Claims:We Claim:

1. A low pressure circuit (LPC) (100) of a common-rail fuel injection system, comprising:
a fuel supply pump (102) adapted to pressurize drawn fuel and discharge the fuel from common rail through a plurality of the injectors,
a fuel tank (106 ) connected to the fuel supply pump (102), by way of a filter (104) and adapted to accumulate the fuel at high pressure;
characterized in that
an accumulator (110) connected to the low pressure circuit (LPC) (100) and adapted to support the LPC (100) by compensating pressure variation at inlet port of the fuel supply pump (102), and
a two-way valve (114) disposed in return lines from the fuel supply pump (102) wherein said two-way valve (114) is adapted to control the fuel going to the fuel tank (106) and the accumulator (110 ), based on the pressure variation.

2. The low pressure circuit (LPC) (100) as claimed in claim 1, wherein said two-way valve (114) is an electronically controlled two-way valve (114) fixed in return lines from the fuel supply pump (102).

3. The low pressure circuit (LPC) (100) as claimed in claim 2, wherein said two-way valve (114) is a fuel control valve that can be actuated between a closed position and an open position allowing fuel goes to the fuel tank (106) and to the accumulator (110) based on pressure variation.

4. The low pressure circuit (LPC) (100) as claimed in claim 1, wherein said fuel filter (104) comprising a pressure sensor (116) further configured to sense the fuel inlet pressure at fuel pump (102) and send signals to an electronic control unit ECU (112) when fuel level reaches a predetermined limit of the fuel in the accumulator (110).

5. The low pressure circuit (LPC) (100) as claimed in claim 4, wherein on receiving signals from the pressure sensor (116) said ECU (112) triggers the two-way valve (114) to open its ends for fuel flow towards the fuel tank (106) or the accumulator (110) based on the sensed fuel inlet pressure at fuel pump (102).
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] Present invention relates to a fuel supply apparatus with modified Low Pressure circuit (LPC) to control fuel inlet pressure at higher altitude, for a suction based FIE (fuel injection equipment) system in a fuel pump of a vehicle.

Background of the invention
[0002] In the existing common rail fuel injection system, the most common failure is cavitation or “vapor lock”, combination of heat or too much inlet restriction can create this operating condition Such cavitation erosion experienced in a fuel injection system of a engine greatly deteriorates the engine performance and reliability. Sometimes when vehicles operate at higher altitude than sea level say for example above 2500m, the atmospheric pressure drops for example 0.3 bar abs against the specified limit say for example 0.5 to 1 bar abs. Due to this pressure drop, cavitation occurs inside the fuel pump leading to damages inside and at the end the pump fails. The end results are often permanent, even after the cause of cavitation is addressed. Typically, even short bouts of cavitation will damage the fuel pump, resulting in direct loss of capacity and efficiency. This damage to the pump results in operating conditions that quickens cavitation exposure at each use. Eventually, the fuel system resorts to complete failure to build or maintain pressure.

[0003] The prior art, DE10108175C1 discloses a fuel pump which has a high pressure line (11), a piston pump (21) membrane store (31). A 2/2 path valve is controlled by a membrane (35) of the membrane store, which closes the valve to keep the fuel supply to the piston pump flowing, so that an emergency driving function is maintained if the membrane store fails.

[0004] Another prior art, US9200605B2 discloses an apparatus for preventing cavitation damage to a diesel engine fuel injection pump comprises a valve member mounted on a barrel port to shut the barrel port during an early stage of fuel compression performed by the upward movement of a plunger to increase the pressure in the barrel port, a valve housing installed in the deflector or the barrel of a pump housing to support the valve member, and a pressure control valve constituted by a spring interposed between the valve member and the valve housing to elastically support the valve member. The barrel port is shut to increase the pressure therein during the early stage of fuel compression, and when the pressure of fuel in the barrel port exceeds a level higher than an open level, the barrel port opens to discharge fuel.

Brief description of the accompanying drawing
[0005] Different modes of the invention is disclosed in detail in the description and illustrated in the accompanying drawings:

[0006] Figure 1 illustrates modified low pressure circuit for a common-rail fuel injection system of a vehicle, in accordance with embodiments of the invention.

Detailed description of the embodiments
[0007] Fig. 1 illustrates a low pressure circuit 100 for an engine with a modified design, for a common-rail fuel injection system for an engine for a vehicle. The low pressure circuit (LPC) 100 includes a fuel supply pump 102, a fuel filter 104, a fuel tank 106, an accumulator 110 and a two-way valve 114 amongst other components such as common rail, fuel injectors and others. Each component is described in further detail below.

