GB2472570A

GB2472570A - A method of indicating a neutral offset error of a transmission gear selector

Info

Publication number: GB2472570A
Application number: GB0913675A
Authority: GB
Inventors: Phil George Whiffin; Adam Keith Leatherland; Robert Alan Palin; Themi Philemon Petridis; Ian Halleron
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2009-08-06
Filing date: 2009-08-06
Publication date: 2011-02-16
Anticipated expiration: 2029-08-06
Also published as: CN101994824A; CN101994824B; DE102010033244B4; GB2472570B; GB0913675D0; DE102010033244A1

Abstract

A vehicle 10 has an engine 12 that provides an input to a transmission 14. A gear selector 16 for the transmission gear has a corresponding nominal position for each of the selected gears. Independently from the gear selector position it is determined whether the transmission 14 is in an odd numbered gear or an even numbered gear; the position of the gear selector 16 is sensed when this determination is made. A neutral position of the gear selector 16 for the neutral gear is calculated using the sensed position of the gear selector 16. A neutral gear offset position is determined from the known neutral offset and the nominal position for the neutral gear. The neutral gear offset position is compared to the calculated neutral position, and a correction is indicated for the known neutral offset when the neutral gear offset position varies from the calculated neutral position by more than a predetermined amount.

Description

METHOD FOR INDICATING OFFSET ERROR IN A VEHICLE TRANSMISSION

The present invention relates to a method for indicating gear offset error in a vehicle transmission.

In many vehicles, particularly those with manual transmissions, it can be important to know when the transmission is in a neutral position. Various vehicle systems may rely on an accurate reading that the transmission is in neutral. For example, an engine stop-start routine may be run under certain vehicle conditions, such as when the transmission is in neutral. An engine stop-start routine helps to conserve fuel and reduce emissions by automatically stopping the engine when it is determined that the engine is not required. In one example, an engine may be automatically stopped when the transmission is in neutral and the vehicle operator releases the clutch pedal, such as may occur at a stoplight or during other extended stopping conditions. Then, when the operator depresses the clutch pedal--i.e., disengages the clutch--and shifts from neutral into a forward or reverse gear, the engine may be automatically started.

In order for systems, such as an engine stop-start system, to function properly, it is important that the vehicle control system receive accurate information regarding whether the transmission is in neutral. One way to do this is to provide a sensor that determines when a gear selector has entered a detent associated with a particular gear. In a practical application, each of the odd numbered gears of a transmission may have a single detent position, each of the even numbered gears may have a single detent position, while neutral has its own detent position. In such cases, the sensor may be able to determine whether the transmission is in an even numbered gear, odd numbered gear, or neutral, by detecting a position of the gear selector relative to the particular detent.

Because a transmission is an extremely complex system made up of many components, each of which has a manufacturing tolerance associated with it, the actual position of the gear selector when it is centered in the neutral detent may differ from a nominal position calculated based on nominal engineering dimensions. A full tolerance stack-up analysis of the transmission allows an accurate neutral region to be calculated--i.e., a region for the gear selector wherein the transmission is definitely in neutral. If this calculated neutral region is too wide, however, then it may be necessary to provide an offset from the nominal position to accurately locate the calculated region.

The type of offset referred to above can be calculated for a given transmission based on the actual components used in the transmission, and it is often determined near the end of the line in the manufacturing process. Thus, for a given transmission, a known offset will be calculated and programmed into a vehicle control system for the vehicle in which the transmission will be installed. Under these conditions, a sensor reading indicating a position of the gear selector can be automatically adjusted by a vehicle control system, such as a powertrain control module (PCM), so that the reading of the sensor accurately reflects the position of the gear selector.

Although the application of an offset, such as described above, may provide accurate information throughout the life of the vehicle, it is possible that a transmission, gear selector linkage, position sensor, or some combination of these will be changed at some time during the life of the vehicle. When this occurs, the offset described above may need to be recalculated for the new components. If the new calculation is not performed, or it is inaccurate, this could lead to inaccurate readings regarding the transmission gear. Therefore, a need exists for a vehicle and a method for determining when a transmission offset needs to be corrected.

