Patent Publication Number: US-2023144575-A1

Title: Working machine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims foreign priority to European patent application No. 21207212.8 filed on Nov. 9, 2021, the disclosure and content of which is incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a working machine. In particular, the working machine comprises at least one electric traction motor for propelling the vehicle, wherein charging of a re-chargeable energy storage system is achieved by raising a load implement body of the working machine. Although the invention will mainly be directed to a working machine in the form of a dump truck, the invention may also be applicable for other types of working machines at least partially propelled by an electric traction motor, such as e.g., an excavator, an articulated hauler provided with a tiltable body, etc. 
     BACKGROUND 
     The propulsion systems of working machines are continuously developed to meet the demands from the market. A particular aspect relates to the emission of environmentally harmful exhaust gas. Therefore, working machines propelled by electric machines receiving electric power from a re-chargeable energy storage system, e.g., a battery has been increasingly popular. 
     The re-chargeable energy storage system is however in need of charging at regular intervals when operating the working machine. The working machine thus needs to be driven to a charging station for charging of the energy storage system. 
     US 2015/0283907 describes a charging system of a working machine. The charging system in US 2015/0283907 is formed by a pantograph arranged on the dump body and is raised to be in contact with an overhead trolley line when charging the battery of the working machine. 
     However, the solution described by US 2015/0283907 involves the addition of an expensive component for charging. Also, the pantograph needs to be separately controlled by a control system of the vehicle, thereby requiring additional control strategies for proper functionality. 
     It is therefore a desire to simplify the charging of working machines, which is also less expensive and requires a lower number of additional components. 
     SUMMARY 
     It is thus an object of the present invention to at least partially overcome the above described deficiencies. 
     According to a first aspect, there is provided a working machine, comprising a working machine frame structure, at least one electric machine configured to propel the working machine, a re-chargeable energy storage system electrically connected to the at least one electric machine, wherein the at least one electric machine is operable by electric power received from the re-chargeable energy storage system, a load implement body configured to receive a load, the load implement body being pivotably connected to the working machine frame structure at a pivot joint, and an electrical charge element electrically connected to the re-chargeable energy storage system, the electrical charge element being arranged on a surface portion of the load implement body and configured to, in a charging state, receive electric power from a vertically elevated power source, wherein the working machine is configured to bring the electrical charge element into the charging state by rotation of the load implement body around the pivot joint. 
     The wording “load implement body” should be construed as a body of the working machine which is able to receive and carry load. The load implement body should be able to be lifted from a lower position to an upper, elevated position in which the electrical charge element is arranged in the charging state. As defined above, the load implement body is pivotably connected to the working machine frame structure. According to an example embodiment, the working machine may be a dump truck of which the load implement body is a dump body. Other alternatives are also conceivable, such as a working machine in the form of an excavator. In the latter example, the load implement body preferably comprises an excavator bucket. 
     The electrical charge element is an element which is able to receive electric power from the power source, and configured to transmit the electric power to the re-chargeable energy storage system. The electrical charge element is preferably electrically insulated to the load implement body for preventing electric power to be transmitted into the load implement body. Further, the re-chargeable energy storage system is arranged to receive electric power, i.e. be charged, and to transmit the electric power to the at least one traction motor of the vehicle for propulsion thereof. 
     Moreover, bringing the electrical charge element into the charging state may be executed by a control unit connected to the load implement body. Hereby, the working machine receives a signal indicative of a desire to charge the re-chargeable energy storage system, and controls the load implement body to rotate the load implement body around the pivot joint for lifting at least a portion of the load implement body to the elevated position, and thus in turn lift the electrical charge element to receive electric power from the vertically elevated power source. 
     The control unit may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device. The control unit may also, or instead, include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. Where the control unit includes a programmable device such as the microprocessor, microcontroller or programmable digital signal processor mentioned above, the processor may further include computer executable code that controls operation of the programmable device. 
