Patent Publication Number: US-2012037472-A1

Title: Apparatus for actuating a postive shifting element shiftable at least between two shifting positions

Description:
This application is a National Stage completion of PCT/EP2010/055102 filed Apr. 19, 2010, which claims priority from German patent application Ser. No. 10 2009 002 661.4 filed Apr. 27, 2009. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to an apparatus for actuating a form-locking shift element which can be shifted at least between three shifting positions. 
     BACKGROUND OF THE INVENTION 
     In transmission devices known from practical application, rotating components such as transmission shafts or so-called idler gears are engaged into or disengaged from a flow of power of a transmission device via shift elements in a manner depending on the operating state, in order to attain various transmission ratios or transmission ratio ranges of a transmission device, and to switch therebetween. 
     In an embodiment of the shift elements as friction-locking shift elements, transmission ratios can be changed, preferably without interruption of tractive force, while maintaining a high level of driving comfort. Disengaged friction-locking shift elements are characterized by unwanted drag torques, however, which lower the efficiency of a transmission device. 
     Transmission devices provided with form-locking shift elements can be operated with greater efficiency since substantially lower drag torques occur in the region of form-locking shift elements, as is known. In contrast to transmission devices provided with friction-locking shift elements, transmission ratio changes involving form-locking shift elements can be carried out without interruption of tractive force only by employing further suitable measures which, however, increase the amount of construction space required in a transmission device and result in additional production costs. 
     Moreover, form-locking shift elements can be engaged or disengaged mainly only in the region of the synchronization point thereof, or near the synchronization point thereof, which is why structurally complex measures or complex control-related measures, via which form-locking shift elements can be synchronized in a targeted manner, are provided in practical applications to attain desired shift times. 
     Form-locking shift elements are often in the form of synchronizing mechanisms which, in order to synchronize the shift elements, include regions via which the differences in rotational speeds between the shift element halves can be compensated for within predefined times by friction engagement. However, such synchronizing mechanisms are subject to an unwanted high level of wear, which is disadvantageous, and are characterized by the need for a large amount of construction space. 
     On the control side, form-locking shift elements of vehicle transmission devices are guided, for instance, by corresponding guidance of engine rotational speed in the direction of the synchronized state thereof, and are subsequently disengaged or engaged. 
     In automated transmissions, form-locking shift elements are actuated via shift forks, for example, which can be driven electromechanically. Alternatively, form-locking connections between shafts of automated transmissions without synchronizing mechanisms or shift forks are activated or deactivated using pneumatically or hydraulically actuated, form-locking shift elements, for example. The functionality of such transmission devices can be ensured, however, only if sufficient sealing is provided in the region of supply lines and in the region of the shift elements themselves. 
     In order to operate vehicle transmission devices comprising form-locking shift elements with a desired level of spontaneity while maintaining a high level of driving comfort, appropriate shift times of form-locking shift elements must be attained with actuation that simultaneously takes driving comfort into account. To implement these requirements, an actuating speed must be varied depending on the operating state of a transmission device or the form-locking shift elements. The actuating speed of a form-locking shift element during operating states of a transmission device that are not critical to driving comfort can be designed to be faster than during operating states during which an actuating speed of a form-locking shift element that is too high impairs driving comfort to an undesired high extent. 
     A form-locking shift element is actuated with high actuating speeds during operating state progressions of a form-locking shift element during which the shift element is disengaged, to ensure short shift times and a high level of driving comfort. In contrast, a form-locking shift element is actuated only with low actuating speeds and high actuating forces during operating states in which the shift element is disengaged or engaged, in order to reliably attain a requested transmission ratio change in a transmission device without impairing driving comfort, and to overcome friction when the claws engage or disengage. 
     In the case of the above-described actuation of form-locking shift elements of transmission devices, which is known from practical application, high complexity of open-loop and closed-loop control is required to vary the actuating speed of form-locking shift elements, however, since the drive energy that is provided by a drive device that actuates a form-locking shift element must be changed depending on a current operating state of the form-locking shift element or the transmission device. 
     SUMMARY OF THE INVENTION 
     The problem addressed by the present invention is therefore that of providing a device for the actuation of a form-locking shift element of a transmission device, by means of which actuation of the form-locking shift element can be varied to the desired extent in a simple, low-cost manner. 
