High pressure pump having plunger

[0056] As shown in FIG. 3, in a high pressure pump 70 of the second embodiment, an annular plate 72 is provided on the side of the cylinder 22 with respect to the oil seal 19. The annular plate 72 radially surrounds the small diameter portion 16 of the plunger 14. The inner circumferential periphery of the annular plate 72 and the outer circumferential periphery of the small diameter portion 16 form a small gap 74 therebetween, such that the plate 72 does not disturb reciprocation of the small diameter portion 16. In this structure, even when dust is formed in the sliding part between the sliding portion 15 and the cylinder 22 through the sliding operation therebetween, the gap 74 can restrict this dust from intruding into another sliding part between the oil seal 19 and the small diameter portion 16, for example. Thus, the oil seal 19 can be protected from being damaged.

[0057] As shown in FIG. 4, in a high pressure pump 80 of the third embodiment, a filter 82 is provided midway through the communication passage 310 to remove foreign matters. The filter 82 restricts foreign matters, which is contained in fuel supplied into the high pressure pump 80, from intruding into the sliding part between the oil seal 19 and the small diameter portion 16. In this structure, the oil seal 19 can be protected from being damaged due to intrusion of foreign matters.

[0058] As shown in FIG. 5, in a high pressure pump 90 of the fourth embodiment, the fuel chamber 308 is formed midway through the communication passage 310, instead of being formed around the small diameter portion 16 of the plunger 14. The fuel chamber 308 communicates with a lower space 312 located on the lower side of the step 17 between the sliding portion 15 and the small diameter portion 16. In this structure, even when the location of the fuel chamber 308 is changed, decrease in pressure of fuel in the inlet chamber 302 can be reduced, and pulsation, which arises in pressure of fuel in the inlet chamber 302 as the plunger 14 reciprocates, can be reduced, similarly to the first embodiment.