     The present invention is based on the insight that electric charging of the re-chargeable energy storage system can be performed without the use of any additional mechanisms such as e.g., a pantograph. To put it differently, the present invention uses the implement to operate as a pantograph. Hence, electric charging is performed by already existing components of the working machine, with the slight addition of the electrical charge element. Also, charging can by the present invention be performed with conventional vertically elevated power sources, also commonly referred to as charging poles, or automatic charging poles. Accordingly, the invention is applicable for vertically elevated power sources which are also configured to supply electric power to vehicles using a pantograph. A further advantage is thus also that the overall cost for implementing the charging infrastructure in the working machine is reduced. 
     Furthermore, the vertically elevated power source may be positioned at an unloading position of a work site. In such a situation, the working machine can unload material from the load implement body while simultaneously charging the re-chargeable energy storage system. In other words, the material is unloaded at the same time as the re-chargeable energy storage system is charged with electric power. 
     According to an example embodiment, the electrical charge element may be arranged stationary on the surface portion of the load implement body when the load implement body rotates around the pivot joint. Accordingly, when the load implement body moves up and/or down, the electrical charge element follows motion of the load implement body. 
     According to an example embodiment, the surface portion may have a surface normal facing away from the working machine frame structure. In other words, the surface normal faces the vertically elevated power source. 
     According to an example embodiment, the surface portion of the load implement body may be arranged on a vertical upper portion of the load implement body. Hereby, only a simple and convenient motion of the load implement body is necessary to bring the electrical charge element into the charging state. 
     According to an example embodiment, the surface portion of the load implement body may be arranged on a longitudinally opposite side of the load implement body in comparison to the pivot joint. Accordingly, the charging element is preferably arranged at an outer position of a lever arm formed by the load implement body thereby ensuring that the electrical charge element, and no other portions of the load implement body will accidentally contact the vertically elevated power source. 
     According to an example embodiment, the electrical charge element may be a conductive charge element. According to an example embodiment, the conductive charge element may be configured to be brought into the charging state by mechanically connect conductive charge element with the vertically elevated power source. A conductive charge element is advantageous as it conducts electric power with a high utilization ratio. 
     According to an example embodiment, the electrical charge element may be an inductive charge segment. According to an example embodiment, the inductive charge element may be configured to be brought into the charging state by position the inductive charge element in the vicinity of the vertically elevated power source. An advantage is that the electrical charge element is not in need of being in physical contact with the vertically elevated power source. Hereby, wear of components, i.e., the electrical charge element as well as the vertically elevated power source is reduced. 
     According to an example embodiment, the load implement body may be configured to transition between a first state in which a longitudinal extension of the load implement body is parallel with the longitudinal extension of the working machine frame structure, and a second state in which the longitudinal extension of the load implement body is inclined relative to the longitudinal extension of the working machine frame structure. 
     According to an example embodiment, the load implement body may be configured to transition between the first and second states by rotation of the load implement body around the pivot joint. According to an example embodiment, the working machine may be a dump truck. The transition between the first and second states is thus executed in the same manner as when unloading material from the load implement body, i.e., when unloading material from the dump body of the dump truck. When the working machine is e.g., an excavator, the transition between the first and second states is executed by raising the excavator bucket. Accordingly, and according to an example embodiment, the electrical charge element may be brought into the charging state when the load implement body assumes the second state. 
     According to an example embodiment, the second state may define a maximum allowable inclination between the load implement body and the working machine frame structure. 
     According to an example embodiment, the working machine may be an autonomously controlled working machine. 
     The autonomously controlled working machine may thus be operated from an operator command station of the work site, or be pre-programmed to follow a route for performing the operations at the work site, etc. 
     According to an example embodiment, the working machine may further comprise a control unit connected to the re-chargeable energy storage system and to an autonomously controlled steering system of the working machine, the control unit comprising control circuitry configured to receive a signal indicative of state of charge level of the re-chargeable energy storage system, compare the state of charge level with a predetermined threshold limit, and control the autonomously controlled steering system to operate the working machine to a charging station comprising a vertically elevated power source when the state of charge level is below the predetermined threshold limit, and control the load implement body to rotate around the pivot joint to bring the electrical charge element into the charging state when arriving at the charging station. 
