FR2538456A1 - FUEL INJECTION PUMP, ESPECIALLY FOR INTERNAL COMBUSTION ENGINE OF THE DIESEL TYPE - Google Patents

Abstract

The invention relates to a fuel injection pump for a diesel engine comprising a piston movable in a guide body having near the bottom dead center of the piston an intake hole and, a little higher, a discharge hole. The flow through the discharge hole 16 is controlled by a valve 20, the shutter member 23 of which is blocked in an open position by an energized electromagnet 30. As soon as the latter is released, the valve 20 closes under the effect of the pressure. (CF DRAWING IN BOPI)

Description

The invention relates to a fuel injection pump, particularly for

  internal combustion engines of the diesel type, compot both a piston movable in a guide body in which it carries the piston guide body having, in the region of the dead center of the piston, at least one intake hole opening into the chamber pump, and, in addition, shifted a small gap to the top point of the piston, a discharge hole, the piston being provided with appropriate control bor and controlling the amount of fluid injec An injection pump of this In this case, the additional discharge hole has a relatively small cross-section and operates as a choke whereby, at the start of the discharge, a partial amount of the fuel can be removed. This is intended to achieve a faster decay of the discharge characteristic when the rotational speed of the camshaft decreases.

  On the other hand, the present invention aims to develop

  for a fuel injection pump of this kind, having a

  additional hole for discharge, so as to allow a

  continued injection, this development should be

  realized with means as simple and reliable as possible.

  According to the invention, this object is achieved by the fact that the discharge flow of the fuel through the discharge hole is controlled by a valve whose shutter member can be blocked at

  a rest position authorizing the discharge, this blocking being

  by means of stopping, and by the fact that after release of these stop means, the shutter member is brought, by the fuel discharging, to its working position prohibiting the discharge of fuel.

  The idea behind the invention is that the beginning of injection

  It can be modified continuously in a wide range if this discharge hole is controlled by a valve closing rapidly. The closure time of the valve must then be of the order of 0.5 ms. very fast is achieved, according to the invention, by the fact that, to close this valve whose shutter member is stopped by stop means when it is at its rest position, the pressure is used.

fuel coming out of this hole.

  The stop means which block the shutter member of the valve at the rest position, a position for which this break hole

  load is open, can be pneumatically or hydraulically controlled

  However, these are preferably stop

  electromagnetically, which can be used because

  to the electromagnet a reverse current pulse and, thus, abbreviated

  further reduce the closing time of the valve.

  To return the shutter member to the rest position, it is possible to use any other return member As, during the suction stroke of the piston, it is established, in-the

  pump chamber, a depression that supports the movement of

  shutter stroke and, as it flows during this suction stroke a sufficient time to open the valve, it follows that we can use simple return springs to recall

the shutter of this valve.

  In order to keep the valve stress as small as possible, it must be ensured that the gap between the inlet hole and the discharge hole is chosen so that the

  -Piston pump has almost reached, or even partially re-

  covered the discharge hole when, for the start of the injection as late as possible, the shutter member is brought to its working position is thus avoided the action of the high pressure of the pump

on the shutter of the valve.

  The different objects and characteristics of the invention

  will now be detailed in the description that follows, made

  as a non-limitative example, referring to the single figure

  of the appended drawing which shows a partial view, in section, of

  of a fuel injection pump essential for the invention.

tion.

  A pump piston, 11, carries with the possibility of displac-

  This piston displaces the fuel out of the pump chamber 12 via a valve 13 into an injection line 14. An intake hole 15 passes through the body of the piston. Piston guide 10 and opens into the pump chamber 12, in the region of the bottom dead point (shown) of the piston. In addition, the piston guide body 10 additionally has an offset discharge hole 16.

  towards the top dead center of the piston.

  A valve-type valve, generally designated by the reference 20, makes it possible to control this discharge hole. The casing 21 of this valve 20 is mounted directly on the piston guide body 10 so that the conical seat 22 of the valve , opening

  towards the discharge hole 16 is centered relative thereto.

