DE102006061568A1 - Method for operating combustion engine, preferably for motor vehicle, involves supplying compressed air outside full-load operation to engine - Google Patents

Abstract

A method for operating a combustion engine (10) requires storing compressed air at times in a compressed air store (58), combusting fuel at times in a combustion chamber (18), driving a piston (16) and supplying compressed air to the combustion engine (10) at least at times outside a full-load-operating-state.

Description

State of technology

The The invention relates to a method for operating an internal combustion engine according to the preamble of claim 1.

From the DE 10 2004 028 216 A1 It is known to use the internal combustion engine at least temporarily, for example in a partial load operation, as a compressor and thereby to store compressed air in a pressure accumulator. The stored compressed air can then be supplied to the combustion chambers in a full-load operating state of the internal combustion engine, thereby increasing the filling and ultimately the torque. Thus, such an internal combustion engine has a "boost" function by which, for example, during an overtaking of a vehicle, in which such an internal combustion engine is installed, a lasting up to a few seconds significant and significant increase in torque can be effected.

epiphany the invention

task The present invention is a method for operating a To provide internal combustion engine, which has a compact design of the Internal combustion engine allows with good start and emission characteristics and at the same time a long life.

These The object is achieved by a method according to claim 1. Advantageous developments are in subclaims specified. Important features are further in the following description and indicated in the drawing, these features also in very different Combinations for the invention may be essential without being referred to in detail.

at the method according to the invention the compressed air of the internal combustion engine is at least temporarily also outside a full load operating condition fed. Thus, the scope of application of the pure "boost" function is significantly expanded. According to the invention was namely recognized that outside too a full load operating condition in certain operating situations or a need for certain components of the internal combustion engine for the feed compressed air. This need is achieved by the method according to the invention covered. In this case, the internal combustion engine in the non-fired operation be used as a compressor, so that eliminates an additional compressor can. This can be done, for example, by installing an additional Brennraumventils be realized, through which the air, the was compressed in the combustion chamber, enters the pressure accumulator. By Such a combustion chamber valve can, as explained below, be discharged from the accumulator again in the combustion chamber.

In a first preferred embodiment, the compressed air is supplied to a first igniting combustion chamber for a direct start. Such a direct start is for example in the DE 31 171 44 A1 discloses, the disclosure of which is expressly made the subject of the present disclosure. In such a direct start, the internal combustion engine is started without the aid of a starter. It is usually planned only for internal combustion engine with gasoline direct injection and spark ignition. The cylinder filling with the engine stopped is a decisive factor for the start success. By injecting compressed air into the first firing combustion chamber accelerates this particularly powerful, which increases the starting reliability.

there can the feeder the compressed air from a current temperature of the internal combustion engine depend. The main shortcoming of the starter-free direct start is namely the start reliability at very high temperatures. Therefore, to the pressure accumulator too spare, for example, compressed air can only be supplied when the internal combustion engine has a particularly high temperature.

Further It is conceivable that the air is added to fuel before it gets into the combustion chamber. This corrects the defect that occurs with Direct fuel injection direct injection, the mixture formation only possible with low charge turbulence is. By the method according to the invention the mixture formation becomes more homogeneous overall.

Further is contemplated according to the invention, that heats the compressed air and then fed to a combustion chamber becomes. This can be during direct start or at the start of the internal combustion engine then done if this and / or the environment is a very low Have temperature. This can improve the mixture formation become. The inventive method However, not only limited to the start of the engine, but can basically done so long until the combustion chamber temperature for a good mixture formation is sufficiently high. Again, that warming the Air from a temperature of the internal combustion engine and / or the environment depend can save resources.

Alternatively, the air may also first be cooled and then fed to a combustion chamber. This is advantageous if the internal combustion engine is very hot and thus the Gemi processing is impaired.

proposed Also, that the compressed air is an exhaust duct between an exhaust valve and a catalyst supplied and at the same time the internal combustion engine with fuel surplus is operated. This development of the invention is related with a special catalyst heating strategy. In such, the internal combustion engine with fuel surplus operated. With the addition of air between the exhaust valves and the catalyst can in this case a chemical reaction of this excess fuel respectively. This after-reaction releases heat, which makes the catalyst faster heats up, making the catalyst faster in its operating range and can bring its full power. By the method according to the invention can be on a previously common Additional pump can be dispensed with.

A another particularly advantageous embodiment of the method according to the invention is that the compressed air is a secondary system the internal combustion engine is supplied to the pressurization. This is based on the idea that there are numerous systems Internal combustion engine gives that for their operation a certain hydraulic or pneumatic pressure need. This is mostly at the start of the engine mostly not yet. This deficiency is due to the development of the invention Fixed.

