DE4241571A1 - Internal combustion engine operating method - Google Patents

Abstract

The engine (10) exhaust gas is filtered by at least one filter arrangement in a stationary system, pref. in a test system, whose output gas is filtered by a filter arrangement (12) in an exhaust pipe and with a cleaning device (14).The press. in the exhaust pipe is measured and a choke flap (18) in the pipe is adjusted so that the press. in the pipe is held at an essentially constant value, variable within narrow limits, according to the revolution rate and engine load. When a defined press. is reached with the choke open the cleaning device is activated to clean the filter.

Description

The invention relates to a method for operating a Internal combustion engine according to the preamble of claim 1 and one Facility to carry out the procedure.

Internal combustion engines, in particular with diesel fuels generate operated engines (hereinafter referred to as diesel engines) Exhaust gas containing particles, in particular soot particles. For prevention the emission of these particles are in the exhaust pipes Filter arrangements used, among other things, a so-called Ceramic monoliths in which the particles are held. There the pores or openings in the filter assembly over time can clog and thereby increase the exhaust gas back pressure, the Filters are cleaned, which can be done in different ways. A known filter arrangement comprises a burner for cleaning when a certain load of the filter arrangement is reached Particles and therefore due to reaching a certain back pressure is ignited in the exhaust pipe and the particles burn off. For measurement of pressure has the filter arrangement at its exhaust gas inlet connection a pressure sensor whose signals are evaluated so that the burner is ignited.  

If such a filter arrangement, for example in a Truck is installed, then the filter assembly during the Operation of the truck can be cleaned, but no major Measures must be taken to keep the exhaust gas back pressure constant hold. It is sufficient if the back pressure has a certain maximum value does not exceed. If an internal combustion engine, for example a diesel engine being tested in a test bench, then it is necessary to achieve reproducibility of the measured values certain parameters are always kept constant, even the smallest Avoid fluctuations in these parameters.

The object of the invention is a method of the aforementioned To create a way with which in particular the exhaust gas back pressure is exactly constant is held. Furthermore, a facility is to be specified with which the procedure can be carried out.

This object is achieved by the characterizing Features of claim 1.

By providing the throttle valve in the exhaust pipe and by the appropriate control based on that measured in the exhaust pipe Pressure can be changed by changing the position of the throttle valve in the exhaust pipe depending on the speed of the internal combustion engine be kept at a constant value. The arrangement is adjustable that, for example, the exhaust back pressure at a certain speed a value of plus / minus 10 mbar is kept constant. If at cleaned filter arrangement the exhaust back pressure only Δp = 20 mbar is, but the required exhaust gas back pressure should be 40 mbar, then the throttle valve is moved into the closed position until the required exhaust gas back pressure of 40 mbar is reached. Now changes the back pressure due to loading the filter arrangement with particles increases If he turns on, the throttle valve is opened until the Back pressure is generated exclusively by the filter arrangement, and if, for example, the maximum permissible back pressure Δp = 60 mbar  is reached, the burner is switched on, so that the Filter assembly is burned freely.

The back pressure Δp is of course a function of the load and Rotational speed; at higher load and higher speed the target back pressure is higher. The back pressure Δp is controlled by a so-called PID controller controlled depending on the speed. The position is changed the throttle valve.

There is also the possibility to measure the exhaust gas temperature however, no significant influence on the operating range Back pressure Δp. The temperature only needs to be measured to To enable test comparisons. With very strong temperature fluctuations could, however, the density of the exhaust gas and thus the back pressure Δp to be influenced. As indicated, this is practical in the operational area not the case and neglect.

The facility to carry out the procedure will solved according to the invention by the characterizing features of the claim 3rd

There are several options: With large motors, several filters can be connected in parallel, wherein the exhaust pipe is one of the number of filter arrangements corresponding number of line sections at a branch point divides. In the section between the engine and the division point or branch point, the throttle valve is housed. It there is also the possibility of dividing each section between the To assign a throttle valve to the branching point and the filter arrangement, then a suitable control for the individual throttle valves becomes necessary; of course, the throttle valves in the can be adjusted substantially at the same time.

For small engines, such as those that have one  Output of nominal power of 5 kW, the exhaust gas of the engines can on or several filter arrangements are given; here it goes without saying a throttle valve is required for each small engine.

Further advantageous embodiments of the invention and others Improvements can be found in the other claims.

Using the drawing in which some embodiments of the Invention are shown, the invention and others advantageous refinements and improvements of the invention are explained and described:

Show it:

Fig. 1 is a schematic representation of an engine assembly having a filter assembly,

Fig. 2 is a diagram of the back pressure Δp over the engine running time and

FIGS. 3 to 5 show three different embodiments of an inventive arrangement.

