JP2010209802A - Fuel injection pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection pump which is excellent in wear resistance and seizure resistance. <P>SOLUTION: The fuel injection pump 10 is provided with a drive shaft 20, a cam 21, a plurality of bushes 22, a cam ring 23, a plunger 24, and a pump housing. The drive shaft 20 is driven by an engine, and the cam 21 provided to the drive shaft 20 in an eccentric state rotates with the drive shaft 20. The cam ring 23 is provided on the outer periphery of the cam 21 with flexible rotation and makes orbital motion by the rotation of the drive shaft 20. The plurality of bushes 20 are provided between the cam 21 and the cam ring 23. One end of the plunger 24 is brought into contact with the predetermined surface of the cam ring 23, and the plunger 24 makes a reciprocating movement by the orbital motion of the cam ring 23. The pump housing supports the plunger 24 so that it can make a reciprocating movement and forms a fuel pressurization room 40 where fuel is pressurized by the other end of the plunger 24. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection pump for an internal combustion engine (hereinafter, the internal combustion engine is referred to as an “engine”).

  2. Description of the Related Art Conventionally, a fuel injection pump having a drive shaft that rotates with a camshaft of an engine is known. Specifically, a member that transmits a driving force such as a cam ring to the drive shaft is assembled to an eccentric cam, and the movable member reciprocates by a cam ring that revolves without rotating as the drive shaft rotates. Fuel injection pumps are known. In such a fuel injection pump, the fuel sucked into the fuel pressurizing chamber is pressurized and fed by the reciprocating drive of the movable member.

By the way, in the case of a pump in which the cam ring slides directly with the movable member and the movable member reciprocates, the contact pressure between the inner peripheral surface of the cam ring and the outer peripheral surface of the cam is high. There is a risk that the outer peripheral surface will be worn and the sliding part will burn.
In recent years, there has been a demand for further improvement in fuel injection pressure in order to improve engine output and reduce substances discharged from the engine. Therefore, the pressure acting on the contact surface between the inner peripheral surface of the cam ring and the outer peripheral surface of the cam tends to increase, and in this case, the problem of seizure of the sliding portion becomes particularly significant.

  As a technique for solving such a problem, as shown in FIG. 4A, a bush is provided between the cam ring and the cam, and is formed between the inner peripheral surface of the cam ring and the outer peripheral surface of the cam. The sliding surface wear and seizure are reduced. Further, in order to reduce wear and seizure of the sliding surface, a technique is disclosed in which the sliding surface of the bush protrudes radially inward from the both ends in the axial direction to the central portion in the axial direction (for example, , See Patent Document 1).

Japanese Patent Laid-Open No. 2003-193938

However, even if the technique disclosed in Patent Document 1 is used to further improve the fuel injection pressure, the surface pressure load and the sliding speed of the sliding surface increase, resulting in seizure of the sliding surface. There is concern.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection pump having excellent wear resistance and seizure resistance.

  The fuel injection pump according to claim 1, which has been made to solve the above-described problem, includes a drive shaft, a cam, a plurality of bushes, a cam ring, a movable member, and a pump housing. The drive shaft is driven by the engine. The cam is provided eccentric to the drive shaft and rotates together with the drive shaft. The cam ring is rotatably provided on the outer periphery of the cam, and performs a revolving motion by the rotation of the drive shaft. The plurality of bushes are provided between the cam and the cam ring. One end of the movable member abuts against a predetermined surface of the cam ring, and reciprocates by the revolving motion of the cam ring. For example, the movable member can be embodied as a plunger. The pump housing supports the movable member so as to be reciprocally movable and forms a fuel pressurizing chamber in which fuel is pressurized by the other end of the movable member.

  Here, particularly in the present invention, a plurality of bushes between the cam and the cam ring are rotatable relative to each other. Since the plurality of bushes can rotate with each other, the relative peripheral speed between the cam and the cam ring can be reduced. Therefore, even if the surface pressure applied to the sliding surface of the cam ring that comes into contact with the cam increases, the value of peripheral speed × surface pressure can be reduced. Accordingly, it is possible to prevent further pressure increase of the fuel and wear and seizure between the bush and the cam when the poor fuel is used. That is, the fuel injection pump is excellent in wear resistance and seizure resistance.

  Preferably, the plurality of bushes include, for example, a cam ring bush press-fitted into the cam ring and at least one roller bush rotatable with respect to the cam ring bush. If it does in this way, the relative peripheral speed between a cam and a cam ring will be buffered by sliding between a roller bush and a cam. Therefore, the relative peripheral speed between the cam and the cam ring is reduced, and wear and seizure between the bush and the cam can be prevented.

