JP7769583B2 - fuel injection pump - Google Patents

Description

The present invention relates to a fuel injection pump.

Fuel injection pumps used in fuel injection systems for internal combustion engines are equipped with a tappet that reciprocates axially as the cam rotates, causing a plunger to reciprocate. The tappet is pressed against the cam by the force of the plunger spring via a spring seat, and reciprocates according to the cam profile as the cam rotates. This causes the plunger to reciprocate, drawing fuel into the pressurized chamber and pressurizing the fuel in the pressurized chamber before it is pumped out (see, for example, Patent Document 1).

In such a fuel injection pump, if the plunger becomes stuck inside the plunger barrel, the spring seat connected to one end of the plunger is left at the top dead center position along with the plunger, and the tappet and spring seat are separated. As a result, the tappet is no longer subjected to a pressing load from the plunger spring against the cam, allowing it to move freely. This prevents the tappet from following changes in the cam profile, and the tappet may be struck by the cam, resulting in damage to the cam.

In response to this, as shown in Figure 5, bolt holes 105 and 107 are formed in the spring seat 101 and tappet body 103, respectively, and the spring seat 101 and tappet body 103 are fastened together with a fastening bolt 109. This prevents the spring seat 101 and tappet body 103 from separating, thereby minimizing damage to the tappet.

Japanese Patent Application Publication No. 5-106532

However, a structure using fastening bolts requires the creation of threaded bolt holes in the spring seat and tappet. Furthermore, this structure requires the work of tightening the fastening bolts during assembly, which can reduce work efficiency.

The present invention aims to provide a fuel injection pump that requires simple processing and allows the spring seat and tappet to be fastened together through a simple assembly procedure.

In order to solve the above problems, one aspect of the present invention provides a fuel injection pump comprising: a plunger inserted into the plunger barrel so as to be slidable back and forth in the axial direction and pressurizing fuel in a pressurization chamber located at one axial end; a tappet housed in a tappet sliding hole so as to be slidable back and forth in the axial direction; a plunger spring that urges the tappet in a direction opposite the pressurization chamber; and a spring seat engaged with the other end of the plunger and supporting one end of the plunger spring; the plunger and tappet reciprocating as the cam rotates, introducing fuel into the pressurization chamber and pressurizing and pumping the fuel; the tappet and spring seat each have through holes that communicate with each other, and are fastened together by locking members that are inserted into the through holes and locked to the tappet and spring seat, respectively.

As explained above, the present invention requires only simple processing and allows the spring seat and tappet to be fastened together through a simple assembly process.

1 is a cross-sectional view showing an example of the configuration of a fuel injection pump according to an embodiment of the present invention; FIG. 2 is a cross-sectional view showing a tappet of the fuel injection pump according to the embodiment. FIG. 4 is another cross-sectional view showing the tappet of the fuel injection pump according to the embodiment. FIG. 2 is a perspective view showing an example of a locking member according to the embodiment. FIG. 1 is a cross-sectional view showing a tappet in a conventional fuel injection pump.

The following describes in detail an embodiment of the fuel injection pump of the present invention. However, this embodiment shows only one aspect of the present invention and does not limit the invention, and can be modified as desired within the scope of the present invention. In addition, parts with the same reference numerals in each drawing indicate the same components, and descriptions will be omitted where appropriate.

Figure 1 is a cross-sectional view showing an example configuration of a fuel injection pump according to this embodiment. Components not necessary for explaining the present invention are omitted from Figure 1.

The fuel injection pump 1 is used to inject and supply pressurized high-pressure fuel to an internal combustion engine. The fuel injection pump 1 comprises a pump housing 2, a plunger barrel 5 fitted into the pump housing 2, a plunger 7, and a pressure chamber 6 defined by the plunger barrel 5 and plunger 7. A delivery valve 4 and a holder 17 are attached above the plunger barrel 5, and the holder 17 is screwed to the pump housing 2.

A fuel intake/exhaust port 5b is formed in the plunger barrel 5. A fuel reservoir chamber 9 is formed between the pump housing 2 and the plunger barrel 5, facing the intake/exhaust port 5b. The plunger 7 is inserted into the plunger insertion hole 5a of the plunger barrel 5 so that it can rotate axially and slide vertically. The plunger 7 is formed with an axial fuel passage 7b and an inclined lead 7a that communicates with the axial fuel passage 7b.

The plunger 7 also has an upper edge portion 11 and a lower beveled edge portion 12. The upper edge portion 11 is formed by the edge of the upper end surface of the plunger 7. The beveled edge portion 12 is formed by the upper end of the beveled lead 7a. As the plunger 7 moves in the axial direction, these upper edge portions 11 and beveled edge portions 12 move over the opening 14 of the intake/exhaust port 5b. In this case, the upper edge portion 11, which determines the start of pumping, closes the opening 14 of the intake/exhaust port 5b, starting fuel pumping, and the beveled edge portion 12, which determines the end of pumping, opens the opening 14 of the intake/exhaust port 5b, ending fuel pumping.

