DE102017128183A1 - Method for controlling an internal combustion engine in a combined heat and power plant and device for detecting operating parameters of an internal combustion engine in a combined heat and power plant - Google Patents

Abstract

In a method for controlling an internal combustion engine (1) in a combined heat and power plant, the signal sequence of a series of increments (10, 11) is detected. One of the increments (11) is offset relative to the other increments (10). Thus, the time profile of the speed over the crankshaft revolution and the direction of rotation of the crankshaft (3) can be detected. As a result, versatile controls of the internal combustion engine (1) can be realized.

Description

The invention relates to a method for controlling an internal combustion engine in a cogeneration plant, wherein operating parameters such as a rotational speed or a rotational angle of a crankshaft of the internal combustion engine are detected, in which a sensor generates a signal in each case when detecting an arranged on a rotary body and driven by the crankshaft increments , Furthermore, the invention relates to a device for detecting operating parameters of an internal combustion engine in a combined heat and power plant, with arranged over the circumference of a rotating body driven by a rotating body increments, with a fixed sensor for generating a signal upon detection of one of the increments.

The EP 1 222 376 B1 discloses a misfire detection in which an angle sensor wheel disposed on the crankshaft has a series of regularly arranged teeth with two teeth omitted. A sensor detects a passing of the teeth. A controller connected to the sensor detects the tooth gap at the increased distance of the signal edges. The derivation of operating parameters of the internal combustion engine from the signals is limited.

From the WO 2013/026534 A1 a method for operating an internal combustion engine has become known, in which an enrichment of a mixture and an ignition coil charging takes place as a function of detected angular accelerations of a crankshaft.

The DE 102 54 479 B4 discloses a method for detecting combustion misfires of an internal combustion engine.

In particular arranged in cogeneration plants internal combustion engines usually reach very long operating times and therefore subject to increased compared to internal combustion engines of motor vehicles wear.

The invention is based on the problem of further developing a method of the type mentioned at the outset such that it can be used in a variety of applications and requires particularly low structural complexity. Furthermore, a device for detecting operating parameters of an internal combustion engine in a combined heat and power plant to be created, which is particularly simple.

The first problem is solved according to the invention in that the signal sequence of a series of regularly spaced increments and a reference offset offset from the row is detected, that time intervals between the signals are detected and that from the time intervals the speed and a reference mark defined by the reference increment be determined.

As a result of this design, the pulse sequence generated by the increments has two adjacent pulse sequences at the same rotational speed, the distances of which differ from the intervals between the pulses of the regularly arranged increments. This can be determined by a corresponding evaluation of the signal sequence in a control device of the internal combustion engine, the rotational direction, the rotational speed and a reference mark for the rotation angle of the internal combustion engine. This can be controlled by a simple evaluation of the signal sequences of the ignition, regulate the power, affect the smoothness of the engine and drive an electric starter. The inventive method is so versatile and requires thanks to the invention, a particularly low structural complexity. Preferably, in addition, the direction of rotation of the crankshaft is determined from the time intervals of the signals.

A wear of the components of the internal combustion engine can be kept particularly low according to another advantageous embodiment of the invention, when the electric power output of a driven by the internal combustion engine generator is detected and if the control of at least one of the parameters of the ignition timing or the charge of an ignition coil in dependence Power output of the generator takes place. Furthermore, this design allows the regulation of various parameters of the internal combustion engine at rated power.

A safe start of the internal combustion engine can be easily ensured according to another advantageous embodiment of the invention, when the ignition is set at the start of the engine from stored maps of environmental and operating conditions. The ambient and operating conditions may be, for example, temperature, air pressure, humidity of the intake air or a cooling water temperature of the internal combustion engine.

An accurate power control under full load by continuous adjustment of the ignition can be easily achieved according to another advantageous embodiment of the invention, when the ignition is varied in operation as a function of the electric power output of the generator.

