JPS62165571A - Pressure control structure for fuel injection device - Google Patents

Abstract

PURPOSE:To make it possible to preferably control fuel injection over the entire operating range of an engine, by providing a fuel pressure detecting means having such an arrangement that a fuel pump is operated when the pressure of fuel fed to a fuel injection valve is below a set lower limit fuel pressure, and the operation of the pump is stopped when it is above a set upper limit fuel pressure. CONSTITUTION:The drive of a fuel pump 4 is controlled in accordance with a signal from a fuel pressure detecting means such as a pressure detector 3 or the like which is disposed in a fuel passage 6 for introducing fuel to a fuel injection valve 12 in an engine 1. Further, a pressure regulating valve 7 is arranged in the vicinity of the fuel injection valve 2 in the fuel passage 6, and a fuel return passage 10 disposed therein with a return valve 9 is laid downstream of the fuel injection valve 2. The pressure detector 3 includes a fuel accumulator 11 having a casing 16 in which a fuel pressure chamber 19 and a pressure chamber 20 is sectioned by means of a flexible membrane 18, and is provided with a first limit switch 13 which is closed when the fuel pressure in the fuel injection valve 2 is below a set lower limit fuel pressure, and a second limit switch 13 which is closed when the fuel pressure exceeds a set upper limit fuel pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a pressure horn control structure for a fuel injection device, and in particular to a fuel injection device that maintains the fuel pressure of an injection valve constant by controlling the operation of a fuel pump. This invention relates to a pressure control structure for a device.

<Prior Art> Generally, the fuel pressure of a fuel injection device is controlled by using the intake pipe pressure downstream of the throttle valve of the internal combustion engine as a control pressure to control the fuel flow d supplied to the injection valve. In such a fuel injection device, when the engine is operating, the fuel pump continues to operate under the same operating conditions regardless of the amount of fuel consumed by the engine. However, when the engine is running, the amount of fuel consumed is low, so the fuel pump supplies excess fuel.
By returning excess fuel to the fuel tank using the pressure horn adjustment valve, excess fuel is prevented from being supplied to the intake tract. In addition, it is necessary to keep in mind that at high temperatures, part of the fuel supplied to the injection valve may turn into fuel vapor and cause percolation. was prevented.

<Problems to be Solved by the Invention> Therefore, the fuel pump consumes approximately constant energy regardless of the amount of fuel it actually supplies to the injection valves, especially when the engine is in an idling state. There is a problem in that the fuel pump wastes energy in some cases. In view of these problems in the prior art, the main purpose of the present invention is to constantly detect the fuel pressure of fuel being pumped to the injection valve and incorporate it as a parameter for fuel pump control, thereby controlling changes in engine operating conditions. It is an object of the present invention to provide a pressure control structure for a fuel injection device that can supply fuel according to the fuel pump as quickly and smoothly as possible and eliminate wasteful consumption of energy for fuel pump operation.

<Problem S: Means for Solving> According to the present invention, the purpose is to provide an injection valve that injects and supplies fuel to the intake passage, a fuel pump that pressurizes and feeds fuel to the injection valve, and a throttle valve. In a pressure control structure for a fuel injection device comprising a pressure regulating valve for maintaining a constant fuel pressure of an injection valve using downstream intake pipe internal pressure as a control pressure, the fuel pressure of the injection valve is a set lower limit. A pressure control structure for a fuel injection device, characterized by comprising a fuel pressure detection means having a contact point that operates the fuel pump when the fuel pressure is lower than the fuel pressure and stops the operation of the fuel pump when the fuel pressure is higher than the set upper limit fuel pressure, and the above-mentioned pressure control structure for a fuel injection device. a fuel pressure detection means having a contact point that operates the fuel pump when the fuel pressure of the injection valve is below a set lower limit fuel pressure and stops the operation of the fuel pump when the fuel pressure is above the set upper limit fuel pressure, and provided on the downstream side of the injection valve. Pressure for a fuel injection device, comprising: a fuel return passage having a return valve; and a temperature detection means having a contact point that opens the return valve when the temperature near the injection valve is equal to or higher than a set temperature. This is achieved by providing a control structure.

