WO1998009060A1 - Liquid gas engine - Google Patents

Abstract

A liquid gas engine has at least one combustion chamber (4) into which a liquid gas/air mixture is introduced and ignited. The liquid gas motor has an injection device (1) which injects liquid gas through an injection nozzle (2). According to the invention, the injection nozzle (2) opens into the combustion chamber (4), and so the liquid gas is directly injected into the combustion chamber. The direct injection of the liquid gas creates ideal combustion conditions, in particular since the liquid gas which evaporates in the combustion chamber (4) has a cooling effect which is particularly advantageous under a high load. The disclosed liquid gas engine is preferably provided with an injection device (1) designed as an alternating piston pump which works based on the principle of accumulation of energy.

Description

 LIQUID GAS ENGINE

The invention relates to a liquid gas engine.

LPG engines are spark-ignited gasoline engines that are fed with LPG.

Liquefied petroleum gas, also known as LPG (Liquified Petrolium Gas), has propane and butane as its main components. It is produced during the extraction of crude oil and in refinery processes and can be liquefied under pressure. Liquid gas is characterized by a high octane number (RON> 100).

LPG engines differ from gasoline engines in that they have a different mixture preparation, which is due to the high evaporation tendency of the LPG. Liquid gas is supplied as liquid under pressure to the engine in appropriate pressure lines. In an evaporator, the liquid gas is converted into the gaseous state with the supply of heat. The evaporator is a heat exchanger to which heated cooling water is fed in order to heat and vaporize the liquefied petroleum gas. The evaporator is combined with a pressure regulator to keep the now gaseous liquid gas in a certain pressure range. The liquefied gas is then fed to a gas / air mixer which mixes liquefied gas with air. Such a gas / air mixer is known for example from DE 33 32 923 C2. The mixer consists of a ring element which supplies liquid gas to a central air flow passing through the ring element and swirls it with it.

The company DAF has a LPG engine for buses under the Type designation LT 160 LPG presented. This LPG engine corresponds to a diesel engine that has been converted to a LPG engine. In contrast to the known LPG engines, the engine presented by DAF is equipped with a LPG injection system that injects LPG into an intake duct. This injection system corresponds completely to those currently used in gasoline engines (cars). When the liquid gas is injected into the intake duct, the vapor temperature of the liquid gas should reduce the mixture temperature and improve efficiency. This cooling by evaporation can lead to icing of the injection valves in the start-up phase and when the air humidity is high, which means that operation at cold outside temperatures cannot be guaranteed. This could be counteracted by mixture preparation with simultaneous heating, as is known from the already common liquid gas engines. However, heating an ignitable mixture poses considerable dangers.

The invention has for its object to provide a liquid gas engine that is simple in construction and ensures safe operation with high power output.

The object is achieved by a liquid gas engine with the features of claim 1. Advantageous refinements are specified in the subclaims.

The liquid gas engine according to the invention is a gasoline engine with a high-pressure injection device which injects liquid gas directly into the combustion chamber. As a result, the liquid gas in the liquid state, in which it can be handled easily and safely, is conducted to the combustion chamber of the engine.

With the injection device, the liquid liquefied gas is injected directly into the combustion chamber, atomized and evaporated. The transition from the liquid to the gaseous state of matter thus takes place only in the combustion chamber. This results in Before advantages, since only the amount necessary for an ignition process is injected and the simultaneous compression of the liquefied gas / air mixture in the combustion chamber counteracts the cooling by the evaporation of the liquefied gas, so that icing of the injection device is prevented even during the cold starting phase and safe operation is guaranteed.

In addition, in the liquefied petroleum gas engine according to the invention, the very fine atomization of the liquefied gas injected with high pressure ensures an excellent distribution in the combustion chamber and the sudden evaporation of the liquefied gas results in perfect mixing of the fuel with the air contained in the combustion chamber, so that the combustion mixture after ignition ideally burns. With this, the advantageous properties of the liquid gas, such as high specific calorific value (> = 46.1 MJ / kg) and high knock resistance, come into their own, so that, in contrast to known liquid gas engines, no loss of performance compared to comparable gasoline engines has to be accepted.

The invention is explained in more detail by way of example with reference to the drawing. Show it:

1 schematically shows a single-cylinder liquid gas engine with an injection device,

2 shows the injection device shown in FIG. 1 in longitudinal section,

3 shows an armature of FIG. 2 in cross section, an armature,

4 shows in cross section a valve body of the injection device shown in FIG. 2,

Fig. 5 shows a crank loop motor in partial section.

