Engine brake apparatus for a turbocharged IC engine

The invention relates to an engine braking device for a turbocharged internal combustion engine according to the preamble of claim 1, a method according to the preamble of claim 18 for operating the engine braking device as well as 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 is provided with its own auxiliary braking device. In a typical operation of such an auxiliary braking device always ensures a conversion of the turbocharger from a power or drive device to a braking device, when an auxiliary braking is required. This is generally done by modifying the exhaust and / or Ansaugzeitsteuerung of the turbocharger in such a manner that a movement of the cylindrical piston is converted by the lowest possible power loss to the greatest possible power loss and that is when the braking of the turbocharger is performed. Such power absorption uses the principle of an air compressor, ie the cylinder piston practicing on the trapped in the cylinders of the engine air work from when braking is required.

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

According to a first approach is attempted by reducing the exhaust-side cross-section effective to increase the pressure in the exhaust conduit so as to some extent to achieve a back pressure which is transmitted to the gas in the cylinder volume of the internal combustion engine. Due to the higher pressure in the cylinder interior cylinder pistons have a greater perform work, which ultimately leads to a brake. This is implemented in different ways in practice:

In the <patcit id="pcit0001" dnum="DE19543190A1"><text>DE 195 43 190 A1</text></patcit> is an auxiliary braking device for a supercharged internal combustion engine described, which is provided with an exhaust gas turbine with an adjustable guide variably adjustable turbine geometry. The vane structure comprises guide vanes which can be adjusted by means of an actuator so that the effective, that is effective turbine cross section of the turbine is varied. In this way, different high exhaust back pressures can be realized in a section between the cylinders and the turbocharger, whereby the power of the turbine and the power of the compressor can be adjusted according to need depending on the operating state of the internal combustion engine.

To achieve an engine braking effect in the brake mode of the internal combustion engine, this guide baffle is placed in a stowed position such that the effective turbine cross-section is significantly reduced. In a line section between the cylinders and the turbine, a high exhaust backpressure builds so on, with the result that flue gas at high velocity flows through the channels between the vanes of the turbine 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 is set by the compressor under increased boost pressure. Thereby the cylinder intercooled acted upon with a higher boost pressure, exhaust gas side is located between the cylinder outlet and the turbocharger, increased exhaust back pressure at which counteracts a discharge of the compressed air in the cylinder through open brake valves in the exhaust line into it. In the engine braking mode, the piston compression work against the high pressure in the exhaust pipe is required to do, creating a more or less strong braking effect is achieved depending on the position of the guide grid.

Additionally or alternatively to this provided with guide grids turbines may also be provided a flap which in the exhaust line downstream of the turbine is arranged. This flap can be pivoted to a braking operation of the engine braking device transversely or substantially transversely in the exhaust pipe, thus reducing the effective cross section in the exhaust line, whereby upstream increased in the direction of the cylinder outlets of the pressure in the exhaust pipe, and thus a braking effect is achieved. A turbocharger with such a flap is z. B.<patcit id="pcit0002" dnum="DE4024572"><text>DE 40 24 572</text></patcit> described.

According to a second concept may be provided for increasing the engine braking power, exhaust gas recirculation, that is activated during engine braking operation. In this case, exhaust gas from the exhaust conduit during an engine braking mode usually having unburned combustion air and which has by the compression in the cylinders at an increased temperature level, again supplied to the cylinders of the internal combustion engine.

In the <patcit id="pcit0003" dnum="DE19853127A1"><text>DE 198 53 127 A1</text></patcit> is described with EGR such engine braking device. There, the exhaust gas is branched off upstream of the turbocharger and upstream in the direction of the cylinder inlets is mixed with the compressed in the compressor of the turbocharger combustion air of the intake and supplied to the cylinders. In the line for exhaust gas recirculation, a check valve is provided. This check valve is also required to compensate for differences in pressure between the exhaust side and the charge air-side line.

A method of operating an engine braking device for a turbocharged internal combustion engine is, moreover, from the <patcit id="pcit0004" dnum="DE19931009A1"><text>DE 199 31 009 A1</text></patcit> known.

