DE102010056507A1 - Method for checking the function of an LPG retrofit system in a motor vehicle - Google Patents

Abstract

The invention relates to a method for checking the function of a retrofit system for an alternative fuel in a motor vehicle (1), which was set up with an internal combustion engine (2) for the original operation with a regular fuel, the method comprising at least the following steps: A) operating the Motor vehicle (1) and the retrofit system (24); B) comparing at least one electronic input signal which reaches at least one electronic input (23) of the retrofit system (24) via at least one electronic connection (25) of the motor vehicle with at least one reference signal which is transmitted to a second control unit (6) of the retrofit system ( 24) is deposited; and C) outputting a warning signal if the at least one electronic input signal deviates from the at least one stored reference signal.

Description

The invention relates to a method for functional testing of an LPG retrofit system in a motor vehicle. With such a retrofit system, an internal combustion engine of the motor vehicle, which is originally set up for operation with a regular fuel, can be retrofitted for operation with an alternative fuel.

An internal combustion engine in today's conventional motor vehicles is typically originally designed for operation with gasoline and / or diesel. These fuels are referred to below as regular fuels. The term "original" here means that the internal combustion engine is set up, for example, by the manufacturer of the motor vehicle for operation with the regular fuel. A retrofit system is then retrofitted to the motor vehicle to ensure that the motor vehicle can be operated in addition to the regular fuel with an alternative fuel. The subsequent installation can also be done in a factory of the motor vehicle manufacturer immediately after the completion of the motor vehicle in the original state. It is both possible that the motor vehicle after installation of the retrofit system can only be operated with the alternative fuel as well as that after installation of the retrofit system both the operation with the regular fuel and the operation with the alternative fuel is possible.

Typical alternative fuels are, for example, easily evaporating fuels and in particular LPG [LPG = Liquified Petroleum Gas]. The retrofitting of a motor vehicle for operation with LPG has become very attractive lately, because LPG is often cheaper, in contrast to conventional regular fuels. In addition, internal combustion engines with LPG can often operate with lower pollutant emissions than is possible with conventional, regular fuels.

Retrofit systems for LPG operation are typically offered in kit form by a manufacturer for certain types of automobiles and are often installed in smaller repair shops. Installation or assembly can lead to installation errors. In addition, the automation of certain assembly steps in such smaller workshops is difficult to implement. In a smaller workshop very different types of motor vehicles are very often provided with retrofit systems, so that for the installation of a retrofit system regularly very individual assembly steps are required, which accordingly performs a mechanic only very rarely. This also increases the susceptibility to errors. Such assembly errors do not always affect the ride comfort noticeable, so that these assembly errors are difficult to recognize. The problem, however, is that possibly the combustion processes do not run with the desired quality, which may be disadvantageous, at least in terms of fuel consumption and / or the actual exhaust emissions.

Based on this prior art, it is an object of the present invention to solve the technical problems described or alleviate. In particular, a particularly advantageous method for installing a retrofit system is to be proposed in which installation errors can be effectively avoided.

These objects are achieved by a method for functional testing of a retrofit system in a motor vehicle according to the features of claim 1. Further advantageous embodiments and implementations of the method are given in the dependent formulated claims. The features listed individually in the claims are combinable with each other in any technologically meaningful manner and can be supplemented by explanatory facts from the description, wherein further embodiments of the invention are shown.

• A) Betreiben des Kraftfahrzeuges und des Nachrüstsystems;
• B) Vergleichen von zumindest einem elektronischen Eingangssignal, das über zumindest einen elektronischen Anschluss des Kraftfahrzeuges in zumindest einen elektronischen Eingang des Nachrüstsystems gelangt mit zumindest einem Referenzsignal, welches in einem zweiten Steuergerät des Nachrüstsystems hinterlegt ist; und
• C) Ausgabe eines Warnsignals, wenn das zumindest eine elektronische Eingangssignal von dem zumindest einen hinterlegten Referenzsignal abweicht.

