FR2737253A1 - TWO-STROKE INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

Engine, the compression cylinder (11) of which has an injection chamber (20) connected to a fuel injection device (22). The chamber is connected to the combustion chamber (13) by a blast port (202) in the combustion cylinder (11). To improve the blowing of the fuel stored in the injection chamber (20), the crankcase (10) or the cylinder (11) incorporates a reciprocating piston air compressor (25) whose chamber (24) communicates with the chamber (15) of the housing (10) during the suction stroke and is connected by a pressure check valve (26) to the injection chamber (20).

Description

STATE OF THE ART The invention relates to an internal combustion engine with

  two-stroke, in particular for a controlled tool, comprising at least one crankcase with a combustion cylinder guiding in axial sliding a combustion piston delimiting on one side a combustion chamber and during its stroke the piston controls a suction light for combustion air, an exhaust light for exhaust gases and at least one bypass channel connecting the chamber of the

  crankcase to the combustion chamber, a crankshaft

  quin housed in the crankcase and coupled by a connecting rod to the piston of the combustion chamber, a chamber

  separate fuel injection into the combustion cylinder

  tion this chamber being connected by an opening of insuffla-

  tion to the combustion chamber and through an opening

  injection to a fuel injection device and a

  alternative tone driven by the crankshaft to inject the fuel transferred to the injection chamber by the device

fuel injection.

  In a two-stroke internal combustion engine, known corresponding to this type (document EP 0 514 982 A1), a guide sleeve is inserted in the injection chamber; this sleeve is closed relative to the combustion chamber by a spring loaded shutter valve having a shutter cone. The guide sleeve or liner receives the reciprocating piston driven back and forth by a connecting rod

  an auxiliary crankshaft, guided outside. The crankshaft

  auxiliary quin is driven by a toothed belt and a

  toothed wheel carried by the crankshaft for the cylinder

  bustion. In addition to the injection port of the fuel injection device, the injection chamber also

  an opening for the common supply of air and oil.

  The mixture of fuel, air and oil arriving in the

  injection chamber passes under the effect of the suction stroke

  tion of the piston, over the overflow partitions in the injection chamber and from there into the volume delimited by the

  shut-off valve and the front wall of the piston, for

  worm in the shirt. During the pis- transfer stroke

  alternative tone, the piston closes the overflow partitions and compresses the trapped mixture until the pressure is sufficient to open the shut-off valve. When this valve or flap opens, the mixture is sprayed under pressure directly into the combustion chamber of the combustion cylinder. The metering of the quantity of fuel in the injection chamber is done by means of a solenoid valve. According to another two-stroke engine also known (documents DE 37 27 266 Al or DE 41 25 593 Al), the dosage of

  fuel is made using a piston diaphragm pump ground-

  licit by the pressure prevailing in the crankcase;

  this pump injects a direct, metered amount of fuel

  in the combustion chamber of the combustion cylinder via an injection line and an injector, depending on the

  pressure inside the crankcase.

Advantages of the invention

  The present invention relates to a combustion engine

  internal two-stroke of the type defined above, characterized in that the reciprocating piston is part of an air compressor with reciprocating piston integrated in the crankcase

  or in the combustion cylinder and whose combustion chamber

  tion is connected by a pressure check valve to the injection chamber and connected for the suction stroke of the

  reciprocating piston to the inner chamber of the crankcase-

quin.

  The internal combustion engine according to the invention offers on the one hand the advantage that the metering of the fuel and the injection of fuel can be adjusted separately from one another and independently. This not only results in an extremely precise metering of the fuel, but also the start of the blowing of fuel into the combustion chamber of the combustion cylinder can be influenced in order to achieve better combustion of the mixture. Furthermore, the constructive means implemented for blowing fuel by an air compressor with reciprocating piston provided inside the

  crankcase or in the separate combustion cylinder

  are very weak means because the reciprocating piston

  is directly coupled, without transmission, to the crankshaft

  dragging the combustion piston rod. It is not necessary

  be sure to have a particular lubrication of the compressor nor a pa-

  link particular. Avoid any exposed shut-off valve

  with hot combustion gas from the combustion chamber.

