JPH03260343A - Two-stage type timer for fuel injection pump - Google Patents

Abstract

PURPOSE:To facilitate assemblage and adjustment of a timer having a timer piston displaced in two stages against a plurality of springs by combining one spring with the low pressure side cover to compose an assembly independent from the other spring. CONSTITUTION:When an internal combustion engine speed reaches its idle rotational speed, fuel pressure in a pump chamber 2 and pressure in a high pressure chamber 8 are increased, so that a timer piston 5 is subjected to the right displacement on the first stage by a predetermined stroke S1 against a first spring 9. When the internal combustion engine speed reaches its normal rotational speed, the timer piston 5 is subjected to the second stage displacement to compress a second spring 10. Then, the second spring 10 composes an assembly A by comprising a stepped tubular guide 12, an adjusting screw 13, a spacer 21, a locking member 15 and a cover 11. The locking member 15 is loosened with the assembly A kept as it is and the adjusting screw 13 is pivoted so as to adjust a load on the second spring 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-stage timer for a distributed fuel injection pump.

[Conventional technology and its technical issues]

A hydraulic timer is commonly used as a means for adjusting the injection start timing of a distributed fuel injection pump according to the engine speed. In this hydraulic timer, in order to improve engine output and reduce harmful exhaust gases, two springs with different spring constants are used, and different set loads of these springs are sequentially applied to the timer piston to displace the timer piston in stages. The composition is Utility Model No. 62-18852
It is publicly known in Publication No. 7.

By the way, due to the characteristics of this type of timer, if the inflection point varies, the amount of advance at the output point and mode point will vary.
Even in the same engine, the output characteristics may change, so careful adjustment, especially adjustment of the set load of the second spring, is very important.

The reason for this is that the first spring adjusts the advance angle in response to changes in engine speed in the low engine speed range7, while the second spring uses the resultant force of the first spring to activate the timer. This is because it opposes the hydraulic pressure applied to the piston and determines the starting point (mode point) of the normal operation advance angle. From the standpoint of workability and efficiency, it is desirable that the timer be easy to assemble and adjust; however, the prior art has not been effective in this regard. That is, first, in the prior art, the first spring, the spring receiver seat, the stopper, the second spring, and the cover are each independent, and they are sequentially assembled outside the back of the timer lid to form an assembly. Assembling the timer required a lot of trouble.

Further, in this prior art, a set load is applied to the second spring only when the cover is fixed to the pump housing. For this reason, it is not easy to check the set load of the second spring, and when adjusting the initial set load of the second spring after assembling the timer, loosening the fixing bolt and removing the cover will cause the
The seat of the spring and bridge will pop out together. Moreover, since the shim for adjusting the setting force was attached to the inner boss part of the cover, it was necessary to remove the second spring from the cover each time, set the second spring on the cover again, and redo the assembly. It is very troublesome to adjust and change the set load of This was devised to solve the problem, and its purpose was to improve the workability of timer assembly, and to separate the setting force adjustment of the second spring, which is important for advance angle characteristics, from the adjustment of the first spring. It is an object of the present invention to provide a two-stage timer of this type which can be uniquely performed easily and accurately, and which can obtain good advance angle characteristics.

[Means to solve the problem]

In order to distantly relate to the above object, the present invention provides a timer piston that is disposed in a distribution type fuel injection pump and is displaced in response to fuel oil pressurized by a feed pump and supplied into a pump chamber; A timer comprising two springs with different spring constants disposed on the side, and configured such that the springs act firstly on a timer piston under different set loads, and the timer piston is displaced in stages. The timer includes a first spring disposed at the bottom of the timer piston on the low pressure side via a stroke adjustment shim, and a second spring assembly integrated with the cover on the low pressure side, and the second spring assembly is engaged with the rear end. an outward flange for stopping, an inward flange at the tip that can come into contact with the stroke adjustment shim, a stepped cylindrical guide in the middle that has seat parts of a first spring and a second spring on the inner and outer surfaces, and a stepped cylindrical guide inside the cover. The second spring has a seat head, an adjustment screw extending through the bottom wall of the cover, and a locking member for locking the adjustment screw outside the cover.

