FR2821123A1 - HIGH PRESSURE FUEL INJECTION PUMP COMPRISING A MEMBRANE ACCUMULATOR AND OVERPRESSURE PROTECTION - Google Patents

Abstract

High pressure fuel pump for an internal combustion engine comprising a piston pump (21) delivering fuel from a supply line (3) into a high pressure line (11), a flow control valve (29) ) which controls a bypass (27) of the piston pump (21), as well as a diaphragm accumulator (31). A diaphragm (35) of the diaphragm accumulator (31) controls a 2/2-flight valve installed in the fuel supply line (3); this 2/2-way valve is open when the two sides of the membrane (35) are subjected to a pressure difference, and closed if the two sides of the membrane (35) reign the same pressure.

Description

suddenly the instant of opening of said injector (1).

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State of the art

  The invention relates to a high pressure fuel pump.

  sion for an internal combustion engine comprising a piston pump

  ton, a fuel supply line, a high pressure line, the piston pump delivering fuel from a supply line into the high pressure line, with a flow control valve which controls a bypass of the pump with pistons,

  as well as a membrane accumulator.

  In this high pressure fuel pump used

  o for example in common rail injection installations, the

  metering control valve provides adjustment of the pump flow to

  pistons. As soon as the fuel pump has delivered enough fuel

  While in the high pressure line, the flow metering valve opens and establishes the hydraulic connection between the high pressure line and the fuel line. As a result, the piston pump will not dethite

  more in the high pressure line, but in the supply. This re-

  piston pump gulation improves pump performance at high

  pressure because the piston pump receives much less work when

  that it works only in relation to the low pressure prevailing

  in the fuel supply line.

  By the opening of the metering valve, the bypass and the fuel supply line suddenly receive a pressure rise leading to considerable mechanical stresses on the detection installation. To at least partially absorb these pressure peaks, a membrane accumulator is provided in the pipe.

fuel supply.

  During the suction stroke of the piston pump, it

  creates a very low pressure in the fuel supply line, which entails the risk of vapor bubble formation and the risk of

  so cavitations. The pressure in the fuel supply line is low

  burant, because the quantity of fuel sucked by the piston pump is greater than the quantity of fuel which arrives in the line

  Power. In this situation, the membrane accumulator

  at least partially holds the pressure in the fuel supply line so as to effectively prevent the development of bubbles

steam.

  If the membrane accumulator is for example neutralized by the rupture of its membrane, the bypass and the supply line

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  in fuel are fully exposed to the pressure spikes mentioned

  above, which leads to their more or less long term destruction.

  In addition, without a membrane accumulator, there is a risk of cavitation effects during the suction stroke of the piston pump, which damages

s also this pump.

  The present invention aims to develop a pump

  high pressure fuel for an internal combustion engine,

  taking a membrane accumulator, and this pump in case of

  failure of the diaphragm accumulator does not produce unacceptable pressure peaks, and avoids the cavitation effect in the

high pressure pump.

  To this end, the invention relates to a fuel pump with

  high pressure of the type defined above, characterized in that a mem-

  diaphragm accumulator brane controls a 2/2 way valve s installed in the fuel supply line so that this 2/2 way valve is open when the two sides of the membrane are subjected to a pressure difference , and that this 2/2 way valve is

  closed if the same pressure prevails on both sides of the membrane.

  Advantages of the invention o In the event of a diaphragm rupture or other leak in the diaphragm accumulator, there will be pressure balancing in the high pressure fuel pump, between the spaces separated by the diaphragm , which neutralizes the mem brane accumulator. The diaphragm position variation in the event of pressure balancing is used to control the 2/2 way valve which cuts the fuel supply to the piston pump. Under these conditions, the internal combustion engine stops and the detection system is not subjected to

no damage.

  Due to the simplicity of construction, the cost of this overpressure protection is low; moreover, given the very small footprint required, the overpressure safety can be integrated into existing high pressure fuel pumps without requiring significant constructive modifications. This eliminates significant development costs. The 3s overpressure safety according to the invention is moreover much more economical than a variant of equipment of the injection installation with a pressure sensor in the membrane accumulator or in the fuel supply and a

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  corresponding monitoring function in the control unit

the installation of detection.