  As the compressor compression chamber fills with combustion gas from inside the crankcase

  crankshaft, and that this pressurized air produces insuff-

  fuel flation, this controls the start of insufflation depending on the load; the pressure in the crankcase

  of the crankshaft varies according to the setting of a shutter

  depending on the load at the air intake opening so that the pressure required to

  opening of the pressure relief valve in the chamber

  combustion, is reached earlier in full

  load and later in partial load which is

  due to a corresponding variation in the start of the breath

  tion. As the introduction of fuel into the injection chamber takes place before the start of blowing into the combustion chamber, the vaporization of the fuel in the

  injection chamber begins before insufflation which pro-

  then a better spraying of the fuel

insufflation.

  According to other advantageous characteristics:

  - the reciprocating piston has a seal cooperating with the pa-

  inner king of the reciprocating cylinder which for racing

  suction of the piston allows the passage of combustion air

  tion from the crankcase chamber to the pressure chamber and which during the compression stroke of the reciprocating piston seals it relative to the inner wall of the reciprocating cylinder; the blowing orifice of the injection chamber opens into the overflow channel or into the wall of the combustion cylinder below the exhaust port of the exhaust gases; - The opening pressure of the pressure retaining valve is adjusted between the compression chamber and the injection chamber at a pressure of the order of 2 bars; - the fuel injection device is connected to the chamber

  injection by a throttling device and a double pump

  ble diaphragm driven by compressed air from the crankcase-

  brequin, which transfers fuel from a fuel tank, includes a metering valve downstream of the

  double diaphragm pump, this valve preferably being

  read in the form of a 2/2-way drawer distributor

  with spring return, as well as a pressure limiter

  linked to the output of the double diaphragm pump.

  According to a preferred embodiment of

  the invention, the reciprocating piston air compressor is made

  read by the combustion piston in the form of a stepped piston, with

  a rear part of the piston of smaller diameter, and penetrates

  trant in a guide jacket held in the combustion cylinder and thus forming the combustion chamber with the inner wall of the combustion cylinder, the front face of the guide jacket and the annular shoulder representing the active surface of the reciprocating piston at the level of the stepped piston. The connecting line which serves for the injection chamber is displaced in the overflow channel and can

  be made by corresponding holes. These means

  tructives minimize the manufacturing means used for the compressor and require only a combustion piston made in the form of a stepped piston and a

  additional jacket to be fixed in the combustion cylinder.

  According to another embodiment of the invention, an annular leakage interval between the reciprocating piston and

  the shirt, allows in addition to the variation of start of breath

  tion dependent on the load, also to obtain a variation in the start of insufflation dependent on the speed of rotation allowing better combustion of the fuel to have lower consumption and better quality of the exhaust gas. The displacement of the start of the injection as a function of the rotation speed results from the fact that the leakage interval at low rotation speeds allows a much larger quantity of air to escape at the time of the stroke. transfer of the reciprocating piston from the combustion chamber to return to the crankcase chamber, as is the case at higher rotational speeds, when the leakage interval always decreases. At low speeds, the pressure to open the pressure check valve in the connection line to the injection chamber is reached later than at high speeds so that the fuel blowing from the

  the injection chamber advantageously begins later at the

the rotational speeds.

  According to an alternative embodiment of the invention, the reciprocating piston air compressor can be produced by

  placing in the radial direction a cylinder or

  green towards the inner chamber of the crankcase-

  brequin, and guiding a reciprocating piston, axial. The reciprocating piston is connected by a connecting rod to the crankshaft of the crankcase.

  crankshaft so that at the bottom dead center of the combustion piston

  tion, the reciprocating piston is substantially at its top dead center. This realization of the compressor is slightly more

  costly in terms of manufacturing but it offers the same

  my advantages than those described initially.

