JPH0510502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fuel injection pump, also called a bottle type, and particularly to its fuel injection amount control structure.

[Technical background of the invention]

Conventionally, a fuel injection pump that supplies fuel to a diesel engine has a structure shown in FIGS. 1 to 3. That is, in the figure, 1 is a pump housing, and a cylinder 2 is provided within this pump housing 1, and a plunger 3 is slidably fitted into this cylinder 2. The lower end of the plunger 3 is in contact with a tapepet assembly 5 via a spring seat 4. The tapet assembly 5 has a cylindrical tapet body 6.
A roller pin 7 is attached inside the roller pin 7, and a cam roller 8 is rotatably fitted into the roller pin 7. The cam roller 8 is in rolling contact with a camshaft 9 that rotates in synchronization with the engine, and as the tapepet assembly 5 is reciprocated by the rotation of the camshaft 9, the plunger 3 is moved in the axial direction of the cylinder 2. It is made to move back and forth. Note that the return movement of the plunger 3 is performed by a spring 10.

Reference numeral 11 denotes a fuel suction hole opened in the side wall of the cylinder 2, and this fuel suction hole 11 is communicated with a fuel supply port 13 through a fuel reservoir 12. The plunger 3 has a spiral or other inclined lead 14 formed at its upper end, and when the lead 14 opens the fuel intake hole 11 when the plunger 3 moves downward, the fuel reservoir 1
2, fuel is introduced into the pressure feeding chamber 15. When the plunger 3 moves upward, the lead 14 is connected to the fuel suction hole 11.
When it is closed, the fuel in the pressure feeding chamber 15 is pressurized, and this fuel is forced to open the discharge valve 16 and is forced to be fed from the fuel discharge port 17 to the engine side. Note that by operating the nut 18 and adjusting the set load of the spring 19, the opening pressure of the discharge valve 16 is varied and the fuel discharge pressure is adjusted.

20 is a control sleeve whose upper end portion 20
a is fitted to the cylinder 2 so as to be rotatable. Further, the lower end portion of this sleeve 20 is engaged with the plunger 3 so as to rotate integrally therewith. This engagement structure is shown in FIG.
That is, a large-diameter portion is formed in the middle of the plunger 3, and planar portions 3a, 3a that are machined to face each other are formed in this large-diameter portion. Opposed to this, the lower part of the sleeve 20 includes a flat part 3a,
Fitting portions 20b, 20b that fit into the portion 3a are formed. These flat parts 3a, 3a and the fitting part 20
By engagement with b and 20b, the sleeve 20 and the plunger 3 can rotate together around the axis. In addition, when the plunger 3 reciprocates, only the plunger 3 moves in the axial direction.

A flange 21 is formed at the upper end of the sleeve 20, and a ball 22 is brazed or welded to this flange 21. A rack 23 is attached to the pump housing 1.
The ball 22 is slidably held between arm portions 24, 24 shown in FIG. 3 formed on this rack 23. Although not shown, the rack 23 is moved in the direction of arrow A in FIG. 3 by a governor that responds to the operation of an accelerator operator.

Therefore, when the rack 23 is moved in the direction of arrow A, the control sleeve 20 is rotated because the balls 22 are pushed in the circumferential direction of the sleeve, and this rotation of the sleeve 20 causes the engagement of the flat parts 3a, 3a. Since the rotation is transmitted to the plunger 3 through the sleeve 20, the plunger 3 is also rotated by the same amount as the sleeve 20. Since the rotation of the plunger 3 changes the relative position between the inclined lead 14 and the fuel suction hole 11, the opening timing of the fuel suction hole 11 during the stroke of the plunger 3 is changed. Based on this, the fuel injection amount is controlled.

By the way, conventionally, as shown in FIG. 2, a gap l is secured between the sleeve 20 and the large diameter part 3b of the plunger 3, which is a part perpendicular to the planar parts 3a, 3a. , plunger 3
In order to reduce the frictional resistance with the sleeve 20 when the sleeve 20 moves back and forth, it had a clearance of about 0.3 to 0.5 mm.

[Problems with background technology]

However, by operating the rack 23 in the direction of arrow A, the ball 22 can be passed through the sleeve 2.
When rotating 0, the ball 22 and the arm part 24,
24 are displaced relative to each other in the radial direction, and at this time, if the contact resistance is large, a force that moves the ball 22 in the radial direction is generated. In such a case, sleeve 20
is fitted into cylinder 2 only at its upper part,
In addition, since a large gap l is secured with respect to the plunger 3, the axis of the sleeve 20 is tilted. Due to this inclination, the upper end 20a of the sleeve 20
It often happens that the sleeve 20 hits the cylinder 2 partially, and the sleeve 20 bites into the cylinder 2, obstructing the movement of the sleeve 20 and making it impossible to control the fuel injection amount with high precision.

[Purpose of the invention]

The present invention was developed based on the above circumstances, and its purpose is to prevent the sleeve from tilting, eliminate the occurrence of biting between the sleeve and the cylinder, and ensure the control of the fuel injection amount over a long period of time. The purpose is to provide a fuel injection pump that can perform

[Summary of the invention]

Therefore, the wall surface portion of the sleeve of the fuel injection pump of the present invention has a portion that faces the outer circumferential surface of the plunger with a predetermined clearance therebetween, and a portion that approaches the outer circumferential surface of the plunger and has a portion that faces the outer circumferential surface of the plunger with a predetermined clearance therebetween. Opposing portions are formed with a small minute clearance interposed therebetween. Therefore, when the sleeve tries to tilt, the plunger comes into contact with the approaching portion of the opposing sleeve via a small clearance, and the sleeve is prevented from tilting. In addition, since the wall portion of the sleeve is formed so as to partially approach the outer circumferential surface of the plunger, the sleeve is processed so that the entire wall portion faces the outer circumferential surface of the plunger with a minute clearance. Compared to the case of manufacturing, the wall surface portion can be formed so as to precisely realize local minute clearances, so that processing and manufacturing of the wall surface portion is easier.

