JPH01216034A - Fuel feed device for engine - Google Patents

Abstract

PURPOSE:To prevent lowering of an engine output, by a method wherein, in a device having a fuel feed means to select gas fuel or gasoline to feed it, when an engine temperature exceeds a given value during running by means of gasoline, the fuel feed means is controlled to the gas fuel side. CONSTITUTION:A float chamber 30 to which the one end of a gasoline feed passage 32 is connected is situated to a carburetor 20, and a solenoid valve 35 for feeding gasoline is located in a passage 32 running to a gasoline tank 38. A mixer part 40 to feed LPG as fuel is mounted to the carburetor 20, and a vaporizer 45 is coupled to a venturi part 41 through an LPG delivery passage 42. The vaporizer 45 has a primary chamber 51 connected to an LPG cylinder 47 through an LPG feed passage 48 in which a solenoid valve 55 for feeding LPG is located. The solenoid valves 35 and 55 are controlled so as to be switched to operation by means of LNG when it is decided by a CPU 100 that a cooling water temperature exceeds a given value during running by means of gasoline.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is designed to selectively supply an engine with gas fuel such as liquefied petroleum gas (LPG) and gasoline. The present invention relates to an engine fuel supply system.

(Prior Art) In a fuel supply system for an engine that uses LPG as fuel, for example, as shown in Japanese Utility Model Application No. 61-198556, there is a gap between an LPG cylinder for fuel storage and an intake passage of the engine. A pressure regulating device called a vaporizer is disposed in the engine, which regulates the pressure of LPG fuel from an LPG cylinder and supplies it to a mixer section provided in an intake passage.

Engines that use LPG as fuel are said to be better from a fuel cost standpoint than engines that use gasoline, but they are somewhat inferior in terms of output performance. Ru. Therefore, LPG and gasoline are prepared as fuels, and it is considered that they can be used by selectively switching between them as needed.

(Problem to be solved by the invention) When gasoline is used as engine fuel,
When the engine temperature or intake temperature is high, a large amount of gasoline may vaporize in the fuel supply system, causing so-called percolation or vapor lock.
There is a tendency for excess or insufficient fuel to be supplied into the intake passage from the carburetor or fuel injection valve, and on the other hand, when gas fuel such as LPG is used as fuel, such a situation may occur. Considering these circumstances, in engines that are used by selectively switching between gas fuel and gasoline as described above, the temperature of the engine and the intake part are high, and the gasoline If gasoline is selected as the fuel when a large amount of gasoline is vaporized, there is a risk that the amount of fuel supplied to the engine will be excessive or insufficient, and the required output may not be obtained. occurs.

In view of such a situation, the present invention provides a solution to the problem that when gasoline is used as a fuel when the temperature of the engine or a temperature related thereto is high, a situation where fuel is not properly supplied to the engine is likely to occur; Focusing on the fact that such a situation does not occur when gas fuel is used, a state in which gas fuel is supplied to the engine and a state in which gasoline is supplied are selectively taken, and the temperature of the engine is controlled. Another object of the present invention is to provide a fuel supply system for an engine that does not cause a reduction in output even when the related temperature is high.

(Means for Solving the Problem) In order to achieve the above-mentioned object, a fuel supply device for an engine according to the present invention provides a fuel supply system that selectively supplies gas fuel and gasoline to the engine. In addition to the temperature detecting means, a temperature detecting means and a fuel switching means are provided, and when the fuel supply means is in a state of supplying gasoline, the temperature of the engine detected by the temperature detecting means or a temperature related thereto is a predetermined value. In this case, the fuel switching means causes the fuel supplying means to supply gas fuel.

(Function) In the engine fuel supply device according to the present invention having the above-described configuration, when the engine temperature detected by the temperature detection means or the temperature related thereto is equal to or higher than a predetermined value, the fuel supply device according to the present invention has the configuration as described above. When the supply means is in a state of supplying gasoline, the fuel switching means causes the fuel supply means to take a state of supplying gas fuel instead of gasoline.