  A cheap realization, that is to say a realization

  low cost manufacturing of the internal combustion engine

  dull two-stroke is obtained if in addition to the realization of the reciprocating piston by a stepped form of the combustion piston,

  according to another embodiment of the invention, the device

  fuel injection device for metering the fuel comprises a piston diaphragm pump, driven by the air pressure prevailing in the crankcase, a valve

  intake and an exhaust valve in the form of a check valve

  turntable, and connected at the outlet by a throttle member to the injection chamber and at the inlet to a transfer pump

  upstream. Such a two-stroke internal combustion engine is ro-

  bust, not very sensitive to incidents and requires no bat-

  because it does not contain electrical components.

Drawings

  The present invention will be described below in detail.

  more detailed with the help of exemplary embodiments

  shown schematically in the accompanying drawings in which:

  - Figure 1 is a longitudinal section of a mo-

  two-stroke internal combustion engine with a fuel injection device shown in the form of a block diagram, - Figure 2 is a longitudinal section of a variant of an internal combustion engine with two times,

  - Figure 3 is a longitudinal section of a mo-

  two-stroke internal combustion torch corresponding to another

example of realization.

  Description of the exemplary embodiments

  The two-stroke internal combustion engine shows

  felt in longitudinal section in FIG. 1 is used in particular for

  drag portable tools such as sections -

  neuses, grinders, shears, but also a driver

  motorcycle, motor boat, lawn mower

  zon. This engine comprises in known manner at least one crankshaft casing 10 with a combustion cylinder 11 receiving in axial sliding a piston 12 whose front face delimits

  a combustion chamber 13 in the head of the cylinder

  bustion 11. The combustion chamber 13 is connected by at least

  an overflow channel 14 to the chamber 15 of a crankcase-

  brequin 10. The wall of the combustion cylinder 11 includes a suction light 16 for the combustion air, connected to an air suction channel controlled by a throttle valve and a

  exhaust light 17 for exhaust gases; this lu-

  mine is connected to the exhaust.

  During the stroke of the piston 12, the suction light 16, the exhaust light 17 and the opening 141 on the side of the combustion chamber of the bypass channel 14 are closed and released in a certain order by the piston of combustion 12. The stroke of the combustion piston 12 is transformed by a connecting rod 18 into a rotational movement of a

  crankshaft 19 housed in crankshaft housing 10.

  The combustion cylinder 11 comprises at the bypass channel 14, a fuel injection chamber; this chamber has an injection opening 201, a

  blowing opening 202 and compressed air opening 203.

  The blowing opening 202 is located in the opening 141 on the side of the combustion chamber of the overflow channel 14; it can also be produced by drilling in the wall of the cylinder leading to the combustion chamber 13; this drilling is then located under the displacement plane in which the outlet lumen is located. The injection orifice 201 is connected via a throttling member 21 to a

  fuel injection device 22 which will be described later

  laughingly. The compressed air opening 203 is connected to a ca-

  nal link 23 leading to the combustion chamber 24 of a linear piston air compressor 25 housed in the combustion cylinder 11. A pressure relief valve 26 equips the link channel 23; for a compression pressure prevailing in the compression chamber 24, for example greater than

  2 bars, this valve opens in the direction of the injection chamber

tion 20.

  In the embodiment of FIG. 1, the linear piston air compressor 25 is constituted by the

  production of the combustion piston 12 in the form of a pis-

  ton stepped and by the introduction of a guide jacket 27 in the combustion cylinder 11; the piston portion 121 of smaller diameter enters this jacket in which it is guided in axial sliding. The compression chamber 24 is thus formed frontally by the front face of the sleeve 27 and by the annular shoulder 122 of the stepped parts of the combustion piston 12 as well as internally by the external wall of the piston part 121 of smaller diameter and externally through the wall of the combustion cylinder 11. The fitting of the jacket 27 and the piston portion 121 of smaller diameter are chosen to leave an annular leakage interval 28. When the combustion piston 12 goes up in the combustion cylinder 11, air arrives in the chamber 15 of the crankshaft housing 10 by the suction light 16 once released by the combustion piston

  12. In this way, the combustion chamber 24 of the compressor

25 is filled with air.