All the above auxiliary braking devices of a turbocharged internal combustion engine, however, are designed for so-called single-stage turbocharger. However, modern turbocharger may have a two-stage turbocharging.

An internal combustion engine with such a two-stage turbocharging system designed for example in the <patcit id="pcit0005" dnum="DE19837978A1"><text>German Offenlegungsschriften DE 198 37 978 A1</text></patcit> and <patcit id="pcit0006" dnum="DE19514572A1"><text>DE 195 14 572 A1</text></patcit> described. In such two-stage turbocharged internal combustion engines, the turbocharger group on each one arranged in series with one another high-pressure stage and low pressure stage. The exhaust gas from the engine flows through the high pressure turbine here first and then the low pressure turbine. Similarly, for charging the cylinders provided for charge air is first then compressed by a low pressure compressor and a high pressure compressor and, optionally, fed by a cooling of the charge air in a heat exchanger the charge air side of the internal combustion engine. In a typical mode of operation, the turbocharger is operated in two stages at the lower speed ranges of the internal combustion engine. With increasing speed can on stage compression only the low pressure compressor are switched, for example by means of the exhaust-side bypass lines, the high-pressure turbine is completely or at least partially bridged. Logically, also the high-pressure compressor via a charge-air side provided pipe switch is completely bypassed in this case.

Another internal combustion engine according to claim 1, first part, with two-stage turbocharging system is from the <patcit id="pcit0007" dnum="JP1182533A"><text>JP 01 182533 A</text></patcit> known.

In such two-stage turbochargers which are each arranged in series turbines and compressors are designed for different charging pressures. This has the consequence that often a huge design effort for realizing the above-mentioned auxiliary braking device is required in practice. For example, in each case to obtain an optimum auxiliary braking mode for the various operating modes of the two-stage turbocharger, a plurality of tubular switches are essential to achieve the desired respective pressures in the exhaust lines and charge air lines. Such braking devices are therefore very expensive to manufacture, with the extra effort does not improve braking quality. Especially with very small turbochargers, which come with a low capacity for use primarily in internal combustion engines, such an auxiliary braking device has not yet been satisfactorily resolved.

The present invention is therefore the object of providing an improved braking device of a two-stage turbocharger of an internal combustion engine.

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

Advantageous refinements and developments of the invention are respectively the dependent claims and the description with reference to the drawing.

The invention is explained in detail using the exemplary embodiments shown in the figures of the drawing. It shows:<dl id="dl0001"><dt>figure 1</dt><dd>a schematic representation of a two-stage turbocharged internal combustion engine with regulating valve in the exhaust manifold;</dd><dt>figure 2</dt><dd>an embodiment of an inventive internal combustion engine, two-stage turbocharged with attached exhaust gas recirculation line;</dd><dt>figure 3</dt><dd>a two-stage turbocharged internal combustion engine according to Figure 1 with variable turbine geometry;</dd><dt>figure 4</dt><dd>a two-stage turbocharged internal combustion engine according to Figure 1 with a designed as a twin-flow turbine high pressure turbine;</dd><dt>figure 5</dt><dd>a two-stage turbocharged internal combustion engine according to Figure 1, in which the closure body between the high pressure stage and low pressure stage is arranged;</dd><dt>figure 6</dt><dd>a schematic representation of a particularly preferred embodiment of a two-stage turbocharged internal combustion engine according to the invention.</dd></dl>

In all figures of the drawing, identical or functionally identical elements - have been given the same reference characters - unless otherwise indicated. In all figures of the drawings Further, the direction of the exhaust stream as well as the charge air stream is denoted by arrows in the corresponding lines.

While FIG. 1 illustrates the principle of a two-stage internal combustion engine, Figures 2 and 6 show the embodiments of the invention. The figures 3 to 5 schematically illustrate variants of embodiment of internal combustion engines, which can be integrated in an advantageous manner in the embodiments of the invention shown in Figures 2 and 6. FIG. Along with this form of the invention.