By doing so, there is a risk that the engine temperature or related temperatures will be high and a large amount of gasoline will vaporize in the fuel supply system, leading to a situation where there is an excess or shortage of fuel supplied to the intake passage. In some cases, if gasoline is being supplied as fuel, gaseous fuel, which does not pose such a risk, is supplied instead of gasoline. As a result, an appropriate amount of fuel is supplied to the engine, and a reduction in engine output is avoided.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an engine fuel supply system according to the present invention together with the main parts of an engine installed in an automobile that operates by selectively supplying gas fuel and gasoline to which the system is applied.

In FIG. 1, an engine E having a cylinder head 7 and a cylinder block 8 has intake valves 11 . Exhaust valve 129 spark plug 13 and piston 1
4 etc., and the intake system is provided with an intake passage 5 that guides intake air introduced via the air cleaner 9 to the combustion chamber 15 of the engine E, and the intake passage 5 has a predetermined angle. A vaporizer 20 is interposed at the position.

The carburetor 20 is provided with a primary side intake passage section 16 and a secondary side intake passage section 17 in which venturis 23 and 24 are formed. 17 are provided with throttle valves 18 and 19, respectively. The carburetor 20 is provided with a main port 21 connected to a main system fuel passage and a slow port 22 connected to a slow system fuel passage in a known manner.
Through this, an amount of fuel corresponding to the operating state of the engine E is supplied to the intake passage 5.

The carburetor 20 also includes a float chamber 30, and the float chamber 30 has a needle valve 34 attached thereto.
One end of the gasoline supply passage 32 is connected via the gasoline supply passage 32 . A fuel pump 26 is disposed in the gasoline supply passage 32, and a control unit 100 (described later)
A normally-closed type gasoline supply solenoid valve 35 that is in an open state when a valve opening driving signal Cp is supplied from the gasoline supply passage 32 is disposed, and the other end of the gasoline supply passage 32 stores gasoline as fuel. It opens at a position close to the bottom of the gasoline tank 38. Gasoline stored in the gasoline tank 38 is forced through the gasoline supply passage 32 by the fuel pump 26 and supplied to the float chamber 30 through the needle valve 34.

The needle valve 34 is linked to the float 28, which is displaced according to the level of gasoline in the float chamber 30, and is opened or closed relative to one end of the gasoline supply passage 32. Note that when the needle valve 34 or the gasoline supply solenoid valve 35 is closed, the gasoline led from the gasoline tank 38 to the fuel pump 26 is returned from the fuel pump 26 to the gasoline tank 38 through the return passage 36.

In addition to this configuration, the carburetor 20 is provided with a mixer section 40 having venturis 39 and 41 for supplying LPG as fuel to the carburetor 20. One end of an LPG delivery passage 42 is open in the bench area 41, and the other end of the LPG delivery passage 42 is connected to a vaporizer 45.

The vaporizer 45 is of a two-stage decompression type having a known configuration, and is connected from an LPG cylinder 47 to an LPG supply passage 48.
It has a primary firebox 51 that depressurizes the LPG supplied through the firebox 51 to a constant pressure, and a secondary chamber 52 that depressurizes the LPG supplied from the firebox 51 to approximately atmospheric pressure. The depressurized LPG is led out to an LPG delivery passage 42. A preheater 53 is disposed in the LPG supply passage 48 to prevent the LPG supply system from freezing due to the latent heat of vaporization of LPG, and the preheater 53 is set in the open state when the valve opening drive signal Cq is supplied from the control unit 100. Normally closed type LPG supply solenoid valve 55
is installed.

A control unit 10 controls the above-mentioned gasoline supply solenoid valve 35 and LPG supply solenoid valve 55.
0, a detection signal Sw corresponding to the cooling water temperature of the engine E obtained from the water temperature sensor 50 that detects the temperature of the cooling water circulating in the cylinder head 7 and the cylinder block 8;
When the fuel changeover switch 60 operated by the driver etc. is turned on, a signal Sg is supplied from the signal forming section 62 to indicate that gasoline has been selected as the fuel by the driver etc. Other detection signals necessary for controlling the engine E, not shown, are also supplied.