  According to a variant of the invention, the accumulator with mem-

  brane is a diaphragm accumulator charged by a spring, so that regardless of the type of waterproofing defect or end of the diaphragm, we will have a determined actuation force

  to control the 2/2 way valve.

  According to another development of the invention, the 2/2 way valve is a seat valve and under these conditions, in a particularly advantageous manner; the seat valve comprises a nozzle and a closure member fixed to the membrane, and the nozzle comprises a seat

  sealing cooperating with the shutter member.

  This protects the pump simply and very reliably

  at high pressure against excessively high pressures.

  s As an alternative, the 2/2-way valve can be a drawer distributor, which allows to benefit from the advantages of the drawer distributor

  in the high pressure pump according to the invention.

  According to another embodiment of the invention, the membrane accumulator is provided in the fuel supply, which improves the supply of the piston pump during the suction stroke. As a variant, the membrane accumulator can also be installed in the bypass, which makes it possible to absorb pressure peaks in the immediate vicinity of the place of their creation and to achieve more effective protection of the fuel pump at high pressure

  against such pressure spikes.

  According to another development of the invention, the 2/2 way valve comprises at least one throttling member or a diaphragm and the throttling member or the diaphragm allow in the closed position of the 2/2 way valve , to a small extent, the suction of fuel from the fuel supply line to the piston pump.

  In this case, according to another characteristic, the dia-

  phragm is produced as transverse drilling in the nozzle. Thus in the event of a 3s failure of the diaphragm accumulator, the internal combustion engine may continue to operate with a reduced supply of

  fuel and thus reduced pressures in the high pressure line

  if we. The driver of the vehicle equipped with such a high pres pump

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  sion can benefit from emergency operation allowing it to re-

  join the nearest garage. Due to the reduced fuel flow

  rant and the resulting reduction in power from the internal combustion engine, the control unit will recognize a faulty operation of the engine and activate a warning light such as a

dashboard light.

  Drawings In addition, the bypass leads into a segment of the fuel supply line downstream of the memory accumulator.

o brane.

  The present invention will be described below in more detail with the aid of embodiments represented in the appended drawings, in which: - Figure 1 is a block diagram of an exemplary embodiment of an installation of detection according to the invention, - Figure 2 shows a first embodiment of a membrane accumulator according to the invention with overpressure protection, and - Figure 3 shows a second embodiment of renlisation of an accumulator with

  membrane according to the invention equipped with overpressure protection.

  Description of the embodiments:

  FIG. 1 shows a block diagram of an injection installation for an internal combustion engine, this installation being

  equipped with a fuel pump 1. The high pressure fuel pump

  sion 1 is supplied with fuel from the tank 5 by 2s via a fuel supply 3, 3a, 3b. The fuel is delivered by an electric low pressure pump 7, from the tank by delivering into the fuel supply 3. A low regulator

  pressure 9 adjusts the pressure in the supply line 3.

  The high pressure pump 1 according to the invention in the embodiment shown here, delivers via a high pressure line 11 into a common rail 13 connected to the injectors 15. The common rail 13 includes a pressure limiting valve 17 and

  a pressure sensor 19. FIG. 1 does not show the

  command which regulates and controls the 3s injection system, the signal transmission lines, the lines

  power supply and other means.

  The high pressure fuel pump 1 comprises for example a piston pump 21 produced as a radial piston pump. The piston pump 21 delivers the fuel from the supply line 3 into the high pressure line 11. To avoid a return of fuel from the high pressure line 11 in the piston pump 21 and from this pump 21 in the supply line. supply 3b, a first non-return valve 23 is provided in the high pressure line 11 and a

  second non-return valve 25 in the supply line 3b.

  The flow control of the piston pump 21 is ensured by a bypass 27 connecting the high pressure line 11 to the supply line 3 and by a metering or flow control valve.

  o 29 installed in bypass 27.

