Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B25/00—Engines characterised by using fresh charge for scavenging cylinders
  • F02B25/26—Multi-cylinder engines other than those provided for in, or of interest apart from, groups F02B25/02 - F02B25/24
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L9/00—Valve-gear or valve arrangements actuated non-mechanically
  • F01L9/10—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic
  • F01L9/16—Pneumatic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B33/00—Engines characterised by provision of pumps for charging or scavenging
  • F02B33/02—Engines with reciprocating-piston pumps; Engines with crankcase pumps
  • F02B33/04—Engines with reciprocating-piston pumps; Engines with crankcase pumps with simple crankcase pumps, i.e. with the rear face of a non-stepped working piston acting as sole pumping member in co-operation with the crankcase
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M69/00—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel
  • F02M69/08—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel characterised by the fuel being carried by compressed air into main stream of combustion-air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M69/00—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel
  • F02M69/10—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel peculiar to scavenged two-stroke engines, e.g. injecting into crankcase-pump chamber
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B75/00—Other engines
  • F02B75/02—Engines characterised by their cycles, e.g. six-stroke
  • F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
  • F02B2075/025—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle two

Definitions

• the present invention relates to the field of two-stroke engines with controlled pneumatic injection.
• the present invention relates to the command and control of pneumatic fuel injection, in two-stroke single-cylinder or multi-cylinder engines.
• a conventional way of controlling pneumatic injection is to connect the valves to a camshaft.
• This purely mechanical solution is not very flexible to use since each cam requires a precise movement of a valve and moreover, the camshaft supporting several cams, it is a given general movement which is imposed from the outset of all the cams.
• This technology therefore generates a general command common to all the valves of the camshaft. Adjustment is difficult and a problem with one of the cams and / or the valves can have repercussions on all the other parts involved.
• More flexible control systems are known, based in particular on pressure variations between different chambers cooperating with the movement of the valve.
• French patents FR 2 656 653 and FR 2 656 656 describe multi-cylinder two-stroke engines in which the pneumatic fuel injection is carried out thanks to pressure differences between different chambers.
• This prior art specifically relates to engines having several cylinders since the pressure differences are created thanks to the angular offset existing between the cycles of the different cylinders.
• the objective of the present invention is to simplify this technology and above all to be able to apply it to single-cylinder engines, which the above-mentioned prior art in no way allows.
• the object of the invention is to use the different pressure variations inherent in the operation of a cylinder to automatically actuate a pneumatic fuel injection device in this cylinder.
• this prior solution applies to single-cylinder engines or engines having several cylinders operating completely independently of each other.
• the connections and the pressure sources used are different.
• One of the problems underlying the present invention is therefore linked to the control of pneumatic injection. According to the present invention, it is a question of shifting the pneumatic injection and more precisely of delaying it with each engine cycle, with respect to an engine according to the prior art.
• motors such as for example those described in the patent application EN. 94/10782 cited above or in French application FR 2 656 653, are fitted with a flange placed in the pump housing for controlling the air flow rate necessary for pneumatic injection.
• flanges are parts added to the engine, which therefore make it more expensive, with the need to have precise adjustments.
• the present invention offers a simpler solution by not requiring a flange for controlling the air flow.
• the engine according to the invention further comprises a first connecting means between the second chamber and the cylinder, intended to delay the opening of the valve by controlling the pressure in said chamber.
• the engine according to the invention further comprises a second connection means between the first chamber and said cylinder, said second connection having a length greater than said first connection.
• said second link has a branch branch in relation to the first link.
• said second connection is made between the first chamber of the movement control means of a valve belonging to a first cylinder and a second cylinder.
• the motor further comprises a second connecting means which opens at one end into said pump housing and through the other end into said first chamber.
