Patent Publication Number: US-2023157204-A1

Title: Self-propelled work apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority of European patent application no. 21210473.1, filed Nov. 25, 2021, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The disclosure relates to a self-propelled work apparatus having a chassis and at least one tool and with a drive motor for driving the tool. The tool is height-adjustable with respect to the chassis and a setting unit is provided to set the relative position of the tool with respect to the chassis. The setting unit includes an actuating motor and a setting gear. The setting gear rotates by less than one full revolution between a first, lower end position of the tool and a second, upper end position of the tool. 
     BACKGROUND 
     CN 107996124 A has disclosed a lawnmower with a setting unit for the tool, which setting unit includes an actuating motor and a setting gear. The setting gear has an eccentric pin which engages into a mount for the motor. 
     SUMMARY 
     It is an object of the disclosure to provide a self-propelled work apparatus wherein the position of the tool can be detected in a simple manner. 
     According to the disclosure, a detection device is provided to detect the height position of the tool. The detection device includes encoding elements on a setting gear and at least one detector. The at least one first encoding element for the first end position differs here from the at least one second encoding element for the second end position. 
     The encoding elements and detector permit a detection of the height position of the tool in a simple way. By virtue of the fact that the encoding elements for the first end position and for the second end position differ from one another, the end positions can be detected unambiguously by the at least one detector. The height position of the tool can be brought about in a simple way by way of detection of an end position and determination of the position of the tool starting from this end position, for example via further encoding elements. 
     A simple construction and precise detection of the height position including the detection of the end positions are achieved if two detectors are provided which are arranged at a predefined spacing from one another. By virtue of the fact that two detectors are provided, a simple configuration of the encoding elements is possible, for example via different lengths of the encoding elements in the circumferential direction. Encoding elements of different lengths can be detected in a simple way in a manner which is dependent on whether one detector or the two detectors detect(s) at least one encoding element. 
     In a simple embodiment, the encoding elements are formed by projections or the absence of projections. The gaps which are formed between the projections are detected by the at least one detector just like the projections. Simple encoding is possible by way of suitable arrangement of the projections and the gaps between the projections. 
     In a simple embodiment, the detector is an optical detector. Optical detectors are, in particular, laser light sources and suitable associated receivers. Other types of detectors, for example magnetic detectors such as Hall sensors which interact with magnets, mechanical switches, electric contacts, for example rubbing contacts and associated actuating elements, can also be advantageous, however. Here, the magnets, actuating elements or the like form the encoding elements. 
     In order to achieve precise positioning of the setting gear and detector, it is advantageously provided that the setting gear and the at least one detector are connected fixedly to a guide part of single-part configuration. The setting gear is advantageously mounted directly in the guide part. The detectors are advantageously fixed on a common component, the position of which with respect to the guide part can be set in order to compensate for tolerances. As a result, manufacturing tolerances between the setting gear and detectors are minimized in a simple way. As a result, a precise detection of the height position of the tool is made possible. 
     The setting unit advantageously includes a worm gear which is driven by the actuating motor. The worm gear can preferably be mounted on the guide part. Another arrangement of the worm gear can also be advantageous, however. The worm gear can preferably engage into the setting gear. Accordingly, the worm gear and setting gear form a single-stage transmission. In an alternative embodiment, a multiple-stage transmission can also be provided which transmits the rotational movement of the worm gear to the setting gear. In an embodiment, the setting gear is configured as a spur gear. 
     The drive motor is advantageously guided on the chassis via at least one, in particular via two linear guides. As a result, tilting of the drive motor with respect to the chassis is prevented. One linear guide preferably permits a movement of the drive motor with respect to the chassis transversely with respect to the longitudinal direction of the linear guide. Accordingly, this linear guide is configured as a floating bearing. The movement of the drive motor with respect to the chassis transversely with respect to the longitudinal direction of the linear guide can be provided, for example, in order to compensate for manufacturing tolerances or in order to compensate for length changes of the components under the influence of temperature. The other linear guide is preferably configured as a fixed bearing, and does not permit a movement of the drive motor with respect to the chassis transversely with respect to the longitudinal direction of the linear guide. 
