FIELD OF THE INVENTION

This invention related to a Fuel Pump with an Integrated Pressure Sensor.

BACKGROUND OF THE INVENTION

The common-rail fuel injection system is one of the advanced fuel injection systems that are being used in modern diesel engines. The main advantage of the common-rail fuel injection system is that it can vary the injection timing and duration over a broad range. This is accomplished by separating pressure generation from fuel injection. The components of the common-rail fuel injection system can be classified into two major categories. The first category of components is the one which perform the action of fuel supply to the low pressure side of the system and the second category include high pressure components.

The first category of components includes components which supply fuel from the fuel tank to the fuel pump. The high pressure side of the common-rail system consists of the high pressure pump which increases the pressure of the fuel to the system pressure. The high pressure fuel flows through the high pressure pipes and is collected in the fuel rail. The rail in turn is connected to the injectors with high pressure pipes. The fuel is injected into the cylinders of the engine when the nozzle of the injector is opened. The pumping action of the high pressure pump, the injector activation timing is controlled by an Electronic Control Unit. Various sensors are used to perform a wide range of control actions so as to attain good performance. The sensors provide vital system information which is used to calculate the adequate injection timing and duration.

Different sensors are used in the system to ensure proper functioning of the common-rail fuel injection system. One of them is the rail pressure sensor (RPS). As the name suggests the rail pressure sensor is usually mounted on the rail to measure and monitor the pressure of fuel in the rail. The rail pressure sensor measures the pressure in the fuel rail in the common-rail accumulator-type injection system. The sensing element in the sensor is a steel diaphragm onto which deformation resistors have been vapor deposited in the form of a bridge circuit. When pressure is applied to one of the diaphragm faces, the resistances of the bridge resistors change due to diaphragm deformation.

The rail pressure sensor is conventionally assembled onto the fuel rail as the rail pressure sensor is designed to snugly fit into the fuel rail of the common-rail fuel injection system. One issue with assembling the rail pressure sensor on the rail is that the machining and fitting operation is of critical importance. Even a slight error in the machining and fitting operation of the rail pressure sensor would lead to a variation in pressure in the rail. The variation of pressure in the rail would lead disturbing the injection cycle to the engine. Due to such critical nature of locating the rail pressure sensor on the rail the operation of machining and fitting is very expensive and time consuming.

In case of modern low cost vehicle, where the main aim is to reduce the cost of the vehicle, mounting the rail pressure sensor on the rail would increase the cost prohibitively and hence is not a viable option. Also in vehicles which use a smaller capacity engine such as a one cylinder or two cylinders the use of the rail itself increases the cost of the vehicle. However measuring and monitoring of pressure of the fuel that is sent to the fuel injectors is essential.

It is an object of this invention is to overcome the limitations of the conventional methods of locating the rail pressure sensor.

ADVANTAGES OF THE INVENTION

The advantages of the invention as claimed in the independent claim are as follows. The integration of the pressure sensor into the fuel pump eliminates the need of an accumulator/rail this reduces the cost of the fuel injection system in a vehicle. The pressure sensor still continues to measure and monitor the pressure of the fuel that is sent to the fuel injectors. This ensures that there is no compromise in the functioning of the pressure sensor and that of the fuel injection system.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

Figure 1 illustrates a schematic block diagram of the fuel pump in accordance with this invention;

Figure 2a illustrates a detailed schematic drawing of the delivery valve holder of the fuel pump in accordance with this invention; and

Figure 2b illustrates a sectional view of the delivery valve holder of the fuel pump in accordance with this invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 illustrates a schematic block diagram of the fuel pump 10 used in a fuel injection system. The fuel pump 10 comprises a pump body 12 comprising a first pump driving end 14 and a second fuel delivery end 16. The fuel pump 10 comprises at least one inlet located in proximity of the first pump driving end 14 of the fuel pump 10. A delivery valve holder 18 is mounted at the fuel delivery end 16 and a pressure sensor 20 is integrated in the delivery valve holder 18. From the fuel pump 10 the pressurized fuel is sent to the fuel injectors 22 through high pressure fuel lines 24.

