JPH0826820B2 - Liquefied petroleum gas supply device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel supply device for an internal combustion engine that uses liquefied petroleum gas (LPG) as a fuel.

[Conventional technology]

As a prior art related to the present invention, Japanese Patent Application Laid-Open No. 61-126364
Japanese Patent Laid-Open No. 61-207868 is known.

In the liquefied petroleum gas fuel supply system for an internal combustion engine disclosed in the above-mentioned JP-A-61-126364, two fuel passages are formed in parallel, and one fuel passage is based on an electric signal from a control device. An opening degree variable control valve is arranged in which the opening degree is continuously changed by a controlled step motor. A power valve that is opened / closed by an on / off signal from the control device is arranged in the other fuel passage. The variable opening control valve is controlled so that the air-fuel ratio has a predetermined value according to the operating conditions of the engine. On the other hand, the power valve is closed during normal operation, but is switched from closed to open during acceleration operation with high load, and the fuel amount is increased by the amount of fuel passing through the fuel passage opened by the power valve. The air-fuel mixture is corrected to rich, improving acceleration operation performance.

Further, in the control method of the fuel supply device for an internal combustion engine disclosed in Japanese Patent Laid-Open No. 61-207868, the air-fuel ratio of the air-fuel mixture is always properly corrected in accordance with the intake air temperature, the cooling water temperature, the acceleration, etc. This is a control method that can be performed.

[Problems to be solved by the invention]

In a liquefied petroleum gas supply device for an internal combustion engine having a variable opening control valve whose opening is variable by a step motor and a power valve, an air-fuel ratio is controlled to lean when the throttle valve has a small opening and a throttle valve is used. The air-fuel ratio is controlled to be rich at high load when the opening degree of is large. Therefore, when the opening of the throttle valve becomes equal to or larger than a predetermined opening, there is a problem that the air-fuel ratio is largely changed by the fuel supply from the power valve, and the drivability is deteriorated. In other words, the mixture rapidly changes from lean to rich at the moment when the power valve is switched from closed to closed in order to shift from steady operation to acceleration operation in the vehicle, so the torque generated by the engine changes suddenly and the air-fuel ratio is switched. There is a problem that the shock caused by is large.

The present invention focuses on the above-mentioned problems, eliminates a sudden change in the air-fuel ratio when the power valve is switched from closed to open, and liquefied petroleum gas for an internal combustion engine capable of preventing a shock during acceleration of the vehicle. An object is to provide a supply device.

[Means for solving problems]

In the liquefied petroleum gas supply device for an internal combustion engine according to the present invention in accordance with this object, an opening degree variable control valve whose opening degree is continuously varied by a step motor controlled based on an electric signal from an electronic control device is arranged. Has a first fuel system and a second fuel system in which a power valve that is opened / closed by an on / off signal from the electronic control unit is arranged. When the load is low, the power valve is closed and opened. Liquefied petroleum gas as an internal combustion engine that controls the air-fuel ratio by supplying fuel from the variable degree control valve and controls the air-fuel ratio by supplying fuel from both the variable opening degree control valve and the power valve when the load is high. In the electronic control device, when the power valve is switched from closed to open and the opening of the throttle valve is equal to or larger than a predetermined opening, the electronic control device is applied when the power valve is closed. The function of adding a correction value that increases the step value of the step motor to the step motor control map of step 1 above, and when the correction value reaches a predetermined value, the power valve is opened and the step motor is operated by the power valve. And a function of controlling based on the second step motor control map applied at the time of opening.

[Action]

In the liquefied petroleum gas supply device for an internal combustion engine configured as described above, when the load increases and the power valve is switched from closed to open, the electronic control device based on the correction value immediately before the power valve is opened. Signal, the step motor is controlled so that the opening degree of the opening degree control valve gradually increases. As a result, the air-fuel ratio of the air-fuel mixture is controlled to gradually become rich, and the power valve is switched to open when the air-fuel ratio reaches the predetermined air-fuel ratio. At the same time, the step motor is controlled to decrease the opening degree of the opening degree control valve based on the second step motor control map.