Further, the present invention has a first spring disposed at the bottom of the timer piston on the low pressure side via a stroke adjustment shim, and a second spring assembly independent of the cover on the low pressure side, and the second spring assembly is arranged at the front end of the timer piston. A movable receiver that can come into contact with the bottom of the timer piston includes a seat, a cylindrical capsule with a second spring whose one end is seated on the seat, a locking member that is threadedly engaged with a screw on the outer periphery of the cylindrical capsule, and the locking member. and a cover that is screwed onto and covers the cylindrical capsule behind the cylindrical capsule.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 and 2 show a first embodiment of a timer according to the invention.

1 is a pump housing, and 2 is a pump chamber formed inside the pump housing 1, to which fuel is supplied by a feed pump (not shown) that is driven in relation to the engine rotation speed.

3 is a roller holder disposed in the pump chamber 2; 1 holds a roller 30 in contact with the cam surface of a disc cam to which the proximal end of a plunger (not shown) is fixed; the plunger is pressed against the re-roller holder side by a plunger spring; Therefore, as the vehicle shaft rotates, it rotates while reciprocating along the cam surface, thereby pressurizing the fuel supplied from the pump chamber and pumping it to each cylinder.

4 is a timer, which includes a timer piston 5 slidably fitted into a cylinder 20 formed below the pump chamber 2, and a first piston 5 having a different spring constant on the opposite side. It has a second spring 9.10.

A pin lever 6 whose one end is fixed to the roller holder 3 is engaged with the timer piston 5, and a fuel pressure introduction hole 50 communicating with the pump chamber 2 is formed.

The other end of this fuel pressure introduction hole 50 opens into a high pressure chamber 8 surrounded by the cylinder 20 and the high pressure side cover 7, and the balance between the pressure applied to this high pressure chamber 8 and the springs 9 and 10 causes the timer piston to is displaced, thereby rotating the roller holder 3 via the pin lever 6.

Such a structure is similar to a conventional timer, but in the present invention, first, a protrusion 53 is provided in the center portion of the timer piston 5 surrounded by a cylindrical portion 51, and the first spring 9 is attached to the bottom portion 52 of the timer piston 5. One end is supported via a stroke adjustment shim 17. The second spring 10 is configured as a spring assembly A independent of the first spring 9.

In the first embodiment, the second spring assembly A includes a stepped cylindrical guide 12, a second spring 10, a ring-shaped spacer 21 that locks the stepped cylindrical guide 12, a cover 11, and an adjustment screw 13. and a lock member 15.

The stepped cylindrical guide 12 has a thick outward flange 120 at its rear end (low-pressure side), and an inward flange 121 that can abut against the stroke adjustment shim 17 at its tip. Further, a stepped portion 123 as a seat portion is formed in the middle, and the inner surface of this stepped portion 123 supports one end of the second spring 1o, and the outer surface supports the other end of the first spring 9. .

In this embodiment, the inward flange 121 is composed of a stepped cylindrical guide 12 and a flanged short tube 12a as a separate member,
It is integrated by being fitted into the stepped cylindrical guide 12, and the flange portion 124 at the rear end comes into contact with the outer surface of the stepped portion 123, thereby functioning as a center load adjustment shim for the first spring 9. Instead, as in the second embodiment described later, the stepped cylindrical guide 12 is made integrally up to the inward flange, and a separate set load adjustment shim 19 is attached to the stepped portion 12.
It may be placed in 3.

In this embodiment, the flange 120 of the stepped cylindrical guide 12 is stopped by a recessed step 212 connected to the edge of the through hole of the ring spacer 21.

On the other hand, the cover 11 has a cap shape and has a flange 110 on the front portion that overlaps with the ring-shaped spacer 21. A screw hole 113 is penetrated through the center of the cover 11, and an adjustment screw 1 is inserted into this screw hole 113.
3 is screwed on.

The adjustment screw 13 is attached to the stepped portion 112 of the cover 11.
It has an integral sheet head 130 that is movable along the inner surface of the cylindrical portion with a retraction limit of .
0 supports the other end of the second spring 10. An annular groove is provided on the outer periphery of the seat head 130, and an O-ring 25 is attached to the annular groove to prevent fuel oil from leaking from the screw hole 113 to the outside. The adjustment screw 13 protrudes outward from the cover 11, and a locking member 15 is screwed into that portion.

