JP2000145572A - Fuel injection pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress seizure between the external surface of tappets and the internal wall surface of fuel pumps by reducing their contact surface pressure. SOLUTION: A tappet 31 is supported for free reciprocation within a housing bore provided radially outwardly of the fuel pressure chamber of a pump housing. The tappet 31 has externally a cylindrical portion 311 adapted to slide on the internal wall surface of the housing bore, and tapering portions 312 and 313 at ends 312a and 313a whose outside diameter is set smaller than that of the cylindrical portion 311. Even if the tappet 31 is slanted to bring both ends 312a and 313a into contact with the internal wall surface of the housing bore, the radial force that a cam applies to the tappet 31 can place both tapering portions 312 and 313 into surface contact with the internal wall surface of the housing bore to reduce the contact surface pressure and thus resultant seizure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine (hereinafter referred to as "internal combustion engine").
The present invention relates to a fuel injection pump for an "internal combustion engine".

[0002]

2. Description of the Related Art Conventionally, there has been provided a movable member such as a tappet or a plunger which reciprocates in an axial direction by a power transmitting member such as a cam which receives a driving force, and the movable member applies a fluid sucked into a pressurizing chamber. Pressurizing pumps are known. In the case of a pump in which the cam slides directly on the movable member and reciprocates the movable member, the contact area between the cam and the movable member is small and the surface pressure is high. There is a risk that the sliding portion between the cam and the movable member will seize.

Therefore, as disclosed in, for example, Japanese Patent Application Laid-Open No. 6-249133, a cam ring is provided between the cam and the movable member so as to be able to contact the movable member in a plane-to-plane manner. 2. Description of the Related Art There is known a fuel injection pump having a configuration capable of reducing the surface pressure in a fuel injection pump.

[0004]

However, when the movable member is driven, a force acts on the tappet sliding on the cam ring in a direction transverse to the movement direction of the tappet by the cam. The tappet is provided so as to be able to reciprocate inside a housing hole provided radially outside the pressure chamber in which the plunger reciprocates. Since the outer diameter of the tappet is smaller than the inner diameter of the housing hole, when the lateral force acts as described above, the tappet tilts and the contact area between the both end portions of the outer peripheral surface of the tappet and the inner wall surface of the housing hole becomes extremely large. Become smaller. Therefore, the contact surface pressure between both ends of the outer peripheral surface of the tappet and the inner wall surface of the housing hole is increased, and seizure occurs on the outer peripheral surface of the tappet, so that there is a problem that the pressure of the pump cannot be increased. The above publication is aimed at reducing the contact surface pressure between the cam ring and the tappet, and is not intended to reduce the contact surface pressure between the tappet and the inner wall surface of the housing hole.

Accordingly, an object of the present invention is to reduce the contact surface pressure between the movable member and the inner wall surface of the fuel injection pump,
In particular, it is an object of the present invention to provide a fuel injection pump capable of reducing seizure on the outer peripheral surface of a tappet. Another object of the present invention is to provide a fuel injection pump that can reduce seizure on the outer peripheral surface of the tappet with a simple structure.

[0006]

According to the fuel injection pump of the present invention, the seizure at the contact surface between the tappet for transmitting the driving force of the internal combustion engine to the plunger for pressurizing the fuel and the pump housing is provided. It has a seizure reduction structure that reduces it. Therefore, by reducing the frictional force generated between the tappet and the pump housing by the seizure reduction structure, the contact surface pressure at the contact part between the tappet and the pump housing is reduced, so that seizure at the contact part can be reduced. .

According to the fuel injection pump of the second aspect of the present invention, a plurality of cylinder portions are provided. For example, in a fuel injection pump in which a plurality of cylinders are provided, such as a radial plunger type fuel injection pump, even when the cam ring and the tappet hit one side due to interference between the plungers caused by the plunger pumping fuel, the tappet is The tappet is tilted so as to absorb the one-side contact by the seizure reduction structure. Therefore, the cam ring and the tappet can be prevented from hitting each other, and surface contact can be ensured, so that seizure at the contact point between the cam ring and the tappet can be reduced.

According to the fuel injection pump of the third aspect of the present invention, the tappet has a cylindrical portion at an axial center portion, one end and the other end whose outer diameter is smaller than the outer diameter of the cylindrical portion,
The seizure reduction structure is a structure in which the outer diameter of the outer peripheral surface decreases from the cylindrical portion to one end and the other end. Therefore, even if the tappet is tilted in the pump housing due to the force in the direction transverse to the reciprocating sliding direction of the tappet acting on the contact surface between the cam ring and the tappet, the face contact between the tappet and the pump housing can be maintained. As a result, the contact surface pressure at the contact portion between the tappet and the pump housing is reduced, and burn-in at the contact portion can be reduced.

