JPH06100115B2 - Fuel supply device for LP gas engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for an LP gas engine, and more particularly to a fuel supply device for an LP gas engine having improved startability.

(Prior Art) Conventionally, a method of forcibly increasing the fuel supply amount at the time of starting has been adopted as a means for improving the startability of an LP gas engine. For example, Japanese Examined Patent Publication No. 61-9506 discloses cranking of the engine. And a fuel switching device that automatically switches the fuel supplied to the vaporizer in order to selectively supply the gas-phase fuel when the engine temperature is a low temperature equal to or lower than a predetermined value, and to selectively supply the liquid-phase fuel when the engine temperature is lower than a predetermined value. An electromagnetic start for forcibly increasing the amount of fuel from the primary decompression chamber of the vaporizer to the secondary decompression chamber when the fuel is switched to the gas phase fuel by the fuel switching device and during cranking, and canceling the fuel increase after the cranking is completed. A fuel supply device for an LP gas engine provided with a fuel increasing device is disclosed.

(Problems to be solved by the invention) By the way, even if the ignition switch is turned off to stop the engine, the engine does not stop immediately but rotates for a short time due to inertia, and the mixture remaining in the intake manifold in the meantime. Stop after the air has been purged. on the other hand,
When the ignition switch is turned off, fuel cannot be supplied from the vaporizer. Therefore, like the fuel supply device for the conventional LP gas engine described above, even if the fuel supply amount is forcibly increased during cranking, when the engine is started next time, almost all the air-fuel mixture in the combustible range remains in the intake manifold. Since it is not, it is inevitable to delay the engine start at least until the fuel reaches the combustion chamber of the engine through the intake manifold.

An object of the present invention is to provide a fuel supply device for an LP gas engine, which can solve such problems and shorten the time required for starting.

(Means for Solving the Problems) According to the configuration of the present invention in accordance with the above object, an electromagnetic valve disposed in a slow fuel passage that connects the primary decompression chamber of the vaporizer and the mixer, and electrically disconnects the slow fuel passage, The gist of the present invention is to have a control means for opening the solenoid valve for a certain period of time when the ignition switch is turned off.

(Operation) According to the above configuration, when the ignition switch is turned off to stop the engine, the slow fuel passage is turned on for a certain period of time thereafter, and fuel is replenished from the primary decompression chamber to the mixer during that time. Therefore, after the ignition switch is turned off, even if the engine rotates due to inertia and the air-fuel mixture in the intake manifold is scavenged, a new air-fuel mixture in the combustible range is formed in the intake manifold after the engine is stopped. As a result, at the time of the next start, this air-fuel mixture flows into the combustion chamber of the engine, so that the time required for the start is shortened.

(Example) Below, the Example of this invention is described in full detail based on drawing. FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention.

In FIG. 1, 1 is a vaporizer, and a central partition wall 2
It has a room 3 and a room 4 of a closed structure partitioned by. Room 3 has primary diaphragm 5 and primary decompression chamber 6
Is divided into a primary pressure regulation chamber 7 and the primary decompression chamber 6 is a casing.
It is connected to a fuel tank 10 through an LP gas inflow passage 8 and a pipe 9 formed in 1a, and a pipe 11 is provided with a filter 11 and a solenoid valve 12 which is closed when the engine is stopped and shuts off fuel supply to the vaporizer 1. It is set up.