• the motor according to the invention may include a third connection means between the pump housing and the first connection means.
• a third connection means can be provided between the first and the second connection means.
• FIG. 1 shows, by a simplified longitudinal section, a two-stroke engine equipped with a means 82 for controlling the movement of a valve. More precisely, the means 82 is placed on the cylinder head of the engine. This means is described. in its structure, for example in the patent application EN. 94/10782.
• the means 82 essentially comprises, in addition to its envelope (not referenced) fixed on the cylinder head, a flexible membrane 89 which separates two chambers 95a and 95b subjected to different pressures as it will be explained later.
• the valve 86 the movement of which is controlled by the means 82, has a head resting on its seat in the closed position.
• the valve stem is connected to the flexible membrane 89 which is itself fixed along its periphery to the interior wall of the envelope.
• a third conduit 87 (or capacity) opens towards the base of the valve 86 and serves to convey a fuel mixture which is injected into the combustion chamber when the valve 86 opens.
• a return spring is interposed between the flexible membrane 89 and the upper surface of the cylinder head in order to help the membrane to act against the pressure in the upper chamber 95a and in the capacity 87.
• a piston 112 moves in the cylinder 111 which comprises a combustion chamber 113.
• Said cylinder 111 communicates at its lower part with a pump casing 115.
• the pump housing 115 comprises, in a conventional manner, an air intake nozzle 119 on which a valve 120 is placed.
• the fresh air introduced into the casing 115 and compressed by the piston 112 is injected into the cylinder 111, by means of transfer conduits such as 121 opening into the cylinder through openings 122.
• the burnt gases are evacuated from the cylinder 111 by a pipe 123.
• the conduit 87 opens at its end 127 opposite to that which opens into the control device 82, directly into the pump housing 115.
• the opening 127 is preferably controlled by a non-return valve or any other means capable of closing this opening as soon as the pressure in the pump casing 115 becomes lower than the pressure in the conduit 87 which is therefore used as storage capacity pressure.
• the pipe 92 which communicates by one of its ends with the chamber 95b of the device 82, opens into the cylinder 113 by its other end.
• the pipe 92 opens into the cylinder 113 at a level close to that of the exhaust pipe 123.
• the opening and closing of the pipe 92 are controlled by the movement of the piston, approximately at the same time as the opening and closing of the exhaust 123.
• the level depends on the pressure that one wants to obtain in the chambers.
• the upper chamber 95a is, according to this embodiment, open to admission, therefore at a rather constant pressure. It can also be closed. Its pressure then depends on the position of the membrane 89, that is to say the pressure in the second chamber 95b.
• the pressure in the lower chamber 95b follows the variations indicated in the figure by the dotted curve B. In this figure also appear the pressure in the cylinder 113 (curve A in solid lines) and the pressure in the capacity 87 (curve C) for the fuel mixture; this latter pressure being close to the maximum pressure prevailing in the pump housing 115.
• a pressure wave therefore leaves the cylinder and joins the lower chamber 95b, quickly and with little loss of pressure; the length of the pipe 92 is quite short.
• the valve would begin to open around 120, 130 ° crankshaft. According to the present invention, the valve opens only around 180 ° crankshaft approximately. This delay in opening depends on the level of the stitching of the pipe 92 in the cylinder. It also depends on the length of said pipe: here very short (about 15 cm), anyway shorter than in the prior art.
• the instant of opening of the valve 86 depends on the dimension (surface) of the membrane 89 and on the force of the associated return spring.
• the injection ends when the cylinder pressure becomes greater than the pressure in capacity 87.
• FIG. 3 illustrates an embodiment of the invention which differs from the first by the addition of a pipe 921 which at one end opens into the cylinder 111, for example at the same level as the pipe 92.
• the length of the pipe 921 is greater than that of the pipe 92 so that the pressure wave, coming from the cylinder 111, arrives in the upper chamber 95a after the arrival in 95b of that of the pipe 92.
• FIG. 5 illustrates this phenomenon.
• curve B relates to the variation in pressure in the lower chamber
• curve D relates to the variation in pressure in the upper chamber.
• FIG. 5 shows that the arrival of the pressure wave in the lower chamber 95b, which corresponds to the strong rise in pressure, occurs around 120 ° V.
• the shape of the pressure wave in the upper chamber is different from that in the lower chamber; this is due to the fact that the valve begins to open.
• the volume of the upper chamber increases significantly (in proportion) and the maximum pressure reached is significantly lower than that of the chamber.