     The drive motor is advantageously arranged in a motor mount. The motor mount can have, for example, a mount pot which is open towards the top and in which the drive motor is arranged. One simple embodiment arises if the motor mount has an elastic portion which is supported on the linear guide. The elastic portion is advantageously deformed transversely with respect to the longitudinal direction of the linear guide in the case of a movement of the motor mount with respect to the chassis. If the motor mount performs a movement with respect to the chassis transversely with respect to the longitudinal direction of the linear guide, the elastic portion absorbs this transverse movement by way of deformation. A movement of this type transversely with respect to the longitudinal direction of the linear guide can arise, for example, on account of length changes as a result of temperature changes. The elastic portion is configured, in particular, in one piece on the motor mount. The elastic portion is particularly advantageously formed by way of a correspondingly thin-walled configuration of regions of the motor mount. As a result, a simple construction with few individual parts is achieved. The linear guide is advantageously configured on the guide part. 
     The rotational axis of the setting gear preferably runs perpendicularly with respect to the adjusting direction of the setting unit. The setting gear is coupled, in particular at a spacing from its rotational axis, to the drive motor. On account of the coupling at a spacing from the rotational axis, an adjustment of the position of the drive motor and therefore of the position of the tool is possible via an eccentric pin or the like. As a result, a simple construction and an advantageous adjustment are achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described with reference to the drawings wherein: 
         FIG.  1    shows a diagrammatic illustration of a self-propelled lawnmower in plan view; 
         FIG.  2    shows a diagrammatic longitudinal section of the lawnmower from  FIG.  1   ; 
         FIG.  3    shows a perspective illustration of the drive motor, motor mount and setting unit in a lower end position of the motor mount; 
         FIG.  4    shows a side view of the arrangement from  FIG.  3   ; 
         FIG.  5    shows a plan view in the direction of the arrow V in  FIG.  4   ; 
         FIG.  6    shows a side view in the direction of the arrow VI in  FIG.  5   ; 
         FIG.  7    shows a section along the line VII-VII in  FIG.  6   ; 
         FIG.  8    shows a section along the line VIII-VIII in  FIG.  7   ; 
         FIG.  9    shows the region of the sliding element and the guide from  FIG.  8    in an enlarged illustration; 
         FIG.  10    shows a section along the line X-X in  FIG.  7   ; 
         FIG.  11    shows a sectional illustration in accordance with  FIG.  8    in a middle position of the motor mount; 
         FIG.  12    shows a section along the line XII-XII in  FIG.  11   ; 
         FIG.  13    shows a section along the line XIII-XIII in  FIG.  12   ; 
         FIG.  14    shows a sectional illustration in accordance with  FIG.  8    in an uppermost end position of the motor mount; 
         FIG.  15    shows a section along the line XV-XV in  FIG.  14   ; and, 
         FIG.  16    shows a section along the line XVI-XVI in  FIG.  14   . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG.  1    shows a lawnmower  1  in a diagrammatic illustration as an embodiment for a self-propelled work apparatus. The self-propelled work apparatus can also be a different work apparatus, however. The lawnmower  1  has a hood  2  which covers the tool of the lawnmower  1 , a diagrammatically shown blade  4  in the embodiment. Moreover, the lawnmower  1  has a plurality of wheels  3 , with which the lawnmower  1  can be moved over the ground. 
       FIG.  2    shows a diagrammatic section through the lawnmower  1 . The lawnmower  1  is situated in a storage position  13 . In the storage position  13 , the lawnmower  1  is stored on a flat, horizontal storage surface  12 . Here, the wheels  3  of the lawnmower  1  are on the floor. In the embodiment, the lawnmower  1  has two rear, laterally arranged wheels  3  with a great diameter, and a front, centrally arranged, small wheel  3 . In the embodiment, the front wheel  3  is arranged below the hood  2 . 
