DE102005032636A1 - Fuel supply system functionality evaluation method for motor vehicle`s internal combustion engine, involves detecting temporal fuel flow using ultrasonic flow measurement, and estimating functionality of system based on temporal flow - Google Patents

Abstract

The method involves detecting temporal flow of a fuel flow by using ultrasonic flow measurement, and the functionality of a fuel supply system (10) of an internal combustion engine (12) is estimated based on the temporal flow of the fuel supply. The measurement is detected by using an ultrasonic flow sensor, which is not belonged to a fuel supply system. The sensor is non-invasively coupled and decoupled with a fuel guiding section of the fuel supply system. Independent claims are also included for the following: (1) a control device of a fuel supply system in a motor vehicle (2) a diagnosing device for the evaluation of functionality of a fuel supply system of a motor vehicle based on a volume flow recorded in a fuel supply system.

Description

The The invention relates to a method for assessing operability a fuel supply system of a motor vehicle on the Based on a detected in the fuel supply system fuel flow.

Further The invention relates in its device aspect both a control unit of a such fuel supply system as an external diagnostic device.

Such a method is from the DE 199 28 548 A1 known. This document further discloses a device for detecting a leakage of a fuel injection system, without distinguishing between a controller and an external diagnostic device. At the subject of DE 199 28 548 A1 a fuel volume flow taken from a fuel tank is detected and compared with an injection volume flow predetermined by the engine control in the same time unit. Subsequently, a difference of the two volume flows is formed and compared with a limit value which is read from a memory of the engine control and calculated in dependence on operating parameters of the engine. If the difference in the volume flows is greater than the limit value, a leakage signal is output and countermeasures are taken by the engine control to prevent damage to the engine or pollution of the environment by the leakage. It is in the DE 199 28 548 A1 In particular, the high-pressure pump considered as a critical component in which a leak, for example, can lead to the ingress of fuel in a lubricating oil circuit of the internal combustion engine. The leakage detection presented there should work with minimal device-technical effort. To detect the volume flow taken from the fuel tank, a measurement of a change in the tank filling level per unit time or an indirect determination of a pressure difference between two measuring points on a low-pressure side of the high-pressure line is proposed. As an alternative, the use of other flowmeters, for example, the use of differential pressure flowmeters (throttling devices, magnetic-inductive flow meters, etc.) called.

Advantages of invention

in the Contrary to this prior art which detects individual values of volume flows, Form differences and compare the differences with a threshold, the process of the invention is characterized according to claim 1, characterized in that a time course of at least a fuel flow is detected and that the functionality judged on the basis of the time course of the fuel flow becomes. The fuel flow may be a volume flow or act around a mass flow. Furthermore, a control device according to the invention of the beginning mentioned type in that it is programmed to together with an external diagnostic device to carry out such a procedure. Accordingly, an inventive diagnostic device of the beginning mentioned type in that it is programmed to together with a control unit the fuel supply system to perform such a method.

These Open features Options, to detect other faults besides a leak. So is from the temporal course possibly also an undesirable change of flow characteristics of flow rate actuators of the fuel supply system detectable, which is not associated with leakage. In addition, to Example malfunction of a high-pressure pump with several pump elements be detected if this malfunction, for example, with irregularities between the flow rates individual pump elements is connected without this being a Lead to leakage would.

With Looking at embodiments of the method is preferred that the Volume flow is detected by means of an ultrasonic flow measurement.

The Propagation speed of an ultrasonic signal is of the flow rate the medium in which it spreads. From the term of the Ultrasonic signals between transmitter and receiver is therefore the flow velocity of the medium, here the fuel, determinable. With known flow cross section then results in a volume flow of the fuel as a product of Flow area and the specific flow rate. The ultrasonic flow measurement has the particular advantage that The measurement can be made non-invasively, because ultrasonic waves also penetrate solids and therefore the sensors are mounted on the outer wall of conduits can be without the function, in particular the tightness, of the fuel supply system to impair. An undesirable Throttling of the flow or a weakening of the pressure resistance of the Fuel supply system therefore does not occur.

