FR2881478A1 - PILOT INJECTION PUMP - Google Patents

Abstract

The present invention adds a separate pilot pumping chamber (40) and associated pumping pistons (36a, 36b) and cam followers (54, 56) axially offset from the main pumping chamber (34) and pumping pistons. (42a, 42b). The axis of the bores (38a, 38b) of pilot pistons is angularly offset from the axis of the bores (32a, 32b) of main pistons so that the pilot pistons (36a, 36b) are actuated by a different set of bosses of cam of the cam profile (52). This arrangement allows one pumping chamber to be filled while the other pumping chamber is being discharged. Discharge passages (58, 60) from respective pump chambers are provided with orifices for supplying the pilot and main fuel pulses to the same discharge port.

Description

The present invention generally relates to high-pressure pumps

  pressure for fuel injection systems and, more particularly, a rotary distribution fuel pump for such systems.

  Motorized vehicles must comply with increasingly stringent emission and noise emission limits. A published study has shown that noise and emissions from internal combustion engines are influenced by time variations in fuel flow through injector spray holes, known as "flow shape". "of the injection. Considerable work has been devoted to controlling the flow shape and timing of injection in response to the specific requirements of a particular engine application. Previous work to control the shape of the injection flow includes modifications to the injector assembly and the fuel pump.

  One type of fuel pump of particular interest for the present invention is a rotary distribution fuel pump.

  In this type of well-known fuel pump, a dispensing rotor rotates inside a substantially tubular hydraulic head. The dispensing rotor has a pair of reciprocating opposed pistons, a displacement of which is regulated by cam bosses of an inwardly directed cam ring spaced angularly. The cam ring of a rotary distribution fuel pump usually has a cam boss for each cylinder of the engine. Cam diametrically opposed bosses operate on cam followers to simultaneously operate the pump pistons. Passages in the distribution rotor sequentially coincide with the fuel supply passage in the hydraulic head to supply fuel to a pumping chamber defined between the two opposed reciprocating pistons. Rotation of the distribution rotor interrupts communication between the fuel supply passage of the hydraulic head and the pumping chamber. Continuous rotation of the delivery rotor causes the cam follower rollers to be engaged with a pair of diametrically opposite cam bosses. The cam bosses act through rollers and cam pads to force the pistons inward and put the fuel contained in the pump chamber under pressure at a high injection pressure. The pressurized fuel from the pumping chamber is fed through a fuel supply passage to one of a series of discharge passages extending from the pumping chamber to the surface of the dispensing rotor. The discharge passages sequentially coincide with distributor ports associated with the fuel injector for each cylinder of the internal combustion engine.

  Fuel is sent to the rotary distribution fuel pump by a transfer pump, generally classified in the pump assembly. Fuel pressurized by the transfer pump flows into the pump chamber when the intake ports are aligned with each intake passage. It is possible, by extending the compression stroke of each pumping cycle, to provide the appropriate timing for a pilot and primary injection. However, by extending the compression stroke of each cam boss, the rotational angle available to return the pump pistons and fill the fuel pumping chamber is necessarily reduced. An appropriate rate is limited because the period of time provided by the available rotational angle ultimately leaves insufficient time to fill the pumping chamber for the next injection event.

  There is a need in the art of a rotary distribution fuel pump that increases the appropriate rate available to provide pilot and primary injection events.

  A rotary distribution fuel pump according to aspects of the present invention adds a separate pilot pumping chamber and associated pumping pistons and cam followers axially offset from the main pumping chamber and pumping pistons. The axis of the pilot piston bores is angularly offset from the axis of the main piston bores so that the pilot pistons are actuated by a different set of cam bosses of the cam profile. This arrangement allows one pumping chamber to be filled while the other pumping chamber is being discharged. A pilot injection event may occur ahead of the main injection without filling problems because each pumping chamber fills once for an injection event that includes pilot and main injections.

  Intake / discharge passages of the pilot and main pumping chambers are provided with orifices for receiving water. fuel from the same intake port and fuel fed under pressure to the same discharge port. A fuel spill control valve is arranged to fluidly communicate with the discharge port during delivery of a pressurized fuel. When actuated, the fuel spill control valve connects the discharge port to a low fuel pressure zone, allowing regulation of the outlet of both pumping chambers by the conventional spill method, pumping, spill. Alternatively, the output of the two pump chambers can be regulated by a modulation of the fuel intake pressure where a fuel intake time in the pump chambers.