     The lawnmower  1  has a chassis  6 , on which the wheels  3  and the hood  2  are fixed. The hood  2  is supported via mounts  11  on the chassis  6 . Here, the hood  2  is advantageously arranged such that it can be moved to a limited extent with respect to the chassis  6 . 
     As  FIG.  2    also shows, the blade  4  is arranged on a drive shaft  7  of a drive motor  8 . The blade  4  is driven rotationally about a rotational axis  64  by the drive motor  8  during operation. 
     In the embodiment, the drive motor  8  is an electric motor. The drive motor  8  is arranged in a motor mount  9 . The drive motor  8  is fixed on the motor mount  9  in such a way that the drive motor  8  can be moved with the motor mount  9  with respect to the chassis  6 . The motor mount  9  can be adjusted with respect to the chassis  6  in a vertical direction  14  via a setting unit  10 . The vertical direction  14  is the direction which runs vertically in the storage position  13 . During the setting operation, the motor mount  9  moves at least partially in the vertical direction  14 , with the result that setting of the height position of the blade  4  with respect to the ground is possible. Here, the adjusting direction can also be inclined with respect to the vertical direction  14 . A controller  5  is provided in order to actuate the drive motor  8  and the setting unit  10 . In the embodiment, the controller  5  is arranged on the chassis  6 . An arrangement on the motor mount  9  can also be advantageous, however. 
       FIG.  3    perspectively shows the drive motor  8 , the motor mount  9  and the setting unit  10 . The setting unit  10  includes a guide part  20  which is connected fixedly to the chassis  6  ( FIG.  2   ). In the embodiment, fastening openings  49  are provided in the base region of the guide part  20  to this end. In the embodiment, the guide part  20  includes a receiving portion  48 , in which the motor mount  9  is arranged movably. The motor mount  9  can be moved in the vertical direction  14  which is shown in  FIG.  4   . 
       FIGS.  3  to  10    show the motor mount  9  and the drive motor  8  in a first, lower end position  30 . As  FIGS.  4  to  6    show, the setting unit  10  is arranged on the guide part  20  on one side of the motor mount  9 . The setting unit  10  includes an actuating motor  15 . The actuating motor  15  drives a worm gear  16  which is shown in  FIG.  7   . In the embodiment, the rotational axis  17  of the worm gear  16  is arranged perpendicularly with respect to the rotational axis  50  of the drive motor  8 . The rotational axis  50  of the drive motor  8  coincides with the rotational axis  64  of the blade  4 . In the storage position  13  ( FIG.  2   ), the rotational axis  17  of the worm gear  16  lies horizontally. 
     The setting unit  10  includes a setting gear  18  which is mounted such that it can be rotated about a rotational axis  19 . In the embodiment, the rotational axis  19  is arranged perpendicularly with respect to the rotational axis  17  of the worm gear  16 . The rotational axis  19  lies horizontally in the storage position  13 . In the embodiment, the setting gear  18  is mounted on the guide part  20 . The setting gear  18  has a bearing support  24  which is mounted rotatably on a bearing surface  21  of the guide part  20 . The bearing surface  21  is advantageously of cylindrical configuration, and the bearing support  24  has outwardly protruding ribs for bearing against the bearing surface  21 . The actuating motor  15  and the worm gear  16  are also mounted on the guide part  20 . In the embodiment, the worm gear  16  engages directly into the setting gear  18 . In one alternative embodiment, further transmission stages can also be provided. 
     The setting gear  18  supports an eccentric pin  34  ( FIG.  8   ) on its side which faces the motor mount  9 . The eccentric pin  34  supports a sliding element  35  which will be described in greater detail in the following text. The sliding element  35  is mounted rotatably on the eccentric pin  34 . The motor mount  9  has two guide surfaces  37  and  38 , between which the eccentric pin  34  with the sliding element  35  is arranged. The guide surfaces  37  and  38  form a guide  36  with the sliding element  35 . In the storage position  13 , the guide  36  is oriented horizontally. A different orientation of the guide  36  can also be advantageous, however. In the case of a rotation of the setting gear  18 , the eccentric pin  34  moves in the vertical direction  14  and, as a result, brings about a movement of the guide part  20  in the vertical direction  14 . The movement of the eccentric pin in the horizontal direction, that is, perpendicularly with respect to the vertical direction  14 , which is caused by the rotation of the setting gear  18  brings about a displacement of the sliding element  35  with respect to the guide surfaces  37  and  38 . In the case of the rotational movement of the setting gear  18 , the eccentric pin  34  rotates in the sliding element  35 . 
