tank 7 have a small capacity, to thus increase a fuel pressure. Accordingly, a flow rate is increased so that fuel for acceleration is supplied. In addition, when the opening degree of the throttle valve 24 is large and a capacity of the surge tank 7 is reduced from the small capacity, the diaphragm 8 is displaced to the position to make the surge tank 7 have a large capacity, to decrease the fuel pressure, thereby decreasing the flow rate. Therefore, the flow rate can be suitably controlled both at the time of acceleration and at the time of deceleration.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a system for supplying gaseous fuel to an engine, and more specifically, for supplying fuel depending on venturi negative pressure of a mixer in an intake path. The present invention relates to a device having a function of properly supplying fuel during deceleration.

"Prior art" Gaseous fuel obtained by gasifying liquefied gas fuel such as LPG or LNG using a vaporizer, or gaseous fuel such as CNG or city gas, is brought to a predetermined negative pressure slightly lower than atmospheric pressure using a regulator. A system is well known in which the air is regulated and sucked in according to the venturi negative pressure of a mixer in the intake passage of the engine, and the flow rate is controlled by a main jet along the way and supplied to the engine.

In this system, it is preferable for the gaseous fuel to be maintained at a constant pressure from the regulator outlet to the main jet in order to properly control the flow rate. On the other hand, when the throttle valve of the mixer is operated at a rapid rate, that is, during transient operations such as during engine acceleration/deceleration, the response of the regulator to changes in fuel flow rate corresponding to changes in venturi negative pressure is delayed, so the pressure remains constant. is no longer maintained, making it impossible to properly control the flow rate, and as a result, the exhaust state and drivability of the engine deteriorate.

As a countermeasure, as shown in FIG.
Attempts have been made to install a surge tank 56 between the main jet 55 and the regulator 51 of the fuel passage 54 extending from the fuel passageway 54 to the venturi 53 of the mixer 52, and to have the surge tank 56 absorb pressure changes.

However, it is preferable that the surge tank 56 has a large capacity to cope with an increase in fuel flow rate such as during acceleration, and a small capacity to reduce the response delay of the regulator 51 when the fuel flow rate decreases such as during deceleration. is preferred. Therefore, in order to not only appropriately increase and supply acceleration fuel but also appropriately reduce fuel during deceleration, the required capacity should be set to an extent that can absorb pressure fluctuations due to hysteresis of the regulator 51 during steady operation. It was necessary to respond to both of these conflicting characteristics. That is, the surge tank 56 cannot be provided with the function of appropriately controlling the flow rate both during acceleration and deceleration.

[Problem to be Solved by the Invention] The problem to be solved by the present invention is to appropriately control the flow rate during transient operation when sucking gaseous fuel from the regulator and sending it to the mixer according to the venturi negative pressure. The point is that it is not possible. That is, it is an object of the present invention to provide a fuel supply device for a gas engine that is equipped with a mechanism that can properly control the flow rate both during acceleration and deceleration.

[Means for Solving the Problems] The present invention has solved the above-mentioned problems of a fuel supply device for a gas engine, which includes a regulator, a mixer, and a fuel passage connecting these, by the following means.

That is, the volume of the surge tank installed between the fuel passage regulator and the main jet is variable so that it has a large capacity in the low engine load range and a small capacity in the high engine load range.

More specifically, a part of the wall of the surge tank is formed by a diaphragm, and the volume of the surge tank is changed by displacing the diaphragm, and the diaphragm is displaced by negative pressure in the intake passage or by the displacement of the throttle valve. It is preferable to displace it depending on the position.

[Function] In the region where the opening degree of the throttle valve is small, that is, when the engine is under no load or under low load, the diaphragm is displaced to a position where the surge tank has a large capacity. When the throttle valve opening increases during acceleration, the diaphragm moves to a position where the surge tank has a small capacity, increasing the fuel pressure and increasing the flow rate to supply accelerating fuel. Further, when the throttle valve opening is large and the surge tank is decelerated from a state of small capacity, the diaphragm is displaced to a position where the surge tank has a large capacity, lowering the fuel pressure and reducing the flow rate. This allows the fuel flow rate to change quickly and appropriately in response to changes in the venturi negative pressure during acceleration and deceleration.

[Example] The present invention will be described in detail with reference to the drawings.

In FIG. 1, air that has passed through an air cleaner 1 is mixed with gaseous fuel in a mixer 2, and is supplied to an engine 4 through an intake manifold 3. - On the other hand, the gaseous fuel adjusted to a predetermined negative pressure slightly lower than atmospheric pressure by the regulator 5,
The fuel is sent to the venturi 21 of the mixer 2 through the fuel passage 6, and is sent from the main nozzle 22 to the intake passage 23 according to the venturi negative pressure.
is sucked out. The fuel passage 6 has a main jet 61 that controls the flow rate of gaseous fuel, and a first surge tank 7 is installed upstream thereof.

The surge tank 7 has a structure in which the inside of a housing 71 is partitioned by a diaphragm 8 into a fuel chamber 72 and a negative pressure chamber 9. The negative pressure chamber 9 is located slightly downstream of the idle position of the throttle valve 24 in the intake passage 23. A return spring 11 is installed at a location that becomes upstream as the opening increases, communicating through a negative pressure passage 10 and biasing the diaphragm 8 toward the fuel chamber 72.

