Engine brake apparatus for a turbocharged IC engine

The invention relates to an engine braking device for a turbocharged internal combustion engine, a method for Operating the engine braking device and an internal combustion engine with such an engine braking device.

In the field of turbocharged internal combustion engines it is known that in addition to the engine brake of the internal combustion engine and the turbocharger with its own auxiliary braking device is provided. In a typical operation, always makes such an auxiliary braking device for converting the turbocharger of a power or drive means to a braking device, when an auxiliary braking operation is required. This is generally done by modifying the exhaust and / or Ansaugzeitsteuerung of the turbocharger in such a manner that a movement the cylinder piston of the lowest possible power loss converted to the largest possible power loss is specifically, when the braking of the turbocharger is performed. Such power absorption applies the principle of Air compressor, ie the cylinder piston to the practice in the engine's cylinders trapped air from working, when braking is required.

There are here two fundamentally different concepts, with the aid of a turbocharger, an auxiliary braking device to realize for an internal combustion engine:

According to a first approach is attempted by reducing of the exhaust-side effective cross-section of the pressure in the to increase exhaust pipe so as to some extent a backpressure to obtain the on the gas in the cylinder volume of the internal combustion engine Gets transferred. Due to the higher pressure in the Cylinder interior must cylinder piston a larger work perform, which ultimately leads to a brake. This is implemented in different ways in practice:

In DE 195 43 190 A1 is an auxiliary braking device for described a supercharged internal combustion engine with a Exhaust gas turbine with an adjustable guide variably adjustable turbine geometry is provided. The Guide grid comprises vanes, with the help of an actuator so can be set so that the effective, ie effective turbine cross section of the turbine is varied. This allows depending on the operating state of the internal combustion engine different high exhaust back pressures in a portion be realized between the cylinders and the turbocharger, whereby the power of the turbine and the power of the compressor can be adjusted as required.

To the braking operation of the internal combustion engine an engine braking effect achieve, this guide grid is in a stowed position so placed that the effective turbine cross-section significantly is reduced. In a line section between the Cylinders and the turbine a high exhaust back pressure builds up so with the consequence of that exhaust at high speed through the channels between the vanes of the turbine flows and the turbine wheel supplied with a high pulse. The turbine power is transmitted to the compressor, after which the charge air supplied to the engine by the compressor is put under increased boost pressure. Thereby, the Cylinder intercooled acted upon with a higher boost pressure, gas side is located between the cylinder outlet and the turbocharger increased exhaust back pressure at which the a draining in the cylinder compressed air through open brake valves in the exhaust system in counteracting. In the engine braking mode the plunger must compression work against the high pressure perform in the exhaust line, whereby depending on the position of the Guide grid reaches a more or less strong braking effect becomes.

Additionally or alternatively to this provided with guide grids Turbines can also be provided a flap which in the exhaust line downstream of the turbine is arranged. This flap can in a braking operation of the engine braking device transversely or substantially transversely pivoted in the exhaust line be and so reduces the effective cross-section in the exhaust line, whereby upstream in the direction of increased cylinder outlets of the pressure in the exhaust line, and thus a braking effect is achieved. A turbocharger with a such flap is described for. example, in DE 40 24 572.

According to a second concept is to increase the engine braking power an exhaust gas recirculation are provided in Engine braking operation is activated. In this case, exhaust gas from the Exhaust gas line, usually during an engine braking operation comprising unburned combustion air and by the compression in the cylinders a higher temperature level comprises again the cylinders of the internal combustion engine supplied.

In DE 198 53 127 A1 is such an engine braking device described with exhaust gas recirculation. There, the exhaust gas is diverted upstream of the turbocharger and upstream in the direction of Cylinder inlets with the compressed in the compressor of the turbocharger Combustion air of the intake tract and mixed the cylinders supplied. In the line for the exhaust gas recirculation a check valve is provided. This check valve is also necessary to pressure differences between the the exhaust side and the charge air side line to compensate.

All the above auxiliary braking means a turbocharged However, the internal combustion engine is only available for so-called single-stage Turbocharger designed. Modern turbochargers may however have a two-stage turbocharging.

