DE102015215334A1 - Method for expanding the temperature range of use of seals, device for carrying out the method, computer program and computer program product - Google Patents

Abstract

The invention relates to a method for expanding the temperature range of use of seals (42), which are used in a magnetic circuit (36, 38) which comprises a magnetic coil (38). The inventive method is characterized in that a measure (66, 72) for the temperature of the seal (42) is determined that the determined measure (66, 72) for the temperature of the seal (42) with a temperature threshold ( 78) is compared and that, when the temperature is below the temperature threshold (78), a heating of the seal (42) is made.

Description

The invention relates to a method for expanding the temperature range of use of seals, in particular elastomeric seals, which are used in a magnetic circuit containing a magnetic coil, such as in an electromagnetically actuated valve or in an electromagnetically actuated reciprocating pump.

The invention further relates to a computer program and a computer program product with a program code stored on a machine-readable carrier for carrying out the method.

State of the art

In order to meet today's emissions legislation, a NOx storage catalyst (NSC) is used to clean exhaust gases of an internal combustion engine, which can cache and reduce nitrogen oxides (NO, NO ₂ ). For this purpose, the nitrogen oxides are first stored in the NOx storage catalytic converter. If the absorption capacity of the NOx storage catalytic converter is exhausted, a rich exhaust gas mixture is set by an engine controller. In this case, the nitrogen oxides temporarily stored in the NOx storage catalyst are reduced to nitrogen.

This method works well in the low and medium load and temperature ranges. In order to comply with future exhaust gas regulations, the high-load area for exhaust gas purification must also be integrated.

So that the NOx storage catalytic converter reduces nitrogen oxides even in high-load operation and at high temperatures, it must be operated in the so-called DiAir mode. DiAir stands for "Diesel NOx Aftertreatment by Adsorbed Intermediate Reductants". Here hydrocarbons (hydro carbons) are metered in front of the NOx storage catalyst, which is also referred to as HCI (Hydro Carbons Injection). As a rule, additional fuel is metered into the exhaust gas passage upstream of the NOx storage catalytic converter.

For this purpose, a special reagent dosing system is required, which from the assemblies:
Injection unit, essentially consisting of a metering valve and a heat sink,
Dosing unit, essentially consisting of a pressure stage (eg a feed pump) and a pressure sensor, and
Control unit, z. B. implemented as hardware and / or software in the engine control exists.

Of particular importance in this reagent dosing system is the metering valve in the injection unit. These metering valves contain a magnetic coil, wherein by means of energization of the solenoid an armature is moved, which is mechanically connected to a valve needle or designed as such, and which opens the valve against a spring force, so that the reagent, which is under high pressure, in the exhaust passage can be injected. In the magnetic circuit of the metering valve, an elastomeric seal may be used, which is specified for a predetermined temperature range.

In the published patent application DE 10 2007 017 458 A1 a method for operating a metering valve is described, which is arranged in the exhaust passage of an internal combustion engine and which is controlled for metering a reagent having a first current profile. Determined is a measure of the temperature of the metering valve, which is compared with a temperature threshold. If the measure of the temperature of the metering valve is below the temperature threshold, a control of the metering valve for heating the metering valve is provided with a different current profile from the first current profile.

The second current profile can be realized by means of a DC voltage or by means of an AC voltage. The amount of DC voltage is set such that still no opening of the metering valve can take place. If an AC voltage is provided as a second current profile, the frequency of the AC voltage is set so high that the valve does not open due to the mechanical inertia. A heating of the electromagnetically actuated metering valve may be required if a urea-water solution is provided as the reagent or a precursor of a reagent, which is needed in an SCR catalyst for the reduction of NOx components of the exhaust gas of the internal combustion engine, there is the danger freezing at a temperature below about -11 ° C.

To provide the required pressure of the reagent or precursor of the reagent required to introduce the reagent into the exhaust passage of the internal combustion engine, a reciprocating pump may be provided which includes a movable armature operating as a piston. With each stroke of the reciprocating pump, a certain amount of the reagent is conveyed, whereby a delivery pressure arises. A reciprocating pump includes a magnetic circuit with a magnetic coil, wherein the magnet armature is moved by means of energization of the magnetic coil. For sealing the moving parts of the reciprocating pump of immovable parts, at least one seal, preferably an elastomeric seal is provided.