<Operation> As described above, according to the present invention, fuel at a constant pressure is supplied to the injection valve by controlling the operation of the fuel pump according to changes in engine operating conditions. It becomes possible to supply fuel in just the right amount. In addition, in a configuration in which a return valve is provided in the fuel return passage, the normally closed return valve is opened in response to temperature fluctuations due to changes in engine operating conditions, and fuel vapor is directed to the fuel return passage. By flowing down, percolation that can occur at high temperatures can be prevented.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a fuel path system diagram showing a pressure control structure based on the present invention. A communicating fuel passage is provided downstream of the injection valve 2 that injects fuel into the combustion chamber and intake passage of the engine 1. Fuel pressure P of the fuel pumped to 2
f is always input. Fuel pump 4 that pumps fuel
is provided on the upper wall inside the fuel tank 5, and is driven by the output signal from the pressure detector 3, so that the fuel tank 5
The fuel inside is supplied to the injection valve 2 through a fuel passage 6 and a pressure regulating valve 7 provided close to the injection valve 2. Also,
The temperature in the vicinity of the injection valve 2 is constantly input to a temperature detector 8 such as a bimetal that is provided in the vicinity of the injection valve 2 . A fuel return passage 10 equipped with a return valve 9 is provided downstream of the injection valve 2, and when the detected temperature Tf input to the temperature detector 8 is equal to or higher than the set temperature T1, the return valve is activated by an output signal. The valve 9 is opened to allow the fuel vapor at high temperature to flow back into the fuel tank 5 via the fuel return passage 10. The pressure detector 3 is installed on the earthen wall inside the fuel tank 5, and as shown in FIG. It is composed of a first limit switch 13 and a second limit switch 14, which control the operation of the limit switch 13 and the second limit switch 14.

The fuel accumulator 11 has a fuel pressure inlet 15 on the upper surface.
The interior of the casing 16 is divided into a fuel pressure chamber 19 and a pressure chamber 20 by a diaphragm 18 that is flexibly stretched between the inner side wall surfaces of the casing 16 via a retainer 17. The pressure chamber 20 is filled with the gas 12 that urges the diaphragm 18 upward toward the fuel pressure chamber 19 .

In the fuel pressure chamber 9, the first limit switch 13 is provided on the inner upper wall surface of the casing 16, and is closed when the fuel pressure (detected fuel pressure) Pf introduced from the fuel pressure inlet 15 becomes lower than the set lower limit fuel pressure P1. The switch of the fuel pump 4 is opened to start operation. In the pressure chamber 20, the second limit switch 14 is provided on the bottom wall surface of the casing 16, and is closed when the detected fuel pressure Pf becomes equal to or higher than the set upper limit fuel pressure 22, and the switch of the fuel pump 4 is closed. open and stop operation. The set lower limit fuel pressure P1 and the set upper limit fuel pressure P2 are set to higher pressures than the fuel pressure adjusted by the pressure regulating valve 7 when the intake pipe internal pressure is at its maximum pressure. As clearly shown in FIG. 3, the pressure regulating valve 7 has a lower casing 21 provided with a fuel port 22 through which pressurized fuel flows and a fuel outlet 23 communicating with the injection valve 2. It is being

The upper casing 24 is provided with a negative pressure inlet 25 that communicates with an intake passage of the internal combustion engine. These two casings 21, 24 sandwich the diaphragm 26 and are fixed to each other by caulking. The diaphragm 26 divides the cavity defined within the casing into a negative pressure chamber 27 and a pressure chamber 28. A valve support 29 is attached to the center of the diaphragm 26 by a retainer 30, and a compression coil spring 31 interposed between the retainer 30 and the upper wall surface of the negative pressure chamber 27 is urged downward toward the pressure chamber 28 side. A cylindrical valve body 32 is located in the center of the two valve supports on the pressure chamber 28 side.
is protruding downward. A circular valve hole 33 is formed on the side surface of the valve body 32 on the fuel outlet 23 side.

A fuel inlet pipe 34 is press-fitted into the fuel inlet 22, and the tip of the inlet pipe 34 is oscillatably fitted inside the valve body 32. A counterbore surface 35 is formed, and an O-ring 36 is held in an annular gap defined by the counterbore surface 35 and the enlarged diameter portion 34a of the fuel inflow pipe 34, thereby ensuring the liquid tightness of the fuel inflow pipe 34. Furthermore, a circular fuel outlet 3 having the same diameter as the valve hole 33 is provided at the tip of the fuel inlet pipe 34 on the valve hole 33 side.
7 have been established. The fuel outlet 37 is provided vertically offset from the valve hole 33 so as to constitute a variable throttle valve in which the opening area of the fuel passage increases as the pressure inside the intake pipe downstream of the throttle valve increases. ing.