  The size of the piston (diameter) associated with each pumping chamber can be optimized to produce a shape of the desired flow rate of a fuel feed from the pump. The phase difference between the two pumping events is regulated by the angular offset between the pilot and main piston bore axes.

  Other features and advantages of the invention will emerge more clearly on reading the description below, made with reference to the accompanying drawings, in which: FIG. 1 is a side sectional view of an injection pump 10 of FIG. rotary distribution fuel according to aspects of the present invention; Figure 2 is a left end sectional view of the rotary feed fuel injection pump of Figure 1; and FIG. 3 is a graphical representation of fuel delivery rate, pumping piston movement, pilot and main control valve alignment, and the flow valve operation of one embodiment. exemplary functional arrangement of the rotary distribution fuel pump of FIG. 1 according to aspects of the present invention.

  An exemplary embodiment of a rotary distribution fuel injection pump according to the present invention is shown in FIGS. 1 and 2 and is generally designated by numeral 10. A substantially tubular hydraulic head 12 having one end forward 14 and a trailing end 16 defines a plurality of substantially coplanar fuel inlet ports 18 circumferentially spaced around the head and a plurality of substantially coplanar fuel dispensing ports 20 circumferentially spaced around the head . A substantially cylindrical dispensing rotor 22 is coaxially closely received in the tubular and supported hydraulic head 12 for rotation therein. The distribution rotor 22 has a front portion 24 extending axially from the front end of the hydraulic head and a rear portion 26 disposed in level (at 28) with respect to the hydraulic head 12. The front portion 24 of the rotor dispensing device comprises a fixing device 30 for engaging a rotary drive (not shown).

  The front end 24 of the dispensing rotor defines a first pair of substantially coplanar piston bores 32a, 32b radially extending from a first pumping chamber 34. A pump piston 36a, 36b is located for reciprocating movement in each piston bore 32a, 32b, respectively. The forward end 24 of the timing rotor also defines a second pair of substantially coplanar piston bores 38a, 38b extending from a second pump chamber 40 offset axially from the first pumping chamber 34. A pump piston 42a, 42b is located for reciprocating movement in each second piston bore 38a, 38b, respectively. A first inlet / outlet passage 48 extends from the first pumping chamber 34 to the surface of the rotor 22 for sequential alignment with each of the inlet ports 18 and the discharge ports 20. A second inlet / outlet passage 50 extends from the second pumping chamber 40 to the rotor surface for sequential alignment with each of the inlet ports 18 and the discharge ports 20. Figure 1 shows the first and second inlet / outlet passages 48, 50 in solid lines in a rotational position aligned with a discharge port. The first and second input / output passages 48, 50 are shown broken line in a rotational position aligned with an inlet port 18. Sequential alignment of the first and second intake / discharge passages 48, 50 with the inlet ports 18 and the discharge ports 20 occurs when the rotor 22 is driven within the hydraulic head 12.

  A stationary cam profile 52 surrounds the forward end 24 of the delivery rotor 22. A first set of cam followers 54 are located between the first pair of pump pistons 36a, 36b and the cam profile 52. A second set of cam followers 56 are located between the second pair of pump pistons 42a, 42b and the cam profile. As shown in more detail in FIG. 2, pairs of angularly spaced cam bosses actuate the two pairs of pump pistons 36a, 36b and 42a, 42b to provide two pulses of pressurized fuel. The bores 32a, 32b and 38a, 38b in which the respective pairs of reciprocating pistons are arranged in a relative angular orientation so that one pumping chamber is filled while the other pumping chamber is in process. discharge. In the illustrated embodiment, the two pressurized fuel pulses are applied to a common discharge port associated with a single injector to produce a pilot injection event ahead of a main injection. The phase difference between the two pumping events is established by the radial position of the piston bores relative to the cam bosses used to drive the respective pairs of pumping pistons.

  In the embodiment shown, a mechanical assembly accomplishes a coordinated actuation of the pairs of pump pistons. A means for the timing of operation of the pump chamber pairs includes the cam profile 52, the cam followers 54, 56 and the angular offset between the Al axis of the pilot piston bores 32a, 32b and the axis. A2 bores 38a, 38b of main pistons. In the rotational position shown in Fig. 2, the pilot pulse is generated by the pilot pistons 36a, 36b is nearly completed and the main pulse generated by the main pumping pistons 42a, 42b is about to begin. The cam profile 52 shown produces six overlapping and overlapping pilot / main high pressure fuel pulses for each complete rotation of the rotor 22 relative to the hydraulic head 12. Each overlapping pilot / main fuel pulse is clocked to correspond to a fluid communication between the respective intake / discharge passage 48, 50 and the discharge port 20 associated with the injector for a motor cylinder (not shown). Although a particular mechanical assembly is illustrated to effect coordinated actuation of the pilot and main pistons, other means for the timing of actuation of the pistons may be produced by those skilled in the art. For example, the single cam surface 52 shown may be divided into two cam surfaces axially aligned with the cam followers of the respective sets of pistons. Other hydraulic or electromechanical means intended for the rhythm of the actuation of the pilot pistons relative to the main pistons may be produced by those skilled in the art and it is intended that they be grouped together under the terms of the claims "means intended for rhythm ".

