JPH03145565A - Fuel feeding device for engine - Google Patents

Abstract

PURPOSE:To assure the invariably correct action of a fuel pressure regulator by opening a return passage reaching a fuel tank at the high position of a pressure regulating chamber maintaining the fuel of the fuel pressure regulator at the nearly constant positive pressure, and providing a throttle controlling the fuel flow on the return passage. CONSTITUTION:A fuel pump, a fuel pressure regulator 25 and a fuel flow regulator 55 are provided on the outside face of a main body 1 provided with a fixed Venturi 3 and a throttle valve 4 on an intake path 2 extended in the vertical direction in this device. The fuel pressure regulator 25 feeds the fuel regulated to the nearly constant positive pressure to a main nozzle 48 with a variable effective area via a metering needle 79, and the fuel flow regulator 55 operates the metering needle 79 in response to the difference between the Venturi negative pressure and the intake negative pressure. A return passage 50 provided with a throttle 51 in the middle reaching a fuel tank is opened at the high position of a pressure regulating chamber 36 maintaining the fuel of the fuel pressure regulator 25 at the nearly constant positive pressure, and the gas separated from fuel can be immediately discharged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for supplying fuel (gasoline) to a small displacement engine.

[Prior Art] Among the carburetors that are widely used as a means of supplying fuel to relatively small displacement engines that drive small vehicles, industrial machinery, generators, etc., fixed venturi carburetors are used for low-speed fuel and Because the main fuel is supplied through a separate passage, the fuel connection tends to be unstable and the passage configuration is complicated.Variable venturi carburetors have many parts that require extremely high machining precision, such as the venturi piston and its guide. I have a problem. In addition, float-type fuel adjustment means cannot cope with large inclinations, and belly-type ones can cope with various postures, but the fuel control accuracy is poor.

On the other hand, in contrast to the above-mentioned carburetor that sucks fuel into the intake passage using a venturi negative pressure, there is a so-called injection carburetor that was put into practical use during World War II as a countermeasure against freezing in aircraft engine carburetors. The Strombarb type carburetor manufactured by Bendex is widely known as this carburetor, and the fuel pressure control valve is driven by the differential pressure between the venturi inlet dynamic pressure and the venturi negative pressure, and the fuel flow control valve is linked to the throttle valve. , fuel is injected into the intake passage at positive pressure via a fuel injection valve driven by venturi negative pressure.

Although such a so-called injection carburetor has the advantage of highly accurate fuel control in various postures, the three valves mentioned above are arranged in series in the fuel passage, and the fuel supply for starting and acceleration is difficult. Japanese Patent Laid-Open No. 1-3203 discloses a fuel supply device having a structure in which only a fuel pressure regulating means is disposed in the fuel passage, which improves the drawback that the fuel system is extremely complicated due to the provision of a separate means.
It is disclosed in Publication No. 1.

The technology disclosed in the above-mentioned publication was provided by the inventor and patent applicant of the present invention, and is a fuel pressure regulator that adjusts fuel to a substantially constant positive pressure and sends it to a main nozzle that opens into an intake passage. and a fuel flow regulator that operates a metering needle that changes the effective area of the main nozzle in response to the differential pressure between the venturi negative pressure and the intake manifold negative pressure to increase or decrease the effective area in accordance with the engine intake air amount.

However, the pressure regulating chamber that maintains the fuel in the fuel pressure regulator at a nearly constant positive pressure is equipped with a diaphragm that controls the fuel sent from the fuel pump according to the fuel pressure in the pressure regulating chamber. Since it has a sealed structure that is separated from the atmosphere, when air bubbles separate from the temporarily stagnant fuel in the pressure regulation chamber or fuel vapor is generated, these accumulate in the upper part of the pressure regulation chamber and prevent the movement of the diaphragm. This causes the problem that the fuel pressure cannot be properly controlled.