Under such a configuration, the control unit 100 controls switching of the fuel supply mode of gasoline and LPG to the engine as follows.

The control unit 100 detects that the detection signal Sw indicates that the cooling water temperature Tw is higher than a predetermined value T1, for example, a temperature around 0°C, and lower than a predetermined value T2, for example, a temperature around 100°C. In this case, the signal forming section 62
Based on whether or not the signal Sg is supplied through the fuel selector switch 60, it is determined whether gasoline is selected as the fuel, and if it is determined that gasoline is selected as the fuel, the gasoline supply Solenoid valve 35
The valve opening drive signal Cp is supplied to the LPG supply solenoid valve 55, and the supply of the valve opening drive signal Cq to the LPG supply solenoid valve 55 is stopped. The supply of the valve opening drive signal Cp to the electromagnetic valve 35 is stopped, and the valve opening drive signal Cq is supplied to the LPG supply electromagnetic valve 55.

As a result, when gasoline is selected as the fuel by the driver etc. while the cooling water temperature Tw is in the range from value T1 to value T2, the gasoline supply solenoid valve 35
is opened, and the LPG supply solenoid valve 55 is closed, so that gasoline in the gasoline tank 38 can be supplied into the float chamber 30 by the fuel pump 26 through the gasoline supply solenoid valve 35. At the same time, the LPG is transferred from the LPG cylinder 47 to the vaporizer 45.
As a result, an amount of gasoline corresponding to the operating state of the engine E is supplied into the carburetor 20 through the main boat 21 and the slow port 22. Further, when LPG is selected as the fuel, the gasoline supply solenoid valve 35 is closed, and the LPG supply solenoid valve 55 is opened, so that gasoline is supplied from the gasoline tank 38 to the float chamber 30. At the same time, LPG is supplied from the LPG cylinder 47 to the vaporizer 45, and as a result, the supply of gasoline to the vaporizer 20 is stopped, and LPG is supplied from the vaporizer 45 to the vaporizer 20 through the LPG delivery passage 42. is supplied.

Therefore, when the cooling water temperature Tw is in the range from value T to value T8, the will of the driver etc. is respected, and when gasoline is used, compared to when LPG is used, Greater power is obtained, whereas fuel costs are saved when LPG is used compared to when gasoline is used.

In addition, when it is detected that the cooling water temperature Tw is lower than the value T1, not only when gasoline is selected as the fuel by the driver, but also when LPG is selected as the fuel, the LPG The LPG supply system, including the vaporizer 45, etc., is likely to freeze due to latent heat of vaporization, so in order to avoid this, the roll unit 1 on the controller
00, the valve opening drive signal Cp is supplied to the gasoline supply solenoid valve 35, and the supply of the valve opening drive signal Cq to the LPG supply solenoid valve 55 is stopped, and the state in which gasoline is supplied as fuel is restored. It will be done.

Furthermore, when it is detected that the cooling water temperature Tw is greater than or equal to the value 12, the control unit 1
00, the supply of the valve-opening drive signal Cp to the gasoline supply solenoid valve 35 is stopped, and the valve-opening drive signal Cq is supplied to the LPG supply solenoid valve 55, so that L as fuel is supplied.
A state is assumed in which PG is supplied. By doing so, when the engine E is in a high temperature state and there is a risk that a large amount of gasoline will vaporize and vapor lock or percolation will occur that will hinder the fuel supply to the carburetor 20, gasoline will be selected as the fuel. Even in the case where such earthquakes occur, LPG will be supplied that does not cause such earthquakes, and even when the temperature of engine E is high, an appropriate amount of fuel will be supplied to the engine and the output will be maintained. A drop ring is effectively avoided.