The invention relates to a method for checking the function of a retrofit system for an alternative fuel in a motor vehicle, which was set up with an internal combustion engine for the original operation with a regular fuel, the method having at least the following steps:

• A) operating the motor vehicle and the retrofit system;
• B) comparing at least one electronic input signal, which passes via at least one electronic connection of the motor vehicle in at least one electronic input of the retrofit system with at least one reference signal, which is stored in a second control device of the retrofit system; and
• C) output of a warning signal when the at least one electronic input signal deviates from the at least one stored reference signal.

The invention therefore relates in particular to a method for checking the function of the retrofit system immediately after the installation of a retrofit system for an internal combustion engine of the motor vehicle to enable the new operation with an alternative fuel, the internal combustion engine originally (ie previously only) was designed for operation with a regular fuel.

• A1) Verbinden von zumindest einem elektronischen Eingang des Nachrüstsystems mit zumindest einem elektronischen Anschluss des Kraftfahrzeuges;
• A2) Durchführen eines Testlaufes des Kraftfahrzeuges und des Nachrüstsystems.

Especially for this purpose (functional test immediately after installation), it is advantageous if step A) takes place immediately after installation of the retrofit system and comprises the following processes:

• A1) connecting at least one electronic input of the retrofit system with at least one electronic connection of the motor vehicle;
• A2) Performing a test run of the motor vehicle and the retrofit system.

It is also possible that the function check of the retrofit system is also carried out at a later time, such as in normal driving.

The control unit of the retrofit system is referred to here as a second control unit, because it is used in a motor vehicle subsequently to an engine control of the motor vehicle. This on-board engine control is referred to below as the first controller.

Electronic inputs to the retrofit system are typically realized in the form of connection sockets on the second control unit and / or electrical connection lines on the second control unit, which can be connected to specific electronic terminals of the motor vehicle. With electronic terminals of the motor vehicle here any electronic contacts on the motor vehicle are meant, which are connectable to the retrofit system. The electronic connections do not have to be provided by the motor vehicle manufacturer, so that a fitter for connection to the electronic inputs of the retrofit system must cut through predetermined cables, for example, and then connect them to the retrofit system with the aid of electronic connection terminals.

When installing a retrofit system in a motor vehicle, it is often necessary to connect certain components or specific electronic inputs of the retrofit system with certain electronic terminals of the motor vehicle. This can lead to confusion. Consequently, a greater number of electronic terminals of the motor vehicle may face a smaller number of electronic inputs of the retrofit system, and due to lack of markings in the engine compartment, connection failures may occur. It is also possible that in each case the same numbers of electronic inputs to the retrofit system and electronic connections are opposite to the motor vehicle. It may be difficult for the installer to determine which port needs to be connected to which input. For example, four electronic ports may face four electronic inputs. The installer then has 24 different ways to assign the electronic connections to the electronic inputs. Combinations of both situations are also conceivable. Frequently, the electronic connections of the motor vehicle are visually the same or very similar, so that a distinction for the fitter is very difficult.

For this reason, the present invention proposes to carry out a test run of the motor vehicle with the retrofit system as part of the installation of the retrofit system in a motor vehicle. During this test run, a comparison is then carried out in step B) of the method according to the invention. In this comparison, the electronic input signals, which reach the retrofit system via the electronic connections, are compared with reference signals which are stored in a control unit of the retrofit system. These reference signals can be individually stored by the manufacturer of the retrofit system in the retrofit system for the respective type of motor vehicle, for which the retrofit system is provided. In this way, installation errors of the retrofit system can be detected easily and automatically.

The issuing of a warning signal in step C) of the method according to the invention can be effected, for example, by connecting the second control unit of the retrofit system to a signal lamp of the onboard diagnosis of the motor vehicle, and this signal lamp is activated if the output of a warning signal occurs in step C) , This ensures that no motor vehicle with a faulty connected retrofit system leaves a workshop.