An internal combustion engine with such a two-stage-trained Charging system is for example in the German Published patent applications DE 198 37 978 A1 and DE 195 14 572 A1 described. In such two-stage turbocharged internal combustion engines , the turbocharger group each in series mutually arranged high-pressure stage and low pressure stage on. The exhaust gas from the engine first flows through here the High-pressure turbine, and then the low pressure turbine. In Similarly, the provided for recharging the cylinder First charge air from a low pressure compressor and then compressed by a high pressure compressor and, optionally, after cooling of the charge air in a heat exchanger the charge air side of the internal combustion engine is supplied. In a typical mode of operation of the turbocharger at lower is Speed ​​ranges of the internal combustion engine is operated in two stages. With increasing speed can on stage compression switched exclusively the low pressure compressor be, for example by means of exhaust-side bypass lines the high pressure turbine completely or at least partially is bridged. It makes sense in this case and the high pressure compressor via a charge air side provided Pipe switch completely bypassed.

In such two-stage turbochargers are each in series arranged turbines and compressors for different Boost pressures designed. This has, in practice, means that a huge design effort for the realization of abovementioned auxiliary braking device is required. Around For example, in each case an optimum auxiliary braking mode the different operating modes of the two-stage turbocharger to obtain a plurality of tube switches are essential to each the desired pressures in the exhaust pipes and achieve charge air lines. Such braking devices are therefore very expensive to manufacture, wherein the additional expenses not improve braking quality result Has. Especially with very small turbochargers which all before in internal combustion engines with small displacement for use come, such an auxiliary braking device is not yet been satisfactorily resolved.

The present invention is therefore based on the object, an improved braking device of a two-stage turbocharger an internal combustion engine to provide.

This object is achieved by a braking device solved with the features of claim 1. Further this object is achieved by a method for operating the Braking device having the features of claim 18 and an internal combustion engine having the features of patent claim 24 dissolved.

Accordingly, there is provided:<ul><li>An engine braking device for a turbocharged Internal combustion engine, with an at least two stages formed Charging system, the high-pressure stage, at least one and at least one of the high-pressure stage and / or the low pressure stage exhaust side downstream and comprising charge air side upstream low-pressure stage, with at least one outlet channels with the Internal combustion engine connected and the exhaust side Internal combustion engine downstream arranged exhaust pipe, with at least one closure body which in a exhaust side of the low pressure stage downstream Region of the exhaust line is arranged, wherein the closure body is formed such that the exhaust flow rate and thereby requires a pressure in the exhaust line is changed so that the engine braking power by according to need is adjustable (claim 1). </li><li>A method for operating an engine braking device for a turbocharged internal combustion engine, that means the control device, a first pressure in the front the high pressure turbine exhaust line arranged in a function from a brake mode to a predetermined value is set (claim 18).</li><li>An internal combustion engine having an engine block which has at least comprising a cylinder and at least one Charge-air inlet and at least one exhaust outlet comprises with a designed as a braking device charging (Claim 24).</li></ul>

Advantageous refinements and developments of the invention are the sub-claims and the description with Reference to the drawing.

The invention is described with reference to the figures of the Drawing specified embodiments explained in more detail. It shows:<dl tsize="7"><dt>figure 1</dt><dd>a schematic representation of a first embodiment an inventive two-stage supercharged internal combustion engine with control valve in the exhaust manifold;</dd><dt>figure 2</dt><dd>a second embodiment of the invention, two-stage turbocharged internal combustion engine according to figure 1 with attached exhaust gas recirculation line;</dd><dt>figure 3</dt><dd>a third exemplary embodiment of the invention, two-stage turbocharged internal combustion engine according to figure 1 with variable turbine geometry; </dd><dt>figure 4</dt><dd>a fourth embodiment of the invention, two-stage turbocharged internal combustion engine according to Figure 1 with a twin-flow turbine trained high-pressure turbine;</dd><dt>figure 5</dt><dd>a fifth exemplary embodiment of the invention, two-stage turbocharged internal combustion engine corresponding to Figure 1 wherein the closure body between the high-pressure stage and the low-pressure stage is disposed;</dd><dt>figure 6</dt><dd>a schematic representation of a sixth, particularly preferred embodiment of an inventive two-stage turbocharged Internal combustion engine.</dd></dl>

are in all figures of the drawing identical or functionally identical Elements - unless otherwise indicated - with like reference numerals have been provided. In all figures of the Drawing was also the direction of the exhaust stream and of the charge air flow by the arrows in the corresponding Lines designated.