According to a first aspect of the invention there is provided a method for determining when a correction is desired for a known neutral offset in a vehicle including an engine providing an input to a transmission having at least one numbered gear and a neutral gear, the vehicle further including a gear selector for selecting the transmission gear, the gear selector having a corresponding nominal position for each selected gear, the method comprising indicating a correction is desired for the known neutral offset when a first offset position based on the known neutral offset to a nominal position of the gear selector for a particular one of the gears varies by more than a predetermined amount from one of: a parameter based on a sensed position of the gear selector for the particular one of the gears; and a calculated neutral position of the gear selector for the neutral gear based on a sensed position of the gear selector for the particular one of the gears.

For convenience the term "neutral gear" refers to a neutral position of the transmission even though the vehicle is out of gear when it is in neutral.

The transmission may have at least one odd numbered gear and at least one even numbered gear, the method comprising indicating a correction is desired for the known neutral offset when the first offset position, beinq an offset position of the gear selector for the neutral gear, varies by more than a predetermined amount from the calculated neutral position of the gear selector based on: (i) at least one sensed position of the gear selector when it is determined independently from the gear selector position that the transmission is in an odd numbered gear, and (ii) at least one sensed position of the gear selector when it is determined independently from the gear selector position that the transmission is in an even numbered gear.

The calculated neutral position of the gear selector may be based on at least two sensed positions of the gear selector when it is determined independently from the gear selector position that the transmission is in an odd numbered gear, and at least two sensed positions of the gear selector when it is determined independently from the gear selector position that the transmission is in an even numbered gear, the calculated neutral position of the gear selector being based on: (i) a statistical parameter for the sensed positions of the gear selector for each of the determined odd numbered gear positions; and (ii) a statistical parameter for the sensed positions of the gear selector for each of the determined even numbered gear positions.

The calculated neutral position of the gear selector may be based on an algorithm defined as: Scalc = ((Sodd + X) + (Seven -Y))/2, where Scalc is the calculated neutral position, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear, X is a known relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and Y is a known relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear.

The calculated neutral position of the gear selector may be based on an algorithm that applies a known relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and a known relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear, the relationships being equal, and the algorithm being defined as: Scalc = (Sodd + Seven)/2, where Scalc is the calculated neutral position, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, and Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear.

The method may comprise indicating a correction is desired for the known neutral offset when the first offset position based on the known neutral offset to a nominal position of the gear selector for a non-neutral gear varies by more than a predetermined amount from the sensed position of the gear selector for the non-neutral gear.

Suitably, the predetermined amount is a minimum positional difference that would allow a sensed position of the gear selector to indicate the transmission is in a certain gear when it is not in the certain gear.

Preferably, the step of determining independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear is based on the speed of the engine and the speed of the vehicle.

According to a second aspect of the invention, there is provided a method for determining when a correction is desired for a known neutral offset in a vehicle including an engine providing an input to a transmission having at least one odd numbered gear, at least one even numbered gear, and a neutral gear, the vehicle further including a gear selector for selecting the transmission gear, the gear selector having a corresponding nominal position for each selected gear, the method comprising: determining independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear; sensing the position of the gear selector when it is determined that the transmission is in the odd numbered gear or the even numbered gear; calculating a neutral position of the gear selector for the neutral gear using the sensed position of the gear selector; determining a neutral gear offset position from the known neutral offset and the nominal position for the neutral gear; comparing the neutral gear offset position to the calculated neutral position; and indicating a correction is desired for the known neutral offset when the neutral gear offset position varies from the calculated neutral position by more than a predetermined amount.

Preferably the step of determining independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear is repeated such that it is determined at least once that the transmission is in an odd numbered gear and at least once that the transmission is in an even numbered gear, and the step of sensing the position of the gear selector is repeated such that the position of the gear selector is sensed at least once when it is determined that the transmission is in an odd numbered gear and at least once when it is determined that the transmission is in an even numbered gear, and the step of calculating a neutral position of the gear selector for the neutral gear utilizes the sensed position of the gear selector in an odd numbered gear and the sensed position of the gear selector in an even numbered gear.

A relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear may be the same as a relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear, and the step of calculating a neutral position may include executing the following formula: Scalc = (Sodd + Seven)/2, where Scalc is the second parameter, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, and Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear.

Preferably, a known relationship exists between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and another known relationship may exists between the gear selector position for an even numbered gear and the gear selector position for the neutral gear, and the step of calculatinq a neutral position of the gear selector for the neutral gear further utilizes the known relationships.