A stationary test bench is shown schematically in Fig. 1. The test bench comprises an internal combustion engine 10 to be installed in a stationary manner, which is designed as a diesel engine. The combustion process generates exhaust gases which are fed via an exhaust pipe 11 to a filter arrangement 12 in which the exhaust gas is cleaned of particles; The cleaned exhaust gas is discharged into the ambient atmosphere in the direction of arrow P. The filter arrangement 12 comprises a filter 13 and a burner 14 , which serves to clean the filter 13 .

In the exhaust pipe 11 there is a pressure sensor 15 in the vicinity of the engine 10 , with which the pressure prevailing in the exhaust pipe 11 is measured. This pressure is measured as Δp, the pressure difference between the exhaust gas back pressure and the ambient pressure. The signals generated by the pressure sensor 15 are fed via a signal line 16 to a controller 17 , in which the measured values Δp are compared with a setpoint pressure Δp setpoint. In the direction of flow behind the pressure sensor 15 there is a throttle valve 18 , which can be adjusted by a drive 19 (shown in dashed lines) from a closed to an open position and back. The drive 19 is controlled via a signal line 20 , with which the drive 19 is connected to the controller 17 .

The pressure signals measured by the pressure sensor 15 can be supplied to a control unit 21 , with which a solenoid valve 22 is controlled, which is located in a fuel line 23 , via which fuel is supplied to the burner 14 . When the pressure in the exhaust pipe exceeds a certain value, the burner 14 is started by supplying the burner 14 with fuel and combustion air, the valve 22 being opened. A temperature sensor 24 monitors the burner 14 to prevent the burner from overheating. As soon as the burner 14 has an excessively high temperature, the valve 22 is closed. In addition, in the filter 13, a temperature sensor 25 is installed that monitors the temperature of the filter 13 and blows at an excessively high temperature which can arise, for example by combustion of the particles, means actuates the extinguishing agent, for example, nitrogen or the like in the filter.

It goes without saying that a filter arrangement can also be used in which the cleaning is carried out by means of other means, for example by means of substances having a catalytic or other effect. Instead of then igniting the burner, the substances mentioned are supplied to the filter when a certain maximum pressure Δp is reached in the exhaust line 11 .

The mode of operation of the arrangement according to FIG. 1 will be explained with reference to FIG. 2.

Time t is plotted on the abscissa and pressure Δp on the ordinate. Up to a certain point in time t0, there is a pressure Δp0 in the exhaust gas line 11 which is generated by the slightly closed throttle valve 18 . When starting, the pressure Δp will increase to the setpoint Δp set in the period from t0 to t1, still with the flap slightly closed, and from time t1 the throttle valve 18 will be adjusted according to the pressure Δp to such an extent that the pressure curve within the exhaust gas line 11 remains constant. This constant value is the value Δp target. At about the time t2, the throttle valve 18 is completely open and due to the loading of the filter 13 , the pressure Δp increases to the value Δp max; when this maximum value Δp max is reached, the burner 14 is switched on and the filter 13 is cleaned until the permissible minimum pressure Δp0 is reached; this is the case at time t4, and then the flap 18 is closed again to such an extent that the pressure Δp target is reached and maintained; this is the case at time t5 and the throttle valve 18 keeps the pressure at the value Δp set constant again; the process that has expired between times t1 to t5 is then repeated.

The value Δp target is from the speed of the motor 10 according to the formula:

Δp target = f (n)

depending on
f is function
n is the speed of the motor 10 .

The value Δp target can be, for example, 10 mbar at a specific speed; the maximum value Δp max is then 60 mbar and the minimum value Δp0 is 40 mbar. Due to the position of the throttle valve 18 , the minimum value Δp0 is maintained in any case. The flap 18 is kept almost closed until this minimum value Δp0 is reached, for example when the engine starts.

The controller 17 is a so-called PID controller, with which the position of the throttle valve 18 is controlled or regulated.

FIG. 3 shows a motor 30, the exhaust pipe 31 includes a throttle 32nd Behind the throttle valve 32 is a branching point 33 , in which the exhaust pipe 31 is divided into several sections 34 , 35 , 36 . . . divided, in which filter arrangements 37 , 38 and 39 are located. The mode of operation in this arrangement according to FIG. 3 is the same as that according to FIG. 2.

In the arrangement according to FIG. 4, an engine 40 is provided with an exhaust pipe 41 , which is divided into sections 43 , 44 and 45 at a branching point 42 . Of course, more line sections can also be provided. A throttle valve 46 , 47 and 48 is located in the individual line sections and filter elements 49 a, 49 b, 49 c are inserted downstream in the individual line sections 43 , 44 and 45 .