It is also preferred that the ultrasonic flow measurement is detected by means of at least one ultrasonic flow sensor, which does not belong to the fuel supply system and with fuel-carrying portions of the Kraftstoffver system can be coupled and decoupled non-invasively.

These Embodiment has the advantage that the ultrasonic flow sensor not for to provide each fuel supply system in each motor vehicle is, but as a diagnostic tool for a variety of motor vehicles in workshops or as part of a tape end diagnosis at the end of a manufacturing process can be used.

A Another preferred embodiment is characterized in that the time course in connection with a drive at least a flow actuator is detected.

By the activation of a flow actuator become defined conditions generated, on which a functional Fuel supply system with defined reactions answers. Deviations from the defined reactions therefore show malfunctions the fuel supply system, the cause of the malfunction by varying the attachment of the flow sensor and by varying the control signals can be limited.

Prefers is also that with a fuel supply system with one on a low pressure side of a high pressure pump arranged metering unit as a flow actuator a Zumesseinheits-actuating signal in a predetermined manner in time is varied and the time course as a time course of a Fuel flow determined by the high pressure pump as the difference of fuel flows which is detected in a high pressure pump inlet and a high pressure pump return become.

These Design allows in particular a review of the characteristic of the metering unit and thus a review of Functioning of the Metering unit.

alternative or in addition it is preferred that in a fuel supply system with at least an injection valve as a flow control valve, an injection valve actuating signal is temporally varied in a predetermined manner and the temporal Course as a time course of a fuel flow through the high-pressure pump determined as the difference of fuel flows which is detected in a high pressure pump inlet and a high pressure pump return become.

alternative or in addition is preferred that the time course as a time course a fuel flow in a leading away from the high-pressure pump High pressure line is determined.

These Design allows a review of operability of the component grouping of high-pressure pump and metering unit. Becomes for example, the flow over the at least one injection valve is reduced in a defined manner, the volume flow generated by the high pressure pump must be in the range of the high pressure pump leading away high pressure line likewise fall in a defined way. Furthermore, this configuration allows a diagnosis of individual pump elements of the high pressure pump. High-pressure pumps usually have several pump elements, each individually posts to the flow rate supply the high pressure pump. The individual contributions form in the course of the fuel flow in the high-pressure line. A lack or shows a strong dispersion of the values of the individual contributions a malfunction of the pump elements.

By Detection of fuel flows on the low pressure side, ie in the high pressure pump inlet and in the high pressure pump return, and additionally in the high pressure line, as well as by normalizing the fuel flow in the high pressure line on the difference of fuel flows on the Low pressure side can additionally the efficiency of the high pressure pump after a change in a flow control signal be assessed.

Prefers it is also that the metering unit actuating signal and / or the injection valve actuating signal from a controller of the motor vehicle at the request of an external, with the control unit temporarily connected diagnostic device is changed.

By This configuration will be in the control unit anyway existing control routines to carry out of the method used. The external diagnostic device must then only trigger the appropriate control routine in the control unit, in the the diagnostic device for example, a changed one Engine speed request. The controller responds to the request with a change the injection quantity to the changed Set the speed.

A Another preferred embodiment provides that signals of the ultrasonic flow sensor the diagnostic device supplied and that assessment alone in the diagnostic device, alone in the connected control unit, or partially in the diagnostic device and partly in the controller.

By this configuration, there are many possible applications. The fact that the signals of the ultrasonic flow sensor are supplied to the diagnostic device, the circuitry and software for processing and evaluation of these signals does not have in each Steuerge advises each vehicle to be present. A judgment alone in the diagnostic device allows, for example, an adaptation of test routines by changing comparatively few diagnostic devices, or stored therein characteristic curves, maps and / or programs. An assessment that takes place solely in the control unit permits a highly individualized individualization of test routines. Distributing assessment functions to the diagnostic device and controller allows any possibility between these extremes to be used.