1 shows a schematic view of a first Embodiment of a braking device according to the invention.

In Figure 1, reference numeral 1 is an internal combustion engine designated. The internal combustion engine 1 is in the present embodiment as six-cylinder diesel engine formed in line construction and thus has six in number arranged mutually cylinder 2. The internal combustion engine 1 has a fresh air side 3 and an exhaust side 4, wherein the inlets 7 to the fresh air side 3 with a charge-air manifold 5 and the outlets 8 of the internal combustion engine 1 is connected on the exhaust side 4 with two exhaust manifolds 6 are.

The internal combustion engine 1 is with a reference numeral 10 designated turbocharger charged. The turbocharger 10 is present embodiment, two-stage design. On Such a two-stage turbocharger 10 includes a high-pressure stage 11 and a low pressure stage 12. The high-pressure stage 11 consists of a high pressure turbine 13 and a high pressure compressor 14 to one another via a common shaft 15 are rigidly coupled. The low-pressure stage 12 is accordingly from a low pressure turbine 16 and a low pressure compressor 17, which also has a common shaft 18 are coupled together. The high pressure stage 11 is the Low-pressure stage 12 upstream.

The turbine wheel diameter of the low pressure turbine 16 is in the present embodiment is greater than that of the high pressure turbine 13 is formed, the impeller diameter ratio between low and high pressure turbine typically, but not necessarily, in the range 1.2 to 1.8 lies. In the same way, the compressor wheel of the high pressure compressor 14 has a smaller diameter than the compressor wheel the low pressure compressor 17 on.

The exhaust manifold 6 is connected upstream to the exhaust gas lines 20, 21, 22, via which the exhaust gas from the cylinders 2 the internal combustion engine 1 can be derived. Similarly Example, charge air lines 23, 24, 25 which are connected upstream of the charge air manifold fifth Via the charging air lines 23, 24, 25 and the compressor 14, 17 is the cylinders 2 of the internal combustion engine 1 charge air supplied.

The two turbines 13, 16 are mutually connected in series , said high pressure turbine 13 to the low pressure turbine 16 is connected via the exhaust pipe 21 and the low pressure turbine 16 in the flow direction of exhaust gas is disposed upstream. Similarly, the low pressure compressor are 17 and the high pressure compressor 14 in series arranged to each other and via a charge air conduit 24 to each other , said low pressure compressor 17 in Flow direction of the charge air to the high pressure compressor 14 is disposed upstream.

Furthermore, a first charge air cooler 26 is provided in the the charge air line 24 between the two compressors 14, 17 is arranged. A second charge air cooler 27 is in the charge air line 25 between the high pressure compressor 14 and inlets 7 of the internal combustion engine 1 arranged. If necessary may on one or in extreme cases, on both intercoolers 26, to dispense 27th

The invention now a variable closure device 30 provided here as a regular or controllable valve is trained. The closure device 30 can, however, as airbrakes, throttle, slide or the like be formed. About one connected to the control valve 30 Actuator 31, the valve 30 is adjustable. The Closure device 30 can not shown in Figure 1 on a Regulating or control device regulated or controlled be formed. The function of such a control device or control device is explained below with reference Figure 6 described in greater detail.

Unlike Figure 1, the arrangement according to Figure 2 In addition, an exhaust gas recirculation line 32. The exhaust gas recirculation line 32 branches off from the exhaust pipes 20, consisting of the Exhaust manifolds 6 come from and branches in the charge air line 25, the high pressure compressor 14 with the charge air manifold 5 combines a. The particular advantage of in Figure 2 arrangement shown is that due the pressure conditions in the exhaust pipes 6, 20 and the Charge air lines 5, 25 provided no non-return valve is and moreover, as explained below , is is also not necessary.