Alternatively or additionally, the functional check can also be carried out at a later point in time, in particular during normal driving operation. In this procedure, the assembly step A1) for connecting the at least one electronic input of the retrofit system to the at least one electronic connection of the motor vehicle is then carried out earlier. Thus, for example, an error of the assignment of electronic connections of the motor vehicle to electronic inputs of the retrofit system can be detected, which is triggered during a repair of the motor vehicle. During a repair, it is possible for a fitter to incorrectly reconnect disconnected connections between electronic terminals and electronic inputs of the retrofit system. Also can be detected by the operating method when an electronic connection of the Motor vehicle unintentionally triggers during operation of an electronic input of the retrofit system. This can happen, for example, due to vibrations.

The method according to the invention for operating a motor vehicle is particularly advantageous if an output of a warning signal only occurs in step C if a deviation between the at least one electronic input signal and the at least one stored reference signal is determined at least over a period of 5 s [seconds] , In particular, if the method is carried out continuously during operation of the motor vehicle, a repeat of the functional test can be carried out first. Only when the (negative) result repeats, the output of a warning signal should occur. It has been found that if there is a deviation for more than 5 s [seconds], there is a high probability of a mounting error or a mounting error.

If there is a corresponding time delay, it is also particularly advantageous if the test run described in step A1) of the method lasts for at least 5 seconds, preferably at least 10 seconds, and particularly preferably at least 30 seconds.

The methods according to the invention are particularly preferred when the alternative fuel is LPG [LPG = Liquefied Petroleum Gas]. Consequently, in particular, a method for functional testing of an LPG retrofit system is specified here.

Furthermore, the method is advantageous if the electronic connections of the motor vehicle are first signal lines for the injection signals for the operation of the motor vehicle with the regular fuel. Thus, in particular, a method for checking the electrical connection to the first signal conductors for the injectors is specified.

Especially with these signal lines, it can easily lead to confusion by the fitter. For each cylinder of a motor vehicle there is typically a separate signal line for the injection signal. These signal lines are identical on a regular basis. So it can easily come to confusion by the fitter. As a reference signal in the control unit of the retrofit system then advantageously a firing order of the internal combustion engine is stored (stored). In steady-state engine operation, the user is virtually unaware that the first signal lines for the injection signals have been reversed when connected to inputs to the retrofit system. The injection order of the engine is then wrong, but the engine runs despite the wrong injection order. Only in dynamic engine operation with load changes, the smoothness of the internal combustion engine adversely affected by the exchange. The emission values are also significantly worsened in this case. With the function check proposed here, this can be easily avoided.

In the method for operating a motor vehicle, it should be noted that deviations in the firing order of the motor vehicle can frequently occur in particular during overrun phases, in which the internal combustion engine is essentially driven by the inertia of the motor vehicle, and during particularly dynamic operating phases. Regularly, the injection is hidden selectively in such a cylinder selective cylinder, whereby the regular injection order is left. It can thus happen that deviations between the stored reference signals and the electronic input signals can occur, although the installation of the retrofit system was done correctly and the first signal lines of the motor vehicle are correctly connected to the electronic inputs of the retrofit system. For this reason, it is advantageous if the method according to the invention for operating a motor vehicle in coasting phases and in particularly dynamic operating phases of the internal combustion engine is not carried out. Deviations between the stored reference signals and the input signals in these phases are advantageously not taken into account. There is voretilhafterweise no output of a warning signal in such phases.

In other words, it is registered in which order the injection pulses arrive at the second control unit of the (LPG) retrofit system. This sequence is compared with the firing order stored in the second control unit. Deviations of the sequence generate an error. It should be noted that it may not come to an error detection during coasting phases / vehicle dynamics interventions. At the beginning of a coasting phase, the injection is masked cylinder selectively, whereby the regular injection order is also left (skip pattern). Therefore, injection suppression is detected (not all cylinders inject) and in this case no error is set.

The method according to the invention is also particularly advantageous if the electronic connections of the motor vehicle are second signal lines to a relay for controlling a fuel pump for delivery of the regular fuel. Thus, in particular, a method for checking the electrical interconnection toward the second signal conductors towards the fuel pump to promote the regular fuel indicated.