[Problems to be Solved by the Invention] The present invention thus seeks to solve the problem that the above-mentioned technology has, in which air and fuel vapor accumulate in the pressure regulating chamber of the fuel pressure regulator, making it impossible to properly control the fuel pressure. It is an object of the present invention to provide a fuel supply device that can discharge air and fuel vapor from a pressure regulating chamber without impairing the normal function of a fuel pressure regulator.

[Means for Solving the Problems] The present invention includes an intake passage having a fixed venturi and a throttle valve, a main nozzle that opens into the intake passage and whose effective area is variable with a metering needle, and adjusts the fuel to a substantially constant positive pressure. and a fuel pressure regulator that sends the fuel to the main nozzle, and operates the metering needle in accordance with the differential pressure between the venturi negative pressure and the intake negative pressure on the side of the throttle valve or downstream thereof, so as to correspond approximately to the engine intake air amount. In order to solve the above-mentioned problems of an engine fuel supply system including a fuel regulator that changes the effective area of the main nozzle, the following measures have been taken.

That is, a return passage that reaches the fuel tank is opened at a high point in the pressure regulating chamber that maintains the fuel in the fuel pressure regulator at a substantially constant positive pressure, and a throttle that restricts the fuel flow rate is provided in the return passage.

Alternatively, a temperature valve that closes when the temperature is low and has a small opening and opens wide when the temperature is high is provided in the return passage instead of the throttle.

[Effect: When air bubbles in the fuel separate or fuel vapor is generated in the pressure regulating chamber, these are immediately discharged through a return passage connected to a high place to prevent the fuel pressure in the pressure regulating chamber from going out of order. The temperature valve prevents a portion of the fuel from flowing into the return passage more than necessary, and also allows the fuel vapor, which is generated in large quantities at high temperatures, to be freely discharged.

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

A fixed venturi 3 and a throttle valve 4 are installed in a single intake passage 2 extending in the vertical direction of the main body l, and a fuel pump 5, a fuel pressure regulator 25, and a fuel flow regulator are installed on the outer surface of the main body l. 55 are provided.

Referring to FIG. 5, the fuel pump 5 is constructed by stacking a pump membrane 6 made of a diaphragm, a pump body 7, a partition membrane 8° made of a diaphragm, and a cover 9 in this order on one side of the main body 1, and tightening them together with a set screw. The attachment is fixed, and a pulse chamber 11. in which a pump spring 10 is inserted is inserted between the main body 1 and the pump membrane 6. A pump chamber 12 is formed between the pump membrane 6 and the pump body 7, a suction chamber 13 and a discharge chamber 14 are formed between the pump body 7 and the partition membrane 8,
This is a well-known pulse type diaphragm pump that has an atmospheric chamber 15 between a partition membrane 8 and a cover 9, and the pulse pressure generated in the crankcase of the engine is introduced into the pulse chamber 11 through a pulse pressure passage 16. It is also conventional to reciprocate the membrane 6 to suck the fuel that has entered the suction chamber 13 from the fuel inlet 17 into the re-pump chamber 12 through the inlet check valve 18 and then discharge it into the discharge chamber 14 through the outlet check valve 19. is the same as Incidentally, the inlet check valve 18 and the outlet check valve 19 are made of a rubber plate, and are supported by the pump body 7 in a cantilevered manner by a rivet 2o.

Referring to FIG. 5.6, the fuel pressure regulator 25 has a pressure regulating valve 26 and a pressure regulating chamber 36 arranged on a side surface of the main body I different from the above. The pressure regulating valve 26 is a valve chamber 2 connected to the discharge chamber 14 of the fuel pump 5 by a fuel introduction passage 21.
7. Valve body 28 and valve spring 29 inserted into valve chamber 27;
It has a valve seat 30 , and a valve seat opening 31 that communicates the valve chamber 27 and the pressure regulating chamber 36 is opened and closed by the valve body 28 . Valve body 2
The guide spar 32 extending toward the rear of the valve body 8 is tightly fitted into the guide hole 34 of the plug 33 that is fixed to the carburetor body 1 and closes the valve chamber 27, causing the valve body 28 to reciprocate linearly, and extending toward the front of the valve body 28. The actuator 35 loosely passes through the valve seat opening 31 and protrudes into the pressure regulating chamber 36 and is in contact with the diaphragm 37 . This diaphragm 3
7 is fixed to the main body 1 overlappingly with the regulator body 38, and an atmospheric chamber 39 is formed between the diaphragm 37 and the regulator body 38, and a pressure regulating spring 40 is inserted therein.