Figure 2a illustrates detailed schematic drawing of the delivery valve holder of the fuel pump in accordance with this invention. The delivery valve holder 18 has one inlet 26 and two outlets 28. The inlet 26 and two outlets 28 of the delivery valve holder 18 have threads along their outer surfaces. The threads on the outer surface of the inlet 26 allow the delivery valve holder 18 to be fixed firmly to the fuel pump body 12 at the fuel delivery end. An axial bore 30 is provided in the inlet 26 along the axis represented by the letter Y and an axial bore 32 is provided in the outlets 28 along the axis represented by the letter X as seen in figure 2b.

The pressure sensor 20 is integrated into the delivery valve holder 18. The pressure sensor 20 is located along the axis represented 'Y\ The pressure sensor 20 is an electronic controlled sensor. A plug-in housing 34 (seen in figure 2a and 2b) is mounted at the end of the delivery valve holder 18 which is away from the end which is mounted on the second fuel delivery end 16 of the fuel pump 10. The plug-in housing 34 holds all the components which allows the pressure sensor 20 to communicate with an electronic control unit (not shown in the drawings) which controls the fuel injection cycles of an engine. The plug-in housing 34 can be either press fit or snap fit onto the delivery valve holder 18. The plug-in housing 34 ensures easy serviceability of the pressure sensor 20 and also the electronic components which are located in the plug-in housing 34. The pressure sensor 20 is electronic controlled this ensures accuracy of measurement and better control of fuel injection cycles.

The working of the fuel pump 10 with the integrated pressure sensor 20 can be explained as follows. The fuel pump 10 receives fuel from a fuel tank at a certain pressure. The fuel pump comprises a piston which is usually a cam follower. The piston reciprocates in the pump body thereby increasing the pressure of the fuel that it receives from the fuel tank. The pressurized fuel is sent toward the second fuel delivery end 16. From the fuel delivery end 16 it enters the axial bore 30 provided in the inlet 26 of the delivery valve holder 18. It follows from the axial bore 30 to the axial bore 32 in the outlets 28 of the delivery valve holder. The integrated pressure sensor 20 measures the pressure of the fuel. The information regarding the pressure is sent to an electronic control unit. If the pressure of the fuel is high enough then this high pressure fuel is sent to the injectors through high pressure fuel lines as shown in figure 1.

One of the most important aspects of the fuel pump 10 in accordance with this invention is that it can be effectively used in smaller engine capacity vehicles. Also in vehicles which require less pressure sensitive fuel system the fuel pump with the integrated pressure sensor can be used effectively. Another advantage of the fuel pump wherein the pressure sensor 20 is integrated into the delivery valve holder in accordance with this invention is that the number of components used in the fuel injection system are reduced which reduces cost of the overall system. Another advantage of the integrating the pressure sensor with the fuel pump is that it is simpler operation to integrate the pressure sensor with the fuel pump in comparison with mounting the rail pressure sensor on the rail.

It must be understood that the embodiments explained in the description above are only illustrative and do not limit the scope of the invention. The scope is only limited by the scope of the claim. Many modifications in terms of the means of integrating the pressure sensor to the fuel pump are envisaged and are within the scope of this invention.

WE CLAIM:

1. A Fuel Pump (10) comprising

(i) a pump body (12) comprising a first pump driving end (14) and a second fuel delivery end (16);

(ii) at least one fuel inlet located in proximity of said first pump driving end (14);
Characterized in that

a delivery valve holder (18) is mounted at said fuel delivery end (16); and a pressure sensor (20) integrated in said delivery valve holder (18).

2. The fuel pump (10) as claimed in claim 1, wherein said delivery valve holder (18) has an inlet (26) and an axial bore (30) adapted to receive pressurized fuel from the fuel delivery end (16).

3. The fuel pump (10) as claimed in claim 1, wherein said delivery valve holder (18) has at least one outlet (28) and an axial bore (32) adapted to delivery high pressure fuel to at least one injector.

4. The fuel pump (10) as claimed in claim 1, wherein said pressure sensor (20) is integrated into said delivery valve holder (18) in a manner such that said pressure sensor (20) is able to measure pressure of fuel in said axial bore (32).

5. The fuel pump (10) as claimed in claim 1, wherein a plug-in housing (36) is mounted on the delivery valve holder (18) at the end away from the end which is mounted on the second fuel delivery end (16) of the fuel pump (10).

6. The fuel pump (10) as claimed in claim 5, wherein the plug-in housing (36) comprises components adapted to allow communication between said pressure sensor (20) and an electronic control unit.