1 shows a schematic representation of the principle of a braking device.

In figure 1 is denoted by reference numeral 1, an internal combustion engine. The internal combustion engine 1 is formed as a six-cylinder diesel internal combustion engine in series construction, and thus has six in series with one another arranged on the 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 engine 1 is connected on the exhaust side 4 with two exhaust manifolds 6th

The internal combustion engine 1 is charged via a turbocharger indicated by reference numeral 10th The turbocharger 10 is formed by way of example in two stages. Such a two-stage turbocharger 10 comprises a high pressure stage 11 and a low pressure stage 12th The high-pressure stage 11 consists of a high pressure turbine 13 and a high pressure compressor 14, which are rigidly coupled to one another via a common shaft 15th The low pressure stage 12 is similarly composed of a low pressure turbine 16 and a low pressure compressor 17, which are also coupled by a common shaft 18 with each other. The high-pressure stage 11 is the low-pressure stage upstream 12th

The turbine wheel diameter of the low pressure turbine 16 by way of example 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 is. Similarly, the compressor wheel of the high-pressure compressor 14 has a smaller diameter than the compressor wheel of the low pressure compressor 17th

The exhaust manifold 6 is connected upstream exhaust pipes 20, 21, 22, through which the exhaust gas can be discharged from the cylinders 2 of the internal combustion engine first In the same way the charge air lines 23, 24, 25 are provided, which are connected upstream of the charge air manifold fifth Via the charging air lines 23, 24, 25 and the compressors 14, 17 to the cylinders 2 of the internal combustion engine 1 is supplied to the charge air.

The two turbines 13, 16 are arranged to each other in series, wherein the high-pressure turbine 13 is connected to the low pressure turbine 16 via the exhaust pipe 21 and the low pressure turbine 16 is arranged upstream in the flow direction of the exhaust gas. Similarly, the low pressure compressor 17 and the high pressure compressor 14 are arranged to each other in series and connected to one another via a charging air duct 24, wherein the low pressure compressor 17 is arranged upstream of the high pressure compressor 14 in flow direction of the charge air.

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

A variable locking device 30 is provided, which is embodied here as a regular or controllable valve. The closure device 30 can also be designed as a brake flap, throttle, slide or the like. About one connected to the control valve 30 actuator 31, the valve 30 is adjustable. The closure device 30 can be configured regulated or controlled via a regulating or control device not shown in FIG. 1 The function of such a control device or control device will be described below with reference to Figure 6 in more detail.

Unlike Figure 1, the arrangement according to FIG 2, according to the invention on an exhaust gas recirculation line 32nd The exhaust gas recirculation line 32 branched from the exhaust pipes 20 which come from the exhaust gas collecting lines 6, from branches and in the charge air line 25, which connects the high pressure compressor 14 with the charge air manifold 5, a. The particular advantage of the arrangement shown in Figure 2 is that due to the pressure conditions in the exhaust pipes 6, 20 and the charge-air lines 5, 25 no check valve is provided and moreover, as will be explained further below, also is not required.

In contrast to the arrangement in Figure 1, the turbocharged internal combustion engine 1 According to figure 3 a turbocharger 10 which comprises a high pressure turbine 13 with variable turbine geometry (VTG). The functionality of a variable turbine geometry is indicated in the figures with an arrow.

In contrast to the arrangement in Figure 1, the turbocharged internal combustion engine according to Figure 4 designed as a twin-flow turbine high pressure turbine. 13 This twin-flow high-pressure turbine 13 consists of two mutually parallel turbine wheels 13A, 13B, which together - coupled - typically rigid. Typically, but not necessarily, these two turbine wheels 13A, 13B the same flow cross-section of the turbine channels.

In contrast to the arrangement in Figure 1, the closure device 30 is arranged between the high pressure stage and low pressure stage 11, 12 when the internal combustion engine according to FIG. 5 Since the brake flap 30 acts here directly on the high-pressure stage, this arrangement is distinguished from the arrangement in Figure 1 by the fact that a higher speed and accuracy of control of the high pressure stage 11 is possible.