  When the combustion piston 12 goes down, the pressure stroke of the compressor 25 begins with the closing

  of the suction light 16. The air in the compression chamber

  sion 24 is compressed and for example a higher pressure

  less than 2 bars, this air is ejected through the pressure valve

  pressure retainer 26 which opens in the combustion chamber

  tion 20. The leakage interval 28 allows part of the air

  compressed to escape into chamber 15 of the crankcase-

  quin 10. This exhaust effect decreases as the

  tesse de rotation increases so that the pressure required to open the check valve 26 in the pressure chamber

  compression is reached more quickly at rotational speeds

  tion than at low crankshaft speeds-

  quin. The air supplied to the injection chamber 20 from the compression chamber 24 of the compressor 25 is blown into the injection chamber 20 by the fuel injection device 22, from the injection chamber 20 through its blowing orifice 202 to be blown into the combustion chamber 13 of the combustion cylinder 11. The start of blowing varies because as indicated above, this start depends on

  the speed of rotation as well as the load; the pressure

  gaining in the crankcase 10 and thus the pressure of

  the air which arrives in the compression chamber 24 also varies

  according to the setting of the throttle flap according to

  the charge in the air intake channel upstream of the

  aspiration 16; the compression pressure for example greater than 2 bars is thus reached sooner or later

in compressor 25.

  The fuel injection device 22 comprises a double diaphragm pump 30, driven by the pressure of the

  chamber 15 of the crankcase 10 for transferring the

  fuel from the fuel tank 31.

  Such a double diaphragm pump 30 is for example

  ple described in document DE 42 23 758 Al. An ac-

  tive 33 delimited by a membrane 32 in the double membrane pump 30 is connected by a pipe 34 to the chamber 15 of the crankshaft housing 10. The membrane 33 controls a pump membrane 36 by a pusher 35; this membrane 36 delimits a pump chamber 37. The pump chamber 37 is connected by a suction valve 38 to a fuel supply 39 of the tank 31. The outlet of the chamber 37 of the pump is connected on the one hand to a solenoid valve 40 and on the other hand to a limiter

  pressure 41. The pressure maintained by the pressure relief valve

  41 in the pressure line between the pressure chamber 37 and the metering solenoid valve 41 is for example set to

  3 bars. As long as the valve-shaped solenoid 40

  2/2-way valve is closed, the fuel supplied by the double-diaphragm pump 30 from the tank 31 returns via the pressure relief valve 41 in the tank 31. When the metering valve 40 switches to the on position, the fuel passes by the throttle member 21 in the fuel injection chamber 20. The quantity of fuel dosed

  in the injection chamber 20 is defined by the duration of com-

mutation of the metering valve 40.

  Not to use electrical components

  like the metering valve 40, the car injection device

  burant 22 shown in Figure 2 ensures the metering of the fuel

  rant using a diaphragm pump 42 subjected to the pressure of the crankshaft 10. The construction and operation of such a diaphragm pump are for example described in the document DE 37 27 266 Ai. A membrane 43 delimits an active chamber 44 connected by a pipe 45 to the chamber 15 of the crankshaft housing 10. A pump piston 46 is fixed in the middle of the membrane 43; this piston is guided in a pump cylinder 47 and delimits by its front face a pump chamber 48. The pump chamber 48 is connected by an inlet valve 49 to the outlet of a supply pump 50, upstream; this pump is also actuated by the pressure prevailing in the crankcase 10; it sucks fuel in a circuit passing through the fuel supply 39 to

  from a fuel tank 31 to return the fuel to the tank 31 by a fuel return 51. During the suction stroke of the pump piston 46, the fuel-tank passes through the valve inlet 49 in the form of a check valve

  return arriving in the pump chamber 48. This quantity of fuel is transferred during the pressure stroke of the

  pump piston 46 by a valve-shaped outlet valve 52

  pet non-return to arrive in the car injection chamber

  burant 20 through the throttle member 21. The quantity of fuel thus stored is defined by the stroke of the piston of

pump 46.

