Abstract:
A method for recognition of the synchronization position and the end of the synchronization operation in an automated shiftable transmission with an electromotive shift actuator is disclosed, which is characterized in that the rotational speed of the shift actuator is detected and the synchronization position, as well as the end of the synchronized operation, is determine based upon the change of the rotational speed.

Description:
CROSS-REFERENCE 
   This application is the US national stage application of International Application No. PCT/DE02/00159, which claims priority to German patent application nos. 101 04 102.0 and 101 26 708.8. 
   TECHNICAL FIELD 
   The present invention relates to methods and apparatus for recognizing the synchronization position and the end of the synchronization operation of an automatic shiftable transmission having an electrically-driven shift actuator. 
   BACKGROUND OF THE RELATED ART 
   Shiftable transmissions for motor vehicles have long been known in many different forms. In the past, a shiftable transmission was primarily understood to be a manually-shiftable transmission, in which the driver of a motor vehicle equipped with this type of shiftable transmission selects the shift path and performs the gear shift operation by hand via a shift lever. In addition to these manually-shiftable transmissions, it has also been known in the meantime to use automated shiftable transmissions when the operation of selecting and shifting the selected gear stage is executed, for example, according to programmed control by actuators provided in the shiftable transmission. 
   During operation, an automated shiftable transmission of this kind is subjected to normal wear and tear on its component parts, e.g., the synchronizing means, which wear and tear can lead to displacement of the middle synchronization position. The middle synchronization position is defined herein as a mean position value during the synchronization operation. The blocking position of the synchronizing means can vary somewhat from shift operation to shift operation, because the shift sleeve can engage in the synchronizer ring differently and unpredictably from shift operation to shift operation. 
   However, accurate knowledge of the synchronization position is important, as the synchronization position should be quickly reached by the shift actuator in order to shorten the shift time. In addition, the shift actuator should also quickly arrive at its end position (i.e., the gear engaged position) at the end of the synchronization operation. 
   When the shift actuator reaches the synchronization position, the synchronizing means exerts a blocking effect on the shift actuator as a result of the synchronization operation, which leads to an increase in the load current of the actuators. It has already been known to detect the start of the synchronization by this increase in the load current. 
   However, detecting the load current is comparatively complicated and expensive and furthermore, can only produce a result with regard to a change of the synchronization position within the bounds of a continuous determination of the actuator position, as the position of the actuator when the load current increases must be known. 
   SUMMARY OF THE INVENTION 
   Thus, an object of the present invention is to provide methods and apparatus, by which, in a less expensive manner, a change of the synchronization position and the end of the synchronization operation can be recognized. 
   The invention is achieved by the solution of this object in accordance with the features and aspects of the present teachings provided herein. Advantageous embodiments of these features and aspects are described further below and a representative apparatus for performing methods according to the present teachings is shown in  FIG. 5 . Reference to elements shown in  FIG. 5  is provided throughout this summary and the following detailed description. 
   According to the invention, methods and apparatus for recognizing the synchronization position and the end of the synchronization operation of an automated shiftable transmission  11  having an electromotive shift actuator  13  are provided, in which the rotational speed of the shift actuator  13  is detected and the synchronization position, as well as the end of the synchronization operation, are determined based upon changes in the rotational speed. 
   By detecting the rotational speed of the shift actuator  13  over time, it is possible to determine the path along which the shift actuator  13  has moved. Therefore, even without a continuous determination of the actuator position, according to this method, it is possible to determine that the synchronization position that has been reached when the rotational speed of the shift actuator  13  undergoes a predetermined threshold value (rotational speed) change within a predetermined time interval. 
   The rotational speed of the shift actuator  13  can be detected by sensors  14  that generate a predetermined number of pulses per revolution of the actuator shaft. By measuring the pulse frequency and/or the timed pulse interval, it is possible to determine the rotational speed of the shift actuator  13 . It is also possible to determine geometric intervals by adding the pulses. 
   Therefore, according to the invention, if it is determined that the rotational speed of the shift actuator  13  has experienced a clear decline (reduction) within a certain time interval, then it is concluded that the synchronization position has been reached. 