  In the illustrated embodiment, each dispensing orifice 20 on the hydraulic head 12 has discharge passages 58, 60 which coincide sequentially with the first and second intake / discharge passages 48, 50 from the pump chambers 34, 40. , respectively. Discharge passages 58, 60 communicate with a common discharge opening 62 at the surface of the head 12. Each inlet orifice 18 on the hydraulic head 12 has intake passages 64, 66 which coincide sequentially with the first and second intake / discharge passages 48, 50, respectively. Intake passages 64, 66 communicate with a common inlet opening 68 at the surface of the head 12.

  The rear portion of the pump 10 has an internal cavity 70. A discharge control valve 72 is located in the cavity.

  A control passage 74 extends from the control valve 72 to a control port 76 at the rotor surface for sequential alignment with a regulating passage 78 communicating with the discharge opening 62 at the surface. hydraulic head.

  The illustrated configuration of the hydraulic head 12 allows the regulation of a fuel pressure at the dispensing orifices 20 by means of a single regulating valve 72. The hydraulic head 12 is configured to bring the output of the two pump chambers 34, 40 to a common discharge port. Alternatively, the hydraulic head 12 could be configured to bring the outlet of each pumping chamber 34, 40 to separate discharge ports (not shown).

  The piston diameter can be optimized according to the application. In the embodiment shown, the diameter of the pump pistons 36a, 36b is smaller than the diameter of the pump pistons 42a, 42b. This arrangement will produce pump movements 80, 84 and pump flow rates 82, 86 which are different for the two pump chambers 34, 40 as shown in FIG. 3. It will be noted that the two sets of pistons are actuated by the same profile. of cam, so that if pump chamber sizes and pumping piston diameters are the same, the pumping rate for both pumping chambers will be constant. By varying the pumping rates of the respective chambers, it is possible to tailor the shape of the flow rate of a pump outlet as shown graphically in FIG. 3. It can be seen that the maximum pump flow rate 90 for the first chamber is less than the maximum pump flow 92 of the second chamber. Since both sets of pistons are actuated by the same cam profile 52, the fuel delivery rate will increase linearly during the overlap 88 of one fuel supply from one pump chamber to the next. The piston bores 32a, 32b and 38a, 38b are arranged relatively to each other and the cam profile 52 in such a way that the second pumping chamber begins feeding 94 while a fuel supply coming from the first pumping chamber decreases. 96.

  Figure 3 shows relationships between components in the rotary distribution fuel pump 10 shown. Curves 82 and 86 show the pumping rate of the first and second pumping chambers 34, 40, respectively, in cubic millimeters (mm 3 / deg). Curve 98 shows the shape over time of a coincidence of the first intake / discharge passage 48 with the passage 58 leading to the discharge port. The curve 100 illustrates the shape over time of a coincidence of the second intake / discharge passage 50 with the passage 60 leading to the discharge port. The curves 98 and 100 show the shape in time of a fluid communication between the pump chambers 34, 40 and the discharge orifice 20 corresponding to their different discharge phases. The curve 102 shows the shape in time of a coincidence between the first intake / discharge passage 48 and the passage 64 leading to the inlet port 18. The curve 104 shows the shape in time of a coincidence between the second intake / discharge passage 50 and the passage 66 leading to the inlet orifice 18. The curves 102 and 104 show the shape in time of a fluid communication between the pumping chambers 34, 40 and the inlet orifice 18 corresponding to the filling phases of the pumping chambers. Figure 3 clearly shows that the first pumping chamber is being discharged 98 while the second pumping chamber is being filled 104 and that the second pumping chamber is being discharged 100 while the first pumping chamber is being filled 102.

  The curve 106 shows the shape in time of a coincidence between the regulating passage 74 and the regulating orifice 76 communicating with the discharge orifice. Curve 106 represents fluid communication between control valve 72 and discharge port 20. Curves 108 and 109 show the time-course of a control valve actuation, representing a "flow" of fuel pressurized from the discharge port to a low-pressure zone. This shows a method of "outlet flow flow" regulating the output of the two pump chambers 34, 40. Note that the control valve 72 is in fluid communication with the discharge port 20 for a time covering a large portion of the discharge phases of both the first and the second pump chambers 34, 40.