     The device according to the invention for actuating a form-locking shift element of a transmission device, which can be shifted at least between two shifting positions, is designed with a drive device and a drive converter device for converting rotational drive motion of the drive device into translatory actuating motion of the form-locking shift element. By means of the shift element, two transmission shafts of the transmission device are interconnected in a rotationally fixed manner in one or two shifting positions, while the transmission shafts are decoupled from one another in a further shifting position of the shift element. 
     The drive converter device comprises a first component having at least one control curve and a second component operatively connected thereto, which are connected in the region of the control curve to a component of the form-locking shift element, which is connected to one of the transmission shafts in a rotationally fixed manner and is axially displaceable. A drive device-side, rotational relative motion between the first component and the second component of the drive converter device can be converted to translatory relative motion of the component of the shift element, wherein the control curve has a smaller absolute slope, at least in curve regions that are equivalent to the shifting positions of the form-locking shift element, in accordance with the translatory actuating motion of the shift element than in curve regions equivalent to the regions between the shifting positions of the form-locking shift element. 
     Due to the fact that the slopes of the control curve differ in sections, the translatory motion of the component of the form-locking shift element varies throughout the shift travel of the form-locking shift element while the drive power of the drive motor remains constant, thereby making it possible to cover shift travel ranges between the individual shifting positions of the form-locking shift element during which the transmission shafts are decoupled from each other, which is not critical to driving comfort, at a higher shift speed and without great forces, and making it possible to cover shift travel ranges during which a rotationally fixed connection between two transmission shafts is established or released, which are therefore shift ranges that are critical to driving comfort, at a lower shift speed and with a greater shift force, without the need to provide complex open-loop and closed-loop control in the region of the drive device. 
     This means that a varying shift speed of a form-locking shift element in the device according to the invention is obtained with high driving comfort and mainly using design means that can be manufactured at low cost, which are also characterized by a low construction space requirement and require only one small electric motor. 
     In an advantageous development of the device according to the invention, the absolute slope of the control curve in curve regions that are equivalent to a disengaged operating state of the form-locking shift element between the shifting position and a further shifting position, and between the further shifting position and an additional shifting position of the form-locking shift element, during which transmission shafts are interconnected in a rotationally fixed manner, is greater than that of the other curve regions of the control curve, thereby enabling shift times of transmission devices comprising the device according to the invention to be reduced compared to conventionally designed transmission devices in a simple, low-cost manner while maintaining a high level of driving comfort, or predefined shift times can be attained with less complexity and a high level of driving comfort. 
     In a further advantageous embodiment of the device according to the invention, the absolute slope of the control curve in curve regions that are equivalent to operating state progressions of the form-locking shift element during which a rotationally fixed connection between two of the transmission shafts is established or released in the region of the form-locking shift element via the component of the shift element, is greater than that of the curve regions that are equivalent to the shifting positions of the form-locking shift element. Therefore, the form-locking shift element can be held in the shifting positions of the form-locking shift element without application of an additional holding force, e.g. via self-inhibition, due to the smaller absolute slope, and a low shift speed combined with great shift force, i.e. great engagement or disengagement force, is attained due to the higher absolute slope in the curve regions during which a rotationally fixed connection between two of the transmission shafts is established or released in the region of the form-locking shift element via the component of the shift element. 
     In a structurally simple and low-cost embodiment of the device according to the invention, the component of the shift element is operatively connected to the first component and to the second component of the drive converter device in the region of at least one annular groove via at least one bolt element, wherein rotational disengagement between the component of the shift element and the first component and the second component of the drive converter device can be attained in the region between the bolt element and the annular groove of the component of the shift element. 
     In a simple embodiment of the device according to the invention, which can be manufactured at low cost, the second component is connected to the first component and to the component of the shift element in the region of at least one slot via the at least one bolt element. 
     During an engagement procedure of a form-locking shift element, in unfavorable operating states of the shift element, it is possible that the shift element cannot be engaged to the desired extent due to a tooth-on-tooth position while the claws of the form-locking shift element bear against one another in the region of the face surfaces thereof. A form-locking shift element cannot be engaged until the claws of the shift element halves to be interconnected rotate relative one another 
     To prevent the need to shut off the drive of the drive device during such situations, a further embodiment of the device according to the invention comprises a spring device between the drive device and the drive converter device for the intermediate storage of rotational drive energy of the drive device. The mechanical power delivered by the drive device is therefore stored for the interim in the region of the spring device. If the form-locking shift element can be moved into the engaged operating state thereof, e.g. via the release of the tooth-on-tooth position, or if it is possible to shift through in the region of the form-locking shift element, the potential energy stored in the region of the spring device supports the drive device as the component of the shift element is displaced further, thereby making it possible to attain the shortest shift time possible despite the phased delay. 
