JP6663645B2 - Method and apparatus for operating a feed pump - Google Patents

Description

  The invention relates to a method for operating a feed pump having an electromagnetic coil and a mover, said feed pump being a component of a metering unit, by means of which the exhaust gas aftertreatment of an internal combustion engine is performed. In the system, a liquid for reducing nitrogen oxides is metered into the exhaust gas stream via an injection unit in front of the catalyst structure group of the exhaust gas aftertreatment system as viewed in the flow direction of the exhaust gas. About the method.

  The invention further relates to a device for implementing the method according to the invention, in particular a control unit.

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

  This method works well in low or average load ranges, for example in the temperature range. In order to comply with future emissions regulations, it is necessary to monitor the limits of the high-load range.

In order for the nitrogen oxide storage catalyst (NSC) to reduce nitrogen oxides even at a high load operation and at a high temperature, 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 and injected before the nitrogen oxide storage catalyst, which is called HCI (Hydro Carbons Injection "hydrocarbon injection"). For this purpose, additional diesel fuel is usually metered into the exhaust line.

For this, a special DiAir metering system is required, which consists of the following groups of structures:
An injection unit mainly comprising 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 executing within the engine control as, for example, hardware and / or software;
Consists of

  As exhaust gas components or subsystems, DiAir components are subject to very strict requirements by the Emission Control Law. Within on-board diagnostics (OBD), all sub-components are monitored for their correct and incorrect function.

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

  Patent Literature 1 describes a method and an apparatus for controlling mechanical movement of a solenoid valve mover. An electromagnetic coil is provided for operating the solenoid valve mover. After the kinetic current is interrupted by the solenoid 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 armature, is monitored, thereby producing the inductance voltage. Each of the applied signals is increased to a detectable signal level by an external energy source. It is further described that the inductance voltage of the electromagnetic coil is monitored by a measuring coil.

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

  According to DE 199 08 316 A1 a method and a device 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 the control of the electromagnet and is evaluated in order to detect the movement of the armature. In this case, a continuous current measurement of the actual current in the coil windings 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 German Offenlegungsschrift 102 12092

  However, none of the above documents disclose a control operation that guarantees a predetermined operation of the feed pump over its useful life. It is an object of the present invention to provide a corresponding method.

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

  The object of the method is solved by the features of claims 1 to 7.

  According to the present invention, the feed pump is controlled and operated, and at this time, the movement of the mover is performed within a predetermined time limit after the control, and the coil current generated at this time falls within a predetermined current limit value. A check is made to see if there are any. This guarantees a reliable function of the feed pump, since the feed pump is driven within its operating range over its useful life. The feed pump is operated only with a current within the required required current range. The feed pump itself, as well as the components required for control, such as power switches, output stages, etc., are protected against overload and thus against premature failure.

In a preferred manner, the coil current flowing through the electromagnetic coil of the feed pump is read via the control unit of the feed pump and, by means of a software algorithm, the time point (t _BMP ) for the start of the movement of the armature and / or The point of time when the armature stops (t _MSP ) and the corresponding current value for starting the movement of the armature ( _IBMP ) and / or the current value for stopping the armature ( _IMSP ) are determined. This is done by evaluating the time derivative of the current change, e.g. 348498 and R.I. No. 346347, which is described in an unpublished patent application by the present applicant.

  According to a particularly preferred variant of the method, during the pulling phase, via the adaptation of the pulse width modulation control of the electromagnetic coil, the gradient of the current increase generated, and thus indirectly the start of movement of the mover and the movement of the mover The time of child suspension is affected. In this case, a fixed voltage effective value is set by the variable duty ratio. A large PWM duty ratio, which simultaneously produces a high effective voltage value, means a steep current increase. A small PWM duty ratio that produces a correspondingly low effective voltage value means a gradual increase in current. This ensures that the predetermined current characteristic range is maintained both at the start of the movement of the mover and at the time of the stop of the mover, and that particularly unacceptable current values are not generated.