The power supply of a retrofit system z. B. via the power supply of a fuel pump to promote a regular fuel. The power supply of such a fuel pump is normally set up so that in the case of an accident of the motor vehicle deactivation of the fuel pump takes place, so that no more fuel is conveyed. The shutdown of the fuel pump is purely mechanical, ie in particular without the intervention of software, so that the shutdown is particularly safe. This behavior of the fuel pump for the regular fuel can be used advantageously to achieve a complete shutdown of the retrofit system in the event of an accident. Depending on the design and model of the motor vehicle, however, the relay of the fuel pump differ. For example, the size or the occupancy of the individual electronic connections of these relays is different. This can easily lead to confusion of the second signal lines on the relay when installing the retrofit system. If there is such confusion, the aftermarket system may not automatically shut down in the event of an accident. This error would not be detected in the regular operation of the motor vehicle with the retrofit system, but only in the event of an accident. But then the error would already have a drastic effect, because no shutdown of the retrofit system would take place. This would be very critical because LPG is extremely flammable. If the corresponding assignment of the second signal lines of the relay in the form of reference signals stored in a control unit of the retrofit system (stored), a detection of such mounting errors is possible.

With proper installation of the retrofit system, the voltage signal may therefore only be present when the internal combustion engine is running. If it is now detected that the internal combustion engine is stationary (no injection signals present) and the safety power supply signal is nevertheless applied to the second control unit, a corresponding error is indicated. It should be noted, however, that the gasoline fuel pump can run for a short time (eg, less than 3 seconds) even when the internal combustion engine is stopped (eg, when opening the door to generate gasoline pressure). If necessary, this must be checked separately and taken into account before the warning signal is issued.

The methods according to the invention are also particularly advantageous if in addition a shutdown of the retrofit system takes place in step C). When switching off the retrofit system typically the supply of the internal combustion engine is deactivated with the alternative fuel. It is additionally possible to activate the fuel supply with the regular fuel to ensure further operation of the internal combustion engine, although a shutdown of the retrofit system has been done.

The methods according to the invention are also particularly advantageous if the at least one reference signal is a reference signal sequence. A reference signal sequence for the method according to the invention can be, for example, the injection order of the internal combustion engine already described.

In the context of the invention, a retrofit system for an internal combustion engine is proposed, wherein the retrofit system has a second control device, which is set up for carrying out the method according to the invention.

In particular, reference signals and a comparison routine are stored in the second control device, wherein the comparison routine is adapted to perform a comparison of the reference signals with input signals, which pass through electronic inputs of the second control device in the second control device.

Most preferably, the second control device comprises a data processing program that can perform this method independently (together with corresponding sensors, voltmeters, etc.). For this purpose, the second control device can also comprise memory means in which the reference signals and / or currently detected measured values (for the comparison) are permanently and / or temporarily stored.

The particular advantages and embodiments described for the methods according to the invention can be applied to the retrofit system according to the invention. The same applies to the particular advantages and embodiments shown for the retrofit system according to the invention. These are each applicable to the inventive method and transferable.

In the context of the invention, a motor vehicle is proposed, comprising an internal combustion engine which is selectively operable with a regular fuel or an alternative fuel, wherein the motor vehicle is equipped with a retrofit system for operation with the alternative fuel according to the previously described type.

The invention and the technical environment will be explained in more detail with reference to FIGS. The figures show particularly preferred embodiments, to which the invention is not limited. In particular, it should be noted that the figures and in particular the illustrated proportions are only schematic. Show it:

1 a motor vehicle having an internal combustion engine and a retrofit system for operation with an alternative fuel;

2 : A second control unit of a retrofit system; and

3 : a flow chart of the method according to the invention.