The valve body 28 of the pressure regulating valve 26 opens and closes the valve seat port 31 according to the position of the diaphragm 37 determined by the fuel pressure in the pressure regulating chamber 36 and the spring loads of the valve spring 29 and the pressure regulating spring 40. When the fuel pressure in the pressure regulating chamber 36 becomes high, the valve closes, and when it becomes low, the valve opens, and the fuel 1 is sent from the fuel pump 5 to the valve chamber 27.

The fuel pressure in the pressure regulating chamber 36 is maintained at a constant positive pressure within this range.

A protective cover 41 is removably fixed to the outside of the regulator body 38 with screws 42, and the space surrounded by these covers a plate-shaped bimetal 44 that is cantilevered to the regulator body 38 with screws 43. Built-in bimetal chamber 45
is formed. A bimetal rod 46 that passes through the regulator body 38 and contacts the diaphragm 37 is connected to the free end of the bimetal 44 . When the temperature is low, the bimetal 44 pushes the bimetal rod 46 to move the diaphragm 37 toward the pressure regulating chamber 36, widening the pressure regulating valve 26, and transferring a large amount of fuel sent from the fuel pump 5 to the pressure regulating chamber 36. When the temperature is high, the bimetallic rod 46 separates from the diaphragm 37 and returns the diaphragm 37 to its normal position to adjust the fuel to a constant positive pressure within the range.

Referring to FIG. 4.6, the fuel in the pressure regulating chamber 36 passes through a fuel passage 47 formed in the main body l, and enters a main nozzle (or needle jet) 48 that protrudes toward the narrowest part of the fixed venturi 3. It is injected from the tip, mixes with intake air, and is supplied to the engine.

The fuel passage 47 is opened by a solenoid valve 49 when the engine is running, but is closed when the engine is stopped.

The fuel passage 47 opens at a lower part of the pressure regulation chamber 36, and a return passage 50 which reaches a fuel tank (not shown) opens at the highest part of the pressure regulation chamber 36.

Next, referring to FIG. 4.5, the fuel flow regulator 55 includes a housing 57 fixed to another side of the main body 1 with a diaphragm 56 in between, and a negative pressure installed in the housing 57. It has a control valve 80. The housing 57 side of the diaphragm 56 forms a first negative pressure chamber 58, the main body 1 side forms a second negative pressure chamber 59, and the first negative pressure chamber 5
8 is a first negative pressure path 6 opened at the narrowest part of the fixed venturi 3
0 and an auxiliary negative pressure path 61 having a throttle 99 and opening into the pulse chamber 11 of the fuel pump 5 by a negative pressure control valve 80 . The second negative pressure chamber 59 opens into the intake passage 2 on the side of the throttle valve 4 in the idle position, is connected to a second negative pressure passage 62 having a throttle 69, and is further connected to the first negative pressure chamber 58. A pressure spring 63 and a balance spring 64 that press the diaphragm 56 are inserted into the second negative pressure chamber 59, respectively.

Referring to FIG. 3.4.7, the first negative pressure passage 60 includes a first correction passage 65 that opens into the intake passage 2 on the opposite side of the throttle valve 4 in the idle position, and a first correction passage 65 that opens into the intake passage 2 upstream of the fixed venturi 3. It has a second correction passage 67 that opens into the intake passage 2 on the side. These correction passages 65 and 67 have throttles 66 and 68, so that even if the venturi negative pressure changes suddenly, the pressure change is softened until it passes through the first negative pressure path 60 and enters the first negative pressure chamber 58. so that the diaphragm 56 is not moved impulsively.