A first valve lever 14 pivotally supported by a shaft 13 is provided at the opening of the LP gas inflow passage 8 on the side of the primary decompression chamber 6 so as to cut off the LP gas inflow passage 8. The liquid LP gas flowing from the fuel tank 10 into the LP gas inflow path 8 pushes the first valve lever 14 open by its own pressure and enters the primary decompression chamber 6, where it is depressurized and vaporized. When the pressure in the primary decompression chamber 6 reaches a predetermined pressure, the first diaphragm 5 is biased to the left in the figure against the action of the first regulator spring 15 provided in the primary pressure regulation chamber 7, and the first diaphragm hook 16 causes the first diaphragm 5 to move. First
The valve lever 14 is biased to the closing side to shut off the LP gas inflow passage 8. When the pressure in the primary decompression chamber 6 decreases due to the consumption of fuel, the first valve lever 14 is biased to the open side and LP
The gas inflow path 8 is connected to allow the fuel to flow from the fuel tank 12 into the primary decompression chamber 6. In this way, the first valve lever 14
Keeps the pressure in the primary decompression chamber 6 at a constant predetermined pressure by repeatedly disconnecting the LP gas inflow passage 8.

The chamber 4 is divided into a secondary decompression chamber 18 and a secondary pressure regulation chamber 19 by a second diaphragm 17, and the secondary decompression chamber 18 is connected to the primary decompression chamber 6 by a passage 20 penetrating the central partition wall 2 and is also main. It is connected to the venturi portion 31 of the mixer 30 via the fuel passage 21 so that the venturi negative pressure is exerted. A second valve lever 23 pivotally supported by a shaft 22 for opening and closing the passage 20 is provided at the opening of the passage 20 on the side of the secondary decompression chamber 18, and a second regulator spring 24 is provided.
Is biased to the closing side by. This second valve lever
The second diaphragm 17 is biased to the left side in the figure by the Venturi negative pressure exerted on the secondary decompression chamber 18, and is biased to the open side via the presser 25 to communicate with the passage 20, or While being biased to the closed side by the two regulator springs 24, the fuel introduced from the passage 20 into the secondary decompression chamber 18 is depressurized to almost atmospheric pressure, and the pressure is kept constant. Then, the fuel in the secondary decompression chamber 18 is delivered to the mixer 30 via the main fuel passage 21 by the Venturi negative pressure, is mixed there with intake air, and is supplied to the engine (not shown) through the intake manifold 33.

The primary pressure adjusting chamber 7 is communicated with the secondary decompression chamber 4 via a passage (not shown), and the secondary decompression chamber 4 is open to the atmosphere via a passage 1b formed in the casing 1a.

Next, the primary decompression chamber 6 is connected to the venturi portion 31 of the mixer 30 via the slow fuel passage 26, and the slow fuel passage
26 is a solenoid valve that is controlled by the output signal of the control unit 27 to selectively connect and disconnect the slow fuel passage 26.
28 are provided.

The control unit 27 includes a starter switch 29a operated when the engine is started, an ignition switch 29b operated when the engine is ignited, and an LP gas mixer 30.
A throttle switch 29c that is turned on when the throttle valve 32 is in the idle opening position and is turned off when the throttle valve 32 is not in the idle opening position, and a rotation speed detection unit 29d that detects an engine rotation speed and outputs a rotation speed signal, Temperature detection means 29e that detects the temperature of engine cooling water and outputs a temperature signal
And are connected. And control unit 27
Can be configured using a microcomputer that preferably operates according to a predetermined program.

Hereinafter, an example of a control method when the control unit 27 is configured using a microcomputer will be described based on the flowchart shown in FIG.

First, in step 101, it is judged whether or not the starter switch 29a is operated, and if the starter switch 29a is on, that is, if the engine is started, step 11
3, the solenoid valve 28 has a preset duty ratio A
(%) Controls the opening. Therefore, simultaneously with the cranking, the fuel is supplied from the primary decompression chamber 6 to the mixer 30 through the slow fuel passage 26. By properly setting the duty ratio A, an appropriate amount of fuel necessary for starting is supplied through the slow fuel passage 26.