  In this case, according to a variant of the method, according to a variant of the feed pump, the movement of the armature starts (BMP) and the coil current generated at that time and / or the time of armature stop (MSP), and The operation is performed such that the set coil current falls within an allowable current characteristic change range preset by the minimum time point and the maximum time point, and the upper and lower current limit values.

  According to a similarly preferred variant, for the control, the target time for the armature stop and / or the target time for the start of the armature movement and the corresponding target time for the armature stop are obtained. The current and / or the target current at the start of the armature movement are preset and compared with the corresponding actual values. In this case, the adjustment characteristics of the armature movement are analyzed, in which the effects of disturbances, such as fluctuations in the battery voltage, possible armature friction, the effects of diaphragm viscosity and temperature, etc., influence the adjustment characteristics. It is corrected in such a format.

  In consideration of satisfying the legal regulations related to the on-board diagnosis (OBD), if the current characteristic change range is out of the allowable range, a failure in the feed pump is estimated and a corresponding level is determined in a higher-level engine control device. It is preferable to register the failure.

  According to a preferred use of the method, which has a variant embodiment, the method is used in a metering system, by means of which the nitrogen oxides are produced during high-load operation of an internal combustion engine configured as a diesel engine. In order to reduce the amount of hydrocarbons, hydrocarbons as diesel fuel are metered into the exhaust gas passage in front of the nitrogen oxide storage catalyst in the flow direction of the exhaust gas, and the metering system is configured as a structure group, It has an injection unit which consists essentially of a metering valve and a cooling body, a metering unit which consists essentially of a feed pump 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 for PKW (passenger cars), for nitrogen oxide reduction. In the DiAir mode, as mentioned at the outset, diesel fuel is additionally injected, especially during high-load operation of the internal combustion engine. Furthermore, this fuel injection is also used to increase the temperature of the exhaust gas during regeneration of the diesel particulate filter (DPF).

  Basically, this method is also suitable in an exhaust gas aftertreatment system in which an ammonia decomposition liquid, for example, an aqueous urea solution is metered into an exhaust gas passage in front of an SCR catalyst to reduce nitrogen oxides. Used in. Even in such a system, a reliable functional form of the feed pump is obtained. Corresponding legal regulations relating to on-board diagnostics (OBD) can also be complied with by the method.

  The object of the invention is attained in that the control unit comprises a device for carrying out the method, in particular analysis software for checking the movement of the armature, and a control device and a PWM adjusting member. You. In this case, it is implemented at least in part on software, and the control unit may be configured as a separate unit or as an integral component of a higher-level engine control. By means of the control device and the PWM adjusting member, the time of the start of the armature movement and the time of the armature stop and the generated current value are influenced via the gradient of the generated current increase, whereby the current value is permitted. Adaptation of the pulse width modulation control is performed so as to remain within the characteristic range.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

1 is a schematic diagram illustrating an example of a technical environment of the present invention. 1 is a schematic diagram of a metering system. 4 is a first variation characteristic graph schematically illustrating a temporal current characteristic variation for a reciprocating piston of a metering system. 5 is a second change characteristic graph showing different current changes for the reciprocating piston. 9 is a third change characteristic graph showing a 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 stream 20 is guided. The exhaust gas passage 30 has an exhaust gas purification device, which in the embodiment shown is arranged as a catalyst-coated component in the direction of flow of the exhaust gas, and is initially nitrogen oxidized. It has a substance 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). The injection unit 70 reduces carbon dioxide in order to reduce nitrogen oxides at high temperatures during high load operation. Hydrogen (HC) is injected during the DiAir phase, for example, in the form of fuel. Further, 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, together with the metering unit 80, belongs to one metering system 60, which is controlled by the control unit 101. The functionality of the control unit 101 is executed by a host engine control device 100 and an ECU (Electronic Control Unit) based on software and / or hardware, as is common in diesel engines.

