SE541366C2

SE541366C2 - A method for checking a functionality of an inlet valve of a pumping element in a high-pressure accumulator fuel injection system

Info

Publication number: SE541366C2
Application number: SE1751534A
Authority: SE
Inventors: André Åkerberg
Original assignee: Scania Cv Ab
Priority date: 2017-12-13
Filing date: 2017-12-13
Publication date: 2019-08-27
Also published as: BR112020010885A2; DE112018005727T5; SE1751534A1; WO2019117786A1

Abstract

In a method for checking a functionality of a high-pressure accumulator fuel injection system of an internal combustion engine (1) the proper function of each inlet valve (10, 11) to a pumping element (7, 8) of a high-pressure pump (6) is checked by driving the pump while demanding a zero fuel flow therefrom and simultaneously controlling the injector (-s) (5) connected to the accumulator to be closed. The pressure inside the accumulator is measured at a frequency resulting in a plurality of pressure measuring values during each stroke of a pumping element (7, 8) and it is determined that there is a malfunction of the inlet valve (10, 11) of a pumping element when the pressure measuring values increase and increase substantially with respect to the pressure measuring values of at least one other pumping element during a pump stroke of the pumping element associated with that inlet valve.

Description

A method for checking a functionality of an inlet valve of a pumping element in a high-pressure accumulator fuel injection system TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for checking a functionality of a high-pressure accumulator fuel injection system of an internal combustion engine, in which said system comprises: a high-pressure accumulator, a high-pressure pump with a plurality of pumping elements connected in parallel to sequentially feed fuel to the high-pressure accumulator, at least one injector connected to the high-pressure accumulator for injecting fuel into a cylinder of the engine and an inlet valve for each said pumping element arranged in a fuel line to that pumping element, as well as an arrangement for carrying out such a method according to the preamble of the appended independent arrangement claim.

The invention is not restricted to such methods carried out for a high-pressure accumulator fuel injection system for injection of any particular fuel, into a cylinder or cylinders of an internal combustion engine, but diesel and ethanol may be mentioned by way of examples. Furthermore, the invention relates to such systems for internal combustion engines designed for any type of use, such as in industrial applications, in grinding machines and all types of motor vehicles, although the invention is particularly applicable to utility vehicles, especially wheeled utility vehicles, such as trucks or lorries and buses.

For proper function of the internal combustion engine it is vital that the pressure inside the high-pressure accumulator may be kept at a desired level, but when problems to obtain this occur there are multiple components in the fuel feeding system to which the highpressure accumulator fuel injection system belongs that could cause these problems, such as a leaking IMV, bad venturi and bad inlet valve of the high-pressure pump. This makes it hard to pinpoint which of these components that is causing the problem.

BACKGROUND ART US 6 526 948 discloses a method of the type defined in the introduction through which measures are taken for detecting malfunctions of individual pumping elements of the high-pressure pump in a high-pressure accumulator fuel injection system of an internal combustion engine in a motor vehicle. This is done by measuring pressure changes in the high-pressure accumulator depending upon changes occurring in the individual pumping elements. An average pressure increase is determined for each individual pumping element and these pressure increases are compared with each other for determining any defect of any pumping element. These measurements are, however, rather complicated and it is a desire to improve the reliability thereof.

SUMMARY OF THE INVENTION The object of the present invention is to provide a method and an arrangement of the type defined in the introduction being improved in at least some aspect with respect to such methods and arrangements already known.

This object is with respect to the method obtained by providing such a method with the features listed in the characterizing part of appended patent claim 1.

Accordingly, by driving the high-pressure pump while demanding a zero fuel flow therefrom and simultaneously controlling said at least one injector to be closed while measuring the pressure inside the high-pressure accumulator at a frequency resulting in a plurality of pressure measuring values during each stroke of each pumping element and comparing the development of pressure measuring values obtained during a pumping stroke of each pumping element with the corresponding development of pressure measuring values for the other pumping elements of the high-pressure pump, the functionality of each said inlet valve may be determined by determining that there is a malfunction of an inlet valve of a pumping element having a said development of pressure measuring values increasing and increasing substantially with respect to the development of pressure measuring values of at least one other pumping element. The pumping element with a said development of the lowest increase and no or substantially no noticeable increase will then function as reference. This method will deliver a highly reliable result, since inlet valves properly functioning shall with the injectors closed result in a pressure inside the high-pressure accumulator being uninfluenced by the actions of the pumping elements. Thus, by using this method it is possible to rule out, or pinpoint, certain issues with said inlet valves and rule out errors that will affect the pump elements equally, such as temperature.

