JP2535946B2 - Fuel supply control device for LPG engine - Google Patents

Description

The present invention relates to a fuel supply control device for an engine that uses liquefied petroleum gas as a fuel.

[Prior Art] An engine using liquefied petroleum gas as fuel (hereinafter simply referred to as
Called the LPG engine. ), Two fuel passages are normally provided in parallel, and one fuel passage is provided with a control valve with a variable opening (usually the opening is controlled by a step motor, which will be simply referred to as a step valve hereinafter). The other fuel passage is provided with a control valve (hereinafter simply referred to as a power valve) that opens and closes the fuel passage.

The step valve, which is a variable opening control valve, has its opening controlled based on the basic step number determined by the engine speed and the load, for example, the intake pipe pressure. By controlling the opening of the step valve, the fuel supplied to the engine during operation is controlled to a predetermined amount. On the other hand, the power valve is closed during normal operation (hereinafter referred to as open control) to prevent fuel from being supplied to the engine.
During acceleration, the valve is opened to increase the fuel supply amount and improve acceleration response.

Conventionally, in such an LPG engine, when the lean signal of the air-fuel ratio from the O ₂ sensor is continuously output for a predetermined time or longer, the power valve is switched to the open state, so that the step valve fails near the fully closed state. A fuel supply control device has been proposed which prevents abnormal heating of a catalyst for purifying exhaust gas when it does not operate due to disconnection or the like (see "liquefied petroleum gas fuel supply for internal combustion engine" in Japanese Patent Laid-Open No. 62-85157). apparatus").

[Problems to be Solved by the Invention] However, in the fuel supply control device for the LPG engine described above, it is possible to prevent abnormal heating of the catalyst when the air-fuel ratio of the LPG engine becomes over lean, but When abnormal heating of the catalyst occurs due to poor ignition, which is another cause, the amount of fuel supply becomes too large and the air-fuel ratio of the engine shifts to the rich side simply by switching the power valve to the open state. On the contrary, there is a problem that it promotes abnormal heating of the catalyst.

The present invention has been made in view of the above problems, not to mention abnormal heating of the catalyst due to over lean of the air-fuel ratio, it is also possible to prevent abnormal heating of the catalyst caused by poor ignition, fuel of the LPG engine An object is to provide a supply control device.

Structure of the Invention [Means for Solving the Problems] In order to achieve the above object, the present invention has the following structures as means for solving the problems.
That is, as illustrated in FIG. 1, the fuel supply control device for an LPG engine of the present invention includes a venturi M3 and a liquefied petroleum gas source M4 formed in an intake passage M2 of an engine M1 that uses liquefied petroleum gas as a fuel. A first fuel passage M5 communicating with the first fuel passage M5; a variable control valve M6 provided in the first fuel passage M5 for controlling the amount of fuel passing through the first fuel passage M5; and the first fuel passage M5. Separately from the Venturi M3
And a liquefied petroleum gas source M4, and a second fuel passage M7, and an on-off valve M8 provided in the second fuel passage M7 for switching the second fuel passage M7 to an open state or a closed state, Based on the operating state including at least the load of the engine M1 determines the opening target value of the variable control valve M6, the variable control valve control means M9 for controlling the opening of the variable control valve M6, and the on-off valve M8. An on-off valve control means M10 for controlling opening and closing, and a fuel supply control device for an LPG engine comprising: a catalyst heating state detecting means for detecting a heating state of an exhaust gas purifying catalyst M12 provided in an exhaust passage M11 of the engine M1. M13, the catalyst M12 detected by the catalyst heating state detection means M13
When the heating state of the above is a predetermined heating state or more, the opening target value determined by the variable control valve control means M9 is corrected to the closing side, and the opening / closing valve is controlled via the opening / closing valve control means M10. Valve correction control means M14 to switch M8 to open state
, And is the gist.

Here, the catalyst heating state detection means M13 may be any as long as it can directly or indirectly detect the heating state of the catalyst M12, for example, an exhaust temperature sensor provided in the exhaust passage M11, or in front of the driver's seat. An exhaust temperature lamp or the like provided on the console located at this position corresponds to this.