With Looking at embodiments of the control unit is preferred that it programmed to at least together with an external diagnostic device to perform one of the above embodiments of the method. The same applies to the diagnostic device.

Further Advantages will be apparent from the description and the attached figures.

It it is understood that the above and the following yet to be explained features not only in the specified combination, but also in other combinations or alone, without to leave the scope of the present invention.

drawings

embodiments The invention are illustrated in the drawings and in the following description explained. In each case, in schematic form:

1 a fuel supply system of an internal combustion engine;

2 a portion of a fuel line of the fuel supply system of the 1 ;

3 a flowchart as an embodiment of a method according to the invention; and

4 another embodiment of the method.

description the embodiments

1 shows a fuel supply system 10 an internal combustion engine 12 , For the operation of the internal combustion engine 12 Fuel is from a high-pressure accumulator 14 via an arrangement of at least one injection valve 16 in combustion chambers of the internal combustion engine 12 injected. For this purpose, the arrangement of at least one injection valve 16 for example, with injection pulse widths ti from a control unit 18 driven. Each injection valve 16 thus provides a flow actuator of the fuel supply system 10 represents.

To determine the injection pulse widths ti, the control unit processes signals of various operating parameters of the internal combustion engine 12 like its speed n, combustion chamber filling, torque request by the driver and so on. Representing corresponding sensors is in the 1 a speed sensor 19 shown. The injection pressure in the high-pressure accumulator 14 prevails, is by a high-pressure pump 20 generates the fuel with a correspondingly high pressure via a high-pressure line 22 in the high-pressure accumulator 14 promotes. The in high pressure storage 14 prevailing pressure is caused by a high pressure sensor 24 detected and as an electrical signal to the controller 18 pass, which therefrom a control signal TV_26 for a pressure control valve 26 that forms the high pressure accumulator 14 via a return line 28 to a fuel tank 30 or more generally, to a low pressure side of the fuel supply system 10 , relieved. The return line 28 is also the arrangement of at least one injection valve 16 connected to return uninsulated leakage fuel to the low pressure side of the fuel supply system.

The high pressure pump 20 which is usually considered by the internal combustion engine 12 mechanically driven piston pump is realized, has on its low pressure side a metering unit 32 from the control unit 18 controlled by a control signal TV_32, to a fuel flow from the fuel tank 30 to the high pressure pump 20 that via a high pressure pump inlet 34 takes place, to steer. The high pressure pump inlet 34 is from a prefeed pump 36 in the fuel tank 30 can be arranged, fed with a low-pressure fuel flow. Typical values for the low pressure are in the order of 10 bar, while typical values of the pressure on the high pressure side, for example the injection pressure, are of the order of 10 ³ bar. The metering unit 32 has, for example, a slide, which is moved with a duty cycle as a control signal TV_32, while a flow cross section on the low pressure side of the high pressure pump 20 affected. With closing control of the metering unit 32 thus increases the flow resistance in the high-pressure pump inlet 34 and the high pressure pump 20 receives correspondingly less fuel on its low pressure side and then promotes correspondingly less fuel in the high pressure line 22 ,

In the high pressure pump inlet 34 is optional a fuel temperature sensor 38 disposed a fuel temperature T_K as an electrical signal to the controller 18 passes. Through the metering unit 32 flowed fuel that is not from the high pressure pump 20 in the high pressure line 22 is fed via a high-pressure pump return 40 in the fuel tank 30 back. The object of 1 represents a typical fuel supply system 10 whose functionality can be assessed with the features indicated above. It is understood, however, that fuel supply systems of a different construction can also be diagnosed by the features listed above and explained in greater detail below.

To assess the operability of such fuel supply systems, such as the fuel supply system 10 , At least one time course of a fuel flow in a fuel-carrying line of the fuel supply system 10 captured and the functioning of the fuel supply system 10 is then judged on the basis of the time course of the fuel flow.