Referring to FIGS. 4 and 8, the second negative pressure chamber 59 is connected to the second negative pressure path 6.
In addition to the main body 1, a correction passage 70 is connected to the atmosphere, for example, the inside of an air cleaner (not shown), and this correction passage 70 is branched into two on the air intake side. A needle piece 73 at the tip of an adjustment screw 72 screwed in manually and adjustable from the outside is inserted into the second branch passage 74, and a temperature valve 75 is provided in the second branch passage 74. temperature valve 75
has a needle-shaped valve body 77 attached to the free end of a cantilevered plate-shaped bimetal 76, and when the temperature is low, the valve hole 78
Open wide and close when the temperature is high.

(For the J pressure control valve 80, refer to Figures 5 and 9.
, valve seats 82 and 83 provided facing each other on both sides of the valve chamber 81.
, a valve body 84 built into the valve chamber 81 . The first valve seat 82 surrounds the opening of the first negative pressure path 60 to the valve chamber 81, and the second valve seat 83 surrounds the opening of the auxiliary negative pressure path 61 to the valve chamber 81. surrounding the opening to. Return spring 85
presses the valve body 84 against the second valve seat 83 to open the auxiliary negative pressure path 61
, and serves to communicate the first negative pressure passage 60 with the first negative pressure chamber 58 via the valve chamber 81 and the outlet passage 86.

The second valve seat 83 and a part of the auxiliary negative pressure path 61 are formed on a guide piece 87 fixed to the housing 57, and the valve body 84 is formed on a guide piece 87 fixed to the housing 57.
A rod 89 extending from the auxiliary negative pressure path 61 loosely passes through the guide hole 88 of the guide piece 87 in front thereof in an airtight manner and projects into the atmospheric chamber 90 . The atmospheric chamber 90 is formed by a recess in the housing 57, and its open end surface is covered with a diaphragm 9 that is integrally fixed to the housing 57, overlapping the cover 91.
2, but communicates with the atmosphere by an opening 111 with an air filter 110 (FIG. 2),
A portion surrounded by the cover 91 and the diaphragm 92 forms a negative pressure chamber 93, in which a starting spring 94 is inserted, and a portion of the intake path 2 downstream of the throttle valve 4 and the throttle 95.
They are connected by a negative pressure passage 96 having a .

A metering needle 79 is fixed to the center of the diaphragm 56 of the fuel flow regulator 55.
9 crosses the second negative pressure chamber 59 , passes through the guide 23 , and is inserted into the main nozzle 48 located on the opposite side of the fixed venturi 3 . In front of the tip of the metering needle 79, a stopper 98 is disposed at the tip of a screw 97 that is screwed into the main body 1 so as to be manually adjustable from the outside, and protrudes into the fuel passage 47 behind the main nozzle 48.

The metering needle 79 controls the venturi negative pressure introduced into the first negative pressure chamber 58 through the first negative pressure path 60 and the throttle introduced into the second negative pressure chamber 59 through the second negative pressure path 62 in the normal operating state of the engine. The diaphragm 5 is determined by the intake negative pressure on the side of the valve 4 and the loads of the pressure spring 63 and balance spring 64.
The main nozzle 48 reciprocates in a straight line depending on the position of the main nozzle 48, and changes the effective area of the main nozzle 48 to change the fuel flow rate supplied to the engine. That is, when the throttle valve 4 is at the idle position or at a small opening, a high negative pressure is generated in the boat 62a of the second negative pressure path 62 that opens into the intake path 2, and since the venturi negative pressure is low, the diaphragm 56 moves largely toward the second negative pressure chamber 59, reducing the effective area of the main nozzle 48. When the throttle valve 4 opens wide, the difference between the venturi negative pressure and the intake negative pressure on the sides of the throttle valve 4 becomes small, and when the opening is greater than the opening, the venturi negative pressure becomes higher, so the diaphragm 56 closes in the first negative pressure chamber. 58 to increase the effective area of the main nozzle 48. By such movement of the diaphragm 56, the intake air amount and the fuel flow rate can be made basically proportional, and the air-fuel ratio can be kept constant.