The liquid gas engine according to the invention has an injection device 1, which injects liquid gas directly into a combustion chamber 4 of the liquid gas engine via an injection nozzle 2. The combustion chamber is in a manner known per se by a cylinder 5, a cylinder head 11 and a piston 12 limited. An injector 2 and a spark plug 10 are arranged in the cylinder head 11. The injection nozzle 2 is connected to the injection device 1 via a line 72. The injection device is connected via a liquid gas supply line 113 and a liquid gas return line 92 to a pressure tank 111 (shown schematically in simplified form in FIG. 1).

In the liquid gas supply line 113, the liquid gas is above the vapor pressure of z. B. 8-12 bar to ensure that it can not evaporate in the supply line 113. Liquid gas not discharged from the injection device 1 is returned to the pressure tank 111 via the liquid gas discharge line 92. The injection device 1 conveys the liquid gas in short pressure surges at a pressure of 40 bar, preferably 60 bar, to the injection nozzle 2, at which the intermittently injected liquid gas is atomized in very fine droplets distributed over the combustion chamber 4. The droplets evaporate suddenly in the air fed into the combustion chamber 4 via the inlet channel 8. The result is an ideally mixed fuel / air mixture which can be ignited by the spark plug 10. The ignition timing is controlled by an electronic control device 6 in accordance with several parameters, such as, for example, the outside temperature, the crankshaft position and the amount of liquid gas injected. Due to the high calorific value of the liquid gas, it is advisable to delay the ignition timing somewhat compared to comparable petrol engines. The spent exhaust gas is then discharged from the combustion chamber 4 via an exhaust gas duct 3.

As a result of the direct injection of liquid gas according to the invention, the cooling effect generated by the evaporation of the liquid gas occurs in the combustion chamber 4. At a lower load, in which the amount of liquid gas injected is small, the cooling effect is correspondingly low and is compensated for by the compression generated by the compression stroke of the piston 12. When the load is high, there is a much larger amount of liquid in the combustion chamber 4 injected. The cooling effect is increased accordingly, so that a significant increase in efficiency is achieved with large loads due to the "internal" cooling.

The injection device 1 is preferably designed as an electromagnetically driven reciprocating piston pump 1, which works according to the energy storage principle, so that the liquid gas is injected into the combustion chamber 4 with short pressure surges. Reciprocating pumps 1 of this type are known, for example, from DE 41 06 _{04 1} 5 A and DE 42 06 817 A.

An embodiment of the reciprocating pump is shown in Figures ₂ to 4.

The reciprocating piston pump 1 has an essentially elongated cylindrical pump housing 15 with an armature bore 16, a valve bore 17 and a pressure chamber bore 18, which are each introduced one after the other in the pump housing 15 and form a passage extending through the entire pump housing 15. The armature bore 16 is arranged behind the valve bore 17 in the injection direction and the pressure chamber bore 18 is arranged in front of the valve bore 17 in the injection direction. The bores 16, 17, 18 are arranged concentrically to the longitudinal axis 19 of the pump housing 15, the armature bore 16 and the pressure chamber bore 18 each having a larger inner diameter than the valve bore 17, so that the armature bore 16 and the valve bore 17 through a first ring step 21 and the valve bore 17 and the pressure chamber bore 18 are separated from one another by a second annular step 22.

The armature bore 16 delimits an armature space 23 in the radial direction, in which an approximately cylinder-shaped armature 24 is arranged such that it can move back and forth in the longitudinal axis direction. The armature space is delimited in the axial direction to the front by the first annular step 21 and to the rear by a front end face 25 of a cylindrical sealing plug 26 which is screwed into the end of the armature bore 16 which is open to the rear in the injection direction. The armature 24 is formed from a substantially cylindrical body with a front and rear end face 28, 29 and a lateral surface 30 in the injection direction. From the rear end face 28 to approximately the longitudinal center of the armature 24, material is removed from the armature circumferential area, so that the armature 24 has a conical surface 31 that extends from the rear to the front. The armature 24 is inserted with play between its outer surface 30 and the inner surface of the armature bore 16, so that when the armature 24 moves back and forth in the armature bore 16, this only touches the inner surface of the armature bore 16 when the armature 24 is tilted, as a result of which the friction between the armature 24 and the armature bore 16 is kept low. The provision of the conical surface 31 on the armature 24 further reduces the contact and thus the friction surface, as a result of which the friction between the armature 24 and the inner surface of the armature bore 16 and thus also the heat development is further reduced. The armature 24 is provided in the region of its lateral surface 30 with at least one, preferably two or more grooves 32 running in the longitudinal axis direction. The armature 24 has a cross-sectional shape (FIG. 3) with two laterally arranged semicircular elements 24a and with two wide, flat grooves 32 in the area between the semicircular elements 24a. A continuous bore 33 is made centrally on the armature 24 in the longitudinal axis direction.