Especially this is advantageous if the secondary system comprises a lubrication system. In the currently mostly used gear pumps for the pressure build-up usual Lubricating systems in internal combustion engines is a certain minimum speed the internal combustion engine required to one for the lubrication of all Stock sufficient oil pressure provide. This speed usually corresponds to the idle speed. As long as this speed is not reached, it can lead to a contact between the bodies to be lubricated come. By the development of the invention The lubrication system can already before a start of the internal combustion engine be pressurized, so that already at the first turns the crankshaft of the engine lubricated the bearings sufficiently are. About that In addition, by such pressurized already before the start Lubricating system Any existing hydraulic camshaft adjustment Already ready for the first revolutions of the internal combustion engine be what the starting behavior and the emission behavior of such Internal combustion engine can improve. This will increase the life of the Internal combustion engine decisively improved.

A Realization of such a pneumatically pressurized lubrication system, The most simple is that with the compressed Air is applied to one side of a pressure transducer, the other Side applied to the lubrication system. This is easy, even one pressure ratio can be realized by such a pressure transducer.

Short description the drawings

Hereinafter, a particularly preferred embodiment of the present invention will be explained in more detail with reference to the accompanying drawings. The only 1 shows a schematic representation of an internal combustion engine.

embodiment the invention

An internal combustion engine carries in 1 Overall, the reference number 10 , It includes several cylinders, of which for purposes of illustration 1 however, only one with the reference numeral 12 is shown. The other cylinders are, however, identically constructed.

The cylinder 12 includes a cylinder head 14 that together with a piston 16 a combustion chamber 18 limited. Fresh air enters the combustion chamber 18 via an inlet valve 20 and a suction tube 22 , Fuel enters the combustion chamber 18 directly through an injector 24 one in the combustion chamber 18 Existing fuel-air mixture is from a spark plug 26 inflamed. Hot combustion gases are emitted from the combustion chamber 18 via an exhaust valve 28 and an exhaust pipe 30 derived. The exhaust gases are through a catalyst 32 cleaned of pollutants.

In operation of the internal combustion engine 10 is about the piston 16 a crankshaft 34 set in rotation. For optimum operation of the internal combustion engine 10 become the opening and closing times of the inlet valve 20 and the exhaust valve 28 via respective adjustable camshafts 36 and 38 adjusted.

The cylinder 12 also has a compressed air inlet and outlet 40 to which a compressed air line 42 connected. This leads to a combustion chamber valve 44 , which is designed as a two / two-way valve with an open and a closed position. From the combustion chamber valve 44 guides the compressed air line 42 continue to a heater 46 with an electrical supply 48 connected is. From the heater 46 guides the compressed air line 42 to a fuel injection valve 50 which is connected to a fuel supply 52 connected. This is the same fuel supply as the injector 24 supplies the fuel directly into the combustion chamber 18 injects. About a branch point 54 guides the compressed air line 42 continue to a shut-off valve 56 , and from there to a compressed air storage 58 , This one is with a heat sink 60 provided, on which in turn cooling fins 62 are formed.

From the branch point 54 branches from the compressed air line 42 a secondary air line 64 off, via a shut-off valve 66 to a nozzle 68 leads. This is in the exhaust pipe 30 between exhaust valve 28 and catalyst 32 arranged. From the branch point 54 further branches a pressure line 70 off, via a shut-off valve 72 to a pressure transducer 74 leads. This includes in a housing 76 a stepped piston 78 , on the one hand a compressed air chamber 80 and on the other hand, a lubricant chamber 82 limited. The lubricant chamber 82 leads via a lubricant line 84 to a crankshaft bearing 85 as well as to the bearings (not shown) of the two camshafts 36 and 38 and to their adjusting devices, also not shown. The lubricant line 84 is also still with a gear pump 86 connected.

The operation of the internal combustion engine 10 is controlled by a control device 88 controlled and regulated. This receives signals from various sensors, such as a pressure sensor 90 , which is the hydraulic pressure in the area of the crankshaft bearing 85 detected, as well as from a temperature sensor 92 , which is the temperature of the exhaust gas immediately upstream of the catalyst 32 detected. Furthermore, receives the control and regulating device 88 Signals from a pressure sensor 94 , which is the current pressure in the compressed air reservoir 58 detected. To be controlled by the control and regulating device 88 various adjusting devices, such as the combustion chamber valve 44 , the electrical supply 48 the heater 46 , the fuel injection valve 50 , the shut-off valve 56 , the shut-off valve 66 , the shut-off valve 72 , the adjustment of the two camshafts 36 and 38 , as well as at least indirectly the spark plug 26 as well as the injector 24 ,

Compressed air is in the compressed air reservoir 58 stored in that in the non-fired operation of the internal combustion engine 10 For example, in a coasting operation, the combustion chamber valve 44 and the shut-off valve 56 , with closed valves 66 and 72 , in each case during the compression stroke in the combustion chamber 18 open and thereby the in the combustion chamber 18 compressed air through the combustion chamber valve 44 and the compressed air line 42 in the compressed air storage 58 is directed. On this can the compressed air storage 58 be supplied with compressed air, without an additional compressor is required.

