JP2015197102A - Method and device for operating feed pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for operating a feed pump including a solenoid coil and a movable element in which the device is driven over a life period within a specified operation range and it is detected whether or not a troubled part is present in the feed pump.SOLUTION: This invention relates to a method and device for injecting, under adjusted volume, reduction liquid for reducing nitrogen oxides into an exhaust gas flow through an injection unit 70 at an aftertreatment system for exhaust gas of an internal combustion engine 1 by a volume adjustment unit 80, in particular, relates to a control unit 101. A feed pump is operated under control and in this case, an operation of a movable element is carried out within a predetermined limited time after control and a coil current generated at this time is inspected whether or not its value is within a specified current limit value. In one hand, since the feed pump is driven over its life time within a predetermined operation range, a positive function of the feed pump is guaranteed and in the other hand, it is detected whether or not any trouble is present within an on-board diagnosis range.

Description

  The present invention is a method for operating a feed pump having an electromagnetic coil and a mover, wherein the feed pump is a constituent part of a metering unit, and the exhaust gas aftertreatment of an internal combustion engine by the metering unit In the system, the liquid for reducing nitrogen oxides is metered into the exhaust gas stream via the injection unit in front of the catalyst structure group of the exhaust gas aftertreatment system as viewed in the exhaust gas flow direction. Regarding the method.

  The invention further relates to an apparatus, in particular a control unit, for carrying out the method according to the invention.

In order to meet today's exhaust gas regulations, nitrogen oxide storage catalysts (NSC) are mainly used in the small diesel field. Nitrogen oxide (NO, NO ₂ ) can be reduced in the exhaust gas pipe by the nitrogen oxide storage catalyst. For this purpose, nitrogen oxides are first stored in the catalyst. When the storage capacity of the catalyst is full, the rich exhaust gas mixture is adjusted by the engine controller. At this time, the nitrogen oxides intermediately stored in the catalyst are reduced to nitrogen.

  This method works well at low or average load ranges, such as temperature ranges. In order to comply with future exhaust gas regulations, it is necessary to monitor the limit value of the high load range.

In order for the nitrogen oxide storage catalyst (NSC) to reduce nitrogen oxides even during high load operation and at high temperatures, the nitrogen oxide storage catalyst must be operated in a so-called DiAir mode. DiAir represents a "Di esel NOx Aftertreatment by A dsorbed I ntermediate R eductants" ( Diesel NOx aftertreatment with occluded reducing intermediate). In this case, hydrocarbons (Hydro Carbons) are metered in front of the nitrogen oxide storage catalyst, which is called HCI (Hydro Carbons Injection). For this purpose, additional diesel fuel is usually metered into the exhaust gas line.

For this, a special DiAir metering system is required, which consists of the following structural groups:
An injection unit mainly consisting of a metering valve and a cooling body;
A metering unit mainly consisting of a compression stroke (eg a feed pump) and a pressure sensor;
A control unit that runs in the engine control device as hardware and / or software, for example;
Consists of.

  As a component or partial system related to exhaust gas, the DiAir component is subjected to extremely strict requirements by the exhaust gas regulation law. Within the scope of on-board diagnostics (OBD), all subcomponents are monitored for their correct and incorrect functions.

  In a Diair metering system, monitoring the feed pump during the compression stroke of the metering unit is extremely important. The feed pump is generally configured as a reciprocating piston pump. In this case, the mover is moved under the control of an electromagnetic coil, and the mover feeds liquid through the diaphragm, and the pressure required for injection is supplied. Form. In this case, it is particularly important to monitor the movement of the mover.

  Patent Document 1 describes a method and an apparatus for controlling the mechanical movement of an electromagnetic valve mover, and an electromagnetic coil is provided for operating the electromagnetic valve mover. In this case, the electromagnetic coil After the kinetic current is interrupted by the electromagnetic valve, the inductance voltage assigned to the mechanical interruption point (BOP, EIP) in the electromagnetic coil, which is caused by the movement of the solenoid valve mover, is monitored and is thereby generated. Each of the received signals is increased to a detectable signal level by an external energy source. Furthermore, it is described that the inductance voltage of the electromagnetic coil is monitored by the measuring coil.

  Patent Document 2 describes a liquid metering injection system for metering a liquid into fuel or metering into exhaust gas generated at the time of combustion. An electrically operable metering pump device for supplying the liquid to be metered from the metering fluid tank to the medium to be mixed with the metering fluid, and generated during operation of the metering pump device A detection device for detecting an operation value representing the characteristics of the metering pump device, the operation value is compared with at least one reference value, and the operation state of the metering pump device is determined based on the comparison result. A comparison / determination device for determining. In this case, in particular, the coil current through the pump is evaluated and compared with at least one reference value in relation to the differences between the various operating conditions.