In the bore 33 of the armature 24, a delivery piston tube 35 is inserted, which forms a central passage space 36. A plastic ring 37 is seated on the front end face 29 of the armature 24 and is penetrated by the delivery piston tube 35. An anchor spring 38 is supported on the plastic ring 37 and extends to a corresponding bearing ring 39. This bearing ring 39 is seated on the first ring stage 21 in the armature bore 16.

The delivery piston tube 35 is non-positively connected to the armature 24. The unit consisting of feed piston tube 35 and armature 24 is referred to below as feed piston element 44. The delivery piston element 44 can also be formed in one piece or in one piece his .

A guide tube 40 is seated in the valve bore 17 in a form-fitting manner and extends rearward into the armature space 23 into the area within the spiral spring 38. At the front end of the guide tube 40 in the injection direction, an outwardly projecting ring web 41 is provided, which is supported on the second ring step 22 to the rear. The annular web 41 does not extend completely radially to the inner surface of the pressure chamber bore 18, so that a narrow, cylindrical gap 42 is formed between the annular web 41 and the pressure chamber bore 18. The guide tube 40 is secured against axial displacement to the rear by the annular web 41.

The delivery piston tube 35 which is non-positively connected to the armature 24 extends forward into the guide tube 40 and backwards into an axial blind bore 43 of the sealing plug 26, so that the delivery piston tube 35 both at its front end 45 in the injection direction and at its rear end 46 is performed. Through this two-sided guide at the ends 45, 46 of the elongated delivery piston tube 35, the delivery piston element 44 is guided without tilting, so that undesired friction between the armature 24 and the inner surface of the armature bore 16 can be reliably avoided.

In the front area of the guide tube 40, a valve body 50 is axially displaceably mounted, which forms a substantially cylindrical, elongated, peg-shaped solid body with a front and rear end face 51, 52 and a jacket surface 53. The outer diameter of the valve body 50 corresponds to the clear width of the passage in the guide tube 40. An annular web 54 is provided on the outer surface 53 of the valve body 50 and is arranged approximately at the end of the front third of the valve body 50. The ring web 41 of the guide tube 40 forms an abutment for the ring web 54 of the valve body 50 in the rest position of the valve body 50, so that it cannot be moved further back. The valve body 50 is on its circumference with three grooves 55 extending in the longitudinal axis direction (Fig. 4). The ring web 54 is interrupted in the area of the grooves 55.

The rear end face 52 of the valve body 50 is conical at its edge region and interacts with the end face of the front end 45 of the delivery piston tube 35. The three-dimensional shape of the front end 45 of the delivery piston tube 35 is adapted to the rear end face 52 of the valve body 50, in which the inner edge of the delivery piston tube 35 is chamfered and the wall of the delivery piston tube 35 is somewhat worn away on the inside. The delivery piston tube 35 thus forms with its front end 45 a valve seat 57 for the valve body 50. If the valve body 50 bears against the valve seat 57 with its rear end face 52, the passage through the grooves 55 made in the area of the lateral surface of the valve body 50 is blocked .

The area of the valve body 50 protruding forward from the guide tube 40 into the pressure chamber bore 18 is surrounded by a pressure chamber body 60, which consists of a cylinder wall 61 and a front end wall 62, a hole or bore 63 being made centrally in the end wall 62 . With its cylindrical wall 61, the pressure chamber body 60 is positively inserted in the pressure chamber bore 18, with its end faces 64 located at the free end of the cylinder wall 61 being arranged abutting the outwardly projecting annular web 41 of the guide tube 40, with radial through bores 65 in the pressure chamber body 60 are provided, which creates a connection between the pressure chamber 66 and the fuel supply bore 76.