According to an embodiment of the invention it is determined that there is a malfunction of an inlet valve of a pumping element having a said development of pressure measuring values increasing and increasing by a least 100 %, at least 200 % or at least 300 % with respect to the development of the pressure measuring values of at least one other pumping element. If said other pumping element has an inlet valve functioning properly this will result in no noticeable pressure increase inside the high-pressure accumulator during a pumping stroke thereof, and already a minor malfunction of an inlet valve of another pumping element will cause an increase of pressure measuring values during a pumping stroke of that pumping element being so much higher than the pressure increase associated with the former pumping element, so that it will be easy to with a high reliability detect an inlet valve not functioning properly.

According to another embodiment of the invention the method is carried out on an engine of a motor vehicle, such as a wheeled motor vehicle, especially in the form of a truck or a lorry or a bus. The method according to the invention is particularly suitable to be carried out when such a motor vehicle is subjected to maintenance work for checking the proper function of the high-pressure pump of the high-pressure accumulator fuel injection system of said engine to clean an inlet valve not functioning properly, replace any defect component thereof, such as a broken spring, or replacing the inlet valve when not possible to repair as a consequence of for instance ageing.

The object of the present invention is with respect to the arrangement for checking a functionality of a high-pressure accumulator fuel injection system of an internal combustion engine obtained by providing an arrangement according to the independent claim directed thereto. Advantages of such an arrangement and the embodiment thereof defined in the dependent claim appear clearly from the above discussion of the method according to the invention and embodiments thereof.

The invention also relates to a computer program, a computerreadable medium, an electronic control unit, an internal combustion engine and a motor vehicle according to the appended claims directed thereto.

Further advantageous features as well as advantages of the present invention appear from the description following below.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the appended drawings, below follows a specific description of an embodiment of the invention cited as an example.

In the drawings: Fig. 1 is a simplified schematic view showing a motor vehicle with an internal combustion engine having a high-pressure accumulator fuel injection system upon which the method according to the present invention is applicable, Fig. 2 is a graph of the pressure P measured inside the high-pressure accumulator of an internal combustion engine of the type shown in Fig. 1 versus time t while carrying out the method according to an embodiment of the present invention, Fig. 3 is a graph illustrating the effect of the pumping strokes of the individual pumping elements on the pressure measured inside the high-pressure accumulator when carrying out the method according to said embodiment, Fig. 4 is a flow chart illustrating the steps carried out in a method according to said embodiment of the invention, and Fig. 5 illustrates schematically an electronic control unit according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION A part of an internal combustion engine 1 in a motor vehicle 2 with a plurality (six) of cylinders 3 and a high-pressure accumulator fuel injection system to which a method according to the invention is applicable is very schematically illustrated in Fig. 1. This system comprises a high-pressure accumulator 4 or a common rail with one injector 5 for each cylinder connected thereto for injecting fuel into a cylinder of the engine. A high-pressure pump 6 is configured to feed fuel to the high-pressure accumulator 4 and has for that sake two pumping elements 7, 8 connected in parallel and controlled by a control unit 9 to pump sequentially. Each such pumping element has a separate inlet valve 10, 1 1 controlled by said control unit 9 and connected to an IMV 12 of the pump connecting the pump 6 to a low pressure part of the fuel feeding system of the vehicle.

A sensor 13 is configured to measure the fuel pressure prevailing in the high-pressure accumulator 4 at a frequency resulting in a plurality of pressure measuring values during each stroke of each pumping element 7, 8 and send information thereof to a member 14 integrated with the control unit 9 and configured to evaluate the pressure measuring values obtained through the pressure sensor.