According to the fuel injection pump according to the fourth or fifth aspect of the present invention, the seizure reduction structure can be tapered or elliptical, so that the contact between the tappet and the pump housing can be achieved with a simple structure. The surface pressure can be reduced, and the burn-in at the contact portion can be reduced.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention; (First Embodiment) FIG. 3 shows a fuel supply system for a diesel engine using a fuel injection pump according to a first embodiment of the present invention. The drive shaft 11 of the fuel injection pump 1 is connected to the pump housing 10 by a bearing 14 and a journal 15.
It is supported rotatably. The cam 12 is formed integrally with the drive shaft 11. An annular cam ring 13 is fitted around the outer periphery of the cam 12.

The inner gear type feed pump 20 has an outer gear 21 and an inner gear 22. When the inner gear 22 rotates together with the drive shaft 11, fuel is sucked from the fuel tank 45 through the fuel passage 50, and the sucked fuel is pressurized and sent out from the fuel passage 51 to the fuel chamber 16. The fuel chamber 16 is connected to the return passage 5 via the throttle 60.
Communicates with 2. When the fuel pressure in the fuel chamber 16 becomes equal to or higher than a predetermined pressure, the regulating valve 61 is opened, and the excess fuel in the fuel chamber 16 returns from the fuel passage 50.

The metering valve 40 is an electromagnetic valve for metering the amount of fuel sucked into the fuel pressurizing chamber 54 from the fuel chamber 16 via the fuel suction passage 53 and the check valve 62 in accordance with the operating condition of the engine. The valve member 41 is biased toward a valve seat 44 by a spring 42, that is, urged in a valve closing direction. Solenoid 43
When the power is turned on, the valve member 4 is moved away from the valve seat 44 against the urging force of the spring 42, that is, in the valve opening direction.
1 is aspirated. By controlling the control current value supplied to the solenoid 43, the opening area of the valve portion formed by the valve member 41 and the valve seat 44 is controlled, and the amount of fuel sucked into the fuel pressurizing chamber 54 is adjusted.

The plunger 30 is reciprocally driven by the cam 12 via the cam ring 13 and the tappet 31 as the drive shaft 11 rotates. When the plunger 30 descends in the direction of the drive shaft 11, it draws fuel into the fuel pressurizing chamber 54, Drive shaft 11
When rising in the opposite direction, the intake fuel is pressurized. The pressurized fuel is supplied from the fuel passage 55 to the common rail 46 via the check valve 63. The common rail 46 accumulates fuel having a pressure fluctuation supplied from the fuel injection pump 1 and maintains the fuel at a constant pressure. High-pressure fuel is supplied from the common rail 46 to an injector (not shown).

Next, the structure of a driving force transmission system for transmitting driving force from the driving shaft 11 to the plunger 30 will be described in detail with reference to FIGS. FIG. 2 is II-II of FIG.
It is a line sectional view. In consideration of easy understanding of the configuration, the metering valve 4
0, check valve 62, fuel intake passage 53 and fuel passage 55
2 is shown in a different position from FIG. 3 in FIG. The cam 12 having a circular cross section is formed integrally with the drive shaft 11 so as to be eccentric. A bush 17 is press-fitted into the inner periphery of the cam ring 13 formed in an annular shape, and the cam ring 13 is slidable between the inner peripheral wall of the bush 17 and the outer peripheral wall of the cam 12.
Are fitted to the cam 12. A contact surface 13 a that slides on a sliding surface 34 a of the tappet shoe 34 is formed on an outer peripheral wall of the cam ring 13.

The tappet shoe 34 is pressed into the cam ring 13 side of the tappet 31 to form a sliding surface 34a which slides on the contact surface 13a of the cam ring 13 to improve the wear resistance due to the contact with the cam ring 13. ing. The tappet 31 is slidably supported on an inner wall 18 of a housing hole provided radially outside the fuel pressurizing chamber 54 of the pump housing 10. As shown in FIG. 1, the tappet 31 has a cylindrical shape and a substantially H-shaped vertical cross section.
The plunger 30 is housed on the side, and the tappet shoe 34 is pressed into the cam ring 13 side. Since the outer diameter of the tappet 31 is smaller than the inner diameter of the housing hole 18, the tappet 31
A clearance exists between the outer peripheral surface of the housing and the inner wall surface 18a of the housing hole 18. Cam ring 1 by cam 12
3 is applied to the contact surface 13a of the tappet 3 and the sliding surface 34 of the tappet shoe 34 in the radial direction of the tappet 31.
1 tappet end 312a and tappet end 313a
Is inclined in the clearance so as to contact the inner wall surface 18a of the housing hole 18.