If the starter switch 29a is off, then in step 102 it is determined whether or not the ignition switch 29b is on. Ignition switch 29b to stop the engine
When is turned off, the timer built in the microcomputer is set to the time T ₁ in step 103, and it is determined in step 104 whether or not there is a timeout. And step 10 unless it times out
In step 5, the solenoid valve 28 is controlled to be opened with the duty ratio B, and when the time-out occurs, the routine proceeds to step 107, where the solenoid valve 28 is controlled to be closed and the fuel supply is stopped. The time T ₁ and the duty B set by the timer are set during the slow fuel passage.
It is set in advance by an experiment or the like so that the fuel supplied to the mixer 30 through 26 forms an air-fuel mixture in the combustible range in the intake manifold 33. Therefore, after the ignition switch 29b is turned off, even if the engine rotates due to inertia, a mixture in the combustible range is formed in the intake manifold 33, so that when the engine is started next time, this mixture enters the combustion chamber of the engine. Inflow and reduce start-up time.

Next, when the ignition switch 29b is turned on, that is, when the engine is ignited, in step 106, the reference starting rotation speed NE ₁ stored in advance in the ROM of the microcomputer and the rotation speed signal are input from the rotation speed detecting means 29d. The engine speed NE thus determined is compared. Reference starting speed
NE ₁ is a standard for determining whether or not the engine has started normally and has reached the required starting speed. If the engine speed NE is lower than the reference starting speed NE ₁ , the engine will start due to some trouble. Is not completed normally, the routine proceeds to step 107, where the solenoid valve 28 is controlled to be closed,
The fuel supply is stopped.

When the engine speed NE is larger than the reference starting speed NE ₁ and the engine start is normally completed, it is determined in step 108 whether or not the throttle valve 32 is at the idle opening position. When the accelerator pedal (not shown) is depressed and the vehicle shifts to acceleration, the timer is set to time T ₂ in step 109, it is determined in step 110 whether or not there is a timeout, and if the timeout does not occur, in step 111, the electromagnetic wave is set. The valve 28 is controlled to open at the duty ratio C (%), and when the time T ₂ has elapsed, step 113
Then, the opening control is performed with the duty ratio A. Since the duty ratio C is set larger than the duty ratio A, during acceleration,
A large amount of fuel is supplied.

When the throttle valve 32 is in the idle opening position and the throttle switch 29c is in the ON state, the engine speed NE input as the speed signal in step 112 and the cooling water temperature THW input as the temperature signal from the temperature detecting means 29e. Based on the above, it is determined whether the operating state of the engine is idle operation or deceleration operation. The characteristic curve shown in FIG. 3 is stored in advance in the ROM of the microcomputer. The characteristic curve in FIG. 3 is a reference for determining whether the operating state is the idle operation or the deceleration operation such as long downhill running based on the engine speed and the cooling water temperature. NE, cooling water temperature on the horizontal axis
It is displayed by taking THW. Then, when the input engine speed NE and the input cooling water temperature THW are within the region α surrounded by the vertical and horizontal axes and the characteristic curve, the engine is in the idle operation state, and when it is outside the region α, the deceleration operation is performed. Indicates that the state is.

However, when the rotational speed NE and the cooling water temperature THW are outside the range α, that is, during deceleration operation, the routine proceeds to step 107, where the solenoid valve 28
Is closed and the fuel supply is stopped. On the other hand, when it is in the region α, that is, during idle operation, the routine proceeds to step 113, where the solenoid valve 28 is controlled to communicate with the duty ratio C.

In this embodiment, the solenoid valve 28 is duty controlled,
It may be simply on / off control.

As described above, according to the first embodiment, when the ignition switch 29b is turned off to stop the engine, the solenoid valve 28 is controlled to be open for a certain period of time, during which fuel flows from the primary pressure reducing chamber 6 to the slow fuel passage 26. It is replenished to the mixer 30 through. Therefore, after the ignition switch 29b is turned off, even if the engine rotates due to inertia and the air-fuel mixture in the intake manifold 33 is scavenged, the fuel supplied after the ignition switch 29b is turned off (engine stopped state) mixes the combustible range. Air is formed and this mixture is
Since it flows into the combustion chamber of the engine, the starting time is shortened.