[Operation] In the fuel supply control device for an LPG engine of the present invention configured as described above, the variable control valve control means M9 allows the first
The target opening value of the variable control valve M6 provided in the fuel passage M5 is determined based on the operating state of the engine M1 including at least the load, and the liquefied petroleum gas source M4 passes through the first fuel passage M5 to the venturi M3. It controls the amount of fuel supplied, and is supplied from the liquefied petroleum gas source M4 to the venturi M3 via the second fuel passage M7 by the on-off valve control means M10 at times other than normal operation such as acceleration. The supply of fuel is controlled. Moreover, when the heating state of the exhaust gas purifying catalyst M12 detected by the catalyst heating state detecting means M13 is a predetermined heating state or more, the valve correction control means M14 determines the variable control valve control means M9. The opening target value is corrected to the closing side, and the opening / closing valve M8 is switched to the open state via the opening / closing valve control means M10. Therefore, the catalyst
Even if the open / close valve M8 is switched to the open state when M12 is in a heating state above a predetermined level, the opening target value of the variable control valve M6 is corrected to the close side, and therefore the venturi M3 has an excessive fuel amount. To keep the air-fuel ratio in the lean range without being supplied.

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail.

FIG. 2 is a schematic configuration diagram of an engine (hereinafter simply referred to as LPG engine) system using liquefied petroleum gas as a fuel supply control device for an LPG engine which is an embodiment of the present invention.

The LPG engine 1 is in communication with an air cleaner 3 via an intake manifold 2, takes in outside air from the air cleaner 3, and also communicates with a venturi 4 formed in the intake manifold 2 via an ordinary fuel passage 5 and an acceleration fuel passage 6 to an LPG engine 1. Liquefied petroleum gas from regulator 7 (hereinafter simply LPG
Call. ) Is taken in, the mixture of the outside air and LPG is exploded and burned to obtain a driving force, and then the exhaust gas is discharged from the exhaust manifold 8 to the outside. In addition,
The normal fuel passage 5 and the accelerating fuel passage 6 are heated by the cooling water of the LPG engine 1, and the LP flowing through these passages 5 and 6
The vaporization of G is promoted.

Further, the opening degree of the normal fuel passage 5 is controlled by the step motor 9 provided in the middle of the normal fuel passage 5, and the acceleration fuel passage 6 is controlled.
Is opened by a power valve 10 provided midway in the acceleration fuel passage 6 only during acceleration. On the other hand, the intake amount of the air-fuel mixture of outside air and LPG is determined by the opening degree of the throttle 11 provided in the intake manifold 2. Further, the exhaust gas discharged from the exhaust manifold 8 is purified by passing through the three-way catalyst 12, and a part of the exhaust gas is recirculated to the exhaust system by the so-called exhaust gas recirculation device 13. The swirl device 14 attached to the upper part of the LPG engine 1
The swirl flow of the air-fuel mixture is generated in the cylinder of the engine 1. Power valve 10, exhaust gas recirculation device
The swirl device 14 and the swirl device 14 are turned on and off by negative pressure switching valves 16, 17, and 18, respectively. Also, by the negative pressure switching valve 19,
The slow lock valve 22 that opens and closes the slow fuel passage 21 that supplies the fuel for idle is turned on and off, thereby performing fuel cut and the like during deceleration. The check valves 16a and 19a respectively connected to the negative pressure switching valves 16 and 19 prevent the power valve 10 and the slow lock valve 22 from malfunctioning when the negative pressure of the intake manifold 2 is reduced.
Each of these negative pressure switching valves 16, 17, 18, 19 is electrically connected to an electronic control unit (hereinafter simply referred to as an ECU) 23, and its on / off timing is controlled. Also,
The ECU 23 includes an intake air temperature sensor 24 that detects the temperature of the outside air drawn from the air cleaner 3, a water temperature sensor 25 that detects the cooling water temperature of the LPG engine 1, a pressure sensor 26 that detects the pressure inside the intake manifold 2, and an opening of the throttle 11. A throttle sensor 27 for detecting the temperature, an O ₂ sensor 28 for detecting the oxygen concentration in the exhaust gas discharged from the exhaust manifold 8, an exhaust temperature sensor 29 for detecting the temperature of the exhaust gas, and a rotational speed of the LPG engine 1. A rotation speed sensor 31 attached to the distributor 30, a vehicle speed sensor 32 that detects a vehicle speed in conjunction with an axle (not shown), etc. are connected. The ECU 23 controls the negative pressure switching valves 16, 17, 18, 19 according to the output signals output from these sensors, and is attached to the step motor 9, injector 33, and LPG engine 1 described above. The distributor 30 and the like are preferably controlled. The injector 33 is installed in the intake manifold 2 closer to the LPG engine 1 than the throttle 11 and injects fuel when the LPG engine 1 is started.