1 shows a motor vehicle 1 with an internal combustion engine 2 , which is adapted for operation with either a regular fuel or an alternative fuel. The alternative fuel may be a slightly evaporating fuel (such as LPG), while the regular fuel is gasoline or diesel. The alternative fuel is in the motor vehicle 1 with second injectors 4 on the combustion chambers 11 the internal combustion engine 2 distributed. In 1 is simplified only a combustion chamber 11 the internal combustion engine 2 shown. The combustion chamber 11 is via the intake pipe 8th with air and fueled. Exhaust gases escape from the combustion chamber 11 over the exhaust pipe 9 out. In addition, there is the combustion chamber 11 a spark plug 18 for ignition of the operation of the internal combustion engine 2 in the combustion chamber 11 present ignitable mixture of fuel and air. The suction line 8th can be compared to the combustion chamber 11 with a valve 10 be closed. The same applies to the exhaust pipe 9 opposite the combustion chamber 11 with a valve 10 be closed.

In operation with regular fuel, the internal combustion engine 2 from the first controller 5 controlled. The first controller 5 is in particular the engine control of the motor vehicle. A regular fuel (diesel / gasoline) then passes through the first injector 3 in the intake pipe 8th the internal combustion engine 2 , Per combustion chamber 11 the internal combustion engine 2 is in each case a first injector 3 intended. The first injectors 3 be through the regular fuel supply system 30 supplied with regular fuel. The regular fuel supply system 30 has a fuel pump 29 to promote regular fuel and a relay 28 for controlling the power supply of the fuel pump 29 on. The relay 28 in particular, provides an emergency shutdown of the fuel pump 29 in the case of an accident of the motor vehicle 1 for sure.

Should the motor vehicle 1 operated with alternative fuel (LPG), via the switch 7 a switchover to the alternative fuel. The switch 7 is in the 1 set such that a fuel supply with alternative fuel and the fuel supply of the internal combustion engine 2 is interrupted with regular fuel. The fuel supply with alternative fuel is thus according to 1 from the second controller 6 which in turn controls information from the first controller 5 can master (master-slave operation). The second control unit 6 and the switch 7 can, as shown here, be integrated with each other in one component. In particular, it is also possible that signals from the first control unit 5 to the first injectors 3 also the second control unit 6 (optionally) happen. This is also shown here.

The second control unit 6 may receive and process various other information to control the injection of alternative fuel. For example, a lambda input 13 provided, via which a lambda value (oxygen content in the exhaust gas) of the exhaust system, not shown, of the internal combustion engine 2 in the second control unit 6 can get. A temperature sensor 21 optionally determines the cooling water temperature of the internal combustion engine 2 in the cooling circuit 12 the internal combustion engine 2 , Also the signal of this temperature sensor 21 can from the second controller 6 be recycled. The second control unit 6 calculated from the first injection signal, which it from the first control unit 5 receives and which actually to control the first injector 3 is provided, in combination with the other the second control unit 6 available information or parameters, a second injection signal for the second injector 4 introducing the alternative fuel (LPG) into the intake manifold 8th the internal combustion engine 2 injects.

Per combustion chamber 11 the internal combustion engine 2 is a second injector 4 intended. The second injector 4 gets the alternative fuel from the tank 16 , The alternative fuel gets out of the tank 16 out with the conveyor unit 17 promoted and passes through the supply line 14 to the second injector 4 , In the return line 15 is a pressure sensor 20 intended. The supply line 14 and the return line 15 , The Tank 16 , the conveyor unit 17 , the second injectors 4 and the second controller 6 together form the retrofit system 24 which z. B. as a kit each adapted for certain types of motor vehicles 1 is made available.

In the context of the method according to the invention, on the one hand, the connection of the first signal lines 26 from the first controller 5 to the second controller 6 be monitored. These are electronic input signals, which are connected via electronic connectors 25 on the first controller 5 in electronic inputs 23 at the second control device 6 arrive, monitored.

In addition, with this method the connection of second signal lines 27 to the second controller 6 be monitored. The second signal lines 27 are the electrical contacts on a relay 28 a fuel pump 29 , For monitoring the connection of the second signal lines 27 Be electronic input signals, which are connected via electronic connectors 25 at the relay 28 in electronic inputs 23 at the second control device 6 get checked.