For optimum adjustment of the two-stage turbocharger 10 at the operating conditions of the internal combustion engine 1 channel 13A, 13B of the dual twin-flow pressure turbine 13 is provided a bypass line in advantageously symmetrical circuit ever. These each branch of the exhaust manifold as running, separate pipes 20A, 20B from bypass the twin-flow turbine 13, and open at the same loading of the single-flow low-pressure turbine 16 into the common rail 21 a. Each bypass line 33A, 33B is provided with a downstream of the diversion tube arranged switches 34A, 34B, which can be configured for example as a control valve. This tube switches 34A, 34B are advantageously in the exhaust manifold or in the housing of the high pressure turbine 13 also integrated and can be designed as a slide valve, damper, throttle or the like and as a program-controlled unit, for example, a CPU, are also commonly driven either individually or.

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

Figure 6 shows a schematic representation of a particularly preferred embodiment of a two-stage turbocharged internal combustion engine according to the invention. The preferred arrangement in figure 6 consists essentially of a combination of different embodiments of an internal combustion engine 1 according to Figures 1 - 4. The internal combustion engine 1 is here with a control valve 30, an exhaust gas recirculation line 32, bypass lines 33A, 33B having therein tube switches 34A, 34B equipped. In addition, the high-pressure stage 11 is a twin-flow high-pressure turbine 13, in which the high-pressure turbine 13A, 13B each having a variable turbine geometry.

At this point it should be noted that the low-pressure turbine 12 can be naturally formed as a twin-flow turbine. In addition, the low-pressure turbine 12 may additionally or alternatively also comprise a variable turbine geometry.

Figure 6 shows, in addition to a controller 40th The controller 40 has data inputs and 41 data outputs 42nd Via the data inputs 41 analog measurement values, such as the temperature or pressure of exhaust gas or charge air, the number of revolutions of the engine, etc., or digital data, for example, be coupled. Depending on these data and from a predetermined program of the control device 40 generates these control signals which are tapped at the outputs 42 of the control device 40th

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

Further, a throttle 35 is provided, which is disposed connected in the exhaust gas recirculation line 32nd This will typically also be set or activated via the control device 40th

May additionally be provided a further, not shown in Figure 6, exhaust gas recirculation, in which a partial amount of the recirculated exhaust gas is supplied to any other desired point of the charge air side. Typically, but not necessarily, to about 50% of the exhaust gas of the internal combustion engine 10 of the charge air side 3 is returned.

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

The six-cylinder diesel engine 1 is charged in two stages via a turbocharger 10th For this purpose a double-flow high-pressure stage 11 of a single-flow low-pressure stage 12 is connected upstream. On the driven from the twin-flow 13A, 13B and the low pressure turbine 16. compressor 14 and 17 the charge air is compressed, cooled in the two charge air coolers 26, 27, (0 ≥) mixed at a certain proportion with exhaust gas from the exhaust gas recirculation line 32 and the charge air side 3 the internal combustion engine 1 is supplied.

To control the reed switch 30, 33A, 33B, the closure body and of their geometry variably adjustable turbines 13, 16 as a function of operating parameters A1 - At these are connected to an electronic engine controller 40, for example, a CPU of an operational optimum division exhaust gas mass flow provides. Due to the 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, which is the secondary braking operation of the turbocharger 10 is of particular importance.