By determining the on-board diagnostic guidelines (OBD) and given the required accuracy in the example of an SCR catalyst system, the metering pressure must be monitored. For this purpose, the current which flows through a solenoid coil in the lifting magnet of a reciprocating pump, which transports the urea-water solution in a delivery module of the SCR catalyst system, and the timing of the armature movement are measured. A change in the temperature of the solenoid causes a change in the coil current. At a higher temperature, the internal resistance of the solenoid increases and the current required to move the armature is reached more slowly. By means of a mathematical model, the time of the armature stop of a pumping movement with inclusion of the coil internal resistance, i. H. the coil temperature and the vehicle electrical system voltage are converted into a pressure which counteracts the movement of a magnet armature. This calculation can be used to control an SCR catalyst system to a constant pressure. For this, however, the knowledge of the magnetic coil temperature is necessary at all times.

In the published patent application DE 10 2011 088 708 A1 Such a method for determining the temperature of the magnetic coil of a reciprocating pump is described. The known method comprises determining a supply voltage of a lifting magnet of the reciprocating pump, determining a coil current of the magnetic coil, calculating the temperature-dependent electrical resistance of the magnetic coil and determining a temperature increase of the magnetic coil relative to a reference temperature from the electrical resistance of the magnetic coil and an electrical reference resistance of the magnetic coil at the reference temperature. By direct or indirect determination of the supply voltage of the solenoid and the coil current of the solenoid all necessary parameters are detected to calculate the electrical resistance of the solenoid. Alternatively, a calculation of the electrical resistance of the magnetic coil over a characteristic curve is possible.

It is an object of the invention to provide a method and an apparatus for extending the temperature range of use of seals, in particular elastomeric seals, which are used in a magnetic circuit containing a magnetic coil, such as in an electromagnetically actuated valve or in particular in an electromagnetically actuated reciprocating pump.

The object is achieved by the features specified in the independent method claim as well as in the independent device claim.

Disclosure of the invention

The procedure according to the invention for expanding the temperature range of use of seals, which is used in a magnetic circuit containing a magnetic coil, is characterized in that a measure of the temperature of the seal is determined that the determined measure of the temperature of the seal with a temperature Threshold value is compared and that, when the temperature is below the temperature threshold, a heating of the seal is made.

The procedure according to the invention avoids operating the seal for a long time at low temperatures, in which the seal is still brittle and accordingly the tightness of a system containing the magnetic circuit is not ensured, which must be absolutely tight under all conditions. For this purpose, an over-dimensioning of the seal, in particular with regard to the permissible temperature range, has been required hitherto, which is no longer necessary with the procedure according to the invention, so that a simpler, cheaper seal is sufficient.

Advantageous developments and refinements of the procedure according to the invention are each objects of dependent method claims.

One embodiment provides for the heating of the gasket indirectly by means of a current supply to the magnetic coil of the magnetic circuit. As a result, a separate heating element can be saved.

Another embodiment provides the heating with a clocked operation of a drive signal of the magnetic coil, in which the magnetic coil is driven with pulse width modulated heating pulses.

The current during the heating pulses is set such that a predetermined current threshold is not exceeded, the current threshold being set such that the system containing the magnetic circuit is barely performing any action. The current threshold is preferably determined experimentally. The current threshold can also be equated with an effective current, taking into account the time.

If the magnetic circuit is provided with the magnetic coil in a motor vehicle with an internal combustion engine, preferably for example in a reagent dosing system for dosing a reagent upstream of a catalyst disposed in an exhaust passage of the internal combustion engine, provides a further embodiment that as a measure of the temperature of the seal the temperature of a cooling water circuit of the internal combustion engine is used.

Alternatively or additionally, a measure of the temperature of the seal can be determined from the electrical resistance of the magnetic coil.

Other alternatives for determining at least one measure of the temperature of the seal are given in the following description.

The device according to the invention for carrying out the method provides a specially prepared control unit which is able to carry out the individual method steps and to initiate the required actions.