2 schematically shows a second controller 6 a retrofit system for operating a motor vehicle with an alternative fuel. The second control unit 6 has electronic inputs 23 on that with electronic connections 25 of the motor vehicle, not shown here must be connected. The electronic connections 25 are optically indistinguishable. For a fitter who has the electronic inputs 23 on the control unit 6 with the electronic connections 25 is therefore the correct assignment of the electronic connections 25 to the electronic inputs 23 regularly problematic. Therefore, it is advantageous if in the second control device 6 corresponding reference signals and comparison routines for the inventive method are stored.

3 shows a flowchart of the inventive method. It can be seen that the method steps A) to C) are each carried out in succession. It can also be seen that two different procedures are possible. In a procedure, a connection of a plurality of electronic inputs of the retrofit system with at least one electronic connection of the retrofit system in step A1) takes place at the beginning. In the second procedure, this process step A1) is omitted. As a result, the second process control can also be carried out regularly during operation of the motor vehicle.

With the invention it is now possible that installation errors are automatically detected (without intervention of the installer) and an error message is output on the diagnostic interface. In addition, the system can be switched off automatically and the fault lamp can be switched on. In particular, this avoids the danger that an incorrectly wired car leaves the workshop.

LIST OF REFERENCE NUMBERS

1

motor vehicle

2

Internal combustion engine

3

first injector

4

second injector

5

first control unit

6

second control unit

7

switch

8th

suction

9

exhaust pipe

10

Valve

11

combustion chamber

12

Cooling circuit

13

Lambda input

14

supply line

15

Return line

16

tank

17

delivery unit

18

spark plug

19

pressure regulator

20

pressure sensor

21

Cooling water temperature sensor

22

Injector

23

electronic input

24

retrofit system

25

electronic connection

26

first signal line

27

second signal line

28

relay

29

Fuel pump

30

regular fuel supply system

Claims (10)

Method for checking the function of a retrofit system for an alternative fuel in a motor vehicle ( 1 ), with an internal combustion engine ( 2 ) was set up for the original operation with a regular fuel, the method having at least the following steps: A) operating the motor vehicle ( 1 ) and the retrofit system ( 24 ); B) comparing at least one electronic input signal, which via at least one electronic connection ( 25 ) of the motor vehicle in at least one electronic input ( 23 ) of the retrofit system ( 24 ) comes with at least one reference signal, which in a second control device ( 6 ) of the retrofit system ( 24 ) is deposited; and C) outputting a warning signal if the at least one electronic input signal deviates from the at least one stored reference signal. Method according to claim 1, wherein step A) takes place immediately after installation of the retrofit system and comprises the following processes: A1) connecting at least one electronic input of the retrofit system to at least one electronic connection of the motor vehicle; A2) Performing a test run of the motor vehicle and the retrofit system. Method according to one of the preceding claims, wherein in step C) an output of a warning signal only takes place if a deviation between the at least one electrical input signal and the at least one stored reference signal is determined at least over a period of 5 seconds. Method according to one of the preceding claims, wherein the alternative fuel is LPG [LPG = Liquified Petroleum Gas]. Method according to one of the preceding claims, wherein the electronic connections ( 25 ) of the motor vehicle ( 1 ) first signal lines ( 26 ) for the injection signals for the operation of the motor vehicle ( 1 ) with the regular fuel. Method according to one of the preceding claims, wherein the electronic connections ( 25 ) of the motor vehicle ( 1 ) second signal lines ( 27 ) on a relay ( 28 ) for controlling a fuel pump ( 29 ) for the promotion of regular fuel. Method according to one of the preceding claims, wherein in step C) additionally a shutdown of the retrofit system ( 24 ) he follows. Method according to one of the preceding claims, wherein the at least one reference signal is a reference signal sequence. Retrofit system ( 24 ) for an internal combustion engine ( 1 ), whereby the retrofit system ( 24 ) a second control device ( 6 ), which is set up to carry out a method according to one of the preceding claims. Motor vehicle ( 1 ) comprising an internal combustion engine ( 2 ) which is selectively operable with a regular fuel or an alternative fuel, wherein the motor vehicle ( 1 ) with a retrofit system ( 24 ) is equipped for operation with the alternative fuel according to claim 9.

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