The step of calculating a neutral position may include executing the following formula: Scalc = ((Sodd + X) + (Seven -Y))/2, where Scalc is the second parameter, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear, X is the known relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and Y is the known relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear.

Preferably, the predetermined amount is a minimum positional difference that would allow a sensed position of the gear selector to indicate the transmission is in a certain gear when it is not in the certain gear.

Suitably, the step of determining independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear includes: determining a speed of the engine; determining a speed of the vehicle; and applying a known relationship between the speed of the engine, the speed of the vehicle, and the transmission gears.

According to a third aspect of the invention, there is provided a vehicle including a system for determining when a correction is desired for a known neutral offset, the vehicle comprising an engine, a transmission receiving an input from the engine and having at least one numbered gear and a neutral gear, a gear selector for selecting the transmission gear, the gear selector having a corresponding nominal position for each selected gear, a sensor for sensing the position of the gear selector, and a control system including at least one controller, the control system being configured to indicate a correction is desired for the known neutral offset when a first offset position based on the known neutral offset to a nominal position of the gear selector for a particular one of the gears varies by more than a predetermined amount from one of: (i) a parameter based on a sensed position of the gear selector for the particular one of the gears; and (ii) a calculated neutral position of the gear selector for the neutral gear based on a sensed position of the gear selector for the particular one of the gears.

Preferably, the control system is configured to indicate a correction is desired for the known neutral offset when the first offset position based on the known neutral offset to a nominal position of the gear selector for a non-neutral gear varies by more than a predetermined amount from the sensed position of the gear selector for the non-neutral gear.

Suitably, the transmission has at least one odd numbered gear and at least one even numbered gear, and the method comprises indicating a correction is desired for the known neutral offset when the first offset position, beinq an offset position of the gear selector for the neutral gear, varies by more than a predetermined amount from the calculated neutral position of the gear selector based on: (i) at least one sensed position of the gear selector when it is determined independently from the gear selector position that the transmission is in an odd numbered gear; and (ii) at least one sensed position of the gear selector when it is determined independently from the gear selector position that the transmission is in an even numbered gear.

Preferably, the calculated neutral position of the gear selector is based on an algorithm defined as: Scalc = ((Sodd + X) + (Seven -Y))/2, where Scalc is the calculated neutral position, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear, -10 -X is a known relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and Y is a known relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear.

In some embodiments of the present invention, the control system will apply the known neutral offset to a nominal position of the neutral gear--that is, the !vparticular one of the gears!! mentioned above is, in this instance, neutral. In this case, the first offset position is the value the sensor should read when the gear selector is in the center of the neutral position detent. Then, using the relationship between the engine speed and the speed of the vehicle, for example, it can be determined -11 -independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear. The sensor then provides a signal to the control system when this determination is made. Because there is, in any given transmission, a known relationship between the gear selector positions for an odd numbered gear and the neutral gear, and the gear selector positions for an even numbered gear and the neutral gear, the sensed position of the odd numbered gear or even numbered gear described above can be used to calculate the center position of the neutral gear.

The comparison would then be made between the calculated center of the neutral position and the!vfirst offset position!v, which in this case is the offset position of the gear selector for the neutral gear. If the comparison of these two values shows that the calculated value is outside an allowable tolerance to the offset position of the gear selector for the neutral gear--i.e., the first offset position--then a correction for the known neutral offset is indicated. A control system, such as the PCM, may indicate the desired correction, by providing a signal to the vehicle operator on the dashboard, such as an audio, visual, or tactile signal, or some combination thereof, or the indication may be in the form of modifying certain features or functions, such as disabling an automatic engine stop-start function.

In other embodiments of the present invention, the position of the gear selector may be determined for an odd numbered gear and an even numbered gear. Moreover, multiple readings can be taken for each odd numbered gear position and each even numbered gear position and a statistical -12 -parameter can be determined--e.g., a mean, a median, etc. Using these values in the known relationship between the positions of the odd numbered gears and the neutral gear, and the even numbered gears and the neutral gear, may provide additional accuracy to the calculation of the center of the neutral position for the gear selector, as described in detail above.

Embodiments of the present invention may also apply the known neutral offset to the position of the gear selector for an odd numbered gear or an even numbered gear.

