Plunger-type pump and cam driven element thereof

Technical field

[0001] The present application relates to a plunger-type pump, in particular to a high-pressure plunger-type pump having a cam driven element, wherein a direction of reciprocating motion of a plunger is perpendicular to a driving camshaft.

Background art

[0002] Plunger-type pumps are widely used in high-pressure fuel systems. In a plunger-type pump, a camshaft pushes a plunger to reciprocate in a plunger cavity, so as to pressurize fuel and output high-pressure fuel.

[0003] A cam driven element is used in a plunger-type pump; fig. 1 shows a schematic sectional view of a cam driven element 10. A roller 3 is installed on a tappet body 1 by means of a pin 2; the roller 3 and the pin 2 cooperate in a sliding fashion and are thereby capable of relative rotation. The rotatable roller 3 rolls along a camshaft (not shown) and thereby drives the tappet body 1 to move in reciprocating motion up and down in a tappet cavity of a pump housing (not shown). However, the pin 2 and the tappet body 1 cooperate in a sliding fashion, therefore during operation, the pin will experience wear relative to the tappet body 1; moreover, the pin 2 can be displaced axially relative to the tappet body 1 and thereby contact a sidewall of the tappet cavity, causing wear.

[0004] Thus, there is a need for improvement, to overcome the technical problems in the prior art.

SUMMARY OF THE INVENTION

[0005] The present application mainly solves the problem that a cam driven element and a plunger-type pump wear readily and are not durable.

[0006] To solve the abovementioned technical problem, one aspect of the present application provides a cam driven element, comprising:

a tappet body, provided with a rolling cavity having sidewalls, the rolling cavity having a longitudinal opening located between the sidewalls, wherein a first pin hole and a second pin hole are disposed so as to run through two opposite said sidewalls of the rolling cavity respectively in a transverse direction;

a pin comprising, distributed along the axial direction thereof, a first region, a third region and a second region, wherein the third region is located between the first region and the second region, the first region is installed in the first pin hole, the second region is installed in the second pin hole, the third region is located in the rolling cavity, the diameter of the first region is neither greater than the diameter of the second region nor greater than the diameter of the third region, and the first region and the first pin hole are fitted together so as to be incapable of relative rotation; and a roller, installed on the third region of the pin so as to be capable of rotating relative to the pin, the roller being located in the rolling cavity and being at least partially exposed outside the rolling cavity through the opening.

[0007] Another aspect of the present application provides a plunger-type pump, comprising a housing, a camshaft installed so as to be capable of rotating relative to the housing about a rotation axis, a plunger, and the abovementioned cam driven element, the plunger being installed so as to be capable of moving to and fro relative to the housing in an extension direction and a retraction direction, wherein the extension direction is perpendicular to the rotation axis, the extension direction is opposite to the retraction direction, the plunger-type pump sucks in fluid when the plunger moves in the retraction direction, and the plunger-type pump outputs fluid when the plunger moves in the extension direction; the cam driven element is installed between the camshaft and the plunger, and converts a driving force of rotational motion of the camshaft to a driving force for driving linear motion of the plunger.

[0008] According to the present application, since the first region of the pin and the first pin hole are fitted together so as to be incapable of relative rotation, there is no frictional damage between the pin and the tappet body, and the pin will not move relative to the tappet body in the axial direction of the pin, so wear to the pump housing caused by the pin ends is avoided, hence the plunger-type pump and the cam driven element are long-lasting and durable. The diameter of the second pin hole is greater than the diameter of the first pin hole, and the diameter of the first region is no greater than the diameter of the second region, therefore the pin can be easily installed on the tappet body through the second pin hole.

Description of the accompanying drawings

[0009] A fuller understanding of the present application will be gained by reading the detailed explanation of particular embodiments below with reference to the accompanying drawings. Here:

Fig. 1 shows a schematic sectional view of a cam driven element in an existing particular embodiment.

Fig. 2 shows a schematic diagram of a plunger-type pump according to a particular embodiment of the present application.

Fig. 3 shows a schematic sectional view of a cam driven element according to a particular embodiment of the present application.

Fig. 4 shows a schematic sectional view of a cam driven element according to a second particular embodiment of the present application.

Fig. 5 shows a schematic sectional view of a cam driven element according to a third particular embodiment of the present application.

Particular embodiments

[0010] Referring to figs. 2 to 5, a plunger-type pump 100 according to a specific embodiment of the present application comprises a housing 4, a camshaft 5, a plunger 6 and a cam driven element 10. The camshaft 5 is installed so as to be rotatable relative to the housing 4 about a rotation axis X; the plunger 6 is installed so as to be capable of moving to and fro relative to the housing 4 in an extension direction Fl and a retraction direction F2. The rotation axis X extends transversely; the extension direction Fl is perpendicular to the rotation axis X, being vertically upward; the retraction direction F2 is opposite to the extension direction Fl, being vertically downward. When the plunger 6 moves in the retraction direction F2, the plunger-type pump 100 sucks in fluid from a fuel feed pipeline (not marked); when the plunger 6 moves in the extension direction Fl, the plunger-type pump 100 pressurizes fuel, and when a required fuel pressure is exceeded, outputs fuel from a fuel nozzle 8.