In contrast to the arrangement in Figure 1, the turbocharged Internal combustion engine 1 according to Figure 3 a turbocharger 10 that a high pressure turbine 13 with variable turbine geometry (VTG) has. The functionality of a variable Turbine geometry is in all the figures with an arrow indicated.

In contrast to the arrangement in Figure 1, the turbocharged Internal combustion engine according to Figure 4 is a twin-flow turbine as trained on high-pressure turbine. 13 These Twin-flow high-pressure turbine 13 consists of two parallel arranged mutually turbine wheels 13A, 13B, which together - Coupled - typically rigid. Typically, but not necessarily, these two turbine wheels 13A, 13B the same cross-sectional flow channels of the turbine on.

In contrast to the arrangement in Figure 1 is in fifth Embodiment in Figure 5, the locking device 30 disposed between the high-pressure stage and the low pressure stage 11, 12 is. Since the brake flap 30 here directly to the high-pressure stage acts, this arrangement is distinguished over the arrangement in Figure 1 by the fact that a higher accuracy and speed of control of the high pressure stage 11 is possible.

For optimum adjustment of the two-stage turbocharger 10 at the operating states of the internal combustion engine 1 is per channel 13A, 13B of the dual twin-flow pressure turbine 13 a Bypass line in advantageously symmetrical circuit provided. These each branch of the exhaust manifold as executed, separate pipes 20A, 20B from bypass the twin-flow turbine 13 and open at the same impingement the single-flow low-pressure turbine 16 in the common Line 21 a. Each bypass line 33A, 33B is provided with a downstream diversion arranged tube switch 34A, 34B, the example, be designed as a control valve can, provided. This tube switches 34A, 34B are advantageously in the exhaust manifold or in the housing of the high pressure turbine 13 co-integrated and can as a slide valve, flap, his throttle or the like is performed, and as a program-controlled unit, for example, a CPU, both individually or be driven jointly.

Advantageously, but not necessarily, the Turbine wheels 13A, 13B of the twin-flow high-pressure turbine 13 operated synchronously.

Figure 6 shows a schematic representation of a sixth, particularly preferred embodiment of an inventive two-stage turbocharged internal combustion engine. The preferred arrangement in figure 6 consists essentially of a combination of the different forms of Internal combustion engine 1 according to Figures 1 - 4. The Internal combustion engine 1 is here with a control valve 30, a Exhaust gas recirculation line 32, bypass pipes 33A, 33B therein provided pipe switches 34A, 34B equipped. additionally , the high-pressure stage 11 is a twin-flow high-pressure turbine 13, in which the high-pressure turbine 13A, 13B in each case having a variable turbine geometry.

At this point it should be noted that the low pressure turbine 12 course designed as a twin-flow turbine can be. Moreover, additionally or alternatively the low pressure turbine 12 also includes a variable turbine geometry exhibit.

Figure 6 shows, in addition to a controller 40th The Controller 40 has data inputs and 41 data outputs 42. About the data inputs 41 are, for example, analog Measured variables such as the temperature or pressure of exhaust gas or the charge air, the number of revolutions of the engine, etc., or digital data can be coupled. Depending on this information and generated by a predetermined program of the control means 40 these control signals, at the outputs 42 of the control device 40 tapped.

The data outputs 42 are connected via a plurality of control lines 43-46 with the control valves 34A, 34B, with the twin-flow pressure turbine 13, with the low-pressure turbine 12, and connected to the actuator 31 of the control valve 30th

Further, a throttle 35 is provided in the exhaust gas recirculation line is arranged connected 32nd This is typically also be adjusted via the control device 40 or is activated.

In addition, not yet shown another, in Figure 6 be provided exhaust gas recirculation, in a subset the recirculated exhaust gas to any other desired point the charge-air side is supplied. Typically, but not necessarily, is up to about 50% of the exhaust gas of the Internal combustion engine 10 of the charge air Page 3 returned.

