JPH0419353A - Fuel supplier for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent excessive increase in fuel by providing a relief valve and an orifice portion in a communication passage branching from a fuel supply passage located at the discharge side of a fuel pump and by opening the relief valve to return surplus fuel to a fuel tank when a state is reached wherein the engine operation is in a condition of low load and the engine room is at a prescribed high temperature. CONSTITUTION:The fuel pump 51 which is accommodated within a fuel tank 61 comprises a pump housing 4 including a suction port 1 and a discharge port 3, the pump housing 4 having a pump chamber 5 in its interior. The pump chamber 5 is interiorly provided with an impeller 7 being driven by a drive motor. The fuel pump 51 further comprises a casing 10 and is formed with a communication passage 20 for communication between a fuel discharge space in the casing 10 and the interior of the fuel tank 61, an electromagnetic relief valve 21 being disposed in the passage 20. An orifice portion 28 is provided, in the passage 20, at a position thereof which is nearer to the fuel discharge space in the casing 10 than the position of a valve body 24. When a state of idle operation is reached in which the cooling water temperature becomes higher than a prescribed temperature and a throttle valve 42 is substantially closed, an electromagnetic coil 27 of the relief valve 21 is made 'on' to cause the valve body 24 to retreat against the urging force of a spring 25, thereby to open the passage 20. Thus, surplus fuel is returned to the fuel tank 61 via the communication passage 20 for its circulation within the fuel tank 61.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a fuel supply device for an internal combustion engine.

(Prior Art) In a conventional electronically controlled fuel injection type internal combustion engine, a fuel supply device to a fuel injection valve (fuel injector) is configured as shown in FIG. 8, for example.
124569, etc. That is, the fuel in the fuel tank 61 is sucked in and discharged by the fuel pump 62 and supplied to the fuel injection valve 65 via the fuel supply passage 64 in which the filter 63 is interposed. fuel supply passage 64
A pressure regulator 66 that opens when the pressure of
By returning the fuel to the fuel tank 61 through the
The supply pressure to 5 is controlled to be approximately constant. The fuel injection valve 65 opens in response to an actuation signal from a control unit (not shown) that controls the fuel injection amount according to various operating conditions of the engine, and injects fuel into the intake passage.

<Problems to be Solved by the Invention> Nowadays, the engine room of an internal combustion engine, where the fuel injection valve 65 and the like are installed, has various devices installed in a high density, and due to the increase in aerodynamic characteristics, etc. It has a structure that easily traps heat.

Here, as mentioned above, the excess fuel is transferred to the pressure regulator 6.
However, when the engine is in a low load state such as when the engine is in an idling state, the amount of fuel injected is not large, so a large amount of fuel with an increased temperature is returned to the fuel tank 61. will return to. As a result, the temperature of the fuel in the fuel tank 61 may rise and exceed the steam generation temperature, and there is a risk that steam will be generated in the fuel, causing a problem with startability during a warm restart (hot restart). There was that.

Further, as a measure against evaporative gas from the fuel tank 61, for example, the following fuel purge system is provided.

In this device, when the pressure inside the fuel tank 61 reaches a positive pressure equal to or higher than a predetermined value, the evaporated gas inside the fuel tank is guided to the canister and adsorbed and collected, and the fuel adsorbed on the canister is passed through the purge line. It is introduced into the intake passage and supplied to the engine.

The purge line is equipped with a diaphragm valve that is controlled to open and close in response to throttle negative pressure, and the diaphragm valve is controlled so that fuel is purged to the engine in a predetermined appropriate purge area. be done.

However, if the canister purge is increased as a measure against steam generation due to the rise in fuel temperature, there is a risk that over-richness will occur and rich engine stall will occur. For this reason, some fuel pump terminal voltage control (FPCV) is implemented to control the discharge amount of the fuel pump 62, but this leads to an increase in cost.

The present invention has been made in view of the above-mentioned conventional situation, and an object of the present invention is to prevent unnecessary fuel supply from a fuel pump with a simple configuration and to prevent a rise in fuel temperature.

<Means for Solving the Problems> Therefore, as shown in FIG. 1, the present invention provides a fuel pump for an internal combustion engine in which fuel from a fuel tank is sucked by a fuel pump and fed under pressure to a fuel injection valve via a fuel supply passage. In the supply device, a normally closed relief valve and an orifice are provided in a communication passage that branches from the fuel supply passage downstream of the impeller discharge port of the fuel pump and communicates with the fuel tank, and a low-load valve that detects low-load conditions is provided in the communication passage that branches off from the fuel supply passage downstream of the impeller discharge port of the fuel pump and communicates with the fuel tank. a condition detecting means; an engine room temperature detecting means for detecting a temperature in the engine room; and an engine room temperature detecting means for opening the relief valve when a low load condition is detected and it is detected that the engine room is at a high temperature higher than a predetermined temperature. A relief valve control means for controlling the valve and returning surplus fuel to the fuel tank is provided.