     The control unit may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device. The control unit may also, or instead, include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. Where the control unit includes a programmable device such as the microprocessor, microcontroller or programmable digital signal processor mentioned above, the processor may further include computer executable code that controls operation of the programmable device. 
     Further features of, and advantages will become apparent when studying the appended claims and the following description. The skilled person will realize that different features may be combined to create embodiments other than those described in the following, without departing from the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as additional objects, features, and advantages, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments, wherein: 
         FIG.  1    is a lateral side view illustrating an example embodiment of a working machine in the form of a dump truck; 
         FIG.  2    is a lateral side view of the  FIG.  1    working machine during charging of the re-chargeable energy storage system according to an example embodiment; and 
         FIG.  3    is a lateral side view of a working machine in the form of an excavator according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness. Like reference character refer to like elements throughout the description. 
     With particular reference to  FIG.  1   , there is depicted a working machine  100 . The exemplified working machine  100  of  FIG.  1    is a dump truck  101 . In yet further detail, the dump truck  101  in  FIG.  1    comprises a front unit  103  and a rear unit  105 , where the front  103  and rear  105  units are connected to each other by an articulation joint  107 . The dump truck  101  in  FIG.  1    may thus also be referred to as an articulated dump truck, or an articulated hauler. The dump truck may however equally as well be arranged in the form of a fixed hauler where the front  103  and rear  105  units are fixed to each other. The working machine  100  is preferably operated at a working site, in particular a confined working site in the below described example when the working machine  100  is an autonomously controlled working machine  100 . 
     The front unit  103  comprises a pair of steerable wheels  120 , while the rear unit  105  comprises a pair of frontmost rear wheels  122  and a pair of rearmost rear wheels  124 . The pair of steerable wheels  120  of the front unit  103  are connected to an electric machine  130  arranged to propel the working machine  100 . Although not depicted in  FIG.  1   , the pair of frontmost rear wheels  122  and/or the pair of rearmost rear wheels  124  may, as an alternative or as a complement, be provided with an electric machine for propulsion. Hence, the working machine  100  may be two-wheel driven, four-wheel driven and/or six-wheel driven. However, the following will only describe the working machine  100  with the electric machine  130  arranged on the steerable wheels  120  of the front unit  103 . Further, the working machine  100  also comprises a re-chargeable energy storage system  104  electrically connected to the electric machine  130  for supply of electric power to the electric machine  130 . The re-chargeable energy storage system  104  is preferably arranged in the form of a vehicle battery and is in  FIG.  1    exemplified as arranged on the front unit  103 . 
     Further, the rear unit  105  comprises a working machine frame structure  102  carrying a load implement body  106 . The load implement body  106  is in  FIG.  1    exemplifies as a dump body  105  of the dump truck  101 . The load implement body  106  comprises an open box structure  111  configured to receive a load. The specific type of load may of course vary depending on the application of use, but can be e.g. mud, sand, rocks, gravel, etc. The load implement body  106  is pivotably connected to the working machine frame structure  102  at a pivot joint  108  of the working machine frame structure  102 . The pivot joint  108  is arranged at a longitudinal rear end of the working machine  100 , pivotably connecting a rear end of the load implement body  106  to a rear end of the rear unit  105  to each other. The load implement body  106  is thus pivotable around a geometric axis extending laterally of the working machine  100 . The load implement body  106  is also connected to the working machine frame structure  102  at a longitudinal front end by an extendible and retractable cylinder, which is illustrated in further detail in  FIG.  2   . 