  For example, as shown in claim 3, it is preferable that the cam, the plurality of bushes, and the cam ring have different sliding surface materials adjacent to each other. In this way, it is possible to prevent the same material from being easily burned. Furthermore, for example, as shown in claim 4, the roller bush may be made of a material whose outer side in the radial direction is different from the inner side. In this case, the hardness and lubricity of the roller bush can be increased by the characteristics of the two materials, and seizure that occurs when the same material is used can also be prevented.

  According to a fifth aspect of the present invention, it is preferable that at least one end of the cam ring in the axial direction is provided with a side plate that prevents the bush from coming off. If it does in this way, it can control that a roller bush comes off at the time of high-speed rotation. Therefore, it can suppress that a bush pulls out and a friction arises between pump housings.

  Moreover, as shown in Claim 6, the side plate is good also as being provided in the both ends of the axial direction of a cam ring. Even if it does in this way, it can control that a bush comes off.

It is sectional drawing which shows the fuel-injection pump of one Embodiment of this invention. It is sectional drawing which shows the drive shaft, cam, bush, and cam ring of the fuel injection pump of one Embodiment of this invention. It is the III-III sectional view taken on the line of FIG. It is a schematic diagram which shows the relationship between the cam of the conventional and the fuel pump of this invention, a bush, and a cam ring. It is sectional drawing which shows the drive shaft, cam, bush, and cam ring of the fuel injection pump of other embodiment of this invention. It is sectional drawing which shows the drive shaft, cam, bush, and cam ring of the fuel injection pump of other embodiment of this invention. It is sectional drawing which shows the drive shaft, cam, bush, and cam ring of the fuel injection pump of other embodiment of this invention.

  Hereinafter, a plurality of embodiments of a fuel injection pump of the present invention will be described with reference to the drawings. The fuel injection pump according to the present embodiment is mounted on a vehicle and used to pump low-pressure fuel from a fuel tank, pressurize it, and send the high-pressure fuel to a common rail.

(One embodiment)
A fuel injection pump of this embodiment is shown in FIG. As shown in FIG. 1, the fuel injection pump 10 includes a housing body 11 and two cylinder heads 12 and 13. The housing body 11 is made of aluminum, and the cylinder heads 12 and 13 are made of iron. In this embodiment, the cylinder head 12 and the cylinder head 13 are formed in substantially the same shape, but are formed at different positions such as screw holes and fuel passages. On the other hand, the formation positions of the screw holes and the fuel passages can be made the same, and the shapes of the cylinder head 12 and the cylinder head 13 can be made the same.

  As shown in FIG. 1, the housing body 11 supports the drive shaft 20 in a rotatable manner. The drive shaft 20 has a cam 21. As shown in FIG. 3, the cam 21 is eccentric with respect to the drive shaft 20, has a circular cross section, and is formed integrally with the drive shaft 20. A substantially square cam ring 23 is supported on the outer periphery of the cam 21. A plurality of bushes 22 are interposed between the cam ring 23 and the cam 21. As the plurality of bushes 22 rotate relative to the cam 21, the cam ring 23 revolves as the drive shaft 20 rotates.

  Next, the plurality of bushes 22 of this embodiment will be described in detail. As shown in FIGS. 2 and 3, the plurality of bushes 22 include a roller bush 221 and a cam ring bush 222. The roller bushing 221 has a ring shape and is slidably provided between the cam 21 and the cam ring 23. The cam ring bush 222 is a ring-shaped member and is fixed to the inner periphery of the cam ring 23. Further, the cam ring bush 222 may be slidably inserted into the inner periphery of the cam ring 23.

  As shown in FIG. 3, the cam 21, the roller bush 221, the cam ring bush 222, and the cam ring 23 are adjacent to each other and in close contact. The members that are in contact with each other are preferably formed of different materials. Further, the cam 21, the roller bush 221, the cam ring bush 222, and the cam ring 23 are preferably made of a material having high hardness (for example, iron, copper, aluminum alloy, or ceramic) in order to reduce the frictional force. For example, the cam 21 is made of iron, the roller bush 221 is made of aluminum or ceramic, the cam ring bush 222 is made of copper, and the cam ring 23 is made of iron.