An embodiment of the device provides a current sensor for detecting the current flowing through the magnetic coil of the magnetic circuit current.

The computer program according to the invention provides that all steps of the method according to the invention are executed when it runs on a computer.

The inventive computer program product with a program code stored on a machine-readable carrier executes the method according to the invention when the program is executed on a computer.

Further advantageous developments and refinements of the procedure according to the invention will become apparent from the description.

An embodiment of the invention is illustrated in the drawing and explained in more detail in the following description.

drawing

1 shows a technical environment in which a method according to the invention runs,

2a shows a drive signal of a solenoid of a reciprocating pump,

2 B shows symbolizes a mean current flowing through the magnetic coil as a function of time,

2c shows a drive signal of a solenoid coil of a reciprocating pump during a heating operation and

2d shows symbolizes a mean flowing through the solenoid current as a function of time during the heating operation.

Detailed description

The inventive method and the device according to the invention for extending the temperature range of use of seals, in particular elastomeric seals assumes that the seal is contained in a magnetic circuit which contains a magnetic coil. The magnetic circuit with the magnetic coil is provided for triggering an action such as the actuation of an electromagnetic valve or, for example, the actuation of a reciprocating pump. In these applications, the seal is provided for sealing between mechanically moving parts of the magnetic circuit, wherein in particular a sealing of mechanical components to a liquid of importance.

A preferred field of application of the method according to the invention is given in an electromagnetically actuated valve and in particular in an electromagnetically actuated reciprocating pump. Such a reciprocating pump is provided for example in a reagent dosing as a pressure pump, which doses a reagent in the exhaust passage of an internal combustion engine upstream of a catalyst.

In the following exemplary embodiment, it is assumed by way of example that the seal is used in a reciprocating pump of a reagent dosing system.

Therefore, should 1 a reagent dosing system 10 show which one in a tank 12 stored reagent 14 in an exhaust duct 16 an internal combustion engine 18 upstream of an exhaust gas purification device 20 dosed.

For the reagent 14 it may, for example, be fuel, including the internal combustion engine 16 is supplied, which is taken from a fuel circuit. The reagent realized as fuel serves, for example, for regenerating one in the exhaust gas purification device 20 contained NOx storage catalyst of embedded NOx compounds, according to the aforementioned DiAir operation at a high load of the internal combustion engine 18 and a correspondingly high temperature of the NOx storage catalyst 20 a higher dosing rate specified is considered at a lower load of the internal combustion engine 18 ,

Fuel as a reagent 14 can also be metered, on a catalytically active surface in the exhaust gas purification device 20 exothermic for heating the exhaust gas purification device 20 or another exhaust purification device downstream of the exhaust purification device 20 is arranged.

For the reagent 14 It may also be, for example, a urea-water solution as a precursor of the reagent ammonia upstream of an SCR catalyst in the exhaust passage 16 is dosed.

The internal combustion engine 18 contains a cooling circuit 22 , its temperature 24 a control unit 30 is made available.

The reagent 14 is from a pump 32 on a pressure of for example 10 brought bar and by means of a metering valve 34 metered, wherein the metering valve 34 determines the reagent rate.

The pump 32 is realized as a reciprocating pump having a movably arranged in a central opening armature 36 and a magnetic coil 38 contains. The anchor 36 and the magnetic coil 38 as well as the anchor 36 and the magnetic coil 38 surrounding metal parts form a magnetic circuit 36 . 38 ,

The magnetic coil 38 is on a coil carrier 40 arranged. At the front end of the bobbin 40 with the magnetic coil 38 is a seal 42 provided, which is realized as an O-ring. The seal 42 forms a first sealing surface 44 between the seal 42 and the anchor 36 and a second sealing surface 46 between the seal 42 and a guide sleeve 48 , The anchor 36 is with a not shown in detail reciprocating the pump 32 connected with the anchor 36 a reciprocating motion in the guide sleeve 48 during energization of the magnetic coil 38 performs.

The magnetic coil 38 is from the controller 30 by means of a pump signal 50 driven. At every pulse of the pump signal 50 leads the anchor 36 a stroke movement, so that a certain volume of the pump 32 is encouraged.

