Patent Publication Number: US-2021188429-A1

Title: Transmission

Description:
RELATED APPLICATION DATA 
     This application is a continuation of International Patent Application No. PCT/CN2019/104145, filed Sep. 3, 2019, which claims the benefit of European Patent Application No. 18193762.4, filed Sep. 11, 2018, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The invention relates to a transmission comprising a first component and a second component, which are journaled for rotation relative to each other, and a locking mechanism for rotationally locking the first component and the second component relative to each other in a predetermined mutual rotation position. 
     BACKGROUND 
     In some technical fields, a shaft with a propeller may have to be locked against rotation during certain operation conditions. It may be a propeller driven by a motor or a propeller driven by the wind for generating electrical power, for instance. 
     For example, for a roadable aircraft, such as an aircraft that can be converted into an automotive vehicle capable of driving on a road, the propeller has to be disconnected from the driveline during road driving when the motor drives the wheels. When the propeller is disconnected for road driving, the propeller has to be kept stationary to prevent spinning of the propeller by the wind. Further, for other reasons, such as for reducing the air resistance and achieving balance, the angular position of the propeller will be predetermined, and the propeller will be kept in this specific position in the automotive mode. For a three-bladed propeller where the angular distance between each pair of two adjacent propeller blades is 120°, one propeller blade will usually be kept vertically in an upper position. 
     A drawback of known locking devices used for locking the propeller during the automotive mode is the addition of components to the transmission making the design more complicated, space-consuming and costly. 
     SUMMARY 
     An objective of the invention is to provide a transmission having a lock that can be used for locking a component, such as a propeller, while enabling at least some problem with known locking devices to be reduced or eliminated. 
     The objective is achieved by a transmission comprising a first component and a second component which are journaled for rotation relative to each other, and a locking mechanism for rotationally locking the first component and the second component relative to each other in a predetermined mutual rotation position, wherein the transmission comprises a magnetic field sensor arranged for measuring a relative rotation position of the first component and the second component while the first component and the second component are rotating relative to each other. 
     The invention is based on the insight that by such a transmission, locking of a component can be performed with few additional components in a reliable way since the knowledge of the relative rotation position makes it possible to match the engagement of the first component and the second component such that the locked predetermined mutual rotation position can be achieved. Further, the mechanical design of the locking mechanism can be non-complicated. The first component can be a propeller shaft and the second component can be a housing in which the propeller shaft is journaled. 
     The locking mechanism can comprise a lock unit displaceable in an axial direction for engagement of the first component and the second component. The lock unit can be arranged on the first component. For engagement of the first component and the second component the lock unit is displaced such that the lock unit will engage also the second component. 
     The lock unit is preferably a sleeve. The sleeve can be provided with internal splines for engagement with the first component and the second component. 
     For example, the transmission may have at least two modes selectable by the locking mechanism, a first stationary mode where the first component and the second component are locked relative to each other in the predetermined mutual rotation position and a second driving mode where the first component is connected to a drive motor for rotating the first component relative to the second component. Hereby, the lock is integrated in the transmission in a rational way providing a safe lock, since disconnection of the driving mode can be automatically performed when the stationary mode is to be activated by displacement of the lock unit, and vice versa. 
     It should be stressed that by the expression “predetermined mutual rotation position” is meant a certain position selected for rotationally locking the first component and the second component relative to each other with respect to their respective angular position, as opposed to any random position of a finite number of possible mutual rotation positions. 
     The number of predetermined mutual rotation positions in which the first component and the second component can be locked relative each other by the locking mechanism can be varied. For some applications there is only one such predetermined mutual rotation position. In other applications a few predetermined mutual rotation positions are possible, and often the number of predetermined mutual rotation positions is in the interval 1-5. For example, for a three-bladed propeller, three predetermined mutual rotation positions can be used since it will be possible to lock the propeller in three equivalent positions giving the same symmetry provided that the angular distance between two adjacent propeller blades is 120°. 