  According to Patent Document 3, a method and an apparatus for operating an electromagnet in an intrinsically safe DC circuit are known. In this case, the actual current in the coil winding is continuously measured after control of the electromagnet and evaluated to detect the movement of the mover. In this case, continuous current measurement of the actual current in the coil winding of the electromagnet is also used to detect electrical, electronic, mechanical or electromagnetic malfunctions in the valve.

German Patent No. 3730523 German utility model registration No. 0102002 specification German Patent Publication No. 10212092

  However, none of the above documents discloses a control operation that guarantees a predetermined operation of the feed pump over its service life. The object of the present invention is therefore to provide a corresponding method.

  It is a further object of the present invention to provide a corresponding device for carrying out this method.

  Said object of the method is solved by the features of claims 1-7.

  According to the present invention, the feed pump is controlled and operated, and at this time, the mover is moved within a predetermined time limit after the control, and the coil current generated at this time is within a predetermined current limit value. A check is made to see if it exists. This ensures the reliable functioning of the feed pump since the feed pump is driven within a predetermined operating range over its service life. The feed pump is operated only by current within the required required current range. Thus, the feed pump itself as well as the components necessary for control, such as power switches, output stages, etc., are protected against overloads and thus against premature failure.

In a preferred form, the coil current flowing through the feed pump electromagnetic coil is read via the feed pump control unit and, by means of a software algorithm, the time point (t _BMP ) for the movement start of the mover and / or The time point (t _MSP ) at which the mover is stopped, and the current value (I _BMP ) and / or the current value for stopping the mover corresponding to the start of movement of the mover (I _MSP ) are determined. This is done by evaluating the time derivative of the current change. 348498 and R.C. Described in an unpublished patent application having 346347.

  According to a particularly preferred method variant, during the pulling phase, the slope of the current increase that has occurred, and thus indirectly the start of movement of the mover and the movement of the mover through the adaptation of the pulse width modulation control of the electromagnetic coil. Affects the point of child stop. In this case, a fixed voltage effective value is set according to the variable duty ratio. At the same time, a large PWM duty ratio that produces a high voltage effective value means a steep increase in current. A small PWM duty ratio resulting in a correspondingly low voltage rms value means a gentle increase in current. As a result, the predetermined current characteristic range is maintained both at the start of movement of the mover and at the stop of the mover, and it is ensured that a current value that is not particularly unacceptable.

  In this case, according to a variant embodiment of the method, the feed pump generates the mover movement start (BMP) and the coil current and / or mover stop time (MSP) generated at that time and at that time. The coil current is operated so as to be within an allowable current characteristic change range preset by the minimum and maximum time points and the upper and lower current limit values.

  Similarly, according to a preferred variant, for the purpose of control, the target point for moving the mover and / or the target point for starting the mover movement and the corresponding target for stopping the mover The current and / or the target current at the start of the mover movement are preset and compared with the corresponding actual values. In this case, the adjustment characteristics of the mover motion are analyzed, where disturbance effects such as battery voltage fluctuations, possible mover friction, diaphragm viscosity and temperature effects, etc. affect the adjustment characteristics. It is corrected in such a form.

  In view of meeting legal regulations related to on-board diagnostics (OBD), if the allowable current characteristics change range is exceeded, a fault in the feed pump is inferred and appropriate in the upper engine controller. It is preferable that the failure is registered.

  According to a preferred use of the method, which has a variant embodiment, the method is used in a metering system, by means of this metering system, during high load operation of an internal combustion engine configured as a diesel engine, nitrogen oxides In order to reduce the exhaust gas, hydrocarbons as diesel fuel are metered into the exhaust gas passage in front of the nitrogen oxide storage type catalyst as seen in the flow direction of the exhaust gas, It has an injection unit generally consisting of a metering valve and a cooling body, a metering unit consisting of a feed pump generally configured as a reciprocating piston pump, a pressure sensor and a control unit. This metering system is also known as the DiAir system and is used in particular for small diesel internal combustion engines, for example PKW (passenger cars), for nitrogen oxide reduction. In the DiAir mode, as described at the beginning, diesel fuel is additionally injected particularly during high-load operation of the internal combustion engine. Furthermore, this fuel injection is also used to raise the temperature of the exhaust gas during regeneration of the diesel particulate filter (DPF).