The dosing rate is set by the control unit 30 by means of a dosing signal 52 fixed, which the metering valve 34 is supplied.

At low temperatures, the gasket becomes 42 brittle. If the temperature drops further, the glazing must be glazed 42 be counted. The at least one seal 42 is to be dimensioned such that at all operating temperatures a reliable seal of the reciprocating pump is given to prevent the uncontrolled escape of reagent, in the present case in particular of fuel.

According to the invention, a heating of the seal 42 provided at low temperatures to the seal 42 To bring as soon as possible in a temperature range in which the risk of embrittlement does not occur.

In the illustrated embodiment, the heating is to be indirectly by a in the magnetic coil 38 generated heat loss done.

The control unit 30 contains a pump signal detection 60 who made a dosing request 62 and a heating request 64 be provided, and which the pump signal 50 sets.

The starting temperature can, for example, a calculated cooling of the seal 42 after switching off the reagent dosing system 10 determined from the temperature at the time of shutdown of the reagent dosing system 10 and a measured ambient air temperature. Alternatively or additionally, the starting temperature from the calculated cooling of the internal combustion engine 18 after switching off the internal combustion engine 18 respectively.

In the embodiment shown is as a measure 66 for the temperature of the seal 42 the temperature 24 of the cooling circuit 22 the internal combustion engine 18 used. A measure 66 for the temperature of the seal 10 becomes a heating signal setting 68 provided the measure 66 for the temperature of the seal 42 with a temperature threshold 70 compares and, depending on the comparison result, the heating demand 64 provides.

Alternatively or additionally, as a further measure 72 for the temperature of the seal 42 a measure 72 for the temperature of the magnetic coil 38 the reciprocating pump 32 be used. The further measure 72 is also the heating signal determination 68 provided the measure 72 with the temperature threshold 70 compares and, depending on the comparison result, the heating demand 64 provides.

The further measure 72 for the temperature of the seal 42 may be from an estimate of the temperature of the solenoid coil 38 by means of the magnetic coil 38 flowing current i to be determined during the activation of the solenoid 38 flows. The current i is from a current sensor 74 captured and the control unit 30 made available.

The detected current i becomes a resistance detection 74 made available from the current i and the time change di / dt of the current i and from the inductance L of a magnetic circuit 36 . 38 , which is the magnetic coil 38 and the anchor 36 includes the resistance of the solenoid coil 38 determined. The connection is through: u = L di / dt given, omitting the sign. The inductance L relates the time change di / dt of the current i with the induced voltage u. This results in the resistance R, which is independent of the operating voltage. R = L di / dt / i.

Starting from the known resistance R, for example, 20 ° C can, taking into account the known temperature coefficient of the winding material of the magnetic coil 38 the currently detected resistance R in the currently available measure 72 for the temperature of the seal 42 be converted.

In the presence of the measure 66 or the other measure 72 for the temperature of the seal 42 decides the heating signal definition 68 by comparison with the temperature threshold 70 whether a heating request 64 is issued. The temperature threshold 70 may be at 0 ° C, for example.

If the temperature threshold is undershot 70 becomes the heating demand 64 provided and the pump signal setting 60 made available. Thereupon, the pump signal setting is initiated 60 by means of the pump signal 50 an energization of the solenoid 38 , which, however, deviates from the current during normal dosing operation.

The pump signal 50 during normal dosing operation is in 2a shown. Instead of the two pulses shown 76 Preferably, a plurality of pulses is provided. Each pump drive pulse 76 actuates the pump 32 for a hub. In 2 B is symbolized the mean current i shown during normal dosing due to the occurrence of the pump drive pulses 76 occurs. The steepness of the rising and falling edge of the current i depends in particular on the inductance L of the magnetic coil 38 in conjunction with the magnet armature 36 from. The duration of the pump drive pulses 76 During the normal dosing operation is set to a time that leads to a current i, in each case a current threshold 78 exceeds. The current threshold 78 is set such that a current i, which is the current threshold 78 exceeds, to actuate the anchor 36 the pump 32 leads. The optionally additionally present pump drive pulses 76 are in 2 B unrecorded.