Therefore, the air-fuel ratio changes smoothly until the power valve is opened, and at the same time when the power valve is opened, the amount of fuel supplied from the variable opening control valve decreases. There is no change, and the shock at the time of acceleration due to the sudden change in torque is suppressed to a small level.

〔Example〕

A preferred embodiment of a liquefied petroleum gas supply device for an internal combustion engine according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, 1
Indicates an internal combustion engine that uses liquefied petroleum gas (hereinafter referred to as "LPG") as a fuel. In this internal combustion engine 1, a mixture of LP gas and air is supplied to the intake port 4 from the carburetor 2 and the intake manifold 3, and the mixture is sucked into the combustion chamber 5 from the intake port 4.

The capletter 2 is provided with a venturi portion 7 provided in the middle of the intake passage 6, and a main fuel port 8 and a power fuel port 9 opened toward the intake passage 6 in the venturi portion 7.
And a throttle valve 10 provided midway in the intake passage downstream of the venturi portion 7, and an idle operation bypass air passage provided by bypassing the throttle valve 10.
11 and has. The main fuel port 8 is connected to the LPG regulator 15 via the main fuel passage 12 as the first fuel system.
It is connected to the. The LPG regulator 15 is a device that includes a primary decompression chamber and a secondary decompression chamber, and vaporizes and regulates LPG. Similarly, the power fuel port 9 is connected to the LPG regulator 15 via a power fuel passage 13 as a second fuel system.

The main fuel passage 12 flows through the main fuel passage 12.
A variable opening control valve 16 for adjusting the flow rate of LP gas is provided. This variable opening control valve 16 is an electronic control unit (ECU) 1
Step motor 1 controlled based on electrical signals from 7
The opening is controlled by 8. The step motor 18 performs a step operation according to the value of the control signal output from the ECU 17, for example, the pulse number of the pulse signal, and the step value increases according to the increase of the pulse number so that the valve element 19 moves toward the larger opening degree. It is designed to be moved.

In the middle of the power fuel passage 13, the power fuel passage 13
A power valve 20 for opening and closing is provided. The power valve 20 is opened and closed by an on / off signal from the ECU 17. Power valve 20 is a drive lever
It is connected to a diaphragm device 23 via 22, and the diaphragm device 23 is connected to a negative pressure switching valve (VSV) 26. In other words, the power valve 20 is driven to be closed when the negative pressure is introduced to the negative pressure chamber 24 of the diaphragm device 23, whereas the power valve 20 is opened when the negative pressure is not introduced to the negative pressure chamber 24. It is designed to be driven. VSV26 is E
When the engine is connected to the CU17 and the load on the engine becomes high, the power valve 20 is opened, and the LP of a predetermined flow rate is supplied from the power fuel port 9.
It is designed to eject gas.

An air cleaner 27 is located at the upstream end of the intake passage 6, and an intake air temperature sensor 28 is provided between the air cleaner 27 and the venturi portion 7. A pressure sensor 30 that measures the intake pipe negative pressure is provided immediately downstream of the throttle sensor 29 that detects the opening degree of the throttle valve 10.

The fuel of the second fuel system is supplied from the primary decompression chamber of the LPG regulator 15. The fuel passage of the second fuel system is branched on the way into a slow passage 31 and an auxiliary fuel passage 33 that is provided immediately downstream of the carburetor throttle valve 10 and supplies fuel to an auxiliary fuel injector 32 that injects auxiliary fuel. The fuel supply to these passages is controlled by the slow lock valve 34.

The slow lock valve 34 is opened and closed by a negative pressure switching valve (VSV) 36 which is connected to the intake passage 6 via a check valve 35 and switches the supply pressure to the slow lock valve 34 between the intake pipe negative pressure and the atmospheric pressure. Be seen.

The VSV 36 and the auxiliary fuel injector 32 are connected to the ECU 17. VSV36 operates based on a signal from the ECU 17, and the operation opens and closes the slow lock valve 34,
Fuel is supplied or cut to the slow passages 31 and 33. In addition, the auxiliary fuel injector 32 is
Based on the signal from 7, it is possible to change the fuel injection amount when the fuel cut is restored. ECU17 has
An ON / OFF signal of an air conditioner (not shown) is input, and the ECU 17 incorporates a circuit for variably controlling a signal sent to the auxiliary fuel injector 32 based on the ON / OFF signal. Further, a reference position signal and a crank angle signal, which are signals for calculating the rotation speed, are input to the ECU 17 from a distributor 38 connected to the ECU 17 via an igniter 37. Further, a throttle fully closed position signal from the throttle sensor 29 is also input to the ECU 17, so that it is possible to determine when the engine is decelerating.