The pressure chamber body 60 delimits with its interior a pressure chamber 66 into which the valve body 50 can immerse and pressurize the fuel in the pressure chamber 66. At its rear region in the injection direction, which extends approximately over half the length of the pressure chamber body 60, the pressure chamber has a larger clear width than in the previous their area. The larger clear width in the rear area is dimensioned such that the valve body 50 with its ring web 54 and a slight play can dip into the pressure chamber 66, whereas the clear width of the front area is dimensioned such that only for the ring web 54 front area of the valve body 50 and a coil spring 67 surrounding this area is sufficient space. As a result, the pressure chamber 66 is made only slightly larger than the space required during the injection process of the valve body 50.

The coil spring 67 is seated at one end on the inside of the end wall 62 of the pressure chamber body 60 and is at its other end on the valve body 50 and in particular on the annular web 54, so that it pushes the valve body 50 and the pressure chamber body 60 apart.

The pressure chamber body 60 is axially fixed in the injection direction to the front by a connecting piece 70 which is screwed into the end of the pressure chamber bore 18 which is open to the front. The connecting piece 70 limits the position of the pressure chamber body 60 in the axial direction to the front, so that the coil spring 67 biases the valve body 50 to the rear. On the outside, the connection piece is formed with an opening 71 for connecting the fuel delivery line 72 (FIG. 1). The connecting piece 70 has a bore 73 which is continuous in the longitudinal axis direction and in which a standing pressure valve 74 is accommodated. The ^~~ Standdruck- valve is preferably located adjacent to the pressure chamber body 60th

The pressure chamber body 60 is provided on its outer surface with an annular groove 68, in which a plastic sealing ring 69 is mounted, which seals the pressure chamber body 60 against the inner surface of the pressure chamber bore 18.

A liquid gas supply opening 76 in the area of the pressure chamber bore 18 is provided on the pump housing 15 for the supply of liquid gas. brought so that they can communicate with the holes 65 in the pressure chamber body 60. On the outside of the pump housing 15, the liquid gas supply opening 76 is surrounded by a holder 77 for a liquid gas supply valve 78 which is screwed into the holder 77. The LPG supply valve 78 is designed as a one-way valve with a valve housing 79. The valve housing 79 has two axially aligned bores 80, 81, the bore 80 on the pump housing side having a larger inner diameter than the bore 81, so that an annular step is formed between the two bores which forms a valve seat 82 for a ball 83. The ball 83 is biased against the valve seat 82 by a spring 84, which is supported in the area around the liquid gas supply opening 76 on the pump housing 15 in the bore 80, so that liquid gas supplied from outside lifts the ball 83 from the valve seat 82 so that the liquefied gas is supplied through the bore 80 and the liquefied gas supply opening 76 into the pressure chamber bore 18.

From the pressure chamber 66 extends through the grooves 55 of the valve body 50, the distance between the valve seat 57 of the delivery piston tube 35 and the rear end face 52 of the valve body 50 and the passage space 36 of the delivery piston tube 35 into the blind hole 43 of the sealing plug 26. Das The blind hole or the blind bore 43 is arranged running in the longitudinal axis direction and opens into the armature space 23, the blind hole 43 extending over approximately two thirds to three quarters of the length of the sealing plug 26. One, preferably two or more long bores 88 extends from the rear region of the blind hole 43 to the peripheral region 89 of the front end face 25 of the sealing plug 26, so that a communicating connection is established between the armature space 23 and the blind hole 43.

At the peripheral area of the first ring stage, an outwardly leading bore 90 is introduced as a liquid gas drain opening. The bore 90 is extended on the outside by a connecting piece 91 for connecting the liquid gas return line 92 (FIG. 1). The cylindrical sealing plug 26 has a circumferential, outwardly projecting annular web 93 on its outer surface. The ring web 93 also serves, among other things, for the axial fixing of a locking ring 94 encompassing the pump housing 15 on the outside or a coil housing cylinder 95 arranged directly adjacent to the locking ring 94. In cross section, the locking ring 94 forms two legs 96, 97 arranged at right angles to one another, one leg 96 rests on the outside of the pump housing 15 and the other leg 97 protrudes outwards and rests on the coil housing cylinder. The bobbin case cylinder 95 consists of a cylinder wall 98 and a cylinder base 99, which is connected laterally to the cylinder wall 98 and points inwards and has a hole, so that the bobbin case cylinder 95 points from the rear to the bobbin case 15 with the cylinder base 99 to the rear is pushed on until the cylinder wall 98 abuts a housing wall 100 projecting vertically outward from the coil housing 15 and thus delimits an annular chamber 101 with an approximately rectangular cross section for receiving a coil 102.