     According to one embodiment, the lock unit has at least one recess for interacting with a magnetic field generated by the magnetic field sensor, wherein said at least one recess is arranged for indicating a rotation position of one of the first component and the second component. For example, the lock unit can be arranged on the first component and rotationally locked to the first component for rotating together with the first component. 
     The rotation position of the second component can be fixed and known. Hereby, the rotation position of the first component can be determined and when it is matching the rotation position of the second component, the lock unit can be displaced such that the predetermined mutual rotation position of the first component and the second component is achieved. 
     According to a further embodiment, said at least one recess is arranged on an outer surface of the lock unit, wherein the depth of the recess varies along a circumferential direction of the lock unit. Hereby, a signal from the magnetic field sensor which signal varies with the recess depth during rotation of the lock unit relative to the magnetic field sensor can be received. For example, by analysing a signal based on the derivative of the magnetic field disturbance, the rotation position of the lock unit can be determined. 
     According to a further embodiment, the lock unit is provided with at least one magnetized portion for interacting with the magnetic field sensor, said at least one magnetized portion being arranged for indicating the rotation position of one of the first component and the second component. For example, the lock unit can be arranged on the first component and rotationally locked to the first component for rotating together with the first component. The rotation position of the second component can be fixed and known. Hereby, the rotation position of the first component can be determined and when it is matching the rotation position of the second component, the lock unit can be displaced such that the predetermined mutual rotation position of the first component and the second component is achieved. 
     According to a further embodiment, said at least one magnetized portion is arranged such that the magnetic field of the magnetized portion varies along a circumferential direction of the lock unit. Hereby, a signal from the magnetic field sensor which signal varies with the rotation position of the lock unit during rotation thereof can be received. For example, by analysing a signal based on the magnitude of the magnetic field, the rotation position of the lock unit can be determined. 
     In addition to measurement of the relative rotation position of the first component and the second component, the magnetic field sensor can be arranged for measuring an axial position of the lock unit and/or a relative rotation speed of the first component and the second component. Hereby, it is possible to further adapt the starting time for displacement of the lock unit and the requisite displacement speed of the lock unit to the current conditions. 
     A further objective of the invention is to provide a method that can be used for locking a component. This objective is achieved by method for locking a first component and a second component relative to each other in a transmission, wherein the first component and the second component of the transmission are journaled for rotation relative to each other and the transmission comprises a locking mechanism for rotationally locking the first component and the second component relative to each other in a predetermined mutual rotation position, which method comprises the step of measuring a relative rotation position of the first component and the second component by means of a magnetic field sensor while the first component and the second component are rotating relative to each other, and activating the locking mechanism for rotationally locking the first component and the second component relative to each other in the predetermined mutual rotation position based on the relative rotation position measured by means of the magnetic field sensor. 
     According to another aspect of the invention, a further objective is to provide a roadable aircraft comprising a transmission having a lock that can be used for locking a propeller of the aircraft. 
     The advantages of the method and the roadable aircraft are substantially the same as the advantages already discussed hereinabove with reference to the different embodiments of the transmission. Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples. 
       In the drawings: 
         FIG. 1A  is a perspective view of a roadable aircraft, 
         FIG. 1B  is a rear view of the roadable aircraft shown in  FIG. 1A , 
         FIG. 2  is a partly cut side view of a transmission in a neutral mode, 
         FIG. 3  is an end view of the transmission showing a propeller in a locked state, 
         FIG. 4A  is a front view of a locking mechanism of the transmission in  FIG. 2 , 
         FIG. 4B  is a side view of the locking mechanism in  FIG. 4A , 
         FIGS. 5A and 5B  show interaction between a magnetic field and a sleeve of the locking mechanism, 
         FIGS. 6A and 6B  show interaction between a magnetic field and a variant of a sleeve of the locking mechanism, 
         FIGS. 7A and 7B  are schematical side views of further sleeve variants of the locking mechanism, and 
         FIG. 8  is a flow chart showing an example embodiment of a method. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1A and 1B  show a roadable aircraft  1 .  FIG. 1A  shows the aircraft  1  in a perspective view and  FIG. 1B  shows the aircraft  1  in a rear view. The aircraft  1  can be converted into an automotive vehicle capable of driving on a road and interacting with a land-based traffic system. The aircraft  1  is shown when used as an automotive vehicle during road driving. In the automotive mode, the propeller  2  is disconnected from the driveline since the motor is used for driving the wheels  3 . When the propeller  2  is disconnected for road driving, the propeller  2  is preferably kept stationary to prevent spinning of the propeller by the wind. For reducing the air resistance and achieving balance, for instance, the propeller  2  will be kept in a specific position in the automotive mode. For a three-bladed propeller  2  as illustrated in  FIGS. 1A and 1B , where the angular distance  4  between each pair of propeller blades  5   a ,  5   b ;  5   b ,  5   c ;  5   c ,  5   a  is 120°, one propeller blade  5   a  will usually be kept vertically in an upper position. Thus, the upper propeller blade  5   a  is directed in a vertical direction  6 , at least as long as the aircraft  1  is standing on a substantially even ground  7 , and each of the other propeller blades  5   b ,  5   c  is directed obliquely downwards. 