   During the synchronization operation, a synchronizing means  12  temporarily exerts a blocking effect against further movement of the shift actuator  13 . When the blocking effect is released at the end of the synchronization operation, the rotational speed of the shift actuator  13  will increase again. 
   Because the wear behaviour of the automated shiftable transmission  11  can lead to gear-specific changes in the shift characteristics of the transmission  11 , it is proposed according to the invention that the synchronization position is determined independently of the end of the synchronization operation for each gear stage of the automated shiftable transmission  11 . 
   By using such a method according to the invention, it is therefore possible to identify gear-specific changes of the synchronization position and also to determine the gear-specific end of the synchronization operation. 
   Changes in the synchronization position of the relevant gear stages of the automated shiftable transmission  11  during operation can therefore be taken into account by determining the synchronization position and by using this synchronization position as the assumed target synchronization position during the next gear change operation for the relevant gear stage in order to control the shift actuator  13 . Similarly, by continuously monitoring the rotational speed of the shift actuator  13 , it is possible to determine whether the synchronization operation has concluded. The end of the synchronization operation can be recognized, e.g., by a parabolic or a generally linear increase in the rotational speed of the shift actuator  13  over time. 
   In this way, it is therefore possible to determine (a) changes in the synchronization position in the direction towards the neutral position of the transmission or away from same, and also (b) changes in the time duration of the synchronization operation. Thus, for example, if the current supply to the shift actuator  13  is increased before the conclusion of the synchronization operation, only an insignificant acceleration of the shift actuator  13 , and thus a small change of its rotational speed, results. Consequently, it can be concluded from this small speed change that the synchronization operation has not yet ended. This knowledge can then be used during a subsequent gear change operation and a corresponding synchronization so as to accordingly delay the start of the increase of the current supply to the shift actuator  13 , thereby avoiding a stretching of the shift elasticity. 
   Conversely, if the end of the synchronization is known, it is therefore possible to increase the load current for the shift actuator  13  without any further delay, so that the end position of the shift actuator  13  on its travelling path to the engaged gear stage can be rapidly reached. This leads to a shortening of the travelling time of the shift actuator  13  to reach the end position and thus to a shortening of the time required for completion of the gear shift operation. 
   It is thereby proposed according to the invention that the determined synchronization position is stored in a memory device  16 . Then, at the next gear change operation, the determined synchronization position is read out from the memory device  16  and is used as the target synchronization position for movement to the synchronization position effected by the shift actuator  13 . For this purpose, a volatile memory can be provided and the determined synchronization position is stored in the volatile memory during operation of the shiftable transmission. Therefore, the gear-specific last synchronization positions, which are in use when the automated shiftable transmission equipped motor vehicle is stopped, can be utilized during the next vehicle driving operation. These values may then be written into a non-volatile memory after stopping the vehicle, e.g., which vehicle stoppage is controlled by an ignition signal, and then read out during the next vehicle start-up so as to be again stored in the volatile memory. 
   The stored synchronization position is thereby up-dated with the actually determined synchronization position when the stored synchronization position deviates from the determined synchronization position. Therefore, changes in the synchronization position will not lead to changes in the shift characteristics of the transmission  11 . 
   It is further proposed according to the invention that the up-dating is performed when the determined synchronization position changes, as compared with the stored synchronization position, for the individual gear stages of the automated shiftable transmission  11 , in different directions in relation to the neutral position. In other words, this means, e.g., that an up-date will be performed when the actually determined synchronization position of the first gear is displaced towards the neutral position and the actually determined synchronization position of the third gear is displaced in a direction away from the neutral position 
   On the other hand, when the gear-specific synchronization positions for all gears have changed or have been displaced in the same direction, it can be assumed that the entire shift pattern has moved altogether. Therefore, an adaptation (change) of the synchronization position for the individual gear stages is not necessary in this case. 
   According to a further development of the method according to the invention, it is further proposed that the up-date is performed only when the shiftable transmission  11  has warmed up to its operating temperature, wherein a sensor is provided on the shiftable transmission in order to detect the temperature thereof and/or a predetermined operating time of the shiftable transmission is allowed to elapse in order to ensure that the transmission has been sufficiently operated to have reached its normal operating temperature. An allowance is thereby made of the fact that, if the operating parameters of the automated shiftable transmission  11  do not remain substantially the same, such as e.g. the oil viscosity within the transmission  11 , an adaptation mistake could result. Such a mistake can be avoided by waiting to perform the up-date until the transmission  11  has warmed up to its operating temperature. 