     Moreover, the working machine  100  comprises an electrical charge element  110 . The electrical charge element  110  is electrically connected to the re-chargeable energy storage system  104  by means of electric wiring  140 . The electrical charge element  110  is thus an electrical contact point serving as an interface between the re-chargeable energy storage system  104  and a power source  114  of a charging station  160 , which charging station power source is configured to, when connected to the electrical charge element  110 , charge/re-charge the re-chargeable energy storage system  104 . 
     As can be seen in  FIG.  1   , the electrical charge element  110  is arranged on the load implement body  106 . In further detail, the electrical charge element  110  is arranged on a surface portion  112  arranged on a vertical upper portion of the load implement body and on a longitudinally opposite side of the load implement body  106  in comparison to the pivot joint  108 . Preferably, the electrical charge element  110  is electrically isolated from the load implement body  106 . Thus, when the electrical charge element  110  receives electric power from the power source  114  as will be described in further detail below with reference to  FIG.  2   , electric power is prevented from being transmitted into the load implement body  106 . The electrical insulation may be obtained by using an electrically isolating material for connecting the electrical charge element  110  to the surface portion  112  of the load implement body  106 . As an alternative, the surface portion  112  of the load implement body  106  may by itself be formed by an isolating material. 
     Furthermore, the electrical charge element  110  is arranged stationary on the surface portion  112  relative to the load implement body  106  and has a surface normal facing away from the working machine frame structure  102 . Hence, the surface normal of the electrical charge element  110  is facing substantially vertically upwards and moves upwards and downwards by the upward and downward motion of the load implement body  106 . 
     Moreover, the working machine also comprises a control unit  200 . The working machine  100  is preferably an autonomously controlled working machine and the control unit  200  is, as will be described further below, configured to operate the vehicle, i.e., navigate the working machine, and control the operation of the electric machine  130 . The control unit  200  is also connected to the re-chargeable energy storage system  104  for determining e.g., the state-of-charge level of the re-chargeable energy storage system  104 . The control unit  200  is also configured to control the load implement body which will be described below. 
     The working machine  100  depicted in  FIG.  1    is thus arranged in a state where the load implement body  106  is positioned in a load receiving state. Hence, when the load implement body  106  is arranged in this state, the cylinder connecting the longitudinal front end of the load implement body  106  to the working machine frame structure  102  is retracted, and the load implement body  106  can receive material. Also, when the load implement body  106  is positioned in a load receiving state, the working machine  100  is allowed to be propelled and operated at the working site. 
     In order to describe charging/re-charging of the re-chargeable energy storage system  110  of the present invention in further detail, reference is made to  FIG.  2   .  FIG.  2    is a lateral side view of the  FIG.  1    working machine  100  during charging of the re-chargeable energy storage system according to an example embodiment. In  FIG.  2   , the electric wiring between the electrical charge element  110  and the re-chargeable energy storage system  104  has been omitted but should of course be construed as forming part of the working machine also for  FIG.  2   . 
     As can be seen in  FIG.  2   , the power source  114  is a vertically elevated power source  114 . Thus, the power source  114  is thus vertically elevated relative to ground level  400 . According to the exemplified embodiment depicted in the figures of the present disclosure, the vertically elevated power source  114  is arranged on a pole  160  attached to the ground level  400  and extending vertically from the ground level  400 . 
     When the re-chargeable energy storage system  104  in in need of charging, which may e.g., be determined by the control unit  200  receiving a signal indicative of a state-of-charge level of the re-chargeable energy storage system  104  falling below a predetermined threshold limit, the working machine  100  is operated to a position in the vicinity of the pole  160 . The control unit  114  thereafter controls the load implement body  106  to tilt around the pivot joint  108 . In particular, the control unit  200  controls the cylinder  202  to raise the front end of the load implement body  106 . The load implement body  106  is rotated around the pivot joint  108  until the electrical charge elements is brought into a charging state, in which charging state the electrical charge element receives electric power from the vertically elevated power source  114 . 