     In order for it to be possible for the height position of the motor mount  9  and therefore the height position of the blade  4  to be detected, a detection device  32  is provided. The detection device  32  includes at least one detector  25 . In the embodiment, two detector  25  are provided, as  FIG.  10    shows. The detectors  25  are configured to detect encoding elements  26 ,  27 ,  28 ,  29  when they move past the at least one detector  25 . In the embodiment, the detectors  25  are configured as optical detectors, for example light barriers with laser light. The encoding elements  26  and  27  are formed by projections on the setting gear  18 . The encoding elements  28  and  29  are formed by missing projections. The encoding element  29  is shown in  FIG.  10   . As  FIG.  10    also shows, the encoding elements  26  to  29  are arranged on a circular path around the rotational axis  19 . In the case of the rotational movement of the setting gear  18 , the encoding elements  26  to  29  move past the detectors  25  and are detected. As a result, the rotational position of the setting gear  18  and therefore the height position of the guide part  20 , the drive motor  8  and the blade  4  can be determined. 
     As  FIG.  7    shows, the worm gear  16  is mounted in a bearing surface  22  of the guide part  20 . The bearing surface  22  is preferably configured as a hollow cylinder. As  FIG.  7    also shows, all the elements of the setting unit  10  apart from the controller  5  ( FIG.  2   ) and the detectors  25  are mounted directly on the guide part  20 . The guide part  20  is closed by a cover  51 . In the embodiment, the detectors  25  are held on the cover  51 . The cover  51  is fixed on the guide part  20  via at least one screw  70  in the embodiment. The screw  70  is guided with a small amount of play in the cover  51 , with the result that, in the case of the positioning of the cover  51  on the guide part  20 , a compensation of small tolerances is possible. A different arrangement of the detector  25 , in particular on the guide part  20 , can also be advantageous, however. 
       FIG.  8    shows the mounting of the motor mount  9  on the guide part  20 . The motor mount  9  and the guide part  20  form two linear guides  44  and  45 . The longitudinal direction  46  of the linear guides  44  and  45  is oriented in the vertical direction  14  in the storage position  13 . The linear guides  44  and  45  in each case have a guide piece  52  which protrudes between the sliding tracks  53  of each linear guide  44 ,  45  which lie opposite one another and is guided between them. In the embodiment, the first linear guide  44  is configured as a fixed bearing, and the second linear guide  45  is configured as a floating bearing. The first linear guide  44  does not permit any movement of the motor mount  9  with respect to the guide  20  in the direction perpendicularly with respect to the longitudinal direction  46 . The guide piece  52  is advantageously guided without play between the sliding tracks  53  within the context of the manufacturing tolerances. In order to compensate for tolerances and length changes, the second linear guide  45  has elastic portions  47 , on which the guide piece  52  of the motor mount  9  which protrudes between the sliding tracks  53  of the linear guide  45  which lie opposite one another can be deformed. As a result, the elastic portions  47  permit a relative movement of the guide part  20  with respect to the sliding tracks  53  perpendicularly with respect to the longitudinal direction  46 . 
       FIGS.  8  and  9    also show the eccentric pin  34  with the sliding element  35  and the guide  36 . As  FIG.  8    shows, the eccentric pin  34  is configured as a hollow pin in the embodiment. As  FIG.  9    shows, the eccentric pin  34  has a center axis  43 . As  FIG.  8    shows, the rotational axis  19  of the setting gear  18  is at a spacing f from the center axis  43  of the eccentric pin  34 . The distance covered by the blade  4  between the upper end position  31  and the lower end position  30  is advantageously less than twice the spacing f, in particular less than 1.8 times the spacing f. 
