Claims:We Claim

1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising:
a bushing (12);
a bore (14) defined in said bushing (12) and adapted to receive a control rod (16) therein, wherein said control rod (16) is adapted to reciprocate within the bore (14) defined in said bushing (12);
a start quantity limiting cap (18) secured to said control rod (16), said start quantity limiting cap (18) comprising a head portion (20) and a shank portion (22) extending from said head portion (20), said shank portion (22) comprising screw threads (24) that are defined on its inner surface that mates with said control rod (16) and said bushing (12) to secure said start quantity limiting cap (18) to said control rod (16) and to said bushing (12); characterized in that
a projection (26) extending from an inner surface of said head portion (20), said projection (26) adapted to mate against said control rod (16) to facilitate sealing said start quantity limiting cap (18) against said control rod (16).

2. The high pressure fuel pump (10) in accordance with Claim 1 wherein the projection (26) comprises a tapered portion that extends from the inner surface of said head portion (20), wherein an end of said tapered portion mates against said control rod (16) to facilitate sealing said start quantity limiting cap (18) against said control rod (16).

3. The high pressure fuel pump (10) in accordance with Claim 1 wherein the projection (26) forms an integral part of said start quantity limiting cap (18) of said high pressure fuel pump (10).
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a start quantity limiting cap for a high pressure fuel pump.

Background of the invention
[0002] JP 57052683 A describes a pump for power steering. To ease controlling pump discharge by varying the quantity of working oil per stroke of a plunger, which is discharged into a discharge passage, by rotating a plunger in such a manner that the force required to vary the pump discharge may be reduced. To ease controlling pump discharge by varying the quantity of working oil per stroke of a plunger, which is discharged into a discharge passage, by rotating a plunger in such a manner that the force required to vary the pump discharge may be reduced. When the pump discharge should be varied, for example, reduced, a cap is loosened so that a control rod may slide via both a spring and a piston. As a result, a plunger rotates and moves via both a pin and a rotate moving member, and when the plunger is, for example, at the lower dead point, the distance between the fore end of the plunger and an escape passage increases. Accordingly, the escape passage is closed, permitting the working oil to be discharged, only after the plunger has traveled from the lower dead point a longer distance than before, which allows less working oil than before to be discharged into a discharge passage. When the pump discharge should be increased, the cap is moved in the opposite direction with the above, increasing the energizing force of the spring so that the plunger may be kept at the maximum discharge position.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a high pressure fuel pump depicting a start quantity limiting cap in one embodiment of the invention.

Detailed description of the embodiments
[0004] Figure 1 illustrates a high pressure fuel pump 10 depicting a start quantity limiting cap 18. The high pressure fuel pump 10 comprises a bushing 12 and a bore 14 defined in the bushing 12, the bore 14 adapted to receive a control rod 16 therein. The control rod 16 is adapted to reciprocate within the bore 14 defined in the bushing 12. A start quantity limiting cap 18 is secured to the control rod 16, the start quantity limiting cap 18 comprising a head portion 20 and a shank portion 22 extending from the head portion 20, the shank portion 22 comprising screw threads 24 that are defined on its inner surface that mates with the control rod 16 and the busing 12, to secure the start quantity limiting cap 18 to the control rod 16 and to the bushing 12. A projection 26 extends from an inner surface of the head portion 20, the projection 26 adapted to mate against the control rod 16 to facilitate sealing the start quantity limiting cap 18 against the control rod 16.

[0005] The high pressure fuel pump 10 comprises a bushing 12 that is secured to a housing 8 of the high pressure fuel pump 10. A bore 14 is defined in the bushing 12, wherein the bore 14 is adapted to receive a control rod 16 therein. In the exemplary embodiment, the control rod 16 is adapted to reciprocate within the bore 14 that is defined in the bushing 12. In order to prevent the control rod 16 from reciprocating within the bore 14 that is defined in the bushing 12, a start quantity limiting cap 18 is secured to the control rod 16. The start quantity limiting cap 18 comprises a head portion 20, and a shank portion 22 that extends from the head portion 20. The shank portion 22 comprises screw threads 24 that are defined on its inner surface and mates with the control rod 16 and the bushing 12 to secure the start quantity limiting cap 18 to the control rod 16 and with the bushing 12. In the exemplary embodiment, a projection 26 extends from an inner surface of the head portion 20 of the start quantity limiting cap 18. The projection 26 when pressed against the control rod 16 and secured thereto prevents the control rod 16 from translating as it is held in place by the start quantity limiting cap 18.

[0006] In the exemplary embodiment, the projection 26 comprises a tapered portion. More specifically, the projection 26 extends from the inner surface of the head portion 20 and culminates in a head portion 30 that is defined at the end of the tapered portion. The head portion 30 that is defined at the end of the tapered portion of the projection 26 mates against the control rod 16 to facilitate sealing the start quantity limiting cap 18 against the control rod 16. Therefore, due to the head portion 20 that is defined at the end of the tapered portion of the projection 26 that mates with the control rod 16, the control rod 16 is prevented from translating both in the forward direction and in the aft direction, and is securely held in place by means of the start quantity limiting cap 18.

[0007] In an exemplary embodiment, the projection 26 forms an integral part of the start quantity limiting cap 18 of the high pressure fuel pump 10. In an alternate exemplary embodiment, the projection 26 may be secured / fastened on to the inner surface of the head portion 20 by means of a fastener that is known in the art. Therefore, due to the projection 26 that is secured / fastened on to the inner surface of the head portion 20 the projection 26 presses against the control rod 16, thereby preventing the control rod 16 from translating in the direction of the start quantity limiting cap 18 when the start quantity limiting cap 18 is secured to the control rod 16.

[0008] 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 dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.