Incidentally, 48 is an oxygen concentration sensor attached to the exhaust pipe 39,
Reference numeral 40 denotes an exhaust temperature sensor and 41 denotes an engine water temperature sensor, and these signals are also input to the ECU 17. 42 is the EGR valve
The VSV that controls the operation of 43, the VSV that controls the operation of the swirl control valve (SCV) 45 that controls the flow direction of the intake air, and the operation of these VSV are also controlled based on the signal from the ECU 17.

The first step motor control map applied to the ECU 17 when the power valve 20 is closed when the power valve 20 is switched from closed to open and the opening of the throttle valve 10 is equal to or larger than a predetermined opening. Correction value SVL that increases the step value of the step motor over time in (S ₃ MAP)
It has a function to add. In addition, the ECU 17 opens the power valve 20 when the correction value SVL reaches the predetermined value KVL, and sets the step motor 18 to the second step motor control map (S ₁ MA) which is applied when the power valve 20 is open.
It has a function to control based on P).

3 and 4 show control maps of the step motor. FIG. 3 shows a first step motor control map applied when the power valve 20 is in a closed state. As shown in the figure, the horizontal axis indicates the engine speed N.
E, the vertical axis is the intake pipe negative pressure PM. Therefore, when the load is low, the step motor 18 is controlled based on the relationship between the two, and the opening of the variable opening control valve 16, that is, the position of the valve body 18 is adjusted to one of the areas A to D. FIG. 4 shows a second step motor control map that is applied when the load increases and the power valve 20 is in the open state. As with the above, the horizontal axis represents the engine speed NE and the vertical axis represents the vertical axis. The intake pipe negative pressure PM is taken into. In other words, the step motor 18 is controlled from the relationship between the two during high load such as acceleration.
The position of the valve body 18 of the variable opening control valve 16 is adjusted to any one of the areas E to I.

Next, the operation of the above liquefied petroleum gas supply device for an internal combustion engine will be described.

First, the control of the variable opening control valve 16 and the power valve 20 will be described based on the flow chart of FIG. As shown in the figure, first, the CPU in the ECU 17 is interrupted at the required time, and it is determined in step 101 whether the power valve 20 is open or closed. As a result, the power valve
If 20 is closed, the routine proceeds to step 102, where it is judged if the opening VL of the throttle valve 10 is equal to or larger than a predetermined opening Tθ. Here, if the opening VL of the throttle valve 10 is larger than the predetermined opening Tθ, the routine proceeds to step 103, where a flag FSVL indicating whether correction control of the step motor is being performed is determined. At the beginning of the routine, FSVL = 0, that is, step motor correction control is not performed, so the routine proceeds to step 104, where the flag FSVL is set. Next, the routine proceeds to step 105, where the correction amount of the step motor is initialized to zero, and then the routine proceeds to step 106 where a timer for counting the correction cycle amount of the step motor is started. Then, in step 107, the correction amount SVL is added to the first step motor control map (S ₃ MAP).
The step motor is controlled with the value obtained by adding the step position as the step position, and the routine proceeds to step 116 where the routine is ended.

Returning to the previous step, if the power valve 20 is opened in step 101, that is, if it is in a high load state, the process directly proceeds to step 114, and the step motor 18 is the second step motor control map (S ₁ MAP). Engine speed NE of
The step position is calculated by the intake pipe negative pressure PM, and the opening degree of the opening degree control valve 16 is adjusted. Then step 116
And the routine is ended. In step 102, the opening VL of the throttle valve 10 is set to the predetermined opening Tθ.
If it is below, that is, if it is in the low load state, the routine proceeds to step 115, where the step motor 18 is the engine speed NE of the first step motor control map (S ₃ MAP),
The step position is calculated by the intake pipe negative pressure PM, and the opening degree of the opening degree control valve 16 is adjusted. Then step 116
And the routine ends.