     The propeller  2  is arranged on a propeller shaft of a transmission of the roadable aircraft  1 . The transmission will be described hereinafter with reference to the remaining figures. 
       FIG. 2  shows the transmission  8  in a partly cut side view. Although the transmission is described herein with reference to a vehicle application, such a transmission could also be used in other applications. 
     The transmission  8  comprises a first component  9  and a second component  10  which are journaled for rotation relative to each other by a bearing  11 . In the example embodiment illustrated in  FIG. 2 , the first component is a propeller shaft  9  on which the propeller  2  is arranged and the second component is a housing  10  of the transmission  8 . The housing  10  constitutes a fixed point on the aircraft  1 . The transmission  8  further comprises a locking mechanism  12  for rotationally locking the first component  9  and the second component  10  relative to each other in a predetermined mutual rotation position. 
     The locking mechanism  12  comprises a lock unit  13 . The lock unit  13  could be any suitable means for rotationally locking the first component and the second component to each other. The lock unit  13  is displaceable in an axial direction  16  for engagement of the first component  9  and the second component  10 . The lock unit  13  can be arranged on the first component  9 . In the example embodiment illustrated in  FIG. 2 , the lock unit is a sleeve  13  which is arranged on the first component  9 . The transmission  8  suitably comprises a hub  15  arranged on the first component on which hub  15  the sleeve  13  is arranged. The hub  15  is fixed relative to the first component  9 . The sleeve  13  is rotationally locked to the hub  15  and thereby rotationally locked relative to the first component  9  but is displaceable in the axial direction  16  relative to the hub  15 . The hub  15  can have external splines and the sleeve  13  can have internal splines forming a spline joint. 
     Further, the locking mechanism comprises a dog ring  14  which is rotationally locked to the second component  10 . The dog ring  14  is suitably provided with external splines corresponding to the internal splines of the sleeve  13 . Thus, the sleeve  13  is rotationally locked relative to the first component  9  and the dog ring  14  is rotationally locked relative to the second component  10 , and the sleeve  13  and the dog ring  14  are axially displaceable relative to each other for engagement of the sleeve  13  and the dog ring  14  such that the first component  9  and the second component  10  are rotationally locked relative to each other. 
     The sleeve  13  and the dog ring  14  should be engaged only in a mutual rotation position corresponding to the predetermined mutual rotation position of the first component  9  and the second component  10 . In the example embodiment illustrated in  FIG. 2  (and  FIGS. 1A and 1B ) the predetermined mutual rotation position of the first component  9  and the second component  10  corresponds to a predetermined rotation position of the propeller  2  arranged on the propeller shaft  9 . Thus, the propeller  2  is locked relative to the air craft  1  in the way as described hereinabove with reference to  FIGS. 1A and 1B . 