The inclined edge portion 12 is also inclined relative to the axial direction of the plunger 7, and by changing the phase of the axial rotation of the plunger 7, the timing at which the inclined edge portion 12 opens the opening 14 of the intake/exhaust port 5b changes, making it possible to adjust the amount of fuel pumped by the pump. In this embodiment, the intake/exhaust port 5b, fuel reservoir chamber 9, and inclined edge portion 12 are provided in two sets with a phase difference of 180°.

A control sleeve S1 is fitted onto the outer periphery of the plunger barrel 5, and a groove St is formed in the lower part of the control sleeve S1 into which the flange 7c of the plunger 7 fits. Therefore, by rotating the control sleeve S1 using the control rack L1, the plunger 7 is displaced in the axial rotation direction, changing the relative positions of the axial fuel passage 7b and inclined lead 7a with respect to the intake/exhaust port 5b.

A spring seat 8 is engaged with the lower end 7d of the plunger 7, and the plunger 7 is biased downward via the spring seat 8 by the elastic force of a plunger spring 29. The lower end 7d of the plunger 7 and the spring seat 8 are pressed into contact with a tappet 30, which in turn is pressed into contact with a cam fixed to a camshaft (not shown). The tappet 30 is housed in a tappet sliding hole 2a provided in the pump housing 2 so that it can slide back and forth. As the camshaft and cam rotate, the tappet 30 moves back and forth according to the cam profile. This causes the plunger 7 to move back and forth in the axial direction.

Figures 2 and 3 are explanatory diagrams showing the fastening structure of the tappet 30 and spring seat 8. Figures 2 and 3 each show a cross section of the cylindrical tappet 30 cut along its axial direction, including the axis, at positions that are 90 degrees out of phase with each other.

The tappet 30 is composed of a tappet body 31, roller pin 41, bearing 43, and tappet roller 45. The tappet body 31 has a cylindrical shape with a circular cross section that matches the cross-sectional shape of the tappet sliding hole 2a. A recess 32 is formed in the upper part of the tappet body 31 (on the plunger 7 side) in which the spring seat 8 is disposed. The recess 32 is formed in a cylindrical shape that can accommodate the circular spring seat 8. The spring seat 8 has an engagement portion 8a on its upper surface with which the lower end of the plunger 7 engages.

The lower part of the tappet body 31 also has a roller accommodating recess 33 in which the tappet roller 45 is positioned. Pin insertion holes 38a and 38b are formed on either side of the roller accommodating recess 33, and a roller pin 41 is inserted into these holes. The tappet roller 45 is rotatably supported on the roller pin 41 via a bearing 43. The tappet body 31 and roller pin 41 each have pin insertion holes 39 and 41a that communicate with each other, and a fixing pin 47 is lightly press-fitted across the two pin insertion holes 39 and 41a, thereby assembling the roller pin 41 to the tappet body 31.

The tappet body 31 also has oil holes 37a and 37b that connect the recess 32 and the roller accommodating recess 33. The oil hole 37 allows the lubricating oil in the tappet sliding hole 2a of the pump housing 2 to flow out toward the cam chamber when the tappet 30 rises, and allows the lubricating oil to flow into the tappet sliding hole 2a when the tappet 30 descends. This suppresses pressure fluctuations within the tappet sliding hole 2a, ensuring that the reciprocating movement of the tappet 30 and plunger 7 is not hindered.

The spring seat 8 and tappet body 31 each have two sets of through holes 35, 36 that communicate with each other. The two sets of through holes 35, 36 consist of large-diameter holes 35a, 36a and small-diameter holes 35b, 36b formed in the spring seat 8, and holes 35c, 36c formed in the tappet body 31, respectively, and extend from the top surface of the spring seat 8 to the roller-accommodating recess 33 in the tappet body 31. A locking member 50 is inserted into the through holes 35, 36.

Figure 4 shows a perspective view of the locking member 50 used in the fuel injection pump 1 according to this embodiment. The locking member 50 is configured in a generally U-shape, with two legs 51a, 51b and a base 55 connecting the two legs 51a, 51b. The tips of the two legs 51a, 51b are provided with bent portions 53a, 53b. The two legs 51a, 51b are inserted into the through holes 35, 36 formed in the spring seat 8 and the tappet body 31, respectively. The bent portions 53a, 53b at the tips of the two legs 51a, 51b are locked to the edges of the holes 35c, 36c of the tappet body 31 where they open into the roller accommodating recess 33 (see Figure 2).

The base 55 of the locking member 50 is semicircular and is positioned along the outer periphery of the engagement portion 8a of the spring seat 8, with which the lower end 7d of the plunger 7 engages. A portion of the base 55 engages with the edge of the large-diameter holes 35a, 36a of the spring seat 8, where they open to the upper surface of the spring seat 8 (see Figures 2 and 3). In this manner, in this embodiment, the base 55 of the locking member 50 is engaged with the spring seat 8, and the bent portions 53a, 53b at the tips of the two legs 51a, 51b are engaged with the tappet body 31, fastening the tappet 30 and spring seat 8 together.