Next, the operation of the above embodiment will be explained. First, the fuel pressure Pf detected by the fuel detector 3 is the set upper limit fuel pressure 2.
If the fuel pressure Pf rises to 2 or more, the diaphragm 18
moves downward against the gas pressure of the filled gas 12, and the fuel detector 3
The second limit switch 14 of the fuel pump 4 is closed and the second limit switch 14 of the fuel pump 4 is closed.
Open the switch to deactivate it. When the detected fuel pressure Pf falls below the set temperature T1, the diaphragm 18 moves upward due to the gas pressure of the sealed gas 12, the first limit switch 13 of the fuel detector is closed, and the switch of the fuel pump 4 is closed. Close it and start working. Further, when the temperature Tf near the injection valve 2 detected by the temperature detector 8 rises to 1 or more below the set temperature at which fuel vapor is generated, the contact of the temperature detector 8 is closed and the return valve 9 is closed. The switch is closed, the return valve 9 is opened, and the fuel vapor is returned to the fuel tank 5 via the fuel return passage 10. The detected temperature T
When f falls below the set temperature T1, the contact of the temperature detector 8 is opened, the switch of the return valve is opened,
The return valve 9 is closed to block the fuel return passage.

In the above embodiment, a fuel return passage 10 with a return valve 9 is provided on the downstream side of the injection valve 2, and the return valve 9
Although the valve is opened by the temperature detector 8, the fuel return passage 10 having the return valve 9 may be omitted.

<Effects of the Invention> As described above, according to the present invention, since the operation of the fuel pump is controlled by comparing the fuel pressure of the fuel supplied to the injection valve with the set pressure value, a suitable Fuel injection control can be performed. In addition, in a configuration with a fuel return passage, the temperature near the injection valve is compared with the set temperature, and fuel vapor that may occur at high temperatures is returned to the fuel return passage. Percolation can be prevented. Therefore, the operation of the fuel pump is controlled according to changes in the operating conditions of the engine, and appropriate fuel is supplied, so that energy is not wasted for operating the fuel pump, and energy is saved. In addition, fuel consumption is reduced, air-fuel ratio control is excellent, fuel vapor generation is prevented, and engine drivability is improved, so the effects are extremely large.

[Brief explanation of drawings]

FIG. 1 is a fuel path system diagram equipped with a pressure control structure based on the present invention. FIG. 2 is a longitudinal sectional view showing details of a pressure detector used in the same structure. FIG. 3 is a vertical sectional view showing details of the pressure regulating valve used in the same structure. 1... Engine 2... Injection valve 3... Pressure horn detector 4... Fuel pump 5... Fuel tank 6... Fuel passage 7... Pressure adjustment valve 8.
... Temperature detector 9 ... Return valve 10 ... Fuel return passage 11 ... Fuel accumulator 12 ... Filled gas

Claims (5)

[Claims] (1) An injection valve that injects fuel into the intake passage, a fuel pump that pressurizes the fuel and sends it to the injection valve, and maintains the fuel pressure of the injection valve at a constant level using the intake pipe pressure downstream of the throttle valve as a control pressure. In a pressure control structure for a fuel injection device, the fuel pump is operated when the fuel pressure of the injector is below a set lower limit fuel pressure, and when the fuel pressure is above a set upper limit fuel pressure. 1. A pressure control structure for a fuel injection device, comprising a fuel pressure detection means having a contact point for stopping the operation of a fuel pump. (2) The fuel pressure detection means includes a fuel accumulator;
2. The pressure control structure for a fuel injection device according to claim 1, further comprising a pressurizing means for pressurizing the fuel stored in the fuel accumulator to a pressure equal to or higher than the set upper limit fuel pressure. (3) The pressure regulating valve is a variable throttle type valve in which the opening area of the fuel passage increases as the intake pipe pressure downstream of the throttle valve increases, which is the control pressure. A pressure control structure for a fuel injection device according to item 1 or 2. (4) A patent claim characterized in that the set lower limit fuel pressure and the set upper limit fuel pressure are set to higher pressures than the fuel pressure adjusted by the pressure regulating valve at the time of the maximum pressure in the intake pipe downstream of the throttle valve. A pressure control structure for a fuel injection device according to any one of items 1 to 3. (5) An injection valve that injects fuel into the intake passage or combustion chamber, a fuel pump that pressurizes the fuel and sends it to the injection valve, and a control pressure that controls the pressure inside the intake pipe downstream of the throttle valve to keep the fuel pressure of the injection valve constant. In a pressure control structure for a fuel injection device, the fuel pump is operated when the fuel pressure of the injector is below a set lower limit fuel pressure, and the fuel pressure is below a set upper limit. a fuel pressure detection means having a contact that stops the operation of the fuel pump when the fuel pressure is exceeded; a fuel return passage provided on the downstream side of the injection valve and having a return valve; 1. A pressure control structure for a fuel injection device, comprising: temperature detection means having a contact point for opening a valve.