The plunger 30 is connected to the pump housing 10.
Are slidably supported in a fuel pressurizing chamber 54 formed in the same manner. The plunger 30 is attached to the tappet 3 by a spring 32 via a lower sheet 36 fitted into the reduced diameter portion 35.
It is biased to one side. An end of the fuel pressurizing chamber 54 on the opening side is sealed with a stopper 70. As shown in FIG.
The outer peripheral surface of the tappet 31 is provided with tapered portions 312 and 313 at both ends of the cylindrical portion 311. A cylindrical portion 311 that slides on the inner wall surface 18a of the housing hole 18 is provided at a center portion of the tappet 31. Tapered portions 312 and 313 formed so as to be smaller than the diameter are provided.

In this embodiment, the burn-in reducing means of the tappet 31 is set to have a shape satisfying the following equation. θ1 = θ L1 + L2 = L Here, θ is the angle at which the tappet 31 is inclined in the housing hole 18 due to the force acting in the radial direction of the tappet 31, and θ1 is the axis of the outer peripheral surface of the cylindrical portion 311 as shown in FIG. This is the angle formed between the direction extension line and the inclined surfaces of the tapered portions 312 and 313. L1 and L2 are the lengths of the tapered portions 312 and 313 in the tappet axial direction, respectively, and L is the length of the cylindrical portion 311 in the tappet axial direction.

The tappet 31 is formed such that a quarter from the tappet end 312a and a quarter from the tappet end 313a are tapered portions 312 and 313 in the axial direction, and the remaining central portion is a cylindrical portion 311. ing.

Next, the operation of the fuel injection pump 1 will be described. The cam 12 rotates with the rotation of the drive shaft 11,
The cam ring 13 revolves as the cam 12 rotates.
As the cam ring 13 revolves, the tappet 31 and the plunger 30 reciprocate.

When the plunger 30 at the top dead center is lowered with the revolution of the cam ring 13, the pressure in the fuel pressurizing chamber 54 decreases, and fuel flows from the check valve 62 into the fuel pressurizing chamber 54. At this time, the plunger 30 is
2 is sucked upward by the negative pressure inside, but lowers integrally with the tappet 31 because it is urged downward by the spring 32 via the lower sheet 36. When the plunger 30 that has reached the bottom dead center rises again toward the top dead center, the check valve 62 closes, and the fuel pressure in the fuel pressurizing chamber 54 increases. When the fuel pressure in the fuel pressurizing chamber 54 rises above the fuel pressure in the fuel passage 55, the check valve 63 opens, and high-pressure fuel is supplied from the fuel passage 55 to the common rail 46.

Since the tappet 31 is provided with the tapered portions 312 and 313, the tappet 31 is inclined inside the housing hole 18 due to the radial force of the tappet 31 generated at the contact surface between the cam ring 13 and the tappet 31. In this case, the two tapered portions 312 and 313 are
Since the inner surface 18a makes surface contact with the inner wall surface 18a, the contact surface pressure can be reduced by increasing the contact area, and burn-in on the outer peripheral surface of the tappet 31 is reduced.

According to the fuel injection pump of the first embodiment, even when the tappet is inclined in the housing of the fuel injection pump, the outer peripheral surface of the tappet and the inner wall surface of the housing can be in surface contact. Further, the contact surface pressure between the pump housing and the tappet is reduced, and seizure of the tappet can be reduced with a simple structure.

(Second Embodiment) FIG. 4 shows a tappet of a fuel injection pump according to a second embodiment of the present invention. Components substantially the same as those in the first embodiment are denoted by the same reference numerals. In the second embodiment, the tappet end 3
14a and the outer diameter of the tappet end 315a
The crowning portions 314 and 315 have a curved surface having a large radius and protruding in the radial direction so as to be smaller than the outer diameter of the first and second outer diameters.
It may be. The crowning portions 314 and 315 are provided such that the vertical cross section of the tappet 31 is an arc having a large radius protruding outside the outer peripheral surface.