The ring-shaped spacer 21 is connected to the flange 110 of the cover 11 and the O-ring 2 while the stepped cylindrical guide 12 is locked.
3, and are connected to the flange 110 and the ring-shaped spacer 21 by a plurality of screws 24 arranged around the circumference. In this state, it is fixed to the pump housing 1 with a plurality of bolts 22 arranged out of phase with the screws 24.

3 and 3-A show a second embodiment of the invention. In this embodiment, the second spring assembly A
includes a one-step cylindrical guide 12, a second spring 10,
Although it includes a cover 11, an adjustment screw 13, and a locking member 15, unlike the first embodiment, a ring-shaped spacer is not used, and the stepped cylindrical guide 12 is directly locked to the cover 11. . That is, a ring-shaped stopper 115 protruding into the cover is attached to a portion of the cover 11 at approximately the same level as the flange 110, and the stepped cylindrical guide 1 is attached to the ring-shaped stopper 115.
Two outward flanges 120 are locked.

A clip is used as the ring-shaped stopper 115, and in the embodiment shown in FIG.
It is attached to 14. In the embodiment shown in FIG. 3-A, a threaded groove 114a is formed from the end surface of the cover 11, a ring-shaped stopper 115 is arranged at the back of the threaded groove 114a, and the screw ring 116 is screwed into the threaded groove 114a to be fixed. There is.

In the second embodiment, the stepped cylindrical guide 12 is integrated up to the inward flange 121 at the tip, and the first spring set load adjustment shim 19 is disposed on the stepped portion 123. It goes without saying that instead of this, it would be very good to use a separate member type as in the first embodiment. The other configurations are the same as in the first embodiment, and in order to avoid duplication of explanation, the same parts are denoted by the same reference numerals.

4 to 6 show a third embodiment of the present invention. In this embodiment, the second spring assembly A includes a cylindrical capsule 12 containing a second spring 10.
a, a spacer 21 having a screw hole that is screwed into a screw 125 on the outer periphery of the cylindrical capsule 12a, a locking member 15 that is screwed onto the cylindrical capsule 12a rearward of the spacer 21, and a rear portion of the cylindrical capsule 12a. It consists of a cover 11 surrounding the end.

The cylindrical capsule 12a replaces the stepped cylindrical guide 12, and consists of a straight cylindrical body having an inward flange 121 at the front end.
A movable seat 14 is disposed from which a shaft portion 142 protrudes and a flange portion 140 at the rear end is guided along the inner surface of the cylinder 12a.One end of the second spring 10 is supported by the flange portion 140, and the cylinder body A seat member 27 that supports the other end of the second spring 10 is attached to the rear end portion.

The shaft portion 142 of the movable seat 14 faces the protrusion 53 of the timer piston 5, and is for regulating the stroke of the first spring.

In FIG. 6-A, the cylindrical body has an open rear end, and an inward flange 121 is integrally formed with the cylindrical body.
The seat member 27 is made of a snap ring and is attached to the inner surface near the rear end of the cylinder, and the set load of the second spring 10 is adjusted by supporting the adjustment shim 16 of a desired thickness on the snap ring. It has become.

In FIG. 6-B, the cylindrical body has an end wall on the rear end side, and a snap ring is engaged as an inward flange 121 at the opening at the front end to support the movable seat 14. The seat member 27 is movably attached to the rear end wall of the cylinder.

Specifically, the seat member 27 has a seat head 270 and a screw shaft 2, similar to the adjustment screw of the first embodiment.
71, the screw shaft 271 is threaded through a screw hole in the rear end wall of the cylindrical body, and is secured with a lock nut 272. In this case, the seat member 27 is moved by loosening the lock nut 272 and rotating the screw shaft 271, so that the set load of the second spring 10 is adjusted.

In FIG. 4, a locking member 15 is screwed onto the outer periphery of the cylindrical capsule 12a, an O-ring 28 disposed in the recess of the locking member 15 contacts the outer surface of the spacer 21, and is sealed. O placed on the inner surface of the end
The ring 29 is sealed by contacting the rear end surface of the locking member 15, and the bolt 2 passed through the through hole provided in the spacer 21 is sealed.
2 is fixed to the pump housing 1.