In embodiments such as these, the first offset position is now an offset position for the odd numbered gear or the even numbered gear, rather than the neutral gear. As an example, the known neutral offset may be applied directly to the position of the gear selector for one of the odd numbered gears. When it is determined independently from the gear selector whether the transmission is in an odd numbered gear or an even numbered gear, the odd numbered gear is chosen.

Then, when the signal is received indicating the position of the gear selector when that determination is made, the offset position for the odd numbered gear--i.e., the first offset position--can be compared directly to the sensed position of the gear selector for the odd numbered gear.

Embodiments such as these take advantage of the known relationship between the gear selector position for the odd numbered gears and the neutral gear, and apply the known neutral offset directly to the odd numbered gear, thereby reducing the calculations involved and the complexity of the algorithm programmed into the control system. Of course the same or similar steps can be performed applying the known neutral offset to an even numbered gear.

-13 -Embodiments of the invention also include a method for determining when a correction is desired for a known neutral offset in a vehicle. The steps include determining independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear, and sensing the position of the gear selector when it is determined that the gear selector position is in the odd numbered gear or the even numbered gear. Additional steps include calculating a neutral position of the gear selector for the neutral gear using the sensed position of the gear selector. As mentioned above, this calculation may employ a single sensed position of an odd numbered gear or an even numbered gear, it may employ a combination of sensed positions for an odd numbered gear and an even numbered gear, or it may employ a number of readings for either or both of the odd numbered gears or the even numbered gears.

A neutral gear offset position is then determined from the known neutral offset and the nominal position for the neutral gear. The neutral gear offset position is then compared to the calculated neutral position, and a correction is indicated as desired for the known neutral offset when the neutral gear offset position varies from the calculated neutral position by more than a predetermined amount. This predetermined amount can be based on, for example, the tolerance stack-up for the particular transmission.

The invention will now be described by way of example with reference to the accompanying drawings of which:-FIGURE 1 is a schematic representation of a vehicle in accordance with embodiments of the present invention; -14 -FIGURE 2 is a schematic representation of a portion of a transmission having a zero neutral offset; and FIGURE 3 is a schematic representation of a portion of a transmission having a non-zero neutral offset.

Figure 1 is a schematic representation of a vehicle 10 in accordance with an embodiment of the present invention. The vehicle 10 includes an engine 12 and a transmission 14 that receives an input from the engine 12.

The transmission 14 has in one non-limiting example six forward gears and a reverse gear. A gear selector 16 is used by a vehicle operator to select the transmission gear, and as shown by directional arrows 18, 20, it moves a linkage 22 in various directions to select the transmission gear. A sensor 24 detects movement of a magnet 26 when the linkage 22 is moved by the gear selector 16. The sensor 24 sends signals to a vehicle control system, which in the embodiment shown in Figure 1, is a PCM 28. Although shown as a single controller, a control system for a vehicle, such as the vehicle 10, may include software controllers, hardware controllers, or some combination thereof. To the extent that the control system is made up of more than one controller, the controllers may communicate with one another, for example, through a controller area network (CAN).

Turning to Figures 2 and 3, two different versions of a transmission, such as the transmission 14, are schematically illustrated. Specifically, in Figure 2, a transmission 14' is illustrated as having a zero neutral offset. For example, a neutral detent region 31 is centered between sensor reading values C and D. As shown in Figure 2, the center of the neutral detent region 31 is generally -15 -horizontally centered in the schematic transmission 14', above which is a line 30 illustrating the gear selector movement detected by the sensor 24. Therefore, in the transmission 14', the actual center position of the neutral detent region generally coincides with the center of the gear selector movement.

For each of the group of odd numbered gears, even numbered gears, and the neutral gear, Figure 2 also illustrates a schematic representation of a detent profile.

This profile 32 approximates the physical characteristics of a portion of the linkage 22 in that each gear selection has a detent position to fall into when the transmission 14' is shifted into that gear. Specifically, each of the odd numbered gears 1, 3, 5 will fall into a detent 34, which is located between sensor reading values A and B. Similarly, the linkage 22 will fall into a detent 36 for each of the even numbered gears, which is located between sensor reading values E and F. As described above, the neutral detent region is generally centered between sensor reading values C and D, and the linkage 22 will fall into the detent 38 when the neutral gear is selected.