     In a structurally simple embodiment of the device according to the invention, which is characterized by simple assembly, the spring device is provided between a drive ring element, which can be driven by an electric motor of the drive device, and the second component of the drive converter device. 
     To prevent oscillations in the region of the spring device, the spring device in the advantageous development of the device according to the invention has, in the installed state, a preload to which potential energy can be stored in the region of the spring device when an actuating force is applied that is greater than a threshold force. Therefore, no potential energy is stored in the spring device in the region of the spring device during shift procedures during which shift-through can be carried out without delay in the region of the form-locking shift element, or during which a rotationally fixed connection between the transmission shafts is released without delay, or during non-delayed disengagement procedures of the form-locking shift element. This is attained by way of a spring device that has been preloaded accordingly, in the region of which potential energy is stored starting at a certain level of force. 
     A development of the device according to the invention which is particularly favorable in terms of construction space and is characterized by low manufacturing costs comprises a transmission device between a motor output shaft of the electric motor of the drive device, and the drive ring element, in the region of which a rotational motion of the electric motor is stepped down, and therefore only small amounts of drive torque need to be applied in the region of the electric motor to actuate the form-locking shift element. 
     In a development of the device according to the invention, which is favorable in terms of construction space, the components of the drive converter device and the form-locking shift element are disposed coaxially to one another and are preferably engaged, whereby the device requires minimal construction space particularly in the axial direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages and advantageous developments of the invention will become apparent from the claims and the embodiment, the principle of which is described with reference to the drawings. 
       They show: 
         FIG. 1  a highly schematicized depiction of a device for actuating a form-locking shift element of a transmission device, which can be shifted between three shifting positions; 
         FIG. 2  an exploded depiction of the device according to  FIG. 1 ; 
         FIG. 3  a partial longitudinal sectional view of the device according to  FIG. 1 ; and 
         FIG. 4  a partial view of a shape of a control curve of a first component of a drive converter device of the device according to  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a transmission device  1  comprising a device  2  for actuating a form-locking shift element which can be shifted between three shifting positions S 1 , S 2  and S 3 , which comprises a drive device  4  and a drive converter device  5  shown in greater detail in  FIG. 2  and  FIG. 3  for converting rotational drive motion of the drive device  4  into translatory actuating motion of the form-locking shift element  3 . 
     By means of the shift element  3 , two transmission shafts  6  and  7 , or  7  and  8  are interconnected in a rotationally fixed manner in a first shifting position S 1  and in a second shifting position S 2 , while the transmission shafts  6  and  7 , or  7  and  8  are decoupled from one another in a third shifting position S 3  of the shift element  3 . 
     The drive converter device  5  comprises a first component  9  having three control curves  9 A and  9 B distributed around the circumference of the first component  9 , and a second component  10  which is operatively connected thereto, which are connected via bolt elements  11 A and  11 B in the region of the control curves  9 A and  9 B and the slots  10 A,  10 B of the second component  10  to a component  12  of the form-locking shift element, which is connected to the transmission shaft  7  in a rotationally fixed manner and is axially displaceable. 
     The two components  9  and  10  of the drive converter device  5  are operatively connected via bolt elements  11 A and  11 B which engage in an annular groove  13  of the component  12  of the form-locking shift element  3  in a manner such that different rotational speeds between the component  12  of the form-locking shift element  3  and the components  9  and  10  of the drive converter device  5  can be attained with low frictional losses, and drive device-side rotational relative motion between the first component  9  and the second component  10  is converted into translatory motion of the component  12  of the shift element  3 . 
     The control curves  9 A and  9 B of the first component  9  of the drive converter device  5  have a shape depicted in greater detail in  FIG. 4 , which is characterized by slopes which vary in sections of the curve in accordance with the translatory actuating motion of the component  12  of the shift element  3 . The control curves  9 A,  9 B have a smaller absolute slope in curve regions K 1 , K 2  and K 3  which are equivalent to the shifting positions S 1  to S 3  of the form-locking shift element  3 , than in curve regions K 4  to K 7  which are equivalent to the regions between the shifting positions S 1  to S 3  of the form-locking shift element  3 . 