A particularly high smoothness of the internal combustion engine can be ensured according to another advantageous embodiment of the invention, if from the signal sequence and the known time course of the rotational speed as a function of the rotational angle of the crankshaft, a ratio for the smoothness of the internal combustion engine is determined and if at least one of the parameters of the ignition timing or the charge of the ignition coil is controlled in dependence on the ratio of smoothness.

A reliable start of the internal combustion engine is ensured according to another advantageous embodiment of the invention, when the charging current of the ignition coil for starting the internal combustion engine according to the state of wear of the spark plug is specified. The wear state of the spark plug may be taken from an operating hours wear map, or it is assumed that the spark plug is worn at the wear limit.

An unnecessarily high charging current of the ignition coil with a new spark plug can be according to another advantageous embodiment of the invention easily avoided if the charging current is reduced so far in operation until the ratio of smoothness has reached a planned value. Preferably, a safety factor is added to the charging current to ensure safe operation of the internal combustion engine.

To further reduce the wear of the spark plug and the ignition coil, it contributes according to another advantageous embodiment of the invention, when the top dead center of the ignition and the top dead center during gas exchange of the internal combustion engine are detected and ignition of the spark plug at top dead center of the gas exchange is prevented , The two upper dead centers can be easily distinguished by the rotational speed as a function of the angle of rotation of the crankshaft.

A change of boundary conditions in the operation of the internal combustion engine can be according to another advantageous embodiment of the invention easily considered in the control of the internal combustion engine when the reduction of the charging current and or the variation of the ignition timing is repeated at intervals.

The second mentioned problem, namely the provision of a device for detecting operating parameters of an internal combustion engine in a cogeneration plant, which is particularly simple, is inventively achieved in that one of the increments is designed as a reference increment and offset from a regular spacing of the other increments.

By virtue of this configuration, the one reference increment has a shortened distance to the one adjacent increment and an increased distance to the other adjacent increment compared to the regular spacing of the increments. Thus, the offset relative to the regular spacing of the other increments arranged offset reference increment is suitable as a reference point for the rotational angle of the crankshaft. A scanning of the staggered reference increment and its adjacent increments therefore leads to signal sequences of different time intervals. Thus, the reference point of the crankshaft is easily detected. In addition, the direction of rotation can be easily recognized by the different distances between the signal sequences. For redundancy, two sensors are preferably arranged opposite the increments.

The device designed according to another advantageous embodiment of the invention structurally particularly simple when the number of increments on the rotation body is X, wherein X-1 increments are spaced by an angle of 360 ° / X from the next increment and that a Bezugsinkrement a Distance of about 2/3 * 360 ° / X to the one adjacent increment and a distance of 4/3 * 360 ° / X to the other adjacent increment. In a preferred practical embodiment, the rotary body 80 Increments, where 79 increments are spaced 4.5 ° from the next increment, and the reference increment is spaced 3 ° from the one adjacent increment and 6 ° apart from the other adjacent increment.

To further simplify the structural design of the device, it contributes according to another advantageous embodiment of the invention, when the body of revolution is made of ferromagnetic material, when the increments and the Bezugsinkrement are generated by material removal of the ferromagnetic material and when the sensor is designed as Indutkivgeber. This ensures reliable inductive detection of the increments and the reference increment.

The device is in accordance with another advantageous embodiment of the invention versatile for controlling the internal combustion engine used when a control unit is designed to detect an electric power output of a driven by the internal combustion engine generator.

• 1 schematisch einen Schaltplan eines Blockheizkraftwerkes,
• 2 den Drehzahlverlauf über einen Arbeitsspiel einer Brennkraftmaschine,
• 3 ein Diagramm zur Ermittlung eines Ladestroms einer Zündspule in Abhängigkeit von Betriebsstunden einer Zündkerze,
• 4 ein Flussdiagramm eines Verfahrens zur Einstellung eines Zündzeitpunktes,
• 5 ein Flussdiagramm eines Verfahrens zur Einstellung eines Ladestroms.