Also, by operating the starter switch 29a, the slow fuel passage 2
Since the solenoid valve 28 that opens and closes 6 is controlled to open and close, fuel is supplied at the same time as cranking, and the startability of the LP gas engine can be improved.

Furthermore, the starter switch 29a and the ignition switch 29
b, based on the outputs of the throttle switch 29c, the rotation speed detecting means 29d, and the temperature detecting means 29e, it automatically determines whether the engine is in the idle operation state or the deceleration operation state, and opens and closes the solenoid valve 28 during the idle operation. The fuel is controlled to supply the required amount of fuel, and the solenoid valve 28 is controlled to be closed to stop the fuel supply during deceleration operation such as when traveling on a long slope. Therefore, the fuel supply can be controlled appropriately and promptly according to the operating state.

Next, a second embodiment of the present invention is shown in FIG. First mentioned above
In the embodiment, the control unit 27 including a microcomputer is used as the control means of the solenoid valve 28.
In the embodiment, instead of this, the solenoid valve 28 is controlled by the drive circuit 40 shown in FIG.

In FIG. 4, 41 is a battery, 42 is an ignition switch, 43 is a backflow prevention diode, 44 is a resistor, 45 is a capacitor, 46 is a drive coil of the solenoid valve 28, and a series circuit of a resistor 44 and a capacitor 45 and The drive coil 46 is connected to the battery 41 through the ignition switch 42 and the backflow prevention diode 43, and the negative side of the battery 41 is body-grounded.

According to this drive circuit 40, when the ignition switch 42 is turned on, the capacitor 45 is charged and the drive coil
Since the solenoid 46 is energized, the solenoid valve 28 is opened and the slow fuel passage 26 is conducted. On the other hand, when the ignition switch 42 is turned off to stop the engine, the battery 41 and the drive coil 46 are disconnected from each other, but since a discharge current from the capacitor 45 flows in the drive coil 46, the ignition switch 42 is turned off for a certain period of time T. The open state of the solenoid valve 28 is maintained by ₁ and fuel is replenished to the mixer 30 from the slow fuel passage 26 during that time. This delay time T ₁ can be adjusted by appropriately setting the resistance value of the resistor 44 and the capacitance of the capacitor 45.

(Effects of the Invention) According to the present invention, a solenoid valve is provided in the slow fuel passage connecting the primary decompression chamber of the vaporizer and the mixer, and the solenoid valve is opened for a certain period of time after the ignition switch is turned off. With this configuration, when the ignition switch is turned off to stop the engine, the slow fuel passage is made conductive for a certain period of time thereafter, and fuel can be replenished from the primary pressure reducing chamber to the mixer through the slow fuel passage. As a result, after the ignition switch is turned off, even if the engine rotates due to inertia and the air-fuel mixture in the intake manifold is scavenged, a new air-fuel mixture in the combustible range is newly prepared in the intake manifold. Can be shortened.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention, FIG. 2 is a flow chart diagram showing a control method by a control unit of the present embodiment, and FIG. 3 is a reference for distinguishing between idle operation and deceleration operation. Engine speed-cooling water temperature characteristic curve, FIG. 4 is a configuration diagram of a drive circuit used in the second embodiment of the present invention. 1 ... Vaporizer, 6 ... Primary decompression chamber, 26 ... Slow fuel passage, 27 ... Control unit (as control means), 28 ... Solenoid valve, 29b, 42 ... Ignition switch, 30 ... Mixer , 40 …… Drive circuit (as a control means).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadao Inao 1-1-1 Kyowa-cho, Obu-shi, Aichi Aisan Industry Co., Ltd. (56) References Flat 2-1471 (JP, Y2)

Claims (1)

[Claims] 1. A solenoid valve which is disposed in a slow fuel passage connecting a primary decompression chamber of a vaporizer and a mixer, and which shuts off conduction of the slow fuel passage, and when the ignition switch is turned off, the solenoid valve is operated for a certain period of time. A fuel supply device for an LP gas engine, which is provided with a control means for performing an opening operation.