The assessment is preferably carried out as part of a workshop visit or a tape end test, in which a diagnostic device 42 to the control unit 18 is connected to control signals and data in the 1 both are referred to as DS, with the controller 18 exchange. For example, the fuel flow becomes parallel in the high pressure pump inlet 34 at a measuring point 44 and in the high pressure pump return 40 at a measuring point 46 measured, so that a difference of the detected fuel flows a flow through the metering unit 32 indicates. Alternatively or additionally, the fuel flow is at a measuring point 48 in the high pressure line 22 detected. For detecting the time profiles of the fuel flows, a fuel volume flow is preferably first detected, which in the case of the optional fuel temperature sensor 38 can be converted into a fuel mass flow.

For detecting the volume flow or the volume flows, an ultrasonic flow sensor is preferred 54 whose working principle is described below with reference to the 2 is explained. 2 shows in detail a section 50 a fuel line of the fuel supply system 10 , where the section 50 for example to one of the in the 1 shown measuring points 44 . 46 or 48 belongs. On walls 52 of the section 50 becomes non-invasive an ultrasonic flow sensor 54 fastened, wherein the attachment can be achieved for example by a clamping fit. The ultrasonic flow sensor 54 has a first transceiver 56 and a second transceiver 58 on, which work alternately and in each case complementary to each other as a transmitter or receiver of ultrasonic signals. The arrow 57 Gives the direction of the section 50 flowing fuel flow. The transceiver 56 sends an ultrasonic signal in the direction of flow 57 to the transceiver 58 and the transceiver 58 sends an ultrasonic flow sensor against the flow direction 57 to the transceiver 56 , Both transceivers 56 . 58 are to the diagnostic device 42 connected, which from the transit time difference of the ultrasonic signals, the flow rate of the fuel in the flow direction 57 certainly. This measuring principle is known in principle and is offered for example by Flexim for industrial applications. From the known flow cross-section and the detected flow velocity, the volume flow is formed as a product of the two variables mentioned. With additional consideration of the fuel temperature T_K, the fuel mass flow can be determined.

3 shows a flowchart as an embodiment of a method according to the invention, as in the subject of the 1 through the composite of control unit 18 and diagnostic device 42 is processed, if ever an ultrasonic flow sensor 54 at the measuring point 44 and at the measuring point 46 is arranged. The difference in the measuring points 44 and 46 detected fuel flows Q_34 and Q_40 then gives the fuel flow Q_32 through the metering unit 32 so that the timing of this fuel flow Q_32 through the metering unit 32 to assess the functionality of the metering unit 32 is used. To do this, the diagnostic device commands 42 the control unit 14 in one step 60 , the metering unit 32 closing to drive. The closing control can, for example, be such that a volume flow Q_32_soll (t) decreases in a ramp over the time t, as shown in FIG 3 next to the step 60 is shown. The closing is done, for example, so that only a predetermined minimum amount of fuel through the metering unit 32 flows.

Subsequently, by evaluating the signals at the measuring points 44 and 46 attached ultrasonic flow sensors 54 a detection of an actual value Q_32_act (t) of the volume flow through the metering unit 32 in one step 62 , The amount d of the difference between the actual volume flow Q_32_ist (t) and the desired volume flow Q_32_soll (t) is determined in step 64 formed and then in the step 66 compared with a threshold value S. If the difference is smaller than the threshold value S, the flow chart branches to the step 68 in which the metering unit 32 is judged to be functional (OK in the first place). Otherwise, the flow chart branches from the step 64 in the step 70 in which the metering unit 32 is judged to be inoperative (not OK). Right next to the step 66 is in the 3 a time course 71 the actual volumetric flow Q_32_act (t) together with the nominal volumetric flow 72 and an allowable deviation bandwidth resulting from the threshold S. The time course 71 remains in this case within the allowed deviation bandwidth and therefore identifies a functioning metering unit 32 ,