The invention allows numerous embodiments. To further clarify its basic principle, one of them is shown in the drawing and will be described below. This shows in

• 1 schematically a circuit diagram of a combined heat and power plant,
• 2 the speed curve over a working cycle of an internal combustion engine,
• 3 a diagram for determining a charging current of an ignition coil as a function of operating hours of a spark plug,
• 4 a flowchart of a method for setting an ignition timing,
• 5 a flowchart of a method for setting a charging current.

1 schematically shows a circuit diagram of a combined heat and power plant with an internal combustion engine 1 and a generator 2 , On a crankshaft 3 the internal combustion engine 1 is a rotation body 4 , For example, arranged a flywheel. A control unit 5 which, for example, with a frequency converter 6 communicating via a CAN bus is with one in front of the rotational body 4 arranged sensor 7 , an ignition coil 8th and the generator 2 connected. The ignition coil 8th supplies a spark plug 9 the internal combustion engine 1 with electricity. The control unit 5 detects the electric power output of the generator 2 and the signals of the sensor 7 , Furthermore, the control unit controls the charging current for the ignition coil 8th and the spark timing of the spark plug 9 and an unillustrated actuator for power control of the internal combustion engine 1 about the amount of fuel supplied. On the rotation body are 80 increments 10 arranged, of which 79 are spaced by 4.5 °. One of the increments is a reference increment 11 formed and from the one adjacent increment 10 by 3 ° and from the other adjacent increment 10 spaced at 6 °.

The frequency converter shown schematically 6 serves to connect the generator 2 to an unillustrated external power grid. A schematically illustrated hydraulic module 12 used to connect the cogeneration plant to an external heating circuit, not shown.

2 schematically shows two speed curves over a cycle of the internal combustion engine 1 , The working cycle of the internal combustion engine 1 extends in a single-cylinder four-stroke engine over 720 ° rotation of the crankshaft 3 , The speed curve labeled I indicates during operation of the internal combustion engine 1 course, while the speed curve marked with II denotes a trailed course, in which no ignition takes place. The course marked II thus corresponds to the course when starting the internal combustion engine 1 before the ignition. In the diagram, two top dead centers are marked, one of which marks the top dead center of the ignition with Z-OT and the top dead center of the gas exchange with W-OT. The diagram shows that the two top dead centers can be distinguished by the different speed curves.

In the following, the method for controlling the internal combustion engine will be explained.

The power fine control is carried out under full load by continuous adjustment of the ignition timing. This adaptation is shown in a flow chart in 4 shown. In the present case, the method for fine control of the actual electrical power is used. The power specification is made by external request or energy management. The nominal power is set qualitatively by the speed and the corresponding amount of fuel via a mechanical actuator with an accuracy of approx. 1%. Based on stored, dependent on various environmental and operating conditions maps is in one step Z1 the current operating point a fixed ignition timing (map setpoint) specified. In the present internal combustion engine 1 To reduce the peak temperature in the combustion chamber and the concomitant reduction of nitrogen oxide emissions, the ignition timing is relatively late and thus far from the maximum efficiency. In this area, the shift of the ignition point has a very large influence on the electrical power of the combined heat and power plant. In step Z2 the output of the generator is recorded.

In an angular range of 1 ° crankshaft revolution KW will now in one step Z3 via a control algorithm, the ignition with a resolution of 0.1 ° CA steps by the predetermined ignition timing from the map varies depending on performance deviation. The characteristic setpoint value was chosen such that the variation in the range of 1 ° CA around the nominal value of the characteristic map does not lead to a notable increase in the nitrogen oxide emissions. The control algorithm works like a P-controller and adjusts the ignition timing proportionally to the power deviation between actual and setpoint value. This is to comply with the rated power with an accuracy of less than +/- 0.5%.

In addition, the rated power can be regulated over a range of about 2% by means of a purely electronic ignition timing variation. The use of the mechanical actuator can thereby be kept largely low, which significantly reduces the wear of the mechanical actuator. In addition, the frequency converter can be relieved by the implemented fine-tuning of the power and the electrical feed-in power can be smoothed. In step Z4 will be at set intervals the detection of the power output and the variation of the ignition timing repeated.