  Basically, this method is also suitable for an exhaust gas aftertreatment system in which an ammonia decomposition solution such as an aqueous urea solution is metered into the exhaust gas passage in front of the SCR catalyst in order to reduce nitrogen oxides. Used in. Even in such a system, a reliable function type of the feed pump can be obtained. Appropriate legal regulations related to on-board diagnostics (OBD) can also be observed by the method.

  The problem with respect to the device is solved by the fact that the control unit comprises a device for carrying out the method, in particular analysis software for checking the movement of the mover, and a control device and a PWM adjustment member. The In this case, the control unit may be implemented at least partially based on software, and the control unit may be configured as a separate unit or as an integral component of the host engine controller. The current at which the current value is allowed by the control device and the PWM adjustment member, via the slope of the increase in the generated current, affecting the start of the mover movement, the stop of the mover and the generated current value. Adaptation of pulse width modulation control is performed so as to remain within the characteristic range.

  The present invention will be described in detail below with reference to the embodiments shown in the drawings.

It is the schematic which shows the example of the technical environment of this invention. It is the schematic of a metering system. 6 is a first variation characteristic graph schematically showing temporal current characteristic variation for a reciprocating piston of a metering system. FIG. 6 is a second variation characteristic graph showing different current variations for the reciprocating piston. FIG. 6 is a third change characteristic graph showing the current change for a reciprocating piston within a possible current characteristic change range. It is a block diagram of the evaluation method by this invention.

  FIG. 1 shows an example of a technical environment in which the method according to the invention can be used. In this case, the drawings are limited to the components necessary to explain the invention.

  FIG. 1 shows an example of an internal combustion engine 1 configured as a diesel engine. The internal combustion engine 1 includes an engine block 10 and an exhaust gas passage 30, and exhaust gas is exhausted in the exhaust gas passage 30. A gas flow 20 is guided. The exhaust gas passage 30 has an exhaust gas purification device. In the illustrated embodiment, the exhaust gas purification device is arranged in the exhaust gas flow direction as a catalyst-coated component, and is first oxidized with nitrogen. It has a material storage catalyst 40 (NSC) and a diesel particulate filter 50 (DPF). An injection unit 70 is provided in the exhaust gas passage 30 in front of the nitrogen oxide storage catalyst 40 (NSC), and this injection unit 70 is carbonized to reduce nitrogen oxide at a high temperature during high load operation. Hydrogen (HC) is injected during the DiAir phase, for example in the form of fuel. Furthermore, this fuel injection may be used to increase the temperature of the exhaust gas during regeneration of the diesel particulate filter 50 (DPF).

  The injection unit 70 belongs to one metering system 60 together with the metering unit 80, and the metering system 60 is controlled by the control unit 101. The functionality of the control unit 101 is executed by the host engine control device 100 and ECU (Electronic Control Unit) based on software and / or hardware, as is common in diesel engines.

  Returning a high-pressure pump (not shown) for fuel injection of the internal combustion engine 1 to a metering unit 80, also called PSU-HCI (Power Supply Unit for Hydro Carbon Injection) Diesel fuel is supplied from the pipeline via the inlet 81. Excess fuel is guided back to the tank 90 (see FIG. 2) via the outlet 83. The injection unit 70 has a water cooling device 72 in order to protect the components mounted in the injection unit 70 against high temperatures in the exhaust gas passage 30.

  FIG. 2 schematically shows further details of the metering system 60. Within the metering unit 80, the pressure of the diesel fuel is increased to an injection pressure, typically 10 bar, by a feed pump configured as a reciprocating piston pump 86 from the inlet 81 via a feed path 82. When a quantitative request is made to the metering system 60, the metering valve 71 which is a constituent part of the injection unit 70 is opened. Monitoring and control of the metering system 60 and hydraulic diagnosis are performed via a pressure sensor 87. Valves 85 are provided in front of and behind the reciprocating piston pump 86 in the direction of diesel fuel flow, and these valves prevent backflow or retraction. By the return device 88, excess fuel due to leakage, for example, is sent into the tank 90 through the outlet 83 in the return path 84.

  The reciprocating piston pump 86, the pressure sensor 87 and the metering valve 71 are controlled by the control unit 101 or obtain feedback from these components, for example regarding the current and temperature flowing through the electromagnetic coil of the reciprocating piston pump 86. .

  Ensuring that the mover is attracted within the reciprocating piston pump 86 during the peak phase 207, thereby ensuring that the high coil current 201 generates a strong magnetic force during this phase, and that during the hold phase 208 the energy supply or In order to reduce the output loss, the reciprocating piston pump 86 is controlled by the control unit 101 via a so-called “Peak & Hold” current characteristic change. This type of current characteristic change 203 is schematically illustrated in the first change characteristic graph of FIG. Coil current 201 due to the electromagnetic coil is shown in relation to time 202. In a general form, control is performed via pulse width modulation (PWM).