At this time, the burn-in reducing means is set to have a shape satisfying the following equation. d1 = L1 × sin θ = d2 = L2 × sin θ L1 + L2 = L Here, θ is an angle at which the tappet 31 is inclined in the housing hole 18 by a force acting in the radial direction of the tappet 31, and d1 and d2 are cylindrical portions 311. Of the tappet end 314a and the outside diameter of the tappet end 315a are halved. L1 and L
2 is the length of the crowning portions 314 and 315 in the tappet axial direction, and L is the length of the cylindrical portion 311 in the tappet axial direction.

In the second embodiment, the tappet 3
1 is provided with the crowning portions 314 and 315, so that when the tappet 31 is inclined inside the housing hole 18 due to the radially acting force of the tappet generated at the contact surface between the cam ring 13 and the tappet 31, two crownings are formed. The portions 314 and 315 are the inner wall surfaces 18 of the housing holes 18.
Since the surface contact is made with a, the contact surface pressure can be reduced by increasing the contact area, and the seizure of the outer peripheral surface of the tappet 31 is reduced.

In the first and second embodiments,
The description has been given of the fuel injection pump in which the cam ring 13 revolves with the rotation of the cam 12 so that the cam ring 13 and the tappet 31 slide. However, the fuel injection pump in which the cam ring 13 and the tappet 31 are in flat contact without sliding. The configuration of the present invention may be applied.

Third Embodiment FIG. 5 shows a fuel injection pump according to a third embodiment of the present invention. Components substantially the same as those in the first embodiment are denoted by the same reference numerals. In the above-described first and second embodiments, the one-cylinder fuel injection pump has been described. However, the configuration of the present invention can be applied to two or more cylinder fuel injection pumps. Therefore, in a third embodiment, a fuel supply system for a diesel engine using a three-cylinder fuel injection pump will be described with reference to FIG.

As shown in FIG. 5, the fuel injection pump 1 has three plungers 30 at 120 ° intervals on the outer periphery of the drive shaft 11.
Is arranged. A fuel pressurizing chamber 54 is formed on the end face of each plunger 30 on the side opposite to the drive shaft. Further, a fuel passage 80 is connected to each fuel pressurizing chamber 54 via a check valve 62. The fuel passage 80 is provided with one metering valve 40 disposed downstream of the feed pump 20.
From the downstream side to each fuel pressurizing chamber 54 in three directions.

On the other hand, the fuel passage 5 is provided in the three fuel pressurizing chambers 54.
5 is connected via a check valve 63 and the other end of the fuel passage 55 is connected to a common rail 46. The fuel passage 55 supplies the fuel pressurized in the fuel pressurizing chamber 54 to the common rail 46. In addition, common rail 4
From 6, high-pressure fuel is supplied to injectors provided in each cylinder of the engine (not shown). The cam ring 13 rotatably provided on the eccentric cam 12 of the drive shaft 11 includes:
On the outer peripheral surface, 120 is provided so as to correspond to three plungers 30.
Flat contact surfaces 13a are formed at intervals of °. Tappet shoe 34 and tappet 3 in contact with contact surface 13a
The configuration of No. 1 is the same as the above-described first and second embodiments.

When the drive shaft 11 rotates, the reciprocating motion of each plunger 30 is sequentially executed with a phase shift of 120 °. The fuel metered by the metering valve 40 is supplied to the fuel pressurizing chamber 54 corresponding to the plunger 30 descending from the top dead center among the three plungers 30. Then, the fuel supplied into the fuel pressurizing chamber 54 is pressurized by the plunger 30 rising to the fuel pressurizing chamber 54 side, and is supplied to the common rail 46.

As described above, according to the fuel injection pump 1 of the third embodiment, the cam ring 13 and the tappet 31 come into contact with each other, so that the tappet 31 is in the housing hole 18 as in the first and second embodiments. Even if the tappet 31 is inclined by the taper portion or the crowning portion provided on the tappet 31,
8 is in surface contact with the outer surface of the tappet 31, so that the burn-in of the outer peripheral surface of the tappet 31 can be reduced.

Further, by providing the tappet 31 with a tapered portion or a crowning portion, the following effects can be obtained in the fuel injection pump 1 according to the third embodiment.