  Although a preferred embodiment of the foregoing invention has been presented for purposes of illustration, the foregoing description should not be construed as limiting the present invention. Therefore, various modifications, adaptations and variations can be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims (13)

  A rotary distribution injection pump (10) having a rotor (22) having a plurality of main piston pistons (42a, 42b) operated simultaneously for supplying a high pressure fuel sequentially through a passage (58, 60). ) to a plurality of discharge ports (20) each associated with a respective fuel injector, the improvement comprising: a separate plurality of pilot pump pistons (36a, 36b) actuated simultaneously and a pilot pumping passage fluid-connectable partner at said discharge ports, and means for timing the actuation of the pilot pistons (36a, 36b) for overlap phasing in advance with respect to the operation of the main pistons (42a, 42b), a fuel ejected by the pilot pistons (36a, 36b) through the associated pilot passage being brought to a discharge port in advance on a fuel brought to the same orifice discharge head from the main discharge pistons (42a, 42b).   An improved rotary distribution fuel pump (10) according to claim 1, comprising a cam profile (52) surrounding said main and pilot pumping pistons (42a, 42b, 36a, 36b) and a cam follower (54, 56) between each of said main and pilot pumping pistons (42a, 42b, 36a, 36b) and said cam profile (52), wherein said main pumping pistons (42a, 42b) reciprocate in bores ( 32a, 32b) of main pistons having a common first axis (A 1) and said pilot pumping pistons (36a, 36b) reciprocate in said pilot piston bores (38a, 38b) having a second common axis (A2) said timing means having an angular offset between said first and second axes (A1, A2).   An improved rotary distribution fuel pump (10) according to claim 1, wherein said main pumping pistons (42a, 42b) reciprocate in bores (32a, 32b) of substantially coplanar main pistons communicating with a chamber pump (24) and said pilot pump pistons (36a, 36b) reciprocate in substantially coplanar pilot piston bores (38a, 38b) in communication with a pilot pump chamber (40), said rotor ( 22) having a rotational axis and said main piston bores (32a, 32b) are axially offset along said rotational axis relative to said pilot piston bores (38a, 38b).   A rotary distribution fuel pump (10) having a plurality of simultaneously operated main pumping pistons (42a, 42b) for supplying a high pressure fuel sequentially to a plurality of discharge ports (20) each associated with a respective fuel injector, a method of providing a pilot exhaust with the main evacuation to each injector, comprising simultaneously actuating a plurality of pilot pistons (36a, 36b), in overlap phasing in advance relative to the actuating the main pistons (42a, 42b) and bringing the fuel discharged from the pilot pistons (36a, 36b) to the same discharge port in advance of the fuel supplied from the main evacuation.   A rotary delivery fuel injection pump (10) comprising: (a) a substantially tubular hydraulic head (12) having a front end (14) and a rear end (16), a plurality of ports (18) substantially coplanar fuel inlet members circumferentially spaced about the head (12), and a plurality of substantially coplanar fuel delivery ports (20) circumferentially spaced around the head (12); (b) a substantially cylindrical rotor (22) coaxially closely located within the head (12) and supported for rotation therein, said rotor (22) having a front portion (241 extending axially from the front end (14) of the hydraulic head (12) and a rearward bearing portion (26) in the head, said front portion (24) to include means for engaging a rotary drive; (c) a first a plurality of substantially coplanar piston bores (32a, 32b) located in the forward end (14) and extending radially to a first common pumping chamber (34), each of said first piston bores (32a, 32b) having a reciprocating piston therein; (d) a second plurality of substantially coplanar piston bores (38a, 38b) located in the forward end (14) and radially extending to a second chamber (40) common pumping e, each of said second piston bores (38a, 38b) having a pump piston located therein for reciprocating movement; (e) a first inlet / outlet passage (48) extending through the rotor (22) from the first pumping chamber (34) to the surface of the rotor (22) for sequential alignment with each of the ports intake (18) when the rotor is driven; (f) a second inlet / outlet passage (50) extending through the rotor (22) from the second pumping chamber (40) to the surface of the rotor (22) for sequential alignment with each of the ports inlet (18) when the rotor (22) is driven; (g) a stationary cam profile (52) having a plurality of angularly spaced bosses surrounding the first and second pumping pistons (36a, 36b, 42a, 42b), respectively; (h) a cam follower means located between each pumping piston (36a, 36b, 42a, 42b) and the cam profile (52); (i) a rotation of the rotor (22) producing (i) simultaneous reciprocating movement of said first pump pistons (36a, 36b) between a charging phase