The coil housing cylinder 95 and the locking ring 94 are thus clamped between the housing wall 100 and the ring web 93 of the sealing plug 26 and fixed in their axial position. The leg 96 of the locking ring 94 is chamfered on the inner edge of its end face, a sealing ring 103, such as, for example, between the bevel formed therein and the ring web 93. B. an O-ring is clamped.

The coil 102 is approximately rectangular in cross section and is cast into a support body cylinder 104 with a U-shaped cross section by means of epoxy resin, so that the coil 102 and the support body cylinder 104 form a one-piece coil module. The support body cylinder 104 has a cylinder wall 105 and two side walls 106, 107, which protrude radially from the cylinder wall 105 and delimit the space for the coil 102, the cylinder wall 105 extending laterally beyond the rear side wall 106, so that its end face 108, the face 109 of the side walls 106, 107 and the inner surfaces of the cylinder wall 106 and the front side wall 107 fit positively in the annular chamber 101.

In the area of the pump housing 15, which is arranged between the coil 102 and the armature space 23, a material 110 with low magnetic conductivity, e.g. Copper, aluminum, stainless steel, introduced to avoid a magnetic short circuit between the coil 102 and the armature 24.

In this initial position, a liquid gas under a pre-pressure is supplied from the liquid gas tank into the pressure chamber 66 by means of the feed pump 112 and the liquid gas supply line 113 through the liquid gas supply valve 78. From the pressure chamber 66, the liquid gas flows through the grooves 55 introduced in the jacket area of the valve body 50, through the guide tube 40 into the gap between the valve seat 57 of the delivery piston tube 35 and the rear end face 52 of the valve body and through the passage space 36 of the delivery piston 35 into the blind hole

43 of the sealing plug 26. From the rear end region of the blind hole 43, the pressurized liquid gas flows through the bores 88 of the sealing plug 26 and floods the armature space, the regions of the armature space in front of and behind the armature 24 through the grooves 32 made in the armature 24 are communicating with each other, so that the entire anchor space is filled with liquid gas. Through the bore 90 and the connecting piece 91, the liquefied gas is passed through a liquefied gas return line 92 back into the liquefied gas tank 111.

There is thus the starting position of the delivery piston element

44 a from the liquid gas supply valve 78 via the pressure chamber 66, the passage space 36 of the delivery piston 35, the blind hole 43 and the bore 88 in the plug 26, the armature space 23 and the bore 90 with the connecting piece 91 extending flow path for the liquid gas, so that liquid gas continuously is fed and flushed through the passage, the pressure chamber being supplied and flooded directly from the liquid gas tank 111 becomes .

The admission pressure of the liquid gas is greater than the pressure drop occurring in the flow path, so that a continuous purging of the reciprocating piston pump 1 is ensured, and is lower than the passage pressure of the auxiliary pressure valve 74, so that no liquid gas is conveyed into the combustion chamber 4 in the starting position of the delivery piston element 44 .

If the coil 102 is excited by the application of an electrical current, the armature 24 is moved forward in the impact or injection direction by the magnetic field generated in this way. The movement of the armature 24 and the delivery piston tube 35 connected to it in a non-positive manner acts during a forward stroke over the length s (corresponds to the distance between the valve seat 57 of the delivery piston tube 35 and the rear end face 52 of the valve body 50 in the starting position) only the spring force of the spring 38 counter. The spring force of the spring 38 is so soft that the armature 24 is moved almost without resistance, but is still sufficient for returning the armature 24 to its starting position. The armature 24 "floats" in the pressure space 23 filled with liquid gas, the liquid gas being able to flow back and forth between the areas in front of and behind the armature 24 in the armature space 23, so that no pressure opposing the armature 24 is built up. The delivery piston element 44, consisting of the armature 24 and the delivery piston tube 35, is thus continuously accelerated and stores kinetic energies ^.

The use of an injection device operating according to the energy storage principle enables the injection of liquid gas under high pressure with very short injection pulses. With such an injection device, it is also possible to inject the liquefied petroleum gas during a work cycle with several injection pulses, for example in order to introduce a large amount of liquefied gas into the combustion chamber under high load or to effect charge stratification in the case of liquefied petroleum gas in the area of the spark plug at the time of ignition is enriched. Instead of the embodiment of the reciprocating piston pump 1 with a return line 92 described above, one without a return line can also be used, which can be connected to conventional liquid gas tanks.

