CONTROLLING A FUEL INJECTION SOLENOID VALVE

Abstract

A device and a method are provided for controlling a magnetic valve which has a coil and an armature which is displaceable by magnetic force, by means of which armature a closure element is displaceable for the purposes of injecting fuel into a combustion chamber, the method includes the steps of: energizing the coil with a voltage in accordance with a first voltage profile in order to generate a first electrical current through the coil; determining a first profile as a function of a first magnetic flux and the first current; identifying, in the first profile, a first characteristic of at least one first start of displacement at which the armature begins to displace the closure element, generating a second voltage profile and energizing the coil in accordance with the second voltage profile, such that, in a second profile, as a function of a second magnetic flux and a second current, a second characteristic of a second start of displacement is more similar to a reference characteristic than the first characteristic.

Claims

1. A method for controlling a magnetic valve, comprising the steps of: providing a coil (3) for producing a magnetic force; providing an armature (9) which is displaceable by the magnetic force generated by the coil; providing a closure element (11) which is displaceable by the armature; providing a combustion chamber, the closure element being displaceable for the purposes of injecting fuel (19) into the combustion chamber (23); energizing the coil (3) with a voltage (84) in accordance with a first voltage profile in order to generate a first electrical current (81) through the coil (3); determining a first profile (31, 37) as a function of a first magnetic flux () and the first current (i); identifying, in the first profile, a first characteristic of at least one first start of displacement (I) at which the armature (9) begins to displace the closure element (11); generating a second voltage profile and energizing the coil in accordance with the second voltage profile, such that, in a second profile, as a function of a second magnetic flux and a second current, a second characteristic of a second start of displacement (I) is more similar to a reference characteristic than the first characteristic.

2. The method as claimed in claim 1, further comprising the steps of: providing a first curve of a coordinate system; and providing a second curve of the coordinate system; representing the first profile and the second profile by the first curve (31, 37) and the second curve respectively in a coordinate system in which the current (i) is plotted along one axis and the magnetic flux () is plotted along another axis.

3. The method of claim 2, further comprising the steps of providing a pole piece in contact with the armature when the magnetic valve is in a fully open position such that at least one of the first characteristic or the second characteristic includes at least one of a gradient or a position on at least one of the first curve or the second curve, and at least at the respective start of displacement (I) along at least one section of an opening movement of the closure element between the start of displacement (I) and a contact state (II) in which the armature abuts against the pole piece in order to end the opening movement, and the reference characteristic includes at least one of a reference gradient or a reference position.

4. The method of claim 3, further comprising the steps of identifying the respective start of displacement (I) as a point or region at which a gradient of at least one of the first curve or the second curve changes.

5. The method of claim 3, further comprising the steps of identifying the respective contact state (II) as a point or region at which a gradient of at least one of the first curve or the second curve changes.

6. The method of claim 3, further comprising the steps of: providing a boost phase; energizing of the coil in accordance with the second voltage profile at a time before the first contact state (II), such that the second voltage profile has a different, in particular lengthened, shortened or interrupted, duration of the boost phase (85) in relation to the first voltage profile.

7. The method of claim 6, further comprising the steps of energizing of the coil in accordance with the second voltage profile at a time after the first contact state (II), such that the second voltage profile has at least one of a different duration of the boost phase (85) in relation to the first voltage profile, or an interrupted boost phase (85).

8. The method of claim 3, further comprising the steps of: determining the respective characteristic as a function of at least one section of at least one of the first curve or the second curve beyond the contact state (II); selecting the second voltage profile such that the section (34) has fewer alternating gradients.

9. The method of claim 8, further comprising the steps of: providing at least one reference data set (31, 37), including a reference curve of current and magnetic flux when there is a low level of bouncing of the armature on the pole piece; performing a test on the operation of the magnetic valve using the at least one reference data set for the locating of the second voltage profile.

10. An engine control unit for controlling a magnetic valve (1), comprising: a coil (3) for producing a magnetic force; an armature (9) which is displaceable by the magnetic force produced by the coil; a closure element which is displaceable by the armature; a combustion chamber, the closure element being displaceable for injecting fuel (19) into the combustion chamber (23); a driver (4) for energizing the coil (3) with a voltage (84) in accordance with a first voltage profile in order to generate a first electrical current (81) through the coil (3); a determination module (6) which determines a first profile as a function of a first magnetic flux and the first current, and identifies in the first profile a first characteristic of at least one first start of displacement (I) at which the armature (9) begins to displace the closure element (11); wherein the driver (4) generates a second voltage profile and energizes the coil in accordance with the second voltage profile, such that in a second profile, as a function of a second magnetic flux and a second current, a second characteristic of a second start of displacement is more similar to a reference characteristic than the first characteristic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention will now be discussed with reference to the appended drawings. The invention is not restricted to the illustrated or described embodiments.

[0044] FIG. 1 illustrates, in a schematic sectional illustration, a magnetic valve which is controlled in accordance with a method according to embodiments of the present invention;

[0045] FIG. 2 illustrates graphs of reference data and state trajectories and measurement data of a magnetic valve to be controlled according to embodiments of the present invention;

[0046] FIG. 3 illustrates graphs of reference data and state trajectories and measurement data of a magnetic valve to be controlled according to embodiments of the present invention;

[0047] FIG. 4 illustrates quantity characteristic curves for injectors with and without bouncing, in accordance with the prior art;

[0048] FIG. 5 illustrates graphs of state trajectories obtained by means of different actuation voltage profiles;

[0049] FIG. 6 illustrates graphs for illustrating magnetic valve actuation or injector actuation;

[0050] FIG. 7A is a graph illustrating bouncing behavior of an armature of a magnetic valve controlled according to embodiments of the present invention;

[0051] FIG. 7B is a graph illustrating the stroke of the armature versus time, where the armature is controlled according to embodiments of the present invention;

[0052] FIG. 7C is a second graph illustrating the stroke of the armature versus time, where the armature is controlled according to embodiments of the present invention; and

[0053] FIG. 7D is a graph illustrating the actuation profiles of an armature, where the armature is controlled according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

[0055] The magnetic valve 1 illustrated in a schematic sectional illustration in FIG. 1 has a coil 3 to which a voltage may be applied such that a current flow through the coil 3 occurs for the purposes of building up a magnetic field. Here, the magnetic field points substantially in a longitudinal direction 5 of a guide cylinder 7. The magnetic field acts on a ferromagnetic armature 9 which is displaceable within the guide cylinder 7. By means of displacement of the armature 9, a nozzle needle 11 or a closure element of the magnetic valve 1 may be displaced in the longitudinal direction 5, in particular as a result of contact of the armature 9 with a ring-shaped driver 13 which is fixedly connected to the closure element 11.

[0056] In the open state illustrated in FIG. 1, a closure ball 15 has been retracted out of a conical seat 17, such that fuel 19 may pass through an opening 21 in the seat into a combustion chamber 23 for the purposes of combustion. In the fully open state, the armature 9 bears against a pole piece 27, and is displaced no further upward.

[0057] In a closed state of the magnetic valve 1 which is not illustrated in FIG. 1, the armature 9 is, in the absence of a current flow through the coil 3, displaced downward by a restoring spring 25, such that the driver 13 together with the closure element 11 is also displaced downward such that the closure ball 15 bears sealingly against the conical seat 17, such that fuel 19 cannot pass into the combustion chamber 23. In this downwardly displaced state of the armature 9, the driver 13, and likewise the armature 9, has moved through at least a working stroke 12 (during which the armature 9 and the driver 13 are in contact), and optionally also an additional idle stroke 10, in which a gap exists between the armature 9 and the driver 13.

[0058] FIG. 1 also shows a device 2 for controlling the magnetic valve 1 according to an embodiment of the present invention. For this purpose, the device 2 has a driver 4 which is designed to, via a measurement and control line 8, energize the coil 3 with a voltage in accordance with various voltage profiles in order to generate a respective electrical current through the coil 3. For this purpose, the device 2 has a determination module 6 for determining profiles or curves as a function of a respective magnetic flux and a current flowing through the coil 3, for example the -i curves, which are illustrated by way of example in FIGS. 2, 3 and 5. Furthermore, the determination module 6 is designed to identify, in the first profile, a first characteristic of at least a first start of displacement at which the armature begins to displace the closure element. The determination module 6 is furthermore designed to, together with the driver 4, modify the original or first voltage profile, and/or determine a second voltage profile, such that a characteristic of the respective start of displacement is more similar to a reference characteristic than the original or first characteristic.

[0059] In particular, the device 2 is designed to carry out a method for controlling a magnetic valve according to an embodiment of the present invention.

[0060] At the end of the opening process, the armature 9 bounces when it abuts against the pole piece 27. As a result, the armature may be elastically repelled, and the abutment and repulsion may occur repeatedly, such that the armature may perform a bouncing movement. The bouncing movement leads to uncertainties and inaccuracies in a quantity of the fuel 19 injected into the combustion chamber 23.

[0061] Embodiments of the present invention are aimed at reducing the bouncing through the performance of control interventions into a voltage profile or into a voltage progression in accordance with which the coil 3 is actuated. Here, a measurement and analysis of the interlinked magnetic flux L are performed. For this purpose, the interlinked magnetic flux L may be calculated from the current flowing through the coil 3, the voltage applied to the coil 3, and the ohmic resistance of the coil 3. The measured voltage u(t) is composed of an ohmic component (i(t)*R) and an inductive component (u.sub.int(t)). The inductive voltage is in this case calculated from the derivative with respect to time of the interlinked magnetic flux, wherein L is dependent on the change in current i(t) and the air gap x(t).

[00001]$u\left(t\right)=i\left(t\right).Math.R+u_{\mathrm{ind}}=i\left(t\right).Math.R+\frac{d.Math..Math.\left(i,x\right)}{\mathrm{dt}}=i\left(t\right).Math.R+\left(\frac{d.Math..Math.\left(i,x\right)}{\mathrm{di}}.Math.\frac{\mathrm{di}}{\mathrm{dt}}+\frac{d.Math..Math.\left(i,x\right)}{\mathrm{dt}}.Math.\frac{\mathrm{dx}}{\mathrm{dt}}\right)$

[0062] In the case of slow actuation, the magnetic component of the induction as a result of change in current is small.

[00002]$u_{\mathrm{ind}.Math..Math.1}=\frac{d.Math..Math.\left(i,x\right)}{\mathrm{di}}.Math.\frac{\mathrm{di}}{\mathrm{dt}}$

[0063] The mechanical part of the induction as a result of the armature movement then describes the strokes (idle stroke and/or working stroke) of the magnetic valve.

[00003]$u_{\mathrm{ind}.Math..Math.2}=\frac{d.Math..Math.\left(i,x\right)}{\mathrm{dx}}.Math.\frac{\mathrm{dx}}{\mathrm{dt}}$

[0064] Through rearrangement and integration, the interlinked mechanical flux may be calculated as follows:

=(u(t)i(t)R)dt

[0065] FIG. 2 illustrates a graph 29 with a state trajectory 31 during an attraction (that is to say during an opening process), and a trajectory 33 during a fall (that is to say during a closing process), of the magnetic valve 1 (here for the case with idle stroke). Here, the current i flowing through the coil 3 is plotted on an abscissa 30, and the magnetic flux L calculated in accordance with the above equation is plotted on the ordinate 32. The trajectory 31 may be determined for example during a method for controlling the magnetic valve, for example by measurement of current and voltage and calculation of the magnetic flux as discussed above. From a comparison with reference data or reference trajectories not illustrated in FIG. 2, a suitable voltage profile may be determined in order to prevent bouncing. The points I, II, I, II in FIG. 2 denote characteristic states during the opening process. Here, the idle stroke from 134 m to 90 m, that is to say the attraction of the armature 9 during the idle stroke, takes place between the points I and II. The working stroke from 90 m to 0 m, that is to say the attraction of the armature 9 during the working stroke, takes place between the points I (start of displacement) and II (contact state). In the region II-I, the armature bears against the driver 13.

[0066] In embodiments of the present invention, for a magnetic valve without idle stroke (FIG. 3 below) or with idle stroke (FIG. 2), the region of the trajectory 31 at the point I and/or up to the point II is evaluated. Here, in the region I-II, a gradient of the trajectory 31 changes in relation to the sections situated before and after the region. Furthermore, in the section between points I and II, the gradient changes from a positive value to a negative value.

[0067] In FIG. 2, for example for a magnetic valve with idle stroke in a region 34 after the second state II at which the armature 9 abuts against the pole piece 27 for the first time, an undulating line may be seen which indicates the bouncing. In embodiments of the present invention, different voltages (for example in accordance with the voltage profiles described below with reference to FIG. 6) are applied to a given magnetic valve, and it is possible in each case for the -I curves to be determined and evaluated. Voltage profiles which do not exhibit bouncing, that is to say in particular do not exhibit undulating lines in the region 34, may be characterized as advantageous, and may be used for the actual actuation of the magnetic valve. Other voltage profiles which give rise to sinuous lines or undulating lines or disturbances in the region 34 may be excluded from serving as actuation voltage profiles for the magnetic valve 1. From a set of training data, it is possible for predictions to be made on the basis of a determined voltage profile (for example boost voltage level, boost voltage duration, holding voltage level, holding voltage duration), whereby any occurring bouncing could be predicted.

[0068] FIG. 3 illustrates a graph 35 which illustrates trajectories 37 and 39 during an attraction and a fall of the armature 9 of the magnetic valve 1, in the case in which the magnetic valve 1 does not exhibit an idle stroke. Since the idle stroke is absent in the trajectory 37 illustrated in FIG. 3, the characteristic points I and II illustrated in FIG. 2 are absent. The working stroke from 50 m to 0 m takes place between the points I and II. Here, the trajectory 37 has a bend at the point I, at which bend a positive gradient changes to a negative gradient.

[0069] FIG. 4 illustrates a graph in which an injection time TI in milliseconds is plotted on an abscissa 60 and the injection quantity MF in milligrams is plotted on an ordinate 62. Here, the injection time denotes the time duration for which the injection valve is open. The curve 63 illustrates the quantity characteristic curve for a magnetic valve which exhibits bouncing, and the curve 65 illustrates the case of an injection valve which exhibits no bouncing or only a very low level of bouncing.

[0070] For the injection valve which exhibits only a very low level of bouncing (curve 65), there is an almost linear relationship between the injection time and the injection quantity, at any rate for injection times which are greater than a threshold value (approximately 0.3 ms) which is denoted by reference designation 67. For the magnetic valve which exhibits bouncing (curve 63), in a region 69 of short injection times, there is an intense deviation from a linear characteristic, that is to say from a linear relationship between the injection time and the injection quantity. In the case of conventional methods, an injection time in the region 69 is avoided for such magnetic valves. Thus, in the prior art, it would not be possible to perform or implement relatively short injection times, in particular in a range between approximately 0.3 ms and 0.4 ms, because a monotonous gradient is not realized.

[0071] Embodiments of the present invention determine the magnetic flux at an early stage during an opening movement or during an opening process of the magnetic valve, and perform a control intervention at an early point in time by virtue of the voltage applied to the coil being set such that bouncing that is expected to occur is reduced.

[0072] The form of the -I curve in the case of different actuation voltages (3 V . . . 18 V) is illustrated in FIG. 5 by trajectories 47 (excitation voltage 18 V), 49 (excitation voltage 6 V), 51 (excitation voltage 12 V) and 53 (excitation voltage 3 V). As may be seen from FIG. 5, with increasing voltages, it becomes increasingly more difficult to reliably detect the states I and II, because only small changes in gradient occur. For example, in the case of an excitation voltage of 18 V, it may be difficult to reliably detect the state I. Therefore, a measurement of reference curves or a measurement for determining a stroke in the case of relatively small excitation voltages, for example between 3 V and 12 V, may be performed. The curves 47, 49, 51 and 53 illustrated in FIG. 5 may represent measurement data or reference data.

[0073] FIG. 6 illustrates three graphs 70, 72 and 74 which illustrate an actuation of a magnetic valve according to embodiments of the present invention.

[0074] Here, the time in microseconds is plotted in each case on the abscissae 76. The level of the voltage applied to the coil 3 is plotted on the ordinate 78 of the graph 70, the level of the current through the coil 3 is plotted on the ordinate 80 of the graph 72, and the injection rate (that is to say injection quantity per unit time) of the fuel in the case of the magnetic valve being actuated in accordance with the voltage profile of the graph 70 is plotted on the ordinate 82 of the graph 74.

[0075] The voltage profile 84 in the graph 70 of FIG. 6 includes a boost phase 85, a holding phase 87 and a depletion phase 91. During the boost phase 85, a boost voltage of approximately 50 V or even up to 65 V is applied to the coil 3 for the purposes of opening the valve 1. The boost voltage is maintained for a time duration of between 300 s and 600 s. In particular, the boost voltage is maintained until a defined current value or a maximum time duration is reached. In the boost phase 85, the armature or needle movement occurs, and therefore the stroke signal in the -I curve is weak. This may be the case in particular if a conventional armature is used which generates very high eddy currents in the case of relatively high boost voltages.

[0076] In the conventional method, the needle bouncing may be identified only indistinctly, and an adaptation of the electrical actuation to the needle movement in order to reduce the bouncing may be difficult in this case.

[0077] The graph 72 shows, by means of a curve 81, the current profile that arises in the coil owing to the voltage profile 84. At the start of the boost phase 85, the current 81 rises intensely, and reaches a maximum at the end of the boost phase. During the holding phase 87, the current decreases, but the valve is held open in this phase and is regulated substantially to a value of zero after the completion of the depletion phase 91. Beyond the phase 91, the magnetic valve is closed.

[0078] The curve 83 of the graph 74 shows the injection rate as a function of the time. After the completion of the boost phase 85, the injection rate has risen to a certain value, which is maintained, aside from small fluctuations, during the holding phase 87. The time point denoted by the reference designation 90 represents a time point of complete injector opening.

[0079] The injection rate profile 83 may in this case exhibit a high degree of correspondence or correlation with the needle movement. Despite the complete opening of the injector (armature makes contact with pole piece), the actuation voltage is maintained, and thus the accelerating magnetic force continues to be increased, which conventionally leads to increased bouncing. The bouncing processes may differ between the individual injectors, because the injectors open at different times, and thus the force profiles after the complete opening may differ. Furthermore, the damping characteristics of the injectors may differ owing to the respective geometry of the damping gap.

[0080] Embodiments of the present invention permit a control intervention through modification of the voltage profiles, for example of the voltage profile 84 which is illustrated in the graph 70 of FIG. 6. By means of a recorded -I curve, it is the case in one embodiment of the present invention that the injector movement is identified (in particular also online during operation of a vehicle), and the actuation is modified such that the bouncing behavior is reduced. For this purpose, it is for example possible for the needle movement (state I and/or state II) to be determined in the -I curve, and for the associated actuation to be optimized with regard to bouncing, for example through modification of the peak current level (of the current 81) or through interruption of the actuation voltage (voltage 84, for example during the boost phase 85, during the holding phase 87 or a combination of both).

[0081] For example, the entire needle movement between the first state I and the second state II may be identified (see for example FIGS. 2 and 3), and the actuation may be adapted such that the gradients d/di during the movement are identical for different injectors (adaptation to setpoint value or reference curve). If the first state I is incorporated into the identification, then the needle movement may, even after the start of the movement, be moved onto a bouncing-minimized path through suitable actuation, that is to say a regulating intervention may be performed already before the bouncing process. Such a regulating intervention before the bouncing may in this case comprise, for example, an identification of the first state I and an execution of predefined actuation/pilot control before or during the first state I (for example, the current value in the first state I may be adapted or set with the addition of a defined current difference of with the addition of a lengthening of the boost phase).

[0082] Alternatively or in combination therewith, it is also possible for a regulating intervention to be performed after the abutment of the armature against the pole piece, for example by virtue of the second state II being identified and predefined actuation/pilot control being executed in the second state II (for example, the current value in the second state with the addition of a defined current difference or with the addition of an elongation of the boost phase or interruption of the boost phase with subsequent continuation).

[0083] FIGS. 7A, B, C and D show graphs which illustrate the armature behavior for different situations if actuation is performed in accordance with embodiments of the invention: without bouncing (solid line, curves denoted by a), with bouncing (dotted line, curves denoted by b) and with soft landing (dashed line, curves denoted by c).

[0084] The bouncing is identified in the PSI-I curve 92a, 92b or 92c respectively in FIG. 7A. To minimize the bouncing, the duration of the boost phase 85 of the actuation profiles 84a, 84b, 84c is lengthened for the subsequent actuations, and thus the force on the armature is increased during the abutment (see FIG. 7D).

[0085] Another solution is a so-called soft landing. Here, the armature is decelerated already before it reaches the pole piece as a result of shortening of the duration of the boost phase, and the abutment thus occurs with reduced momentum, which in turn reduces or prevents the bouncing.

[0086] In FIG. 7B, the armature stroke is illustrated versus the time for the various cases as curves 94a, 94b, 94c.

[0087] In FIG. 7C, the current is illustrated versus the time for the various cases as curves 96a, 96b, 96c.

[0088] In a particular embodiment of the invention, it is proposed that an injector be used in which no or reduced eddy currents occur. In such a case, it may be possible for the -I curves to be implemented even in the case of standard actuation (for example with 65 V boost voltage).

[0089] The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.