  FIG. 4 is a second variation graph 200, also showing the coil current 201 associated with time 202, with the regular current for the lifting magnet of the reciprocating piston pump 86 during the peak phase 207 and hold phase 208. In this case, a predetermined amount of fuel is sent into the feed path 82 of the metering unit 80 for each stroke. From this current change, the start time 209 (BMP) and the mover stop 210 (MSP) time can be determined. A corresponding algorithm for determining the starting time point 209 (BMP) and the mover stop 210 (MSP) is the internal reference number R.P. 348498 and R.C. 346347, which is described in particular in a patent application not yet published by the present applicant.

  Actually, based on hardware constraints, the collaborative work between components having a set operating range is limited. Therefore, the coil current 201 necessary for the reliable operation of the pump, i.e. to attract the mover, is not provided within the entire operating range or to protect the output stage used for control. Shut off early.

FIG. 4 shows a PWM1-current change 205 as an example. In the PWM1-current change 205, the start time point 209 (BMP) or the mover stop 210 (MSP) is omitted. This is because the magnetic force is not high enough for the mover stroke. This is the case for example in hot coils. The hot coil allows only small currents below the lower limit current limit 212I _min based on high electrical resistance and therefore generates only a small attractive force.

The PWM2-current change 206 further illustrated in FIG. 4 reaches, for example, the output stage limit or cut-off or saturation, where the start time point 209 (BMP) and the time point of the mover stop 210 (MSP) are the upper limit current limit value 211I. _A state in which the current changes above _max is shown. This is the case, for example, when the electromagnetic coil is at room temperature and thus has a small electrical resistance. As a result, a relatively high current is generated, thereby reaching the output stage limit. As shown in FIG. 4, the position of the start time point 209 (BMP) and the time point of the mover stop 210 (MSP) are shifted in the current-time graph.

  In order to guarantee the predetermined operation of the pump over its service life, the method according to the invention assumes operation of the feed pump controlled by a DiAir system. This function ensures that the mover motion is carried out within a defined time and that the generated coil current 201 is within the allowed current-time range necessary for reliable operation.

FIG. 5 shows an allowable current characteristic change range 215 in the third change characteristic graph 200. The current characteristic change range 215 is between the upper limit current limit value 211I _max and the lower limit current limit value 212I _min. In relation to the current coil current 201 and in relation to the allowed time window between the maximum time 214t _max and the minimum time 213t _min . Current characteristic change 203 having a starting time point 209 (BMP) and a current value position corresponding thereto, and a mover stop 210 (MSP) and a time point corresponding to the current value increase control frequency (PWM +) Alternatively, it is possible to move within the allowable current characteristic change range 215 when the control frequency decreases (PWM−). If it is out of this range, a failure occurs.

As schematically shown in the block diagram 300 of FIG. 6, the coil current 201 of the lifted magnet is read via the measuring device 315 and provided to the software. This is performed, for example, by a measurement shunt provided in the control unit 101. The actual time MSP305t _MSP and / or the actual time BMP307t _BMP and the corresponding actual current MSP306I _MSP and / or actual current BMP308I _BMP are determined by the coil current 201 via a software algorithm, in which case the evaluation method is internal Reference number R. 348498 and R.C. The evaluation method described in the above-mentioned specification of the present applicant having 346347 can be used.

By means of the closed loop control circuit, the desired target time point MSP301t _MSP and / or the target time point BMP303t _BMP and the corresponding target current MSP302I _MSP and / or target current BMP304I _BMP are provided by the characteristic map unit 309, in this case the actual value The time and current values are subtracted from the corresponding target values in the subtractor 310, and the difference is supplied to the control device 311.

  Through the adaptation of the pulse width modulation control during the pulling phase, which is performed in the PWM adjustment member 312, the slope of the generated current increase is influenced, thereby indirectly starting the mover start point 209 (BMP). And the time for the mover stop 210 (MSP) is preset. In this case, a fixed voltage effective value of, for example, 12V is set according to the variable duty ratio. At the same time, a large PWM duty ratio that produces a high voltage effective value means a steep increase in current. A small PWM duty ratio resulting in a correspondingly low voltage rms value means a gentle increase in current.