The liquid gas engine according to the invention is preferably designed in the manner of a boxer engine as a crank loop engine. It essentially consists of two opposing cylinders 5 and 5 'arranged in the same axis, in which the working pistons 12 reciprocate in a straight line. The pistons are each connected to their piston rods 153, which also only perform linear reciprocating movements. The piston rods 153 are articulated with their inner ends to a centrally located, rotating crankshaft drive 154, which converts the linear movements of the piston rods into a rotary movement. The crank loop drive is located in a crank loop housing 155 to which the cylinders 5 and 5 'are fastened via partition walls 156. The crank loop drive has a crank loop frame 152, which includes a straight link 158 arranged transversely to the piston rod 153. A sliding block 159, in which a crank pin 160 of a crankshaft is rotatably mounted, moves in the link 158. Such crank loop motors are known for example from DE 29 62 391 AI, DE 32 18 320 AI and EP 187 930 B1.

As a two-stroke engine, these engines can easily be provided with separate lubrication so that the lubricant does not get into the combustion chamber. The combination of liquid gas direct injection with a crank-loop engine operated as a two-stroke engine results in an engine with a low power-to-weight ratio and extremely low pollutant emissions.

Claims

EXPECTATIONS 1. LPG engines with at least one combustion chamber (4), in which a liquefied gas / air mixture is introduced and ignited, the liquefied petroleum gas engine having an injection device (1) which sprays liquid gas via an injection nozzle (2), characterized in that the injection device ( 1) is designed as an injection pump (1) and the injection nozzle (2) opens into the combustion chamber (4), so that the liquid gas is injected directly into the combustion chamber (4). 2. LPG engines according to claim 1, characterized in that the injection device (1) is designed as a high-pressure injection device which, for example, can inject liquid gas with an injection pressure of at least 40 bar, preferably with an injection pressure of about 60 bar. 3. LPG engines according to claim 1 and / or 2, characterized in that the combustion chamber (4) is limited by a cylinder (5), a cylinder head (11) and a piston (12). 4. LPG engines according to claim 3, characterized in that the injector (2) and a spark plug (10) are arranged in the cylinder head (11). 5. LPG engines according to one or more of claims 1 to 4, characterized in that a control device (6) is provided which is connected to the spark plug (10), the control device (6) controlling the ignition timing in accordance with a number of parameters, such as, for example, the outside temperature and the crankshaft position. LPG engines according to one or more of claims 1 to 5, characterized in that the injection device (1) is a reciprocating piston pump (1) which operates according to the energy storage principle, in particular according to the solid-state energy storage principle. Liquid gas engines according to claim 6, characterized in that the reciprocating piston pump is designed with a delivery piston element (44) which stores kinetic energy during an almost resistance-free acceleration phase, which is suddenly transmitted to liquid gas in a pressure chamber (66), so that a pressure surge for spraying of liquid gas is generated by the injection nozzle (2), the means interrupting the resistance-free acceleration phase being a valve which comprises a valve body (50) and a valve seat (57) formed on the delivery piston element (44) and the pressure chamber (66 ) closes, as a result of which the kinetic energy of the delivery piston element (44) is transferred to the fuel enclosed in the pressure chamber (66), the valve seat (57) and the valve body (50) at the end (45) of the delivery piston element (40) at the front in the injection direction. 44) are arranged so that the D Pressure chamber (66) is spatially separated from the delivery piston element (44). LPG engines according to claim 7, characterized in that the pressure chamber (66) is provided with a liquid gas supply opening (76) for supplying liquid gas, the liquid gas supply opening (76) being arranged on a pump housing (15) surrounding the pressure chamber (66) and connected to the liquid gas supply line (113) is, so that the pressure chamber (66) fresh pressurized liquid gas is supplied. 9. LPG engines according to claim 7 and / or 8, characterized in that the injection device is designed as an electromagnetically operated reciprocating pump (1) with a solenoid (102) and the delivery piston element (44) driven by the coil (102), the delivery piston element ( 44) has an approximately cylindrical armature (24) and an elongated delivery piston tube (35), the ends (45, 46) of the delivery piston tube (35) extending in the longitudinal axis direction beyond the anchor (24) and in each case with recesses which can be displaced in a form-fitting manner and in the longitudinal axis direction are stored. 10. LPG engines according to claim 9, characterized in that the delivery piston tube (35) is non-positively connected to the armature (24), the valve seat (57) being arranged at the front end (45) of the delivery piston tube (35). 