[Embodiments of the invention]

An embodiment of the present invention will be described below based on FIGS. 4 and 5.

Note that FIG. 4 shows the improved structure in the middle part of FIG. 1, and the other structures may be the same as those in FIGS. 1 and 3, so their explanation will be omitted.

At the lower end of the control sleeve 20 of this embodiment, fitting parts 20b, 20b, which are engagement surfaces that engage with the flat parts 3a, 3a of the plunger 3, are formed. The two cylindrical wall portions 20c, 20c connected to the fitting portions 20b, 20b are connected to the plunger 3.
is formed so as to face the large diameter portions 3b, 3b of , with a predetermined clearance therebetween. Further, a large diameter portion 3 is provided approximately at the center of the wall portions 20c, 20c.
a protrusion 4 protruding toward b, 3b;
0,40 are provided. For this reason, the protrusion 40,
40 and the large diameter portions 3b, 3b of the plunger 3, a minute clearance δ smaller than the predetermined clearance that allows the plunger 3 to reciprocate is provided, and this δ is 0.1 mm or less. It is set.

According to such a configuration, the flat portion 3a of the ball 22, the plunger 3,
3a (shown in the direction of arrow B in the center of FIG. 5) and the sleeve 20 tends to tilt, it faces the large diameter portions 3b, 3b of the plunger 3 through a small clearance δ. protrusion 40,
40, the plunger 3 contacts. Therefore, the sleeve 20 does not tilt significantly, and the upper end of the sleeve 20 does not bite into the cylinder 2.

Also, wall portions 20c, 20 of this sleeve 20
c, large diameter portion 3b via minute clearance δ,
Since the protrusions 40, 40 facing 3b are partially formed, it is only necessary to partially improve the clearance accuracy in the protrusions 40, 40 of the entire wall portions 20c, 20c. For this reason, the wall portion 20
c, 20c only need to be processed and manufactured so that the partial clearances at the protrusions 40, 40 are minute, making it easy to process the wall portions 20c, 20c, and by extension, to process the entire sleeve 20. can be easily done.

Note that the present invention has an arm 2 on the sleeve 20 side.
4 and 24, and a ball 22 may be attached to the rack 23 side to control the rotation of the sleeve 20.

〔Effect of the invention〕

As described above, since the wall portion of the sleeve has a portion that faces the outer circumferential surface of the plunger with a small clearance therebetween, it is possible to prevent the sleeve from tilting. Therefore, the sleeve does not bite into the cylinder, the sleeve can be reliably controlled over a long period of time, and the fuel injection amount can be controlled with high precision. Moreover, since the wall surface portion of the sleeve is formed so as to be partially close to the plunger, it is only necessary to process it so as to accurately realize a small local clearance. Therefore, the wall portion can be easily processed and manufactured, and the entire sleeve can be easily processed.

[Brief explanation of drawings]

Figures 1 to 3 show conventional fuel injection pumps, with Figure 1 being an overall sectional view, Figures 2 and 3 showing conventional fuel injection pumps.
The figures are cross-sectional views taken along the - line and - line in FIG. 1, respectively. 4 and 5 show one embodiment of the present invention, FIG. 4 is a sectional view showing an improved structure in the middle part of FIG. 1, and FIG.
It is a sectional view along a line. 1...Pump housing, 2...Cylinder, 3
... Plunger, 9 ... Camshaft, 11 ... Fuel intake hole, 14 ... Inclined lead, 16 ... Discharge valve, 2
0... Control sleeve, 22... Ball (control means), 23... Rack (control means), 3a, 3a...
...Plane part, 3b, 3b...Large diameter part, 40, 40...
...Protrusion, 60,60...Reduced diameter part, δ...Minute clearance.

Claims (1)

[Scope of Claims] 1. A plunger is slidably provided in the cylinder, the plunger is reciprocated by a camshaft to inject fuel, and is fitted into the cylinder so as to be rotatable in the circumferential direction. The control sleeve is rotated from the outside via a control mechanism, and the rotation of the sleeve is transmitted to the plunger by engagement between the sleeve and a flat part formed on the plunger, and as the plunger is rotated, the plunger is rotated. In a fuel injection pump that controls the amount of fuel injection by adjusting the relative position between an inclined lead formed in the cylinder and a fuel suction hole opened in the cylinder, the plunger has a cylindrical shape, and a part of the outer peripheral surface of the plunger has a cylindrical shape. the flat portion is formed on the sleeve, and the sleeve includes: an engagement surface formed inside the sleeve that engages with the flat portion of the plunger; and an engagement surface formed inside the sleeve that engages with the flat portion of the plunger. and a portion that approaches the outer peripheral surface of the plunger and faces the outer peripheral surface of the plunger through a minute clearance smaller than the predetermined clearance, thereby preventing the sleeve from tilting. A fuel injection pump comprising: a wall portion having a portion; and a wall portion having a portion.