Also shown in Figure 2 is an illustration of the concept of the known positional relationship between an odd numbered gear detent region 33 and the neutral detent region 31, and the known relationship between an even numbered gear detent region 35 and the neutral detent region 31. The vehicle and method of the present invention take advantage of this relationship in order to provide an indicator of when it is desirable to correct a known neutral offset. For example, if the vehicle 10 is serviced and the transmission 14' is replaced, the new transmission may not have a zero -16 -neutral offset. In such a case, it may be desirable to know that the offset needs to be recalculated, and that one or more vehicle systems may need to be disabled until the neutral offset has been updated.

Figure 3 illustrates another transmission 14" that has a non-zero neutral offset. As readily discerned from a comparison of the transmissions 14' and 14" in Figures 2 and 3, each of the detent regions has shifted to the left in the transmission 14" from its previous position in the transmission 14' . In fact, as shown in Figure 3, each of the detent regions is shifted by an offset (c) illustrated by the arrow 40. The dashed line 42 represents the nominal center of the neutral detent region if the transmission 14" did not have a neutral offset. Figure 3 also shows that the relationship between the odd numbered gear detent region 33' and the neutral detent region 31' (shown as!VXF!) has remained the same as the relationship between these two regions in the transmission 14' shown in Figure 2.

Similarly, the relationship between the even numbered gear detent region 35' and the neutral detent region 31' (shown as!vyU) is also the same as in the transmission 14' In some embodiments of the present invention, a control system, such as the PCM 28 shown in Figure 1, may execute an algorithm that performs the following method. In one example, the known neutral offset (c) shown in Figure 3 can be applied to a nominal position of the gear selector 16 for the neutral gear. This is illustrated in Figure 3, where the arrow 40 begins at the nominal position indicated by the dashed line 42, and shifts the center of the neutral detent region to the left by the offset amount (c) . As shown in Figure 3, the relationships between the odd -17 -numbered gear detent region 33' and the neutral detent region 31', as the even numbered gear detent region 35' and the neutral detent region 31' remain unchanged as compared to the transmission 14' shown in Figure 2, which has a zero neutral offset. It is worth noting here that although the neutral offset (c) and the relative positions of the neutral detent regions are illustrated as linear measurements, they may also be angular. Indeed, any system of coordinates that is effective to describe the neutral offset and the relative positions of the detent regions can be used.

Returning to the method described above, the neutral gear offset position that was determined from the known neutral gear offset and the nominal position for the neutral gear is illustrated as Snoffset, and may be referred to generically as a!vfirst offset position!!. Another step of the method determines independently from the position of the gear selector 16 whether the transmission 14" is in an odd numbered gear or an even numbered gear. This can be done, for example, using the relationship between the engine speed and the vehicle speed. A tachometer may provide the engine speed to the vehicle control system, for example, the PCM 28. The vehicle speed may be determined by any effective means, although a convenient and efficient way to make this determination is to use the wheel speed sensors associated with an antilock brake system. Because there is a known relationship between the vehicle speed and the output speed of the transmission 14", and because the engine 12 provides an input to the transmission 14", the transmission gear can be determined.

When the determination of the transmission gear is made, the position of the gear selector 16 is sensed by the -18 -sensor 24, which sends a signal to the PCM 28; this sensed position may be referred to generically as a!vfirst parameter!!. Because there is a known relationship between the odd and even numbered gear detent regions and the neutral detent region, a neutral position of the gear selector for the neutral gear can be calculated using the position of the gear selector that was sensed by the sensor 24 as described above. For example, if it was determined independently from the gear selector 16 that the transmission 14" was in an odd numbered gear--this is indicated in Figure 3 by the sensor reading S0dd--then the calculation of the neutral position of the gear selector for the neutral gear (Scac) may involve a simple subtraction: Scac = S0dd -X. The calculated neutral position of the gear selector (Scac, which may be referred to generically as a !!second parameter!!) can be compared to the value of Snoffset.

If Scaic varies from Snoffset by more than a predetermined amount, the method may provide an indication to a vehicle operator that a correction is desired for the neutral offset in the transmission 14". In addition to providing such an indicator, a control system of the vehicle 10, such as the PCM 28, may initiate, inhibit, or modify certain functional systems within the vehicle 10 according to a predetermined program. For example, if it is determined that it is desired to correct the neutral offset for the transmission 14", the PCM 28 may disable an automatic engine stop-start function, which may also reside within the PCM 28. As noted above, the PCM 28 may communicate with one or more other controllers to affect other systems within the vehicle 10.