The pump signal 50 during heating is in 2c shown. The pump signal 50 should be realized during the heating operation as a pulse width modulated signal, wherein by means of the duty cycle of heating pulses 80 the rms value of in 2d shown current i at most assumes a value at which the armature of the pump 32 the reciprocating pump 32 just does not perform any lifting movement. In 2d is symbolized the mean value of the effective current i shown. This is the case when the current i is below the current threshold 78 lies. The duty cycle is preferably determined experimentally, wherein the duty cycle in addition to the measure 66 . 72 for the temperature of the seal 42 can depend.

Due to the greater friction at lower temperatures, a higher duty cycle, corresponding to a higher rms value of the current i, may be provided than at higher temperatures, but still below the temperature threshold 78 lies. The heating impulses 80 are only during pump drive pauses or between successive pump drive pulses 76 provided.

Once the measure 66 . 72 for the temperature of the seal 42 the temperature threshold 70 exceeds, the heating signal setting decreases 68 the heating requirement 64 back so that the normal dosing operation of the pump 32 without the alone or in addition to the pump drive pulses 76 occurring heating impulses 80 is continued.

The inventively provided guide sleeve 48 supports the implementation of the method according to the invention in that the heat transfer from the magnetic coil 38 to the seal 42 due to the heat conduction in the guide sleeve 48 is improved, causing a faster heating of the seal 42 is reached. For this purpose, the guide sleeve 48 a close thermal contact both to the solenoid coil 38 as well as to the seal 42 on. The anchor 36 is in the guide sleeve 48 guided.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102007017458 A1 [0008]
• DE 102011088708 A1 [0012]

Claims (11)

Method for expanding the temperature range of use of seals ( 42 ), which are in a magnetic circuit ( 36 . 38 ) are used, which is a magnetic coil ( 38 ), characterized in that a measure ( 66 . 72 ) for the temperature of the seal ( 42 ) it is determined that the measure ( 66 . 72 ) for the temperature of the seal ( 42 ) with a temperature threshold ( 70 ) and that when the temperature is below the temperature threshold ( 70 ), a heating of the seal ( 42 ) is made. A method according to claim 1, characterized in that the heating of the seal ( 42 ) indirectly by means of an energization of the magnetic coil ( 38 ) is carried out. A method according to claim 2, characterized in that the heating with a clocked operation ( 50 ) is carried out, wherein the magnetic coil ( 38 ) with pulse width modulated heating pulses ( 80 ) is driven. A method according to claim 3, characterized in that the current (i) during the heating pulses ( 80 ) a predetermined current threshold ( 78 ), the current threshold ( 78 ) is set to a value at which the magnetic circuit ( 36 . 38 ) does not perform any action. Method according to claim 1, characterized in that the dimension ( 72 ) for the temperature of the seal ( 42 ) from the electrical resistance (R) of the magnetic coil ( 38 ) is determined. Method according to claim 1, characterized in that as a measure ( 66 ) for the temperature of the seal ( 42 ) the temperature of a cooling water circuit ( 22 ) an internal combustion engine ( 18 ) is used. Device for expanding the temperature range of use of seals ( 42 ), which are in a magnetic circuit ( 36 . 38 ) are used, which is a magnetic coil ( 38 ), characterized in that a specially prepared control device ( 30 ) is provided for carrying out the method according to one of the preceding claims. Apparatus according to claim 7, characterized in that a current sensor ( 74 ) for the determination of the by the magnetic coil ( 38 ) flowing current (i) is provided. Apparatus according to claim 7, characterized in that the magnetic coil ( 38 ) in a reciprocating pump ( 32 ) is arranged and that the reciprocating pump ( 32 ) a guide sleeve ( 48 ), which has a thermal contact both to the magnetic coil ( 38 ) as well as to the seal ( 42 ) having. A computer program that performs all the steps of a method as claimed in any one of claims 1 to 6 when running on a computer. A computer program product comprising program code stored on a machine-readable medium for performing the method of any one of claims 1 to 6 when the program is run on a computer.

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