     As examples, the number of predetermined mutual rotation positions of the first component  9  and the second component  10  can be 1 or 3 when using a propeller with three propeller blades. In the first case, it is always the same propeller blade  5   a  that is directed in the vertical direction  6  when the propeller is locked. However, in the other case, due to the symmetry, the propeller  2  can be locked such that any of the propeller blades  5   a ,  5   b ,  5   c  is directed in the vertical direction  6 , since there are three equivalent locking positions for the propeller  2 . 
     The sleeve  13  can be displaceable in the axial direction  16  by means of a shift fork  50  of a gear actuator. The gear actuator is schematically illustrated in  FIG. 4A . 
     The transmission  8  has preferably at least two modes selectable by displacement of the sleeve  13 . In the example embodiment illustrated in  FIG. 2 , the transmission  8  has a first stationary mode where the first component  9  and the second component  10  are locked relative to each other in the predetermined mutual rotation position as previously described hereinabove. In this stationary mode the sleeve is axially displaced (to right in  FIG. 2 ) such that the sleeve  13  and the dog ring  14  are engaged. The transmission  8  has also a second driving mode where the first component is connected to a drive motor (not shown) for rotating the first component  9  relative to the second component  10 . In this driving mode the sleeve  13  is axially displaced (to left in  FIG. 2 ) such that the sleeve  13  and a further dog ring  17  are engaged. Finally, the transmission  8  has also a neutral mode where the first component  9  and the second component  10  are not rotationally locked relative to each other and the first component  9  is disconnected from the drive motor. In this neutral mode, the sleeve  13  is arranged in a centre position on the hub  15  not engaging any of the dog rings  14 ,  17 , as illustrated in  FIG. 2 . 
       FIG. 3  shows the transmission  8  in an end view where the transmission is in the locked mode corresponding to  FIG. 1B . The propeller shaft  9  and the propeller  2  are locked relative to the housing  10  in the predetermined mutual rotation position. One blade  5   a  of the three-bladed propeller  2  is positioned in the vertical direction  6 . 
       FIG. 4A  shows in a front view the sleeve  13 , the dog rings  14 ,  17  and the gear actuator  51  with the shift fork  50 . Further, the transmission  8  comprises a magnetic field sensor  60  arranged for measuring a relative rotation position of the first component  9  and the second component  10  while the first component and the second component are rotating relative to each other. In other words; the transmission  8  comprises the magnetic field sensor  60  for measuring a relative angular position of the first component and the second component while at least one of the first component and the second component is rotating about an axis  61 . This measurement is performed before displacement of the sleeve  13 , optionally after synchronization by means of a synchronizer (not shown), when the first component  9  and the second component  10  are disengaged. 
     In the example embodiment illustrated in  FIG. 2 , the first component is the propeller shaft  9  which rotates, and the second component is the housing  10  of the transmission  8 . The rotation position of the housing  10  is fixed (not rotating) and known. This means that it is sufficient to measure the rotation position of the sleeve  13  to determine the relative rotation position of the first component and the second component. However, although not further described herein, in another application the transmission could comprise one or more sensors. For example, a first sensor for measuring an angular position of the first component and a second sensor for measuring an angular position of the second component. 
     The magnetic sensor  60  is suitably arranged at a fixed point, preferably attached to the housing of the transmission by means of any suitable attachment means. 
     As shown in the side view in  FIG. 4B , the sleeve  13  can have at least one recess  63  for interacting with a magnetic field generated by the magnetic field sensor  60 . The recess  63  can be arranged for indicating a rotation position of one of the first component and the second component. Here the recess  63  is arranged for measuring the rotation position of the sleeve  13  and thereby the rotation position of the first component  9 . By knowledge of the position of the recess relative to the first component, the relative position of the first component and the second component can be measured by the magnetic field sensor  60 . 
     As further illustrated in  FIG. 4B , there are three such recesses  63  indicating possible rotation positions of the sleeve  13  for engagement with the dog ring  14  such that the first component  9  and the second component  10  can be locked relative to each other in the predetermined mutual rotation position. The angle  64  between two adjacent recesses  63  is 120°. These three recess positions correspond to the three equivalent propeller positions previously described and illustrated hereinabove. 