Further, a key switch 34 and a starter motor 35 as a starting device for the LPG engine 1 are provided.

Even if the step motor 9 is controlled to be fully closed when the power valve 10 is in the open state, the power valve 10 has its opening area in advance so that the air-fuel ratio does not become over lean so as to cause misfire. Has been defined.

Next, the ECU 23 will be described. Figure 3 shows E
It is a block diagram showing a configuration of CU23.

The ECU 23 is a well-known central processing unit (CPU) 51, read-only memory (ROM) 52, random access memory (RAM)
53, a backup RAM 54 for storing stored data, and the like, are configured as a logical operation circuit in which these are connected to an external input circuit 55, an external output circuit 56, etc. by a bus 57.

The external input circuit 55 includes the intake air temperature sensor 24, the water temperature sensor 25, the pressure sensor 26, the throttle sensor 27, the O ₂ sensor 28, the exhaust temperature sensor 29, the rotation speed sensor 31, and the vehicle speed sensor 32 described above.
Also, the key switch 34 and the like are connected, and the CPU 51 reads a signal output from each sensor or the like as an input value via the external input circuit 55. Based on these input values, the CPU 51 uses the step output motor 9 connected to the external output circuit 57, the negative pressure switching valves 16 to 19 and the distributor.
31 and the injector 32 are controlled.

In the ROM 52 of the ECU 23, the programs of various processing routines described below and the basic step number of the step motor for obtaining the air-fuel ratio on the lean side of the logical air-fuel ratio are set to the rotational speed of the LPG engine 1 and the intake air. The map A for lean control determined by the intake pressure in the manifold 2 and the basic step number of the step motor for obtaining the logical air-fuel ratio and the air-fuel ratio richer than the logical air-fuel ratio are also determined by the rotational speed and the intake pressure. Various maps such as the predetermined stoichiometric control map B are stored in advance.

Next, the air-fuel ratio control process of the LPG engine executed by the ECU 23 will be described with reference to the flowcharts shown in FIGS. The “step motor control routine” shown in FIG. 4 represents only the processing indicating the control of the step motor 9 for operating the opening degree of the normal fuel passage 5 among the processing executed by the ECU 23, This is a process that is periodically executed by the

First, when the processing shifts to this routine, step 100
Then, the power valve 10 that controls the opening and closing of the acceleration fuel passage 6
The power valve from the external output circuit 56 to see if the
It is judged from whether or not an ON signal is output to the negative pressure switching valve 16 of 10. When it is determined that the power valve 10 is in the ON state, the process proceeds to step 102, the acceleration state is determined, and the ROM
Using the map B for stoichiometric control stored in advance in 52, the current rotational speed NE of the LPG engine 1 detected by the rotational speed sensor 31 and the current intake pressure in the intake manifold 2 detected by the pressure sensor 26 are stored. The basic step number S of the step motor 9 is calculated based on PM and the power valve
When it is determined that 10 is not in the on state, step 10
4, the normal operation state is determined and the lean control map A previously stored in the ROM 52 is used to determine the current rotational speed NE.
Based on the intake pressure PM and the intake pressure PM, the basic step number S of the step motor 9 is calculated.

After the execution of step 102 or step 104, the process proceeds to step 106, and it is determined whether the three-way catalyst 12 is in a heating state above a predetermined level, the exhaust temperature TH output from the exhaust temperature sensor 29.
Judgment is made based on whether EA is equal to or higher than the predetermined temperature T0. When it is determined that the three-way catalyst 12 is in a heating state equal to or higher than the predetermined value, in step 108, the calculated basic step number S is multiplied by the catalyst heating correction coefficient KOT to correct the basic step number S. The catalyst heating correction coefficient KOT is a predetermined value smaller than "1", and in the present embodiment, it takes a value of 0.8, for example. On the other hand, if it is determined in step 106 that the three-way catalyst 12 is not in the heating state above the predetermined level, the process of step 108 is skipped and the process proceeds to the subsequent step.

In the following step 110, the basic step number S is multiplied by the feedback correction coefficient FAF, the intake air temperature correction coefficient FTHA, and the water temperature correction coefficient FTHW, and the basic step number S is corrected to the target step number ST of the step motor 9. This feedback correction coefficient FAF is a value obtained during feedback control during acceleration, and will be described in detail later.