  Return of 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 Hydrocarbon Injection) Diesel fuel is supplied from a pipe via an inlet 81. Excess fuel is guided back to the tank 90 (see FIG. 2) through the outlet 83. The injection unit 70 has a water cooling device 72 to protect 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. In the metering unit 80, the pressure of the diesel fuel is increased from the inlet 81 via a feed path 82 by a feed pump configured as a reciprocating piston pump 86 to the injection pressure, typically 10 bar. When a quantitative request is made to the metering system 60, a metering valve 71, which is a component of the injection unit 70, is opened. The monitoring and control of the metering system 60 and the hydraulic diagnosis are performed via a pressure sensor 87. Valves 85 are provided before and after the reciprocating piston pump 86 in the flow direction of the diesel fuel, respectively, and these valves prevent backflow or retreat. In the return path 84, surplus fuel due to, for example, leakage is sent to the tank 90 via the outlet 83 by the return device 88.

  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 on the current and temperature flowing through the electromagnetic coil of the reciprocating piston pump 86. .

  Ensure that the armature is drawn in the reciprocating piston pump 86 during the peak phase 207, thereby ensuring that the high coil current 201 creates a strong magnetic force during this phase, and that the energy supply or In order to reduce the power 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. The coil current 201 due to the electromagnetic coil is shown in relation to time 202. In a general form, the control is performed via pulse width modulation (PWM).

  FIG. 4 is a second graph 200 showing the coil current 201 also related to time 202, showing a regular current for the lifting magnet of the reciprocating piston pump 86 during the peak phase 207 and the hold phase 208. A change 204 is shown in which a predetermined amount of fuel is delivered into the feed path 82 of the metering unit 80 on 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 point 209 (BMP) and the armature stop 210 (MSP) is described in internal reference number R.A. 348498 and R.I. No. 346347, in particular in an unpublished patent application by the present applicant.

  In practice, cooperation between components having a set operating range is limited due to hardware constraints. Thus, the coil current 201 required for reliable operation of the pump, i.e. for attracting the armature, is not provided in the entire operating range or to protect the output stage used for control for protection. Cut off early.

FIG. 4 further shows, by way of example, a PWM1-current change 205, in which the start time 209 (BMP) or the armature 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. Hot coil, based on the high electrical resistance, not only a small current below the lower limit of the current limit 212I _min permissible, therefore less attracted force only occur.

The PWM2-current change 206 further illustrated in FIG. 4 reaches, for example, the output stage limit or cutoff or saturation, and the start time point 209 (BMP) and the armature stop 210 (MSP) time point are the upper current limit value 211I _It shows a state with a current change above _max . This is the case, for example, when the electromagnetic coil is at room temperature and therefore has a low electrical resistance. As a result, a relatively high current is generated, thereby reaching the power stage limit. As shown in FIG. 4, the position of the start point 209 (BMP) and the point of the armature stop 210 (MSP) are shifted in the current-time graph.

  In order to guarantee a predetermined operation of the pump over its service life, the method according to the invention presupposes a DiAir system-controlled operation of the feed pump. This function ensures that the armature movement is performed within a defined time and that the generated coil current 201 is within the allowed current-time range required for reliable operation.

FIG. 5 shows, in the third change characteristic graph 200, an allowable current characteristic change range 215, which is between the upper limit current limit value 211I _max and the lower limit current limit value 212I _min. And the allowed time window between the maximum instant 214t _max and the minimum instant 213t _min . The start time point 209 (BMP) and the current characteristic change 203 with the position of the current value corresponding thereto, and the armature stop 210 (MSP) and the time point for the corresponding current value are determined by increasing the control frequency (PWM +). Alternatively, when the control frequency is decreased (PWM-), it is possible to move within the allowed current characteristic change range 215. Any deviation from this range may cause a failure.

As schematically shown in the block diagram 300 of FIG. 6, the coil current 201 of the lifting 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 instant _MSP 305t _MSP and / or the actual instant _BMP 307t _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.I. The evaluation method described in the applicant's specification having 346347 can be used.

By means of the closed-loop control circuit, the desired target time MSP301t _MSP and / or the target time BMP303t _BMP and the corresponding target current MSP302I _MSP and / or target current BMP304I _BMP are provided by the characteristic map unit 309, in which 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 performed in the PWM adjustment member 312, it influences the gradient of the generated current increase, and thus indirectly, the start point 209 (BMP) of the armature And a time point for the armature stop 210 (MSP) is preset. In this case, a fixed voltage effective value of, for example, 12 V is set by the variable duty ratio. A large PWM duty ratio, which simultaneously produces a high effective voltage value, means a steep current increase. A small PWM duty ratio that produces a correspondingly low effective voltage value means a gradual increase in current.