  When the flow control valve 29 is open (as shown in Figure 1), the piston pump 21 does not deliver fuel to the high pressure line 11 but only in the

bypass 27.

  s As soon as the flow control valve 29 is closed, during the supply stroke of the piston pump 21, a pressure is established in this pump 21 and the latter flows in the high pressure line 11 as soon as the pressure in the pump 21 exceeds that prevailing in the high pressure line 11 downstream of the first non-return valve 23. If the flow control valve 29 is opened during the transfer stroke, this induces a pressure surge in the conduct

  feed 3; this pressure surge (water hammer) can damage

  manage the components upstream of the piston pump 21, namely the tank s see 5, the low pressure pump 7, the low pressure regulator 9 or the connection elements such as the quick couplings of the high pressure pump. To reduce these pressure peaks, the fuel supply line 3 is equipped with a diaphragm accumulator 31. The diaphragm accumulator 31 which is only shown here in my

  schematic, consists of a housing 33, the cavity of which is subdivided

  seated in two chambers by a membrane 35. If the membrane 35 is

  intact, it separates the two chambers in a liquid-tight manner.

  In the first chamber of the housing 33, there is a compression spring 37 which bears against the membrane 35 and against the housing 33. The second 3s chamber of the housing 33 is connected to the fuel supply line

  3 and thus it is filled with fuel. As soon as the pressure surge

  above above arrives in the diaphragm accumulator, the com spring

  pressure 37 compresses and thus absorbs the energy of the pressure tip

  if we. If during the suction stroke, the piston pump 21 sucks fuel from the supply line 3, at a high speed, this causes a strong pressure drop in the fuel supply line 3, 3a, 3b, because the power delivered by the

  low pressure pump 7 is not sufficient to compensate for this increase

  brutal statement of the request. As soon as the pressure drops in the con-

  feed line 3, the compression spring 37 pushes the diaphragm o 35 of the diaphragm accumulator 31 towards the second chamber

  and thus expels the fuel from the accumulator 31 back into the con-

  fuel line 3. The diaphragm accumulator 31 thus has two functions

  tions: firstly it protects the detection installation against dangerous pressure shocks, and secondly it ensures a sufficient supply of fuel s from the supply line 3b to the piston pump 21

during the suction stroke.

  When the membrane 35 of the membrane accumulator 31 loses its sealing, the fuel also passes into the first chamber, so that the membrane accumulator can no longer function. Figure 2 shows a first embodiment of a membrane accumulator 31 according to the invention with protection against overpressure. This accumulator is shown in section. The same parts as above have the same references. Box 33 of

  s the membrane accumulator 31 is made in two parts. Both par-

  parts of the housing bear the references 33a, 33b. The first chamber 39 of the diaphragm accumulator 31 houses the compression spring 37 which is supported by the support plate 41 against the diaphragm 35. The supply

  3a opens into the second chamber 43 of the membrane accumulator.

  n / a A ball-shaped closure member 45 is provided on the underside

  the membrane 35. This member bears against a nozzle 47. The fuel sucked in by the pump piston 21 not shown in FIG. 2, must then pass through the nozzle 47 before arriving via the second segment 3b of the con fuel supply with fuel 3 at the level of the valve and year

  ss ti-retour 25 and finally in the piston pump.

  In the position shown, the compression spring 37 pushes the closure member 45 against the sealing seat 49 of the nozzle and thus seals the first segment 3a of the fuel supply by separating it from the second segment 3b. The piston pump 21 can no longer draw fuel and the internal combustion engine stops. This situation represented in FIG. 2 only occurs if the same pressure prevails in the first chamber 39 and in the second chamber 43. This can occur in the event of rupture of the membrane 35 or if its sealing in relation to the housing 33 disappears. In this case, the diaphragm accumulator 31 can no longer perform its damping function, so that the internal combustion engine should be stopped. Even when the engine is stopped, if the low pressure pump 7 is not re

  o presented in Figure 2, does not deliver, there is such a pressure balance.

