Claims:We Claim
1. An actuator (10) for a control rack (12) of a high pressure fuel pump (1), said actuator (10) comprising:
a cylinder (11) coupled to said control rack (12) of said high pressure fuel pump (1);
a piston (14) located within said cylinder (11), said piston (14) coupled to said control rack (12) and adapted to translate said control rack (12) to facilitate shutting off fuel supply from said high pressure fuel pump (1).

2. The actuator (10) for a control rack (12) of a high pressure fuel pump (1) in accordance with Claim 1 wherein said cylinder (11) comprises a first chamber (16) and a second chamber (18), said piston (14) separating said first chamber (16) from said second chamber (18).

3. The actuator (10) for a control rack (12) of a high pressure fuel pump (1) in accordance with Claim 2 further comprising a valve element (20) coupled upstream from said first chamber (16), said valve element (20) controls a flow of fluid to said first chamber (16).

4. The actuator (10) for a control rack (12) of a high pressure fuel pump (1) in accordance with Claim 3 wherein said valve element (20) is one of a pneumatically actuated valve, a hydraulically actuated valve or an electrically actuated valve.

5. The actuator (10) for a control rack (12) of a high pressure fuel pump (1) in accordance with Claim 3 further comprising one of an air accumulator (22) or an oil accumulator (22) in flow communication with said valve element (20), one of said air accumulator (22) and said oil accumulator (22) adapted to supply fluid to said valve element (20).

6. A high pressure fuel pump (1), said high pressure fuel pump (1) comprising:
a pump housing (13);
a control rack (12) positioned within said pump housing (13), a first end of said control rack (12) in engagement with a piston of said high pressure fuel pump (1);
an actuator (10) connected to said control rack (12), said actuator (10) comprising:
a cylinder (11) coupled to said control rack (12) of said high pressure fuel pump (1);
a piston (14) located within said cylinder (11), said piston (14) coupled to said control rack (12) and adapted to translate said control rack (12) to facilitate shutting off fuel supply from said high pressure fuel pump (1).

7. The high pressure fuel pump (1) in accordance with Claim 6 wherein said cylinder (11) comprises a first chamber (16) and a second chamber (18), said piston (14) separating said first chamber (16) from said second chamber (18).

8. The high pressure fuel pump (1) in accordance with Claim 7 further comprising a valve element (20) coupled upstream from said first chamber (16), said valve element (20) controls a flow of fluid to said first chamber (16) to facilitate translating said piston (14) in the second chamber (18).

9. The high pressure fuel pump (1) in accordance with Claim 8 wherein said valve element (20) is one of a hydraulically actuated valve, and an electrically actuated valve.

10. The high pressure fuel pump (1) in accordance with Claim 6 wherein said piston (14) may be actuated one of hydraulically and pneumatically. , Description:Field of the invention
[0001] This invention relates to an actuator for a control rack of a high pressure fuel pump.

Background of the invention
[0002] U.S. Patent Application Number 4,785,917A describes an automatic transmission apparatus comprising a friction clutch coupled to an output shaft of an engine, a clutch actuator for operating the friction clutch, a parallel shaft type gear transmission, the input shaft of which is coupled to the friction clutch, a gear position changer for changing the speed ratio of the transmission, and a rack actuator for operating the control rack of a fuel injection pump. A signal from a drive state-detector is used to determine a change in the speed ratio of the transmission. The rack actuator gradually moves the control rack to an idling speed position, after which the clutch actuator disengages the friction clutch. The gear position changer is operated in accordance with the disengagement of the friction clutch, so that the speed ratio of the transmission is changed accordingly. The control rack is moved, so that the rotational speed of the output shaft substantially coincides with the input shaft of the transmission, and the clutch actuator moves the friction clutch in the engagement direction. When the difference in the rotational speed of the output shaft and the input shaft of the transmission has decreased below a predetermined value during the operation of the clutch actuator, the rack actuator gradually moves to a position corresponding to the degree of depression of the accelerator pedal.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates an actuator connected to a control rack of a high pressure fuel pump in accordance with one embodiment of the invention.