     According to a non-limiting example embodiment, the electrical charge element is a conductive charge element. In such a case, the electric charge element is brought into the charging state by mechanically connect conductive charge element with the vertically elevated power source. However, the electrical charge element may as an alternative be an inductive charge segment. In such a case, the electric charge element is brought into the charging state by positioning the inductive charge element in the vicinity of the vertically elevated power source. The wording “in the vicinity of” should be construed as a distance where electric power is able to be transmitted from the vertically elevated power source to the inductive charge element. 
     In yet further detail, when charging of the re-chargeable energy storage system is to be carried out, the control unit  200  controls the load implement body  106  to transition from a first state in which a longitudinal extension of the load implement body  106  is parallel with the longitudinal extension of the working machine frame structure  102 , to a second state in which the longitudinal extension of the load implement body  106  is inclined relative to the longitudinal extension of the working machine frame structure  102 , which inclination is achieved by rotating the load implement body  106  around the pivot joint  108 . 
     Preferably, the second state, i.e., when the electrical charge element is brought into the charging state, preferably defines a maximum allowable inclination of the pivot joint. The second state thus preferably corresponds to the same position of the load implement body  106  as when unloading material at the working site. 
     In order to describe a further working machine  100  forming part of the present invention, reference is made to  FIG.  3   .  FIG.  3    is a lateral side view of a working machine  100  in the form of an excavator  201  according to an example embodiment. 
     In a similar vein as the above described dump truck  101  depicted in  FIGS.  1  and  2   , the excavator  201  also comprises a schematically illustrated electric machine  130  for propelling the excavator  201 . The electric machine  130  is connected to ground engaging members in the form of continuous tracks  230 . Furthermore, the excavator  201  also comprises a re-chargeable energy storage system  104  electrically connected electric machine  130 , as well as a control unit  200  for controlling operation of the excavator  201 . 
     Moreover, the excavator  201  comprises a load implement body  106 . The load implement body  106  comprises a bucket  205 . The bucket  205  is connected to a boom  220 , which in turn is pivotably connected to a frame structure  102  of the excavator  201  at a pivot joint  108 . Thus, the load implement body  106  should thus be construed as comprising both the bucket  205  as well as the boom  220 . 
     Moreover, the excavator  201  comprises an electrical charge element  110 . The electrical charge element  110  is arranged on the bucket  205  and electrically connected to the re-chargeable energy storage system  104  by means of electric wiring  140  arranged along the boom  220 . 
     Charging of the re-chargeable energy storage system  104  of the excavator  201  is executed in a similar manner as for the dump truck  101  described above in relation to  FIGS.  1  and  2   . In particular, when charging the re-chargeable energy storage system  104 , the electric charge element  110  is brought into the charging state, in which charging state the electrical charge element  110  receives electric power from the vertically elevated power source  114 . In yet further detail, the electrical charge element  110  is brought into the charging state by rotating the load implement body  106 , and in particular the boom  220 , around the pivot joint  108  until electric power can be transmitted between the vertically elevated power source  114  and the electrical charge element  110 . 
     Furthermore, and as indicated above, the working machines  100  depicted in  FIGS.  1 - 3    are preferably autonomously controlled working machines. This is particularly depicted in  FIGS.  1 - 2   , where the working machine  100  lacks an operator cabin. The control unit  200  is thus preferably connected to an autonomously controlled steering system of the working machine  100 . The control unit  200  comprising control circuitry which during autonomously controlled operation of the vehicle is configured to receive a signal indicative of state of charge level of the re-chargeable energy storage system. The control circuit compares the state of charge level with a predetermined threshold limit. When the state of charge level is below the predetermined threshold limit, there is a need/desire to re-charge the re-chargeable energy storage system. The control circuit hereby controls the autonomously controlled steering system to operate the working machine to a charging station comprising the above described vertically elevated power source  114 . 
     When arriving at the charging station, the control circuitry controls the load implement body  106  to rotate around the pivot joint  108  to bring the electrical charge element  110  into the above described charging state. The re-chargeable energy storage system  104  is hereby charge by electric power from the charging station. 
     It is to be understood that the present disclosure 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.