[0008] The fuel supply pump 102 is adapted to pressurize drawn fuel and discharge the fuel from common rail through a plurality of the injectors. In operation, the fuel flows from the fuel tank 106 to the fuel pump 102 after being filtered from the fuel filter 104. The fuel tank 106 is in fluid communication with the fuel filter 104. The fuel filter 104 is in fluid communication with the fuel pump 102. The fuel tank 106 is connected to the fuel pump 102, by way of the filter 104 and adapted to accumulate the fuel.

[0009] The fuel filter 104 is disposed in fuel inlet line and adapted to remove foreign matters contained in the fuel discharged from the fuel pump 102. The fuel filter 104 removes foreign matters such as dust, and water included in the fuel supplied to the engine in order to prevent mechanical friction and rusting in sliding portions of the pump 102 and the like. The working of the components of the common-rail fuel injection system is not explained in detail, as it is known in the state of the art.

[0010] With specific reference to this disclosure the focus can be laid on the low pressure circuit of the fuel injection system. The low pressure circuit with reference to this disclosure is defined as the flow paths of the fuel injection system that carry low pressure fuel. Typically, the low pressure fuel flows in a downstream path from the fuel tank 106 to the fuel filter 104 and then to the fuel pump 102.

[0011] The accumulator 110 is connected to the low pressure circuit LPC 100 and adapted to support the LPC 100 by compensating pressure variation at inlet port of the fuel supply pump 102. In one exemplary embodiment of the invention, the accumulator 110 is adapted to compensate the pressure differences at higher altitudes. In this embodiment of the invention, the accumulator is located in the LPC 100 just before the fuel pump 102.

[0012] The two-way valve 114 is disposed in return lines from the fuel supply pump 102. The two-way valve 114 is adapted to control the fuel going to the fuel tank 106 and the accumulator 110, based on the pressure variation. In one embodiment, the two-way valve is an electronically controlled valve which is fixed in return lines from the fuel supply pump 102. Herein, the two-way valve 114 is a fuel control valve that can be actuated between a closed position and an open position allowing fuel goes to the fuel tank 106 and to the accumulator 110 based on pressure variation.

[0013] In one embodiment, the fuel filter 104 includes a pressure sensor 116 further configured to sense the inlet pressure at fuel pump 102 and send signals to an electronic control unit ECU 112 when fuel level reaches a predetermined limit of the fuel in the accumulator 110. On receiving signals from the pressure sensor 116 the ECU 112 triggers the two-way valve 114 to open its ends for fuel flow towards the fuel tank 106 or the accumulator 110 based on the sensed fuel inlet pressure at fuel pump 102.

[0014] The present invention addresses the low-pressure circuit (LPC) design issue especially in case of pressure difference occurred due to higher altitude. In general, the inlet or suction side of a fuel pump is the point of lowest pressure. When the pressure on the fuel is too low, air bubble form inside the fuel pump, and as the fuel accelerates pressure increases and the air bubbles collapse. This rapid creation and subsequent collapse of the air bubbles causes cavitation in fuel pumps. Due to the partial pressure drop at higher altitudes air bubbles are generated inside the fuel pump as a results pump cavitation occurs, which is critical for the fuel pump.

[0015] In operation, the pressure sensor 116 in the fuel filter 104 sense the inlet pressure of the fuel and transmit this signal to the ECU 112 for monitoring. The two-way valve 114 which is fixed in the return lines 105 from the fuel pump 102 gets actuated by the further signals from the ECU 112. From two ways of the valve 114, one end opens towards the fuel tank 106 and other end towards the accumulator 110 based on the signals received from the ECU 112. When the pressure drops below a specified limit, the valve 114 is in the return lines opens its end towards the accumulator 110 so that the fuel goes to the accumulator 114. Herein, the accumulator 110 is intended to accumulate the fuel and compensate the pressure difference at inlet port of the fuel pump 102 by increasing the fuel pressure. The fuel level in the accumulator 110 can also be monitored and when it gets filled, the accumulator 110 transmits the signals to the ECU 112 so that the valve 114 will open its end towards the fuel tank 106. The process continues until the vehicle comes to the altitude where the pressure is within the specified limit. When the inlet pressure comes within the limit, the low pressure circuit (LPC) 100 will work in its usual layout. With this arrangement, the fuel pump 102 will function properly even at higher altitudes and thus the problem of cavitation can be eliminated.

[0016] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.