Claims:We Claim
1. A high pressure fuel pump, said high pressure fuel pump comprising:
a control rack (16), said control rack (16) adapted to be translated to facilitate rotating at least one pinion (18) of said high pressure fuel pump; characterized in that
a magnetic element (12) positioned proximate to an end of said control rack (16), said magnetic element (12) adapted to attract said control rack (16) over a range of engine operating speeds to prevent rotating said at least one pinion (18) of said high pressure fuel pump in said range of the engine operating speeds.

2. The high pressure fuel pump in accordance with Claim 1 wherein said magnetic element (12) is coupled to a sleeve, said sleeve adapted to receive said control rack (16) therein.

3. The high pressure fuel pump in accordance with Claim 1 wherein said magnetic element (12) is a permanent magnet.

4. The high pressure fuel pump in accordance with Claim 1 wherein said magnetic element (12) is an electromagnet.

5. The high pressure fuel pump in accordance with Claim 4 wherein an engine control unit is connected to said electromagnet, said engine control unit adapted to energize said electromagnet to facilitate attracting said control rack (16) towards said electromagnet.
, Description:Field of the invention
[0001] This invention relates to a high pressure fuel pump and more particularly to a control rack of the high pressure fuel pump.

Background of the invention
[0002] US 6138641 A describes a very compact and inexpensive fuel injection device for auto-ignited internal combustion engines that can be mounted on existing internal combustion engines to replace conventional fuel injection devices. The fuel injection device has one or more high pressure pumps that feed fuel into a supply tank from which the fuel may be supplied through proportioning valves to injection valves. The pressure in the supply tank is maintained by an automatic control system for the high pressure pumps, the outputs of which are controlled by a control rod that adjusts a plunger of the high pressure pumps provided with a slanting edge.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a schematic diagram of a control rack assembly of a high pressure fuel pump.

Detailed description of the invention
[0004] A high pressure fuel pump is described. The high pressure fuel pump comprises a control rack 16, the control rack 16 adapted to be translated to facilitate rotating at least one pinion 18 of the high pressure fuel pump. A magnetic element 12 is positioned proximate to an end of the control rack 16, the magnetic element 12 adapted to attract the control rack 16 over a range of engine operating speeds to prevent rotating at least one pinion 18 of the high pressure fuel pump in the range of the engine operating speeds.
[0005] Figure 1 illustrates a schematic diagram of a control rack assembly 10 of a high pressure fuel pump. The control rack assembly 10 comprises a control rack 16 that may be adapted to translate. The translation of the control rack 16 causes a rotation of a plurality of pinions 18 that are in engagement with the control rack 16. The rotation of the plurality of pinions 18 causes a rotation of a plurality of plungers of the high pressure fuel pump. The rotation of each of the plungers with the translation of each of the plungers of the high pressure fuel pump causes fuel to be discharged out of the high pressure fuel pump to a high pressure line, which will be injected in an atomized form to the engine cylinder by means of an injector.
[0006] A magnetic element 12 is positioned proximate to the control rack 16. The magnetic element 12 is fastened on the sleeve 14 that in turn is fastened on to the housing of the high pressure fuel pump. The magnetic element 12 houses the permanent magnet. The sleeve 14 supports both sides of the control rack 16. An end of the control rack 16 is positioned adjacent to the permanent magnet and slides within the sleeve 14. The control rack 16 is attracted to the permanent magnet that is positioned within the magnetic element 12.
[0007] In an alternate exemplary embodiment, an engine control unit (not shown) is connected to an electromagnet that is positioned within the magnetic element 12. The engine control unit is adapted to energize the electromagnet to facilitate attracting the control rack 16 towards the electromagnet.
[0008] A working of the control rack 16 of the high pressure fuel pump is described as an example. During the starting up of the high pressure fuel pump, the control rack 16 is translated away from the magnetic element 12. The magnetic force of the permanent magnet causes the control rack 16 to be attracted towards the permanent magnet. As the engine speed continues to increase, the translatory force acting on the control rack 16 continues to increase. The permanent magnet prevents the control rack 16 from translating away from the magnetic element 12 until the engine speed reaches a threshold speed. As a consequence, the plurality of pinions 18 do not rotate. Hence, each plunger of the high pressure fuel pump that is coupled to each of the plurality of pinions 18 do not rotate. Therefore the stroke length of each plunger of the high pressure fuel pump is not increased. As a consequence, the high pressure fuel pump continues to deliver a reduced quantity of fuel until the threshold engine speed has been attained. After the threshold engine speed has been attained, the control rack 16 translates away from the magnetic element 12 as the translatory force acting on the control rack 16 exceeds the attractive force of the magnetic element 12, thereby causing a sudden increase in the quantity of fuel that is delivered from the high pressure fuel pump. The advantage of positioning the magnetic element 12 proximate to an end of the control rack 16 is to enable restriction in the movement of the control rack 16 over a range of engine operating speeds. This prevents black smoke from being emitted from the engine due to the restricted quantity of fuel that is admitted from the high pressure fuel pump to the engine in that range of engine operating speeds. As example, the range of engine operating speeds is 0-800 rpm.
[0009] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to leverage and dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the claims