     Each recess  63  is arranged on an outer surface  65  of the sleeve  13  and the depth  66  of the recess  63  varies along a circumferential direction  67  of the sleeve  13 . Thus, the radial distance from the centre  68  of the sleeve  13  to the outer periphery thereof varies along the circumferential of the sleeve  13 . This means that the signal from the magnetic field sensor  60  will vary along the circumferential of the sleeve, i.e. vary when the sleeve rotates about the axis  61 . 
       FIGS. 5A and 5B  show the interaction of a magnetic field generated by the magnetic field senor  60  and the sleeve  13  when the sleeve is rotating. In  FIG. 5A  a part of the sleeve  13  is schematically illustrated. The sleeve  13  has an outer periphery  65  and a recess  63  that passes the magnetic field sensor  60  when the sleeve is rotating. In in  FIG. 5A , also the magnetic field sensor  60  is schematically illustrated. When the sleeve is rotating (and the sensor is fixed) the distance between the sensor  60  and the sleeve  13  will vary due to the recess  63 . The signals provided by the magnetic field sensor  60  is in turn dependent on the distance between the sleeve  13  and the magnetic field sensor  60 , and thus dependent on the rotation position of the sleeve as well. 
     In  FIG. 5B  the signal  70  from the magnetic field sensor  60  is illustrated. The signal  70  is represented by the change of the disturbance of the magnetic field caused by the sleeve  13 . In other words; the signal is based on the derivative of the magnetic field disturbance. Since the distance between the sleeve  13  and the magnetic field sensor  60  is constant during the first part (on the left side in  FIG. 5A ) when the sleeve  13  is rotated (counterclockwise in the example), the signal is constant during a first part. Thereafter the distance increases along a first slope  71  of the recess  63  until the magnetic field sensor  60  faces a flat bottom  72  of the recess  63 . Thus, along the first slope  71  the signal indicates a negative derivative, and along the flat bottom  72  the signal is constant. Thereafter the distance decreases along a second slope  73  of the recess  63  until the magnetic field sensor  60  and the recess  63  have passed each other. Thus, along the second slope  73  the signal indicates a positive derivative. After the recess  63  the signal is constant again since there is no change of the distance between the sleeve  13  and the magnetic field sensor  60 . This signal generated by the magnetic field sensor  60  can then be used for determining the current rotation position of the sleeve  13 . 
       FIGS. 6A and 6B  show the interaction of a magnetic field generated by the magnetic field senor  60  and a variant of the sleeve  13 ′ when the sleeve is rotating. In  FIG. 6A  the sleeve  13 ′ has a recess  63 ′ without a flat bottom portion. Instead a curved bottom portion  74  forms a smooth transition between a first slope  71 ′ and a second slope  73 ′ of the recess  63 ′ of the sleeve  13 ′. Accordingly, the signal  70 ′ is somewhat different from the signal in  FIG. 5B  as can be seen in  FIG. 6B . From the start of the first slope  71 ′ until the magnetic field sensor  60  faces a bottom point  75  of the recess (which also can be a centre point of the recess) where the distance between the sleeve  13 ′ and the magnetic field senor  60  is greatest, the signal indicates a negative derivative. From the bottom point  75  to the end of the second slope  73 ′ the signal indicates a positive derivative. Before and after the recess  63 ′, the signal is constant in the same way as already described with reference to  FIGS. 5A and 5B . Since the derivative changes characters at the bottom point  75  a very precise rotation position of the sleeve  13 ′ can be achieved. 
       FIGS. 7A and 7B  show further variants of a sleeve  13 ″ provided with at least one magnetized portion  80  for interacting with the magnetic field sensor. The sleeve is schematically shown in side views. Instead of a recess said at least one magnetized portion  80  is arranged for indicating the rotation position of the sleeve and thereby the rotation position of the first component. By knowledge of the position of the magnetized portion  80  relative to the first component  9 , the relative position of the first component  9  and the second component  10  can be measured by the magnetic field sensor  60 . 