Next, at step 103, the flag FSVL = 1 at the next time interruption, so in this case, step
Proceeding to step 108, it is determined in step 108 whether the timer has passed a predetermined time. Here, if the elapsed time does not reach the predetermined cycle T ₀ , the process directly proceeds to step 107, and the step motor 18 is controlled. When the predetermined time has elapsed, step 109
Go to and increment the correction value SVL,
In step 110, it is determined whether or not has reached a predetermined value KVL. As a result, when the correction value SVL does not reach the predetermined value KVL, the process proceeds to step 106 to restart the timer,
This routine ends. In step 110, if the correction value SVL has reached the predetermined value KVL, proceed to step 111 to open the power valve 20, clear the flag FSVL indicating that the correction control is in progress in step 112, and end this correction control. To do. Then, the process directly proceeds to step 113, the step motor 18 is controlled based on the second step motor control map (S ₁ MAP) applied when the power valve is opened, and the routine ends.

In this way, immediately before the power valve 20 is closed to open, as shown in FIG. 5, the opening variable control valve 16 is opened with a certain step value in the first step motor control map over time. Correction value SV so that the degree gradually increases
Since L is added up to the predetermined value KVL, the amount of LP gas supplied from the variable opening control valve 16 to the venturi section 7 is gradually increased, and the air-fuel ratio is changed little by little until the point P at which the power valve 20 is opened. It Then, the opening degree of the opening degree control valve 16 is returned to an appropriate opening degree as shown by an arrow Q at the same time when the power valve 20 is opened. Therefore, the change of the air-fuel ratio becomes significantly smoother than that of the conventional device, the torque fluctuation of the engine due to the control of the air-fuel ratio is suppressed to a small level, and the shock during acceleration is suppressed to a substantially negligible level.

〔The invention's effect〕

As described above, in the case of the liquefied petroleum gas supply device for an internal combustion engine of the present invention, the electronic control device adds the correction value to the first step motor control map when the power valve is switched from closed to open. The step valve is controlled so that when the correction value reaches the predetermined value, the power valve is opened and the step motor is controlled based on the second step motor control map. Therefore, the power valve is switched from closed to open. The change in the air-fuel ratio over time can be smoothed. As a result, the torque fluctuation of the engine is suppressed to a small level, and it is possible to obtain the effect that it is possible to prevent the occurrence of shock due to air-fuel ratio control during acceleration.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a liquefied petroleum gas supply device for an internal combustion engine according to an embodiment of the present invention, FIG. 2 is a flow chart of control in the device of FIG. 1, and FIG. 3 is first step motor control. FIG. 4 is a map of the second step motor control map, and FIG. 5 is a graph showing the elapsed time and the opening of the variable opening control valve when the correction value is added to the step value of the first step motor control map. FIG. 10 …… Throttle valve 12 …… First fuel system (main fuel passage) 13 …… Second fuel system (power fuel passage) 16 …… Variable opening control valve 17 …… Electronic control unit (ECU) 18… … Step motor 20 …… Power valve S ₃ MAP …… First step motor control map S ₁ MAP …… Second step motor control map SVL …… Correction value

Claims (1)

[Claims] 1. A first fuel system in which a variable opening control valve whose opening is continuously changed by a step motor controlled based on an electric signal from an electronic control device is arranged, and the electronic control device. A second fuel system in which a power valve that is opened / closed by an ON / OFF signal from the engine is disposed, and the power valve is closed when the load is low, and the air-fuel ratio is controlled by fuel supply from the variable opening control valve. However, in a high-load internal combustion engine that uses liquefied petroleum gas as a fuel to control the air-fuel ratio by supplying fuel from both the variable opening control valve and the power valve, the electronic control unit controls the power valve from closing. When the opening of the throttle valve becomes equal to or larger than a predetermined opening when switching to open, the first step motor control map that is applied when the power valve is closed is shown as time passes. A function for adding a correction value for increasing the step value of the step motor, and a second step motor for opening the power valve when the correction value reaches a predetermined value and for applying the step motor when the power valve is open. A liquefied petroleum gas supply device for an internal combustion engine, which has a function of performing control based on a control map.