Because there is also a known relationship between the position of the even numbered gear detent region 35' and -19 -the neutral gear detent region 31', the method described above may include additional steps that can lead to an increase in accuracy in the calculation of the Scac value.

For example, the step of determining independently from the position of the gear selector 16 whether the transmission 14" is in an odd numbered gear or an even numbered gear can be repeated until it is determined at least once that the transmission 14" is in an odd numbered gear and at least once that the transmission 14" is in an even numbered gear.

The position of the gear selector 16 is then sensed by the sensor 24 at least once when it is determined that the transmission is in an odd numbered gear and at least once when it is determined that the transmission is in an even numbered gear. In this example, the second parameter (Scac) may be calculated according to the following formula: Scaic = ( (So + X) + (Seven -Y) ) /2, where 5cac is the second parameter, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, 5even is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear, X is a known relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and Y is a known relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear.

As shown in the formula above, 5cac can be determined using both the relationship between the odd -20 -numbered gear detent region 33' and the neutral detent region 31'--this positional relationship is designated as !VX!v in Figure 3--and the relationship between the even numbered gear detent region 35' and the neutral detent region 31', which is designated as flY!!.

In still other embodiments of the present invention, the values for S0dd and Seven may be sensed multiple times when the transmission is determined to be in an odd numbered gear, and multiple times when the transmission is determined to be in an even numbered gear. Then, a statistical parameter is calculated for the sensed positions of the gear selector 16 for each of the determined odd numbered gear positions and each of the determined even numbered gear positions. The statistical parameters may be, for example, a mean of the sensed values, a median of the sensed values, or the statistical parameters may be something more elaborate such as the mean or median of only a portion of the data collected, where certain outlier values are discarded.

The algorithm that uses both the!!X!! and U!! relationships may be, in some cases, further simplified.

For example, in some transmissions the positional relationship between the odd numbered gear detent region and the neutral detent region is the same as the positional relationship between the even numbered gear detent region and the neutral detent region. Using the nomenclature provided in Figures 2 and 3, this means that in such cases X = Y. In this case, the formula described above can be simplified to the following: 5cac = (Sodd + Seven) /2, where 5cac is the second parameter, -21 -S0dd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, and Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear.

Regardless of the formula used, the value of 5cac can then be compared directly to the value of Snoffset, for example, by subtracting the two values. If it is determined that the difference between these two values is more than a predetermined amount, a step is performed to indicate the desirability of correcting the neutral offset for the transmission under evaluation. The predetermined amount used can be determined, for example, from a tolerance stack-up of the various transmission components. That is, the predetermined amount can be a value above which the difference between 5cac and Snoffset indicates that an erroneous reading of the transmission gear is possible. In the case where the positions and relationships are linear measurements, this value may be in millimeters or centimeters. Alternatively, when the positions are indicated by angles, the predetermined value may be a particular angle above which the difference between 5cac and Snoffset indicates a desire to correct the neutral offset for the transmission.

In some embodiments of the present invention, the algorithm and method described above may be further simplified by foregoing the determination of Scac and applying the neutral offset to a particular one of the gears that is not the neutral gear. In the embodiments described above, the known neutral offset was applied to a nominal -22 -position of the gear selector 16 for the neutral gear. This yielded the value Snoffset illustrated and described in accordance with Figure 3. This was referred to generically as a first offset position.

It is also possible, however, for the first offset position to be defined as an offset position for the gear selector 16 for a non-neutral gear. For example, instead of applying the known neutral offset to the neutral gear, it can be applied to one of the odd numbered gears or one of the even numbered gears. In this case, a determination is still made independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear. The position of the gear selector is sensed when it is determined that the transmission is in the odd numbered gear or the even numbered gear, and this sensed position (the first parameter) can be compared directly to the first offset position--i.e., the value determined by applying the known neutral offset to the nominal position of the gear selector for the non-neutral gear. If it is one of the odd numbered gears that is chosen as the particular gear to which the known neutral offset is applied, the following formula may be used: Sodd offset = Soddnomjna -c, where Sodd offset is the offset position of the gear selector 16 for the odd numbered gear, also referred to as the!vfirst offset position!!, Soddnominai is the nominal position of the gear selector 16 for the odd numbered gear, and c is the known neutral offset.