<Function> If the low load condition detection means detects a low engine load condition and the engine room temperature detection means detects that the engine room is hotter than a predetermined temperature, the engine requires only a small amount of fuel. , and because the temperature of surplus fuel that is not pumped to the fuel injection valve may rise due to the heat generated from the engine, the relief valve is opened by the relief valve control means to return the surplus fuel to the fuel tank.

Further, even when the relief valve is open, since the orifice is provided in a part of the flow path, the supply pressure by the fuel pump is ensured by the orifice, and the pressure feeding of fuel by the fuel pump is not hindered.

<Example> Embodiments of the present invention will be described below based on the drawings.

Incidentally, the same elements as those in the conventional example are given the same reference numerals and the explanation thereof will be omitted.

FIG. 4 shows the overall configuration of a fuel supply system for an internal combustion engine according to the first embodiment of the present invention, in which fuel in a fuel tank 61 is sucked in and discharged by a fuel pump 51 built into the fuel tank 61, and filtered into a filter 63. The fuel is supplied to the fuel injection valve 65 through the interposed fuel supply passage 64.

An internal combustion engine (not shown) has an intake duct 41. Air is sucked in via the throttle valve 42. Also, throttle valve 4
2 is provided with a throttle valve opening sensor 43 that detects the opening of the throttle valve, and a water temperature sensor that detects the cooling water temperature Tw facing the water jacket of the engine to indirectly detect the temperature inside the engine room. 44 are provided.

That is, the water temperature sensor 44 constitutes engine room temperature detection means. Further, the throttle valve opening sensor 43 can detect idling operation when the opening is below a predetermined opening. Incidentally, since the idle operating state is an operating state with a small fuel flow rate, it is a low load state, so the throttle valve opening sensor 43 functions as a low load condition detection means.

Further, the control unit 45 includes CPU, ROM, R
It is equipped with a microcomputer including an AM and an input/output interface, and receives input signals from various sensors, performs arithmetic processing as described below, and controls the operation of an electromagnetic relief valve as described below.

Here, as the fuel pump 51, a non-displacement type circumferential flow pump as shown in FIG. 2 is used.

That is, a pump chamber 5 is provided in a pump housing 4 having an inlet 1 and an outlet 3.

The second pump chamber 5 includes an impeller 7 that is rotationally driven by an electric motor (not shown).

As shown in FIG. 3, the impeller 7 has a structure in which a plurality of grooves 8 are formed on the front and back peripheral parts, respectively, and the blades 2 are provided between the grooves 8.

The fuel sucked in from the suction port 1 by the rotational drive of the impeller 7 is formed between the inner circumferential wall of the pump chamber 5 and the outer circumferential wall of the impeller 7 by the rotational force of the groove 8 formed in the impeller 7. The fuel is pumped to the discharge port 3 through the fuel pumping gap 9, passes through the casing 10, and is connected to a fuel supply passage 6 from a fuel outlet (not shown) formed in the upper part of the casing 10.
4 to the fuel injection valve 65.

Here, as a configuration according to the present invention, a communication passage 20 that penetrates the wall of the pump housing 4 and communicates the fuel discharge space inside the casing 10 with the inside of the fuel tank 61 is formed, and the communication passage 20 is provided with an electromagnetic type. A relief valve 21 is provided.

A valve seat 23 is formed on the inner peripheral surface of the communication passage 20. In order to ensure sealing performance, a valve body 24 made of an elastic material such as fluorocarbon rubber is disposed to face the valve seat 23 and to be movable in the axial direction.

The valve body 24 is elastically biased in the direction of seating on the valve seat 23, that is, in the valve closing direction, by a coil spring 25, one end of which is engaged with the outer locking portion 24b of the valve body 24. Further, an electromagnetic coil 27 is wound around a core portion 26 to which the other end of the coil spring 25 is locked. The operation of the electromagnetic coil 27 is controlled by the control unit 45 as described above.

Furthermore, the casing 10 is
An orifice portion 28 is provided on the side near the upper fuel discharge space, and by narrowing the discharge port area, a drop in fuel supply pressure is prevented when the electromagnetic relief valve 21 is opened.

In this configuration, when the electric motor (not shown) is driven and the fuel pump 51 supplies fuel to the fuel injection valve 65, the electromagnetic relief valve 21 is controlled according to the flowchart shown in FIG.

In step 1 (denoted as Sl in the figure, the same applies hereinafter), it is determined from the detection signal of the water temperature sensor 44 whether the cooling water temperature Tw is equal to or higher than a predetermined temperature.

In step 2, it is determined from the detection signal of the throttle valve opening sensor 43 whether or not the throttle valve 42 is in an idling operating state.