To determine the smoothness of the internal combustion engine, the time profile of the rotational speed over the rotation angle is determined from the signals of the sensor, in order to determine therefrom an index for smooth running. This characteristic figure results from the difference between the angular acceleration per revolution section and a stored course of ideal combustion in the region of the power stroke.

The ratio of smoothness is used to the amount of charge of the ignition coil 8th to reduce to the currently necessary value. The background here lies in the relationship between the present electrode wear on the ignition coil 8th and the spark duration necessary for stable combustion of the spark. In connection between the burning time and the ignition, it was found that, after a certain burning time, no significant advantages in the ignition, in terms of smoother running and lower HC emissions, can be detected.

The burning time of the spark is limited by the amount of charge in the ignition coil and the amount of breakdown voltage. In addition, the burning time in addition to the ignition also has an influence on the burning or wear of the spark plug electrodes.

Since in the present engine the power requirement is covered at a nearly constant medium pressure, the spark plug breakdown voltage depends almost exclusively on the electrode spacing. As the electrode gap becomes larger as a result of wear and tear as a result of the operating hours of the spark plug, the required ignition energy and the charging current required for it increase, as is apparent in US Pat 3 is shown.

The setting of the charging current to the current engine and spark plug state is implemented as follows and is in 5 shown in a flow chart:

To start and to warm up the engine 1 gets in one step L1 a fixed charging current for charging the ignition coil 8th given to a worn spark plug 9 oriented with high breakdown voltage. During operation of the internal combustion engine 1 in the cogeneration plant is now in step L2 the charging current has been reduced until the smoothness index has reached the specified value. Subsequently, in step L3 the current determined. On the thus determined current strength, a safety factor is now added and with this calculated current in the step L4 the ignition coil 8th loaded and the internal combustion engine 1 operated.

This process, starting with the reduction of the charging current, can be done after each start or in one step L5 cyclically repeated at predetermined intervals, each start of the internal combustion engine 1 of the combined heat and power plant takes place with a fixed charging current. Either the charging current ascertained in advance is stored and recalled, or a new adaptation of the charging current takes place via the running smoothness index just after each start.

To ensure the charging current control circuit, the charging current is actively measured. Thus manufacturing tolerances in the charging circuit can be compensated.

Notwithstanding the method described above, the charging current of the ignition coil 8th also independent of the smoothness based on the operating hours of the spark plug 9 and the in 3 set characteristic can be set. For this purpose, it is necessary to transmit to the engine control the time of Zündkerzteausch. From this point on, a characteristic is now traversed as a function of the engine running time and the respective operating point, which predetermines the ignition coil charging current. However, it must always be the previous term of the spark plug 9 be specified.

The characteristic was empirically determined and based on empirical values of the present internal combustion engine 1 , Decisive here is the number of ignition cycles per spark plug 9 , wherein these in the stationary-operated internal combustion engine 1 is calculated on the crankshaft speed and the running time of the system.

It is known that in a 4-stroke gasoline engine every other revolution of the crankshaft 3 an ignition take place. One might think of using a separate camshaft sensor, which in turn requires an increased construction effort.

The speed and reference mark detection described above is used to determine the rotational irregularity of the increments 10 having rotating body 4 to detect the top dead center of the ignition Z-OT over a single working cycle. For this purpose, the height of the speed difference per revolution is detected and compared with a stored setpoint. The speed difference between the fired and towed internal combustion engine 1 is in 2 shown.

During the start of the internal combustion engine 1 With the help of the flywheel-side reference mark transmitter, an ignition signal is generated per engine revolution.

In the starting area and in the starting area of the internal combustion engine 1 Each crankshaft revolution is ignited, thus ensuring that the mixture is ignited and the second spark is ignited freely in the top dead center of the gas exchange W-OT.