When the device of the invention is manufactured, the fuel pressure regulator 25;
Main nozzle 48, fuel flow regulator 55, metering needle 79
The fuel flow rate supplied to the engine from the main nozzle 48 may differ from the engine required flow rate due to dimensional errors or assembly errors. In such a case, turn the adjustment screw 72 to move the needle piece 73 back and forth to change the effective area of the first branch path 71 and change the amount of air introduced into the second negative pressure chamber 62. By making the negative pressure at 69 higher or lower than the standard value, the movement of diaphragm 56 is modified to match the fuel flow rate with the engine required flow rate.

Furthermore, when the diaphragm 56 moves sharply toward the second negative pressure chamber 59 due to the high negative pressure when the throttle valve 4 is in the idle position, the metering needle 79 is inserted abnormally deeply into the main nozzle 48 and the fuel is The flow rate may be reduced below the engine required flow rate. Alternatively, there is a fear that the throttle valve 4 may suddenly close from the open position and the negative pressure in the second negative pressure chamber 59 will suddenly increase, causing the diaphragm 56 to overstroke and cause the metering needle 79 to collide with the main nozzle 48, causing damage. be. To do this, turn the screw 97 to move the stopper 98 back and forth, so that the tip of the metering needle 79 hits the stopper 98 at a position where a proper flow of fuel is supplied at idle, or at a position slightly before hitting the main nozzle 48. Adjust so that no more can be inserted.

Next, the operation when the engine starts will be explained.

Relatively small displacement engines that drive small vehicles, industrial machinery, generators, etc. have governors, and the throttle valves that control the amount of intake air are half open or fully open when the engine is stopped.

The engine starts with the throttle valve open and rapidly begins to rotate at high speed, but when it reaches that speed, the governor works to close the throttle valve to the idle position, and then the driver operates the throttle valve to open it as required. It is something that should be taken as a degree.

For this reason, when the engine is cranking, the venturi negative pressure, the intake negative pressure on the side of the throttle valve 4, the throttle valve 4
The intake negative pressure on the downstream side of the throttle valve 4 is low. Therefore, the negative pressure introduced into the negative pressure chamber 93 connected to the downstream side of the throttle valve 4 by the negative pressure passage 96 is low, and the starting spring 94 causes the diaphragm 92 to Move it toward the atmospheric chamber 90 and push the rod 89, press the valve body 84 against the first valve seat 82, and open the first negative pressure path 6.
0 is closed and the auxiliary negative pressure path 61 is opened.

The average value of the pulse pressure generated in the engine crankcase is negative regardless of whether it is a 2-cycle engine or a 4-cycle engine, and is negative from the auxiliary negative pressure path 61 to the valve chamber 81. Negative pressure is introduced into the first negative pressure chamber 58 via the outlet passage 86 . Therefore, the diaphragm 56 is connected to the first negative pressure chamber 58.
The starting fuel supplied from the main nozzle 48 can be increased by moving a little towards the main nozzle 48. When the engine completely explodes, the intake negative pressure becomes higher than during cranking, so the negative pressure introduced into the negative pressure chamber 93 becomes higher, causing the diaphragm 92 to move toward the negative pressure chamber 93 and away from the rod 89. Therefore, the valve body 84 is moved to the first valve seat 8 by the spring force of the return spring 85.
2 and is pressed against the second valve seat 83, and the first negative pressure path 6
0 is communicated with the first negative pressure chamber 58.