11. LPG engines according to claim 10, characterized in that the valve body (50) is an elongated substantially cylindrical solid body which is axially displaceably mounted in a guide tube (40), the valve body (50) on its circumference with the extending in the longitudinal direction Grooves (55) are provided, which form a passage from the pressure chamber into a passage space (36) within the delivery piston tube (35), the passage is blocked when the delivery piston tube (35) rests with its valve seat (57) on the valve body (50), as a result of which the pressure chamber (66) is closed. 12. LPG engines according to claim 10, characterized in that the valve body is a ball (50a), wherein a ball seat (41a) is provided which forms an abutment for the ball (50a) so that it cannot be moved further back , and the ball seat (41a) has at least one groove (41b) which forms a passage from one of the pressure chambers (66) into a passage space (36) within the delivery piston tube (35), the passage being blocked when the valve seat (57 ) abuts the valve body (50), whereby the pressure chamber (66) is closed. 13. LPG engine according to one or more of claims 9 to 12, characterized in that the approximately cylindrical armature (24) has a front and rear end face (28, 29) and a lateral surface (30) in the injection direction, and one of the has the rear end face (28) up to approximately the longitudinal center of the armature (24) from the rear to the front outside conical surface (31). 14. LPG engine according to one or more of claims 9 to 13, characterized in that the reciprocating pump (1) has a pump housing (15) with an armature bore (16) in which an armature space (23) through the armature bore (16), in Backward injection direction is limited by a plug (26, 26a) and forward injection direction by a first ring step (21), in which the armature (24) by a magnetic coil (102) and a spring acting on the armature (24) in the longitudinal direction (38) is reciprocated, the anchor (24) is formed on its jacket area with at least two grooves (32) that run as symmetrically as possible from the circumference in the longitudinal axis direction. 15. LPG engine according to claim 14, characterized in that the armature (24) assumes an initial state by the spring action of the spring (38) when the coil (102) is switched off, and in this initial state of the pressure chamber (66) by the Grooves (55) in the valve body (50) and the passage space (36) of the conveying body (35) and through a blind hole (43) or one or more bores (38) a continuous flow path for supplied pressurized liquid gas is formed in the sealing plug (26). 16. LPG engine according to claim 15, characterized in that the armature space (23) is connected via an outwardly leading bore (90) and a connecting piece (91) to the liquid gas discharge line (92). 17. LPG engine according to claim 14 or claim 14 and claim 15 and / or claim 16, characterized in that the sealing plug (26a) is provided with a through-hole with which liquefied petroleum gas is discharged from the injector into the liquefied gas discharge line (92). 18. LPG engine according to claim 17, characterized in that a cross-flow bore (125) is provided, through which liquefied petroleum gas can be supplied directly in the armature space (23), and the sealing plug (26a) has bores (88) which the armature space (23) Connect with a continuous bore of the sealing plug (26a) so that a cross-flow path for flushing the armature space (23) is formed, which is independent of is a passage space (36) in the delivery piston element (44). 19. LPG engine according to claim 8 or claim 8 and one or more of claims 9 to 6, characterized in that the pressure chamber (66) is limited by a parking pressure valve (74) that opens from a predetermined pressure and the passage into a fuel delivery line (72) to the injection nozzle (2). 20. LPG engine according to one or more of claims 7 to 19, characterized in that the pressure chamber (66) is only slightly larger than the space required for the pushing motion of the valve body (50) during the injection process. 21. LPG engine according to one or more of claims 1 to 20, characterized in that the LPG engine is designed as a two-stroke engine. 22. LPG engine according to one or more of claims 1 to 21, characterized in that the LPG engine is designed as a crank-loop engine. 23. A method of operating a liquefied petroleum gas engine according to one or more of claims 1 to 22, wherein the liquefied petroleum gas engine has a combustion chamber, characterized in that liquid gas is injected intermittently directly into the combustion chamber by means of an injection device (1) designed as an injection pump (1). 24. The method according to claim 23, characterized in that the liquid gas is injected under high pressure of at least 40 bar, preferably 60 bar. 25. The method according to claim 23 and / or 24, characterized in that a piston pump working according to the energy storage principle, in particular according to the solid-state energy storage principle, is used as an injection device.