in which fuel is drawn into the first pump chamber (34) through an inlet port (18) and the first inlet / outlet passage (48) and a first discharge stage in which the attracted fuel is pressurized and discharged through the first intake passage (48). discharge and a discharge port, (ii) a simultaneous reciprocating movement of said second pump pistons (42a, 42b) between a charging phase in which fuel is drawn into the second pump chamber (40) through a an intake port (18) and a second intake passage (50) and a second intake / delivery stage in which the attracted fuel is pressurized and discharged through the second inlet / outlet passage (50). towards a hole of re injection disposal; and (j) wherein the first and second discharge phases are sequential, said first and second intake / discharge passages (48, 50) are configured to bring said first and second fuel evacuations to the same discharge port and said first and second fuel evacuations partially overlap in time.   The rotary delivery fuel injection pump (10) according to claim 5, wherein each delivery port (20) comprises a first delivery passage (58) in the head, which can be aligned with said first pumping ( 48) in the rotor (22), a second discharge passage (60) in the head (12) which can be aligned with said second inlet / outlet passage (50) in the rotor (22). and a common discharge opening (62) at the surface of the head (12).   The rotary distribution fuel injection pump (10) according to claim 5, wherein each intake port (18) comprises a first intake passage (64) in the head (12), which can be aligned with said first inlet / outlet passage (48) in the rotor (22), a second inlet passage (66) in the head (12) which can be aligned with said second inlet / outlet passage (50) in the rotor (22), and a common intake opening (68) at the surface of the head (12).   The rotary distribution fuel injection pump (10) according to claim 5, wherein the rear portion (26) of the rotor (22) has an internal cavity (70), a discharge control valve (72) located in the cavity (70), a regulating passage (78) extending from the regulating valve (72) to a regulating orifice (76) at the surface of the rotor (22) for sequential alignment with each of the orifices discharge head (12), an operation of the control valve (72) diverting a fuel into said control cavity (70) and thereby limiting the amount of fuel discharged from the pump through the discharge port.   The rotary distribution fuel injection pump (10) according to claim 8, wherein each discharge port in the head (12) has a regulating passage (74, 78) extending from the opening of delivery (62) in the head (12) to the regulating orifice (76).   The rotary distribution fuel injection pump (10) according to claim 5, wherein the first cam profile (52) and a diameter of said first pistons (36a, 36b) define first quantity and chamber exhaust flow rate. pump and the cam profile (52) and a diameter of said second pistons (42a, 42b) define second pump chamber discharge amount and flow rate, and the first discharge amount is less than the second delivery amount and the first discharge rate is slower than the second discharge rate.   The rotary delivery fuel injection pump (10) according to claim 5, wherein said first piston bores (32a, 32b) have a first common axis and said second piston bores (38a, 38b) have a second axis. common, an angular offset between said first and second axes timing the first and second discharge phases such that the total discharge rate of fuel fed to a discharge port during the overlap of the first and second discharge phases increases linearly.   The rotary delivery fuel injection pump (10) according to claim 5, wherein the first and second discharge phases have respective maximum delivery rates, said first piston bores (32a, 32b) have a first common axis. and said second piston bores (38a, 38b) have a second common axis, an angular offset between said first and second axes timing the first and second discharge phases such that the second discharge phase begins while the first flow rate repression decreases from its maximum.   A rotary fuel injection pump (10) comprising: a hydraulic head (12) with an outer surface and defining a cylindrical bore, said hydraulic head (12) having a plurality of intake ports (18); substantially coplanar fuel and a plurality of substantially coplanar fuel delivery ports (20); a rotor (22) received in said bore comprising: a plurality of pump main pistons (42a, 42b) which are simultaneously actuated to bring a main pulse of high pressure fuel through a main discharge passageway (58) sequentially to each of said fuel delivery ports (20); a plurality of pump pilot pistons (36a, 36b) that are simultaneously actuated to drive a high pressure fuel pilot pulse through a pump pilot passage sequentially to each of said fuel delivery ports (20); and an actuator assembly for actuating said pump pilot pistons (36a, 36b) and said pump main pistons (42a, 42b), wherein said pilot pulse is supplied to each of said pump delivery ports (20). fuel ahead of said main pulse and said pilot and main pulses overlap partially in time at each of said fuel delivery ports (20).