As described above, increasing the fuel flow rate when starting the engine is effective when the temperature is low, and for this purpose, the temperature valve 100 is provided in the auxiliary negative pressure path 61. This temperature valve 100 is of a cantilever type. It has a needle-shaped valve body 102 attached to the free end of a plate-shaped bimetal 101, and the valve hole 103 opens wide when the temperature is low and closes when the temperature is high. Therefore, when the engine is started when the temperature is high, the first negative pressure path 60 is closed by the negative pressure control valve 80 and the auxiliary negative pressure path 60 is closed.
1 is closed by the temperature valve +00 and becomes 0, so the first negative pressure chamber 58 is at atmospheric pressure. Therefore, the diaphragm 56 moves toward the second negative pressure chamber 59 and reduces the flow rate of fuel supplied from the main nozzle 48 until the engine completely explodes.

Furthermore, when the pulse pressure generated in the engine crankcase is introduced into the first negative pressure chamber 58, if the average value of the pulse pressure is low, the diaphragm 56 cannot be sufficiently suctioned to increase the amount of fuel.

For this purpose, a one-way valve 105 is provided in the auxiliary negative pressure path 6I. This one-way valve +05 has a spherical valve body 106 and a spring 107, as shown in FIG.
When the negative pressure component of the pulse pressure sent from the pulse chamber 11 acts on the valve body 106, it compresses the spring 107 and opens the valve hole 108. Therefore, when the engine is cranked, the first negative pressure chamber 58 can be at a high negative pressure.

After the engine has completely exploded, the throttle valve 4 is wide open as described above, so the rotational speed increases rapidly, and then the governor operates to close the throttle valve 4 to the idle position. At this time, in order to prevent the boat 62a opened to the intake path 2 of the second negative pressure path 62 from suddenly shifting from the upstream side to the downstream side of the throttle valve 4 and the pressure in the second negative pressure chamber 59 to change suddenly. , a plurality of boats 62a are provided in the axial direction of the intake passage 2. Furthermore, since the venturi negative pressure decreases as the throttle valve 4 closes, there is a concern that the pressure in the first negative pressure chamber 58 may change rapidly. Therefore, a plurality of boats 65a opening into the intake passage 2 of the first correction passage 65 are provided in the axial direction of the intake passage 2. These boats 62a, 65
With the arrangement a, it is possible to avoid sudden changes in the pressures of the first negative pressure chamber 58 and the second negative pressure chamber 59 when the throttle valve 4 moves near the idle position, thereby stabilizing the movement of the diaphragm 56. Do not change the fuel flow rate suddenly or overstroke the metering needle 79 to cause a large deviation in the fuel flow rate.

The second negative pressure path 62 can also be opened into the intake path 2 on the downstream side of the throttle valve 4, as disclosed in Japanese Patent Application Laid-Open No. 1-32031. in this case.

In order to avoid sudden changes in the pressure in the second negative pressure chamber 59, the throttle 69 and the needle piece 73 of the correction passage 70 work effectively.

As seen in FIG. 4, the second negative pressure passage 62 is connected to the lowest position of the second negative pressure chamber 59, and the correction passage 70 is connected to the highest position.
When connected, the fuel that has passed through the metering needle 79 and entered the second negative pressure chamber 59 is discharged together with the air through the second negative pressure path 62 to the intake path 2, and is stored in the second negative pressure chamber 59. The needle piece 73 that adjusts the effective area of the first branch path 71 of the correction passage 70 that is not affected by the air flow controls the air flow rate introduced into the second negative pressure chamber 59 to reduce the negative pressure of the second negative pressure chamber 59. The temperature valve 75 of the second branch 74 opens the valve hole 78 wide when the temperature is low, and works to adjust the position of the diaphragm 56 and thus the fuel flow rate supplied from the main nozzle 48. A large amount of air is introduced into the negative pressure chamber 59, the negative pressure in the second negative pressure chamber 59 is lowered, and the diaphragm 56 is moved more toward the first negative pressure chamber 58 than usual, thereby increasing the fuel flow rate. work.

The gist of the present invention is as shown in FIG.
The reason is that the return passage 50 that reaches the fuel tank is opened at a high point of No. 6.