  In the arithmetic unit 313, the adjustment characteristics of the armature movement are analyzed, whereby the interference characteristics 314, such as fluctuations in the battery voltage, possible armature friction, the influence of the diaphragm viscosity and temperature, etc., have an influence. receive. The effects of these disturbances 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 storage 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 control device 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 stage 208 Hold stage 209 Start point (BMP)
210 Mover stop (MSP)
211 Upper limit current limit 212 Lower limit current limit 213 Minimum time 214 Maximum time 215 Current characteristic change range 300 Block diagram 301 Target time MSP
302 Target current MSP
303 Target BMP
304 Target current BMP
305 Actual MSP
306 Actual current MSP
307 Actual BMP
308 Actual current BMP
309 Characteristic map unit 311 Controller 312 PWM adjustment member 313 Operation unit 314 Influence of disturbance 315 Measurement device

Claims (7)

A method for operating a feed pump having an electromagnetic coil and a mover, said feed pump being a component of a metering unit (80), wherein said metering unit (80) is used to operate an internal combustion engine (1). In the exhaust gas aftertreatment system of the present invention, 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 flow direction of the exhaust gas. In a metered injection via unit (70),
The feed pump is controlled and operated. At this time, the movement of the mover is performed within a predetermined time limit after the control, and the coil current (201) generated at this time is within a predetermined current limit value. is intended to check whether,
In the step of attracting the mover, the start of movement of the mover and the stop time of the mover are set by affecting the gradient of the generated current increase through the adaptation of the pulse width modulation control of the electromagnetic coil. And
A method for operating a feed pump, characterized in that the liquid is supplied to the metering unit (80) from a return line of a high-pressure pump for fuel injection of an internal combustion engine (1).   The coil current (201) flowing through the electromagnetic coil of the feed pump is read in via the control unit (101) of the feed pump and, by means of a software algorithm, the time and / or for the start of the movement of the mover The method according to claim 1, wherein a time point of the stop and a corresponding current value for starting the movement of the armature and / or for stopping the armature are determined. When the movement of the mover is started and the coil current (201) generated at that time and / or the time of the stop of the mover and the coil current (201) generated at that time are set to the minimum time, And operating within a permitted current characteristic change range (215) preset by a maximum time point and upper and lower current limit values (211 and 212). Or the method of 2 . For control, a target time for the armature stop and / or a target time for the start of the armature movement, and a corresponding target current at the time of the armature stop and / or It sets a target current at the start of advance, and comparing the actual value of the corresponding method according to any one of claims 1 to 3. When the current characteristic change range (215) is out of the allowable range, a fault in the feed pump is estimated, and a corresponding fault is registered in a higher-level engine control device (100). The method according to any one of claims 1 to 4 . In use of the method according to any one of claims 1 to 5, wherein the method used in the system (60) metering the, by the metering system (60), an internal combustion engine that is configured as a diesel engine ( During the high load operation of 1), in order to reduce nitrogen oxides, hydrocarbons as diesel fuel are disposed in the exhaust gas passage (in front of the nitrogen oxide storage catalyst (40) in the flow direction of the exhaust gas). The metering system (60) is metered into the metering system (30) and is configured as a structure group as an injection unit (70) including a metering valve (71) and a cooling body, and a reciprocating piston pump (86). A use comprising a metering unit (80) comprising a feed pump, a pressure sensor (87) and a control unit (101). A control unit (101) which is a device for operating a feed pump, 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), the liquid for reducing the nitrogen oxides is viewed in the exhaust gas flow direction by the metering unit (80) in the exhaust gas aftertreatment system. In the form of metering into the exhaust gas stream (20) via an injection unit (70) before the element,
Analysis software for checking the movement of the armature, wherein the control unit (101) is a device for performing the method according to any one of claims 1 to 6 , and a control device (311). ) And a PWM adjusting member (312).

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