In the 1 shown internal combustion engine 10 does not have a separate electric starter. Instead, the internal combustion engine 10 started via a so-called "direct start procedure". In such a case is at a stationary internal combustion engine 10 by a deliberately initiated combustion in a closed combustion chamber, for example, the combustion chamber drawn here 18 , the multi-cylinder internal combustion engine 10 The piston 16 accelerated out of the state. Is this first ignition in the combustion chamber 18 sufficiently powerful, the subsequent combustion cylinder can the internal combustion engine 10 accelerate up to idle speed.

A problem with such a direct start method, however, is the start-up reliability at high temperature of the internal combustion engine 10 , The cylinder filling decreases because of the fixed geometric conditions and the decreasing density of the air with increasing temperature. For this reason, in the present internal combustion engine 10 at a direct start the combustion chamber valve 44 and the shut-off valve 56 opened and thereby compressed air in the first igniting combustion chamber 18 blown. This compressed air is due to the heat sink 60 and the cooling fins 62 cooled, causing the air filling in the combustion chamber 18 is improved again. At least the combustion chamber valve 44 will be closed again. By this addition in the combustion chamber 18 Existing air mass becomes the first combustion in the combustion chamber 18 even more powerful, what the starting reliability of the internal combustion engine 10 increased overall.

However, it is found that the internal combustion engine 10 not hot, but is very cold, for example, after resting for a long time at low outside temperatures, is compressed air from the compressed air reservoir during blowing 58 over the shut-off valve 56 , the compressed air line 42 and the combustion chamber valve 44 the electrical supply 48 the heater 46 activated and thereby the injected compressed air (or, when injecting fuel through the fuel injection valve 50 , the injected fuel-air mixture heated). By such a preheating of the injected air (or the injected fuel-air mixture) at low temperatures of the internal combustion engine, the mixture formation in the combustion chamber 18 be improved, which also increases the start reliability. This leads to a more complete combustion of the fuel / air mixture. The start becomes more reliable and powerful. Likewise, the required fuel mass is reduced, which simplifies the design of the fuel system. The largest injection quantity from the injector 24 in the combustion chamber 18 is to be introduced, namely that injection quantity is usually that in a direct start at very low temperatures of the internal combustion engine 10 is required. In addition, by a sol Ches method even the emission behavior of the internal combustion engine 10 improved.

As is known, the catalyst is needed 32 a certain minimum operating temperature to that through the exhaust pipe 30 To clean flowing exhaust gas in a satisfactory manner. Immediately after the start of the cold engine 10 indicates the catalyst 32 this operating temperature is not up yet. It is therefore desirable to use the catalyst 32 To heat up as quickly as possible to the required minimum operating temperature. For this purpose, in the present case immediately after the start of the internal combustion engine 10 the shut-off valve 66 open and thereby air in the exhaust pipe 30 between exhaust valve 28 and catalyst 32 blown. At the same time, the internal combustion engine 10 operated with excess fuel. The extra and in the combustion chamber 18 unburned fuel now reacts with the additional in the exhaust pipe 30 introduced compressed air in a chemical exothermic reaction. This increases the temperature of the exhaust gas, which is the catalyst 32 is fed, causing the catalyst 32 heated up faster.

Before the internal combustion engine 10 is started at all, but are the first of all the shut-off valve 56 and the shut-off valve 72 open. This will cause the pressure transducer 74 pressurized, so that also the lubricant line 84 is pressurized. Corresponding are the crankshaft bearings 85 supplied with lubricant, even before the internal combustion engine 10 ever started. Also the adjustment of the camshafts 36 and 38 are ready in this way, even before the internal combustion engine 10 ever starts. Due to the prevailing oil pressure in the crankshaft bearings 85 There friction is reduced, which in turn the start reliability of the engine 10 improved. In addition, the wear of the bearing shells (not shown) is reduced, and this even before the gear pump 86 ever starts operating. Because of the pressure transducer 74 a stepped piston 78 may include, in the lubricant line 84 a significantly higher pressure can be achieved than in the compressed air reservoir 58 prevails. Usually, the pressure transducer 74 only active during startup, for a very short time (usually less than 1 second). The corresponding shut-off valve 72 So it's only open for a short time.