   The stored synchronization position is used to control the shift actuator  13 , so that the shift actuator  13  reduces the speed of the travelling movement of the shift elements in the shiftable transmission  11  before reaching the target synchronization position. A large mechanical strain on the shift actuator  13  and shift elements is thereby avoided. 
   According to another aspect of the present teachings, when a change (displacement) of the synchronization position in relation to the neutral position is determined to exceed a predetermined threshold displacement distance, an action notification is issued. This action notification can be, e.g., a corresponding entry in the fault memory of the vehicle. In this case, when the next vehicle maintenance is done, suitable remedial measures can be performed, such as e.g., replacing worn synchronizing rings in the transmission  11 . 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be explained in further detail with reference to the drawings in which: 
       FIG. 1  shows a graphic illustration of the position of the shift actuator  13  over time during a transmission synchronization operation. 
       FIG. 2  shows an illustration to explain the identification of displacements of the synchronization position with respect to the neutral position and the gear engaged position. 
       FIG. 3  shows an illustration for explaining a unidirectional displacement of the entire shift pattern. 
       FIG. 4  shows an illustration for explaining the importance of the synchronization position. 
       FIG. 5  shows a representative apparatus for performing the methods described herein. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 1 , the curved lines  1  and  2  each represent the shift operation when a “neutral-distant” synchronization position is present, while the curved lines  3  and  4  each represent the shift operation for a “neutral-close” synchronization position. According to the term “neutral-distant,” a change (displacement) of the synchronization position, as determined by a controller  15 , away from the neutral position is meant and, according to the term “neutral-close,” a change (displacement) of the determined position in a direction towards the neutral position is correspondingly meant. 
   As shown in  FIG. 1 , the shift actuator  13 , as illustrated over time, is at first moved linearly and is then braked near the synchronization position or synchronization operation. A blocking effect is exerted against further movement of the shift actuator  13  during the synchronization operation. Therefore, this means that the shift actuator  13  is braked and becomes practically stationary until time point A. However, a force is continued to be applied to the shift actuator  13  and the continued application of the force leads, after time point B, to an acceleration of the shift actuator  13 , and thereby an increase in the rotational speed of the shift actuator  13 . 
   Curved line  1  shows a parabolic-shaped path with a high acceleration, whereas curved line  2  represents a path with a reduced acceleration. Because the beginning of the controlled acceleration of the shift actuator  13  according to curved line  2  would be selected too early, the blocking effect of the synchronization would still be exerted against the shift actuator  13  and thus only a slight acceleration of the shift actuator  13  would result. By monitoring the rotational speed of the shift actuator  13  during a next following shift operation, a path can therefore be utilized according to curved line  1 , by which the controlled acceleration starts later, i.e., after the blocking action of the synchronization has ceased. This later acceleration leads to an overall faster shift operation, because the acceleration is greater, and also leads to a reduction of the mechanical strain on the shift actuator  13  and the synchronizing means  12 , because the shift actuator  13  does not work against synchronization while the synchronizing means  12  is still exerting the blocking effect. 
   Curved lines  3  and  4  of  FIG. 1  show similar conditions with a synchronization position closer to the neutral position. By detecting the end of the synchronization operation, it is thus also possible with a synchronization position lying closer to the neutral position to change the position of the shift actuator  13 , as expressed by curved line  3 , and thus to attain a reduction in the shift time. In comparison, curved line  4  shows again, for clarity, a premature assumed end of the synchronization operation with a corresponding lengthening of the time period until reaching the end position of the shift actuator  13 , i.e., the “gear engaged” position. 
   Using two examples (cases),  FIG. 2  shows that a change in the synchronization position can be concluded or recognized. 