This return passage 50 allows air bubbles contained in the fuel to pass through the pressure regulating chamber 3.
6, or when the fuel generates steam due to high temperature after the engine has stopped, these air and fuel vapors are discharged. Further, while the engine is operating, the fuel flow rate sent from the fuel pump 5 to the pressure regulating chamber 36 is set to be greater than the amount required by the engine so that a portion of the fuel returns to the fuel tank through the return passage 50. In this embodiment, a portion of the fuel that increases at low temperatures or that is required when the engine is under high load is returned to the return path more than necessary. A throttle 51 is provided at the entrance of the return passage 50 in order to prevent the flow through the return passage 50 and to prevent the discharge of air and steam from being obstructed.

FIG. 11 shows another embodiment for discharging air and fuel vapor from the pressure regulating chamber 36 of the fuel pressure regulator 25 into the fuel tank. In this embodiment, a temperature valve +51 is provided in a return passage +50 that opens at the highest point of the pressure regulating chamber 36 and reaches a fuel tank (not shown). This temperature valve 151 has a needle-shaped valve body 153 attached to the free end of a cantilevered plate-shaped bimetal 152, and when the temperature is low, the valve hole 154 is closed or slightly opened, and when the temperature is high, the valve hole 154 is closed or slightly opened. By doing so, a portion of the fuel that increases when the temperature is low is not allowed to flow into the return passage 150 more than necessary, and fuel vapor can be freely discharged when the temperature is high.

[Effects of the Invention] According to the present invention, since the return passage is opened at a high place in the pressure regulating chamber where the fuel of the fuel pressure regulator is maintained at a substantially constant positive pressure and temporarily retained, Nt is removed from the fuel. This is to immediately exhaust air and fuel vapor to prevent the fuel pressure in the pressure regulating chamber from going out of order.

In addition, when a throttle is installed in the return passage, there is no need to worry about unnecessarily escaping a portion of the fuel and causing engine malfunction, and when a temperature valve is installed, the fuel vapor that is generated in large quantities at high temperatures can be freely discharged. However, it shall not impair the normal functioning of the fuel pressure regulator.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing one embodiment of the present invention, Fig. 2 is a partially cutaway front view, Fig. 3 is an enlarged sectional view taken along the line A-A in Fig. 1, and Fig. 4 is a 1, FIG. 5 is an enlarged sectional view taken along line C-G in FIG. 2, FIG. 6 is an enlarged sectional view taken along line D-D in FIG. Figure 7 is an enlarged partial cross-sectional view taken along line E-E in Figure 2, and Figure 8 is F in Figure 1.
- An enlarged partial cross-sectional view taken along line F, Figure 9 is GG in Figure 1.
FIG. 1O is a diagram illustrating the relationship between the overall parts and the passage, and FIG. 11 is a sectional view showing a different embodiment of the return passage of the fuel pressure regulator.

Claims (1)

[Scope of Claims] 1. An intake passage having a fixed venturi and a throttle valve, a main nozzle that opens into the intake passage and whose effective area is variable with a metering needle, and a main nozzle that adjusts fuel to a substantially constant positive pressure. A fuel pressure regulator that sends fuel to the nozzle operates the metering needle according to the differential pressure between the venturi negative pressure and the intake negative pressure on the side of the throttle valve or downstream thereof, and controls the main nozzle in accordance with the engine intake air amount. a fuel flow regulator for varying the effective area of the fuel pressure regulator; a return passage reaching a fuel tank at a high point in the pressure regulating chamber for maintaining the fuel in the fuel pressure regulator at a substantially constant positive pressure; A fuel supply device characterized in that the return passage is open and a throttle for restricting the fuel flow rate is provided in the return passage. 2. In place of the throttle in the engine fuel supply system according to claim 1, a temperature valve is provided in the return passage, which closes or has a small opening when the temperature is low and opens wide when the temperature is high. fuel supply device.