     In the present case, the drive device  4  is in the form of an electric motor  14 , the rotational drive energy of which is transferred and stepped down via a transmission apparatus  17 , which is in the form of a spur gear transmission in the present case, disposed between a motor output shaft  15  of the electric motor  14  of the drive device  4  and a drive ring element  16  of the drive converter device  5 . It is therefore easily possible to dimension the electric motor  14  in regard to the torque capacity thereof in a manner that is favorable in terms of construction space and cost. Depending on the particular application, it is also possible to design the transmission apparatus as a worm gear pair or to use another suitable transmission. 
     Two different connections (modes) can be attained by utilizing the drive device  4  and the form-locking shift element  3  of the device  2 . This takes place via the interconnection of the transmission shaft  7 , which is an output shaft in the present case, with the transmission shaft  6  or the transmission shaft  8 , which can be connected to one another or decoupled from one another using the form-locking shift element  3  which is designed as a form-locking claw clutch in the present case. The component  12  or the selector sleeve of the form-locking shift element  3  is disposed on the output shaft  7  in a rotationally fixed and axially movable manner, wherein the selector sleeve  12  is moved to the desired extent by the drive device  4  or the shift actuation to be described below in greater detail. 
     The components of the drive converter device  5  and the form-locking shift element  3  are disposed coaxially to one another and are engaged in the present case, whereby the device  2  requires minimal construction space in the axial direction, and the annular disk of the first component  9 , which is relatively narrow in the axial direction, and in which the control curves  9 A and  9 B are disposed, can be utilized in entirety. 
     When the drive device  4  is active, the axial motion of the selector sleeve  12  results from the conversion of the rotational drive of the electric motor  14  into translatory drive motion carried out in the region of the switching device of the drive converter device  5 . The conversion takes place via the correspondingly designed control curves  9 A and  9 B of the first component  9  of the drive converter device  5 , which is a hollow shaft of the transmission device  1  secured to the housing. The control curves  9 A and  9 B extend along a helix at a slant relative to the circumferential direction of the first component  9 , and so the bolt elements  11 A and  11 B also change their axial position when the bolt elements  11 A and  11 B rotate relative to the first component  9 . The bolt elements  11 A and  11 B are displaced via the drive ring element  16  and the second component  10 , which is operatively connected thereto, when the electric motor is driven accordingly. 
     Due to the above-described, varying slope of the control curves  11 A and  11 B in the curve sections K 1  to K 7 , the axial actuating speed of the selector sleeve  13  varies along the shift travel thereof despite the constant rotational speed of the electric motor  14 . For instance, the control curves  9 A and  9 B have a small absolute slope in the curve regions K 1  and K 3  to enable the selector sleeve  13  to attain self-locking in the shifting positions S 1  and S 2 , in which the form-locking shift element  3  establishes a rotationally fixed connection between the transmission shafts  6  and  7 , or  7  and  8 , and to enable the selector sleeve  13  to be held without an additional application of holding force in the first or second shifting position S 1  or S 2  of the form-locking shift element  3 . 
     It is possible to vary the slope of the control curves  9 A and  9 B in the curve regions K 1  and K 3  within the shaded regions B 1  and B 3  in order to hold the component  12  of the form-locking shift element  3  in the first shifting position S 1  thereof or in the second shifting position S 2  thereof without additional holding force. The boundaries of the slope ranges B 1  and B 3  represent a negative slope or an expansion, respectively, for holding claws of the form-locking shift element  3  in the particular shifting position S 1  or S 2 , via an undercut, for example. 
     The curve regions K 4  to K 7  are designed with a greater absolute slope than exists in the curve regions K 1  and K 3 , although with a smaller slope than in the curve regions K 5  and K 6 , in order to attain a low axial actuating speed of the component  12  of the form-locking shift element  3  in the presence of high actuating force. The curve regions K 4  and K 7  are equivalent to operating state progressions of the form-locking shift element  3 , during which claws  19 ,  20  of the form-locking shift element  3  are being engaged or disengaged with claws  21  of the transmission shaft  6 , or with claws  22  of the transmission shaft  8 . Via the selected slope of the control curves  9 A and  9 B, a high disengagement force can be provided in particular when a form-locking connection is released in the region of the form-locking shift element  3 . 