The operation of a turbocharged internal combustion engine 1 is generally known and, for example, in the above- cited documents described in detail, so that is subsequently it received only very briefly:

The six-cylinder diesel engine 1 is a Turbocharger 10 two-stage charging. This requires a double-flow high-pressure stage 11 of a single-flow low-pressure stage 12 upstream. About the of the twin current 13A, 13B and the low pressure turbine 16 driven compressor 14 and 17 the charge air is compressed in the two charge air coolers 26, cooled 27, with a certain percentage (≥ 0) with Exhaust gas from the exhaust gas recirculation line 32 are mixed and the charge air side 3 of the internal combustion engine 1 is supplied.

To control the reed switch 30, 33A, 33B, the closure body and the adjustable variable in geometry Turbines 13, 16 in dependence on operating parameters A1 - On these are connected to an electronic engine control 40, for example, a CPU connected to the operational optimum for a Distribution of the exhaust gas mass flow provides. By possible setting of different pass rates, flow rates and turbine positions advantageously obtained an additional degree of freedom for the allocation of the total Amount of exhaust gas of the auxiliary brake operation of the turbocharger 10 is of particular importance.

The method of operation of the auxiliary braking device driven turbocharger 10 of the invention based Figure 6 illustrates in more detail:

In closed bypass valves 34a, 34b and a controllable Exhaust brake valve 30 is an increased engine braking power represented, caused by an increased exhaust gas pressure through the small high-pressure stage 11 is possible. Using of different sized channels 13A, 13B of the high-pressure twin turbine 13 and with separate control of the respective Bypass valves 34A, 34B, the corresponding speed range be optimally adapted in the braking mode. The different Channel diameters of the two high-pressure turbines 13A, 13B may be due to their variable turbine geometry specifically by suitable control of the motor controller 40 set to. This allows a differential division the exhaust gas mass flow at high pressure and low pressure stage 11, 12 split.

This exhaust gas mass flow can therefore influence as follows:<sl><li>1. leaves With a suitable setting of the control valve 30 the effective cross section of the exhaust pipe 22 targeted set to. </li><li>2. The high-pressure turbines 13A, 13B and advantageously and the low pressure turbine 16 have a variable Turbine geometry. With a suitable control , the effective channel cross section of the respective Turbines more or less be large.</li><li>3. Use the bypass valves 34A, 34B can be adjusted, what proportion of the exhaust gas, the high-pressure turbine 13A, 13B flows through and how much of the high-pressure turbine 13A, 13B bridged.</li></sl>

Through the above measures, ie by appropriate control and / or regulating the aforementioned elements can be defined an exhaust-side pressure P1 in the exhaust pipes 6, 20 and thus also set in the cylinders. 2 In a particularly advantageous embodiment, especially in the presence an exhaust gas recirculation line 32 in accordance with Figure 6, can thus be ensured that the exhaust side pressure P1 in the exhaust lines 20 is always greater than the charge air-side Pressure P2 in the charge air line 25. As this always a pressure gradient between the exhaust side and upload airside is the area of ​​the exhaust gas recirculation line 32, is Here advantageously, no check valve in the exhaust gas recirculation line 32 required.

In a further advantageous embodiment, it can be ensured be that of the exhaust-side pressure P1 is always constant remains.

Additionally, through a different size of the channels 13A, 13B of the twin-flow turbine 13 with separate control the bypass valves 34A, 34B, an optimized dose of recirculated exhaust gas amount (EGR amount) to the respective desired Operating state allows. An additional EGR-valve, as for example in the state of the aforementioned Technology is imperative, is not necessary here.

6 shows yet a throttle 35 in the exhaust gas recirculation line 32 is arranged through which the exhaust gas mass flow through the Exhaust gas recirculation line 32 in addition with a suitable control can be dosed. This allows the engine characteristics specifically influenced, for example, the engine operating values with regard to the emission of pollutants (N_ox, CO, CO₂) and in terms of fuel consumption largely optimal can be set. The particular advantage of this Exhaust gas recirculation according to the invention is that the Exhaust stream already solely by the pressure difference between the exhaust side and charge air side is guaranteed. Therefore, it is fully sufficient to merely a flow restrictor in the exhaust gas recirculation line to provide 32, wherein to this - as already mentioned - without significantly affecting the Function of the auxiliary brake means be omitted can.