Further, the intake air temperature correction coefficient FTHA is the map C shown in FIG.
The intake air temperature TH detected by the intake air temperature sensor 24
It is obtained by the interpolation method based on A. Map C
As shown in the figure, the intake air temperature correction coefficient FTHA is configured to increase as the intake air temperature THA becomes smaller, and the target number of steps of the step motor 9 in the cold state is increased. Driving performance has been improved. On the other hand, the water temperature correction coefficient FTHW is obtained by an interpolation method based on the cooling water temperature THW detected by the water temperature sensor 25 using the map D shown in FIG. As shown in the figure, the map D shows that as the cooling water temperature THW becomes smaller, the water temperature correction coefficient F becomes larger.
THW is configured to decrease, and in view of the fact that the fuel heated by the cooling water liquefies during cold and the fuel supply amount increases too much, the target number of steps of the step motor 9 is decreased to Driving performance is improved.

In the following step 120, the current step number SNOW representing the step number of the step motor 9 is read from the backup RAM 54, and in the following step 130, the current step number S
Compare NOW with the target step number ST. When the CPU 51 outputs a rotation command to the step motor 9 via the external output circuit 56, the current number of steps SNOW
Is the value written as the current step number SNOW. In steps 130 to 170, a process of matching the current step number SNOW, which indicates the step number of the step motor 9, with the target step number ST is performed.

(A) First, in step 130, the target step number ST
= SNOW is determined, it is not necessary to drive the step motor 9 because the current step number SNOW of the step motor 9 is equal to the target step number ST that is the target, and in that state, it is skipped to "RETURN". This routine ends.

(B) In step 130, target step number ST> SNOW
If it is determined that the current step number SNOW representing the number of steps of the step motor 9 is smaller than the target step number ST, the CPU 51 outputs a forward rotation instruction to increase the number of steps of the step motor 9 to the external output circuit 56. The step motor 9 is rotated forward by one step (step 140), and the current step number SNOW representing the step number of the step motor 9 is incremented (step 150). ".

(C) In step 130, target step number ST <SNOW
If it is determined that the current step number SNOW representing the step number of the step motor 9 is larger than the target step number ST, the CPU 51 outputs a reverse rotation command to decrement the step number of the step motor 9 After the motor 9 is reversely rotated by one step (step 160) and the current step number SNOW is decremented (step 170),
The process ends to "RETURN" and the routine is finished.

The number of steps of the step motor 9 is made to match the target number of steps ST by repeatedly executing the above-mentioned processes (a) to (c).

Next, the feedback correction coefficient FAF used in step 110 of the "step motor control routine" will be described. FIG.
6 is a flowchart showing a "FAF calculation routine". This “feedback correction coefficient FAF calculation routine” is a subroutine that is periodically executed similarly to the “step motor control routine”.

First, in step 200, feedback (hereinafter simply F
Call / B. ) It is determined whether or not the control condition is satisfied. This F / B control condition is satisfied at the time of acceleration, and is determined by setting a flag at the time of acceleration in another processing routine. If it is determined that the F / B control condition is satisfied during acceleration, the process proceeds to step 210. Step 2
At 10, it is judged from the output signal of the O ₂ sensor 28 whether or not the air-fuel ratio is rich. If it is determined that the air conditioner is rich, the processes of steps 220 to 300 as the next process are executed.

In step 220, it is determined by the flag YOX whether the air-fuel ratio was lean when this processing routine was executed last time. If the value of the flag YOX is “0”, the process proceeds to the next step 230 assuming that the previous time was lean. That is, according to the judgment of steps 210 and 220, step 230
When the process is advanced to, it is judged that the air-fuel ratio has switched from lean to rich. Subsequent steps
In 230, the arithmetic average of the current F / B correction coefficient FAF and the old F / B correction coefficient FAFO at the time of shifting from the previous rich to lean is calculated in order to calculate the average correction coefficient FAFAV during F / B control. , The average F / B correction coefficient FAFAV during the F / B control is processed. In the subsequent series of processing steps 240 to 270,
The F / B correction coefficient FAF is used as the old F / B correction coefficient FAFO (step 24
0), the value obtained by subtracting the skip amount a from the F / B correction coefficient FAF is set as a new F / B correction coefficient FAF (step 250), and then the value of the flag YOX is set to "1" (step 270). Then
The air-fuel ratio fluctuation cycle counter KCNT, which will be described later, is incremented by a value of 1 (step 280), and this routine is once ended. The value Y1 of the flag YOX indicates that the air-fuel ratio is rich.