  The two-stroke internal combustion engine with a crankcase 10 and at least one combustion cylinder 11 corresponds in an identical manner to that of the two-stroke internal combustion engine described and represented in FIG. 1. The references used on this occasion correspond to those of the embodiment shown in FIG. 2. However, these

  references have not been included in FIG. 2.

  Figure 3 shows another embodiment of a two-stroke internal combustion engine with compressor

  air with linear piston 25, integrated, the assembly being shown

  tee in schematic longitudinal section. The two-stroke internal combustion engine corresponds to those of FIGS. 1 and 2 except for the construction of the compressor 25 so that the same

  elements that those already described bear the same references.

  The crankcase 10 is provided radially with a translation cylinder 53 opening into the chamber 15 of the crankcase; this cylinder 53 guides in axial sliding a reciprocating piston 54. The piston 54 is connected by a connecting rod 55 to the crankshaft 19 so that when the piston

  combustion 12 occupies the bottom dead center, the translational piston

  tion 55 occupies substantially its top dead center in the cylinder

  dre of translation 53. The compression chamber 24 delimited by the translation piston 54 in the translation cylinder

  53 for compressor 25 is connected by a pressure line

  sion 56 externally bypassing the crankcase 10 and the combustion cylinder 11 to the compressed air port 203

  of the fuel injection chamber 20 of the fuel cylinder

  bustion 11. A pressure check valve 26 also equips

  the pressure line 56. A seal 57 is fixed to the piston 54; this seal is made in the form of an air pump seal which allows the passage of air during the suction stroke

  piston 54 of the inner chamber 15 of the crankcase-

  quin 10 to the compression chamber 24; during the compression stroke of the piston 54, the seal ensures

  the seal between the piston 54 and the inner wall of the cy-

  line 53 and thus closes the combustion chamber 24.

  The operation of the compressor 25 is the same as that of the compressor 25 of FIG. 1. When the pressure increases in the combustion chamber 24, for example when it exceeds 2 bars, the pressure check valve 26 opens and the quantity of fuel transferred to the injection chamber 20 by the fuel injection device is ejected directly from the blowing orifice 202 into the combustion chamber 13. Like the pressure in the chamber 15 of the crankcase 10 varies depending on the shutter setting

  throttle in the air intake duct connected to the

  suction 16, the pressure required to open the pressure check valve 26 in the combustion chamber 24 is reached after a more or less long stroke of the piston 54. The fuel blowing from the injection chamber 20 is

  does so ahead or behind the angle of ro-

  tation of the crankshaft. As the position of the throttle valve depends on the load, this also displaces the start of the blowing of fuel from the injection chamber 20 by

load function.

  The two-stroke internal combustion engine shows

  shown schematically in Figure 3, equipped with a linear piston air compressor, integrated for blowing fuel

  can be applied to both the fuel injection device

  rant 22 shown in Figure 1 than the fuel injection device 22 shown in Figure 2. This device is connected by the throttle member 21 to the injection port

  201 of the fuel injection chamber 20.

Claims (9)