4 shows a further embodiment in which the ultrasonic flow sensors 54 also at the measuring points 44 and 46 in the 1 are attached. The diagnostic device 42 commands the controller 18 at the subject of 4 in step 74 a sudden adjustment of the arrangement of at least one injection valve 16 fuel quantity Q_16_soll to be injected by a change of injection pulse widths ti, as it is qualitatively right next to the step 74 in the case of an increase of Q_16_soll. In this case, the pressure control valve 26 kept closed. The sudden adjustment of the injection quantity can be done, for example, by the fact that the control unit 14 an increased or decreased setpoint for the speed n of the internal combustion engine 12 pretends. The high pressure pump 20 The then increasing or decreasing quantity request Q_16_soll must follow within a predefinable time interval dt with a correspondingly increased or reduced delivery rate Q_20_ist. The specification of a target value for the rotational speed has the advantage over other interventions that no impermissible rotational speeds, in particular no excessively high rotational speeds, occur in the case of changes in the injection quantities. For statistical protection, the change in the amount of fuel to be injected for different operating points, by initial speed values and / or target speed values and / or pressures in the high-pressure accumulator 14 are defined, repeated.

The delivery rate, which is an actual fuel flow Q_20_is through the high pressure pump 20 corresponds, results in the step 78 as the difference d1 of the fuel flows Q_34 in the high-pressure pump inlet 34 and Q_40 high pressure pump return 40 that in the step 76 were recorded.

In step 80 it is checked whether the difference d1 follows the target fuel flow Q_16_soll defined by the speed command value default with a deviation that is within a predetermined allowable bandwidth defined by the threshold value S1. The query in step 80 is preferably performed after a predetermined period of time dt after a change of Q_16_soll.

Will the query in step 80 in the affirmative, the high-pressure pump 20 in step 82 assessed as functional (i.o.). Otherwise, the high pressure pump will 20 in step 84 not sufficiently functional (NO).

Alternatively to an increased setpoint specification Q_16_soll of the arrangement of at least one injection valve 16 injected fuel flow can also reduce the setpoint specification in step 74 respectively. The reduction is preferred when the pressure control valve is closed 26 triggered by a reduction in the speed n by a predetermined value. The high pressure pump 20 must then follow the reduced setpoint specification with a correspondingly reduced flow rate. An insufficient or insufficiently rapid reduction of the flow rate indicates an undesired Nachförderung the high-pressure pump 20 down, for example, by a malfunction of the metering unit 32 is produced.

In contrast to the detection of the flow rate d1 = Q_20_ist as difference of fuel flows Q_34, Q_40 in the high-pressure pump inlet 34 and high pressure pump return 40 in step 76 The flow rate d1 can also be used with only one ultrasonic flow sensor 54 , the measuring point 48 in the high pressure line 22 of the 1 is attached to be detected.

This embodiment additionally allows a limitation of possible malfunctions of the high pressure pump by an evaluation of the time course of the detected fuel flow over time as a function of the number of pump elements of the high pressure pump 20 and with the speed n of the internal combustion engine 10 correlating speed of a drive of the high-pressure pump 20 ,

So can be checked whether over a predetermined rotation angle alpha, from the speed signal n is derivable, a suitable number k_soll of delivery strokes of the pump elements in the temporal History maps. Too small a number k of delivery strokes (k <k_soll) indicates a failure of one or more pump elements.

As an alternative or in addition, a scattering width SB of the delivery strokes, which map as maxima over time, can be evaluated. A spread exceeding a predetermined threshold indicates a malfunction of high pressure valves each between a single pump element and the high pressure line 22 are arranged.

Another alternative provides that fuel flows at all three measuring points 44 . 46 . 48 be detected and that in the high pressure line 22 , that is at the measuring point 48 detected fuel flows to a difference of the low pressure side, so at the measuring points 44 and 46 , collected fuel currents are normalized. The normalized size represents a degree of delivery or efficiency of the high-pressure pump 20 In this alternative, too, the flow rate of the high-pressure pump must follow a changed setpoint injection quantity requirement within a predetermined time.