  As soon as the low pressure pump 7 delivers fuel, the membrane 35 is lifted by the fuel pressure in the second chamber 43; the shutter member leaves the sealing seat 49 and the piston pump 21 can suck fuel. A protection against overpressure is thus created in a simple manner by means of a shutter member 45 on the underside of the membrane 35 and of a nozzle 47 in the second segment 3b of the supply pipe in fuel; this protection prevents the fuel detection system from being damaged

  caused by a faulty membrane 35.

  FIG. 3 shows a second embodiment of a high pressure pump according to the invention with a mem brane accumulator 31, the assembly being only shown partially. This second embodiment differs from the first example shown in FIG. 2 essentially in that the underside of the membrane 35 is made as a closure member and the nozzle 47 has a folded edge that functions as a sealing seat 49 This embodiment is particu

  extremely economical and very compact.

  The nozzle 47 of the second embodiment has a transvereal bore 51 functioning as a throttle member or so diaphragm and even if the membrane 35 is applied against the sealing seat 49, it is possible to have a reduced passage of fuel from the first segment 3a from the fuel supply line to the second segment 3b of this line. Thus, the internal combustion engine can operate in emergency mode; the quantity of fuel, limited to tra ss towards the transverse bore 51 results in a reduction in the speed of rotation and the power supplied by the internal combustion engine. In addition, there will be no high pressure peaks when opening the flow control valve 29 as when the combustion engine

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  internal tion runs at full load. This effectively prevents the risk of damage by pressure shocks and the effect of cavitation

in the piston pump 21.

  In the second exemplary embodiment according to FIG. 3, the branch 27 opens into the fuel supply segment 3b 3. Thus the membrane 35 is stressed only over a small area with the pressure peaks coming from the branch 27, which significantly increases its life expectancy. In addition the pressure peaks of the bypass 27 are damped by the transverse bore 51 operating

  o as a throttling organ, so that the amplitude of the pressure acts

  health on the parts of the low pressure system located upstream of the diaphragm accumulator 31 is reduced significantly. This reduces mechanical stresses, for example those acting on the line segment 3a of the fuel supply line, on the low pressure regulator 9 and on the low pressure pump 7, that is to say

that we increase their reliability.

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Claims (8)

  1) High pressure fuel pump for an internal combustion engine comprising a piston pump, a fuel supply line (3), a high pressure line (11), the piston pump (21) s supplying fuel a supply line (3, 3a, 3b) in the high pressure line (11), with a flow control valve (29) which controls a bypass (27) of the piston pump (21), thus a diaphragm accumulator (31), characterized in that a diaphragm (35) of the diaphragm accumulator (31) controls a 2/2 way valve installed in the fuel supply line (3) so that this 2/2 way valve is open when the two sides of the diaphragm (35) are subjected to a pressure difference, and that this 2/2 way valve is closed if on both sides of the diaphragm (35) reign is the same pressure.   2) High pressure fuel pump according to claim 1, characterized in that the diaphragm accumulator (31) is a charged diaphragm accumulator by a spring.   3) High pressure fuel pump according to claim 1, characterized in that   the 2/2 way valve is a seat valve.   4) High pressure fuel pump according to claim 3, characterized in that the seat valve has a nozzle (47) and a closure member (45) fixed to the membrane (35), and the nozzle (47) has a sealing seat (49)   cooperating with the shutter member (45).    ) High pressure fuel pump according to claim 1, characterized in that   the 2/2 way valve is a slide valve.   3s 6) High pressure fuel pump according to claim 1, characterized in that 28211 23   the membrane accumulator (31) is installed in the pipe fuel supply (3).   7) High pressure fuel pump according to claim 1, characterized in that   the membrane accumulator (31) is installed in the bypass (27).   8) High pressure fuel pump according to claim 1, characterized in that o the 2/2 way valve comprises at least one throttling member or a diaphragm and the throttling member or the diaphragm allow in the position of 2/2 way valve closed, to a small extent, the fuel intake from the fuel supply line (3) to the piston pump (1).   9) High pressure fuel pump according to claim 8, characterized in that   the diaphragm is a transverse bore (51) produced in the nozzle (47).   10) High pressure fuel pump according to claim 1, characterized in that the bypass (27) opens into a segment (3b) of the fuel supply line (3) downstream of the membrane accumulator (31 ).