Once the internal combustion engine 1 has approached the requested power range, now with the help of high-accuracy speed detection on the maximum speed difference per power stroke of the corresponding cycle of the internal combustion engine 1 determined. This is due to the fact that during the compression stroke, the engine speed drops to a minimum and the combustion in the power stroke, the engine speed increases to its maximum. In addition, this speed difference in fired operation is about twice as high as when the internal combustion engine 1 be hauled or would give no performance. Through the reference increment 11 on the rotation body 4 Now, the speed minimum or the maximum speed can be assigned to the corresponding clocks, which is used to switch off the "unnecessary" Zündfunkens.

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

• EP 1222376 B1 [0002]
• WO 2013/026534 A1 [0003]
• DE 10254479 B4 [0004]

Claims (13)

Method for controlling an internal combustion engine (1) in a combined heat and power plant, wherein operating parameters such as a rotational speed or a rotational angle of a crankshaft (3) of the internal combustion engine (1) are detected, wherein a sensor (7) in each case generates a signal upon detection of a rotational body (4) arranged and by the crankshaft (3) driven increments (10, 11) generated, characterized in that the signal sequence of a series of regularly spaced increments (10) and a reference to the row offset reference increment (11) is detected that temporal Distances between the signals are detected and that from the time intervals, the rotational speed and a reference of the increment (11) fixed reference mark are determined. Method according to Claim 1 , characterized in that the electric power output of a generator (2) driven by the internal combustion engine (1) is detected and that the control of at least one of the parameters of the ignition timing or the charge of an ignition coil (8) in dependence on the power output of the generator (2) he follows. Method according to Claim 1 or 2 , characterized in that the ignition timing at the start of the internal combustion engine (1) is defined from stored maps of environmental and operating conditions. Method according to at least one of Claims 1 to 3 , characterized in that during operation of the ignition timing in dependence on the electric power output of the generator (2) is varied. Method according to at least one of Claims 1 to 4 , characterized in that from the signal sequence and the known time advance of the rotational speed as a function of the rotational angle of the crankshaft (3) an index for the smoothness of the internal combustion engine (1) is determined and that at least one of the parameters of the ignition timing or the charge of the ignition coil (8) is regulated depending on the key figure of the running smoothness. Method according to at least one of Claims 1 to 5 , characterized in that the charging current of the ignition coil (8) for starting the internal combustion engine (1) according to the state of wear of the spark plug (9) is specified. Method according to at least one of Claims 1 to 6 , characterized in that during operation of the charging current is reduced so far until the index of smoothness has reached a predetermined value. Method according to at least one of Claims 1 to 7 , characterized in that the top dead center of the ignition and the top dead center during gas exchange of the internal combustion engine (1) are detected and that ignition of the spark plug (9) is prevented at the top dead center of the gas exchange. Method according to at least one of Claims 1 to 8th , characterized in that the reduction of the charging current and / or the variation of the ignition timing is repeated at intervals. Device for detecting operating parameters of an internal combustion engine (1) in a cogeneration plant, with increments (10, 11) arranged over the circumference of a rotation body driven by a crankshaft (3), with a fixed sensor (7) for generating a signal upon detection of a of the increments (10, 11), characterized in that one of the increments is designed as a reference increment (11) and offset from a regular spacing of the other increments (10). Device after Claim 10 , characterized in that the number of increments (10, 11) on the rotary body (4) is X, wherein X-1 increments (10) are spaced by an angle of 360 ° / X from the next increment (10) and the a reference increment (11) has a distance of approximately 2/3 * 360 ° / X to the one adjacent increment (10) and a distance of 4/3 * 360 ° / X to the other adjacent increment (10). Device after Claim 10 or 11 , characterized in that the rotary body (4) is made of ferromagnetic material, that the increments (10) and the Bezugsinkrement (111) are produced by material removal of the ferromagnetic material and that the sensor (7) is designed as Indutkivgeber. Device according to at least one of Claims 10 to 12 , characterized in that a control unit (5) for detecting an electric power output of a of the internal combustion engine (1) driven generator (2) is formed.

Images