Claims:We claim:
1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising:
a housing (12);
a plunger (14) inserted within said housing (12), said plunger (14) adapted to reciprocate within said housing (12);
a roller tappet (16) coupled to an end of said plunger (14), said roller tappet (16) coupled to a first portion of a permanent magnet (18); characterized in that
a cam (20) is positioned proximate to said permanent magnet (18) such that an air gap (22) is maintained between an opposite second portion of said permanent magnet (18) and said cam (20).

2. The high pressure fuel pump (10) in accordance with Claim 1, further comprising a plurality of electrical coils (23) positioned within said cam (20), said plurality of electrical coils (23) adapted to magnetize said cam (20).

3. The high pressure fuel pump (10) in accordance with Claim 1, further comprising at least one capacitor plate (24) coupled circumferentially to said cam (20), said at least one capacitor plate (24) adapted to measure if the air gap (22) between said cam (20) and the opposite second portion of said permanent magnet (18) is above a threshold air gap.

4. A control unit (26) in electronic communication with a cam (20) of a high pressure fuel pump (10), said control unit (26) adapted to:
determine a value of air gap (22) between said cam (20) and a permanent magnet (18) of said high pressure fuel pump (10) based on a value of capacitance of at least one capacitor plate (24) that is coupled to said cam (20); and
supply electric power to electrical coils (23) that are positioned within said cam (20) to facilitate maintaining an air gap (22) between said permanent magnet (18) and said cam (20) based on the determined value of the air gap (22). , Description:Field of the invention:
[0001] This disclosure relates to a high pressure fuel pump, and more particularly to an apparatus for actuating a plunger of the high pressure fuel pump by means of electro-magnetic induction.

Background of the invention:
[0002] IN Patent Application Number 201641010315 describes a high pressure fuel pump 10. The high pressure fuel pump 10 comprises a pump housing 12 and a plunger 14 provided within a bore 16 defined within the pump housing 12. The plunger 14 is adapted to reciprocate within the bore 16 of the pump housing 12. A permanent magnet 18 is coupled to the plunger 14. At least one electromagnet is positioned proximate to the permanent magnet 18, the permanent magnet 18 attracted and repelled to the at least one electromagnet by actuation of the electromagnet to facilitate reciprocating the plunger 14 within the bore 16 of the pump housing 12.

Brief description of the accompanying drawings:
[0003] An embodiment of the disclosure is described with reference to the following accompanying drawings:
[0004] Figure 1 illustrates a high pressure fuel pump in accordance with this disclosure;
[0005] Figure 2 illustrates a control unit in electronic communication with a cam.