In FIG. 5, an arrangement is shown, are connected to a single filter assembly 53 wherein a plurality of motors 50, 51 and 52. Throttle valves 58 , 59 and 60 are located in line sections 54 , 55 and 56 , which lie between motors 50 to 52 and a branch point 57 . A branching section 61 with the filter arrangement 53 lies behind the branching point 57 .

The throttle valves 32 , 46 to 48 and 58 to 60 are controlled in the same way as the throttle valve 18 of FIG. 1, so that there is no need to go into this here.

Of course, all types of surface or Depth filters are used where cleaning by burning off he follows. As mentioned above, other substances can also be used for cleaning are provided, for example liquid catalysts. When a Burner is provided, then the particles are at about 650 degrees burned, and if liquid catalysts are injected, then the ignition temperature of the accumulated particles can decrease, so that the temperature of the exhaust gas along with the liquid catalyst is sufficient to burn out the particles from the filters. Instead of that or to turn on the burners would then control the Spraying process initiated. It is also a combination of burners and catalytically active substance possible.

The arrangement according to FIG. 1 is essentially to be used in stationary diesel engine test benches. Of course, all types of internal combustion engines in which exhaust gases are formed in which there are particles can be equipped with the arrangement according to the invention according to FIGS. 1 to 5. The assignment according to the invention of the throttle valve 18 or the other throttle valves to the pressure sensor 15 is necessary because the parameters, for example the exhaust gas temperatures and in particular the exhaust gas backpressure Δp, are narrowly limited in order to achieve precise comparison measurements and reproducible measured values.

The arrangement according to FIG. 3 and FIG. 4 can then be used in an appropriate manner, if a relatively powerful motor to be associated with 30 and 40 filter assemblies individually for the amount of exhaust gas are too small. It is then expedient to connect several filter arrangements in parallel and to use the throttle valve as indicated in FIGS. 3 and 4.

The arrangement of FIG. 5 is inserted substantially in so-called small motors, wherein each motor 50, 51 and 52, for example, 5 kW of power outputs. Of course, each engine 50 , 51 and 52 is assigned a throttle valve 58 , 59 and 60 with its own control system.

It is known that in motor vehicles using a Diesel engine are operated to provide a filter assembly; at these filter arrangements are not associated with throttle valves Pressure sensors and corresponding control devices have been used.

Claims (7)

1. A method of operating at least one internal combustion engine, the exhaust gas with at least one filter arrangement in a stationary system, preferably in a test system, the exhaust gas is filtered with a filter arrangement located in an exhaust pipe, having a cleaning device, characterized in that the pressure in the exhaust pipe is measured and an adjustable throttle valve arranged in the exhaust line is adjusted such that the pressure in the exhaust line is kept at a variable, essentially constant pressure value depending on the speed and load of the internal combustion engine. 2. The method according to claim 1, characterized in that at Reaching a predetermined pressure value with the throttle valve open the cleaning device for cleaning the filter arrangement in operation is set. 3. Device for performing the method according to one of the Claims 1 or 2, for at least one internal combustion engine, in whose exhaust pipe is at least one filter arrangement with a associated cleaning device for cleaning the filter arrangement located, characterized in that in the exhaust pipe at least one Pressure sensor and at least one throttle valve are provided. 4. Device according to claim 3, characterized in that the pressure sensor ( 15 ) is connected to a control device ( 17 ) with which one of the throttle valve ( 18 ) associated drive motor ( 19 ) can be controlled. 5. Device according to one of claims 3 and 4, characterized in that an internal combustion engine ( 30 ) are assigned at least two filter arrangements which are each arranged in a line section ( 34 , 35 , 36 ) which at a branch point ( 33 ) of the Branch exhaust pipe ( 31 ), and that a throttle valve and a pressure sensor with a control system are arranged in the exhaust pipe ( 31 ) between the engine ( 30 ) and the branch point ( 33 ). 6. Device according to one of the preceding claims, characterized in that at least two filter arrangements ( 46 , 47 and 48 ) are assigned to an internal combustion engine, which in a branching point ( 42 ) of the exhaust pipe ( 41 ) branching line sections ( 43 , 44 , 45 ) are arranged, and that in each line section ( 43 , 44 and 45 ) there is a throttle valve with a control system, the pressure sensor being inserted in the exhaust line ( 41 ). 7. Device according to one of the preceding claims, characterized in that at least one internal combustion engine ( 50 , 51 and 52 ) is assigned to a filter arrangement ( 53 ), wherein in the line sections assigned to the individual motors ( 54 , 55 and 56 ) each have a pressure sensor and a throttle valve ( 58 , 59 and 60 ) with a control system are used, and the line sections ( 54 , 55 and 56 ) are connected to a branching point ( 57 ) to which an exhaust gas line ( 61 ) connects, in which the filter arrangement ( 53 ).