     In the embodiment, the sliding element  35  is of mirror-symmetrical configuration with respect to a first plane of symmetry  54  which lies between the guides  37  and  38 . The first plane of symmetry  54  is oriented in the longitudinal direction  42  of the guide  36 . In the embodiment, the sliding element  35  is, moreover, of symmetrical configuration with respect to a second plane of symmetry  55  which runs perpendicularly with respect to the first plane of symmetry  54  and through the center axis  43 . The sliding element  35  has at least one sliding surface  39 ,  40 . The sliding element  35  bears by way of the at least one sliding surface  39 ,  40  against at least one guide surface  37 ,  38 . In the embodiment, two sliding surfaces  39 ,  40  are provided on each guide surface  37  and  38 . The sliding surfaces  39  have an outer side  56  which lies at a spacing from the other sliding surface  40  which bears against this guide surface  37 ,  38 . The sliding surfaces  40  have an outer side  57  which lies at a spacing from the other sliding surface  39 . The outer sides  56 ,  57  are at a spacing e from one another. The guide surfaces  37  and  38  are oriented parallel to one another and are at a spacing a from one another. The spacing a can be, for example, a few centimetres. The spacing e is advantageously at least 50%, in particular at least 80%, of the spacing a of the guide surfaces  37  and  38 . As a result, tilting or canting of the sliding element  35  between the guide surfaces  37  and  38  is prevented. 
     The sliding element  35  has a hub  59  which surrounds the eccentric pin  34 . In the embodiment, a plain bearing is formed between the hub  59  and the eccentric pin  34 . In each case two arms  58  extend from the hub  59  in the direction of each guide surface  37  and  38 . The arms  58  are of elastic configuration, with the result that the sliding surfaces  39  and  40  bear in an elastically prestressed manner against the guide surfaces  37  and  38 . The arms  58  have a center axis  60  which runs very flatly with respect to the guide surfaces  37  and  38 . The center axis  60  advantageously encloses an angle α of less than 30°, in particular of less than 20°, with an associated guide surface  37 ,  38 . 
     The sliding surfaces  39  and  38  are advantageously at a spacing b which is measured parallel to the guide surfaces  37  and  38 . The spacing b of the two sliding surfaces  39  and  40  is advantageously at least 30%, in particular at least 50%, of the spacing a of the guide surfaces  37  and  38 . 
     In order to ensure that the arms  58  cannot be overloaded, at least one stop  41  is provided which limits the deformation of an arm  58 . A stop  41  is advantageously provided adjacently with respect to each arm  58 . In the embodiment, a stop  41  which protrudes between two sliding surfaces  39  and  40  is provided on each guide surface  37  and  38 . In the unloaded state which is shown in  FIG.  9   , the stop  41  is at a spacing d from the associated guide surface  37 ,  38 . If the worm gear  16  is rotated and the eccentric pin  34  is moved as a result, the stop  41  which lies at the front in the movement direction of the eccentric pin  34  can bear against the associated guide surface  37 ,  38  and thus ensure a satisfactory transmission of the actuating movement. The stop  41  is arranged between the sliding surfaces  39  and  40 . The sliding surfaces  39  and  40  are at a spacing c, measured parallel to the guide surfaces  37  and  38 , from the center axis  43  of the eccentric pin  34 . In the embodiment, the spacing c is greater than the radius of the eccentric pin  34 . In the embodiment, all the sliding surfaces  39 ,  40  of the sliding element  35  are at the same spacing, measured in the longitudinal direction  42  of the guide  36 , from the center axis  43  of the eccentric pin  34 . 
