CLIAMS:We claim,

1. A timing device (10) for a high pressure pump, said timing device (10) comprising:
a roller ring (12);
a plurality of rollers (14) coupled to said roller ring (12);
a pin (16) comprising a first end (18) and a second end (20), said first end (18) coupled to said roller ring (12), said second end (20) coupled to a piston (22), wherein a first end (23) of said piston (22) is coupled to a spring element (24); characterized in that
an electromechanical actuator (26) coupled to a second end (25) of said piston (22), said electromechanical actuator (26) actuates said piston (22) to facilitate advancing said timing device (10).
2. The timing device (10) in accordance with Claim 1 wherein said electromechanical actuator (26) is connected to an engine control unit (28).
3. The timing device (10) in accordance with Claim 2 wherein said electromechanical actuator (26) displaces said piston (22) to a displacement, wherein the displacement is a function of a magnitude of a signal received from said engine control unit (28).
4. The timing device (10) in accordance with Claim 3 wherein the magnitude of the signal received from said engine control unit (28) is a function of at least one signal received from a speed sensor, a control lever position sensor, and a temperature sensor.
5. The electromechanical actuator (26) in accordance with Claim 4 wherein said electromechanical actuator (26) is connected to an engine control unit (28).
6. The electromechanical actuator (26) in accordance with Claim 5 wherein said electromechanical actuator (26) actuates said piston (22) to a displacement, wherein the displacement is a function of a magnitude of a signal received from said engine control unit (28)
7. The electromechanical actuator (26) in accordance with Claim 6 wherein the magnitude of the signal received from said engine control unit (28) is a function of at least one signal received from a speed sensor, a control lever position sensor, and a temperature sensor.
8. An engine control unit (28) connected to an electromechanical actuator (26) of a timing device (10) of a high pressure pump, said engine control unit (28) adapted to:
receive a first signal from at least one of a speed sensor, a control lever position sensor, and a temperature sensor; and
actuating said electromechanical actuator (26) in dependence of said first signal.
,TagSPECI:Field of the invention
[0001] This invention relates to a timing device used in combination with a high pressure pump.

Background of the invention
[0002] A timing device is used in a conventional high pressure pump. In order to compensate for injection and ignition lag, the timing device is required to advance the high pressure pump’s injection timing as the engine’s speed increases. In the absence of a timing device, fuel injection occurs at the engine’s top dead centre at all engine speeds. With the use of the timing device, injection of fuel occurs prior to or after the piston approached top dead centre at different engine speeds. At low engine speeds, the roller ring will be in a retracted position. However at higher engine speeds, the timing device is required to be advanced to ensure that the cam disc comes in contact with the timing device before the piston of the engine approaches the top dead centre position.

[0003] DE Patent Application Number 2729807A describes a series of rollers 7 that are carried on a timing ring 4. The rollers 7 support a cam disc which drives the followers on the ends of pump pistons. A pin 5 through the timing ring 4 is held in a piston 9. The piston 9 is moved against a spring 10 by hydraulic pressure generated by the engine speed and carries the pin 5 with it to rotate the timing ring 4. This alters the position of the cam disc and thus the injection timing. The rotation of the timing ring 4 is limited by a lug 20 projecting into a slot 21 in the timing ring 4. The lug is moved by a drum 16 which is rotated by a lever 22.

Brief description of the accompanying drawings
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0005] Figure 1 illustrates an electro mechanical device in contact with a piston of a timing device in one embodiment of the invention.

Detailed description of the embodiments

[0006] Figure 1 illustrates a timing device 10 for a high pressure pump. The timing device 10 comprises a roller ring 12 and a plurality of rollers 14 coupled to the roller ring 12. A pin 16 comprises a first end 18 and a second end 20. The first end 18 is coupled to the roller ring 12 and the second end 20 is coupled to a piston 22. A first end 23 of the piston 22 is coupled to a spring element 24. An electromechanical actuator 26 is coupled to a second end 25 of the piston 22. The electromechanical actuator 26 actuates the piston 22 to facilitate advancing the timing device 10.

[0007] In another aspect, an electromechanical actuator 26 for a timing device 10 in a high pressure pump is described. The electromechanical actuator 26 is coupled to a piston 22 of the timing device 10, wherein the electromechanical actuator 26 actuates the piston 22 to facilitate advancing the timing device 10.