In FIG. 5, the cover 11 is stepped,
The locking member 15 is built into the stepped portion 117.

(Effect of the example) Next, the operation and effect of the embodiment will be explained.

FIG. 7 schematically shows the advance angle characteristics according to the present invention.

When the engine speed is less than the idle speed N, even if the high pressure chamber 8 of the timer to which the fuel in the pump chamber 2 is led rises, it will not overcome the first spring 9, and therefore the timer will not be able to overcome the first spring 9. The piston 5 is kept in the retard position as shown in Figure III. At this time, in the first embodiment and the second embodiment, the second spring 10 presses the seat portion 123 of the stepped cylindrical guide 12, but the stepped cylindrical guide 12 has its other end directed outwardly toward the flange 123. does not move, so the first spring 9 is maintained at a predetermined set load.

That is, in the first embodiment, the outward flange 120 is engaged with the recessed step 212 of the ring-shaped spacer 21, and in the second embodiment, the outward flange 120 is engaged with the stopper 115 within the cover 11. On the other hand, in the third embodiment, the cylindrical capsule 12a is
It doesn't move because it's screwed into it.

When the engine speed reaches the idle speed N1, the fuel pressure in the pump chamber 2 increases accordingly.

Since the pressure in the high pressure chamber 8 increases, the timer piston 5 is displaced to the right by the stroke S1 in FIGS. 1, 3, and 4 against the set load of the first spring 9. This period is the first stage of displacement of the timer piston 5 until the torque point is reached. In the first and second embodiments, the stroke S□ is until the inward flange 121 abuts against the stroke adjustment shim 17 at the bottom of the timer piston. In the third embodiment, this is until the tip of the shaft portion of the movable seat 14 comes into contact with the protrusion 53 . The slope of the timer advance amount until this torque point is reached is determined by the characteristics of the first spring 9, and can be arbitrarily adjusted using the stroke adjustment shim 17 and the set force adjustment shim 19.

When this torque point is reached, the spring force of the first spring 9 is fixed, and the resultant force with the set load of the second spring 10 opposes the displacement of the timer piston 5, and while they are balanced, the timer advances. The angle remains constant. Then, when the rotational speed of the mechanism further increases to the normal operation angular start rotational speed (mode point) NZ, the timer piston 5 overcomes the resultant force and a second stage displacement of compressing the second spring 10 is performed. At this time, in the first embodiment and the second embodiment, the stepped cylindrical guide 12 comes into contact with the stroke adjustment shim 17 and moves together, and in the third embodiment, the tip of the shaft portion of the movable seat 14 The movable seat 14 retreats inside the cylindrical body with the movable seat 14 in contact with the protrusion 53.

When the engine speed further increases and reaches the output point N3, the end surface of the cylindrical portion 51 of the timer piston 5 is connected to the spacer 21.
(1st and 3rd embodiments) or the inner surface of the cover flange (2nd embodiment)
example), thereby reaching the full stroke.

The mode point N2 is determined by the set load of the second spring 10, and therefore it is desired that its adjustment be as precise and easy as possible.

In the present invention, the second spring 10 is not a separate component; in the first embodiment, the stepped cylindrical guide 12, the adjustment screw 13, the spacer 210, the locking member 15, and the cover 11 constitute an assembly. Also, in the second embodiment.

The stepped cylindrical guide 12, the adjustment screw 13, the locking member 15, and the cover 11 constitute an assembly A.

Therefore, if the locking member 15 is loosened and the adjustment screw 13 is rotated while maintaining this assembly A, the seat head 130 will move in the axial direction, so the set load of the second spring 10 can be arbitrarily changed within a certain range. I can do it. Moreover, the adjustment screw 13 is cover 1.
Since the cover 1 is threaded through the cover 11, it can be easily adjusted from the outside without removing the cover 11 one by one. Even when it becomes necessary to fine-tune the mode point, the external operation of rotating the locking member 15 and adjustment screw 13 is sufficient without removing the cover 11 at all. The number of man-hours required is extremely small.