If YES is determined in Steps 1 and 2, the engine cooling water temperature will rise due to heat from the engine body, and this temperature rise will cause the temperature in the engine room to rise, and the temperature of the fuel passing through the engine room to rise. Furthermore, since it is determined that the fuel injection amount is not large and the engine is in an idling state, a large amount of fuel whose temperature has increased will return to the fuel tank 61 via the fuel return passage 67. Therefore, proceed to step 3 and install the electromagnetic coil 27.
is turned ON, the valve body 24 is opened against the coil spring 25, and the excess fuel is returned to the fuel tank 61 via the communication passage 20 without being supplied downstream from the fuel pump 51, and the excess fuel is returned to the fuel tank 61 within the fuel tank 61. Circulate.

Further, if it is determined NO in step 1 or step 2, proceed to step 4, turn off the electromagnetic coil 27, close the valve body 24 by the coil spring 25,
Fuel is supplied downstream from the fuel pump 51.

Furthermore, the electromagnetic relief valve 21 is
Since the supply pressure is prevented from decreasing when the fuel passes through the fuel injection valve 65, even if the supply amount to the fuel injection valve 65 decreases, the supply pressure to the fuel injection valve 65 is controlled to be substantially constant. A stable fuel supply can be ensured.

Therefore, as explained above, according to this embodiment, a large amount of fuel whose temperature has increased is prevented from returning to the fuel tank 61, so that the temperature of the fuel in the fuel tank 61 does not increase, and the temperature of the fuel in the fuel increases. The orifice portion 28 ensures stable fuel supply while suppressing steam generation.

Furthermore, the canister barge does not increase and there is no need to perform fuel pump terminal voltage control, etc., leading to cost reduction.

Next, a second embodiment according to the present invention will be described based on FIG. 6, and the same elements as those in FIG. 4 will be given the same reference numerals and explanations will be omitted.

In the first embodiment of the present invention, the fuel pump 51 having the electromagnetic relief valve 21 is used as the fuel pump, but the electromagnetic relief valve 21 does not need to be provided integrally with the fuel pump 51, and the second embodiment In the embodiment, as shown in FIG. 6, the electromagnetic relief valve 2 is installed in the middle of a communication passage 52 that branches from a fuel supply passage 64 and communicates with a fuel tank 61.
The configuration is such that an electromagnetic relief valve 53 that has the same effect as 1 is interposed.

Further, an orifice portion 54 similar to the orifice portion 28 is provided.
is provided between the electromagnetic relief valve 53 and the fuel supply passage 64.

Also in the second embodiment, surplus fuel is not supplied to the fuel injection valve 65, but passes through the communication path 52 to the fuel tank 61.
Therefore, it is possible to prevent the temperature inside the fuel tank 61 from rising, and the orifice portion 54 allows stable fuel supply.

In the embodiment described above, it is determined whether or not it is in an idling state based on the detection signal of the throttle valve opening sensor 43, and thereby it is determined whether or not it is in a low load state. However, the low load condition is detected as follows. You can.

That is, the basic fuel injection amount Tp and the engine speed N are taken as representative of the engine operating conditions, and when the operating conditions are in the region S shown in FIG. 7, a low load condition with a small fuel flow rate is established. You may judge that.

<Effects of the Invention> As explained above, according to the present invention, since the relief valve is provided to return high temperature surplus fuel to the fuel tank, unnecessary fuel is not supplied from the fuel pump to the engine room. This prevents the fuel temperature from rising. Further, since the orifice portion is formed in a part of the fuel supply passage, even if the relief valve is opened, pressure feeding by the fuel pump is not affected, and stable fuel supply can be ensured.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a sectional view of the pump housing portion of the circumferential flow pump according to the first embodiment of the present invention, FIG. 3 is a perspective view of the impeller, and FIG. The figure is an overall configuration diagram of a fuel supply system for an internal combustion engine according to the embodiment shown above, FIG. FIG. 7 is a diagram showing the engine low load operating conditions, and FIG. 8 is a diagram showing the entire configuration of a conventional fuel supply system. 4... Pump housing 7... Impeller 20,
52...Communication path 21.53...Solenoid relief valve 24...Valve body 27...Solenoid coil 28.
54... Orifice part 43... Throttle valve opening sensor 44... Water temperature sensor 45... Control unit 51... Fuel pump patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Tomiji Sasashima male

Claims (1)

[Claims] In a fuel supply system for an internal combustion engine, in which fuel from a fuel tank is sucked in by a fuel pump and fed under pressure to a fuel injection valve via a fuel supply passage, a fuel supply passage is branched from a fuel supply passage downstream of an impeller discharge port of the fuel pump and communicated with the fuel tank. In addition to providing a normally closed relief valve and an orifice in the communication passage,
A low load condition detection means for detecting a low load condition; an engine room temperature detection means for detecting a temperature inside the engine room; 1. A fuel supply device for an internal combustion engine, comprising: relief valve control means for opening the relief valve and returning surplus fuel to a fuel tank.