   In the example illustrated in Case 1, the actual synchronization position (ST) lies farther away from the neutral position than the synchronization position (SV), which was utilized or assumed by the controller  15  (e.g., stored in memory  16 ), which are shown in  FIG. 5 . This fact is concluded because the stationary position (SS) was determined to be above the utilized (stored) synchronization position SV. This stationary position (SS) is also shown in  FIG. 1  and corresponds to the position of the shift actuator  13  after braking (i.e., the horizontal portion of the curved lines shown in  FIG. 1 ) and is utilized during the synchronization operation. 
   At the end of the synchronization operation, a large acceleration (A&gt;) is apparent, which corresponds in  FIG. 1  to the portion of curved lines  1 – 4  that is characterized as a steep parabola, so that an adaptation, i.e. a correction of the assumed synchronization position (SV) utilized by the controller  15 , is appropriate. This determined synchronization position can then be stored as the new target synchronization position in the memory  16  of the controller  15 . 
   Case 2 shows that the actual synchronization position (ST) lies closer to the neutral position than the assumed (stored) synchronization position (SV). A low acceleration (A&lt;) is present. Because the assumed synchronization position (SV) was assumed to be above the stationary position (SS) and the actual synchronization position (ST), the actuator  13  has had to work against the blocking effect of the synchronizing means  12  during the synchronization operation. An adaptation of the assumed (stored) synchronization position (SV) in the direction closer to the neutral position is thus appropriate. 
     FIG. 3  shows an illustration to explain a unidirectional displacement of the entire shift pattern. In relation to the neutral position, a change (displacement) of the synchronization position for each forward gear has occurred in the same direction, which direction change is shown by the upwardly directed arrows. Therefore, it can be concluded that the entire shift pattern has moved altogether and an adaptation of the assumed synchronization position (SV) by the controller  15  is thus not necessary. 
   Lastly,  FIG. 4  serves to explain the importance of the synchronization position. The controller  15  uses the assumed synchronization position SV to brake the shift actuator  13  just before reaching the stationary position SS. This acceleration/braking pattern enables arrival at the stationary position SS as fast as possible, thereby shortening the time for the gear change operation, without however “moving into” the synchronization position with a still high speed of the shift actuator, as this would result in a “bounce back” of the shift actuator  13 , due to the blocking effect being exerted by the synchronizing means  12 . 
   If the assumed synchronization position SV used by the controller  15  is located too far in the neutral-distant direction (i.e., away from the neutral position), then no braking takes place before reaching the actual synchronization position ST and the shift actuator  13  must absorb the forces that are generated by the direct contact with the synchronizing means  12 , which leads to the above-noted bounce-back. With a too neutral-close assumed synchronization position SV (i.e., the assumed synchronization position SV is too close to the neutral position), the result is a premature braking of the shift actuator  13 . In this case, the shift actuator  13  will “creep” slowly towards the stationary position SS and the duration of the drive force interruption during a gear change operation will increase accordingly. These changes will have the effect of reducing shift comfort. But, with a correctly assumed synchronization position SV (e.g., as a result of an adaptation performed at the previous shift operation), the high mechanical strain on the shift actuator  13 , on the one hand, ceases and on the other hand, a short time results for the gear change operation. Consequently, the drive force interruption is relatively short. 
   For further features of the invention, which have not been explained in more detail above, reference is expressly made to the claims. 
   The patent claims filed with the application are proposed wordings without prejudice to obtaining broader patent protection. The applicant reserves the right to claim further combinations of features disclosed until now only in the description and/or drawings. 
   References made in the dependent claims refer to the further design of the subject of the main claim using the features of the relevant dependent claims; they are not to be regarded as dispensing with obtaining an independent subject protection for the combination of features of the dependent claims referred to. 
   Since the subject matter of the dependent claims can form independent inventions, as compared with prior art known by the priority date of this application, the applicant reserves the right to make them the subject of independent claims or divisional applications. They can also contain independent inventions that have a configuration independent of the subjects of the preceding dependent claims. 
   The embodiments are not to be regarded as restricting the invention. Rather, numerous modifications and amendments are possible within the scope of the present disclosure, in particular, those variations, elements and combinations and/or materials that can be derived by the expert as a solution of the object, for example, by combination or modification of individual features, elements or method steps contained in the drawings and described in connection with the general description and embodiments as well as claims, and by combinable features that lead to a new subject or new method steps or sequence of method steps, insofar as they relate to manufacturing, test and work methods.