Accordingly, the result of the diagnosis is a statement about the delivery rate of the high-pressure pump 20 , As an alternative to evaluating a difference between a setpoint value Q_16_soll and an actual value Q_16_ist1 at a specific time, it is also possible to evaluate the time that elapses between a change in the setpoint value Q_15_soll and an adjustment of the actual value Q_16_ist1. Exceeding a corresponding threshold then also shows a malfunction of the high-pressure pump 20 at.

Claims (11)

Method for assessing the operability of a fuel supply system ( 10 ) of a motor vehicle ( 12 ) on the basis of one in the fuel supply system ( 10 fuel flow (Q_32_actual.Q_34, Q_40, Q_20_act), characterized in that a time history of the fuel flow (Q_32_act.Q_34, Q_40, Q_20_act) is detected and that the operability is determined on the basis of a time course of the fuel flow (Q_32_act. Q_34, Q_40, Q_20_ist). Method according to claim 1, characterized in that that the fuel flow (Q_32_ist. Q_34, Q_40, Q_20_ist) with help an ultrasonic flow measurement is detected. A method according to claim 2, characterized in that the ultrasonic flow measurement using at least one ultrasonic flow sensor ( 54 ) not belonging to the fuel supply system ( 10 ) and fuel-bearing sections ( 50 ) of the fuel supply system ( 10 ) can be coupled and decoupled non-invasively. Method according to at least one of the preceding claims, characterized in that the time profile in conjunction with a control of at least one flow control actuator ( 16 . 32 ) of the fuel supply system ( 10 ) is detected. Method according to claim 4, characterized in that in a fuel supply system ( 10 ) with one on a low pressure side of a high pressure pump ( 20 ) arranged metering unit ( 32 ) is varied as a flow rate actuator a Zumesseinheits-control signal (TV_32) in a predetermined manner and the time course as a time course of a fuel flow (Q_32_ist) by the high-pressure pump ( 20 ) is determined as the difference of fuel flows which are in a high pressure pump inlet ( 34 ) and a high pressure pump return ( 40 ). Method according to claim 4, characterized in that in a fuel supply system ( 10 ) with at least one injection valve ( 16 ) as the flow rate control element, an injection valve actuating signal (ti) is temporally varied in a predetermined manner, and the time profile as a time profile of a fuel flow (Q_20_act) is varied by the high-pressure pump ( 20 ) is determined as the difference of fuel flows (Q_34, Q_40), which in a high-pressure pump feed ( 34 ) and a high pressure pump return ( 40 ). Method according to at least one of claims 3 and 4, characterized in that the time profile as a time profile of a fuel flow (Q_20_ist) in one of the high-pressure pump ( 20 ) leading away high pressure line ( 22 ) is determined. Method according to at least one of Claims 4 to 7, characterized in that the metering unit actuating signal (TV_32) and / or the injection valve actuating signal (ti) are generated by a control unit (T). 18 ) of the motor vehicle at the request of an external, with the control unit ( 18 ) Intermittently connected diagnostic device ( 42 ) will be changed. Method according to at least one of claims 3 to 7, characterized in that signals of the ultrasonic flow sensor ( 54 ) the diagnostic device ( 42 ) and that the judgment is made in the diagnostic device alone ( 42 ), only in the connected control unit ( 18 ), or partially in the diagnostic device ( 42 ) and partly in the control unit ( 18 ) takes place. Control unit ( 18 ) of a fuel supply system ( 10 ) in a motor vehicle, characterized in that it is programmed, together with an external diagnostic device ( 42 ) to carry out at least one of the methods according to claims 1 to 9. Diagnostic device ( 42 ) for assessing the operability of a fuel supply system ( 10 ) of a motor vehicle on the basis of a vehicle in the fuel supply system ( 10 ), characterized in that it is programmed, together with a control unit (Q_32_ist. Q_34, Q_40, Q_20_ist) 18 ) of the fuel supply system ( 10 ) at least one of the methods according to claims 1 to 9 durchzufüh ren.