• the additional line 921 has little influence on the duration of the injection but on the other hand it influences the amplitude of the movement of the valve, since it "adds" a pressure to that of the upper chamber. This additional force is advantageous because it allows the use of a spring of greater stiffness, which facilitates the closing of the valve.
• FIG. 4 illustrates an embodiment very close to that of FIG. 3, the difference being that the additional line 921 leads to the line 92 instead of the connection to the combustion chamber.
• the effect is the same as that of FIG. 3.
• FIG. 5 therefore illustrates the operation of the engine according to FIG. 4. It will not be further discussed.
• Figures 6 and 7 relate to an embodiment of the invention according to which at least two cylinders are used.
• the upper chamber 95a of one of the cylinders is connected via a pipe 926 to another cylinder 111 '.
• This other cylinder is also equipped with means 82 'for assisting the valve, the lower chamber 95b' of which is connected to said cylinder.
• Figure 7 illustrates the effect of this shift.
• the pressure wave arrives with a delay of about 90 ° crankshaft with respect to the lower chamber (curved B). This delay is due to the angular offset between the two cylinders.
• the delay is controllable by the length of the conduit 926 as well as by the position of the tap in the other cylinder 111 '.
• FIG. 7 shows very well the effect of the length of the conduit on the duration of the signal.
• the pressure wave of curve E has a shorter duration than the pressure wave of curve D of figure 5.
• the pressure peak of curve E "lasts" about 60 ° V while in FIG. 5, the pressure peak of curve D extends over 100 ° V.
• the effect of the speed will be less significant: the travel time of the pressure signal expressed in seconds varies little with the speed, but the variation is significant when it is expressed in crankshaft degree.
• FIG. 8 shows a two-stroke engine comprising the same elements as that of FIG. 1 and also having an additional pipe 922 opening on the one hand into the upper chamber 95a and on the other hand into the pump housing 115.
• the pipe additional 922 has a length greater than that of the pipe 92 and the pressure diagram is obtained according to FIG. 9.
• the latter resembles that of FIG. 2, the curves A, B and C being the same.
• the curve F which corresponds to the pressure in the upper chamber 95a connected to the pump housing 115.
• the pressure wave is different from that of the lower chamber.
• the pressure peak occurs in the lower chamber around 130 ° crankshaft and in the upper chamber around 170 ° crankshaft.
• the maximum value of the pressure in the upper chamber is around 1.4 bars. It is much lower than the maximum value in the lower chamber (more than 2 bars).
• the valve 86 begins to open when the pressure in the upper chamber is higher than that in the lower chamber, ie around 180 ° crankshaft. Without this assistance mode, the opening of the valve begins around 140 ° crankshaft.
• the end of the injection is around 240 ° crankshaft when the pressure in the cylinder becomes significantly higher than the pressure in capacity 87.
• FIG. 10 illustrates an embodiment close to that of FIG. 8; however a line 923 is added; it connects the pump housing 115 to the pipe 92.
• FIG. 12 Another embodiment of the invention is illustrated in FIG. 12 with the pressures according to FIG. 13. Basically, this embodiment reproduces that of FIG. 8, it comprises the same pipes.
• connection 924 between line 92 and line 922.
• a sharp increase is indeed seen on curve H pressure around 170 ° crankshaft. This is due to the arrival of the pressure wave coming from the cylinder via the link 924.
• the opening of the valve begins with the arrival of this wave, ie around 170 ° crankshaft. The time of this opening is determined by the lengths in the different pipes 92, 922, 924.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Chemical & Material Sciences (AREA)
• Output Control And Ontrol Of Special Type Engine (AREA)
• Valve Device For Special Equipments (AREA)
• Reciprocating Pumps (AREA)
• Fuel-Injection Apparatus (AREA)
• Valve-Gear Or Valve Arrangements (AREA)
• Supercharger (AREA)
• Fluid-Driven Valves (AREA)
• Electrically Driven Valve-Operating Means (AREA)
• Control Of Transmission Device (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=9489371

Family Applications (1)

Country Status (8)

Families Citing this family (11)

Family Cites Families (12)

• 1996
  • 1996-02-12 FR FR9602048A patent/FR2744764B1/fr not_active Expired - Fee Related
• 1997
  • 1997-01-31 EP EP97400225A patent/EP0789138B1/fr not_active Expired - Lifetime
  • 1997-01-31 AT AT97400225T patent/ATE191541T1/de not_active IP Right Cessation
  • 1997-01-31 DE DE69701585T patent/DE69701585T2/de not_active Expired - Fee Related
  • 1997-02-05 TW TW086101440A patent/TW338088B/zh active
  • 1997-02-10 JP JP9026659A patent/JPH09228847A/ja active Pending
  • 1997-02-12 CN CN97102441A patent/CN1083932C/zh not_active Expired - Fee Related
  • 1997-02-12 US US08/799,760 patent/US5752477A/en not_active Expired - Fee Related

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