In addition, in situations where the LPG supply system freezes due to the latent heat of vaporization of LPG, or where fuel supply problems such as vapor lock or percolation occur due to the vaporization of a large amount of gasoline, the fuel supply amount may be reduced. Since this is likely to occur during high-load operation, the fuel supply mode may be switched as described above only during such high-load operation.

The control unit 100 that performs the above-described control is configured using, for example, a microcomputer, and an example of a program executed by the microcomputer in such a case will be explained based on the flowchart in FIG. 2.

In the program shown in the flowchart of FIG. 2, after the start, in process 101, the detection signal S
In the following decision 102, it is determined whether the cooling water temperature Tw of the engine E where the detection signal Sw is detected is below the value T1,
If it is determined that the cooling water temperature Tw is equal to or lower than the value TI, in process 103, the supply of the valve opening drive signal Cq to the LPG supply solenoid valve 55 is stopped, and the valve opening drive signal Cq is stopped to the gasoline supply solenoid valve 35. Send out the drive signal Cp and return to the original state. As a result, a state is established in which gasoline is supplied as fuel.

Further, if it is determined in decision 102 that the cooling water temperature Tw is higher than the value T, then decision 10
Proceed to step 4, and the cooling water temperature Tw is the value T! Determine whether or not the above is true. Then, when it is determined that the cooling water temperature Tw is equal to or higher than the value T2, in the subsequent process 105, the LP
A valve opening drive signal Cq is sent to the G supply solenoid valve 55, and a valve opening drive signal Cp is sent to the gasoline supply solenoid valve 35.
Stop the supply of and return to normal. As a result, L as fuel
A state is assumed in which PG is sent out.

On the other hand, if it is determined in decision 104 that the cooling water temperature Tw is lower than the value T2, decision 10
6, it is determined based on the signal Sg whether the fuel changeover switch 60 is turned on, that is, whether gasoline is selected as the fuel by the driver, and the fuel changeover switch 60 is turned off. If it is determined that the fuel selector switch 60 is in the on state, process 105 is executed as described above and the process returns to the previous state.If it is determined that the fuel selector switch 60 is in the on state, process 103 is executed as described above. Execute and return.

In the above example, the fuel supply mode is switched based on the engine cooling water temperature Tw, but the fuel supply mode is not limited to this, and the fuel supply mode is switched based on the temperature of the engine itself or the intake temperature, etc. The mode may be switched.

(Effects of the Invention) As is clear from the above explanation, according to the engine fuel supply device according to the present invention, gasoline and LPG can be used as fuel.
When the temperature of the engine or its related temperature exceeds a predetermined value, a large amount of gasoline vaporizes in the fuel supply system and is supplied into the intake passage. If gasoline is selected as the fuel in a situation where there is a risk of an excess or shortage of fuel, a gas that does not pose such a risk may be substituted for gasoline. Therefore, even when the engine temperature or related temperatures are high, the appropriate amount of fuel is supplied, effectively preventing a situation where the engine output is reduced. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of an engine fuel supply system according to the present invention together with the main parts of an automobile engine to which the system is applied, and FIG. 2 is a control unit provided in the example shown in FIG. 2 is a flowchart showing an example of a program executed by a microcomputer when the microcomputer is used in the present invention. In the figure, E is the engine, 20 is the carburetor, 35 is the gasoline supply solenoid valve, 38 is the gasoline tank, 45 is the vaporizer, 47 is the LPG cylinder, 55 is the LPG supply solenoid valve,
60 is a fuel selection switch, and 100 is a control unit. Patent applicant Mazda Motor Corporation

Claims (1)

[Scope of Claims] Fuel supply means for selectively supplying gas fuel and gasoline to the engine, temperature detection means for detecting the temperature of the engine or a temperature related thereto, and the fuel fuel switching means for causing the fuel supply means to take a state of supplying gas fuel when the temperature detected by the temperature detection means is equal to or higher than a predetermined value while the supply means takes a state of supplying gasoline; An engine fuel supply system comprising: