EP0185945A2 - Moving part extreme position sensing device - Google Patents

Abstract

A method for detecting an extreme value position of a moving part by a position detection element (17) is proposed, in particular for detecting the idle position of the throttle valve (12) of an internal combustion engine (10) with the aid of a potentiometer. A stored value (extreme value) corresponding to the extreme value position is corrected when deviating measured values are detected, provided that these deviating measured values lie in a correction range around the extreme value. The range of motion of the movable part must lie within the range that can be detected by the position detection element (17). After a specified number of identical measured values have been recorded in the correction range during an operating cycle, such a measured value is stored as a new extreme value. This new extreme value is changed cyclically, preferably before each operating cycle, by a predetermined value from the outermost position in order to make the adaptation dynamic. This method has a very small hysteresis with high accuracy of the detection of the extreme value position, the full functionality being achieved again after a short time even under irregular operating conditions.

Description

State of the art

The invention is based on a method according to the type of the main claim, in particular for detecting the idle position of the throttle valve of an internal combustion engine.

From DE-OS 24 42 373 an electrically controlled, intermittently operating fuel injection system with an injection signal generation is known, which is based on the speed and the throttle valve position. The throttle valve position is detected there using a potentiometer. With a view to optimum fuel metering, it is necessary that the throttle valve position is detected very precisely, particularly in the area of relatively small throttle valve opening angles. For example, to set the idle, an idle position of the throttle valve must be recognized, for which purpose an idle switch is usually used. However, the idle stop is subject to changes both by adjusting the idle speed and by mechanical wear on the stop. The . However, the idle position of the throttle valve must be within a very small angular range of approx. 0.3 ° can be recognized, because only there the air flows are small enough to keep the torque change when switching the fuel on and off by the overrun fuel cut-off function within tolerable limits.

From DE-OS 34 28 87.9 a digital method for idle detection is known, in which the wiper track of the position sensing element designed as a potentiometer is divided into increments. A stored limit value is updated with a specific time constant depending on the measured values. For tracking, however, a constant angular stroke between the minimum and maximum values must be taken into account, in which case this entire measuring range is then tracked. This method is not particularly suitable for non-linear potentiometers.

The invention has for its object to improve the known in the prior art method so that with high accuracy and rapid adaptation, even with irregular operating conditions and large angle differences, an extreme value can be adapted isolated, without the opposite extreme value one Could exert influence.

Advantages of the invention

The inventive method with the characterizing features of the main claim solves this problem and has the advantage that an exact setting and detection of this position is ensured by a very low hysteresis and reliable detection of the idle position.

Advantageous developments and improvements of the method specified in the main claim are possible due to the features specified in the subclaims.

drawing

An embodiment of the invention is shown in the drawing and explained in more detail in the following description. FIG. 1 shows an overview of an electronically controlled injection system, in which the throttle valve position and the speed are processed as the most important operating parameters, FIG. 2 shows a flow diagram as an exemplary embodiment of the invention, FIG. 3 shows various examples of an irregular displacement of the idling position and its correction, and FIG. 4 shows a flow diagram to explain the operation of the idle detection.

Description of the embodiment

Figure 1 discloses the basic structure of an electrically controlled and preferably intermittent fuel injection system, based on signals of the speed and the throttle valve position angle. Such an arrangement is e.g. known from the aforementioned DE-OS 24 42 373.

An internal combustion engine 10 receives intake air via an intake pipe 11 with a throttle valve 12 and has. an exhaust pipe 13. A speed sensor 14 detects the instantaneous speed of the crankshaft and, together with the position α of the throttle valve 12, determines an injection signal t _p for an injection valve 15 assigned to the intake manifold 11 In addition to the speed and the throttle valve position, other operating parameters such as the temperature and the lambda value are fed in. This is indicated by further inputs of the control unit 16.

The positionoC of the throttle valve 12 is detected by a potentiometer 17 and supplied to the control unit 16 as a measured value M. The operating voltage of the potentiometer of, for example, drops over the entire slider path of the potentiometer 17. 5 volts off. If you divide the slider track into increments, then there are 256 increments in the case of 8 bits over the entire slider track. Since the mechanical adjustment range of the throttle valve 12 must lie within the adjustment range of the potentiometer, a specific data word results for the mechanical throttle valve stop A (idle position), which corresponds to a very small voltage or a small number of increments. In Figure 3, the mechanical stop A corresponds to nine increments. The idle position of the throttle valve can shift due to mechanical displacement of the potentiometer relative to the throttle valve, aging, wear of the stops and other error influencing variables. Through constant adaptation, the exact idle position should always be recognizable in a purely electronic manner.

The mode of operation of the adaptation will be explained below with reference to FIGS. 2 and 3. The adaptation process starts 20 after the supply voltage (for example, ignition lock) is switched on, after the internal combustion engine has started and after the engine temperature has exceeded a certain threshold. This represents the beginning of an operating cycle, which occurs when the internal combustion engine or the supply voltage is switched off is ended. This is followed by an initialization 21 in which four memory cells or. Registers F, H, G and I are set to the value 0. Finally, in method step 22, the stored value of the idle position S _{LL is} increased by one increment. The query step 23 now takes place, with which it is determined whether the measured value M present at the moment is greater than the stored idle value ^S _LL .

If this condition applies, it is checked in query step 24 whether this measured value M lies outside a partial correction range which is limited by the value S _LL on the one hand and S _{LL + 2} on the other. If this is the case, the condition M> S _{LL + 2 is} fulfilled, the register F is set to the value 1 in step 25 and, after a delay time of 10 ms, a return to the query step 23 in a program loop. The cycle for querying the measured value M is specified in method step 26. The loop 23 to 26 is now run through until the measured value M falls within the correction range.

If the condition of the query step 24 is thus no longer met, a check is carried out in the query step 27 as to whether the register value of the register H> 2. At this point in time, this condition is not met, so that it is now checked in query step 28 whether the register F has the value 1, which is now the case. Now it is checked in query step 29 whether the measured value M has already occurred before (M _i = M _i-1 ). Since this is not the case, the register H is set to the value 0 in step 30 - the value 0 is present at this point in time anyway - and the query step 23 is returned after the predefined cycle time. Steps 23, 24, 27, 28 and 29 are now run through again, provided the corresponding conditions are still present. In query step 29 it is now determined that the Measured value M has already occurred once, so that register H is now incremented by the value 1 in method step 31. The register F is then set to the value 0 in method step 32 and returned to the query step 23 after the intended cycle time.

If the same measured value M is still available, steps 24, 27, 28 are carried out, it being determined in query step 28 that register F no longer has the value 1, so that method steps 32 and 26 lead to the query step 23 is returned. As long as the measured value M does not change, the described loop is run through without changes until the measured value M rises above the value S _{LL + 2} (query step 24), whereby in step 25 the register F is reset to the value 1. This loop 23, 24, 25, 26 is now run through until the measured value M no longer fulfills the condition of the query step 24.

For further incrementation of the register H in method step 31, it is necessary that the condition of query step 29 is fulfilled, that is to say that the measured value M that has been recorded has already been recorded identically beforehand. In this case the register H can be incremented by 1 to the value 2.

In order to fulfill the condition of query step 27 (H> 2), it is therefore necessary that the loop 1 (23, 24, 25, 26), the loop 2 (23, 24, 27, 28, 29, 30, 26), loop 3 (23, 24, 27, 28, 29, 31, 32, 26) and then loop 1 and loop 3 again in double interplay. In other words, if the measured value M is detected identically four times, with the last three times, at least one measurement value must occur in between that fulfills the query condition 24, Then in method step 33 this measured value M is stored as a new idle value S _LL . Since the register H is then reset to the value 0 in method step 30, the entire method sequence must be repeated in order to change the value S _LL again. It is assumed that a measured value that occurs several times in an identical manner in the vicinity of the stored idle value must be the actual idle value.

If it is found in query step 23 that the measured value M is smaller than the stored idle value 8LL, it can be concluded immediately that this measured value M is at least closer to the actual idle value than the stored idle value does. The question of whether this measured value is close to the stored idle value is therefore superfluous. In query step 34, it is therefore immediately checked whether the memory content of the register G> 2, which is not the case at this time. In query step 35, it is then determined that the measured value M has not yet occurred, so that the registers G and I are set to the value 0 and the value 1 via method steps 36, 37 and via method step 26 to the query step again 23 is returned. In the next run, after the query steps 23, 34, 35, in step 38, the register G is incremented, since it was now determined in query step 35 that the measured value M has already occurred once. The loop 23, 34, 35, 38, 26 is now run through until the register G reaches the value 3, provided that the measured value M is retained in an identical manner. Now, in process step 39, this measured value M, which has occurred several times, is stored as a new idle value S _LL and then the register G is reset to the value 0 and the register I is reset to the value 1.

In Figure 3, the measured value should correspond to the idling stop value A. The stored idle value is shown with double hatching in each case, while the two increments adjoining it on the right, which are simply hatched, represent the part of the correction range located to the right of the idle value.

In line a, the stored idle value corresponds to the value 5. In this operating cycle, only the loop 23, 24, 25, 26 can be run through. In the subsequent operating cycle, the stored idle value increases in method step 22 by one increment (line b), but the loop 23, 24, 25, 26 is also run through again.

In the third operating cycle shown in column c, condition 24 is no longer fulfilled, ie the measured value is now in the correction range. If - as described - an identical measured value M now occurs four times in an identical manner, this measured value is stored as a new idle value S _LL in the same operating cycle as is shown in column d. In the subsequent fourth operating cycle, the new idle value is first incremented again in method step 22, as shown in column e. In query step 23 it is now determined that the measured value is smaller than the stored idle value, so that according to the above statements, after four identical occurrences, this measured value is stored as a new idle value, as shown in column f.

As columns g and h show, if the stored idle value is undershot by the measured value in the same operating cycle, the stored idle time is determined anew, regardless of how large the deviation from the previous idle value is.

As an alternative to method step 22, at the beginning of an operating cycle, the stored idle value can be increased by a number of increments instead of by one increment, which correspond to the maximum possible idle position of the throttle valve during warming up of the internal combustion engine. This number of increments corresponds, for example, to an angular position of 20 °. In this case, of course, the engine temperature does not apply as a starting condition in process step 20. At the start of warming up, the throttle valve angle is set to a high idling value, which is then recorded and stored using process steps 34 to 39. If the idle angle slowly decreases as far as the engine temperature increases, the stored idle value follows this changing value by constant adaptation. At least one successfully completed adaptation process should be awaited for idle detection.

FIG. 4 explains the logical decision in control unit 16 whether the idle position is present or not. For this purpose, query step 40 queries whether the current measured value M is smaller than the stored idle value S _LL increased by three increments, that is to say whether the measured value lies within a hatched area according to FIG. 3. If this is not the case, no idle position is recognized in method step 41. If, on the other hand, the conditions apply, it is checked in query step 42 whether register I contains the value 1. This is only the case if at least one measured value that is below the idle value S _{LL was} previously detected (see method steps 35 and 37). This query step 42 is for safe Detection of the idling is necessary if, in method step 22, an increase in the stored idling value S _LL by a large amount at the beginning of an operating cycle has occurred, which is above the idling position during warm-up. On the other hand, if, according to FIG. 2, the stored idle speed S _{LL was increased by} only one increment, the query step 42 can be omitted. In method step 43, the idle position is then identified when the condition of query step 40 and, if applicable, query step 42 is present.

If the values of a characteristic curve or a characteristic map are selected by the measured values of the throttle valve position in the control unit 16, for example to determine the injection time, then after an adaptation, i.e. after a shift in the idle position compared to the originally entered value, a corresponding shift in the characteristic curve or the map. The newly determined and stored idle value is stored in a non-volatile or buffered memory and is available again when the internal combustion engine is started again.

Of course, the described method is not limited to the detection of the idle position of a throttle valve, but is in principle suitable for the detection of an end position of any movable part which can carry out both linear and non-linear movements. Furthermore, the invention is not only limited to the detection of an initial position of such a movable part, but can also be used to detect the end position or any extreme displacement. Finally, in addition to potentiometers, there are also other position detection devices, such as Optical, inductive and capacitive systems can be used.

If there is no stored extreme value at the first start of operation or if this extreme value has been disturbed or deleted, an initialization adaptation can preferably be provided, which is initiated, for example, by connecting a specific control unit pin to ground. This enables the control unit to recognize that an initialization adaptation is to be carried out. During this operating mode, the smallest measured value that occurs is interpreted as an idle value. Apart from a plausibility check, the adaptation is not subject to any stationary or dynamic restrictions. The plausibility check can consist, for example, of whether the recorded measured values lie within a range that is at all possible as an extreme value position.

Claims (7)

1.Method for detecting an extreme displacement of a movable part by a position detection element, in particular for detecting the idle position of the throttle valve of an internal combustion engine, wherein a stored value (extreme value) corresponding to the extreme value position is corrected when different measured values are detected and the range of movement of the movable part within the lies by the position detection element, characterized in that a correction area is defined around the extreme value, 'that after detection of a fixed number of identical measured values in this correction area during such an operating cycle, such a measured value is stored as a new extreme value and that the stored extreme value is cyclically changed a predetermined value is changed from the outer position veg. 2. The method according to claim 1, characterized in that the correction range extends from the outermost position, which can be detected by the position detection element (17), via the stored extreme value to a fixed number of increments behind this extreme value. 3. The method according to claim 1 or 2, characterized in that in at least a part of the correction range, preferably the part facing away from the outermost position from the stored extreme value, identical measured values are only recorded if in between measurements outside the correction range are recorded. 4. The method according to claim 1, characterized in that the cyclical change of the stored extreme value takes place before each operating cycle. 5. The method according to claim 4, characterized in that the change is an increment in each case. 6. The method according to claim 4 for detecting the position of the throttle valve of an internal combustion engine, characterized in that the change is in each case an angle corresponding number of increments which corresponds at least to the idle throttle valve angle required in the warm-up phase of the internal combustion engine. 7. The method according to any one of the preceding claims, characterized in that an initialization adaptation can be switched on by a switching signal, during which the smallest occurring measurement value is interpreted and stored as an extreme value.

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