This is similar to the algorithms and methods described above, except that the offset!vc!v is applied to an -23 -odd numbered gear rather than the neutral gear. Then, when it is determined independently from the gear selector position that the transmission is in an odd numbered gear, and the position of the gear selector is sensed, this sensed position (SOdd) is compared directly to Sodd offset without having to perform the calculation to determine Scac. An algorithm and method encompassing these steps is less complex and may be faster to perform than the embodiments described above that use a position of the neutral gear.

Although an odd numbered gear was chosen for the example immediately above, it is understood that the same principle can be applied to an even numbered gear for the transmission.

-24 -

Claims

Claims 1. A method for determining when a correction is desired for a known neutral offset in a vehicle including an engine providing an input to a transmission having at least one numbered gear and a neutral gear, the vehicle further including a gear selector for selecting the transmission gear, the gear selector having a corresponding nominal position for each selected gear, the method comprising indicating a correction is desired for the known neutral offset when a first offset position based on the known neutral offset to a nominal position of the gear selector for a particular one of the gears varies by more than a predetermined amount from one of: a parameter based on a sensed position of the gear selector for the particular one of the gears; and a calculated neutral position of the gear selector for the neutral gear based on a sensed position of the gear selector for the particular one of the gears.
2. The method of claim 1, wherein the transmission has at least one odd numbered gear and at least one even numbered gear, and the method comprises indicating a correction is desired for the known neutral offset when the first offset position, being an offset position of the gear selector for the neutral gear, varies by more than a predetermined amount from the calculated neutral position of the gear selector based on: (i) at least one sensed position of the gear selector when it is determined independently from the gear selector -25 -position that the transmission is in an odd numbered gear, and (ii) at least one sensed position of the gear selector when it is determined independently from the gear selector position that the transmission is in an even numbered gear.
3. The method of claim 2, wherein the calculated neutral position of the gear selector is based on at least two sensed positions of the gear selector when it is determined independently from the gear selector position that the transmission is in an odd numbered gear, and at least two sensed positions of the gear selector when it is determined independently from the gear selector position that the transmission is in an even numbered gear, the calculated neutral position of the gear selector being based on: (i) a statistical parameter for the sensed positions of the gear selector for each of the determined odd numbered gear positions; and (ii) a statistical parameter for the sensed positions of the gear selector for each of the determined even numbered gear positions.
4. The method of claim 2, wherein the calculated neutral position of the gear selector is based on an algorithm defined as: Scalc = ((Sodd + X) + (Seven -Y))/2, where Scalc is the calculated neutral position, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, -26 -Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear, X is a known relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and Y is a known relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear.
5. The method of claim 2, wherein the calculated neutral position of the gear selector is based on an algorithm that applies a known relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and a known relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear, the relationships being equal, and the algorithm being defined as: Scalc = (Sodd + Seven)/2, where Scalc is the calculated neutral position, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, and Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear.
6. The method of claim 1, wherein the method comprises indicating a correction is desired for the known neutral offset when the first offset position based on the known -27 -neutral offset to a nominal position of the gear selector for a non-neutral gear varies by more than a predetermined amount from the sensed position of the gear selector for the non-neutral gear.
7. The method of claim 1, wherein the predetermined amount is a minimum positional difference that would allow a sensed position of the gear selector to indicate the transmission is in a certain gear when it is not in the certain gear.
8. The method of claim 2, wherein the step of determining independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear is based on the speed of the engine and the speed of the vehicle.
9. A method for determining when a correction is desired for a known neutral offset in a vehicle including an engine providing an input to a transmission having at least one odd numbered gear, at least one even numbered gear, and a neutral gear, the vehicle further including a gear selector for selecting the transmission gear, the gear selector having a corresponding nominal position for each selected gear, the method comprising: determining independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear; sensing the position of the gear selector when it is determined that the transmission is in the odd numbered gear or the even numbered gear; -28 -calculating a neutral position of the gear selector for the neutral gear using the sensed position of the gear selector; determining a neutral gear offset position from the known neutral offset and the nominal position for the neutral gear; comparing the neutral gear offset position to the calculated neutral position; and indicating a correction is desired for the known neutral offset when the neutral gear offset position varies from the calculated neutral position by more than a predetermined amount.
10. The method of claim 9, further comprising: repeating the step of determining independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear such that it is determined at least once that the transmission is in an odd numbered gear and at least once that the transmission is in an even numbered gear, and repeating the step of sensing the position of the gear selector such that the position of the gear selector is sensed at least once when it is determined that the transmission is in an odd numbered gear and at least once when it is determined that the transmission is in an even numbered gear, and wherein the step of calculating a neutral position of the gear selector for the neutral gear utilizes the sensed position of the gear selector in an odd numbered gear and the sensed position of the gear selector in an even numbered gear.