R E V E N D I C A T I ONS   1) Two-stroke internal combustion engine, in particular for a controlled tool, comprising at least one crankcase   (10) with a combustion cylinder (11) sliding guide   axially a combustion piston (12) delimiting on one side   a combustion chamber (13) and during its travel the pis-   your order a suction light (16) for the combustion air   rant, an exhaust port (17) for the exhaust gases and at least one bypass channel (14) connecting the chamber (15) of the crankcase (10) to the combustion chamber (13), a crankshaft (19) housed in the crankcase (10) and coupled by a connecting rod (18) to the piston (12) of the chamber   combustion chamber, a fuel injection chamber (20), separate   In the combustion cylinder (11), this chamber is connected by an insufflation opening (202) to the combustion chamber (13) and by an injection opening (201) to a   fuel injection device (22) and an alternating piston   tif (12, 54) driven by the crankshaft (19) to inject the   fuel transferred to the injection chamber (20) by the dispo-   fuel injection device (22), characterized in that the reciprocating piston (12, 54) is part of a compressor   air with reciprocating piston (25) integrated in the crankcase-   brequin (10) or in the combustion cylinder (11) and the   combustion chamber (24) is connected by a check valve   pressure bar (26) to the injection chamber (20) and connected for the suction stroke of the reciprocating piston (12, 54) to the   inner chamber (15) of the crankcase (10).   2) internal combustion engine according to claim 1, characterized in that to achieve the reciprocating piston air compressor (25), the combustion piston (12) is in the form of a stepped piston having a piston part (121) , rear of smaller diameter on the side opposite to that of the combustion chamber (13) and this   piston part immersed in a guide sleeve (27) hand-   held in the combustion cylinder (11) and defines with a   inner wall of the combustion cylinder (11), one front face   tale of the guide jacket (27) and an annular shoulder (122) representing the active surface of the reciprocating piston and corresponding to the step of the piston, to define the combustion (24).   3) Internal combustion engine according to claim 2, characterized by an annular leakage gap (28) between the piston part   (121) of small diameter and the guide jacket (27).   4) Internal combustion engine according to any one of the   vendications 2 or 3, characterized in that the pressure check valve (26) equips a connecting pipe (23) provided in the bypass channel (14) and is arranged between the combustion chamber (24) and the chamber injection (20).   ) Internal combustion engine according to claim 1, characterized in that   the reciprocating piston air compressor (25) includes the   ter of crankshaft (10) with a cylinder (53) applied radially-   ment, open towards the chamber (10) of the crankcase, cylinder guiding in axial sliding the reciprocating piston (54) connected by a connecting rod (55) to the crankshaft (19)   so that at the bottom dead center of the combustion piston (12), the piston   your alternative tone (54) is at its top dead center.   6) Internal combustion engine according to claim 5, characterized in that the reciprocating piston (54) has a seal (57) cooperating with the inner wall of the reciprocating cylinder (53) which for the suction stroke of the piston (54) allows the combustion air to pass from the chamber (15) of the crankshaft housing (10) to the pressure chamber (24) and which during the compression stroke of the reciprocating piston (54) seals   this in relation to the inner wall of the alternating cylinder tif (53).   7) Internal combustion engine according to any one of the   vendications 1 to 6, characterized in that   the blowing orifice (202) of the injection chamber (20)   mouth in the overflow channel (14) or in the wall of the   combustion cylinder (11) below the exhaust light exhaust gas (17).   8) Internal combustion engine according to any one of the   Vendications 1 to 7, characterized in that the opening pressure of the pressure relief valve (26) is adjusted between the compression chamber (24) and the   injection chamber (20) at a pressure of the order of 2 bars.   9) Internal combustion engine according to any one of the   vendications 1 to 8, characterized in that the fuel injection device (22) is connected to the injection chamber (20) by a throttle member (21) and a double diaphragm pump (30) driven by compressed air from the crankcase (10), which transfers fuel from a fuel tank (31), includes a metering valve (40) downstream of the double diaphragm pump (30),   valve preferably being made in the form of a dispenser   2/2 way drawer with spring return, as well as a   pressure relief valve (41) connected to the outlet of the double pump ble membrane (30).   10) Internal combustion engine according to any one of the   vendications 1 to 8, characterized in that the fuel injection device (22) is connected to the injection chamber (20) by the throttle member, comprises a piston pump in the form of a membrane (42) driven by   compressed air from the crankcase (10) and having a   inlet valve and an outlet valve (49, 52) in the form of   non-return valve and a supply pump, upstream, (50) re-   linked to the intake valve (49) and which transfers the fuel   rant from a fuel tank (31).