The method according to the present invention is directed to check the proper function of each inlet valve 10, 11 of the high-pressure pump, and this is done by driving the high-pressure pump while demanding a zero fuel flow therefrom and simultaneously controlling the injectors 5 to be closed. The pressure inside the highpressure accumulator 4 is during this driving of the pump measured by the sensor 13 by high speed sampling, i.e. at a frequency resulting in a plurality, such as more than 20, measurements during a pump stroke of each pumping element. The graph shown in Fig. 2 shows the development of the pressure P inside the highpressure accumulator 4 versus time t and how the pressure is substantially constant during pump strokes of one of the pumping elements followed by a substantial increase during a pump stroke of the other pumping element. By using one of the pumping elements, let say the pumping element 7 with pump strokes not influencing the pressure inside the accumulator 4, as the reference and comparing it with the pressure development during pump strokes of the other pumping element 8 it may be determined that there is a malfunction of the inlet valve 1 1 .

The graph shown in Fig. 3 shows the pressure increase ?p obtained through each pump stroke of the pumping element 7 (PS7) and the pumping element 8 (PS8) clearly pointing out the inlet valve 11 of the pumping element 8 as defect.

Fig. 4 illustrates a flow chart of a method according to an embodiment of the present invention carried out for a high-pressure accumulator fuel injection system of an internal combustion engine of the type shown in Fig. 1 for checking a functionality thereof. The method is started with a step S1of continuing to drive the highpressure pump at a zero fuel flow demand. While driving the pump the injector (-s) of the high-pressure accumulator is kept closed as defined as a step S2. While driving the pump and keeping the injector(-s) closed the pressure inside the high-pressure accumulator is measured at high frequency during each stroke of each pumping element in a step S3. In a subsequent step S4the development of pressure measuring values of each pumping element is compared with that of other pumping element. Then in a step S5the question is asked “Has a pumping element during a pump stroke a development of pressure measuring values increasing and increasing substantially with respect to such development of another pumping element?”. When the answer to this question is yes it is in a step S6determined that there is a malfunction of an inlet valve to the pumping element, and if the answer to the question is no it is in a step S7 determined that there is no malfunction of any inlet valve of a pumping element.

Computer program code for implementing a method according to the invention is with advantage included in a computer program which can be read into the internal memory of a computer, e.g. the internal memory of an electronic control unit of a motor vehicle. Such a computer program is with advantage provided via a computer program product comprising a data storage medium which can be read by a computer and which has the computer program stored on it. Said data storage medium is for example an optical data storage medium in the form of a CD ROM disc, a DVD disc etc., a magnetic data storage medium in the form of a hard disc, a diskette, a cassette tape etc., or a flash memory or a memory of the ROM, PROM, EPROM or EEPROM type. Fig. 5 illustrates very schematically an electronic control unit 9 comprising an execution means 15, e.g. a central processor unit (CPU), for execution of computer software. The execution means 15 communicates with a memory 16, e.g. of the RAM type, via a data bus 17. The control unit 9 comprises also a non-transitory data storage medium 18, e.g. in the form of a flash memory or a memory of the ROM, PROM, EPROM or EEPROM type. The execution means 15 communicates with the data storage medium 18 via the data bus 17. A computer program comprising computer program code for implementing a method according to the invention, e.g. in accordance with the embodiment illustrated in Fig. 4, is stored on the data storage medium 18.

The invention is of course in no way restricted to the embodiments described above, since many possibilities for modifications thereof are likely to be obvious to one skilled in the art without having to deviate from the scope of invention defined in the appended claims.

Claims

1. A method for checking a functionality of a high-pressure accumulator fuel injection system of an internal combustion (1) engine, in which said system comprises: a high-pressure accumulator (4), a high-pressure pump (6) with a plurality of pumping elements (7, 8) connected in parallel to sequentially feed fuel to the high-pressure accumulator, at least one injector (5) connected to the high-pressure accumulator (4) for injecting fuel into a cylinder (3) of the engine (1) and an inlet valve (10, 11) for each said pumping element arranged in a fuel line to that pumping element, characterized in that the proper function of each said inlet valve (10, 11) is checked by • driving the high-pressure pump (6) while demanding a zero fuel flow therefrom and simultaneously controlling said at least one injector (5) to be closed, • measuring the pressure inside the high-pressure accumulator (4) at a frequency resulting in a plurality of pressure measuring values during each stroke of each pumping element (7, 8), • comparing the development of pressure measuring values obtained during a pumping stroke of each pumping element (7, 8) with the corresponding development of pressure measuring values for the other pumping elements of the high-pressure pump (6), and • determining that there is a malfunction of an inlet valve (10, 11) of a pumping element having a said development of pressure measuring values increasing and increasing substantially with respect to the development of pressure measuring values of at least one other pumping element.