-29 -
11. The method of claim 10, wherein a relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear is the same as a relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear, and wherein the step of calculating a neutral position includes executing the following formula: Scalc = (Sodd + Seven)/2, where Scalc is the second parameter, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, and Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear.
12. The method of claim 10, wherein a known relationship exists between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and another known relationship exists between the gear selector position for an even numbered gear and the gear selector position for the neutral gear, the step of calculating a neutral position of the gear selector for the neutral gear further utilizing the known relationships.
13. The method of claim 12, wherein the step of calculating a neutral position includes executing the following formula: Scalc = ((Sodd + X) + (Seven -Y))/2, where Scalc is the second parameter, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, -30 -Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear, X is the known relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and Y is the known relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear.
14. The method of claim 9, wherein the predetermined amount is a minimum positional difference that would allow a sensed position of the gear selector to indicate the transmission is in a certain gear when it is not in the certain gear.
15. The method of claim 9, wherein the step of determining independently from the gear selector position whether the transmission is in an odd numbered gear or an even numbered gear includes: determining a speed of the engine; determining a speed of the vehicle; and applying a known relationship between the speed of the engine, the speed of the vehicle, and the transmission gears.
16. A vehicle including a system for determining when a correction is desired for a known neutral offset, the vehicle comprising an engine, a transmission receiving an input from the engine and having at least one numbered gear and a neutral gear, a gear selector for selecting the transmission gear, the gear selector having a corresponding -31 -nominal position for each selected gear, a sensor for sensing the position of the gear selector, and a control system including at least one controller, the control system being configured to: indicate a correction is desired for the known neutral offset when a first offset position based on the known neutral offset to a nominal position of the gear selector for a particular one of the gears varies by more than a predetermined amount from one of: (i) a parameter based on a sensed position of the gear selector for the particular one of the gears; and (ii) a calculated neutral position of the gear selector for the neutral gear based on a sensed position of the gear selector for the particular one of the gears.
17. The vehicle of claim 16, wherein the control system is configured to indicate a correction is desired for the known neutral offset when the first offset position based on the known neutral offset to a nominal position of the gear selector for a non-neutral gear varies by more than a predetermined amount from the sensed position of the gear selector for the non-neutral gear.
18. The vehicle of claim 16, wherein the transmission has at least one odd numbered gear and at least one even numbered gear, and the method comprises indicating a correction is desired for the known neutral offset when the first offset position, being an offset position of the gear selector for the neutral gear, varies by more than a predetermined amount from the calculated neutral position of the gear selector based on: -32 - (i) at least one sensed position of the gear selector when it is determined independently from the gear selector position that the transmission is in an odd numbered gear; and (ii) at least one sensed position of the gear selector when it is determined independently from the gear selector position that the transmission is in an even numbered gear.
19. The vehicle of claim 18, wherein the calculated neutral position of the gear selector is based on an algorithm defined as: Scalc = ((Sodd + X) + (Seven -Y))/2, where Scalc is the calculated neutral position, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear, X is a known relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and Y is a known relationship between the gear selector position for an even numbered gear and the gear selector position for the neutral gear.
20. The vehicle of claim 18, wherein the calculated neutral position of the gear selector is based on an algorithm that applies a known relationship between the gear selector position for an odd numbered gear and the gear selector position for the neutral gear, and a known relationship between the gear selector position for an even numbered gear -33 -and the gear selector position for the neutral gear, the relationships being equal, and the algorithm being defined as: Scalc = (Sodd + Seven)/2, where Scalc is the calculated neutral position, Sodd is the sensed position of the gear selector when it is determined that the transmission is in an odd numbered gear, and Seven is the sensed position of the gear selector when it is determined that the transmission is in an even numbered gear.
21. A method substantially as described herein with reference to the accompanying drawings.
22. A vehicle substantially as described herein with reference to the accompanying drawings.-34 -