  In the arithmetic unit 313, the adjustment characteristic of the mover motion is analyzed, and the adjustment characteristic is influenced by the influence 314 of disturbance, for example, battery voltage fluctuation, possible mover friction, diaphragm viscosity and temperature influence. receive. These interference effects 314 can be corrected by control.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 10 Engine block 20 Exhaust gas flow 30 Exhaust gas passage 40 Nitrogen oxide occlusion type catalyst 50 Diesel particulate filter 60 Metering system 70 Injection unit 71 Metering valve 72 Water cooling device 80 Metering unit 81 Inlet 82 Feed path 83 Outlet 84 Return path 85 Valve 86 Reciprocating piston pump 87 Pressure sensor 88 Return device 90 Tank 100 Engine controller 101 Control unit 200 Change characteristic graph 201 Coil current 202 Time 203 Current characteristic change 204 Current change 205 PMW1-Current change 206 PWM2-Current change 207 Peak phase 208 Hold phase 209 Start point (BMP)
210 Mover stop (MSP)
211 Upper limit current limit value 212 Lower limit current limit value 213 Minimum time point 214 Maximum time point 215 Current characteristic change range 300 Block diagram 301 Target time point MSP
302 Target current MSP
303 Target time BMP
304 Target current BMP
305 Actual time MSP
306 Actual current MSP
307 Actual BMP
308 Actual current BMP
309 Characteristic map unit 311 Control device 312 PWM adjustment member 313 Arithmetic unit 314 Influence of interference 315 Measuring device

Claims (8)

A method for operating a feed pump having an electromagnetic coil and a mover, wherein the feed pump is a constituent part of a metering unit (80), and the metering unit (80) causes an internal combustion engine (1) to operate. In the exhaust gas aftertreatment system, a liquid for reducing nitrogen oxides is injected into the exhaust gas stream (20) in front of the catalyst structure group of the exhaust gas aftertreatment system as viewed in the exhaust gas flow direction. In the method of metered injection via the unit (70),
The feed pump is controlled, and at this time, the mover is moved within a predetermined time limit after the control, and the coil current (201) generated at this time is within a predetermined current limit value. A method for operating a feed pump, characterized by checking whether.   The coil current (201) flowing through the electromagnetic coil of the feed pump is read via the control unit (101) of the feed pump, and the time point for starting the movement of the mover and / or the mover by means of a software algorithm The method according to claim 1, wherein a current value for starting the movement of the mover and / or a current value for stopping the mover corresponding to the time of the stop is determined.   During the pulling phase, through the adaptation of the pulse width modulation control of the electromagnetic coil, it influences the slope of the current increase that has occurred, and thus indirectly the moment of movement of the mover and the moment of stop of the mover. A method according to claim 1 or 2, characterized.   When the movement of the mover is started, the coil current (201) generated at that time and / or the point of time when the mover is stopped, and the coil current (201) generated at that time are minimum And operating within a permissible current characteristic change range (215) preset by a maximum time point and upper and lower current limit values (211, 212). 4. The method according to any one of items 1 to 3.   For control purposes, the target time point for the mover stop and / or the target time point for the start of the mover movement, and the corresponding target current and / or the mover movement 5. The method according to claim 1, wherein the starting target current is preset and compared with a corresponding actual value.   If the allowable current characteristic change range (215) is deviated, a failure in the feed pump is estimated and a corresponding failure is registered in the upper engine controller (100). The method according to any one of 1 to 5.   Use of the method according to any one of claims 1 to 6, wherein the method is used in a metering system (60) and is configured as a diesel engine by the metering system (60). In order to reduce nitrogen oxides during high-load operation of 1), hydrocarbons as diesel fuel are exhausted in the exhaust gas passage (in front of the nitrogen oxide storage catalyst (40) as seen in the flow direction of the exhaust gas). 30), the metering system (60), as a structural group, is composed of an injection unit (70) composed of a metering valve (71) and a cooling body, and a reciprocating piston pump (86). Use, comprising a metering unit (80) comprising a configured feed pump, a pressure sensor (87) and a control unit (101). A device for operating a feed pump, in particular a control unit (101), which is a component of a metering unit (80), configured as a reciprocating piston pump (86) having an electromagnetic coil and a mover, In the exhaust gas aftertreatment system of the internal combustion engine (1) by the metering unit (80), the liquid for reducing nitrogen oxides is seen in the flow direction of the exhaust gas and the catalyst configuration of the exhaust gas aftertreatment system In the form of metered injection in the exhaust gas stream (20) via the injection unit (70) in front of the element,
Device for carrying out the method according to any one of claims 1 to 7, in particular the analysis software for checking the movement of the mover, and the control device (311). And a device for operating the feed pump, characterized in that it comprises a PWM adjustment member (312).

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