[0008] In a further aspect, an engine control unit 28 is connected to an electromechanical actuator 26 of a timing device 10 of a high pressure pump. The engine control unit 28 is adapted to receive a first electronic signal from at least one of a speed sensor, a control lever position sensor, and a temperature sensor. The engine control unit 28 is adapted to transmit a second electronic signal to the electromechanical actuator 26 to facilitate actuating the electromechanical actuator 26, wherein the second electronic signal is a function of the first electronic signal.

[0009] The timing device 10 includes a roller ring 12. The roller ring 12 includes an outer ring and an inner ring that is radially inward from the outer ring. The roller ring 12 includes a plurality of rollers 14 coupled between the outer ring and the inner ring of the roller ring 12. The roller ring 12 is coupled to the piston 22 by means of a pin 16. Specifically, the pin 16 comprises a first end 18 and a second end 20. The first end 18 of the pin 16 is coupled to the roller ring 12, while the opposite second end 20 of the pin 16 is coupled to the piston 22.

[00010] The piston 22 includes a first end 23 and an opposite second end 25. The first end 23 of the piston 22 is in contact with a spring member 24 and is biased against the spring member 24. The second end 25 of the piston 22 is coupled to an electromechanical actuator 26 via linkages 29. Specifically, the electromechanical actuator 26 is adapted to displace the piston 22 against the force of the spring member 24 to facilitate advancing the timing device 10.

[00011] When the electromechanical device 26 actuates the second end 25 of the piston 22, the piston 22 translates against a force of the spring member 24 towards the left. Therein, the second end 20 of the pin 16 that is coupled to the piston 22 is actuated along with the piston 22 due to the translation of the piston 22. The actuation of the pin 16 caused the roller ring 12 to rotate in a clockwise direction. Thereby, the plurality of rollers 14 that are coupled between the outer ring and the inner ring of the roller ring 12 rotate with the roller ring 12 in the clockwise direction. The rotation of the rollers 14 in the clockwise direction causes the cam disc to advance with respect to the plurality of rollers 14. The movement of the cam disc with respect to the plurality of rollers 14 causes advancement of the timing device 10.

[00012] The principle of working of the timing device 10 for the high pressure pump is now explained as an example. The engine control unit 28 receives a plurality of engine parameters from a plurality of sensors such as a speed sensor, a control lever position sensor, a temperature sensor, and the like. Based on a two dimensional map that is stored in the engine control unit 28 and an input value of engine speed, control lever position, and temperature received by the engine control unit 28 from the various sensors, the engine control unit 28 determines the magnitude of a displacement that is required of the piston 22 against the force of the spring member 24 to advance the timing device 10. The engine control unit 28 transmits an electronic signal to the electromechanical device 26, wherein the magnitude of the electronic signal indicates the displacement by which the piston 22 is required to be actuated against a force of the spring member 24 to facilitate advancing the timing device 10.

[00013] On receiving the electronic signal from the engine control unit 28, the electromechanical actuator 26 actuates the second end 25 of the piston 22 against the force of the spring member 24. Therein, the pin 16 that is coupled to the piston 22 is actuated. As a consequence of the pin 16 being actuated, the roller ring 12 and hence the rollers 14 are rotated in a direction that facilitates advancing the rollers 14 against the cam disc of the high pressure pump. This mechanism of advancing the rollers 14 against the cam disc of the high pressure pump facilitates delivering fuel from the high pressure pump into the engine cylinders prior to the engine piston approaching the top dead centre position.

[00014] The above described timing device 10 for the high pressure pump facilitates advancing the timing device 10 against the cam disc of the high pressure pump. Moreover, the use of the electromechanical actuator 26 to actuate the piston 22 facilitates controlling the oscillations of the piston 22 that previously occurred when the piston 22 was actuated using pressurized fuel. Moreover, hysteresis and fuel leakage problems that resulted from the use of pressurized fuel in actuating the piston 22 are also avoided.

[00015] It must be understood that the embodiments explained in the above detailed description is only illustrative and does not limit the scope of this invention. The scope of this invention is limited only by the scope of the claims. Many modification and changes in the embodiments aforementioned are envisaged and are within the scope of this invention.