     In the present case, the curve regions K 5  and K 6  represent so-called displacement ranges of the component  12  of the form-locking shift element  3  and are equivalent to operating states of the form-locking shift element  3  during which the form-locking shift element  3  is disengaged. Since the curve regions K 5  and K 6  are designed with a greater slope than the curve regions K 1 , K 2 , K 3 , K 4  and K 7 , shifting can be carried out within a desired short shift time. 
     The curve region K 2 , which is equivalent to the third shifting position S 3  of the form-locking shift element  3 , is designed with a smaller absolute slope relative to the curve regions K 5  and K 6 , to avoid having to stop the electric motor  14  using a drive motor of the form-locking shift element  3  during synchronization, for example. This results from the fact that the third shifting position S 3  of the form-locking shift element  3  is the neutral position or the neutral operating state of the form-locking shift element  3 , in which neither the transmission shaft  6  nor the transmission shaft  8  is connected to the transmission shaft  7 , and which is maintained along the small slope of the curve region K 2  and, therefore, by a low shift speed of the component  12  of the form-locking shift element  3  along a time interval that is long compared to the shift time intervals between the shifting positions S 1  and S 3 , and S 2  and S 3 . 
     The shape of the control curve  9 A and of the control curve  9 B depicted in  FIG. 4  has a qualitatively analogous shape relative to a bisecting line S for each shift side of the form-locking shift element  3 , although a quantitative adaptation of the curve shape of the control curves  9 A and  9 B to various claw geometries of the form-locking shift element  3  and the transmission shaft  6  and  8  is possible. 
     The rotational drive of the electric motor  14  is transferred by the drive ring element  16  to the second component  10  of the drive converter device  5  via a preloaded spring device  18 , wherein rotational relative motion between the drive ring element  16  and the second component  10  that is greater, starting at an actuating force, than a predefined threshold value brings about a change in the potential energy of the spring device  18 . Due to the preload of the spring device  18 , an actuating force that exceeds the threshold force is required to rotate the second component  10  relative to the drive ring element  16 , and is stored in the region of the spring device  18 . 
     If a shift-through initially cannot be completed, for instance, in the region of the form-locking shift element  3  due to a tooth-on-tooth position, or due to the claws  19  or  20  of the form-locking shift element colliding with the claws  21  or  22  of the transmission shaft  6  or the transmission shaft  8 , the rotational drive energy introduced by the electric motor  14  into the system is stored for the interim in the region of the spring device  18 . If the blockade in the region of the form-locking shift element  3  preventing the shift-through in the region of the form-locking shift element  3  is released, for example, via a rotational speed difference between the shift element halves of the form-locking shift element  3  that is required for the shift-through, the potential energy stored in the region of the spring device  18  supports the electric motor  14  in the acceleration of the selector sleeve  12 , whereby the shift time of the form-locking shift element  3  is kept short. 
     Moreover, oscillations between the second component  10  and the drive ring element  16 , which impair the functionality of the device  2 , are prevented when shifting takes place unobstructed via the preload of the spring device  18  and the friction relative to the second component  10  and the adjusting collar of the drive converter device  5  and the spring device  18 . 
     The device according to the invention is basically characterized in that minimal axial construction space is required, and a form-locking shift element can be shifted within desired short shift times using a small electric motor. The device according to the invention is also characterized by a small number of parts, and can therefore be manufactured at low cost. Moreover, complex test stand evaluations and adjustments of a transmission device comprising the device can be replaced by lower cost simulations, during which the operating parameters and component parameters are fine-tuned. 
     REFERENCE CHARACTERS 
     
         
           1  transmission device 
           2  device 
           3  form-locking shift element 
           4  drive device 
           5  drive converter device 
           6  to  8  transmission shaft 
           9  first component 
           9 A,  9 B control curve 
           10  second component 
           10 A,  10 B slot 
           11 A,  11 B bolt element 
           12  component of the form-locking shift element 
           13  annular groove of the form-locking component 
           14  electric motor 
           15  motor output shaft 
           16  drive ring element 
           17  transmission apparatus 
           18  spring device 
           19 ,  20 ,  21 ,  22  claws 
         B 1 , B 3  slope range 
         K 1  to K 7  curve range of the control curve 
         S bisecting line 
         S 1  to S 3  shifting position of the form-locking shift element