Of course, the invention is not limited to two-stage turbocharger trained limited, but can Rather expand to three- or multi-stage turbocharger.

The two turbocharger stages are in the present embodiment advantageously part of a single turbocharger and are thus in this case a turbocharger integrated. However, these beneficial integration is two Turbocharger stages in a turbocharger not mandatory, but it could be the same function also by two separate, successively reach turbochargers connected, although this arrangement assembly technology and because of the higher cost is less preferred.

Finally, the invention is not limited to diesel engines limited in-line six cylinder design, but can be applied to any internal combustion engines with any number of whatever arranged Expand cylinders.

In the above embodiments, the low-pressure stage one towards the high-pressure stage of larger diameter the respective turbine wheels. However, this is not mandatory, but it would also be conceivable, that the two turbine stages a same turbine wheel exhibit or the high-pressure stage the larger having wheel diameter.

In the above embodiments, each A Controlling the closure body (valves, butterfly valves, pipe switch etc.), and geometry of the turbine by the motor control described. Of course, leave some or also control all of these items elsewhere or by a specially provided control device to the desired operating state to adjust. The setting of the closure body or the turbine geometry can be electrically, pneumatically, hydraulically or be carried out mechanically.

In summary it can be stated that by such described designed two-stage turbocharger in complete Departure from previously known solutions specifically adjustable, the flue gas side pressure, in particular a constant Printing, in a very simple manner can be adjusted without a structurally complex, expensive solution prior Technology must be taken into account.

The present invention was from the foregoing description as shown, the principle of the invention and its practical application in the best possible to explain, however, can be understood that the invention with suitable modification realized in diverse other embodiments.

LIST OF REFERENCE NUMBERS

<dl tsize="1" compact="compact"><dt>1</dt><dd>Internal combustion engine</dd><dt>2</dt><dd>cylinder</dd><dt>3</dt><dd>Charge air side</dd><dt>4</dt><dd>exhaust side</dd><dt>5</dt><dd>Charge-air manifold</dd><dt>6</dt><dd>Exhaust manifold</dd><dt>7</dt><dd>inlets</dd><dt>8th</dt><dd>outlets</dd></dl><dl tsize="8" compact="compact"><dt>10</dt><dd>turbocharger</dd><dt>11</dt><dd>High-pressure stage</dd><dt>12</dt><dd>Low pressure stage</dd><dt>13</dt><dd>High pressure turbine</dd><dt>13A, 13B</dt><dd>Turbine wheels of the twin-flow high-pressure turbine, channel</dd><dt>14</dt><dd>High-pressure compressors</dd><dt>15</dt><dd>wave</dd><dt>16</dt><dd>Low pressure turbine</dd><dt>17</dt><dd>Low pressure compressor</dd><dt>18</dt><dd>wave</dd></dl><dl tsize="12" compact="compact"><dt>20, 20A, 20B</dt><dd>flues</dd><dt>21, 22</dt><dd>flues</dd><dt>23, 24, 25</dt><dd>Charge air lines</dd><dt>26, 27</dt><dd>Intercooler</dd></dl><dl tsize="8" compact="compact"><dt>30</dt><dd>Valve</dd><dt>31</dt><dd>actuator</dd><dt>32</dt><dd>Exhaust gas recirculation line</dd><dt>33A, 33B</dt><dd>bypass lines</dd><dt>34A, 34B</dt><dd>Bypass valves, pipe switch</dd><dt>35</dt><dd>Flow restrictor</dd></dl><dl tsize="7" compact="compact"><dt>40</dt><dd>Controller, motor control </dd><dt>41</dt><dd>data inputs</dd><dt>42</dt><dd>data outputs</dd><dt>43-46</dt><dd>control lines</dd></dl><dl tsize="2" compact="compact"><dt>P1</dt><dd>the flue gas side pressure</dd><dt>P2</dt><dd>intercooled sided printing</dd></dl>