       FIG.  10    shows the detection device  32  in detail. The setting gear  18  supports the encoding elements  26  to  29  which are arranged in a circular manner around the rotational axis  19 . The encoding elements  26  and  27  are configured as projections. Each detector  25  has a transmitter  61  and a receiver  62 . The arrangement of the transmitters  61  and receivers  62  can also be swapped. In the embodiment, the detectors  25  are optical detectors, and the transmitters  61  emit light, in particular laser light, and the receivers  62  receive the light and evaluate the received light intensity. If a projection of an encoding element  26  or  27  passes between the transmitter  61  and receiver  62  of a detector  25 , the receiver  62  is concealed and the signal which is received from the transmitter  61  is attenuated. In the embodiment, the detectors  25  are optical detectors. The detectors  25  can also be other types of detectors  25 , however, for example magnetic detectors  25  such as Hall sensors which interact with magnets which form the encoding elements, mechanical switches or electrical contacts, for example rubbing contacts or the like. 
     The two detectors  25  are arranged at an angular spacing β from one another. The angular spacing β is greater than the circumferential angle, over which an encoding element  26  or  28  extends. Here, the angular spacing β is measured between the center axes of the detectors  25 . The encoding elements  28  are formed by a missing projection, that is, the gap between two encoding elements  26  which follow one another. The encoding elements  26  and  28  extend in each case over an angle γ which can be, for example, 1.5 times the angular spacing β. The angular spacing β and the angle γ are preferably adapted to one another in such a way that only one of the detectors  25  is concealed by an encoding element  26  in each position in a region between the end positions  30  ( FIG.  7   ) and  31  ( FIG.  14   ) of the blade  4 . 
     In that lower end position  30  ( FIG.  4   ) of the blade  4  and the motor mount  9  which is shown in  FIGS.  3  to  10   , an encoding element  29  is arranged in the region of one of the detectors  25 . The encoding element  29  extends over an angular spacing which corresponds at least to the angle β. In the embodiment, the encoding element  29  is a missing projection. If the two receivers  62  of the detector  25  receive a signal which is not attenuated, the motor mount  9  is therefore situated in its first, lower end position  30 . 
     If the motor mount  9  moves out of the lower end position  30  in the direction of its upper end position  31  ( FIGS.  14  to  16   ), the encoding elements  26  and  27  move past the detector  25 . The receivers  62  are concealed partially by the encoding elements  26  in every position, with the result that the received signal is weaker than in the first, lower end position  30 . The changing signal strength can be evaluated by the controller  5 . The position of the motor mount  9  can be determined, starting from one end position  30 ,  31 , by counting the encoding elements  26  and  27  which are guided past the detector  25 . On account of the eccentric pin  34  which changes in a non-linear manner in the vertical direction  14  with respect to the adjusting angle of the setting gear  18 , a non-linear relationship arises between the number of encoding elements  26 ,  27  which are guided past the detector  25  and the distance which is covered by the motor mount  9  and the blade  4 . This is to be taken into consideration in the evaluation.  FIGS.  11  to  13    show the arrangement in a middle position of the motor mount  9  and the blade  4 . The eccentric pin  34  has moved from the lower end position  30  to the middle position with respect to the guide surfaces  37  and  38 , from one to its other horizontal end position. The eccentric pin  34  moves from the middle position to the upper end position  31  back again into its starting position. The sliding element  35  is preferably situated in the first end position  30  and the second end position  31  relative to the guide surfaces  37  and  38  in the same position. 
       FIG.  14    shows the motor mount  9  in its second, upper end position  31 . In this position, an encoding element  27  is arranged in the region of the detector  25 . The encoding element  27  for the second, upper end position  31  differs from the encoding element  29  for the first, lower end position  30 . The encoding elements  27  and  29  also differ from the encoding elements  26  and  28  for positions between the end positions  30  and  31 .  FIG.  16    shows the arrangement of the encoding element  27  in the region of the detector  25 . As  FIG.  16    shows, the two receivers  62  of the detector  25  are concealed at least partially by the encoding element  27 . As a result, the second, upper end position  31  is unambiguously identifiable for the controller  50 . In the case of the movement of the motor mount  9  from the lower end position  30  to the upper end position  31 , the sliding element  35  has moved in the direction of the second linear guide  44  and back. 
     It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.