Next, the operation of an auxiliary brake means operated as a turbocharger 10 of the invention is explained in detail with reference to FIG 6:

With closed bypass valves 34A, 34B and a controllable exhaust brake flap 30 an increased engine braking power can be displayed, which is made possible by an increased exhaust gas pressure caused by the small high-pressure stage 11th Using different sized channels 13A, 13B of the high-pressure turbine 13 and twin, with separate control of the respective bypass valves 34A, 34B of the corresponding speed range in the braking mode can be adjusted optimally. The different channel diameters of the two high-pressure turbines 13A, 13B can be set in a targeted 40 because of their variable turbine geometry by suitable control of the motor controller. This allows a differential division of the exhaust gas mass flow at high-pressure and low-pressure stage 11, split 12th

This exhaust gas mass flow can therefore influence as follows:<ol><li>1. With a suitable setting of the control valve 30 is the effective cross section of the exhaust pipe 22 can be adjusted specifically. </li><li>2. The high-pressure turbine 13A, 13B, and advantageously also the low-pressure turbine 16 are on a variable turbine geometry. With a suitable control of the effective channel cross section of the respective turbines may be selected to be large, more or less.</li><li>3. Use the bypass valves 34A, 34B can change the effect of the exhaust gas, the high-pressure turbines 13A, 13B flows through and what proportion bridges the high-pressure turbines 13A, 13B.</li></ol>

Through the above measures, ie by suitable control and / or regulating the aforementioned elements can be defined an exhaust-side pressure P1 in the exhaust pipes 6, 20 and therefore also set in the cylinders. 2 In a particularly advantageous embodiment, especially in the presence of an exhaust gas recirculation line 32 according to 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. Since thus always a pressure differential between the is the flue gas side and charge air-side area of ​​the exhaust gas recirculation line 32, no check valve is here advantageously in the exhaust gas recirculation line 32 is required.

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

In addition, enables an optimized proportioning of recirculated exhaust gas amount (EGR amount) to the operating condition desired in each case by a different size of the channels 13A, 13B of the twin-flow turbine 13 with separate control of the bypass valves 34A, 34B. An additional EGR valve, as is imperative, for example, in the aforementioned prior art, is not necessary here.

6 shows yet a throttle 35 is disposed in the exhaust gas recirculation line 32 through which the exhaust gas mass flow through the exhaust gas recirculation line 32 at a suitable control can be additionally dosed. This allows the engine characteristics directly influence, for example, the engine operation amounts to the emission of pollutants (N_OX, CO, CO₂may be) and adjusted largely optimal in terms of fuel consumption. The particular advantage of EGR according to the invention is that the exhaust gas flow is already ensured solely by the pressure difference between the exhaust side and charge air side. Therefore, it is entirely sufficient to merely provide a flow restrictor in the exhaust gas recirculation line 32, wherein this - as already mentioned - can also be omitted without significantly affecting the function of the auxiliary braking device.

Of course, the invention is not restricted to a two-stage turbocharger trained, but can rather also on three or enhance staged turbochargers.

The two turbochargers are steps in the present embodiment advantageously part of a single turbocharger and are thus integrated in a housing of this turbocharger. However, these beneficial integration of two turbocharger stages in a turbocharger not mandatory, but it could be achieved, although this arrangement assembly technology and because of the higher cost is less preferred the same function through two separate, connected one after the turbocharger.

Finally, the invention is not limited solely to diesel internal combustion engines in-line six cylinder design, but can be extended to any internal combustion engine having any number of howsoever arranged cylinders.

In the illustrations of Figures 1 to 6, in particular the embodiment of Figures 2 and 6 has finished the low pressure stage to a high-pressure stage with respect to the larger diameter of the respective turbine wheels. However, this is not mandatory, but it is also conceivable that the two turbine stages have an identical turbine wheel and the high-pressure stage has the larger wheel diameter.

Above control of the closure body (valves, butterfly valves, pipe switch, etc.) as well as the turbine geometry has been described by the motor controller respectively. Of course, leave some or all of these elements and otherwise control or adjust through a specially provided control device to the desired operating state. The setting of the closure body and the turbine geometry can be driven electrically, pneumatically, hydraulically or mechanically.

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

LIST OF REFERENCE NUMBERS

<dl id="dl0002" 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 id="dl0003" 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 id="dl0004" 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 id="dl0005" 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 id="dl0006" 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 id="dl0007" compact="compact"><dt>P1</dt><dd>the flue gas side pressure</dd><dt>P2</dt><dd>intercooled sided printing</dd></dl>