Detailed description of the embodiments:
[0006] A high pressure fuel pump 10 is described. The high pressure fuel pump 10 comprises a housing 12 and a plunger 14 inserted within the housing 12, the plunger 14 adapted to reciprocate within the housing 12. A roller tappet 16 is coupled to an end of the plunger 14, the roller tappet 16 coupled to a first portion of a permanent magnet 18. A cam 20 is positioned proximate to the permanent magnet 18 such that an air gap 22 is maintained between an opposite second portion of the permanent magnet 18 and the cam 20.
[0007] Moreover, a control unit 26 in electronic communication with a cam 20 of a high pressure fuel pump 10 is described. The control unit 26 is adapted to determine a value of air gap 22 between the cam 20 and a permanent magnet 18 of the high pressure fuel pump 10 based on a value of capacitance of at least one capacitor plate 24 that is coupled to the cam 20. The control unit is used to supply electric power to electrical coils 23 that are positioned within the cam 20 to facilitate maintaining an air gap 22 between the permanent magnet 18 and the cam 20 based on the determined value of the air gap 22.
[0008] Figure 1 illustrates a high pressure fuel pump 10. The high pressure fuel pump 10 includes a housing 12. A plunger 14 is positioned within the housing 12 such that the plunger 14 reciprocates within the housing 12. A roller tappet 16 is coupled to an end of the plunger 14. The roller tappet 16 actuates the plunger 14 as will be explained in detail below. A permanent magnet 18 is coupled to an end of the roller tappet 16. A first portion of the permanent magnet 18 is coupled to the roller tappet 16. An opposite second portion of the permanent magnet 18 is positioned proximate to a cam 20. The cam 20 contains a plurality of electrical coils 23. The electrical coils 23 are positioned within the cam 20 and facilitates magnetizing the cam 20 when supplied with electric power. The electric power that is supplied to the electrical coils 23 to facilitate magnetizing the cam 20 may be supplied from an external source such as a battery. The magnitude of the electric power that is supplied to the electrical coils 23 is proportional to an extent to which the cam 20 is magnetized.
[0009] An air gap 22 is defined between the permanent magnet 18 and the cam 20. The air gap 22 facilitates maintaining a magnetic force of repulsion between the permanent magnet 18 and the cam 20. A first capacitor plate 24 is coupled about a periphery of the cam 20. A second capacitor plate 25 is coupled about an opposite periphery of the cam 20. The first capacitor plate 24 and the second capacitor plate 25 are each secured to the cam 20 by using any fastening means that is known in the art. The first capacitor plate 24 and the second capacitor plate 25 each facilitate measuring a displacement of the air gap 22 that exists between the permanent magnet 18 and the cam 20 and measuring if the air gap 22 is above a threshold air gap 22. The first capacitor plate 24 and the second capacitor plate 25 each transmit an electronic signal to a control unit 26 that is indicative of a magnitude of the air gap 22 that exists between the permanent magnet 18 and the cam 20. The control unit 26 is in electronic communication with the cam 20. Based on the magnitude of the electronic signal that is received by the control unit 26, the air gap 22 that exists between the permanent magnet 18 and the cam 20 can be varied. A reference position of the air gap 22 that should exist between the permanent magnet 18 and the cam 20 is stored in a memory of the control unit 26. Based on the difference between the reference position of the air gap 22 and the actual value of air gap 22 that exists between the permanent magnet 18 and the cam 20, the magnitude of the electric power supplied by the control unit 26 to the cam 20 may be varied. At least one spring member is positioned between the plunger 14 and a top dead center of the high pressure fuel pump 10. The at least one spring member facilitates restoring the plunger 14 back to its bottom dead center position after the plunger 14 has reached it top dead center position.
[00010] The working of the high pressure fuel pump 10 is described as an example. The control unit 26 supplies electric power to the electrical coils 23 of the cam 20. Due to the forces of repulsion that exist between the cam 20 and the permanent magnet 18, the permanent magnet 18 along with the roller tappet 16 are translated in the upward direction. The first capacitor plate 24 and the second capacitor plate 25 each determine a magnitude of the air gap 22 that exists between the cam 20 and the permanent magnet 18 and transmits a corresponding signal to the control unit 26 that is indicative of the magnitude of the air gap 22. As the cam 20 that is coupled to a drive shaft rotates, the air gap 22 that exists between the cam 20 and the permanent magnet 18 decreases. In order to maintain a magnitude of the air gap 22 that exists between the cam 20 and the permanent magnet 18 steady, the control unit 26 supplies the electrical coils 23 of the cam 20 with an increase in electric power. The increase in the electric power supplied by the control unit 26 to the electrical coils 23 of the cam 20 facilitates increasing the force of repulsion between the permanent magnet 18 and the cam 20. Therefore, the magnitude of the air gap 22 that exists between the cam 20 and the permanent magnet 18 remains steady throughout the movement of the roller tappet 16 to the top dead center position of the high pressure fuel pump 10. After the plunger 14 has reached its top dead center position, the at least one spring member that is located within the high pressure fuel pump 10 applies a tensile force on the plunger 14 that causes the plunger 14 to translate downwardly to its bottom dead center position.
[00011] The high pressure fuel pump 10 containing the cam 20 and the permanent magnet 18 facilitates decreasing the inertia of the high pressure fuel pump 10, while at the same time providing a more responsive reciprocating motion of the roller tappet 16. Moreover, as there is no contact between the cam 20 and the permanent magnet 18, there are no frictional energy losses developed in the high pressure fuel pump 10.
[00012] 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.