The locking member 50 is constructed using a material that is resistant to deformation during use of the fuel injection pump 1. The locking member 50 may be formed, for example, from a steel wire. Furthermore, because the locking member 50 is constructed from wire, it has a predetermined degree of elasticity. This allows the locking member 50 to be easily inserted into the through-holes 35, 36 and the bent portions 53a, 53b to be engaged with the tappet body 31. Specifically, the two legs 51a, 51b of the locking member 50 are bent inward in the U-shape and inserted into the two through-holes 35, 36 of the spring seat 8 and the tappet body 31. The locking member 50 is then pushed in until the base 55 of the locking member 50 abuts the top surface of the spring seat 8, after which the two legs 51a, 51b are released. As a result, the bent portions 53a and 53b at the tips of the two legs 51a and 51b are engaged with the edges of the holes 35c and 36c in the tappet body 31.

This fastening structure is constructed by placing the spring seat 8 in the recess 32 of the tappet body 31, inserting the two legs 51a, 51b of the locking member 50 into the through-holes 35, 36, respectively, from the spring seat 8 side, and then locking the bent portions 53a, 53b at the tips of the two legs 51a, 51b with the edges of the holes 35c, 36c of the tappet body 31. Therefore, even when the lower end 7d of the plunger 7 is engaged with the spring seat 8, the spring seat 8 and tappet 30 can be easily fastened together. Furthermore, because the locking member 50 has a predetermined elasticity, it can also be easily removed when disassembling the spring seat 8 and tappet 30.

In addition, the through holes 35, 36 formed in the spring seat 8 and tappet body 31 do not need to be threaded holes, which simplifies the process of forming the through holes 35, 36.

As described above, the fuel injection pump 1 according to this embodiment has a structure for fastening the tappet 30 and spring seat 8, which does not require the machining of screw holes. Furthermore, a simple structure is used for fastening the spring seat 8 and tappet 30, making it easy to assemble and disassemble the spring seat 8 and tappet 30.

The above describes in detail preferred embodiments of the present invention with reference to the accompanying drawings, but the present invention is not limited to such examples. It is clear that a person with ordinary skill in the technical field to which the present invention pertains can conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that these naturally fall within the technical scope of the present invention.

For example, the configuration of the locking member that fastens the spring seat and tappet is not limited to the example in the above embodiment. While the locking member in the above embodiment is configured as a U-shape with two legs, the two legs may be separated and configured as multiple locking members that lock onto the spring seat and tappet, respectively.

Furthermore, the configuration of the fuel injection pump described in the above embodiment is merely an example, and the configuration and shape of each component may be different. Furthermore, there are no limitations on the type of pump, as long as it is configured to fasten a tappet and a spring seat.

1: fuel injection pump, 2: pump housing, 4: delivery valve, 5: plunger barrel, 5a: plunger insertion hole, 6: pressure chamber, 7: plunger, 7a: inclined lead, 7b: axial fuel passage, 8: spring seat, 9: fuel reservoir chamber, 11: upper edge portion, 12: inclined edge portion, 14: opening, 30: tappet, 35, 36: through hole, 50: locking member, 51a, 51b: legs, 53a, 53b: bent portion, 55: base

Claims (2)

a plunger (7) inserted into a plunger barrel (5) so as to be slidable back and forth in the axial direction and pressurizing fuel in a pressurizing chamber (6) provided at one end side of the plunger barrel (5); a tappet (30) accommodated in a tappet sliding hole (2a) so as to be slidable back and forth in the axial direction; a plunger spring (29) urging the tappet (30) in a direction opposite to the pressurizing chamber (6); and a spring seat (8) engaged with the other end side of the plunger (7) and supporting one end of the plunger spring (29), wherein the plunger (7) and the tappet (30) reciprocate in accordance with rotation of a cam to introduce fuel into the pressurizing chamber (6) and pressurize and pump the fuel,
the tappet (30) and the spring seat (8) each have through holes (35, 36) communicating with each other, and are fastened together by locking members (50) that are inserted into the through holes (35, 36) and locked to the tappet (30) and the spring seat (8), respectively. The tappet (30) and the spring seat (8) each have two sets of through holes (35, 36) that communicate with each other,
The locking member (50) is U-shaped and has two legs (51 a, 51 b) that are inserted into the two pairs of through holes (35, 36), respectively, and a base (55) that connects the two legs (51 a, 51 b),
The two legs (51a, 51b) of the locking member (50) are inserted into the two pairs of through holes (35, 36) from the spring seat (8) side, respectively;
2. The fuel injection pump according to claim 1, wherein the base portion (55) is engaged with the spring seat (8), and bent portions (53a, 53b) provided at the tip ends of the two legs (51a, 51b) are engaged with the tappet (30), thereby fastening the tappet (30) and the spring seat (8).