  As shown in FIG. 4B, the roller bushing 221 is divided into an outer layer 221a and an inner layer 221b, and can have a two-layer structure. The outer layer 221a and the inner layer 221b of the roller bush 221 are made of different materials. In this embodiment, the cam 21 is made of iron. The inner layer 221b of the roller bushing 221 is made of copper, aluminum or ceramic, and the outer side 221a is made of iron. Finally, the cam ring bush 222 is made of copper or aluminum, and the cam ring 23 is made of iron. Thus, the cam 21, the roller bush 221, the cam ring bush 222, and the cam ring 23 have high hardness and can be adjacent to each other with different materials.

  Further, a plurality of roller bushings 221 can be provided. For example, when the space between the cam 21 and the cam ring 23 is sufficient, a plurality of roller bushings 221 made of different materials can be provided. In addition, a plurality of roller bushings 221 made of different materials with sufficiently high hardness can be provided even if formed thin.

  In order to prevent the roller bushing 221 from coming off between the cam 21 and the cam ring 23, side plates 251 are provided at both ends in the axial direction of the cam ring 23. The side plate 251 is formed in an annular shape at both end portions of the cam ring 23. In the case of this embodiment, as shown in FIG. 2, the side plate 251 has an L-shaped cross section, and a protruding portion 251b protrudes in the axial direction from the periphery of the disc portion 251a. By this protruding portion 251b, the side plate 251 is fitted into the cam ring 23 and the roller bushing 221 is prevented from coming off.

  As shown in FIG. 5, the side plate 252 has an I-shaped cross section, and may be directly fitted into the inner peripheral wall of the cam ring 23.

Furthermore, as shown in FIG. 6, the side plate 253 may be provided only on one side of one end of the cam ring 23. In this case, the protruding plate 23a can be formed on the inner peripheral wall edge on the other end side of the cam ring 23 in the radial direction.
As shown in FIG. 7, the side plates 251, 252 and 253 may not be provided.

  Two plungers 24 are arranged in the orthogonal direction of the drive shaft 20. These plungers 24 are opposed to each other with the cam ring 23 interposed therebetween. The plunger 24 has a plunger head 243. Further, the plunger head 243 protrudes from the plunger 24 in the radial direction. A spring 26 is disposed between the protruding portion of the plunger head 243 and the cylinder heads 12 and 13. The spring 26 biases the plunger head 243 toward the cam ring 23 side. The end surface of the plunger head 243 urged by the spring 26 and the outer wall surface of the cam ring 23 are in contact with each other to form a sliding surface. The interior of the housing 11 is filled with fuel, and the sliding surface formed by the cam ring 23 and the plunger head 243 is lubricated with fuel.

  Cylinders 12a and 13a are formed inside the cylinder heads 12 and 13, respectively. A plunger 24 as a movable member is supported by these cylinders 12a and 13a so as to be able to reciprocate. A fuel pressurizing chamber 40 is formed by the inner peripheral surfaces of the cylinders 12 a and 13 a, the end surface of the check member 31, and the other end of the plunger 24. As shown in FIG. 1, a fuel inflow portion 30 and a fuel discharge portion 50 are connected to the fuel pressurizing chamber 40.

  The fuel inflow portion 30 includes a check member 31 and a fuel inflow passage 32. The fuel is sucked into the fuel pressurizing chamber 40 from the fuel inflow passage 32. The check member 31 prevents the fuel from flowing backward from the fuel pressurizing chamber 40 to the fuel inflow passage 32.

  As shown in FIG. 1, the fuel discharge part 50 on the one cylinder head 12 side is provided in the axial direction of the drive shaft 20 and has a check member 51 and a fuel discharge passage 52. The pressurized fuel is discharged from the fuel pressurizing chamber 40 via the fuel discharge passage 52. The check member 51 prevents the fuel from flowing backward from the fuel discharge passage 52 to the fuel pressurizing chamber 40. The other cylinder head 13 side merges with the fuel discharge part 50 on the one cylinder head 12 side through a pipe (not shown).

  Next, the operation of the fuel injection pump 10 will be described. The cam 21 rotates with the rotation of the drive shaft 20, and the cam ring 23 revolves without rotating as the cam 21 rotates. Along with the revolution of the cam ring 23, the outer wall surface of the cam ring 23 and the end surface of the plunger head 243 slide to the left and right, and the plunger 24 is reciprocated up and down.

  FIG. 1 shows a state where the plunger 24 is located at the top dead center due to the revolution of the cam ring 23. When the plunger 24 at the top dead center moves to the bottom dead center side as the cam ring 23 revolves, the fuel discharged from the internal feed pump passes through the check member 31 from the fuel inflow passage 32 to the cylinder head 12 side. It flows into the fuel pressurizing chamber 40.