On the other hand, when it is determined in step 220 that the value of the flag YOX is “1”, the processing executes the processing of steps 280 to 300. Here, when the process proceeds to step 280 based on the determination in steps 210 to 220, it indicates that the air-fuel ratio is maintaining a rich state. Step 28
At 0, it is determined whether the timer counter CNT is a constant C or more. This timer counter CNT is incremented in a processing routine by a hardware interrupt having a shorter cycle than this routine. If the timer counter CNT is less than or equal to the constant C, the routine returns to "RETURN" to end this routine. If the timer counter CNT exceeds the constant C, the constant b is subtracted from the F / B correction coefficient FAF in step 290, and then the timer The value of the counter CNT is cleared to "0" (step 300), and this routine ends. That is, step 2
In the case of 80 to 300, the value of the F / B correction coefficient FAF is subtracted by a constant b every predetermined time.

The processing of steps 210 to 300 described above is processing for the case where the air-fuel ratio is rich, and is processing for reducing the F / B correction coefficient FAF. In contrast to the process of decreasing the F / B correction coefficient FAF, the processes of steps 320 to 400 are processes in the case where the air-fuel ratio is lean, and are processes for increasing the F / B correction factor FAF.

First, if it is determined in step 210 that the air-fuel ratio is lean, the process proceeds to step 320. In step 320, the YOX
Is determined whether or not the value of is “1”. YO
If the value of X is "1", the process proceeds to steps 330 to 37.
Execute 0. When the process proceeds to step 330 based on the determinations in steps 210 and 320, it means that the air-fuel ratio has switched from rich to lean. The processing of steps 330 and 340 is the same as the processing of steps 230 and 240, and is the average F / B correction coefficient FAFA during F / B control.
V is calculated (step 330), and the value of the F / B correction coefficient FAF is
A B correction coefficient FAFO is set (step 340). Continued Step 35
At 0, after adding the skip amount a to the F / B correction coefficient FAF to make a new F / B correction coefficient FAF, the value of the flag YOX is set to “0”.
(Step 370), and this routine ends.

On the other hand, when it is determined in step 320 that the value of the flag YOX is “0”, the processing executes the processing of steps 380 to 400. Here, when the process proceeds to step 380 based on the determinations in steps 210 and 320, it indicates that the air-fuel ratio is maintaining a lean state. Step 380
Steps 400 to 400 are the opposite of steps 280 to 300, and the value of the F / B correction coefficient FAF is
It is a process that increases only.

The timing chart of FIG. 9 shows the processing contents of the above steps 200 to 400. As can be seen from FIG. 9, the F / B correction coefficient FAF is increased / decreased according to the air-fuel ratio signal detected by the O ₂ sensor 28 and is controlled so as to approach the logical air-fuel ratio.

If it is determined in step 200 that the F / B control condition is not satisfied, the F / B correction coefficient FAF and the old F / B
The value of the B correction coefficient FAFO is set to "1" (step 410), and this routine ends.

Next, the "power valve opening / closing control routine" of FIG. 6 for controlling the opening / closing of the power valve 10 will be described.

First, in step 500, it is determined whether or not the engine is starting. This is specifically determined by whether or not the key switch 34 is at the start position. If it is determined in step 500 that the engine is not started, the process proceeds to step 510.
Then, it is determined whether the cooling water temperature THW detected by the water temperature sensor 25 is smaller than the predetermined value a. If it is determined in step 510 that the value is equal to or greater than the predetermined value a, the process proceeds to step 520, and it is determined whether the opening degree Tθ of the throttle 11 detected by the throttle sensor 27 is larger than the predetermined value b. When it is determined in step 520 that the value is equal to or less than the predetermined value b, the process proceeds to step 530, and it is determined whether the vehicle speed SPD detected by the vehicle speed sensor 32 is smaller than the predetermined value c. When it is determined in step 530 that the value is equal to or greater than the predetermined value c, the process proceeds to step 540, and the exhaust temperature THEA output from the exhaust temperature sensor 29 is used to determine whether the three-way catalyst 12 is in a heating state equal to or higher than the predetermined value. It is determined from whether or not the temperature is equal to or higher than the predetermined temperature T0. If it is determined that the three-way catalyst 12 is not in the heating state above the predetermined value, the process is step
Proceed to 550. In step 550, a signal for turning on the power valve 10 is output to the negative pressure switching valve 16 of the power valve 10 to open the acceleration fuel passage 6. On the other hand, steps 500 to 5
When the affirmative judgment is made in 40, the processing is step 560.
To the negative pressure switching valve 16 of the power valve 10
A signal for turning off 10 is output, and the acceleration fuel passage 6 is closed.
After executing the processing of step 550 or step 560, the processing exits to "RETURN" and this routine is once terminated.