[0011] The cam driven element 10 is installed between the camshaft 5 and the plunger 6; a roller 3 is mated in a rolling fashion with the camshaft 5, and under the driving action of the camshaft 5 causes a tappet body 1 to push the plunger 6 to move in the extension direction Fl. An elastic component 7 applies an elastic force to the plunger 6, which force gives the plunger 6 a tendency to move in the retraction direction F2. Two plungers 6 of the plunger-type pump 100 are shown in fig. 2; a plunger 6 on the left is in an extended state, whereas a plunger 6 on the right is in a retracted state. [0012] The cam driven element 10 comprises the tappet body 1, a pin 2 and the roller 3. The bottom of the tappet body 1 is provided with a rolling cavity 13 enclosed by cylindrical sidewalls 14; the rolling cavity 13 has an opening 17 provided in a longitudinal direction between the sidewalls 14. A first pin hole 11 and a second pin hole 12 are disposed so as to run through two opposite sidewalls 14 of the rolling cavity 13 respectively. The diameter of the second pin hole 12 is greater than the diameter of the first pin hole 11. A pushing part 15 is disposed at the top of the tappet body 1. The pushing part 15 is opposite the rolling cavity 13 in the longitudinal direction, takes the form of a projection, and is used for pushing the plunger 6. In the particular embodiment shown in fig. 2, the elastic component 7 is a helical spring, and an annular groove 16 is provided on the periphery of the pushing part 15, the groove 16 being used to accommodate a component (not marked), on which the elastic component 7 is installed, on the plunger 6. The first pin hole 11 and the second pin hole 12 run through the sidewalls 14 of the rolling cavity 13 in a transverse direction. Most of the roller 3 is located in the rolling cavity 13, and the roller is at least partly exposed outside the rolling cavity 13 through the opening 17. As shown in the figure, an upper part of the roller 3 is located in the rolling cavity 13, and a lower part is exposed outside the rolling cavity 13.

[0013] The pin 2 comprises, distributed along the axial direction thereof, a first region 21, a third region 23 and a second region 22. The third region 23 is located between the first region 21 and the second region 22; the first region 21 is installed in the first pin hole 11, the second region 22 is installed in the second pin hole 12, and the third region 23 is located in the rolling cavity 13. The diameter of the first region is neither greater than the diameter of the second region 22 nor greater than the diameter of the third region 23; moreover, the first region 21 and the first pin hole 11 are fitted together so as to be incapable of relative rotation. The roller 3 is installed on the third region 23 of the pin 2 so as to be capable of rotating relative to the pin 2.

[0014] Figs. 3 to 5 show three feasible particular embodiments according to the present application.

[0015] In fig. 3, the diameters of the first region 21, the second region 22 and the third region 23 are the same. At the time of installation, the pin 2 is passed through the second pin hole 12 and inserted into the first pin hole 11; since the diameter of the second pin hole 12 is slightly larger than the diameter of the first pin hole 11, there is an interference fit between the first region 21 and the first pin hole 11, whereas there is a gap fit between the second region 22 and the second pin hole 12.

[0016] In fig. 4, the diameter of the first region 21 is the same as the diameter of the third region 23, but less than the diameter of the second region 22. At the time of installation, the pin 2 is passed through the second pin hole 12 and inserted into the first pin hole 11; since the diameter of the second pin hole 12 is larger than the diameter of the first pin hole 11, the first region 21 and the third region 23 of the pin 2 can be easily passed through the second pin hole 12; finally, there is an interference fit between the first region 21 and the first pin hole 11, and at the same time there is also an interference fit between the second region 22 and the second pin hole 12.

[0017] In fig. 5, the diameter of the first region 21 is less than the diameter of the third region 23, i.e. a step is formed between the first region 21 and the third region 23; moreover, the diameter of the third region 23 is less than the diameter of the second region 22. At the time of installation, the pin 2 is passed through the second pin hole 12 and inserted into the first pin hole 11; since the diameter of the second pin hole 12 is larger than the diameter of the first pin hole 11, the first region 21 and the third region 23 of the pin 2 can be easily passed through the second pin hole 12; finally, there is an interference fit between the first region 21 and the first pin hole 11, and at the same time there is also an interference fit between the second region 22 and the second pin hole 12, with the step between the first region 21 and the third region 23 being stopped at the sidewall 14 and thereby locating the pin 2 effectively in the axial direction thereof.

[0018] In particular embodiments shown in the figures, an interference fit is achieved between the pin 2 and the pin holes 11, 12. In other feasible particular embodiments, a manner of fitting which does not allow relative rotation such as bonding, welding or riveting may be employed to fix the pin 2 in the pin holes 11, 12.

[0019] The particular embodiments above are merely intended to explain the present application, and do not limit it. Those skilled in the art could make various changes and alterations in form without departing from the scope of the present application. Therefore all equivalent technical solutions also fall within the category of the present application, and the scope of patent protection of the present application should be defined by the claims.