The fuel supplied from the fuel injection pump 1 to the common rail 46 changes according to the operation state of the diesel engine. For example, when the amount of fuel required by the common rail 46 is large, the amount of fuel supplied from the metering valve 40 to the fuel injection pump 1 via the fuel passage 80 also increases. Therefore, the periods in which the fuel supplied to each of the fuel pressurizing chambers 54 is pressurized by the plunger 30 and pressure-fed to the common rail 46 may overlap. If the amount of fuel to be supplied to the common rail 46 is large depending on the operation state of the engine, the overlap of the pumping periods is caused by the plunger 30 and the fuel pressurizing chamber 5
During pressurized pumping of the fuel in 4, another plunger 30 also starts pressurized pumping of the fuel.

As described above, when the pressurizing and pumping periods overlap in a plurality of fuel pressurizing chambers, the driving reaction force of the plunger 30 on the side of the fuel pressurizing chamber which has started pressurizing and pressurizing acts on the cam ring 13. . Therefore, the relative rotation position of the cam ring 13 rotatably provided on the cam 12 of the drive shaft 11 with respect to the cam 12 is determined by the contact position of the plunger 30 with the tappet shoe 34 where the driving reaction force is generated first. Will be done. When the pressurizing and feeding is started in another fuel pressurizing chamber in a state where the rotation position of the cam ring 13 has already been determined, the tappet shoe 34 attached to the plunger 30 which has started the pressurizing and pressing corresponds to the cam ring 13. The contact surface 13a may be partially contacted. When the contact occurs, the contact area between the contact surface 13a of the cam ring 13 and the tappet shoe 34 is reduced, so that the surface pressure on the contact surface is excessively increased, which may cause seizure.

However, as described in the first embodiment and the second embodiment, since the tapered portion or the crowning portion is provided at both ends of the cylindrical portion 311 of the tappet 31, the tappet 31 can absorb one side. Tilt,
The surface contact between the contact surface 13a of the cam ring 13 and the tappet shoe 34 can be maintained. Therefore, even if the periods for pressurizing and feeding the fuel in the fuel pressurizing chamber overlap, the occurrence of seizure between the tappet shoe and the cam ring can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a tappet of a fuel injection pump according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II of FIG. 3, showing a fuel supply system using the fuel injection pump according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a fuel supply system using the fuel injection pump according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a tappet of a fuel injection pump according to a second embodiment of the present invention.

FIG. 5 is a schematic sectional view showing a fuel supply system using a fuel injection pump according to a third embodiment of the present invention.

[Description of Signs] 1 Fuel injection pump 10 Pump housing 11 Drive shaft 12 Cam 13 Cam ring 18 Housing hole 30 Plunger 31 Tappet 311 Cylindrical portion 312, 313 Tapered portion (seizing reduction structure) 314, 315 Crowning portion (seizing reduction structure) 54 Fuel pressurizing chamber (cylinder) 312a, 313a, 314a, 315a Tappet end

Claims (5)

[Claims] 1. A fuel injection pump for supplying high-pressure fuel to an internal combustion engine, comprising: a pump housing; a cylinder portion provided in the pump housing; A plunger for pressurizing the fuel drawn into the internal combustion engine, a cam that rotates together with a drive shaft of the internal combustion engine, a cam ring that is slidably mounted on the outer periphery of the cam and the cam, A tappet that transmits a driving force of the internal combustion engine to the plunger and that can slide back and forth in the pump housing, wherein the tappet reduces an image sticking at a contact surface between the tappet and the pump housing. A fuel injection pump comprising: 2. A fuel injection pump for supplying high-pressure fuel to an internal combustion engine, comprising: a pump housing; a plurality of cylinders provided in the pump housing; A plurality of plungers for pressurizing the fuel sucked into the cylinder portion; a cam rotating with a drive shaft of the internal combustion engine; a cam ring slidably mounted on the outer periphery of the cam with the cam; and the cam ring. A plurality of tappets that come into contact with each other on a plane to transmit the driving force of the internal combustion engine to the plurality of plungers and that can reciprocate in the pump housing; and the plurality of tappets are respectively the tappet and the tappet. A fuel having a seizure reduction structure for reducing seizure at a contact surface with the pump housing. Injection pump. 3. The seizure reduction structure of the tappet includes a cylindrical portion provided at a central portion in the axial direction and having substantially the same outer diameter, and one end and the other end having an outer diameter smaller than the outer diameter of the cylindrical portion. The fuel injection pump according to claim 1, wherein an outer diameter of the outer peripheral surface decreases in a direction from the cylindrical portion to the one end and the other end. 4. The fuel injection pump according to claim 3, wherein the burn-in reduction structure is tapered. 5. The fuel injection pump according to claim 3, wherein the burn-in reducing structure has a crowning shape.