Therefore, according to the fuel supply control device for the LPG engine of the present embodiment described in detail above, during normal operation, the step motor 9 is controlled by the feedback control of the air-fuel ratio and the correction control based on the intake air temperature THA and the cooling water temperature THW. The target step number ST is set, and the amount of fuel flowing through the normal fuel passage 5 is optimally controlled according to the operating state. Further, at the time of starting, the cooling water temperature THW is smaller than the predetermined value a, the opening Tθ of the throttle 11 is larger than the predetermined value b, or the vehicle speed SPD is smaller than the predetermined value c, the power valve 10 is turned on. When turned on, the acceleration fuel passage 6 is opened, and the fuel supplied to the intake manifold 2 is increased. Moreover,
When the three-way catalyst 12 is in a heating state above a predetermined value, that is, when the exhaust temperature THEA output from the exhaust temperature sensor 29 is equal to or higher than the predetermined temperature T0, the power valve 10 operates even in the normal operation range. Opened and step motor 9
Is controlled to the close side (by calculating by correcting the target number of steps ST with the catalyst correction coefficient KOT.) For this reason, the air-fuel ratio becomes over lean and misfires, and the three-way catalyst
Even if 12 is in a heating state above a predetermined level, by switching the power valve 10 to the open state, over lean of the air-fuel ratio can be eliminated, and abnormal heating of the three-way catalyst 12 due to over lean can be prevented. it can. Further, even if the power valve 10 is opened, by controlling the step motor 9 to the closing side, the air-fuel ratio can always be kept in the lean region, and abnormal heating of the three-way catalyst 12 due to ignition failure can be prevented. Can also be prevented. In this way, abnormal heating of the three-way catalyst 12 can be completely prevented, and deterioration of emission due to performance deterioration of the three-way catalyst 12 can be prevented.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment and can be implemented in various modes without departing from the scope of the present invention. Of course.

As described above in detail, the fuel supply control device for the LPG engine of the present invention prevents abnormal heating of the catalyst due to over lean of the air-fuel ratio, and also prevents abnormal heating of the catalyst caused by poor ignition. It is possible to prevent deterioration of emission due to deterioration of catalyst performance.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating the basic configuration of the present invention, and FIG. 2 is a schematic configuration diagram of an LPG engine system as a fuel supply control device for an LPG engine according to an embodiment of the present invention.
FIG. 3 is a block diagram showing the configuration of the electronic control unit, FIGS. 4 to 6 are flow charts showing processes executed by the electronic control unit, FIG. 7 is a graph showing a map C, and FIG. Is a graph showing map D, and FIG. 9 is a timing chart showing the relationship between the air-fuel ratio signal and the feedback correction coefficient FAF. 1 …… LPG engine 2 …… Intake manifold 4 …… Venturi 5 …… Normal fuel passage 6 …… Acceleration fuel passage 8 …… Exhaust manifold 9 …… Step motor 10 …… Power valve 12 …… Three-way catalyst 23 …… Electronic control unit 28 …… O ₂ sensor 29 …… Exhaust temperature sensor 54 …… Backup RAM

Claims (1)

(57) [Claims] 1. A first fuel passage that connects a venturi formed in an intake passage of an engine using liquefied petroleum gas as a fuel and a liquefied petroleum gas source; and a first fuel passage provided in the first fuel passage. A variable control valve that controls the amount of fuel passing through one fuel passage; a second fuel passage that communicates the venturi with a liquefied petroleum gas source through a route different from the first fuel passage; An opening / closing valve provided in the fuel passage for switching the second fuel passage to an open state or a closed state; and setting an opening target value of the variable control valve based on an operating state of the engine including at least a load, A fuel supply control device for an LPG engine, comprising: a variable control valve control means for controlling an opening degree of a variable control valve; and an opening / closing valve control means for controlling opening / closing of the opening / closing valve. For exhaust gas purification Catalyst heating state detecting means for detecting the heating state of the catalyst, and when the heating state of the catalyst detected by the catalyst heating state detecting means is a predetermined heating state or more, the variable control valve control means determines And a valve correction control means for switching the open / close valve to the open state via the open / close valve control means, and correcting the fuel flow control of the LPG engine. apparatus.