In this embodiment having such a configuration, the negative pressure passage 1o transfers high negative pressure downstream of the throttle valve 24 to the negative pressure chamber 9 when the opening degree of the throttle valve 24 is small, that is, when the engine 4 is idling and under low load. to displace the diaphragm 8 toward the negative pressure chamber 9. That is, the fuel chamber 72 of the surge tank 7 is maintained at a constant large capacity, and the main jet 61 is regulated by the regulator 5.
The pressure fluctuation caused by the regulator 5 of the gaseous fuel, which is flow-controlled and sent to the mixer 2, is absorbed.

When acceleration operation is performed from the state shown in FIG. 1 and the throttle valve 24 is opened wide and the negative pressure passage 10 begins to introduce the low negative pressure upstream of the throttle valve 24 into the negative pressure chamber 9, the diaphragm 8 opens. It is displaced toward the fuel chamber 72 by the spring force of the return spring 11 . Therefore, the fuel chamber 72 has a small capacity, temporarily increases the fuel pressure, increases the flow rate, and supplies the accelerating fuel to the mixer 2. That is, the response delay of the regulator 5 when the venturi negative pressure increases is compensated by the surge tank 7 increasing the fuel pressure, and the fuel can be quickly and appropriately supplied to correspond to the increase in fuel flow rate due to acceleration operation. can.

During steady operation when the opening degree of the throttle valve 24 is large and the negative pressure on the downstream side thereof is introduced into the negative pressure chamber 9, the value of the negative pressure varies depending on the load of the engine 4 and the opening degree of the throttle valve 24. However, since it is considerably lower than the negative pressure on the downstream side in the low opening range, the diaphragm 8 can be displaced toward the fuel chamber 72 by appropriately setting the spring load of the return spring 11. I can do it. Therefore, the fuel chamber 72 is maintained at a constant small capacity and absorbs pressure fluctuations caused by the regulator 5.

When the throttle valve 24 closes during deceleration, high negative pressure on the downstream side is introduced into the negative pressure chamber 9, so the diaphragm 8 is displaced toward the negative pressure chamber 9 and returns to the state shown in FIG. Therefore, the fuel chamber 72 has a large capacity and temporarily lowers the fuel pressure.
This reduces the flow rate sent to the mixer 2. That is,
The response delay of the regulator 5 when the venturi negative pressure becomes low can be compensated for by lowering the fuel pressure in the surge tank 7, and fuel can be quickly and appropriately supplied in response to the decrease in fuel flow rate due to deceleration operation.

2 and 3 show different embodiments of the mechanism for displacing the diaphragm 8, respectively.

In FIG. 2, a diaphragm 8 is coupled to the plunger of a solenoid 13 that is excited by an electric signal sent from an electronic controller 12. A signal is input, and an electric signal is output that displaces the diaphragm 8 in the same manner as described above.

Figure 3 shows a throttle valve 2 with a push rod 15 protruding from the diaphragm 8.
4, and the return spring 11 is inserted into the fuel chamber 72, and the throttle valve 24
The opening/closing operation of the diaphragm 8 is transmitted to the diaphragm 8 via the link mechanism 16, and the diaphragm 8 is displaced in the same manner as described above.

[Effects of the Invention] According to the present invention, the volume of the pressure-absorbing surge tank installed in the fuel passage is variable so that it has a large capacity in the low load range of the engine and a small capacity in the high load range, thereby reducing transient operation. The gaseous fuel sometimes sent to the mixer can be quickly and appropriately controlled in flow rate regardless of the regulator, thereby improving the exhaust state and drivability of the engine.

[Brief explanation of drawings]

Fig. 1 is a layout diagram showing an embodiment of the present invention, Figs. 2 and 3 are partial diagrams showing different embodiments of the invention, and Fig. 4 is a layout diagram of a conventional example. ! , 4... Engine, 5... Regulator, 6... Fuel passage, 7
...Surge tank, 8...Diaphragm, 10...
・Negative pressure passage, 11... Return spring, 12... Electronic controller, 13... Solenoid, 14... Opening sensor,
16...Link mechanism, 21...Venturi, 23.
... Intake path, 24... Throttle valve, 61... Main jet 1. 1")

Claims (1)

[Claims] 1. The regulator has a regulator that adjusts the gaseous fuel to a predetermined pressure, a mixer installed in the intake passage and to which the gaseous fuel is sent in accordance with the venturi negative pressure, and a main jet for controlling the flow rate. In a gas engine fuel supply system comprising a fuel passage from the fuel passage to the venturi; a surge tank installed between the regulator of the fuel passage and the main jet has a large capacity in a low load range of the engine, and has a large capacity in a high load range of the engine. A fuel supply device characterized by having a variable volume with a small capacity. 2. The gas according to claim 1, wherein a part of the wall of the surge tank is a diaphragm, and the diaphragm is displaced by negative pressure at a point downstream of the throttle valve idle position of the intake path and upstream as the opening increases. Engine fuel supply system. 3. The fuel supply system for a gas engine according to claim 1, wherein a part of the wall of the surge tank is a diaphragm, and the diaphragm is displaced by a solenoid activated by an electric signal according to the opening degree of a throttle valve in the intake passage. 4. The fuel supply system for a gas engine according to claim 1, wherein a part of the wall of the surge tank is a diaphragm, and the diaphragm is displaced by a link mechanism linked to a throttle valve in the intake passage.