JPH0223818Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a fuel return device in a fuel supply section of an internal combustion engine.

(Prior art) In order to prevent the occurrence of vapor lock and percolation caused by an increase in ambient temperature during fuel supply, a fuel return device returns a portion of the fuel pumped by the fuel pump to the fuel pump. This is a device that suppresses abnormal temperature rise of fuel by returning it from the discharge part of the fuel tank or the inlet part of the float chamber of the carburetor to the fuel tank via a return passage. As shown, since the flow area of the return passage is constant, the return flow rate is constant regardless of the engine ambient temperature.

(Problem that the invention aims to solve) For this reason, according to the conventional example, during extremely low speed operation at high temperatures in the summer, sufficient return flow cannot be obtained, and the temperature of the fuel rises, causing vapor lock, etc. On the other hand, during warm-up operation at low temperatures in winter, the return flow rate becomes more than necessary, preventing the fuel from rising in temperature, and causing a problem in that it takes time to atomize the fuel.

This problem occurs when the fuel pump is a mechanical type that pumps fuel in conjunction with the rotation of the camshaft, as in the present invention, and because it has to be installed near the engine, the heat transmitted from the engine This is particularly problematic due to the special circumstances of being susceptible to high temperatures.

Further, Japanese Patent Publication No. 57-32229 discloses a flow control valve that solves this problem. This valve and its temperature sensing part are built into the fuel pump, and the flow rate can be controlled according to the temperature of the fuel pump. However, the temperature of the fuel pump is greatly influenced by the heat of the engine, and does not reflect the ambient temperature much.

For this reason, the flow rate control by the flow rate control valve tends to be far from the actual fuel temperature, and proper control cannot be expected.

(Means for solving the problem) A mechanical fuel pump that pumps fuel in conjunction with the rotation of a camshaft, and a return passage that returns a portion of the fuel pumped by the fuel pump to the fuel tank. In the fuel return device for an internal combustion engine, which includes a flow rate control valve that is provided in the return passage and continuously changes the flow path area of the return fuel, the temperature sensing part of the charge control valve is integrated with the fuel pump, Moreover, the fuel pump is characterized in that most of its portion is provided so as to protrude into the space around the outer circumference of the fuel pump.

(Function) According to the above configuration, the temperature-sensing part of the flow control valve is integrated with the mechanical fuel pump, which easily becomes hot due to heat conduction from the engine, and most of the part protrudes into the outer space of the fuel pump. The temperature-sensing section detects the composite temperature of the heat conduction from the fuel pump, which is affected by the engine temperature, and the ambient temperature of the fuel pump, which is detected by the protruding majority of the space around the fuel pump. Since the return flow rate is continuously changed accordingly, the temperature of the fuel, which increases due to the influence of the engine and the atmosphere, can be precisely controlled in accordance with the actual temperature change of the fuel.

(Embodiment) The embodiment of the present invention shown in FIG.
This relates to a fuel return device to which the starting end of the discharge section return passage 2 is connected. Fuel in the fuel tank 3 is sucked into the fuel pump 1 via a tank-side fuel supply passage 4. In this embodiment, a mechanical pump is used as the fuel pump 1, which sucks in and discharges fuel using a diaphragm 6 that moves up and down in conjunction with the rotation of a camshaft 5. The fuel sucked into the fuel pump 1 passes through a suction valve 7 and a discharge valve 8, and then enters a discharge chamber 9 formed in the fuel pump 1.
to go into. A carburetor-side fuel supply passage 10 and a return passage 2 are connected to the discharge chamber 9. The fuel entering the carburetor side fuel supply passage 10 is sent to the float chamber 12 of the carburetor 11. On the other hand, the fuel that has entered the return passage 2 is returned to the fuel tank 3.

The return port 13 located at the starting end of the return passage 2 is provided with a thermostatic flow control valve 14 that continuously variably controls the flow area of the return port 13 . A temperature sensing portion (for example, filled with wax) 15 of the flow rate control valve 14 is provided integrally with the fuel pump 1, and most of the portion thereof protrudes into the space around the outer circumference of the fuel pump 1. .

The fuel pump 1 is provided so as to be linked to the rotation of the camshaft 5, and is located close to the engine and easily becomes high temperature due to heat conduction from the engine. In addition to this, it is possible to immediately detect the temperature rise trend of the fuel based on the heat transfer from the fuel pump 1, but the thermal influence from the engine is so large that it is difficult to accurately detect the temperature rise of the fuel itself. On the other hand, temperature sensing part 1
5 protrudes into the outer space of the fuel pump 1, and by sensing the engine ambient temperature, that is, the ambient temperature of the fuel pump 1 affected by the outside temperature, etc., this ambient temperature and the fuel pump 1 can be detected.
The flow control valve 14 can be controlled in accordance with the actual fuel temperature based on the combined temperature with the heat conduction from the fuel.

Therefore, the flow rate control valve 14 does not work to increase the return amount only when the temperature of the fuel pump 1 increases, but works to increase the return amount of fuel when the ambient temperature increases. This makes it possible to detect fuel temperature rises without delay and properly, to ensure that the fuel is kept below the upper limit temperature, and to reliably prevent the occurrence of vapor lock, percolation, etc. caused by abnormal fuel temperature rises. can.

Furthermore, as the temperature of the fuel pump 1 and the ambient temperature decrease, the temperature sensing section 15 senses a decrease in the temperature of the fuel, and the flow control valve 14 operates to reduce the return amount of fuel, thereby delaying the decrease in the temperature of the fuel. Therefore, it is possible to properly detect the temperature of the fuel and atomize the fuel by keeping the fuel at a temperature higher than or equal to the lower limit temperature, thereby avoiding a situation where the time required for warm-up operation becomes longer.

In the embodiment of the present invention shown in FIG. 2, the valve body 16 of the flow control valve 14 is formed into a tapered shape so that the flow rate of fuel flowing into the return passage 2 can be controlled more accurately.

The present invention can be configured in various ways other than those shown in the above embodiments. For example, the flow control valve 14
As the flow control valve 14, a combination of a solenoid valve and a thermoswitch can be used.
may be provided in the middle or at the end of the return passages 2, 2a.

(Effects of the invention) Since the present invention has the above structure and function,
In the fuel return device of an internal combustion engine, it prevents the fuel from becoming abnormally heated due to the heat from the engine or the influence of the engine atmosphere temperature that varies depending on the season, etc., which may cause vapor lock or percolation. Heat conduction from the mechanical fuel pump, which is easily affected by engine heat, and the engine ambient temperature are important in order to avoid problems such as poor atomization and longer warm-up times due to a drop in fuel temperature below the lower limit temperature. In other words, by detecting the composite temperature of the fuel pump's ambient temperature influenced by outside temperature, etc., the fuel return flow rate can be properly controlled in accordance with the actual fuel temperature change to ensure that the objective is achieved. Can be done.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention, and FIG. 2 is a sectional view of main parts of another embodiment of the present invention. 1... Fuel pump, 2, 2a... Return passage, 5... Camshaft, 14... Flow rate control valve,
15...Temperature sensing part.

Claims (1)

[Scope of utility model registration request] A mechanical fuel pump that pumps fuel in conjunction with the rotation of the camshaft, a return passage for returning a portion of the fuel pumped by the fuel pump to the fuel tank, and a In a fuel return device for an internal combustion engine, which is equipped with a flow control valve that continuously changes the flow path area of the return fuel, the temperature sensing part of the flow control valve is integrated with the fuel pump, and most of the part is located around the outside of the fuel pump. A fuel return device for an internal combustion engine, characterized in that it is provided so as to protrude into space.