On the other hand, in the third embodiment, since the second spring 10 is a cylindrical capsule 12a, the cover 11 is removed and the fourth
In the embodiments shown in FIGS. and 5, it is sufficient to insert the shim 16 inside the snap ring serving as the seat member 27, and if the cylindrical capsule 12a has the structure shown in FIG. It is only necessary to rotate the screw shaft 271, so it is simple.

In the first and second embodiments, the stroke and the starting characteristics of the first spring 9 can be freely adjusted by removing the assembly A and changing the shims 17, 19 (124). Further, in the third embodiment, when the locking member 15 is loosened and the cylindrical capsule 12a is rotated, the cylindrical capsule 12a itself moves in the axial direction, so that the first stage stroke adjustment can be easily performed.

In addition, 1. In the second and third embodiments, the installation of the cover 11 does not sometimes compress the second spring 12, so the timer assembly workability is also good, and the internal parts of the distribution type fuel injection pump are completely changed. It can be carried out without

〔Effect of the invention〕

According to the first aspect of the present invention described above, a timer for a distribution fuel injection pump includes a timer piston and two springs having different spring constants disposed on the opposite side thereof, and the springs are set in different sets. In a timer configured to sequentially act on a timer piston under a load to cause stepwise displacement of the timer piston, the second spring is combined with the low-pressure side cover to form an assembly independent of the first spring. Therefore, it is possible to improve the ease of assembling the timer, and the adjustment work of the set load of the second spring, which determines the mode point, can be easily and accurately performed from the outside without having to remove the cover each time. Excellent effects such as being able to suppress the width of variation in characteristics to a small level can be obtained.

According to the second aspect of the present invention, the second spring and the catch are housed in a single capsule.

Even if the cover is removed, the set load of the second spring can be easily adjusted without being disassembled. Also, since the capsule can be moved in the axial direction of the cylinder, the stroke of the first stage can be easily adjusted from the outside. You can get excellent results by being able to do it.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a first embodiment of the present invention, Fig. 2 is a sectional view showing the first embodiment at the stage of installing the second spring assembly, and Fig. 3 is a sectional view showing a second embodiment of the invention. 3-A is a sectional view showing another aspect of the second spring assembly in the second embodiment, FIG. 4 is a sectional view showing the third embodiment of the present invention, and FIG. 5 is a sectional view showing the third embodiment. 6-A and 6-B are sectional views showing other aspects of the second spring assembly in the example; FIGS.
The figure is a diagram illustrating timer advance angle characteristics in the present invention.

Claims (2)

[Claims] (1) A timer piston installed in a distribution type fuel injection pump and displaced in response to the fuel oil pressurized by the feed pump and supplied into the pump chamber, and two timer pistons with different spring constants placed on the opposing side. Equipped with a spring,
The timer is configured such that the spring sequentially acts on the timer piston under different set loads to displace the timer piston in stages, wherein the timer is disposed at the bottom of the low pressure side of the timer piston via a stroke adjustment shim. and a second spring assembly integrated with the cover on the low pressure side, and the second spring assembly has an outward flange for locking at the rear end and can abut against the stroke adjustment shim at the tip an inward flange, a stepped cylindrical guide having seat portions of a first spring and a second spring on the inner and outer surfaces in the middle, and a bottom wall of the cover having a seat head of the second spring inside the cover; A two-stage timer for a fuel injection pump, comprising: an adjustment screw that extends through the cover; and a locking member that locks the adjustment screw outside the cover. (2) A timer piston installed in the distribution fuel injection pump and displaced in response to the fuel oil pressurized by the feed pump and supplied into the pump chamber, and two timer pistons with different spring constants placed on the opposing side. Equipped with a spring,
The timer is configured such that the spring sequentially acts on the timer piston under different set loads to displace the timer piston in stages, wherein the timer is disposed at the bottom of the low pressure side of the timer piston via a stroke adjustment shim. and a second spring assembly that is independent of the low-pressure side cover, and the second spring assembly has a movable receiving seat that can come into contact with the bottom of the timer piston at its front end, and a second spring assembly that has one end seated on the movable receiving seat. A cylindrical capsule provided with two springs, a locking member that is threadedly engaged with a screw on the outer periphery of the cylindrical capsule, and a cover that is threadedly engaged with and covers the cylindrical capsule behind the locking member. 2 of fuel injection pumps featuring
Staged timer.