     The sleeve can have one or more such magnetized portions  80 , each providing a magnetic field. The magnetized portion  80  can be arranged such that the magnetic field of the magnetized portion varies along a circumferential direction  67 ″ of the lock unit  13 ″. Each such magnetized portion  80  can in turn be divided into two or more sections  81  with different magnetic polarity. The polarity of the sections  81  can be different from each other such that the magnetic field varies along the circumferential direction  67 ″ of the sleeve  13 ″. For example, as illustrated in  FIG. 7A , the sections  81  can be arranged with alternating polarity as indicated by the arrows  82 . As illustrated in  FIG. 7B , a magnetization of the sleeve  13 ″ where the magnetic field varies gradually along the magnetized portion  80  can also be used. Such magnetization can be achieved by magnets arranged in a suitable Halbach array for instance. 
     The sleeve  13 ″ can be made in one piece or the sleeve may comprise a first ring with the splines and second magnetized ring that is clamped onto the outer surface of the first ring such that the first ring and the second ring sleeve are rotationally locked relative to each other. 
     As schematically illustrated in  FIG. 4A , for performing the method as described herein, a control unit  90  for controlling the gear actuator  51  is provided. The control unit  90  is configured to continuously receive input data  91  from the magnetic field sensor  60 . The control unit  90  is further configured to provide output data  92  based on the received input data  91  for controlling the gear actuator  51 . The control unit  90  can be electrically connected to the gear actuator  51  for transferring signals between the control unit  90  and a drive unit  93  of the gear actuator  51 . 
     The control unit  90  may comprise one or more microprocessors and/or one or more memory devices or any other components for executing computer programs to perform the method. Thus, the control unit is preferably provided with a computer program for performing all steps of any embodiment of the method described herein. Furthermore, the control unit can be part of a controller used also for other functions of the gear actuator or any other function of the transmission or be provided as a separate unit connectable to a controller. 
     The invention also relates to a method for locking a first component and a second component relative to each other in a transmission. As previously described, the first component  9  and the second component  10  of the transmission  8  are journaled for rotation relative to each other and the transmission comprising a locking mechanism  12  for rotationally locking the first component and the second component relative to each other in a predetermined mutual rotation position. As it regards further device features, reference is made to the description of the transmission  8  hereinabove. 
     The method comprises the step of measuring a relative rotation position of the first component  9  and the second component  10  by means of a magnetic field sensor  60  while the first component and the second component are rotating relative to each other, and activating the locking mechanism  12  for rotationally locking the first component  9  and the second component  10  relative to each other in the predetermined mutual rotation position based on the relative rotation position measured by means of the magnetic field sensor  60 . 
       FIG. 8  shows a flow chart of one example embodiment of the method. In a first step S 1 , signals from the magnetic field sensor  60  are transferred to the control unit  90 . See also  FIG. 4A . The control unit  90  continuously reads the signals originating from measurements on the sleeve  13  performed by the magnetic field sensor  60 . In a second step S 2  the axial position of the sleeve is detected based on the signals received from the magnetic field sensor  60 . In a third step S 3  the rotation speed of the sleeve is detected based on the signals received from the magnetic field sensor  60 . In a fourth step S 4 , the detected rotation speed is compared to a target speed interval. 
     If the measured speed is within the target speed interval (“YES” in  FIG. 7 ), then in a fifth step S 5  the rotation position of the sleeve is continuously detected to find a rotation position of the sleeve where engagement of the sleeve and the dog ring can be performed. Should the rotation speed be out of the target speed interval (“NO” in  FIG. 7 ), reading of sensor signals continues until the speed has reached a value within the interval. Preferably, the interval will include speeds from 0 up to an upper threshold value, above which engagement of the sleeve is not possible. 
     In a sixth step S 6 , when the speed is in the target speed interval and a rotation position of the sleeve  13  suitable for engagement has been detected, the sleeve  13  is displaced by the gear actuator  51  for engagement of the sleeve  13  and the dog ring  14 . As previously described, the relative rotation position of the sleeve  13  and the dog ring  14  is selected such that the first component  9  and the second component  10  are locked relative to each other in the predetermined mutual rotation position. 
     It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.