Detailed description of the invention
[0004] Figure 1 illustrates an actuator 10 for a control rack 12 of a high pressure fuel pump 1. The actuator 10 comprises a cylinder 11 coupled to the control rack 12 of the high pressure fuel pump 1. A piston 14 is located within the cylinder 11, the piston 14 coupled to the control rack 12 and adapted to translate the control rack 12 to facilitate shutting off fuel supply from the high pressure fuel pump 1.
[0005] Moreover, a high pressure fuel pump 1 is described. The high pressure fuel pump 1 comprises a pump housing 13 and a control rack 12 positioned within the pump housing 13, a first end of the control rack 12 in engagement with a piston of the high pressure fuel pump 1. An actuator 10 is connected to the control rack 12, the actuator 10 comprising a cylinder 11 coupled to the control rack 12 of the high pressure fuel pump 1. A piston 14 is located within the cylinder 11, the piston 14 coupled to the control rack 12 and adapted to translate the control rack 12 to facilitate shutting off fuel supply from the high pressure fuel pump 1.
[0006] The high pressure fuel pump 1 comprises a pump housing 13. A piston is provided within the pump housing 13. A helix is defined on the piston and facilitates decreasing a quantity of fuel that is delivered from the high pressure fuel pump 1. A control rack 12 is coupled to the piston and facilitates rotating the piston. When the piston is rotated by means of the control rack 12, the helix that is defined on the piston is consequently rotated. Due to the helix of the piston coming in contact with an inlet of the high pressure fuel pump 1 during the compression stroke of the high pressure fuel pump 1, a lesser quantity of fuel is delivered from the high pressure fuel pump 1 to its fuel injectors. As the helix that is defined on the piston is rotated to a greater extent, the quantity of fuel that is delivered from the high pressure fuel pump 1 decreases rapidly thereby delivering a far lesser quantity of fuel through its fuel injectors. When the piston is rotated by the control rack to a maximum possible extent, the helix coincides with the inlet port and hence all the fuel that is delivered through the inlet of the high pressure fuel pump 1 is channeled out of the high pressure fuel pump 1 via the helix that is defined in the piston. Therefore, no fuel is delivered from the high pressure fuel pump 1, thereby leading to no fuel being delivered through the fuel injectors. As a consequence, the engine is shut off.
[0007] A tank 22 is connected to an inlet of the cylinder 11 and supplies fluid to an actuator 10 of the high pressure fuel pump 1. A valve element 20 is in flow communication with the tank 22 and controls a flow of fluid from the tank 22 to the actuator 10 of the high pressure fuel pump 1. In an embodiment, the tank 22 supplies oil / compressed air to the actuator 10 of the high pressure fuel pump 1. The actuator 10 comprises a cylinder 11 that is coupled to the control rack 12 of the high pressure fuel pump 1. A piston 14 is located within the cylinder 11. The piston 14 is coupled to the control rack 12 and adapted to translate the control rack 12 to facilitate shutting off fuel supply from the high pressure fuel pump 1.
[0008] The cylinder 11 comprises a first chamber 16 and a second chamber 18. The piston 14 separates the first chamber 16 from the second chamber 18. The valve element 20 is in flow communication with the first chamber 16 and supplies fluid to the first chamber 16. When the valve element 20 is in an open position, fluid flows from the tank 22 to the first chamber 16. The flow of fluid from the tank 22 to the first chamber 16 causes the piston 14 to translate against the force of the spring member 19. The translation of the piston 14 against the force of the spring member 19 causes a translation of the control rack 12. The translation of the control rack 12 causes a rotation of the piston of the high pressure fuel pump 1. When the piston of the high pressure fuel pump 1 is rotated by the control rack 12 to a maximum possible extent, all the fluid that is delivered to the inlet of the high pressure fuel pump 1 is channeled out of the high pressure fuel pump 1 via the helix that is defined in the piston. Therefore, no fuel is delivered from the high pressure fuel pump 1, thereby leading to no fuel being delivered from the fuel injectors. As a consequence, the engine is shut off.
[0009] After the engine has been shut off, the piston of the high pressure fuel pump 1 rotates, thereby translating the control rack 12 due to the restoring force of the spring member 19. The translation of the control rack 12 due to the restoring force of the spring member 19 causes the piston 14 to return to its original position. The piston 14 applies a force on the fluid that is present in the first chamber 16 that causes it to flow into the tank 22 via the valve element 20.
[0010] A working of the high pressure fuel pump 1 is described as an example. When it is required to shut off the fuel supply from the engine, a user actuates the valve element 20 electronically. Therein, fluid from the tank 22 flows to the first chamber 16 of the actuator 10 via the valve element 20. In an exemplary embodiment, the tank 22 is one of an air accumulator and an oil accumulator. Moreover, the fluid for operating the actuator 10 is brake oil that is channeled from the vehicle braking system to enable shutting off the engine. The pressure of fluid in the first chamber 16 causes the piston 14 to translate against the force of the spring member 19. The translation of the piston 14 against the force of the spring member 19 causes the rack 12 to translate. The translation of the rack 12 causes a rotation of the piston in the housing 13. The rotation of the piston in the housing 13 causes the helix of the piston to align with the inlet of the high pressure fuel pump 1. When the piston is rotated by the control rack 12 to a maximum possible extent, all the fuel that is delivered through the inlet of the high pressure fuel pump 1 is channeled out of the high pressure fuel pump 1 via the helix that is defined in the piston. Therefore, no fuel is delivered from the high pressure fuel pump 1 thereby leading to no fuel being delivered from the fuel injectors. As a consequence, the engine is shut off.
[0011] 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 levers are envisaged and form a part of this invention. The scope of the invention is only limited by the claims.