2. A method according to claim 1 , characterized in that it is determined that there is a malfunction of an inlet valve (10, 11) of a pumping element (7, 8) having a said development of pressure measuring values increasing and increasing by at least 100 %, at least 200 % or at least 300 % with respect to the development of pressure measuring values of at least one other pumping element.

3. A method according to claim 1 or 2, characterized in that it is carried out on an engine (1) of a motor vehicle (2), such as a wheeled motor vehicle, especially in the form of a truck or a lorry or a bus.

4. An arrangement for checking a functionality of a high-pressure accumulator fuel injection system of an internal combustion engine (1), in which said system comprises: a high-pressure accumulator (4), a high-pressure pump (6) with a plurality of pumping elements (7, 8) to sequentially feed fuel to the high-pressure accumulator, at least one injector (5) connected to the high-pressure accumulator (4) for injecting fuel into a cylinder (3) of the engine, an inlet valve (10, 1 1) for each said pumping element (7, 8) arranged in a fuel line to that pumping element and a sensor (13) configured to measure the fuel pressure prevailing in said high-pressure accumulator (4), characterized in that the arrangement is configured to check the proper function of each said inlet valve (10, 11), that it comprises a control unit (9) configured to control the highpressure pump (6) to operate while demanding a zero fuel flow therefrom and simultaneously control said at least one injector (5) to be closed, that the control unit is configured to control said pressure sensor (13) to measure the fuel pressure inside the high-pressure accumulator (4) at a frequency resulting in a plurality of pressure measuring values during each stroke of each pumping element (7, 8), and that the arrangement further comprises a member (14) configured to evaluate said pressure measuring values obtained through said pressure sensor (13) by comparing the development of pressure measuring values obtained through said pressure sensor (13) during a pumping stroke of each pumping element (7, 8) with a corresponding development of pressure measuring values for the other pumping elements of the high-pressure pump and to determine that there is a malfunction of an inlet valve (10, 11) of a pumping element having a said development of pressure measuring values increasing and increasing substantially with respect to the development of the pressure measuring values of at least one other pumping element.

5. A computer program comprising instructions which, when the computer program is executed by a computer, causes the computer to carry out the method according to any of claims 1-3.

6. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any of claims 1 -3.

7. An electronic control unit comprising an execution means (15), a memory (16) connected to the execution means and a data storage medium (18) which is connected to the execution means (15) and on which the computer program code of a computer program according to claim 5 is stored.

8. An internal combustion engine comprising at least one cylinder (3) and a high-pressure accumulator fuel injection system, which comprises: a high-pressure accumulator (4), a high-pressure pump (6) with a plurality of pumping elements (7, 8) connected in parallel to sequentially feed fuel to the high-pressure accumulator, at least one injector (5) connected to the high-pressure accumulator for injecting fuel into said at least one cylinder (3) of the engine (1), an inlet valve (10, 11) for each said pumping element (7, 8) arranged in the fuel line to the pumping element (10, 11) and a sensor (13) configured to measure the fuel pressure prevailing in said high-pressure accumulator (4), characterized in that it is provided with an arrangement according to claim 4 configured to check the proper function of each said inlet valve (10, 11) of the high-pressure accumulator fuel injection system.

9. A motor vehicle, especially a wheeled motor vehicle, in particular a heavy wheeled motor vehicle, such as a truck or a lorry or a bus, characterized in that it is provided with a combustion engine (1) provided with an arrangement according to claim 4 and/or an electronic control unit (9) according to claim 7 and/or an internal combustion engine (1) according to claim 8.