In an embodiment, not shown, branches to the compressed air inlet and outlet 40 leading compressed air line 42 unlike the secondary air line 64 and the pressure line 70 from the lowest point of the compressed air storage 58 from. This has the following meaning: When compressing and expanding the air in the compressed air reservoir 58 condenses the existing moisture in the air and is reflected as condensation at the lowest point of the compressed air reservoir 58 low. By the said compressed air line 42 at the lowest point of compressed air storage 58 is connected, for example, the direct start of the internal combustion engine 10 not just pure air or, when operating the fuel injector 50 , no fuel / air mixture through the compressed air inlet and outlet 40 in the combustion chamber 18 blown, but a fuel / air / water mixture. As a result, on the one hand prevents the volume available for the compressed air in the compressed air reservoir 58 gradually decreases. On the other hand, the additional injection of water into the combustion chamber 18 An additional amount of ignition cores created that ignite the fuel in the combustion chamber 18 favor. Alternatively, but also not shown, could also be the secondary air line 64 from the lowest point of compressed air storage 58 branch. In this case, for example, in the uncontrolled overrun operation, the condensed water could easily into the exhaust pipe 30 be drained.

From the above functional description of in 1 illustrated internal combustion engine 10 shows that in all the illustrated method, the compressed air from the compressed air reservoir 58 especially for the start of the internal combustion engine 10 and the initial operation of the internal combustion engine 10 is used, ie outside a full load operating condition. Although this is the description of the in the beginning 1 illustrated embodiment is not explicitly mentioned, it is understood that the drawn there internal combustion engine 10 very suitable for driving a motor vehicle.

In 1 is a gasoline engine shown. The basics of air injection, for example, to pressurize the lubricant line 84 however, are equally applicable to a diesel internal combustion engine. Also, the injection of heated air into the combustion chamber 18 to improve the mixture formation when starting the internal combustion engine can also be applied to a diesel internal combustion engine, even if there is a common direct start, of course, can not be provided. In such a case, moreover, the control of the electric heater 46 . 48 be taken over by the control of the glow plug.

From the above, one also recognizes that the combustion chamber valve 44 must have a relatively high dynamics, whereas the other shut-off valves, in particular the shut-off valve 56 , do not have to have such high dynamics, so can be made relatively inexpensive. When designing the shut-off valve 56 the design focus can be mainly on the tightness, since this is closed when the engine is switched off and the pressure in the compressed air reservoir 58 should be able to hold as long as possible. In principle, all valves shown can be inexpensively designed as solenoid valves.

Claims (12)

Method for operating an internal combustion engine ( 10 ), preferably for driving a motor vehicle, in which at least temporarily fuel in a combustion chamber ( 18 ) and thereby a piston ( 16 ) is driven, and in the temporarily compressed air in a pressure accumulator ( 58 ) and the internal combustion engine ( 10 ) is temporarily supplied, characterized in that the compressed air of the internal combustion engine ( 10 ) is at least temporarily supplied outside a full load operating condition. A method according to claim 1, characterized in that the compressed air for a direct start of a first igniting combustion chamber ( 18 ) is supplied. A method according to claim 2, characterized in that the supply of the compressed air from a current temperature of the internal combustion engine ( 10 ) depends. Method according to one of claims 2 or 3, characterized in that the air is added to fuel before it enters the combustion chamber ( 18 ). Method according to one of the preceding claims, characterized characterized in that the compressed air is heated or cooled and then fed to a combustion chamber becomes. A method according to claim 5, characterized in that the heating or cooling of the air from a temperature of the internal combustion engine ( 10 ) and / or the environment. Method according to one of the preceding claims, characterized in that the compressed air an exhaust pipe ( 30 ) between an outlet valve ( 28 ) and a catalyst ( 32 ) and at the same time the internal combustion engine ( 10 ) is operated with excess fuel. Method according to one of the preceding claims, characterized in that the compressed air is a secondary system ( 82 - 86 ) of the internal combustion engine ( 10 ) is supplied to the pressurization. Method according to claim 8, characterized in that the secondary system is a lubrication system ( 82 - 86 ). A method according to claim 9, characterized in that with the compressed air, a compressed air chamber ( 80 ) of a pressure transducer ( 74 ), which is connected to a lubricant chamber ( 82 ) the lubrication system ( 82 - 86 ). Method according to one of claims 8 to 10, characterized in that the compressed air to the secondary system ( 82 - 86 ) before a start of the internal combustion engine ( 10 ) is supplied. Method according to one of the preceding claims, characterized in that condensate, which is obtained during the compression and expansion of the air, with the compressed air to the combustion chamber ( 18 ) is supplied.