  As shutter member 23 of the valve, it is a valve member 6 is used, on which is formed a rod 24 which passes through

  a bore 25 in the valve housing 21 In the drawing, this organism

  valve shutter 23 is shown in its rest position, in which the discharge hole 16 is substantially open since the fuel can flow out of the pump chamber 12, via this

  discharge hole 16, the opening section 26 of the valve, the

wise 25 and channels 27.

  In this rest position, the valve shutter member 23 is stopped by stop means generally designated by the reference 30. These stop means 30 comprise an electromagnet 31, with an iron core 32, a magnetic coil 33 and movable armature 34 To this armature 34 is secured a set screw 35 which enters a hole 36 formed in the core of

  32 and that serves as a stop for the stem 24 of the obturator

  valve driver 23 Two return springs 37 taking a bearing.

  fixed on the carcass forming mount, maintain the armature 34 in the position shown, even when the electromagnet 31 is

not excited.

  In the following, the mode of operation of this fuel injection pump shown in the drawing is explained in more detail, admitting, for a start, that the valve shutter member 23 occupies the rest position shown and that, in this

  position, it is blocked by the force of the excited electromagnet, 31.

  During the discharge stroke of the piston 11 of the pump, the inlet hole 15 is first closed. However, even when this intake hole 15 is closed, there is no fuel backflow in the first place. the injection line 14 because the fuel can flow out of the pump chamber 12 via the discharge hole 16, skirting the valve cone 23 The outflow of the fuel thus has the effect that a closing force acts on the valve stem 8, in the closing direction F This force

  However, the closing force is insufficient to overcome the force of electro-

  The valve 20 therefore remains open first.

  This being the case, depending on the speed of rotation, or

  any other interesting parameter, it is terminated, at a decisive moment

  terminated, at the excitation of the electromagnet 31 The stop means blocking the valve shutter member at the rest position are

  thus released The force of the magnet then decreases rapidly and

  is less than the closing force F acting on the shutter member 23 and this force then displaces the valve cone in

  the closing direction, against the force of the return springs 37.

  The cross-section of the opening 26 thus becomes smaller, and the pressure drop in this region becomes greater and greater, which results in an increase in the closing force F. The shutter member 23 is thus brought to its working position in which it is applied with sealing on the valve seat 22. There can then no longer be any flow of fuel out of the pump chamber 12, via the discharge hole 16 and the

  Injection process begins The discharge hole 16 which occurs

  lanyard in the valve housing 21 is closed.

  The piston Il of the pump then ends its race of

  The valve 13 is open, and the fuel is pushed out of the chamber 12 of the pump, into the injection line 14. The end of the injection process is conventionally caused by control edges arranged on the valve. piston 11, pump and control holes in the piston guide body 10 When the injection process is complete, there is only a slight pressure in the chamber 12 of the pump, so that the springs of recall 37 bring back the armature 34, thus also the shutter member 23, from the working position to the rest position This return movement further receives the support of the force of the electromagnet 31 which is then again excited and depression that is established in the chamber 12 of the pump during the back stroke of the piston 11 of the pump The electromagnet 31 re-excited has the effect that after each injection process, the organ shutter 23 is again

  stuck in his rest position It is only during the next

  It is the work of the piston of the pump that these means stop working.

  Electromagnetically, they will be released by suppressing the excitation of the electromagnet, or by applying a reverse current pulse, which further reduces the closing time of the valve. The distance A between the intake hole 15 and the hole of

  outlet 16 is chosen so that the piston 11 of the pump reaches

  almost eliminates the discharge hole 16, or even covers it partially when, for the start of injection as late as possible, the valve shutter member is brought to the working position.

  happens that the shutter member 23 of the valve is not sol-

  licit too long by the high pressure of the pump In addition, the latest injection start is determined not by the edge

  of the discharge hole 16 but exclusively by the process of iron-

setting of the valve 20.