  When the plunger 24, which has reached the bottom dead center due to the revolution of the cam ring 23, rises again toward the top dead center and the check member 31 on the cylinder head 12 side is closed, the fuel pressure in the fuel pressurizing chamber 40 rises. . When the fuel pressure in the fuel pressurizing chamber 40 rises higher than the fuel pressure in the fuel discharge passage 52, the check member 51 opens. When the check member 51 is opened, the fuel pressurized in the fuel pressurizing chamber 40 is sent to the fuel discharge passage 52 and supplied from the fuel discharge passage 52 to a common rail (not shown). Although the fuel discharge part on the other cylinder head 13 side is not shown, it operates alternately with the same configuration as the fuel discharge part 50 on the cylinder head 12 side described above.

  The common rail accumulates the pressure-fluctuated fuel supplied from the fuel pump 10 and keeps it at a constant pressure. The fuel stored in the common rail is supplied to an injector (not shown).

  As described above, in the fuel pump 10 of this embodiment, the roller bush 221 and the cam ring bush 222 are provided between the cam 21 and the cam ring 23, and a plurality of bushes can rotate with each other. Therefore, even if the circumferential speed of the cam ring surface is reduced and the surface pressure applied to the sliding surface of the cam ring 23 in contact with the cam 21 is increased, the value of circumferential speed × surface pressure can be reduced. Accordingly, it is possible to prevent further pressure increase of the fuel and wear and seizure between the bush and the cam when the poor fuel is used.

  Moreover, according to this form, the cam 21 is made of iron. The inner layer 221b of the roller bushing 221 is made of copper, aluminum or ceramic, and the outer layer 221a is made of iron. Finally, the cam ring bushing 222 is made of copper or aluminum, and the cam ring is made of iron. Therefore, the cam 21, the roller bush 221, the cam ring bush 222, and the cam ring 23 can be made of different materials. Therefore, the hardness and lubricity of the roller bush can be increased, and seizure caused by using the same material can be suppressed.

  By having the side plate 251 at the end of the cam ring 23 in the axial direction, the roller bushing 221 is sandwiched. Therefore, it is possible to prevent the roller bush from coming off when rotating at high speed. Therefore, it is possible to suppress the occurrence of friction between the roller bushing 221 and the pump housing.

  As mentioned above, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of invention, it can implement with a various form.

10: Fuel injection pump, 11: Housing body (pump housing), 12: Cylinder head (pump housing), 12a: Cylinder, 13: Cylinder head (pump housing), 13a: Cylinder, 20: Drive shaft, 21: Cam, 22: Plural bushes, 221: Roller bushing, 222: Cam ring bush, 23: Cam ring, 24: Plunger, 243: Plunger head, 251, 252, 253: Side plate, 30: Fuel inflow part, 31: Check member, 32 : Fuel inflow passage, 40: cylinder, 41: fuel pressurizing chamber, 50: fuel discharge section, 51: check member, 52: fuel discharge passage

Claims (6)

A fuel injection pump for supplying high pressure fuel to an internal combustion engine,
A drive shaft driven by an internal combustion engine;
A cam provided eccentric with respect to the drive shaft;
A cam ring which is rotatably provided on the outer periphery of the cam and performs a revolving motion by rotation of the drive shaft;
A plurality of bushes provided between the cam and the cam ring and rotatable relative to each other;
A movable member whose one end is in contact with a predetermined surface of the cam ring and reciprocates by the revolving motion of the cam ring;
A fuel injection pump comprising: a pump housing which supports the movable member so as to be reciprocally movable and forms a fuel pressurizing chamber in which fuel is pressurized by the other end of the movable member. The fuel injection pump according to claim 1, wherein
The plurality of bushes include a cam ring bush press-fitted into the cam ring, and at least one roller bush rotatable with respect to the cam ring bush. The fuel injection pump according to claim 1 or 2,
The fuel injection pump according to claim 1, wherein the cam, the plurality of bushes, and the cam ring are made of different sliding surfaces. The fuel injection pump according to any one of claims 1 to 3,
2. The fuel injection pump according to claim 1, wherein the roller bush is made of a material having a radially outer side and a different inner side. In the fuel injection pump according to any one of claims 1 to 4,
A fuel injection pump characterized in that a side plate for preventing the bush from coming off is provided at least at one end in the axial direction of the cam ring. The fuel injection pump according to claim 5, wherein
The fuel injection pump according to claim 1, wherein the side plates are provided at both ends of the cam ring in the axial direction.

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