  Tests have shown that valve closing times of less than 0.5 ms can be achieved by following this principle. Such short valve closing times are likely to permit continuous variation of the injection start during that the pump piston moves between the upper edge of the inlet hole 15 and the upper edge of the hole

  16 Valve closing times are as short as

  not be obtained with a drawer, electromagnetic actuated-

  which would close the exit hole 16 transversely to the di-

  output of such systems with a drawer for

  sea dump hole 16 are rather conceivable for two

  stages of adjustment of the beginning of injection.

  In the embodiment shown in the drawing, the valve 20 is mounted directly on the piston guide body. Of course, it is also possible to envisage a solution in which this valve 20 is a separate component connected to the hole.

  However, in this case, the persons

  Charges for this conduct would lead to an increase in valve closing times. This is why the valve will be available.

  as close as possible to the relief hole.

  In the exemplary embodiment shown, the return springs 37 serve as return members to return the shutter member 23 to the rest position. However, as a return member, it is also possible to use an additional electromagnet,

  or else another hydraulic or pneumatic return member.

  Of course, the stop means could be designed

  In particular, we could consider ways of

  end comprising a return element displaced on the trajectory of the rod 24, transversely to the direction of the movement of

the shutter member 23.

  Finally, it should be noted that, even in the event of a defect of the valve 20, the injection pump can operate, but, of course, does not operate under optimal operating conditions. for example, the shutter member 23

  of the valve 20 remains at the represented rest position, for which

  the fuel can flow through the dump hole -16, the start

  Injection is controlled by the upper edge of this discharge hole.

  On the other hand, in the case where the valve 20 is closed

  manence, the beginning of injection is controlled by the upper edge of the

intake hole 15.

  In the end, using, to close a valve, the

  flow pressure of the fuel flowing through the discharge hole

  16, a fuel injection pump is created in which the start of injection can be continuously modified, in a range

  extended, in a very simple way Such a fuel injection pump

  can be easily adapted to different conditions of

  operation of the diesel engine.

  It is obvious that the foregoing descriptions have been

  data as a non-limitative example and that many variants

  can be envisaged without departing from the scope of the invention.

-2538456

Claims (6)

  A fuel injection pump, particularly for a diesel-type internal combustion engine, comprising a piston movable in a guide body in which it carries, this piston guide body having, in the region of the bottom dead center of the piston, at least one intake hole opening into the pump chamber, and, in addition, shifted by a small gap to the top dead center of the piston, a   discharge hole, the piston being provided with appropriate control edges   requested and controlling the amount of fluid to be injected, characterized   in that the discharge flow of the fuel through the test hole   load (16) is controlled by a valve (20) whose shutter member (23) can be locked at a rest position allowing the discharge, this blocking being carried out by stop means (30), and in that after releasing these stop means (30), the shutter member (23) is   brought by the discharging fuel to its working position.   banning the discharge of fuel.   Injection pump according to claim 1, characterized   in that the shutter member (23) can be locked in its posi-   resting by the force of an excited electromagnet (31).   Injection pump according to claim 2, characterized   in that, in order to release the arresting means (30), the supply current of the electromagnet (31) is interrupted and / or   reverse current pulse is applied to this electromagnet (31).   4 Injection pump according to at least one of the claims   previous conditions, characterized in that during the   piston bottom (11) of the pump, the shutter member (23) is brought from the working position to the rest position by a return member. Injection pump according to claim 4, characterized in that return springs (37) serve as   recall to recall the shutter member (23).   6 Injection pump according to at least one of the claims   characterized in that the gap (A) between the inlet hole (15) and the discharge hole (16) is selected so that   the piston (11) of the pump has almost reached, or even partially   covered the discharge hole (16) when, for the start of injection as late as possible, the shutter member (23)   is brought to his working position.   Injection pump according to at least one of the claims   previous arrangements, characterized in that the housing (21) of the   ve (20) is mounted directly on the piston guide body (10)   in that the valve has a conical seat (22) opening towards the discharge hole (16) and preferably centered with respect thereto (16), and in that the shutter member (23) is in the form of a valve cone, comprises a rod (24) which passes through the housing (21) of the valve and which is in interaction with   a movable armature (34) of an electromagnet (31).